线性代数网上学习系统的开发与研究

本文简要介绍线性代数学习网站的系统研究与开发设计．涉及到网络数据库、ASP、界面设计等多种技术.该线性代数网上学习系统为老师和学生提供了交流平台，其界面美观、操作简便．具有良好的应用前景.     

Spectrum Slicing for Multiple Access Channels with Heterogeneous Services

Wireless mobile networks from the fifth generation (5G) and beyond serve as platforms for flexible support of heterogeneous traffic types with diverse performance requirements. In particular, the broadband services aim for the traditional rate optimization, while the time-sensitive services aim for the optimization of latency and reliability, and some novel metrics such as Age of Information (AoI). In such settings, the key question is the one of spectrum slicing: how these services share the same chunk of available spectrum while meeting the heterogeneous requirements. In this work we investigated the two canonical frameworks for spectrum sharing, Orthogonal Multiple Access (OMA) and Non-Orthogonal Multiple Access (NOMA), in a simple, but insightful setup with a single time-slotted shared frequency channel, involving one broadband user, aiming to maximize throughput and using packet-level coding to protect its transmissions from noise and interference, and several intermittent users, aiming to either to improve their latency-reliability performance or to minimize their AoI. We analytically assessed the performances of Time Division Multiple Access (TDMA) and ALOHA-based schemes in both OMA and NOMA frameworks by deriving their Pareto regions and the corresponding optimal values of their parameters. Our results show that NOMA can outperform traditional OMA in latency-reliability oriented systems in most conditions, but OMA performs slightly better in age-oriented systems.     

基于GMRBAC模型的GIS系统安全控制方法研究

针对GIS系统应用程序的复杂性和安全性等特点,对基于角色的访问控制基本模型进行了深入研究,提出一种多粒度安全访问控制扩展模型GMRBAC,分析了GMRBAC模型的基本框架结构和用户可信度评估条件。尝试将GMRBAC模型引入到GIS复杂软件体系中,利用多粒度访问权限操作和可信度评估条件的有效结合,为GIS系统智能访问控制应用提供一种新的解决方案。实践表明,改进后的GMRBAC模型具有较强的可靠性和通用性,能够较好地应用于城镇智能供热决策系统中,具有广泛的应用前景。     

Analysis of Transmission Performance in SUPERPONs

In this work we study how optical amplifiers can deeply improve the performance of the passive optical networks (PONs), permitting a large number of optical network units (ONUs), transmitting at high bit rate. These high-capacity networks are called SUPERPONs, and we show how to achieve a network with 8,192 ONUs with a transmission in the downstream direction up to 10 Gbit/s.     

多信道接入微谐振环波长选择开关特性

对一种新型结构微谐振环波长选择开关的特性进行了研究.分析了器件的工作状态和相应的开关操作,利用新型光强传递函数公式,对器件不同工作状态的光谱响应和不同开关操作的开关响应进行了数值模拟,讨论了耦合系数和损耗对光谱响应和开关响应的影响.结果表明,该器件可以实现三个信道同时接入、两个信道同时接入、单信道接入以及无信道接入等四种方式的信号波长选择性接入.多信道接入方式的开态串扰性能变差,关态的串扰性能不受影响.实现器件上述接入方式之间转换的开关操作可以分成三类,开关操作达到最佳关态串扰时的小微环折射率变化值都在6.0×10－3左右,而实现完全开关时的小微环折射率变化值小于8.0×10－4,表明易于通过热-光效应实现开关操作,并且温度调制的控制容差较大.损耗对器件开关特性的影响结果表明可根据损耗的实际数值,优化信道关闭时的微环折射率取值.     

Experimental Investigation on Transmission Control Protocol Throughput Behavior in Optical Fiber Access Networks

ABSTRACT

This article describes an experimental investigation on the behavior of transmission control protocol in throughput measurements to be used in the verification of the service-level agreement between the Internet service provider and user in terms of line capacity for ultra-broadband access networks typical of fiber-to-the-x architectures. It is experimentally shown different conditions in high bandwidth-delay product links where the estimation of the line capacity based on a single transmission control protocol session results are unreliable. Simple equations reported in this work, and experimentally verified, point out the conditions in terms of packet loss, time delay, and line capacity, that allow consideration of the reliability of the measurement carried out with a single transmission control protocol session test by adopting a suitable measurement time duration.     

基于VBA与Access的有机化学人名反应查询系统的开发与设计

人名反应是有机化学的重要组成部分,采用计算机来高效地分类、检索这些人名反应,可以大力促进有机化学的学习和科研工作。基于微软Access数据库和VBA编程语言,开发了有机化学人名反应交互查询系统,实现了有机化学人名反应的名称、反应过程、反应机理和实例的查询及编辑。软件能够实现按人名、反应类型、官能团等查询、浏览和打印等操作。软件的用户管理、数据管理等附加功能保证了软件的安全性,实现了软件生命力的延续。     

虚拟数据中心的功率有效嵌入算法(英文)

针对虚拟化技术中,数据中心能源消耗问题,本文研究功率有效的虚拟数据中心嵌入算法.该算法由功率感知嵌入算法、准入策略算法和碎片整理算法三部分组成.在树形网络拓扑结构中,提出功率感知的嵌入算法,得到虚拟数据中心的最低功耗嵌入方式;在动态虚拟网络业务环境中,一般嵌入算法会造成功率波动,通过业务接入策略减少功率波动;随着业务动态地进入和离开,物理网络中出现计算资源碎片,提出碎片整理算法,通过虚拟机迁移的方法,提高服务器的利用率.仿真和评估证明:随着时间的推移,算法能减少功率开支并有效降低功率波动.     

基于光环路正交频分多址无源光网络的光拍频噪声避免方案及性能仿真(英文)

在正交频分多址无源光网络上行传输中,不同光网络单元的上行信号如果采用相同波长的不同激光器将会产生光拍频噪声,使得光网络单元的无色性难以实现.本文以正交频分多址无源光网络为研究对象,通过对系统结构的研究和相关公式的推导,分析了信号上行传输中光拍频噪声的产生原因和避免方式.针对下行发送上行载波结合光线路终端相干接收的光拍频噪声避免方案进行了仿真研究.分析了系统的抗色散方案以及色散累积和训练序列长度对系统性能的影响,给出了优化的参数设置,为系统实际应用提供了理论参考.     

A practical radio frequency fingerprinting scheme for mobile phones identification

Radio frequency fingerprint (RFF) has attracted a remarkable surge of attention to wireless transmitter identification due to the inimitable hardware imperfection. However, most RFF-based schemes devised in controlled environments are unable to reach the claimed performance in real-world scenarios. This paper proposes a practical RFF identification method for mobile phones in Global System for Mobile (GSM) system. Specifically, the instantaneous amplitude of near-transient part in normal burst (NB) is regarded as RFF that extracted from up-link communications. In addition, an anomaly filtering and stacking (AFS) method is introduced to obtain stable RFF in Time Division Multiple Access (TDMA) system. Lastly, the impacts of frequency point and sending power variations on RFF are fully dissected in comparison experiments. Experiments on 10 mobile phones show that the proposed RFF scheme yields 99.17% True Acceptance Rate (TAR) in real wireless environments. Experiments also show that the varying transmission power decreases the accuracy of RFF identification.