200920201070 李世忠_外文文献
本科毕业设计外文文献翻译
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学生姓名：李世忠
学院：信息工程学院
系别：计算机系
专业：计算机科学与技术
班级：计算机09-1班
指导教师：王晓荣讲师
李来普工程师
二○一三年六月
Application Fundamentals
Android applications are written in the Java programming language. The Android SDK tools compile the code—along with any data and resource files—into an Android package, an archive file with an .apk suffix. All the code in a
single .apk file is considered to be one application and is the file that
Android-powered devices use to install the application.
Once installed on a device, each Android application lives in its own security sandbox:
The Android operating system is a multi-user Linux system in which each application is a different user.
By default, the system assigns each application a unique Linux user ID (the ID is used only by the system and is unknown to the application). The system sets permissions for all the files in an application so that only the user ID assigned to that application can access them.
Each process has its own virtual machine (VM), so an application's code runs in isolation from other applications.
By default, every application runs in its own Linux process. Android starts the process when any of the application's components need to be executed, then shuts down the process when it's no longer needed or when the system must recover memory for other applications.
In this way, the Android system implements the principle of least privilege. That is, each application, by default, has access only to the components that it requires to do its work and no more. This creates a very secure environment in which an application cannot access parts of the system for which it is not given permission.
However, there are ways for an application to share data with other applications and for an application to access system services:
It's possible to arrange for two applications to share the same Linux user ID, in which case they are able to access each other's files. To conserve system resources, applications with the same user ID can also arrange to run in the same Linux process
and share the same VM (the applications must also be signed with the same certificate).
An application can request permission to access device data such as the user's contacts, SMS messages, the mountable storage (SD card), camera, Bluetooth, and more. All application permissions must be granted by the user at install time.
That covers the basics regarding how an Android application exists within the system. The rest of this document introduces you to:
1、The core framework components that define your application.
2、The manifest file in which you declare components and required device features for your application.
3、Resources that are separate from the application code and allow your application to gracefully optimize its behavior for a variety of device configurations.
Application Components
Application components are the essential building blocks of an Android application. Each component is a different point through which the system can enter your application. Not all components are actual entry points for the user and some depend on each other, but each one exists as its own entity and plays a specific role—each one is a unique building block that helps define your application's overall behavior.
There are four different types of application components. Each type serves a distinct purpose and has a distinct lifecycle that defines how the component is created and destroyed.
Here are the four types of application components:
Activities
An activity represents a single screen with a user interface. For example, an email application might have one activity that shows a list of new emails, another activity to compose an email, and another activity for reading emails. Although the activities work together to form a cohesive user experience in the email application, each one is independent of the others. As such, a different application can start any one of these activities (if the email application allows it). For example, a camera
application can start the activity in the email application that composes new mail, in order for the user to share a picture.
An activity is implemented as a subclass of Activity and you can learn more about it in the Activities developer guide.
Services
A service is a component that runs in the background to perform long-running operations or to perform work for remote processes. A service does not provide a user interface. For example, a service might play music in the background while the user is in a different application, or it might fetch data over the network without blocking user interaction with an activity. Another component, such as an activity, can start the service and let it run or bind to it in order to interact with it.
A service is implemented as a subclass of Service and you can learn more about it in the Services developer guide.
Content providers
A content provider manages a shared set of application data. You can store the data in the file system, an SQLite database, on the web, or any other persistent storage location your application can access. Through the content provider, other applications can query or even modify the data (if the content provider allows it). For example, the Android system provides a content provider that manages the user's contact information. As such, any application with the proper permissions can query part of the content provider (such as ContactsContract.Data) to read and write information about a particular person.
Content providers are also useful for reading and writing data that is private to your application and not shared. For example, the Note Pad sample application uses a content provider to save notes.
A content provider is implemented as a subclass of ContentProvider and must implement a standard set of APIs that enable other applications to perform transactions. For more information, see the Content Providers developer guide.
Broadcast receivers
A broadcast receiver is a component that responds to system-wide broadcast announcements. Many broadcasts originate from the system—for example, a broadcast announcing that the screen has turned off, the battery is low, or a picture was captured. Applications can also initiate broadcasts—for example, to let other applications know that some data has been downloaded to the device and is available for them to use. Although broadcast receivers don't display a user interface, they may create a status bar notification to alert the user when a broadcast event occurs. More commonly, though, a broadcast receiver is just a "gateway" to other components and is intended to do a very minimal amount of work. For instance, it might initiate a service to perform some work based on the event.
A broadcast receiver is implemented as a subclass of BroadcastReceiver and each broadcast is delivered as an Intent object. For more information, see the BroadcastReceiver class.
A unique aspect of the Android system design is that any application can start another application’s component. For example, if you want the user to capture a photo with the device camera, there's probably another application that does that and your application can use it, instead of developing an activity to capture a photo yourself. You don't need to incorporate or even link to the code from the camera application. Instead, you can simply start the activity in the camera application that captures a photo. When complete, the photo is even returned to your application so you can use it. To the user, it seems as if the camera is actually a part of your application.
When the system starts a component, it starts the process for that application (if it's not already running) and instantiates the classes needed for the component. For example, if your application starts the activity in the camera application that captures a photo, that activity runs in the process that belongs to the camera application, not in your application's process. Therefore, unlike applications on most other systems, Android applications don't have a single entry point (there's no main() function, for example).
Because the system runs each application in a separate process with file permissions that restrict access to other applications, your application cannot directly activate a component from another application. The Android system, however, can. So, to activate a component in another application, you must deliver a message to the system that specifies your intent to start a particular component. The system then activates the component for you.
Activating Components
Three of the four component types—activities, services, and broadcast receivers—are activated by an asynchronous message called an intent. Intents bind individual components to each other at runtime (you can think of them as the messengers that request an action from other components), whether the component belongs to your application or another.
An intent is created with an Intent object, which defines a message to activate either a specific component or a specific type of component—an intent can be either explicit or implicit, respectively.
For activities and services, an intent defines the action to perform (for example, to "view" or "send" something) and may specify the URI of the data to act on (among other things that the component being started might need to know). For example, an intent might convey a request for an activity to show an image or to open a web page. In some cases, you can start an activity to receive a result, in which case, the activity also returns the result in an Intent (for example, you can issue an intent to let the user pick a personal contact and have it returned to you—the return intent includes a URI pointing to the chosen contact).
For broadcast receivers, the intent simply defines the announcement being broadcast (for example, a broadcast to indicate the device battery is low includes only a known action string that indicates "battery is low").
The other component type, content provider, is not activated by intents. Rather, it is activated when targeted by a request from a ContentResolver. The content resolver handles all direct transactions with the content provider so that the component that's performing transactions with the provider doesn't need to and
instead calls methods on the ContentResolver object. This leaves a layer of abstraction between the content provider and the component requesting information (for security).
There are separate methods for activating each type of component:
You can start an activity (or give it something new to do) by passing
an Intent to startActivity() or startActivityForResult() (when you want the activity to return a result).
You can start a service (or give new instructions to an ongoing service) by passing an Intent to startService(). Or you can bind to the service by passing
an Intent to bindService().
You can initiate a broadcast by passing an Intent to methods
like sendBroadcast(), sendOrderedBroadcast(), or sendStickyBroadcast().
You can perform a query to a content provider by calling query() on
a ContentResolver.
For more information about using intents, see the Intents and Intent
Filters document. More information about activating specific components is also provided in the following documents: Activities, Services, BroadcastReceiver and Content Providers.
Declaring components
In the
In the
You must declare all application components this way:
1、
2、
3、
4、
Activities, services, and content providers that you include in your source but do not declare in the manifest are not visible to the system and, consequently, can never run. However, broadcast receivers can be either declared in the manifest or created dynamically in code (as BroadcastReceiver objects) and registered with the system by calling registerReceiver().
Declaring component capabilities
As discussed above, in Activating Components, you can use an Intent to start activities, services, and broadcast receivers. You can do so by explicitly naming the target component (using the component class name) in the intent. However, the real power of intents lies in the concept of intent actions. With intent actions, you simply describe the type of action you want to perform (and optionally, the data upon which you’d like to perform the action) and allow the sy stem to find a component on the device that can perform the action and start it. If there are multiple components that can perform the action described by the intent, then the user selects which one to use.
The way the system identifies the components that can respond to an intent is by comparing the intent received to the intent filters provided in the manifest file of other applications on the device.
When you declare a component in your application's manifest, you can optionally include intent filters that declare the capabilities of the component so it can respond to intents from other applications. You can declare an intent filter for your component by adding an
For example, an email application with an activity for composing a new email might declare an intent filter in its manifest entry to respond to "send" intents (in order to send email). An activity in your application can then create an intent with the “send” action (ACTION_SEND), which the system matches to the email application’s “send” activity and launches it when you invoke the intent
with startActivity().
For more about creating intent filters, see the Intents and Intent
Filters document.
Declaring application requirements
There are a variety of devices powered by Android and not all of them provide the same features and capabilities. In order to prevent your application from being installed on devices that lack features needed by your application, it's important that you clearly define a profile for the types of devices your application supports by declaring device and software requirements in your manifest file. Most of these declarations are informational only and the system does not read them, but external services such as Google Play do read them in order to provide filtering for users when they search for applications from their device.
For example, if your application requires a camera and uses APIs introduced in Android 2.1 (API Level 7), you should declare these as requirements in your manifest file. That way, devices that do not have a camera and have an Android version lower than 2.1 cannot install your application from Google Play.
However, you can also declare that your application uses the camera, but does not require it. In that case, your application must perform a check at runtime to determine if the device has a camera and disable any features that use the camera if one is not available.
Here are some of the important device characteristics that you should consider as you design and develop your application:
Screen size and density
In order to categorize devices by their screen type, Android defines two characteristics for each device: screen size (the physical dimensions of the screen) and screen density (the physical density of the pixels on the screen, or dpi—dots per inch). To simplify all the different types of screen configurations, the Android system generalizes them into select groups that make them easier to target.
The screen sizes are: small, normal, large, and extra large.
The screen densities are: low density, medium density, high density, and extra high density.
By default, your application is compatible with all screen sizes and densities, because the Android system makes the appropriate adjustments to your UI layout and image resources. However, you should create specialized layouts for certain screen sizes and provide specialized images for certain densities, using alternative layout resources, and by declaring in your manifest exactly which screen sizes your application supports with the
For more information, see the Supporting Multiple Screens document.
Input configurations
Many devices provide a different type of user input mechanism, such as a hardware keyboard, a trackball, or a five-way navigation pad. If your application requires a particular kind of input hardware, then you should declare it in your manifest with the
Device features
There are many hardware and software features that may or may not exist on a given Android-powered device, such as a camera, a light sensor, bluetooth, a certain version of OpenGL, or the fidelity of the touchscreen. You should never assume that a certain feature is available on all Android-powered devices (other than the
availability of the standard Android library), so you should declare any features used by your application with the
Platform Version
Different Android-powered devices often run different versions of the Android platform, such as Android 1.6 or Android 2.3. Each successive version often includes additional APIs not available in the previous version. In order to indicate which set of APIs are available, each platform version specifies an API Level (for example, Android 1.0 is API Level 1 and Android 2.3 is API Level 9). If you use any APIs that were added to the platform after version 1.0, you should declare the minimum API Level in which those APIs were introduced using the
It's important that you declare all such requirements for your application, because, when you distribute your application on Google Play, the store uses these declarations to filter which applications are available on each device. As such, your application should be available only to devices that meet all your application requirements.
For more information about how Google Play filters applications based on these (and other) requirements, see the Filters on Google Play document.
Application Resources
An Android application is composed of more than just code—it requires resources that are separate from the source code, such as images, audio files, and anything relating to the visual presentation of the application. For example, you should define animations, menus, styles, colors, and the layout of activity user interfaces with XML files. Using application resources makes it easy to update various characteristics of your application without modifying code and—by providing sets of alternative resources—enables you to optimize your application for a variety of device configurations (such as different languages and screen sizes).
For every resource that you include in your Android project, the SDK build tools define a unique integer ID, which you can use to reference the resource from your application code or from other resources defined in XML. For example, if your application contains an image file named logo.png (saved in
the res/drawable/ directory), the SDK tools generate a resource ID
named R.drawable.logo, which you can use to reference the image and insert it in your user interface.
One of the most important aspects of providing resources separate from your source code is the ability for you to provide alternative resources for different device configurations. For example, by defining UI strings in XML, you can translate the strings into other languages and save those strings in separate files. Then, based on a language qualifier that you append to the resource directory's name (such
as res/values-fr/ for French string values) and the user's language setting, the Android system applies the appropriate language strings to your UI.
Android supports many different qualifiers for your alternative resources. The qualifier is a short string that you include in the name of your resource directories in order to define the device configuration for which those resources should be used. As another example, you should often create different layouts for your activities, depending on the device's screen orientation and size. For example, when the device screen is in portrait orientation (tall), you might want a layout with buttons to be vertical, but when the screen is in landscape orientation (wide), the buttons should be aligned horizontally. To change the layout depending on the orientation, you can define two different layouts and apply the appropriate qualifier to each layout's directory name. Then, the system automatically applies the appropriate layout depending on the current device orientation.
For more about the different kinds of resources you can include in your application and how to create alternative resources for various device configurations, see theApplication Resources developer guide.
From: https://www.wendangku.net/doc/0f9882421.html,/guide/components/fundamentals.html
应用基础
Android应用程序使用Java作为编程语言。Android SDK工具将代码、数据以及资源文件编译成为扩展名为.apk的Android软件包。一个apk文件代表一个Android应用程序，Android使用apk文件来安装应用?
一经安装在一个设备上，每个Android应用程序就生存在自己的安全沙箱里面：
Android操作系统是一个多用户的Linux系统，每个应用程序代表一个不同的用户。
默认情况下，系统为每个应用程序赋予一个唯一的Linux用户ID（这个用户ID只供系统内部使用，应用程序本身并不知晓这个用户ID）。系统使用这个用户ID为应用程序的所有文件设置权限，因此只有这个用户ID才可以访问这些文件。
每个进程都有自己的虚拟机，所以应用程序之间的代码在物理上是隔离的。
默认情况下，每个应用程序在自己的Linux进程里面运行。Android在应用程序的任意组件运行的时候启动这个进程，然后当不再需要该应用程序的组件或者当系统需要为其它应用程序腾出内存的时候Android会关闭该进程。
通过这种方式，Android系统实现了最小特权原则。就是说默认情况下，每个应用程序只对工作所必需的组件拥有访问权。这样就创建了一个非常安全的环境，在这个环境中，每个应用程序都无法访问它未被授权的系统组件。
然而通过下面几种方式可以使应用程序之间共享数据，而且可以使应用程序访问系统服务：
可以使两个应用程序共享同一个Linux用户ID，这样它们就可以访问彼此的文件。为了节省系统资源，具备相同用户ID的应用程序可以共享同一个Linux 进程和虚拟机（这些应用程序必须被赋予相同的证书）。
应用程序可以申请访问设备数据的权限，比如联系人，短信，可挂载的存储（SDcard），相机，蓝牙等等。所有的应用程序权限必须在安装时被用户授予。
上述内容介绍了Android应用程序与系统的基础知识。下面将为您介绍：
1、定义应用程序的核心框架组件。
2、用于声明组件和设备需求的清单文件。
3、资源，独立于应用程序代码，允许应用程序根据不同的设备配置优化其
行为。
应用程序组件(Application Components)
应用程序组件是Android应用程序的核心构建块。每个组件表示一个不同的点，系统通过这个点与你的应用程序进行交互。并不是所有的组件都是直接面向用户的点，有一些组件之间是具备依赖关系的，但是每个组件都作为一个独立的实体扮演特定的角色—每个组件都是一个独一无二的构建块，帮助你定义应用程序的整体行为。
一共有4种类型的应用程序组件。每种类型的组件都服务于不同的目的，具备不同的生命周期。
下面就开始介绍这4种类型的应用程序组件：
活动(Activities)
一个Activity代表了用户界面的一个独立屏幕。例如，一个电子邮件应用程序必需有一个Activity用来显示邮件列表，一个Activity用来写邮件，一个Activity用来读邮件。尽管在电子邮件应用程序中这些Activity共同工作从而形成一种聚合的用户体验，但是事实上它们是相互独立的。因此，一个不同的应用程序可以启动这些Activity中的任意一个（在电子邮件应用程序允许的情况下）。例如，为了方便用户共享图片，相机应用程序可以启动电子邮件应用程序中用于写邮件的Activity。
服务(Services)
服务是运行于后台，执行长时间/耗时操作或者远程操作的组件。服务没有用户界面。例如，当用户在与另外一个应用程序交互的时候，可能一个播放音乐的服务正在后台运行，或者它可能用于获取网络数据而不阻塞用户与Activity 的交互。其它组件，比如Activity，可以启动一个服务，也可以绑定到一个服务从而可以与服务进行交互。
广播接收器(Broadcast receivers)
广播接收者可以接收系统范围的广播/通知。许多广播源自系统——例如，屏幕关闭，电量不足，或者拍照事件。应用程序也可以发送广播—例如，通知其它应用程序数据下载完成。尽管广播接受者并没有用户界面，但是在接收到
广播时，它们可以创建一个状态栏的通知以提醒用户。不过，更常见的情况是，广播接收者作为其它组件的门户只做很少量的工作。例如，它可能仅仅只是在接收到某个广播/通知的时候启动某个服务来处理相应的工作。
广播接受者被实现为BroadcastReceiver的子类，每个广播都是一个Intent 对象。
内容提供者(Content providers)
内容提供者可以管理应用程序需要共享的数据。你可以选择将数据存储在文件系统，SQLite数据库，Web，以及应用程序可以访问到的任意其它持久存储。借助内容提供者，一个应用程序可以查询甚至修改另外一个应用程序的数据（在内容提供者允许的情况下）。例如，Android系统提供了一个管理联系人信息的内容提供者。因此，任何具备相应权限的应用程序都可以通过这个内容提供者查询、修改联系人信息。
内容提供者对于访问应用程序私有数据也是有用的。例如，NotePad示例应用程序使用内容提供者保存笔记。
内容提供者被实现为ContentProvider的子类，而且必须实现一组标准接口来使其它应用程序执行相应的事务。从ContentProviders开发者指南你可以获取更多关于内容提供者的信息。?
每当出现一个需要被特定组件处理的请求时，Android会确保那个组件的应用程序进程处于运行状态，或在必要的时候启动它?并确保那个相应组件的实例的存在，必要时会创建那个实例?
Android系统设计的独特之处在于任何应用程序都可以调用其它应用程序的组件。例如，如果你的应用程序想让用户拍照，而且其它应用程序已经实现了一个拍照组件，这个时候你就可以直接使用它的拍照组件儿不需要自己重新实现一次。你不必要将你的应用程序代码链接到那个相机应用程序。相反，你可以简单的启动相机应用程序的拍照Activity，然后拍照。拍照完成的时候，照片会返回到你的应用程序，这时你就可以使用这张照片了。从用户的角度来看，拍照组件似乎是你的应用程序的一部分。
当系统启动一个组件的时候，它会首先启动组件所属应用程序的进程（如果该进程尚未运行的话），然后创建组件类的实例。例如，如果你的应用程序启动了相机应用程序的拍照Activity并且拍照，拍照Activity其实是运行在相机应
用程序的进程里，而不是你的应用程序进程。因此，和其它系统上应用程序的区别在于，Android应用程序并没有单一的入口点（例如，不具备main函数）。
由于在Android系统中每个应用程序运行在独立的进程中，并且每个应用程序并不具备访问其它应用程序文件的权限，所以你的应用程序是不能直接激活其它应用程序的组件的。然而，Android系统具备激活其它应用程序组件的能力。因此，为了激活其它应用程序的组件，你必须在你的应用程序中向Android 系统发送一个描述你意图的消息，然后Android系统解析这个消息，激活目标组件。
激活组件(Activating Components)
四种组件中的三种——Activity，服务，以及广播接受者—是通过被称“意图”的异步消息激活的。“意图”与组件的映射在运行时完成（你可以将这种映射关系想象为向其它组件发出某种请求的信使），不论该组件是否属于你的应用程序。
“意图”其实是一个Intent对象，它定义了激活特定组件或者激活特定类型组件的消息——“意图”可以是明确的，也可以是隐含的。
就Activity和服务来说，“意图”定义了需要执行的动作（例如，“看”或者“发送”某样东西）并且指定了目标数据的URI（组件激活所需要的参数）。例如，某个“意图”可能需要请求某个Activity显示一张图片或者打开一个Web页面。在某些情况下，你激活某个Activity是为了获取某种结果，这种情况下，目标Activity会将结果存储在Intent对象中返回（例如，你可以发送一个让用户选择联系人的“意图”并将选择的联系人返回给你—返回的“意图”包含一个指向联系人信息的URI）。
就广播接受者来说，“意图”只是简单的定义了需要广播的通知（例如，一条广播可能只是包含一个指示“电量过低”的字符串）。
另外一种组件，内容提供者，并不是通过“意图”激活的。内容提供者是在响应ContentResolver的请求时被激活的。内容解析者负责所有与内容提供者的直接交互。这样就在内容提供者和请求信息的组件之间添加了一层抽象（为了安全考虑）。
激活每种组件的方法如下：
你可以通过发送一个“意图”给startActivity（）或者startActivityForResult（）
（当你希望获取Activity的返回结果时）来启动Activity或者给Activity分配新的任务。
你可以通过发送一个“意图”给startService（）来启动一个服务或者给正在运行的服务发送新的指令。你也可以通过发送一个“意图”给bindService（）来绑定到一个服务。
你可以通过发送一个“意图”给sendBroadcast（），sendOrderedBroadcast（），或者sendStickyBroadcast（）来产生一个广播。
清单文件
在启动应用程序组件之前，Android系统必须通过读取应用程序清单文件来确定组件是否存在。应用程序必须在清单文件中声明它的所有组件，而且清单文件必须位于应用程序工程的根目录。
除了声明组件，清单文件还有一些其它责任，例如：
1、声明应用程序需要的权限，比如访问网络或者访问联系人信息。
2、声明应用程序兼容的最低API版本。
3、声明应用程序的硬件和软件需求，例如相机，蓝牙服务，或者多点触控屏幕。
4、声明应用程序依赖的库（不包括Android框架API），例如GoogleMapslibrary。
声明组件
清单文件的主要功能是告知系统应用程序所拥有的组件。例如，清单文件可以按照下述方式声明Activity：
android：label=“@string/example_label”…> … 你必须按照如下方式声明所有组件： 1、 2、 3、 4、 如果源代码包含的Activity、服务或者内容提供者没有在清单文件中声明，那么它们对系统是不可见的，因此，它们永远不会运行。然而，广播接收者既可以在清单文件中声明也可以在代码中动态创建并通过调用registerReceiver（）来注册。 声明组件的能力 正如上面所讨论的那样，你可以使用“意图”启动Activity、服务和广播接收者。你可以在“意图”中明确指定目标组件的类名称。然而，“意图”的实际动作其实是“意图”动作。使用“意图”动作，你只需要简单的描述需要执行的动作类型（还可以指定执行动作需要的数据）并允许系统在设备商找到可以执行这个动作的组件然后启动它。如果有多个组件可以执行目标动作，则由用户从中选择一个。 系统通过比较“意图”与应用程序清单文件中的“意图过滤器”来确定能够执行“意图”的组件。 当你在清单文件中声明一个组件的时候，你可以选择包含一个描述该组件能力的“意图过滤器”，这样该组件就能够响应其它应用程序发送的“意图”了。你通过为为组件声明元素添加一个 例如，邮件应用程序负责创作邮件的Activity可能会声明一个响应“发送”（目的是发送邮件）“意图”的“意图过滤器”。这样你的应用程序就可以创建一个具备“发送”动作（ACTION_SEND）的“意图”，然后调用startActivity（），这时系统就会将“发送”“意图”映射到邮件应用程序并启动它。 声明运行程序所需的条件 Android支持的设备多种多样，而且它们在功能和特性上存在差别。为了避免你的应用程序安装在缺少必需功能的设备上，在清单文件中清晰的声明应用程序的硬件和软件需求就显得尤为重要。系统并不读取这部分声明信息，但是扩展服务例如Android电子市场在搜索应用的时候会读取这些信息并过滤。 例如，如果你的应用程序基于Android2.1（APILevel7）并且需要相机，你应该在清单文件中声明这些需求。这样如果Android版本低于2.1或者没有相机就不能从电子市场安装你的应用程序。 然而，你也可以声明你的应用程序需要但不必须有相机的支持。这种情况下，应用程序必须在运行时检测设备是否有相机，如果没有相机则禁用相关功能。 下面是在设计和开发应用程序时需要考虑的一些重要的设备特征： 屏幕尺寸和分辨率 为了按照屏幕类型对设备归类，Android为每种设备定义了两个特征：屏幕尺寸（屏幕的物理尺寸）和屏幕分辨率（屏幕的物理像素分辨率）。为了简化不同类型的屏幕配置，Android系统将这些特征作了概括。 屏幕尺寸：小，正常，大，特别大。 屏幕分辨率：低分辨率，中等分辨率，高分辨率，特高分辨率。 默认情况下，你的应用程序兼容所有屏幕尺寸和分辨率，因为Android系统会为你的UI布局和图像文件作适当调整。然而，你应该根据屏幕尺寸和分辨率提供特定的布局和图像资源，并且在清单文件的 输入配置 许多设备提供不同的用户输入机制，比如键盘，跟踪球或者五向导航。如果你的应用程序需要特定类型的输入硬件，你应该在清单文件的 平台版本 不同的Android设备经常会运行不同的Android版本，例如Android 1.6或者Android 2.3。后续版本通常会包括对前期版本扩展之后的API。为了标识可用的API版本，每个平台版本被指定了一个API Level（例如，Android 1.0是API Level1，Android2.3是API Level9）。如果你使用了任何平台版本1.0之后的API，你应该在 声明所有这些需求是非常重要的，因为，当你在电子市场发布Android应用程序的时候，电子市场会使用这些信息去过滤设备可用的软件。因此，你的应用程序应当只能使那些满足所有应用程序需求的设备获取。 应用程序资源 Android应用程序不只包含代码—它也需要独立于代码的资源，例如图像、音频文件以及其它可视化相关的资源。例如，你应当使用XML文件定义动画、菜单、风格、颜色以及Activity用户界面的布局。通过提供多套可选资源，我们可以在不修改代码的情况下很容易的更新应用程序的各种特征，为特定设备提供优化之后的资源（比如不同的语言、屏幕尺寸）。 SDK构建工具会为你包含进Android工程的每一个资源项生成一个唯一的整型ID，你可以使用这个ID在代码或者其它XML资源文件中引用这个资源项。例如，如果你的应用程序包含一个名为logo.png的图像文件（保存在res/drawable/目录），SDK工具会为它生成一个名为R.drawable.logo的资源ID，你可以使用这个ID引用这个图像并且将它插入用户界面。 代码与资源隔离的一个重要方面是，你可以为不同的设备配置提供不同的资源集。例如，通过将UI字符串定义在XML文件中，你可以将字符串翻译成其它语言并存储在单独的文件中。然后根据你附加到资源目录名称上的语言标识符（例如res/values-fr/包含对应的法语字符串）和用户设置，Android系统会为你的UI选择合适的语言。 Android通过标识符支持多种可选资源。标识符是包含在资源目录名称中的短字符串，它用于匹配设备配置和资源。例如，依赖于设备屏幕方向和尺寸，你应该为Activity定义不同的布局。当屏幕是纵向的时候，你也许需要按钮是垂直排列的，但是当屏幕是横向的时候，按钮应该水平排列。为了根据屏幕方 机械设计 摘要：机器是由机械装置和其它组件组成的。它是一种用来转换或传递能量的装置，例如：发动机、涡轮机、车辆、起重机、印刷机、洗衣机、照相机和摄影机等。许多原则和设计方法不但适用于机器的设计，也适用于非机器的设计。术语中的“机械装置设计”的含义要比“机械设计”的含义更为广泛一些，机械装置设计包括机械设计。在分析运动及设计结构时，要把产品外型以及以后的保养也要考虑在机械设计中。在机械工程领域中，以及其它工程领域中，所有这些都需要机械设备，比如：开关、凸轮、阀门、船舶以及搅拌机等。 关键词：设计流程设计规则机械设计 设计流程 设计开始之前就要想到机器的实际性，现存的机器需要在耐用性、效率、重量、速度，或者成本上得到改善。新的机器必需具有以前机器所能执行的功能。 在设计的初始阶段，应该允许设计人员充分发挥创造性，不要受到任何约束。即使产生了许多不切实际的想法，也会在设计的早期，即在绘制图纸之前被改正掉。只有这样，才不致于阻断创新的思路。通常,还要提出几套设计方案，然后加以比较。很有可能在这个计划最后决定中,使用了某些不在计划之内的一些设想。 一般的当外型特点和组件部分的尺寸特点分析得透彻时，就可以全面的设计和分析。接着还要客观的分析机器性能的优越性，以及它的安全、重量、耐用性，并且竞争力的成本也要考虑在分析结果之内。每一个至关重要的部分要优化它的比例和尺寸，同时也要保持与其它组成部分相协调。 也要选择原材料和处理原材料的方法。通过力学原理来分析和实现这些重要的特性，如那些静态反应的能量和摩擦力的最佳利用，像动力惯性、加速动力和能量；包括弹性材料的强度、应力和刚度等材料的物理特性，以及流体润滑和驱动器的流体力学。设计的过程是重复和合作的过程，无论是正式或非正式的进行，对设计者来说每个阶段都很重要。 最后，以图样为设计的标准，并建立将来的模型。如果它的测试是符合事先要 PLC控制下的电梯系统 由继电器组成的顺序控制系统是最早的一种实现电梯控制的方法。但是，进入九十年代，随着科学技术的发展和计算机技术的广泛应用，人们对电梯的安全性、可靠性的要求越来越高，继电器控制的弱点就越来越明显。 电梯继电器控制系统故障率高，大大降低了电梯的可靠性和安全性，经常造成停梯，给乘用人员带来不便和惊忧。且电梯一旦发生冲顶或蹲底，不但会造成电梯机械部件损坏，还可能出现人身事故。 可编程序控制器(PLC)最早是根据顺序逻辑控制的需要而发展起来的，是专门为工业环境应用而设计的数字运算操作的电子装置。鉴于其种种优点，目前，电梯的继电器控制方式己逐渐被PLC控制所代替。同时，由于电机交流变频调速技术的发展，电梯的拖动方式己由原来直流调速逐渐过渡到了交流变频调速。因此，PLC控制技术加变频调速技术己成为现代电梯行业的一个热点。 1. PLC控制电梯的优点 (1)在电梯控制中采用了PLC，用软件实现对电梯运行的自动控制，可靠性大大提高。 (2)去掉了选层器及大部分继电器，控制系统结构简单，外部线路简化。 (3)PLC可实现各种复杂的控制系统，方便地增加或改变控制功能。 (4) PLC可进行故障自动检测与报警显示，提高运行安全性，并便于检修。 (5)用于群控调配和管理，并提高电梯运行效率。 (6)更改控制方案时不需改动硬件接线。 2.电梯变频调速控制的特点 随着电力电子技术、微电子技术和计算机控制技术的飞速发展，交流变频调速技术的发展也十分迅速。电动机交流变频调速技术是当今节电、改善工艺流程以提高产品质量和改善环境、推动技术进步的一种主要手段。变频调速以其优异的调速性能和起制动平稳性能、高效率、高功率因数和节电效果，广泛的适用范围及其它许多优点而被国内外公认为最有发展前途的调速方式 交流变频调速电梯的特点 ⑴能源消耗低 ⑵电路负载低，所需紧急供电装置小 在加速阶段，所需起动电流小于2.5倍的额定电流。且起动电流峰值时间短。由于起动电流大幅度减小，故功耗和供电缆线直径可减小很多。所需的紧急供电 译文资料： 机器人 首先我介绍一下机器人产生的背景，机器人技术的发展，它应该说是一个科学技术发展共同的一个综合性的结果，同时，为社会经济发展产生了一个重大影响的一门科学技术，它的发展归功于在第二次世界大战中各国加强了经济的投入，就加强了本国的经济的发展。另一方面它也是生产力发展的需求的必然结果，也是人类自身发展的必然结果，那么随着人类的发展，人们在不断探讨自然过程中，在认识和改造自然过程中，需要能够解放人的一种奴隶。那么这种奴隶就是代替人们去能够从事复杂和繁重的体力劳动，实现人们对不可达世界的认识和改造，这也是人们在科技发展过程中的一个客观需要。 机器人有三个发展阶段，那么也就是说，我们习惯于把机器人分成三类，一种是第一代机器人，那么也叫示教再现型机器人，它是通过一个计算机，来控制一个多自由度的一个机械，通过示教存储程序和信息，工作时把信息读取出来，然后发出指令，这样的话机器人可以重复的根据人当时示教的结果，再现出这种动作，比方说汽车的点焊机器人，它只要把这个点焊的过程示教完以后，它总是重复这样一种工作，它对于外界的环境没有感知，这个力操作力的大小，这个工件存在不存在，焊的好与坏，它并不知道，那么实际上这种从第一代机器人，也就存在它这种缺陷，因此，在20世纪70年代后期，人们开始研究第二代机器人，叫带感觉的机器人，这种带感觉的机器人是类似人在某种功能的感觉，比如说力觉、触觉、滑觉、视觉、听觉和人进行相类比，有了各种各样的感觉，比方说在机器人抓一个物体的时候，它实际上力的大小能感觉出来，它能够通过视觉，能够去感受和识别它的形状、大小、颜色。抓一个鸡蛋，它能通过一个触觉，知道它的力的大小和滑动的情况。第三代机器人，也是我们机器人学中一个理想的所追求的最高级的阶段，叫智能机器人，那么只要告诉它做什么，不用告诉它怎么去做，它就能完成运动，感知思维和人机通讯的这种功能和机能，那么这个目前的发展还是相对的只是在局部有这种智能的概念和含义，但真正完整意义的这种智能机器人实际上并没有存在，而只是随着我们不断的科学技术的发展，智能的概念越来越丰富，它内涵越来越宽。 下面我简单介绍一下我国机器人发展的基本概况。由于我们国家存在很多其 我国第三方物流中存在的问题、原因及战略选择 【摘要】我国物流业发展刚刚起步，第三方物流的理论和实践等方面都比较薄弱。本文指出我国第三方物流存在的问题在于国内外第三方物流企业差距、物流效率不高、缺乏系统性管理、物流平台构筑滞后、物流管理观念落后等。分析了产生上述问题的原因，并提出了精益物流、中小型第三方物流企业价值链联盟、大型第三方物流企业虚拟化战略等三种可供选择的第三方物流企业发展战略。 【关键词】第三方物流；精益物流战略；价值链联盟；虚拟化战略 1引言 长期以来，我国国内企业对采购、运输、仓储、代理、包装、加工、配送等环节控制能力不强，在“采购黑洞”、“物流陷井”中造成的损失浪费难以计算。因此，对第三方物流的研究，对于促进我国经济整体效益的提高有着非常重要的理论和实践意义。本文试图对我国策三方物流存在的问题及原因进行分析探讨，并提出第三方物流几种可行的战略选择。 物流的定义 在完成商业交易之后,物流将以最低成本和最高效益的方式执行将商品从供应商(卖方)流转到顾客(买方)的过程。这就是物流的定义。在物流过程中,既需要诸如物流设施和设备(物流运输工具等)的硬件,也需要对物流实施信息化管理进行物流标准化。此外,政府和物流组织的支持也不可或缺。 物流的三大主要功能 (1)创造时间价值:同种商品因所处时间的不同而有着不同的价值。在商品流转过程中,往往会处于某种停滞的状态,物流的专业术语就称之为储存。储存创造了商品的时间价值。 (2)创造场所价值: 同种商品因所处位置的不同而有着不同的价值。这种因商品流转过程中而产生的附加增值称之为物流的场所价值。 (3) 同配送加工价值:有时,物流活动也能创造配送加工价值,这种物流加工主要改变商品的长度、厚度和包装形态。物流中经常提到的“分割成更小的部分”就是配送加工中最为常见的形式。大多数物流加工都能创造商品的附加价值。 机械外文文献翻译 Overall position of Agricultural Mechanization in Turkey Agricultural equipment and machinery are the indispensable part of agricultural activities. If these instruments, which are used in various stages of production, are not used properly, there may be some problems. So, how can we use them properly ? As the proverb goes, “It is the want of care that makes the field bare”. They return the money and efforts invested in them if they are maintained well. Ploughs, which were being used in our country up until recently, resemble those ploughs of the various tribes that lived in Anatolia long time ago. It is because one society gets use of societies that lived before. Some of the black ploughs that were being used up until recently resemble the ploughs that had been used in the ancient Rome. The first agricultural school was established in the Ottoman Empire in 1846. The first domestic heavy ploughs was manufactured i n Izmir 90 years ago, and tractor was introduced 80 years ago. However, it was only the foundation of the Republic that the tractor began to be used in agricultural activities. Agricultural mobilization began with modern agricultural practices in the Atatürk Forest Farm, which was founded by the Great Atatürk. Use of modern agricultura l equipment was encouraged, 人工智能的形成及其发展现状分析 冯海东 （长江大学管理学院荆州434023） 摘要：人工智能的历史并不久远，故将从人工智能的出现、形成、发展现 状及前景几个方面对其进行分析，总结其发展过程中所出现的问题，以及发展现状中的不足之处，分析其今后的发展方向。 关键词：人工智能，发展过程，现状分析，前景。 一．引言 人工智能最早是在1936年被英国的科学家图灵提出，并不为多数人所认知。 当时，他编写了一个下象棋的程序，这就是最早期的人工智能的应用。也有著名的“图灵测试”，这也是最初判断是否是人工智能的方案,因此，图灵被尊称为“人工智能之父”。人工智能从产生到发展经历了一个起伏跌宕的过程，直到目前为止，人工智能的应用技术也不是很成熟，而且存在相当的缺陷。 通过搜集的资料，将详细的介绍人工智能这个领域的具体情况，剖析其面临的挑战和未来的前景。 二．人工智能的发展历程 1. 1956年前的孕育期 (1) 从公元前伟大的哲学家亚里斯多德(Aristotle)到16世纪英国哲学家培根(F. Bacon)，他们提出的形式逻辑的三段论、归纳法以及“知识就是力量”的警句，都对人类思维过程的研究产生了重要影响。 （2）17世纪德国数学家莱布尼兹(G..Leibniz)提出了万能符号和推理计算思想，为数理逻辑的产生和发展奠定了基础，播下了现代机器思维设计思想的种子。而19世纪的英国逻辑学家布尔（G. Boole）创立的布尔代数，实现了用符号语言描述人类思维活动的基本推理法则。 （3） 20世纪30年代迅速发展的数学逻辑和关于计算的新思想，使人们在计算机出现之前，就建立了计算与智能关系的概念。被誉为人工智能之父的英国天才的数学家图灵（A. Tur-ing）在1936年提出了一种理想计算机的数学模型，即图灵机之后,1946年就由美国数学家莫克利（J. Mauchly）和埃柯特（J. Echert）研制出了世界上第一台数字计算机，它为人工智能的研究奠定了不可缺少的物质基础。1950年图灵又发表了“计算机与智能”的论文，提出了著名的“图灵测试”，形象地指出什么是人工智能以及机器具有智能的标准，对人工智能的发展产生了极其深远的影响。 （4） 1934年美国神经生理学家麦克洛奇(W. McCulloch) 和匹兹(W. Pitts )建立了第一个神经网络模型，为以后的人工神经网络研究奠定了基础。 2. 1956年至1969年的诞生发育期 (1)1956年夏季，麻省理工学院（MIT)的麦卡锡（J．McCarthy）、明斯基（M. Minshy）、塞尔夫里奇（O. Selfridge)与索罗门夫(R. Solomonff)、 IBM的洛 本份文档包含：关于该选题的外文文献、文献综述 一、外文文献 文献信息 标题: Business Logistics Performance Measurement in Third-Party Logistics: An Empirical Analysis of Australian Courier Firms 作者: Michael W; Ferry J; Ahmad A 出版物名称: International Journal of Business and Information 卷: 10;期: 3;页: 323-336 年份: 2015 Business Logistics Performance Measurement in Third-Party Logistics: An Empirical Analysis of Australian Courier Firms ABSTRACT This paper presents an empirically validated measurement model of logistics performance in Australian courier firms. In third-party logistics firms, logistics performance directly influences both internal and external stakeholders/customers. The courier firm is an important model of third-party logistics. In this study, all measures are validated by both academics and practitioners. Empirical data for the study was collected through a web-based survey. A total of 162 responses were used to verify the measurement model of structural equation modeling. Results indicate that the logistics performance measurement has high reliability and validity in the study. This measurement model contributes to the business performance literature. It provides insight to assess logistics performance in the postal/courier industry. In addition, the measures can be generalized for different business management purposes. Keywords: Performance measurement, logistics performance, business logistics, supply chain management, postal/courier industry 1. INTRODUCTION During the last couple of decades, the logistics industry has boomed worldwide, and competition in the third-party logistics (3PLs) market is now very intensive. The Manufacturing Engineering and Technology—Machining Serope kalpakjian；Steven R.Schmid 机械工业出版社2004年3月第1版 20.9 MACHINABILITY The machinability of a material usually defined in terms of four factors: 1、Surface finish and integrity of the machined part; 2、Tool life obtained; 3、Force and power requirements; 4、Chip control. Thus, good machinability good surface finish and integrity, long tool life, and low force And power requirements. As for chip control, long and thin (stringy) cured chips, if not broken up, can severely interfere with the cutting operation by becoming entangled in the cutting zone. Because of the complex nature of cutting operations, it is difficult to establish relationships that quantitatively define the machinability of a material. In manufacturing plants, tool life and surface roughness are generally considered to be the most important factors in machinability. Although not used much any more, approximate machinability ratings are available in the example below. 20.9.1 Machinability Of Steels Because steels are among the most important engineering materials (as noted in Chapter 5), their machinability has been studied extensively. The machinability of steels has been mainly improved by adding lead and sulfur to obtain so-called free-machining steels. Resulfurized and Rephosphorized steels. Sulfur in steels forms manganese sulfide inclusions (second-phase particles), which act as stress raisers in the primary shear zone. As a result, the chips produced break up easily and are small; this improves machinability. The size, shape, distribution, and concentration of these inclusions significantly influence machinability. Elements such as tellurium and selenium, which are both chemically similar to sulfur, act as inclusion modifiers in 伺服电机 1. 伺服电机的定义 伺服电动机又称执行电动机，在自动控制系统中，用作执行元件，把所收到的电信号转换成电动机轴上的角位移或角速度输出。分为直流和交流伺服电动机两大类，其主要特点是，当信号电压为零时无自转现象，转速随着转矩的增加而匀速下降。伺服电机在伺服系统中控制机械元件运转的发动机. 是一种补助马达间接变速装置。伺服电机可使控制速度, 位置精度非常准确。将电压信号转化为转矩和转速以驱动控制对象。转子转速受输入信号控制，并能快速反应，在自动控制系统中作执行元件，且具有机电时间常数小、线性度高、始动电压低等特点。 2. 伺服电机工作原理 1.伺服主要靠脉冲来定位，基本上可以这样理解，伺服电机接收到1 个脉冲，就会旋转1 个脉冲对应的角度，从而实现位移，因为，伺服电机本身具备发出脉冲的功能，所以伺服电机每旋转一个角度，都会发出对应数量的脉冲，这样，和伺服电机接受的脉冲形成了呼应，或者叫闭环，如此一来，系统就会知道发了多少脉冲给伺服电机，同时又收了多少脉冲回来，这样，就能够很精确的控制电机的转动，从而实现精确的定位，可以达到0.001mm有刷电机成本低，结构简单，启动转矩大，调速范围宽，控制容易，需要维护，但维护方便（换碳刷），产生电磁干扰，对环境有要求。无刷电机体积小，重量轻，出力大，响应快，速度高，惯量小，转动平滑，力矩稳定。控制复杂，容易实现智能化，其电子换相方式灵活，可以方波换相或正弦波换相。电机免维护，效率很高，运行温度低，电磁辐射很小，长寿命，可用于各种环境。 2. 交流伺服电机也是无刷电机，分为同步和异步电机，目前运动控制中一般都用同步电机，它的功率范围大，可以做到很大的功率。大惯量，最高转动速度低，且随着功率增大而快速降低。因而适合做低速平稳运行的应用。 3. 永磁交流伺服电动机简介 20 世纪80 年代以来，随着集成电路、电力电子技术和交流可变速驱动技术的发展，永磁交流伺服驱动技术有了突出的发展，各国著名电气厂商相继推出各自的交流伺服电动机和伺服驱动器系列产品并不断完善和更新。交流伺服系统已成为当代高性能伺服系统的主要发展方向，使原来的直流伺服面临被淘汰的危机。90 年代以后，世界各国已经商品化了的交流伺服系统是采用全数字控制的正弦 人工智能 【摘要】：人工智能是一门极富挑战性的科学，但也是一门边沿学科。它属于自然科学和社会科学的交叉。涉及的学科主要有哲学、认知科学、数学、神经生理学、心理学、计算机科学、信息论、控制论、不定性论、仿生学等。人工智能(Artificial Intelligence)，英文缩写为AI。它是研究、开发用于模拟、延伸和扩展人的智能的理论、方法、技术及应用系统的一门新的技术科学。人工智能是计算机科学的一个分支，它企图了解智能的实质，并生产出一种新的能以人类智能相似的方式做出反应的智能机器，该领域的研究包括机器人、语言识别、图像识别、自然语言处理和专家系统等1。 【关键词】：人工智能；应用领域；发展方向；人工检索。 1．人工智能描述 人工智能(Artificial Intelligence) ，英文缩写为AI。它是研究、开发用于模拟、延伸和扩展人的智能的理论、方法、技术及应用系统的一门新的技术科学2。人工智能是计 算机科学的一个分支，它企图了解智 能的实质，并生产出一种新的能以人 类智能相似的方式作出反应的智能 机器，该领域的研究包括机器人、语 言识别、图像识别、自然语言处理和 专家系统等。“人工智能”一词最初 是在1956 年Dartmouth学会上提出 的。从那以后,研究者们发展了众多 理论和原理,人工智能的概念也随之扩展。人工智能是一门极富挑战性的科学，从事这项工作的人必须懂得计算机知识，心理学和哲学。人工智能是包括十分广泛的科学，它由不同的领域组成，如机器学习，计算机视觉等等，总的说来，人工智能研究的一个主要目标是使机器能够胜任一些通常需要人类智能才能完成的复杂工作。但不同的时代、不同的人对这种“复杂工作”的理解是不同的。例如繁重的科学和工程计算本来是要人脑来承担的，现在计算机不但能完成这种计算, 而且能够比人脑做得更快、更准确，因之当代人已不再把这种计算看作是“需要人类智能才能完成的复 1.蔡自兴，徐光祐.人工智能及其应用.北京：清华大学出版社，2010 2元慧·议当人工智能的应用领域与发展状态〖Ｊ〗．2008 Automobile Brake System汽车制动系统 The braking system is the most important system in cars. If the brakes fail, the result can be disastrous. Brakes are actually energy conversion devices, which convert the kinetic energy (momentum) of the vehicle into thermal energy (heat).When stepping on the brakes, the driver commands a stopping force ten times as powerful as the force that puts the car in motion. The braking system can exert thousands of pounds of pressure on each of the four brakes. Two complete independent braking systems are used on the car. They are the service brake and the parking brake. The service brake acts to slow, stop, or hold the vehicle during normal driving. They are foot-operated by the driver depressing and releasing the brake pedal. The primary purpose of the brake is to hold the vehicle stationary while it is unattended. The parking brake is mechanically operated by when a separate parking brake foot pedal or hand lever is set. The brake system is composed of the following basic components: the “master cylinder” which is located under the hood, and is directly connected to the brake pedal, converts driver foot’s mechanical pressure into hydraulic pressure. Steel “brake lines” and flexible “brake hoses” connect the master cylinder to the “slave cylinders” located at each wheel. Brake fluid, specially designed to work in extreme conditions, fills the system. “Shoes” and “pads” are pushed by the slave cylinders to contact the “drums” and “rotors” thus causing drag, which (hopefully) slows the c ar. The typical brake system consists of disk brakes in front and either disk or drum brakes in the rear connected by a system of tubes and hoses that link the brake at each wheel to the master cylinder (Figure). Basically, all car brakes are friction brakes. When the driver applies the brake, the control device forces brake shoes, or pads, against the rotating brake drum or disks at wheel. Friction between the shoes or pads and the drums or disks then slows or stops the wheel so that the car is braked. 可编程电源能够接收AC和DC输入功率 背景 许多电子设备，如电脑，个人数字助理（PDA）、移动电话、光盘和盒式磁带播放器等，目的是供电从交流（AC）和直流（DC）10个电源。交流电源包括墙壁插座，而直流电源可包括电池和车辆电源，如汽车点烟器和飞机座椅电源（如授权系统）。为了从这些交流和直流电源接收功率，电子设备通常必须具有多个独立的功率转换电源供应。此外，每个电子设备可以接收在不同要求的电流或电压下的操作功率。这些业务的要求也会改变关于电子设备的状态（例如，是否电子设备的电池正在充电）。 电力电子设备如计算机、人工提供外部电源。这个外部电源可能是一个开关电源的重量可能接近一磅，可能是约八英寸长，四英寸宽，高约四英寸。在此外，电源可包括固定输出电缆或固定输入电缆和插头，使之更加困难压缩存储。因此，这样的外部电源贡献子—大量额外的重量，电脑用户必须携带他或她允许电池充电和电气插座或其他电源的操作。此外，外部电源可以笨重，不可获得在典型情况下，便携式电子设备，如笔记本电脑和子笔记本电脑。 日本，一个单独的电源可能需要需要每个外围设备，如打印机、外部存储器（例如，磁盘驱动器）或类似。因此，用户需要电源消耗和增加一些不必要的重量空间。这些电源可设计用于与一个特定类型的交流或直流电源。因此，特别是便携式电子设备，它是可取的，能够接收电力从任何数量的交流和直流电源，用户可能需要不断进行适用于多种电源的多电源可能提供的来源。 这些缺陷在解决，编号6266261，5636110，5838554，6091611，and6172884，它描述了可编程电源。这个输出可以耦合英特尔：多变的技巧电源输出电缆或终端。一双电源转换为交流和直流电源输入信号转换成直流电源输出信号也是描述.这些引用，但是，不披露电源可以紧包装和容易存储.他们也没有描述如何互换提示可能是方便和紧凑的存储以防止大坝，这可能是特别有问题，提示小的尺寸。 其他讨论电力供应的参考接收交流和直流电源输入简单有效。例如，美国专利号，描述具有固定输入电缆和用于接收交流和直流电源输入信号的插头用于将直流输出电缆传输到电子设备的固定输出电缆和连接器。此外，该物参考并描述任何用于将交流或直流输入功率信号我各种特性的输入功率匹配为直流电源输出信号需要一个以上的电子设备。 电源在包括固定的交流输入插头，DC插件可安装，电源可以获得直流电源输入回答信号与等人参考，输入电缆的交流输入插头称为固定。虽然直流插头附件和输出电缆 中英文翻译 (文档含英文原文和中文翻译) 摘要：自从―一万村‖市场项目开展以来，连锁超市就开始在农村地区发展起来。物流和分配是连锁超市运作过程中的纽带，在超市的平稳运作中起到重要作用。本土超市涌现出的很多问题，现在逐渐成为超市发展的瓶颈。在这篇论文中，作者将会分析现今存在于中国农村超市的物流和分配方面的问题，然后提供一些相应策略解决这个问题。 关键词：农村地区，货品分配，策略规划，物流，连锁超市。 1 介绍 自从―一万村‖市场项目开展以来，连锁超市作为一个新的运作系统及销售模式，开始在广阔的农村地区发展。这些连锁超市带领农民提高消费水平、缩小城乡差异、提升农村地区和农村市场现代流通的发展。连锁超市在农民中很受欢迎。然而，物流和分配是连锁超市的核心，却仍非常薄弱。分配的优势是超市运作成本、利润及相关合伙人附加利润的关键。在当前经济危机的形势下，解决农村超市物流及分配方面的问题，对农村市场的发展、经济的发展以及建设一个社会主义新农村都非常关键。 1.1农村连锁超市物流及分配的一些概念和特点 分配是一个经济活动，是企业家基于消费者需求，用最有效的方式在分配中心或其它地点储存货物，并且把这些货物运送到在合理经济框架内的其他客户。它包含购买、储存、分类、货物处理、递送及其它活动。它是一个物流活动的方式，结合了特别的、完整的业务流程。在农村地区，农民和农产品独特，所以，与城市物流分配相比，有着一些不同的特点。 1.2农村地区的主要物流和分配问题 A．低均匀分布率和高运作成本 根据商务部调查，自从―一万村‖市场项目开展以来，农村连锁超市的覆盖率已经达到超过60%，但是分配率却只有40%。这个数字不仅低于国内连锁超市60%的平均运送率，也大大低于国外连锁超市高于80%的运送率。均匀分配有利于统一采购。商店不能得益于连锁。这就会导致高物流成本。 B．不合理的物流和分配模式，导致信息读取效率不高 最近，农村连锁超市的物流和分配渠道主要由分配中心、农产品和供应市场合作社、第三方物流和分配系统组成。事实上，这三种分配方式也同样面临着高物流成本的问题。许多连锁超市没有建立自己的分配中心，因而不能满足分配服务的需求。即使一些连锁超市建立了自己的分配中心，也仍然存在很大问题。大多数农村超市规模较小，缺少建立分配中心的资金，因此，一些分配中心不能满足超市分配的需求。农村连锁商店分布较广，单个的连锁超市分配还是比较有限。收入比分配中心的建立和运作成本还要低。 C．分配中心的延后建立、低下技术水平、低分配水平 农村连锁超市的分配中心改造和扩大都是基于原来的仓库，这并不能满足连锁超市的服务需求。这些分配中心只能用来当仓库、储存及运输，缺少了深层的货品加工容量、信息加工以及反馈功能。这些基础设施不够，也缺少了机械化的检测、加工、冰冻、冷藏、包装及其它设备。电脑信息管理系统也远远不够，导致了不能及时进行与供应商、总部以及分部的数据交换。很难有效地管理物流信息，所以所有功能的协作及整合程度仍然非常低。 D．不充分的信息共享系统 农村连锁超市的信息系统构建是相对落后的。电子订货系统、电子数据互换系统以及增值网络系统都还没有使用。决策和信息管理系统也远远不够。很难在 外文出处：《Manufacturing Engineering and Technology—Machining》 附件1：外文原文 Manipulator Robot developed in recent decades as high-tech automated production equipment. I ndustrial robot is an important branch of industrial robots. It features can be program med to perform tasks in a variety of expectations, in both structure and performance a dvantages of their own people and machines, in particular, reflects the people's intellig ence and adaptability. The accuracy of robot operations and a variety of environments the ability to complete the work in the field of national economy and there are broad p rospects for development. With the development of industrial automation, there has be en CNC machining center, it is in reducing labor intensity, while greatly improved lab or productivity. However, the upper and lower common in CNC machining processes material, usually still use manual or traditional relay-controlled semi-automatic device . The former time-consuming and labor intensive, inefficient; the latter due to design c omplexity, require more relays, wiring complexity, vulnerability to body vibration inte rference, while the existence of poor reliability, fault more maintenance problems and other issues. Programmable Logic Controller PLC-controlled robot control system for materials up and down movement is simple, circuit design is reasonable, with a stron g anti-jamming capability, ensuring the system's reliability, reduced maintenance rate, and improve work efficiency. Robot technology related to mechanics, mechanics, elec trical hydraulic technology, automatic control technology, sensor technology and com puter technology and other fields of science, is a cross-disciplinary integrated technol ogy. First, an overview of industrial manipulator Robot is a kind of positioning control can be automated and can be re-programmed to change in multi-functional machine, which has multiple degrees of freedom can be used to carry an object in order to complete the work in different environments. Low wages in China, plastic products industry, although still a labor-intensive, mechanical hand use has become increasingly popular. Electronics and automotive industries that 外文资料译文 Power Electronics Electromagnetic Compatibility The electromagnetic compatibility issues in power electronic systems are essentially the high levels of conducted electromagnetic interference (EMI) noise because of the fast switching actions of the power semiconductor devices. The advent of high-frequency, high-power switching devices resulted in the widespread application of power electronic converters for human productions and livings. The high-power rating and the high-switching frequency of the actions might result in severe conducted EMI. Particularly, with the international and national EMC regulations have become more strictly, modeling and prediction of EMI issues has been an important research topic. By evaluating different methodologies of conducted EMI modeling and prediction for power converter systems includes the following two primary limitations: 1) Due to different applications, some of the existing EMI modeling methods are only valid for specific applications, which results in inadequate generality. 2) Since most EMI studies are based on the qualitative and simplified quantitative models, modeling accuracy of both magnitude and frequency cannot meet the requirement of the full-span EMI quantification studies, which results in worse accuracy. Supported by National Natural Science Foundation of China under Grant 50421703, this dissertation aims to achieve an accurate prediction and a general methodology. Several works including the EMI mechanisms and the EMI quantification computations are developed for power electronic systems. The main contents and originalities in this research can be summarized as follows. I. Investigations on General Circuit Models and EMI Coupling Modes In order to efficiently analyze and design EMI filter, the conducted EMI noise is traditional decoupled to common-mode (CM) and differential-mode (DM) components. This decoupling is based on the assumption that EMI propagation paths have perfectly balanced and time-invariant circuit structures. In a practical case, power converters usually present inevitable unsymmetrical or time-variant characteristics due to the existence of semiconductor switches. So DM and CM components can not be totally decoupled and they can transform to each other. Therefore, the mode transformation led to another new mode of EMI: mixed-mode EMI. In order to understand fundamental mechanisms by which the mixed-mode EMI noise is excited and coupled, this dissertation proposes the general concept of lumped circuit model for representing the EMI noise mechanism for power electronic converters. The effects of unbalanced noise source impedances on EMI mode transformation are analyzed. The mode transformations between CM and DM components are modeled. The fundamental mechanism of the on-intrinsic EMI is first investigated for a switched mode power supply converter. In discontinuous conduction mode, the DM noise is highly dependent on CM noise because of the unbalanced diode-bridge conduction. It is shown that with the suitable and justified机械设计设计外文文献翻译、中英文翻译、外文翻译
PLC控制下的电梯系统外文文献翻译、中英文翻译、外文翻译
人工智能专业外文翻译-机器人
第三方物流外文文献(原文与翻译)培训课件
机械外文文献翻译
文献综述_人工智能
第三方物流文献综述及外文文献资料
Manufacturing Engineering and Technology(机械类英文文献+翻译)
伺服电机外文文献翻译
论文《人工智能》---文献检索结课作业
汽车制动系统(机械、车辆工程毕业论文英文文献及翻译)
程控电源外文翻译
连锁超市物流中英文对照外文翻译文献
机械手臂外文文献翻译、中英文翻译、外文翻译
电气类外文翻译---电力电子系统的电磁兼容问题