Managing Real-Time Distributed Multimedia Applications 1 Chapter I Managing Real-Time Distr
人力资源HRM英文对应
人力资源HRM英文对应Introduction人力资源HRM 英文对应in the field of management is the process of managing employees in an organization, with the aim of enhancing their performance and productivity. It involves implementing policies and practices that are directed towards ensuring that employees' skills, knowledge, and abilities are utilized to achieve company goals. HRM plays a critical role in the success of any organization, as it is responsible for recruiting, training, and managing employees. This paper will explore the different aspects of HRM and their English equivalents.Recruitment and SelectionRecruitment and selection are crucial parts of the HRM process. Recruitment involves attracting and sourcing potential employees, while selection involves assessing and choosing the right candidate for a job. Some of the English terms used in this phase of HRM include:1. Job posting - This refers to the process of advertising a job vacancy within an organization.2. Applicant tracking system (ATS) - This refers to software used to track and manage job applicants.3. Interview - This refers to the process of assessing and evaluating job applicants to determine their suitability.4. Selection criteria - This refers to the qualifications, experience, and other requirements that a candidate must possess to be considered for a job.Training and DevelopmentThe process of training and developing employees is essential for ensuring they have the necessary skills and knowledge to perform their jobs effectively. The following are some English terms used in this phase of HRM:1. On-the-job training - This refers to training an employee receives while performing their job.2. E-learning - This refers to training that is delivered online through a learning management system (LMS).3. Soft skills - These are interpersonal skills required for a job, such as communication, teamwork, and time management.4. Performance appraisal - This refers to the process of evaluating an employee's performance against pre-determined objectives and targets.CompensationCompensation is one of the critical aspects of HRM, as it involves the determination of salaries, bonuses, and benefits thatemployees receive for their services. The following are some English terms used in this phase of HRM:1. Wage - This refers to the hourly or daily rate that an employee earns.2. Salary - This refers to the amount of money an employee earns on an annual basis.3. Allowances - These are additional payments or perks that employees receive for their services, such as housing allowance, travel allowance, and medical insurance.4. Bonus - This refers to a special payment made to employees in addition to their regular salary or wage.Human Resource PlanningHuman resource planning involves forecasting the number and types of employees that an organization needs to achieve its objectives. The following are some English terms used in this phase of HRM:1. Workforce analysis - This refers to the process of analyzing an organization's current workforce to identify the skills and knowledge gaps that need to be filled.2. Talent management - This refers to the process of identifying, developing, and retaining key employees in an organization.3. Succession planning - This refers to the process of identifying potential successors for senior-level positions in an organization.4. Diversity and inclusion - These are policies and practices aimed at ensuring that employees from diverse backgrounds are treated fairly and equitably.ConclusionIn conclusion, the human resource management (HRM) process involves various aspects, including recruitment and selection, training and development, compensation, and human resource planning. These aspects are all critical to the success of an organization, and they require various English terms and concepts to convey their meaning effectively. Therefore, it is essential for HR professionals and managers to have a good understanding of the English equivalents of these concepts to operate effectively in increasingly globalized work environments.。
霍尼韦尔 全自动流量分析仪说明手册说明书
THE NEEDSEvides Waterbedrijf required measurement of turbidity and flow to monitor water quality in the distribution network and manage the network. Until recently, this data had been recorded manually and analysed with outdated equipment. This process no longer fitted with the strategic pillar “digitising primary processes” which was an important aim of the Netherlands water provider. Evides Waterbedrijf developed an all-in-one measuring device which allowed them to make all distribution network measurements. During the measurement process, turbidity, flow and GPS location were all recorded and logged in real-time from the field. This data could be used to determine water quality of the distribution network, assess the effectiveness of previously implemented drainage actions and continue to optimise drainage plans. The process being largely automated. The flow meter was part of the total standpipe solution which was lightweight and easy to dismantle in the field.THE SOLUTIONTo support the needs of EvidesWaterbedrijf, Honeywell Smart Energyoffered their Q4000 electromagneticmeter as part of the standpipe solution.Featuring high quality design andengineering, Honeywell’s Q4000electromagnetic water meter is builtfor maintaining highly accurateperformance and lasting durabilityin demanding environments.With an unrestricted flow tube with nomoving parts and a 10-year batterylife, the Q4000 offers unrivalledperformance for an electromagneticwater meter. Delivering consistentaccuracy over a wide flow-ratemeasuring range, the meter can beadapted to suit either predominantlyhigh or low flow rates, and is ideal fordistribution network applications.The Q4000 is a high-performingelectromagnetic meter, ideal for networkmanagement and leakage monitoring.HON EYWELL’SW A TER M ETERCase StudySupports Accurate Real-Time Distribution Network AnalysisGood quality water supply is provided for the entire population in the Netherlands. Water consumption is one of the lowest in developed countries at 128 litres per capita per day and water leakage in the distribution network is one of the lowest in the world at only 6%.The Q4000 water meter forms part of the total standpipe solution.The Q4000 from Honeywell Smart Energy is a high-performing electromagnetic meter, ideal for bulk flow metering applications such as network management and leakage monitoring.-It has a fast continuous sampling rate, providing highly accurate and reliable measurement.-The Q4000’s extremely tough stainless steel constructionensures a long working life, while its lightweight body makes storage, transportation and installation both simpler and safer.-With an unrestricted flow tube, the Q4000 ensures minimal pressureABOUT EVIDES WATERBEDRIJFEvides Waterbedrijf supplies safe and clean drinking water 24 hours a day, 365 days a year to 2.5 millioncustomers and the business community in Zeeland, in the South West of Holland and the Brabantse Wal.Additionally, Evides Waterbedrijf offers tailor-made industrial water services to large industrial customers in the Netherlands, Belgium and Germany.THE BENEFITSloss, even at the highest flowrates, resulting in reduced network system pressures, helping to prevent leakage from burst pipes. -A large, bright and easy-to-read LCD, showing volume and instantaneous flow rate, is ideal for real-time network control and water management. -With the Q4000’s 10-yearcontinuous battery life and no need for calibration, expensive regular maintenance is a thing of the past. -With bi-directional pulse outputs, the Q4000 provides dependable connectivity to critical water management systems including AMR and data logging devices.All rights reserved.The company’s policy is one of continuous product improvement and the right is reserved to modify the specifications contained herein without notice. These products have been manufactured with current technology and in accordance with the applicable referenced standards.SS-20-2 ENG | 02/20© 2020 Honeywell International Inc.For more informationElster Water Metering Ltd130 Camford Way Sundon Park, Luton Bedfordshire, LU3 3AN United Kingdom T +44 1582 846400F +44 1582 564728*************************。
实时控制系统的应用：异步串行通信协议说明书
1300 Henley Court Pullman, WA 99163509.334.6306Lab 4b: Application of Asynchronous Serial Communications Protocol for Real-time ControlRevised May 23, 2017This manual applies to Unit 4, Lab 4b.1 Objectives1. To control and monitor the operations of a stepper motor using serial communications between a PIC32microprocessor and a computer terminal.2. To implement real-time control using a preemptive foreground-background task scheduling scheme.3. Simulate an environment that provides both local and remote control of a real-time system.2Basic Knowledge1. Elements of ASCII text encoding .2. I/O configuration for PPS Processors .3. How to initialize special function using the PLIB functions.4. How to program the PIC32 processor to both generate and receive and decode serial text data.3 Equipment List3.1 Hardware1. Basys MX3 trainer board2. Workstation computer running Windows 10 or higher, MAC OS, or Linux3. 2 Standard USB A to micro-B cables4. 4-wire stepper motor5.5V, 4A DC power supplyIn addition, we suggest the following instruments:6. 3.2 SoftwareThe following programs must be installed on your development work station:1. Microchip MPLAB X® v3.35 or higher2. PLIB Peripheral Library3. XC32 Cross Compiler4.WaveForms 2015 (if using the Analog Discovery 2)5.PuTTY Terminal Emulation.4 Project Takeaways1.Knowledge of a PC terminal emulation program.2.How to develop a library of PIC32 software to provide bi-directional communications of single charactersand strings of characters.3.How to generate and decode ASCII text strings.4.How to implement a human-machine interface (HMI) using point-to-point serial communications.5 Fundamental ConceptsSerial communication is the process of sending data one bit at a time, sequentially, over a communication channel or computer bus. This is in contrast to parallel communication, where several bits are sent as a whole on a link with several parallel channels. Both parallel and serial communications have handshaking requirements to synchronize data transfers. Although parallel communications generally have a speed advantage over serial communications, the primary advantage for serial communications is the reduced number of processor I/O pins and connecting wires or conductors.6 Problem StatementIt requires all of the elements of software code developed and hardware used in previous labs, as well as additional hardware and software to support the serial communications with the PC. This project will require you to input text data from the serial port that will set the direction, mode, and speed of the stepper motor. This interface will be in addition to all of the controls provided in Lab 2b. The text from the serial port will be echoed to the LCD. It will be good for you to review the documentation on how the following text manipulating functions are implemented: printf, sprintf, scanf, and strcmp.7 Background InformationLab 4a introduced the basic concepts of UARTs and asynchronous serial communications. Lab 4b extends that knowledge by specifying a system that is capable of two independent control and monitoring locations which is common to many industrial applications, such as gantry cranes and processing plants. In this lab, the switches and push buttons on the Basys MX3, as used in lab 2b, will perform the local control functions. The Basys MX3 LCD will be used as the local display. The UART serial connection will provide the basic control and display functionality using a workstation terminal emulator program.8 Lab 4b8.1 Requirementsmunications will use the PC terminal emulation program for a bit rate of 38400, even parity, 8 databits, and one stop bit.2.Local Control Specifications of Stepper Motora.Direction and Mode controli.BTNR controls the direction of rotor rotation of the stepper motor.ii.BTND controls the stepper motor step mode.iii.The speed of rotation must be the same regardless of stepper mode operation.b.The speed of rotation is set by the hexadecimal value set on the eight slide switches. SW7 is themost significant bit and SW0 is the least significant bit.c.The speed of the motor is to be displayed on the 4-digit 7-segment LED display in RPM.d.The four digits of the Basys MX3 7-segment display are continually updated with a 1 mspersistence (each digit must be turned on for 1 ms). The four digits will be lit in a round-robinfashion in a foreground operation managed by Timer 1 ISR.e.Stepper motor outputs are changed in the Timer 1 ISR using the period as determined by theslide switch settings. The period is determined by converting RPM to ms delay between steps.f.The BTNC push button controls the ON/OFF state of the LED0 in a push-on/push-off manner.i.When LED0 is changed to “ON,” print “Stepper motor under local control” on the serialmonitor. Then read switches and push buttons to set the stepper motor operations andreport the status of the remote serial monitor via UART 4.ii.When LED0 is changed to “OFF,”print “Stepper motor under remote control.” Followed by the message “Enter data [DIR] [MODE] [###] for [DIR] = CW or CCW, [MODE] = FULLor HALF, and [###] = stepper motor speed in RPM” to the remote serial monit or viaUART 4.3.Remote Control Specificationsa.Any change of the stepper motor operations made by local controls must be reported to theserial terminal using the format “[DIR] [MODE] [###]” for [DIR] = “CW” or “CCW”, [MODE] =“FULL” or “HALF”, and “[###]: = stepper motor speed in RPM.”b.When the system is under remote control operation, stepper motor control is implementedusing a command string in the following format: [DIR] [MODE] [###][RETURN] where the textfields are described in 2.f.ii. above. The [RETURN] character is generated when the monitor“Enter” key is pressed. All command fields must contain valid text or range of numbers,otherwise the entire command is ignored and an error message is sent back to the monitor usingthe text “Bad entry\n\r.”8.2 Design Phase1.Develop a data flow diagram for the software components needed for the requirements of Lab 4b.2.Schematic diagrams: Provide a block diagram of the equipment used for Lab 4b.3.Flow diagrams: Provide a complete software control flow diagram for Lab 4b.4.Develop a test plan that lists each requirement stated in section 8.1, including a column for PASS/FAIL. 8.3 Construction Phaseunch a new Microchip MPLAB X project called Lab4b. Add the config_bits.h file to the project.2.Add lab4b.c file to project Lab4b. The initialization segment of the main function should configure all I/Opins, initialize UART 4, initialize the Timer 2 interrupts, set LED0 on (indicating local operating mode), and set all global variables.3.Add all stepper motor files used in Lab 2b to the project.4.Add the UART functions developed for Lab 4a.5.This program will contain the function main and process the serial text. Put the following tasks inside thewhile(1) loop:a.Check for BTNC being pressed.b.Check if a command line of text has been entered.c.The direction and mode string variables can be decoded using the string compare function“strcmp.” An example of using this function would be:x = strcmp(mode_txt,”FULL”);d.Only if the st ring of data in mode_txt is exactly equal to FULL will the value of “x” equal zero. Youmust include <string.h> to be able to use this function.e.After decoding the string data, set the global variables that control direction, mode, and stepdelay (computed from RPM setting).8.4 Testing1.Run the project. Complete the test plan that was developed above.9 Questions1.Why is it appropriate that the UART getstrU4 function be a background process?2.What are the advantages of using serial communications to link to processors?3.What are the disadvantages of using serial communications to link to processors?10 References1.PIC32MX330/350/370/430/450/470 Family Data Sheet2.“Using the USART in Asynchronous Mode”,/downloads/en/DeviceDoc/usart.pdf3.“Asynchronous Communications with the PICmicro® USART”,/downloads/en/AppNotes/00774a.pdf4.RS-232, RS-422, RS-423, RS-485 Asynchronous communications.Appendix A: Basys MX3 Schematic DrawingsFigure A.1. PIC32MX370 to FT232RQR IC schematic diagram.Figure A.2. LCD and switches on the Basys MX3 that controls the stepper motor speed.Figure A.3. PuTTY screenshot generating LCD display.Figure A.4. PuTTY screenshot of serial configuration for 19200 BAUD and ODD parity.Appendix B: Allocating a Heap in MPLAB XIf when compiling your project you see an error like: "ld.exe Error: A heap is required, but has not been specified," this is because you need to specify a heap size by setting “Run” ->“Set Project Configuration” -> “Customize…”. Go to the “xc32-ld” category (under “XC32 (Global Options)”) -> “Heap size (bytes)” to “0” The configuration window should look like Fig. B.1. Click on the “Apply” button followed by clicking on the “OK” button. See/mplabx:creating-a-heap.Figure B.1. Allocating Heap size.。
操作系统心得体会
操作系统心得体会英文回答：The operating system plays a vital role as the core software in managing a computer's hardware and software resources. Throughout my learning experiences, I have gained a comprehensive understanding of the various concepts related to operating systems, which has not only broadened my technical knowledge but also enhanced my problem-solving and critical thinking skills.The understanding of the different types of operating systems, such as real-time, time-sharing, and distributed systems, has equipped me to grasp the distinctions in their functionality and applications. Real-time systems, commonly employed in domains requiring immediate response,prioritize the execution of tasks within strict deadlines, making them suitable for industries like aviation and manufacturing. Time-sharing systems, often found in multi-user environments, efficiently allocate system resourcesamong multiple users, allowing them to execute their tasks concurrently. Distributed systems, on the other hand, excel in coordinating resources across multiple interconnected computers, enabling seamless collaboration and data sharing.Moreover, I have developed a strong grasp of memory management techniques employed by operating systems, including paging and segmentation. Paging divides the physical memory into fixed-sized units called pages, enhancing memory utilization and reducing fragmentation. Segmentation partitions memory into variable-sized segments, allowing each segment to be assigned specific protection attributes, boosting security and flexibility. These techniques provide a foundation for efficient memory usage and protection against unauthorized access.Furthermore, my understanding of process scheduling algorithms has illuminated how operating systems prioritize and manage the execution of processes. Algorithms such as First-Come First-Serve (FCFS), Shortest Job First (SJF),and Round Robin contribute to optimizing resourceutilization and minimizing turnaround time. Selecting theappropriate algorithm depends on the specific requirements and characteristics of the system. For instance, FCFS is straightforward and fair, while SJF prioritizes shorter jobs, improving average response time. Round Robin, on the other hand, ensures fairness by allocating time slices to each process, preventing any single process from monopolizing resources.Beyond theoretical knowledge, practical experiences through hands-on projects have solidified my understanding of operating systems. I have worked with popular operating systems like Linux and Windows, exploring their functionalities and troubleshooting common issues. Configuring system settings, optimizing performance, and managing user accounts were integral parts of these projects. These experiences have not only honed mytechnical proficiency but also fostered my ability to apply knowledge in real-world scenarios.In conclusion, my journey in learning about operating systems has been an enriching and enlightening experience.I have acquired a comprehensive understanding of thefundamental concepts, including types of operating systems, memory management, process scheduling, and practical system administration. These experiences have equipped me with a solid foundation in operating systems, which will prove invaluable as I navigate future technical endeavors and advance my career.中文回答：操作系统作为计算机的核心软件，负责管理计算机的硬件和软件资源，发挥着至关重要的作用。
时间管理大师的英语
时间管理大师的英语时间管理在现代社会变得越来越重要。
无论你是学生、职场人士还是自由职业者，都需要高效地管理时间来完成各种任务和目标。
而作为一个时间管理大师，掌握一些与时间管理相关的英语词汇和短语无疑会让你更加游刃有余地处理各项任务。
下面是一些与时间管理相关的英语词汇和短语：1.Time management - 时间管理2.Prioritize - 优先考虑3.Deadline - 截止日期4.Procrastination - 拖延5.Productivity - 生产力6.Efficiency - 效率7.Time tracking - 时间跟踪8.Time allocation - 时间分配9.Time blocking - 时间块10.Multitasking - 多任务处理11.Time waster - 浪费时间的人或事物12.Interruption - 干扰13.Focus - 专注14.Distraction - 分心15.Time management tools - 时间管理工具16.To-do list - 待办事项清单17.Time audit - 时间审计18.Goal setting - 目标设定19.Time log - 时间日志20.Meeting efficiency - 会议效率了解这些词汇和短语可以帮助你更好地与他人讨论和学习时间管理的技巧和策略。
除了词汇和短语，掌握一些英语句型也是非常有帮助的。
下面是一些常用的英语句型，可以帮助你表达关于时间管理的观点和建议：1.I need to prioritize my tasks in order to be more productive. - 为了提高生产力，我需要优先处理我的任务。
2.Setting deadlines for my tasks helps me stay motivated. - 给我的任务设定截止日期可以帮助我保持动力。
时间管理者英语手抄报
Powerful functionality, allowing for better time planning and management.
Disadvantage
Need to learn how to use it, and there may be issues with complex operations.
Persist in exercise and maintain good physical health
Summary
Persisting in exercise can enhance physical fitness, enhance resistance, and help better cope with the challenges of work and life.
VS
Detailed description
Good sleep quality can help people maintain a clear mind and abundant energy, which helps improve work efficiency and quality of life. At night, it is advisable to minimize the use of electronic devices and create a quiet and comfortable sleeping environment.
Avoid disБайду номын сангаасractions
Remove distractions like social media or notifications to stay focused on your work
HR专业词典(中文版)
English 25 %ile 360° feedback 50 %ile 75 %ile 90 %ile a holistic approach to all workforce programs a piecemeal approach Abilities Absenteeism Accelerating Premium Accident Frequency Accident Insurance Accident Investigation Accident Loss Accident Prevention Accident Proneness Accident Severity Accident Severity Rate Accident Work Injury Accountability Accountant Accounting Department Accounting Manager Accounting Supervisor/Senior Accountant Achievement Need Achievement Test Action Learning Action Research Active Practice Actual Total Cash Ad hoc seminar Adjourning Administration Administration Department Administration Manager Administration Officer Administrative Director Administrative Level Administrative Line Administrator ADR-Alternative Dispute Resolution Adventure learning Adverse Impact Advertisement Recruiting Affective Commitment Affiliation Need
提高人效 工作清单
提高人效工作清单英文回答：Improving productivity is crucial for any individual or organization. To enhance efficiency and effectiveness, itis important to have a well-organized work list or task management system. Here are some strategies and tips to improve productivity and manage work effectively:1. Prioritize tasks: Start by listing down all the tasks you need to accomplish. Then, prioritize them based on their importance and urgency. This will help you focus on the most critical tasks first and avoid wasting time on less important ones. For example, I always start my day by creating a to-do list and marking tasks as high, medium, or low priority. This allows me to stay focused on what needs to be done first.2. Break down tasks: Large and complex tasks can be overwhelming and lead to procrastination. To overcome this,break down big tasks into smaller, more manageable subtasks. This will make it easier to tackle them and provide a sense of progress. For instance, if I have to write a report, I divide it into sections like introduction, analysis, and conclusion. This approach helps me stay motivated and complete the report efficiently.3. Set deadlines: Assigning deadlines to tasks createsa sense of urgency and helps in better time management. Make sure to set realistic deadlines that allow for adequate time to complete the task without rushing. Additionally, consider using the "SMART" goal-setting framework, which stands for Specific, Measurable, Achievable, Relevant, and Time-bound. This will ensure that your deadlines are clear and achievable. For example, I set a deadline for each task on my to-do list and make sure to allocate enough time for each task based on its complexity and importance.4. Eliminate distractions: Distractions cansignificantly reduce productivity. Identify common distractions in your work environment and take steps tominimize or eliminate them. This may include turning off notifications on your phone, closing unnecessary tabs on your computer, or finding a quiet workspace. Additionally, consider using productivity tools or apps that can help you stay focused and block distractions. For instance, I use a website blocker app that restricts access to social media sites during work hours, allowing me to concentrate on my tasks without getting sidetracked.5. Delegate tasks: Learn to delegate tasks that can be done by others. Delegating not only helps in distributing workload but also allows you to focus on more important and high-value tasks. Identify tasks that can be assigned to team members or colleagues who have the necessary skills and knowledge. This will not only increase efficiency but also foster teamwork and collaboration. For example, I often delegate administrative tasks to my assistant, freeing up my time to focus on strategic initiatives.6. Take regular breaks: Working continuously without breaks can lead to burnout and decreased productivity. It is important to take short breaks between tasks or worksessions to relax and recharge. This can be as simple as taking a walk, doing some stretching exercises, or engaging in a quick conversation with a colleague. These breaks help in maintaining focus and energy levels throughout the day. For instance, I take a 10-minute break every hour tostretch and relax my mind. This helps me stay refreshed and productive.中文回答：提高人效对于个人和组织来说都至关重要。
操作系统概念第六版重点部分中文答案
1.1 What are the three main purposes of an operat ing system?1 To provide an en vir onment for a computer user to execute programs on computerhardware in a convenient and ef ?cie nt manner.2 To allocate the separate resources of the computer as n eeded to solve the problemgive n. The allocati on process should be as fair and ef ?cie nt as possible.3 As a control program it serves two major functions: (1) supervision of the execution of user programs to preve nt errors and improper use of the computer, and (2) man age- ment of the operati on and con trol of I/O devices.环境提供者，为计算机用户提供一个环境，使得能够在计算机硬件上方便、高效的执行程序资源分配者，为解决问题按需分配计算机的资源，资源分配需尽可能公平、高效控制程序监控用户程序的执行，防止岀错和对计算机的不正当使用管理I/O设备的运行和控制1.2 List the four steps that are n ecessary to run a program on a completely dedicatedmachi ne.An swer: Gen erally, operati ng systems for batch systems have simpler requireme nts tha n for pers onal computers. Batch systems do not have to be con cer ned with in teract ing with a useras much as a personal computer. As a result, an operating system for a PC must be concernedwith resp onse time for an in teractive user. Batch systems do not have such requireme nts.A pure batch system also may have not to handle time sharing,whereas an operating systemmust switch rapidly betwee n differe nt jobs.木有找到中文答案1.6 Define the esse ntial properties of the follow ing types of operat ing systems:a. Batchb. In teractivec. Time shar ingd. Real timee. Networkf. Distributeda. Batch. Jobs with similar n eeds are batched together and run through the computer as a group by an operator or automatic job seque ncer. Performa nee is in creased by attempting to keep CPU and I/O devices busy at all times through buffering, off-line operati on, spooli ng, and multiprogram ming. Batch is good for executi ng large jobs that need little interaction; it can be submitted and picked up later.b. In teractive. This system is composed of many short tran sacti ons where the results of the n ext tran sacti onmay be un predictable. Resp onse time n eeds to be short (sec on ds) since the user submits and waits for the result.c. Time shar in g.Thissystemsuses CPU scheduli ng and multiprogram ming to provide econo mical in teractive use of a system. The CPU switches rapidly from one user toano ther. In stead of hav ing a job de? ned by spooled card images, each program readsits next control card from the terminal, and output is normally printed immediately to the scree n.d. Real time. Often used in a dedicated application, this system reads information fromsen sors and must resp ond with in a ?xed amou nt of time to en sure correct perfor-man ce.e. Network.f. Distributed.This system distributes computati on among several physical processors.The processors do not share memory or a clock. In stead, each processor has its own local memory. They commu ni cate with each other through various commu ni cati on lin es, such as a high-speed bus or teleph one line.a. Batch相似需求的Job分批、成组的在计算机上执行，Job由操作员或自动Job程序装置装载；可以通过采用buffering, off-line operation, spooling, multiprogramming 等技术使CPU 禾口I/O不停忙来提高性能批处理适合于需要极少用户交互的Job。
计算机专业英语Unit3
Unit 3 Section 2 Passage A
• Categories of Operating Systems
While the majority of computers we see happen to be using one “type” of operating system performing the same functions, operating systems can be branched into several different types as well. Operating systems may be categorized by different standards. Here are some of common types:
• •
• •
Unit 3 Section 1
•
Zhang Ning: Well, there might many causes for system crash. One of them is software. The simplest operation like installing and uninstalling might cause a crash in system. Problems within the system may also do that, so you have to be very careful when deleting DLL files, modifying Windows registry, or upgrading the operating system. Another cause is the hardware problem. Have you tried backing up the files? It would be a great help in system restoration when the problem doesn’t lie in the hardware. Cheng Hong: The service personnel installed a ghost program for me when I bought the computer. Will I lose the data in my hard disk if it is restored? Qian Liang: Not except the data on C: drive, where files on your desktop or in My Documents are stored. You may move them into other locations with a bootable disk or under DOS if there are any. Cheng Hong: There are a lot of learning materials in My Documents and on the desktop. Would you please help me transfer them? It might save me the trouble of calling for customer services, and what’s more important, I’d learn a lot from you. Qian Liang: No problem.
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Chapter IManaging Real-TimeDistributed MultimediaApplicationsVana KalogerakiHewlett Packard Laboratory, USAMichael Melliar-Smith and Louise E. MoserUC Santa Barbara, USADistributed multimedia applications are characterized by timing constraints and end-to-end quality of service (QoS) requirements, and, therefore need efficient management mechanisms to respond to transient changes in the load or the availability of the resources. This chapter presents a real-time distributed multimedia framework, based on the Common Object Request Broker Architecture (CORBA), that provides resource management and Quality of Service (QoS) for CORBA applications. The framework consists of multimedia components and resource management components. The multimedia components produce multimedia streams, and combine multimedia streams generated by individual sources into a single stream to be received by the users. The resource management components provide QoS guarantees during multimedia transmissions based on information obtained from monitoring the usage of the system’s resources.INTRODUCTIONReal-time distributed multimedia environments have set forth new challenges in the management of processor and network resources. High-speed networks and powerful end-systems have enabled the integration of new types of multimedia applications, such as, video-on-demand, teleconferencing, distance learning and collaborative services, into today’s computer environments. Multimedia applications are variable in nature, as they handle a combination of continuous data (such as audio and video) and discrete data (such as text, images and control information) and impose strong requirements on data transmis-sion, including fast transfer and substantial throughput.Copyright © 2002, Idea Group Publishing.The technical requirements necessary to achieve timeliness are obviously more difficult to satisfy in distributed systems, mostly because of the uncertain delays in the underlying communication subsystem. This difficulty is further exacerbated by the hetero-geneity of today’s systems with respect to computing, storage and communication resources and the high levels of resource sharing that exist in distributed systems. Multimedia tasks may involve components located on several processors with limited processing and memory resources and with shared communication resources. Different transport mechanisms, such as TCP or UDP can be used for data transfer within local- or wide-area networks.Distributed object computing (DOC) middleware is software built as an independent layer between the applications and the underlying operating system to enable the applica-tions to communicate across heterogeneous platforms. At the heart of the middleware resides an object broker, such as the OMG’s Common Object Request Broker Architecture (CORBA), Microsoft’s Distributed Component Object Model (DCOM) or Sun’s Java Remote Method Invocation (RMI). Multimedia technologies can take advantage of the portability, location transparency and interoperability that middleware provides to enable efficient, flexible and scalable distributed multimedia applications.Developing a system that can provide end-to-end real-time and QoS support for multimedia applications in a distributed environment is a difficult task. Distributed multimedia applications are characterized by potentially variable data rates and sensi-tivity to losses due to the transmission of data between different locations in local- or wide-area networks and the concurrent scheduling of multiple activities with different timing constraints and Quality of Service (QoS) requirements. Several QoS architec-tures (Aurrecoechea & Campbell & Hauw, 1998) that incorporate QoS parameters (such as response time, jitter, bandwidth) and QoS-driven management mechanisms across architectural layers, have emerged in the literature. Examples include the QoS Broker, COMET’s Extended Integrated Reference Mode (XRM), the Heidelberg QoS model and the MAESTRO QoS management framework. Providing end-to-end QoS guaran-tees to distributed multimedia applications, requires careful orchestration of the proces-sor resources, as multimedia interactions may lead to excessive utilization and poor quality of service and multimedia applications can easily suffer quality degradation during a multimedia session caused by network saturation or host congestion. Efficient management of the underlying system resources is therefore essential to allow the system to maximize the utilization of the processors’ resources and to adapt to transient changes in the load or in the availability of the resources.The goals of this chapter are to present a distributed framework for coordinating and managing the delivery of real-time multimedia data. The framework manages the transmis-sion of real-time multimedia data and uses current resource measurements to make efficient management decisions.CORBAThe Common Object Request Broker Architecture (CORBA) (Object Management Group, 1999) developed by the Object Management Group (OMG) has become a widely accepted commercial standard for distributed object applications. CORBA provides an architecture and platform-independent programming interfaces for portable distributed object computing applications.The CORBA core includes an Object Request Broker (ORB) which acts as the message bus that provides the seamless interaction between client and server objects. CORBAInterface Definition Language (IDL) describes the functional interface to the objects and the type signatures of the methods that the object embodies. IDL interfaces are mapped onto specific programming languages (e.g., Java, C/C++, etc.). From the IDL specifications, an IDL compiler generates stubs and skeletons that are used for the communication between the client and server objects. Both the implementation details and the location of the server object are kept hidden from the client objects. Interoperability is achieved using the General Inter-ORB Protocol (GIOP) and the TCP/IP-specific Internet Inter-ORB Protocol (IIOP). CORBA’s independence from programming languages, computing platforms, and network-ing protocols makes it highly suitable for the development of distributed multimedia applications and their integration into existing distributed systems.RELATED WORKBecause of its general applicability, the OMG streaming standard (Object Manage-ment Group, 1997) has provoked interest in areas such as telecommunications, biomedicine, entertainment and security. McGrath & Chapman (1997) have successfully demonstrated that the A/V streaming specification can be used for telecommunication applications. Mungee & Surendran & Schmidt (1999) have developed an audio/video streaming service based on the OMG’s A/V Streams model.Several researchers have focused in providing QoS support for distributed multimedia applications. Hong & Kim & Park (1999) have defined a generic QoS Management Information Base (MIB) which consists of information objects that represent a set of layered QoS parameters, organized into four logical groups: service, application, system and network. Le Tien & Villin & Bac (1999) have used m-QoS and resource managers responsible for the QoS mapping and monitoring of multimedia applications and for managing the QoS of the resources.Waddington & Coulson (1997) have developed a Distributed Multimedia Component Architecture (MCA) that extends the CORBA and DCOM models to provide additional mechanisms and abstractions for continuous networked multimedia services. MCA exer-cises the use of those foundation object models by using object abstractions in the form of interfaces to encapsulate and abstract the functionality of multimedia devices and processing entities. MCA presents a solution which incorporates support for real-time continuous media interactions; configuration, control and QoS management of distributed multimedia ser-vices; dual control/stream interfaces and support for basic multimedia object services, including event handling, timer and callback services.Szentivanyi & Kourzanov (1999) have provided foundation objects that define different aspects of multimedia information management. Their approach is built on two notions: (1) a model that covers all related aspects of media management, such as storage, streaming, query, manipulation and presentation of information of several media-types, and (2) a distributed architecture that provides distribution, migration and access for the object model and its realization in a seamless, configurable and scalable manner.Several research efforts have concentrated in enhancing non-CORBA distributed multimedia environments with resource management capabilities. Alfano & Sigle (1996) discuss the problems they experienced at the host and network levels when executing multimedia applications with variable resource requirements. Nahrstedt & Steinmetz (1995) have employed resource management mechanisms, emphasizing on host and network resources, to guarantee end-to-end delivery for multimedia data transmission and to adaptwhen system resource overloading occurs. Rajkumar & Juvva & Molano & Oikawa (1998) have introduced resource kernels to manage real-time multimedia applications with different timing constraints over multiple resources.OVERVIEW OF THE MULTIMEDIAFRAMEWORKDesired FeaturesOur CORBA framework for managing real-time distributed multimedia applications is responsible for dynamic QoS monitoring and adaptation over changing processor and network conditions. End-users receive multimedia streams from different sources without the need to know the exact location of the sources or to have specialized processors to capture the multimedia data. The framework satisfies QoS requirements expressed by the users through a combination of system design choices (e.g., assigning priority/importance metrics to the multimedia objects) and physical configuration choices (e.g., allocating memory and bandwidth).The framework has the following design objectives:1.To reduce the cost and difficulty of developing multimedia applications. End usersshould be engaged with a convenient way of expressing their QoS requirements without having to address low-level implementation details. Information such as the port number or the host address of the endpoints should be kept transparent to the users.2.To satisfy the QoS requirements and to meet the timing constraints specified by theusers. User QoS requirements are translated into application-level parameters and are mapped into requirements for system-level resources. Providing QoS-mapping mecha-nisms is beneficial to the system because it is more systematic and therefore can largely reduce potential user errors. Monitoring functions determine QoS violations that can cause quality degradation and lead to poor system performance.3.To coordinate the transmission and synchronization of multimedia streams. Livesynchronization requires both intra-stream and inter-stream synchronization (Biersack & Geyer, 1999). Intra-stream synchronization refers to maintaining continuity withina single multimedia stream, while inter-stream synchronization refers to preservingthe temporal relationships between media units of related streams. Live synchroniza-tion requires the capture and playback/display of multimedia streams at run-time and, therefore, can tolerate end-to-end delay on the order of a few hundred milliseconds.4.To balance the load on the resources and to minimize system overheads. Dynamicconfiguration management is essential to deal with complex, scalable and evolving multimedia environments. Multimedia objects must be distributed evenly across the processors with respect to their resource requirements and dependency constraints. Structure of the FrameworkThe framework manages multimedia applications and the underlying system resources in an integrated manner. The framework consists of multimedia components for managing the transmission and delivery of multimedia data and resource management components for managing the multimedia components and monitoring the underlying system resources, as shown in Figure 1.Figure 1: The architectural components of the frameworkThe multimedia components consist of Suppliers that produce streams of multimedia data, a Coordinator that receives multimedia streams from different sources and combines them into a single stream, and Consumers that receive a single stream and separate the different flows in the stream for individual playback or display.The resource management components consist of Profilers that measure the usage of the resources, Schedulers that schedule the tasks of the multimedia objects and a Resource Manager that allocates the multimedia objects to the processors and takes appropriate actions to satisfy resource requirements.The Resource Manager is implemented as a set of CORBA objects that are allocated to various processors across the distributed system and replicated to increase reliability; logically, however, there is only a single copy of the Resource Manager. The Resource Manager maintains a global view of the system and is responsible for allocating the multimedia objects to the processors.The Resource Manager works in concert with the Profilers and the Schedulers. The Profiler on each processor monitors the behavior of the multimedia objects and measures the current load on the processors’ resources. It supplies information to the Resource Manager, which adapts the allocations over changing processing and networking conditions. The Scheduler on each processor exploits the information collected from the Resource Manager to schedule the multimedia objects on the processor.The multimedia components of the framework are implemented as a set of CORBA objects. The Resource Manager decides the location of those objects across the system based on the utilizations of the processors’ resources, the users’ QoS requirements and the communication among the multimedia objects. The Coordinator uses a reliable totally-ordered group communication system to multicast the multimedia data to the Consumers to achieve synchronization of the streams.QUALITY OF SERVICE FOR DISTRIBUTED MULTIMEDIA APPLICATIONS Quality of Service (QoS) represents the set of those quantitative and qualitative characteristics that are needed to realize the level of service expected by the users (Vogel & Kerherve & Bochmann & Gecsei, 1995). There are typically many layers that determine the actual end-to-end level of service experienced by an application. User QoS parameters are translated into application level parameters and are mapped into system-level (processor, network) parameters to control the system resources. The QoS mapping is still an open research issue, largely because there are numerous ways (Alfano & Sigle, 1996) to describe QoS for each layer. The QoS mapping is performed by the resource management compo-nents of the framework, which enables the user to specify QoS requirements without having to map the QoS parameters into parameters for the underlying layers. The QoS parameters are expressed as (name,value) pairs.User QoS ParametersTo enable users to express their QoS requirements in a simple and convenient manner, a graphical user interface is provided. User QoS parameters are specified in terms of a level of service (such as best effort or best quality) or properties that the user requires. The user must be prepared to pay a higher price when higher Quality of Service is desired. For example, a high-resolution video stream incurs a higher price in terms of increased delivery delay.User QoS requirements are expressed in terms of the media type (i.e., audio or video) and a set of media format parameters such as the color space or the data size (i.e., width and height) of an image, or the compression technique for the frames of a video stream. Users can also specify timing constraints such as start and end delivery times, the desired rate of transmission, the worst-case end-to-end delay and the maximum jitter. The QoS specified by the user includes media-specific parameters, if additional hardware or software con-straints are imposed.Application LayerApplication QoS parameters describe the characteristics of the media requested for transfer. Some of the user’s parameters (e.g., end-to-end delay, rate of transmission) can be used directly as application QoS parameters, while others are translated into QoS parameters for the application. For example, for a video stream, the frame size is determined by the image height, width and color of an uncompressed image as specified by the user, and is computed as Frame_size = Width * Height * Color_resolution.A multimedia application has an associated level of service metric, which is explicitly defined by the user or is determined by the resource management components of the framework based on the user’s QoS parameters and the other multimedia applications running in the system. In addition, priority metrics can be associated with the multimedia application as a whole or as individual frames. For example, in MPEG compression, video I-frames contain the most important information and, therefore, should have a higher priority than P-frames or B-frames. Application QoS parameters may also include media-specific information, such as the format of the video source (i.e., PAL or NTSC), the pixel data type, the compression pattern (i.e.,IBP pattern for MPEG-1 compression), the bit rate and the number of images to be skipped between captures for a video transmission. The rate oftransmission can be derived from the IMAGE_SKIP parameter and the format of the video source. The maximum number of buffers determines the maximum number of images that a video card can store.System LayerWhile perception of QoS can vary from user to user and from application to application, user and application QoS requirements must be translated into system param-eters in order to monitor and control the system resources.The processor layer determines whether there are sufficient resources to accommodate the user and application requirements. Typical parameters of this layer are the utilization of the CPU, the size of the memory, the available disk space, and the load imposed by special devices used for multimedia processing. This layer also encompasses the scheduling strategy used to schedule the multimedia objects on the processors’ resources.The network layer determines the transport requirements for the multimedia applica-tion, including the transport protocol to be used for the delivery of packets, and packet-related parameters such as packet size, priority, ordering, transfer rate, round-trip delay, packet error and loss rate. Different multimedia streams experience random delays in the delivery of multimedia data due to the heterogeneity of the underlying communication infrastructure. Ideally, the network would deliver the multimedia data as they are generated with minimal or bounded delay.DEVELOPING A DISTRIBUTED MULTIMEDIA FRAMEWORK FOR CORBACORBA A/V Streaming SpecificationThe CORBA A/V streaming specification (Object Management Group, 1997) defines a basic set of interfaces for implementing a multimedia framework that leverages the portability and flexibility provided by the middleware. The principal components of the framework are:1.Multimedia Device (MMDevice): A multimedia device abstracts one or more items ofhardware. Typical multimedia devices can be physical devices, such as a microphone,a video camera or a speaker, or logical devices, such as a video clip. A MMDevice canpotentially support a number of streams simultaneously. For each individual stream,a virtual device and a stream endpoint connection are created.2.Virtual Device (Vdev): A virtual multimedia device represents the device-specificaspects of a stream. Virtual devices have associated configuration parameters, such as the media format and the coding scheme of the transmitted stream. For instance, a video camera might be capable of transmitting both JPEG and MPEG formats in the data streams. A multimedia device can contain different virtual multimedia devices with different characteristics, and different virtual devices can refer to the same physical device.3.Stream Endpoint (StreamEndPoint): A stream endpoint terminates a stream within amultimedia device and represents the transport-specific parameters of the stream. A stream endpoint specifies the transport protocol and the host name and port number of the transmitting endpoints.4.Stream: A stream represents continuous media transfer between two or more virtualmultimedia devices. Each stream is supported by the creation of a virtual multimedia device and a stream endpoint connection representing the device specific and network specific aspects of a stream endpoint. A stream may contain multiple flows, each flow carrying data in one or both directions.5.Stream Controller (StreamCtrl): A stream controller abstracts continuous mediatransfer between virtual devices. It supports operations to control (start, stop) the stream as a whole or the individual flows within the stream. The StreamCtrl interface is used by the application programmer to set up and manage point-to-point or multipoint streams.Our framework uses the components of the A/V streaming specification as building blocks for the multimedia components. The advantage is that the A/V streaming specifica-tion allows the framework to hide the underlying implementation details. Multimedia Components of the FrameworkFigure 2 shows the UML representation of the multimedia components of the framework. The multimedia components are based on a three-layered object structure. Multimedia suppliers and consumers are represented by the Supplier and Consumer objects, respectively. Multimedia streams that originate from different Suppliers are transmitted to the Coordinator object for multiplexing as a single stream before being forwarded to the Consumers. The Coordinator object is a key component of our framework. It is responsible for the synchronization of the streams that the user wishes to receive so that individual buffers at the endpoints are not required.The SupplierThe Supplier (Figure 3) represents the stream endpoint from which the multimedia data are derived. The Supplier defines the media to be transferred using the MMDevice interface. Typical configuration parameters of the MMDevice object are the type (i.e., video camera, microphone) or the name (i.e.,“Star Wars”) of the media. The Supplier is implemented as a CORBA object and, therefore, can be located on any of the processors, but typically is associated with the physical location of the multimedia device. For example, to obtain live images from a camera or to listen to a live conversation, specific physical devices must be selected. On the other hand, to playback a video clip from a file, any of the processors can be chosen.The Supplier uses the virtual multimedia device (VDev) object to configure the specific flow transfer (i.e., by setting the video format for a video transfer) and the StreamEndPoint object to define the host address where the Supplier is located.The CoordinatorThe Coordinator (Figure 4) multiplexes different streams originating from different sources into a single stream to be transmitted to the Consumers. Specific transport parameters are associated with the Coordinator through the StreamEndPoint interface. These parameters define the host address where the Coordinator is located and the port number to which it listens. To accommodate a large number of consumers, different Coordinator objects can be configured to receive different multimedia streams. The Coordinator is an essential component of the framework and, therefore, is replicated for fault tolerance (Kalogeraki & Gunopulos, 2000).Figure 2: UML representation of the multimedia components of the frameworkFigure 3: The SupplierFigure 4: The CoordinatorFigure 5: The ConsumerThe ConsumerThe Consumer (Figure 5) receives a single stream of multimedia data from the Coordinator and separates the flows that originate from different sources. These flows are subsequently supplied to video and audio buffers to be viewed or played, respectively. Compressed video images must be decompressed before they are displayed by the Con-sumer.The Consumer is associated with the MMDevice interface, where multiple VDev objects can be created to represent the various flows that the object is expected to receive. Typical parameters of the VDev object are image displays and speakers. The host address where the Consumer is located is defined using the StreamEndPoint interface.RESOURCE MANAGEMENTMultimedia applications have high resource requirements, and lack of resource management mechanisms can lead to transmission problems with multimedia objects competing for limited unmanaged resources. Pre-planned allocations are usually notefficient because they can result in overloaded resources as the multimedia environment evolves over time. To provide efficient delivery of multimedia data, the framework employs resource management components that consist of a Profiler and a Scheduler for each processor and a global Resource Manager for the system (Kalogeraki & Moser & Melliar-Smith, 1999).The ProfilersThe Profiler for each processor measures the current load on the processor’s resources (i.e., CPU, memory, disk) and the bandwidth being used on the communication links. The Profiler also monitors the messages exchanged between the objects and uses the information extracted from the messages to measure the execution and communication times of the objects and compute the percentage of the resources used by the objects during execution. The Profilers supply their measurements as feedback to the Resource Manager.During operation, the Profilers may detect overloaded or insufficient resources to provide the Quality of Service required by the user. The QoS can change either because of an explicit request by the user (for example, when the user desires a higher level of service) or implicitly while the application executes.In both cases, the Profiler reports the monitored change of the QoS parameters to the Resource Manager which can initiate negotiation with the user so that alternative QoS parameters can be selected.The SchedulersThe Scheduler on each processor specifies an ordered list (schedule) for the method invocations on the objects on that processor, which defines how access to the CPU resources is granted. The schedule is based on the least-laxity scheduling algorithm. In least-laxity scheduling, the laxity of a task is defined as: Laxity = Deadline -Remaining_Computation_Time, where Deadline is the interval within which the task must be completed and Remaining_Computation_Time is the estimated remaining time to complete the multimedia task. The Scheduler calculates the Deadline and the Remaining_Computation_Time for each task, thus deriving the task laxity. The task with the least laxity is assigned the highest real-time priority, and tasks are then scheduled according to the real-time priorities assigned by the Scheduler.The Resource ManagerThe Resource Manager is implemented as a set of CORBA objects that are allocated to various processors across the distributed system. The Resource Manager objects are replicated for fault tolerance; logically, however, there is only a single logical copy of the Resource Manager in the system. All the replicas of the Resource Manager perform the same operations in the same order, and, therefore have the same state.The Resource Manager maintains a system profile that includes the physical configu-ration of the system (various resources along with their specific characteristics) and the multimedia objects running on the processors. As new requests are introduced, the Resource Manager determines whether it can satisfy those requests, by considering the available resources and the other multimedia applications running in the system. To make accurate decisions, the Resource Manager uses current system information, obtained from the Profilers, that increase the likelihood of meeting the QoS requirements specified by the user. For example, if a service requested by the user is available on more than one processor, the。