关键词： 分子机械   模拟   动力学   建模  

摘要： 从纳米尺度了解结构和材料的动力学性能有着重要的意义。对分子机械动力学的研究现状进行概括和总结,介绍目前常用的分析模型,展望未来的研究方向和热点。

关键词： 2杆柔体   移动机械手   有限元法   运动学   动力学   耦合  

摘要： 研究了移动2杆柔体机械手动力学问题。该移动机械手由弹性-阻尼悬架轮式移动载体和2杆柔体机械手组成,并假定移动载体以恒线速度通过不规则路面。综合采用经典有限元法并引入中间单元坐标系和浮动坐标法,以回避由单元刚体运动所导致的弹性构件非零应变,从而精确描述机械手弹性变形与参考运动间的动力学耦合问题。综合利用拉格朗日原理和牛顿-欧拉方程并在笛卡儿坐标系下,以简洁的矩阵、矢量形式构建了该系统的完整动力学模型。采用数值方法给出了该动力学模型正解的仿真结果。通过与刚-柔体模型、刚体模型仿真结果的比较,证实该柔体系统存在动力学耦合现象及构件弹性振动对系统性能有负面影响。

关键词： 表面机械研磨处理   纳米材料   晶粒生长动力学   镍   热稳定性  

摘要： 利用表面机械研磨处理(SMAT)技术在纯Ni上制备一定厚度的纳米晶表层,利用X射线衍射(XRD)和透射电镜(TEM)研究了纳米晶Ni的晶粒生长动力学,计算了描述晶粒生长动力学的时间指数n和晶粒生长激活能Q。研究表明,纳米晶Ni在423～723 K退火时的时间指数n约为0.14。当纳米晶Ni在423～523 K退火时,其晶粒生长激活能Q为32.1 kJ/mol,表明在这一温度区间内晶粒生长由晶界和亚晶界的微结构重新排列所控制;当纳米晶Ni在523～723 K退火时,晶粒生长激活能Q为121.3 kJ/mol,表明在这一温度区间内晶粒生长由晶界扩散所控制。TEM观察表明纳米晶Ni在较高温度下退火时出现异常的晶粒长大现象。

关键词： 机械设计制造   工程学院   机电一体化技术   工程技术研究中心   实验教学示范中心   热能与动力工程   国家级精品课程   机械电子工程  

摘要： 机械与动力工程学院于1951年开办冶金与石油装备类专业，设有机械设计制造及其自动化、机械电子工程、热能与动力工程3个普通本科专业，以及机电一体化技术、机电设备维修与管理、液压与气动技术、数控技术4个专科专业。学院有省部级重点建设学科1个、工程技术研究中心2个，国家级精品课程1门，重庆市实验教学示范中心2个。

关键词： 底盘测功机   轮式工程机械   功率   动力性能  

摘要： 采用工程机械底盘输出功率、底盘传动系统损耗功率为工程机械动力性能的评价指标,通过选用直流电机作为工程机械阻力加载机构,选用合理的滚筒机构以及传感器对工程机械底盘输出功率进行测试.分析发动机的动力传输路线,通过测试数据评判工程机械发动机以及传动系统,对轮式工程机械的底盘维修提供有力的数据支持.

关键词： 工程机械行业   机械产业   提速   助推   机械工业   设备制造商   BICES   日本建筑  

摘要： 由中国工程机械工业协会联手美国设备制造商协会、日本建筑机械工业协会、韩国建筑机械工业协会联合主办的全球工程机械产业大会将在第十一届北京BICES展会期间举办，该次大会主题定为”机会、融合、应变“，将重点讨论”未来中国与全球工程机械产业的发展机遇“、”中国与全球工程机械行业如何深度融合，协同发展，

关键词： CO2-H2O solutions   QMCF-MD   hydrogen bond   vibrational spectrum   greenhouse effects  

摘要： Structure and dynamics of a carbon dioxide molecule in water were studied by an ab initio quantum mechanical charge field molecular dynamics (QMCF-MD) simulation. Radial distribution functions, angular distribution functions, and coordination number distributions as well as dynamical data such as mean ligand residence time and vibrational spectra were utilized for the evaluation of physico-chemical properties of hydrated CO2. These data served for an assessment of hydrogen bonding between solute and solvent molecules. All the results evaluated were compared with available experimental results leading to a good agreement between theoretical and experimental data. The average lifetime of hydrogen bonding between H2O and CO2 resulted as 0.61 ps, which is higher than the hydrogen bonding lifetime of pure water. The vibrational frequencies were also calculated for all the modes of hydrated CO2 to demonstrate the influence of solvent molecules on the IR spectrum of the solute. (C) 2010 Wiley Periodicals, Inc. Int J Quantum Chem 111: 1370-1378, 2011

关键词： Multiple Virtual Storage   Precursor Cell Lymphoblastic Leukemia-Lymphoma   Chronic lymphocytic leukemia   Cell Death   Kinetics   Adult Acute Lymphoblastic Leukemia   tumor necrosis  

摘要： Clinical trials using vaccine measles virus (MV) as anticancer therapy are already underway. We compared the oncolytic potential of MV in two B-cell malignancies;adult acute lymphoblastic leukemia (ALL, an aggressive leukemia) and chronic lymphocytic leukemia (CLL, an indolent leukemia overexpressing Bcl-2) using patient-derived material. In vitro, distinct cytopathological effects were observed between MV-infected primary ALL and CLL cells, with large multinucleated syncytia forming in ALL cultures compared to minimal cell-to-cell fusion in infected CLL cells. Cell viability and immunoblotting studies confirmed rapid cell death in MV-infected ALL cultures and slower MV oncolysis of CLL cells. In cell lines, overexpression of Bcl-2 diminished MV-induced cell death providing a possible mechanism for the slower kinetic of MV oncolysis in CLL. In vivo, intratumoral MV treatment of established subcutaneous ALL xenografts had striking antitumor activity leading to complete resolution of all tumors. The antitumor activity of MV was also evident in disseminated ALL xenograft models. In summary, both ALL and CLL are targets for MV-mediated lysis albeit with different kinetics. The marked sensitivity of both primary ALL cells and ALL xenografts to MV oncolysis highlights the tremendous potential of MV as a novel replicating-virus therapy for adult ALL.

关键词： EXPERIMENTS   STRAINS & stresses (Mechanics)   COUPLINGS (Gearing)   TEMPERATURE measurements   CRYSTAL grain boundaries   MOTION  

摘要： Recent results of experimental research into stress-induced grain boundary migration in aluminum bicrystals are reported. Boundary migration under a shear stress was observed to be coupled to a lateral translation of the grains for planar symmetrical aOE (c) 100 > tilt boundaries. This coupling proved to be the typical migration mode of any aOE (c) 100 > tilt boundary, no matter whether low- or high-angle, low I pound CSL coincidence or non-coincidence boundary. The measured ratios of normal boundary motion to the tangential displacement of grains are in an excellent agreement with theoretical predictions. The migration-shear coupling is also observed for asymmetrical aOE (c) 100 > boundaries. Measurements of the temperature dependence of coupled boundary migration revealed that there is a specific misorientation dependence of migration activation parameters. Grain boundaries can act during their motion under the applied stress as sources of lattice dislocations that leads to the generation and growth of new grains in the boundary region. The rate of stress-induced boundary migration decreases with increasing solute content in aluminum. Both the migration activation enthalpy and the pre-exponential mobility factor were found to increase with rising impurity concentration.

关键词： Kinetics  

摘要： This article focuses on the mechanically induced reactivity of boehmite prepared by thermal decomposition of gibbsite. Boehmite, which retained the morphology of gibbsite, was characterized by a specific surface area of 264 m(2)/g. Mechanical activation (MA) was carried out in a planetary mill up to 240 minutes. The samples were characterized in terms of morphology, characteristic particle diameters, Brunauer Emmett Teller (BET) specific surface area (SSA(BET)), microcrystallite dimension (MCD), microstrain (epsilon) and Fourier transform infrared spectroscopy. The reactivity was construed from the kinetics of thermal transformation of boehmite into gamma-Al2O3. The transformation observed between 600 K and 900 K (327 A degrees C and 627 A degrees C), manifested itself as two overlapping peaks in the differential thermogravimetric plot. These peaks correspond to two stages of dehydroxylation involving Al2OH and AlOH groups in succession. The peaks were resolved using Gaussian deconvolution. The reactivity was assessed separately for the two stages by comparing the fraction reacted in MA samples (alpha) with that of nonactivated sample (alpha (ref)). During both stages, enhanced kinetics, as revealed by alpha-alpha (ref) plots, indicated an increase in reactivity with MA. The transformation mechanism conformed to n (th) order reaction (f[alpha] = [1 - alpha] (n) with n = 1.3-1.5 in both stages). Values of n remained similar for the activated and reference samples. Activation energies (E (a)) for the first and second dehydroxylation stages were respectively 115 and 300 kJ/mol for the nonactivated sample. E (a) for the second stage decreased exponentially to a value of 222 kJ/mol after 240 minutes of milling. An anomalous negative correlation between reactivity and SSA(BET) was observed. Reactivity parameters were strongly correlated with MCD and epsilon. A plausible explanation for the observed correlations is presented.