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少年人生 2005年第23期 28-37页

作者：于言舒

step distribution of Yb filling fraction during microstructural evolution in skutterudites

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Journal of Advanced Ceramics 2019年第1期8卷 62-71页

作者： Jing MEI Zheng YAO Shuya ZHU Dongli HU Ying JIANG Juanjuan XING Hui GU Lidong CHEN School of Materials Science and Engineering and Materials Genome Institute Shanghai University State Key Laboratory of High Performance Ceramics and Superfine Microstructure Shanghai Institute of Ceramics Chinese Academy of Sciences

To achieve a better material for thermoelectric power generation device, filled skutterudite Yb0.3 Co_4 Sb_(12) samples were fabricated by melting-quenching-annealing-spark plasma sintering(SPS)method. Two sets of samples, before and after SPS, were investigated. In both the two sets of samples,the average grain size of the samples increases monotonously with the increase of annealing time,while Yb filling fraction firstly increases and then decreases. Yb not filling into the skutterudite remains at the grain boundaries in the form of Yb_2 O_3 after SPS, which could be quantified by the spatially difference method of energy dispersive spectra. step distribution of Yb filling fraction was observed in the samples annealed for 1 h, which was caused by the microstructural evolution from the peritectic phases to the skutterudite phase. The sample annealed for 3 days and SPS sintered possesses the maximum value of Yb filling fraction 0.249 and the maximum ZT value of 1.24 at 850 K. These results are helpful to better understand the microstructural evolution and Yb filling behavior in skutterudite materials.

关键词： skutterudite ytterbium filling fraction microstructure step distribution

Analysis and evaluation of electromagnetic vibration and noise in permanent magnet synchronous motor with rotor step skewing

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Science China(Technological Sciences) 2019年第5期62卷 839-848页

作者： DONG QiChao LIU XinTian QI HongZhong SUN Chao WANG YanSong School of Mechanical and Automotive Engineering Shanghai University of Engineering Science Guangzhou Automobile Group CO. LTD Automotive Engineering Institute

In this paper, a multi-physics simulation model capable of electromagnetic noise prediction is established, and the effectiveness of the established simulation model in predicting and evaluating electromagnetic noise is verified. Based on the verified motor model, a rotor step skewing model which can affect electromagnetic noise is proposed, and the influence of the skewing angle on electromagnetic noise is investigated in detail. By studying the spectral characteristics of the low-order radial magnetic force which has a great influence on electromagnetic noise, the distribution of electromagnetic noise characteristics of the permanent magnet synchronous motor(PMSM) with or without the rotor step skewing is compared and analyzed. Therefore, it lays a technological foundation for predicting and suppressing the electromagnetic vibration noise of electric vehicle(EV) driving motor in the electromagnetic design.

关键词： PMSM electromagnetic noise step skewing multi-physics simulation model spectrum analysis

Noise cancellation of a multi-reference full-wave magnetic resonance sounding signal based on a modified sigmoid variable step size least mean square algorithm

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Journal of Central South University 2017年第4期24卷 900-911页

作者： TIAN Bao-feng ZHOU Yuan-yuan ZHU Hui JIANG Chuan-dong YI Xiao-feng Key Laboratory of Geo-Exploration Instrumentation Ministry of Education (Jilin University)Changchun 130026 China College of Instrumentation and Electrical Engineering Jilin University Changchun 130026 China

Nano-volt magnetic resonance sounding(MRS) signals are sufficiently weak so that during the actual measurement, they are affected by environmental electromagnetic noise, leading to inaccuracy of the extracted characteristic parameters and hindering effective inverse interpretation. Considering the complexity and non-homogeneous spatial distribution of environmental noise and based on the theory of adaptive noise cancellation, a model system for noise cancellation using multi-reference coils was constructed to receive MRS signals. The feasibility of this system with theoretical calculation and experiments was analyzed and a modified sigmoid variable step size least mean square(SVSLMS) algorithm for noise cancellation was presented. The simulation results show that, the multi-reference coil method performs better than the single one on both signal-to-noise ratio(SNR) improvement and signal waveform optimization after filtering, under the condition of different noise correlations in the reference coils and primary detecting coils and different SNRs. In particular, when the noise correlation is poor and the SNR<0, the SNR can be improved by more than 8 dB after filtering with multi-reference coils. And the average fitting errors for initial amplitude and relaxation time are within 5%. Compared with the normalized least mean square(NLMS) algorithm and multichannel Wiener filter and processing field test data, the effectiveness of the proposed method is verified.

关键词： magnetic resonance sounding signal multi-reference coils adaptive noise cancellation sigmoid variable step size least mean square (SVSLMS)

Numerical and analytical investigations for the SOI LDMOS with alternated high-k dielectric and step doped silicon pillars

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Chinese Physics B 2020年第3期29卷 460-467页

作者： Jia-Fei Yao Yu-Feng Guo Zhen-Yu Zhang Ke-Meng Yang Mao-Lin Zhang Tian Xia College of Electronic and Optical Engineering&College of Microelectronics Nanjing University of Posts and TelecommunicationsNanjing 210023China National and Local Joint Engineering Laboratory of RF Integration and Micro-Assembly Technology Nanjing 210023China School of Electrical Engineering University of VermontBurlingtonVT 05405USA

This paper presents a new silicon-on-insulator(SOI) lateral-double-diffused metal-oxide-semiconductor transistor(LDMOST) device with alternated high-k dielectric and step doped silicon pillars(HKSD device). Due to the modulation of step doping technology and high-k dielectric on the electric field and doped profile of each zone, the HKSD device shows a greater performance. The analytical models of the potential, electric field, optimal breakdown voltage, and optimal doped profile are derived. The analytical results and the simulated results are basically consistent, which confirms the proposed model suitable for the HKSD device. The potential and electric field modulation mechanism are investigated based on the simulation and analytical models. Furthermore, the influence of the parameters on the breakdown voltage(BV) and specific on-resistance(R_(on,sp)) are obtained. The results indicate that the HKSD device has a higher BV and lower R_(on,sp) compared to the SD device and HK device.

关键词： high-k dielectric step doped silicon pillar model breakdown voltage

THEORY FOR step AND PULSE METHOD OF SUPERCRITICAL FLUID CHROMATOGRAPHY

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Chinese Journal of Chemical Engineering 1996年第4期4卷 54-62页

作者：赵锁奇王仁安杨光华石油大学（北京）重质油加工国家重点实验室北京 102200 石油大学（北京）重质油加工国家重点实验室北京

The paper presents a general retention formula for supercritical fluid chromatography at finite concentration. A new chromatographic rate theory based on the fugacities of solutes instead of concentrations is developed, thus relieving the restrictions of linear isothermal distribution and infinite dilution. An expression for retention values of a N component system including solvent is obtained by combining the rate theory with the mass balance equation of solutes in chromatography. It is shown that there are N-1 characteristic retention peaks for N components and the retention time can be calculated directly from the equilibrium properties of the components in both mobile phase and stationary phase at the given conditions. The theory can be reduced to the well known formula for infinite dilution and to the result of step-pulse theory in gas chromatography under low pressure at finite concentration. Supercritical fluid chromatography may eventually prove itself to be a useful reseach tool in the field of phase equilibrium and thermodynamic properties of supercritical fluid system.

关键词： supercritical fluid chromatography fugacity step and pulse finite concentration retention time

Numerical simulation of flow separation over a backward-facing step with high Reynolds number

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Water Science and Engineering 2019年第2期12卷 145-154页

作者： Fang-fang Wang Shi-qiang Wu Sen-lin Zhu State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering Nanjing Hydraulic Research Institute

Large eddy simulation (LES) explicitly calculates the large-scale vortex field and parameterizes the small-scale *** this study,LES and κ-ε models were developed for a specific geometrical configuration of backward-facing step (BFS).The simulation results were validated with particle image velocimetry (PIV) measurements and direct numerical simulation (DNS).This LES simulation was carried out with a Reynolds number of 9000 in a pressurized water tunnel with an expansion ratio of *** results indicate that the LES model can reveal largescale vortex motion although with a larger grid-cell ***,the LES model tends to overestimate the top wall separation and the Reynolds stress components for the BFS flow simulation without a sufficiently fine ***,LES is a potential tool for simulating separated flow controlled by large-scale vortices.

关键词： Large eddy simulation κ-ε model Backward-facing step Direct numerical simulation Large-scale vortices Particle image velocimetry

Applying a step Approach Method in Solving the Multi-Frequency Radiation From a Complex Obstacle

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Computer Modeling in Engineering & Sciences 2016年第7期112卷 59-73页

作者： Jui-Hsiang Kao Department of Systems Engineering and Naval Architecture National Taiwan Ocean UniversityKeelungTaiwanR.O.C

In this paper,a step approach method in the time domain is developed to calculate the radiated waves from an arbitrary obstacle pulsating with multiple *** computing scheme is based on the Boundary Integral Equation and derived in the time domain;thus,the time-harmonic Neumann boundary condition can be *** the present method,the values of the initial conditions are set to zero,and the approach process is carried forward in a loop from the first time step to the *** each time step,the radiated pressure on each element is *** several loops,the correct radiated pressures can be obtained.A sphere pulsating with a monopole frequency in an infinite acoustic domain is calculated *** result is compared with the analytical solution,and both of them are in good ***,a complex-shaped radiator is taken as the studied *** pulsating frequency of this case is multiple,and the waves propagate in half *** is shown that the present method can treat multiple-frequency pulsation well,even when the radiator is a complex shape,and a robust convergence can be attained quickly.

关键词： step approach method Time domain Radiated waves Multiple frequencies Boundary integral equation Neumann boundary condition

The reflection of regular and irregular waves by a partially perforated caisson breakwater on a step bed

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Acta Oceanologica Sinica 2009年第4期28卷 107-117页

作者： LIU Yong LIYucheng TENG Bin XIA Zhisheng Key Laboratory of Ocean Engineering Ocean University of China Qingdao 266100 China State Key Laboratory of Coastal and Offshore Engineering Dalian University of Technology Dalian 116024 China Key Laboratory of Water ＆ Water ＆ Sediment Science and Water Hazard Prevention Changsha 410076 China

This study examines the reflection of regular and irregular waves from a partially perforated caisson breakwater located on a step bed. The step bed is treated as an idealized rubble mound foundation. Based on the linear potential theory, an analytical solution is developed to calculate the reflection coefficient of the structure subjected to regular waves. The matched eigenfunction expansion method is used for the solution. The regular wave method is also extended to irregular waves using a linear transfer function. The calculated results obtained for limiting cases are exactly the same as corresponding results given by the previous researchers. The present predictions also agree well with experimental data in the published literatures. Numerical experiments are conducted to examine the variations of the reflection coefficient versus its main effect factors, and some interesting results are presented.

关键词： partially perforated caisson step irregular waves reflection coefficient

DESCENT DIRECTION STOCHASTIC APPROXIMATION ALGORITHM WITH ADAPTIVE step SIZES

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Journal of Computational Mathematics 2019年第1期37卷 76-94页

作者： Zorana Luzanin Irena Stojkovska Milena Kresoja Department of Mathematics and Informatics Faculty of SciencesUniversity of Novi Sad Novi SadSerbia Department of Mathematics.Faculty of Natural Sciences and Mathematics Ss.Cyril and Methodius UniversitySkopjeMacedonia

A stochastic approximation (SA)algorithm with new adaptive step sizes for solving unconstrained minimization problems in noisy environment is *** adaptive step size scheme uses ordered statistics of fixed number of previous noisy function values as a criterion for accepting good and rejecting bad *** scheine allows the algorithm to move in bigger steps and avoid steps proportional to 1/k when it is expected that larger steps will improve the *** algorithin with the new adaptive scheme is defined for a general descent *** ahnost sure convergence is *** performance of new algorithm is tested on a set of standard test problems and compared with relevant *** results support theoretical expectations and verify efficiency of the algorithm regardless of chosen search direction and noise *** results on probleins arising in machine learning are also *** regression problem is considered using real data *** results suggest that the proposed algorithln shows proinise.

关键词： Unconstrained optimization Stochastic optimization Stochastic approximation Noisy function Adaptive step size Descent direction Linear regression model