检索结果-南通市图书馆

Effect of duct Geometry on Shock Wave discharge

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of thermal Science 2006年第4期15卷 349-354页

作者： Y.-H.Kweon Y.Miyazato t.Aoki H.-d.Kim t.Setoguchi department of Energy and Environmental Engineering Kyushu UniversityKasuga 816-8580Japan Faculty of Environmental Engineering The University of KitakyushuKitakyushu 808-0135Japan School of Mechanical Engineering Andong National UniversityAndong 760-749Korea department of Mechanical System Engineering Saga UniversitySaga 840-8502Japan

this paper describes computational work to understand the unsteady flow-field of a shock wave discharging from an exit of a duct and impinging upon a flat plate. A flat plate is located downstream, and normal to the axis of the duct. the distance between the exit of the duct and flat plate is changed. In the present study, two different duct geometries （i.e., square and cross section） are simulated to investigate the effect of duct geometry on the un-steady flows of a shock wave. In computation, the total variation diminishing （tVd） scheme is employed to solve three-dimensional, unsteady, compressible, Euler equations. Computations are performed over the range of shock Mach number from 1.05 to 1.75. Computational results can predict the three-dimensional dynamic behaviour of the shock wave impinging upon the flat plate. the results obtained show that the pressure increase generated on the plate by the shock impingement depends on the duct geometry and the distance between the duct exit and plate, as well as the shock Mach number. It is also found.t.at for the duct with cross-section, the unsteady loads acting on the flat plate are less, compared with the square duct.

关键词： unsteady flow compressible flow shock wave shock impingement duct geometry

Cleaning properties of dry adhesives

在线全文

学校读者我要写书评

暂无评论

Science China(technological Sciences) 2010年第11期53卷 2942-2946页

作者： J. P. díAZ téLLEZ d. SAMEOtO C. MENON MENRVA Group School of Engineering Science Simon Fraser University department of Mechanical Engineering University of Alberta

In this paper we present a study into the cleaning properties of synthetic dry adhesives. We have manufactured the adhesive micro-fibres through a low-cost, high yield fabrication method using Sylgard 184 Polydimethylsiloxane (PdMS) as the structural material. We deliberately contaminated the adhesive samples with different sized particles in the micro and macro scales and tested different cleaning methods for their efficacy with respect to each particle size. We investigated different cleaning methods, which included the use of wax moulding, vibration and pressure sensitive adhesives. For adhesion testing we used a custom system with a linear stage and a force sensor indenting a hemispherical probe into the adhesive surface and measuring the pull-off force. to characterize the cleaning efficacy we visually inspected each sample in a microscope and weighed the samples with a microgram-accuracy analytical balance. Results showed.t.at the moulding method induced adhesion recovery in a greater percentage than the other cleaning methods and even helped with the recovery of collapsed posts in some cases. On the other hand pressure sensitive adhesives seem to have the upper hand with regards to certain particle sizes that can potentially pose problems with the moulding method.

关键词： biomimetic dry adhesive PdMS self-cleaning gecko climbing

GENERALIZAtIONS OF KY FAN’S tHEOREM ON BESt APPROXIMAtIONS

在线全文

学校读者我要写书评

暂无评论

Analysis in theory and Applications 2009年第2期25卷 109-116页

作者： t. d. Narang department of Mathematics Guru Nanak dev University

In 1969, Ky Fan^[3] proved.t.at for any continuous function f from a compact convex subset M of a normed linear space X into X, there exists x E M such that ｜｜f（x） - x｜｜ = dist（f（x）,M）. Since then, there have appeared several generalizations, extensions and applications of this result. this paper also deals with some extensions and generalizations of this result when the underlying spaces are convex metric spaces.

关键词： upper semi-continuous map compact map proper map affine map almostaffine map acyclic map K-mapping star-shaped set

SOME RESULtS ON BESt APPROXIMAtION IN SPACES WItH CONVEX StRUCtURE

在线全文

学校读者我要写书评

暂无评论

Analysis in theory and Applications 2008年第1期24卷 67-73页

作者： t. d. Narang Guru Nanak dev University India

Some generalizations of the result proved by S.P. Singh [J. Approx. theory 25（1979）, 89-90] are presented in convex metric spaces. the results proved contain several known results on the subject.

关键词： convex metric space convex set starshaped set non-expansive map affinemap

REdUCtION BEHAVIOR OF IRON ORE PELLEtS CONtAININGCARBON UNdER NON-ISOtHERMAL CONdItION

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2000年第5期13卷 1059-1067页

作者： X.M.Yang Y.S.Xie d.G.Wang d.B.Huang t.J.Yang L.t.Kong Institute of Chemical Metallurgy The Chinese Academy of Sciences Beijing 100080China University of Science and technology Beijing Beijing 100083China

the reduction behavior of iron ore pellets containing carbon under non-isothermal condition in the temperature range from 573 to 1373 K was investigated in a laboratory scale setup. the test results show that carbon content has no obvious effect on reduction degree of composite pellets (C/O mole ratio=1.0) by CO in the temperature range from 573 to 1373 K under linear temperature-rising program; reduction degree of iron ore pellets containing carbon is large in 90%CO-10%CO2 mixture than that of in 100%CO atmosphere or in 80%CO-20%CO2 mixture; the s type temperature-rising program has a better effect than that of linear one in increasing the reduction degree; and reduction degree of slower linear temperature-rising program is greater than that of faster one, but the final reduction degrees, i.e., those at the highest temperature are about the same for various CO partial pressures or temperature-rising programs. the kinetic analysis also shows that the reduction of iron ore-carbon composite pellets by CO or CO-CO2 mixture under non-isothermal condition should be controlled by surface reaction, and the apparent reduction activation energy changes with the reduction progress under various test conditions.

关键词： iron ore pellet containing carbon reduction behavior kinetics activation energy non-isothermal

Finite element simulations on the mechanical properties of MHS materials

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2007年第1期23卷 65-75页

作者： Z. Y. Gao t. X. Yu d. Karagiozova department of Mechanical Engineering Hong Kong University of Science &Technology Clear Water Bay Kowloon Hong Kong China Institute of Mechanics Bulgarian Academy of Sciences Acad. G. Bonchev Street Block 4 Sofia 1113 Bulgaria

Finite element simulations are carried out to examine the mechanical behavior of the metallic hollow sphere （MHS） material during their large plastic deformation and to estimate the energy absorbing capacity of these materials under uniaxial compression. A simplified model is proposed from experimental observations to describe the connection between the neighboring spheres, which greatly improves the computation efficiency. the effects of the governing physical and geometrical parameters are evaluated; whilst a special attention is paid to the plateau stress, which is directly related to the energy absorbing capacity. Finally, the empirical functions of the relative material density are proposed for the elastic modulus, yield strength and plateau stress for FCC packing arrangement of hollow spheres, showing a good agreement with the experimental results obtained in our previous study.

关键词： Cellular material Hollow sphere Large plastic deformation Numerical simulation FEM

Optimization Study of a Coanda Ejector

在线全文

学校读者我要写书评

暂无评论

Journal of thermal Science 2006年第4期15卷 331-336页

作者： H.d.Kim G.Rajesh t.Setoguchi S.Matsuo School of Mechanical Engineering Andong National University388Songcheon-dongAndongGyeongbuk 760-749Korea department of Mechanical Engineering Saga University1HonjoSaga 840-8502Japan

the Coanda effect has long been employed in the aerospace applications to improve the performances of various devices. this effect is the ability of a flow to follow a curved contour without separation and has well been utilized in ejectors where a high speed jet of fluid emerges from a nozzle in the ejector body, follows a curved surface and drags the secondary flow into the ejector. In Coanda ejectors, the secondary flow is dragged in the ejector due to the primary flow momentum. the transfer of momentum from the primary flow to the secondary flow takes place through turbulent mixing and viscous effects. the secondary flow is then dragged by turbulent shear force of the ejector while being mixed with the primary flow by the persistence of a large turbulent intensity throughout the ejector. the performance of a Coanda ejector is studied mainly based on how well it drags the secondary flow and the amount of mixing between the two flows at the ejector exit. the aim of the present study is to investigate the influence of various geometric parameters and pressure ratios on the Coanda ejector performance. the effect of various factors, such as, the pressure ratio, primary nozzle and ejector configurations on the system performance has been evaluated based on a performance parameter defined elsewhere. the performance of the Coanda ejector strongly depends on the primary nozzle configuration and the pressure ratio. the mixing layer growth plays a major role in optimizing the performance of the Coanda ejector as it decides the ratio of secondary mass flow rate to primary mass flow rate and the mixing length.

关键词： Coanda ejector compressible mixing layer flow dragging mixing length induced flow

FINItE ELEMENt ANALYSIS FOR MICROStRUCtURE EVOLUtION IN HOt FINISHING ROLLING OF StEEL StRIPS

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2007年第2期20卷 79-86页

作者： Z.d. Qu S.H. Zhang d.Z. Li Z.t. Wang Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China College of Material Science and Engineering Taiyuan University of Science andTechnology Taiyuan 030024 China Shenyang Ligong University Shenyang 110168 China

A computer model that describes the evolution of microstructures during the hot finishing rolling of SS400 steel has been proposed. It has been found.t.at the microstructure strongly depends on processing of materials and on their parameters, which affected the history of the thermomechanical variables, such as temperature, strain, and strain rate. to investigate the microstructural evolutions during the hot finishing rolling process, the rigid-thermoviscoplastic finite element method （FEM） has been combined with dynamic recrystallization, static recrystallization, and grain growth models. the simulation results show a good agreement with those from the prediction software online.

关键词： finite element method (FEM) finishing rolling microstructure evolution recrystallization

A brief review on/μSR studies of unconventional Fe-and Cr-based superconductors

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2018年第12期61卷 3-24页

作者： A.Bhattacharyya d.t.adroja M.Smidman V.K.Anand ISIS Facility Rutherford Appleton LaboratoryChiltonDidcot OxonOX11OQXUK department of Physics Ramakrishna Mission Vivekananda Educational and Research InstituteHowrah 711202India Highly Correlated Matter Research Group Physics DepartmentUniversity of JohannesburgAuckland Park 2006South Africa Center for Correlated Matter and department of Physics Zhejiang UniversityHangzhou 310058China Helmholtz-Zentrum Berlin fur Materialien und Energie GmbH Berlin D-14109Germany

Muon spin relaxation/rotation(μSR) is a vital technique for probing the superconducting gap structure, pairing symmetry and time reversal symmetry breaking, enabling an understanding of the mechanisms behind the unconventional superconductivity of cuprates and Fe-based high-temperature superconductors, which remain a puzzle. Very recently double layered Fe-based superconductors having quasi-2 d crystal structures and Cr-based superconductors with a quasi-1d structure have drawn considerable attention. Here we present a brief review of the characteristics of a few selected Fe-and Cr-based superconducting materials and highlight some of the major outstanding problems, with an emphasis on the superconducting pairing symmetries of these materials. We focus on μSR studies of the newly discovered superconductors ACa_2Fe_4As_4F_2(A = K, Rb, and Cs), thFeAsN, and A_2Cr_3As_3(A = K, Cs), which were used to determine the superconducting gap structures, the presence of spin fluctuations, and to search for time reversal symmetry breaking in the superconducting states. We also briefly discuss the results of μSR investigations of the superconductivity in hole and electron doped BaFe_2As_2.

关键词： unconventional superconductors iron-based superconductors Cr-based superconductors superconducting pairing symmetry time reversal symmetry muon spin rotation/relaxation