Design and optimization of hybrid resonant loops for efficient wireless power transfer

Frequency splitting, caused by magnetic overcoupling, is a great challenge in resonant wireless power transfer, which leads to decrease of transfer efficiency. In this paper, to avoid the frequency splitting, a new design of hybrid resonant loops with an inner coil positioned in the transmitter is proposed for efficient power transfer. It is shown to suppress dramatic variation of mutual inductance when the distance between transmitter and receiver decreases. Analytical expressions of the mutual inductance and the transfer efficiency for the proposed resonant wireless power transfer system are calculated. To obtain a relatively uniform mutual inductance with respect to the distance, the proposed resonant loops are optimized. Simulation and experiments are also performed to validate the effectiveness of the proposed resonant loops in eliminating the frequency splitting. The transfer efficiency remains higher than 80% when the transfer distance decreases below a critical value where frequency splitting occurs for conventional resonant loops. Furthermore, lateral and angular misalignments between the resonant loops are also considered and investigated. The results indicate that the proposed resonant loops are also applicable in suppressing the frequency splitting even in case of misalignments.     

Tension-tension fatigue behavior of unidirectional SiC/Si3N4 composite with strong and weak interface bonding at room temperature

In this paper, the tension-tension fatigue behavior of unidirectional SiC/Si₃N₄ ceramic-matrix composite with strong and weak interface bonding at room temperature has been investigated using a micromechanical approach. The hysteresis loops models considering different interface slip cases have been developed to establish the relationships between fatigue hysteresis loops, hysteresis dissipated energy, hysteresis modulus, and the interface shear stress. The damage evolution process under tension-tension fatigue loading has been analyzed using hysteresis loops. By comparing experimental fatigue hysteresis dissipated energy with theoretical computational values, the interface shear stresses of SiC/Si₃N₄ composite with weak and strong interface bonding were obtained for different cycle numbers. The fatigue life S‒N curves and broken fibers fraction versus cycle number curves corresponding to different fatigue peak stresses have been predicted. For SiC/Si₃N₄ with strong interface bonding, the fatigue limit stress approaches to 75% tensile strength, which is much higher than that of composite with weak interface bonding, i.e., 58% tensile strength, due to the higher interface shear stress degradation rate for weak bonding interface.     

COMPILE TIME PARTITIONING OF NESTED LOOP ITERATION SPACES WITH NON-UNIFORM DEPENDENCES*

In this paper we address the problem of partitioning nested loops with non-uniform (irregular) dependence vectors. Parallelizing and partitioning of nested loops requires efficient inter-iteration dependence analysis. Although many methods exist for nested loop partitioning, most of these perform poorly when parallelizing nested loops with irregular dependences. Unlike the case of nested loops with uniform dependences these will have a complicated dependence pattern which forms a non-uniform dependence vector set. We apply the results of classical convex theory and principles of linear programming to iteration spaces and show the correspondence between minimum dependence distance computation and iteration space tiling. Cross-iteration dependences are analyzed by forming an Integer Dependence Convex Hull (IDCH). Every integer point in this IDCH corresponds to a dependence vector in the iteration space of the nested loops. A simple way to compute minimum dependence distances from the dependence distance vectors of the extreme points of the IDCH is presented. Using these minimum dependence distances the iteration space can be tiled. Iterations within a tile can be executed in parallel and the different tiles can then be executed with proper synchronization. We demonstrate that our technique gives much better speedup and extracts more parallelism than the existing techniques.     

Effect of the support and added oxides on the bistability observed in the oxidative dehydrogenation of 2-propanol over copper-supported catalysts

A bistability phenomenon has been observed in the oxidative dehydrogenation of 2-propanol over supported copper catalysts. Cu/Al₂O₃ and Cu/CeO₂ have been prepared by room temperature adsorption of the copper amino complex on the supports. The comparison of the hysteresis observed when the partial pressure of oxygen is varied, indicates that there is an important effect of the support. This effect is explained by the variation in specific surface areas of the supports and in their reducibilities. The possible influence of a second phase (-Sb₂O₄, SnO₂, Bi₂O₃ and NiO) added to the copper catalysts has also been studied.     

PWM整流器无电感双闭环控制

提出一种无电感双闭环控制策略实现对PWM整流器的控制。该无电感双闭环控制无需电感值,具有电流稳态正弦度高、鲁棒性强、动态响应快的优点。     

有竖井隧道自然风压的研究

运用回路自然风压理论对有竖井隧道自然风压进行了研究 ,提出在有竖井隧道中自然风压的大小和方向均会发生变化 ,并将影响竖井主风机工作 ,在通风设计及运营通风管理中应给予重视。     

导爆管复式闭合网路分系统串联起爆技术应用

介绍了导爆管复式闭合网路分系统串联起爆技术,并对网路连接方式、优越性、系统与系统之间串联雷管延时时间等进行了描述。该起爆网路有效地解决了复杂环境大规模石方快速施工和爆破振动大之间的矛盾,为露天矿及石方爆破工程的网路选择、系统优化设计及应用提供了实践经验与参考。     

Reduced-complexity simulation of the effect of non-stationary interference on DMT-based DSL systems

One of the factors affecting the performance of DSL systems is non-stationary interference, comprising of impulse noise and radio-frequency ingress (RFI). The evaluation of the impact of non-stationary interference becomes increasingly important as DSL systems operate at higher rates and the SNR margins are lowered. Because of the complexity of the models of non-stationary interference, simulations are often used for the accurate prediction of the performance of DSL systems. This study begins with a discussion on some issues that pertain to the simulation of the impact of non-stationary disturbances on DSL systems. Then, a reduced-complexity simulation method of the effect of non-stationary interference on DMT-based DSL systems is presented. It is argued that the method is a good candidate for the simulation of the impact of low-energy non-stationary disturbances. In addition to reducing the computations, it is shown that the method does not cause a significant loss of accuracy of the predicted error rate.     

Detection and Diagnosis of Plant‐Wide Oscillations

This paper presents some emerging techniques for detection and root‐cause diagnosis of plant‐wide oscillations, and demonstrates their efficacy through a successful industrial case study. The recently proposed autocorrelation function based method (Thornhill et al., J. Proc. Control 13, 91–100, 2003a) is used for detection of oscillations in the process measurements. Signals having common oscillations are analyzed for the presence of valve stiction using higher order statistical methods (Choudhury et al., Automatica 40, 1719–1728, 2004b) . A method employing changes in controller gain is proposed for distinguishing an internally generated oscillation from an external oscillatory disturbance. This method of changing controller gain is used to confirm the presence of control valve stiction. The proposed techniques have been used successfully to identify the root cause of plant‐wide oscillations in an industrial case study using routine operating data.     

逆变侧交流电压畸变下HVDC运行特性分析

推导了逆变侧交流母线电压存在畸变时锁相环的输出特性和阀换相特性,揭示了谐波电压对逆变侧定熄弧角控制器和低压限电流控制器(VDCOL)带来影响的机理,解释了谐波电压的存在会减小逆变侧延迟触发角的指令值、降低直流系统传输容量的原因。针对交流母线电压谐波畸变情况下定熄弧角控制不能很好跟踪其整定值的问题,通过减小电流偏差控制的增益,有效减小定熄弧角控制在交流电压畸变时的稳态误差量,降低了传递容量的损失。提出了谐波影响下直流系统稳态工作点的计算方法。PSCAD/EMTDC仿真验证了理论分析的正确性、改进措施的有效性和计算方法的准确性。