Strong Diffie-Hellman-DSA Key Exchange

To provide authentication to the Diffie-Hellman key exchange, a few integrated key exchange schemes which provide authentication using the DSA signature have been proposed in the literature. In this letter we point out that all of the previous Diffie-Hellman-DSA schemes do not provide security against session state reveal attacks. We also suggest a strong Diffie-Hellman-DSA scheme providing security against session state reveal attacks as well as forward secrecy and key independence     

Optical Fiber Polarization Interferometer for Performance Improvement in Radio-Over-Fiber Systems

An extinction ratio tunable optical fiber polarization interferometer (OFPI) is proposed and implemented to increase the optical modulation depth in radio-over-fiber (RoF) systems by suppressing the optical carrier power. The extinction ratio of the OFPI can be simply tuned by adjusting the polarization state of the launched RoF signal. Experimental results illustrate that the receiver sensitivity and dynamic range of RoF systems are greatly improved using the proposed scheme.     

Channel state-aware joint dynamic cell coordination scheme using adaptive modulation and variable reuse factor in OFDMA downlink

This paper proposes three different dynamic cell coordination schemes using adaptive link adaptation and variable frequency reuse for OFDMA downlink cellular networks, which are composed of greedy cell coordination for flat fading channel, dynamic maximum C/I cell coordination (DMCC), and dynamic proportional fairness cell coordination (DPFCC) for frequency selective fading channel. The performances of the proposed dynamic cell coordination schemes are compared to those with no cell coordination schemes and static reuse coordination schemes using conventional proportional fair (PF) scheduling in terms of system throughput and fairness. Simulation results demonstrate that the proposed schemes allow the radio network controller (RNC) and base stations (BSs) to apply different reuse factors on each subchannel in consideration of different interference conditions of individual users so as to increase the system throughput and guarantee QoS requirement of each user on the multicell environment, where the performance of conventional OFDMA downlinks might have become degraded due to persistent interference from other cells. In frequency flat fading, the proposed dynamic schemes achieve, on average, a 1.2 times greater system throughput than no cell coordination, a 1.4 times greater static cell coordination and a 3 times greater simplified subchannel allocation scheme (SSAS) (Kim et al. in Proceedings of IEEE VTC spring’04, vol. 3, pp. 1821–1825, 2004). In frequency selective fading, the proposed scheme, DMCC, showed a 2.6 times greater throughput than that of a single reuse factor of one for all subcarriers, and DPFCC demonstrated a single reuse factor as good as one.     

Controlled Synthesis of Various Hollow Cu Nano/MicroStructures via a Novel Reduction Route

Hollow Cu nano/microstructures are prepared by reduction of CuSO₄ · 5 H₂O with glucose by using a mild hydrothermal process. The X‐ray powder diffraction and energy‐dispersive X‐ray analysis indicate that the products are pure Cu and of cubic phase. The morphology of the products can be controlled between nanotubes and microspheres assembled from hollow nanoparticles by adjusting the concentration of sodium dodecyl sulfate. A series of experiments confirm that the concentration of the glucose and NaOH also play important roles in the formation of the hollow Cu nano/microstructures.     

White light emission from Dy3+-doped LiLuF4 single crystal grown by Bridgman method

Lithium lutetium fluoride （LiLuF4） single crystals doped with different Dy3＋ ion concentrations were grown by Bridgman method. The Judd-Ofelt （J-O） strength parameters （Ω2, Ω4, Ω6） of Dy3＋ in LiLuF4 crystal are calculated according to the measured absorption spectra and the J-O theory, by which the asymmetry of the Dy3＋：LiLuF4 single crystal and the possibility of attaining stimulated emission from 4F9/2 level are analyzed. The capability of the Dy3＋：LiLuF4 crystal in generating white light by simultaneous blue and yellow emissions under excitation with ultra- violet light is produced. The effects of excitation wavelength and doping concentration on chromaticity coordinates and photoluminescence intensity are also investigated. Favorable CIE coordinates, x=0.319 3 and y=0.349 3, can be obtained for Dy3＋ ion in 2.701% molar doping concentration under excitation of 350 nm.     

基于二元饱和度的信号交叉口延误分析

为提高信号交叉口通行能力,利用二元饱和度方法,对交叉口单相位的车辆做延误分析,推导了适用于任意交通情况的路口延误模型,并对该模型进行算例分析。通过基于传统饱和度与二元饱和度控制约束条件下仿真对比验证,本延误模型计算简单易实现、在较高饱和度下路口车辆排队长度比传统饱和度控制方式短,另外时延也得到一定改善。     

面向云计算的业务支撑系统数据架构实施策略

首先从纯理论角度介绍云计算的概念及云计算的些应用,重点分析了运营商云计算的现状,初步探讨了运营商建设云计算架构策略的关键点;对运营商实施云计算策略的关键点：数据统一策略和数据服务策略进行了介绍;对数据统策略,主要从数据模型层面进行统,对于数据服务策略主要是进行分层设计的思路。     

一种用于APFC的模拟乘法器设计

在有源功率因数校正技术(APFC)中,通过对乘法器的输出与电感电流的峰值比较,控制功率开关管的开启与关断,使输入电流峰值包络跟随输入电压,功率因数理论上为单位值。而提高乘法器的线性度,减小非线性误差成为研究模拟乘法器的一个重要方向。本文提出的模拟乘法器采用有源衰减器显著的增大了输入信号电压范围,更重要的是在有源衰减电路中引入负反馈有效的减小了乘法器的非线性误差。基于CSMC 0.5um BCD工艺,采用Hspice进行仿真验证,在电源电压5V条件下,乘法器的一输入端的输入范围为0~2V,非线性误差小于0.6%,另一输入端的输入范围为1~4V,非线性误差小于0.3%。总谐波失真小于1.8%。     

CDMA移动核心网扁平化中的问题探讨

摘要：目前CDMA核心网以软交换技术为核心,在移动核心网软交换适应未来IMS、全IP网络进程中,移动核心网扁平化即IP承载网承载语音是非常重要的一环。本文以山西电信为例就移动核心网软交换扁平化进程中的问题作几点探讨。     

单脉冲激光减小超声速飞行器波阻的实验研究

利用激光等离子体减小超声速飞行器的气动阻力是一种新概念减阻方式。根据单脉冲激光减小超声速飞行器波阻瞬态流场的特点,建立了超声速条件下单脉冲激光能量沉积减阻实验系统,利用高分辨率的纹影系统拍摄激光能量沉积产生的激波与弓形激波相互作用过程,分析了激光减小超声速飞行器波阻的机理,以实验手段验证了激光等离子体可以减小超声速飞行器波阻,为研究高重复频率激光减阻提供了实验测试方案。