线路两相短路故障电流控制的新方法

两相短路后,传统方法是切除故障线路,但这可能导致系统潮流大转移并可能引起系统不稳定,造成大面积停电事故。为此提出一种新型的故障电流控制器及与之对应的控制方法。故障电流控制器由串联变压器、并联变压器、2个可调电感以及有载调节开关构成,嵌入在线路的两端,工作时等效于电压源和电感的串联。两相故障后,改变与并联变压器原边相连开关的位置,将改变故障电流控制器等效电压源电压的相位,使故障相线路发送端(接受端)的电压源电压与超前(滞后)于故障相的电源电压同相,再协调控制2个可调电感,能独立控制其等效电压源电压的幅值和电感值,适当地控制这2个分量,能控制故障相间的线电流等于正常电流,该状态下线路的故障电流不仅为0,同时故障线路的电流也等于其正常运行时的电流,并在此基础上提出了两相短路故障电流的控制策略,建立了与之对应的控制系统。该方法能保持故障线路的继续运行,提高了线路供电的可靠性。实验证明了故障电流控制器能控制故障线路上的电流,使其等于正常运行电流,同时理论分析和仿真结果也证明了提出的故障电流控制器以及与之对应的两相短路电流的控制原理、控制策略的正确性。     

Mechanism-based targeting of NMDA receptor functions

NMDA receptors (NRs) are key signaling proteins in the central nervous system and represent important targets for drug development in several neurologic disorders. They are critically involved with fundamental brain processes, and thus indiscriminate pharmacological suppression of NR currents has seen only modest therapeutic success so far. Targeting harmful NR receptor activities while sparing the receptor’s vital functions requires a better understanding of the complexity of NR activation reaction; of the range of mechanisms that modulate discrete receptor activities; and of the consequences of this modulation on specific receptor functions. A quantitative account of the NR activation pathway was recently proposed and validated. It describes the gating reaction as a sequential, multi-step process rather than a binary, on-off switch. Alongside isoform-specific modulators, state-specific modulators may represent sophisticated interventions with high potential for narrow, functional specifi city. Here I review physiologic mechanisms that control NR responses; the salient features of the NR activation reaction; and discuss the model’s validity and its implications for drug development and characterization.Submitted 25 May 2005; accepted 29 June 2005     

Rate-compensated synaptic events in antarctic fish: Consequences of homeoviscous cold-adaptation

Summary At ambient sub-zero temperatures, muscles from antarctic fish produce spontaneous postsynaptic currents (MEPCs) of significantly shorter duration than those of temperate fishes. Fast decay of antarctic MEPCs is a predictable consequence of the increased membrane fluidity attributable to fatty acid unsaturation in cold-adapted animals.We wish to thank the Antarctic Division of the New Zealand Department of Scientific and Industrial Research, and the staff of Scott Base, without whom this work could not have been done. The work was supported financially by grants from the New Zealand University Grants Committee and from the Auckland University Research Committee. We are also grateful to members of the United States Antarctic Research Program, in particular Dr A. L. DeVries, for advice and assistance.     

介观环的持续电流与Berry相因子

本文研究处于铁磁自旋波的非均匀磁场中介观环的持续电流及几何位相，求出了准粒子的激发谱及电荷流，讨论了相关的Ｂｅｒｒｙ相因子。     

铁磁自旋波对Texture介观环中持续电流的影响

利用自旋波理论研究某种晶体结构中介观环的持续电流．发现自旋波的量子涨落将影响介观中的持续电流、电流振幅随温度的变化由赝Ｄｅｂｙｅ－Ｗａｌｌｅｒ系数决定．在低温极限下．赝Ｄｅｂｙｅ－Ｗａｌｌｅｒ系数仍不为零．     

FBD法及其在牵引供电系统中的应用

为了能够检测电气化铁路供电系统中的谐波、无功和负序电流,在有限维线性空间理论的基础上,分析比较了FBD法和三相电路瞬时无功功率理论,指出三相电路瞬时无功功率理论可以看作FBD法的特例。提出了一种基于FBD法的检测方法,并将该方法应用于牵引变电所新型电能质量调节器。分析得出:检测方法中低通滤波器的性能直接影响到包含电能质量调节器的牵引供电系统的稳态、动态性能。滤波器的延时越大,稳态时检测精度越高,动态响应越慢。仿真结果验证了检测方法与系统特性分析的正确性。     

A nonlinear viscoelastic model for bed mud transport due to waves and currents

In estuaries and coasts, mud transport due to waves and tidal currents has an important influence on the shoaling control of harbours and waterways and pollutant dispersion. Based on the investigation of rheologic behaviour, a nonlinear viscoelastic model is proposed. A calculating method for bed mud transport velocity is established, in which the influence of irregular character of waves is considered. Comparison of calculated results with the flume experimental results shows a rough agreement.     

地磁感应电流水平与行星际扰动的关系分析

地磁感应电流(geomagnetically induced currents,简称GIC)取决于地磁场变化。地磁场变化受电离层、磁层和行星际等各空间的扰动变化所驱动。认识GIC与空间扰动参数的关系可尝试预测、预报GIC及其影响。利用斯皮尔曼相关系数分析了1999—2005年间芬兰输气管线GIC数据与ACE卫星记录的行星际扰动参数(Bs,Ey,V,Pk,|B|,ε)的相关性。结果表明,这些参数与GIC都具有较好的相关性;其中,Pk和|B|是与GIC相关性最好的两个参数。在大磁暴GIC事件中V的相关度最高,特大磁暴GIC事件中Ey相关度最好。如果把GIC分成三个级别,即GIC≥10A,GIC≥20A,GIC≥30A,相关性最好的参数分别为Ey,Pk和|B|。统计GIC事件的行星际源发现,所有事件的行星际源中包含鞘层结构(SH)的比例高达82.8%,30A以上GIC的行星际源都包含有磁云结构(MC)。综合分析表明,预测GIC的影响可以考虑这些条件。     

地磁暴感应地电场的大地电性结构建模方法

探明磁暴期间地面感应电场的分布情形是正确计算地磁感应电流(GIC)和预测磁暴次生灾害影响的前提。根据电磁场唯一性定理,从求解磁暴感应地电场的角度出发,提出了一种复杂大地电导率结构的建模方法;该方法的特点是只建大地导体区模型,通过模型的边界条件反映地磁场的变化情况及感应地电流在地下的流通情形。采用有限元法求解了典型地电结构下的磁暴感应地电场,通过对比数值方法和解析方法求得的地面电场结果,验证了建模方法的可靠性。进一步采用该方法研究了无法解析求解的复杂地电结构的磁暴感应地电场问题,建模思路和方法为评估磁暴和GIC的管网效应提供了分析工具。