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PROGRESSES ON TECHNOLOGIES OF DRIVING AND CONTROLLING MICRO FLUIDS

2002, 32(1): 1-16. doi: 10.6052/1000-0992-2002-1-J2000-067

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With the development of microfluidic systems,especially, biochips and the technology of "Lab-on-a-chip", the technologies of driving and controlling the fluids flowing in structures in micro or even nano scale are receiving more and more attentions. Compared with the driving and controlling technologies of macrofluids, those of microfluids are more complicated and diversified because of more factors affecting microflows. In this paper, flow properties of microfluids are first discussed with an emphasis on the driving and controlling technologies and thedifferences between micro and macro scales. Then, the present driving and controlling technologies of microfluids are analyzed and compared with each other. Their advantages and disadvantages are respectively discussed.

SOME NONLINEAR PROBLEMS IN MICROSYSTEM DYNAMICS

2002, 32(1): 17-25. doi: 10.6052/1000-0992-2002-1-J2000-048

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Microsystems, or microelectromechanical systems (MEMS), are a new and fast developing, interdisciplinary field. Microsystem dynamics is an important part of microsystem science. Microsystems, generally, are of inherent nonlinearity. In this paper, some nonlinear problems in microsystem dynamics are summed up from the angles of modelling, analysis, design, control, experiment, measurement, material, microfabrication, and so on, and the prospects of research directions in the future are given.

ADVANCES OF GENETIC ALGORITHMS IN STRUCTURAL OPTIMIZATION

2002, 32(1): 26-40. doi: 10.6052/1000-0992-2002-1-J2000-084

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As a newly developed algorithm, the genetic algorithm, arose from the theory of evolution and genetics. It is of globalconvergence and parallelism. Now it has become an important partof computation intelligence. The paper briefly introduces the procedure of simple genetic algorithm and its mathematical foundation. Some developments and evaluations of encoding, convergence and operators are discussed in details. The constraint handling and the choice of fitness function are analyzed. Some suggestions for further research are given.

A REVIEW OF RESEARCHES ON THE RESIDUAL STRESS IN THERMAL SPRAY COATINGS

2002, 32(1): 41-56. doi: 10.6052/1000-0992-2002-1-J2000-068

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An overview is presented of the development of researches on residual stresses in thermal spray coatings. It includes some new ideas on the origins of the residual stresses, the main experimental techniques for measurement of the residual stresses, the analytic models for determining the distributions of the residual stresses, and their effects on interface toughness. Finally, some prospective research topics in this field, which are interesting both in science and engineering, are given.

1-3 TYPE PIEZOELECTRIC FIBER COMPOSITES AND THEIR RESEARCH PROGRESS

2002, 32(1): 57-68. doi: 10.6052/1000-0992-2002-1-J2000-074

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1-3 type piezoelectric fiber composites and related research progree were reviewed in this paper. From the point of view of the theoretical analysis, parameter identification, numerical methods and experimental approaches, its macroscopic characteristic parameters were illustrated. The existing methods for processing fine-scale 1-3 type piezoelectric fiber composites were compared. Also its applications, prospective applications in acoustics, medicine, control, aeronautics and astronautics and future research directions were reviewed. Finally, several important research directions of 1-3 type piezoelectric fiber composites were pointed out.

A SURVEY ON STIFFNESS REDUCTION MODELS OF FIBER REINFORCED PLASTICS UNDER CYCLIC LOADING

2002, 32(1): 69-80. doi: 10.6052/1000-0992-2002-1-J2000-049

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Stiffness reduction models of fiber reinforced polymer composite laminates published in recent two decades were reviewed in the present paper. According to their methodologies, these models were classified as theoretical models, semi-empirical models and empirical models. The theoretical models are those entirely based on the mechanical analysis and include mainly shear-lag models, fracture models, elasticity mechanics models and etc. Theoretical models establish the relationships between micro damage mechanism and macro stiffness reduction of the laminates. The empirical models were established based on experimental data, so an empirical model is often simple and easy to understand and to apply. The semi-empirical models are those between the theoretical and the empirical ones.

REVIEW ON MODELING OF THERMOMECHANICAL FATIGUE BEHAVIOR FOR FIBER-REINFORCED METAL MATRIX COMPOSITES

2002, 32(1): 81-91. doi: 10.6052/1000-0992-2002-1-J2000-063

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More attention has been paid to the behavior of thermomechanical fatigue (TMF) of fiber-reinforced metal matrix composites. In this review, main results of the theoretical work conducted recently in this field are discussed. For the thermomechanical cycle behavior, the models of the axial nature based on micromechanical methods and the models of the transversal nature based on fracture and damage mechanics are included. For evaluating thermomechanical fatigue life, two models are deduced fromthe transerval nature of materials. The influence of the metal matrix's microstructure on the fatigue life is also discussed.

ADVANCES IN NUMERICAL STUDIES OF TURBULENT IMPINGING JET FLOW AND HEAT TRANSFER

2002, 32(1): 92-108. doi: 10.6052/1000-0992-2002-1-J2000-102

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Turbulent jet impingement is widely used inengineering applications and industrial processes as such surface heating, electronic cooling, paper drying and material cutting because of their high level of momentum and local heat transfer. Due to the complexity of the flow , the jet impingement is also used as an excellent test case for validation of turbulence models. Additionally, the aerodynamic interactions between turbulent lift jets and ground plane have great effects on the performance of V/STOL aircraft. There have been many publications related to theoretical analyses, experimentalmeasurements and numerical simulations of such flows. A selection of recent publications with regard to numerical simulations of the turbulent impinging jet flow and heat transfer are reviewed in this paper. The emphasis is on the assessment of the abilities of various turbulence models in predicting the impinging jet flow and heat transfer. The existing problems and the research prospects in this field are discussed.

COHERENT STRUCTURES IN TURBULENT ROUND JETS

2002, 32(1): 109-118. doi: 10.6052/1000-0992-2002-1-J2000-079

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Reviews have been presented on the understandings of coherent structures in round turbulent jets. Experiments and numerical work on that field are summarized. The flowvisualizations, improved LDA and PDA diagnostic, the digital PIV and other experimental methods are compared. Simulation results by vortex method, large-eddy simulation (LES), direct numerical simulation (DNS) are also discussed.

THE ADVANCES ON THE VARIABLE MASS FLOW IN HORIZONTAL WELLS

2002, 32(1): 119-127. doi: 10.6052/1000-0992-2002-1-J2000-064

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This paper reviews the latest advances on the variable mass flow with wall inflow in horizontal wellbores. The discussions mainly focus on the following topics: thecalculation of the horizontal wellbore flow pressure and the oil output; the formula for wall frictional factor correlation with various influx; and the mechanical analysis of flow resistance loss within the wellbore with radial inflow. Especially, the calculation of flow resistance factor of variable mass flow in introduced. The mechanism of the flowloss of two-phase variable mass flow and the advances on the numerical simulation of horizontal wellbores are also discussed.

NEW PROGRESS ON NON-FOURIER HEAT CONDUCTION

2002, 32(1): 128-140. doi: 10.6052/1000-0992-2002-1-J2001-065

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A more comprehensive review on non-Fourier heat conduction is presented in this paper. Our new achievements in this research field, such as analytical solution ofnon-Fourier hyperbolic heat conduction in hollow sphere, experimental study and numerical simulation of non-Fourier heat conduction phenomenon in porous material under room temperature, "instantaneous thin layer" model for non-Fourier heat conduction, coupled analysis of non-Fourier heat conduction and non-Fick mass transfer and molecular dynamics simulation of non-Fourier heat conduction, are added.Additionally, some further research topics are proposed.

EVOLVING MATERIAL STRUCTURES OF SMALL FEATURE SIZES

2002, 32(1): 141-150. doi: 10.6052/1000-0992-2002-1-J2001-066

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Modern electronic and photonic devices are solid structures of small feature sizes. During fabrication and use, diffusive processes can relocate matter, so that the structures evolve over time. A film may break into droplets, and a conducting line may grow cavities. Stress and electric current have long been understood as forces that drive the changes. Evidence has accumulated that, while important, these forces are insufficient to account for diverse experimental phenomena, suggesting forces of other physical origins also operate. Ina structure, collective actions of atoms, electrons, and photonscontribute to the free energy. When the structure changes itsconfiguration, the free energy also changes. The free energy change defines a thermodynamic force which, in its turn, drives the configurational change of the structure. This article illustrates the concepts with specific phenomena. Emphasis is placed on physical descriptions of forces of diverse origins, including elasticity, electrostatics, capillarity, electric current, composition gradient, photon dispersion, and electron confinement. The effects of some of these forces are particularly significant in structures of small feature sizes, say, between a few to hundreds of nanometers. Insights into these forces are increasingly valuable as devices miniaturize. This area of research holds great promises for solid mechanics innovation.

2002, 32(1): 151-153. doi: 10.6052/1000-0992-2002-1-J2002-017

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2002, 32(1): 154-154. doi: 10.6052/1000-0992-2002-1-J2002-018

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2002 Vol. 32, No. 1

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