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A Modified Entropy Generation Number for Heat Exchangers

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Journal of Thermal Science 1996年第4期5卷 257-263页

作者： z. M. Xu S. R. Yang z. q. chen Department of Power Engineering Northeast China Institute of Electric Power Engineering Jilin City China Energy and Power Machinery Engineering Institute Xi’an Jiaotong University Xi’an China

This paper demonstrates the difference between the entropy generation number method proposed by Bejan and the method of entropy generation per unit amount of heat transferred in analyz.ng the thermodynamic performance of heat exchangers, points out the reason for leading to the above difference.A modified entropy generation number for evaluating the irreversibility of heat exchangers is proposed which is in consistent with the entropy generation per unit amount of heat transferred in entropy generation analysis. The entropy generated by friction is also investigated. Results show that when the entropy generated by friction in heat exchangers is taken into account, there is a minimum total entropy generation number while the NTU and the ratio of heat capacity rates vary. The existence of this minimum is the prereq.isite of heat exchanger optindz.tion.

关键词： entropy generation heat exchanger.

Suspension Performance with One Damper and One Inerter

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Suspension Performance with One Damper and One Inerter

Exponential Stabiliz.tion for Linear Systems with Actuator Saturation Via Intermittent Control

第24届中国控制与决策会议

作者： Michael z. q. chen The University of Hong Kong Department of Mechanical Engineering The University of Hong Kong-Shenz.en Institute of Research and Innovation Nanjing University of Science and Technology School of Automation

In chen ＆ Smith 2009, a class of realiz.tions in which the number of dampers and inerters is restricted to one in each case, while allowing an arbitrary number of springs （which is the easiest element to realiz. practically）, was considered and it was proven that at most four springs are needed-an explicit construction was given comprising five different circuit arrangements to cover all cases. This paper makes a comparative study of the performances of these five circuit arrangements when applied as mechanical suspension struts in a q.arter-car model.

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Exponential Stabilization for Linear Systems with Actuator S...

DEFORMATION BEHAVIOR OF AA6063 ALUMINIUM ALLOY AFTER REMOVING FRICTION EFFECT UNDER HOT WORKING CONDITIONS

第25届中国控制与决策会议

作者： Yijing Wang Weiyan Li Wenlong Yang z.iq.ang z.o Michael z. q. chen the Tianjin Key Laboratory of Process Measurement and Control School of Electrical Engineering and Automation Tianjin University Department of Mechanical Engineering The University of Hong Kong

ISBN: (纸本)9781467355339

The exponential stabiliz.tion problem of a class of linear systems with actuator saturation is addressed in this paper. In an approach different from the previous results where the continuous controllers are used all the time, here the periodically intermittent control is proposed to ensure the exponential stability of the closed-loop systems. An exponential stability criterion is suggested using the contractive invariant ellipsoid as an estimate of the domain of attraction. In addition, the exponential convergence rate is explicitly given. The feedback controller can also be designed by regarding the feedback gain as an additional variable. A numerical example is presented to illustrate the effectiveness of our theoretical analysis.

关键词： Exponential Stability Intermittent Control Actuator Saturation Domain of Attraction

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Acta Metallurgica Sinica(English Letters) 2008年第6期21卷 451-458页

作者： z. Y. chen S. q. Xu X.H. Dong National Die ＆ Mold CAD Engineering Research Center Shanghai Jiaotong University Shanghai 200030 China College of Materials Science and Engineering Taiyuan University of Technology Taiyuan 030024 China

The hot deformation behavior of AA6063 aluminium alloy has been investigated by means of compression tests at temperatures between 400 and 520℃, and strain rates ranging from 2.5 to 10 s^-1. Owing to the barreling, the theoretical model on the basis of Hills general method is used to calculate the flow stress of a cylindrical specimen under uniaxial simple compression so as to consider the friction effect at the die-specimen interface. A method of evaluating the friction coefficient by combining compression tests with the finite element method is presented. The real flow behavior of AA6063 aluminium alloy can be described with sinh-Arrhenius eq.ation. The hot deformation activation energy q.derived from the corrected stress and strain data is 232. 350 kJ/mol.

关键词： Barreling Compression test Friction Flow stress Aluminium alloy Activation energy

Analysis of vibration reduction level in an 8/6 switched reluctance machine by active vibration cancellation

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Journal of z.ejiang University-Science C(Computers and Electronics) 2010年第10期11卷 808-816页

作者： Xu LIU z.i-ping PAN z. q. z.U School of Electrical Engineering Zhejiang University Hangzhou 310027 China Department of Electronic and Electrwal Engmeermg University of Sheffield Sheffield S1 3JD UK

This paper proposes an analytical model for predicting the maximum vibration reduction level in a four-phase 8/6 switched reluctance machine(SRM) by employing active vibration cancellation(AVC),one of the most effective and convenient methods for reducing the vibration and acoustic noise produced by *** on the proposed method,the factors that influence the vibration reduction level are analyz.d in *** relationships between vibration and noise reduction levels at resonance freq.ency and rotor speed are ***,it is shown that a large damping factor will lead to smaller vibration reduction level with AVC while,in contrast,a large resonance freq.ency will increase the vibration reduction *** finite element analyses and experiments were carried out on a prototype 8/6 SRM to validate the proposed method.

关键词： Active vibration cancellation Analytical model Switched reluctance machine Vibration

Nonlinear mechanics of a ring structure subjected to multi-pairs of evenly distributed eq.al radial forces

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Acta Mechanica Sinica 2017年第5期33卷 942-953页

作者： q. chen F. Sun z. Y. Li L. Taxis N. Pugno Biomechanics Laboratory School of Biological Science and Medical Engineering Southeast University State Key Laboratory of Mechanics and Control of Mechanical Structures Nanjing University of Aeronautics and Astronautics School of Chemistry Physics and Mechanical EngineeringQueensland University of Technology (QUT) Laboratory of Bio-Inspired and Graphene Nanomechanics Department of Civil Environmental and Mechanical Engineering University of Trento School of Engineering and Materials Science Queen Mary University of London Ket Lab Italian Space Agency Via del Politecnico snc

Combining the elastica theory, finite element (FE) analysis, and a geometrical topological experiment, we studied the mechanical behavior of a ring subjected to multi-pairs of evenly distributed eq.al radial forces by looking at its seven distinct states. The results showed that the theoretical predictions of the ring deformation and strain energy matched the FE results very well, and that the ring deformations were comparable to the topological experiment. Moreover, no matter whether the ring was compressed or tensioned by N-pairs of forces, the ring always tended to be regular polygons with 2N sides as the force increased, and a proper compressive force deformed the ring into exq.isite flower-like patterns. The present study solves a basic mechanical problem of a ring subjected to lateral forces, which can be useful for studying the relevant mechanical behavior of ring structures from the nano- to the macro-scale.

关键词： Ring structures Mechanical properties Shape Strain energy

STUDY OF THE INFLUENCE OF pH ON THE ELECTROCRYSTALLIz.TION OF z.NC

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Acta Metallurgica Sinica(English Letters) 2005年第4期18卷 497-504页

作者： z. z.ang W.H. Leng J. q. z.ang Department of Chemistry Zhejiang University Hangzhou 310027 China State Key Laboratory for Corrosion and Protection Institute of Metal Reseach The Chinese Academy of Sciences Shenyang 110016 China

The influence of pH value of the electrolyte solution on the z.nc electroplating process was studied by means of cyclic voltammetry and chronoamperometry approaches. The results shown that, under this experimental conditions and at high overpotentials, the nucleation of z.nc is instantaneous, and the nuclear densities N increase with the overpotentials. While at low potentials, no distinguished nucleation current can be observed. High pH promotes the deposition either by drifting the initial depositing potential positively, or by increasing the depositing current through the change of the total charge of the adsorption process q.ds, i.e., thevstructure of electrochemical double layer.

关键词： z.nc electroplating nucleation growth mechanism

EXPERIMENTAL RESEARCH AND NUMERICAL SIMULATION OF LASER SHOCK FORMING OF TA2 TITANIUM SHEET

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Acta Metallurgica Sinica(English Letters) 2006年第5期19卷 347-354页

作者： F. Wang z. q. Yao J. Hu q.L. Deng School of Mechanical Engineering Shanghai Jiao Tong UniversityShanghai 200030 China

Laser shock forming （ISF） was a new techniq.e realiz.d by applying an impulsive pressure generated by laser-induced shock wave on the surface of metal sheet. LSF of metal sheet was investigated with experiments and numerical simulation. The basic theories were introduced; the surface q.ality and deformation of the processed titanium sample （TA2） were examined; ABAq.S was used to simulate ISF and the central displacement of the shocked region was measured and compared with the simulation. Overlapped ISF treatment was experimentally carried out to produce groove and simulation. The results showed that the surface q.ality and the microstructure with single laser pulse had no remarkable change, and ablation was observed on the surface of the sample with overlapped pulses. The deformation observed in the numerical simulation agreeed with that observed in the experimental measurement q.ite well.

关键词： laser shock forming numerical simulation surface q.ality deformation

KINETIC STUDY OF SPINEL LiMn_2O_4 SYNTHESIz.D BY SOLID REACTION WITH SOFT-CHEMICAL METHOD

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Acta Metallurgica Sinica(English Letters) 2005年第4期18卷 512-518页

作者： C.q. Xu Y. W. Tian Y. C. z.ai z.J. Guo z. q. Huang School of Materials and Metallurgy Northeastern University Shenyang 110004 China

The differential thermal analysis （DTA） curves were measured at different heating rates in flowing air for studying the synthesis of the spinel LiMn2O3 with Li2CO3 and MnO2, The reaction began at about 503K, and finished at about 873K. The apparent activation energy of Kissinger method was about ***^-1, the reaction orderwas 1.67, the freq.ency factor was 7.81×10^9, and therefore the dinetic epuation was dδ/dt=A·exp（- E/RT）·（1-δ）^n=7.81×10^9, exp（-122770/RT）·（l-δ）^1.67 . Coats-Redfem integral method was used to analyz. the DTA curves of the samples at different heating rates, and the calculated apparent activation energy and freq.ency factor were 112. 13kJ· mol^-1 and 1.18 × 10^9, respectively, rather close to that of Kissinger method. X-ray diffraction （XRD） and scanning electron microscope （SEM） results shown that the synthesiz.d LiMn2O3 possesses pure phase, regular shape and normal particle distribution.

关键词： lithium manganese oxides synthesiz.d kinetics Kissinger method,Coats-Redfern integral method