关键词： 动力机械测试技术   课程改革   思考   实践  

摘要： 《动力机械测试技术》是热能与动力工程专业的专业课程,也是一门实践性很强的课程。为此,本课题组拟以从教学内容及教学组织方式等方面进行改革,着重培养学生的工程实践与创新能力,以期为地方院校开展测试技术的教学提供可能的可以借鉴的模式。

关键词： 中国航空学会   学术讨论会   动力机械   动力传输   岳阳市   南京航空航天大学   西北工业大学   北京航空航天大学  

摘要： 中国航空学会第十六届机械动力传输专业委员会学术讨论会于2013年11月27日至29日在湖南省岳阳市召开来自南京航空航天大学、西北工业大学、北京航空航天大学、上海理工大学、中国航空学会动力分会、《航空动力学报》、中航工业发动机公司、中航商发公司、沈阳发动机设计研究所、中国航空动力机械研究所、中航工业航空动力控制系统研究所。

关键词： Molecular dynamics   Graphene   Graphene ribbon resonator  

摘要： We investigated the mechanical responses of the nanoindented graphene-nanoribbon (GNR)-resonator using classical molecular dynamics simulations. The nanoindented force in this work was applied to the GNR's local point and then, GNR-resonator's frequency could be tuned by a nanoindented depth. We found the hardening or the softening of the GNR during its nanoindented-deflections, and such properties were recognized by the shift of the resonance frequency. The linear elastic regime in low applied force is explicitly separated with the non-linear elastic regime in high applied force. In particular, at the threshold point, a very small change of the nanoindented depth can cause great change in the resonance frequency, and this property can enable the GNR to be applied to electromechanical relay switching. devices and the quantum-computer in quantum-mechanical coupling as well as mass detectors, pressure sensors, accelerometers, and alarms. (C) 2013 Elsevier B.V. All rights reserved.

关键词： rockslide   dynamics   modeling   deglaciation   Voight's law  

摘要： Long-term observations of large active rockslides show accelerating deformation over many thousands of years since the last deglaciation. The effect of deglaciation on slope stability is however poorly understood due to (1) limited long-term observations and (2) a complex interaction between glacier retreat and hydrogeological, mechanical, and morphological processes. To assess the sensitivity of rockslide dynamics to these different processes, a model of progressive damage through intact rock mass is developed in this study, based on the finite element method. This model uses time-to-failure laws based on rock laboratory creep experiments. It is able to reproduce progressive damage localization along shear bands associated with strain rate acceleration as observed during tertiary creep. The model reproduces the different phases of deformation associated with morphologies typical of large rockslides. This model is thus suitable for simulating the dynamics of large rockslides and the transition from initiation to rapid sliding. The sensitivity of rockslide kinematics and morphology to different mechanical properties is analyzed. This analysis shows that the time evolution of the rockslide can be inferred with the knowledge of only one time parameter, independent of the knowledge of the mechanical properties of the rock mass. This parameter is here chosen as the time when the summit slope displacement has reached 10 m, a parameter that can be estimated with cosmogenic dating. The model is then used to study the effects of deglaciation on the valley flank stability and the formation of large rockslides. This study shows that the deglaciation velocity can affect the morphology of the rockslide, with the shear band of the rockslide emerging at higher elevation as the velocity decreases. We also show that the response to the deglaciation can last several thousands of years after the glacier retreat.

关键词： Glasses   metallic   Rapid solidification processing   Simulations   atomistic   Electronic structure   calculation   Mechanical properties   theory  

摘要： Cu-Zr Metallic glasses (MG) are considered to be composed of Icosahedral-like (ICO) clusters that may be distorted, truncated and/or interconnected. Aiming in gaining insight on the role of these units in the solidification-glass formation processes, as well as under mechanical solicitation, we performed detailed analysis of the electronic density of states, based on the Density Functional Theory, of the basic ICO-like clusters that were extracted from Cu65Zr35 equilibrium Molecular Dynamics (MD) configurations at various temperatures within the range from 2000 K to 300 K. In line with previous studies, we found that the d valence electrons of the Zr shell atoms occupy states close to the Fermi level, while s-s and d-s electronic hybridizations of the Cu-core/Cu-shell with the Cu shell atoms, respectively, occur at lower energy states and account for the deformation of the clusters, which is exclusively accomplished by these Cu-Cu distortions. Moreover, we found that upon quenching the mean atomic distances of the ICOs are decreasing due to shortening of the Cu-core/shell - Cu shell bonds, resulting in shifts of the corresponding states towards lower energies. Interestingly, it came out that the temperature dependence of these energies is linear, exhibiting slope changes at the melting and glass transition points. We applied the same analysis on ICOs extracted from Cu50Zr50 MD configurations under tensile solicitation from where we deduced the alterations that are caused in the electronic densities of states. These results could be of use for the understanding of the bonding characteristics of Cu-Zr model MGs and the mechanisms for the accommodation of the mechanical deformation. (C) 2013 Elsevier Ltd. All rights reserved.

关键词： cardiac hypertrophy   actin assembly   phosphoinositide   mechano-transduction   CapZ tentacle  

摘要： Mechanical stress causes filament remodeling leading to myocyte hypertrophy and heart failure. The actin capping protein Z (CapZ) tightly binds to the barbed end of actin filaments, thus regulating actin assembly. The hypothesis is that the binding between CapZ and the actin filament is modulated through phosphatidylinositol 4,5-bisphosphate (PIP2) and how the COOH-terminus of CapZ beta 1 regulates this binding. Primary neonatal rat ventricular myocytes (NRVMs) were strained at 10% amplitude and 1-Hz frequency. Dot blotting measured the PIP2 amount, and affinity precipitation assay assessed the direct interaction between PIP2 and CapZ beta 1. Fluorescence recovery after photobleaching of green fluorescent protein-CapZ beta 1 and actin-green fluorescent protein after 1 h of strain shows the dynamics significantly increased above the unstrained group. The increases in CapZ and actin dynamics were blunted by neomycin, suggesting PIP2 signaling is involved. The amount of PIP2 dramatically increased in NRVMs strained for 1 h. With a ROCK or RhoA inhibitor, changes were markedly reduced. Subcellular fractionation and antibody localization showed PIP2 distributed to the sarcomeres. More PIP2-bound CapZ beta 1 was found in strained NRVMs. Less PIP2 bound to the CapZ beta 1 with its COOH-terminus intact than in the COOH-terminal mutant of CapZ beta 1, suggesting some inhibitory role for the COOH-terminus. Myocyte hypertrophy normally induced by 48 h of cyclic strain was blunted by dominant negative RhoA or neomycin. This suggests that after many hours of cyclic strain, a possible mechanism for cell hypertrophy is the accumulation of thin filament assembly triggered partially by the increased PIP2 level and its binding to CapZ.

关键词： GAUGE field theory   LATTICE field theory   FINITE size scaling (Statistical physics)   CHIRALITY   FIELD theory (Physics)  

摘要： We investigate the chiral properties of SU(2)C gauge theory with six flavors, i.e., six light Dirac fermions in the fundamental representations by lattice simulation, and point out that the spontaneous breakdown of chiral symmetry does not occur in this system. The quark mass dependence of the mesonic spectrum provides evidence for such a possibility. The decay constant tends to be increased by the finite size effect, which is opposite to the behavior predicted by chiral perturbation theory and indicates that the long distance dynamics in the six-flavor theory could be different from the theory with chiral symmetry breaking. The subtracted chiral condensate, whose utility is demonstrated by the simulation of two-flavor theory, is shown to vanish in the chiral limit within the precision of available data.

关键词： 管道施工机械手   虚拟样机建模   动力学仿真  

摘要： 管道施工机械手用于铺设地下大型水泥管道。为了能够准确模拟机械手的工作过程,为物理样机的设计和制造提供参数依据,采用Solidworks、Adams建立机械手虚拟样机的联合建模方法。为了能够实现仿真过程与实际工作状态的高度一致,保证仿真结果准确反映实际工况,在虚拟样机的运动副中添加外力等效摩擦力,对油缸铰接销轴柔性处理,以及添加过渡轴解决冗余约束等。对机械手虚拟样机进行了管道对接过程的动力学仿真,提取了相关仿真数据,并与实验样机的实验数据进行了对比。结果表明:仿真模型基本与实验样机相符,仿真数据基本准确、可靠。

关键词： 多体动力学   逆动力学模型   数值仿真  

摘要： 考虑到移动串联机械手不能很好地满足高速、大负载、准确作业的性能要求,提出了一种新颖的轮式悬架移动并联机械手构型。为实现建模的通用性与完备性,基于多体动力学,在笛卡尔坐标下构建了系统逆动力学模型,并据此分别对移动串联机械手和移动并联机械手进行了逆动力学数值仿真,以验证建模方法的正确性和新构型移动机械手的动力学性能。仿真结果的比较、分析表明,与串联构型相比,移动并联机械手的系统刚度有所提高,且不必增大能耗为代价;电机驱动力矩有所降低,有利于电机的选型和控制策略的制定。

关键词： (110.4500) Optical coherence tomography   (170.2655) Functional monitoring and imaging  

摘要： Pulmonary alveoli have been studied for many years, yet no unifying hypothesis exists for their dynamic mechanics during respiration due to their miniature size (100-300 mu m dimater in humans) and constant motion, which prevent standard imaging techniques from visualizing four-dimensional dynamics of individual alveoli in vivo. Here we report a new platform to image the first layer of air-filled subpleural alveoli through the use of a lightweight optical frequency domain imaging (OFDI) probe that can be placed upon the pleura to move with the lung over the complete range of respiratory motion. This device enables in-vivo acquisition of four-dimensional microscopic images of alveolar airspaces (alveoli and ducts), within the same field of view, during continuous ventilation without restricting the motion or modifying the structure of the alveoli. Results from an exploratory study including three live swine suggest that subpleural alveolar air spaces are best fit with a uniform expansion (r(2) = 0.98) over a recruitment model (r(2) = 0.72). Simultaneously, however, the percentage change in volume shows heterogeneous alveolar expansion within just a 1 mm x 1 mm field of view. These results signify the importance of four-dimensional imaging tools, such as the device presented here. Quantification of the dynamic response of the lung during ventilation may help create more accurate modeling techniques and move toward a more complete understanding of alveolar mechanics. (C) 2013 Optical Society of America