外文翻译及中文译文
Java编程语言外文翻译、英汉互译、中英对照
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外文翻译原文及译文学院计算机学院专业计算机科学与技术班级学号姓名指导教师负责教师Java(programming language)Java is a general-purpose, concurrent, class-based, object-oriented computer program- -ming language that is specifically designed to have as few implementation dependencies as possible. It is intended to let application developers "write once, run anywhere" (WORA), meaning that code that runs on one platform does not need to be recompiled to run on another. Java applications are typically compiled to byte code (class file) that can run on any Java virtual machine(JVM) regardless of computer architecture. Java is, as of 2012, one of the most popular programming languages in use, particularly for client-server web applications, with a reported 10 million users. Java was originally developed by James Gosling at Sun Microsystems (which has since merged into Oracle Corporation) and released in 1995 as a core component of Sun Microsystems' Java platform. The language derives much of its syntax from C and C++, but it has fewer low-level facilities than either of them.The original and reference implementation Java compilers, virtual machines, and class libraries were developed by Sun from 1991 and first released in 1995. As of May 2007, in compliance with the specifications of the Java Community Process, Sun relicensed most of its Java technologies under the GNU General Public License. Others have also developed alternative implementations of these Sun technologies, such as the GNU Compiler for Java and GNU Classpath.Java is a set of several computer software products and specifications from Sun Microsystems (which has since merged with Oracle Corporation), that together provide a system for developing application software and deploying it in across-platform computing environment. Java is used in a wide variety of computing platforms from embedded devices and mobile phones on the low end, to enterprise servers and supercomputers on the high end. While less common, Java appletsare sometimes used to provide improved and secure functions while browsing the World Wide Web on desktop computers.Writing in the Java programming language is the primary way to produce code that will be deployed as Java bytecode. There are, however, byte code compilers available forother languages such as Ada, JavaScript, Python, and Ruby. Several new languages have been designed to run natively on the Java Virtual Machine (JVM), such as Scala, Clojure and Groovy.Java syntax borrows heavily from C and C++, but object-oriented features are modeled after Smalltalk and Objective-C. Java eliminates certain low-level constructs such as pointers and has a very simple memory model where every object is allocated on the heap and all variables of object types are references. Memory management is handled through integrated automatic garbage collection performed by the JVM.An edition of the Java platform is the name for a bundle of related programs from Sun that allow for developing and running programs written in the Java programming language. The platform is not specific to any one processor or operating system, but rather an execution engine (called a virtual machine) and a compiler with a set of libraries that are implemented for various hardware and operating systems so that Java programs can run identically on all of them. The Java platform consists of several programs, each of which provides a portion of its overall capabilities. For example, the Java compiler, which converts Java source code into Java byte code (an intermediate language for the JVM), is provided as part of the Java Development Kit (JDK). The Java Runtime Environment(JRE), complementing the JVM with a just-in-time (JIT) compiler, converts intermediate byte code into native machine code on the fly. An extensive set of libraries are also part of the Java platform.The essential components in the platform are the Java language compiler, the libraries, and the runtime environment in which Java intermediate byte code "executes" according to the rules laid out in the virtual machine specification.In most modern operating systems (OSs), a large body of reusable code is provided to simplify the programmer's job. This code is typically provided as a set of dynamically loadable libraries that applications can call at runtime. Because the Java platform is not dependent on any specific operating system, applications cannot rely on any of the pre-existing OS libraries. Instead, the Java platform provides a comprehensive set of its own standard class libraries containing much of the same reusable functions commonly found in modern operating systems. Most of the system library is also written in Java. For instance, Swing library paints the user interface and handles the events itself, eliminatingmany subtle differences between how different platforms handle even similar components.The Java class libraries serve three purposes within the Java platform. First, like other standard code libraries, the Java libraries provide the programmer a well-known set of functions to perform common tasks, such as maintaining lists of items or performing complex string parsing. Second, the class libraries provide an abstract interface to tasks that would normally depend heavily on the hardware and operating system. Tasks such as network access and file access are often heavily intertwined with the distinctive implementations of each platform. The and java.io libraries implement an abstraction layer in native OS code, then provide a standard interface for the Java applications to perform those tasks. Finally, when some underlying platform does not support all of the features a Java application expects, the class libraries work to gracefully handle the absent components, either by emulation to provide a substitute, or at least by providing a consistent way to check for the presence of a specific feature.The success of Java and its write once, run anywhere concept has led to other similar efforts, notably the .NET Framework, appearing since 2002, which incorporates many of the successful aspects of Java. .NET in its complete form (Microsoft's implementation) is currently only fully available on Windows platforms, whereas Java is fully available on many platforms. .NET was built from the ground-up to support multiple programming languages, while the Java platform was initially built to support only the Java language, although many other languages have been made for JVM since..NET includes a Java-like language called Visual J# (formerly named J++) that is incompatible with the Java specification, and the associated class library mostly dates to the old JDK 1.1 version of the language. For these reasons, it is more a transitional language to switch from Java to the .NET platform, than a first class .NET language. Visual J# was discontinued with the release of Microsoft Visual Studio 2008. The existing version shipping with Visual Studio 2005will be supported until 2015 as per the product life-cycle strategy.In June and July 1994, after three days of brainstorming with John Gage, the Director of Science for Sun, Gosling, Joy, Naughton, Wayne Rosing, and Eric Schmidt, the team re-targeted the platform for the World Wide Web. They felt that with the advent of graphical web browsers like Mosaic, the Internet was on its way to evolving into the samehighly interactive medium that they had envisioned for cable TV. As a prototype, Naughton wrote a small browser, Web Runner (named after the movie Blade Runner), later renamed Hot Java.That year, the language was renamed Java after a trademark search revealed that Oak was used by Oak Technology. Although Java 1.0a was available for download in 1994, the first public release of Java was 1.0a2 with the Hot Java browser on May 23, 1995, announced by Gage at the Sun World conference. His announcement was accompanied by a surprise announcement by Marc Andreessen, Executive Vice President of Netscape Communications Corporation, that Netscape browsers would be including Java support. On January 9, 1996, the Java Soft group was formed by Sun Microsystems to develop the technology.Java编程语言Java是一种通用的，并发的，基于类的并且是面向对象的计算机编程语言，它是为实现尽可能地减少执行的依赖关系而特别设计的。
温室大棚智能传感器中英文外文翻译文献
温室大棚智能传感器中英文外文翻译文献(含：英文原文及中文译文)英文原文Smart Infrared Temperature SensorsP RayKeeping up with continuously evolving process technologies is a major challenge for process engineers. Add to that the demands of staying current with rapidly evolving methods of monitoring and controlling those processes, and the assignment can become quite intimidating. However, infrared (IR) temperature sensor manufacturers are giving users the tools they need to meet these challenges: the latest computer-related hardware, software, and communications equipment, as well as leading-edge digital circuitry. Chief among these tools, though, is the next generation of IR thermometers— the smart sensor.Today’s new smart IR sensors represent a union of two rapidly evolving sciences that combine IR temperature measurement with high-speed digital technologies usually associated with the computer. These instruments are called smart sensors because they incorporate microprocessors programmed to act as transceivers for bidirectional, serial communications between sensors on the manufacturing floor and computers in the control room (see Photo 1). And because the circuitry is smaller, the sensors are smaller, simplifying installation in tight orawkward areas. Integrating smart sensors into new or existing process control systems offers an immediate advantage to process control engineers in terms of providing a new level of sophistication in temperature monitoring and control.Integrating Smart Sensors into Process LinesWhile the widespread implementation of smart IR sensors is new, IR temperature measurement has been successfully used in process monitoring and control for decades (see the sidebar, “How Infrared Temperature Sensors Work,” below). In the past, if process engineers needed to ch ange a sensor’s settings, they would have to either shut down the line to remove the sensor or try to manually reset it in place. Either course could cause delays in the line, and, in some cases, be very dangerous. Upgrading a sensor usually required buying a new unit, calibrating it to the process, and installing it while the process line lay inactive. For example, some of the sensors in a wire galvanizing plant used to be mounted over vats of molten lead, zinc, and/or muriatic acid and accessible only by reaching out over the vats from a catwalk. In the interests of safety, the process line would have to be shut down for at least 24 hours to cool before changing and upgrading a sensor.Today, process engineers can remotely configure, monitor, address, upgrade, and maintain their IR temperature sensors. Smart models with bidirectional RS-485 or RS-232 communications capabilities simplifyintegration into process control systems. Once a sensor is installed on a process line, engineers can tailor all its parameters to fit changing conditions—all from a PC in the control room. If, for example, the ambient temperature fluctuates, or the process itself undergoes changes in type, thickness, or temperature, all a process engineer needs to do is customize or restore saved settings at a computer terminal. If a smart sensor fails due to high ambient temperature conditions, a cut cable, or failed components, its fail-safe conditions engage automatically. The sensor activates an alarm to trigger a shutdown, preventing damage to product and machinery. If ovens or coolers fail, HI and LO alarms can also signal that there is a problem and/or shut down the line.Extending a Sensor’s Useful LifeFor smart sensors to be compatible with thousands of different types of processes, they must be fully customizable. Because smart sensors contain EPROMs (erasable programmable read only memory), users can reprogram them to meet their specific process requirements using field calibration, diagnostics, and/or utility software from the sensor manufacturer.Another benefit of owning a smart sensor is that its firmware, the software embedded in its chips, can be upgraded via the communications link to revisions as they become available — without removing the sensor from the process line. Firmware upgrades extend the working life of asensor and can actually make a smart sensor smarter.The Raytek Marathon Series is a full line of 1- and 2-color ratio IR thermometers that can be networked with up to 32 smart sensors. Available models include both integrated units and fiber-optic sensors with electronic enclosures that can be mounted away from high ambient temperatures.(see Photo 1). Clicking on a sensor window displays the configuration settings for that particular sensor. The Windows graphical interface is intuitive and easy to use. In the configuration screen, process engineers can monitor current sensor settings, adjust them to meet their needs, or reset the sensor back to the factory defaults. All the displayed information comes from the sensor by way of the RS-485 or RS-232 serial connection.The first two columns are for user input. The third monitors the sensor’s parameters in real time. Some parameters can be changed through other screens, custom programming, and direct PC-to-sensor commands. Parameters that can be changed by user input include the following:∙Relay contact can be set to NO (normally open) or NC (normally closed).∙Relay function can be set to alarm or setpoint.∙Temperature units can be changed from degrees Celsius to degreesFahrenheit, or vice versa.∙Display and analog output mode can be changed for smart sensors that have combinedone- and two-color capabilities.∙Laser (if the sensor is equipped with laser aiming) can be turned on or off.∙Milliamp output settings and range can be used as automatic process triggers or alarms. ∙Emissivity (for one-color) or slope (for two-color) ratio thermometers values can be set. Emissivity and slope values for common metal and nonmetal materials, and instructions on how to determine emissivity and slope, are usually included with sensors.∙Signal processing defines the temperature parameters returned. Average returns an object’s average temperature over a period of time; peak -hold returns an object’s peak temperature either over a period of time or by an external trigger.∙HI alarm/LO alarm can be set to warn of improper changes in temperature. On some process lines, this could be triggered by a break in a product or by malfunctioning heater or cooler elements.∙Attenuation indicates alarm and shut down settings for two-color ratio smart sensors. In this example, if the lens is 95% obscured, an alarm warns that the temperature results might be losing accuracy (known as a “dirty window” alarm). More than 95% obscurity can trigger anautomatic shutdown of the process.Using Smart SensorsSmart IR sensors can be used in any manufacturing process in which temperatures are crucial to high-quality product.Six IR temperature sensors can be seen monitoring product temperatures before and after the various thermal processes and before and after drying. The smart sensors are configured on a high-speed multidrop network (defined below) and are individually addressable from the remote supervisory computer. Measured temperatures at all sensor locations can be polled individually or sequentially; the data can be graphed for easy monitoring or archived to document process temperature data. Using remote addressing features, set points, alarms, emissivity, and signal processing, information can be downloaded to each sensor. The result is tighter process control. Remote Online Addressability In a continuous process similar to that in Figure 2, smart sensors can be connected to one another or to other displays, chart recorders, and controllers on a single network. The sensors may be arranged in multidrop or point-to-point configurations, or simply stand alone.In a multidrop configuration, multiple sensors (up to 32 in some cases) can be combined on a network-type cable. Each can have its own “address,” allowing it to be configured separately with different operating parameters. Because smart sensors use RS-485 or FSK (frequency shiftkeyed) communications, they can be located at considerable distances from the control room computer — up to 1200 m (4000 ft.) for RS-485, or 3000 m (10,000 ft.) for FSK. Some processes use RS-232 communications, but cable length is limited to <100 ft.In a point-to-point installation, smart sensors can be connected to chart recorders, process controllers, and displays, as well as to the controlling computer. In this type of installation, digital communications can be combined with milliamp current loops for a complete all-around process communications package.Sometimes, however, specialized processes require specialized software. A wallpaper manufacturer might need a series of sensors programmed to check for breaks and tears along the entire press and coating run, but each area has different ambient and surface temperatures, and each sensor must trigger an alarm if it notices irregularities in the surface. For customized processes such as this, engineers can write their own programs using published protocol data. These custom programs can remotely reconfigure sensors on the fly—without shutting down the process line.Field Calibration and Sensor UpgradesWhether using multidrop, point-to-point, or single sensor networks, process engineers need the proper software tools on their personal computers to calibrate, configure, monitor, and upgrade those sensors.Simple, easy-to-use data acquisition, configuration, and utility programs are usually part of the smart sensor package when purchased, or custom software can be used.With field calibration software, smart sensors can be calibrated, new parameters downloaded directly to the sensor’s circuitry, and the sensor’s current parameters saved and stored as computer data files to ensure that a complete record of calibration and/or parameter changes is kept. One set of calibration techniques can include one-point offset and two- and three-point with variable temperatures:• One-point offset. If a single temperature is used in a particular process, and the sensor reading needs to be offset to make it match a known temperature, one-point offset calibration should be used. This offset will be applied to all temperatures throughout the entire temperature range. For example, if the known temperature along a float glass line is exactly 1800°F, the smart sensor, or series of sensors, can be calibrated to that temperature.• Two-point. If sensor readings must match at two specific temperatures, the two-point calibration shown in Figure 3 should be selected. This technique uses the calibration temperatures to calculate a gain and an offset that are applied to all temperatures throughout the entire range. • Three-point with variable temperature. If the process has a wide range of temperatures, and sensor readings need to match at threespecific temperatures, the best choice is three-point variable temperature calibration (see Figure 4). This technique uses the calibration temperatures to• Three points If the process has a wi de temperature range, the sensor reading must meet three specific temperatures. The best choice is a three-point temperature calibration. This technique uses the calibration temperature to calculate two gains and two offsets. The first gain and offset apply to all temperatures below the midpoint temperature and at all midpoints above the second plate. Three-point calibration is less common than multiple single-dot, but occasionally manufacturers need to implement this technology to meet specific standards.On-site calibration software also allows the use of routine diagnostic methods, including power supply voltage and relay tests that are run on smart sensors. The result is that the process engineer knows that the sensor works best and it makes it easier to do some necessary troubleshooting.3. ConcludesThe new generation of intelligent infrared temperature sensors requires process engineers to keep up with changes brought about by new production technologies and increased production. They can now configure as many sensors as possible to meet the needs of their particular control process and extend the lifespan of these sensors, far beyond theprevious “not smart” designs. Due to the increased production speed, equipment downtime must be reduced. By monitoring equipment as much as possible and fine-tuning temperature variables without the need for shutdown processes, engineers can maintain efficient processes and deliver high-quality products. The digital processing components and communication capabilities of smart infrared sensors provide a degree of flexibility, security, and ease of use that have not been achieved to date.Infrared (IR) radiation is an electromagnetic spectrum that includes radio waves, microwaves, visible light, and ultraviolet light, as well as gamma rays and X-rays. The IR is between the visible part of the spectrum and radio waves. Infrared wavelengths are usually expressed in micrometers and the spectral range is from 0.7 to 1000 microns. Only the 0.7-14 micron band is used for infrared temperature measurement.Using advanced optical systems and detectors, non-contact infrared thermometers can focus on almost any part or part of the 0.7-14 μm band. Because each object (except blackbody) emits the best infrared energy at a specific point along the infrared wavelength of the line, each process may require a unique sensor model with specific optics and detector types. For example, a sensor, a narrow concentration of polyethylene and related materials concentrated in the 3.43 μm spectral ran ge suitable for measuring surface temperature. A sensor is set at 5 microns to measure the glass surface. Light sensors are used for metal and metal foils. Thebroader spectral range is used to measure lower temperature surfaces such as paper, cardboard, poly, and aluminum foil composites.An object reflects the increase or decrease of emission infrared energy through its temperature. It is emitted energy, measured at the target emissivity, which indicates the temperature of an object.Emissivity is a term used to quantify the energy and light emitting properties of different materials and surfaces. Infrared sensors have an adjustable emissivity setting, usually from 0.1 to 1.0, allowing accurate measurement of several surface types of temperature. The emitted energy comes from an object and reaches the infrared sensor through its optical system, which focuses on one or more light-sensitive detectors on the energy source. The detector's infrared energy is then converted into electrical signals, which in turn are converted into temperature values based on the sensor's calibration equation and the target's emissivity. This temperature value can be displayed on the sensor or converted to a digital output in a smart sensor and displayed on the computer terminal.中文译文智能红外温度传感器P Ray跟上不断发展的工艺技术对工艺工程师来说是一向重大挑战。
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。
关于杜邦分析法的外文翻译
外文资料及中文译文作者姓名***专业财务管理指导教师姓名***专业技术职务副教授外文资料FIVE WAYS TO IMPROVE RETURN ON EQUITYThe Du Pont Model: A Brief HistoryThe use of financial ratios by financial analysts, lenders, academic researchers, and small business owners has been widely acknowleged in the literature. (See, for example, Osteryoung & Constand (1992), Devine & Seaton (1995), or Burson (1998) The concepts of Return on Assets (ROA hereafter) and Return on Equity (ROEhereafter) are important for understanding the profitability of a business enterprise. Specifically, a “return on” ratio illustrates the relationship between profits and the investment needed to generate those profits. However, these concepts are often “too far removed from normal activities” to be easily understood and useful to many managers or small business owners. (Slater and Olson, 1996)In 1918, four years after he was hired by the Du Pont Corporation to work in its treasury department, electrical engineer F. Donaldson Brown was given the task of untangling the finances of a company of which Du Pont had just purchased 23 percent of its stock. (This company was General Motors!) Brown recognized a mathematical relationship that existed between two commonly computed ratios, namely net profit margin (obviously a profitability measure) and total asset turnover (an efficiency measure), and ROA. The product of the net profit margin and total asset turnover equals ROA, and this was the original Du Pont model, as illustrated in Equation 1 below.Eq. 1: (net income / sales) x (sales / total assets) = (net income / total assets) i.e. ROAAt this point in time maximizing ROA was a common corporate goal and the realization that ROA was impacted by both profitability and efficiency led to the development of a system of planning and control for all operating decisions within a firm. This became the dominant form of financial analysis until the 1970s. (Blumenthal, 1998)In the 1970s the generally accepted goal of financial management became “maximizing the wealth of the firm’s owners” (Gitman, 1998) and focus shifted from ROA to ROE. This led to the first major modification of the original Du Pontmodel. In addition to profitability and efficiency, the way in which a firm financed its activities, i.e. its use of “leverage” became a third area of attention for financial managers. The new ratio of interest was called the equity multiplier, which is (total assets / equity). The modified Du Pont model is shown in Equations 1 and 2 below.Eq. 2: ROA x (total assets / equity) = ROEEq. 3: (net income / sales) x (sales / total assets) x (total assets / equity) = ROE The modified Du Pont model became a standard in all financial management textbooks and a staple of introductory and advanced courses alike as students read statements such as: “Ultimately, the most important, or“bottom line” accounting ratio is the ratio of net income to common equity (ROE).” (Brigham and Houston, 2001)The modified model was a powerful tool to illustrate the interconnectedness of a firm’s income statement and its balance sheet, and to develop straight-forward strategies for improving the firm’s ROE.More recently, Hawawini and Viallet (1999) offered yet another modification to the Du Pontmodel. This modification resulted in five different ratios that combine to form ROE. In their modification they acknowlege that thefinancial statements firms prepare for their annualreports (which are of most importance to creditorsand tax collectors) are not always useful tomanagers making operating and financialdecisions. (Brigham and Houston, p. 52) T heyrestructured the traditional balance sheet into a“managerial balance sheet” which is “a moreappropriate tool for assessing the contribution ofoperating decisions to the firm’s financialperformance.” (Hawawini and Viallet, p.68)This restructured balanc e sheet uses the conceptof “invested capital” in place of total assets, andthe concept of “capital employed” in place oftotal liabilities and owner’sequity found on thetraditional balance sheet. The primary differenceis in the treatment of the short-ter m “workingcapital” accounts. The managerial balance sheet uses a net figure called “working capital requirement” (determined as: [accounts receivable + inventories + prepaid expenses] – [accounts payable + accrued expenses]) as a part of invested capital. These accounts then individually drop out of the managerial balance sheet. A more detailed explanation of the managerial balance sheet is beyond the scope of this paper, but will be partially illustrated in an example. The “really” modified Du Pont mode l is shown below in Equation 4.Eq. 4: (EBIT / sales) x (sales / invested capital) x (EBT / EBIT) x (invested capital / equity) x (EAT / EBT) = ROE(Where: invested capital = cash + working capital requirement + net fixed assets) This “really” modified model still maintains the importance of the impact of operating decisions (i.e. profitability and efficiency) and financing decisions (leverage) upon ROE, but uses a total of five ratios to uncover what drives ROE and give insight to how to improve this important ratio.The firm’s operating decisions are those that involve the acquisition and disposal of fixed assets and the management of the firm’s operating assets (mostly inventories and accounts receivable) and operating liabilities (accountspayable and accruals). These are captured in thefirst two ratios of the “really” modified Du Pontmodel. These are:1. operating profit margin: (Earnings Before Interest & Taxes or EBIT / sales)2. capital turnover: (sales / invested capital)The firm’s financing decisions are those that determine the mix of debt and equity used to fund the firm’s operating decisions. These are captured in the third and fourth ratios of the “really” modified model. These are:3. financial cost ratio: (Earnings Before Taxes or EBT / EBIT)4. financial structure ratio: (invested capital / equity)The final determinant of a firm’s ROE is the incidence of business taxation. The higher the taxrate applied to a firm’s EBT, the lower its ROE. This is cap tured in the fifth ratio ofthe “really”modified model.5. tax effect ratio: (Earnings After Taxes or EAT / EBT)The relationship that ties these five ratios together is that ROE is equal to their combined product. (See Equation 4.)Example of A pplying the “Really” Modified Du Pont ModelTo illustrate how the model works, consider the income statement and balance sheet for the fictitious small firm of Herrera & Company, LLC.Income StatementNet Sales …………………………………………………….. $766,990C ost of Goods Sold ………………………………………….. (560,000) Selling, General, & Administrative Expenses ………………. (143,342) Depreciation Expense ……………………………………….. (24,000) Earnings Before Interest & Taxes …………………………… $ 39,648Interest Expense ……………………………………………... (12,447) Earnings Before Taxes ………………………………………. $ 27,201Taxes ………………………………………………………… (8,000) Earnings After Taxes (net profit) ……………………………. $ 19,201Balance SheetCash ……………………….$ 40,000 Notes Payable ………………… $ 58,000 Pre-paid Expenses ………... 12,000 Accounts Payable …………….. 205,000 Accounts Receivable ……… 185,000 Accrued Expenses ……………. 46,000 Inventory ………………….. 200,000 Current Liabilities ……………. $309,000 Current Assets ……………. $437,000 Long-Term DebtL and/Buildings …………… 160,000 Mortgage ……………………. 104,300Equipment ………………… 89,000 8-Year Note ………………… 63,000Less: Acc. Depreciation …... (24,000) Owner’s Equity ……………….. 185,700Net Fixed Assets ………….. $225,000 Total Liabilities & Equity …….. $662,000 Total Assets ………………. $662,000Computation of ROE1. Operating Profit Margin = $39,648 / $766,990 = .05172. Capital Turnover = $766,990 / $411,000* = 1.86623. Financial Cost Ratio = $27,201 / $39,648 = .68614. Financial Structure Ratio = $411,000 / $185,700 = 2.21325. Tax Effect Ratio = $19,201 / $27,201 = .7059ROE = .0517 x 1.8662 x .6861 x 2.2132 x .7059 = .1034** or 10.34%* Invested Capital = Cash ($40,000) + Working Capital Requirement [$185,000 + $200,000 + $12,000] –[$205,000 + $46,000] (or $146,000) + Net Fixed Assets ($225,000) = $411,000** Note that this is the same as conventional computation of ROE: $19,201 / $185,700 = .1034Conclusions & ImplicationsThe “really” modified Du Pont model of ratio analysis can demystify relatively complex financial analysis and put strategic financial planning at the fingertips of any small business owner or manager who takes the (relatively little) time needed to understand it. Each operating and financial decision can be made within a framework of how that decision will impact ROE. Easily set up on a computer model (such as a spreadsheet), one can see how decisions “flow through” to the bottom line, which facilitates coordinated financial planning. (Harrington & Wilson,1986).In its simplest form, we can say that to improve ROE the only choices one has are to increase operating profits, become more efficient in using existing assets to generate sales, recapitalize to make better use of debt and/or better control the cost of borrowing, or find ways to reduce the tax liability of the firm. Each of these choices leads to a different financial strategy.For example, to increase operating profits one must either increase sales (in a higher proportionthan the cost of generating those sales) or reduce expenses. Since it is generally more difficult toincrease sales than it is to reduce expenses, a small business owner can try to lower expenses by determining: 1) if a new supplier might offer equivalent goods at a lower cost, or 2) if a website might be a viable alternative to a catalog, or 3) can some tasks currently being done by outsiders be done in-house. In each case net income will rise without any increase in sales and ROE will rise as well. Alternatively, to become more efficient, one must either increase sales with the same level of assets or produce the same level of sales with less assets. A small business owner might then try to determine: 1) if it is feasible to expand store hours by staying open later or on weekends, or 2) if a less expensive piece of equipment is available that could replace an existing (more expensive) piece of equipment, or 3) if there is a more practical way to produce and/or deliver goods or services than is presently being used.Further, small business owners can determine if they are using debt wisely. Refinancing an existing loan at a cheaper rate will reduce interest expenses and, thus, increase ROE. Exercising some of an unused line of credit can increase the financial structure ratio with a corresponding increase in ROE. And, taking advantage of tax incentives that are often offered by federal, state,and local taxing authorities can increase the tax effect ratio, again with a commensurate increase in ROE.In conclusion, ROE is the most compre-hensive measure of profitability of a firm. It considers the operating and investing decisions made as well as the financing andtax-related decisions. The “really” modified Du Pont model dissects ROE into five easily computed ratios that can be examined for potential strategies for improvement. It should be a tool that all business owners, managers, and consultants have at their disposal when evaluating a firm and making recommendations for improvement.中文译文真实修改的杜邦分析：五种方式改善股东权益回报率杜邦模型：简史运用财务比率进行分析已经被财务分析家，贷款人，学术研究人员和小企业主在文献资料里广泛运用。
车牌识别外文文献翻译中英文
外文文献翻译(含：英文原文及中文译文)文献出处：Gao Q, Wang X, Xie G. License Plate Recognition Based On Prior Knowledge[C]// IEEE International Conference on Automation and Logistics. IEEE, 2007:2964-2968.英文原文License Plate Recognition Based On Prior KnowledgeQian Gao, Xinnian Wang and Gongfu XieAbstract - In this paper, a new algorithm based on improved BP (back propagation) neural network for Chinese vehicle license plate recognition (LPR) is described. The proposed approach provides a solution for the vehicle license plates (VLP) which were degraded severely. What it remarkably differs from the traditional methods is the application of prior knowledge of license plate to the procedure of location, segmentation and recognition. Color collocation is used to locate the license plate in the image. Dimensions of each character are constant, which is used to segment the character of VLPs. The Layout of the Chinese VLP is an important feature, which is used to construct a classifier for recognizing. The experimental results show that the improved algorithm is effective under the condition that the license plates were degraded severely.Index Terms - License plate recognition, prior knowledge, vehiclelicense plates, neural network.I. INTRODUCTIONV ehicle License-Plate (VLP) recognition is a very interesting but difficult problem. It is important in a number of applications such as weight-and-speed-limit, red traffic infringement, road surveys and park security [1]. VLP recognition system consists of the plate location, the characters segmentation, and the characters recognition. These tasks become more sophisticated when dealing with plate images taken in various inclined angles or under various lighting, weather condition and cleanliness of the plate. Because this problem is usually used in real-time systems, it requires not only accuracy but also fast processing. Most existing VLP recognition methods [2], [3], [4], [5] reduce the complexity and increase the recognition rate by using some specific features of local VLPs and establishing some constrains on the position, distance from the camera to vehicles, and the inclined angles. In addition, neural network was used to increase the recognition rate [6], [7] but the traditional recognition methods seldom consider the prior knowledge of the local VLPs. In this paper, we proposed a new improved learning method of BP algorithm based on specific features of Chinese VLPs. The proposed algorithm overcomes the low speed convergence of BP neural network [8] and remarkable increases the recognition rate especially under the condition that the license plate images were degrade severely.II. SPECIFIC FEA TURES OF CHINESE VLPSA. DimensionsAccording to the guideline for vehicle inspection [9], all license plates must be rectangular and have the dimensions and have all 7 characters written in a single line. Under practical environments, the distance from the camera to vehicles and the inclined angles are constant, so all characters of the license plate have a fixed width, and the distance between the medium axes of two adjoining characters is fixed and the ratio between width and height is nearly constant. Those features can be used to locate the plate and segment the individual character. B. Color collocation of the plateThere are four kinds of color collocation for the Chinese vehicle license plate .These color collocations are shown in table I.TABLE IMoreover, military vehicle and police wagon plates contain a red character which belongs to a specific character set. This feature can be used to improve the recognition rate.C. Layout of the Chinese VLPSThe criterion of the vehicle license plate defines the characters layout of Chinese license plate. All standard license plates contain Chinese characters, numbers and letters which are shown in Fig.1. The first one is a Chinese character which is an abbreviation of Chineseprovinces. The second one is a letter ranging from A to Z except the letter I. The third and fourth ones are letters or numbers. The fifth to seventh ones are numbers ranging from 0 to 9 only. However the first or the seventh ones may be red characters in special plates (as shown in Fig.1). After segmentation process the individual character is extracted. Taking advantage of the layout and color collocation prior knowledge, the individual character will enter one of the classes: abbreviations of Chinese provinces set, letters set, letters or numbers set, number set, special characters set.(a)Typical layout(b) Special characterFig.1 The layout of the Chinese license plateIII. THE PROPOSED ALGORITHMThis algorithm consists of four modules: VLP location, character segmentation, character classification and character recognition. The main steps of the flowchart of LPR system are shown in Fig. 2.Firstly the license plate is located in an input image and characters are segmented. Then every individual character image enters the classifier to decide which class it belongs to, and finally the BP network decides which character the character image represents.A. Preprocessing the license plate1) VLP LocationThis process sufficiently utilizes the color feature such as color collocation, color centers and distribution in the plate region, which are described in section II. These color features can be used to eliminate the disturbance o f the fake plate ’ s regions. The flowchart of the plate location is shown in Fig. 3.Fig.3 The flowchart of the plate location algorithmThe regions which structure and texture similar to the vehicle plate are extracted. The process is described as followed:Here, the Gaussian variance is set to be less than W/3 (W is the character stroke width), so 1P gets its maximum value M at the center of the stroke. After convolution, binarization is performed according to a threshold which equals T * M (T<0.5). Median filter is used to preserve the edge gradient and eliminate isolated noise of the binary image. An N * N rectangle median filter is set, and N represents the odd integer mostly close to W.Morphology closing operation can be used to extract the candidate region. The confidence degree of candidate region for being a license plate is verified according to the aspect ratio and areas. Here, the aspect ratio is set between 1.5 and 4 for the reason of inclination. The prior knowledge of color collocation is used to locate plate region exactly. The locating process of the license plate is shown in Fig. 4.2) Character segmentationThis part presents an algorithm for character segmentation based on prior knowledge, using character width, fixed number of characters, the ratio of height to width of a character, and so on. The flowchart of the character segmentation is shown in Fig. 5.Firstly, preprocess the license the plate image, such as uneven illumination correction, contrast enhancement, incline correction and edge enhancement operations; secondly, eliminating space mark which appears between the second character and the third character; thirdly, merging the segmented fragments of the characters. In China, all standard license plates contain only 7 characters (see Fig. 1). If the number of segmented characters is larger than seven, the merging process must be performed. Table II shows the merging process. Finally, extracting the individual character’ image based on the number and the width of the character. Fig. 6 shows the segmentation results. (a) The incline and broken plate image, (b) the incline and distort plate image, (c)the serious fade plate image, (d) the smut license plate image.where Nf is the number of character segments, MaxF is the number of the license plate, and i is the index of each character segment.The medium point of each segmented character is determined by:(3)where 1i Sis the initial coordinates for the character segment, and 2i S is thefinal coordinate for the character segment. The d istance between two consecutive medium points is calculated by:(4)Fig.6 The segmentation resultsB. Using specific prior knowledge for recognitionThe layout of the Chinese VLP is an important feature (as described in the section II), which can be used to construct a classifier for recognizing. The recognizing procedure adopted conjugate gradient descent fast learning method, which is an improved learning method of BP neural network[10]. Conjugate gradient descent, which employs a series of line searches in weight or parameter space. One picks the first descent direction and moves along that direction until the minimum in error is reached. The second descent direction is then computed: this direction the “ conjugate direction” is the one along which the gr adient does not change its direction will not “ spoil ” the contribution from the previous descent iterations. This algorithm adopted topology 625-35-N as shown in Fig. 7. The size of input value is 625 (25*25 ) and initial weights are with random values, desired output values have the same feature with the input values.As Fig. 7 shows, there is a three-layer network which contains working signal feed forward operation and reverse propagation of error processes. The target parameter is t and the length of network outputvectors is n. Sigmoid is the nonlinear transfer function, weights are initialized with random values, and changed in a direction that will reduce the errors.The algorithm was trained with 1000 images of different background and illumination most of which were degrade severely. After preprocessing process, the individual characters are stored. All characters used for training and testing have the same size (25*25 ).The integrated process for license plate recognition consists of the following steps:1) Feature extractingThe feature vectors from separated character images have direct effects on the recognition rate. Many methods can be used to extract feature of the image samples, e.g. statistics of data at vertical direction, edge and shape, framework and all pixels values. Based on extensive experiments, all pixels values method is used to construct feature vectors. Each character was reshaped into a column of 625 rows’ feature vector. These feature vectors are divided into two categories which can be used for training process and testing process.2) Training modelThe layout of the Chinese VLP is an important feature, which can be used to construct a classifier for training, so five categories are divided. The training process of numbers is shown in Fig. 8.As Fig. 8 shows, firstly the classifier decides the class of the inputfeature vector, and then the feature vector enters the neural network correspondingly. After the training process the optimum parameters of the net are stored for recognition. The training and testing process is summarized in Fig. 9.(a) Training process(b)Testing processFig.9 The recognition process3) Recognizing modelAfter training process there are five nets which were completely trained and the optimum parameters were stored. The untrained feature vectors are used to test the net, the performance of the recognition system is shown in Table III. The license plate recognition system is characterized by the recognition rate which is defined by equation (5).Recognition rate =(number of correctly read characters)/ (number of found characters) (5)IV. COMPARISON OF THE RECOGNITION RA TE WITH OTHER METHODSIn order to evaluate the proposed algorithm, two groups of experiments were conducted. One group is to compare the proposed method with the BP based recognition method [11]. The result is shown in table IV. The other group is to compare the proposed method with themethod based on SVM [12].The result is shown in table V. The same training and test data set are used. The comparison results show that the proposed method performs better than the BP neural network and SVM counterpart.V. CONCLUSIONIn this paper, we adopt a new improved learning method of BP algorithm based on specific features of Chinese VLPs. Color collocation and dimension are used in the preprocessing procedure, which makes location and segmentation more accurate. The Layout of the Chinese VLP is an important feature, which is used to construct a classifier for recognizing and makes the system performs well on scratch and inclined plate images. Experimental results show that the proposed method reduces the error rate and consumes less time. However, it still has a few errors when dealing with specially bad quality plates and characters similar to others. This often takes place among these characters (especially letter and number): 3—8 4—A 8—B D—0.In order to improve the incorrect recognizing problem we try to add template-based model [13] at the end of the neural network.中文译文基于先验知识的车牌识别Qian Gao, Xinnian Wang and Gongfu Xie摘要- 本文介绍了一种基于改进的BP（反向传播）神经网络的中国车牌识别（LPR）算法。
汽车发动机外文文献翻译中英文参考
汽车发动机外文文献翻译(含：英文原文及中文译文)文献出处：Talom M. AUTOMOTIVE ENGINE[J]. Applied Thermal Engineering, 2013, 2(3):39-45.英文原文AUTOMOTIVE ENGINETalom M1 Engine Classification and Overall MechanicsThe automobile engines can be classified according to: (1) cycles, (2) cooling system, (3) fuel system, (4) ignition method, (5) valve arrangement, (6) cylinder arrangement, (7) engine speed.Engines used in automobiles are the internal combustion heat engines. The burning of gasoline inside the engine produces high pressure in the engine combustion chamber. This high pressure force piston to move, the movement is carried by connecting rods to the engine crankshaft. The crankshaft is thus made to rotate: the rotary motion is carried through the power train to the car wheels so that they rotate and the car moves.The engine requires four basic systems to run (Fig. 2-1). Diesel engines require three of these systems. They are fuel system, ignition system (except diesel), lubricating system andcooling system. However, three other related systems are also necessary. These are the exhaust system, the emission-control system, and the starting system. Each performs a basic job in making the engine run.2 Engine Operating PrinciplesThe term “stroke” is used to describe the movem ent of the piston within the cylinder. The movement of the piston from its uppermost position (TDC, top dead center) to its lowest position (BDC, bottom dead center) is called a stroke. The operating cycle may require either two or four strokes to complete. Most automobile engines operate on the four stroke cycle.In four-stroke engine, four strokes of the piston in the cylinder are required to complete one full operating cycle. Each stroke is named after the action. It performs intake, compression, power, and exhaust in that order.The intake strokeThe intake stroke begins with the piston near the top of its travel. As the piston begins its descent, the exhaust valve closes fully, the intake valve opens and the volume of the combustion chamber begins to increase, creating a vacuum. As the piston descends, an air/fuel mixture is drawn from the carburetor into the cylinder through the intake manifold. The intake stroke endswith the intake valve close just after the piston has begun its upstroke.Compression strokeAs the piston is moved up by the crankshaft from BDC, the intake valve closes. The air/fuel mixture is trapped in the cylinder above the piston. Future piston travel compresses the air/fuel mixture to approximately one-eighth of its original volume (approximately 8:1 compression ratio) when the piston has reached TDC. This completes the compression stroke. Power strokeAs the piston reaches TDC on the compression stroke, an electric spark is produced at the spark plug. The ignition system delivers a high-voltage surge of electricity to the spark plug to produce the spark. The spark ignites, or sets fire to, the air/fuel mixture. It now begins to burn very rapidly, and the cylinder pressure increases to as much as 3-5MPa or even more. This terrific push against the piston forces it downward, and a powerful impulse is transmitted through the connecting rod to the crankpin on the crankshaft. The crankshaft is rotated as the piston is pushed down by the pressure above it.Exhaust strokeAt the end of the power stroke the camshaft opens theexhaust valve, and the exhaust stroke begins. Remaining pressure in the cylinder, and upward movement of the piston, force the exhaust gases out of the cylinder. At the end of the exhaust stroke, the exhaust valve closes and the intake valve opens, repeating the entire cycle of events over and over again.3 Engine Block and Cylinder HeadEngine BlockThe engine block is the basic frame of the engine. All other engine parts either fit inside it or fasten to it. It holds the cylinders, water jackets and oil galleries (Fig. 2-4). The engine block also holds the crankshaft, which fastens to the bottom of the block. The camshaft also fits in the block, except on overhead-cam engines. In most cars, this block is made of gray iron, or an alloy (mixture) of gray iron and other metals, such as nickel or chromium. Engine blocks are castings.Some engine blocks, especially those in smaller cars, are made of cast aluminum. This metal is much lighter than iron. However, iron wears better than aluminum. Therefore, the cylinders in most aluminum engines are lined with iron or steel sleeves. These sleeves are called cylinder sleeves. Some engine blocks are made entirely of aluminum.Cylinder SleevesCylinder sleeves are used in engine blocks to provide a hard wearing material for pistons and piston rings. The block can be made of one kind of iron that is light and easy to cast while the sleeves uses another that is better able to stand up wear and tear.There are two main types of sleeves: dry and wet (Fig. 2-5).Dry sleeve Wet sleeveCylinder HeadThe cylinder head fastens to the top of the block, just as a roof fits over a house. The underside forms the combustion chamber with the top of the piston. In-line engine of light vehicles have just one cylinder head for all cylinders; larger in-line engines can have two or more. Just as with engine blocks, cylinder heads can be made of cast iron or aluminum alloy. The cylinder head carries the valves, valve springs and the rockers on the rocker shaft, this part of valve gear being worked by the pushrods. Sometimes the camshaft is fitted directly into the cylinder head and operates on the valves without rockers. This is called an overhead camshaft arrangement.GasketThe cylinder head is attached to the block with high-tensile steel studs. The joint between the block and the head must begas-tight so that none of the burning mixture can escape. This is achieved by using cylinder head gasket. Gaskets are also used to seal joins between the other parts, such as between the oil pan, manifolds, or water pump and the blocks.Oil PanThe oil pan is usually formed of pressed steel. The oil pan and the lower part of cylinder block together are called the crankcase; they enclose, or encase, the crankshaft. The oil pump in the lubricating system draws oil from the oil pan and sends it to all working parts in the engine. The oil drains off and run down into the pan. Thus, there is a constant circulation of oil between the pan and the working parts of the engine.4 Piston Assembly, piston rings, The piston pin ,Connecting Rods, Crankshafts And FlywheelPistonPiston rings and the piston pin are together called the piston assembly.The piston is an important part of a four-stroke cycle engine. Most pistons are made from cast aluminum. The piston, through the connecting rod, transfers to the crankshaft the force created by the burning fuel mixture. This force turns the crankshaft.To withstand the heat of the combustion chamber, the piston must be strong. It also must be light, since it travels at high speeds as it moves up and down inside the cylinder. The piston is hollow. It is thick at the top where it takes the brunt of the heat and the expansion force. It is thin at the bottom, where there is less heat. The top part of the piston is the head, or crown. The thin part is the skirt. Most pistons have three ring grooves at the top. The sections between the ring grooves are called ring lands.piston ringsPiston rings fit into ring grooves near the top of the piston. In simplest terms, piston rings are thin, circular pieces of metal that fit into grooves in the tops of the pistons. In modern engines, each piston has three rings. (Piston in older engines sometimes had four rings, or even five.) The inside surface of the ring fits in the groove on the piston. The ring's outside surface presses against the cylinder walls. Rings provide the needed seal between the piston and the cylinder walls. That is, only the rings contact the cylinder walls. The top two rings are to keep the gases in the cylinder and are called compression rings. The lower one prevents the oil splashed onto the cylinder bore fro m entering the combustion chamber, and is called an oil ring.The piston pinThe piston pin holds together the piston and the connecting rod. This pin fits into th e piston pin holes and into a hole in the top end of the connecting rod. The top end of t he rod is much smaller than the end that fits on the crankshaft. This small end fits inside the bottom of the piston. The piston pin fits through one side of the piston, through the small end of the rod, and then through the other side of the piston. It holds the rod firmly in place in the center of the piston. Pins are made of high-strength steel and have a hollow center. Many pins are chrome-plated to help them wear better. A piston pin fits into a round hole in the piston. The piston pin joins the piston to the connecting rod. The thick part of the piston that holds the piston pin is the pin boss. Connecting RodsThe connecting rod little end is connected to the piston pin.A bush made from a soft metal, such as bronze, is used for this joint. The lower end of the connecting rod f its the crankshaft journal. This is called the big end. For this big-end bearing, steel-backed lead or tin shell bearings are used. These are the same as those used for the main bearings. The split of the big end is sometimes at an angle, so that it is small enough t o be withdrawn through the cylinder bore. The connecting rod ismade from forged alloy steel.CrankshaftsThe crankshaft is regarded as the “backbone” of the engine (Fig. 2-7). The crankshaft, in conjunction with the connecting rod, converts the reciprocating motion of the piston to the rotary motion needed to drive the vehicle. It is usually made from car-bon steel which is alloyed with a small proportion of nickel. The main bearing journals fit into the cylinder block and the big end journals align with the connecting rods. At the rear end of the crankshaft is attached the flywheel, and at the front end are the driving wheels for the timing gears, fan, cooling water and alternator. The throw of the crankshaft, . the distance between the main journal and the big end centers, controls the length of the stroke. The stroke is double the throw, and the stroke length is the distance that the piston travels from TDC to BDC and vice versa.中文译文汽车发动机Talom M1发动机分类和一般力学（1）循环，（2）冷却系统，（3）燃料系统，（4）点火方法，（5）阀门布置，（6）气缸布置，（7）发动机速度。
步行机器人中英文对照外文翻译文献
步行机器人中英文对照外文翻译文献(文档含英文原文和中文翻译)图1 远程脑系统的硬件配置图2 两组机器人的身体结构图3 传感器的两个水银定位开关图4 层次分类图5 步行步态该输入处理器是作为参考程序块和一个图像搜索窗口形象该大小的搜索窗口取决于参考块的大小通常高达16 * 16且匹配。
该处理器计算价值块在搜索窗口，还找到最佳匹配块，这就是其中的最低当目标平移时块匹配是非常有力的。
然而，普通的块匹配方法当它旋转时无法跟踪目标。
为了克服这一困难，我们开发了一种新方法，跟随真正旋转目标的图6 双足步行图6 双足步行图7 双足步行实验图8 一系列滚动和站立运动通过集成传感器网络转型的综合为了使上述描述的基本动作成为一体，我们通过一种方法来描述一种被认为是根据传感器状况的网络转型。
图9显示了综合了基本动作机器人的状态转移图：两足行走，滚动，坐着和站立。
这种一体化提供了机器人保持行走甚至跌倒时的problems and advance the study of vision-based behaviors, we have adopted a new approach through building remote-brained robots. The body and the brain are connected by wireless links by using wireless cameras and remote-controlled actuators.As a robot body does not need computers on-board,it becomes easier to build a lightweight body with many DOFS in actuation.In this research, we developed a two-armed bipedal robot using the remote-brained robot environment and made it to perform balancing based on vision and getting up through cooperating arms and legs. The system and experimental results are described below.2 The Remote-Brained SystemThe remote-brained robot does not bring its own brain within the body. It leaves the brain in the mother environment and communicates with it by radio links. This allows us to build a robot with a free body and a heavy brain. The connection link between the body and the brain defines the interface between software and hardware. Bodies are designed to suit each research project and task. This enables us advance in performing research with a variety of real robot systems[10].A major advantage of remote-brained robots is that the robot can have a large and heavy brain based on super parallel computers. Although hardware technology for vision has advanced and produced powerful compact vision systems, the size of the hardware is still large. Wireless connection between the camera and the vision processor has been a research tool. The remote-brained approach allows us to progress in the study of a variety of experimental issues in vision-based robotics.Another advantage of remote-brained approach is that the robot bodies can be lightweight. This opens up the possibility of working with legged mobile robots. AsFigure 4 shows some of the classes in the programming environent for remote-brained robot written in Euslisp. The hierachy in the classes provides us with rich facilities for extending development of various robots.4 Vision-Based BalancingThe robot can stand up on two legs. As it can change the gravity center of its body by controling the ankle angles, it can perform static bipedal walks. During static walking the robot has to control its body balance if the ground is not flat and stable.In order to perform vision-based balancing it is re-quired to have high speed vision system to keep ob-serving moving schene. We have developed a tracking vision board using a correlation chip[l3]. The vision board consists of a transputer augmented with a special LSI chip(MEP[14] : Motion Estimation Processor) which performs local image block matching.The inputs to the processor MEP are an image as a reference block and an image for a search window.The size of the reference blsearch window depends on the size of the reference block is usually up to 32 by 32 pixels so that it can include 16 * 16 possible matches. The processor calculates 256 values of SAD (sum of absolute difference) between the reference block and 256 blocks in the search window and also finds the best matching block, that is, the one which has the minimum SAD value.Clock is up to 16 by 16 pixels.The size of the search window depends on the size of the reference block is usually up to 32 by 32 pixels so that it can include 16 * 16 possible matches. The processor calculates 256 values of SAD (sum of absolute difference) between the reference block and 256 blocks in the search window and also finds the best matching block, that is, the one which has the minimum SAD value.Block matching is very powerful when the target moves only in translation. However, the ordinary block matching method cannot track the target when it rotates. In order to overcome this difficulty, we developed a new method which follows up the candidate templates to real rotation of the target. The rotated template method first generates all the rotated target images in advance, and several adequate candidates of the reference template are selected and matched is tracking the scene in the front view. It remembers the vertical orientation of an object as the reference for visual tracking and generates several rotated images of the reference image. If the vision tracks the reference object using the rotated images, it can measures the body rotation. In order to keep the body balance, the robot feedback controls its body rotation to control the center of the body gravity. The rotational visual tracker[l5] can track the image at video rate.5 Biped WalkingIf a bipedal robot can control the center of gravity freely, it can perform biped walk. As the robot shown in Figure 2 has the degrees to left and right directions at the ankle position, it can perform bipedal walking in static way.The motion sequence of one cycle in biped walking consists of eight phases as shown in Figure 6. One step consists of four phases; move-gravity-center-on-foot,lift-leg, move-forward-leg, place-leg. As the body is described in solid model, the robot can generate a body configuration for move-gravity-center-on-foot according to the parameter of the hight of the gravity center. After this movement, the robot can lift the other leg and move it forward. In lifting leg, the robot has to control the configuration in order to keep the center of gravity above the supporting foot. As the stability in balance depends on the hight of the gravity center, the robot selects suitable angles of the knees.Figure 7 shows a sequence of experiments of the robot in biped walking6 Rolling Over and Standing UpFigure 8 shows the sequence of rolling over, sitting and standing up. This motion requires coordination between arms and legs.As the robot foot consists of a battery, the robot can make use of the weight of the battery for the roll-over motion. When the robot throws up the left leg and moves the left arm back and the right arm forward, it can get rotary moment around the body. If the body starts turning, the right leg moves back and the left foot returns its position to lie on the face. This rollover motion changes the body orientation from face up to face down. It canbe verified by the orientation sensor.After getting face down orientation, the robot moves the arms down to sit on two feet. This motion causes slip movement between hands and the ground. If the length of the arm is not enough to carry the center of gravity of the body onto feet, this sitting motion requires dynamic pushing motion by arms. The standing motion is controlled in order to keep the balance.7 Integration through Building Sensor-Based Transition NetIn order to integrate the basic actions described above, we adopted a method to describe a sensor-based transition network in which transition is considered according to sensor status. Figure 9 shows a state transition diagram of the robot which integrates basic actions: biped walking, rolling over, sitting, and standing up. This integration provides the robot with capability of keeping walking even when it falls down.The ordinary biped walk is composed by taking two states, Left-leg Fore and Right-leg Fore, successively.The poses in ‘Lie on the Back’ and ‘Lie on the Face’are as same as one in ‘Stand’. That is, the shape ofthe robot body is same but the orientation is different.The robot can detect whether the robot lies on the back or the face using the orientation sensor. When the robot detects falls down, it changes the state to ‘Lie on the Back’ or ‘Lie on the Front’ by moving to the neutral pose. If the robot gets up from ‘Lie on the Back’, the motion sequence is planned to exe cute Roll-over, Sit and Stand-up motions. If the state is ‘Lie on the Face’, it does not execute Roll-over but moves arms up to perform the sitting motion.8 Concluding RemarksThis paper has presented a two-armed bipedal robot which can perform statically biped walk, rolling over and standing up motions. The key to build such behaviors is the remote-brained approach. As the experiments have shown, wireless technologies permit robot bodies free movement. It also seems to change the way we conceptualize robotics. In our laboratory it has enabled the development of a new research environment, better suited to robotics and real-world AI.The robot presented here is a legged robot. As legged locomotion requires dynamic visual feedback control, its vision-based behaviors can prove the effectiveness of the vision system and the remote-brained system. Our vision system is based on high speed block matching function implemented with motion estimation LSI. The vision system provides the mechanical bodies with dynamic and adaptive capabilities in interaction with human. The mechanical dog has shown adaptive behaviors based on distance。
电容器中英文对照外文翻译文献
电容器中英文对照外文翻译文献(文档含英文原文和中文翻译)译文:1电容器的选择本文为电化学双层电容器或超级电容器提供在一台常规电容器，简明的介绍新生的电化学双电层电容器或超级电容器。
电容器是存放电能并且协助过滤的根本电路元素。
电容器有二个主要应用; 其中之一是充电或释放电的作用。
这个作用适用于电源平流滤波电路，微型计算机备用电路和利用期间充电或释放电的定时器电路。
其他是阻拦DC 流程的作用。
这个作用适用于提取或消灭特殊频率的过滤器。
这是其中不可或缺的优秀电路所需的频率特性。
电解电容是在充分的标度商业化的下一代电容器。
他们类似电池在细胞建筑，但是阳极和负极材料依然保持不变。
他们是铝，钽和两个陶瓷电容电解质的地方与他们所使用的液体固体分离器/ 对称的电极。
电化学电容器（EC），往往被称为超级电容器或超级电容，存储电荷的双层电荷在1层表面电解质界面，主要在高电位表面的碳。
由于高电位表面是薄的双重层，所以这些设备可以有一个非常高的比和体积电容。
这使得他们能够结合以前无法实现的电容用无限的电荷密度/放电循环寿命。
每单元的工作电压，只受击穿电位电解质的影响，通常<1或“<3伏的每个细胞水性或有机电解质分别。
该存储的概念电力能源双电层这是形成于界面之间的固体电解质和一直都知道自19世纪末期。
第一电气设备使用双层充电储存在报告1957年H.I.贝克尔的通用电气（美国专利2800616）。
不幸的是，贝克尔的设备是不切实际的，同样一个充斥电池，电极都需要沉浸在一个容器电解质，并且该设备从未商业化。
贝克尔那样做了，但是随后发现电容值已经被标准石油化学家公司俄亥俄州（索奥）的罗伯特A赖特迈尔发明并且现在正在普遍使用。
他的专利（美国3288641），在1962年年底提出并获1966年11月，和一个后续专利（美国专利3536963）由资深研究员索奥唐纳德L.布斯在1970年，形式为基础随后的专利和期刊数百文章涉及ec技术的所有方面。
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车床用于车外圆、端面和镗孔等加工的机床称作车床。
车削很少在其他种类的机床上进行，因为其他机床都不能像车床那样方便地进行车削加工。
由于车床除了用于车外圆还能用于镗孔、车端面、钻孔和铰孔，车床的多功能性可以使工件在一次定位安装中完成多种加工。
这就是在生产中普遍使用各种车床比其他种类的机床都要多的原因。
两千多年前就已经有了车床。
现代车床可以追溯到大约1797年，那时亨利•莫德斯利发明了一种具有把主轴和丝杆的车床。
这种车床可以控制工具的机械进给。
这位聪明的英国人还发明了一种把主轴和丝杆相连接的变速装置，这样就可以切削螺纹。
车床的主要部件：床身、主轴箱组件、尾架组件、拖板组、变速齿轮箱、丝杆和光杆。
床身是车床的基础件。
它通常是由经过充分正火或时效处理的灰铸铁或者球墨铸铁制成，它是一个坚固的刚性框架，所有其他主要部件都安装在床身上。
通常在球墨铸铁制成，它是一个坚固的刚性框架，所有其他主要部件都安装在床身上。
通常在床身上面有内外两组平行的导轨。
一些制造厂生产的四个导轨都采用倒“V”，而另一些制造厂则将倒“V”形导轨和平面导轨结合。
由于其他的部件要安装在导轨上并（或）在导轨上移动，导轨要经过精密加工，以保证其装配精度。
同样地，在操作中应该小心，以避免损伤导轨。
导轨上的任何误差，常常会使整个机床的精度遭到破坏。
大多数现代车床的导轨要进行表面淬火处理。
以减少磨损和擦伤，具有更大的耐磨性。
主轴箱安装在床身一端内导轨的固定位置上。
它提供动力。
使工件在各种速度下旋转。
它基本上由一个安装在精密轴承中的空心轴和一系列变速齿轮---类似于卡车变速箱所组成，通过变速齿轮，主轴可以在许多中转速的旋转。
大多数车床有8～18中转速，一般按等比级数排列。
在现代车床上只需扳动2～4个手柄，就能得到全部挡位的转速。
目前发展的趋势是通过电气的或机械的装置进行无级变速。
由于车床的精度在很大程度上取决于主轴，因此主轴的结构尺寸较大，通常安装在紧密配合的重型圆锤滚子轴承或球轴承中。
主轴中有一个贯穿全长的通孔，长棒料可以通过该孔送料。
主轴孔的大小是车床的一个重要尺寸，因为当工件必须通过主轴孔供料时，它确定了能够加工棒料毛坯的最大外径尺寸。
主轴的内端从主轴箱中凸出，其上可以安装多种卡盘、花盘和挡筷。
而小型的车床长带有螺纹截面供安装卡盘之用。
很多大车床使用偏心夹或键动圆锥。
这些附件组成了一个大直径的圆锥体，以保证对卡盘进行精确地装配，并且不用旋转这些笨重的附件就可以琐定后松开卡盘或花盘。
主轴由电动机经V带或无声链装置提供动力。
大多数现代车床有5～15马力的电动机，为硬质合金和金属陶瓷合金刀具提供足够的动力，进行高速切削。
尾座组件主要有三部分组成。
底座与床身的内侧导轨配合，并可以在导轨上做纵向移动，底座上有一个可以使整个尾座组件夹紧在任意位置上的装置。
尾座安装在底座上，可以沿键槽在底座横向移动，使尾座与主轴箱中的主轴对中并为切削锥体提供方便。
尾座组件的第三部分是尾座套筒，它是一个直径通常在2～3英寸之间的刚制空心圆柱轴。
通过手轮和螺杆，尾座套筒可以在尾座体中纵向移入和移出几英寸。
活动套筒的开口一端具有莫氏锥度，可以用于安装顶尖或诸如钻头之类的各种刀具。
通常在活动套筒的外表面刻有几英寸的刻度，以控制尾座的前后移动。
锁定装置可以使套筒在所需要的位置上夹紧。
拖板组件用于安装和移动切削工具。
拖板上一个相对平滑的H形铸件，安装在床身外侧导轨上，并可在上面移动。
大拖板上有横向导轨，使横向托板可以安装在上面，并通过丝杆使其运动，丝杆由一个小手柄和刻度盘控制。
横拖板可以带动刀具垂直于工件的旋转轴线切削。
大多数车床的刀架安装在复式刀座上，刀座上有底座，底座安装在横拖板上，可绕垂直轴和上刀架转动。
上刀架安装在底座上，可用手轮和刻度盘控制一个短丝杆使其前后移动。
溜板箱装在大拖板前面，通过溜板箱内的机械装置可以手动和动力驱动大拖板以及动力驱动横拖板。
通过转动溜板箱前的手轮，可以手动操作拖板沿床身移动。
手轮的另一端与溜板箱背面的小齿轮连接，小齿轮与齿条啮合，齿条倒装在床身前上边缘的下面。
利用光杆可以将动力传递给大拖板和横拖板。
光杆上有一个几乎贯穿于整个光杆的键槽，光杆通过两个转向相反并用键连接的锤齿轮传递动力。
通过溜板箱前的换向手柄可使啮合齿轮与其中的一个锤齿轮啮合，为大拖板提供“向前”或“向后”的动力。
适当的离合器或者与齿条小齿轮连接或者与横拖板的螺杆连接，使拖板纵向移动或使横拖板横向移动。
对于螺纹加工，丝杆提供了第二种纵向移动的方法。
光杆通过摩擦离合器驱动拖板移动，离合器可能会产生打滑现象。
而丝杆产生的运动是通过溜板箱与丝杆之间的直接机械连接来实现的，对开螺母紧紧包合丝杆。
当对开螺母闭合时，可以沿丝杆直接驱动拖板，而不会出现打滑的可能性。
现代车床有一个变速齿轮箱，齿轮箱的输入端由车床主轴通过合适的齿轮传动驱动。
齿轮箱的输出端与光杆和丝杆连接。
主轴就是这样通过齿轮传动链驱动变速齿轮箱，在带动丝杆和光杆，然后带动拖板，刀具就可以按主轴的转数纵向地或横向地精确移动。
一台典型的车床的主轴每转一圈，通过光杆可以获得从0.002到0.118英寸尺寸范围内的48种进给量；而使用丝杆可以车削从1.5到92牙/英寸范围内的48种不同螺纹。
一些老式的或廉价的车床为了能够得到所有的进给量和加工出所有螺纹，必须更换主轴和变速齿轮箱之间的齿轮系中的一个或两个齿轮。
LATHESThe basic machines that are designed primarily to do turning , facing and boring are called lathes . Very little turning is done on order types of machines tool , and none can do it with equal facility .Because lathe can do boring , facing , drilling , and , reaming in addition to turning ,their versatility permits several operations to be performed with a single setup of the work-piece . This accounts for the fact that lathes of various types are more widely used in manufacturing than any other machine tool .Lathes in various forms have existed for more than two thousand years . Modern lathes date from about 1797 , when Henry Maud-sley developed one with a lead-screw . It provided controlled , mechanical feed of the tool . This ingenious Englishman also developed a change-gear system that could connect the spindle and lead-screw and thus enables thread to be cut .Lathe Construction . The essential components of a lathe are depicted in the block diagram of Fig.15-1. These are the bed , headstock assembly , tailstock assembly , carriage assembly , quick-change gear box , and the lead-screw and feed rod .The bed is the backbone of a lathe .It is usually made of well-normalized or aged gray or nodular cast iron and provides a heavy , rigid frame on which all the other basic components mounted . Two sets of parallel , longitudinal ways , inner and outer , are contained in the bed , usually on the upper side . Some makes use an inverted V-shape for all four ways , whereas others utilize one inverted V and one flat way in one or both sets . Because several other accuracy of alignment . Similarly , proper precaution should be taken in operating a lathe to assure that the ways are not damaged . Any inaccuracy in them usually means that the accuracy of the entire lathe is destroyed .The ways on most modern lathes are surface hardened to offer greater resistance to wear and abrasion .The headstock is mounted in a fixed position on the inner ways at one end of lathe bed . It provides a powered means of rotating the work at various speeds . It consists , essentially , of a hollow spindle , mounted in accurate bearings , and a set of transmission gears-similar to a truck transmission-through which the spindle can be rotated at a number ofspeeds . Most lathes provided from eight to eighteen speeds , usually in a geometric ratio , and on modern lathes all the speeds can be obtained merely by moving from two to four levers . An increasing trend is to provided a continuously variable speed range through electrical or mechanical drives .Because the accuracy of a lathe is greatly dependent on the spindle , it is of heavy construction and mounted in heavy bearings , usually preloaded tapered roller or ball types . A longitudinal hole is an important size dimension of a lathe because it determines the maximum size of bar stock that can be machined when the material must be fed through the spindle .The inner end of the spindle protrudes from the gear box and contains a means for mounting various types of chucks , face plate , and dog plate on it . Whereas small lathes often employ a threaded section to which the chucks are screwed , most large lathes utilize either cam-lock or key-drive taper noses . These provide a large-diameter taper that assures the accurate alignment of the chuck , and a mechanism that permits the chuck or face plate to be locked or unlocked in position without the necessity of having to rotate these heavy attachments .Power is supplied to the spindle by means of an electric motor through a V-belt or silent –chain drive . Most modern lathes have motors of from 5 to 15 horsepower to provide adequate power for carbide and ceramic and ceramic tools at their high cutting speeds .The tailstock assembly consists , essentially , of three parts . A lower casting fits on the inner ways of the bed and can slide longitudinally thereon , with a means for clamping the entire assembly in any desired location . An upper casting fit on the lower one and can be moved transversely upon it on some type of keyed ways . This transverse motion permits aligning the tailstock and headstock spindles and provides a method of turning tapes . The third major component of the assembly is the tailstock quil . This is a hollow steed cylinder , usually about 2 to 3 inches in diameter , that can be moved severed inches longitudinally in and out of the upper casting by means of a handwheel and screw . The open end of the quill hole terminates in a Morse taper in which a lathecenter , or various tools such as drills , can be held . A graduated scale , several inches in length , usually is engraved in the outside of the quill to aid in controlling its motion in and out of the upper casting . A locking device permits clamping the quill any desired position .The carriage assembly provides the means for mounting and moving cutting tools . The carriage is a relatively flat H-shaped casting that rest and moves on the outer set of ways on the bed . The transverse bar of the carriage contains ways on which the cross slide is mounted and can be moved by means of a feed screw that is controlled by a small hand-wheel and a graduated dial . Through the cross slide a means is provided for moving the lathe tool in the direction normal to the axis of rotation of the work .On most lathes the tool post actually is mounted on a compound rest . This consists of a base , which is mounted on the cross slide so that it can be pivoted about a vertical axis , and an upper casting . The upper casting is mounted on ways on this base so that it can be moved back and forth and controlled by means of a shout lead screw operated by a hand-wheel and a calibrated dial .Manual and powered motion for the carriage , and powered motion for the cross slide , is provided by mechanisms within the apron , attached to the front of the carriage . Manual movement of the carriage along the bed is effected by turning a hand-wheel on the front of the apron , which is geared to a pinion on the back side . This pinion engages a rack that is attached beneath the upper front edge of the bed in an inverted position .To impart powered movement to the carriage and cross slide , a rotating feed rod is provided . The feed rod , which contains a keyway throughout most of its length , passes through the two reversing bevel pinions and is keyed to them . Either pinion can be brought into mesh with a mating bevel gear by means of the reversing lever on the front of the apron and thus provide “forward” or “reverse” power to the carriage . Suitable clutches connect either the rack pinion or the cross-slide screw to provide longitudinal motion of the carriage or transverse motion of cross slide .For cutting threads , a second means of longitudinal drive isprovided by a lead screw . Whereas motion of the carriage when driven by the feed-rod mechanism takes place through a friction clutch in which slippage is possible , motion through the lead screw is by a direct , mechanical connection between the apron and the lead screw . This is achieved by a split nut . By means of a clamping lever on the front of the apron , the split nut can be closed around the lead screw . With the spit nut closed , the carriage is moved along the lead screw by direct drive without possibility of slippage .Modern lathes have a quick-change gear box . The input end of this gear box is driven from the lathe spindle by means of suitable gearing . The output end of the gear box is connected to the feed rod and lead screw . Thus , through this gear train , leading from the spindle to the quick-charge gear box , thence to the lead screw and feed rod ,and them to the carriage , the cutting tool can be made to move a specific distances , either longitudinally or transversely , for each revolution of the spindle .A typical lathe provides , through the feed rod , forty-eight feeds ranging from 0.0012 inch to 0.118 inch per revolution of the spindle , and , through the lead screw , leads for cutting forty-eight different threads from 1.5 to 92 per inch . On some older and some cheaper lathes , one or two gears in the train between the spindle and the change gear box must be changed in order to obtain a full range of threads and feeds .。