冰雪微波遥感研究进展

对微波冰雪遥感及应用研究作了概要的介绍,重点介绍了海冰遥感监测与相关数据的应用、分析和处理,同时,介绍了微波遥感在我国冰川积雪、冻土研究中的应用及成果,并对微波冰雪遥感研究的前景作了简要的分析和展望。     

分布式的附网存储系统的设计与实现

设计并实现了一种高性能的分布式附网存储系统,并详细介绍了其工作原理、设计流程和主要程序段。     

A dual-driven adaptive video system over WLAN

This paper proposes a dual-driven adaptive (D2D-Adap) video server system over wireless local area network (WLAN). In the system, the status of the wireless channel is monitored at the sender side, And at the receiver side. the packet loss rate, delay etc. are measured and fed back to the sender. The status information from both sides is used to adapt the encoding and transmission rate of the video in the server. The adaptation scheme in the proposed system can estimate the network channel situation accurately and quickly and can provide better video communication service over WLAN. The simulation and test results show that the proposed system can respond to the changes of the wireless channel quickly and therefore provide smoother video to clients.     

中心式结构僵尸网络的检测方法研究

从近年发展趋势看,僵尸网络的结构正呈现多样化发展的趋势,中心式结构僵尸网络因控制高效、规模较大成为网络安全最大的威胁之一.中心式结构僵尸网络采用一对多的命令与控制信道,而且僵尸主机按照预定的程序对接收到的命令做出响应,因此,属于同一僵尸网络的受控主机的行为往往具有很大的相似性与同步性.针对中心式结构僵尸网络命令控制流量的特点,本文提出一种基于网络群体行为特点分析的检测方法并用于僵尸网络的早期检测与预警.实际网络流的实验表明,本方法能够有效检测当前流行的中心式结构僵尸网络.     

A channel equalizer using reduced decision feedback Chebyshev functional link artificial neural networks

In this paper, a reduced decision feedback Chebyshev functional link artificial neural network (RDF-CFLANN) is proposed for the design of a nonlinear channel equalizer. An RDF-CFLANN structure uses functional expansion utilities to nonlinearly transform its input signals into the output space. In most MLP structures, one or more hidden layers are needed to nonlinearly map the input signals to the output signal space. Therefore, the complexity of the RDF-CFLANN structure is generally much lower than that of an MLP structure. In addition, the required amount of computing at the training mode can also be reduced. The comparisons of the mean squared error (MSE) and the average transmission bit error rate (BER) among RDF-CFLANN, DF-CFLANN and CFLANN are presented in this paper. Simulation results demonstrate that RDF-CFLANN presents the best performance among the three structures.     

Estimation of Quantum Channels with Finite Resources

We examine the problem of determining the parameters that describe a quantum channel. It is assumed that the users of the channel have at best only partial knowledge of it and make use of a finite amount of resources to estimate it. We discuss simple protocols for the estimation of the parameters of several classes of channels that are studied in the current literature. A quantitative measures of the quality of the estimation schemes can be given on the basis of the standard deviation or of the fidelity. Protocols that employ entangled particles are also discussed. The use of entangled particles as a nonclassical resource enhances the estimation quality of some classes of quantum channel. Further, the methods presented here can be extended to higher dimensional quantum systems. PACS: 03.67.Hk     

Evaluation of the HUT modified snow emission model over lake ice using airborne passive microwave measurements

The algorithms designed to estimate snow water equivalent (SWE) using passive microwave measurements falter in lake-rich high-latitude environments due to the emission properties of ice covered lakes on low frequency measurements. Microwave emission models have been used to simulate brightness temperatures (Tbs) for snowpack characteristics in terrestrial environments but cannot be applied to snow on lakes because of the differing subsurface emissivities and scattering matrices present in ice. This paper examines the performance of a modified version of the Helsinki University of Technology (HUT) snow emission model that incorporates microwave emission from lake ice and sub-ice water. Inputs to the HUT model include measurements collected over brackish and freshwater lakes north of Inuvik, Northwest Territories, Canada in April 2008, consisting of snowpack (depth, density, and snow water equivalent) and lake ice (thickness and ice type). Coincident airborne radiometer measurements at a resolution of 80 × 100 m were used as ground-truth to evaluate the simulations.The results indicate that subsurface media are simulated best when utilizing a modeled effective grain size and a 1 mm RMS surface roughness at the ice/water interface compared to using measured grain size and a flat Fresnel reflective surface as input. Simulations at 37 GHz (vertical polarization) produce the best results compared to airborne Tbs, with a Root Mean Square Error (RMSE) of 6.2 K and 7.9 K, as well as Mean Bias Errors (MBEs) of −8.4 K and −8.8 K for brackish and freshwater sites respectively. Freshwater simulations at 6.9 and 19 GHz H exhibited low RMSE (10.53 and 6.15 K respectively) and MBE (−5.37 and 8.36 K respectively) but did not accurately simulate Tb variability (R = −0.15 and 0.01 respectively). Over brackish water, 6.9 GHz simulations had poor agreement with airborne Tbs, while 19 GHz V exhibited a low RMSE (6.15 K), MBE (−4.52 K) and improved relative agreement to airborne measurements (R = 0.47). Salinity considerations reduced 6.9 GHz errors substantially, with a drop in RMSE from 51.48 K and 57.18 K for H and V polarizations respectively, to 26.2 K and 31.6 K, although Tb variability was not well simulated. With best results at 37 GHz, HUT simulations exhibit the potential to track Tb evolution, and therefore SWE through the winter season.     

Iterative multi-user detection and decoding for space-time block coding systems

1 Introduction Recently space–time coding (STC) techniques [1] are designed to combat fading in wireless links by utilizing multiple antenna systems, in which transmit diversity and coding gains can be exploited without sacrificing additional power and b…     

基于IFDMA-SIMO系统的信道压缩

高速数据传输IFDMA(interleaved frequency-division multiple-access)系统中,信道扩展将导致严重的符号间干扰,为此,根据IFDMA-SIMO(single-input multiple-output)系统特性,提出了一种新的基于IFDMA-SIMO系统的信道压缩算法。仿真和比较表明,该算法在保持多用户信号正交的基础上,能有效地抑制多径干扰。     

互联网通信技术的应用研究

介绍了互联网通信技术的特点、应用和发展,提出了一些新的方法,解决了互联网通信过程中的信息访问资源浪费、信息阻塞和信道负担增加的问题。