卡尔曼滤波器在传感器软故障诊断中的应用

传感器发生软故障的特征是变化缓慢、不易检测。为克服传感器检测这一缺点设计了一种软故障诊断算法。该算法是在多重故障假设基础上,使用卡尔曼滤波器产生残差,采用加权二乘方（Weighted Sum of Squared Residuals,WSSR）方法对滤波残差进行处理,从而方便快速地检测出传感器的软故障,并实现隔离和重构。仿真实验表明,算法能很好地实现传感器软故障的检测、隔离和重构,不会发生误报和漏报现象。     

IP网络故障诊断与排除方法探讨

介绍IP网络的开放系统互连参考模型OSI,详细描述IP网络故障诊断技术、诊断流程和分层诊断技术,论述网络故障排除的一般步骤,探讨网络光缆故障的诊断方法和IP网络路由交换机设备常用接口故障的排除方法,为提高网络故障诊断水平打下结实基础,保证网络可靠运行.     

面向磁盘故障预测的机器学习方法比较

磁盘是保存数据的重要载体,提高磁盘的可靠性和数据可用性具有重要意义。现代磁盘普遍支持SMART协议,用来监控磁盘的内部工作状态。采用机器学习方法,分析磁盘的SMART信息,实现对磁盘故障的预测。所采用的机器学习方法包括反向神经网络、决策树、支持向量机以及简单贝叶斯,并采用实际磁盘SMART数据进行验证与分析。基于上述数据,对不同机器学习方法的有效性及其效果进行了对比。结果表明,决策树方法的预测率最好,支持向量机方法的误报率最低。     

Dogmas in the assessment of usability evaluation methods

Usability evaluation methods (UEMs) are widely recognised as an essential part of systems development. Assessments of the performance of UEMs, however, have been criticised for low validity and limited reliability. The present study extends this critique by describing seven dogmas in recent work on UEMs. The dogmas include using inadequate procedures and measures for assessment, focusing on win–lose outcomes, holding simplistic models of how usability evaluators work, concentrating on evaluation rather than on design and working from the assumption that usability problems are real. We discuss research approaches that may help move beyond the dogmas. In particular, we emphasise detailed studies of evaluation processes, assessments of the impact of UEMs on design carried out in real-world systems development and analyses of how UEMs may be combined.     

The influence of failure criteria on the design optimization of stacked-ply composite flywheels

This paper presents some approaches to the optimal design of stacked-ply composite flywheels. The laminations of the disk are constructed such that the principal fiber direction is either tangential or radial. In this study, optimization problems are formulated to maximize the energy density of the flywheel. This is accomplished by allowing arbitrary, continuous, variation of the orientation of the fibers in the radial plies. The paper compares designs based on minimizing cost functions related to the (1) the maximum stress, (2) the maximum strain, and (3) the Tsai–Wu failure criteria. It is shown that the optimized designs provide an improvement in the flywheel energy density when compared to a standard stacked-ply design. The results also show that, for a given disk design, the estimate of the energy density can vary greatly depending on the failure criteria employed.     

Effect of seed layer stress on the fabrication of monolithic MEMS microstructure

This paper reported the effect of seed layer stress on the fabrication of monolithic polymer-metal MEMS microstructure and what is a better material for the seed layer. The monolithic microstructure is gaining more and more attentions in MEMS application, especially in three-dimensional microstructure and inkjet printhead. The polymer–metal MEMS microstructure can be fabricated by combining the lithography and electroforming technologies. It is an integrated technology by batch process at low cost. The metal seed layer with large stress will lead to cracks and failure during the process integration. Several metal materials and thicknesses were studied to find a better candidate as the seed layer for the monolithic MEMS microstructure. The relationship between the monolithic MEMS structure and seed layer selection is also discussed. The lower residual stress of seed layer will result in a better surface condition for the followed integration process. The pure Ti metal and two-layer Ti/Au composite are the better seed layer materials in this study for the followed electroforming process of the monolithic polymer-metal MEMS microstructure.     

Estimation of failure rate using random and partition testing

Failure rate, given an operational profile, is a common measure of reliability. A number of approaches to estimating failure rate are described and it is demonstrated that, under certain conditions, a functional partition can provide a better estimator than random-testing-based estimators. © 1997 John Wiley & Sons, Ltd.     

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.     

Effects of microstructure of films on CVD diamond X-ray detectors

Although the unique properties of chemical vapor deposition (CVD) diamond films have made it a candidate material for radiation detectors, the polycrystalline nature of the films has severely limited the development of CVD diamond detectors. In this work, three CVD diamond films with different microstructure were grown by using a hot-filament chemical vapor deposition (HFCVD) technique and were fabricated as CVD diamond detectors. The electric contact is good ohmic for bias voltage up to 150 V. 5.9 keV ⁵⁵Fe X-ray was used to measure the photocurrent and the pulse height distribution (PHD). For the detector based on the best quality film, the dark-current of 16.0 nA and the net photocurrent of 15.9 nA are obtained at an electric field of 50 kV cm⁻¹. The PHD peak is well separated from the noise pedestal, indicating a high counting efficiency and a low detection limit.     

Applying asynchronous parallel characteristic methods for solving systems of hyperbolic PDEs

We propose asynchronous parallel algorithms for numerically solving systems of hyperbolic partial differential equations. The algorithms are based on the solutions along the characteristic directions. We show that the characteristic directions can be computed in parallel without the need for sharing information or synchronizing on a common time step. This permits the development of efficient asynchronous parallel algorithms. Our solutions cover the cases when the characteristic lines are intersected to form shock waves. We discuss the time performance of our algorithms as well as their implementation on a parallel computer.Supported by the R&D administration of the Ministry of Defense and the Ministry of Immigration Absorption, Israel.     

Influence of the phase diagram on the diffuse interface thickness and on the microstructure formation in a phase-field model for binary alloy

A phase-field model is used to investigate the responses of planar interfaces and of eutectic microstructures on the different shapes of the phase diagram in binary alloy systems. Numerical solutions of the dynamic field equations show that the interfacial profile and the thickness of the diffuse boundary layer depend on the segregation of the alloy components. The simulations are presented for different openings of binary phase diagrams. A strong influence of the phase diagram on the evolution of eutectic microstructures is found and quantitatively evaluated by defining an appropriate measure. The results are interpreted in terms of weighting the different contributions in the phase-field equation.     

A comparison of usability evaluation methods for evaluating e-commerce websites

The importance of evaluating the usability of e-commerce websites is well recognised. User testing and heuristic evaluation methods are commonly used to evaluate the usability of such sites, but just how effective are these for identifying specific problems? This article describes an evaluation of these methods by comparing the number, severity and type of usability problems identified by each one. The cost of employing these methods is also considered. The findings highlight the number and severity level of 44 specific usability problem areas which were uniquely identified by either user testing or heuristic evaluation methods, common problems that were identified by both methods, and problems that were missed by each method. The results show that user testing uniquely identified major problems related to four specific areas and minor problems related to one area. Conversely, the heuristic evaluation uniquely identified minor problems in eight specific areas and major problems in three areas.     

Effect of numerical integration on meshless methods

In this paper, we present the effect of numerical integration on meshless methods with shape functions that reproduce polynomials of degree k1. The meshless method was used on a second order Neumann problem and we derived an estimate for the energy norm of the error between the exact solution and the approximate solution from the meshless method under the presence of numerical integration. This estimate was obtained under the assumption that the numerical integration scheme satisfied a form of Green’s formula. We also indicated how to obtain numerical integration schemes satisfying this property.     

Robustness of Fourier estimator of integrated volatility in the presence of microstructure noise

The finite sample properties of the Fourier estimator of integrated volatility under market microstructure noise are studied. Analytic expressions for the bias and the mean squared error (MSE) of the contaminated estimator are derived. These formulae can be practically used to design optimal MSE-based estimators, which are very robust and efficient in the presence of noise. Moreover an empirical analysis based on a simulation study and on high-frequency logarithmic prices of the Italian stock index futures (FIB30) validates the theoretical results.     

软件可靠性测试的加速机理研究

从软件的失效机理出发,对比硬件失效分析了软件失效的特性,结合软件测试的机理,阐述了软件可靠性测试的机理,并在此基础上研究了软件可靠性测试存在加速的可能性,提出了实现加速的思想和方法。     

Silicon anisotropic etching in alkaline solutions II on the influence of anisotropy on the smoothness of etched surfaces

Experiments were carried out with anisotropic etching of Si(100) in alkaline solutions from the point of view of surface quality. The circumstances needed to obtain surfaces of various level of smoothness were established. The problem why etched surface is of mirror-like quality, texturized, i.e., covered on the whole with random inequality (sometime of pyramids shape) as well ones covered with single separated hillocks is discussed in the term of anisotropy. Some analogies between random texturizing, obtaining the hillocks and etching through a patterned SiO₂ mask were stated.     

Modeling the influence of individual and employment factors on musculoskeletal disorders in fabrication industry

This study was designed to identify the individual and employment factors that influence highly frequent, less severe self‐reported musculoskeletal disorder pain incidences among welders. A self‐reporting questionnaire to measure two individual factors (age and experience), six employment factors (physical workload, working hours, shift work, nature of employment, mode of apprenticeship training, and association with present employer), along with a modified Nordic questionnaire response sheet was used to collect data. The survey was conducted among welders employed in a fabrication cluster in a southern part of India. A total of 987 completed questionnaires (response rate: 66%) were analyzed using the SPSS program. The analysis showed that two employment factors, “shift work” and “mode of apprenticeship training” significantly influence self‐reported musculoskeletal disorder pain. The mode of apprenticeship training was found to influence musculoskeletal disorder pain in the neck region for annual prevalence and causes annual disability in neck and upper back regions. Similarly, shift work was found to influence musculoskeletal disorder pain in the shoulder and neck regions for weekly and annual prevalence and causes annual disability in shoulder, wrist/hands, upper back, and hip/thigh/buttock regions among welders. These factors can be considered as points for targeting intervention efforts.     

浅谈软件测试技术

随着计算机的普及,软件系统已经深入到生活的各个方面,从普通的计算机软件,到银行或超市的终端系统,甚至到手机的软件系统。对软件质量的要求也在不断提高,但现实中软件系统的质量和稳定性却不尽人意,不论采用什么技术和什么方法,软件中仍然会有错误存在。在对软件测试技术相关基本概念研究解析的基础上,分析了软件测试起源与发展,保证软件产品的质量、提高产品的可靠性。     

Mechanical loading on the low back in three methods of refuse collecting

The mechanical loading on the low back was studied in three different current methods of refuse collecting: in polythene bags, two-wheeled mini-containers and large four-wheeled containers. To this end the most prominent activities of each collecting method were performed in a laboratory. On the basis of movement analysis, force measurements and biomechanical modelling, spinal compressive and shear forces were estimated. From these forces and from the frequency of activities during the working day (assessed in a preliminary field study) the low-back stress in each collecting method was evaluated. In the bag-method, peak forces when throwing the bags ranged from 3341 to 5179?N (average compression) and from 284 to 673?N (shear) among the different conditions studied. The act of picking up bags also showed rather high forces (exceeding the NIOSH limit for disc compression in most cases). The frequency of exposure to these forces in the field is rather high (workers pick up and throw on average 807 times each day). The mini-container method compares favourably to the bags method. Peak compressive and shear force in tilting/pushing and pulling mini-containers ranged from 1657 to 2654?N and from 123 to 248?N respectively. Also, the frequency of stressful events in the Held is lower in this method. In the large container method extremely high peak forces (e.g. compression ranged from 4991 to 5810N) were observed in the task of putting the empty container back from street level to sidewalk level (surmounting the kerb). The frequency of activities like pushing, pulling and lifting the large container in the field is much lower compared with activities in the other methods. On the basis of the frequency and magnitude of spinal forces it was concluded that the mini-containers should be preferred to the bags. If kerbs are removed at container places and tasks are performed by two instead of a single person, the large container method would form another good alternative to the stressful task of collecting refuse in bags.     

独立故障串并联控制系统可靠性的最优化研究

研究了独立故障的串并联复式控制系统在单个或多个约束条件下的可靠性最优化问题。从系统的物理概念出发,提出了一种混合方法。按照连续变量平衡提高各级串联环节的可靠性,分析得出了在约束条件下各个环节的并联个数的计算公式和简化计算思路。