基于分段信号假设检验的方差估计算法

针对传感器测量噪声变化导致加权数据融合精度下降的问题,提出一种新的方差估计算法.方差估计采用自适应移动数据窗,窗口长度由多元假设检验的结果决定.假设检验环节首先应用信号分段处理方法与中心极限定理,使得检验统计量满足正态分布,简化了后续计算与理论推导.然后根据马尔可夫状态转移理论和最大后验概率准则,实现测量噪声方差变化的快速检测.通过与典型算法的仿真对比,验证所提算法克服了典型方法的局限性,能够保证加权数据融合具有更高精度.     

Distributing test cases more evenly in adaptive random testing

Adaptive random testing (ART) has recently been proposed to enhance the failure-detection capability of random testing. In ART, test cases are not only randomly generated, but also evenly spread over the input domain. Various ART algorithms have been developed to evenly spread test cases in different ways. Previous studies have shown that some ART algorithms prefer to select test cases from the edge part of the input domain rather than from the centre part, that is, inputs do not have equal chance to be selected as test cases. Since we do not know where the failure-causing inputs are prior to testing, it is not desirable for inputs to have different chances of being selected as test cases. Therefore, in this paper, we investigate how to enhance some ART algorithms by offsetting the edge preference, and propose a new family of ART algorithms. A series of simulations have been conducted and it is shown that these new algorithms not only select test cases more evenly, but also have better failure detection capabilities.     

模数转换器应用电路中的常见问题及解决方案

详细介绍了在设计模数转换器应用电路中遇到的常见问题及解决方案,有利于读者更好的设计应用电路。     

Design of test inputs and their sequences in multi-function system testing

This discussion paper addresses combinatorial models in system testing from the perspective of system usage (utilization) and corresponding examination of system functions and their groups. Thus the following aspects of multi-function system testing are under study: analysis of system requirements and revelation of atomic system functions and their relationships, analysis of system function groups (clusters), design of the most important test inputs and sequences of the test inputs. The basic combinatorial problem is: composition of the best (the most important) test input(s) for each group of atomic system functions. Additional combinatorial problems are the following: (a) design of test input sequence for a trail (chain) of function clusters, (b) design of collection of test input sequences as covering of function cluster digraph, (c) structural fusion of unit test results. Numerical and real world examples illustrate the proposed approach. Mark Sh. Levin received the M.S. degree in Radioengineering from Moscow Techn. Univ. for Communication and Informatics (1970), the M.S. degree in Mathematics from ‘Lomonosov’ Moscow State Univ. (1975), the Ph.D. degree in Systems Analysis and Combinatorial Optimization from Inst. for System Analysis of Russian Acad. of Sci. (1982). His research interests include systems engineering, decision making, combinatorial optimization, and applications. Currently Dr. Levin is with Inst. for Inform. Transmission Problems of Russian Acad. of Sci. (Moscow) as a Senior Research Scientist. He is a member of ACM, IEEE, SIAM, Int. Soc. on MCDM, Int. Soc. of Appl. Intel., and OR Society of Israel. Mark Last received his Ph.D. degree in Industrial Engineering from Tel Aviv Univ. (2000). Dr. Last is a faculty member at Dept. of Information Systems Engineering of Ben-Gurion Univ. (Israel) and affiliated as a visiting faculty at National Inst. for Systems Test and Productivity (Univ. of South Florida, USA). His research interests include information systems, knowledge discovery and data mining, fuzzy sets and fuzzy logic, and software testing. He is a member of IEEE Computer Society and ACM.     

Effects of computer-based testing on test performance and testing motivation

Computer-based testing (CBT) is a green computing strategies used to reduce paper consumption. However, some scholars have questioned the effectiveness of CBT and suggested for conducting systematic studies on CBT to carefully check its reliability and validity before opting for it. Recently, some studies have evaluated the effectiveness of CBT by comparing it with paper–pencil testing (PPT), and the findings were inconsistent. Besides this, most of these studies have been conducted using quasi or basic experimental designs without identifying testing effects on test takers. The limitation of these design is testing effects might occur when a participant in the control or treatment group is tested at least twice on a same test, and it influences the outcomes of taking a posttest, therefore, the findings might be misinterpreted. This study employed a Solomon four-group experimental design (2 × 3 factorial design) on a group of student teachers (n = 140) to compare CBT and PPT on test performance (test scores), testing time and testing motivation. Results indicated that the CBT mode is more reliable in terms of internal and external validity. The CBT significantly reduced testing time and developed stronger self-efficacy, intrinsic and social testing motivation in the participants.     

基于USB的实时心音信号采集系统

设计了一款基于USB的心音信号采集系统。该系统包括心音采集电路、USB通信和上位机显示。通过心音传感器将采集到的数据进行放大去噪处理,经由A/D转换通过USB将数据传送到上位机,并以波形的形式实时显示采集到的数据。该系统可以准确、实时地显示并听到采集到的心音信号。     

On the estimation of adequate test set size using fault failure rates

Test set size in terms of the number of test cases is an important consideration when testing software systems. Using too few test cases might result in poor fault detection and using too many might be very expensive and suffer from redundancy. We define the failure rate of a program as the fraction of test cases in an available test pool that result in execution failure on that program. This paper investigates the relationship between failure rates and the number of test cases required to detect the faults. Our experiments based on 11 sets of C programs suggest that an accurate estimation of failure rates of potential fault(s) in a program can provide a reliable estimate of adequate test set size with respect to fault detection and should therefore be one of the factors kept in mind during test set construction. Furthermore, the model proposed herein is fairly robust to incorrect estimations in failure rates and can still provide good predictive quality. Experiments are also performed to observe the relationship between multiple faults present in the same program using the concept of a failure rate. When predicting the effectiveness against a program with multiple faults, results indicate that not knowing the number of faults in the program is not a significant concern, as the predictive quality is typically not affected adversely.     

小波变换在奇异信号检测中的应用

介绍了小波变换的基本概念，阐述了小波变换的奇异性和信号变化剧烈处的关系。通过对实际信号的处理，表明该方法在奇异信号检测和局部化分析方面具有优异特性。     

Independent testing of compiler phases using a test case generator

Since a compiler phase depends on previous phases for input, it can be difficult to do timely independent unit testing of some phases. This can make integration more difficult and reduce overall quality. A test case generator has been used to circumvent this problem by providing an independent source of phase test inputs. Using a context-free grammar augmented with contextsensitive constructs, a test case generator can generate intermediate language graphs in textual form.     

模糊免疫算法及其在金属磁记忆检测中的应用

将模糊聚类算法原理引入到免疫算法中,形成无监督学习的模糊免疫算法,并基于该算法建立起智能分析模型,对金属磁记忆检测信号特征进行分析。实验表明,基于该算法建立的模型对实验材料的状态识别能够达到较高的准确率。     

The automated generation of test cases for compilers

The testing of a compiler is a difficult process, since often a very high quality product is expected by the user, particularly with respect to the compiler's correctness. This paper seeks to review the main methods that have been proposed for the automation of part of this process, using the automatic generation of test cases and the automatic checking of the results. It then summarizes the advantages and disadvantages of the general approach and highlights several areas for further research.     

一种LFM信号参数估计的新方法

提出了基于降维处理的LFM信号参数估计新方法。其基本思路是对信号进行数学变换,将LFM信号的中心频率估计转换为对正弦信号频率的估计,得中心频率估计值;基于解线性调频处理并对信号进行对应中心频率处的单值点DFT得到单值幅度谱,进而得到调频斜率估计值。新方法在较低的计算复杂度下,能获得较高精度的参数估计值。计算机仿真结果表明了该方法的有效性。     

Effects of window size and load on estimated myoelectric signal power spectrum

The main objective of this study was to investigate the effects of window size on estimated surface myoelectric signal (MES) parameters in frequency domain. Seven healthy male subjects participated in this study. All subjects were required to perform a sustained isometric muscle contraction corresponding to 25, 50 and 100% of the Maximum Voluntary Contraction (MVC). MES was recorded by surface electrodes for a period of 6 s. Seven different window sizes (64, 128, 256, 512, 1024, 2048, and 4096 ms) were used to estimate the power spectrum. The results obtained showed that the window size has a significant effect on the estimated characteristic frequencies of the power spectrum. The minimum window size that can be used to estimate the power spectrum was found to be 0.5 seconds. The loading level was found to have a significant effect on the frequency domain characteristics. It was observed that the frequencies below the 75th fractile tend to shift upward as the load increases. The upward shift in higher frequencies (≥75th fractile) was reversed as the load reached MVC, which indicates that during a constant isometric contraction the shape of the spectrum changes as the force level is increased. The results obtained in this study show that the use of a single spectral variable such as the median frequency may not be sufficient for capturing all the spectral modifications of the MES.     

多径软扩频信号伪码周期盲估计

针对多径信道下因多径衰落造成软扩频信号伪码周期难以估计的问题,提出了一种基于二次功率谱的多径软扩频信号伪码周期盲估计方法。首先,将一般的单径软扩频信号扩展到多径模型;然后,在多径软扩频信号模型的基础上计算信号的一次功率谱;其次,将求出的一次功率谱作为输入信号计算信号的二次功率谱,理论分析表明信号的二次功率谱在伪码周期整数倍处将会出现峰值谱线;最后,通过检测峰值谱线间的间距就可以实现多径软扩频信号的伪码周期估计。通过仿真实验表明,在伪码周期估计正确率为100%、伪码序列长度为127位和255位时,所提方法比时域相关法提高信噪比约1 dB和2 dB;在同一对比条件下,所需要的平均累加次数均少于时域相关法。实验结果表明,所提方法对伪码周期进行估计,在减少计算量的同时,还提高了估计的正确率。     

Stability analysis of periodic orbit of an adaptive notch filter for frequency estimation of a periodic signal

Online frequency estimation of a sinusoidal signal is a classical problem and has many practical applications. Recently an adaptive notch filter (ANF) with global convergence property has been developed for frequency estimation of a pure sinusoidal signal. This paper addresses a modified ANF structure that can estimate the fundamental frequency of any periodic signal including pure sinusoidal signals. To prove the stability of the modified ANF, the paper introduces a new theorem that shows for any periodic signal, there exists a locally asymptotically stable periodic orbit of this ANF by which the frequency estimation becomes feasible. This alternative stability proof is simple and uses widely known mathematical tools, and therefore alleviates the problem complexity even when the input signal is a pure sinusoidal signal. A further contribution of this paper is obtaining a necessary and sufficient condition in terms of design parameters for local asymptotical stability of the modified ANF. This condition, obtained from the numerical study of Floquet multipliers of a linear time-varying periodic system, provides a strict stability region in the modified ANF design parameters space.     

Robust detection of sensor faults by means of a statistical test

The problem of detecting sensor faults in the presence of modelling errors is addressed. In order to avoid false alarms, a statistical test is proposed in which the effects of undermodelling are properly taken into account using a stochastic embedding technique. The test concentrates on checking whether a weighted sum of prediction errors exceeds a particular threshold. The effectiveness of the test is demonstrated on a laboratory test rig.     

回归测试中测试用例集优化方法的研究

回归测试是软件演化过程中频繁进行的且开销巨大的一项任务,测试用例集的优化程度直接影响着测试的成本和效率。针对回归测试过程的特点,提出一种对测试用例集优化的新方法,即通过对测试用例集进行必要的消除冗余和调整排序,完成了对初始测试用例集的精简以及执行顺序的确定过程,使得有限的测试资源得到科学合理的分配。实验结果表明,相对于以往的测试用例集优化方法,新方法的效率和资源分配的合理性均有了显著的提高。     

多阶微分采样及其在高速ADC系统中的应用

首先阐明了多阶微分采样的原理,给出了更为简洁的完美重构条件。然后根据该条件导出了多阶微分采样完美重构滤波器组的频谱响应和理想的冲激响应。时理想滤渡器的冲激响应进行了延迟、截断和加窗来得到可实现的有限冲激（FIR）重构滤波器组,从而实现了高速的多阶微分采样型ADC系统。理论分析和仿真结果说明本文设计的重构滤波器组可以对多阶微分采样进行很好的重构,整个系统信纳比（SINAD）平均可迭83．3dB,无伪波动态范围（SFDR）平均达102．7dB。     

基于LabVIEW的简支梁振动信号测试分析系统

为了改进振动工程测试实验,改善教学方法,提高实验效果,基于LabVIEW开发了一种针对简支梁的振动信号测试分析系统。下位机采用具有丰富片上资源、较高数据处理能力的C8051F350单片机进行振动数据的采集,并通过RS—232串口与上位机通信,实现信号数据的传输;上位机软件开发基于功能强大的图形化编程虚拟仪器LabVIEW开发平台,完成振动数据采集的实时显示、并对其进行时域、频域分析和数据存储等功能。实际应用证明该系统稳定、可靠,满足实验要求,将LabVIEW应用于实验教学中,大大提高了学生的学习兴趣,达到了提高实验效果和教学质量的目的。     

低信噪比OFDM信号符号周期盲估计

针对认知无线电系统中正交频分复用(OFDM)信号参数估计这一重要问题,利用OFDM信号的循环谱实现了符号周期的盲估计。首先证明了加循环前缀矩形脉冲成型的OFDM信号具有循环平稳性,然后分别在无噪声和低信噪比条件下,以单载波信号的循环谱为基础,利用OFDM信号各子载波的正交性,从理论上推导出了OFDM信号的循环谱表达式。最后通过对连续信号和离散信号进行仿真,得到了相同的循环谱图,并且在低信噪比条件下,利用循环谱实现了OFDM信号符号周期的盲估计。