浅谈GC-150型过速限制和分段关闭装置在紫兰坝电站的实践

水轮发电机组过速保护系统主要是由事故配压阀和纯机械过速保护装置组成。当机组发生过速时,机组的过速保护系统会按照设计流程准确动作及时关闭导叶接力器,以使机组停机,避免水轮发电机组发生飞逸现象。紫兰坝电站GC-150型过速限制及分段关闭结构装置至投运至今,结构性能比较稳定,发生事故时均能可靠动作。

抽水蓄能电站主进水阀操作时间异常分析与处理

抽水蓄能电站输水通道设置主进水阀,一般为球阀结构,在电站运维检修中扮演至关重要的角色。主进水阀开、关时间有设计要求,也是设备健康状态重要指标之一。电站运维人员通过对比分析,发现主进水阀开、关时间异常,进而发现两侧接力器位置不一致,机械锁定销无法投入。通过原因分析与排查,最终确定为机械锁定侧接力器无杆腔截流阀阀芯脱落失效导致开、关时间异常,阀芯卡塞至活塞盘与下端盖之间导致主进水阀关闭后接力器无法正常落位,机械锁定无法正常投入。

A DESIGN OF 0.25μm CMOS SWITCH

Single-Pole Double-Throw （SPDT） broadband switch has been designed in a 0.25gm Complementary Metal Oxide Semiconductor （CMOS） process. To optimize the performance of isolation and insertion loss, based on normal design, the effects of Gate Series Resistances （GSR） on insertion loss and switching time are analyzed for the first time. The compatible GSRs are chosen by the analyses. The fabricated chips were tested and the results show the switch isolation from DC （Direct Current） to 1GHz exhibits 55dB and insertion loss lower than 2.1 dB.

New scheme of optical switch technology of time division

The optical time division switch scheme using optical scanning was proposed in this paper.Quick switching can be realized by the optical element and optical system based on the proposed scheme.The modulation velocity of the proposed scheme can be of the order of nanosecond,which is quick enough for the next generation of optical communication.This scheme will be a key technology in the optical network.The principle of the scheme is studied.The structure of the scheme is proposed and the performance is analyzed.

SWITCHING CHARACTERISTICS AND ANALYSIS OF RESONANT TUNNELING DIODES

Resonant tunneling diode （RTD） of AlAs/InGaAs/AlAs double barrier-single well structure was designed and fabricated. The devices showed current-voltage characteristics with peak-valley current ratio of 4 ： 1 at room temperature. The scattering parameter of RTD was measured by using an HP8510（C） network analyzer. Equivalent circuit parameters were obtained by curve fitting and optimized. The RTD switching time was estimated using the measured capacitance and average negative differential resistance. The minimum rise time of the sample was estimated to be 21 ps.

Optimization on temperature efficiency and switch time of thin-walled regenerator with perturbation analysis

The heat transfer characteristic of honeycomb ceramic regenerator was optimized by the perturbation analytical-numerical method. The results show that there is a temperature efficiency peak and the corresponding optimal switch time. The decrease of air oxygen concentration leads to the decrease of maximum temperature efficiency. Optimal switch time is directly proportional to the matrix thickness. The solid heat conduction along the flow direction and the regenerator heat storage capacity of the unit volume have no impact on maximum temperature efficiency and optimal switch time. The temperature efficiency tendency based on the semi-analysis is the same as dispersion combustion tests with low oxygen concentration, and optimal switch time of 2-4 s agrees well with that of 4 s in high-temperature gasification tests. The possibility of design, operate and control a thin-walled regenerator with high efficiency by means of the perturbation method is proved.

Predictive Spectrum Sensing Strategy Based on Reinforcement Learning

In this paper,we consider a cognitive radio(CR) system with a single secondary user(SU) and multiple licensed channels.The SU requests a fixed number of licensed channels and must sense the licensed channels one by one before transmission.By leveraging prediction based on correlation between the licensed channels,we propose a novel spectrum sensing strategy,to decide which channel is the best choice to sense in order to reduce the sensing time overhead and further improve the SU's achievable throughput.Since the correlation coefficients between the licensed channels cannot be exactly known in advance,the spectrum sensing strategy is designed based on the model-free reinforcement learning(RL).The experimental results show that the proposed spectrum sensing strategy based on reinforcement learning converges and outperforms random sensing strategy in terms of long-term statistics.

Global Synchronization of Directed Networks with Fast Switching Topologies

Global synchronization of a class of directed dynamical networks with switching topologies is investigated.It is found that if there is a directed spanning tree in the fixed time-average of network topology and the time-averageis achieved sufficiently fast,then the network will reach global synchronization for sufficiently large coupling strength.

Optimal control problem in an epidemic disease SIS model with stages and delays

Based on literature [J. Q. Li, Z. E. Ma and F. Q. Zhang, Stability analysis for an epidemic model with stage structure, J. Appl. Math. Comput. 9 （2008） 1672-1679], incorporating the recovery of the infected population with the length of the infectious periods, a modified epidemic disease SIS model with delay and stage was investigated. First, the criteria keeping stability with delay were given. Next, in order to lower the level of the infected individuals and minimize the cost of treatment, mixed, early and late therapeutic strategies were introduced into our model, respectively. Then we investigated the existence and uniqueness of optimal controls. And then, we expressed the unique optimal control in terms of the solution of the optimality systems. Finally, by numerical simulations, several important results were acquired： （1） The terminal time influenced the early optimal control largely. In detail, for a shorter terminal time it was optimal to initiate treatment with maximal effort at the start of the epidemic and continue treatment with maximal effort until the switch time was arrived. But for a longer terminal time, the maximal treatment effort need not be a prerequisite at the start or end of the epidemic but it was obligatory at the metaphase of the epidemic. （2） For our SIS model, minimizing the total infectious burden of the disease can be achieved by only early optimal treatment tactics. （3） For a disease with a shorter infectious period time,more cost would be spent to control the disease in order to achieve the optimal control objective. Otherwise, a relative lower cost would be to control the disease with a longer infectious period.

OUTPUT VARIABLE STRUCTURE CONTROL FOR TIME-INVARIANT LINEAR TIME-DELAY SINGULAR SYSTEM

Synthesis and design of output variable structure controller for time-invariant linear timedelay singular system are studied. In the case that the system is regular and the system index is one, switching function with integral compensator and variable structure controller are designed, which guarantee that the sliding mode is asymptotically stable and the solution trajectory of the system arrives at the switching manifold in limited time. The design method is applicable to the systems which can be regularized. Finally, a numerical example is given to demonstrate effectiveness and simplicity of the design method.

Plasma density evolution in plasma opening switch obtained by a time-resolved sensitive He-Ne interferometer

To understand the formation process of vacuum gap in coaxial microsecond conduction time plasma opening switch(POS),we have made measurements of the line-integrated plasma density during switch operation using a time-resolved sensitive He-Ne interferometer.The conduction current and conduction time in experiments are about 120 kA and 1 s,respectively.As a result,more than 85%of conduction current has been transferred to an inductive load with rise time of 130 ns.The radial dependence of the density is measured by changing the radial location of the line-of-sight for shots with the same nominal POS parameters.During the conduction phase,the line-integrated plasma density in POS increases at all radial locations over the gun-only case by further ionization of material injected from the guns.The current conduction is observed to cause a radial redistribution of the switch plasma.A vacuum gap forms rapidly in the plasma at 5.5 mm from the center conductor,which is consistent with the location where magnetic pressure is the largest,allowing current to be transferred from the POS to the load.