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外文文献原稿和译文原稿Sodium Polyacrylate:Also known as super-absorbent or “SAP”(super absorbent polymer), Kimberly Clark used to call it SAM (super absorbent material). It is typically used in fine granular form (like table salt). It helps improve capacity for better retention in a disposable diaper, allowing the product to be thinner with improved performance and less usage of pine fluff pulp. The molecular structure of the polyacrylate has sodium carboxylate groups hanging off the main chain. When it comes in contact with water, the sodium detaches itself, leaving only carboxylions. Being negatively charged, these ions repel one another so that the polymer also has cross-links, which effectively leads to a three-dimensional structure. It has hige molecular weight of more than a million; thus, instead of getting dissolved, it solidifies into a gel. The Hydrogen in the water (H-O-H) is trapped by the acrylate due to the atomic bonds associated with the polarity forces between the atoms. Electrolytes in the liquid, such as salt minerals (urine contains 0.9% of minerals), reduce polarity, thereby affecting superabsorbent properties, especially with regard to the superabsorbent capacity for liquid retention. This is the main reason why diapers containing SAP should never be tested with plain water. Linear molecular configurations have less total capacity than non-linear molecules but, on the other hand, retention of liquid in a linear molecule is higher than in a non-linear molecule, due to improved polarity. For a list of SAP suppliers, please use this link: SAP, the superabsorbent can be designed to absorb higher amounts of liquids (with less retention) or very high retentions (but lower capacity). In addition, a surface cross linker can be added to the superabsorbent particle to help it move liquids while it is saturated. This helps avoid formation of "gel blocks", the phenomenon that describes the impossibility of moving liquids once a SAP particle gets saturated.History of Super Absorbent Polymer ChemistryUn til the 1980’s, water absorbing materials were cellulosic or fiber-based products. Choices were tissue paper, cotton, sponge, and fluff pulp. The water retention capacity of these types of materials is only 20 times their weight – at most.In the early 1960s, the United States Department of Agriculture (USDA) was conducting work on materials to improve water conservation in soils. They developed a resin based on the grafting of acrylonitrile polymer onto the backbone of starch molecules (i.e. starch-grafting). The hydrolyzed product of the hydrolysis of this starch-acrylonitrile co-polymer gave water absorption greater than 400 times its weight. Also, the gel did not release liquid water the way that fiber-based absorbents do.The polymer came to be known as “Super Slurper”.The USDA gave the technical know how several USA companies for further development of the basic technology. A wide range of grating combinations were attempted including work with acrylic acid, acrylamide and polyvinyl alcohol (PVA).Since Japanese companies were excluded by the USDA, they started independent research using starch, carboxy methyl cellulose (CMC), acrylic acid, polyvinyl alcohol (PVA) and isobutylene maleic anhydride (IMA).Early global participants in the development of super absorbent chemistry included Dow Chemical, Hercules, General Mills Chemical, DuPont, National Starch & Chemical, Enka (Akzo), Sanyo Chemical, Sumitomo Chemical, Kao, Nihon Starch and Japan Exlan.In the early 1970s, super absorbent polymer was used commercially for the first time –not for soil amendment applications as originally intended –but for disposable hygienic products. The first product markets were feminine sanitary napkins and adult incontinence products.In 1978, Park Davis (d.b.a. Professional Medical Products) used super absorbent polymers in sanitary napkins.Super absorbent polymer was first used in Europe in a baby diaper in 1982 when Schickendanz and Beghin-Say added the material to the absorbent core. Shortly thereafter, UniCharm introduced super absorbent baby diapers in Japan while Proctor & Gamble and Kimberly-Clark in the USA began to use the material.The development of super absorbent technology and performance has been largely led by demands in the disposable hygiene segment. Strides in absorption performance have allowed the development of the ultra-thin baby diaper which uses a fraction of the materials – particularly fluff pulp – which earlier disposable diapers consumed.Over the years, technology has progressed so that there is little if any starch-grafted super absorbent polymer used in disposable hygienic products. These super absorbents typically are cross-linked acrylic homo-polymers (usually Sodium neutralized).Super absorbents used in soil amendments applications tend to be cross-linked acrylic-acrylamide co-polymers (usually Potassium neutralized).Besides granular super absorbent polymers, ARCO Chemical developed a super absorbent fiber technology in the early 1990s. This technology was eventually sold to Camelot Absorbents. There are super absorbent fibers commercially available today. While significantly more expensive than the granular polymers, the super absorbent fibers offer technical advantages in certain niche markets including cable wrap, medical devices and food packaging.Sodium polyacrylate, also known as waterlock, is a polymer with the chemical formula [-CH2-CH(COONa)-]n widely used in consumer products. It has the ability to absorb as much as 200 to 300 times its mass in water. Acrylate polymers generally are considered to possess an anionic charge. While sodium neutralized polyacrylates are the most common form used in industry, there are also other salts available including potassium, lithium and ammonium.ApplicationsAcrylates and acrylic chemistry have a wide variety of industrial uses that include: ∙Sequestering agents in detergents. (By binding hard water elements such as calcium and magnesium, the surfactants in detergents work more efficiently.) ∙Thickening agents∙Coatings∙Fake snowSuper absorbent polymers. These cross-linked acrylic polymers are referred to as "Super Absorbents" and "Water Crystals", and are used in baby diapers. Copolymerversions are used in agriculture and other specialty absorbent applications. The origins of super absorbent polymer chemistry trace back to the early 1960s when the U.S. Department of Agriculture developed the first super absorbent polymer materials. This chemical is featured in the Maximum Absorbency Garment used by NASA.译文聚丙烯酸钠聚丙烯酸钠，又可以称为超级吸收剂或者又叫高吸水性树脂，凯博利克拉克教授曾经称它为SAM即：超级吸收性物质。

北斗定位-毕业论文外文文献翻译

外文文献原稿和译文原稿Beidou positioningPrefaceNavigation satellite systems can provide all time, all weather and high accuracy positioning, navigation and timing services to users on the earth surface or in the near-earth space. It is an important space inf rastructure, which extends people’s range of activities and promotes social development. Satellite navigation is bringing up revolutionary changes to the world politics, economy, military, technology and culture.With a long history and a splendid culture, China is one of the important cradles of early human civilization. In ancient times, Chinese people used the Big Dipper (Beidou) for identifying directions, and invented the world’s first navigation device, the ancient compass (Sinan), which was a great contribution to the development of world civilization. In modern society, the Chinese-built BeiDou（COMPASS） system will become another contribution to the mankind.In early 1980s, China began to actively study the navigation satellite systems in line with C hina’s conditions. In 2000, BeiDou Navigation Demonstration System is basically established, which made China the third nation in possession of an independent navigation satellite system following the United States and Russia. At present, China is steadily accelerating the construction of the BeiDou Navigation Satellite System, and has already successfully launched 10 satellites so far.The BeiDou system will meet the demands of China’s national security, economic development, technological advances and social progress, safeguard national interests and enhance the comprehensive national strength. The BeiDou system will commit to providing stable, reliable and quality satellite navigation services for global users. Along with other GNSS providers, the BeiDou system will jointly promote the development of satellitenavigation industry, make contributions to human civilization and social development, serve the world and benefit the mankind.I. System DescriptionThe BeiDou system is comprised of three major components: space constellation, ground control segment and user terminals. The space constellation consists of five GEO satellites and 30 non-GEO satellites. The GEO satellites are positioned at 58.75°E, 80°E, 110.5°E, 140°E and 160°E respectively. The non-GEO satellites include 27 MEO satellites and three IGSO satellites. The MEO satellites are operating in an orbit with an altitudeof 21,500 km and an inclination of 55°, which are evenly distributed in three orbital planes. The IGSO satellites are operating in an orbit with an altitude of 36,000 km and an inclination of 55°, which are evenly distributed in three inclined geo-synchronous orbital planes. The subsatellite track for the three IGSO satellites are coincided while the longitude of the intersection point is at 118°E, with a phase difference of 120°.Ground control segment consists of several Master Control Stations (MCS), Upload Stations (US) and a network of globally distributed Monitor Stations (MS). The main tasks of MCS are to collect observing data from each MS, to process data, to generate satellite navigation messages, wide area differential data and integrity information, to perform mission planning and scheduling, and to conduct system operation and control. The main tasks of Upload Stations include completing the upload of satellite navigation messages, wide area differential data and integrity information, controlling and managing the payload. The tasks of Monitor Stations include continuous tracking and monitoring of navigation satellites, receiving navigation signals, sending observational data to the Master Control Station for the satellites orbit determination and time synchronization.The user terminals include various BeiDou user terminals, and terminals compatible with other navigation satellite systems, to meet different application requirements from different fields and industries.The time reference for the BeiDou Navigation Satellite System uses BeiDou Time (BDT). BDT’s length of second is a SI second. BDT was zero at 0:00:00 on Janu ary 1, 2006 Coordinated Universal Time (UTC). BDT is a continuous system, traceable to the UTC time maintained by the National Time Service Center (NTSC) of ChineseAcademy ofSciences, which is referred to as UTC (NTSC). The leap seconds with UTC information is broadcasted in the navigation messages. The difference between BDT and UTC maintains within 100ns.The coordinate framework of BeiDou system adopts China Geodetic Coordinate System 2000 (CGCS2000).Upon the full system completion, the BeiDou Navigation Satellite System can provide positioning, navigation and timing services to worldwide users. It can also provide wide area differential services with the accuracy of 1m and short messages services with the capacity of 120 Chinese characters each time.·Main functions: positioning, velocity measurement, one-way and two-way timing, short messages·Service area: global·Positioning accuracy: better than 10m·Velocity accuracy: better than 0.2m/s·Timing accuracy: 20nsII. System DevelopmentThe BeiDou system has followed the development concept of starting with regional services first and expanding to global services later. A three-step development strategy has been taken, with specifics as follows:Phase I: BeiDou Navigation Satellite Demonstration System. In 1994, Chinastarted the construction of BeiDou Navigation Satellite Demonstration System. In 2000, two BeiDou navigation experiment satellites were launched, and the BeiDou Navigation Satellite Demonstration System was basically established. In 2003, the third BeiDou navigation experiment satellite was launched, further enhancing the performance of the BeiDou Navigation Satellite Demonstration System.BeiDou Navigation Satellite Demonstration System consists of three major components: space constellation, ground control segment and user terminals. The space constellation includes three geostationary orbit (GEO) satellites, positioned at longitude of 80 degrees East, 110.5 degrees East and 140 degrees East respectively above the equator. Ground control segment consists of the ground control center and a number of calibrationstations. The ground control center is to complete satellite orbit determination, ionospheric correction, user location determination and user short message information exchange and processing. The calibration ground control stations are mainly to provide the distance measurement and correction parameters to the ground control center.The user terminals include the hand-held type, vehicle type, command type and other types of terminals, capable of position service application, location coordinates information receiving and other functions.The main functions and performance specifications of the BeiDou Navigation Satellite Demonstration System are as follows:·Main functions: positioning, one-way and two-way timing, short message communications;·Service Area: China and the surrounding areas;·Positioning Accuracy: better than 20 meters;·Timing Accuracy: 100 ns one-way, two-way 20 ns;·Short message communications: 120 Chinese characters per time.Phase II: BeiDou Navigation Satellite (regional) System. In 2004, Chinastarted construction of BeiDou Navigation Satellite System. In 2007, the first satellite, a round medium earth orbit satellite (COMPASS-M1) was launched. By 2012, the BeiDou system will consist of 14 satellites, including five GEO satellites, five IGSO satellites (two in-orbit spares), and four MEO satellites.The functions and performance parameters of BeiDou Navigation Satellite (regional) System are as follows:·Main functions: positioning, velocity measurement, one-way and two-way timing, short message communications;·Service Area: China and part of Asia- Pacific region ;·Positioning Accuracy: better than 10 meters;·Velocity Accuracy: better than 0.2 m/s;·Timing Accuracy: 50 ns;·Short message communications: 120 Chinese characters per message.Phase III: BeiDou Navigation Satellite System will completely be established by 2020.III. System ApplicationsSince it was officially brought into service in 2003, the BeiDou Navigation Satellite Demonstration System has been widely used in transportation, marine fisheries, hydrological monitoring, weather forecasting, forest fire prevention, timing for communication systems, power distribution, disaster mitigation, national security, and many other fields, which has been resulting in significant social and economic benefits. Particularly, the system has played an important role in the South China frozen disaster, earthquake relief in Wenchuan, SichuanProvince and Yushu, Qinghai Province, the Beijing Olympic Games, and the Shanghai World Expo.—In the field of transportation, built on the Beidou Navigation Satellite Demonstration System, applications such as Xinjiang Satellite Navigation Monitoring System of Public Transport, the Highway Infrastructure Safety Monitoring System, and the Port Scheduling High-precision Real-time Position Monitoring System, have promoted the BeiDou system and achieved a good demonstration effect.—In marine fisheries, built on the BeiDou Navigation Satellite Demonstration System, the marine fisheries integrated information service platform has provided vessel position monitoring, emergency rescue, information distribution, fishing boats in and out of port management and other services to the fishery administration departments.—The hydrological monitoring system, based on the BeiDou Navigation Satellite Demonstration System, has realized the real-time transmission of hydrological forecast information in mountainous regions, which has improved the accuracy o f the disaster forecasting and has helped the planning and scheduling programs for the flood and drought control.—In the field of weather forecasting, a series of BeiDou terminal equipment have been developed for weather forecast, and various practical and feasible system solutions have been worked out to address the automatic data transmission issues for the China Meteorological Administration and a number of local weather centers and stations.—In the field of forest fire prevention, the BeiDou Navigation Satellite Demonstration System has been successfully used in forest fire prevention system. Its positioning and short message communication services have achieved good results.—In the field of time synchronization for communication systems, the successful implementation of BeiDou two-way timing demonstration program has achieved breakthroughs in some key technical areas such as long distant fiber technology, and an integrated satellite-based timing system has been developed.—In the field of power distribution, built on the BeiDou Navigation Satellite Demonstration System, the successful implementation of power system time synchronization demonstration program has created basis for the high precision applications such as the electric accident analysis, the electricity early warning and protection systems.—In the field of disaster mitigation, the navigation, positioning, short message communications and position reporting capabilities of the BeiDou Navigation Satellite Demonstration System have provided services for the nationwide real-time disaster relief commanding and dispatching, emergency communications, rapid reporting and sharing of disaster information, which has significantly improved the rapid response of the disaster emergency relief and decision-making capability.Upon the full completion, the BeiDou Navigation Satellite System will provide more high-performance positioning, navigation, timing and short-message communication services for civil aviation, shipping, railways, finance, postal and other industries.IV. International Exchange and CooperationThe international exchange and cooperation for the BeiDou Navigation Satellite System will be carried out in an active and pragmatic way, which is in line withChina’s foreign policies, focusing on China's basic tasks and strategic objectives for the construction of navigation satellite systems, using the domestic and international markets and resources in a coordinated way. The international exchange and cooperation will be proceeded in a phased, focus-centered, non-discriminatory and selective approach in accordance with the overall development plan of China's navigation satellite system. It will be built upon the basis of equality, mutual benefit, mutual complementarity, peaceful utilization and mutual development and the generally accepted principles of the international laws.The BeiDou Navigation Satellite System adheres to the open and friendly attitude, and has already carried out extensive exchanges and consultation with the countries that have navigation satellite systems, to promote navigation satellite system compatibility and interoperability globally. Through the exchange and cooperation with countries that do not have a navigation satellite system, we also support their use of the existing resources globally and share the benefits of the satellite navigation development.China's international exchange and cooperation in the field of satellite navigation started in the 1990s. In nearly 20 years, various forms of activities have been carried out with extensive results.In 1994, under the framework of International Telecommunication Union(ITU),China started the BeiDou Navigation Satellite System frequency coordination activities. Satellite network information was submitted in accordance with the BeiDou system construction plan and progress. International frequency coordination has been carried out in a phased, step by step, focus-centered approach. China has actively participated bilateral frequency coordination activities with Europe, the UnitedStates and Russia, and has actively taken part in the World Radiocommunication Conference and the meetings of ITU study groups and working groups.China, as an important member of the International Committee on Global Navigation Satellite Systems (ICG), has participated in every ICG General Assembly Meeting and the ICG Providers Forum. In 2007, China became one of the four core providers designated by the organization. Focusing on compatibility and interoperability, China has carried out the extensive exchange and cooperation with the other navigation satellite systems in the world. The Technical Working Group (TWG) on compatibility and interoperability between BeiDou and Galileo was established. Until now, seven TWG meetings have been held.China actively participates, organizes and hosts international academic exchanges on satellite navigation, which include the American Institute of Navigation (ION) Conferences, the International Symposium on GPS/GNSS (ISGNSS), Munich Satellite Navigation Summit and other international conferences and forums. The China academic conferenceon satellite navigation is held annually, together with many other forums and seminars.China encourages and supports domestic research institutions, industrial enterprises, universities and social organizations, under the guidance of the government policy, to carry out international exchanges, coordination and cooperation activities with other countries and international organizations in the fields of the compatibility and interoperability, satellite navigation standards, coordinates frame, time reference, application development and scientific research. China has been actively engaged in international activities in terms of monitoring and assessment of open service for GNSS to promote the BeiDou Navigation Satellite System better serving the global users, and to promote the development of satellite navigation technology.ConclusionThe rapid development of the BeiDou Navigation Satellite System is attributedto China's reform and opening-up policy as well as the sustainable development of economy. As always, China will continue to promote the Global Navigation Satellite System construction and industrial development, to encourage the use of new satellite navigation technologies to provide new services, meeting the growing diversified needs of the people. By actively propelling international exchanges and cooperation, China will realize the compatibility and interoperability between the BeiDou Navigation Satellite System and other navigation satellite systems in the world. China will provide global customers with high performance and highly reliable positioning, navigation and timing services.The Launch Record of BeiDouNavigation Satellites·October 31, 2000, launch of 1st BeiDou navigation experiment satellite.·December 21, 2000, launch of 2nd BeiDou navigation experiment satellite.·May 25, 2003, launch of the 3rd BeiDou navigation experiment satellite.·February 3, 2007, launch of the 4th BeiDou navigation experiment satellite.·April 14, 2007, launch of the 1st BeiDou navigation satellite.·April 15, 2009, launch of the 2nd Beidou navigation satellite.·January 17, 2010, launch of the 3rd BeiDou navigation satellite.·June 2, 2010, launch of the 4th BeiDou navigation satellite.·August 1, 2010, launch of the 5th BeiDou navigation satellite.·November 1, 2010, launch of the 6th BeiDou navigation satellite. ·December 18, 2010, launch of the 7th BeiDou navigation satellite. ·April 10, 2011, launch of the 8th BeiDou navigation satellite. ·July 27, 2011, launch of the 9th BeiDou navigation satellite. ·December 2, 2011, launch of the 10th BeiDou navigation satellite.译文北斗定位前言卫星导航系统可以提供所有的时间，所有天气情况下用户在地球表面或近地空间的高精度定位、导航和授时服务。

外文文献及翻译

外文文献原稿和译文原稿DATABASEA database may be defined as a collection interrelated data store together with as little redundancy as possible to serve one or more applications in an optimal fashion .the data are stored so that they are independent of programs which use the data .A common and controlled approach is used in adding new data and in modifying and retrieving existing data within the data base .One system is said to contain a collection of database if they are entirely separate in structure .A database may be designed for batch processing , real-time processing ,or in-line processing .A data base system involves application program, DBMS, and database.THE INTRODUCTION TO DATABASE MANAGEMENT SYSTEMSThe term database is often to describe a collection of related files that is organized into an integrated structure that provides different people varied access to the same data. In many cases this resource is located in different files in different departments throughout the organization, often known only to the individuals who work with their specific portion of the total information. In these cases, the potential value of the information goes unrealized because a person in other departments who may need it does not know it or it cannot be accessed efficiently. In an attempt to organize their information resources and provide for timely and efficient access, many companies have implemented databases.A database is a collection of related data. By data, we mean known facts that can be recorded and that have implicit meaning. For example, the names, telephone numbers, and addresses of all the people you know. You may have recorded this data in an indexed address book, or you may have stored it on a diskette using a personalcomputer and software such as DBASE Ⅲor Lotus 1-2-3. This is a collection of related data with an implicit meaning and hence is a database.The above definition of database is quite general. For example, we may consider the collection of words that made up this page of text to be usually more restricted. A database has the following implicit properties:● A database is a logically coherent collection of data with some inherent meaning. A random assortment of data cannot be referred to as a database.● A database is designed, built, and populated with data for a specific purpose. It has an intended group of user and some preconceived applications in which these users are interested.● A database represents some aspect of the real world, sometimes called the miniworld. Changes to the miniworld are reflected in the database.In other words, a database has some source from which data are derived, some degree of interaction with events in the real world, and an audience that is actively interested in the contents of the database.A database management system (DBMS) is composed of three major parts: (1) a storage subsystem that stores and retrieves data in files; (2)a modeling and manipulation subsystem that provides the means with which to organize the data and to add, delete, maintain, and update the data; and (3) an interface between the DBMS and its users. Several major trends are emerging that enhance the value and usefulness of database management systems.●Managers who require more up-to-date information to make effective decisions.●Customers who demand increasingly sophisticated information services and more current information about the status of their orders, invoices, and accounts.●Users who find that they can develop custom applications with database systems in a fraction of the time it takes to use traditional programming languages.●Organizations that discover information has a strategic value; they utilize their database systems to gain an edge over their competitors.A DBMS can organize, process, and present selected data elements from the database. This capability enables decision makers to search, probe, and query database contents in order to extract answers to nonrecurring and unplanned questions that aren’t available in regular reports. These questions might initially be vague and/or p oorly defined, but people can “browse” through the database until they have the needed information. In short, the DBMS will “mange” the stored data items and assemble the needed items from the common database in response to the queries of those who aren’t programmers. In a file-oriented system, user needing special information may communicate their needs to a programmer, who, when time permits, will write one or more programs to extract the data and prepare the information. The availability of a DBMS, however, offers users a much faster alternative communications path.DATABASE QUERYIf the DBMS provides a way to interactively enter and update the database ,as well as interrogate it ,this capability allows for managing personal database. However, it does not automatically leave an audit trail of actions and does not provide the kinds of controls necessary in a multi-user organization .There controls are only available when a set of application programs is customized for each data entry and updating function.Software for personal computers that perform some of the DBMS functions has been very popular .Individuals for personal information storage and processing intended personal computers for us .Small enterprises, professionals like doctors, architects, engineers, lawyers and so on have also used these machines extensively. By the nature of intended usage ,database system on there machines are except from several of the requirements of full-fledged database systems. Since data sharing is not intended, concurrent operations even less so ,the software can be less complex .Security and integrity maintenance are de-emphasized or absent .as data volumes will be small, performance efficiency is also less important .In fact, the only aspect of a database system that is important is data independence. Data independence ,as stated earlier ,means that application programs and user queries need not recognize physical organization of data on secondary storage. The importance of this aspect , particularly for the personal computer user ,is that this greatly simplifies database usage . The user can store ,access and manipulate data at ahigh level (close to the application)and be totally shielded from the low level (close to the machine )details of data organization.DBMS STRUCTURING TECHNIQUESSpatial data management has been an active area of research in the database field for two decades ,with much of the research being focused on developing data structures for storing and indexing spatial data .however, no commercial database system provides facilities for directly de fining and storing spatial data ,and formulating queries based on research conditions on spatial data.There are two components to data management: history data management and version management .Both have been the subjects of research for over a decade. The troublesome aspect of temporal data management is that the boundary between applications and database systems has not been clearly drawn. Specifically, it is not clear how much of the typical semantics and facilities of temporal data management can and should be directly incorporated in a database system, and how much should be left to applications and users. In this section, we will provide a list of short-term research issues that should be examined to shed light on this fundamental question.The focus of research into history data management has been on defining the semantics of time and time interval, and issues related to understanding the semantics of queries and updates against history data stored in an attribute of a record. Typically, in the context of relational databases ,a temporal attribute is defined to hold a sequence of history data for the attribute. A history data consists of a data item and a time interval for which the data item is valid. A query may then be issued to retrieve history data for a specified time interval for the temporal attribute. The mechanism for supporting temporal attributes is to that for supporting set-valued attributes in a database system, such as UniSQL.In the absence of a support for temporal attributes, application developers who need to model and history data have simply simulated temporal attributes by creating attribute for the time interval ,along with the “temporal” attribute. This of course may result in duplication of records in a table, and more complicated search predicates in queries. The one necessary topic of research in history data management is to quantitatively establish the performance (and even productivity) differences betweenusing a database system that directly supports attributes and using a conventional database system that does not support either the set-valued attributes or temporal attributes.Data security, integrity, and independenceData security prevents unauthorized users from viewing or updating the database. Using passwords, users are allowed access to the entire database of the database, called subschemas. For example, an employee database can contain all the data about an individual employee, but one group of users may be authorized to view only payroll data, while others are allowed access to only work history and medical data.Data integrity refers to the accuracy, correctness, or validity of the data in the database. In a database system, data integrity means safeguarding the data against invalid alteration or destruction. In large on-line database system, data integrity becomes a more severe problem and two additional complications arise. The first has to do with many users accessing the database concurrently. For example, if thousands of travel agents book the same seat on the same flight, the first agent’s booking will be lost. In such cases the technique of locking the record or field provides the means for preventing one user from accessing a record while another user is updating the same record.The second complication relates to hardware, software or human error during the course of processing and involves database transaction which is a group of database modifications treated as a single unit. For example, an agent booking an airline reservation involves several database updates (i.e., adding the passenger’s name and address and updating the seats-available field), which comprise a single transaction. The database transaction is not considered to be completed until all updates have been completed; otherwise, none of the updates will be allowed to take place.An important point about database systems is that the database should exist independently of any of the specific applications. Traditional data processing applications are data dependent.When a DMBS is used, the detailed knowledge of the physical organization of the data does not have to be built into every application program. The application program asks the DBMS for data by field name, for example, a coded representationof “give me customer name and balance due” would be sent to the DBMS. Without a DBMS the programmer must reserve space for the full structure of the record in the program. Any change in data structure requires changes in all the applications programs.Data Base Management System (DBMS)The system software package that handles the difficult tasks associated with creating ,accessing and maintaining data base records is called a data base management system (DBMS). A DBMS will usually be handing multiple data calls concurrently.It must organize its system buffers so that different data operations can be in process together .It provides a data definition language to specify the conceptual schema and most likely ,some of the details regarding the implementation of the conceptual schema by the physical schema.The data definition language is a high-level language, enabling one to describe the conceptual schema in terms of a “data model “.At the present time ,there are four underling structures for database management systems. They are :List structures.Relational structures.Hierarchical (tree) structures.Network structures.Management Information System(MIS)An MIS can be defined as a network of computer-based data processing procedures developed in an organization and integrated as necessary with manual and other procedures for the purpose of providing timely and effective information to support decision making and other necessary management functions.One of the most difficult tasks of the MIS designer is to develop the information flow needed to support decision making .Generally speaking ,much of the information needed by managers who occupy different levels and who have different levels and have different responsibilities is obtained from a collection of exiting information system (or subsystems)Structure Query Language (SQL)SQL is a data base processing language endorsed by the American NationalStandards Institute. It is rapidly becoming the standard query language for accessing data on relational databases .With its simple ,powerful syntax ,SQL represents a great progress in database access for all levels of management and computing professionals.SQL falls into two forms : interactive SQL and embedded SQL. Embedded SQL usage is near to traditional programming in third generation languages .It is the interactive use of SQL that makes it most applicable for the rapid answering of ad hoc queries .With an interactive SQL query you just type in a few lines of SQL and you get the database response immediately on the screen.译文数据库数据库可以被定义为一个相互联系的数据库存储的集合。

外文文献原稿和译文

外文文献原稿和译文原稿MechanicalandRegenerativeBrakingIntegrationforaHybridElectricVehicleAbstract,namelyanelectricmotorandinternalcombustionengine,whichallowtheelimina tionofidling,,theaddedcostofthehybridelectricsystemhashinderedthesalesofth esevehicles.JapanNorth America automotive companieshavedevelopedandreleasedforsaletheirownhybridelectric unpredictablegasprices,thesalesofhybridelectricvehicleshaveincreaseddramat ically inrecentyears.2.1.1HybridConfigurationsForthepast100yearstheobjectiveofthehybridhasbeentoextendtherangeofelec tricvehiclesandtoovercometheproblemoflongrechargingtimes35.Therearethree ,par allelhybridsandseries/parallelhybrids.Eachconfigurationhasitsadvantagesanddisadvantageswhichwillbediscussedi nthefollowingsections.SeriesHybridsInserieshybridsthemechanicaloutputfromtheinternalcombustionengineisuse dto driveageneratorwhichproduceselectricalpowerthatcanbestoredinthebatteriesor highpowersystemssuchaslargetrucksorlocomotivesbutcanalsobeusedforlowerpowe rpassengervehicles18.2.1.2‘degreeofhybridization’toquantifytheelectrica lpowerpotentialofthesevehicles.ThedegreeofhybridizationrangesfromDOH=0foraconventionalvehicletoDOH=1f oranallelectricvehicle25.Asthedegreeofhybridizationincreases,asmallerICEcanbeusedandoperatedclosertoitsoptimumefficiencyforagreaterproportionoftheti me,.MicroHybrid MicrohybridshavethesmallestdegreeofhybridizationandusuallyconsistofanintegratedstartergeneratorISG2.1.31500 kg100 km/h0 km/h0 km/h50 km/h2.1.42.1.5译文混合动力电动汽车机械和再生制动的整合摘要为了减少对环境的污染和车辆的燃油消耗,混合动力电动汽车已经成为汽车工业的首选方法;混合动力电动汽车通过使用由电动马达和内燃发动机组成的混合动力系统来达到减少环境污染和燃油消耗的目的;混合动力系统消除了怠速,使发动机以一种更有效的方式运行,增加了再生制动的使用;但是,混合动力的成本的增加阻碍了这些车辆的销售;在这里提出一个更具成本效益的电液制动系统的设计;该系统使用电控机械结合的控制方式控制制动助力器产生的推动力,并有足够的时间反应;这个系统使驾驶员清楚地了解机械和再生制动力矩的混合,使再生制动力系统得到有效的控制;一个系统化的设计过程是其次,重点在于展示概念设计方案的可行性和使用虚拟和实物模型的初步设计功用;虚拟和实物模型的结合使用成为验证和开发系统的强大工具,本文将介绍和讨论在设计过程中模型所起到的作用;因为在设计过程中设计者可以获得相关的经验,提倡学生设计实物模型,以提高学生的学习经验;很明显,这正是本文所要提出的;现代混合动力电动汽车随着油价的上涨和环境保护意识的提高,消费者和政府迫使汽车行业开始生产省油和对环境污染小的汽车;一个有前景的方法就是现在实行的混合动力电动汽车;混合动力汽车指的是有两个或两个以上动力来源的车辆;混合动力汽车动力的来源可能有很多的不同,但是现在混合动力汽车最常见的布局是由内燃发动机和电动马达,能量储存系统共同输出动力,这样的车辆就叫混合动力电动汽车;汽车可以同时使用发动机和电动马达输出的动力,从而可以提高汽车的使用性能和效率,进而又可以提高燃油经济性,减少废气的排放,同时还能满足消费者对汽车性能的要求;1997年,丰田成普瑞斯为了第一款混合动力电动汽车,在日本进行了批量生产;本田公司花费了三年的时间进行混合动力电动车的生产,然后进军北美市场;丰田普瑞斯在北美发行几个月后,本田Insight紧随其后也在北美进行发行;混合动力电动车具有再生制动系统的独特优势;在制动过程,通常用于动力输出的电动马达,可以起到发电机的功用,把汽车的动能转化为蓄电池的电能,而不会转化为热能浪费掉;转换的电能可以储存到蓄电池中,然后可以作为电动马达驱动汽车使用的能量;考虑到蓄电池能量密度时,动能转换为电能这个过程就更加重要了;能量密度是指单位体积或质量下能量储存系统所储存的能量;为了说明这一点,我们可以做个对比,4.5公升的汽油通常可以维持一辆汽车行驶50千米;而要把相同的能量储存到蓄电池中,则需要一个质量约为270千克的铅酸蓄电池;这就说明了在汽车行驶过程中能够有效地储存再生制动系统产生的能量的重要性,从而可以保证在提高混合动力电能车性能的前提下,不至使能量储存系统所占体积过大;再生制动系统研究范围本文所提出的再生系统的研究范围是研究再生制动系统和机械制动系统之间相互作用的关系,目的是设计开发出一个低成本的再生制动系统,从而可以应用到未来经济型的混合动力电动汽车上;这个系统可以根据驾驶员的需要进而控制再生制动系统和机械制动系统产生的制动力矩的结合,还应该保证这个过程的平顺性和安全性;再生制动力矩是通过使用的异步电动机的矢量控制算法进行控制的;但是,独立地控制制动踏板产生的机械制动力矩,同时又要保持机械制动系在再生制动系统失效后起到备用作用,这是一个很大的难题;为了解决这个问题,需要研究一个通过减少制动主缸内制动液压来来控制机械制动系统产生的制动力矩的制动系统;混合电动汽车概述混合动力电动车已经成为了可以在短时间内减少汽车污染排放和提高燃油经济型的解决方法之一;在过去的10年几乎所有的主要汽车公司都已经向公众发行销售自己的混合动力电动汽车,混合动力电动汽车的普及和销售在这个世纪有了很明显的增长,随着不可预测的汽油价格的增长和对环境保护的关注,混合动力电动汽车的销售将在最近几年内急剧增长;2.1.1混合动力装置在过去100年来混合动力的研究目标是延长电动汽车的使用寿命,解决蓄电池的长期充电问题;在目前市场,现在主要有三种混合动力装置,这些混合动力装置为串联混合动力,并联混合动力,串并联混合动力;每一种动力装置都有其优点和缺点,这将在以后的章节进行讨论;串联混合动力串联混合动力汽车使用发动机输出的动力来驱动发电机产生电能,这些电能可以储存在蓄电池中,也可以用来驱动电动马达来驱动汽车;在串联混合动力汽车上,发动机和驱动轮之间没有直接的机械连接,串联混合动力往往在高功率系统中使用,如大型货车或火车,也可以应用到低功率的客运车辆上;发动机输出的机械能和蓄电池输出的电能可以通过电子控制器进行控制接合,然后这个电子控制器通过比较驾驶员所需的动力和汽车车速,电动马达输出的转矩,从而决定每个动力源驱动汽车行驶所要输出的能量;在制动过程中,这个电子控制装置可以使电能输出模式转换为再生模式,直接把再生制动系统产生的电能储存在蓄电池内;按照这种布置方式进行设计有很多的优点;发动机可以保持高效率的运行,使发动机产生的电能在蓄电池和驱动马达之间得到分配;发动机在其最高效率的工况下运行,排放可以大大降低,燃烧每体积的燃料可以产生更多的电能;因为串联动力装置结构简单且成本低,这种动力装置很容在汽车上落实;并联混合动力在并联混合动力汽车中,发动机输出的机械功传到变速箱中;发动机输出的机械功和电动马达输出的功在变速箱内进行机械式的接合,混合的机械功用于驱动汽车行驶;在这种混合动力装置结构中,发动机和驱动轮之间有直接的机械连接;在串联混合动力装置中,电子控制器通过比较驾驶员所需的动力和汽车车速,电动马达输出的转矩,从而决定每个动力源驱动汽车行驶所要输出的能量,以满足汽车行驶性能,获得最佳的效率;正如串联混合装置一样,并联混合动力也以相似的方法控制再生制动;并联混合动力装置通常应用到低功率的电动车中,这两种驱动力可以同时使用,提供更高的行驶性能;与串联混合动力系统相比,并联混合动力系统有很多优势;其中最重要的一项优势是效率高,因为在并联混合动力中,电能和机械能只需转换一次,而在串联混合动力中,电能和机械能需要两次转换;由于并联混合动力可以使发动机和电动马大产生的动力同时结合起来,在不损失汽车行驶性能的前提下,可以使用体积小的电动马达,同时也降低了油耗和排放;最后,并联混合动力汽车在行驶过程中只需使发动机运行,而不需要另一个发电机为蓄电池充电;串、并联混合动力串并联混合动力装置结合了串联和并联动力装置的特点;这种混合方式汽车通过使用动力分配装置来控制双动力源电动马达输出动力,发动机输出动力或者两者同时输出驱动汽车行驶;虽然这种装置形式可以获得串联混合动力装置和并联混合动力装置的优点,因为考虑到汽车实际行驶可能性,这种装置的控制算法会变得非常复杂; 2.1.2混合度现在道路上行驶的混合动力电动汽车大多是串联混合动力,并联混合动力,或者串并联混合动力,因此定义一个‘混合度’变量来评价混合动力电动汽车的电能潜能是非常有意义的;混合度变从传统车辆DOH=0到所有电动车DOH=1之间变化,随着混合度的增加,在汽车上可以使用一个比较小的发动机,同时发动机可以在最接近最佳效率的工况下运行很长的时间,这样就可以减少燃油的消耗和废气的排放;电动马达输出的功用P表emP表示;示,发动机输出的功用ice微混合动力微混合指的是最小混合度,通常是由一个连接到发动机曲轴的综合起动发电机组成;在加速和怠速过程中,综合起动发电机使发动机处于关闭状态,从而节约燃油;加速时,在燃油喷入汽缸之前,综合起动发电机使发动机的曲轴加速旋转;在加速过程中,综合起动发电机对发动机起动协助的作用,在制动过程中,综合起动发电机还可以作为发电机向蓄电池充电;和非混合动力汽车相比,微混合动力汽车的燃油经济性可以提高10%左右;轻混合动力轻混合动力和微混合动力结构相似,有一点不同的是其综合起动发电机是经过改进的,其输出的动力可以超过20KW;但是,轻混合动力的能量储存系统只能储存1KWh左右的能量;轻混合动力汽车只有一个很短的纯电动续航能力,但是可以在加速过程中给发动机提供很大的辅助作用;轻混合动力中的电子元件要比微混合动力中的电子元件复杂的多,且在汽车行驶过程中发挥着更大的作用;和非混合动力的汽车相比,轻混合动力汽车的燃油经济性可以提高20%-25%左右;全混合动力在全混合动力汽车上不再使用综合起动发电机,取代它的是一个独立的电动马达和交流发电机、起动机,这些装置也可以起到综合起动发电机的作用;电动马达可以独立驱动汽车行驶,尤其是在城市道路上走走停停的行驶;能量储存系统也得到了改进,这样就提高了汽车纯电动续航能力,减少了发动机的体积,从而提高燃油经济性和减少排放;与非混合动力汽车相比,全混合动力汽车的燃油消耗量可以减少40%-50%;插电式混合动力插电式混合动力汽车在结构上和全混合动力汽车相似,不同的是插电式混合动力汽车有一个比较大的能量储存系统,可以通过与外部电源连接进行充电;在蓄电池储存能量范围内,可以通过电动马达来驱动汽车行驶,但是当蓄电池的能量降到一定水平后,其运行形势就和全混合动力一样了;2.1.3再生制动原理混合动力电动汽车最重要的特点是可以回收大量的制动能量;在制动过程中,电动马达可以作为发电机来运行操作,将制动过程中的动能转换为电能储存到蓄电池中,这些电能就可以被汽车重复使用;但是,车辆的制动性能就将影响到汽车的安全性;在紧急制动状态下,汽车的制动距离要尽可能的短,还要保证制动时汽车有较好的方向稳定性;汽车具有较好的方向稳定性,就需要控制车轮的制动力分配;一般来说,制动时所需的制动力矩比电动马达产生的制动力矩大得多;因此,机械制动系统需要和电子再生制动系统同时存在,这就需要适当的设计以保证制动时的操作稳定性,不至于影响到汽车的安全性;制动时能量消耗由公式可得,一个质量为1500Kg的汽车以100km/h初速度制动到完全停止,需要消耗的动能;如果这些能量的25%可以通过再生制动系统进行回收,当忽略制动和加速过程中的空气阻力,机械摩擦和滚动阻力,假设电动马达的工作效率100%,利用公式可以估算出,这些能量可以使汽车从0km/h加速到50km/h.这就表明,当汽车行驶在城市道路上,汽车不停加速和制动,混合动力电动车的燃油经济性可以大大增加;需要注意的是,制动能量的回收量受到马达的型号和能量转换率的限制;2.1.4再生制动系统目前,通常使用的有两种再生制动方法;这些方法通常称为串联再生制动和并联制动,每种制动策略都有其优点和缺点,本文对此将进行具体讨论;并联再生制动在并联再生制动系统中,电动马达和机械制动系统同时工作,从而使汽车减速;因为机械制动系统不能独立的控制制动力,使制动时的能量转换为热能而不是电能,因此这不是最有效地再生制动方法;但是并联再生制动结构简单成本低,这就成为其一大优势;并联再生制动的机械制动系统只需要稍加修改,而且电动马达的控制算法也可以很容易在汽车上实现;这种制动方法还有一个额外的优势,当再生制动系统发生故障时,机械制动系统可以起到备用的作用;串联再生制动在串联再生制动中,电动马达只有在制动时才起作用;只有当电动马达和能量储存系统无法接受更多制动时所需的能量时,再生制动系统才起作用;串联再生制动需要独立的控制制动力矩,串联再生制动可以高效率的把动能转换为电能,这是其一项优势;但是它的不足之处在于,制动系统结构复杂,成本高;这种制动方式需要制动踏板模拟器,制动系统也需要重新设计,这都会增加其制造成本;因为制动系统需要装有传感器和信息处理器,这就会增加了结构的复杂度;2.1.5目前的再生制动系统目前大多数混合动力电动汽车的再生制动系统都是比较昂贵的电液制动系统;再生制动系统使用制动踏板模拟器来建立驾驶者的制动需求,这个制动踏板模拟器与液压制动电路独立分开;这样再将制动需求按照一定比例转换为再生制动和机械制动需求,然后将机械制动需求发送到由高压液压泵,蓄能器和比例控制阀的系统;比例控制阀根据制动需求,控制制动液以一定的预定值流到每个车轮的制动轮缸中;。

外文参考文献译文及原文【范本模板】

广东工业大学华立学院本科毕业设计（论文）外文参考文献译文及原文系部城建学部专业土木工程年级 2011级班级名称 11土木工程9班学号 23031109000学生姓名刘林指导教师卢集富2015 年5 月目录一、项目成本管理与控制 0二、Project Budget Monitor and Control (1)三、施工阶段承包商在控制施工成本方面所扮演的作用 (2)四、The Contractor’s Role in Building Cost Reduction After Design (4)一、外文文献译文（1）项目成本管理与控制随着市场竞争的激烈性越来越大,在每一个项目中，进行成本控制越发重要。

本文论述了在施工阶段,项目经理如何成功地控制项目预算成本。

本文讨论了很多方法。

它表明，要取得成功，项目经理必须关注这些成功的方法.1。

简介调查显示,大多数项目会碰到超出预算的问……功控制预算成本.2.项目控制和监测的概念和目的Erel and Raz (2000）指出项目控制周期包括测量成……原因以及决定纠偏措施并采取行动。

监控的目的就是纠偏措施的。

.。

标范围内。

3.建立一个有效的控制体系为了实现预算成本的目标，项目管理者需要建立一……被监测和控制是非常有帮助的。

项目成功与良好的沟通密。

决（ Diallo and Thuillier， 2005）.4.成本费用的检测和控制4.1对检测的优先顺序进行排序在施工阶段，很多施工活动是基于原来的计……用完了。

第四,项目管理者应该检测高风险活动，高风险活动最有。

..重要（Cotterell and Hughes, 1995)。

4.2成本控制的方法一个项目的主要费用包括员工成本、材料成本以及工期延误的成本。

为了控制这些成本费用，项目管理者首先应该建立一个成本控制系统：a)为财务数据的管理和分析工作落实责任人员b)确保按照项目的结构来合理分配所有的……它的变化-—在成本控制线上准确地记录所有恰..。

外文参考文献译文及原文

目录1介绍 (1)在这一章对NS2的引入提供。

尤其是，关于NS2的安装信息是在第2章。

第3章介绍了NS2的目录和公约。

第4章介绍了在NS2仿真的主要步骤。

一个简单的仿真例子在第5章。

最后，在第.8章作总结。

2安装 (1)该组件的想法是明智的做法，以获取上述件和安装他们的个人。

此选项保存downloadingtime和大量内存空间。

但是，它可能是麻烦的初学者，因此只对有经验的用户推荐。

(2)安装一套ns2的all-in-one在unix-based系统 (2)安装一套ns2的all-in-one在Windows系统 (3)3目录和公约 (4)目录 (4)4运行ns2模拟 (6)ns2程序调用 (6)ns2模拟的主要步骤 (6)5一个仿真例子 (8)6总结 (12)1 Introduction (13)2 Installation (15)Installing an All-In-One NS2 Suite on Unix-Based Systems (15)Installing an All-In-One NS2 Suite on Windows-Based Systems (16)3 Directories and Convention (17)Directories and Convention (17)Convention (17)4 Running NS2 Simulation (20)NS2 Program Invocation (20)Main NS2 Simulation Steps (20)5 A Simulation Example (22)6 Summary (27)1介绍网络模拟器(一般叫作NS2)的版本，是证明了有用在学习通讯网络的动态本质的一个事件驱动的模仿工具。

模仿架线并且无线网络作用和协议(即寻址算法，TCP，UDP)使用NS2，可以完成。

一般来说，NS2提供用户以指定这样网络协议和模仿他们对应的行为方式。

外文文献及译文格式模版

附件3：（本科毕业论文）文献、资料题目：院专班姓名：张三学号：2001888888指导教师：张九光翻译日期：2005.6.30山东建筑大学毕业设计（或毕业论文，二选一）外文文献及译文，the National Institute of Standards and Technology (NIST) has been working to develop a new encryption standard to keep government information secure ．The organization is in the final stages of an open process of selecting one or more algorithms ，or data-scrambling formulas ，for the new Advanced Encryption Standard (AES) and plans to make adecision by late summer or early fall ．The standard is slated to go into effect next year ． AES is intended to be a stronger ，more efficient successor to Triple Data Encryption Standard (3DES)，which replaced the aging DES ，which was cracked in less than three days in July 1998．“Until we have the AES ，3DES will still offer protection for years to come ．So there is no need to immediately switch over ，”says Edward Roback ， acting chief of the computer security division at NIST and chairman of the AES selection committee ．“What AES will offer is a more efficient algorithm ．It will be a federal standard ，but it will be widely implemented in the IT community ．”According to Roback ，efficiency of the proposed algorithms is measured by how fast they can encrypt and decrypt information ，how fast they can present an encryption key and how much information they can encrypt ．The AES review committee is also looking at how much space the algorithm takes up on a chip and how much memory it requires ．Roback says the selection of a more efficient AES will also result in cost savings and better use of resources ．“DES was designed for hardware implementations ，and we are now living in a world of much more efficient software ，and we have learned an awful lot about the design of algorithms ，”says Roback ．“When you start multiplying this with the billions of implementations done daily ，the saving on overhead on the networks will be enormous ．”……山东建筑大学毕业设计（或毕业论文，二选一）外文文献及译文- 2 -准，以确保政府的信息安全。

人工智能与专家系统外文文献译文和原文

人工智能与专家系统外文文献译文和原文AI研究仍在继续，但与MIS和DDS等计算机应用相比，研究热情的减弱使人工智能的研究相对落后。

然而，在研究方面的不断努力一定会推动计算机向人工智能化方向发展。

2．AI领域AI现在已经以知识系统的形式应用于商业领域，既利用人类知识来解决问题。

专家系统是最流行的基于知识的系统，他是应用计算机程序以启发方式替代专家知识。

Heuritic术语来自希腊eureka，意思是“探索”。

因此，启发方式是一种良好猜想的规则。

启发式方法并不能保证其结果如同DSS系统中传统的算法那样绝对化。

但是启发式方法提供的结果非常具体，以至于能适应于大部分情况启发式方法允许专家系统能像专家那样工作，建议用户如何解决问题。

因为专家系统被当作顾问，所以，应用专家系统就可以被称为咨询。

除了专家系统外，AI还包括以下领域：神经网络系统、感知系统、学习系统、机器人、AI硬件、自然语言处理。

注意这些领域有交叉，交叉部分也就意味着这个领域可以从另一个领域中收益。

3．专家系统的吸引力专家系统的概念是建立在专家知识能够存储在计算机中并能被其他人应用这一假设的基础上的。

专家系统作为一种决策支持系统提供了独无二的能力。

首先，专家系统为管理者提供了超出其能力的决策机会。

比如，一家新的银行投资公司可以应用先进的专家系统帮助他们进行选择、决策。

其次，专家系统在得到一个解决方案的同时给出一步步的推理。

在很多情况下，推理本身比决策的结果重要的多。

4．专家系统模型专家系统模型主要由4个部分组成：用户界面使得用户能与专家系统对话；推理引擎提供了解释知识库的能力；专家和工程师利用开发引擎建立专家系统。

1．用户界面用户界面能够方便管理者向专家系统中输入命令、信息，并接受专家系统的输出。

命令中有具体化的参数设置，引导专家系统的推理过程。

信息以参数形式赋予某些变量。

（1）专家系统输入现在流行的界面格式是图形化用户界面格式，这种界面与Window有些相同的特征。

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流动的：一个快速的，多平台的开放源码的同步化多媒体整合语言唱机Dick C.A. Bulterman, Jack Jansen, Kleanthis Kleanthous, Kees Blom and Daniel Benden CWI: Centrum voor Wiskunde en InformaticaKruislaan 4131098 SJ Amsterdam, The Netherlands+31 20 592 43 00Dick.Bulterman@cwi.nl摘要：本文概述了一个出现在早期的流动性的同步化多媒体唱机。

不同于其它同步化的实现，早期的播放器是一个可重组的同步化引擎，可以定制作为一个实验媒体播放器的核心。

同步化唱机是一个引用了同步化多媒体引擎并可以集成在一个广泛的媒体播放器的项目。

本文是以我们要创造一个新的同步化引擎为动机的综述开始的。

然后论述的是早期媒体播放器的核心架构（包括可扩展性，播放器自定义的集成装置）。

我们以一个关于我们在windows，Mac，Linux版本应用于台式机以及PDA设备上实施流动性例子的体验的讨论结束。

类别和主题描述符：H.5.2 多媒体的信息系统。

H.5.4 超级文本/超级媒体。

一般词汇：试验，性能，验证。

关键词：同步化多媒体整合语言，唱机，公开源代码，演示。

1.动机：早期公开的同步化媒体播放器是一个非常有特色的公开源代码的同步化 2.0播放器，它以研究团体的意图被使用（在我们的研究团体内外）目的是为了研究项目的团体在需要源代码的时候可以访问生产特性的同步化播放器的网站。

它也被用作一个独立的不需要专有的媒体格式的同步化播放器使用，播放器支持一系列同步化2.0配置文件（包括台式机和移动的配置）可以被分配利用在Linux，Macintosh，windows系统的台式机，PDA设备和掌上电脑。

同时现存的几个同步化播放器，包括网络视频播放软件,IE浏览器,小型同步化播放器, GRiNS ,X- GRiNS ，以及各种各样专有移动设备，我们发展流动性唱机有三个原因：准许制作数字以及个人或者课堂使用中的的全部硬拷贝即时没有提供拷贝权限或者商业性的利益分摊，而且在第一页有这种拷贝的注意事项。

服务器上有关于复制以及翻版的分发列表的通知。

需要事先明确具体的许可权以及费用。

早期的播放器所有的同步化工具，是以同步化2.0语言的属性为基础加上扩展功能能够支持高级的动画以及规范可移动设备以3GPP/PSS-6同步化使用.所有的同步化播放器都是针对商业SMIL表达专有媒介。

早期的播发器使用开源的媒体解码器和开源的网络传输协议,以便播放器可以轻松定制广泛的使用范围的研究计划。

我们的目标是建立一个鼓励发展类似的多媒体研究输出的平台,，我们期望的是一个标准的基线播放器的供给,其他研究人员和开发机构可以集中精力到基线播放器的集成扩展(从新媒体的解码器或新的网络控制算法任何一个中)。

这些扩展可以在其它的平台上被共享。

在2004年中期，与螺旋形客户机对照，同时移动到一个GPL核心，早期的播放器支持一个广阔的范围的同步化应用指标构架，它提供了一个准确实现的更完整的同步化语言，它在低资源配置下提供了更好的性能，提供了更多可扩展的媒体播放器架构。

它也提供了一个包含所有媒体解码作为部分开放的客户基础。

活动的目标社区不是媒体内容浏览器，而是多媒体设施开发者，协议和网络。

我们的目标是搞清楚在现有的部分SMIL实现中所产生的多组完整实施,支持甚至异乎寻常的特性的同步化语言。

下面段落提供的是一个播放器架构的介绍和描述的是这个国家的各种各样的流动的实现。

然后我们讨论流动的核心为什么能在其他的项目中使用。

我以一个流动的功能对SMIL的支持的讨论为开始。

2.对SMIL 2.0功能的支持：SMIL 2.0介绍了用于标准构成的50以上模块的10个功能组，这些模块详细补充说明了SMIL 2.0语言的30个XML元素和150个属性，除了定义模块之外，SMIL 2.0 规范也定义了一些SMIL配置文件：收集元素满足一个实现团体的特殊需要的指定面向软件的属性和属性值。

公用配置文件包括完整的SMIL 2.0语言，SMIL要素，3GPP SMIL,XHTML+SMIL和SMIL 1.0 配置文件。

这些配置文件的评论已经是这张纸力所不及的，但是流动发展已经提供了一个能被用作支持各种各样SMIL目标配置文件的自定义的播放器部件的关键核心。

这已经导致准许播放器几乎所有界面接口的一个架构，在某种程度上来说，调整适应的格局，日程安排，媒体处理使交互模块成行以满足个别的属性的需要。

流动的播放器是唯一支持这个构架的播放器。

流动的播放器提供了一种正确实现SMIL 2.0语言的属性，加上提供了对动画功能和定时控制增强模式扩展。

与其它商用的和非商业播放器比较，流动播放器工具不只是一个核心调度引擎，它也提供了完全支持SMIL布局，交互作用，完美控制和网络化设施。

迄今为止流动的装备最好SMIL语言最完整的实施对大多数SMIL语言有效。

3.流动的架构：这个章节提供一个流动核心架构的综述。

然而这个讨论是高水平的，它将提供足够的流动性演示。

3.1高级的接口结构：图1显示出最高水平播放器空想，播放器核心支持高水平控制外部的入口点（包括播放/停止/暂停）和依次管理一系列提供接口到数据来源的外部工厂。

不像其他的播放器视SMIL为一个数据类型,流动的引擎在输入/输出/屏幕/设备接口相互作用中扮演着一个中心的角色。

这个架构准许入口点的类型（而且瞬间评价）存在定制化以及把各种各样的数据输入源和渲染器分离出来。

3.2公共的服务层：图2显示的是一组被用来为播放器进行操作的公共服务。

它们包含操作系统界面，牵引体系界面和支持XML基线功能。

所有的这些服务都是流动性提供的；它们可能也被统一到其它播放器相关的项目或者它们可能被新的对特殊的设备或者算法最佳化的服务部件取代。

图2.流动性的一般服务层3.3播放器公共核心：图3 显示一个流动的公共核心架构抽象的视图。

视图本质上是单一的流动播放器的实体。

尽管只有一个极好的客体表露了各自的服务，在播放器的发展中多样可交互的实现已经被发展应用于所有物体（除了DOM 树）。

例如，多样调度已经发展到SMIL配置文件与操纵力的匹配。

在图形中的箭头表示一个抽象类依赖于其它抽象类提供的服务。

堆叠式箱子表示播放器的一个单一的将要包含多样混合级别执行抽象类的实例。

一个用于声音，一个用于图像，等等。

所有的堆叠式箱子抽象类伴随着一个工厂模式的运行创作所必须的具体的种类而发生。

大多数的播放器的实现是构筑平台独立。

我们将讨论这个平台独立的组成，它被5个单独的播放器实现重复利用。

播放器平台相关部分包括支持实际渲染,用户界面交互和数据源加工和控制。

当播放器活跃起来，这里有一个调度程序的单一实例和布局管理器，这两种依赖于DOM树对象。

多样的数据源实体和可播放的实体被创造. 它们与多样的抽象的渲染曲面相互作用. 这个可播放的抽象类是一个媒体调度接口节点(播放, 停止), 然而渲染器抽象类是一个索引(重新生成).当渲染器抽象类是牵引接口（重新生成），可播放的抽象类对于一个媒体节点是调度程序接口（开始，结束）。

注意不是所有的可演奏都是渲染器（音频，SMIL，动画）。

架构已经被设计为所有的部件都是按照一个供选择的实现可换的。

用这种方法，流动的核心能被迁移到一个专用的SMIL引擎或者一个不是SMIL引擎（比如支持MPEG-4或者其他规格）。

抽象的接口由播放器提供不需要一个“SMIL 在上面”的材料处理的模型。

抽象接口可以被用作其它高水平控制模型（比如在一个XHTML+SMIL 中实现），或者用于管理不是SMIL的低水平的给予补偿（比如时间文本）。

注意为了改进可读性说明，所有的辅助类（线程处理，几何学和颜色处理，等等），几个对于一般的理解不重要的类（播放器驱动引擎，转换滤镜，等等）已经在关系图中略去。

4.实现经历：这个分段将简单的回顾我们实现流动播放器的经历。

我们在SMIL发展中讨论实验平台的应用以及描述一套用来检验流动性播放器核心功能而创建的实验文档。

我们以一个在流动性播放器性能上的讨论结束。

4.1实现平台：一个SMIL配置文件已经被确定了各种各样的平台和设备，实行从台式设备分离出来到移动设备。

为了支持我们在分布式SMIL文档扩展的研究以及提供一个被用于其它研究工作的播放器，我们决定提供各种各样的SMIL实现用于流动的计划。

流动的核心为了给接下来的计划提供支持可被作为一个单一的C++源代码使用。

LINUX：我们的源代码包含制作的文件与RH-8 Linux平台一起使用。

我们为媒体使用FF-MPEG使用提供支持。

Macintosh：流动性支持苹果开发的X 10.3系统。

媒体渲染器可通过支持内部的API通道和FF-MPEG通道使用。

播放器用户界面使用标准的MAC约定和支持。

windows：流动性除了提供传统的Win32而且支持目前一代Windows平台。

它已经在XP系统上做了最广泛的测试(包括家庭机，企业机以及平板电脑）和win 2000系统。

媒体渲染器包含第三方和支持本地连续成像的媒质。

掌上电脑：流动性支持掌上电脑2000，掌上电脑2002以及windows Mobile 2003系统。

掌上电脑实现提供对基础成像，声音和文本工具的支持。

Linux PDA 支持：流动性提供对ZAURUS LINUX-PDA的支持。

媒体支持FF-MPEG库通道，UI支持QT通道。

媒体支持包括音频，图像和简单的文档。

在每一种实现中，我们已经把用于提供支持和控制功能的SMIL列入最初的计划重点。

我们未曾使媒体渲染器最佳化在流动性1.0中释放，但是期待在未来的版本中提供加强支持。

4.2 演示和测试套件：为了证实流动性播放器可以不通过标准的SMIL 测试组实现，几个重要的演示和测试文档已经被分布到播放器核心包括：欢迎界面：一个简短的基本演示包括定时描述，媒体渲染，转换以及动画。

NYC ：一个在台式设备和移动设备上简短的幻灯片放映演示了时间调度，转换以及媒体渲染。

消息：一个复杂的交互式新建文档测试链接，基础事件的激活，高级设计，定时以及媒体集成。

像NYC 一样，这个演示支持分化型的移动设备和台式设备。

链接：一系列的链接和交互式的测试案例。

闪光灯：一个交互式用户指南测验描述了客户化使用形式属性测试以及链接/交互式支持。