MIMO-OFDM系统的自适应多用户分集及性能分析

 本文建立基于随机波束成形和自适应调制的MIMO-OFDM系统的自适应多用户分集系统模型,提出随机波束成形QR接收机的自适应多用户分集资源分配算法及其简化算法,推导在最大化系统吞吐量条件下系统的误码性能.仿真结果表明该算法在用户数很小时使系统性能收敛到特征波束成形系统的性能;当用户数增多时,采用天线分配算法的多用户分集系统能获得比特征波束成形系统更好的性能;将自适应编码调制技术运用到多用户分集系统来提高系统的实际吞吐量和误码性能.     

无线通信系统波束成形与空时分组编码联合处理技术

提出了一种基于三阶循环统计量的波束成形方法。并将该波束成形方法与空时分组编码联合应用,提出了一种基站采用双天线阵列发射,移动终端多天线阵元接收的波束成形与空时分组编码联合处理新方案。本方案对移动终端的接收性能以及整个无线通信系统的容量都具有良好的改善作用。计算机仿真结果也证明了本方案的有效性和优越性。     

预测滤波器在空域盲加性水印系统中的应用

为了提高空域图像水印算法的性能,提出将一种基于载体图像最小平方的预测滤波器用于空域加性水印的嵌入与检测.在嵌入端,用预测滤波器构造空域掩蔽函数,这种用预测残差作为控制嵌入强度的掩蔽函数与人类视觉的感知特性相吻合,在相同的视觉质量下大大提高了水印的嵌入强度.在水印检测时,为了有效抑制载体信号对相关检测器的干扰,采用预测滤...     

Interactive navigation system in smart phone with vibration feedback

The traffic congestion has become an urgent problem to be solved, which appears in the domestic and foreign large and medium-sized cities. Intelligent transportation is one of the important applications of ubiquitous computing. And it''s an important way to ease the traffic congestion of the city. Intelligent navigation system is an important embodiment of intelligent transportation. So far, there have been many kinds of traditional vehicle navigation systems. But when they are in use, drivers will pay extra attention to get the path information through the visual and auditory cues.It''s dangerous for drivers when they drive. At the same time, with the development of science and technology, mobile navigation system has been widely used. The mobile navigation system is a comprehensive system which relates to the field of mobile communication and GPS. The objective of this paper is to develop a smart phone and interaction navigation system based on the feedback of vibration and micro programmed control unit (MCU) control system. When drivers are in the driving process, the new navigation system can avoid the same sense of multiple tasks, which makes each sensory focus on only one independent task. Through the analysis, the system is demonstrated to improve the driving safety.     

多用户MIMO-OFDM系统的子信道可变速率算法

联合考虑随机波束成形和自适应调制建立了MIMO-OFDM系统的自适应多用户分集系统模型,提出了随机波束成形QR接收机的子信道可变速率算法,推导了在最小化系统误码率情况下系统的误码性能。仿真结果表明,该算法在用户数很小时使系统性能收敛到特征波束成形系统的性能;当用户数增多时,采用天线分配算法的多用户分集系统能获得比特征波束成形系统更好的性能;将自适应编码调制技术运用到多用户分集系统,从而提高系统的实际吞吐量和误码性能。     

中、美、加、欧屋面雪荷载规范对比

陈述了我国规范与美国、加拿大和欧盟规范在雪荷载取值方面的差异.结果表明：我国规范的雪荷载计算公式过于简单,不能充分考虑各种相关因素对雪荷载的影响;我国规范规定的屋面雪荷载临界坡度在4本规范中最小;在双坡、拱形和高低屋面中,我国规范的雪荷载剖面与国外规范差异较大;最后给出对我国规范雪荷载取值规定的一些初步修改建议,为我国...     

Multi-objective optimization of membrane structures based on Pareto Genetic Algorithm

A multi-objective optimization method based on Pareto Genetic Algorithm is presented for shape design of membrane structures from a structural view point.Several non-dimensional variables are defined as optimization variables,which are decision factors of shapes of membrane structures.Three objectives are proposed including maximization of stiffness,maximum uniformity of stress and minimum reaction under external loads.Pareto Multi-objective Genetic Algorithm is introduced to solve the Pareto solutions.Consequently,the dependence of the optimality upon the optimization variables is derived to provide guidelines on how to determine design parameters.Moreover,several examples illustrate the proposed methods and applications.The study shows that the multi-objective optimization method in this paper is feasible and efficient for membrane structures;the research on Pareto solutions can provide explicit and useful guidelines for shape design of membrane structures.     

基于分层贝叶斯网络的车辆发动机系统电磁脉冲敏感度评估

提出一种基于分层贝叶斯网络(HBN)的车辆发动机系统电磁脉冲(EMP)敏感度评估方法,从概率角度考虑电磁干扰源位置、极化角度、部件敏感度等参量的随机性,估计发动机系统在强电磁脉冲作用下的失效概率。该方法利用事件树分析(ETA)对电磁脉冲传播过程建模,确定系统周围电磁环境的风险概率,运用电磁拓扑(EMT)分析发动机系统电磁耦合途径。考虑同层单元失效的相关性,以分层贝叶斯网络为框架融合事件树和电磁拓扑理论建立发动机系统电磁脉冲敏感度评估模型,并推导了部件级至系统级的失效概率计算公式。最后以高空核电磁脉冲环境为例,说明了某型号发动机电磁脉冲敏感度评估模型的参数获取方法和模型计算过程,并以超宽带高功率微波为例,进一步说明了本文评估模型的适用性。     

基于等效线性地基的某工业厂房抗震分析

以某生命线工程工业厂房为例,采用等效线性化方法近似考虑地基的非线性特性进行厂房抗震分析,并将计算得到的楼层反应谱作为对比参数,与线性地基假定条件下抗震分析结果进行对比,结果表明:对于剪切波速较低的厂址(剪切波速小于400m/s),线性地基假定条件下厂房地震响应明显大于等效线性地基下的结果,而当地基剪切波速较高时(剪切波速约为1 100m/s),两者计算结果相近,分析结论可为今后建构筑物抗震设计提供参考。     

衰减标准装置建标过程中相关的不确定度评定

衰减是无线电计量的重要参数,建立衰减标准装置,保证衰减的量值可靠传递,是无线电计量的一项重要任务。本文介绍了使用测量接收机作为衰减标准装置的衰减量测量方法,对衰减标准装置的不确定度进行了评定。考虑失配分量的影响,分别评定了固定和可变衰减器的衰减量测量结果的不确定度。