Android移动平台上的目标识别

随着计算机视觉的发展和移动平台处理能力的不断提高,将计算机视觉应用搬到移动平台上的需求将日益增长.其中基于移动平台的目标识别引起了大家极大的兴趣,这主要是因为目标识别算法取得了进步和移动手机已经有能力建立起一个适宜的系统.移动平台开发者们试着使用目标识别技术来建立良好的人机交互接口.这就需要合适的应用程序框架一客户服务器,在新兴的Android移动平台上来实现并测试框架,给出了一个案例学习及其测试结果.实验结果表明了这种框架的可行性.     

Landmark recognition with compact BoW histogram and ensemble ELM

Along with the rapid development of mobile terminal devices, landmark recognition applications based on mobile devices have been widely researched in recent years. Due to the fast response time requirement of mobile users, an accurate and efficient landmark recognition system is thus urgent for mobile applications. In this paper, we propose a landmark recognition framework by employing a novel discriminative feature selection method and the improved extreme learning machine (ELM) algorithm. The scalable vocabulary tree (SVT) is first used to generate a set of preliminary codewords for landmark images. An efficient codebook learning algorithm derived from the word mutual information and Visual Rank technique is proposed to filter out those unimportant codewords. Then, the selected visual words, as the codebook for image encoding, are used to produce a compact Bag-of-Words (BoW) histogram. The fast ELM algorithm and the ensemble approach using the ELM classifier are utilized for landmark recognition. Experiments on the Nanyang Technological University campus’s landmark database and the Fifteen Scene database are conducted to illustrate the advantages of the proposed framework.     

A generic content-based image retrieval framework for mobile devices

Multimedia mobile devices have created new possibilities for developing and accessing a variety of multimedia items such as images, audio and video clips. Personal multimedia items are, nowadays, being consumed at an enormous rate. Therefore, the management of these media items has become a pressing problem. In this paper, a client-server content-based image retrieval framework for mobile platforms is developed, which provides the capability of content-based query and browsing from mobile devices. The proposed framework provides an adaptive user interface and a generic structure, which supports a wide range of mobile devices. In this framework, a client requests the server for retrieval of particular images with a particular content. The server performs a content-based retrieval of images from a selected database and streams the retrieved results back to the client in an efficient way. The query results are transmitted over a wireless network and a certain number of similar images are rendered on the mobile device screen using thumbnail sizes. The proposed framework serves as a basis of content-based image retrieval on mobile devices. It addresses several important challenges such as hardware and software limitations as well as efficient use of the available network bandwidth.     

A dynamic binary translation system in a client/server environment

With rapid advances in mobile computing, multi-core processors and expanded memory resources are being made available in new mobile devices. This trend will allow a wider range of existing applications to be migrated to mobile devices, for example, running desktop applications in IA-32 (x86) binaries on ARM-based mobile devices transparently using dynamic binary translation (DBT). However, the overall performance could significantly affect the energy consumption of the mobile devices because it is directly linked to the number of instructions executed and the overall execution time of the translated code. Hence, even though the capability of today’s mobile devices will continue to grow, the concern over translation efficiency and energy consumption will put more constraints on a DBT for mobile devices, in particular, for thin mobile clients than that for severs. With increasing network accessibility and bandwidth in various environments, it makes many network servers highly accessible to thin mobile clients. Those network servers are usually equipped with a substantial amount of resources. This provides an opportunity for DBT on thin clients to leverage such powerful servers. However, designing such a DBT for a client/server environment requires many critical considerations.In this work, we looked at those design issues and developed a distributed DBT system based on a client/server model. It consists of two dynamic binary translators. An aggressive dynamic binary translator/optimizer on the server to service the translation/optimization requests from thin clients, and a thin DBT on each thin client to perform lightweight binary translation and basic emulation functions for its own. With such a two-translator client/server approach, we successfully off-load the DBT overhead of the thin client to the server and achieve a significant performance improvement over the non-client/server model. Experimental results show that the DBT of the client/server model could achieve 37% and 17% improvement over that of non-client/server model for x86/32-to-ARM emulation using MiBench and SPEC CINT2006 benchmarks with test inputs, respectively, and 84% improvement using SPLASH-2 benchmarks running two emulation threads.     

Studying energy trade offs in offloading computation/compilation in Java-enabled mobile devices

Java-enabled wireless devices are preferred for various reasons. For example, users can dynamically download Java applications on demand. The dynamic download capability supports extensibility of the mobile client features and centralizes application maintenance at the server. Also, it enables service providers to customize features for the clients. In this work, we extend this client-server collaboration further by offloading some of the computations (i.e., method execution and dynamic compilation) normally performed by the mobile client to the resource-rich server in order to conserve energy consumed by the client in a wireless Java environment. In the proposed framework, the object serialization feature of Java is used to allow offloading of both method execution and bytecode-to-native code compilation to the server when executing a Java application. Our framework takes into account communication, computation, and compilation energies to decide where to compile and execute a method (locally or remotely), and how to execute it (using interpretation or just-in-time compilation with different levels of optimizations). As both computation and communication energies vary based on external conditions (such as the wireless channel state and user supplied inputs), our decision must be done dynamically when a method is invoked. Our experiments, using a set of Java applications executed on a simulation framework, reveal that the proposed techniques are very effective in conserving the energy of the mobile client.     

An efficient user authentication and key exchange protocol for mobile client–server environment

Considering the low-power computing capability of mobile devices, the security scheme design is a nontrivial challenge. The identity (ID)-based public-key system with bilinear pairings defined on elliptic curves offers a flexible approach to achieve simplifying the certificate management. In the past, many user authentication schemes with bilinear pairings have been proposed. In 2009, Goriparthi et al. also proposed a new user authentication scheme for mobile client–server environment. However, these schemes do not provide mutual authentication and key exchange between the client and the server that are necessary for mobile wireless networks. In this paper, we present a new user authentication and key exchange protocol using bilinear pairings for mobile client–server environment. As compared with the recently proposed pairing-based user authentication schemes, our protocol provides both mutual authentication and key exchange. Performance analysis is made to show that our presented protocol is well suited for mobile client–server environment. Security analysis is given to demonstrate that our proposed protocol is provably secure against previous attacks.     

Mobile collaborative medical display system

Because of recent advances in wireless communication technologies, the world of mobile computing is flourishing with a variety of applications. In this study, we present an integrated architecture for a personal digital assistant (PDA)-based mobile medical display system that supports collaborative work between remote users. We aim to develop a system that enables users in different regions to share a working environment for collaborative visualization with the potential for exploring huge medical datasets. Our system consists of three major components: mobile client, gateway, and parallel rendering server. The mobile client serves as a front end and enables users to choose the visualization and control parameters interactively and cooperatively. The gateway handles requests and responses between mobile clients and the rendering server for efficient communication. Through the gateway, it is possible to share working environments between users, allowing them to work together in computer supported cooperative work (CSCW) mode. Finally, the parallel rendering server is responsible for performing heavy visualization tasks. Our experience indicates that some features currently available to our mobile clients for collaborative scientific visualization are limited due to the poor performance of mobile devices and the low bandwidth of wireless connections. However, as mobile devices and wireless network systems are experiencing considerable elevation in their capabilities, we believe that our methodology will be utilized effectively in building quite responsive, useful mobile collaborative medical systems in the very near future.     

Developing Java-AWT thin-client applications for limited devices

Developing software for personal wireless devices (PWDs) requires new methods and tools that address the restrictions introduced by these devices' mobile nature. The thin-client applications for limited devices (TCPTE) framework supports the development of thin-client applications for mobile devices with limited resources. Using TCPTE, we can execute Java applications on a server and display their AWT interfaces on a remote client. TCPTE combines the advantages of thin-client computing with the richness of client-server graphical interfaces and lets programmers develop applications for PWDs using the same processes and tools they typically use for desktop applications.     

A scalable architecture for 3D map navigation on mobile devices

Mobile devices such as smart phones or tablets are rapidly increasing their graphics and networking capabilities. However, real-time visualization of 3D maps is still a challenging task to accomplish on such limited devices. In this paper, we describe the principles involved in the design and development of a scalable client–server architecture for delivering 3D maps over wireless networks to mobile devices. We have developed a hybrid adaptive streaming and rendering method that distributes the 3D map rendering task between the mobile clients and a remote server. This architecture provides support for efficient delivery of 3D contents to mobile clients according to their capabilities. As a proof of concept, we have implemented a prototype and carried out exhaustive experiments considering different scenarios and hundreds of concurrent connected clients. The analysis of the server workload and the mobile clients performance show that our architecture achieves a great scalability and performance even when using low-end hardware.     

即时通讯系统的设计与实现

随着以智能手机和平板电脑为代表的移动设备的迅速普及,基于当前企事业单位内部即时通讯技术的实际需求,自主设计并实现一个即时通讯系统,对于企事业单位沟通与交流具有重要意义。项目开发主要分为两部分:客户端使用HBuilder工具进行开发,使用MUI与H5Plus开发移动应用客户端,充分利用当前混合开发技术的优势,实现一次开发即可生成运行在Android、iOS以及小程序端的移动应用;后台服务端使用IntelliJ IDEA开发,使用Netty+SpringBoot框架作为后台的主要框架,利用Nginx+FastDFS分布式文件系统搭建图片服务器,使用MyBatis框架操作MySql数据库。该系统主要功能有聊天、通讯录、扫一扫、添加好友、上传头像以及修改个人信息等功能,对即时通讯系统的搭建有一定的借鉴意义。     

基于J2ME平台的手机语音控制系统

提出了一个基于J2ME平台的手机语音控制系统,该系统结合语音识别和自然语言处理技术,处理手机用户的语音输入,抽取语义信息并显示在手机终端.本系统采用C/S架构,客户端为手机终端,服务器端为PC.在客户端,收集语音输入流并发送给服务器,接收服务器发回的语义信息并显示;在服务器端,接收手机客户端传来的语音流,进行语音识别,自然语言处理,将处理的语义信息发回客户端.该系统能处理同一种手机控制命令的多种自然语言表达方式,能极大方便手机用户的使用.     

基于二维运动机械臂的移动设备测试研究

现有移动设备测试自动化框架大多是侵入性的,故而难以用于一些系统封闭的设备.非侵入式测试可以大大扩展自动测试技术的应用范围.由此,提出了一种基于二维运动机械臂的新型移动设备测试自动化技术.该技术使用可视化脚本表达测试动作,提出视觉引擎驱动二维运动机械臂自动对移动设备进行非侵入性的测试.案例研究表明该框架具有较高的测试执行准确度和速度,有良好的实用价值.     

基于宽度网络架构的单模型主导联邦学习

联邦学习是一种分布式机器学习方法,它将数据保留在本地,仅将计算结果上传到客户端,从而提高了模型传递与聚合的效率和安全性.然而,联邦学习面临的一个重要挑战是,上传的模型大小日益增加,大量参数多次迭代,给通信能力不足的小型设备带来了困难.因此在本文中,客户端和服务器被设置为仅一次的互相通信机会.联邦学习中的另一个挑战是,客户端之间的数据规模并不相同.在不平衡数据场景下,服务器的模型聚合将变得低效.为了解决这些问题,本文提出了一个仅需一轮通信的轻量级联邦学习框架,在联邦宽度学习中设计了一种聚合策略算法,即FBL-LD.算法在单轮通信中收集可靠的模型并选出主导模型,通过验证集合理地调整其他模型的参与权重来泛化联邦模型. FBL-LD利用有限的通信资源保持了高效的聚合.实验结果表明, FBL-LD相比同类联邦宽度学习算法具有更小的开销和更高的精度,并且对不平衡数据问题具有鲁棒性.     

基于用户行为周期的移动设备异常检测方法

本文提出了一种分布式的移动设备异常检测系统,该系统采用客户端-服务器架构,客户端程序在移动设备上持续提取特征并传送给服务器,服务器使用异常检测算法分析特征。根据人类日常活动的规律性以及用户使用移动设备的周期性,我们还提出了一种基于用户行为周期的异常检测方法,通过比较待检测特征向量和以往周期相近时间段的特征向量集的距离即可判定该特征向量是否异常,向量比较时采用不受特征间关联以及特征取值范围影响的马氏距离作为距离衡量的标准。实验证明我们采用的移动设备异常检测系统框架和检测方法能够有效提高对移动设备恶意程序的检测率。     

基于Android平台的工商移动监管系统研究

基于Android手机平台,提出了一种工商移动监管系统的解决方案。该方案主要结合了Openmobster云平台、JBoss服务器和Android手机平台,通过WiFi或3G网络,使外出执法人员通过移动终端进行信息采集并上传至服务器。该系统主要分为服务器、Web客户端和手机客户端三部分,首先介绍了整个系统的框架结构,然后详细分析了各个模块的具体设计与实现,最后在手机上进行了测试,效果良好。     

基于物联网的新型视频监控系统的设计与实现

为了实现包括服务端和客户端的一套简单、稳定、可靠的新型视频监控系统。首先分析了视频监控系统的发展历史和趋势,提出基于移动互联网的视频监控系统方案,并选定Android作为系统实现的平台;明确了需求和目标,设计出系统的整体方案,并搭建了系统的程序框架;再根据系统程序框架的设计,详细地设计并实现了各个子功能模块,其中主要的功能模块有视频采集与视频回显模块,视频预处理模块,视频编解码模块和视频存储模块等;最后,对整个系统进行了综合测试,验证了其功能的完整性,得出系统的性能表现数据。经实验证明,所设计系统使用便利,需求中指定的功能也基本实现,程序的运行稳定高效可靠,能达到预期效果,具有一定的实用性和研究意义。     

Navigating large terrains using commodity mobile devices

We describe a hybrid client-server technique for remote adaptive streaming and rendering of large terrains in resource-limited mobile devices. The technique has been designed to achieve an interactive rendering performance on a mobile device connected to a low-bandwidth wireless network. The rendering workload is split between the client and the server. The terrain area close to the viewer is rendered in real-time by the client. The terrain located far from the viewer is portrayed as view-dependent impostors, rendered by the server on demand. A prototype has been built and an exhaustive set of experiments covering several platforms, wireless networks and a wide range of viewer velocities has been conducted. Results show that the approach is feasible, effective and robust.     

Performance Evolution of Mobile Web-Based Services

The mobile Web's widespread diffusion opens many interesting design and management issues about server infrastructures that must satisfy present and future client demand. Future mobile Web-based services will have growing computational costs. Even requests for the same Web resource will require services to dynamically generate content that takes into account specific devices, user profiles, and contexts. The authors consider the evolution of the mobile Web workload and trends in server and client devices with the goal of anticipating future bottlenecks and developing management strategies.     

基于FTP协议的素材迁移服务器的设计与实现

文中提出的基于FTP协议的素材迁移服务器,与传统的采用FTP协议服务器和客户端进行素材迁移不同,该迁移服务器对传统的迁移模式进行了改进,让客户端从参加数据传输的角色转变为只对数据传输进行控制的角色。很大程度上减少了客户端的工作强度,符合目前流行的"瘦客户端"的软件设计模式。并且在原来的FTP服务器的基础上添加了文件传输代理模块,使客户端不再直接与服务器端进行联系,所有的活动请求都通过代理模块执行。     

基于秘密共享协议的移动数据存储研究

针对移动数据库各方面的资源和能力均受到限制的问题,提出了基于秘密共享协议的移动数据存储方案。在移动客户端的应用程序上采用轻量级内存数据库仅存储少量数据,将大部分移动客户端所需数据存储在数据库服务器上。对存储在数据加密服务器上的敏感数据利用AES加密,对密钥利用秘密共享技术进行拆分后存储在不同的数据存储服务器上,使除了移动客户端的任何一方都不能同时拥有密钥和密文,减轻了移动客户端的存储压力,实现了数据控制权限的分离,保证了移动客户端对数据的访问具有最高权限,提高了数据的安全性。测试实验结果表明,该方案是可行的,具有较好的性能和应用前景。