关键词： 上海交通大学   工程学院   校企合作   中华   可乐   山特   机械   自动化研究所  

摘要： 2012年6月29日上午，上海交通大学机械与动力工程学院和山特维克可乐满大中华区校企合作协议正式签署。出席签约仪式的嘉宾有山特维克可乐满大中华区市场与业务总监彭晓鸿女士、上海交通大学机械与动力工程学院党委书记陶燕敏先生、副院长刘应征先生、陈明教授和制造技术与装备自动化研究所的师生们。

关键词： nanomaterials   solid solutions   mechanical alloying   diffusion  

摘要： Specific features of the kinetics of absorption of atoms of an alloying element by nanostructured alloys which lead to the formation of strongly supersaturated interstitial solid solutions upon plastic deformation of multiphase powder mixtures is discussed. The rate of absorption is shown to substantially depend on the parameters of mechanical action, segregation phenomena at the external and internal boundaries of the solid solution, and mechanisms of plastic deformation of the nanomaterials. Numerical estimates of the parameters that characterize the process of mechanical alloying of the powder mixture of iron with 25 at % carbon are given, which agree satisfactorily with the experimental data.

关键词： Mechanical properties   Molecular dynamics simulation   Graphyne   Tensile deformation   Fracture  

摘要： In this work a series of carbon allotropes related to graphene, called graphyne, graphdiyne, gaphene-3, graphene-4 and graphene-5 are constructed by connecting two adjacent hexagonal rings with different number of acetylenic linkages. Mechanical properties of these monolayer networks are investigated through acting tensile loads on the architectures and molecular dynamics simulations are performed to calculate the fracture strains and associated ultimate stresses. In the armchair loading case, the fracture strain remains nearly unchanged whereas the ultimate strength degrades gradually with longer acetylenic chains. In the zigzag loading situation, the ultimate strength remains nearly the same whereas the fracture strain improves by a little amount with longer acetylenic chains. Furthermore, Young's moduli of all the investigated architectures are computed to analyze the material stiffness at the near equilibrium regime. The obtained results show that these structures are mechanically stable with high strength and stiffness. The unique mechanical property variations of graphyne family against armchair and zigzag loads suggest flexible designations towards functional use of this novel material, especially in the direction-dependent nanomechanical applications. (C) 2012 Elsevier B.V. All rights reserved.

关键词： Biosorption   Zn(II) ion   Pseudo-second-order model   Film diffusion   Diffusivity coefficient  

摘要： The activated carbon was derived from base (0.2M NaOH)-mediated activation of biomass followed by thermal treatment at 1,123 K. The utmost metal ion uptake capacity and sorption percentage of activated carbon derived from eucalyptus biomass were 1.42 mmol g(-1) and 93.42%, respectively. Freundlich isotherm model proved to be superior with higher linear correlation coefficient R-2 = 0.96-0.98. Similarly, it was observed that pseudo-second-order reaction model with lower chi(2) (0.002703-0.009351) and sum of square errors (0.0001-0.0144) value together with higher R-2 (0.98-0.99) ruled in all the possibilities of sorption of Zn(II) ion on activated carbon surface as chemisorption. Bangham's model (R-2 = 0.93-0.95) applicability in the present investigation demarcated the fact that the main rate-controlling step in the sorption of Zn(II) ions on activated carbon surface was film diffusion rather than intraparticle diffusion. The results of diffusivity coefficients (D-f = 7.16 x 10(-6) cm(2) s(-1)) reproduced the analogous viewpoint that film diffusion is quite a dominant step in the biosorption of Zn(II). Delta G, Delta H, and Delta S values obtained through the thermodynamic study of Zn(II) biosorption system were--9798 kJ mol(-1), 34.74 kJ mol(-1), and 107.63 kJ mol(-1) K-1, respectively.

关键词： Vascular disease   Balloon-expandable stent   Parametric stent design   Finite element analysis   Computational fluid dynamics   Stent fatigue life  

摘要： Atherosclerosis, a condition related to cholesterol build-up and thickening of the inner wall of the artery, narrows or occludes the artery lumen. A stent is a miniature medical device deployed in a stenotic artery to restore the blood flow. In this paper, we propose to apply the parametric design concept onto the stent design and integrate it with the developed FEA/CFD models to evaluate several key clinically-relevant functional attributes recommended by the FDA. These key clinical attributes include stresses/strains, fatigue resistance, radial strength, expansion recoil, and wall shear stresses, which have yet to be systematically investigated. Finite element models were developed to predict the mechanical integrity of a balloon-expandable stent at various stages such as crimping onto a balloon catheter, stent expansion, radial strength to resist blood vessels from collapsing, and service life in the human body when subjected to pulsatile blood pressure. Computational fluid dynamics models were developed to predict the wall shear stress distribution in stented arteries. A stent parametric analysis was conducted using the integrated computational schemes to systematically evaluate the effects of varying stent design parameters on key clinically-relevant functional attributes. Each stent design parameter was varied in its dimension from -30% to +30% (compared to the standard case) for sensitivity studies in attempts to find the most dominant design parameter for each key clinical attribute. The developed design/analytical schemes allow us to gain deeper insight into the fundamental stent issues and evaluate the mechanical/hemodynamic behavior of various stent designs. (C) 2012 Elsevier Ltd. All rights reserved.

关键词： Robot manipulators   Uncertain kinematics   Uncertain dynamics   Actuator dynamics   Backstepping method   Task space   Practical implementation  

摘要： This paper, according to practical method in robot manipulator control, introduces a novel robust control approach for trajectory tracking of electrically-driven robotic manipulators in task space. A new task space control scheme is proposed to overcome uncertainties of actuator dynamics, robot dynamics and kinematics. A robust controller is designed based on Lyapunov method, using dynamic delay, backstepping method and unknown bounds of uncertainties. It is proven that the closed loop system has global uniform ultimate boundedness stability. Although, for overcoming the uncertainties in actuator dynamics, robot dynamics and kinematics is a major advantage, the proposed control cannot pass the singular points in task space and there will be malfunctions when it is applied on the practical implementation. Modifications are used to derive a control law which is free of velocity terms and can pass the singular points into task space. The control approach is applied on a two-link elbow robotic manipulator which is driven by permanent magnet de motors and can be applied on up to n-links robotic manipulators, too. The performance of proposed control laws is confirmed by simulations.

关键词： Boron doped graphene   Mechanical properties   Thermal conductivity   Molecular dynamics  

摘要： We investigated the effects of boron atoms substitution on the thermal conductivity and mechanical properties of single-layer graphene using the non-equilibrium molecular dynamics (NEMD) simulations. By performing the uniaxial tension simulations, we observed that substituted boron atoms slightly decrease the elastic modulus and tensile strength of graphene. On the other hand, it was observed that only 0.75% concentration of boron atoms in graphene reduces the thermal conductivity of graphene by more than 60% and leads to vanishing chirality effect. (c) 2012 Elsevier Ltd. All rights reserved.

关键词： SOFC   point defects   surface reaction   mechanism   ABO3 perovskites  

摘要： The compilation of measured effective rate constants for oxygen surface exchange on mixed conducting perovskites, which covers a great variety of compositions ranging from (La,Sr)MnO3 - delta to (La,Sr)(Co,Fe)O3 - delta and (Ba,Sr)(Co,Fe)O3 - delta, demonstrates the importance of ionic conductivity-i.e., high oxygen vacancy concentration as well as vacancy mobility-as a key factor for the surface oxygen exchange rate. This interpretation is corroborated by ab initio calculations, which indicate that the approach of an oxygen vacancy to oxygen intermediates adsorbed on the surface is the rate determining step for a number of perovskites.

关键词： Twist boundary   Misfit dislocation   Molecular dynamics   Yield stress  

摘要： Molecular dynamics simulations were carried out to study the mechanical properties of Cu(001)/Ni(001) interface boundaries with different twist angles subjected to uniaxial loading. The results obtained revealed that square misfit dislocations networks can be observed when the twist angle was lower than 15.124 degrees, and the density of misfit dislocations increased with increasing twist angle. Face defects were formed when the twist angle was higher than 15.124 degrees. It has been found that the interface configuration had a significant effect on the interface strength of the Cu/Ni system. The yield stress was found to decrease first with increasing twist angle and it reached its lowest value at 5.906 degrees twist angle. Subsequently, it increased with increasing twist angle till it reached its highest value at 15.124 degrees of the latter;it then decreased again and finally became almost constant when the twist angle was larger than approximately 20 degrees. (c) 2012 Elsevier B.V. All rights reserved.

关键词： Electrons  

摘要： Two approaches to the description of spin dynamics of electron-nuclear system in quantum dots are compared: the quantum-mechanical one is based on direct diagonalization of the model Hamiltonian and semiclassical one is based on coupled equations for precession of mean electron spin and mean spin of nuclear spin fluctuations. The comparison was done for a model problem describing periodic excitation of electron-nuclear system by optical excitation. The computation results show that scattering of parameters related to fluctuation of the nuclear spin system leads to appearance of an ordered state in the system caused by periodic excitation and to the effect of electron-spin mode locking in an external magnetic field. It is concluded that both models can qualitatively describe the mode-locking effect, however give significantly different quantitative results. This may indicate the limited applicability of the precession model for describing the spin dynamics in quantum dots in the presence of optical pumping.