Response Time in Data Broadcast Systems: Mean,Variance and Tradeoff

Data broadcast has been suggested as a promising method of information dissemination [2,33]. In such an environment, the information server cannot afford to serve the requests from a large population of users individually. Instead, the server uses a broadcast channel to deliver information to all users. A single transmission of a data item satisfies all pending requests for that item. The response time of a request depends on the broadcast time of the desired data item, which is scheduled by the server according to the overall demands for various data items. Therefore, the response time may vary in a large range. We argue that, in addition to mean response time, the variance of response time should also be taken into account by the broadcast scheduler. In this paper, we address the issue of variance optimization in regard to response time. Building on our previous research on mean response time optimization, we propose an algorithm which can minimize the variance of response time. Furthermore, we evaluate an algorithm that facilitates a tradeoff between the mean and variance of response time. Numerical examples that illustrate the performance of our algorithms are also presented.     

面向智能电网的云数据处理系统评价方法

智能电网数据处理系统需要存储从巨量设备端点周期性采集到的海量数据,处理高度并发的读写请求,并要求系统具有良好的可扩展性.新兴的云数据服务系统为我们提供了很好的选择.但是现在云数据服务系统种类繁多,各方面的性能存在差异,如何选择合适的云数据服务系统成为关键问题.基于智能用电场景,提出了一种对云数据服务系统的性能评价和分析方法,并利用该方法评测HBase、Voldemort和Cassandra三者的性能.     

Efficient Self‐Assembly Synthesis of Uniform CdS Spherical Nanoparticles‐Au Nanoparticles Hybrids with Enhanced Photoactivity

The treatment of environmental pollution has become one of the most critical issues in the world. Despite the progress made in the study of semiconductor photocatalysis, it is still a challenge to obtain photocatalysts with high activity through relatively simple fabrication processes. In this work, monodisperse CdS spherical nanoparticles (SNPs) of various sizes and good crystallinity are obtained by only adjusting the starting ratio of reactants and the reaction temperature, exhibiting high photocatalytic performances. The photocatalytic rate constant of the ≈ 100 nm CdS SNPs, especially, is more than double that of P25. Furthermore, 3‐mercaptopropyltrimethoxysilane is used to assist the interaction between ≈ 200 nm CdS SNPs and citrate‐stabilized Au nanoparticles (NPs). The significant increase of photocatalytic activity is confirmed by the degradation of Rodamine B (RhB) under Xe light irradiation. At the optimal Au concentration (0.5 wt%), the prepared nanohybrids show the highest photocatalytic activity, exceeding that of pure CdS two times. The superior photocatalytic performances of the CdS SNPs‐Au nanohybrids can be attributed to the intimate interfacial contact between CdS SNPs and Au NPs, which is a contributing factor to the improvement of transfer and the fate of photogenerated charge carriers from CdS SNPs to Au NPs.     

Nondata-aided error vector magnitude performance analysis over κ−μ shadowed fading channel

The performance prediction of wireless system over κ?μ shadowed fading channels was a challenging problem of wireless communications,which affects transmission scheme design seriously.To solve this problem,a novel method of quantifying the κ?μ shadowed fading channels performance based on nondata-aided error vector magnitude (NDA-EVM) was proposed.NDA-EVM was considered as a new metric to evaluate the change of the channels.The unified model to calculate different modulation order of NDA-EVM was analytically derived by maximum likelihood criterion.Moreover,the relationship between the κ?μ distribution and the NDA-EVM was built by using the attenuation factor of the channel as intermediate variable.Thereafter,the lower bounds of the NDA-EVM over the κ?μ shadowed fading channels were formulated,which was also simplified for various typical channels.The theoretical analysis was taken,moreover,numerical results were also conducted to verify the effectiveness of the derived formulation.It shows that NDA-EVM estimation has the lest root mean square error than data-aided signal to noise ratio (DA-SNR) estimation and error vector magnitude (DA-EVM) estimation over the κ?μ shadowed fading channels.The derived lower bounds closely match the theoretical values,especially at low SNR.In addition,the lower bounds are negatively related to all of the parameters of the κ?μ shadowed fading channels,which make it sensitive to the change of the fading channels.     

Application Aware Topology Generation for Surface Wave Networks-on-Chip

The networks-on-chip （NoC） communication has an increasingly larger impact on the system power consumption and performance. Emerging technologies, like surface wave, are believed to have lower transmission latency and power consumption over the conventional wireless NoC. Therefore, this paper studies how to optimize the network performance and power consumption by giving the packet-switching fabric and traffic pattern of each application. Compared with the conventional method of wire-linked, which adds wireless transceivers by using the genetic algorithm （GA）, the proposed maximal declining sorting algorithm （MDSA） can effectively reduce time consumption by as much as 20.4% to 35.6%. We also evaluate the power consumption and configuration time to prove the effective of the proposed algorithm.     

信标信号频谱在接收机跟踪性能分析上的应用

接收机锁定卫星信标后,经过二次或三次变频将C频段信标转变为70 MHz中频,然后通过解调单元从中频中提取误差信号。通过分析比较信标信号、L频段频率、70 MHz中频信号频谱使跟踪系统的性能指标层次化,从信标频谱中提取有用信息,全面判断数字接收机跟踪性能,对单脉冲跟踪体制下的接收机故障排查具有一定的指导意义。     

羊毛滤料对PM2.5的过滤性能研究

从实验角度研究了羊毛滤料原样、经过纳米TiO2光催化整理后的整理样对PM2.5的过滤效率和阻力,并做了相关比较与分析。实验结果表明:随着风速的增大,相同克重的羊毛滤料对PM2.5的过滤效率逐渐降低,同时阻力大幅增加。随着克重的增加,羊毛滤料对PM2.5的过滤效率增大,过滤阻力也相应增大。经过纳米TiO2整理剂整理后,羊毛滤料整理样对PM2.5的过滤效率有所提高,但是阻力也有了相应的提高。     

光PM-DQPSK调制格式性能研究

对偏振复用-33%归零-差分正交相移键控(PM-33%RZ-DQPSK)和偏振复用-抑制载波归零-差分正交相移键控(PM-CSRZ-DQPSK)调制格式进行了传输性能仿真,在仿真过程中,分别考虑了光纤系统中的偏振模色散(PMD)、色散(CD)和非线性效应(SPM)三种限制因素。仿真结果表明偏振复用系统比非偏振复用系统更易受到PMD、CD和非线性效应的影响。整体来看,PM-CSRZ-DQPSK调制格式的传输性能比PM-33%RZ-DQPSK更为优秀。     

Wi-Fi终端设备性能测试

对终端的WLAN性能测试做了初步的探讨,重点论述了如何通过测试手段来确保Wi-Fi终端设备的性能,以满足企业和消费者对高业务质量的要求。     

对于驾驶机器人性能综合评价的研究

为了综合评价驾驶机器人的驾驶性能,在单纯指标评价的基础上,提出一种新的综合评价方法.经过对驾驶机器人的实测验证,获得的数据证明此方法能时驾驶机嚣人驾驶性能进行定性的、直观的综合评价.