关键词： 上肢康复机器人   机械结构   ADMAS   动力学分析  

摘要： 社会的各个领域已经将如何把机器人技术应用完善作为行业的新思考点,发展机器人技术需要多学科多领域的交叉研究,在工业机器人发展较为成熟的情况下,机器人开始用于医疗方面。进行了上肢康复机器人机械结构设计,其主要由执行机构、驱动机构和控制系统上肢康复机器人这三大部分组成。所设计的上肢康复机器人定位机械臂的设计需要完成器械的抓取、移动以及定位。本该设计结构采用关节式设计,关节型的优点是传动时操作较为精确,零件与零件之间的结构简单,需要用到的空间也较小,使其符合医疗器械的设计要求。本设计主要对机构的执行机构和驱动机构作详细的介绍。完成了上肢康复机器人的ADMAS动力学分析仿真研究,基于Adams的各构件的运动轨迹曲线一致,验证了所做上肢康复机器人运动学分析的正确性,以期为康复医学工作作出相应的贡献。

关键词： Seals   hydrodynamic lubrication   cavitation   surface topography   numerical simulation  

摘要： A two-scale homogenization method for modelling the hydrodynamic lubrication of mechanical seals with isotropic roughness was developed and presented the influence of surface topography coupled into the lubricating domain. A linearization approach was derived to link the effects of surface topography across disparate scales. Solutions were calculated in a polar coordinate system derived based on the Elrod cavitation algorithm and were determined using homogenization of periodic simulations describing the lubrication of a series of surface topographical features. Solutions obtained for the hydrodynamic lubrication regime showed that the two-scale homogenization approach agreed well with lubrication theory in the case without topography. Varying topography amplitude demonstrated that the presence of surface topography improved tribological performance for a mechanical seal in terms of increasing load-carrying capacity and reducing friction coefficient in the radial direction. A Stribeck curve analysis was conducted, which indicated that including surface topography led to an increase in load-carrying capacity and a reduction in friction. A study of macro-scale surface waviness showed that the micro-scale variations observed were smaller in magnitude but cannot be obtained without the two-scale method and cause significant changes in the tribological performance.

关键词： Hydrogen-and fluorine-functionalized SiCNT   Mechanical properties   Polymer nanocomposite   Molecular dynamics simulation  

摘要： The mechanical characteristics of reinforced polymer nanocomposites with Hydrogen (H)- and Fluorine (F)functionalized silicon carbide nanotubes (H-and F-fSiCNTs) are investigated herein using molecular dynamics (MD) simulations. The effects of covalent functionalization and chirality of SiCNT, and diverse polymer materials on Young's modulus, maximum stress, and strain to the failure point, as well as strain energy are studied. The results reveal that by increasing the functionalization degree, the maximum stress, maximum strain, elastic modulus, and strain energy decrease. The tensile strength of polymer nanocomposites containing SiCNT is higher than that of pure polymer and polymers containing functionalized silicon carbide nanotubes (fSiCNTs). It is also found that the incorporation of fSiCNT into the polymer matrix (fSiCNT/polymer) gives rise to a considerable improvement in the ultimate strength of nanocomposites compared to the pure polymer. Polymer nanocomposites reinforced by armchair SiCNTs and fSiCNTs withstand higher maximum stresses and possess less longitudinal Young's modulus as compared to the same systems comprising zigzag nanotubes. In every percent of functionalization, the zigzag F-fSiCNT/polymer tends to have a higher Young's modulus as compared to the zigzag H-fSiCNT/polymer. Similarly, the armchair F-fSiCNTs incorporated into the polyethylene (PE) matrix (FfSiCNTs/PE) are stiffer than the armchair H-fSiCNTs/PE in each weight of functionalization. Moreover, the armchair fSiCNTs/polymer nanocomposites show higher storage of strain energy in comparison with their zigzag counterparts.

关键词： composite insulating paper   composite structure   dielectric properties   mechanical properties   molecular dynamics simulation  

摘要： Reducing the dielectric constant of insulating paper to improve the dielectric coordination performance of the oil-paper systems has always been the research hotspot in the transformer insulation material industry. This paper prepares a novel poly-p-phenylene terephthalamide (PPTA)/cellulose composite paper with low dielectric constant and good mechanical properties. Various PPTA/cellulose mixing structures were established and the dielectric and mechanical properties were simulated via molecular dynamics simulation. Results showed that the PPTA/cellulose composite system had a lower dielectric constant than the cellulose system, for adding PPTA molecular could reduce the free volume of the system and limit the steering polarization of the dipole, as well as decrease the system polarization intensity. Constructing a three-layer structure that contains continuous cellulose middle layer could improve the mechanical properties of the composite system greatly. Experimental results verified the simulation results. The dielectric constant of the three-layer PPTA/cellulose composite paper decreased from 3.98 to 3.49 at 50 Hz, compared to the conventional cellulose paper. Moreover, the tensile strength of the novel three-layer PPTA/cellulose composite paper (thickness: 130 mu m) has reached 9.02 kN/m, increased by 27.6% than the directly mixed composite paper. Molecular dynamics simulation proves to be a promising method for guiding paper modification. Constructing three-layer PPTA/cellulose structure represents an effective way to prepare a low dielectric constant composite insulating paper with good mechanical properties.

关键词： Nanocomposites   graphene silver   deformation   melting point   dislocations  

摘要： The effect of graphene silver (GN/Ag) interface is a key factor to understand glides and shuffles dislocations which affect the thermo-mechanical performance. Here, we report the recital optimization of graphene interaction with silver by molecular dynamics (MD) simulation. To analyse the effect of temperature and stress three orientations of Ag ((1 0 0), (1 1 0), and (1 1 1)) attached with monolayer graphene have been chosen. During the heating process apart from interface, edges in graphene can cause dislocation nucleation. The melting temperature of GN/Ag (1 0 0), GN/Ag (1 1 0), and GN/Ag (1 1 1) were observed as 1190, 1150, and 1250 K. The GN/Ag (1 1 0) shows lowest melting temperature indicated least stable structure . GN/Ag (1 1 1) has a higher melting temperature as compared to other samples due to propagation of shuffle dislocations. Furthermore, all samples have been subjected to uniaxial tensile loading. It was calculated that the stress of GN/Ag (1 0 0), GN/Ag (1 1 0), and GN/Ag (1 1 1) increased 341%, 377%, 386.20% along armchair and 1231%, 1000%, 1289% zigzag direction w.r.t silver. Based on the above-mentioned results, GN/Ag nanocomposites is a potential candidate for thermal management applications.

关键词： 铁路机务管理   铁路机械动力设备   优化管理  

摘要： 随着我国社会主义现代化建设,我国铁路事业也在不断地进行发展,众多新技术,新工艺,新设备被不断的应用到铁路机务系统的生产当中。也正因为此,在铁路机务系统方面,对于机械动力设备的管理使用、保养等各个管理方面也有了更高的管理要求。就目前铁路机务管理中机械动力设备管理,已经不能够完全满足铁路现代化的管理要求,因此,这就需要我们在管理水平方面进行一定的提升。特别是在铁路机务设备管理部门,对于提升设备管理水平及管理能力最为突出,机务系统设备维修保养与管理方面,目前处于传统管理与现代化管理之间。究其原因,影响因素较多,对设备的维护、管理工作产生制约与影响。本文章将重点围绕铁路机务系统机械动力设备优化管理进行浅析。

关键词： 机械通气   静-动脉二氧化碳分压差/动-静脉氧含量差   血流动力学   机械通气时间  

摘要： 目的探讨中心静脉压(CVP)、重症超声联合静-动脉二氧化碳分压差(Pv-aCO_(2))/动-静脉氧含量差(Ca-vO_(2))在机械通气患者容量管理中的指导价值及对血流动力学、乳酸(Lac)、机械通气时间的影响。方法选取2018年6月—2020年6月该院收治的104例脓毒症休克机械通气患者,随机数字表法分为二组,各52例。二组均给予液体复苏治疗,对照组通过监测CVP指导容量管理,观察组在对照组基础上加用重症超声联合(Pv-aCO_(2))/(Ca-vO_(2))指导容量管理。比较二组复苏前、6 h、24 h血流动力学指标[心率(HR)、中心静脉血氧饱和度(ScvO_(2))、平均动脉压(MAP)、(Pv-aCO_(2))/(Ca-vO_(2))]、6 h液体复苏量、血管活性药物用量、机械通气时间、ICU住院时间、急性生理和慢性健康状况评分(APACHEⅡ)、序贯器官衰竭(SOFA)评分、Lac。结果观察组6 h、24 h HR、(Pv-aCO_(2))/(Ca-vO_(2))低于对照组,ScvO_(2)、MAP高于对照组(P<0.05);观察组6h液体复苏量、血管活性药物用量低于对照组,机械通气时间、ICU住院时间短于对照组(P<0.05);观察组6hLac及24hAPACHEⅡ评分、SOFA评分、Lac均低于对照组(P<0.05),以上差异均有统计学意义。结论CVP、重症超声联合(Pv-aCO_(2))/(Ca-vO_(2))应用于机械通气患者容量管理中,可改善机体血流动力学,减少Lac产生,缩短机械通气时间,改善疾病预后,可更精确地指导液体复苏,对机械通气患者容量管理具有重大指导意义。

关键词： 在读研究生   材料成型及控制工程   全日制本科   能源与动力工程   机械制造及其自动化   机械电子工程   工程训练中心   卓越工程师教育培养计划  

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。

关键词： HF   RIMP2   Electron correlation   Ion solvation   Liquid ammonia   Ab initio quantum simulation  

摘要： The impact of electron correlation in quantum mechanical charge field molecular dynamics (QMCF MD) simulations of Cu+ in pure liquid ammonia has been investigated by comparing the results obtained at the Hartree-Fock (HF) level and via resolution-of-identity second order Moller-Plesset perturbation theory (RIMP2). To achieve a manageable computational demand, a rigid-body solvent model was employed to describe the NH3 molecules. The solvation structures observed in both cases have similar characteristics in which tetrahedral [Cu(NH3)(4)](+) dominates with average Cu-N distances of 2.24 (HF) and 2.12 (RIMP2) angstrom, respectively. The ligand dynamics in the first solvation shell of the RIMP2 simulation are notably higher than in the HF case and resulted in the formation of an intermediate [Cu(NH3)(3)](+) complex along the sampling period. Electron correlation effects were found to mainly impact the solvent-solvent hydrogen bonding interaction, thereby providing a more accurate description of the structural properties in terms of the average Cu-N distances along with greatly enhanced ligand exchange dynamics occurring between the first and second solvation shell. (C) 2021 The Author(s). Published by Elsevier B.V.

关键词： 提综臂   辅助旋铆   并联机械手   拉格朗日方法   计算力矩控制   联合仿真   动力学建模  

摘要： 为实现在旋铆加工过程中对零部件的高速、高精度抓取-摆放之目的,以多臂织机提综臂的自动化加工为背景,提出一种新型辅助旋铆并联机械手的动力学建模及控制策略。首先,介绍机器人机构的结构特征及自由度类型;其次,建立闭环矢量方程,得到了位置正逆解的解析表达式,进而通过求导,建立了速度映射模型;再次,基于第一类拉格朗日方法,建立了系统逆刚体动力学模型,得到关于末端执行器广义坐标的驱动力矩函数。在此基础上,设计具有PD补偿的任务空间计算力矩控制策略,并借助ADAMS与Simulink开展联合虚拟仿真,对控制参数进行整定,最终得到最优控制参数的参考值。仿真结果表明:在最大加速度为3 g时,跟踪轨迹与理论轨迹的y向误差小于0.3 mm,z向误差小于0.65 mm,控制效果良好,符合设计预期。