变压器继电保护灵敏度探讨

差动保护是变压器内部故障的主保护,保护必须对所发生的故障能够灵敏地进行反应,这就涉及到差动保护的灵敏度问题。如何快速、正确地校验差动保护的灵敏度对继电保护定值整定工作非常重要。该文以本地区电网220kv变压器为模型,以本地区应用广泛并有代表性的四方csc326D和南瑞Rcs978E两种型号的交压器保护为例对差动灵敏度校验的方法和步骤进行了论述,并总结出了简便、实用的校验方法。     

基于MODBUS自由协议的数据校验方法探究

本文针对于一种实际的MODBUS自由协议在AVR单片机平台上应用中出现的问题展开研究,分析问题出现的原因并提出一种可替代CRC校验的数据校验方法,通过实验验证该方法可以解决在不使用CRC校验的情况下实现较稳定可靠的MODBUS自由协议通信.本文首先介绍MSDBUS协议和自由协议;其次,具体分析一种在中低端单片机例如ATmega8作为MCU的平台上MOCBUS自由协议通信在应用中产生的问题;再次,针对上述问题提出一种数据校验方法和实现.最后,通过实验数据对提出的数据校验方法的效果进行验证.     

低压网络短路电流计算在建筑工程实际中的应用

短路电流计算在低压网络系统中非常重要,关系到事故分析和人身安全,所以电气设计人员需要熟悉低压网络的计算方法,掌握短路电流变化规律。本文介绍了低压网络短路电流的计算方法,并针对高大空间照明配电回路进行了短路电流计算分析,同时对短路配电线缆的热稳定性以及保护电器的灵敏度进行了校验,发现随着照明配电回路距离的增加,当末端灯具接地短路时,可能会出现断路器不能可靠动作的情况,并针对此种情况进行了解决方案分析,为电气设计提供参考。     

阵列可视化噪声源检测中的声-光偏离校准方法研究

针对现有的阵列声成像的声-光偏离校准复杂性的问题,研究了一种传声器阵列声像图和视频图的偏离校准方法,该方法针对声-光偏离(平移、旋转和缩放)基本问题,推导出了校准偏离的公式.设计了一个声-光复合校准器,通过提取视频图像的光源中心坐标和声像图的声源中心坐标,得到一个校验的声-光坐标偏离值.根据不同位置的五次实验,得到五个校验的偏离值,再利用本文建立的校验模型计算出五个修正量,将这些修正量带入传声器阵列的声成像算法中即可实现传声器阵列的声－光偏离校准.实验结果表明该方法的误差度为0.12°,在允许的0.2°范围之内,可以作为传声器阵列声像图和视频图偏离校准的一般方法.     

基于数字相关型全极化微波辐射计的灵敏度分析

灵敏度是表征微波辐射计能够检测到最小亮温变化的能力,是微波辐射计一项重要指标.本文针对数字相关型全极化微波辐射计,提出了一种使用相关器输出的计数值计算各通道灵敏度的方法,并通过了实验验证.对比模拟通道灵敏度和数字通道灵敏度,分析了量化噪声和通道间串扰对灵敏度的影响.     

智能电能表校验过程中报警代码分析与判断

本文主要针对智能电能表校验过程进行简介,论述了在校验过程中对报警代码的分析与判断.     

变压器差动保护平衡系数的矢量分析

平衡系数作为变压器差动保护中的一个重要数据,在保护差流计算、保护装置校验过程中起着关键的作用.所以,对于平衡系数的准确理解和计算,关系到差流计算和保护校验的准确性.文中采用矢量分析的方法直观简明,方便了一线员工的计算分析.     

智能电能表现场校验方法与细节问题分析

作为坚强智能电网的重要组成部分,智能电能表集测量、通信以及微电子等技术于一体.智能电能表和传统电能表相比,对于智能电能表现场校验方面的电能计量专业人员已经提出了更加严格的要求.为此,掌握智能电能表现场校验方法,重视其细节问题极为重要,相关单位必须给予高度重视.本文主要针对智能电能表现场校验方法与细节问题展开深入剖析,旨在确保智能电能表的作用能够被充分的发挥出来.     

无线电导航信标台校验关键要素研究

针对无线电导航信标台校验的实现难点,提出了以GPS RTK为导航定位基准,以综合导航接收机为导航信号处理平台的校验方案.研究了不同导航坐标系下的校验参量统一问题,得到了极坐标导航定位体制的斜距和相对磁方位角校验方法,以及时间基准波束扫描体制的方位角、仰角和反方位角的校验方法.     

数字电能计量系统现场检定要点分析

传统的变电站已经不符合如今的使用要求,数字化变电站已经在目前得到了普遍使用.数字化变电站主要是由高新技术产品组成的,因此在对于数字化变电站进行现场校验时,传统的校验方法显然已经不能只用.对此,本文主要针对于数字电能计量系统的现场检定方法和技术要点做出了相应的分析,希望能够解决目前检定中存在的问题.     

The Sensitivity Function in Variability Analysis

Methods of variability analysis include deterministic approaches, e.g., ``worst case' methods, ``Shmoo Plots,' and probabilistic approaches (Monte Carlo and Moment methods). Most of these use as a point of departure the Taylor Series expansion of the performance function about the nominal operating point with all but first-order terms neglected. The coefficients of the series are the partial derivatives of the performance function with respect to the components evaluated at the nominal operating point. These derivatives when properly normalized become the sensitivity functions used extensively in the study of feedback systems. The purpose of this paper is to bring together various results concerning sensitivity which are of direct use in variability analysis. One of the most useful of these is a relation concerning sensitivity sums which furnishes a valuable check on sensitivity calculation for homogeneous functions. Enough errors have been noted in recent literature to indicate that use of this check should become a routine part of variability analysis wherever it is applicable. Also included are applications to pole-zero sensitivity of electrical networks.     

脉冲激光测距仪灵敏度与消光比研究

本文直接采用模拟测距的消光比测试方法来检测脉冲激光测距仪的灵敏度,可以有效地排除远距离测距中气象差异的影响和地形条件的限制。通过对测试数据的分析并与测距能力相比较表明,本文提出的检测方法是有效的。     

基于PEG算法的QC-LDPC码构造

提出一种QC-LDPC码的构造方法,这种方法利用受约束的PEG算法构造一个符合给定度分布的LDPC码基矩阵,能够保证构造出来的LDPC码短环的数量比较少,且具有线性时间编码.该方法在基矩阵的基础上利用缩短RS码集合的构造方法得到对应位置的偏移地址,以保证所构造的LDPC码的最小码距.最后给出构造的QC-LDPC码与DV...     

基于移位矩阵优化的LDPC码构造

环的存在对准循环LDPC（Low Density Parity Code）码的译码效率造成很大影响,拥有尽可能好的girth分布的校验矩阵对于码的性能改善有着重要的意义。首先对准循环LDPC码校验矩阵的girth分布进行分析,然后在母矩阵和移位矩阵之间设定一个合理的约束关系,使得构造后的校验矩阵最小环长及平均最小环长追求最大化,最后提出了一种易于实现的具有高girth的QC-LDPC（Quasi cyclic-Low Density Parity Code）码构造方法。仿真结果表明,该方法尽量减少码中的短循环,能构造实用化的好码。     

Design of Quasi‐Cyclic Low‐Density Parity Check Codes with Large Girth

In this paper we propose a graph‐theoretic method based on linear congruence for constructing low‐density parity check (LDPC) codes. In this method, we design a connection graph with three kinds of special paths to ensure that the Tanner graph of the parity check matrix mapped from the connection graph is without short cycles. The new construction method results in a class of (3, ρ)‐regular quasi‐cyclic LDPC codes with a girth of 12. Based on the structure of the parity check matrix, the lower bound on the minimum distance of the codes is found. The simulation studies of several proposed LDPC codes demonstrate powerful bit‐error‐rate performance with iterative decoding in additive white Gaussian noise channels.     

The construction method of stabilizer codes for continuous variables

The paper analyzes the basic principles of stabilizer codes, focusing on how to construct stabilizer codes for achieving the continuous-variable quantum error correction. Stabilizer codes can be used in the reconciliation of continuous-variable quantum key distribution system. The construction method of stabilizer codes is very important and it can be turned into finding the check matrix for stabilizer codes. In this paper, a new algorithm called region elimination algorithm for finding the check matrix of stabilizer codes was presented which can seek the voluntary check matrix for continuous-variable stabilizer codes within 8 bit code length quickly and effectively, and it was simulated by Visual C++. The algorithm is mainly realized by initializing search region, reducing the search region and then keeping searching till finding all the commuting generators. The finding of check matrix of stabilizer codes lays important foundations for the further development of stabilizer codes in the continuous-variable quantum key distribution.     

进程完整性及其在软件漏洞检测中的应用

文中提出了一种进程完整性的度量方法,并应用于软件漏洞的检测。该方法利用源码转换和函数调用时的状态信息来实现进程完整性的检测与分析,通过检查进程在运行过程中的完整性度量是否保持为真,来判断进程是否存在漏洞。实验结果表明,这种方法能够在不带来大的性能损失的情况下准确地检测出缓冲区溢出漏洞。     

基于长边缘相关和一致性检测的多传感器图像配准方法

遥感图像的配准特别是当波段相距较远的图像间配准时,由于其相关性小,直接提取的边缘特征中不一致特征所占比例很大,此时直接应用partialHausdorff距离等方法配准往往失效。本文提出了一种基于长边缘相关的图像配准方法,首先对长边缘进行相关计算,然后在相关长边缘的基础上对其余的边缘进行一致性检测。极大提高了边缘特征的一致性。长边缘相关是在比较HuiLi的相关方法基础上提出的改进Freeman链码相关系数方法。一致性特征检测方法是基于V.Randrianarisoa的检测方法并对之进行了改进。最后对一致边缘的相关部分使用最小二乘法得到了配准参数。仿真实验表明本方法对长边缘丰富的图像有很好的配准结果。并且本方法具有配准速度快的优点。     

一种基于BIBD的量子LDPC码构造新方法

利用均衡不完全区组设计(Balance Imcomplete Block Designs,BIBD)的半结构化低密度奇偶校验(Low Density Parity Check,LDPC)码设计方法,该文提出了一种获得自对偶CSS(Calderbank-Shor-Steane)式的量子LDPC码的校验矩阵的新构造方法。由于构造出的量子码校验矩阵稀疏,有且仅有一个4环(girth 4),在置信传播迭代译码算法下可获得良好的性能。数值计算结果表明,对于该构造方法得到的GF(6t+1)和GF(12t+1)量子LDPC码,比基于BIBD的其他构造方法所得到的量子码的码长更长、量子校验矩阵更加稀疏、性能也更加优越。     

A computer-aided diagnosis for locating abnormalities in bone scintigraphy by a fuzzy system with a three-step minimization approach

Bone scintigraphy is an effective method to diagnose bone diseases such as bone tumors. In the scintigraphic images, bone abnormalities are widely scattered on the whole body. Conventionally, radiologists visually check the whole-body images and find the distributed abnormalities based on their expertise. This manual process is time-consuming and it is not unusual to miss some abnormalities. In this paper, a computer-aided diagnosis (CAD) system is proposed to assist radiologists in the diagnosis of bone scintigraphy. The system will provide warning marks and abnormal scores on some locations of the images to direct radiologists' attention toward these locations. A fuzzy system called characteristic-point-based fuzzy inference system (CPFIS) is employed to implement the diagnosis system and three minimizations are used to systematically train the CPFIS. Asymmetry and brightness are chosen as the two inputs to the CPFIS according to radiologists' knowledge. The resulting CAD system is of a small-sized rule base such that the resulting fuzzy rules can be not only easily understood by radiologists, but also matched to and compared with their expert knowledge. The prototype CAD system was tested on 82 abnormal images and 27 normal images. We employed free-response receiver operating characteristics method with the mean number of false positives (FPs) and the sensitivity as performance indexes to evaluate the proposed system. The sensitivity is 91.5% (227 of 248) and the mean number of FPs is 37.3 per image. The high sensitivity and moderate numbers of FP marks per image shows that the proposed method can provide an effective second-reader information to radiologists in the diagnosis of bone scintigraphy.