Numerical calculation of primary slot leakage inductance of a Single-sided HTS linear induction motor used for linear metro

In the paper, the numerical method calculating asymmetric primary slot leakage inductances of Single-sided High-Temperature Superconducting (HTS) Linear Induction Motor (HTS LIM) is presented. The mathematical and geometric models of three-dimensional nonlinear transient electromagnetic field are established and the boundary conditions are also given. The established model is solved by time-stepping Finite Element Method (FEM). Then, the three-phase asymmetric primary slot leakage inductances under different operation conditions are calculated by using the obtained electromagnetic field distribution. The influences of the special effects such as longitudinal end effects, transversal edge effects, etc. on the primary slot leakage inductance are investigated. The presented numerical method is validated by experiments carried out on a 3.5 kW prototype with copper wires which has the same structures with the HTS LIM.     

Single‐Stage ZVS‐PWM AC‐AC Power Converter Using All SiC Power Module for High‐Frequency Induction Heating Applications

This paper presents a novel prototype of a single‐stage zero voltage soft‐switching pulse‐width modulation ‐controlled ac‐ac converter with a silicon carbide (SiC)‐MOSFET/SiC‐SBD power module for high‐frequency (HF) induction heating (IH) applications. The newly developed ac‐ac converter can achieve higher efficiency than a Si‐IGBT/Si‐PN diode power module‐based prototype due to a low ON‐resistance of SiC‐MOSFET and a low forward voltage of SiC‐SBD under the condition of HF switching. The performances of the new prototype converter are evaluated by experiment with a single‐phase IH utensil of ferromagnetic stainless metal, after which the high‐efficiency and low switching noise characteristics due to the all SiC power module are actually demonstrated.     

Thermosensitive bioadhesive gels for the vaginal delivery of sildenafil citrate: in vitro characterization and clinical evaluation in women using clomiphene citrate for induction of ovulation

Objective: The objective of this study is to develop and characterize in situ thermosensitive gels for the vaginal administration of sildenafil as a potential treatment of endometrial thinning occurring as a result of using clomiphene citrate for ovulation induction in women with type II eugonadotrophic anovulation. While sildenafil has shown promising results in the treatment of infertility in women, the lack of vaginal pharmaceutical preparation and the side effects associated with oral sildenafil limit its clinical effectiveness.

Methods: Sildenafil citrate in situ forming gels were prepared using different grades of Pluronic^® (PF-68 and PF-127). Mucoadhesive polymers as sodium alginate and hydroxyethyl cellulose were added to the gels in different concentrations and the effect on gel properties was studied. The formulations were evaluated in terms of viscosity, gelation temperature (T_sol-gel), mucoadhesion properties, and in vitro drug release characteristics. Selected formulations were evaluated in women with clomiphene citrate failure due to thin endometrium (Clinicaltrial.gov identifier NCT02766725).

Results: The T_sol-gel decreased with increasing PF-127 concentration and it was modulated by addition of PF-68 to be within the acceptable range of 28–37?°C. Increasing Pluronic® concentration increased gel viscosity and mucoadhesive force but decreased drug release rate. Clinical results showed that the in situ sildenafil vaginal gel significantly increased endometrial thickness and uterine blood flow with no reported side effects. Further, these results were achieved at lower frequency and duration of drug administration.

Conclusion: Sildenafil thermosensitive vaginal gels might result in improved potential of pregnancy in anovulatory patients with clomiphene citrate failure due to thin endometrium.     

Direct torque control of doubly fedinduction motor using three-level NPCinverter

This article presents the direct torque control (DTC) strategy for the doubly fed induction motor (DFIM) connected to two three-level voltage source inverters (3LVSIs) with neutral point clamped (NPC) structure. This control method allows to reduce the torque and flux ripples as well as to optimize the total harmonic distortion (THD) of motor currents. The use of 3LVSI increases the number of generated voltage, which allows improving the quality of its waveform and thus improves the DTC strategy. The system modeling and control are implemented in Matlab/ Simulink environment. The analysis of simulation results shows the better performances of this control, especially in terms of torque and flux behavior, compared to conventional DTC.     

Survey on Passivity Based Control of Induction Machine

Induction machines (IM) constitute a theoretically interesting and practically important class of nonlinear systems. They are frequently used as wind generators for their power/cost ratio. They are described by a fifth‐order nonlinear differential equation with two inputs and only three state variables available for measurement. The control task is further complicated by the fact that IM are subject to unknown (load) disturbances and the parameters can be of great uncertainty. One is then faced with the challenging problem of controlling a highly nonlinear system, with unknown time‐varying parameters, where the regulated output, besides being unmeasurable, is perturbed by an unknown additive signal. Passivity‐based control (PBC) is a well‐established structure‐preserving design methodology which has shown to be very powerful to design robust controllers for physical systems described by Euler‐Lagrange equations of motion. PBCs provide a natural procedure to "shape" the potential energy yielding controllers with a clear physical interpretation in terms of interconnection of the system with its environment and are robust vis á vis to unmodeled dissipative effects. One recent approach of PBC is the Interconnection and Damping Assignment Passivity‐Based Control (IDA‐PBC) which is a very useful technique to control nonlinear systems assigning a desired (Port‐Controlled Hamiltonian) structure to the closed‐loop. The aim of this paper is to give a survey on different PBC of IM. The originality of this work is that the author proves that the well known field oriented control of IM is a particular case of the IDA‐PBC with disturbance.     

End Effects in Diagonal Type Nonequilibrium Plasma MHD Generators

The authors investigate the influence of the attenuation of magnetic induction on the current distribution etc. in the end regions of the diagonal type nonequilibrium plasma MHD generator by a two-dimensional analysis. The numerical calculations are made for an example of the cesium-seeded helium. As a result, a suitable attenuation of the magnetic induction can make the current distribution very uniform near the end region of generator duct and has little influence on the current distribution in the central part of generator, and the output electrodes can be used without large ballast resistors. Also the internal resistance of the end region and the current concentration at the output electrode edges decrease with the attenuation of magnetic flux density. By the author's investigation, it is made clear that the output electrodes of the diagonal type nonequilibrium plasma MHD generator should be arranged in the attenuation region of the magnetic induction, since arranging them in the attenuation region of magnetic flux density can become useful for the improvement of the electrical characteristics of generator.     

Accurate rotor flux orientation technique for indirect rotor flux oriented control of induction motor drives

Abstract

In this paper, a novel detuning index is first proposed for indicating the proper timing required to correct the rotor time constant of indirect rotor flux oriented controlled single‐cage induction motor drives. This index can faithfully reflect the influence of rotor resistance changes as well as rotor flux changes. It also reduces greatly the number of rotor time constant estimations in practical applications. The theoretical basis of the index and the physical meaning are described in the paper in detail. Based on the proposed index, an on‐line rotor time constant estimator is also proposed to make corrections. Only existing available quantities of the closed loop controller are used for calculating the estimated rotor time constant accurately. Both simulation and experimental results verify the effectiveness of the proposed rotor flux orientation technique. It is seen that the proposed rotor flux orientation technique is suitable for practical applications.     

Validation of a CFD model with a synchronized triple‐lidar system in the wind turbine induction zone

A novel validation methodology allows verifying a CFD model over the entire wind turbine induction zone using measurements from three synchronized lidars. The validation procedure relies on spatially discretizing the probability density function of the measured free‐stream wind speed. The resulting distributions are reproduced numerically by weighting steady‐state Reynolds averaged Navier‐Stokes simulations accordingly. The only input varying between these computations is the velocity at the inlet boundary. The rotor is modelled using an actuator disc. So as to compare lidar and simulations, the spatial and temporal uncertainty of the measurements is quantified and propagated through the data processing. For all velocity components the maximal difference between measurements and model are below 4.5% relative to the average wind speed for most of the validation space. This applies to both mean and standard deviation. One rotor radius upstream the difference reaches maximally 1.3% for the axial component. © 2017 The Authors. Wind Energy Published by John Wiley & Sons, Ltd.     

基于人体感应的智能紫外线消毒控制系统设计

针对办公环境的消毒要求,使用嵌入式微处理器STM32F103C8T6作为控制单元,采用蓝牙作为无线通信协议,再配合红外人体感应模块和语音提示,利用紫外线消毒的特性,设计了一款智能紫外线消毒控制系统。该系统能够远程配置消毒时间段,自动根据配置的时间进行消毒,并在紫外线消毒期间对进入消毒区域进行人体检测和语音提示。既有效完成了办公环境紫外线消毒需求,也避免了紫外线辐射对人体的危害,同时实现了智能化和远程控制,节省了人力和物力。