虚拟三次谐波制动式变压器差动保护的仿真研究

针对虚拟三次谐波制动式变压器差动保护，具体阐述如何利用ATP仿真程序建立适用于该新原理的变压器仿真模型；同时，详细给出了变压器在各种工况下运用此新原理所得到的仿真结果，以说明原理的可行性和保护整定值的选取范围。     

电力系统稳定控制对策表的实时生成

结合理论分析，对所开发的在线暂态稳定控制系统给出了其实现方法。该系统利用实时信息进行在线计算，稳定计算方法采用时域仿真方法描述整个系统的稳定状况。针对给定的预想事故集，自动生成优化紧急控制对策表。对策表的生成方法采用逐步确定罚因子的方法和改进后的稳定计算方法。实际事故发生后，由于子系统“实时匹配”对策表并执行对策。该控制系统不仅具有很高的准确性，而且计算速度满足在线控制的要求。在“华中电网稳定性观测和控制系统”上对华中电网进行了大量的模拟试验；试验表明该系统性能良好。文中给出了其中的一个算例。     

某型船舶电站离散准滑模有功分配控制器设计

利用离散变结构控制理论对某型船舶电站设计了有功分配控制器。分析了抖振产生的原因并给出一种切换带厚度单调递减的改进型控制方案。仿真结果表明，所提方案较好地克服了困扰离散趋近律方法的稳态抖振问题，设计的有功分配控制器可以大大改善并联机组的动态特性，提高了并联系统的鲁棒性。     

发电公司报价决策行为的分析

在电力市场环境下，发电公司从传统的完成发电任务转变为报价竞标发电负荷以获得最大的利润，其目标和行为发生了本质的变化。文中利用博弈论中n人对策理论，对独自竞标和联盟竞标情况下发电公司的行为和市场状况进行了研究。算例表明，联盟未必获得更大的利润，产权不同是防止市场完全垄断的根本。     

输电线路自适应无通道保护(一)故障分析与保护原理

在故障分析的基础上，提出了利用单端故障信息的输电线路全线速动保护原理和动作判据。保护原理由互为补充的两种动作模式－－延时动作模式和瞬时动作模式构成。延时模式利用线路对端开关动作信息加速本端保护动作；瞬时模式根据阻抗继电器Ⅱ段动作定值瞬时动作跳闸，再利用重合闸并根据开关动作后的信息纠正错误动作的结果。保护动作判据由4个独立的故障序分量的比值构成，仿真实验证实了所提保护原理和动作判据的正确性。     

电力市场分析与评估的初步模型及应用

电力市场的安全经济运行需要交易中心对市场进行及时而合理的调节。文中提出了市场分析与评估的概念，初步建立了相应的模型和软件系统。所建立的数学模型考虑了市场成员竞争行为和市场运行规则等，求解结果可以及时揭示系统供需平衡状况和安全隐患。市场分析与评估系统采集相关信息，并在模拟市场运行的基础上评估，得到未来的供需关系、网络充裕度和运行经济性等信息。这些信息不仅可以指导发电公司的竞争行为，减少生产的盲目性，还能辅助交易调度人员的决策安排，保证市场的正常运行。     

Changes in the surface EMG signal and the biomechanics of motion during a repetitive lifting task

The analysis of surface electromyographic (EMG) data recorded from the muscles of the back during isometric constant-force contractions has been a useful tool for assessing muscle deficits in patients with lower back pain (LBP). Until recently, extending the technique to dynamic tasks, such as lifting, has not been possible due to the nonstationarity of the EMG signals. Recent developments in time-frequency analysis procedures to compute the instantaneous median frequency (IMDF) were utilized in this study to overcome these limitations. Healthy control subjects with no history of LBP (n=9; mean age 26.3/spl plusmn/6.7) were instrumented for acquisition of surface EMG data from six electrodes on the thoraco-lumbar region and whole-body kinematic data from a stereo-photogrammetric system. Data were recorded during a standardized repetitive lifting task (load=15% body mass; 12 lifts/min; 5-min duration). The task resulted in significant decreases in IMDF for six of the nine subjects, with a symmetrical pattern of fatigue among contralateral muscles and greater decrements in the lower lumbar region. For those subjects with a significant decrease in IMDF, a lower limb and/or upper limb biomechanical adaptation to fatigue was observed during the task. Increases in the peak box acceleration were documented. In two subjects, the acceleration doubled its value from the beginning to the end of the exercise, which lead to a significant increase in the torque at L4/L5. This observation suggests an association between muscle fatigue at the lumbar region and the way the subject manipulates the box during the exercise. Fatigue-related biomechanical adaptations are discussed as a possible supplement to functional capacity assessments among patients with LBP.     

The IAM-database: an English sentence database for offline handwriting recognition

In this paper we describe a database that consists of handwritten English sentences. It is based on the Lancaster-Oslo/Bergen (LOB) corpus. This corpus is a collection of texts that comprise about one million word instances. The database includes 1,066 forms produced by approximately 400 different writers. A total of 82,227 word instances out of a vocabulary of 10,841 words occur in the collection. The database consists of full English sentences. It can serve as a basis for a variety of handwriting recognition tasks. However, it is expected that the database would be particularly useful for recognition tasks where linguistic knowledge beyond the lexicon level is used, because this knowledge can be automatically derived from the underlying corpus. The database also includes a few image-processing procedures for extracting the handwritten text from the forms and the segmentation of the text into lines and words. Received September 28, 2001 / Revised October 10, 2001     

Characterization of electroplated nickel

 Properties of electroplated nickel such as crystallographic texture, Young's modulus, strength and microstructure strongly depend on the parameter mean current density used for electrodeposition. By means of micro tensile testing mechanical material parameters were determined. At low mean current density (2 mA/cm²) brittle layers with high Young's modulus and high strength were obtained, whereas at high current density (15 mA/cm²) ductile layers with low Young's modulus and low strength were deposited. Received: 10 August 2001/Accepted: 24 September 2001 Parts of the work were carried out within the project ELMINOS, which is supported by the state of North Rhine-Westphalia, Germany. The equipment used for the experiments was funded by the state of North Rhine-Westphalia. We would like to express our sincere gratitude to Mirko Hofmann for his assistance in performing the measurements of indentation hardness. The participation of Cho and Hemker was sponsored by the Defense Advanced Research Projects Agency (DARPA) and Air Force Research Laboratory, Air Force Material Command, USAF, under agreement number F30602-99-2-0553. This paper was presented at the Fourth International Workshop on High Aspect Ratio Microstructure Technology HARMST 2001 in June 2001.     

Stereoscopic view-dependent visualization of terrain height fields

Visualization of large geometric environments has always been an important problem of computer graphics. We present a framework for the stereoscopic view-dependent visualization of large scale terrain models. We use a quadtree based multiresolution representation for the terrain data. This structure is queried to obtain the view-dependent approximations of the terrain model at different levels of detail. In order not to lose depth information, which is crucial for the stereoscopic visualization, we make use of a different simplification criterion, namely, distance-based angular error threshold. We also present an algorithm for the construction of stereo pairs in order to speed up the view-dependent stereoscopic visualization. The approach we use is the simultaneous generation of the triangles for two stereo images using a single draw-list so that the view frustum culling and vertex activation is done only once for each frame. The cracking problem is solved using the dependency information stored for each vertex. We eliminate the popping artifacts that can occur while switching between different resolutions of the data using morphing. We implemented the proposed algorithms on personal computers and graphics workstations. Performance experiments show that the second eye image can be produced approximately 45 percent faster than drawing the two images separately and a smooth stereoscopic visualization can be achieved at interactive frame rates using continuous multiresolution representation of height fields