基于CvM算法的Nakagami衰落信道统计特性检验

Nakagami信道通过不同的衰落因子m可以仿真不同的信道衰落环境,仿真数据与实际测量值吻合度较高,在信道仿真领域得到广泛应用。然而,目前针对Nakagami信道模型的可信性研究较少,缺少科学的比对验证方法。根据典型Nakagami信道的一阶包络序列服从Nakagami分布这一信道统计特性,提出一种基于Cramer-von Mises （CvM）算法的拟合优度检验方法。使用“高斯+瑞利+直流”组合法建立Nakagami衰落信道模型,得到信道输出序列并从中提取包络序列。在此基础上,利用双样本CvM检验算法对包络序列的理论分布和实际分布进行拟合优度检验,实现对Nakagami信道模型的可信性评估。半实物仿真结果表明,与K-S检验、卡方检验和Z检验+卡方检验融合检验算法相比,CvM针对不同m下的Nakagami衰落信道均具有较好的识别性能,同时在可靠性和复杂度方面也具有优势,其对虚警概率为0.01以下的Nakagami衰落信道识别准确率达到92.6%,对样本长度为300 000以上的Nakagami衰落信道平均识别准确率达到96.4%,而当待检验信道为其他信道时,不存在误识别的情况。     

Two types of a passive safety containment for a near future BWR with active and passive safety systems

The paper presents two types of a passive safety containment for a near future BWR. They are named Mark S and Mark X containment. One of their common merits is very low peak pressure at severe accidents without venting the containment atmosphere to the environment. The PCV pressure can be moderated within the design pressure. Another merit is the capability to submerge the PCV and the RPV above the core level. The third merit is robustness against external events such as a large commercial airplane crash. Both the containments have a passive cooling core catcher that has radial cooling channels. The Mark S containment is made of reinforced concrete and applicable to a large power BWR up to 1830 MWe. The Mark X containment has the steel secondary containment and can be cooled by natural circulation of outside air. It can accommodate a medium power BWR up to 1380 MWe. In both cases the plants have active and passive safety systems constituting in-depth hybrid safety (IDHS). The IDHS provides not only hardware diversity between active and passive safety systems but also more importantly diversity of the ultimate heat sinks between the atmosphere and the sea water. Although the plant concept discussed in the paper uses well-established technology, plant performance including economy is innovatively and evolutionally improved. Nothing is new in the hardware but everything is new in the performance.     

Assessment of thermal aging embrittlement in a cast stainless steel valve and its effect on the structural integrity

This paper analyzes the thermal aging embrittlement occurred in a cast stainless steel valve, which is part of the reactor water clean-up (RWCU) system of a Spanish boiling water reactor (BWR) nuclear power plant. The aim is to estimate the current and future state of the material and the corresponding structural integrity of the valve. Given that there is no data available for the experimental characterization of the material, the evolution of the mechanical properties (fracture toughness, yield stress, flow stress and Ramberg-Osgood parameters) has been estimated using the ANL procedure.With the obtained estimations, the critical crack size has been calculated using the European procedure FITNET FFS and the ASME Code.This analysis considers not only the evolution of the mechanical properties up to now but also its future evolution in case there is a life extension of the plant until year 2029.     

非能动先进压水堆核电厂SGTR事故概率安全评价

蒸汽发生器传热管破裂(Steam Generator Tube Rupture,SGTR)事故是核电厂的重要事故之一,并具有其自身的特点。该事故的研究和评价对核电站安全具有较大意义。选取典型非能动先进压水堆核电厂AP1000的SGTR事故进行一级概率安全评价(Probabilistic Safety Assessment,PSA),采用事件树分析方法得到电厂事件发生后系统、设备和人员不同响应所产生的事故序列,然后建立相关系统的故障树模型进行可靠性分析。借助Risk Spectrum软件,计算SGTR事故导致AP1000核电厂的堆芯损伤频率(Core Damage Probability,CDF),并进行堆芯损伤的最小割集分析及重要度和敏感性分析。通过一系列分析得到导致堆芯损伤的重要基本事件,从而找到系统存在的薄弱环节。     

Integrating Safety Critical Software System in Probabilistic Safety Assessment

In the recent times, computer-based systems are frequently used for protection and control of Nuclear Power Plants (NPPs). In the conventional Probabilistic Safety Assessment (PSA), the contribution from software in these computer-based systems was not given necessary attention. However, from operating experience, it has been found failures in such systems can also result in initiating events that have the potential for leading into Core Damage in the event of unavailability of the respective Engineered Safety Features. The impact of a typical computer-based system on PSA of Indian Nuclear Power Plant is demonstrated.     

多维直方图联合概率分布的掩模矩阵降维算法

彩色图像的分量独立处理或感知彩色空间的强度分量处理,都能达到增强图像对比度的效果,但由于没有考虑各个分量之间的联系,不能开发完全的RGB色域。多通道直方图建模技术可以改善上述缺陷,就是通过求取多个分量的直方图联合概率密度函数和累积分布函数,从而得到彩色图像的像素灰度值映射函数,但计算联合直方图的过程也导致了过高的运算复杂度。为了降低计算量,提出了掩模降维的方法,将计算多维直方图的过程转化为了计算一维直方图,从而大大降低了运算复杂度,提高运算速度,增强对比度的效果。     

PUSH技术在远程教育系统中的应用

本文详细讲述了推送(PUSH)技术的基本原理和解决方案,并在此基础上,结合推送技术的应用特点和构建远程教育系统的需求,分析了推送技术应用的战略性意义,以及推送技术在远程教育领域中的适用范围及其实施策略,最后指出我们在应用推送技术时所应关注和深入研究的几个关键技术问题。     

手性药物的液相色谱分析

手性药物的HPLC分析是药物分析中较新的研究领域,综述了近年来手性药物色谱分离的研究进展。对手性衍生化试剂法和手性固定相法的分离机理、检测方法、试剂种类和应用等作了介绍。