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Laminar flow.of micropolar fluid in rectangular microchannels

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Acta Mechanica Sinica 2006年第5期22卷 403-408页

作者： Shangjun Ye Keqin Zhu w. wang Department of Engineering Mechanics Tsinghua University Beijing 100084 China Medical Engineering Division Department of Engineering Queen Mary University of London London E1 4NS UK

Compared w.th the classic flow.on macroscale, flow. in microchannels have some new.phenomena such as the friction increase and the flow.rate reduction. Papautsky and co-w.rkers explained these phenomena by using a micropolar fluid model w.ere the effects of micro-rotation of fluid molecules w.re taken into account. But both the curl of velocity vector and the curl of micro-rotation gyration vector w.re given incorrectly in the Cartesian coordinates and then the micro-rotation gyration vector had only one component in the z-direction. Besides, the gradient term of the divergence of micro-rotation gyration vector w.s missed improperly in the angular moment equation. In this paper, the governing equations for laminar flow. of micropolar fluid in rectangular microchannels are reconstructed. The numerical results of velocity profiles and micro-rotation gyrations are obtained by a procedure based on the Chebyshev collocation method. The micropolar effects on velocity and micro-rotation gyration are discussed in detail.

关键词： Micropolar fluid. Microchannel Flow.ate reduction Chebyshev collocation method

CALCULATION OF SECOND PHASE PARTICLE-GRAIN BOUNDARY INTERACTION RANGE

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Acta Metallurgica Sinica(English Letters) 2008年第1期21卷 8-14页

作者： X.L. wang Y.H. w.i w. wang L.F. Hou College of Materials Science and Engineering Taiyuan University of Technology Taiyuan 030024 China Baosteel Technology Center Baoshan Iron ＆ Steel Co. Ltd. Shanghai 201900 China Manuscript received 20 December 2006

On the basis of the grain boundary equation by HeUman and corresponding analysis of w.rner, this article deals w.th the interaction range betw.en the second-phase particle （SPP） and grain boundary （GB） as view.d from the applicability of grain boundary equation. Also, a new.expression describing the interaction range has been derived, w.ich solves the problem in theory that the interaction range betw.en SPP and GB can only be qualitatively analyzed previously. It is show. that given the interaction position betw.en SPP and GB, the interaction range can be quantitatively determined by use of this expression.

关键词： Second-phase particle Grain boundary Pinning force Surface free energy

Convergence of ADMM for multi-block nonconvex separable optimization models

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Frontiers of Mathematics in China 2017年第5期12卷 1139-1162页

作者： Ke GUO Deren HAN David Z. w. wang Tingting w. School of Mathematical Sciences and Key Laboratory for NSLSCS of Jiangsu Province Nanjing Normal University Nanjing 210023 China School of Civil and Environmental Engineering Nanyang Technological UniversitySingapore 639798 Singapore School of Science Nanjing University of Posts and Telecommunications Nanjing 210023China

For solving minimization problems w.ose objective function is the sum of tw. functions w.thout coupled variables and the constrained function is linear, the alternating direction method of multipliers （ADMM） has exhibited its efficiency and its convergence is w.ll understood. w.en either the involved number of separable functions is more than tw., or there is a nonconvex function~ ADMM or its direct extended version may not converge. In this paper, w. consider the multi-block *** optimization problems w.th linear constraints and absence of convexity of the involved component functions. Under the assumption that the associated function satisfies the Kurdyka- Lojasiew.cz inequality, w. prove that any cluster point of the iterative sequence generated by ADMM is a critical point, under the mild condition that the penalty parameter is sufficiently large. w. also present some sufficient conditions guaranteeing the sublinear and linear rate of convergence of the algorithm.

关键词： Nonconvex optimization separable structure alternating directionmethod of rnultip!iers (.ADMM) Kurdyka-Lojasiew.cz inequality

Experimental Study on Transient Natural Convection in a Cube Enclosure w.th an Isolated Vertical Cyclically Heated Plate

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Journal of Thermal Science 1999年第1期8卷 51-58页

作者： C. M. Ling Q. w. wang w. Q. Tao H. Ozoe School of Energy and Pow.r Engineering Xi’an Jiaotong University Xi’an China Institute of Advanced Material Study Kyushu University 86 Kasuga Japan

The low.frequency cyclical transient natural convection in a cube enclosure w.th an internal isolated vertical heated plate w.s investigated experimentally. A computer-aided experimental system w.s designed to generate the cyclical heating pow.r input and also used for data reduction. The effects of the cyclic heating pow.r input amplitude (from 0 to 8 w. and frequency (from 1/5400 s-1 to 1/600 s-1)as w.ll as the per-cycle time-average pow.r input (from 8 to 24 w. on the transient and time-average Nusselt number w.re parametrically studied. It w.s found that for such cyclical transient natural convection w.th low.frequency, the plate heating pow.r input amplitude and frequency have little effects on the time-average Nusselt number as long as the cyclical time-average heating pow.r input remains the same, although the transient Nusselt number may be significantly affected. Therefore, the modified Grashof number based on the plate average heat flux can be used to characterize the time-average heat transfer process. The plate time-average Nusselt number is about 15% less than the infinite-space Nusselt number. The location of the isolated plate in enclosure does not appreciably influence the time-average heat transfer characteristics of the plate.

关键词： natural convection in enclosure isolated plate transient cyclically heating pow.r input.

SUPERPLASTICITY OF A SiC_w.2024 Al COMPOSITE MADE BY PRESSURE INFILTRATION

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Acta Metallurgica Sinica(English Letters) 2002年第5期15卷 425-430页

作者： X. J. Xu , w. wang and L. CaiJiangsuUniversity of Science and Technology, Zhenjiang 212013, China Jiangsu University of Science and Technology

The superplastic characteristics of the β-SiC w.isker reinforced 2024 aluminum composite, fabricated by pressure infiltration and hot-rolling after extrusion, w.re investigated. The composite has a fine grain size of about 1μm, and exhibits a maximum tensile elongation of 370% in the initial strain rate of 3.3×10-3 s-1 at *** superplastic deformation mechanism of the composite is thought to be grain boundary (interface) sliding accommodated by grain boundary diffusion of aluminum atom and an appropriate amount of liquid phase.

关键词： superplasticity aluminum matrix composites pressure infiltra-tion

STUDY ON Ni-Cr SYSTEM SOLAR SELECTIVE THIN FILMS PREPARED BY MAGNETRON REACTIVE SPUTTERING PROCESS

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Acta Metallurgica Sinica(English Letters) 2002年第2期15卷 203-206页

作者： B. w. wang and H. Shen Guangzhou Institute of Energy Conversion, The Chinese Academy of Sciences, Guangzhou 510070, China Gua.igzhou institute of Energy Conversion The Chinese Acadenw of Sciences

Ni-Cr System solar selective thin solid films w.re prepared by d.c. magnetron reactive sputtering under the atmosphere of O2 and N2. Ni-Cr alloy w.s chosen as target material and copper sheets as substrate. Using SEAL Spectrophotometer and Talystep to analyze the relations betw.en the selective characteristic and the structure, the formation and the thickness of the thin films. The aim is to obtain good solar selective thin films w.th high absorptance and low.emittance, w.ich is applied to flat plate solar heat collectors.

关键词： solar selective thin film magnetron reactive sputtering. absorptance emittance

FEM NUMERICAL SIMULATION OF THE SOFT MEDIUM TUBE EXPANSION PROCESS

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Acta Metallurgica Sinica(English Letters) 2000年第2期13卷 697-701页

作者： J.L. Song and w. w. wang Taiyuan Heavy Machinery Institute, Taiyuan 030024, China

In this paper the soft medium tube expanding process of different loading case and tube sheet structure is simulated w.th FEM. The expanding patterns under different conditions are obtained. The correction of the Sing... 详细信息

关键词： soft medium tube expansion FEM simulation single-tube model

An explicit solution to a three-dimensional w.dge problem considering tw. edges effect

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Friction 2020年第2期8卷 370-383页

作者： L.GUO Z.M.ZHANG w.wang Y.ZHAO P.L.w.NG School of Mechatronic Engineering and Automation Shanghai UniversityShanghai 200444China Department of Mechanical Engineering City University of Hong KongHong Kong SARChina

The paper presents an explicit matrix algorithm to solve the problem of an elastic w.dge w.th three loaded *** algorithm makes use of a recently published concept of transformation matrix,by w.ich the original surface loads are converted to equivalent loads in *** three loaded edges are considered *** developed algorithm is used to study the effects of tw. free edges of a steel block and tapered rollers w.th different contact *** tw. load-free edges can substantially increase deformation if the tw. edges are close in *** results of the tapered roller simulation show.that deformation is considerably sensitive to the contact angle of the tapered *** largest deformation appears at the big end of the ***,empirical formulae for correction factors for the calculation of block or quarter-space deformation based on half-space solutions are summarized.

关键词： contact mechanics tw. edge surfaces finite line contact tapered roller contact

FAST Observations of an Extremely Active Episode of FRB 20201124A:Ⅰ.Burst Morphology

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Research in Astronomy and Astrophysics 2022年第12期22卷 54-69页

作者： D.J.Zhou J.L.Han B.Zhang K.J.Lee w.w.Zhu D.Li w.C.Jing w.-Y.wang Y.K.Zhang J.C.Jiang J.R Niu R Luo H.Xu C.F.Zhang B.J.wang J.w.Xu P.wang Z.L.Yang Y.Feng National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China School of Astronomy University of Chinese Academy of SciencesBeijing 100049China CAS Key Laboratory of FAST NAOCChinese Academy of SciencesBeijing 100101China Department of Physics and Astronomy University of NevadaLas VegasNV 89154USA Kavli Institute for Astronomy and Astrophysics Peking UniversityBeijing 100871China Department of Astronomy Peking UniversityBeijing 100871China CSIRO Space and Astronomy EppingNSW 1710Australia Research Center for Intelligent Computing Platforms Zhejiang LaboratoryHangzhou 311100China

w. report the properties of more than 600 bursts(including cluster-bursts)detected from the repeating fast radio burst(FRB)source FRB 20201124A w.th the Five-hundred-meter Aperture Spherical radio Telescope during an extremely active episode on UTC 2021 September 25–28,in a series of four *** observations w.re carried out in the band of 1.0–1.5 GHz by using the center beam of the L-band 19-beam *** monitored the source in sixteen1 hr sessions and one 3 hr session spanning 23 *** the bursts w.re detected during the first four *** this first paper of the series,w. perform a detailed morphological study of 624 bursts using the tw.-dimensional frequencytime“w.terfall”plots,w.th a burst(or cluster-burst)defined as an emission episode during w.ich the adjacent emission peaks have a separation shorter than 400 *** duration of a burst is therefore alw.ys longer than 1 ms,w.th the longest up to more than 120 *** emission spectra of the sub-bursts are typically narrow.w.thin the observing band w.th a characteristic w.dth of~277 *** center frequency distribution has a dominant peak at about 1091.9 MHz and a secondary w.ak peak around 1327.9 *** bursts show.a frequencydow.w.rddrifting *** on the drifting patterns,w. classify the bursts into five main categories:dow.w.rd drifting(263)bursts,upw.rd drifting(3)bursts,complex(203),no drifting(35)bursts,and no evidence for drifting(121)*** are introduced based on the emission frequency range in the band(low.middle,high and w.de)as w.ll as the number of components in one burst(1,2,or multiple).w. measured a varying scintillation bandw.dth from about 0.5 MHz at 1.0 GHz to 1.4 MHz at 1.5 GHz w.th a spectral index of 3.0.

关键词： (stars:)pulsars:general Physical Data and Processes stars:individual(FRB 20201124A)