安卓系统与IOS系统比较—毕业英文文献翻译

ESEP 2011: 9-10 December 2011, Singapore

An Analysis and Comparison of Open and Closed Mobile

Platforms

Android vs. iPhone

Yinglu ZOUa, , Hao WU b, Jianxin HUANG a,b

a Information Engineering College,7 JianXue Road, JinShui District, ZhengZhou,

450001, China

Abstract

With the release of Android 2.2 Froyo and iPhone 4, the war between open and closed mobile platforms tends to befiercer. Being the representatives of the two parties, Froyo and iOS 4 are quite different at system framework, newfeature, application market and integration model. According to the company spirits of Google and Apple, we do some analyses and comparisons of the above points, explain the differences of Android and iPhone from the shallower to the deeper, then conclude the characteristics of open and closed mobile platforms, aiming at providing an objective reference for researchers of mobile platforms, helping them see clearer into mobile industry. As a result,both Froyo and iOS 4 have their advantages and disadvantages, still they are far from being perfect, there?s room forfurther improvement.

Keywords: Android；iPhone；Froyo；iOS 4；smart phone；mobile platform

1. Introduction

In recent years, the popularity of smart phone kept going up. More and more smart phones are sold anda lot of people are embracing them. Smart phones brought great convenience to users, as well created opportunities for smart phone researchers. That?s to say, the wide spread of smart phones benefited both sides. At the same time, developing of smart phone OS becomes one of the smartest industry. To be a smart phone OS, the system should: 1. Provide services like a PC. 2. Work with a GPU for better visual effects. 3. Allow the user to surf on Internet freely. And apparently, there?re also some weaknesses:1.Limited battery. 2. Poor CPU performance against PC CPU. 3. Small storage. 4. The use of RAM may leads to loss of data when the phone runs out of battery

Now the 2 giants of smart phone OS are Android and iPhone OS. On one side, Android is based on Linux kernel and Dalvik virtual machine, and it is open sourced. The upper layer of Android is Java based,allowing developers to develop Android applications with Google SDK and sell their software in Android Market. On the

other side, iPhone OS, which bases on Unix kernel and Darwin model but is closed sourced,evolves from Mac OS X and is the default OS of iPhone, iPod Touch and iPad. Objective C based software can run in iPhone OS, and just like Android, you can develop your own iPhone applications and upload them onto Apple?s …App Store? for sale [1] [2] [3] [4].

By comparing the latest Android and iPhone OS, Android 2.2 Froyo and iOS 4, we can take a glimpse at the main feature of open and closed smart phone OSs. While the 2 OSs are designed in rather different mentality and functionality, it?s a little early to tell which one is better.

2. Smart Phone OS

2.1. Android

The system architecture of Android consists of 5 layers, which are Linux Kernel, Android Runtime, Libraries, Application Framework and Applications, from bottom to top.

Android provides core services like security, memory management, process management, network stack and drivers, basing on Linux 2.6. Being the abstract layer between software and hardware, the layer of Linux Kernel hides the implementing details of hardware and provides integrated services for upper layer.

Dalvik virtual machine and Java core libraries are included in the layer of Android Runtime, providing most functions in Java core libraries.

The layer of Libraries contains a class of C/C++ libraries for Android components. Those libraries are integrated by the layer of Application Framework and then provided to developers.

The layer of Application Framework provides all kinds of modules for program initialization to simplify the use of components, allowing developers do whatever they want and provide services for other softwares, under the limitation of security, of course.

Mainstream applications are located in the layer of Application, including e-mail, SMS, calendar, Google map, Web browser and contacts. Users interact directly with this layer [1] [2].

The latest version of Android, Android 2.2 Froyo, puts on some new features. They are: 1. Support Flash 10.1, enables user to watch flash on the phone. 2. V8 JavaScript engine in web browser leads to faster Internet data transportation. 3. Big advance in network sharing. You can use the phone as a 3G NIC,or convert 3G signal

to Wi-Fi. 4. Automatically software update. 5. Softwares can be setup in SD card to extend file storages.

2.2. iPhone

iPhone OS is consist of 4 abstract layers: Core OS, Core Service, Media and Cocoa Touch respectively.

Layers of Core OS and Core Service are designed in C language to handle core system services, enabling developers to perform file access, sockets calling and data handling. CFNetwork and SQLite are also parts of these 2 layers.

The layer of Media, according to its name, this layer is used to control video and audio, as well handle 2D and 3D images. The Open GL-ES Quratz part of the layer is coded with C language, while the part of Core-Audio and Core-Animation is Objective C based.

The layer of Cocoa Touch builds a basic framework for all kinds of programs in iPhone. Most programs run in Cocoa Touch layer, and it?s surely Objective C based [3] [4].

The latest iPhone OS is iOS 4. It includes the following new features: 1.Software classification. This

feature enables user to place sorted softwares into different documents, making it clearer to manage. 2. Email integration. One account is for all e-mails from different providers. 3. iBook, originally from iPad, is built in iOS. 4. A brand new Apple Game Center makes iPhone a tremendous entertainment platform.

2.3. Android vs. iPhone

Being the top 2 smart phone OSs, we?re sure that both Android and iPhone have their own advantages and disadvantages. Now let?s take a look at each of them, and see what unique feature they have.

Android 2.2 Froyo fully support multitask, which means you can listen to music while writing blog. And iOS 4, officially announced to be …multitasked?, is in fact a play of concept. Only a few of softwares which are authorized by Apple can run …simultaneously?, whose principle is much easier that multitask:when an application is switched out, its current state is saved and then the system just closes it. And when it?s switched in, we?re back to the previous snapshot [5] [6] [7].

During the publication of Android 2.2 Froyo, Google announced it has …the most fluent web browser?,because the use of V8 JavaScript engine. V8 is a brand new engine, designed for running big size JavaScript application. In some kind of tests, V8

is much faster than JScript from Internet Explorer, SpiderMonkey from Firefox and JavaScriptCore from Safari. It all owe to 3 key parts of V8, they?re fast attribute access, dynamic code generation, effective trash cleaning.

2.3.1. Fast Attribute Access

JavaScript is a kind of dynamic language, which means attributes can be added or deleted at runtime, and they?re frequently changed. Most JavaScript engines use a dictionary style structure to store the attributes of an object, so it requires a whole diction ary search to find the position of attributes in memory.It?s quite inefficient and it?s slower than Java and Smalltalk.

To solve this problem, V8 discarded dynamic search and realized it in a different way: Create hidden classes for objects dynamically. In JavaScript, every time when we?re adding a new attribute to an object,we create a subclass with the new attribute from a hidden class as the super class. It?s a recursive course and the above performance happens only once when we first do this. Later we just use the previous hidden subclass when we?re in the same situation. So there?s no need to repeat operation and create a dictionary. This leads to the save of time and energy, as well make it easier for the implementation of class optimization and inner cache [4].

2.3.2. Dynamic Code Generation

When JavaScript is running for the very first time, V8 translate it directly into local machine code, rather than explain it to bytecode. Attribute access is done by inner cache, which is often translated into instructions by V8 at runtime.

When it comes to the code where certain object is accessed, V8 tries to find the current hidden class. Meanwhile, V8 assumes that all objects in the snippet are described by the same hidden class, so V8 willmodify corresponding inner cache to make the direct use of the hidden class more convenient. If thisassumption is correct, the access of attributes can be all done in only 1 instruction. Even if the predictionfails, inner cache is modified again by V8, which won?t take too muc h time and resource. When one hidden class is shared by a lot of objects, the access speed can be close to most dynamic language access speed. Inner cache and hidden class, mixed with dynamic code and class optimization, improve the efficiency of JavaScript at a large scale [4].

2.3.3. Effective Trash Cleaning

V8 does memory recycles automatically. To guarantee the speed of object distribution, as well cut the time of trash cleaning and clear fragment up, V8 will

interrupt the running application when performing trash cleaning. Mostly, only a small part of object stack is involved in trash cleaning cycle, so the interruption caused little. All location of objects and pointers are logged by V8, so the system won?t take object for pointer and memory overflow is avoided [4].

Besides …the most fluent web browser?, Google collaborated with Adobe and Android 2.2 Froyo fully supports Flash. That?s to say, not only flash media, but all flash web pages can display perfectly on Android. To the contrary, Apple turned down Adobe and take HTML5 as iPhone?s web protocol, making it unable to show some flash based animation.

Android 2.2 Froyo also leads the way in network sharing. Smart phone with Froyo can be connected toa PC as a 3G NIC, and can also conveniently convert 3G signal to Wi-Fi. iOS 4 can do the first too, butfailed to convert 3G to Wi-Fi.

Video conference is both supported by Froyo and iOS 4, but the conditions are different. You can see aFroyo user via camera as long as you get a camera also. However, iOS 4 user can only do video talk toanother iOS 4 user, which is a big limitation.

While Android is ascendant in network interaction, Apple is unique in its friendship and entertainment.The added feature of …software classification? enables user to place sorted softwares into differentdocuments, making it clearer to manage. What?s more, there?re hundreds of thousands applications inApp Store, meaning that iPhone can have up to hundreds of thousands functions. This is a ratherremarkable feature that Apple publicizes.

And the most convincing point given by Apple, is that …Android looks exactly familiar with iPhone.?Although it?s just a subjective sense, the born of iPhone really brought big revolution to the phone industry, and the name …Apple? itself is a world famous brand [7] [8].

3. Open and Closed platforms

3.1. SDK

The most important part of every developing platform is SDK, enable 3rd party developers to make software for the platform. Usually, libraries, debug tools and emulators are included in SDK. Different platforms distribute their SDKs differently. Some SDK is complete free and open, while others are strictly limited.

Developers of open platforms can get and modify part or all of the source code. Google and Linux are leaders of open platforms; they publicized the whole source

code of Android and Linux. The good point is that, platform owners can save a great amount of time and energy developing and maintaining the platform, because 3rd party developers will do this for them. With less money spent on development and maintenance, a relatively low price can attract more and more phone users.

Contrarily, closed platforms lock their source code in the safety and forbid 3rd party accesses. Apple and Microsoft are the representatives of them, they are both closed sourced, but some differences do exists. 3rd party iPhone applications are restricted within narrow limits, for that Apple will look through every application which is uploaded onto …App Store?, and a lot of applications are turned down.Microsoft don?t c heck Windows applications at all, it all depends on the users themselves. You installed the mareware, you suffer the loss.

3.2. Application Market

Market is the medium between developers and users, hence it?s very important. Some predicted that there will be more and more application markets while some don?t think so. In current markets, both do exist. Some specify only one market for their products, while others sell their softwares in various markets.

Softwares from Nokia, Microsoft and Linux Mobile are sold in every market. Developers of these platforms can release their own application in whatever markets, so markets have to compete with each other for a living. This is good for users. However, the lack of universal management may lead to mess and chaos, softwares that have the same functionality exist in different markets, which confuses users a lot.

Correspondingly, sole markets claim that most applications should be sold in them. This kind of monopolization leads to no competitor. …App Store? and ?Andr oid Market? are deputy of sole markets. Normally, iPhone applications can only be found in …App Store?, and Apple will check every one of them by itself. Good news is that every application in …App Store? is officially tested, it?s safe; Bad news is that a lot of pretty good softwares are rejected for various reasons. And a big unofficial mechanism is built by hackers, that is …jailbreak? and …SIM unlock?.

…Jailbreak? is a process that allows iPad, iPhone and iPod Touch users to gain root access and unlock the operating system thus removing any limitations imposed upon them by Apple. Once jailbroken, iPhone users are able to download many extensions and themes previously unavailable through the App Store via installers such as Cydia. A jailbroken iPad, iPhone or iPod Touch is still able to use the App Store and iTunes [9].

And a …SIM lock? is a capability built into GSM phones by mobile phone

manufacturers. Network

providers use this capability to restrict the use of these phones to specific countries and network providers.Generally, phones can be locked to accept only SIM cards based on the International Mobile Subscriber Identity. …SIM unlock? make it possible to use a mobile phone without considering countries and networks specified by mobile phone manufacturers.

However in Android, Google doesn?t test every application at all, so although there?s an official market for Android applications, you can still release your product anywhere you want. Considering security problems, Google banned the use of some com ponents. Like …jailbreak? and …SIM unlock? in iPhone, …root? in Android gives users 100% control of their devices, along with some security risks. …Root? is a process that allows users of cellphones running the Android operating system to attain privileged control (known as "root access") within Android's Linux subsystem, similar to jailbreaking on Apple devices running the iOS operating system, overcoming limitations that the carriers and manufacturers put on such phones. Rooting makes it possible to use custom versions of the Android system such as CyanogenMod, supporting features unavailable in stock ROMs. It also allows for newer versions of Android not supplied by the original device manufacturer. In contrast to iOS jailbreaking, rooting is not needed to run applications not distributed by the official Android Market. It is needed however, when trying to access paid Android applications from countries which are not part of the paid applications market.

3.3. Integration

Some companies focus only on their core industry, i.e. develop an operating system and provide an environment for 3rd party development. Others not only do these, but manage the process of developing a software to publicizing it. Depending on the integration of platforms, we sort them to 4 kinds: full integration platform, market integration platform, device integration platform and no integration platform.

The publicizing model of full integration platform is very strict. Its management ranges from device manufacturing to application release, whose representative is Apple. Apple?s factory produces iPhone,Apple?s …App Store? sells application, Apple?s …iTunes? is the channel of Apple?s resources. The whole process is under Apple?s control.

Market integration platforms commit themselves to developing and selling softwares. Google is one of them. Unlike apple, Google don?t have a factory to

manufacture its own handsets, but only developed Android and set up …Android Market? for Android applications. However, companies like Google definitely have the capability to produce its own devices. Google is in good relationship with HTC, who is the OEM of T-Mobile, O2 and Orange, etc.

Device integration platforms produce their own handsets, but don?t set up application markets. Forexample, RIM makes Black berry, but there?s no official application market for Blackberry. No integration platforms do few things. Microsoft neither makes mobile phones, nor sets up a market.What they do is only developing the operating system: Windows Phone 7.

4. Conclusion

Representatives of open and closed platforms, Android 2.2 Froyo and iOS 4 are both loved and hated.Great browsers are built into them, and their producers are both world famous revolutionary. Android leans to Internet experience, which comes down in one continuous line with Google. But currently, various versions of Android fill the market, and most companies in Open Handset Alliance tend to customize their own Android systems. These facts make Android lack of a general brand image, so people may feel confused a nd say …No? to Android. iPhone OS focuses more on entertainment and it?s very friendly. But Apple is too cool to attract more customers: Diehard fans of Steve Jobs buy every product made by Apple, and people who dislike the style Apple do things may just sniffed at Apple.

Besides, Android 2.2 Froyo succeeds the features of open platforms well. It?s a …users only? platform, because users of Froyo can almost customize everything they want. And members of Open Handset

Alliance tend to provide more choices for users. And iOS 4, typically closed platform member, manages everything ranging from OS development to device manufacturing. It?s a …consider for users? platform.To some extent, users of Android canonizes …free? and …open?, what they care is if they have 100% management of their handsets, no matter whether the OS is called …Android? or …Another?. Apple users are loyal to the brand; they would like to authorize Apple to make decisions for them. So although some iPhone users love physical keyboards, they bought iPhone. In other words, Android users think a lot of …open platform? rather than the brand Google; most iPhone users are follower of Apple, they love the …closed platforms? created by Steve Jobs.

Both Android and iPhone have their unique IDE, SDK and other characteristics. Believe it or not, no perfection exists in the world, so none of today?s mobile

platforms fully meets the needs of users and researchers. The choice of platform boils down to the needs of users and researchers, this article should make the decision easier. Of course the content of this article is time sensitive; platforms will gradually meet the demands of consumers as new technologies emerging.

References

[1] Dave Mark, Jeff LaMarche. “Beginning iPhone 3 Development: Exploring the iPhon e SDK”. 2009.

[2] Erica Sadun. “The iPhone Developer?s Cookbook: Building Application with the iPhone SDK”, 2009.

[3] Ed Burnette. “Hello, Android: Introducing Google?s Mobile Development Platform”, 2009.

[4] W.Frank Ableson, Charlie Collins, Robi Sen. “Un locking Android: A Developer?s Guide”, 2010.

[5] Hee- Yeon Cho, Choon- Sung Nam, Dong- Ryeol Shin. “A Comparison of Open and Closed Mobile Platforms”.

International Conference on Electronics and Information Engineering, 2010.

[6] Ryan C. McKeen, Finis R. P rice III. “DROID v iPHONE”. ABA Journal, 2010.

[7] Mies Ginny, Sullivan Mark. “iPhone 4 vs. Droid X: A Head-to-Head Comparison”. PC World, 2010.

[8] Fleishman, Glenn. “More Options With Tomorrow's Cell Phones”. PC World, 2008.

[9] Keller, Mike. “Jailbreaking Your iPhone: The Pros and Cons”. PC World, 2010.

分析和比较开放和封闭的移动平台

摘要

随着Android 2.2 Froyo和iPhone 4版本的发布，开放式和封闭式的移动平台之间的战争愈演愈烈。作为双方代表，Froyo和iOS4在制度的框架，新功能，应用市场和一体化模式有很大的不同。据谷歌和苹果的公司精神，我们做上述各点的一些分析和比较，说明Android的差异，从iPhone浅向更深，然后得出结论开放式和封闭式的移动平台的特点，目的是为移动平台的研究人员提供客观的参考，帮助他们对移动行业有更清晰的认识。当然，Froyo和iOS4都具有自己的优势和劣势，他们距离完美还有很大的距离，依然有进一步改善的空间。

关键词：Android；iPhone；Froyo；OS 4；智能手机；移动平台

1 介绍

近年来，智能手机的普及率不断攀升。越来越多的智能手机被卖出和很多人都更加青睐于它们。智能手机给用户带来了极大方便，并为智能手机研究者创建了机会。这就是说，智能手机的广泛普及，对双方都有利双方。同时，智能手机操作系统发展成为最智能的行业之一。要成为一个智能手机操作系统，该系统应：1.提供服务PC式的服务。2.使用GPU得到更绚丽的视觉效果。 3.允许用户在互联网上自由地冲浪。显然，它们也有一些弱点：1，电池的限制。 2。较电脑CPU 来说，手机CPU性能差。 3.存储空间小。 4.在手机电池耗尽时，RAM的使用可能会导致数据丢失。

现在智能手机操作系统的两巨头是Android和iPhone OS。一方面，Android 是基于Linux内核，Dalvik虚拟机，它是开源的。上层的Android是基于Java的，允许开发者使用谷歌SDK开发Android应用程序和在Android 市场销售他们的软件。另一方面，iPhone操作系统基于Unix内核和达尔文模型，但它是封源的，是从Mac OS X继承而来，是iPhone，iPod Touch和iPad默认的操作系统。基于C语言的软件可以在iPhone OS上运行，就像Android，你可以开发自己的iPhone应用程序，并上传到苹果的App Store进行销售。

通过比较Android和iPhone OS的最新系统：Android 2.2 Froyo和iOS4，我们可以了解下开放式和封闭式的智能手机操作系统的主要特点。虽然两个操作系统的整体思路和功能设计有很大的不同，它初略分辨出哪一个更好一点。

2 智能手机

2.1 Android

Android系统的体系结构由5层，从底部到顶部分别是Linux内核，Android 运行库，应用框架和应用程序。Android提供的核心服务，如安全，内存管理，

进程管理，网络堆栈和驱动器，是基于Linux2.6的。作为软件和硬件层之间的抽象层，Linux内核隐藏硬件执行的细节，并为上层提供综合服务。

Dalvik虚拟机和Java核心库都包含在Android运行层，提供Java核心库的大多数功能。这些库包含了应用于Android组件的一系列C/C++库。这些库集成了应用框架层，然后提供给开发人员。

应用程序框架层为程序的初始化提供了各种模块，以简化元件的使用，让开发商为所欲为，并提供其他服务软件，当然，在安全性上有所限制。

主流应用程序位于应用层，包括电子邮件，短信，日历，谷歌地图，网页浏览器和接触。用户可以直接与此层交互。

Android的最新版本的Android 2.2 Froyo，提出一些新的特点。它们是：1.支持10.1版本的Flash，使用户可以在手机上观看Flash。2.网页浏览器中的V8 JavaScript引擎使得互联网数据传输更加迅速。 3.在网络共享上有大的进步。你可以将手机作为3G网卡或将3G信号转换为Wi-Fi信号。 4.支持自动软件更新。

5.软件可安装到SD卡以扩展储存空间。

2.2 iPhone

iPhone OS是由4个抽象层组成：核心OS，核心服务，媒体和Cocoa Touch。

核心操作系统和核心服务层使用C语言设计，来处理核心系统服务，使开发人员能够执行文件访问，socket请求和数据处理。 CFNetwork和SQLite同样是这2层一部分。

媒体层，根据其名称，是用来控制视频和音频，以及处理二维和三维图像。这一层中的Open GL-ES Quratz部分是用C语言编码，而音频核心和动画核心的一部分则是基于Objective C编写。

Cocoa Touch层，在iPhone上为应用程序建立了一个基本框架。大多数程序运行在Cocoa Touch层，它也是基于Objective C编写。

最新的iPhone操作系统是iOS4。它包括以下新的特点：1.软件分类。这功能可以使用户将不同分类的软件放入不同的文件中，使它更便于管理。 2。电子邮件整合。一个账户可以使用不同供应商的电子邮件服务。 3。 iBook，源于iPad 的软件，将内置于iOS。 4。一个全新的苹果游戏中心，使iPhone成为一个巨大的娱乐平台。

2.3 Android vs. iPhone

作为智能手机操作系统中最顶尖的两个，我们相信，Android和iPhone都各有自己的优势和缺点。现在，让我们一起来看看这两个系统，看到它们有什么独特的功能。

Android 2.2 Froyo完全支持多任务，这意味着你可以一边听音乐，写博客。

而iOS 4，正式宣布其为“多任务运行”，而事实上，这只是一个概念手法的运用。只有少数被苹果授权的软件可以同时运行，多任务原则更是容易得多，当一个应用程序转出时，其当前状态被保存好，然后系统关闭它。当它又被转换进来时，我们又回到了其以前的快照。

在Android 2.2 Froyo公布时，谷歌宣称其拥有最流畅的网络浏览器，因为使用的V8 JavaScript引擎。 V8是一个全新的引擎，为运行庞大的JavaScript 应用程序而设计。在一些测试中，V8的速度要比Internet Explorer的JScript，火狐的SpiderMonkey和Safari的JavaScriptCore更加迅速。这一切都归功于 V8的3个关键部件，他们可以快速访问属性，动态生成代码，有效进行垃圾的清理。

2.3.1 快速属性访问

JavaScript是一种动态语言，这意味着属性可以在运行时进行添加或删除，并且它们会经常改变。大多数JavaScript引擎使用一种字典式结构来存储对象的属性，因此它需要全局搜索以在内存中找到的属性的位置.It相当低效的属性的位置。这是相当低效的且比Java和Smalltalk慢。

为了解决这个问题，V8废弃了动态搜索，并以不同的方式实现：动态的创建对象的隐藏类。在JavaScript中，每次当我们为对象加入一个新的属性，我们会从隐藏类中创建带有新的属性的子类作为超类。这是一个递归过程，且上述过程只有当我们第一次做时出现。然后，当在相同的情况下，我们只是使用以前的隐藏的子类。因此，没有必要重复操作，并创建一个字典。这会保存时间和精力，以及更容易执行类的优化和内部缓存。

2.3.2 动态代码生成

当JavaScript每次首回运行时，V8将把它直接转换为本地机器代码，而不是解释为字节码。属性的访问是通过内部缓存，它通常在运行时被翻译成V8的指令。

当它来访问某些对象的代码时，V8引擎试图找到当前的隐藏类。同时，V8假设在代码中的所有对象都是相同的隐藏类，所以V8将修改相应的内部缓存，使隐藏类更方便地直接使用。如果这假设是正确的，属性的访问可以使用1个指令就全部完成。即使预测失败，V8会再次修改内部缓存，这不会花费太多的时间和资源。

当一个隐藏类是被很多的对象共享，存取速度可以接近最具活力的语言的访问速度。内部缓存和隐藏类，混合动态代码和类优化，在大规模地改善JavaScript 效率。

2.3.3 有效的垃圾清理机制

V8引擎会对内存进行自动回收。为了保证对象的分配速度，以及削减垃圾清理和内存碎片清理的时间，在执行垃圾清理时，V8会中断正在运行的应用程序。

大多数情况下只有一小部分对象的堆栈参与垃圾清洁周期，所以中断造成小。所有的对象和指针的位置都会被V8记录，这样系统将不会采取对象的指针和内存溢出将会避免。

除了“最流畅的网络浏览器”，谷歌与Adobe进行了合作，Android 2.2 Froyo 充分支持Flash。这就是说，不仅Flash播放器，但所有Flash网页都可以在Android 系统上完美显示。与此相反，苹果拒绝Adobe和HTML5作为iPhone的网络协议，导致其无法显示一些基于Flash的动画。

Android 2.2 Froyo在网络共享的方式上取得了领先。搭载Froyo系统的智能手机可以作为PC的3G网卡，还可以方便地将3G信号转换为WIFI信号。 iOS 4也可以做到第一点，但是不能进行3G和WIFI的转换。

Froyo和iOS4都支持视频会议，但条件是不同的。只要你拥有一个摄像头，你就可以通过它看到使用摄像头的Froyo用户。然而，iOS 4的用户只能与另一个iOS 4的用户进行视频通话，这是一个很大的局限性。

尽管Android在网络互动方面十分优越，苹果却在友好的用户体验和娱乐性上是独一无二的。“软件分类”功能使用户可以讲不同分类的软件放入不同的文件夹中，使它管理更加清晰。更重要的是，在App Store里有数十万的应用程序，这意味着iPhone可以有多达数十万功能。苹果公司宣称，这是一个相当了不起的功能。

苹果最有说服力的一点是，“Android看起来与iPhone完全相似。”虽然它只是一个主观意识，但iPhone的诞生确实给手机行业带来了极大地革命，并命名为“苹果”这一个世界知名品牌。

3 开放式和封闭式平台

3.1 SDK

SDK是每一个开发平台最重要的组成部分，使第三方开发人员在平台上开发软件。通常情况下，库，调试工具和模拟器都包含在SDK。不同平台发布的自己的软件开发工具包是不同的。一些SDK是完全自由和开放的，有些则是有严格限制的。

开放平台的开发人员可以获取和修改一部分或全部源代码。谷歌和Linux开放平台的领导人，他们公布了Android和Linux的整个源代码。优点是，平台所有者可以节省大量的时间和精力开发和维护平台，因为第三方开发者会为做一些事情来帮助平台所有者。随着更少的钱用在开发和维护方面上，相对低廉的价格吸引了越来越多的手机用户。

反之，封闭的平，为了安全封锁了他们的源代码，禁止第三方访问。苹果和微软是其中的代表，他们都封闭源，但也一些差异存在。第三方iPhone应用程序

被限制在狭窄的范围内，苹果将检查每个被上传到“应用商店”的应用程序，且拒绝了很多的应用程序在手机上运行。微软不检查Windows应用程序，所有这一切都取决于用户自己。如果你安装了病毒软件，你自己承担遭受的损失。

3.2 应用商店

市场是开发者和用户之间的介质，因此它是非常重要的。在一些预测认为将会有越来越多的应用市场，而一些不这么认为。在当前的市场，这两种情况都存在。一些人只为他们的产品指定唯一的市场，而其他人则在很多市场销售他们的产品。

诺基亚，微软和Linux的手机软件在每个市场上都有出售。这些平台开发商可以在任何市场发布他们自己的应用程序，使市场为了生存相互竞争。这是为用户好。然而，缺乏统一的管理可能导致市场的混乱，在不同的市场存在很多有相同的功能的软件，用户使用户混淆不清。相应的，唯一的市场声称，大多数应用程序应在其出售。这样的垄断导致没有竞争对手。“应用程序商店”和“Android市场”是唯一的市场代理。

通常情况下，iPhone应用程序只能在'应用商店'找到，苹果将检查他们每个程序。好消息是，每一个App Store的应用都经过官方测试，证实它是安全的。然而坏消息是，很多相当不错的软件因各种原因被拒绝了。于是一个很大的非官方机制由黑客建立起来，也就是“越狱”和“SIM卡解锁”。

“越狱”是一个过程，允许iPad，iPhone和iPod Touch用户获得root访问权限和解锁，从而消除任何由苹果公司的操作系统强加于他们的限制。一旦越狱，iPhone用户可以通过诸如Cydia的安装下载许多以前无法在应用商店应用的扩展和主题。越狱的iPad，iPhone或iPod Touch仍然能够使用的应用程序商店和iTunes。

“SIM卡锁”是GSM手机厂商制作的一种能力。网络供应商使用此功能来限制这些手机使用特定的国家和网络供应商。一般来说，手机可以接受基于国际移动用户的SIM卡被锁定身份。“SIM卡解锁”使人们有可能不考虑国家和由手机厂商指定的网络情况下使用手机。

然而在Android中，谷歌对每一个应用程序没有进行任何测试，因此虽然有官方Android应用市场，仍然可以在你想要的任何地方发布你的产品。考虑安全问题，谷歌禁止使用某些组件。就像iPhone的“越狱”和“SIM卡解锁”，在Android中“Root”也为用户提供了100％对设备的控制，同样也伴随着一些安全隐患。

'Root'是一个过程，在Android的Linux的子系统中，它允许运行Android操作系统的手机用户获得特权控制（称为“Root访问”），类似运行IOS操作系统苹果设备的“越狱”，克服运营商和手机制造商在手机上设置的限制。Root使得

手机可以使用第三方Android版本系统，例如CyanogenMod，如支持许多原生ROM 不能使用的功能。它也可以使用新的Android版本而不只是使用原始设备制造商的版本。相反到iOS越狱，生根是不是需要运行官方Android市场的分布式应用程序。相反于iOS越狱，Root不是需要运行没有在官方Android市场的发布应用程序。而是，当试图运行一些付费应用却不能在本国应用市场购买到的程序。

3.3 继承

一些企业只注重自己的核心产业，即开发一个操作系统，并提供一个第三方开发的环境。其他公司则不仅做这些，为宣传一个软件管理其开发过程。根据整合平台上，我们将他们分成4种：全集成平台，市场集成平台，设备集成平台，并无集成平台。

全集成平台的宣传模式是非常严格的。从设备制造到应用程序的发布都是其管理范围，其代表是苹果。苹果公司的工厂生产iPhone，苹果公司的App Store 销售其应用程序，苹果公司的iTunes是苹果的资源渠道。整个过程都在苹果公司的控制之下。

市场集成平台，致力于开发和销售软件。谷歌就是其中一个。与苹果不同，谷歌没有一个工厂来生产自己的手机，它只开发Android系统和建立装载Android 应用程序的“Android市场”。然而，像谷歌公司绝对有能力生产自己的设备。谷歌与HTC有良好的合作关系，而HTC则是是T-Mobile，O2和Orange等手机网络公司的手机提供商。

设备集成平台生产自己的手机，但不成立应用市场。例如，RIM生产黑莓手机，但有没有黑莓官方应用市场。

无集成平台几乎不做任何事情。微软既不生产手机，也部建立了一个市场。他们只做操作系统的开发：Windows Phone 7。

4.总结

作为开放式和封闭式平台的的代表，Android 2.2 Froyo和iOS4都有优缺点。强大的浏览器内置于手机中，他们的生产商引发了世界手机的变革。Android依靠互联网的经验，这归结其与谷歌的联系。但目前，市场上充斥着各种版本的Android，开放手机联盟中的大多数公司倾向于定制自己的Android系统。这些事实使Android的缺乏统一的品牌形象，所以人们可能感到困惑，并对Android说“NO”。 iPhone OS更侧重于娱乐，它非常友好。但苹果太酷了以至于不能吸引更多的顾客：史蒂夫·乔布斯的忠实粉丝买苹果每个产品，不喜欢苹果风格的人做的事情可能只是“闻闻”苹果罢了。

此外，Android 2.2 Froyo成功之处在于平台开放的特点。这是一个'用户至上'平台，因为升级Froyo的用户几乎可以自定义他们想要的一切。开放手机和成

员联盟往往为用户提供更多的选择。而iOS 4，通常是封闭的平台成员，管理从OS开发到设备制造的一切过程。这是一个'考虑用户的平台。从某种程度上说，Android用户推崇'自由'和'开放'，他们关心的是，如果可以100％管理自己的手机，他们才不关心手机操作系统是否被称为“安卓”或“安他”。苹果用户对苹果这个品牌十分忠诚忠诚，他们愿意授权苹果为他们作出的决定。因此，尽管一些iPhone用户更喜欢物理键盘，但他们还是选择iPhone。换句话说，Android用户更关心“开放的平台”，而不是Google的品牌;而大多数iPhone用户是苹果的追随者，他们爱史蒂夫·乔布斯创造的“封闭平台”。

Android和iPhone都具有其独特的IDE，SDK等特点。不管你信不信，不完美总是存在与这个世界，所以今天的移动平台没有完全满足用户和开发者的要求。平台的选择归结于用户和开发者的需求，本文应使用户决策更加容易。当然这篇文章的内容会因时间而失效;平台将逐步满足消费者的需求，新技术将层出不穷。

英文文献翻译

中等分辨率制备分离的 快速色谱技术 W. Clark Still,* Michael K a h n , and Abhijit Mitra Departm(7nt o/ Chemistry, Columbia Uniuersity,1Veu York, Neu; York 10027 ReceiLied January 26, 1978 我们希望找到一种简单的吸附色谱技术用于有机化合物的常规净化。这种技术是适于传统的有机物大规模制备分离，该技术需使用长柱色谱法。尽管这种技术得到的效果非常好，但是其需要消耗大量的时间，并且由于频带拖尾经常出现低复原率。当分离的样本剂量大于1或者2g时，这些问题显得更加突出。近年来，几种制备系统已经进行了改进，能将分离时间减少到1-3h，并允许各成分的分辨率ΔR f≥（使用薄层色谱分析进行分析）。在这些方法中，在我们的实验室中，媒介压力色谱法1和短柱色谱法2是最成功的。最近，我们发现一种可以将分离速度大幅度提升的技术，可用于反应产物的常规提纯，我们将这种技术称为急骤色谱法。虽然这种技术的分辨率只是中等（ΔR f≥），而且构建这个系统花费非常低，并且能在10-15min内分离重量在的样本。4 急骤色谱法是以空气压力驱动的混合介质压力以及短柱色谱法为基础，专门针对快速分离，介质压力以及短柱色谱已经进行了优化。优化实验是在一组标准条件5下进行的，优化实验使用苯甲醇作为样本，放在一个20mm*5in.的硅胶柱60内，使用Tracor 970紫外检测器监测圆柱的输出。分辨率通过持续时间（r）和峰宽（w,w/2）的比率进行测定的（Figure 1），结果如图2-4所示，图2-4分别放映分辨率随着硅胶颗粒大小、洗脱液流速和样本大小的变化。

论文外文文献翻译3000字左右

南京航空航天大学金城学院 毕业设计（论文）外文文献翻译 系部经济系 专业国际经济与贸易 学生姓名陈雅琼学号2011051115 指导教师邓晶职称副教授 2015年5月

Economic policy,tourism trade and productive diversification （Excerpt） Iza Lejárraga,Peter Walkenhorst The broad lesson that can be inferred from the analysis is that promoting tourism linkages with the productive capabilities of a host country is a multi-faceted approach influenced by a variety of country conditions.Among these,fixed or semi-fixed factors of production,such as land,labor,or capital,seem to have a relatively minor influence.Within the domain of natural endowments,only agricultural capital emerged as significant.This is a result that corresponds to expectations,given that foods and beverages are the primary source of demand in the tourism economy.Hence,investments in agricultural technology may foment linkages with the tourism market.It is also worth mentioning that for significant backward linkages to emerge with local agriculture,a larger scale of tourism may be important. According to the regression results,a strong tourism–agriculture nexus will not necessarily develop at a small scale of tourism demand. It appears that variables related to the entrepreneurial capital of the host economy are of notable explanatory significance.The human development index(HDI), which is used to measure a country's general level of development,is significantly and positively associated with tourism linkages.One plausible explanation for this is that international tourists,who often originate in high-income countries,may feel more comfortable and thus be inclined to consume more in a host country that has a life-style to which they can relate easily.Moreover,it is important to remember that the HDI also captures the relative achievements of countries in the level of health and education of the population.Therefore,a higher HDI reflects a healthier and more educated workforce,and thus,the quality of local entrepreneurship.Related to this point,it is important to underscore that the level of participation of women in the host economy also has a significantly positive effect on linkages.In sum, enhancing local entrepreneurial capital may expand the linkages between tourism and other sectors of the host country.

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农村社会养老保险的现状、问题与对策研究社会保障对国家安定和经济发展具有重要作用，“城乡二元经济”现象日益凸现，农村社会保障问题客观上成为社会保障体系中极为重要的部分。建立和完善农村社会保障制度关系到农村乃至整个社会的经济发展，并且对我国和谐社会的构建至关重要。我国农村社会保障制度尚不完善，因此有必要加强对农村独立社会保障制度的构建，尤其对农村养老制度的改革，建立健全我国社会保障体系。从户籍制度上看，我国居民养老问题可分为城市居民养老和农村居民养老两部分。对于城市居民我国政府已有比较充足的政策与资金投人，使他们在物质和精神方面都能得到较好地照顾，基本实现了社会化养老。而农村居民的养老问题却日益突出，成为摆在我国政府面前的一个紧迫而又棘手的问题。 一、我国农村社会养老保险的现状 关于农村养老，许多地区还没有建立农村社会养老体系，已建立的地区也存在很多缺陷，运行中出现了很多问题，所以完善农村社会养老保险体系的必要性与紧迫性日益体现出来。 （一）人口老龄化加快 随着城市化步伐的加快和农村劳动力的输出，越来越多的农村青壮年人口进入城市，年龄结构出现“两头大，中间小”的局面。中国农村进入老龄社会的步伐日渐加快。第五次人口普查显示：中国65岁以上的人中农村为5938万，占老龄总人口的67.4%.在这种严峻的现实面前，农村社会养老保险的徘徊显得极其不协调。 （二）农村社会养老保险覆盖面太小 中国拥有世界上数量最多的老年人口，且大多在农村。据统计，未纳入社会保障的农村人口还很多，截止2000年底，全国7400多万农村居民参加了保险，占全部农村居民的11.18%，占成年农村居民的11.59%.另外，据国家统计局统计，我国进城务工者已从改革开放之初的不到200万人增加到2003年的1.14亿人。而基本方案中没有体现出对留在农村的农民和进城务工的农民给予区别对待。进城务工的农民既没被纳入到农村养老保险体系中，也没被纳入到城市养老保险体系中，处于法律保护的空白地带。所以很有必要考虑这个特殊群体的养老保险问题。

毕业论文英文参考文献与译文

Inventory management Inventory Control On 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 of

java毕业论文外文文献翻译

Advantages of Managed Code Microsoft intermediate language shares with Java byte code the idea that it is a low-level language witha simple syntax , which can be very quickly translated intonative machine code. Having this well-defined universal syntax for code has significant advantages. Platform independence First, it means that the same file containing byte code instructions can be placed on any platform; atruntime the final stage of compilation can then be easily accomplished so that the code will run on thatparticular platform. In other words, by compiling to IL we obtain platform independence for .NET, inmuch the same way as compiling to Java byte code gives Java platform independence. Performance improvement IL is actually a bit more ambitious than Java bytecode. IL is always Just-In-Time compiled (known as JIT), whereas Java byte code was ofteninterpreted. One of the disadvantages of Java was that, on execution, the process of translating from Javabyte code to native executable resulted in a loss of performance. Instead of compiling the entire application in one go (which could lead to a slow start-up time), the JITcompiler simply compiles each portion of code as it is called (just-in-time). When code has been compiled.once, the resultant native executable is stored until the application exits, so that it does not need to berecompiled the next time that portion of code is run. Microsoft argues that this process is more efficientthan compiling the entire application code at the start, because of the likelihood that large portions of anyapplication code will not actually be executed in any given run. Using the JIT compiler, such code willnever be compiled.

计算机网络-外文文献-外文翻译-英文文献-新技术的计算机网络

New technique of the computer network Abstract The 21 century is an ages of the information economy, being the computer network technique of representative techniques this ages, will be at very fast speed develop soon in continuously creatively, and will go deep into the people's work, life and study. Therefore, control this technique and then seem to be more to deliver the importance. Now I mainly introduce the new technique of a few networks in actuality live of application. keywords Internet Network System Digital Certificates Grid Storage 1. Foreword Internet turns 36, still a work in progress Thirty-six years after computer scientists at UCLA linked two bulky computers using a 15-foot gray cable, testing a new way for exchanging data over networks, what would ultimately become the Internet remains a work in progress. University researchers are experimenting with ways to increase its capacity and speed. Programmers are trying to imbue Web pages with intelligence. And work is underway to re-engineer the network to reduce Spam (junk mail) and security troubles. All the while threats loom: Critics warn that commercial, legal and political pressures could hinder the types of innovations that made the Internet what it is today. Stephen Crocker and Vinton Cerf were among the graduate students who joined UCLA professor Len Klein rock in an engineering lab on Sept. 2, 1969, as bits of meaningless test data flowed silently between the two computers. By January, three other "nodes" joined the fledgling network.

毕业论文(英文翻译)排版格式

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