不锈钢与金基体上电沉积Bi2Te3-ySey薄膜

采用控电位电沉积技术以不锈钢和金为基体制备了Bi2Te3-ySey温差电材料薄膜。通过环境扫描电子显微镜(ESEM)、能量散射光谱(EDS)、X射线衍射光谱法(XRD)等方法,研究了不同基体对Bi2Te3-ySey温差电材料薄膜形貌、组成及结构的影响。结果表明,在含有Bi3 、HTeO2 和Se4 的溶液中,可实现铋、碲、硒三元共沉积,制备出Bi2Te3-ySey温差电材料薄膜。以金为基体电沉积的Bi2Te3-ySey薄膜的表面较平整、致密。在-0.04V沉积电位下,以不锈钢和金为基体电沉积Bi2Te3-ySey薄膜组成分别为Bi2Te2.39Se0.77和Bi2Te2.45Se0.85,且在不锈钢上电沉积制备的Bi2Te3-ySey薄膜的塞贝克系数更高,为-60mV/K。     

Non‐isolated single‐switch DC–DC converters with extended duty cycle for high step‐down voltage applications

Several new topologies of single‐switch non‐isolated DC–DC converters with wide conversion gain and reduced semiconductor voltage stress are proposed in this paper. Most of the proposed topologies are derived from the conventional inverse of SEPIC (Zeta) converter. The proposed topologies can operate with larger switch duty cycles compared with the existing single switch topologies, hence, making them well suitable for high step‐down voltage conversion applications. With extended duty cycle, the current stress in the active power switch is reduced, leading to a significant improvement of the system losses. Moreover, the active power switch in some of the proposed topologies is utilized much better compared to the conventional Zeta and quadratic‐buck converters. The principle of operation, theoretical analysis, and comparison of circuit performances with other step‐down converters are discussed regarding voltage and current stress and switch silicon utilization. Finally, simulation and experimental results for a design example of a 50 W/5 V at 42‐V input voltage operating at 50 kHz will be provided to evaluate the performance of the proposed converters. Copyright © 2014 John Wiley & Sons, Ltd.     

Nd–Fe–B thick films prepared at the high deposition rate of 90 µm/h

After a postannealing process, the magnetic properties of pulsed laser deposition (PLD)‐made Nd–Fe–B film magnets prepared at the deposition rate of 20–90 µm/h showed constant values, and the average values of H_c, B_r and (BH)_max were 1050 kA/m, 0.6 T, and 60 kJ/m³, respectively. The obtained results were comparable to those previously reported. In conclusion, it was found that a maximum deposition rate of 90 µm/h could be achieved without deterioration of magnetic and mechanical properties. © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Low‐power,low‐noise,active‐RC band‐pass filters using a ‘lossy’ LP–BP transformation

A new and straightforward design procedure for simple canonical topologies of allpole, active‐RC, low‐selectivity band‐pass (BP) filters, with low sensitivity to component tolerances is presented. The procedure is primarily intended for discrete‐component, low‐power filter applications using just one amplifier for relatively high‐order filters. The design procedure starts out with an ‘optimized’ low‐pass (LP) prototype filter, yielding an ‘optimized’ BP filter, whereby the wealth of ‘optimized’ single‐amplifier LP filter designs can be exploited. Using a so‐called ‘lossy’ LP–BP transformation, closed‐form design equations for the design of second‐ to eighth‐order, single‐amplifier BP filters are presented. The low sensitivity, low power consumption, and low noise features of the resulting circuits, as well as the influence of the finite gain‐bandwidth product and component spread, are demonstrated for the case of a fourth‐order filter example. The optimized single‐opamp fourth‐order filter is compared with other designs, such as the cascade of optimized Biquads. Using PSpice with a TL081 opamp model, the filter performance is simulated and the results compared and verified with measurements of a discrete‐component breadboard filter using 1% resistors, 1% capacitors, and a TL081 opamp. Copyright © 2011 John Wiley & Sons, Ltd.     

Forecasting of solar irradiance with just‐in‐time modeling

PV power output mainly depends on solar irradiance, which is affected by various meteorological factors. Thus, it is required to predict solar irradiance in the future for the efficient operation of PV systems. In this paper we develop a novel approach for solar irradiance forecasting, in which we combine the black–box model (JIT modeling) with the physical model (GPV data). We investigate the predictive accuracy of solar irradiance over a wide controlled area of each electric power company by utilizing measured data from 44 observation points throughout Japan provided by JMA and 64 points around Kanto provided by NEDO. Finally, we propose an applied forecasting method of solar irradiance to deal with difficulties in compiling databases. We also consider the influence of different GPV default times on solar irradiance prediction. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 182(4): 19–28, 2013; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.22338     

Microstructure and magnetic properties of aerosol‐deposited Sm‐Fe‐N thick films

In this study, the relationship among magnetic properties, Aerosol Deposition (AD) conditions, and microstructures in Sm‐Fe‐N AD films was investigated. The maximum thickness of 145µm was obtained under AD conditions of gas flow rate (gfr)=6liters/min for 10 min. The density of Sm‐Fe‐N films was in the range of 5.43 to 6.24g/cm³, that is, 71 to 81% of the X‐ray density of the Sm₂Fe₁₇N₃ compound reported (7.67g/cm³). The Sm‐Fe‐N AD films showed remanence in the range of 0.38 to 0.42 T, that is, 61 to 68% of that of the Sm‐Fe‐N host powder (0.62 T). The coercivities increased from 1.16 to between 1.74 and 1.79 T after the deposition because the grain size decreased from 1.94µm to 0.32µm. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 158(1): 8–13, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20214     

A systematic method for the development of a three‐phase transformer non‐linear model

In this work, a novel three‐phase transformer non‐linear model is developed. The proposed model takes into account the magnetic core topology and the windings connections. The non‐linear characteristic curve of the core material is introduced by its magnetization curve or by its hysteresis loop using the mathematical hysteresis model proposed by Tellinen or the macroscopic hysteresis model proposed by Jiles–Atherton. The eddy currents effects are included through non‐linear resistors using Bertotti's work. The proposed model presents several advantages. An incremental linear circuit, having the same topology with the magnetic circuit of the core, is used in order to directly write the differential equations of the magnetic part of the transformer. The matrix L _d that describes the coupling between the windings of the transformer is systematically derived. The electrical equations of the transformer can be easily written for any possible connection of the primary and secondary windings using the unconnected windings equations and transformation matrices. The proposed methods for the calculation of the coupling between the windings, the representation of the eddy currents and the inclusion of the core material characteristic curve can be used to develop a transformer model appropriate for the EMTP/ATP‐type programs. Copyright © 2009 John Wiley & Sons, Ltd.     

Preparation of BST thin films on Pt electrode on Si wafer with down-flow LSMCVD reactor

Abstract

A novel type of down-flow LSMCVD (Liquid Source Mist CVD) reactor was developed to prepare a high dielectric BST thin film on Pt electrode on Si wafer. Barium acetate [Ba (OOCCH₃)₂], strontium acetate [Sr (OOCCH₃)₂], and titanium isoproxide [Ti (OC₃H₇ ⁱ )₄] were used as metal sources. Metal sources were dissolved in acetic acid, 1-butanol, or 2-methoxyethanol. BST [Ba/(Ba + Sr) = 0.7] film annealed on Pt/Ti/SiO₂/Si above 650°C was polycrystalline. BST film has a (110) preferred orientation with increasing temperature. Surface roughness of BST film and grain size increased with increasing temperature. The metal-oxygen bond was formed at 650°C as shown in the spectra of FTIR. The depth profiles of elements of BST thin films indicated a uniform composition throughout the film. BST films annealed at 750°C showed a dielectric constant and a tanδ of 390 (thickness: 150 nm) and 0.06 at a frequency of 100 kHz, respectively. The behavior of capacitance of the BST film with bias voltage showed paraelectric property. BST film annealed at 750°C had the leakage current density of 3.2 (μA/cm²) at a bias voltage of 2V.     

A fast time‐domain EM–TCAD coupled simulation framework via matrix exponential with stiffness reduction

We present a fast time‐domain multiphysics simulation framework that combines full‐wave electromagnetism (EM) and carrier transport in semiconductor devices (technology computer‐aided design (TCAD)) for radio frequency (RF) and mixed‐signal modules. The proposed framework features a division of linear and nonlinear components in the EM–TCAD coupled system. The linear portion is extracted and handled independently with high efficiency by a matrix exponential approach assisted with Krylov subspace method. The nonlinear component is treated by ordinary Newton's method yet with a much sparser Jacobian matrix that leads to substantial speedup in solving the linear system of equations. More convenient error management and adaptive control are also available through the linear and nonlinear decoupling. Furthermore, a new form of system formulation is developed to further enhance the efficiency of the proposed framework by reducing the stiffness of EM–TCAD systems via special equation and variable transforms. Copyright © 2015 John Wiley & Sons, Ltd.     

Development of a thermal voltage converter with calculable high‐frequency characteristics

A thermal‐voltage converter for high‐frequency (HF‐TVC) AC–DC transfer standard has been developed. The HF‐TVC was designed such that the frequency characteristic is calculable from the shape and dimension of the input circuit. A new multi‐junction thermal converter element (JSTC04) has been developed, which has a simple and straight heater configuration to minimize the parasitic impedances in the input circuit. The AC–DC difference of the HF‐TVC was evaluated by two independent methods, with agreement better than 7 µV/V up to 1 MHz. © 2011 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Green's function approach for modeling of electrostatic effects in nanoscale fully depleted double‐gate silicon‐on‐insulator metal‐oxide‐semiconductor field‐effect transistors

Exact solution of two‐dimensional (2D) Poisson's equation for fully depleted double‐gate silicon‐on‐insulator metal‐oxide‐semiconductor field‐effect transistor is derived using three‐zone Green's function solution technique. Framework consists of consideration of source–drain junction curvature. 2D potential profile obtained forms the basis for estimation of threshold voltage. Temperature dependence of front surface potential distribution, back surface potential distribution and front‐gate threshold voltage are modeled using temperature sensitive parameters. Applying newly developed model, surface potential and threshold voltage sensitivities to gate oxide thickness have been comprehensively investigated. Device simulation is performed using ATLAS 2D (SILVACO, 4701 Patrick Henry Drive, Bldg. Santa Clara, CA 95054 USA) device simulator, and the results obtained are compared with the proposed 2D model. The model results are found to be in good agreement with the simulated data. Copyright © 2013 John Wiley & Sons, Ltd.     

A single‐phase buck‐boost PFC converter with output‐voltage,ripple‐reducing operation

This paper describes a new single‐phase buck‐boost power‐factor‐correction (PFC) converter with output‐voltage, ripple reducing operation. The converter consists of a conventional buck‐boost PFC converter and an additional switch to obtain a freewheeling mode of the dc inductor current, and is operated by two modulators. The first modulator controls the buck‐boost switch to obtain PFC. The other modulator controls the square value of the instantaneous dc inductor current to perform the output‐voltage‐ripple‐reducing operation. In the two modulations, the time integral value of the input and output currents in each modulation period are controlled directly and indirectly, respectively. Thus, modulation errors or undesirable distortions of the input current and output voltage ripple are eliminated even if the dc inductor current produces large ripple in a low‐frequency range. The theories and combination techniques for the two modulators, implementation, and experimental results are described. © 1998 Scripta Technica, Electr Eng Jpn, 126(2): 56–70, 1999     

High‐frequency measurements of the magnetoresistance effect of thin films

The ac magnetoresistance of thin films at frequencies up to 10 kHz was successfully measured. Patterned electrodes with mechanical flexibility were pressed onto the film surface by using a rubber pad. Induction noises were reduced considerably in comparison to the conventional four‐electrode method. A seven‐electrode system was developed to prevent high‐frequency induction noise, typically induced by leakage flux from the sample edges. It was found that the seven‐electrode system enables magnetoresistance measurements with little induction noise at frequencies up to 10 kHz. © 2000 Scripta Technica, Electr Eng Jpn, 132(2): 1–5, 2000     

Switched‐capacitor‐voltage‐multiplier boost DC–AC inverter with adaptive stages

A multistage switched‐capacitor‐voltage‐multiplier inverter (SCVMI) is proposed with a variable‐conversion‐ratio phase generator and a sinusoidal pulse‐width‐modulation controller for boost DC–AC conversion and high‐efficiency regulation. Its power unit contains: SCVM booster and H‐bridge. The SCVM booster includes two m_c‐stage switched‐capacitor cells and two n_c‐stage switched‐capacitor cells in the interleaving operation to realize DC–DC boost gain of m_c × n_c at most. Here, the variable‐conversion‐ratio phase generator is suggested and adopted to change the running stage number and topological path for a suitable gain level of m × n (m = 1, 2, ?,m_c, n = 1, 2, ?,n_c) to improve efficiency, especially for the lower AC output. The H‐bridge is employed for DC–AC conversion, where four switches are controlled by sinusoidal pulse‐width‐modulation not only for full‐wave output but also for output regulation as well as robustness to source/loading variation. Some theoretical analysis and design include: SCVMI model, steady‐state/dynamic analysis, conversion ratio, power efficiency, stability, capacitance selection, output filter, and control design. Finally, the closed‐loop SCVMI is simulated, and the hardware circuit is implemented and tested. All the results are illustrated to show the efficacy of this scheme. Copyright © 2011 John Wiley & Sons, Ltd.     

On IIR‐based bit‐stream multipliers

We analyze the existing bi‐level IIR‐based bit‐stream multiplier and propose selection criteria for the key design parameter governing droop and phase linearity. Based on the proposed choice of parameter, we then extend the bi‐level design to tri‐ and quad‐level architectures that offer better signal‐to‐noise performance. Hardware complexity and noise performance of these designs are also contrasted with previously proposed FIR‐based bit‐stream multipliers. Useful design guidelines are subsequently drawn. Copyright © 2010 John Wiley & Sons, Ltd.     

A new control strategy with fault ride‐through capability for VSC‐based offshore high power oil pump motor power supply system

In offshore oil platforms, high voltage and power motors (HV motors) are needed when transporting oil to the land. Traditional platform diesel generators cannot support so much power, so the required system must be supplied by the onshore AC grid. In general, when there is a long distance between the offshore platform and the shore, a DC transmission system is more efficient. This paper proposes a power supply approach for these motors using a voltage source converter (VSC) and derives the mathematical model for it. This method combines motor drive theory and studies in DC transmission field. Compared with the traditional motor control, this method, which makes full use of the advantages of VSC, can simplify the control strategy. And by using the Q–U droop characteristic, the strategy improves the system stability and fault ride‐through capability. Simulation is carried out in PSCAD/EMTDC, and the results verify the validity of the control method. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

A hybrid noise canceller with a real‐time adaptive Wiener filter and a geometric‐based voice–activity detector for an automotive application

In real‐time environments a speech recognition system in a car has to receive the driver's voice only while suppressing the background noise. This paper presents a hybrid real‐time adaptive filter that operates within a geometrical zone defined around the head of the desired speaker. Any sound outside of this zone is considered to be noise and is suppressed. As this defined geometrical zone is small, it is assumed that only driver's speech is incoming from this zone. The technique uses three microphones to define a geometric‐based voice–activity detector (VAD) to cancel the unwanted speech coming from outside of the zone. However, when unwanted speech and desired speech are incoming at the same time, the VAD fails to identify the unwanted speech or desired speech. In such a situation an adaptive Wiener filter is switched on for noise reduction. In the case of sole unwanted speech incoming from outside of a desired zone, this speech is muted at the output of the hybrid noise canceller. In the case of desired and unwanted speeches incoming together, the SNR is improved by as much as 20 dB. Copyright © 2009 John Wiley & Sons, Ltd.     

Development of Cockcroft–Walton‐type high‐voltage DC generator with RF air‐core transformer

A new Cockcroft–Walton (CW)‐type high‐voltage DC generator with RF air‐core transformer used as a step‐up transformer has been developed. The design concept of the air‐core transformer is shown, which is operated on the resonance condition between the inductance of the secondary coil and the stray capacitance of CW circuit with the conical‐type coil structure. Adapting the RF air‐core transformer to CW circuit with DC‐300 kV 100 mA, excellent performances have been demonstrated. In the new CW circuit, it results in downsizing of capacitors to operate at higher frequency than conventional ones, and reduction of the volume by approximately 40% has been shown in the typical DC generator with 1 MV 100 mA. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 160(1): 18–26, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20500