毕业论文外文文献翻译Line-Balancing-in-the-Real-World生产线平衡在现实世界
毕业设计(论文)外文文献翻译》
毕业设计(论文)外文文献翻译(本科学生用)题目:低成本激光距离传感器学生姓名:任铎学号:130112021126 学部(系): 光电信息科学与工程专业年级: 13光信(2)班指导教师:张静职称或学位:讲师20 17 年 02 月 25 日结构化线路设备。
这些设备使用光条激光器和偏移相机来确定一组点的范围。
因为激光能量在线上传播,所以难以实现精确的范围,特别是在存在环境光的情况下或且它们的成本和机械脆性将保持高。
点模块。
像Revo设备一样,存在可能被旋转以实现大Sharp IR传感器[9],它使用位置敏感器件(PSDq = fs. (1)∑ I (i) i/ ∑ I (i) .i i6m. I. Iat 6 m, angularthe most common tasks for mobile robots is to 6. 4000readings per second (scans up to 10 Hz) make a mapand navigate in an environment. To do so, 7. Small size,low power (< 2W) the robot needs to sense itsenvironment in an efficient 8. Standard, commercially-available components. way, looking out to somedistance to find obstacles and 9. Low cost: $30 cost tobuild. build a map that is useful for performing taskssuch asvacuuming or delivery. These characteristics make theRevo suitable for consumer While there are manysensors that could be used, laser products, and open the way for high-performance, low-distance sensors are currently the standard sensor in cost mobile robots. Although all of the Revo technologies indoor and outdoor mobile robots. The main reason is the have been used in other devices, to date no-one has utility of the data: an LDS returns distance to objects in its realized that they could be combined to make a low-cost, field of view, unlike (for example) vision sensors, which high-performance sensor. Achieving the above criteria need complicated and error-prone processing before required innovations in design, algorithms, and distances are measured. And unlike other distance sensors integration. The key elements of the Revolenscurve.Figure II-6 Maximum pulse power and Maximum Permissiblebased outer drive has been tested in continuous use over。
毕业设计(论文)外文参考文献译文本
武汉工业学院毕业设计(论文)外文参考文献译文本2011届原文出处IBM SYSTEMS JOURNAL, VOL 35, NOS 3&4, 1996毕业设计(论文)题目音乐图像浏览器的设计与实现院(系)计算机与信息工程专业名称计算机科学与技术学生姓名郭谦学生学号070501103指导教师丰洪才译文要求:1、译文内容须与课题(或专业)有联系;2、外文翻译不少于4000汉字。
隐藏数据技术研究数据隐藏,是一种隐秘的数据加密形式,它将数据嵌入到数字媒体之中来达到鉴定,注释和版权保护的目的。
然而,这一应用却受到了一些限制:首先是需要隐藏的数据量,其次是在“主”讯号受到失真的条件影响之下,对于这些需隐藏数据的可靠性的需要。
举例来说,就是有损压缩以及对有损压缩来说数据遇到被拦截,被修改或被第三方移除等操作的免疫程度。
我们同时用传统的和新式技术来探究解决数据隐藏问题的方法并且对这些技术在以下三个方面的应用:版权保护,防止篡改,和增强型数据嵌入做出评估。
我们能非常方便地得到数字媒体并且潜在地改善了其可移植性,信息展现的效率,和信息呈现的准确度。
便捷的数据访问所带来的负面效果包括以下两点:侵犯版权的几率增加或者是有篡改或修改其中内容的可能性增大。
这项工作的目的在于研究知识产权保护条款、内容修改的相关指示和增加注解的方法。
数据隐藏代表了一类用于插入数据的操作,例如版权信息,它利用“主”信号能够感知的最小变化量来进入到各种不同形式的媒体之内,比如图像、声音或本文。
也就是说,嵌入的数据对人类观察者来说应该是既看不见也听不见的。
值得注意的是,数据隐藏虽然与压缩很类似,但与加密解密技术却是截然不同的。
它的目标不是限制或者管理对“主”信号的存取,而是保证被嵌入的数据依然未被破坏而且是可以恢复的。
数据隐藏在数字媒体中的两个重要应用就是提供版权信息的证明,和保证内容完整性。
因此,即使主讯号遭受诸如过滤、重取样,截取或是有损压缩等破坏行为,数据也应该一直在“主”信号中保持被隐藏的特点。
毕业设计(论文)外文资料和译文格式要求(模板)
成都东软学院外文资料和译文格式要求一、译文必须采用计算机输入、打印,幅面A4。
外文资料原文(复印或打印)在前,译文在后,于左侧装订。
二、具体要求1、至少翻译一篇内容与所选课题相关的外文文献。
2、译文汉字字数不少于4000字。
3、正文格式要求:宋体五号字。
译文格式参见《译文格式要求》,宋体五号字,单倍行距。
纸张纸张为A4纸,页边距上2.54cm、下2.54cm、左3.17cm、右3.17cm。
装订外文资料原文(复印或打印)在前,译文在后封面封面的专业、班级、姓名、学号等信息要全部填写正确。
封面指导教师必须为讲师以上职称,若助教则需要配备一名讲师协助指导。
讲师在前,助教在后。
指导教师姓名后面空一个中文空格,加职称。
页眉页眉说明宋体小五,左端“XX学院毕业设计(论文)”,右端“译文”。
页眉中的学院名称要与封面学院名称一致。
字数本科4000字。
附:外文资料和译文封面、空白页成都东软学院外文资料和译文专业:软件工程移动互联网应用开发班级:2班姓名:罗荣昆学号:12310420216指导教师:2015年 12月 8日Android page layoutUsing XML-Based LayoutsW hile it is technically possible to create and attach widgets to our activity purely through Java code, the way we did in Chapter 4, the more common approach is to use an XML-based layout file. Dynamic instantiation of widgets is reserved for more complicated scenarios, where the widgets are not known at compile-time (e g., populating a column of radio buttons based on data retrieved off the Internet).With that in mind, it’s time to break out the XML and learn how to lay out Android activities that way.What Is an XML-Based Layout?As the name suggests, an XML-based layout is a specification of widgets’ relationships to each other—and to their containers (more on this in Chapter 7)—encoded in XML format. Specifi cally, Android considers XML-based layouts to be resources, and as such layout files are stored in the res/layout directory inside your Android project.Each XML file contains a tree of elements specifying a layout of widgets and their containers that make up one view hierarchy. The attributes of the XML elements are properties, describing how a widget should look or how a container should behave. For example, if a Button element has an attribute value of android:textStyle = "bold", that means that the text appearing on the face of the button should be rendered in a boldface font style.Android’s SDK ships with a tool (aapt) which uses the layouts. This tool should be automatically invoked by your Android tool chain (e.g., Eclipse, Ant’s build.xml). Of particular importance to you as a developer is that aapt generates the R.java source file within your project, allowing you to access layouts and widgets within those layouts directly from your Java code. Why Use XML-Based Layouts?Most everything you do using XML layout files can be achieved through Java code. For example, you could use setTypeface() to have a button render its textin bold, instead of using a property in an XML layout. Since XML layouts are yet another file for you to keep track of, we need good reasons for using such files.Perhaps the biggest reason is to assist in the creation of tools for view definition, such as a GUI builder in an IDE like Eclipse or a dedicated Android GUI designer like DroidDraw1. Such GUI builders could, in principle, generate Java code instead of XML. The challenge is re-reading the UI definition to support edits—that is far simpler if the data is in a structured format like XML than in a programming language. Moreover, keeping generated XML definitions separated from hand-written Java code makes it less likely that somebody’s custom-crafted source will get clobbered by accident when the generated bits get re-generated. XML forms a nice middle ground between something that is easy for tool-writers to use and easy for programmers to work with by hand as needed.Also, XML as a GUI definition format is becoming more commonplace. Microsoft’s XAML2, Adobe’s Flex3, and Mozilla’s XUL4 all take a similar approach to that of Android: put layout details in an XML file and put programming smarts in source files (e.g., JavaScript for XUL). Many less-well-known GUI frameworks, such as ZK5, also use XML for view definition. While “following the herd” is not necessarily the best policy, it does have the advantage of helping to ease the transition into Android from any other XML-centered view description language. OK, So What Does It Look Like?Here is the Button from the previous chapter’s sample application, converted into an XMLlayout file, found in the Layouts/NowRedux sample project. This code sample along with all others in this chapter can be found in the Source Code area of .<?xml version="1.0" encoding="utf-8"?><Button xmlns:android="/apk/res/android"android:id="@+id/button"android:text=""android:layout_width="fill_parent"android:layout_height="fill_parent"/>The class name of the widget—Button—forms the name of the XML element. Since Button is an Android-supplied widget, we can just use the bare class name. If you create your own widgets as subclasses of android.view.View, you would need to provide a full package declara tion as well.The root element needs to declare the Android XML namespace:xmlns:android="/apk/res/android"All other elements will be children of the root and will inherit that namespace declaration.Because we want to reference this button from our Java code, we need to give it an identifier via the android:id attribute. We will cover this concept in greater detail later in this chapter.The remaining attributes are properties of this Button instance:• android:text indicates the initial text to be displayed on the button face (in this case, an empty string)• android:layout_width and android:layout_height tell Android to have the button’swidth and height fill the “parent”, in this case the entire screen—these attributes will be covered in greater detail in Chapter 7.Since this single widget is the only content in our activity, we only need this single element. Complex UIs will require a whole tree of elements, representing the widgets and containers that control their positioning. All the remaining chapters of this book will use the XML layout form whenever practical, so there are dozens of other examples of more complex layouts for you to peruse from Chapter 7 onward.What’s with the @ Signs?Many widgets and containers only need to appear in the XML layout file and do not need to be referenced in your Java code. For example, a static label (TextView) frequently only needs to be in the layout file to indicate where it should appear. These sorts of elements in the XML file do not need to have the android:id attribute to give them a name.Anything you do want to use in your Java source, though, needs an android:id.The convention is to use @+id/... as the id value, where the ... represents your locally unique name for the widget in question. In the XML layout example in the preceding section, @+id/button is the identifier for the Button widget.Android provides a few special android:id values, of the form @android:id/.... We will see some of these in various chapters of this book, such as Chapters 8 and 10.We Attach These to the Java How?Given that you have painstakingly set up the widgets and containers in an XML layout filenamed main.xml stored in res/layout, all you need is one statement in your activity’s onCreate() callback to use that layout:setContentView(yout.main);This is the same setContentView() we used earlier, passing it an instance of a View subclass (in that case, a Button). The Android-built view, constructed from our layout, is accessed from that code-generated R class. All of the layouts are accessible under yout, keyed by the base name of the layout file—main.xml results in yout.main.To access our identified widgets, use findViewById(), passing in the numeric identifier of the widget in question. That numeric identifier was generated by Android in the R class asR.id.something (where something is the specific widget you are seeking). Those widgets are simply subclasses of View, just like the Button instance we created in Chapter 4.The Rest of the StoryIn the original Now demo, the button’s face would show the current time, which would reflect when the button was last pushed (or when the activity was first shown, if the button had not yet been pushed).Most of that logic still works, even in this revised demo (NowRedux). However,rather than instantiating the Button in our activity’s onCreate() callback, we can reference the one from the XML layout:package youts;import android.app.Activity;import android.os.Bundle;import android.view.View;import android.widget.Button; import java.util.Date;public class NowRedux extends Activity implements View.OnClickListener { Button btn;@Overridepublic void onCreate(Bundle icicle) { super.onCreate(icicle);setContentView(yout.main);btn=(Button)findViewById(R.id.button);btn.setOnClickListener(this);upd ateTime();}public void onClick(View view) { updateTime();}private void updateTime() {btn.setText(new Date().toString()); }}The first difference is that rather than setting the content view to be a view we created in Java code, we set it to reference the XML layout (setContentView(yout.main)). The R.java source file will be updated when we rebuild this project to include a reference to our layout file (stored as main.xml in our project’s res/l ayout directory).The other difference is that we need to get our hands on our Button instance, for which we use the findViewById() call. Since we identified our button as @+id/button, we can reference the button’s identifier as R.id.button. Now, with the Button instance in hand, we can set the callback and set the label as needed.As you can see in Figure 5-1, the results look the same as with the originalNow demo.Figure 5-1. The NowRedux sample activity Employing Basic WidgetsE very GUI toolkit has some basic widgets: fields, labels, buttons, etc. Android’s toolkit is no different in scope, and the basic widgets will provide a good introduction as to how widgets work in Android activities.Assigning LabelsThe simplest widget is the label, referred to in Android as a TextView. Like in most GUI toolkits, labels are bits of text not editable directly by users. Typically, they are used to identify adjacent widgets (e.g., a “Name:” label before a field where one fills in a name).In Java, you can create a label by creating a TextView instance. More commonly, though, you will create labels in XML layout files by adding a TextView element to the layout, with an android:text property to set the value of the label itself. If you need to swap labels based on certain criteria, such as internationalization, you may wish to use a resource reference in the XML instead, as will be described in Chapter 9. TextView has numerous other properties of relevance for labels, such as:• android:typeface to set the typeface to use for the label (e.g., monospace) • android:textStyle to indicate that the typeface should be made bold (bold), italic (italic),or bold and italic (bold_italic)• android:textColor to set the color of the label’s text, in RGB hex format (e.g., #FF0000 for red)For example, in the Basic/Label project, you will find the following layout file:<?xml version="1.0" encoding="utf-8"?><TextView xmlns:android=/apk/res/androidandroid:layout_width="fill_parent"android:layout_height="wrap_content"android:text="You were expecting something profound?" />As you can see in Figure 6-1, just that layout alone, with the stub Java source provided by Android’s p roject builder (e.g., activityCreator), gives you the application.Figure 6-1. The LabelDemo sample applicationButton, Button, Who’s Got the Button?We’ve already seen the use of the Button widget in Chapters 4 and 5. As it turns out, Button is a subclass of TextView, so everything discussed in the preceding section in terms of formatting the face of the button still holds. Fleeting ImagesAndroid has two widgets to help you embed images in your activities: ImageView and ImageButton. As the names suggest, they are image-based analogues to TextView and Button, respectively.Each widget takes an android:src attribute (in an XML layout) to specify what picture to use. These usually reference a drawable resource, described in greater detail in the chapter on resources. You can also set the image content based on a Uri from a content provider via setImageURI().ImageButton, a subclass of ImageView, mixes in the standard Button behaviors, for responding to clicks and whatnot.For example, take a peek at the main.xml layout from the Basic/ImageView sample project which is found along with all other code samples at : <?xml version="1.0" encoding="utf-8"?><ImageView xmlns:android=/apk/res/androidandroid:id="@+id/icon"android:layout_width="fill_parent"android:layout_height="fill_parent"android:adjustViewBounds="true"android:src="@drawable/molecule" />The result, just using the code-generated activity, is shown in Figure 6-2.Figure 6-2. The ImageViewDemo sample applicationFields of Green. Or Other Colors.Along with buttons and labels, fields are the third “anchor” of most GUI toolkits. In Android, they are implemented via the EditText widget, which is a subclass of the TextView used for labels.Along with the standard TextView properties (e.g., android:textStyle), EditText has many others that will be useful for you in constructing fields, including:• android:autoText, to control if the fie ld should provide automatic spelling assistance• android:capitalize, to control if the field should automatically capitalize the first letter of entered text (e.g., first name, city) • android:digits, to configure the field to accept only certain digi ts • android:singleLine, to control if the field is for single-line input or multiple-line input (e.g., does <Enter> move you to the next widget or add a newline?)Beyond those, you can configure fields to use specialized input methods, such asandroid:numeric for numeric-only input, android:password for shrouded password input,and android:phoneNumber for entering in phone numbers. If you want to create your own input method scheme (e.g., postal codes, Social Security numbers), you need to create your own implementation of the InputMethod interface, then configure the field to use it via android: inputMethod.For example, from the Basic/Field project, here is an XML layout file showing an EditText:<?xml version="1.0" encoding="utf-8"?><EditTextxmlns:android=/apk/res/androidandroid:id="@+id/field"android:layout_width="fill_parent"android:layout_height="fill_parent"android:singleLine="false" />Note that android:singleLine is false, so users will be able to enter in several lines of text. For this project, the FieldDemo.java file populates the input field with some prose:package monsware.android.basic;import android.app.Activity;import android.os.Bundle;import android.widget.EditText;public class FieldDemo extends Activity { @Overridepublic void onCreate(Bundle icicle) { super.onCreate(icicle);setContentView(yout.main);EditText fld=(EditText)findViewById(R.id.field);fld.setText("Licensed under the Apache License, Version 2.0 " + "(the \"License\"); you may not use this file " + "except in compliance with the License. You may " + "obtain a copy of the License at " +"/licenses/LICENSE-2.0");}}The result, once built and installed into the emulator, is shown in Figure 6-3.Figure 6-3. The FieldDemo sample applicationNote Android’s emulator only allows one application in the launcher per unique Java package. Since all the demos in this chapter share the monsware.android.basic package, you will only see one of these demos in your emulator’s launcher at any one time.Another flavor of field is one that offers auto-completion, to help users supply a value without typing in the whole text. That is provided in Android as the AutoCompleteTextView widget and is discussed in Chapter 8.Just Another Box to CheckThe classic checkbox has two states: checked and unchecked. Clicking the checkbox toggles between those states to indicate a choice (e.g., “Ad d rush delivery to my order”). In Android, there is a CheckBox widget to meet this need. It has TextView as an ancestor, so you can use TextView properties likeandroid:textColor to format the widget. Within Java, you can invoke: • isChecked() to determi ne if the checkbox has been checked• setChecked() to force the checkbox into a checked or unchecked state • toggle() to toggle the checkbox as if the user checked itAlso, you can register a listener object (in this case, an instance of OnCheckedChangeListener) to be notified when the state of the checkbox changes.For example, from the Basic/CheckBox project, here is a simple checkbox layout:<?xml version="1.0" encoding="utf-8"?><CheckBox xmlns:android="/apk/res/android"android:id="@+id/check"android:layout_width="wrap_content"android:layout_height="wrap_content"android:text="This checkbox is: unchecked" />The corresponding CheckBoxDemo.java retrieves and configures the behavior of the checkbox:public class CheckBoxDemo extends Activityimplements CompoundButton.OnCheckedChangeListener { CheckBox cb;@Overridepublic void onCreate(Bundle icicle) { super.onCreate(icicle);setContentView(yout.main);cb=(CheckBox)findViewById(R.id.check);cb.setOnCheckedChangeListener(this);}public void onCheckedChanged(CompoundButton buttonView,boolean isChecked) {if (isChecked) {cb.setText("This checkbox is: checked");}else {cb.setText("This checkbox is: unchecked");}}}Note that the activity serves as its own listener for checkbox state changes since it imple ments the OnCheckedChangeListener interface (via cb.setOnCheckedChangeListener(this)). The callback for the listener is onCheckedChanged(), which receives the checkbox whose state has changed and what the new state is. In this case, we update the text of the checkbox to reflect what the actual box contains.The result? Clicking the checkbox immediately updates its text, as you can see in Figures 6-4 and 6-5.Figure 6-4. The CheckBoxDemo sample application, with the checkbox uncheckedFigure 6-5. The same application, now with the checkbox checkedTurn the Radio UpAs with other implementations of radio buttons in other toolkits, Android’s radio buttons are two-state, like checkboxes, but can be grouped such that only one radio button in the group can be checked at any time.Like CheckBox, RadioButton inherits from CompoundButton, which in turn inherits fromTextView. Hence, all the standard TextView properties for font face, style, color, etc., are available for controlling the look of radio buttons. Similarly, you can call isChecked() on a RadioButton to see if it is selected, toggle() to select it, and so on, like you can with a CheckBox.Most times, you will want to put your RadioButton widgets inside of aRadioGroup. The RadioGroup indicates a set of radio buttons whose state is tied, meaning only one button out of the group can be selected at any time. If you assign an android:id to your RadioGroup in your XML layout, you can access the group from your Java code and invoke:• check() to check a specific radio button via its ID (e.g., group.check(R.id.radio1))• clearCheck() to clear all radio buttons, so none in the group are checked• getCheckedRadioButtonId() to get the ID of the currently-checked radio button (or -1 if none are checked)For example, from the Basic/RadioButton sample application, here is an XML layout showing a RadioGroup wrapping a set of RadioButton widgets: <?xml version="1.0" encoding="utf-8"?> <RadioGroupxmlns:android=/apk/res/androidandroid:orientation="vertical"android:layout_width="fill_parent"android:layout_height="fill_parent" ><RadioButton android:id="@+id/radio1"android:layout_width="wrap_content"android:layout_height="wrap_content"android:text="Rock" /><RadioButton android:id="@+id/radio2"android:layout_width="wrap_content"android:layout_height="wrap_content"android:text="Scissors" /><RadioButton android:id="@+id/radio3"android:layout_width="wrap_content"android:layout_height="wrap_content"android:text="Paper" /></RadioGroup>Figure 6-6 shows the result using the stock Android-generated Java forthe project and this layout.Figure 6-6. The RadioButtonDemo sample application Note that the radio button group is initially set to be completely unchecked at the outset. To pre-set one of the radio buttons to be checked, use either setChecked() on the RadioButton or check() on the RadioGroup from within your onCreate() callback in your activity.It’s Quite a ViewAll widgets, including the ones previously shown, extend View, and as such give all widgets an array of useful properties and methods beyond those already described.Useful PropertiesSome of the properties on View most likely to be used include:• Controls the focus sequence:• android:nextFocusDown• android:nextFocusLeft• android:nextFocusRight• android:nextFocusUp• android:visibility, which controls wheth er the widget is initially visible• android:background, which typically provides an RGB color value (e.g., #00FF00 for green) to serve as the background for the widgetUseful MethodsYou can toggle whether or not a widget is enabled via setEnabled() and see if it is enabled via isEnabled(). One common use pattern for this is to disable some widgets based on a CheckBox or RadioButton selection.You can give a widget focus via requestFocus() and see if it is focused via isFocused(). You might use this in concert with disabling widgets as previously mentioned, to ensure the proper widget has the focus once your disabling operation is complete.To help navigate the tree of widgets and containers that make up an activity’s overall view, you can use:• get Parent() to find the parent widget or container• findViewById() to find a child widget with a certain ID• getRootView() to get the root of the tree (e.g., what you provided to the activity via setContentView())Android 页面布局使用XML进行布局虽然纯粹通过Java代码在activity上创建和添加部件,在技术上是可行的,我们在第4章中做的一样,更常见的方法是使用一种基于XML的布局文件。
毕业论文的外文译文
毕业论文的外文译文Due to the increasing importance of communication and cooperation in today's globalized world, businesses are constantly looking for ways to improve their cross-cultural communication skills. One area where these skills are crucial is in the internationalization of companies, where firms require a deep understanding of the cultural differences in order to be successful. This requires a comprehensive understanding of not only language, but also the cultural norms and values of the target market. In this thesis, we will explore the importance of cross-cultural communication in international businesses and how it can be improved.The primary challenge in cross-cultural communication is the language barrier. While English is the dominant language in international business, many firms find that it's not enough to communicate effectively with their target market. There are cultural differences in the way people use language, as well as differences in nonverbal communication such as body language and facial expressions. For instance, in Japan, it's common to nod and smile even if one does not agree with astatement, whereas in the United States, a lack of disagreement often means agreement. These differences can lead to misunderstandings in business conversations, which can ultimately harm business relationships.In order to overcome these language barriers, companies need to invest in language training for their employees. This training should focus not only on the language itself, but also on the cultural norms and values associated with the language. For example, a Japanese training program might teach students about the concepts of harmony and respect in Japanese culture, and how these values influence the way people communicate with each other. By understanding these cultural norms, employees will be able to communicate more effectively with their Japanese counterparts.Another challenge in cross-cultural communication is understanding the cultural context of business interactions. In some cultures, business is conducted in a more formal manner, with a strong emphasis on hierarchy and protocol. In other cultures, business is more informal and relaxed. Companies need to understand these differences in order to work effectively in international markets.To overcome these context challenges, companies should incorporate cultural training into their employee training programs. Cultural training should focus on the history, customs, and traditions of the target market. It should also address the specific business practices and protocol required for success in that market.In conclusion, cross-cultural communication is a key determinant of success in international businesses. In order to succeed in foreign markets, companies must have a deep understanding of the language, cultural norms, and values of their target market. This requires a comprehensive training program that not only focuses on language skills, but also on the cultural context of business interactions. With the right training and support, companies can improve their cross-cultural communication skills and achieve success in global markets.。
毕业设计论文 外文文献翻译
毕业设计(论文)外文参考文献翻译计算机科学与信息工程系系(院)2008 届题目企业即时通Instant Messaging for Enterprises课题类型技术开发课题来源自选学生姓名许帅专业班级 04计算机科学与技术指导老师王占中职称工程师完成日期:2008年4 月 6 日目录I NSTANT M ESSAGING FOR E NTERPRISE (1)1. Tips (1)2. Introduction (1)3. First things first (2)4.The While-Accept loop (4)5. Per-Thread class (6)6. The Client class (7)企业即时通 (9)1.提示 (9)2.简介 (9)3.首先第一件事 (10)4.监听循环 (11)5.单线程类 (13)6.用户端类 (14)Instant Messaging for Enterprise1. TipsIf Java is, in fact, yet another computer programming language, you may question why it is so important and why it is being promoted as a revolutionary step in computer programming. The answer isn’t immediately obvious if you’re coming from a tr aditional programming perspective. Although Java is very useful for solving traditional standalone programming problems, it is also important because it will solve programming problems on the World Wide Web. What is the Web?The Web can seem a bit of a mys tery at first, with all this talk of “surfing,”“presence,” and “home pages.” It’s helpful to step back and see what it really is, but to do this you must understand client/server systems, another aspect of computing that is full of confusing issues. The primary idea of a client/server system is that you have a central repository of information,some kind of data, often in a database。
毕业设计(论文)外文资料翻译〔含原文〕【范本模板】
南京理工大学毕业设计(论文)外文资料翻译教学点: 南京信息职业技术学院专业:电子信息工程姓名:陈洁学号:014910253034外文出处:《Pci System Architecture 》(用外文写)附件: 1.外文资料翻译译文;2。
外文原文。
附件1:外文资料翻译译文64位PCI扩展1.64位数据传送和64位寻址:独立的能力PCI规范给出了允许64位总线主设备与64位目标实现64位数据传送的机理。
在传送的开始,如果回应目标是一个64位或32位设备,64位总线设备会自动识别.如果它是64位设备,达到8个字节(一个4字)可以在每个数据段中传送。
假定是一串0等待状态数据段。
在33MHz总线速率上可以每秒264兆字节获取(8字节/传送*33百万传送字/秒),在66MHz总线上可以528M字节/秒获取.如果回应目标是32位设备,总线主设备会自动识别并且在下部4位数据通道上(AD[31::00])引导,所以数据指向或来自目标。
规范也定义了64位存储器寻址功能。
此功能只用于寻址驻留在4GB地址边界以上的存储器目标。
32位和64位总线主设备都可以实现64位寻址。
此外,对64位寻址反映的存储器目标(驻留在4GB地址边界上)可以看作32位或64位目标来实现。
注意64位寻址和64位数据传送功能是两种特性,各自独立并且严格区分开来是非常重要的。
一个设备可以支持一种、另一种、都支持或都不支持。
2.64位扩展信号为了支持64位数据传送功能,PCI总线另有39个引脚。
●REQ64#被64位总线主设备有效表明它想执行64位数据传送操作.REQ64#与FRAME#信号具有相同的时序和间隔。
REQ64#信号必须由系统主板上的上拉电阻来支持.当32位总线主设备进行传送时,REQ64#不能又漂移。
●ACK64#被目标有效以回应被主设备有效的REQ64#(如果目标支持64位数据传送),ACK64#与DEVSEL#具有相同的时序和间隔(但是直到REQ64#被主设备有效,ACK64#才可被有效).像REQ64#一样,ACK64#信号线也必须由系统主板上的上拉电阻来支持。
毕业设计(论文)外文文献翻译要求
毕业设计(论文)外文文献翻译要求
根据校教务处对2005届毕业设计(论文)的要求,为提高毕业论文(设计)的质量,经研究决定,2006届毕业论文(设计)要求翻译2篇外文文献(每篇译文的中文字数一般要求2000-3000左右)或外文字符不少于1.5万。
翻译的外文文献应主要选自学术期刊、学术会议的文章、有关著作及其他相关材料,应与毕业论文(设计)主题相关,并作为外文参考文献列入毕业论文(设计)的参考文献。
并在每篇中文译文首页用“脚注”形式注明原文作者及出处,中文译文后应附外文原文。
中文译文的基本撰写格式为题目采用小三号黑体字居中打印,正文采用宋体五号字,行间距一般为固定值20磅,标准字符间距。
页边距为左3cm,右2.5cm,上下各2.5cm,页面统一采用A4纸,使用学校统一规定的封面格式,并按“封面、译文一、外文原文一、译文二、外文原文二”的顺序统一装订,与开题报告一同提交。
计算机学院
2005年9月28日
杭州电子科技大学
毕业设计(论文)外文文献翻译
毕业设计(论文)题目
翻译(1)题目
翻译(2)题目
学院
专业
姓名
班级
学号
指导教师。
毕业设计(论文)外文翻译(原文)
毕业设计(论文)——外文翻译(原文)NEW APPLICATION OF DA TABASERelational databases have been in use for over two decades. A large portion of the applications of relational databases have been in the commercial world, supporting such tasks as transaction processing for banks and stock exchanges, sales and reservations for a variety of businesses, and inventory and payroll for almost of all companies. We study several new applications, which have become increasingly important in recent years.First. Decision-support systemAs the online availability of data has grown, businesses have begun to exploit the available data to make better decisions about increase sales. We can extract much information for decision support by using simple SQL queries. Recently however, people have felt the need for better decision support based on data analysis and data mining, or knowledge discovery, using data from a variety of sources.Database applications can be broadly classified into transaction processing and decision support. Transaction-processing systems are widely used today, and companies have accumulated a vast amount of information generated by these systems.The term data mining refers loosely to finding relevant information, or “discovering knowledge,”from a large volume of data. Like knowledge discovery in artificial intelligence, data mining attempts to discover statistical rules and patterns automatically from data. However, data mining differs from machine learning in that it deals with large volumes of data, stored primarily on disk.Knowledge discovered from a database can be represented by a set of rules. We can discover rules from database using one of two models:In the first model, the user is involved directly in the process of knowledge discovery.In the second model, the system is responsible for automatically discovering knowledge from the database, by detecting patterns and correlations in the data.Work on automatic discovery of rules has been influenced strongly by work in the artificial-intelligence community on machine learning. The main differences lie in the volume of data handled in databases, and in the need to access disk. Specialized data-mining algorithms have been developed to handle large volumes of disk-resident data efficiently.The manner in which rules are discovered depends on the class of data-mining application. We illustrate rule discovery using two application classes: classification and associations.Second. Spatial and Geographic DatabasesSpatial databases store information related to spatial locations, and provide support for efficient querying and indexing based on spatial locations. Two types of spatial databases are particularly important:Design databases, or computer-aided-design (CAD) databases, are spatial databases used to store design information about how objects---such as buildings, cars or aircraft---are constructed. Other important examples of computer-aided-design databases are integrated-circuit and electronic-device layouts.Geographic databases are spatial databases used to store geographic information, such as maps. Geographic databases are often called geographic information systems.Geographic data are spatial in nature, but differ from design data in certain ways. Maps and satellite images are typical examples of geographic data. Maps may provide not only location information -suchas boundaries, rivers and roads---but also much more detailed information associated with locations, such as elevation, soil type, land usage, and annual rainfall.Geographic data can be categorized into two types: raster data (such data consist a bit maps or pixel maps, in two or more dimensions.), vector data (vector data are constructed from basic geographic objects). Map data are often represented in vector format.Third. Multimedia DatabasesRecently, there has been much interest in databases that store multimedia data, such as images, audio, and video. Today multimedia data typically are stored outside the database, in files systems. When the number of multimedia objects is relatively small, features provided by databases are usually not important. Database functionality becomes important when the number of multimedia objects stored is large. Issues such as transactional updates, querying facilities, and indexing then become important. Multimedia objects often have descriptive attributes, such as those indicating when they were created, who created them, and to what category they belong. One approach to building a database for such multimedia objects is to use database for storing the descriptive attributes, and for keeping track of the files in which the multimedia objects are stored.However, storing multimedia outside the database makes it harder to provide database functionality, such as indexing on the basis of actual multimedia data content. It can also lead to inconsistencies, such a file that is noted in the database, but whose contents are missing, or vice versa. It is therefore desirable to store the data themselves in the database.Forth. Mobility and Personal DatabasesLarge-scale commercial databases have traditionally been stored in central computing facilities. In the case of distributed database applications, there has usually been strong central database and network administration. Two technology trends have combined to create applications in which this assumption of central control and administration is not entirely correct:1.The increasingly widespread use of personal computers, and, more important, of laptop or “notebook” computers.2.The development of a relatively low-cost wireless digital communication infrastructure, base on wireless local-area networks, cellular digital packet networks, and other technologies.Wireless computing creates a situation where machines no longer have fixed locations and network addresses. This complicates query processing, since it becomes difficult to determine the optimal location at which to materialize the result of a query. In some cases, the location of the user is a parameter of the query. A example is a traveler’s information system that provides data on hotels, roadside services, and the like to motorists. Queries about services that are ahead on the current route must be processed based on knowledge of the user’s location, direction of motion, and speed.Energy (battery power) is a scarce resource for mobile computers. This limitation influences many aspects of system design. Among the more interesting consequences of the need for energy efficiency is the use of scheduled data broadcasts to reduce the need for mobile system to transmit queries. Increasingly amounts of data may reside on machines administered by users, rather than by database administrators. Furthermore, these machines may, at times, be disconnected from the network.SummaryDecision-support systems are gaining importance, as companies realize the value of the on-line data collected by their on-line transaction-processing systems. Proposed extensions to SQL, such as the cube operation, help to support generation of summary data. Data mining seeks to discoverknowledge automatically, in the form of statistical rules and patterns from large databases. Data visualization systems help humans to discover such knowledge visually.Spatial databases are finding increasing use today to store computer-aided design data as well as geographic data. Design data are stored primarily as vector data; geographic data consist of a combination of vector and raster data.Multimedia databases are growing in importance. Issues such as similarity-based retrieval and delivery of data at guaranteed rates are topics of current research.Mobile computing systems have become common, leading to interest in database systems that can run on such systems. Query processing in such systems may involve lookups on server database.毕业设计(论文)——外文翻译(译文)数据库的新应用我们使用关系数据库已经有20多年了,关系数据库应用中有很大一部分都用于商业领域支持诸如银行和证券交易所的事务处理、各种业务的销售和预约,以及几乎所有公司都需要的财产目录和工资单管理。
毕业设计外文文献翻译【范本模板】
毕业设计(论文)外文资料翻译系别:专业:班级:姓名:学号:外文出处:附件: 1. 原文; 2。
译文2013年03月附件一:A Rapidly Deployable Manipulator SystemChristiaan J。
J。
Paredis, H. Benjamin Brown,Pradeep K. KhoslaAbstract:A rapidly deployable manipulator system combines the flexibility of reconfigurable modular hardware with modular programming tools,allowing the user to rapidly create a manipulator which is custom-tailored for a given task. This article describes two main aspects of such a system,namely,the Reconfigurable Modular Manipulator System (RMMS)hardware and the corresponding control software。
1 IntroductionRobot manipulators can be easily reprogrammed to perform different tasks, yet the range of tasks that can be performed by a manipulator is limited by mechanicalstructure。
Forexample,a manipulator well-suited for precise movement across the top of a table would probably no be capable of lifting heavy objects in the vertical direction. Therefore,to perform a given task,one needs to choose a manipulator with an appropriate mechanical structure.We propose the concept of a rapidly deployable manipulator system to address the above mentioned shortcomings of fixed configuration manipulators。
(完整版)_毕业设计(论文) 外文文献翻译_
毕业设计(论文)外文文献翻译题目:金融银行信用风险管理与知识管理教学院:经济与管理学院专业名称:工商管理学号:学生姓名:谭勤辉指导教师:刘显铭2013 年05 月28 日Managing Credit Risks with Knowledge ManagementforFinancial BanksPan JinDepartment of EconomicsEconomics and Management School of Wuhan UniversityWuhan,Hubei ProvinceChinaAbstract-Nowadays,financial banks are operating in a knowledge society and there are more and more credit risks breaking out in banks.So,this paper first discusses the implications of knowledge and knowledge management, and then analyzes credit risks of financial banks with knowledge management. Finally, the paper studies ways for banks to manage credit risks with knowledge management. With the application of knowledge management in financial banks, customers will acquire better service and banks will acquire more rewards.Index Terms–knowledge management; credit risk; risk management; incentive mechanism; financial banksI.INTRODUCTIONNowadays,banks are operating in a“knowledge society”.So, what is knowledge? Davenport(1996)[1]thinks knowledge is professional intellect,such as know-what, know- be shared and communicated. The awareness of the importance of knowledge results in the critical issue of “knowledge management”.So, what is knowledge management? According to Malhothra(2001)[2], knowledge management(KM)caters to the critical issues of organizational adaptation, survival and competence in face of increasingly discontinuous environmental change. Essentially it embodies organizational processes that seek synergistic combination of data and information processing capacity of information technologies and the creative and innovative capacity of beings. Through the processes of creating,sustaining, applying, sharing and renewing knowledge, we can enhance organizational performance and create value.Many dissertations some special fields. Aybübe Aurum(2004)[3] analyzes knowledge management in software engineering and D.J.Harvey &R.Holdsworth(2005)[4]study knowledge management in the aerospace industry. Li Yang(2007)[5] studies knowledge management in information-based education and Jayasundara&Chaminda Chiran(2008)[6] review the prevailing literature on knowledge management in banking industries. Liang ping and Wu Kebao(2010)[7]study the incentive mechanism of knowledge management inBanking.There are also many papers about risks analysis and risks management. Before the 1980s, the dominant mathematical theory of risks analysis was to describe a pair of random vectors.But,the simplificationassumptions and methods used by classical competing risks analysis caused controversy and criticism.Starting around the 1980s, an alternative formulation of risk analysis was developed,with the identifiability. The new formulation is univariate risk analysis.According to Crowder(2001)[8], David&Moeschberger(1978)[9]and Hougaard(2000)[10],univariate survival risk analysis dominantly, which is based on the i.i.d assumptions(independent and identically distributed) or, at least, based on the independent failure assumption.Distribution-free regression modeling allows one to investigate the influences of multiple covariates on the failure, and it relaxes the assumption of identical failure distribution and to some extent, it also relaxes the single failure risk restriction. However, the independent failures as well as single failure events are still assumed in the univariate survival analysis. Of course,these deficiencies do not invalidate univariate analysis, and indeed, in many applications, those assumptions are realistically valid.Based on the above mentioned studies, Ma and Krings(2008a, 2008b)[11]discuss the relationship and difference of univariate and multivariate analysis in calculating risks.As for the papers on managing the risks in banks, Lawrence J.White(2008)[12]studies the risks of financial innovations and takes out some countermeasures to regulate financial innovations. Shao Baiquan(2010)[13]studies the ways to manage the risks in banks.From the above papers, we can see that few scholars Ⅰis introduction. SectionⅡanalyzes credit risks in banks with knowledge management. SectionⅢstudies ways for banks to manage credit risks with knowledgemanagement. SectionⅣconcludes.II.ANALYZING CREDIT RISKS IN BANKS WITHKNOWLEDGE MANAGEMENTA.Implication of Credit RiskCredit risk is the risk of loss due to a debtor’s non-payment of a loan or other line of credit, which may be the principal or interest or both.Because there are many types of loans and counterparties-from individuals to sovereign governments-and many different types of obligations-from auto loans to derivatives transactions-credit risk may take many forms.Credit risk is common in our daily life and we can not cover it completely,for example,the American subprime lending crisis is caused by credit risk,which is that the poor lenders do not pay principal and interest back to the banks and the banks do not pay the investors who buy the securities based on the loans.From the example,we can find that there are still credit risks,though banks banks includes tacit knowledge and explicit knowledge,which is scattered in different fields.For example, the information about the customers’income, asset and credit is controlled by different departments and different staffs and the information can’t be communicated with others. So it is necessary for banks to set up a whole system to communicate and share the information and knowledge to manage the risks.C.Setting up Incentive Mechanism and Encouraging Knowledge InnovationThe warning mechanism of credit risks depends on the incentive mechanism in banks,so, banks should take out incentive mechanism to urge staffs to learn more knowledge and work creatively to manage credit risks.We can show the incentive mechanism as Fig.1:Fig.1 The model of incentive mechanism with knowledge management From Fig.1,we can see there are both stimulative and punitive measures in the incentive model of knowledge management for financial banks.With the incentive mechanism of knowledge management in financial banks,the staffs will work managing credit risks with knowledge management.We can show them in Fig.2:Fig.2 The blocks of managing credit risksA.Distinguishing Credit RiskDistinguishing credit risks is the basis of risk management.If we can’t recognize the risks,we are unable to find appropriate solutions to manage risks.For example,the United States subprime crisis in 2007 was partly caused by that the financial institutions and regulators didn’t recognize the mortgage securitization risks timely.With knowledge management,we can make out some rules to distinguish credit risks,which are establishing one personal credit rating system for customers and setting up the data warehouse.We can use the system to analyze customers’credit index, customers’credit the changes of customers’property and income to recognize potential risks.B.Assessing and Calculating Credit RiskAfter distinguishing the credit risks,we should assess the riskexposure,risk factors and potential losses and risks, and we should make out the clear links.The knowledgeable staffs in banking should use statistical methods and model and the regulators should establish credit assessment system and then set up one national credit assessment system.With the system and the model of risk assessment,the managers can evaluate the existing and emerging risk factors,such as they prepare credit ratings for internal use.Other firms,including Standard &Poor’s,Moody’s and Fitch,are in the business of developing credit rating for use by investors or other third parties.TableⅠshows the credit ratings of Standard&Poor’s.TABLE ISTANDARD&POOR’S CREDITT RATINGSCredit ratings ImplicationsAAA Best credit quality,extremely reliableAA Very good credit quality,very reliableA More susceptible to economic conditionsBBB Lowest rating in investment gradeBB Caution is necessaryB Vulnerable to changes in economicCCC Currently vulnerable to nonpaymentCC Highly vulnerable to payment defaultC Close to bankruptD Payment default has actually occurredAfter assessing credit risks,we can use Standardized Approach andInternal Rating-Based Approach to calculate the risks.And in this article,we will analyze uncovered loan.To calculate credit risk of an uncovered loan,firstly,we will acquire the bo rrower’s Probability of Default(PD),Loss Given Default(LGD),Exposure at Default(EAD)and Remaining Maturity(M).Secondly,we calculate the simple risk(SR)of the uncovered loan,using the formula as following: SR=Min{BSR(PD)*[1+b(PD)*(M-3)]*LGD50,LGD*12.5} (1)Where BSR is the basic risk weight and b(PD)is the adjusting factor for remaining maturity(M).Finally,we can calculate the weighted risk(WR)of the uncovered loan,using the following formula:WR=SR*EAD (2)From(1)and(2),we can acquire the simple and weighted credit risk of an uncovered loan,and then we can take some measures to ’t repay the loans,banks can get the compensation from the insurance company.(3)Loans Securitization. Banks can change the loans into security portfolio,according to the different interest rate and term of the loans,and then banks can sell the security portfolio to the special organizations or trust companies.D.Managing Credit Risk and Feeding backA customer may acquire the customer’s credit information,credit the data the banks get.By assessing and calculating the risks of the customer,banks can expect the future behavior of the customers and provides different service for different customers. Banks can provide morevalue-added service to the customers who remedial after the risks broke out.In order to set up the warning and feeding back mechanism,banks should score credit of the customers comprehensively and then test the effectiveness and suitability of the measures,which banks use to mitigate risks.Finally, banks should update the data of the customers timely and keep the credit risk management system operating smoothly.IV.CONCLUSIONIn this paper,we first discuss the implications of knowledge and knowledge management.Then we analyze the credit risks of financial banks with knowledge management. Finally,we put forward ways for banks to manage credit risks with knowledge management.We think banks should set up data warehouse of customers’credit to assess and calculate the credit risks,and at the same time,banks should train knowledgeable staffs to construct a whole system to reduce risks and feed back.With knowledge management,banks can take out systemic measures to manage customers’credit risks and gain sustainable profits.ACKNOWLEDGMENTIt is financed by the of China(NO.06JC790032).REFERENCES[1]Davenport,T.H.et al,“Improving knowledge work processes,”Sloan Management Review,MIT,USA,1996,Vol.38,pp.53-65.[2]Malhothra,“Knowledge management for the new world of business,”New York BRINT Institute,2001, software engineering education,”Proceedings of the IEEE International Conference onAdvanced Learning Technologies,2004,pp..[4]D.J.Harvey&R.Holdsworth,“Knowledge management in the aerospace industry,”Proceedings of the IEEE International Professional Communication Conference,2005,pp..[5]Li Yang,“Thinking about knowledge management applications in information-based education,”IEEE International Conference on Advanced Learning Technologies,2007,pp.27-33.[6]Jayasundara&Chaminda Chiran,“Knowledge managemen t in banking industries:uses and opportunities,”Journal of the University Librarians Association of Sri Lanka,2008,Vol.12,pp.68-84.[7]Liang Ping,Wu Kebao,“Knowledge management in banking,”The Conference on Engineering and Business Management,2010, pp..[8]Crowder,M.J.Classical Competing Risks,British:Chapman&Hall, 2001,pp.200.[9]David,H.A.&M.L.Moeschberger,The Theory of Competing Risks, Scotland,Macmillan Publishing,1978,pp.103.金融银行信用风险管理与知识管理摘要:目前,金融银行经营在一个知识型社会中,而且越来越多的信用风险在在银行中爆发。
毕业设计外文文献翻译
毕业设计外文文献翻译Graduation design of foreign literature translation 700 words Title: The Impact of Artificial Intelligence on the Job Market Abstract:With the rapid development of artificial intelligence (AI), concerns arise about its impact on the job market. This paper explores the potential effects of AI on various industries, including healthcare, manufacturing, and transportation, and the implications for employment. The findings suggest that while AI has the potential to automate repetitive tasks and increase productivity, it may also lead to job displacement and a shift in job requirements. The paper concludes with a discussion on the importance of upskilling and retraining for workers to adapt to the changing job market.1. IntroductionArtificial intelligence (AI) refers to the development of computer systems that can perform tasks that typically require human intelligence. AI has made significant advancements in recent years, with applications in various industries, such as healthcare, manufacturing, and transportation. As AI technology continues to evolve, concerns arise about its impact on the job market. This paper aims to explore the potential effects of AI on employment and discuss the implications for workers.2. Potential Effects of AI on the Job Market2.1 Automation of Repetitive TasksOne of the major impacts of AI on the job market is the automation of repetitive tasks. AI systems can perform tasks faster and moreaccurately than humans, particularly in industries that involve routine and predictable tasks, such as manufacturing and data entry. This automation has the potential to increase productivity and efficiency, but also poses a risk to jobs that can be easily replicated by AI.2.2 Job DisplacementAnother potential effect of AI on the job market is job displacement. As AI systems become more sophisticated and capable of performing complex tasks, there is a possibility that workers may be replaced by machines. This is particularly evident in industries such as transportation, where autonomous vehicles may replace human drivers, and customer service, where chatbots can handle customer inquiries. While job displacement may lead to short-term unemployment, it also creates opportunities for new jobs in industries related to AI.2.3 Shifting Job RequirementsWith the introduction of AI, job requirements are expected to shift. While AI may automate certain tasks, it also creates a demand for workers with the knowledge and skills to develop and maintain AI systems. This shift in job requirements may require workers to adapt and learn new skills to remain competitive in the job market.3. Implications for EmploymentThe impact of AI on employment is complex and multifaceted. On one hand, AI has the potential to increase productivity, create new jobs, and improve overall economic growth. On the other hand, it may lead to job displacement and a shift in job requirements. To mitigate the negative effects of AI on employment, it is essentialfor workers to upskill and retrain themselves to meet the changing demands of the job market.4. ConclusionIn conclusion, the rapid development of AI has significant implications for the job market. While AI has the potential to automate repetitive tasks and increase productivity, it may also lead to job displacement and a shift in job requirements. To adapt to the changing job market, workers should focus on upskilling and continuous learning to remain competitive. Overall, the impact of AI on employment will depend on how it is integrated into various industries and how workers and policymakers respond to these changes.。
工业工程英文文献及外文翻译
附录附录1:英文文献Line Balancing in the Real WorldAbstract:Line Balancing (LB) is a classic, well-researched Operations Research (OR) optimization problem of significant industrial importance. It is one of those problems where domain expertise does not help very much: whatever the number of years spent solving it, one is each time facing an intractable problem with an astronomic number of possible solutions and no real guidance on how to solve it in the best way, unless one postulates that the old way is the best way .Here we explain an apparent paradox: although many algorithms have been proposed in the past, and despite the problem’s practical importance, just one commercially available LB software currently appears to be available for application in industries such as automotive. We speculate that this may be due to a misalignment between the academic LB problem addressed by OR, and the actual problem faced by the industry.Keyword:Line Balancing, Assembly lines, OptimizationLine Balancing in the Real WorldEmanuel FalkenauerOptimal DesignAv. Jeanne 19A boîte2, B-1050 Brussels, Belgium+32 (0)2 646 10 741 IntroductionAssembly Line Balancing, or simply Line Balancing (LB), is the problem of assigning operations to workstations along an assembly line, in such a way that the assignment be optimal in some sense. Ever since Henry Ford’s introduction of assembly lines, LB has been an optimization problem of significant industrial importance: the efficiency difference between an optimal and a sub-optimal assignment can yield economies (or waste) reaching millions of dollars per year.LB is a classic Operations Research (OR) optimization problem, having been tackled by OR over several decades. Many algorithms have been proposed for the problem. Yet despite the practical importance of the problem, and the OR efforts that have been made to tackle it, little commercially available software is available to help industry in optimizing their lines. In fact, according to a recent survey by Becker and Scholl (2023), there appear to be currently just two commercially available packages featuring both a state of the art optimization algorithm and auser-friendly interface for data management. Furthermore, one of those packages appears to handle only the “clean” formulation of the problem (Simple Assembly Line Balancing Problem, or SALBP), which leaves only one package available for industries such as automotive. This situation appears to be paradoxical, or at least unexpected: given the huge economies LB can generate, one would expect several software packages vying to grab a part of those economies.It appears that the gap between the available OR results and their dissemination in Today’s industry, is probably due to a misalignment between the academic LB problem addressed by most of the OR approaches, and the actual problem being faced by the industry. LB is a difficult optimization problem even its simplest forms are NP-hard – see Garry and Johnson, 1979), so the approach taken by OR has typically been to simplify it, in order to bring it to a level of complexity amenable to OR tools. While this is a perfectly valid approach in general, in the particular case of LB it led some definitions of the problem hat ignore many aspects of the real-world problem.Unfortunately, many of the aspects that have been left out in the OR approach are in fact crucial to industries such as automotive, in the sense that any solution ignoring (violating) those aspects becomes unusable in the industry.In the sequel, we first briefly recall classic OR definitions of LB, and then review how the actual line balancing problem faced by the industry differs from them, and why a solution to the classic OR problem maybe unusable in some industries.2 OR Definitions of LBThe classic OR definition of the line balancing problem, dubbed SALBP (Simple Assembly Line Balancing Problem) by Becker and Scholl (2023), goes as follows. Given a set of tasks of various durations, a set of precedence constraints among the tasks, and a set of workstations, assign each task to exactly one workstation in such a way that no precedence constraint is violated and the assignment is optimal. The optimality criterion gives rise to two variants of the problem: either a cycle time is given that cannot be exceeded by the sum of durations of all tasks assigned to any workstation and the number of workstations is to be minimized, or the number of workstations is fixed and the line cycle time, equal to the largest sum of durations of task assigned to a workstation, is to be minimized.Although the SALBP only takes into account two constraints (the precedence constraints plus the cycle time, or the precedence constraints plus the number of workstations), it is by far the variant of line balancing that has been the most researched. We have contributed to that effort in Falkenauer and Delchambre (1992), where we proposed a Grouping Genetic Algorithm approach that achieved some of the best performance in the field. The Grouping Genetic Algorithm technique itself was presented in detail in Falkenauer (1998).However well researched, the SALBP is hardly applicable in industry, as we will see shortly. The fact has not escaped the attention of the OR researches, and Becker and Scholl (2023) define many extensions to SALBP, yielding a commondenomination GALBP (Generalized Assembly Line Balancing Problem). Each of the extensions reported in their authoritative survey aims to handle an additional difficulty present in real-world line balancing. We have tackled one of those aspects in Falkenauer (1997), also by applying the Grouping Genetic Algorithm.The major problem with most of the approaches reported by Becker and Scholl (2023) is that they generalize the simple SALBP in just one or two directions. The real world line balancing, as faced in particular by the automotive industry, requires tackling many of those generalizations simultaneously.3 What Differs in the Real World?Although even the simple SALBP is NP-hard, it is far from capturing the true complexity of the problem in its real-world incarnations. On the other hand, small instances of the problem, even though they are difficult to solve to optimality, are a tricky target for line balancing software, because small instances of the problem can be solved closet optimality by hand. That is however not the case in the automotive and related industries (Bus, truck, aircraft, heavy machinery, etc.), since those industries routinely feature Assembly lines with dozens or hundreds of workstations, and hundreds or thousands of Operations. Those industries are therefore the prime targets for line balancing software.Unfortunately, those same industries also need to take into account many of the GALBP extensions at the same time, which may explain why, despite the impressive OR Work done on line balancing; only one commercially available software seemstube currently available for those industries.We identify below some of the additional difficulties (with respect to SALBP) that must be tackled in a line balancing tool, in order to be applicable in those industries.3.1 Do Not Balance but Re-balanceMany of the OR approaches implicitly assume that the problem to be solved involves a new, yet-to-be-built assembly line, possibly housed in a new, yet-to-be-built factory. To our opinion, this is the gravest oversimplification of the classic OR approach, for in practice, this is hardly ever the case. The vast majority of real-world line balancing tasks involve existing lines, housed in existing factories – infect, the target line typically needs tube rebalanced rather than balanced, the need arising from changes in the product or the mix of models being assembled in the line, the assembly technology, the available workforce, or the production targets. This has some far-reaching implications, outlined below.3.2 Workstations Have IdentitiesAs pointed out above, the vast majority of real-world line balancing tasks involves existing lines housed in existing factories. In practice, this seemingly “uninteresting” observation has one far-reaching consequence, namely that each workstation in the line does have its own identity. This identity is not due to any “incapacity of abstraction” on part of the process engineers, but rather to the fact that the workstations are indeed not identical: each has its own space constraints (e.g. a workstation below a low ceiling cannot elevate the car above the operators’ heads),its own heavy equipment that cannot be moved spare huge costs, its own capacity of certain supplies (e.g. compressed air), its own restrictions on the operations that can be carried out there (e.g. do not place welding operations just beside the painting shop), etc.3.3 Cannot Eliminate WorkstationsSince workstations do have their identity (as observed above), it becomes obvious that a real-world LB tool cannot aim at eliminating workstations. Indeed, unless the eliminated workstations were all in the front of the line or its tail, their elimination would create gaping holes in the line, by virtue of the other workstations’ retaining of their identities, including their geographical positions in the workshop. Also, it softens the case that many workstations that could possibly be eliminated by the algorithm are in fact necessary because of zoning constraints.4 ConclusionsThe conclusions inspection 3 stems from our extensive contacts with automotive and related industries, and reflects their true needs. Other “exotic” constraints may apply in any given real-world assembly line, but line balancing tool for those industries must be able to handle at least those aspects of the problem. This is very far from the “clean” academic SALBP, as well as most GALBP extensions reported by Becker and Scholl (2023). In fact, such a tool must simultaneously solve several-hard problems:• Find a feasible defined replacement for all undefined (‘ANY’) ergonomicconstraints on workstations, i.e. One compatible with the ergonomic constraints and precedence constraints defined on operations, as well as zoning constraints and possible drifting operations• Solve the within-workstation scheduling problem on all workstations, for all products being assembled on the line• Assign the operations to workstations to achieve the best average balance, while keeping the peak times at a manageable level. Clearly, the real-world line balancing problem described above is extremely difficult to solve. This is compounded byte size of the problem encountered in the target industries, which routinely feature assembly lines with dozens or hundreds of workstations with multiple operators, and hundreds or thousands of operations.We’ve identified a number of aspects of the line balancing problem that are vital in industries such as automotive, yet that have been either neglected in the OR work on the problem, or handled separately from each other. According to our experience, a line balancing to applicable in those industries must be able to handle all of them simultaneously. That gives rise to an extremely complex optimization problem.The complexity of the problem, and the need to solve it quickly, may explain why there appears to be just one commercially available software for solving it, namely outline by Optimal Design. More information on Outline, including its rich graphic user interface, is available at .References1 Becker C. and Scholl, A. (2023) `A survey on problems and methods in generalized assemblyline balancing', European Journal of Operations Research, in press. Available online at :10.1016/j.ejor.2023.07.023. Journal article.2 Falkenauer, E. and Delchambre, A. (1992) `Genetic Algorithm for Bin Packing and Line Balancing', Proceedings of the 1992 IEEE International Conference on Robotics and Automation, May10-15, 1992, Nice, France. IEEE Computer Society Press, Los Alamitos, CA. Pp. 1186-1192. Conference proceedings.3 Falkenauer, E. (1997) `A Grouping Genetic Algorithm for Line Balancing with Resource Dependent Task Times', Proceedings of the Fourth International Conference on Neural Information Processing (ICONIP’97), University of Otego, Dunedin, New Zealand, November 24-28, 1997. Pp. 464-468. Conference proceedings.4 Falkenauer, E. (1998) Genetic Algorithms and Grouping Problems, John Wiley& Sons, Chi Chester, UK. Book.5 Gary. R. and Johnson D. S. (1979) Computers and Intractability - A Guide to the Theory of NP-completeness, Co., San Francisco, USA. Book.附录2:中文文献生产线平衡在现实世界摘要:生产线平衡(LB)是一种经典旳,精心研究旳明显工业重要性旳运筹学(OR)优化问题。
毕业设计(论文)外文资料及译文(模板)
大连东软信息学院
毕业设计(论文)外文资料及译文
系所:
专业:
班级:
姓名:
学号:
大连东软信息学院
Dalian Neusoft University of Information
外文资料和译文格式要求
一、装订要求
1、外文资料原文(复印或打印)在前、译文在后、最后为指导教师评定成绩。
2、译文必须采用计算机输入、打印。
3、A4幅面打印,于左侧装订。
二、撰写要求
1、外文文献内容与所选课题相关。
2、本科学生译文汉字字数不少于4000字,高职学生译文汉字字数不少于2000字。
三、格式要求
1、译文字号:中文小四号宋体,英文小四号“Times New Roman”字型,全文统一,首行缩进2个中文字符,1.5倍行距。
2、译文页码:页码用阿拉伯数字连续编页,字体采用“Times New Roman”字体,字号小五,页底居中。
3、译文页眉:眉体使用单线,页眉说明五号宋体,居中“大连东软信息学院本科毕业设计(论文)译文”。
大连东软信息学院毕业设计(论文)译文
大连东软信息学院毕业设计(论文)译文
大连东软信息学院毕业设计(论文)译文
大连东软信息学院毕业设计(论文)译文
大连东软信息学院毕业设计(论文)译文。
毕业论文外文文献以及中文译文
Stores like the one in Shenzhen show how much has changed in Chinese retailing. Just two decades ago, shops had surly staff offering a few drab items, often locked safely away in glass cases. Yet there is still a long way to go. Even today, much of the population buys from daily markets or directly from producers. ቤተ መጻሕፍቲ ባይዱrganised retailing remains relatively new. Most Chinese stores are tiny, family-run outfits. China's top 100 chains account for just a tenth of total retail sales.
毕业论文英文参考文献与译文
Inventory managementInventory ControlOn the so-called "inventory control", many people will interpret it as a "storage management", which is actually a big distortion.The traditional narrow view, mainly for warehouse inventory control of materials for inventory, data processing, storage, distribution, etc., through the implementation of anti-corrosion, temperature and humidity control means, to make the custody of the physical inventory to maintain optimum purposes. This is just a form of inventory control, or can be defined as the physical inventory control. How, then, from a broad perspective to understand inventory control? Inventory control should be related to the company's financial and operational objectives, in particular operating cash flow by optimizing the entire demand and supply chain management processes (DSCM), a reasonable set of ERP control strategy, and supported by appropriate information processing tools, tools to achieved in ensuring the timely delivery of the premise, as far as possible to reduce inventory levels, reducing inventory and obsolescence, the risk of devaluation. In this sense, the physical inventory control to achieve financial goals is just a means to control the entire inventory or just a necessary part; from the perspective of organizational functions, physical inventory control, warehouse management is mainly the responsibility of The broad inventory control is the demand and supply chain management, and the whole company's responsibility.Why until now many people's understanding of inventory control, limited physical inventory control? The following two reasons can not be ignored:First, our enterprises do not attach importance to inventory control. Especially those who benefit relatively good business, as long as there is money on the few people to consider the problem of inventory turnover. Inventory control is simply interpreted as warehouse management, unless the time to spend money, it may have been to see the inventory problem, and see the results are often very simple procurement to buy more, or did not do warehouse departments .Second, ERP misleading. Invoicing software is simple audacity to call it ERP, companies on their so-called ERP can reduce the number of inventory, inventory control, seems to rely on their small software can get. Even as SAP, BAAN ERP world, the field ofthese big boys, but also their simple modules inside the warehouse management functionality is defined as "inventory management" or "inventory control." This makes the already not quite understand what our inventory control, but not sure what is inventory control.In fact, from the perspective of broadly understood, inventory control, shouldinclude the following:First, the fundamental purpose of inventory control. We know that the so-called world-class manufacturing, two key assessment indicators (KPI) is, customer satisfaction and inventory turns, inventory turns and this is actually the fundamental objective of inventory control.Second, inventory control means. Increase inventory turns, relying solely on the so-called physical inventory control is not enough, it should be the demand and supply chain management process flow of this large output, and this big warehouse management processes in addition to including this link, the more important The section also includes: forecasting and order processing, production planning and control, materials planning and purchasing control, inventory planning and forecasting in itself, as well as finished products, raw materials, distribution and delivery of the strategy, and even customs management processes.And with the demand and supply chain management processes throughout the process, it is the information flow and capital flow management. In other words, inventory itself is across the entire demand and supply management processes in all aspects of inventory control in order to achieve the fundamental purpose, it must control all aspects of inventory, rather than just manage the physical inventory at hand.Third, inventory control, organizational structure and assessment.Since inventory control is the demand and supply chain management processes, output, inventory control to achieve the fundamental purpose of this process must be compatible with a rational organizational structure. Until now, we can see that many companies have only one purchasing department, purchasing department following pipe warehouse. This is far short of inventory control requirements. From the demand and supply chain management process analysis, we know that purchasing and warehouse management is the executive arm of the typical, and inventory control should focus on prevention, the executive branch is very difficult to "prevent inventory" for the simple reason that they assessment indicatorsin large part to ensure supply (production, customer). How the actual situation, a reasonable demand and supply chain management processes, and thus set the corresponding rational organizational structure and is a question many of our enterprisesto exploreThe role of inventory controlInventory management is an important part of business management. In the production and operation activities, inventory management must ensure that both the production plant for raw materials, spare parts demand, but also directly affect the purchasing, sales of share, sales activities. To make an inventory of corporate liquidity, accelerate cash flow, the security of supply under the premise of minimizing Yaku funds, directly affects the operational efficiency. Ensure the production and operation needs of the premise, so keep inventories at a reasonable level; dynamic inventory control, timely, appropriate proposed order to avoid over storage or out of stock; reduce inventory footprint, lower total cost of inventory; control stock funds used to accelerate cash flow.Problems arising from excessive inventory: increased warehouse space andinventory storage costs, thereby increasing product costs; take a lot of liquidity, resultingin sluggish capital, not only increased the burden of payment of interest, etc., would affect the time value of money and opportunity income; finished products and raw materials caused by physical loss and intangible losses; a large number of enterprise resource idle, affecting their rational allocation and optimization; cover the production, operation of the whole process of the various contradictions and problems, is not conducive to improve the management level.Inventory is too small the resulting problems: service levels caused a decline in the profit impact of marketing and corporate reputation; production system caused by inadequate supply of raw materials or other materials, affecting the normal production process; to shorten lead times, increase the number of orders, so order (production) costs; affect the balance of production and assembly of complete sets.NotesInventory management should particularly consider the following two questions:First, according to sales plans, according to the planned production of the goods circulated in the market, we should consider where, how much storage.Second, starting from the level of service and economic benefits to determine howto ensure inventories and supplementary questions.The two problems with the inventory in the logistics process functions.In general, the inventory function:(1)to prevent interrupted. Received orders to shorten the delivery of goods fromthe time in order to ensure quality service, at the same time to prevent out of stock.(2)to ensure proper inventory levels, saving inventory costs.(3)to reduce logistics costs. Supplement with the appropriate time interval compatible with the reasonable demand of the cargo in order to reduce logistics costs, eliminate or avoid sales fluctuations.(4)ensure the production planning, smooth to eliminate or avoid sales fluctuations.(5)display function.(6)reserve. Mass storage when the price falls, reduce losses, to respond to disasters and other contingencies.About the warehouse (inventory) on what the question, we must consider the number and location. If the distribution center, it should be possible according to customer needs, set at an appropriate place; if it is stored in central places to minimize the complementary principle to the distribution centers, there is no place certain requirements. When the stock base is established, will have to take into account are stored in various locations in what commodities.库存管理库存控制在谈到所谓“库存控制”的时候,很多人将其理解为“仓储管理”,这实际上是个很大的曲解。
12、毕业论文外文参考中文译文
北京航空航天大学北海学院毕业设计(论文)外文文献译文生 姓名班级班级 学号学号 指 导 教 师 设计(论文)题 目浅析戴尔在中国的营销策略 参考外文题目参考外文题目 Customer Satisfaction Is Your Business外文出处外文出处Copyright 2004 Bob Leduc Customer Satisfaction Is Your BusinessRegardless of what business you are in - you arereally in the business of satisfying customers. Thedegree of c ustomer satisfaction you deliverdetermines the level of long-term success you willachieve in business. Make Customer Satisfaction Your Top PriorityDon't just make sales. Create customers - satisfiedcustomers. In addition to the immediate profit theyprovide on the first sale, satisfied customers help youbuild your business in 2 other important ways:1. They become a reservoir of repeat buyers. For some businesses that means repeat buyers for more ofthe sa me product or service. For every business, it means buyers for additional products and services.2. They automatically refer more business to you from their friends and business contacts. This is highlyprofit able business for you because it doesn't cost you any time or money to get it.Never Promise More Than You DeliverNever make any promises you can't (or won't) keep. Nothing alienates customers faster than gettingsomething less than they expect from a business transaction. They won't do business with you again. Andthey will tell e verybody they know about their unhappy experience - causing you to lose future customers.Tip: Handle customer complaints quickly and with a positive attitude. Strive to preserve your relationshipwit h the complaining customer instead of your immediate profit from them. They will reward you later withmore sales and referrals.Always Give Customers More Than They Expect "Over deliver" on quality and service. Always exceed your customers' expectations. You will win their longte rm loyalty. It also makes it difficult for competitors to steal customers from you - even if they have lowerpric es. Customers will not risk an uncertain experience with a competitor when they know they will get morethan they expect from you.Tip: Surprise your customers with unexpected value. If you sell products, include an "unadvertised bonus"wit h every order. If you sell services, get into the habit of doing something extra for every customer or clientwithout charging for it.Let customers know how much you value them.Let your customers know you are always thinking about them. Communicate with them regularly. Forexampl e, create some special deals just for your existing customers. And announce new products orservices to them before you announce them to the general market.Tip: Convert your customers into publicity agents. Develop an incentive for them to tell associates andfriends about the value of your products or services. An endorsement from them is more effective than anyamount of advertising - and it is much cheaper.For example, reward them each time they refer someone who becomes a customer. Your reward can be assim ple as a credit toward their next order from you.You are in the business of satisfying customers regardless of what products or services you provide. Thesatisf ied customers you create will help you build your business by becoming repeat buyers and byreferring new b usiness to you from their friends and associates.指导教师意见指导教师意见 指导教师(签名)指导教师(签名)年 月 日教务处教务处。
毕业设计(论文)外文资料翻译(搭配使用)
毕业设计(论文)外文资料翻译学院:经济管理学院专业:工商管理姓名:毛长雪学号: 070202130外文出处:Industrial Marketing Management附件: 1.外文资料翻译译文;2.外文原文。
(用外文写)附件1:外文资料翻译译文非关键项目的采购定制降低了汽车成本供应链:一个行动研究项目Giancarlo Medeiros Pereira a, Miguel Afonso Sellitto a,Borchardt a, Albert Geiger ba Universidade do Vale do Rio dos Sinos, UNISI NOS Av. UNISINOS, 950, São Leopoldo, RS, Brazilb Instituto Gaúcho de Estudos Automotivos, IGEA, Av. Assis Brasil, 8787, Porto Alegre, RS, Brazil2。
理论框架:供应链发展趋势发现一些行业很难实现可持续竞争优势,甚至难以确保他们的生存,因为该行业的复杂性和活力,他们面临的不确定性之高(巴斯克斯-特洛和埃夫拉,2006)。
在汽车行业,公司有'组织'的将供应商结构化网络化,野中和竹内报告(1986)以及今井野中和Takeuchi(1985)。
他们展示了如何带领厂商达到'主'(或第一层)和中学组(或分供应商第二层)的分包商。
基于成本效益分析,许多生产功能已经被外包到独立运营商和分包商(小田部及美利,2004)。
这种外包允许汽车装配分包商降低他们的总成本,提高质量,节省空间和缩短开发时间(亨克, 2000年)。
拓宽供应商来提高质量,降低基地费用(民,2009)。
这种趋势也可以到在一线和二线的汽车行业的供应商那观察,这也包括被迫外包的份额,其活动规模为较小的组织(Mudambi和助手,1998年)。
毕业设计(论文)外文文献原文及译文
毕业设计(论文)外文文献原文及译文Chapter 11. Cipher Techniques11.1 ProblemsThe use of a cipher without consideration of the environment in which it is to be used may not provide the security that the user expects. Three examples will make this point clear.11.1.1 Precomputing the Possible MessagesSimmons discusses the use of a "forward search" to decipher messages enciphered for confidentiality using a public key cryptosystem [923]. His approach is to focus on the entropy (uncertainty) in the message. To use an example from Section 10.1(page 246), Cathy knows that Alice will send one of two messages—BUY or SELL—to Bob. The uncertainty is which one Alice will send. So Cathy enciphers both messages with Bob's public key. When Alice sends the message, Bob intercepts it and compares the ciphertext with the two he computed. From this, he knows which message Alice sent.Simmons' point is that if the plaintext corresponding to intercepted ciphertext is drawn from a (relatively) small set of possible plaintexts, the cryptanalyst can encipher the set of possible plaintexts and simply search that set for the intercepted ciphertext. Simmons demonstrates that the size of the set of possible plaintexts may not be obvious. As an example, he uses digitized sound. The initial calculations suggest that the number of possible plaintexts for each block is 232. Using forward search on such a set is clearly impractical, but after some analysis of the redundancy in human speech, Simmons reduces the number of potential plaintexts to about 100,000. This number is small enough so that forward searches become a threat.This attack is similar to attacks to derive the cryptographic key of symmetric ciphers based on chosen plaintext (see, for example, Hellman's time-memory tradeoff attack [465]). However, Simmons' attack is for public key cryptosystems and does not reveal the private key. It only reveals the plaintext message.11.1.2 Misordered BlocksDenning [269] points out that in certain cases, parts of a ciphertext message can be deleted, replayed, or reordered.11.1.3 Statistical RegularitiesThe independence of parts of ciphertext can give information relating to the structure of the enciphered message, even if the message itself is unintelligible. The regularity arises because each part is enciphered separately, so the same plaintext always produces the same ciphertext. This type of encipherment is called code book mode, because each part is effectively looked up in a list of plaintext-ciphertext pairs.11.1.4 SummaryDespite the use of sophisticated cryptosystems and random keys, cipher systems may provide inadequate security if not used carefully. The protocols directing how these cipher systems are used, and the ancillary information that the protocols add to messages and sessions, overcome these problems. This emphasizes that ciphers and codes are not enough. The methods, or protocols, for their use also affect the security of systems.11.2 Stream and Block CiphersSome ciphers divide a message into a sequence of parts, or blocks, and encipher each block with the same key.Definition 11–1. Let E be an encipherment algorithm, and let Ek(b) bethe encipherment of message b with key k. Let a message m = b1b2…, whereeach biis of a fixed length. Then a block cipher is a cipher for whichE k (m) = Ek(b1)Ek(b2) ….Other ciphers use a nonrepeating stream of key elements to encipher characters of a message.Definition 11–2. Let E be an encipherment algorithm, and let Ek(b) bethe encipherment of message b with key k. Let a message m = b1b2…, whereeach bi is of a fixed length, and let k = k1k2…. Then a stream cipheris a cipher for which Ek (m) = Ek1(b1)Ek2(b2) ….If the key stream k of a stream cipher repeats itself, it is a periodic cipher.11.2.1 Stream CiphersThe one-time pad is a cipher that can be proven secure (see Section 9.2.2.2, "One-Time Pad"). Bit-oriented ciphers implement the one-time pad by exclusive-oring each bit of the key with one bit of the message. For example, if the message is 00101 and the key is 10010, the ciphertext is01||00||10||01||10 or 10111. But how can one generate a random, infinitely long key?11.2.1.1 Synchronous Stream CiphersTo simulate a random, infinitely long key, synchronous stream ciphers generate bits from a source other than the message itself. The simplest such cipher extracts bits from a register to use as the key. The contents of the register change on the basis of the current contents of the register.Definition 11–3. An n-stage linear feedback shift register (LFSR)consists of an n-bit register r = r0…rn–1and an n-bit tap sequence t =t 0…tn–1. To obtain a key bit, ris used, the register is shifted one bitto the right, and the new bit r0t0⊕…⊕r n–1t n–1 is inserted.The LFSR method is an attempt to simulate a one-time pad by generating a long key sequence from a little information. As with any such attempt, if the key is shorter than the message, breaking part of the ciphertext gives the cryptanalyst information about other parts of the ciphertext. For an LFSR, a known plaintext attack can reveal parts of the key sequence. If the known plaintext is of length 2n, the tap sequence for an n-stage LFSR can be determined completely.Nonlinear feedback shift registers do not use tap sequences; instead, the new bit is any function of the current register bits.Definition 11–4. An n-stage nonlinear feedback shift register (NLFSR)consists of an n-bit register r = r0…rn–1. Whenever a key bit is required,ris used, the register is shifted one bit to the right, and the new bitis set to f(r0…rn–1), where f is any function of n inputs.NLFSRs are not common because there is no body of theory about how to build NLFSRs with long periods. By contrast, it is known how to design n-stage LFSRs with a period of 2n– 1, and that period is maximal.A second technique for eliminating linearity is called output feedback mode. Let E be an encipherment function. Define k as a cryptographic key,(r) and define r as a register. To obtain a bit for the key, compute Ekand put that value into the register. The rightmost bit of the result is exclusive-or'ed with one bit of the message. The process is repeated until the message is enciphered. The key k and the initial value in r are the keys for this method. This method differs from the NLFSR in that the register is never shifted. It is repeatedly enciphered.A variant of output feedback mode is called the counter method. Instead of using a register r, simply use a counter that is incremented for every encipherment. The initial value of the counter replaces r as part of the key. This method enables one to generate the ith bit of the key without generating the bits 0…i – 1. If the initial counter value is i, set. In output feedback mode, one must generate all the register to i + ithe preceding key bits.11.2.1.2 Self-Synchronous Stream CiphersSelf-synchronous ciphers obtain the key from the message itself. The simplest self-synchronous cipher is called an autokey cipher and uses the message itself for the key.The problem with this cipher is the selection of the key. Unlike a one-time pad, any statistical regularities in the plaintext show up in the key. For example, the last two letters of the ciphertext associated with the plaintext word THE are always AL, because H is enciphered with the key letter T and E is enciphered with the key letter H. Furthermore, if theanalyst can guess any letter of the plaintext, she can determine all successive plaintext letters.An alternative is to use the ciphertext as the key stream. A good cipher will produce pseudorandom ciphertext, which approximates a randomone-time pad better than a message with nonrandom characteristics (such as a meaningful English sentence).This type of autokey cipher is weak, because plaintext can be deduced from the ciphertext. For example, consider the first two characters of the ciphertext, QX. The X is the ciphertext resulting from enciphering some letter with the key Q. Deciphering, the unknown letter is H. Continuing in this fashion, the analyst can reconstruct all of the plaintext except for the first letter.A variant of the autokey method, cipher feedback mode, uses a shift register. Let E be an encipherment function. Define k as a cryptographic(r). The key and r as a register. To obtain a bit for the key, compute Ek rightmost bit of the result is exclusive-or'ed with one bit of the message, and the other bits of the result are discarded. The resulting ciphertext is fed back into the leftmost bit of the register, which is right shifted one bit. (See Figure 11-1.)Figure 11-1. Diagram of cipher feedback mode. The register r is enciphered with key k and algorithm E. The rightmost bit of the result is exclusive-or'ed with one bit of the plaintext m i to produce the ciphertext bit c i. The register r is right shifted one bit, and c i is fed back into the leftmost bit of r.Cipher feedback mode has a self-healing property. If a bit is corrupted in transmission of the ciphertext, the next n bits will be deciphered incorrectly. But after n uncorrupted bits have been received, the shift register will be reinitialized to the value used for encipherment and the ciphertext will decipher properly from that point on.As in the counter method, one can decipher parts of messages enciphered in cipher feedback mode without deciphering the entire message. Let the shift register contain n bits. The analyst obtains the previous n bits of ciphertext. This is the value in the shift register before the bit under consideration was enciphered. The decipherment can then continue from that bit on.11.2.2 Block CiphersBlock ciphers encipher and decipher multiple bits at once, rather than one bit at a time. For this reason, software implementations of block ciphers run faster than software implementations of stream ciphers. Errors in transmitting one block generally do not affect other blocks, but as each block is enciphered independently, using the same key, identical plaintext blocks produce identical ciphertext blocks. This allows the analyst to search for data by determining what the encipherment of a specific plaintext block is. For example, if the word INCOME is enciphered as one block, all occurrences of the word produce the same ciphertext.To prevent this type of attack, some information related to the block's position is inserted into the plaintext block before it is enciphered. The information can be bits from the preceding ciphertext block [343] or a sequence number [561]. The disadvantage is that the effective block size is reduced, because fewer message bits are present in a block.Cipher block chaining does not require the extra information to occupy bit spaces, so every bit in the block is part of the message. Before a plaintext block is enciphered, that block is exclusive-or'ed with the preceding ciphertext block. In addition to the key, this technique requires an initialization vector with which to exclusive-or the initial plaintext block. Taking Ekto be the encipherment algorithm with key k, and I to be the initialization vector, the cipher block chaining technique isc 0 = Ek(m⊕I)c i = Ek(mi⊕ci–1) for i > 011.2.2.1 Multiple EncryptionOther approaches involve multiple encryption. Using two keys k and k' toencipher a message as c = Ek' (Ek(m)) looks attractive because it has aneffective key length of 2n, whereas the keys to E are of length n. However, Merkle and Hellman [700] have shown that this encryption technique can be broken using 2n+1encryptions, rather than the expected 22n(see Exercise 3).Using three encipherments improves the strength of the cipher. There are several ways to do this. Tuchman [1006] suggested using two keys k and k':c = Ek (Dk'(Ek(m)))This mode, called Encrypt-Decrypt-Encrypt (EDE) mode, collapses to a single encipherment when k = k'. The DES in EDE mode is widely used in the financial community and is a standard (ANSI X9.17 and ISO 8732). It is not vulnerable to the attack outlined earlier. However, it is vulnerable to a chosen plaintext and a known plaintext attack. If b is the block size in bits, and n is the key length, the chosen plaintext attacktakes O(2n) time, O(2n) space, and requires 2n chosen plaintexts. The known plaintext attack requires p known plaintexts, and takes O(2n+b/p) time and O(p) memory.A second version of triple encipherment is the triple encryption mode [700]. In this mode, three keys are used in a chain of encipherments.c = Ek (Ek'(Ek''(m)))The best attack against this scheme is similar to the attack on double encipherment, but requires O(22n) time and O(2n) memory. If the key length is 56 bits, this attack is computationally infeasible.11.3 Networks and CryptographyBefore we discuss Internet protocols, a review of the relevant properties of networks is in order. The ISO/OSI model [990] provides an abstract representation of networks suitable for our purposes. Recall that the ISO/OSI model is composed of a series of layers (see Figure 11-2). Each host, conceptually, has a principal at each layer that communicates with a peer on other hosts. These principals communicate with principals at the same layer on other hosts. Layer 1, 2, and 3 principals interact only with similar principals at neighboring (directly connected) hosts. Principals at layers 4, 5, 6, and 7 interact only with similar principals at the other end of the communication. (For convenience, "host" refers to the appropriate principal in the following discussion.)Figure 11-2. The ISO/OSI model. The dashed arrows indicate peer-to-peer communication. For example, the transport layers are communicating with each other. The solid arrows indicate the actual flow of bits. For example, the transport layer invokes network layer routines on the local host, which invoke data link layer routines, which put the bits onto the network. The physical layer passes the bits to the next "hop," or host, on the path. When the message reaches the destination, it is passed up to the appropriatelevel.Each host in the network is connected to some set of other hosts. They exchange messages with those hosts. If host nob wants to send a message to host windsor, nob determines which of its immediate neighbors is closest to windsor (using an appropriate routing protocol) and forwards the message to it. That host, baton, determines which of its neighbors is closest to windsor and forwards the message to it. This process continues until a host, sunapee, receives the message and determines that windsor is an immediate neighbor. The message is forwarded to windsor, its endpoint.Definition 11–5. Let hosts C0, …, Cnbe such that Ciand Ci+1are directlyconnected, for 0 i < n. A communications protocol that has C0 and Cnasits endpoints is called an end-to-end protocol. A communications protocolthat has Cj and Cj+1as its endpoints is called a link protocol.The difference between an end-to-end protocol and a link protocol is that the intermediate hosts play no part in an end-to-end protocol other than forwarding messages. On the other hand, a link protocol describes how each pair of intermediate hosts processes each message.The protocols involved can be cryptographic protocols. If the cryptographic processing is done only at the source and at the destination, the protocol is an end-to-end protocol. If cryptographic processing occurs at each host along the path from source to destination, the protocolis a link protocol. When encryption is used with either protocol, we use the terms end-to-end encryption and link encryption, respectively.In link encryption, each host shares a cryptographic key with its neighbor. (If public key cryptography is used, each host has its neighbor's public key. Link encryption based on public keys is rare.) The keys may be set on a per-host basis or a per-host-pair basis. Consider a network with four hosts called windsor, stripe, facer, and seaview. Each host is directly connected to the other three. With keys distributed on a per-host basis, each host has its own key, making four keys in all. Each host has the keys for the other three neighbors, as well as its own. All hosts use the same key to communicate with windsor. With keys distributed on a per-host-pair basis, each host has one key per possible connection, making six keys in all. Unlike the per-host situation, in the per-host-pair case, each host uses a different key to communicate with windsor. The message is deciphered at each intermediate host, reenciphered for the next hop, and forwarded. Attackers monitoring the network medium will not be able to read the messages, but attackers at the intermediate hosts will be able to do so.In end-to-end encryption, each host shares a cryptographic key with each destination. (Again, if the encryption is based on public key cryptography, each host has—or can obtain—the public key of each destination.) As with link encryption, the keys may be selected on a per-host or per-host-pair basis. The sending host enciphers the message and forwards it to the first intermediate host. The intermediate host forwards it to the next host, and the process continues until the message reaches its destination. The destination host then deciphers it. The message is enciphered throughout its journey. Neither attackers monitoring the network nor attackers on the intermediate hosts can read the message. However, attackers can read the routing information used to forward the message.These differences affect a form of cryptanalysis known as traffic analysis.A cryptanalyst can sometimes deduce information not from the content ofthe message but from the sender and recipient. For example, during the Allied invasion of Normandy in World War II, the Germans deduced which vessels were the command ships by observing which ships were sending and receiving the most signals. The content of the signals was not relevant; their source and destination were. Similar deductions can reveal information in the electronic world.第十一章密码技术11.1问题在没有考虑加密所要运行的环境时,加密的使用可能不能提供用户所期待的安全。
3000字的本科毕业外文文献翻译(格式标准)
本科毕业生外文文献翻译学生姓名:指导教师:所在学院:专业:中国·大庆2013 年5 月Chapter 1IntroductionSpread-spectrum techniques are methods by which a signal (e.g. an electrical, electromagnetic, or acoustic signal ) generated in a particular bandwidth is deliberately spread in the frequency domain, resulting in a signal with a wider bandwidth. These techniques are used for a variety of reasons, including the establishment of secure communications, increasing resistance to natural interference and jamming, to prevent detection, and to limit power flux density (e.g. in satellite downlinks).1.1 History Frequency hoppingThe concept of frequency hopping was first alluded to in the 1903 U.S. Patent 723,188 and U.S. Patent 725,605 filed by Nikola Tesla in July 1900. Tesla came up with the idea after demonstrating the world's first radio-controlled submersible boat in 1898, when it became apparent the wireless signals controlling the boat needed to be secure from "being disturbed, intercepted, or interfered with in any way." His patents covered two fundamentally different techniques for achieving immunity to interference, both of which functioned by altering the carrier frequency or other exclusive characteristic. The first had a transmitter that worked simultaneously at two or more separate frequencies and a receiver in which each of the individual transmitted frequencies had to be tuned in, in order for the control circuitry to respond. The second technique used a variable-frequency transmitter controlled by an encoding wheel that altered the transmitted frequency in a predetermined manner. These patents describe the basic principles of frequency hopping and frequency-division multiplexing, and also the electronic AND-gate logic circuit.Frequency hopping is also mentioned in radio pioneer Johannes Zenneck's book Wireless Telegraphy (German, 1908, English translation McGraw Hill, 1915), although Zenneck himself states that Telefunken had already tried it several years earlier. Zenneck's book was a leading text of the time, and it is likely that many later engineers were aware of it. A Polish engineer, Leonard Danilewicz, came up with the idea in 1929.Several other patents were taken out in the 1930s, including one by Willem Broertjes (Germany 1929, U.S. Patent 1,869,695, 1932). During World War II, the US Army Signal Corps was inventing a communication system called SIGSALY for communication between Roosevelt and Churchill, which incorporated spread spectrum, but due to its top secret nature, SIGSALY's existence did not become known until the 1980s.The most celebrated invention of frequency hopping was that of actress Hedy Lamarr and composer George Antheil, who in 1942 received U.S. Patent 2,292,387 for their "Secret Communications System". Lamarr had learned about the problem at defense meetings she had attended with her former husband Friedrich Mandl, who was an Austrian arms manufacturer. The Antheil-Lamarr version of frequency hopping used a piano-roll to change among 88 frequencies, and was intended to make radio-guided torpedoes harder for enemies to detect or to jam. The patent came to light during patent searches in the 1950s when ITT Corporation and other privatefirms began to develop Code Division Multiple Access (CDMA), a civilian form of spread spectrum, though the Lamarr patent had no direct impact on subsequent technology. It was in fact ongoing military research at MIT Lincoln Laboratory, Magnavox Government & Industrial Electronics Corporation, ITT and Sylvania Electronic Systems that led to early spread-spectrum technology in the 1950s. Parallel research on radar systems and a technologically similar concept called "phase coding" also had an impact on spread-spectrum development.1.2 Commercial useThe 1976 publication of Spread Spectrum Systems by Robert Dixon, ISBN 0-471-21629-1, was a significant milestone in the commercialization of this technology. Previous publications were either classified military reports or academic papers on narrow subtopics. Dixon's book was the first comprehensive unclassified review of the technology and set the stage for increasing research into commercial applications.Initial commercial use of spread spectrum began in the 1980s in the US with three systems: Equatorial Communications System's very small aperture (VSAT) satellite terminal system for newspaper newswire services, Del Norte Technology's radio navigation system for navigation of aircraft for crop dusting and similar applications, and Qualcomm's OmniTRACS system for communications to trucks. In the Qualcomm and Equatorial systems, spread spectrum enabled small antennas that viewed more than one satellite to be used since the processing gain of spread spectrum eliminated interference. The Del Norte system used the high bandwidth of spread spectrum to improve location accuracy.In 1981, the Federal Communications Commission started exploring ways to permit more general civil uses of spread spectrum in a Notice of Inquiry docket. This docket was proposed to FCC and then directed by Michael Marcus of the FCC staff. The proposals in the docket were generally opposed by spectrum users and radio equipment manufacturers, although they were supported by the then Hewlett-Packard Corp. The laboratory group supporting the proposal would later become part of Agilent.The May 1985 decision in this docket permitted unlicensed use of spread spectrum in 3 bands at powers up to 1 Watt. FCC said at the time that it would welcome additional requests for spread spectrum in other bands.The resulting rules, now codified as 47 CFR 15.247 permitted Wi-Fi, Bluetooth, and many other products including cordless telephones. These rules were then copied in many other countries. Qualcomm was incorporated within 2 months after the decision to commercialize CDMA.1.3 Spread-spectrum telecommunicationsThis is a technique in which a (telecommunication) signal is transmitted on a bandwidth considerably larger than the frequency content of the original information.Spread-spectrum telecommunications is a signal structuring technique that employs direct sequence, frequency hopping, or a hybrid of these, which can be used for multiple access and/or multiple functions. This technique decreases the potential interference to other receivers while achieving privacy. Spread spectrum generally makes use of a sequential noise-like signalstructure to spread the normally narrowband information signal over a relatively wideband (radio) band of frequencies. The receiver correlates the received signals to retrieve the original information signal. Originally there were two motivations: either to resist enemy efforts to jam the communications (anti-jam, or AJ), or to hide the fact that communication was even taking place, sometimes called low probability of intercept (LPI).Frequency-hopping spread spectrum (FHSS), direct-sequence spread spectrum (DSSS), time-hopping spread spectrum (THSS), chirp spread spectrum (CSS), and combinations of these techniques are forms of spread spectrum. Each of these techniques employs pseudorandom number sequences —created using pseudorandom number generators —to determine and control the spreading pattern of the signal across the alloted bandwidth. Ultra-wideband (UWB) is another modulation technique that accomplishes the same purpose, based on transmitting short duration pulses. Wireless Ethernet standard IEEE 802.11 uses either FHSS or DSSS in its radio interface.Chapter 22.1 Spread-spectrum clock signal generationSpread-spectrum clock generation (SSCG) is used in some synchronous digital systems, especially those containing microprocessors, to reduce the spectral density of the electromagnetic interference (EMI) that these systems generate. A synchronous digital system is one that is driven by a clock signal and because of its periodic nature, has an unavoidably narrow frequency spectrum. In fact, a perfect clock signal would have all its energy concentrated at a single frequency and its harmonics, and would therefore radiate energy with an infinite spectral density. Practical synchronous digital systems radiate electromagnetic energy on a number of narrow bands spread on the clock frequency and its harmonics, resulting in a frequency spectrum that, at certain frequencies, can exceed the regulatory limits for electromagnetic interference (e.g. those of the FCC in the United States, JEITA in Japan and the IEC in Europe).To avoid this problem, which is of great commercial importance to manufacturers, spread-spectrum clocking is used. This consists of using one of the methods described in the Spread-spectrum telecommunications section in order to reduce the peak radiated energy. The technique therefore reshapes the system's electromagnetic emissions to comply with the electromagnetic compatibility (EMC) regulations. It is a popular technique because it can be used to gain regulatory approval with only a simple modification to the equipment.Spread-spectrum clocking has become more popular in portable electronics devices because of faster clock speeds and the increasing integration of high-resolution LCD displays in smaller and smaller devices. Because these devices are designed to be lightweight and inexpensive, passive EMI reduction measures such as capacitors or metal shielding are not a viable option. Active EMI reduction techniques such as spread-spectrum clocking are necessary in these cases, but can also create challenges for designers. Principal among these is the risk that modifying th e system clock runs the risk of the clock/data misalignment.2.2Direct-sequence spread spectrumIn telecommunications, direct-sequence spread spectrum (DSSS) is a modulation technique. As with other spread spectrum technologies, the transmitted signal takes up more bandwidth than the information signal that is being modulated. The name 'spread spectrum' comes from the fact that the carrier signals occur over the full bandwidth (spectrum) of a device's transmitting frequency.2.2.1Features1.It phase-modulates a sine wave pseudorandomly with a continuous string ofpseudonoise (PN) code symbols called "chips", each of which has a much shorter duration than an information bit. That is, each information bit is modulated by a sequence of much faster chips. Therefore, the chip rate is much higher than the information signal bit rate.2. It uses a signal structure in which the sequence of chips produced by the transmitter isknown a priori by the receiver. The receiver can then use the same PN sequence to counteract the effect of the PN sequence on the received signal in order to reconstruct the informationsignal.2.2.2Transmission methodDirect-sequence spread-spectrum transmissions multiply the data being transmitted by a "noise" signal. This noise signal is a pseudorandom sequence of 1 and −1 values, at a frequency much higher than that of the original signal, thereby spreading the energy of the original signal into a much wider band.The resulting signal resembles white noise, like an audio recording of "static". However, this noise-like signal can be used to exactly reconstruct the original data at the receiving end, by multiplying it by the same pseudorandom sequence (because 1 × 1 = 1, and −1 × −1 = 1). This process, known as "de-spreading", mathematically constitutes a correlation of the transmitted PN sequence with the PN sequence that the receiver believes the transmitter is using.For de-spreading to work correctly, the transmit and receive sequences must be synchronized. This requires the receiver to synchronize its sequence with the transmitter's sequence via some sort of timing search process. However, this apparent drawback can be a significant benefit: if the sequences of multiple transmitters are synchronized with each other, the relative synchronizations the receiver must make between them can be used to determine relative timing, which, in turn, can be used to calculate the receiver's position if the transmitters' positions are known. This is the basis for many satellite navigation systems.The resulting effect of enhancing signal to noise ratio on the channel is called process gain. This effect can be made larger by employing a longer PN sequence and more chips per bit, but physical devices used to generate the PN sequence impose practical limits on attainable processing gain.If an undesired transmitter transmits on the same channel but with a different PN sequence (or no sequence at all), the de-spreading process results in no processing gain for that signal. This effect is the basis for the code division multiple access (CDMA) property of DSSS, which allows multiple transmitters to share the same channel within the limits of the cross-correlation properties of their PN sequences.As this description suggests, a plot of the transmitted waveform has a roughly bell-shaped envelope centered on the carrier frequency, just like a normal AM transmission, except that the added noise causes the distribution to be much wider than that of an AM transmission.In contrast, frequency-hopping spread spectrum pseudo-randomly re-tunes the carrier, instead of adding pseudo-random noise to the data, which results in a uniform frequency distribution whose width is determined by the output range of the pseudo-random number generator.2.2.3Benefits∙Resistance to intended or unintended jamming∙Sharing of a single channel among multiple users∙Reduced signal/background-noise level hampers interception (stealth)∙Determination of relative timing between transmitter and receiver2.2.4Uses∙The United States GPS and European Galileo satellite navigation systems∙DS-CDMA (Direct-Sequence Code Division Multiple Access) is a multiple access scheme based on DSSS, by spreading the signals from/to different users with different codes.It is the most widely used type of CDMA.∙Cordless phones operating in the 900 MHz, 2.4 GHz and 5.8 GHz bands∙IEEE 802.11b 2.4 GHz Wi-Fi, and its predecessor 802.11-1999. (Their successor 802.11g uses OFDM instead)∙Automatic meter reading∙IEEE 802.15.4 (used e.g. as PHY and MAC layer for ZigBee)2.3 Frequency-hopping spread spectrumFrequency-hopping spread spectrum (FHSS) is a method of transmitting radio signals by rapidly switching a carrier among many frequency channels, using a pseudorandom sequence known to both transmitter and receiver. It is utilized as a multiple access method in the frequency-hopping code division multiple access (FH-CDMA) scheme.A spread-spectrum transmission offers three main advantages over a fixed-frequency transmission:1.Spread-spectrum signals are highly resistant to narrowband interference. Theprocess of re-collecting a spread signal spreads out the interfering signal, causing it to recede into the background.2.Spread-spectrum signals are difficult to intercept. An FHSS signal simply appearsas an increase in the background noise to a narrowband receiver. An eavesdropper would only be able to intercept the transmission if they knew the pseudorandom sequence.3.Spread-spectrum transmissions can share a frequency band with many types ofconventional transmissions with minimal interference. The spread-spectrum signals add minimal noise to the narrow-frequency communications, and vice versa. As a result, bandwidth can be utilized more efficiently.2.3.1 Basic algorithmTypically, the initiation of an FHSS communication is as follows1.The initiating party sends a request via a predefined frequency or control channel.2.The receiving party sends a number, known as a seed.3.The initiating party uses the number as a variable in a predefined algorithm, whichcalculates the sequence of frequencies that must be used. Most often the period of the frequency change is predefined, as to allow a single base station to serve multiple connections.4.The initiating party sends a synchronization signal via the first frequency in thecalculated sequence, thus acknowledging to the receiving party it has correctly calculated the sequence.5.The communication begins, and both the receiving and the sending party changetheir frequencies along the calculated order, starting at the same point in time.2.3.2 Military useSpread-spectrum signals are highly resistant to deliberate jamming, unless the adversary has knowledge of the spreading characteristics. Military radios use cryptographic techniques to generate the channel sequence under the control of a secret Transmission Security Key(TRANSEC) that the sender and receiver share.By itself, frequency hopping provides only limited protection against eavesdropping and jamming. To get around this weakness most modern military frequency hopping radios often employ separate encryption devices such as the KY-57. U.S. military radios that use frequency hopping include HAVE QUICK and SINCGARS.2.3.3Technical considerationsThe overall bandwidth required for frequency hopping is much wider than that required to transmit the same information using only one carrier frequency. However, because transmission occurs only on a small portion of this bandwidth at any given time, the effective interference bandwidth is really the same. Whilst providing no extra protection against wideband thermal noise, the frequency-hopping approach does reduce the degradation caused by narrowband interferers.One of the challenges of frequency-hopping systems is to synchronize the transmitter and receiver. One approach is to have a guarantee that the transmitter will use all the channels in a fixed period of time. The receiver can then find the transmitter by picking a random channel and listening for valid data on that channel. The transmitter's data is identified by a special sequence of data that is unlikely to occur over the segment of data for this channel and the segment can have a checksum for integrity and further identification. The transmitter and receiver can use fixed tables of channel sequences so that once synchronized they can maintain communication by following the table. On each channel segment, the transmitter can send its current location in the table.In the US, FCC part 15 on unlicensed system in the 900MHz and 2.4GHz bands permits more power than non-spread spectrum systems. Both frequency hopping and direct sequence systems can transmit at 1 Watt. The limit is increased from 1 milliwatt to 1 watt or a thousand times increase. The Federal Communications Commission (FCC) prescribes a minimum number of channels and a maximum dwell time for each channel.In a real multipoint radio system, space allows multiple transmissions on the same frequency to be possible using multiple radios in a geographic area. This creates the possibility of system data rates that are higher than the Shannon limit for a single channel. Spread spectrum systems do not violate the Shannon limit. Spread spectrum systems rely on excess signal to noise ratios for sharing of spectrum. This property is also seen in MIMO and DSSS systems. Beam steering and directional antennas also facilitate increased system performance by providing isolation between remote radios.2.3.4 Variations of FHSSAdaptive Frequency-hopping spread spectrum (AFH) (as used in Bluetooth) improves resistance to radio frequency interference by avoiding using crowded frequencies in the hopping sequence. This sort of adaptive transmission is easier to implement with FHSS than with DSSS.The key idea behind AFH is to use only the “good” frequencies, by avoiding the "bad" frequency channels -- perhaps those "bad" frequency channels are experiencing frequency selective fading, or perhaps some third party is trying to communicate on those bands, or perhaps those bands are being actively jammed. Therefore, AFH should be complemented by a mechanism for detecting good/bad channels.However, if the radio frequency interference is itself dynamic, then the strategy of “badchannel removal”, applied in AFH might not work well. For example, if there are several colocated frequency-hopping networks (as Bluetooth Piconet), then they are mutually interfering and the strategy of AFH fails to avoid this interference.In this case, there is a need to use strategies for dynamic adaptation of the frequency hopping pattern.Such a situation can often happen in the scenarios that use unlicensed spectrum.In addition, dynamic radio frequency interference is expected to occur in the scenarios related to cognitive radio, where the networks and the devices should exhibit frequency-agile operation.Chirp modulation can be seen as a form of frequency-hopping that simply scans through the available frequencies in consecutive order.第一章介绍扩频技术是信号(例如一个电气、电磁,或声信号)生成的特定带宽频率域中特意传播,从而导致更大带宽的信号的方法。
- 1、下载文档前请自行甄别文档内容的完整性,平台不提供额外的编辑、内容补充、找答案等附加服务。
- 2、"仅部分预览"的文档,不可在线预览部分如存在完整性等问题,可反馈申请退款(可完整预览的文档不适用该条件!)。
- 3、如文档侵犯您的权益,请联系客服反馈,我们会尽快为您处理(人工客服工作时间:9:00-18:30)。
毕业设计(论文)外文文献翻译
文献、资料中文题目:生产线平衡在现实世界
文献、资料英文题目:Line Balancing in the Real World 文献、资料来源:
文献、资料发表(出版)日期:
院(部):
专业:
班级:
姓名:
学号:
指导教师:
翻译日期: 2017.02.14
附录
附录1:英文文献
Line Balancing in the Real World
Abstract:Line Balancing (LB) is a classic, well-researched Operations Research (OR) optimization problem of significant industrial importance. It is one of those problems where domain expertise does not help very much: whatever the number of years spent solving it, one is each time facing an intractable problem with an astronomic number of possible solutions and no real guidance on how to solve it in the best way, unless one postulates that the old way is the best way .Here we explain an apparent paradox: although many algorithms have been proposed in the past, and despite the problem’s practical importance, just one commercially available LB software currently appears to be available for application in industries such as automotive. We speculate that this may be due to a misalignment between the academic LB problem addressed by OR, and the actual problem faced by the industry.
Keyword:Line Balancing, Assembly lines, Optimization
Line Balancing in the Real World
Emanuel Falkenauer
Optimal Design
Av. Jeanne 19A boîte2, B-1050 Brussels, Belgium
+32 (0)2 646 10 74
******************************
1 Introduction
Assembly Line Balancing, or simply Line Balancing (LB), is the problem of assigning operations to workstations along an assembly line, in such a way that the assignment be optimal in some sense. Ever since Henry Ford’s introduction of assembly lines, LB has been an optimization problem of significant industrial importance: the efficiency difference between an optimal and a sub-optimal assignment can yield economies (or waste) reaching millions of dollars per year.
LB is a classic Operations Research (OR) optimization problem, having been tackled by OR over several decades. Many algorithms have been proposed for the problem. Yet despite the practical importance of the problem, and the OR efforts that have been made to tackle it, little commercially available software is available to help industry in optimizing their lines. In fact, according to a recent survey by Becker and Scholl (2004), there appear to be currently just two commercially available packages featuring both a state of the art optimization algorithm and a user-friendly interface for data management. Furthermore, one of those packages appears to handle only the “clean” formulation of the pr oblem (Simple Assembly Line Balancing Problem, or SALBP), which leaves only one package available for industries such as automotive. This situation appears to be paradoxical, or at least unexpected: given the huge economies LB can generate, one would expect several software packages vying to grab a part of those economies.
It appears that the gap between the available OR results and their dissemination in Today’s industry, is probably due to a misalignment between the academic LB problem addressed by most of the OR approaches, and the actual problem being faced by the industry. LB is a difficult optimization problem even its simplest forms are NP-hard –see Garry and Johnson, 1979), so the approach taken by OR has typically been to simplify it, in order to bring it to a level of complexity amenable to OR tools. While this is a perfectly valid approach in general, in the particular case of LB it led some definitions of the problem hat ignore many aspects of the real-world problem.
Unfortunately, many of the aspects that have been left out in the OR approach are in fact crucial to industries such as automotive, in the sense that any solution ignoring (violating) those aspects becomes unusable in the industry.
In the sequel, we first briefly recall classic OR definitions of LB, and then review。