微波衰减测量过程失控的原因分析及解决方案

针对高频串联替代法微波衰减测量标准装置测量过程所出现的失控现象 ,从测量标准仪器、被测仪器、测量方法、人为因素等方面分析了失控的原因 ,制定并实施了相应的解决方案 ,使测量过程恢复到统计受控状态     

Relay selection based on MAP estimation for cooperative communication with outdated channel state information

In this paper, we consider an amplify-and-forward (AF) cooperative communication system when the channel state information (CSI) used in relay selection differs from that during data transmission, i.e., the CSI used in relay selection is outdated. The selected relay may not be actually the best for data transmission and the outage performance of the cooperative system will deteriorate. To improve its performance, we propose a relay selection strategy based on maximum a posteriori (MAP) estimation, where relay is selected based on predicted signal-to-noise ratio (SNR). To reduce the computation complexity, we approximate the a posteriori probability density of SNR and obtain a closed-form predicted SNR, and a relay selection strategy based on the approximate MAP estimation (RS-AMAP) is proposed. The simulation results show that this approximation leads to trivial performance loss from the perspective of outage probability. Compared with relay selection strategies given in the literature, the outage probability is reduced largely through RS-AMAP for medium-to-large transmitting powers and medium-to-high channel correlation coefficients.     

量块计量保证方案（MAP）

量块计量保证方案(MAP)是美国NIST近年来推行的一种科学的量值传递方法。它打破了传统的量值传递方法,采用l检验和F检验对量值传递过程进行控制,并通过数据反馈对参加试验室进行综合考核,以确保量值传递的质量。介绍了在我国推广应用量块计量保证方案的实施情况,并进行了技术分析。     

基于GPS／DR的车辆导航系统研究

本文研究了GPS和航位推算系统的组合导航技术，给出了GPS／DR组合导航系统的设计方案。由GPS接收机、压电陀螺仪和车载里程仪组成的多传感器系统通过卡尔曼滤波器实现信息融合，以提高GPS／DR组合系统导航精度。同时也对GPS／DR系统的MAP图像处理、软件流程和工程实现做了简要说明。     

基于混合粒子滤波的载波估计算法

针对粒子滤波载波估计算法的高复杂度、粒子退化及贫化问题,提出了一种基于混合粒子滤波的载波估计方法.该方法引入多阶马尔科夫模型,采用多个非零均值高斯分布的加权和来近似重要性函数的最佳选择,并根据最大后验概率准则规范粒子的迭代计算.仿真结果表明,在非高斯噪声环境下,低轨卫星通信TDMA/DEQPSK(Time Division Multiple Address/Differential Quadrature Phase Shift Keying)数据帧非合作接收载波估计时,与基于经典粒子滤波的载波估计算法相比,提高了粒子"效率",在误码性能相当的情况下,有效降低了计算复杂度.     

实时多任务环境下MAP与BITBUS异构网络互连

ＭＡＰ的应用层提供了多种通信标准，其中ＭＭＳ（制造报文规范）是一种能够满足工厂环境中各种自动化设备之间通信需要的协议。在我国，ＢＩＴＢＵＳ网已被大量使用于底层设备互连，在技术和实现上都较成熟。本文以ＭＡＰ，ＢＩＴＢＵＵ网络体系结构和协议为基础，根据网络互连方法和原则，构造了一个应用层同关，提出了网关的物理模型，从而给出ＭＡＰ网与ＢＴＴＢＵＳ网互连的一种设计方案及在ＡＭＸ实时多任务环境下的互连实现。     

浅议自动测试系统的校准工作

简述了集成电路自动测试系统校准方案的制订、传递与溯源方式的选择以及通过MAP方案解决IC测试设备溯源问题的试用效果。     

Bayesian edge detector for SAR imagery using discontinuity-adaptive Markov random feld modeling

Synthetic aperture radar（SAR）image is severely affected by multiplicative speckle noise,which greatly complicates the edge detection.In this paper,by incorporating the discontinuityadaptive Markov random feld（DAMRF）and maximum a posteriori（MAP）estimation criterion into edge detection,a Bayesian edge detector for SAR imagery is accordingly developed.In the proposed detector,the DAMRF is used as the a priori distribution of the local mean reflectivity,and a maximum a posteriori estimation of it is thus obtained by maximizing the posteriori energy using gradient-descent method.Four normalized ratios constructed in different directions are computed,based on which two edge strength maps（ESMs）are formed.The fnal edge detection result is achieved by fusing the results of two thresholded ESMs.The experimental results with synthetic and real SAR images show that the proposed detector could effciently detect edges in SAR images,and achieve better performance than two popular detectors in terms of Pratt＇s fgure of merit and visual evaluation in most cases.     

射频衰减计量保证方案（MAP）

本文叙述射频衰减计理保证方案(MAP)的数学模型及t检验和F检验方法。MAP是一种新的量值传递方法,中心实验室通过传递标准衰减器的传递,参加实验室用核查标准衰减器,使其参考标准测量过程不确定度控制在一定范围以内。