A New Approach to Support Delay-Sensitive VBR Video in Packet-Switched Networks

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2022年9月英语六级试卷及参考解答

2022年9月英语六级试卷及参照解答英语六级试卷采用多题多卷的形式，大家核对解答时,找出具体选项，忽略套数。

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【听力】Conversation 1M: Welcome to Money Matters - a weekly program that helps you manage your money. Tonight, I'll be tal to Mary Johnson about budgeting.W: Hello, everyone.M: There's a magic about money, when it's not planned for, tracked and kept the record of, it literally disappears.What are some of the steps we can take to prevent this from happening?W: Well, it's all about keeping track of your money.If you don't do that, you'll never be able to set any goals for your budget or have the discipline to stick to them.M: That's easier said than done. I read recently that only 41% of Americans adhere to a budget.W: Yes, but knowing what you earn and what you spend can give you reassurance that you won't get into debt in the first place. You can do this by adding up all of your sources of income you have, and writing them all down on a piece of paper. On the same page, write down all of your monthly expenses.M: I'm always amazed at how much my expenses add up.But designating each item asan income or an expense really helps me have a much better sense of all my spending. W: Right. Most people have no idea how much they spend each day, let alone each week or month, no matter how careful they are. Next, subtract your monthly expenses from income. If the result is positive, you are living within your means. If the result is a negative number, you're going to have to cut back on your spending.M: I'm usually a negative number. I just can't resist the allure of all those prestigious goods.W: Well, it's not a catastrophe, but you do have to make some changes. Try cutting back on those non-essential items, sell some stuff in your attic or shop online to avoid unnecessary temptations like chocolate. Failing that you can always find yourself a part-time job.Q1: What does the man say about the weekly program?Q2: What did the man read recently?Q3: What does the woman suggest the man do first to avoid getting into debt?Q4: What does the woman say about online shopping?Conversation 2M: Hi there. I've come to see the flat. My name is Mark Adams. We spoke on the phone on Wednesday.W: Hi Mark. Come on up. I'll buzz you in green door, on the second floor on the right side. Nice to meet you. I spoke to all your references and they all checked out Okay.So let me show you around the place actually belongs to my mother, but her health isn't great. So we finally managed to persuade her to move in with us and rent this old place out.M：It's a great size, plenty of space, very versatile. I think it's a winner for us.W: Yes. All the appliances are brand new. There's a washing machine and a tumble dryer in the utility room next to the kitchen.M: Lots of closet space two, which is fabulous. My wife has a ridiculous number of shoes. Now, the big question What about noise and the neighbors?W: Well, all the neighbors are elderly, so no noisy kids and the back of the house overlooks a clear and peaceful pond. So it's perfect. If tranquility is what you are loo for.M: That's good news. We've been living in a less than glamorous part of Aberdeen, constantly harassed day and night by noisy neighbors. Getting to work was a nightmare too. As we only have one car. And my wife has to use it as she works nights at the hospital.W: Well, if you like the place it's yours. As soon as I get a contract drawn up with the solicitor, the first month's rent and a deposit are mandatory on signing the contract, then we can work out when is the best day for you to pay rent each month? M: We'll be incredibly happy to be your new tenants. Thank you so much. My wife will be thrilled to get out of the shabby place we are now in and start filling those wardrobes with all those shoes.Q5: What does the woman say about the flat question six?Q6: What is the man's chief consideration in loo for a flat?Q7: What does the man have to do on signing the contract?Q8: Why does the man say his wife will feel very excited if they move into the flat?Passage 1A new study has found a positive correlation between how much television children watch and their parents stress levels. Why? Because the more television kids watch, the more they're exposed to advertising .The more advertising they see, the more likely they are to insist on purchasing items when they go with their parents to the store.This could generate conflict if the parents refuse. All that researchers say can contribute to parents overall stress levels. What's the solution ? Perhaps the most obvious is curtailing screen time.Commercial content is there for a reason :to elicit purchasing behavior, so parents might want to shut off the TV. Researchers can see that this is easier said than done. So they suggest another option. Parents can change how they talk to their kids about purchases. The researchers suggest that parents seek input from their children on family purchasing decisions.They shouldn't try to control all purchases. Instead, parents might tell their children things like: I will listen to your advice on certain products or brands. This type of communication, the researchers assert, can lead to children, ma fewer purchasing demands- that means less parent stress. However,the protective effect of this kind of communication diminishes with greater exposure to television. This is because advertising aimed at children is especially persuasive. Advertisers use an assortment of tactics, such as bright colors, happy music and celebrity endorsements to appeal to children. Plus children don't have the cognitive ability to fully understand advertising's intent that makes them particularly vulnerable to advertisements.Q9: What has the new study found about children watching television?Q10:What are parents advised to do to reduce the impact of TV commercials?Q11: What makes children particularly vulnerable to TV commercials?Passage 2Everyone is supposed to cheer for good guys. And we should only punish the bad guys, but that's not what we always do. Most of the time we do indeed reward good people. We also often punish people who harm others or who aren't good team players, but sometimes the good guys also get punished or criticized specifically because they are so good. This seems baffling because it's detrimental to group cooperation. However, the phenomenon has been discovered in multiple fields and it has been found in every society. Why does this happen? Research suggests a simple reason when one person looks really good, others look bad by comparison. Those others then have an incentive in stopping that person from loo good, especially if they can't or won't compete. After all, we're all judged in comparison with others. When faced withsomeone better, what can a normal person do? One option is to actively compete. A second option is to bring that person down that is to suppress their cooperation or work ethic, and first selfish motives for their actions or imply real or imagined hypocrisy. Other tactics include attac them on unrelated dimensions or punishing them outright. Why does this matter? Critics often attack the motives of people who protect the environment, donate money or work too hard. Such good deeds are dismissed as naive or hypocritical by those who do not perform those deeds. This criticism may ultimately discourage people from doing good deeds.so it's important to recognize these attacks for what they are.Q12: What baffling phenomenon is discussed in the passage?Q13: How are we all judged according to the passage?Q14: What can a normal person do when faced with people who perform better?Q15: what may discourage people from performing good deeds?Lecture 1 雪萱In America, most researchers can see that boys and girls are brought up in different ways, taught different skills and rewarded for different acts. Women, it is agreed excel at certain tasks, men at others. There is little argument that some personality traits appear more dominant in one sex than in the other.All of this, not withstanding, gender differences are very much in the media these days. Since the rise of the women's movement, gender role behavior has come under closer scrutiny. How has this affected friendship? How do the sexes differ in theirfriendship relations? Most preteen children have a best friend who is usually some one of the same sex and similar age.Both sexes share an essentially positive recollection of these childhood friendships, they do not differ in this respect. However, the type of play engaged in during these early friendships is telling of the difference to come. Boys tend to form playgroups that are competitive in nature. Girls groups more frequently revolve around cooperative enterprises. Thus at an early age, boys become concerned with trying hard and winning, while girls by contrast play house and school, engaging in roles that require complimentary support. Spea of their childhood, men recall being highly responsive to and aware of the gender role opinions of other boys. Girls in preteen years appear to be less susceptible to gender role pressure. It is not until the dating years that women report being concerned with feminine behavior. Males for the most part are responsive to the suggestion that their behavior is unmanly at almost any age. These early attitudes reinforced by social conditioning continue to play an active part in the friendships of both sexes during adolescence. This is a period when the majority of males, once again, report a close Alliance with same sex friends.Now, however, with heightened intensity, considerable energy is devoted to competing for position and a definite undercurrent of competition permeates the relationship. Although in dissimilar fashion, females share equally fragile relationships at this age. For them, the bond of loyalty extends only to the line of romantic involvement.This is most apt to be the case in late adolescence when dating and relationships with boys take sharp precedence over sisterhood. Actually dating dilutes the intensity of samesex friendships for men also. For the majority of us, the moment we begin to date seriously, there's a competition between romance and friendship.Q16: What does the speaker say about most preteen children?Q17: What do most males devote much of their energy to during adolescence?Q18: What do children do when they reach late adolescence?Lecture 2Good afternoon. In today's lecture, we'll be tal about how and when to disclose a disability when applying for a job. On average, about 20% of the population has some form of disability. Most countries these days have equal opportunity and non-discrimination laws, yet disabled people often find it hard to decide when, how, and if at all to raise their disability problem with a potential employer. There is uncertainty about how a recruiter will perceive their disability as such many candidates fear they wouldn't be considered for a position as a result of disclosing this personal information. And research has validated this as a genuine concern for many j ob applicants. It’s a natural reaction, but it shouldn't be a reason to stay quiet. People need to remember that they are applying for a position they have the skills and experience to.Discussing a disability with a potential employer may help them make reasonable workplace adjustments in their favor. It's most appropriate to discuss a disabilitywhen they reply to confirm an interview, this information needed to be put up front in their cover letter or resume. because it's probably not relevant to the position itself. Candidates with disabilities should feel they have the power to make their own decisions around sharing this information free from prejudice. If they find an organization that doesn't celebrate diversity and inclusion, it could say a lot about the company's culture, perhaps the organization isn't the right fit. It's important for them to. remember That they are see a manager, an employer that's going to be supportive and continue to give them a great employment experience. Companies sometimes offer candidates the chance to disclose disabilities on their application form, but people shouldn't feel restricted by this method or timing. People should avoid sharing the name of their disability or condition. There is always the risk that the recruiter will research inform that is inaccurate or irrelevant. If people don't think their disability will impact their ability to perform in the advertised position, then it's entirely their entitlement to choose when and whether to share this information.Q19: Why do disabled job applicants feel reluctant to disclose their disability information?Q20: When does the speaker suggest applicants reveal their disability information? Q21: What are people advised to do when filling out their job application form?Lecture 3Smartphones Distract attention and reduce learning because of their potential to offer activities more inviting than study.But what about background sound alone?A group of American researchers compared students' comprehension of verbal material when reading in the presence of background speech, instrumental music or general noise.General noise is neutral such as that from the sound of an air conditioner or fan. Student scores were most depressed in the presence of background speech. Comprehension was slightly better with the presence of music than with speech. However, when they were asked to identify melodies rather than understand text background music interfered more. When the background speech was in a language unfamiliar to participants, there was little, if any hindrance of reading comprehension.British researchers compared the effects of background speech, vocal music, instrumental music, general background noise and silence on short term memory. Background speech had the biggest negative effect. Vocal music was slightly more disruptive than instrumental.In general background noise and silence were least disrupt.It seems the degree of interference from background noise depends on the overlap between the processing required on the task and the processing required to screen out the background noise.The studies suggest that when people read and when they try to remember any verbal material, background speech will inhibit their ability.Instrumental music will have at worst a slight effect.When students write essays, however,other research has found it is best to reduce all background noise as much as possible.Not everyone reacts in the same way to distractions.Other studies suggest some aspects of personality may make a difference.The researchers subjected shy, quiet people and confident, outgoing ones to high arousal or low arousal background music, general noise or silence while as them to remember words.Everyone performed best in the silent condition, but less sociable people were more negatively affected by each of the distractions.So when children are reading and trying to incorporate new material, parents could consider allowing some background music, particularly if it is instrumental and their child is the outgoing type.Q22: What did some American researchers find about students reading comprehension in the presence of background noise?Q23: What do we learn from the British researchers about the degree of interference from background noise?Q24: What is best for students to do when writing essays according to some research?Q25: How do people of different personalities react to distractions according to other studies?听力参照解答1.C) It helps people with budgeting.2.D) Most Americans do not stick to a budget.3.A) Keep track of his money.4.B) It helps avoid unnecessary spending.5.C) It belongs to her mother.6.B) Tranquility.7.B) Pay the first month's rent and a deposit.8.D) She will have plenty of space for her shoes.9. D) The more television they watch, the greater their parents' stress.10. C) Involve children in ma purchasing decisions.11. A) Their limited cognitive ability.12）D Good guys may get unfair treatment13) C In comparsion with others14) B Compete with them actively15) A Being dismissed as hypocritical16.D) They make friends with peers of the same sax.17. A) Competing for position.18. A) They prioritize romance over friendship.19. B) They are worried about being turned down.20. C) When confirming an interview.21. D) Avoid mentioning the name of their disability.22.B) It was the poorest when there was background speech.23.C) It depends on the overlap in processing different kinds of information.24.A) Keep everything as quiet as possible.25. B) Shy quiet people were most adversely impacted.【阅读】词汇理解（1）文章开头开头：The now extinct passenger pigeon has the dubious honor of being the last species anyone ever expected to disappear.（2）解答【解答速查】26-30 LAIMO 31-35 BCHND26. L) estimates27. A) vulnerable28. I) hatched29. M) edible30. O) delicacy31. B) unprecedented32. C) tracts33. H) infinite34. N) depleted35. D) specimen长篇阅读（1）文章标题标题：Is computer coding a foreign language?（2）解答速查36-40 LEKGD 41-45 HBJCM（3）题干、解答和定位处36. Employers attach more importance to applicants' computer skills than their language competence.36. L 【定位】Even with the benefits and skill sets languages provide, recruiters and employers value computer skills more.37. One U.S. state senator proposed that high school students be allowed to study either foreign language or computer coding.37. E【定位】“I think the opportunity to give people a choice is important," says Florida state Senator Jeremy Ring.might as well do computer coding."38. Learning languages broadens students' international perspective and nurtures mutual respect among peoples, according to a high school language teacher.38. K【定位】 We need to find a way to put ourselves at the global table and to treat each other with mutual respect.39. One U.S. state will see to it that programming classes are taught by quality teachers.39. G 【定位】 Instead, the state will provide support for higher quality teachers for programming classes.40. Statistics show while computer-related jobs have been on the rise, foreign languages have become less appealing to American students since mid-1990s.40. D 【定位】Foreign language interest, on the other hand, is declining for the first time since 1995.41. All school subjects are said to be essential to students' well-rounded development.41. H 【定位】…because every subject, whether art, math or language. is a significant contribution to a well-rounded existence.42. There is consensus among most educators that coding should be taught in schools but should not replace foreign language.42. B【定位】Coding should be added to curriculums, but not at the expense of foreign language classes.43. One study showed that foreign language learning improved students' academic performance.43. J【定位】Studies show that bilingualism (双语) correlates with cognitive development, intelligence, memory and problem solving abilities, according to the American Cou44. Being short of funding and qualified teachers, schools lag behind the fast developing computer science field.44. C 【定位】The computer science field is growing faster than schools can keep up because of budget constraints and a lack of skills training for teachers. 45. A distinguished high school language teacher also believes it is advisable to start learning a foreign language at an earlier age.45. M 【定位】I just think it's something you have to start early and not just have something that you do for a couple of years in high school," he says.Passage One（1）文章开头The U.S. and China don’t agree on much these days.（2）解答【解答速查】 46-50 DCABC（3）解答选项内容：46. D) How to stop tech companies from gaining monopoly.47. C) All companies must be regulated by the government.48. A) They can no longer do business independent of tech giants.49. B) They have considered regulatory action to promote fair competition.50. C) They are becoming untrustworthy.Passage Two文章开头：Born from the accessibility of mass air travel, modern解答速查：51-55 DBDAC51. What is the popular assumption about international tourism?D) It contributes to the economy of destination countries and regions.52. What do we learn from some studies about uncontrolled tourism development?B) It incurs local residents' antagonism to tourists.53. Why does the author say local residents of popular destinations often feel frustrated?D)They do not think they benefit as much as they deserve.54. How does the author say local residents in destination communities respond to tourism activity?A)They endeavor to adapt to it.55. What can tourists do to exert more positive impacts on the tourist destinations?C)Use the services provided by local businesses.【翻译】春联贴春联(Spring Festival couplets)是中国人欢度春节的一个重要习俗。

英语二text1。2020解析 -回复

英语二text1。

2020解析-回复题目: The Impact of COVID-19 on Global EducationIntroduction:The COVID-19 pandemic has had a profound impact on various aspects of society, including the field of education. In this article, we will explore the consequences of the pandemic on global education and discuss the challenges and opportunities that have emerged as a result.1. The transition to online learning:[Discuss how the pandemic forced educational institutions worldwide to shift to online learning platforms.]One of the most significant consequences of COVID-19 on global education is the sudden transition to online learning. Schools and universities were forced to close their doors to prevent the spread of the virus, resulting in the adoption of virtual classrooms and remote learning platforms. This shift has posed numerous challenges for both students and educators, such as technical difficulties, lack of access to necessary resources, and the need for alternative teaching methodologies.2. Inequality in access to education:[Address the issue of unequal access to education caused by the transition to online learning.]However, the transition to online learning has also highlighted the deep-rooted inequality in access to education. Many students from low-income families or rural areas lack the necessary devices, internet access, or conducive learning environments to participate fully in online classes. This digital divide has widened the inequality gap, as students in privileged situations continue to receive quality education while their less fortunate counterparts struggle to keep up.3. Mental health and well-being:[Discuss the psychological impact of the pandemic on students and how it has affected their ability to learn.]The pandemic has taken a toll on students' mental health and well-being. The long periods of isolation, fear, and uncertainty have contributed to increased levels of stress, anxiety, and depression. Consequently, students' ability to concentrate andlearn effectively has been hampered. Educational institutions have had to prioritize mental health support services to address these concerns and ensure overall student well-being.4. Innovative teaching methods:[Highlight how the pandemic has sparked innovation in teaching methods.]Despite the challenges, the pandemic has also presented opportunities for innovation in teaching methodologies. Educators have been compelled to explore alternative ways of delivering lessons and engaging students. This has led to the creation of interactive online platforms, virtual reality simulations, and other technological tools to enhance the learning experience. As a result, students have gained exposure to new modes of instruction that could potentially improve their educational outcomes in the long run.5. Lifelong learning and adaptability:[Discuss the importance of adaptability and lifelong learning in the face of global challenges.]COVID-19 has demonstrated the critical importance of adaptability and lifelong learning in a rapidly changing world. The pandemic has forced both students and educators to quickly adapt to new technologies, modes of instruction, and global challenges. As a result, individuals have become more resilient and equipped with valuable skills such as critical thinking, problem-solving, and digital literacy. These skills will be crucial for their future success in an increasingly digital and interconnected world.Conclusion:In conclusion, the COVID-19 pandemic has profoundly impacted global education, resulting in the rapid shift to online learning, exacerbation of educational inequality, and challenges to students' mental health. However, it has also presented opportunities for innovation in teaching methods and highlighted the importance of adaptability and lifelong learning. As countries continue to navigate the challenges posed by the pandemic, it is crucial to address the unequal access to education and prioritize the well-being of students to ensure the continuity of quality education on a global scale.。

ACCA P5 Summary

1Introduction to strategic management accounting1.1I ntroduction to planning, control and decision making☞Strategic planning is the process of deciding on objectives of the organization, on changes in these objectives, on the resource to attain these objectives, and on the policies that are to govern the acquisition, use and disposition of these resources.☞Characteristics of strategic information⏹Long term and wide scope⏹Generally formulated in writing⏹Widely circulated广泛流传⏹Doesn’t trigger direct action, but series of lesser plans⏹Includes selection of products, purchase of non-current assets, required levels ofcompany profit☞Management control: the process by which management ensure that resources are obtained and used effectively and efficiently in the accomplishment of the organisation’s objectives. It is sometimes called tactics ad tactical planning.☞Characteristics of management accounting information⏹Short-term and non-strategic⏹Management control planning activities include preparing annual sales budget⏹Management control activities include ensuring budget targets are reached⏹Carried out in a series of routine and regular planning and comparison procedures⏹Management control information covers the whole organisation, is routinely collected,is often quantitative and commonly expressed in money terms (cash flow forecasts, variance analysis reports, staffing levels⏹Source of information likely to be endogenous内生的☞Characteristics of operational control⏹Short-term and non-strategic⏹Occurs in all aspects of an organisations activities and need for day to dayimplementation of plans⏹Often carried out at short notice⏹Information likely to have an endogenous source, to be detailed transaction data,quantitative and expressed in terms of units/hours⏹Includes customer orders and cash receipts.1.2Management accounting information for strategic planning and control☞Strategic management accounting is a form of management accounting in which emphasis is placed on information about factors which are external to the organisation, as well as non-financial and internally-generated information.⏹External orientation: competitive advantage is relative; customer determination⏹Future orientation: forward- and outward looking; concern with values.⏹Goal congruence: translates the consequences of different strategies into a commonaccounting language for comparison; relates business operations to financial performance.1.3Planning and control at strategic and operational levels☞Linking strategy and operations, if not: unrealistic plans, inconsistent goals, poor communication, inadequate performance measurement.1.3.1Strategic control systems☞Formal systems of strategic control:⏹strategy review;⏹identify milestones of performance( outline critical success factors, short-term stepstowards long-term goals, enables managers to monitor actions)⏹Set target achievement levels (targets must be reasonably precise, suggest strategiesand tactics, relative to competition)⏹Formal monitoring of the strategic process⏹Reward.☞Desired features of strategic performance measures⏹Focus on what matters in the long term⏹Identify and communicate drivers of success⏹Support organisational learning⏹Provide a basis for reward⏹Measurable; meaningful; acceptable;⏹Described by strategy and relevant to it⏹Consistently measured⏹Re-evaluated regularly1.4Benchmarking1.4.1Types of benchmarking☞Internal benchmarking: easy; no innovative or best-practice.☞Industry benchmarking:⏹Competitor benchmarking: difficult to obtain information⏹Non-competitor benchmarking: motivate☞Functional benchmarking: find new, innovative ways to create competitive advantage1.4.2Stages of benchmarking☞Set objectives and determine the area to benchmark☞Establish key performance measures.☞Select organizations to study☞Measure own and others performance☞Compare performance☞Design and implement improvement prgoramme☞Monitor improvements1.4.3Reasons for benchmarking☞Assess current strategic position☞Assess generic competitive strategy☞Spur to innovation☞Setting objectives and targets☞Cross comparisons☞Implementing change☞Identifies the process to improve☞Helps with cost reduction, or identifying areas where improvement is required☞Improves the effectiveness of operations☞Delivers services to a defined standard☞Provide early warning of competitive disadvantage1.4.4Disadvantages of benchmarking☞Implies there is one best way of doing business☞Yesterday’s solution to tomorrow’s problem☞Catching-up exercise rather than the development of anything distinctive☞Depends on accurate information about comparator companies☞Potential negative side effects of ‘what gets measured gets done’.2Performance management and control of the organization2.1Strengths and weaknesses of alternative budget models2.1.1Incremental budgeting☞Is the traditional approach to setting a budget and involves basing next year’s budget on the current year’s results plus an extra amount for estimated growth of inflation next year. ☞Strengths: easy to prepare; can be flexed to actual levels to provide more meaningful control information☞Weaknesses: does not take account of alternative options; does not look for ways of improving performance; only works if current operations are as effective, efficient and economical as they can be; encourage slack in the budget setting process.2.1.2Zero based budgeting☞Preparing a budget for each cost centre from scratch.☞Strengths:⏹Provides a budgeting and planning tool for management that responds to changes inthe business environment.⏹Requires the organization to look very closely at its cost behavior patterns, andimproves understanding of cost-behaviour patterns.⏹Should help identify inefficient or obsolete processes, and thereby also help reducecosts.⏹Results in a more efficient allocation of resources⏹Be particularly useful in not-for-profit organizations which have a focus on achievingvalue for money.☞Weaknesses:⏹Requires a lot of management time and effort⏹Requires training in the use of ZBB techniques so that these are applied properly⏹Questioning current practices and processes can be seen as threatening2.1.3Rolling budgets☞Continuously updated by adding a further period when the earliest period has expired.☞Strengths:⏹Reduce the uncertainty of budgeting for business operating in an unstableenvironment. It is easier to predict what will happen in the short-term.⏹Most suitable form of budgeting for organizations in uncertain environments, wherefuture activity levels, costs or revenues cannot be accurately foreseen.⏹Planning and control is based on a more recent plan which is likely to be morerealistic an more relevant than a fixed annual budget drawn up several months ago.⏹The process of updating the budget means that managers identify current changes( and so can respond to these changes more quickly)⏹More realistic targets provide a better basis on which to appraise managers’performance⏹Realistic budgets are likely to have a better motivational effect on managers.☞Weaknesses:⏹Require time, effort and money to prepare and keep updating. If managers spend toolong preparing/revising budgets, they will have less time to control and manage actual results⏹Managers may not see the value in the continuous updating of budgets⏹May be demotivating if targets are constantly changing⏹It may not be necessary to update budgets so regularly in a stable operatingenvironment.2.1.4Flexible budgets☞Recognizing the potential uncertainty, budgets designed to adjust costs levels according to changes in the actual levels of activity and output.☞Strengths:⏹Finding out well in advance the costs of idle time and so on if the output falls belowbudget.⏹Being able to plan for the alternative use of spare capacity if output falls short ofbudget☞Weaknesses:⏹As many errors in modern industry are fixed costs, the value of flexible budgets as aplanning tool are limited.⏹Where there is a high degree of stability, the administrative effort in flexiblebudgeting produces little extra benefit. Fixed budgets can be perfectly adequate in these circumstances.2.1.5Activity based budgeting☞Involves defining the activities that underlie the financial figures in each function and usingthe level of activity to decide how much resources should be allocated, how well it is being managed and to explain variance from budget.☞Strengths:⏹Ensures that the organisation’s overall strategy and any changes to that strategy willbe taken into account.⏹Identifies critical success factors which are activities that a business must perform wellif it is to succeed⏹Recognizes that activities drive costs; so encourages a focus on controlling andmanaging cost drivers rather than just the costs⏹Concentrate on the whole activities so that there is more likelihood of getting it rightfirst time.☞Weaknesses:⏹Requires time and effort to prepare so suited to a more complex organization withmultiple cost drivers.⏹May be difficult to identify clear individual responsibilities for activities⏹Only suitable for organization which have adopted an activity-based costing system⏹ABBs are not suitable for all organization, especially with significant proportions offixed overheads.2.1.6The future of budgeting☞Criticisms of traditional budgeting⏹Time consuming and costly⏹Major barrier to responsiveness, flexibility and change⏹Adds little value given the amount of management time required⏹Rarely strategically focused⏹Makes people feel undervalued⏹Reinforces department barriers rather than encouraging knowledge sharing⏹Based on unsupported assumptions and guesswork as opposed to sound,well-constructed performance data⏹Development and updated infrequently2.2Budgeting in not-for-profit organizations☞Special issues: the budget process inevitably has considerable influence on organizational processes, and represents the financial expression of policies resulting from politically motivated goals and objectives. The reality of life for many public sector managers is an subjected to(受---支配) growing competition.⏹Be prevented from borrowing funds⏹Prevent the transfer of funds from one budget head to another without compliancewith various rules and regulations⏹Plan one financial year.⏹Incremental budgeting and the bid system are widely used.2.3Evaluating the organisation’s move beyond budgeting2.3.1Conventional budgeting in a changing environment☞Weaknesses of traditional budgets:⏹Adds little value, requires far too much valuable management time⏹Too heavy a reliance on the ‘agreed’ budget has an adverse impact on managementbehavior, which can become dysfunctional(功能失调的) with regard to(关于) the objectives of the organization as a whole⏹The use of budgeting as a base for communicating corporate goals, is contrary to theoriginal purpose of budgeting as a financial control mechanism⏹Most budgets are not based on a rational, causal(因果关系的) model of resourceconsumption, but are often the result of protracted internal bargaining processes.⏹Conformance to budget is not seen as compatible with a drive towards continuousimprovement⏹Traditional budgeting processes have insufficient external focus.2.3.2The beyond budgeting model☞Rolling budgets focus management attention on current and likely future realities within the organizational context, it is seen as an attempt to keep ahead of change, or strictly speaking to be more in control of the response to the challenges facing the organization. ☞Benefits:⏹Creates and fosters a performance climate based on competitive success. Managerialfocus shifts from beating other managers for a slice(部分) of resources to beating the competition.⏹It motivates properly by giving them challenges, responsibilities and clear values asguidelines. Rewards are team-based⏹It empowers operational managers to act by removing resource constraints. Speedingup the response to environmental threats and enabling quick exploitation of new opportunities.⏹It devolves performance responsibilities to operational management who are closer tothe action.⏹It establishes customer-orientated teams that are accountable for profitable customeroutcomes.⏹Creates transparent and open information systems throughout the organization,provides fast, open and distributed information to facilitate control at all levels.3Business structure, IT development and other environmental and ethical issues3.1Business structure and information needs3.1.1Functional departmentation☞Information characteristics and needs: information flows vertically; functions tend to be isolated☞Implications for performance management⏹Structure is based on work specialism⏹Economies of scale⏹Does not reflect the actual business processes by which values is created⏹Hard to identify where profits and losses are made on individual products or inindividual markets⏹People do not have an understanding of how the whole business works⏹Problems of co-ordinating the work of different specialisms.3.1.2The divisional form☞Information characteristics and needs⏹Divisionalisation is the division of a business into autonomous regions⏹Communication between divisions and head office is restricted, formal and related toperformance standards⏹Headquarters management influence prices and therefore profitability when it setstransfer prices between divisions.⏹Divisionalisation is a function of organisation size, in numbers and in product-marketactivities.☞Implications for performance management⏹Divisional management should be free to use their authority to do what they think isright, but must be held accountable to head office⏹ A division must be large enough to support the quantity and quality of managementit needs⏹Each division must have a potential for growth in its own area of operations⏹There should be scope and challenge in the job for the management of the division☞Advantages:⏹Focuses the attention of subordinate(下级) management on business performanceand results⏹Management by objectives can be applied more easily⏹Gives more authority to junior managers, more senior positions⏹Tests junior managers in independent command early in their careers and at areasonably low level in the management hierarchy.⏹Provides an organisation structure which reduces the number of levels ofmanagement.☞Problems:⏹Partly insulated from shareholders and capital markets⏹The economic advantages it offers over independent organisations ‘reflectfundamental inefficiencies in capital markets’⏹The divisions are more bureaucratic than they would be as independent corporation⏹Headquarters management usurp divisional profits by management charges,cross-subsidies, unfair transfer pricing systems.⏹Sometime, it is impossible to identify completely independent products or markets⏹Divisionalisation is only possible at a fairly senior management level⏹Halfway house(中途地点)⏹Divisional performance is not directly assessed by the market⏹Conglomerate diversification3.1.3Network organisations☞Information characteristics and needs: achieve innovative response in a changingcircumstances; communication tends to be lateral(侧面的), information and advice are given rather than instructions(指令) and decisions.☞Virtual teams: share information and tasks; make joint decision; fulfil the collaborative function of a team)☞Implications for performance management⏹Staffing: shamrock organisation⏹Leasing of facilities such as IT, machinery and accommodation(住房)⏹Production itself might be outsourced⏹Interdependence of organisations☞Benefits: cost reduction; increased market penetration; experience curve effects.3.2Business process re-engineering3.2.1Business processes and the technological interdependence betweendepartments☞Pooled interdependence(联营式相互依赖): each department works independently to the others, subjects to achieve the overall goals☞Sequential interdependence(序列式相互依存): a sequence with a start and end point.Management effort is required to ensure than the transfer of resources between departments is smooth.☞Reciprocal interdependence(互惠式相互依存): a number of departments acquire inputs from and offer outputs to each other.3.2.2Key characteristics of organisations which have adopted BPR☞Work units change from functional departments to process teams, which replace the old functional structure☞Jobs change. Job enlargement and job enrichment☞People’s roles change. Make decisions relevant to the process☞Performance measures concentrate on results rather than activities.☞Organisation structures change from hierarchical to flat3.3Business integration3.3.1Mckinsey 7S model☞Hard elements of business behaviour⏹Structure: formal division of tasks; hierarchy of authority⏹Strategy: plans to outperform胜过its competitors.⏹Systems: technical systems of accounting, personnel, management information☞‘soft’ elements⏹Style: shared assumptions, ways of working, attitudes and beliefs⏹Shared values: guiding beliefs of people in the organisation as to why it exists⏹Staff: people⏹Skills: those things the organisation does well3.3.2Teamwork and empowerment☞Aspects of teams:⏹Work organisation: combine the skills of different individuals and avoid complexcommunication⏹Control: control the behaviour and performance of individuals, resolve conflict⏹Knowledge generation: generate ideas⏹Decision making: investigate new developments, evaluate new decisions☞Multi-disciplinary teams:⏹Increases workers‘ awareness of their overall objectives and targets⏹Aids co-ordination⏹Helps to generate solutions to problems, suggestions for improvements☞Changes to management accounting systems⏹Source of input information: sources of data, methods used to record data⏹Processing involved: cost/benefit calculation⏹Output required: level of detail and accuracy of output, timescales involved⏹Response required:⏹When the output is required:3.4Information needs of manufacturing and service businesses3.4.1Information needs of manufacturing businesses☞Cost behaviour:⏹Planning: standard costs, actual costs compared with⏹Decision making: estimates of future costs to assess the likely profitability of a product⏹Control: monitor total cost information☞Quality: the customer satisfaction is built into the manufacturing system and its outputs☞Time: production bottlenecks, delivery times, deadlines, machine speed☞Innovation: product development, speed to market, new process. Experience curve, economies of scale, technological improvements.☞Valuation:☞Strategic, tactical and operational information⏹Strategic: future demand estimates, new product development plans, competitoranalysis⏹Tactical: variance analysis, departmental accounts, inventory turnover⏹Operational: production reject rates, materials and labour used, inventory levels3.4.2Service businesses☞Characteristics distinguish from manufacturing:⏹Intangibility: no substance⏹Inseparability/simultaneity: created at the same time as they are consumed⏹Variability/heterogeneity异质性: problem of maintaining consistency in the standardof output⏹Perishability非持久性:⏹No transfer of ownership:☞Strategic, tactical and operational information⏹Strategic: forecast sales growth and market share, profitability, capital structure⏹Tactical: resource utilisation, customer satisfaction rating⏹Operational: staff timesheets, customer waiting time, individual customer feedback3.5Developing management accounting systems3.5.1Setting up a management accounting system☞The output required: identify the information needs of managers☞When the output is required:☞The sources of input information: the output required dictate the input made3.6Stakeholders’ goals and objectives3.6.1The stakeholder view☞Organisations are rarely controlled effectively by shareholders☞Large corporations can manipulate markets. Social responsibility☞Business receive a lot of government support☞Strategic decisions by businesses always have wider social consequences.3.6.2Stakeholder theory☞Strong stakeholder view: each stakeholder in the business has a legitimate claim on management attention. Management’s job is to balance stakeholder demands:⏹Managers who are accountable to everyone are accountable to none⏹Danger of the managers favour their own interests⏹Confuses a stakeholder’s interest in a firm with a person citizenship of a state⏹People have interest, but this does not give them rights.3.7Ethics and organisation3.7.1Short-term shareholder interest(laissez-faire自由主义stance)☞Accept a duty of obedience to the demands of the law, but would not undertake to comply with any less substantial rules of conduct.3.7.2Long-term shareholder interest (enlightened self-interest开明自利)☞The organisation’s corporate image may be enhanced by an assumption of wider responsibilities.☞The responsible exercise of corporate power may prevent a built-up of social and political pressure for legal regulation.3.7.3Multiple stakeholder obligations☞Accept the legitimacy of the expectations of stakeholders other than shareholders. It is important to take account of the views of stakeholders with interests relating to social and environmental matters.☞Shape of society: society is more important than financial and other stakeholder interests.3.7.4Ethical dilemmas☞Extortion: foreign officials have been known to threaten companies with the complete closure of their local operations unless suitable payments are made☞Bribery: payments for service to which a company is not legally entitled☞Grease money: cash payments to the right people to oil the machinery of bureaucracy.☞Gifts: are regard as an essential part of civilised negotiation.4Changing business environment and external factors4.1The changing business environment4.1.1The changing competitive environment☞Manufacturing organisations:⏹Before 1970s, domestic markets because of barriers of communication andgeographical distance, few efforts to maximise efficiency and improve management practices.⏹After 1970s, overseas competitors, global networks for acquiring raw materials anddistributing high-quality, low-priced goods.☞Service organisations:⏹Prior to the 1980s: service organisations were government-owned monopolies, wereprotected by a highly-regulated, non-competitive environment.⏹After 1980s: privatisation of government-owned monopolies and deregulation, intensecompetition, led to the requirement of cost management and management accounting information systems.☞Changing product life cycles: competitive environment, technological innovation, increasingly discriminating and sophisticated customer demands.☞Changing customer requirements: Cost efficiency, quality (TQM), time (speedier response to customer requests), innovation☞New management approaches: continuous improvement, employee empowerment; total value-chain analysis☞Advanced manufacturing technology(AMT): encompasses automatic production technology, computer-aided design and manufacturing, flexible manufacturing systems and a wide array of innovative computer equipment.4.1.2The limitation of traditional management accounting techniques in achanging environment☞Cost reporting: costs are generally on a functional basis, the things that businesses do are “process es’ that cut across functional boundaries☞Absorption costing(归纳成本计算法)☞Standard costing: ignores the impact of changing cost structures; doesn’t provide any incentive to try to reduce costs further, is inconsistent with the philosophy of continuous improvement.☞Short-term financial measures: narrowly focused☞Cost accounting methods: trace raw materials to various production stages via WIP. With JIT systems, near-zero inventories, very low batch sizes, cost accounting and recording systems are greatly simplified.☞Performance measures: product the wrong type of response☞Timing: cost of a product is substantially determined when it is being designed, however, management accountants continue to direct their efforts to the production stage.☞Controllability: only a small proportion of ‘direct costs’are genuinely controllable in the short term.☞Customers: many costs are driven by customers, but conventional cost accounting does not recognise this.☞The solution: changes are taking place in management accounting in order to meet the challenge of modern developments.4.2Risk and uncertainty4.2.1Types of risk and uncertainty☞Physical: earthquake, fire, blooding, and equipment breakdown. Climatic changes: global warming, drought;☞Economic: economic environment turn out to be wrong☞Business: lowering of entry barriers; changes in customer/supplier industries; new competitors and factors internal to the firm; management misunderstanding of core competences; volatile cash flows; uncertain returns☞Product life cycle:☞Political: nationalisation, sanctions, civil war, political instability☞Financial:4.2.2Accounting for risk☞Quantify the risk:⏹Rule of thumb methods: express a range of values from worst possible result to bestpossible result with a best estimate lying between these two extremes.⏹Basic probability theory: expresses the likelihood of a forecast result occurring⏹Dispersion or spread values with different possible outcomes: standard deviation.4.2.3Basic probability theory and expected valuesEV=ΣpxP=the probability of an outcome occurringX=the value(profit or loss) of that outcome4.2.4Risk preference☞Risk seeker: is a decision maker who is interested trying to secure the best outcomes no matter how small the chance they may occur☞Risk neutral: a decision maker is concerned with what will be the most likely outcome☞Risk averse: a decision maker acts on the assumption that the worst outcome might occur ☞Risk appetite is the amount of risk an organisation is willing to take on or is prepared to accept in pursuing its strategic objectives.4.2.5Decision rules☞Maximin decision rule: select the alternative that offers the least unattractive worst outcome. Maximise the minimum achievable profit.⏹Problems: risk-averse approach, lead to defensive and conservative, without takinginto account opportunities for maximising profits⏹Ignores the probability of each different outcome taking place☞Maximax: looking for the best outcome. Maximise the maximum achievable profit⏹It ignores probabilities;⏹It is over-optimistic☞Minimax regret rule: minimise the regret from making the wrong decision. Regret is the opportunity lost through making the wrong decision⏹Regret for any combination of action and circumstances=profit for best action in shoescircumstances – profit for the action actually chosen in those circumstances4.3Factors to consider when assessing performance4.3.1Political factors☞Government policy; government plans for divestment(剥夺)/rationalisation; quotas, tariffs, restricting investment or competition; regulate on new products.☞Government policy affecting competition: purchasing decisions; regulations and control;policies to prevent the concentration of too much market share in the hands of one or two producers4.3.2Economic environment☞Gross domestic product: grown or fallen? Affection on the demand of goods/services☞Local economic trends: businesses rationalising or expanding? Rents increasing/falling?The direction of house prices moving? Labour rates☞Inflation: too high to making a plan, uncertain of future financial returns; too low to depressing consumer demand; encouraging investment in domestic industries; high rate leading employees to demand higher money wages to compensate for a fall in the value of their wages☞Interest rates: affect consumer confidence and liquidity, demand; cost of borrowing increasing, reducing profitability;☞Exchange rates: impact on the cost of overseas imports; prices affect overseas customers ☞Government fiscal policy: increasing/decreasing demands; corporate tax policy affecting on the organisation; sales tax(VAT) affecting demand.☞Government spending:☞Business cycle: economic booming or in recession; counter-cyclical industry; the forecast state of the economic4.3.3Funding☞Reasons for being reluctant to obtain further debt finance:⏹Fear the company can’t service the debt, make the required capital and interestpayments on time⏹Can’t use the tax shield, to obtain any tax benefit from interest payments⏹Lacks the asset base to generate additional cash if needed or provide sufficientsecurity⏹Maintain access to the capital markets on good terms.4.3.4Socio-cultural factors☞Class: different social classes have different values。

RTMS治疗指南

GuidelinesEvidence-based guidelines on the therapeutic use of repetitive transcranial magnetic stimulation(rTMS)Jean-Pascal Lefaucheur a ,b ,⇑,Nathalie André-Obadia c ,d ,Andrea Antal e ,Samar S.Ayache a ,b ,Chris Baeken f ,g ,David H.Benninger h ,Roberto M.Cantello i ,Massimo Cincotta j ,Mamede de Carvalho k ,Dirk De Ridder l ,m ,HervéDevanne n ,o ,Vincenzo Di Lazzaro p ,Saša R.Filipovic´q ,Friedhelm C.Hummel r ,Satu K.Jääskeläinen s ,Vasilios K.Kimiskidis t ,Giacomo Koch u ,Berthold Langguth v ,Thomas Nyffeler w ,Antonio Oliviero x ,Frank Padberg y ,Emmanuel Poulet z ,aa ,Simone Rossi ab ,Paolo Maria Rossini ac ,ad ,John C.Rothwell ae ,Carlos Schönfeldt-Lecuona af ,Hartwig R.Siebner ag ,ah ,Christina W.Slotema ai ,Charlotte J.Stagg aj ,Josep Valls-Sole ak ,Ulf Ziemann al ,Walter Paulus e ,1,Luis Garcia-Larrea d ,am ,1aDepartment of Physiology,Henri Mondor Hospital,Assistance Publique –Hôpitaux de Paris,Créteil,FrancebEA 4391,Nerve Excitability and Therapeutic Team,Faculty of Medicine,Paris Est Créteil University,Créteil,France cNeurophysiology and Epilepsy Unit,Pierre Wertheimer Neurological Hospital,Hospices Civils de Lyon,Bron,France dInserm U 1028,NeuroPain Team,Neuroscience Research Center of Lyon (CRNL),Lyon-1University,Bron,France eDepartment of Clinical Neurophysiology,Georg-August University,Göttingen,Germany fDepartment of Psychiatry and Medical Psychology,Ghent Experimental Psychiatry (GHEP)Lab,Ghent University,Ghent,Belgium gDepartment of Psychiatry,University Hospital (UZBrussel),Brussels,Belgium hNeurology Service,Department of Clinical Neurosciences,Centre Hospitalier Universitaire Vaudois,Lausanne,Switzerland iDepartment of Translational Medicine,Section of Neurology,University of Piemonte Orientale ‘‘A.Avogadro’’,Novara,Italy jUnit of Neurology,Florence Health Authority,Firenze,Italy kInstitute of Physiology,Institute of Molecular Medicine,Faculty of Medicine,University of Lisbon,Portugal lBrai 2n,Tinnitus Research Initiative Clinic Antwerp,Belgium mDepartment of Neurosurgery,University Hospital Antwerp,Belgium nDepartment of Clinical Neurophysiology,Lille University Hospital,Lille,France oULCO,Lille-Nord de France University,Lille,France pDepartment of Neurosciences,Institute of Neurology,Campus Bio-Medico University,Rome,Italy qDepartment of Neurophysiology,Institute for Medical Research,University of Belgrade,Beograd,Serbia rBrain Imaging and Neurostimulation (BINS)Laboratory,Department of Neurology,University Medical Center Hamburg-Eppendorf,Hamburg,Germany sDepartment of Clinical Neurophysiology,Turku University Hospital,University of Turku,Turku,Finland tLaboratory of Clinical Neurophysiology,AHEPA Hospital,Aristotle University of Thessaloniki,Thessaloniki,Greece uNon-Invasive Brain Stimulation Unit,Neurologia Clinica e Comportamentale,Fondazione Santa Lucia IRCCS,Rome,Italy vDepartment of Psychiatry and Psychotherapy,University of Regensburg,Regensburg,Germany wPerception and Eye Movement Laboratory,Department of Neurology,University Hospital,Inselspital,University of Bern,Bern,Switzerland xFENNSI Group,Hospital Nacional de Parapléjicos,SESCAM,Toledo,Spain yDepartment of Psychiatry and Psychotherapy,Ludwig Maximilian University,Munich,Germany zDepartment of Emergency Psychiatry,CHU Lyon,Edouard Herriot Hospital,Hospices Civils de Lyon,Lyon,France/10.1016/j.clinph.2014.05.0211388-2457/Ó2014International Federation of Clinical Neurophysiology.Published by Elsevier Ireland Ltd.All rights reserved.Abbreviations:AHRS,auditory hallucination rating scale;ALS,amyotrophic lateral sclerosis;AMT,active motor threshold;ARAT,action research arm test;BDI,Beck depression inventory;BDNF,brain-derived neurotrophic factor;BOLD,blood-oxygen-level-dependent;BPRS,brief psychiatric rating scale;CANMAT,Canadian Network for Mood and Anxiety Treatments;CAPS,clinician-administered PTSD scale;Cc,circular coil;CGI,clinical global impression scale;CRPS,complex regional pain syndrome;cTBS,continuous theta burst stimulation;DBS,deep brain stimulation;DCc,double-cone coil;DLPFC,dorsolateral prefrontal cortex;DPD,depersonalization disorder;dPMC,dorsal premotor cortex;ECT,electroconvulsive therapy;EEG,electroencephalography;EMCS,Epidural motor cortex stimulation;FDA,Food and Drug Administration;F8c,ﬁgure-of-eight coil;FCD,focal cortical dysplasia;FDG,18F-ﬂuorodeoxyglucose;(f)MRI,(functional)magnetic resonance imaging;GABA,gamma-aminobutyric acid;H-coil,Hesed coil;HDRS,Hamilton depression rating scale;HF,high-frequency;IFG,inferior frontal gyrus;ISI,interstimuli interval;iTBS,intermittent theta burst stimulation;JTT,Jebsen–Taylor hand function test;LF,low-frequency;LTD,long-term depression;LTP,long-term potentiation;M1,primary motor cortex;MADRS,Montgomery–Asberg depression rating scale;MEP,motor evoked potential;MSO,maximum stimulator output;NICE,National Institute for Health and Clinical Excellence;9HPT,9-hole pegboard test;OCD,obsessive-compulsive disorder;PaD,panic disorder;PANSS,positive and negative symptoms scale;PAS,paired associative stimulation;PD,Parkinson’s disease;PET,positron emission tomography;PT,physical therapy;PTSD,posttraumatic stress disorder;QPS,quadripulse magnetic stimulation;rCBF,regional cerebral blood ﬂow;RMT,resting motor threshold;(r)TMS,(repetitive)transcranial magnetic stimulation;S1,primary somatosensory cortex;S2,secondary somatosensory cortex;SANS,scale for the assessment of negative symptoms;SAPS,scale for the assessment of positive symptoms;SMA,supplementary motor area;SPECT,single photon emission computed tomography;tDCS,transcranial direct current stimulation;TMS,transcranial magnetic stimulation;TPC,temporoparietal cortex;UPDRS,uniﬁed Parkinson’s disease rating scale;VS,vegetative state;Y–BOCS,Yale–Brown obsessive compulsive scale.⇑Corresponding author.Address:Service Physiologie,Explorations Fonctionnelles,Hôpital Henri Mondor,51avenue de Lattre de Tassigny,94010Créteil cedex,France.Tel.:+33149812694;fax:+33149814660.E-mail address:jean-pascal.lefaucheur@hmn.aphp.fr (J.-P.Lefaucheur).1Equal contribution.aa EAM4615,Lyon-1University,Bron,Franceab Brain Investigation&Neuromodulation Lab,Unit of Neurology and Clinical Neurophysiology,Department of Neuroscience,University of Siena,Siena,Italyac Brain Connectivity Laboratory,IRCCS San Raffaele Pisana,Rome,Italyad Institute of Neurology,Catholic University,Rome,Italyae Sobell Department of Motor Neuroscience and Movement Disorders,Institute of Neurology,University College London,London,United Kingdomaf Department of Psychiatry and Psychotherapy III,University of Ulm,Ulm,Germanyag Department of Neurology,Copenhagen University Hospital Bispebjerg,Copenhagen,Denmarkah Danish Research Centre for Magnetic Resonance,Centre for Functional and Diagnostic Imaging and Research,Copenhagen University Hospital Hvidovre,Hvidovre,Denmark ai Parnassia Psychiatric Institute,The Hague,The Netherlandsaj Oxford Centre for Functional MRI of the Brain(FMRIB),Department of Clinical Neurosciences,University of Oxford,United Kingdomak EMG Unit,Neurology Service,Hospital Clinic,Department of Medicine,University of Barcelona,August Pi i Sunyer Biomedical Research Institute(IDIBAPS),Barcelona,Spain al Department of Neurology&Stroke,and Hertie Institute for Clinical Brain Research,Eberhard Karls University,Tübingen,Germanyam Pain Unit,Pierre Wertheimer Neurological Hospital,Hospices Civils de Lyon,Bron,Francea r t i c l e i n f oArticle history:Accepted13May2014 Available online5June2014Keywords:CortexIndicationNeurological disease Neuromodulation Noninvasive brain stimulation Psychiatric diseaseTMSTreatment h i g h l i g h t sNumerous studies have shown that repetitive transcranial magnetic stimulation(rTMS)produced sig-niﬁcant clinical effects in patients with various neurological and psychiatric disorders.This review presents guidelines on the therapeutic use of rTMS issued by a group of European experts. Level A or B evidence supports an efﬁcacy of rTMS protocols in depression,pain,motor stroke and schizophrenia.a b s t r a c tA group of European experts was commissioned to establish guidelines on the therapeutic use of repet-itive transcranial magnetic stimulation(rTMS)from evidence published up until March2014,regarding pain,movement disorders,stroke,amyotrophic lateral sclerosis,multiple sclerosis,epilepsy,conscious-ness disorders,tinnitus,depression,anxiety disorders,obsessive-compulsive disorder,schizophrenia, craving/addiction,and conversion.Despite unavoidable inhomogeneities,there is a sufﬁcient body of evidence to accept with level A(deﬁnite efﬁcacy)the analgesic effect of high-frequency(HF)rTMS of the primary motor cortex(M1)contralateral to the pain and the antidepressant effect of HF-rTMS of the left dorsolateral prefrontal cortex(DLPFC).A LevelB recommendation(probable efﬁcacy)is pro-posed for the antidepressant effect of low-frequency(LF)rTMS of the right DLPFC,HF-rTMS of the left DLPFC for the negative symptoms of schizophrenia,and LF-rTMS of contralesional M1in chronic motor stroke.The effects of rTMS in a number of indications reach level C(possible efﬁcacy),including LF-rTMS of the left temporoparietal cortex in tinnitus and auditory hallucinations.It remains to determine how to optimize rTMS protocols and techniques to give them relevance in routine clinical practice.In addition,professionals carrying out rTMS protocols should undergo rigorous training to ensure the quality of the technical realization,guarantee the proper care of patients,and maximize the chances of success.Under these conditions,the therapeutic use of rTMS should be able to develop in the coming years.Ó2014International Federation of Clinical Neurophysiology.Published by Elsevier Ireland Ltd.All rightsreserved.Contents1.Principles and mechanisms of action of transcranial magnetic stimulation (2152)1.1.Principles (2152)1.2.A summary of possible mechanisms of action (2153)1.3.Distant actions (2154)1.4.Placebo rTMS:methodological criteria and neurobiological effects (2155)2.Clinical applications of rTMS:methodology followed to derive the present guidelines (2156)3.Pain (2156)3.1.Motor cortex target in neuropathic pain (2156)3.2.Non-motor cortical targets in neuropathic pain (2159)3.3.Non-neuropathic pain (2159)4.Movement disorders (2160)4.1.Stimulation of motor or premotor cortex in Parkinson’s disease (2160)4.2.Effects on levodopa-induced dyskinesias in Parkinson’s disease (2163)4.3.HF stimulation of the prefrontal cortex in PD-related depression (2163)4.4.LF stimulation of motor or premotor cortex in dystonia (2164)4.5.Cerebellar stimulation in essential tremor (2165)4.6.Stimulation of the supplementary motor area in Tourette’s syndrome (2165)J.-P.Lefaucheur et al./Clinical Neurophysiology125(2014)2150–220621515.Stroke (2165)5.1.Motor stroke (2166)5.2.Aphasia (2168)5.3.Hemispatial neglect (2169)5.4.Summary (2170)6.Amyotrophic lateral sclerosis (2171)7.Multiple sclerosis (2171)8.Epilepsy (2171)8.1.Influencing factors:anatomical and etiological classification of epilepsies (2172)8.2.Influence of stimulation parameters (2173)8.3.Safety (2173)8.4.Perspectives (2173)9.Disorders of consciousness (2174)10.Alzheimer’s disease (2174)11.Tinnitus (2174)11.1.Target and stimulation frequency (2176)11.2.Methodological considerations (2176)11.3.Conclusions (2177)12.rTMS and psychiatry:general considerations (2177)13.Depression (2177)13.1.General results and influence of the side of stimulation (2178)13.2.Influence of the number of pulses and sessions (2182)13.3.Influence of the frequency of stimulation (2182)13.4.Influence of the targeting method (2183)13.5.Efficacy of rTMS in the treatment of unipolar or bipolar depression (2183)13.6.Efficacy of rTMS in the treatment of depression in special populations (2183)13.7.rTMS compared to antidepressants (2183)13.8.rTMS compared to electroconvulsive therapy (2184)13.9.Conclusions (2184)14.Anxiety disorders (2185)14.1.Post-traumatic stress disorder (2185)14.2.Panic and generalized anxiety disorders (2185)14.3.Conclusions (2185)15.Obsessive compulsive disorder (2185)16.Schizophrenia (2186)16.1.Auditory hallucinations (2186)16.2.Negative symptoms (2188)17.Substance abuse,addiction and craving (2190)18.Conversion (2190)19.Summary of recommendations (2190)Acknowledgments (2192)References (2192)1.Principles and mechanisms of action of transcranial magnetic stimulation1.1.PrinciplesIn1831,Michael Faraday stated his law establishing that a time-varying current creates a magneticﬁeld which,in turn,can induce an electricﬁeld and hence a secondary current within a nearby conducting medium.One hundred andﬁfty years later, Barker et al.(1985)proposed theﬁrst magnetic stimulator designed to stimulate the human brain transcranially,providing the prerequisite for subsequent clinical use of transcranial mag-netic stimulation(TMS)(Barker,1999).A number of TMS tech-niques are nowadays used for routine diagnostic application (Chen et al.,2008).The interested reader is referred to the guide-lines of the International Federation of Clinical Neurophysiology (Rossini et al.,1994).The equipment consists of a high current pulse generator able to produce a discharge current of several thousand amperes that ﬂows through a stimulating coil,generating a brief magnetic pulse withﬁeld strengths up to several Teslas.If the coil is placed on the head of a subject,the magneticﬁeld thus created undergoes little attenuation by extracerebral tissues(scalp,cranial bone,meninges,and cerebrospinalﬂuid layer)and is able to induce an electricalﬁeld sufﬁcient to depolarize superﬁcial axons and to activate neural networks in the cortex.The extent of action of the current density generated into the brain depends on many physical and biological parameters,such as the type and orientation of coil,the distance between the coil and the brain, the magnetic pulse waveform,the intensity,frequency and pat-tern of stimulation,and the respective orientation into the brain of the current lines and the excitable neural rge‘‘cir-cular’’coils(Cc)have a wide action radius(for instance,when placed over the vertex they induce bilateral effects),which limits their use if focal stimulation is sought.Focusing is better with a ‘‘ﬁgure-of-eight’’coil(F8c),reducing the stimulation zone to a few square centimeters(Thielscher and Kammer,2004)and mak-ing it sensitive to coil handle orientation.The‘‘double cone’’angulated coil(DCc)consists of2large circular coils forming an obtuse angle.At the expense of stronger focus,this type of coil is useful for reaching deep targets such as the representation of the lower limbs in the primary motor cortex(M1)located within the inter-hemisphericﬁssure.A better compromise between depth and focus may be obtained with new types of coils that allow a lesser rate of decrease ofﬁeld magnitude as a function of distance(such as the‘‘Hesed-coil’’(H-coil),‘‘C-core coil’’,or2152J.-P.Lefaucheur et al./Clinical Neurophysiology125(2014)2150–2206‘‘circular crown-coil’’,among others)(Roth et al.,2007;Deng et al.,2008;Salvador et al.,2009).Monophasic magnetic pulses are commonly used for single-pulse experiments.Conversely,for reasons of lower energy requirements,repetitive transcranial magnetic stimulation(rTMS), which will be dealt with in this paper,usually requires a biphasic stimulus waveform(Sommer et al.,2006).However,rTMS using monophasic pulses activates a relatively uniform population of neurons and could therefore be more effective in producing sus-tained after-effects than biphasic pulses which generate a more complex pattern of neural activation(Sommer et al.,2002b;Arai et al.,2005).For example,MEP size reduction following1Hz-rTMS delivered over M1(Taylor and Loo,2007)and MEP enhancement following10Hz-rTMS(Arai et al.,2007)are more marked and pro-longed when monophasic pulses are used.In addition,the effects of monophasic and biphasic magnetic pulses can only be compared if the second and decisive phase of the biphasic pulse is taken as the equivalent of the initial monophasic pulse(Di Lazzaro et al., 2001;Sommer et al.,2013).Studies may be confusing when the initial phase of the biphasic pulse is retained for comparison,also given that the direction of the current can be reversed depending on the manufacturer(Kammer et al.,2001).Most of current data on TMS effects have been derived from stimulation of M1in healthy subjects due to the ease of obtaining motor evoked potentials(MEPs).Indeed,a suprathreshold TMS pulse delivered over the precentral region easily evokes a muscle response in normal subjects,the size of this MEP reﬂecting the excitability of motor corticospinal output.When the handle of an F8c is oriented parallel to the interhemispheric midline(postero-anterior direction),motor cortex TMS activates the pyramidal tract only indirectly,through the recruitment of cortical interneurons (Sakai et al.,1997).At spinal level,this is demonstrated by the recording of a succession of descending volleys(‘‘indirect waves’’, I-waves),showing the activation of various interneuronal circuits (Di Lazzaro et al.,1998,2004a).When the handle of an F8c is oriented perpendicular to the interhemispheric midline(latero-medial direction),TMS to the M1area can also directly activate the pyramidal tract,evoking direct waves(D-waves)at spinal level (Di Lazzaro et al.,2003).Thus,when using an F8c,the net effect of TMS will depend on the position and orientation of the coil over a gyrus or a sulcus and the direction of the current induced in the brain.An important principle is that axons rather than cell bodies are preferentially activated by pulsed neurostimulation,with respect to their spatial orientation and diameter(reviewed in Lefaucheur,2008).Therefore,TMS generates local activation but the stimulation is at the origin of biological effects that are not only local but also occur at a distance from the stimulation site via the activated networks.In practice,when using an F8c to stimulate M1,the lowest intensity threshold to elicit MEPs is achieved when the stimulus creates a postero-anterior current that is orthogonal to the central sulcus(Di Lazzaro et al.,2008b),i.e.,with the handle of the F8c ori-ented45°posteriorly and ing the reverse orientation (antero-posterior)makes the latency time increase by several milliseconds and generates late indirect waves(I3-waves).The simplest explanation why the optimal postero-anterior activation of M1elicits MEPs would be that the Brodman area4p in the ante-rior wall of the central sulcus is activated preferentially to area4a at the crown of the precentral gyrus(Geyer et al.,1996;Fox et al., 2004).However,at least for selected parameters of stimulation, there is a preferential activation of pyramidalﬁbers in the most superﬁcial cortical layers(Esser et al.,2005),as also shown by modeling studies(Miranda et al.,2003;Wagner et al.,2004). Therefore,the postero-anterior stimulation of the top of the ante-rior bank of the central sulcus seems to be a good site to activate the motor cortex by TMS,justifying image-guided navigation to improve accuracy and repeatability of M1stimulation(Ahdab et al.,2010;Mylius et al.,2013).Nevertheless,the multiplicity of geometrical conﬁgurations of induced currents and cortical fold-ings seemingly complicates the modeling of axonal activation schemas by TMS/rTMS(Ahdab et al.,2014).Conversely,there is evidence that an opposite currentﬂow(antero-posterior)is better suited for inducing motor cortex plasticity(Sommer et al.,2013).1.2.A summary of possible mechanisms of actionAs mentioned above,the physiological effects of rTMS have been assessed mainly on MEP size changes in response to M1stim-ulation performed in healthy and relatively young subjects.Extrap-olation to non-motor cortical regions,especially under pathological conditions,should therefore be extremely cautious. Pascual-Leone et al.(1992)were among theﬁrst to study the effects of rTMS on motor cortex excitability,by showing that a ser-ies of20consecutive TMS pulses delivered at a frequency greater than2Hz gave rise to signiﬁcant MEP amplitude enhancement. From the results obtained in different studies based on MEP mea-surement in healthy subjects,some form of consensus appeared to consider low-frequency(LF)stimulation(61Hz)as‘‘inhibitory’’and high-frequency(HF)stimulation(P5Hz)as‘‘excitatory’’,with some nuances as a function of the intensity of stimulation and the number of delivered shocks(Siebner and Rothwell,2003).Follow-ing these‘‘classic’’protocols,various new TMS paradigms have been developed,aimed at modifying cortical excitability(reviewed in Lefaucheur(2009a)).One of the most popular is the‘‘theta burst stimulation’’delivered as a continuous(cTBS)or intermittent (iTBS)train,the former protocol being‘‘inhibitory’’and the latter being‘‘excitatory’’,according to the changes produced in MEP size when cTBS/iTBS is applied to the M1of healthy subjects(Huang et al.,2005).Such a dichotomy(‘‘inhibitory’’LF rTMS/cTBS vs.‘‘excitatory’’HF rTMS/iTBS)is appealing,as it is closely reminiscent of the effects of long-term potentiation(LTP)and long-term depression(LTD)of synaptic transmission obtained in the hippo-campus or cerebellum of animal models(Bliss and Lomo,1973; Malenka,1991).However,this dichotomy is not entirely satisfying, and it has been shown that both HF and LF rTMS may have mixed excitatory and inhibitory effects(Houdayer et al.,2008).Even when the effect on the motor cortex appears speciﬁc,doubling the duration of stimulation,for example,can reverse the outcome from inhibition to excitation and vice versa(Gamboa et al.,2010). The underlying mechanisms of‘‘excitatory’’versus‘‘inhibitory’’aspects of rTMS paradigms should also be taken as relative, because MEP increase after‘‘excitatory’’HF rTMS might be in fact the result of a decrease of gamma-amminobutyric acid(GABA)-mediated intracortical inhibition(hence inhibition of inhibition), rather than a direct enhancement of motor cortex excitability (Wu et al.,2000;Di Lazzaro et al.,2001;Ziemann,2004). Conversely,LF rTMS can enhance the net inhibitory corticospinal control,probably via GABA-B transmission,since this protocol lengthens corticospinal silent period duration,as observed in healthy subjects(Cincotta et al.,2003;Daskalakis et al.,2006; Eichhammer et al.,2007)and in patients with movement disorders (Murase et al.,2005;Borich et al.,2009;Filipovic´et al.,2010a).In fact,it should be considered that the effects of the various TMS protocols suppressing or enhancing cortical excitability are not homogeneous and may result from targeting and modulating var-ious cortical circuits(Di Lazzaro et al.,2010,2011).For example,LF rTMS can selectively suppress the excitability of circuits producing late I-waves(Di Lazzaro et al.,2008a),while cTBS reduces the excitability of circuits generating instead the early I-wave(I1) component(Di Lazzaro et al.,2005).On the other hand,it has been recently demonstrated(Hamada et al.,2013)that the concept of ‘‘excitatory’’effect of iTBS vs.‘‘inhibitory’’effect of cTBS on MEPJ.-P.Lefaucheur et al./Clinical Neurophysiology125(2014)2150–22062153size was highly variable between individuals,depending on differ-ences in the interneuronal cortical networks that are preferentially recruited by the TMS pulse.This study also showed that,at a given site of stimulation,different populations of cortical interneurons are more easily activated at different times in the TMS train.This may explain why an rTMS train delivered at5Hz over M1can either increase or decrease cortical excitability according to a con-tinuous or intermittent pattern(Rothkegel et al.,2010).Thus,a comparison between studies using different protocols,even those considered equally‘‘excitatory’’or‘‘inhibitory’’,should be made with caution,in particular regarding TBS.A more recent protocol, called quadripulse magnetic stimulation(QPS)and consisting of repeated trains of4monophasic TMS pulses,is supposed to pro-duce less variable effects on cortical excitability in normal subjects. When delivered over M1,QPS facilitates MEP for interstimuli inter-vals(ISIs)of1.5–10ms and suppresses MEP for ISIs of30–100ms (Hamada et al.,2008a).In fact,QPS modulates intracortical excit-atory circuits of M1in a manner consistent with metaplasticity (see next paragraph),whether QPS priming was delivered over M1or the supplementary motor area(SMA)(Hamada et al., 2008a,2009a).QPS priming over M1or the dorsal premotor cortex (dPMC)can also modulate excitability of the primary somatosen-sory cortex(S1)(Nakatani-Enomoto et al.,2012).Therefore,QPS can be an effective approach to produce sustained clinical effects, but this protocol pattern has not yet been used for therapeutic pur-pose to date.The level of cortical excitability in each subject at baseline, before the stimulation,is an important source of inter-and intra-individual variability of rTMS effects(Siebner and Rothwell, 2003).This could explain why rTMS effects on intracortical inhibi-tion depend more on baseline individual values than on stimula-tion frequency(Daskalakis et al.,2006).For example,when cortical excitability is lowered by a previous session of transcranial direct current stimulation(tDCS),the‘‘classically inhibitory’’LF rTMS may have surprising facilitatory actions(Siebner et al., 2004),while the mirror effect(i.e.,reversal of the facilitatory effect of HF rTMS)can be obtained if cortical excitability is previously tuned to a high pre-stimulus level(Lang et al.,2004).For instance,‘‘facilitatory’’HF rTMS of M1increased intracortical inhibition in patients with chronic pain who showed defective intracortical inhibition at baseline(Lefaucheur et al.,2006a).Generally speaking,previous neuronal activity modulates the capacity for subsequent plastic changes and this major inﬂuence refers to pro-cesses of homeostatic plasticity and metaplasticity(Bienenstock et al.,1982;Abraham and Tate,1997;Turrigiano and Nelson, 2004).Therefore,the impact of disease-related plasticity and ongo-ing pharmacological treatments should also be taken into account when viewing the large variability of biological or clinical effects produced by apparently identical rTMS protocols.Moreover,age, gender and genetic aspects can modify the biological and clinical effect of rTMS.In particular,still rather poorly understood genetic differences contribute to individual liability to‘‘LTP-and LTD-like’’synaptic events produced by rTMS and form a further potential source of variation in therapeutic responses(Hoogendam et al., 2010).Thus,it can be difﬁcult to know whether the failure of a protocol of rTMS to produce a clinical effect in a given study is related to an intrinsic therapeutic inefﬁcacy of the protocol or to the inclusion of non-responders to this protocol arising from the usually large variability of rTMS effects.From therapeutic and rehabilitative perspectives,the main interest of rTMS resides in the persistence of clinical changes well beyond the time of stimulation.The duration of such after-effects increases with the number of stimuli delivered,and may persist minutes to hours or even days after the end of an rTMS session (Chen et al.,1997;Maeda et al.,2000;Touge et al.,2001; Gangitano et al.,2002).Again,such after-effects are reminiscent of the data obtained from animal models,in which long-lasting enhancement of synaptic efﬁcacy(LTP)is reported following repetitive trains of HF electrical stimulation(Bliss and Lomo, 1973).Notwithstanding these striking similarities between rTMS effects and experimental data on long-term synaptic plasticity, Ziemann and other authors(Ziemann,2004;Cooke and Bliss, 2006;Ziemann et al.,2008)have underscored that the plausibility of such a hypothesis was only based on indirect arguments and common output effects.One must be also aware of possible placebo effects in the case of prolonged therapeutic response,with clinical remission persisting up to several months beyond the time of stimulation in patients with chronic disorders.Overall,possible long-lasting after-effects should be considered in rTMS studies with a crossover design,as these usually have a short wash-out period(1week to1month),resulting in a high probability of carry-over effects.Finally,rTMS can interact with spontaneous oscillatory rhythms existing in the cortical circuits activated by the stimulation(Houzéet al.,2013).This may induce an activity-dependent modulation according to phase-locking synchrony between cortical oscillations and the pattern of the stimulation(Bear and Kirkwood,1993; Morris et al.,2003).It is known that the pathophysiology of various brain disorders,such as Parkinson’s disease(PD)(Brown,2006), relies on the existence of pathological rhythms in neural networks between cortical and deep brain structures.Modulating these rhythms may be a valuable therapeutic approach,optimally designed in closed-loop stimulation techniques(Beuter et al., 2014).It is tempting to consider that the frequency-and pattern-dependent therapeutic effects of rTMS could come,at least in part, from an interaction with some altered oscillations involving corti-cal networks(Fuggetta and Noh,2013).All these aspects may contribute to the fact that an rTMS proto-col is effective or not,depending on subtle differences in the parameters of stimulation.For example,in2007,one large,multi-center,randomized,placebo-controlled trial of rTMS in depression, performed in the USA and Australia,showed positive results in favor of the antidepressant efﬁcacy of rTMS and led to Food and Drug Administration(FDA)approval of rTMS for this disease in the USA(O’Reardon et al.,2007b).At the same time,a German and Austrian multicenter trial,also based on10Hz rTMS applied to the left dorsolateral prefrontal cortex(DLPFC),reported a lack of efﬁcacy compared to placebo(Herwig et al.,2007).In fact, several methodological differences might have contributed to this discrepancy,including the intensity of stimulation(120%vs.110% of RMT),the position of the coil(5cm anterior to M1vs.F3),the duration of stimulus train(4s vs.2s)and intertrain interval (26s vs.8s),the number of stimuli per session(3000vs.2000), the total duration of the daily sessions(37.5min vs.16.6min) and protocol(4–6vs.3weeks of stimulation),and most important, the pharmacological treatment(drug-free vs.add-on antidepres-sant medication).Thus,one must be very careful when considering the positive or negative outcome of rTMS studies and should go into the details of the methods for any comparative analysis.This also means that the technique must be rigorous and justiﬁes a very speciﬁc training for rTMS operators.1.3.Distant actionsDepending on the intrinsic properties and geometrical orienta-tion ofﬁbers within the cortical region stimulated,the magnetic stimulus not only activates local interneuronal circuits,but also thoseﬁbers projecting ortho-or antidromically to distant struc-tures(Fox et al.,1997;Siebner et al.,2008;Di Lazzaro et al., 2011;Lefaucheur,2012).One example of these distant effects is inter-hemispheric interaction between homologous networks in both M1cortices,whereby a stimulus delivered over one motor2154J.-P.Lefaucheur et al./Clinical Neurophysiology125(2014)2150–2206。

2023年教师招聘之中学教师招聘综合检测试卷B卷含答案

2023年教师招聘之中学教师招聘综合检测试卷B卷含答案单选题（共45题）1、《史记》记载：“楚越之地，地广人稀……无积聚而多贫。

”《宋书》曾经记载：“江南……地广野丰……一岁或稔，则数郡忘饥。

”江南地区产生这种变化的原因不包括()。

A.中原人南迁。

带来先进的生产技术B.南方战乱较少，社会相对稳定C.南方的自然条件比较优越D.南方文化比北方文化先进【答案】D2、In any country,the"standard ofliving"means the averageperson′s share of the goods and services whichthe country produces. Therefore,a country′s standard of living depends firstand foremost on its capacity to produce wealth."Wealth"in thissense is not money, but"goods"such as food and clothing,and"services"such astransport and entertainment.A.has traded her manufactureB.has established her wealthC.has been an industrialized oneD.has produced surplus manufactured goods【答案】D3、十年前，科学家只把几十种基因突变与疾病挂上钩，现在已经把三千种左右的基因突变与疾病对上号，但要搞清所有基因突变与疾病的关系尚需时日。

这是因为（）。

A.①④C.②④D.①③【答案】D4、根据概念的获得方式，概念可以分为（）。

A.合言概念、选言概念和关系概念B.具体概念和定义概念C.初级概念和二级概念D.科学概念和日常概念【答案】B5、中国共产党十八届三中全会明确提出要使市场在资源配置中起（）作用。

如何加快研制速度英语作文

如何加快研制速度英语作文To expedite the research and development process, several strategies can be implemented:1. Streamline Communication Channels: Effective communication is crucial for swift decision-making and problem-solving. Establishing clear channels of communication between team members, departments, and stakeholders ensures that information flows smoothly and decisions are made promptly.2. Utilize Agile Methodologies: Adopting agile methodologies such as Scrum or Kanban can significantly accelerate the development process. These methodologies promote iterative development, frequent feedback loops, and adaptive planning, allowing teams to respond quickly to changes and deliver value incrementally.3. Empower Cross-Functional Teams: Cross-functional teams bring together individuals with diverse skills andexpertise to tackle complex problems collaboratively. By empowering these teams with autonomy and decision-making authority, organizations can accelerate innovation and problem-solving.4. Implement Rapid Prototyping: Rapid prototyping enables teams to quickly create and test prototypes of new products or features. By gathering feedback early in the development process, teams can identify potential issues and iterate rapidly to improve the final product.5. Embrace Technology: Leveraging advanced technologies such as artificial intelligence, machine learning, and automation can streamline various aspects of the research and development process. From data analysis to testing and validation, technology can automate repetitive tasks and enhance productivity.6. Foster a Culture of Innovation: Encouraging creativity, experimentation, and risk-taking within the organization fosters a culture of innovation. By providing resources, support, and recognition for innovative ideas,organizations can inspire employees to push boundaries and drive progress.7. Collaborate with External Partners: Collaboration with external partners such as research institutions, universities, or industry experts can bring fresh perspectives and additional resources to the table. By leveraging external expertise and resources, organizations can accelerate the pace of innovation and overcome technical challenges more effectively.8. Prioritize and Focus: Prioritizing tasks and focusing on high-impact initiatives is essential for maximizing productivity and efficiency. By identifying critical milestones and allocating resources accordingly, teams can ensure that efforts are directed towards achieving key objectives.9. Continuous Improvement: Embracing a mindset of continuous improvement ensures that processes are constantly refined and optimized. By regularly reviewing performance metrics, soliciting feedback, and implementinglessons learned, teams can identify areas for improvement and enhance their effectiveness over time.10. Manage Risks Proactively: Identifying andmitigating risks early in the development process iscrucial for avoiding delays and setbacks. By conducting thorough risk assessments and developing contingency plans, teams can minimize the impact of unforeseen challenges and keep the project on track.In conclusion, by implementing these strategies, organizations can accelerate the research and development process, bringing innovative solutions to market more quickly and effectively.。

A new approach to improving the grooming performance with dynamic traffic

A new approach to improving the grooming performancewith dynamic traﬃc in SONET ringsKun-hong Liu,Yong Xu*School of Physics and Optoelectronics Technology,Fujian Normal University,Fuzhou,Fujian350007,PR China Received13October2003;received in revised form3March2004;accepted16March2004Available online12May2004Responsible Editor:G.RouskasAbstractTraﬃc grooming is widely employed to minimize the number of ADM’s in today’s WDM rings to reduce the total cost of the network.Since traﬃc often changes over time,the problem of grooming dynamic traﬃc becomes more and more important.In this paper,we use the technique of splitting traﬃc to the grooming of arbitrary dynamically changed traﬃc in a strictly non-blocking way in SONET/WDM rings.Two splitting methods:traﬃc-cutting and traﬃc-dividing are introduced,and the third method,dividing a traﬃcﬁrst and then cutting it,is also proposed.The grooming performance for static and dynamic traﬃc with these three methods is analyzed in detail.A genetic algorithm(GA) based on these methods is puter simulation results under diﬀerent conditions show that our algorithm is eﬃcient in reducing both the numbers of ADM’s and wavelengths required.Ó2004Elsevier B.V.All rights reserved.Keywords:Traﬃc grooming;Evolutionary computation;Splitting;SONET/WDM ring network1.IntroductionMost of today’s optical networks are built on synchronous optical network(SONET)over wavelength-division multiplexing(WDM)rings.In such network architecture,traﬃc grooming is one of the most important ways to reduce the overall network cost and has drawn much attention in the literature in recent years[1–4].But most of previ-ous work in traﬃc grooming mainly focused on reducing the number of ADM’s under static traﬃc pattern.To obtain an optimal solution,a widely adopted way is to divide the grooming problem into two sub-problems.Theﬁrst is to split all the traﬃcs into basic elements and then using them to construct as few circles as possible to minimize the number of wavelengths.The second is to groom the circles onto wavelengths to minimize the number of ADM’s[2].Simulations showed that this is an eﬃcient way of grooming and can bring about good results.With this method it is impor-tant to design appropriate heuristics in these two steps to obtain optimal results.Therefore,in*Corresponding author.Present address:School of Com-puter Science,The University of Birmingham,Edgbaston, Birmingham,West Midlands,B152TT,UK.Tel.:+44-121-414-5142;fax:+44-121-414-2779.E-mail addresses:lkhqz@(K.-h.Liu),y.xu@cs.(Y.Xu).1389-1286/$-see front matterÓ2004Elsevier B.V.All rights reserved.doi:10.1016/net.2004.03.031Computer Networks46(2004)181–195/locate/comnetaddition to the heuristic presented in Ref.[2],a GA-based approach[5]and a simulated annealing approach[3]were proposed to combine the circles onto wavelengths to get better grooming results.In the meantime,a comprehensive approach based on genetic algorithm was also proposed to tackle the problem[6],which did not divide the problem into two phases but manipulated the traﬃc requests on the ring as a whole.All the approaches mentioned above are ap-plied only to static traﬃc patterns.Since static traﬃc is just a special case of the dynamic traﬃc patterns,the grooming of dynamic traﬃc is much more important and general.In the grooming of dynamic traﬃc,there are three grooming classes [9]:strictly non-blocking grooming,wide-sense non-blocking grooming and rearrangeably non-blocking grooming.For a set of traﬃc patterns,if each traﬃc request in the set can be assigned to the existing wavelengths without rearranging the calls among the wavelengths,it is referred to as strictly non-blocking grooming.This is realized by assign-ing the same traﬃc requests in diﬀerent traﬃc patterns to the same wavelengths.In this way,all calls in a new traﬃc pattern can be established without being interrupted when traﬃc changes.As the control and interruption overhead of this grooming type is the lowest,we only discuss this kind of grooming in this paper.The grooming of dynamic traﬃc is much more diﬃcult than the grooming of static traﬃc.Hence, it has not been extensively discussed[7–9]by now. Ref.[7]discussed only the grooming of t-allowable traﬃc requests,in which the traﬃc requests were assumed to be symmetric and each node was al-lowed to source and terminate at most t basic traﬃc elements.The authors used a bipartite graph to match two independently groomed virtual topologies to get the result,which is not so easy to be extended to multiple traﬃc patterns.Further-more,theﬁnal result would depend on the grooming results of the two single virtual topolo-gies.In Ref.[8],the authors proposed a genetic algorithm to solve the dynamic grooming prob-lems based on the ideas of Refs.[2]and[7].They ﬁrst took the traﬃc pattern at each moment as a static one and followed the circle construction approach by employing a genetic algorithm to combine all the circles to obtain a static grooming result.Then they utilized another genetic algo-rithm,by following the ways described in Ref.[7], to match the m virtual topologies to obtain a dy-namic grooming result.As was discussed in[9], grooming by matching virtual topologies always leads to some idle ADM’s for each traﬃc pattern, that is to say,for a certain traﬃc pattern,only a part of the ADM’s may be used,for another,an-other part of the ADM’s may be used,which is also a kind of waste in ADM resources.On the other hand,the two-step GA method would inevitably be very time-consuming.Therefore,we proposed another GA heuristics to deal with the dynamic grooming problems[9],which operated directly on the traﬃc matrices and solved this problem with only one step.Simulations showed that it was eﬃcient in saving ADM’s and wave-lengths.In this paper,we combine this genetic algorithm with traﬃc splitting technique to further improve the grooming performance.We mainly deal with the grooming of dynamic traﬃc in uni-directional rings,but the application of our algo-rithm to bidirectional rings is also discussed.The general unidirectional SONET/WDM rings considered in this paper consist of n nodes num-bered clockwise by0;1;...;nÀ1.The traﬃcﬂows in the same direction.Each node on the ring is equipped with a wavelength add/drop multiplexer (WADM),at which wavelengths are allowed to be selectively added/dropped,and a number of SO NET add/drop multiplexers(ADM’s),each of which can aggregate a number of low-rate traﬃc onto a high-rate circuit.The dynamic traﬃc re-quests are represented by a set of nÂn traﬃc matrix R¼f R m gðm¼0;1;...;MÀ1Þ,each of which represents the traﬃc requests at time t¼m. Each element r mijof the traﬃc pattern R m represents the traﬃc request originating from node i and terminating at node j at time t¼m.Only one traﬃc pattern in this set is activated each time and all the M traﬃc patterns will be constructed one by one as traﬃc changes.The wavelengths and ADM’s used on the ring must be able to allow each of these traﬃc patterns to be established each time after appropriate grooming.The objective of our grooming algorithm is to minimize the total number of ADM’s on the ring while as few182K.-h.Liu,Y.Xu/Computer Networks46(2004)181–195wavelengths as possible are used for changing traﬃc.The rest of this paper is organized as follows. We give the general idea of three splitting methods in Section2,and describe our new heuristics in Section3.Section4gives the computer simulation results along with corresponding discussions.In the last section,we conclude this paper.2.Grooming by splittingSplitting means to divide a traﬃc into smaller parts or shorter segments so as toﬁt into a wavelength.Generally,there are two kinds of splitting.One is to cut a traﬃc into shorter seg-ments so that the shorter segments are easier to be ﬁtted into the remained capacity of the wave-lengths,which we name as the traﬃc-cutting method.With this method,the original single-hopped traﬃc now becomes multi-hopped.The other is to divide a traﬃc into smaller parts oper-ating at lower rates so that the lower-rate parts can be assigned to the remained capacity of the wavelengths,which is referred to as the traﬃc-dividing method.For instance,if a traﬃc request operates at the rate of OC-24but the current wavelength only has a capacity of OC-6left,the part OC-6of the traﬃc will be assigned to it and the rest(OC-18)will be assigned to other wave-length(s).With this method,each traﬃc will stay in single-hopped.The splitting method used in Ref.[2]is based on this method but what diﬀerent from ours is that they divided every traﬃc into basic elements.Our algorithm will operate on the traﬃc matrix directly.Weﬁrst try to assign traﬃcs to the current wavelength as a whole then,if no more traﬃc can be assigned to it,we try the following splitting methods toﬁll the remained capacity of the wavelength.2.1.Traﬃc-cuttingThe basic idea behind the traﬃc-cutting method is that when assigning traﬃcs to wavelengths as a whole,it is often that some link loads of a wave-length are at their full capacity but others are far from that.In this case,cutting a traﬃc into short segments and handling each segment separately to ﬁt the‘‘gaps’’of each wavelength is an eﬃcient way to reduce the total number of ADM’s and wavelengths.This was also observed by Gerstel et al.[10]and Li et al.[11].It was showed that although cutting a traﬃc needs two additional ADM’s,i.e.,in addition to the original two ADM’s,another two are needed at the cut point,it could reduce the total number of ADM’s by sharing them with other existing lightpaths.The number of wavelengths can also be reduced at the same time by assigning more traﬃcs to each of them.Therefore cut-ﬁrst heuristics were used by both Refs.[10,11]to obtain a better solution.But traﬃc grooming was not considered in[10].In Ref.[11],splitting was only used to construct circles, which is diﬀerent from ours to be discussed below. Furthermore,they applied this method only to static traﬃc grooming problems.In our algorithm,a traﬃc is cut only when the following two conditions are satisﬁed:Condition1.One of the end nodes of the traﬃc isalready the dropping node of the cur-rent wavelength and the wavelengthhas another dropping node betweenthe two end nodes of the traﬃc. Condition2.One of the cut segments can be as-signed to that wavelength.Theﬁrst condition ensures that no additional ADM’s are needed to assign one of the cut seg-ments to the current wavelength and the second guarantees that there is enough capacity on the wavelength to accommodate the cut segment. Since the remained segments are shorter than the original traﬃc,it is easier to be assigned to other wavelength to share the same ADM’s with other traﬃcs on that wavelength.Here we notice that what makes ours diﬀerent from the method used in Ref.[11]is that we cut traﬃc only when it is nee-ded but theyﬁrst split all the traﬃcs into basic elements then cut some of the basic elements into segments when needed.This means that they would split each traﬃc into much smaller frag-ments and incline to assign each fragment to dif-ferent wavelength,which will inevitably make aK.-h.Liu,Y.Xu/Computer Networks46(2004)181–195183network more complex and increase the control overhead of the system.On the other hand,since cutting means a connection passing through two or more wavelengths,it will become multi-hopped and some intermediate nodes are needed to bridge the connection though the original connection is just single-hopped.Therefore,cut not only makes logic topology of a network more complex but the signal transmission will be delayed as well when traﬃcs transmit among diﬀerent wavelengths.The more segments a traﬃc is cut into,the more wavelengths the corresponding traﬃc request will pass through,and the longer the delay-time will be.Thus a traﬃc should not be cut into too many segments.In this paper,we only cut a traﬃc into at most two segments.The beneﬁt of the cutting method can be illus-trated by the following example.Table1gives two traﬃc matrices in a4-node ring with traﬃc gran-ularity g¼4.Theﬁrst represents the traﬃc request at one moment and the second at the other.The optimal grooming result with no splitting is given Table2,where‘‘Link load1’’represents the link load at the moment when theﬁrst traﬃc matrix is motivated;‘‘Link load2’’the link load when the second traﬃc matrix is motivated.Table3presents the grooming result by the traﬃc-cutting algo-rithm,where r klijdenotes the k!l segment of traﬃc i!j.In Table2,since the algorithm only assigns traﬃcs to wavelengths as a whole,12 ADM’s and5wavelengths are needed.From this table weﬁnd that most of the link loads for these two sets of traﬃc patterns are not full and half of the links on wavelength5are empty.In Table3, traﬃc r20is cut into two segments2ﬁ3and3ﬁ0. Theﬁrst segment is assigned to W4and the second to W2.Note that after this simple cutting algo-rithm,only10ADM’s and4wavelengths are needed,2ADM’s and1wavelength are saved.From this example we can alsoﬁnd the beneﬁt of grooming in a strictly non-blocking way.If the two traﬃc patterns were treated as a static one,in order to support both of them when traﬃc chan-ges,we have to groom a traﬃc matrix of which each traﬃc request is the maximum of the two patterns,as is shown in Table4.The grooming results are shown in Table5,where‘‘Virtual load’’denotes the link load when the maximum traﬃc is actually established on the ring,‘‘Link load1’’and ‘‘Link load2’’represent the link load at the mo-ment when theﬁrst and the second traﬃc matrix is motivated,respectively.Weﬁnd from this table that in this case each wavelength can only accommodate a node-pair’s traﬃc,which amounts to no grooming,and no link can reach the wave-length’s maximum capacity.The actual link load when either of the two traﬃc patterns is estab-lished is even lower.Furthermore,no traﬃc can be cut to reduce the number of ADM’s in this case. Comparing Tables2and3with Table5weﬁnd that what really makes sense in the strictly non-blocking grooming is that when traﬃc changes over time,it is often that at one moment some traﬃc requests are at their higher level but othersTable1Two traﬃc matrices at two moments in a4-node ring(a)The traﬃc matrix at one moment (b)The traﬃc matrix at anothermomentTable2A grooming result without cutting traﬃcs for dynamic traﬃc patternsWavelength Traﬃc request Dropping nodes Link load1Link load2 W1r10;r01;r12;r210;1;22;4;3;34;4;3;3W2r03;r30;r020;2;34;4;1;24;4;3;2W3r31;r131;32;3;3;23;2;2;3W4r23;r322;33;3;2;33;3;2;3W5r200;20;0;2;20;0;2;2 184K.-h.Liu,Y.Xu/Computer Networks46(2004)181–195are at their lower level,at another moment the situation may be reversed.Thus we can make full use of the dynamics of the changing traﬃc and make some compensation among the traﬃc requirements between diﬀerent pairs of nodes with this grooming scenario.That is to say,at any time, those traﬃcs that are at their high level can be compensated by the traﬃcs that are at their low level,which will certainly save some ADM’s(as well as wavelengths)compared to the grooming of maximum static traﬃc.2.2.Traﬃc-dividingDividing a traﬃc into smaller parts and assigning them to the existing wavelengths by sharing the spare capacity with them is also a good idea of eﬃcient grooming,which will not only cut down the number of wavelengths but also reduce the number of ADM’s as well.So in Ref.[2] traﬃcs were divided into basic elements to con-struct circles to minimize the numbers of ADM’s and wavelengths.In Ref.[1],traﬃc division was considered in the grooming problem where all the traﬃc on the ring is destined to a single node,the egress node.A heuristic algorithm was then pro-posed to divide some traﬃc from a node onto some rings,so as to minimize the number of ADM’s subject to the minimum number of wave-lengths.In this case,minimizing the number of ADM’s is achieved by minimizing the number of split traﬃcs.But again,these two heuristics are applied only to the case of static traﬃc.Our heuristic is quite diﬀerent from the above two algorithms.Firstly,our dividing method is applied only when the following conditions are satisﬁed:Condition3.Both of the end nodes of the traﬃcare already the dropping nodes ofthe current wavelength.Condition4.One of the divided parts can be as-signed to that wavelength.Condition3is to guarantee that no additional ADM’s are added to the current wavelength. Condition4ensures that one divided part of the traﬃc can be assigned to it.Since the remainedTable3A grooming result with cutting traﬃcs for dynamic traﬃc patternsWavelength Traﬃc request Dropping nodes Link load1Link load2 W1r10;r01;r12;r210;1;22;4;3;34;4;3;3W2r03;r30;r02;r30200;2;34;4;1;44;4;3;4W3r31;r131;32;3;3;23;2;2;3W4r23;r32;r23202;33;3;4;33;3;4;3Table4The maximum traﬃc matrix at the twomomentsTable5A grooming result by taking the two traﬃc patterns as a static oneWavelength Traﬃc request Dropping nodes Virtual load Link load1Link load2W1r01;r100;12;2;2;21;2;2;22;1;1;1W2r02;r200;23;3;2;23;3;2;21;1;2;2W3r03;r300;33;3;3;21;1;1;23;3;3;2W4r12;r211;22;3;2;21;2;1;12;3;2;2W5r13;r311;33;3;3;32;3;3;23;2;2;3W6r23;r320;13;3;2;33;3;2;33;3;2;3K.-h.Liu,Y.Xu/Computer Networks46(2004)181–195185traﬃc is only a part of the whole call,it is easier to be assigned to other wavelengths to share the same ADM’s with the traﬃcs already on those wave-lengths.Secondly,we do not try to divide traﬃc into basic elements for the control overhead of the network will be increased with the number of the parts divided.In our algorithm,the amount of the divided traﬃc is determined by the remaining capacity of the current wavelength.A traﬃc is divided only when there is a spare capacity on the wavelength between the end nodes of the traﬃc. After dividing,one part of the traﬃc is assigned to ﬁll up the remained capacity of the current wavelength,the other part is to be assigned to other wavelength(s).Lastly,our method is applied to the grooming of not only static but dynamic traﬃc.Compared to cutting method,in which a call has to pass through two or more wavelengths after cut,in this method,although a call may be carried by two or more wavelengths after divided,each part of it is still single-hopped and the signal transmission is not delayed.Nevertheless,dividing a traﬃc would inevitably make a network’s virtual topology more complex and increase the diﬃculty of network management.So we try to avoid a traﬃc being divided into too many parts.The beneﬁt of this method is illustrated by the following example.The two traﬃc matrices were given in Table1.Table6shows the grooming re-sults with traﬃc division method,where r kij denotesthe k basic low-rate parts of traﬃc i!j.In order to achieve strictly non-blocking grooming,the di-vided parts must be assigned to the same wave-lengths for diﬀerent traﬃc patterns.In this table, traﬃc r20is divided into two basic parts,theﬁrst part is assigned to W1and the second to W2.In this way,only10ADM’s and4wavelengths are pared to the non-split grooming,2 ADM’s and1wavelength are saved.2.3.Synthesized-splittingFrom the above two examples,weﬁnd that traﬃc-cutting and traﬃc-dividing are both beneﬁ-cial for static and dynamic traﬃc grooming in saving ADM and wavelength but they will lead to diﬀerent assignment and grooming results.A good grooming algorithm incorporated with these two splitting methods will bring about better results.In this paper,we will combine these two splitting methods with the genetic algorithm proposed in[9] to achieve better grooming results.Though there is quite diﬀerence between the two splitting methods, the algorithm proposed in this paper will combine them together.After a traﬃc is divided or cut,it can be further split into shorter or smaller parts.It is obvious that the shorter and smaller parts will be easier to be assigned to a new wavelength and this will result in some more savings in ADM’s and wavelengths than the two methods used alone.This combined method will be used as the third splitting method and is referred to as Synthesized-Splitting. With this method,weﬁrst divide a traﬃc into two parts and assign one of them to the current wave-length.Then if necessary,the remained part will be further divided or cut into smaller segments.In this way,a traﬃc can be divided into two or more parts, but we only cut it into two segments to avoid being delayed too much.3.Description of our GA-based algorithmThe framework of the genetic algorithm(GA) used in this paper is basically the same as that described in[9]but with more eﬃcient localTable6A grooming result with dividing traﬃcs for dynamic traﬃc patternsWavelength Traﬃc request Dropping nodes Link load1Link load2W1r10;r01;r12;r21;r1200;1;22;4;4;44;4;4;4W2r03;r30;r02;r1200;2;34;4;2;34;4;4;3W3r31;r131;32;3;3;23;2;2;3 W4r23;r322;33;3;2;33;3;2;3 186K.-h.Liu,Y.Xu/Computer Networks46(2004)181–195improvement algorithms.The (l þk )-strategy is used in reproduction process.The algorithm is outlined as follows:1.Set all the necessary parameters,and let t ¼0;2.Generate an initial population P 0with l individ-uals at random;3.REPEAT:3.1Apply crossover and mutation to the par-ents to produce k oﬀspring;3.2Decode each individual i ði ¼1;2;...;l þk Þwith the splitting methods to assign each call in the M traﬃc patterns to wave-lengths in a strictly non-blocking manner;3.3Evaluate each individual i ði ¼1;2;...;l þk Þin both the parents and the oﬀspring and select l individuals from the (l þk )parents and oﬀspring with the highest ﬁtness value for the next generation;3.4Set t ¼t þ1;4.Until some ‘‘termination criterion’’is violated.The realization of each step is described in the following subsections.3.1.Chromosome representationTo represent chromosome in the GA,we ﬁrst convert the traﬃc matrix R m into an n ðn À1Þ-dimensional vector X m ¼ðx m 0;...;x m k ;...;x mn ðn À1ÞÀ1Þ;m ¼0;1;...;M À1.The connection between the component’s subscripts i ,j of the traﬃc matrix and the vector’s subscript k is given by [9]:k ¼ð2n Ài Þði À1Þ=2þj Ài ;16i 6n À1;i þ16j 6n or 16k 6n ðn À1Þ=2;k ¼ðn ðn À1Þþði À1Þði À2ÞÞ=2þj ;26i 6n ;16j 6i À1or n ðn À1Þ=2þ16k 6n ðn À1Þ:8>>>>>><>>>>>>:ð1ÞA random chromosome with the same dimen-sion and integer genes in the interval ½0;n ðn À1ÞÀ1 is generated to represent a random sequence of the traﬃc elements.Each gene in the chromosome represents the same corresponding traﬃc element in the set of traﬃc vectors X m .The position each gene is at gives the decoding order of the traﬃc elements.3.2.Decoding approach and ﬁtness assignment In strictly non-blocking grooming,each wave-length has to accommodate the same calls when traﬃc changes,thus the chromosome is decoded with each of the M traﬃc patterns one by one.In decoding the chromosome,we noticed that if a wavelength drops at p nodes,it can at most accommodate p ðp À1Þtraﬃcs.If all the p ðp À1Þtraﬃcs are assigned to the wavelength,the num-bers of ADM’s and wavelengths used on the ring must be minimized.Based on this fact,we propose a ﬁrst-ﬁt approach incorporated with a greedy local improvement to decode each chromosome.In this approach,a ﬁrst-encountered traﬃc b k in the chromosome is assigned to the current wave-length if all the traﬃc requests represented by it in the set of M traﬃc patterns can be assigned to it.Then it examines the remained items one by one to assign such traﬃc items to the current wavelength whose source and termination nodes have already been the dropping nodes of it.If such an item b l is found,it is assigned to the current wavelength and the two items (b k þ1and b l )are exchanged,then the algorithm goes on to search for other similar items.After all the remained items have been examined,it tries to assign the next-encountered traﬃc in the chromosome to the current wave-length and then goes on searching again.This process proceeds until one of the link loads of the current wavelength exceeds its maximum.In this way,when a wavelength drops at p nodes,the algorithm will assign as many traﬃcs as possible to it to minimize the numbers of ADM’s and wave-lengths.If no traﬃc can be assigned to the current wavelength as a whole,the local improvement algorithm examines the remaining genes one by one to ﬁnd a traﬃc b l which can be assigned to it by splitting without adding new ADM’s.Algo-rithm 1implements this algorithm.Algorithm 1(decoding a chromosome ).Step 1:k ¼0,s ¼0and w ¼1.Set the split listempty;Step 2:If each of the M traﬃcs represented by thetraﬃc item b k in the chromosome can be assigned to wavelength w ,assign each of them to it.Otherwise,go to Step 11;K.-h.Liu,Y.Xu /Computer Networks 46(2004)181–195187Step3:l¼kþ1;Step4:If each of the M traﬃcs represented by the traﬃc item b l can be assigned towavelength w with no additional ADMadded to it,assign each of them to it,k¼kþ1,exchange traﬃc b k with b l; Step5:l¼lþ1.If l<nðnÀ1Þ,go to Step4; Step6:j¼0.If j P s,go to Step10;Step7:If each of the M traﬃcs represented by the traﬃc item b j in the split list can beassigned to wavelength w with no addi-tional ADM added to it,assign each ofthem to it.Otherwise,go to Step9; Step8:Delete traﬃc b j from the split list and move all the traﬃc items behind it back-ward toﬁll that place,s¼sÀ1.If j<s,go to Step7;Step9:j¼jþ1.If j<s,go to Step7;Step10:k¼kþ1.If k<nðnÀ1Þ,go to Step2; Step11:l¼k.If l P nðnÀ1Þ,go to Step17; Step12:i¼k;Step13:If each of the M traﬃcs represented by the traﬃc item b i can be divided intotwo parts according to Conditions3and4given in Section2.2,divide eachof the M traﬃcs into two parts,and as-sign one of them to wavelength w;theother part is left in the traﬃc matrix; Step14:i¼iþ1,if i<nðnÀ1Þ,go to Step13; Step15:If each of the same segments cut from the M traﬃcs represented by the item b l canbe assigned to wavelength w accordingto Conditions1and2given in Section2.1,cut each of the M traﬃcs into thesame two segments and assign one ofthem to wavelength w,put the other tothe split list,k¼kþ1,s¼sþ1,and ex-change traﬃc b k with b l;Step16:l¼lþ1.If l<nðnÀ1Þ,go to Step15; Step17:w¼wþ1,go to Step2;Step18:Assign the remained traﬃc in the split list to wavelengths in accordance with Steps2–5.Algorithm1decodes a chromosome in a strictly non-blocking way,in which all the traﬃcs or segments represented by the same gene in the chromosome are assigned to the same wave-length.In this algorithm,Steps1–11,and17–18 are the grooming with no splitting;Steps15and 16are employed to accomplish the cutting algo-rithm;Steps12–14accomplish the dividing algo-rithm.Step2tries to assign theﬁrst-encountered traﬃc item b k represented by the chromosome to the current wavelength.Step4examines the remained items one by one to assign such traﬃc items to the current wavelength whose end nodes have already been the dropping nodes of it to minimize the number of ADM’s.Steps7–8assign the traﬃcs in the split list to the current wavelength as a whole with no additional nodes added.Then Step13tries to divide traﬃcs represented by the chromosome into two parts and assign one of them to the cur-rent wavelength without adding nodes.Step15 tries to cut traﬃcs and assign one of the segments to the current wavelength with no additional nodes added.Step17starts to accommodate a new wavelength.At last,Step18assigns the remained traﬃcs in the split list to wavelengths without splitting.In this way,after all the traﬃcs repre-sented by the chromosome have been assigned to appropriate wavelengths,the numbers of ADM’s and wavelengths used in this chromosome can be computed,which determine theﬁtness value of the chromosome.The decoding approach described in Algorithm1applies to all the chromosomes in the population.For each individual,theﬁtness value is deter-mined by the number of ADM’s required after decoding.The one that requires fewer ADM’s gets higherﬁtness value.If two individuals require the same number of ADM’s,a higherﬁtness value is assigned to the one with fewer wavelengths.If the number of wavelengths is the same again,a same ﬁtness value will be assigned to them.Only the l individuals with the highestﬁtness value are se-lected for the next generation.Since we always keep the individuals with the highestﬁtness value for the next generation,as the iteration goes on,the local improvement used in this approach willﬁnally enable the whole popu-lation to evolve toward the global optimum rap-idly.The eﬀectiveness of this algorithm is demonstrated by the computer simulations given in Section5.188K.-h.Liu,Y.Xu/Computer Networks46(2004)181–195。

选择与坚持：跨期选择与延迟满足之比较

第2期
任天虹等 : 选择与坚持：跨期选择与延迟满足之比较
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会通过预实验选择一对较为恰当的 SS 与 LL, 以保证 SS 与 LL 之间的差异既要大到足以使被试愿意选择后者 , 又要小到使 SS 对儿童有足够的诱惑 , 从而避免等待时间的天花板效应与地板效应 (Mischel & Underwood, 1974)。动物实验在跨期选择与延迟满足的研究中都有所涉及 , 这些动物研究的实验范式直观易懂 , 对儿童被试的研究也颇有启示意义。随着研究内容的扩展与研究范式的改进 , 跨期选择与延迟满足在研究对象上有融合的趋势。 3.2 研究内容跨期选择关注被试的时间折扣 (time discounting), 而延迟满足则更关注被试在等待时间上的个体差异、自我控制策略及其有效性 (Ainslie, 1975; Mischel et al., 1989)。如果说跨期选择的研究者将其研究重点放在了计算、分析、推理、权衡等较为高级的认知过程上 , 那么延迟满足的研究者则将其重点放在了情绪、意志力、动机强度等更为基础的本能反应上。时间折扣是跨期选择研究的基本假设 , 也是其研究的重要内容 , 它是指在跨期选择中 , 个体首先会对延迟结果的价值根据其延迟的时间进行一定的折扣, 然后再对两个结果进行比较(Frederick et al., 2002; Scholten & Read, 2010)。经济学家力图找到某一通用的公式来描述折扣程度与结果及延迟时间之间的关系 , 表现为数理模型的优化 ; 心理学家则更关注外界因素对个体时间折扣程度的影响 , 表现为认知神经机制的揭示。延迟满足的研究者并不关注折扣程度 , 他们更加关注等待时间上的个体差异 , 并在实验中细致地检验被试自我控制策略的选择与使用状况 , 这些研究者热衷于以追踪研究揭示儿童在实验中的表现与其个性及行为特征之间的关系 (Mischel et al., 1989)。 3.3 研究范式跨期选择的研究关注被试的选择过程 , 它要求被试做出一系列选择 ; 延迟满足则更关注被试的坚持过程 , 要求被试坚持完成选择后的等待过程。尽管在跨期选择的部分任务中也涉及到等待过程 , 但是它与延迟满足有本质的区别。被试在延迟满足任务中能够自主选择中止等待 , 而在跨期选择任务中则只能消极等待延时结束 (Evans & Beran, 2007)。

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nd Motivation
Future integrated services networks will have to support applications with diverse tra c characteristics and performance requirements. There are three important types of tra c for future integrated services networks: constant bit rate CBR tra c, delay-sensitive variable bit rate or VBR tra c, and best-e ort ABR or available bit rate tra c. Among these, delay-sensitive VBR tra c poses a unique challenge. While resource reservation schemes work best for CBR tra c, and there are many congestion control algorithms based on feedback and re-transmission for best-e ort tra c, there is no consensus on which strategy should be used for VBR tra c, in particular, compressed video. This is due mainly to two con icting design goals: good quality of service and high network utilization. Achieving both goals with bursty tra c is fundamentally di cult. Since a bursty source may generate various amounts of data during di erent time periods, the aggregate amount of tra c generated by many sources sharing the same network resources also varies over time. When the amount of aggregate incoming tra c is greater than the outgoing link speed, packets have to be bu ered. If the situation persists, packets will be dropped due to bu er over ows, which will in turn cause the application's quality of service (QOS) to su er. This problem is compounded by
networks include deterministic service, statistical service, predicted service, and feedback-based schemes. These schemes represent di erent tradeo s in quality of service (QOS), achievable network utilization, and method of dealing with overload. In this paper, we propose a new service that attempts to strike an e cient balance with the above tradeo s. The approach is based on deterministic guarantees with client controlled renegotiation of QOS parameters and graceful adaptation during overload periods. We evaluate the scheme using two traces of MPEG-compressed video and show that, even with simple renegotiation polices and relatively low renegotiation frequencies, high network utilization in the range of 50% to 80% can be achieved. For tra c that is bursty over long intervals, this represents a 100% to 150% improvement in network utilization compared to deterministic service. Compared to statistical and predicted service, our approach allows more graceful and client-controlled QOS degradation during overload period.
Edward W. Knightly EECS Department, UC Berkeley and Sandia National Laboratories
knightly@
Abstract. Previous approaches to supporting video on packet-switched
A New Approach to Support Delay-Sensitive VBR Video in Packet-Switched Networks
Hui Zhang School of Computer Science Carnegie Mellon University
hzhang@
the nature of VBR video tra c: depending on the underlying information content of the video stream, bursts of high rate can persist for time scales on the order of many seconds over the duration of an entire complex, high-motion scene. Bursts of this time scale cannot be absorbed by network bu ers or smoothed at the source because of the excessive delay that this would introduce and the excessive bu er sizes that it would require. Thus, the fundamental problem is that when bursts from many sources collide inside the network, if the rate of the aggregated tra c is greater than the link speed and the situation persists for a certain period, the QOS of some or all connections will su er. Various solutions have been proposed to address the problem, and they represent di erent ways of dealing with the tradeo between QOS and network utilization. Previous solutions can be classi ed according to the following four categories: deterministic service with peak-rate allocation 3], statistical service with probabilistic allocation 5, 9, 13], predicted service with observationbased admission control 2], and feedback based scheme with no resource reservation 4, 6]. Previously proposed solutions for deterministic service eliminate the occurrence of overload situations by reserving resources at the sources' peak rates. While this approach provides the best QOS, it does so at the expense of having low network utilization when peak-to-average rate ratios are high. In various ways, the other three approaches trade a higher network utilization for a potential degradation of QOS. However, they all su er from some limitations. Statistical and predicted services try to control the frequency of the overload situation by exploiting statistical multiplexing (respectively using knowledge of source statistics and queue measurements). However, the overload situation may still happen, and at unexpected times. Additionally, during the overload period, QOS is likely to su er signi cantly for all connections in an uncontrolled and di cult-to-predict way. As well, the QOS may drop signi cantly due to consecutive packet losses. This last problem is exacerbated for VBR video since VBR video may have very long burst lengths, on the order of scene lengths, possibly causing a persistent degradation in service when the bursts do collide. Feedback schemes with no reservations try to adapt and react to overload situations by using network congestion signals to reduce the rates of sources. Such schemes have the advantage that they can gracefully degrade QOS during an overload situation by exploring an important property of the compressed video: most of video compression algorithms have a quality control parameter that, when tuned, will output compressed video at di erent rates and qualities. The drawback of a feedback-based scheme is that, without some round robin type of scheduler at the switch, it won't work unless all sources cooperate. Even with switch support, it still has the fundamental problem that it is impossible to provide di erent types of QOS to di erent applications. In this paper, we study a new approach to support VBR video that utilizes the following two important observations. The rst one is that although compressed video is bursty, it is much more structured than data tra c. While compressed video is bursty because the size of a compressed frame varies from one frame to the next, there is an underly-