接地网故障诊断的数学模型

接地网是变电站安全运行的重要保证,其故障诊断是电力部门十分关注的问题.为了给接地网的故障诊断提供有效的指导,本文对接地网网格导体电阻分布的数学模型进行了深入研究.基于电网理论,借助最小电能消耗原理建立了模拟接地网电阻分布的数学模型.进一步使用全局寻优方法获得其真实电阻分布值,并通过与原始值比较可以判断故障点.仿真计算表明本文所给出的数学模型是可行的,对于接地网故障诊断具有较好的指导作用.     

智能网SCP的两级软件容错策略研究

指出了目前ＳＣＰ在实现方面存在的缺陷，针对其结构和运行机制，提出其软件具有系统级与呼叫级的两级并发性，并基于这个两级并发模型对它的软件容错途径进行了深入的探讨与研究。首次提出了应用软件出错情况下保证所有在线呼叫可靠处理的容错目标，并在ＳＣＰ系统级与呼叫级两个并发层次上给出了切实有效的容错策略或算法。最后对ＳＣＰ软件系统有效度的估算进行了进一步讨论。     

关于电梯安全装置常见故障与排除方法的讨论

安全装置是电梯正常运行的保证,本文简要分析了电梯安全装置在运行过程常见的一些故障及排除方法.     

WiFi6 Dynamic Channel Optimization Method for Fault Tolerance in Power Communication Network

As the scale of power networks has expanded, the demand for multi-service transmission has gradually increased. The emergence of WiFi6 has improved the transmission efficiency and resource utilization of wireless networks. However, it still cannot cope with situations such as wireless access point (AP) failure. To solve this problem, this paper combines orthogonal frequency division multiple access (OFDMA) technology and dynamic channel optimization technology to design a fault-tolerant WiFi6 dynamic resource optimization method for achieving high quality wireless services in a wirelessly covered network even when an AP fails. First, under the premise of AP layout with strong coverage over the whole area, a faulty AP determination method based on beacon frames (BF) is designed. Then, the maximum signal-to-interference ratio (SINR) is used as the principle to select AP reconnection for the affected users. Finally, this paper designs a dynamic access selection model (DASM) for service frames of power Internet of Things (IoTs) and a scheduling access optimization model (SAO-MF) based on multi-frame transmission, which enables access optimization for differentiated services. For the above mechanisms, a heuristic resource allocation algorithm is proposed in SAO-MF. Simulation results show that the method can reduce the delay by 15% and improve the throughput by 55%, ensuring high-quality communication in power wireless networks.     

Fine-Grained Binary Analysis Method for Privacy Leakage Detection on the Cloud Platform

Nowadays cloud architecture is widely applied on the internet. New malware aiming at the privacy data stealing or crypto currency mining is threatening the security of cloud platforms. In view of the problems with existing application behavior monitoring methods such as coarse-grained analysis, high performance overhead and lack of applicability, this paper proposes a new fine-grained binary program monitoring and analysis method based on multiple system level components, which is used to detect the possible privacy leakage of applications installed on cloud platforms. It can be used online in cloud platform environments for fine-grained automated analysis of target programs, ensuring the stability and continuity of program execution. We combine the external interception and internal instrumentation and design a variety of optimization schemes to further reduce the impact of fine-grained analysis on the performance of target programs, enabling it to be employed in actual environments. The experimental results show that the proposed method is feasible and can achieve the acceptable analysis performance while consuming a small amount of system resources. The optimization schemes can go beyond traditional dynamic instrumentation methods with better analytical performance and can be more applicable to online analysis on cloud platforms.     

Electrochromic Systems and the Prospects for Devices

Many inorganic and organic materials exhibit redox states with distinct electronic (UV‐vis) absorption bands. When the switching of redox states generates new or different visible region bands, the material is electrochromic. Electrochromic materials are currently attracting much interest in academia and industry for both their fascinating spectroelectrochemical properties and their commercial applications. In this review some of the most important examples from the major classes of electrochromic materials are highlighted. Examples of their use in both prototype and commercial electrochromic devices are illustrated including car mirrors, windows and sun‐roofs of cars, windows of buildings, displays (see Figure), printing, and frozen‐food monitoring.     

Recursive algorithm for phase retrieval in the fractional fourier transform domain

We first discuss the discrete fractional Fourier transform and present some essential properties. We then propose a recursive algorithm to implement phase retrieval from two intensities in the fractional Fourier transform domain. This approach can significantly simplify computational manipulations and does not need an initial phase estimate compared with conventional iterative algorithms. Simulation results show that this approach can successfully recover the phase from two intensities.     

图象序列中检测运动小目标的递归算法

分析了一种基于卡尔曼滤波理论的时域递归低通滤波算法。这种算法根据运动小目标,背景干扰和噪声在图象序列中的差异,能够抑制背景,增强小目标并将其从相对静止的背景中有效地分离出来。在恒虚警概率条件下,该算法可以在低信噪比的情况下,减小背景干扰和随机噪声的影响,提高信噪比,选取适当的阈值,能够得到清晰的小目标轮廓,通过仿真验证了这种算法的有效性     

Grid optimization for the boundary element method

The quality of solution obtained using the boundary element method (BEM) is dependent on how the boundary is discretized. This is particularly true in domains of complex geometry. A rule for grid optimization for the BEM is derived on the bases of an asymptotic measure of the boundary element error that preserves the number of elements (degrees of freedom). Three example problems are provided to show the advantages of grid optimization in terms of accuracy and cost.     

Building the Confidence of Women Engineering Students With a New Course to Increase Understanding of Physical Devices

This paper discusses the first two offerings of an experimental course designed to overcome women engineering student's anxiety and intimidation about using mechanical and electrical devices. The design and implementation of the initial course are presented, the changes that were made in the second offering of the course are discussed, and feedback from students in the course is summarized. Principles and guidelines applicable to educational experiences aimed at addressing women engineering students' anxiety about hardware that were observed and developed by the authors are presented and discussed. Finally, future activities and plans are outlined.     

Multiple Testing in Regression Models With Applications to Fault Diagnosis in the Big Data Era

Motivated by applications to root-cause identification of faults in multistage manufacturing processes that involve a large number of tools or equipment at each stage, we consider multiple testing in regression models whose outputs represent the quality characteristics of a multistage manufacturing process. Because of the large number of input variables that correspond to the tools or equipments used, this falls in the framework of regression modeling in the modern era of big data. On the other hand, with quick fault detection and diagnosis followed by tool rectification, sparsity can be assumed in the regression model. We introduce a new approach to address the multiple testing problem and demonstrate its advantages over existing methods. We also illustrate its performance in an application to semiconductor wafer fabrication that motivated this development. Supplementary materials for this article are available online.     

Endovascular Metal Devices for the Treatment of Cerebrovascular Diseases

Cerebrovascular disease involves various medical disorders that obstruct brain blood vessels or deteriorate cerebral circulation, resulting in ischemic or hemorrhagic stroke. Nowadays, platinum coils with or without biological modification have become routine embolization devices to reduce the risk of cerebral aneurysm bleeding. Additionally, many intracranial stents, flow diverters, and stent retrievers have been invented with uniquely designed structures. To accelerate the translation of these devices into clinical usage, an in‐depth understanding of the mechanical and material performance of these metal‐based devices is critical. However, considering the more distal location and tortuous anatomic characteristics of cerebral arteries, present devices still risk failing to arrive at target lesions. Consequently, more flexible endovascular devices and novel designs are under urgent demand to overcome the deficiencies of existing devices. Herein, the pros and cons of the current structural designs are discussed when these devices are applied to the treatment of diseases ranging broadly from hemorrhages to ischemic strokes, in order to encourage further development of such kind of devices and investigation of their use in the clinic. Moreover, novel biodegradable materials and drug elution techniques, and the design, safety, and efficacy of personalized devices for further clinical applications in cerebral vasculature are discussed.     

Harmonic Balance Algorithms for the Nonlinear Simulation of HTS Devices

This paper describes the application of Harmonic Balance algorithms to predict nonlinear effects in planar High Temperature Superconductors (HTS) microwave circuits. The resulting algorithms are fast and efficient and can be used both for the characterization of the nonlinearities in the HTS material, and for the prediction of the behavior of an HTS circuit given the parameters of these nonlinearities (such as a dependence of the surface impedance on the current density). Most previously published nonlinear HTS models can be used, because the algorithms are not restricted to a specific model of HTS nonlinearities. Two different types of algorithms are described: (1) algorithms specific for one-dimensional resonators (transmission lines and TM₀₁₀ disk resonators) and (2) an algorithm based on the combination of Method of Moments and Harmonic Balance, applicable to 2D planar structures with few restrictions in their shape. Several cross-checks with theory and measurements are presented.     

Devices for metrological provisions for measuring the volumetric activity of uranium aerosols

Translated from Izmeritel'naya Tekhnika, No. 12, pp. 39–40, December, 1990.     

Bridging the van der Waals Interface for Advanced Optoelectronic Devices

Van der Waals (vdW) heterostructures exhibit excellent optoelectronic properties and novel functionalities. However, their applicability is impeded due to the common issue of the tunneling barrier, which arises from the vdW gap; this significantly increases the injection resistance of the photoexcited carriers. Herein, a generic strategy is demonstrated to eliminate the vdW gap in a broad class of heterostructures. It is observed that the vdW gap in the interface is bridged via strong orbital hybridization between the interface dangling bonds of nonlayered chalcogenide semiconductors and the artificially induced vacancies of transition metal chalcogenides (TMDCs). The photoresponse times of bridged PbS/ReS₂, PbS/MoSe₂, and PbS/MoS₂ are ≈30, 51, and 43 µs, respectively. The photon-triggered on/off ratio of the bridged PbS/MoS₂, ZnSe/MoS₂, and ZnTe/MoS₂ heterostructures exceed 10⁶, 10⁵, and 10⁵, respectively. These are several orders of magnitude higher than common vdW heterostructures. The findings obtained in this study present a versatile strategy for overcoming the performance limitations of vdW heterostructures.