力学进展

ADVANCES IN THE STUDY OF PROPERTIES AND MECHANICS OF SEMICONDUCTOR QUANTUM DOT STRUCTURES

2007, 37(4): 481-495. doi: 10.6052/1000-0992-2007-4-J2006-182

Abstract(2760)

PDF(1155)

Abstract:
Considerable experimental and theoretical studies havebeen carried out in semiconductor quantum dots (QDs) in recent years, sincequantum-dot devices offer a bright prospect of improved electronic andoptical properties due to the zero-dimensional quantum confinement ofcarriers. The elastic field is essential for the analyses ofthe physical and mechanical properties of QDs. In this article, the elementsof the low-dimensional quantum confined systems, the physical properties andthe fabrication techniques of the QDs are reviewed systematically. Inparticular, the researches on mechanics of the semiconductor QDstructures, and the coupling between the elastic field and thephysical properties are discussed.

SHEAR LOCALIZATION, MICROSTRUCTURE EVOLUTION AND FRACTURE UNDER HIGH-STRAIN RATE

2007, 37(4): 496-516. doi: 10.6052/1000-0992-2007-4-J2006-136

Abstract(3328)

PDF(1081)

Abstract:
Investigations on microstructural aspects of adiabaticshear localization under strain rate 10$^{3}$s$^{ - 1}$ to 10$^{4}$ s$^{ -1}$ using EBSD-SEM, TEM and HREM are critically reviewed. The principalfeatures are: the critical condition for the occurrence of shear-bandsshould involve both shear strain and strain rate; the deformed-band formsfirst and the white-etching band follows with further shear deformation;the presence of white-etching bands is generally indicated by differentetching response of the narrow bands; shear band seems to initiate with acrystallographic slip in a favored grain and then propagates into theadjacent grains by co-operative slip or cross-slip, leading to the shearlocalization over the whole cross-section; both grain refinement andtransition from crystalline to amorphous can occur in shear bands; the$\gamma\to\varepsilon\to\alpha'$ transformation may also occur and the new transformed products have acertain orientation relationship with their parent matrix; the sharp drop inthe load-carrying capability of the specimen seems to be closely associatedwith the appearance of a critical coalescence of microcracks or voids in theband; the equiaxed-and distorted-free grains are proposed to attribute tothe rotational recrystallization. On the other hand, the micro-mechanism ofshear localization and fracture subjected to quasi-static and fatigueloadings is different from the dynamic case, namely caused by thedislocation planner slip and not related to thermal effects.Additionally, some further research are suggested.

ADVANCES IN LEFT-HANDED MATERIAL DESIGN AND TRANSPARENCY PHENOMENON

2007, 37(4): 517-536. doi: 10.6052/1000-0992-2007-4-J2006-114

Abstract(2938)

PDF(1160)

Abstract:
Left-handed materials (LHM) have negative permittivity, negativepermeability, and negative refractive index. The propagation mechanism ofelectromagnetic waves in the LHMs is fundamentally different from that inconventional materials. This paper first discusses the intrinsicmechanisms for realizing negative permittivity and negative permeability,then the recent progress in the design and fabrication of LHMs issummarized. Various problems related to LHMs are discussed, including thedefinition of EM energy in an LHM, the retrieving method of effectiveparameters of LHMs, and the parameters influencing the relative bandwidthfor negative refraction of LHMs. The photon tunneling effect andelectromagnetic transparency phenomenon induced by LHMs are reviewed, theneutral inclusion concept in mechanics is particularlydiscussed for the transparency design. In the end, the physical meaning andrealization of acoustic LHMs are briefly introduced, the acoustictransparency phenomenon is discussed by analogy with the electromagneticcounterpart.

A REVIEW ON HYPERSONIC VEHICLES AND KEY TECHNOLOGIES

2007, 37(4): 537-550. doi: 10.6052/1000-0992-2007-4-J2007-028

Abstract(2892)

PDF(1636)

Abstract:
This paper begins with a classical definition of hypersonic, some physicalphenomena pertinent to hypersonic flight, the covered range of the hypersonic flight and the features of design process. The differences betweenAHV(hypersonic airbreathing vehicles) and RHV(hypersonic rocketvehicles) are discussed, with a table showing temperatures. In thesecond part, the paper puts hypersonic vehicles in a militarybackground. A historical perspective of hypersonic vehicles is given inform of a table with milestones, accompanied with some lessons learnedfrom the past and relevant for the future. In the last part, a typical design process, development strategy,technology program, and key technologies of hypersonic airbreathing vehiclesare reviewed.

RESEARCH PROGRESS ON LOW PRESSURE TURBINE INTERNAL FLOWS AND RELATED AERODYNAMIC DESIGN

2007, 37(4): 551-562. doi: 10.6052/1000-0992-2007-4-J2006-131

Abstract(2895)

PDF(1169)

Abstract:
With increasing interests on high altitude Unmanned Aerial Vehicles (UAVs), more and moreattentions have been paid to the research of aero-engines under high altitude, low Reynoldsnumber conditions. This paper reviews the research progress on complex internal flow in low Reynolds number and low pressure turbine (LPT) in recent years. The maintopics include unsteady flow characteristics of LPT, mechanisms of separation and transitionphenomena of boundary layer, mechanisms of periodic wake/boundary layer interactions. Based on flow mechanisms, an aerodynamic design method for lowReynolds number LPT is proposed. The interactions of wake/boundary layer can inhibitseparations and diminish profile losses. Taking unsteady effects into account in the aerodynamicdesign, one can effectively improve blade loading or reduce aerodynamic losses, and finally improvethe performance of LPT. The numerical and experimental results validate this aerodynamic designmethod.

RESEARCH ADVANCES IN DIGITAL HOLOGRAPHY PARTICLE IMAGE VELOCIMETRY

2007, 37(4): 563-574. doi: 10.6052/1000-0992-2007-4-J2006-087

Abstract(3068)

PDF(893)

Abstract:
Digital Holography Particle Image Velocimetry is a verypromising measurement technique for unsteady three-dimensional complex flow.This paper reviews the background and the research advances of thistechnology in the past two decades. Some key problems and applicationrelated problems (such as the reconstruction of the particle field, theresolution of reconstruction, the accuracy of the particle position and thedisplacement, the signal-noise ratio of the digital hologram, the opticalmethod and fast mathematical algorithms for reconstruction, and theextension of measurement volume, etc.) are discussed. At the same time,we also discuss the potentiality of off-axis digital holography and point out the development direction infuture. It is predicted that, with the rapid development of digitalcamera technique, DHPIV will become a new generation of the observationand measurement technology for unsteady three dimensional complex flows inthe coming future, and will be used for difficult problems offluid mechanics.

RECENT ADVANCES IN SEISMIC LIQUEFACTION RESEARCH

2007, 37(4): 575-589. doi: 10.6052/1000-0992-2007-4-J2006-016

Abstract(2745)

PDF(903)

Abstract:
Main framework and topics of seismicliquefaction study are summarized, including the current state of the art and trends, with respect to mechanism of liquefaction, susceptibility ofliquefaction, liquefaction flowslides, liquefaction-induced deformation andnumerical modeling techniques. It is shown that the key issues of seismicliquefaction in practice are related not with strength but with deformation. Theliquefaction-induced deformation evaluation techniques can be diveded into two categories: (1) empirical methods based on statistical analysis ofhistorical seismic liquefaction deformation database and (2) numericalmodeling. Numerical modeling is shown to be an effective tool and havewidespread prospect for analysis of complex boundary value problemsof seismic liquefaction. In future seismic liquefaction research, itis important to improve the existing methods of liquefaction susceptibilityanalysis and liquefaction-induced deformation evaluation by establishing andanalyzing the seismic hazard database. But more emphases should be placed onrevealing the mechanism of seismic liquefaction, developing constitutive models that can describe the stress-strain behavior of sand over a small tolarge strain range during an entire pre- and post-liquefaction process, anddeveloping corresponding numerical algorithms to implement themodels in the simulation of practical boundary-value problems.

STUDIES ON MECHANICAL MECHANISM ABOUT STONE COMMINUTION AND TISSUE TRAUMA IN EXTRA-\\CORPOREAL SHOCK WAVE LITHOTRIPSY

2007, 37(4): 590-600. doi: 10.6052/1000-0992-2007-4-J2006-139

Abstract(3008)

PDF(987)

Abstract:
Extracorporeal shock wave lithotripsy (ESWL) is a mostsuccessful application of shock wave and its focusing technique in clinicalfields. Because of its non-invasive nature, high patient comfortableness and highlithotripsy efficiency with lower costs, this treatment has been at theforefront of treatment of kidney stones. But there are some shortcomings,such as lower lithotripsy efficiency for big stones, short- or long-term sideeffects, nonreversible loss of organ functions. The process ofstone disintegration and concomitant tissue injury caused by actions in ESWL is very complicated.To maximize the effect of stone disintegration and minimizethat of tissue damage, the theoretical study of ESWL, both laboratorial and clinical, hasbeen carried out along with the invention and the improvement of ESWL.Today the mechanism of stone comminution and tissue damage is muchbetter understood, but some important aspects remain to be cleared.While the direct mechanisms of stone comminution and tissue trauma offocusing shock waves are better understood now, its indirect mechanism, the cavitation induced by shockwaves, is not very clear and is still a challenge and a hotspot ofthe researches on ESWL. The standard on the efficiency and the securityof ESWL is in a process of improvement.

“Unified strength theory and its application” 评介

2007, 37(4): 600-600. doi: 10.6052/1000-0992-2007-4-J2007-079

Abstract(2078)

PDF(3294)

Abstract:

A REVIEW ON MECHANOBIOLOGY MECHANISM OF BONE FORMATION AND REMODELING

2007, 37(4): 601-610. doi: 10.6052/1000-0992-2007-4-J2006-041

Abstract(2969)

PDF(1102)

Abstract:
Biomechanics plays a critical role in studies on bonegrowth, remodeling and formation. The essence of bone tissue injury andrepair is the cellular process of bone growth under straining. Although weare well aware of the importance of biomechanics in bone developing andremodeling, the mechanobiological mechanisms of the bone growth inducedand remodeled, which are necessary for the study of bone tissue engineeringin vitro, remain poorly understood. In this paper, we review the recentprogresses of bone biomechanics study, focusing on the relationship betweenbiomechanics and bone growth.

ADVANCES IN THE COMPLEX BRAIN NETWORK

2007, 37(4): 611-613. doi: 10.6052/1000-0992-2007-4-J2006-145

Abstract(2640)

PDF(1094)

Abstract:
The concepts of complex network have recently been applied tostudy real networks such as biology network, social network andtechnology network. With these comcepts, we investigate the segregation and the integration,as the two main functions of the cerebral cortex, on various angles:with respect to structural connectivity, functional connectivity and effective connectivity. The development andevolution of brain network is also discussed in order to reveal the lawdominating the brain functions.

FLUID MECHANICS AND HOMELAND SECURITY

2007, 37(4): 614-627. doi: 10.6052/1000-0992-2007-4-J2007-109

Abstract(2402)

PDF(886)

Abstract:
Homeland security involves many applications of fluidmechanics and offers many opportunities for research and development. Thisreview explores a wide selection of fluids topics in counterterrorism andsuggests future directions. Broad topics range from preparedness anddeterrence of impending terrorist attacks to detection, response, andrecovery. Specific topics include aircraft hardening, blast mitigation,sensors and sampling, explosive detection, microfluidics and labs-on-a-chip,chemical plume dispersal in urban settings, and building ventilation. Alsodiscussed are vapor plumes and standoff detection, nonlethal weapons,airborne disease spread, personal protective equipment, and decontamination.Involvement in these applications requires fluid dynamicists to think acrossthe traditional boundaries of the field and to work with relateddisciplines, especially chemistry, biology, aerosol science, and atmosphericscience.

2007, 37(4): 628-632. doi: 10.6052/1000-0992-2007-4-J2007-115

Abstract(1458)

PDF(1063)

Abstract:

Contents and Subject Index to Advances in Mechanics,Vol.37, 2007

2007, 37(4): 633-640. doi: 10.6052/1000-0992-2007-4-J2007-147

Abstract(1287)

PDF(789)

Abstract:

2007 Vol. 37, No. 4

NoticeMore >

Author CenterMore >

Related linksMore >