电光源混合气体的正确验收方法

采用压力法验收电光源混合气体是不科学的,而采用称重法仅需要简单的精密称重设备和简易操作就可以进行较为科学、准确的验收,便于日常生产进货监测。称重法不仅可以对气体的总量进行检验,而且也能对简单的混合气体配比是否准确做出判断,实现对混合气体的质和量同时验收。     

LabVIEW对串口采样测量数据的处理

LabVIEW处理串口通常采用VISA或ActiveX控件,采用VISA的解决方案简单易行,详细介绍基于VISA对串口数据的处理方法。当数据量比较大,帧频比较高时,串口采样数据处理比较麻烦。为避免接收数据窜字符的问题,设计了自动帧头对准程序,保证数据接收完整可靠。为避免数据分析显示程序与串口数据接收处理的冲突,设计串口接收打包处理程序,对接收数据进行缓存。说明了这2种方法的原理、实现和实际应用程序。并应用于编制伺服运动控制效果测量监控程序。设计分析对比结果表明,方案简单易行、经过处理的数据流结构清晰、明确,易于后续程序处理。为基于LabVIEW的串口数据处理提供一种简单有效的方法。     

煤炭环境对发电市场影响的模糊综合评价

面对常规能源煤炭需求日趋加重的压力,电力的发展将受到制约,分析煤炭环境的影响对发电企业至关重要。煤炭环境对发电市场的冲击影响程度不仅与煤炭供求有关,而且还与煤炭价格、煤炭运输等因素有关。考虑这些因素,确立煤炭环境影响的评价指标,采用模糊综合评价方法进行煤炭环境对发电市场影响的综合评价,判断煤炭环境对发电市场影响所属评价集类别。该方法可以在稳定发电市场运营条件中起到一定的指导和参考作用。     

链条炉燃烧控制系统的数字仿真辅助设计

本文以某台KZL4—13型链条炉为例,详细介绍了锅炉燃烧控制系统的数字仿真设计方法,内容和步骤,并给出了通用仿真程序框图.通过数字仿真,详细地研究了各控制方案的动态特性及调节器和前馈环节的参数对其产生的影响.最后,对各控制方案的主要性能进行比较,分析,挑选出了一最佳方案,并推荐出了该方案中各调节器的类型及最佳的调节器参数.     

基于模糊层次分析法的城市电网规划决策综合评判

作为城市电网规划的决策者通常要面临一个由相互关联的各个部分构成的复杂系统，这种复杂系统的决策问题大都属于多因素决策问题，其解决的关键在于如何在一系列非劣解中确定最优解。介绍了基于三角模糊数的模糊层次分析法，及其在某小区电网规划方案综合评判中应用的过程，为城市电网规划决策综合评判提供了一种新方法。     

The modulation transfer function. A simplified procedure forcomputer-aided quality evaluation in mammography

Regardless of the indisputable benefits of the modulation transfer function (MTF) method to radiographic image quality evaluation, most radiologists simply do not have the means for utilizing it due to the experimental difficulties in its application to mammography practice. One of the most significant difficulties for radiological departments is having the necessary equipment to digitize slit radiographic images-a microdensitometer, for example-to be used in quality assurance programs. Therefore, the authors propose the application of the transfer function method for quality evaluation of mammography equipment using a different procedure. This procedure is based on the calculation of the MTF from a simulated line spread function derived from the focal-spot projection. Since this technique does not need digitized images and can be performed on a PC, it will allow the use of the transfer function method in quality control programs without the constraints associated with the complexity of classical experimental procedures     

A new design strategy for DC/DC LLC resonant converter: Concept,modeling, and fabrication

In this paper, a new design procedure for LLC converter has been introduced. In fact, this method is a computer-based design algorithm based on a numerical technique. In the process of designing, the value of the resonant element is obtained by solving the LLC converter fundamental equation. This converter will be controlled by using state feedback, such as output voltage variable. As a matter of fact, in a control system, the change of output voltage (because of load variation) will affect the switching frequency, so the output voltage will be tuned. In the designing process, the fundamental equations of LLC converter are obtained, and the value of the resonant elements is calculated. Also, a comparison analysis is carried out between the proposed and typical methods. The simulation is done to investigate the validity of the proposed method. Moreover, a prototype is manufactured, and the experimental test is done to evaluate its applicability.     

A study of a unit commitment problem with transmission constraints

Unit commitment problem is an optimization problem to determine the start‐up and shut‐down schedule of thermal units while satisfying various constraints, for example, generation‐demand balance, unit minimum up/down time, system reserve, and so on. Since this problem involves a large number of 0–1 type variables that represent up/down status of the unit and continuous variables expressing generation output, it is a difficult combinatorial optimization problem to solve. The study at present concerns the method for requiring the suboptimum solution efficiently. Unit commitment method widely used solves the problem without consideration of voltage, reactive power, and transmission constraints. In this paper, we will propose a solution of unit commitment with voltage and transmission constraints, based on the unit decommitment procedure (UDP) method, heuristic method, and optimal power flow (OPF). In this method, initial unit status will be determined from random numbers and the feasibility will be checked for minimum start‐up/shut‐down time and demand‐generation balance. If the solution is infeasible, the initial solution will be regenerated until a feasible solution can be found. Next, OPF is applied for each time period with the temporary unit status. Then, the units that have less contribution to the cost are detected and will be shut down based on the unit decommitment rules. This process will be repeated until suboptimal solution is obtained. The proposed method has been applied to the IEEE 118‐bus test system with 36 generating units with successful result. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 144(3): 36–45, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10187     

基于可靠性的电力系统设备备用规划方法

提出基于可靠性的电力系统设备备用规划方法。它对设备可修复失效和老化失效2个模式均进行了模拟。讨论了2个备用分析方法:基于设备组可靠性判据和基于概率费用模型。2个方法可以互相配合,并整合成统一的步骤。用提出的方法所获得的设备备用方案,包括在长期规划期间应购置的备用设备数量和每个备用设备投入的时间。它也能提供短期的设备备用方案。它还能对设备备用方案进行概率的效益/成本分析,因而可以在决策中对其经济上的合理性提供定量的判断。用16台变压器组成的变压器组为例解释了方法的细节,这是在加拿大BCTC公司的一个实际应用。例子中得到2个长期和2个短期变压器备用方案,并对这些方案的可靠性水平和效益/成本比作了比较。所提出的方法和计算步骤能够应用到任何电力系统设备的备用规划。     

基于气象因素粗糙集理论的负荷预测方法

电力负荷受气象因素影响越来越大,如何准确预测负荷中的气象负荷是负荷预测中的一项有意义的课题。本文首先采用粗糙集对影响负荷的气象因素进行规则简约,找到影响负荷的核心气象因素;然后以这些核心因素为坐标寻找与预测日距离最小的历史数据,利用时间序列方法进行预测。经实际系统检验,证明该方法克服了传统气象负荷预测中的主观性,将历史数据的发掘过程量化,便于机器预测。并且预测结果误差小,是一种适用性很强的技术。     

Multidimensional EMG-based assessment of walking dynamics

The electromyogram (EMG) provides a measure of a muscle's involvement in the execution of a motor task. Successful completion of an activity, such as walking, depends on the efficient motor control of a group of muscles. In this paper, we present a method to quantify the intricate phasing and activation levels of a group of muscles during gait. At the core of our method is a multidimensional representation of the EMG activity observed during a single stride. This representation is referred to as a "trajectory." A hierarchical clustering procedure is used to identify representative classes of muscle activity patterns. The relative frequencies with which these motor patterns occur during a session (i.e., a series of consecutive strides) are expressed as histograms. Changes in walking strategy will be reflected as changes in the relative frequency with which specific gait patterns occur. This method was evaluated using EMG data obtained during walking on a level and a moderately-inclined treadmill. It was found that the histogram changes due to artificially altered gait are significantly larger than the changes due to normal day-to-day variability.     

基于空充电流的线路保护带负荷试验方法

电流回路变动过的线路保护须进行带负荷试验后才能投入运行。针对常规带负荷试验存在的耗时长、负荷不稳定、改接线风险性大的问题,提出了利用线路在空充状态下的电容电流进行带负荷试验的方法。首先分析了线路空充电流特性及其在带负荷试验中的适用性,给出了空充电流带负荷试验的适用范围。其次通过与常规带负荷试验进行对比,论证了所提出的带负荷试验方法在电流二次回路改接线过程中的安全性。最后通过某220 kV变电站的现场试验测试了该方法的有效性。结果表明,采用线路空充电流进行带负荷试验可在保证试验精确度的前提下缩减设备操作流程,大幅提升电力设备投产效率。     

空调室外直流风机的无位置传感器启动方法

因成本与可靠性方面的优势,目前空调室外直流风机多采用无位置传感器的驱动方式。其启动过程需要对直流风机进行定位与开环拖动。然而,室外风机在启动过程中受外界风的影响可能无法直接定位;此外,如果外界风力过大,直流风机启动过程可能会出现过电流故障。针对以上问题,本文提出了一种空调室外直流风机的启动方法。该方法可在启动前快速判定风机在外界风作用下的初始转速,并根据初始转速控制直流风机进入不同的动作模式,以确保直流风机的可靠启动。通过在不同的外界风速下直流风机的启动实验验证了方法的有效性。     

A reliable advanced-join system for data multicasting in ITS networks

A number of mobile hosts (MHs) might be densely grouped in an area caused by traffic congestion. In such a situation, the greater part of the MHs will require useful data, such as traffic information, parking information, and other driving-related information. Simultaneous data-transmission broadcasts using a common link are regarded as a suitable medium to distribute this location-dependent information. However, there is no guarantee that MHs can finish receiving the information completely within a limited time. In this paper, we propose a reliable multicast system that consists of a multicast-group-management method called "Advanced-Join (AJ) system", a data-retransmission method, and a data-recovery-processing method. A "base station (BS) multicast group" is defined as the set of BSs in a certain area to which MHs belonging to the same multicast group connect. The AJ system allows a BS that is a member of a BS multicast group to make consolidated join requests to a multicast group on behalf of its MHs. The data-retransmission method determines and processes retransmission data by coordinating retransmission requests from two or more MHs that are members of the same multicast group. The data-recovery-processing method performs interactive data recovery between BSs belonging to the same BS multicast group. By controlling the members of the BS multicast group according to the movement of MHs and deciding the retransmission packets, it is expected that message traffic for the multicast-group management will be reduced, and packet loss during an MHs' movement between BSs will be eliminated. Evaluation results show that about 86.8% of MHs complete data reception with the proposed system, while only two MHs complete reception with the simple broadcast system. In addition, the proposed system with the data-retransmission method needs only two-thirds of BSs compared with that without retransmissions.     

Transmission expansion planning with AC model based on generalized Benders decomposition

This paper proposes a method for solving transmission expansion planning (TEP) problems with application of an AC model. The TEP will be solved by the proposed three-stage procedure. Firstly, a DC model is employed with an application of Benders decomposition to find initial cuts to be used in the next stage. Secondly, the problem is decomposed into investment and operation problems, for which an AC model will be used with initial cuts obtained from the first stage. An optimal plan will be obtained at the end of the second stage. Finally, reactive power optimization is performed. The proposed method is illustrated with a well-known 6-bus Garver system, and then tested with IEEE 24-bus and 75-bus northeastern Thailand systems to demonstrate the advantage of the TEP based on the AC model.     

Design of integrated all-pass filters with linear group delay for analog signal processing applications

This article describes the design of integrated linear group delay filters for analog signal processing (ASP) applications and their implementation through constant-resistance lattice and bridged-T networks. Unlike previously published works, our design method uses a recursive procedure as the basis for the synthesis of a suitable transfer function. Thanks to this method, filters with a more linear group delay characteristic and flat magnitude response can be obtained. Two filters are designed in a 0.13-μm BiCMOS technology to demonstrate the method: a balanced lattice with a negative slope and an unbalanced bridged-T of positive slope.     

一种新的三电平中点电位滞环控制法

该文针对三电平中点电位平衡原理提出了一种中点电位的滞环控制方法，该方法根据当前的PWM组合和各相输出电流方向判断出中点电流方向，通过滞环比较的方式得到中点电压偏向，并由此判断当前PWM对中点电位的作用，将当前的PWM组合中可以实现中点电位平衡的组合重新分配使之有利于中点电位的平衡。该方法独立于具体的PWM调制模式，因此可以胜任各种PWM调制模式下的中点电位调整。而且也可通过调整滞环宽度的方法来调整中点电位的允许波动和开关管开关次数。该文以特定谐波消除PWM方法(SHEPWM)为例，仿真和实验结果显示了很好的中点平衡效果。该方法对三电平中点电位平衡上具有通用性。     

Image perception and enhancement for the visually impaired

Wavelets have been used extensively as a method of extracting information contained in images and even in modeling human physiological data processing. Wavelet implementation for image processing parallels the analysis done by Peli concerning image enhancement and human perception. In this article, wavelets were used to provide a new image enhancement procedure by manipulating the decomposition detail coefficients. The true usefulness of the wavelet coefficients as enhancement tools can only be determined by testing. The only sure statement that can be made about image enhancement for the visually impaired, without first having a better understanding of the human visual system, is that individual subject preferences will be the deciding factor when choosing the optimal enhancement technique. Wavelet enhancements will provide different information to the low-vision observer and may prove to be superior to other enhancement techniques for some patients     

The Network Diagram for a Mechanical System

The reason for this paper is that most of the modern undergraduate textbooks on linear system analysis present the mechanical network with no proof or justification that it will lead to the correct answers. In most textbooks a procedure for writing down the system network is given and then the method for writing down the system equations is shown. Any connection with previous metholds of solving mechanics problems seems to be ignored. In this paper the mechanical network is presented as a natural abstraction of the free-body diagram used in mechanics. The major advantages of this technique are: 1) it may be presented quickly, 2) it is easily understood by the student, and 3) it demonstrates the physical basis for the network approach.     

NiZn系软磁铁氧体材料的种类及应用

NiZn系软磁铁氧体是尖晶石铁氧体材料中的一个重要分支.NiZn系铁氧体材料以其电阻率高、烧结工艺简单、高频性能好等特点而获得广泛应用.本文简要介绍了当前应用前景较好的几类NiZn铁氧体材料及其应用,包括抗EMI系列铁氧体材料、射频宽带NiZn铁氧体材料、功率型NiZn系铁氧体材料和低温烧结NiCuZn铁氧体材料等,同时展望了各自的发展前景.