关键词： 机械设计制造及其自动化   机械工程专业   材料成型及控制工程   国家特色专业   学院  

摘要： 2014年1月原机械与材料学院更名为机械与动力学院,学院现设有机械设计制造及其自动化、机械电子工程、材料成型及控制工程、工业工程、能源与动力工程、核工程与核技术六个本科专业,其中机械设计制造及其自动化为国家特色专业、第二批卓越工程师教育培养计划专业和省本科品牌专业,材料成型及控制工程为第三批卓越工程师教育培养计划专业。拥有机械工程一级硕士点、机械工程专业学位点、机械工程领域工程硕士点、工业工程专业学位点,机械制造及其自动化为湖北省重点学科。目前,在校全日制本科学生近2000人,在读研究生160余人,毕业生的一次就业率一直保持在90%以上。学院拥有水电机械设备设计与维护湖北省重点实验室,工程训练中心等,实验室建筑面积1.2万平米,设备仪器总值2000余万元。

摘要： Plug-in hybrid electric vehicles use a powertrain architecture that includes components of traditional powertrains such as internal combustion engines and transmissions, as well as components found in battery electric vehicles. The combination of both technologies enables vehicles to drive emission free, when using the battery as the energy source, while also providing the typical long driving range offered by traditional combustion engines using liquid fuel as the energy source. The goal of this study is to contribute to the design and analysis of machine elements and components used in a series plug-in hybrid vehicle. This vehicle was built for the University of Washington’s team that competes in the EcoCAR 3 Advanced Vehicle Technology Competition. A motorcycle combustion engine was used in the generator system of the vehicle, and a CAE software GT-Power model was used to analyze the engine’s fuel efficiency. Approximations and estimations of model parameters were used to predict the fluid dynamics, combustion process, energy conversion and heat transfer occurring in the engine. Speed and engine load are varied over a broad range to establish a map for brake specific fuel consumption which is data of value for the development of an optimal generator control strategy. The electric drivetrain used in the series hybrid involves single speed reduction gearboxes between motors and drive shafts. Static and fatigue strength analysis is performed to evaluate the strength of an undersized gearbox part for the re-specification of the material and heat treatment used to increase the part’s strength to an acceptable level. The increased number of powertrain components used in hybrid vehicles, particularly the electric battery, lead to an increased vehicle rear mass. This is accommodated for in the analysis of the vehicle’s rear suspension and the design of a new set of coil springs.

关键词： LD converter slag   Mechanical activation   Oxidation   Isothermal kinetics  

摘要： A thermogravimetric investigation was performed to evaluate the kinetic and thermodynamic parameters and the influence of mechanical activation on oxidation of vanadium-bearing LD (Linz-Donawitz) converter slag. Results indicate that the particle size of d(0.5) significantly decreased from 29 mu m to 0.266 mu m after activation, and the specific surface area based on the BET model increased from 1.324 m(2)/g to 3.289 mm(2)/g. Thermogravimetric investigations were separately performed at 650, 700, 750, 800, 850, 900, 950 and 1000 degrees C. Two distinct stages in the oxidation process were identified. The first stage was controlled by nucleation and growth and the second stage was controlled by 3D diffusion. However, the first stage relatively contributed more to the entire process than the second stage. Kinetic study also reveals that mechanical activation exhibited a significant effect on the oxidation of LD converter slag. Mechanical activation significantly reduced the roasting temperature and shortened the roasting time. The corresponding apparent activation energy Ea and frequency factor A changed from 13.01 kJ/mol to 6.59 kJ/mol and 0.247 min(-1) to 0.141 min(-1) for unmilled and milled slags, respectively.

关键词： 有限元   试验设计方法   近似模型   神经网络   支持向量机   遗传算法   结构动力学优化  

摘要： 针对复杂机械结构动力学优化耗费机时过多的问题,以车载炮炮口扰动为优化目标,车载炮总体结构参数为设计变量,建立了车载炮有限元动力学模型,研究样本点的抽取方法,探索并综合比较多种近似模型的建模方法与预测精度,采用近似模型与遗传算法相结合的方法,优化结构参数,优化效果较好,为复杂非线性机械结构的动力学分析、近似模型建模和优化设计提供了参考与指导。建立了车载炮精细网格模型,研究了车载炮各部分之间的连接关系,探讨了车载炮发射过程中边界条件与载荷的建模,在此基础上建立了车载炮上装部分非线性有限元动力学模型。研究对比了引入三种优化准则的最优拉丁超立方试验设计方法;提出了考虑训练样本点与测试样本点之间距离的遗传拉丁超立方试验设计方法。抽取训练样本与测试样本.并在此基础上进行了车载炮有限元动力学分析,获得了相应车载炮炮口扰动。分别研究了多项式响应面方法、Kriging方法、神经网络方法、支持向量机方法等近似模型技术的建模方法,参数选取方法,及参数的选取对近似模型预测精度的影响。提出了使用10-fold交叉验证法与遗传算法相结合的方法来优化模型参数,有效提高了近似模型的泛化能力。在综合考虑建模复杂程度和模型预测精度的基础上,选择最优的近似方法建立近似模型。提出了采用近似模型与遗传算法相结合的方法进行车载炮结构动力学优化。在所建立近似模型的基础上,构造了炮口扰动优化目标函数,采用遗传算法对目标函数进行求解,实现了车载炮总体结构参数的动力学优化。优化结果表明近似模型与遗传算法相结合的方法应用于复杂机械结构动力学优化设计节省机时并且效果较好。

关键词： Hybrid quantum systems  

摘要： We study the dynamics of a bipartite quantum system in a way such that its formal description keeps holding even if one of its parts becomes macroscopic; the problem is related to the analysis of the quantum-to-classical crossover, but our approach implies that the whole system stays genuinely quantum. The aim of the work is to understand (1) if, (2) to what extent, and possibly (3) how the evolution of a macroscopic environment testifies to the coupling with its microscopic quantum companion. To this purpose we consider a magnetic environment made of a large number of spin-12 particles, coupled with a quantum mechanical oscillator, possibly in the presence of an external magnetic field. We take the value of the total environmental spin S constant and large, which allows us to consider the environment as one single macroscopic system, and further deal with the hurdles of the spin-algebra via approximations that are valid in the large-S limit. We find an insightful expression for the propagator of the whole system, where we identify an effective “back-action” term, i.e., an operator acting on the magnetic environment only, and yet missing in the absence of the quantum principal system. This operator emerges as a time-dependent magnetic anisotropy whose character, whether uniaxial or planar, also depends on the detuning between the frequency of the oscillator and the level splitting in the spectrum of the free magnetic system, induced by the possible presence of the external field. The time dependence of the anisotropy is analyzed, and its effects on the dynamics of the magnet, as well as its relation to the entangling evolution of the overall system, are discussed.

摘要： Minus-one ribosomal frameshifting is a translational recoding mechanism widely utilized by many RNA viruses to generate accurate ratios of structural and catalytic proteins. An RNA pseudoknot structure located in the overlapping region of the gag and pro genes of Simian Retrovirus type 1 (SRV-1) stimulates frameshifting. However, the experimental characterization of SRV-1 pseudoknot (un) folding dynamics and the effect of the base triple formation is lacking. Here, we report the results of our single-molecule nanomanipulation using optical tweezers and theoretical simulation by steered molecular dynamics. Our results directly reveal that the energetic coupling between loop 2 and stem 1 via minor-groove base triple formation enhances the mechanical stability. The terminal base pair in stem 1 (directly in contact with a translating ribosome at the slippery site) also affects the mechanical stability of the pseudoknot. The - 1 frameshifting efficiency is positively correlated with the cooperative one-step unfolding force and inversely correlated with the one-step mechanical unfolding rate at zero force. A significantly improved correlation was observed between - 1 frameshifting efficiency and unfolding rate at forces of 15-35 pN, consistent with the fact that the ribosome is a force-generating molecular motor with helicase activity. No correlation was observed between thermal stability and - 1 frameshifting efficiency.

关键词： Genetics   Stereoselectivity   Free radicals   Bisphenols   Post-translational modification  

摘要： We previously communicated that high alpha-selectivity that can be achieved in intramolecular glycosylations using a rigid bisphenol A template supplemented with linkers of various lengths. Herein, we present our investigation of the mechanistic aspects of the templated synthesis that helped to design an improved template-linker combination. We demonstrate that bisphenol A as the template in combination with phthaloyl linker allows for superior stereoselectivity and yields in glycosylations. Several mechanistic studies explore origins of the enhanced stereoselectivity and yields achieved using the phthaloyl linker.

关键词： PrMg12 alloy   Mechanical milling   Activation energy   Hydrogen storage   Kinetics  

摘要： Mechanical ball milling technology was utilized to synthesize the nanocrystalline and amorphous PrMg11Ni + x wt% Ni (x = 100, 200) alloys. The effect of Ni content and milling time on thermodynamics and kinetics of the alloys were systematically investigated. The hydrogen absorption and desorption properties were analyzed by Sievert's apparatus and differential scanning calorimetry (DSC). Results show that increasing Ni content brings on a slight reduction in thermodynamic parameters (Delta H and Delta S) of the alloys, and it dramatically enhances the hydrogen absorption and desorption kinetics of the alloys. Varying milling time greatly affects the hydrogen storage properties of the alloys. The hydrogen absorption capacity of the alloys first increases and then deceases with the increase of milling time, and the maximum capacity of the alloy is approximately 5.8 wt% and 6.0 wt% for the x = 100 and x = 200 alloys. Moreover, the hydrogen desorption activation energy obviously decreases with increasing the Ni content and ball milling time. (C) 2016 Elsevier B.V. All rights reserved.

关键词： TiAl alloy   High temperature deformation   Grain boundary sliding   Dislocation creep   Diffusion creep   Rate-equation  

摘要： gamma-TiAl-based alloys have attracted intense attentions in the past two decades and are regarded as promising candidate materials for high-temperature applications due to their low density, high specific strength, superior creep and oxidation resistance, etc. It is well known that there are four typical microstructures in TiAl-based alloys, namely, full-lamellar (FL), near-lamellar (NL), duplex (DP) and near gamma (NG). The FL/NL-TiAl alloys possess superior high temperature mechanical performance such as creep resistance, but their deformability is relatively lower. In contrast, the DP/NG-TiAl alloys have much better formability while the creep resistance is reduced. Hence the DP/NG microstructure is preferable for hot-working and thought to the prerequisite for secondary processing, and the present paper is primarily focused on the high temperature deformation behavior of DP/NG-TiAl alloys. Till date, considerable research efforts have been directed towards the deformation kinetics or mechanical properties of various DP/NG-TiAl alloys, and a mass of experimental data has been accumulated. In order to explore their general features of high temperature deformation kinetics, in this paper the tensile/compression mechanical data of various DP/NG-TiAl alloys from the literature published in the past twenty years has been summarized and reviewed. Three deformation mechanisms (dislocation creep, grain boundary sliding and diffusion creep) have been identified, and for each the effects of major factors (i.e., alloy composition, microstructure and grain size) on deformation kinetics have been analyzed and discussed in detail. The results revealed that the high temperature deformation kinetics of DP/NG-TiAl alloys is less sensitive to composition except some dispersion-hardened alloys such as carbon-containing TiAl alloys. Instead, the gamma grain size became the major limiting factor. Based on this observation, a series of unified rate-equations has been successfully dev