前后端协同的时钟树设计方法

提出一种新的高平衡、高可靠性的前端可控时钟树设计方法,解决时钟树需要在后端工具中多次反复以达到满足性能和功耗要求的问题。阐述了从前端优化和后端约束2个方面入手解决时钟树设计中经常会遇到的问题。在此基础上,将前后端方法结合起来完成时钟树设计。结果验证该方法可以减少大约20%的功耗,同时节省了设计时间,该方法可以广泛应用于基于时钟的同步数字电路设计中。     

基于特征点法和直接法VSLAM的研究

基于视觉的同时定位和建图(VSLAM)分为前端和后端,前端包括视觉里程计和回环检测,后端包括后端优化和建图。按照估计相机运动的不同方式,将VSLAM分为特征点法和直接法,首先从这两个方面对前端进行综述,阐述其中的关键技术和最新的研究进展,对比分析不同方法的优缺点;然后详细分析优化后端与滤波器后端的区别,进一步对多个开源代码进行比较研究,分析它们的优劣势和适用场合;再讨论深度学习、语义地图和多机器人在VSLAM领域的研究进展,以及相关技术与VSLAM的结合方式及前景;最后对VSLAM的未来进行展望。     

The Back-End of a Two-Layer Model for a Federated National Datastore for Academic Research VOs that Integrates EGEE Data Management

This paper proposes an architecture for the back-end of a federated national datastore for use by academic research communities, developed by the e-INIS (Irish National e-InfraStructure) project, and describes in detail one member of the federation, the regional datastore at Trinity College Dublin. It builds upon existing infrastructure and services, including Grid-Ireland, the National Grid Initiative and EGEE, Europe’s leading Grid infrastructure. It assumes users are in distinct research communities and that their data access patterns can be described via two properties, denoted as mutability and frequency-of-access. The architecture is for a back-end—individual academic communities are best qualified to define their own front-end services and user interfaces. The proposal is designed to facilitate front-end development by placing minimal restrictions on how the front-end is implemented and on the internal community security policies. The proposal also seeks to ensure that the communities are insulated from the back-end and from each other in order to ensure quality of service and to decouple their front-end implementation from site-specific back-end implementations.     

基于TRANSPUTER多机系统的研究与设计

并行知识库机是利用多机系统的并行性提高知识库系统理效率的专用机，我们研制的并行知识库机由前后端机组成。其中，前端机是一台４８６微机，而后端机是基于ＴＲＡＮＳＰＵＴＥＲ的多机系统，本文重点研究后端机的拓扑结构，与ＰＣ机的接口和存储器的设计等问题。     

集群系统中自适应负载反馈平衡策略的研究

当前在集群系统中，负载平衡策略虽然很多，但是为了减少反馈开销，一般策略为采用在前端估计后端负载，所以不能很好地完成负载平衡的任务。针对这一问题，提出了一种自适应负载反馈平衡策略，各个服务器根据自身负载的变化来决定负载反馈的时机，前端根据负载信息和请求率计算出各个服务器的负载权值，最后根据负载权值来调度服务器处理请求，以实现负载平衡。由于采用了自适应的反馈策略，在获得各个服务器负载信息的同时减少了负载反馈的开销，实现了系统的负载均衡。测试结果表明该策略表现出了一定的优势。     

Extraction of Speaker Features from Different Stages of DSR Front-Ends for Distributed Speaker Verification

The ETSI has recently published a front-end processing standard for distributed speech recognition systems. The key idea of the standard is to extract the spectral features of speech signals at the front-end terminals so that acoustic distortion caused by communication channels can be avoided. This paper investigates the effect of extracting spectral features from different stages of the front-end processing on the performance of distributed speaker verification systems. A technique that combines handset selectors with stochastic feature transformation is also employed in a back-end speaker verification system to reduce the acoustic mismatch between different handsets. Because the feature vectors obtained from the back-end server are vector quantized, the paper proposes two approaches to adding Gaussian noise to the quantized feature vectors for training the Gaussian mixture speaker models. In one approach, the variances of the Gaussian noise are made dependent on the codeword distance. In another approach, the variances are a function of the distance between some unquantized training vectors and their closest code vector. The HTIMIT corpus was used in the experiments and results based on 150 speakers show that stochastic feature transformation can be added to the back-end server for compensating transducer distortion. It is also found that better verification performance can be achieved when the LMS-based blind equalization in the standard is replaced by stochastic feature transformation.     

基于Spring Boot+Vue的学生评奖评优系统的设计与实现

高职院校每年都要对学生进行各类评奖评优的活动,如何公平公正且高效率地评奖评优对学生和教师而言都有着重要意义,能更加激发学生的学习热情,同时也能减轻教师的工作负担,有效节省人力成本.基于此,设计并实现了学生评奖评优系统.系统采用B/S架构,使用前后端分离模式,后端采用Spring Boot+MyBatis实现,前端采用V...     

浅谈后端应用系统性能测试方法

由于后端应用系统的复杂性,业界常用的负载工具很难模拟后端系统的运作。对于应用系统来说,仅通过前 端模拟用户的方式来定位后端应用系统的问题总会差强人意,因此本文提出一种针对后端应用系统的性能测试方法,得出后 端系统的最大处理能力以及扩容的方法,进而提高整个应用系统的性能。     

面向WLAN的移动IPv6 AAA系统研究与实现

针对无线局域网需要对移动IPv6的移动节点（MN）在数据链路层进行访问控制的特点,设计并实现一个支持移动漫游的认证、授权和记账（AAA）系统。该系统由支持802.1x协议的前台无线访问点（AP）、后台EAP认证服务器和Web记账管理服务器,以及在前台和后台之间传递AAA消息的Diameter对等端构成。系统支持多种EAP认证方式、管理域间漫游、以及按流量或时间记账等。     

一种基于智能终端的人体心电信号监护系统设计

设计了一种基于智能终端的人体心电信号监测的系统,通过该系统可以实时连续地检测到被监护者的心电信号。该系统主要包括前端心电信号采集模块和后端心电信号无线发送模块。其中前端采集模块对心电信号进行了预处理;后端心电信号发送模块采用蓝牙无线通信方式,从而实现心电数据短距离无线传输且方便与PDA或Android智能手机等手持终端通信,保证了对被监护者的连续实时监测。     

Network-aware support for mobile distributed teams

An experiment evaluated network-aware support to increase understanding of the factors that are important for successful teamwork in mobile geographically dispersed teams of first responders. Participants performed a simulated search and rescue team task and were equipped with a digitized map and real-time situation updates on the location of other participants in a simulated disaster area. The connection to a server, however, was made deliberately error-prone, leading to occasional losses of network connections. Consequently, participants were not provided with real-time situation updates. To deal with this problem we equipped team members with a network-aware application that signaled network loss to them and adapted the graphical representation of the location of fellow team members accordingly to the quality of location information present. The experiment revealed that presenting complete and reliable geospatial information improves teamwork. Teams connected to a server over a fast and reliable link showed superior performance over teams with no network connection whatsoever to a server. The present study failed, however, to demonstrate the added value of network-aware support when teams had to collaborate in the presence of an unreliable communications infrastructure. Although participants indicated a slight preference for the network-aware application over a condition without support signaling network loss, no differences were observed in team process and outcome measures.     

一种Web集群系统下的QoS控制策略

本文提出了一种在Web集群环境下的QoS控制策略。集群前端分配器以会话单位来分配访问请求,保证后端服务器间负载的合理均衡分配,同时后端服务器采用基于会话的QoS控制策略,实现对集群系统的服务质量控制。     

物联网的产生与发展

物联网是计算机科学技术的新挑战,它的出现将掀起新一次科技革命。物联网有前后端之分,前端是研究的热点,后端是结构和技术的实现,还有待进一步研究。文章介绍了物联网的产生背景、概念与原理、应用、研究与发展。     

嵌入式处理器中的寄存器堆延迟写回技术

为了降低嵌入式处理器中寄存器堆的功耗,提出一种基于限制取指的寄存器堆延迟写回技术.对于嵌入式处理器,传统的寄存器堆延迟写回技术带来的效果并不明显,文中根据处理器前端比后端快的特点,采用限制取指技术提高寄存器堆延迟写回的效果,不仅大幅度地消除了对寄存器堆不必要的写操作,同时也降低了处理器前端的功耗.FPGA平台上的实验结果表明:在不影响程序性能的情况下,应用该技术后,EEMBC程序对定点寄存器堆的写操作减少了35%,对ICache的访问减少了15%,且没有额外的开销.     

一种TCP连接的延迟多次迁移技术

现有的基于内容的Web交换技术不能很好地支持HTTP持久连接(P-HTTP)和流水线请求。提出了一种TCP连接的延迟多次迁移方法(DM-TCPHA),前端FE根据第一个请求将连接迁移到选中的BE,该连接上的后续请求报文由BE来调度,且通过强制手段保证BE在收到客户对HTTP回复的确认报文后再执行迁移。该方法具有TCP迁移高性能的优点,且能很好地支持P-HTTP和流水线请求。     

Efficient Noise Robust Feature Extraction Algorithms for Distributed Speech Recognition (DSR) Systems

The evolution of robust speech recognition systems that maintain a high level of recognition accuracy in difficult and dynamically-varying acoustical environments is becoming increasingly important as speech recognition technology becomes a more integral part of mobile applications. In distributed speech recognition (DSR) architecture the recogniser's front-end is located in the terminal and is connected over a data network to a remote back-end recognition server. The terminal performs the feature parameter extraction, or the front-end of the speech recognition system. These features are transmitted over a data channel to the remote back-end recogniser. DSR provides particular benefits for the applications of mobile devices such as improved recognition performance compared to using the voice channel and ubiquitous access from different networks with a guaranteed level of recognition performance. A feature extraction algorithm integrated into the DSR system is required to operate in real-time as well as with the lowest possible computational costs.In this paper, two innovative front-end processing techniques for noise robust speech recognition are presented and compared, time-domain based frame-attenuation (TD-FrAtt) and frequency-domain based frame-attenuation (FD-FrAtt). These techniques include different forms of frame-attenuation, improvement of spectral subtraction based on minimum statistics, as well as a mel-cepstrum feature extraction procedure. Tests are performed using the Slovenian SpeechDat II fixed telephone database and the Aurora 2 database together with the HTK speech recognition toolkit. The results obtained are especially encouraging for mobile DSR systems with limited sizes of available memory and processing power.     

Improved features and dynamic stream weight adaption for robust Audio-Visual Speech Recognition framework

This paper investigates the enhancement of a speech recognition system that uses both audio and visual speech information in noisy environments by presenting contributions in two main system stages: front-end and back-end. The double use of Gabor filters is proposed as a feature extractor in the front-end stage of both modules to capture robust spectro-temporal features. The performance obtained from the resulted Gabor Audio Features (GAFs) and Gabor Visual Features (GVFs) is compared to the performance of other conventional features such as MFCC, PLP, RASTA-PLP audio features and DCT2 visual features. The experimental results show that a system utilizing GAFs and GVFs has a better performance, especially in a low-SNR scenario. To improve the back-end stage, a complete framework of synchronous Multi-Stream Hidden Markov Model (MSHMM) is used to solve the dynamic stream weight estimation problem for Audio-Visual Speech Recognition (AVSR). To demonstrate the usefulness of the dynamic weighting in the overall performance of AVSR system, we empirically show the preference of Late Integration (LI) compared to Early Integration (EI) especially when one of the modalities is corrupted. Results confirm the superior recognition accuracy for all SNR levels the superiority of the AVSR system with the Late Integration.     

基于C/S体系结构的网络多媒体教室管理系统

多媒体教室管理系统是典型的信息管理系统(MIS),其开发主要包括后台数据库的建立和维护以及前端应用程序的开发两个方面。该系统采用了面向对象的程序设计语言Delphi6.0实现。     

Teams of pushdown automata

We introduce team pushdown automata (PDAs) as a theoretical framework capable of modelling various communication and cooperation strategies in complex, distributed systems. Team PDAs are obtained by augmenting distributed PDAs with the notion of team cooperation or, alternatively, by augmenting team automata with pushdown memory. In a team PDA, several PDAs work as a team on the input word placed on a common one-way input tape. At any moment in time one team of PDAs, each with the same symbol on top of its stack, is active: each PDA in the active team replaces the topmost symbol of its stack and changes state, while the current input symbol is read from the input tape by a common reading head. The teams are formed according to the team cooperation strategy of the team PDA and may vary from one moment to the other. Based on the notion of competence, we introduce a variety of team cooperation strategies. If all stacks are empty when the input word has been completely read, then this word is part of the language accepted by the team PDA. Here we focus on the accepting capacity of team PDA.     

一种支持实时集群系统的双层调度机制

提出一种集群环境下的实时调度机制,它通过前端负载机平衡调度、后端机区分实时和非实时任务队长差调度而提供实时优先服务,有效提高了以往前端机单点调度模式下的集群节点利用率和实时任务响应性.对比实验表明,在保证吞吐率的情况下,实时任务的响应时间明显减少,为分布式实时调度提供了一种可行的设计参考.