关键词： 2D material   mechanical properties   molecular dynamics simulation   phosphorene  

摘要： Although various phosphorene allotropes have been theoretically predicted to be stable at 0 K, the mechanical properties and fracture mechanism at room temperature remain unclear for many of them. We investigate through reactive molecular dynamics simulations at room temperature the mechanical properties of phosphorene allotropes including: five sheets with hexagonal structures (beta-, gamma-, delta-, theta-, and alpha-phosphorene), one sheet with 4-8 membered rings (4-8-P), and two sheets with 5-7 membered rings. High, moderate and slight anisotropies in their mechanical properties are observed, depending on their crystal structures. Their Young's moduli and tensile strength are approximately in the range from 7.3% through 25%, and from 8.6% through 22% of those of graphene, respectively. At the early stage of fracture, eye-shaped cracks are formed by local bond breaking and perpendicular to the tensile direction in hexagonal and 4-8-P sheets. Complete fractures take place with straight cracks in these hexagonal sheets under tension along the zigzag direction and under tension along the square edge direction in the 4-8-P sheet. Crack meandering and branching are observed during the tension of alpha-, beta-, and gamma-phosphorene along the armchair direction;and along the square diagonal direction in the 4-8-P sheet. Under uniaxial tension of two phosphorene sheets with 5-7 atom rings, 12 and 10 membered rings are formed by merging two neighbor heptagons, and a heptagon and its neighbor pentagon, respectively. These 12 and 10 membered rings coalesce subsequently, causing the failure of these two sheets. The results are of great importance in the design of these novel phosphorene allotropes.

关键词： protein content   hyperpolarization   electromechanics   Directly proportional   Cell Size   Membrane Potentials   Cell Volume  

摘要： Cell volume regulation is fundamentally important in phenomena such as cell growth, proliferation, tissue homeostasis, and embryogenesis. How the cell size is set, maintained, and changed over a cell's lifetime is not well understood. In this work we focus on how the volume of nonexcitable tissue cells is coupled to the cell membrane electrical potential and the concentrations of membrane-permeable ions in the cell environment. Specifically, we demonstrate that a sudden cell depolarization using the whole-cell patch clamp results in a 50% increase in cell volume, whereas hyperpolarization results in a slight volume decrease. We find that cell volume can be partially controlled by changing the chloride or the sodium/potassium concentrations in the extracellular environment while maintaining a constant external osmotic pressure. Depletion of external chloride leads to a volume decrease in suspended HN31 cells. Introducing cells to a high-potassium solution causes volume increase up to 50%. Cell volume is also influenced by cortical tension: actin depolymerization leads to cell volume increase. We present an electrophysiology model of water dynamics driven by changes in membrane potential and the concentrations of permeable ions in the cells surrounding. The model quantitatively predicts that the cell volume is directly proportional to the intracellular protein content.

关键词： 空间机械臂简介   动力学模型研究   运动规划研究   目标碰撞策略研究  

摘要： 在自由漂浮状态中,空间机械臂的载体与机械臂之间存在一定的耦合行为。其本身与地面机械臂相比,在运动学、运动学分析等方面相差非常大,地面机械相对来说就比较简单。对于空间机械臂的研究重点是建立在精确地动力学模型和高效的控制策略的基础之上。本文详细的阐述了空间机械臂动力学建模的方法以及精细动力;总结了姿态运动规划、非完整机械臂路径规划以及避奇异位形的机械路径规划的运动方法等运动规划方式;阐述了空间机械臂在捕获目标过程中的动力学模型和控制策略研究。

关键词： failure properties   molecular dynamics   solid polymer electrolyte   viscoelastic properties  

摘要： This reactive molecular dynamics study explores the salt concentration dependence of the viscoelastic and mechanical failure properties of a poly(propylene glycol)/LiPF6-based solid polymer electrolyte (SPE) at a graphitic carbon electrode interface. To account for the finite-size effect of interface-confined SPE films, the properties of two distinct film thicknesses are compared with the respective bulk properties. Additionally, the effect of uniaxial compression in the interface-normal direction on free energy profiles of Li-ion SPE-desolvation is studied. (c) 2018 The Authors. Journal of Polymer Science Part B: Polymer Physics Published by Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 718-730

关键词： 农业机械化   合作社   现代农业   北镇市  

摘要： 北镇市紧紧围绕粮食生产功能区和现代化农业机械化技术推广,大力扶持发展设施完备、功能齐全、管理规范、效益显著、充满活力的农机专业合作社,提高了当地的农机专业化和社会化服务水平,走出了一条规模化经营、机械化生产、社会化服务、产业化发展的农机合作社发展新路。

关键词： 金属材料   机械设备   翻转机构   动力学   建模分析  

摘要： 金属材料机械设备的运转已经是大势所趋,但存在金属材料机械设备还存在自动化运转不够合理的问题,为此提出了金属材料机械设备翻转机构动力学特性建模分析。以金属材料机械设备翻转机构的等效力矩模型以及金属材料机械设备翻转机构的等效转动惯量模型为前提,进行金属材料机械设备翻转机构动力学方程设计,并通过仿真实验对其结果进行分析,以期实现更加有效地金属材料机械设备的运行。

关键词： 无创正压通气(NIPPV)   急性心力衰竭   呼吸衰竭   血流动力学   血氧状态  

摘要： 目的:本研究旨在观察和分析Bi PAP无创正压通气(NIPPV)对于急性心力衰竭并呼吸衰竭的临床效果及血流动力学和血氧状态的影响。方法:选取2011年1月-2014年12月在我院ICU住院治疗的急性心力衰竭合并呼吸衰竭的患者360例,将其随机分为两组。对照组(n=180)常规抗心力衰竭、呼吸衰竭药物治疗;观察组(n=180)在常规抗心力衰竭、呼吸衰竭的药物治疗的基础上采用Bi PAP呼吸机进行无创通气治疗。记录治疗前后的症状、体征、血流动力学以及血氧状态。结果:观察组的治疗总有效率、显效率均明显高于对照组(P<0.05),两组患者治疗前HR、RR、SBP、DBP以及PCO2均无显著差异(均P>0.05),治疗后治疗组的HR、RR、SBP、DBP以及PCO2均明显低于对照组(P<0.05),与对照组比较,差异有统计学意义(P<0.05);另外,两组患者治疗前后p H值无明显改变(P>0.05);观察组治疗后的SPO2、SJVO2改善程度明显好于对照组,差异具有统计学意义(P<0.01)。结论:与传统药物治疗相比较,无创正压机械通气可以明显降低患者的病死率,采用Bi PAP无创通气可明显改善心功能和呼吸功能,提高AHF合并RF的治疗显效率和治疗总有效率,是一种快速安全有效的抢救措施,值得在临床中推广。

关键词： 重症吸入性肺炎   俯卧位   机械通气  

摘要： 目的对重症吸入性肺炎患者应用俯卧位通气的效果进行探讨。方法选取上海交通大学医学院附属瑞金医院北院2015年7月—2017年6月收治的重症吸入性肺炎患者60例,依据随机数字表法分为实验组和常规组,每组各30例。实验组行俯卧位机械通气,常规组行仰卧位机械通气,统计并对比两组血流动力学指标、血气分析指标。结果通气后3小时、6小时实验组Pa CO_2、PaO_2/FiO_2显著高于常规组(P<0.05)。通气后6小时实验组PaO_2显著高于常规组(P<0.05)。机械通气6小时后实验组HR显著高于常规组(P<0.05)。机械通气后3小时、6小时实验组MAP显著高于常规组(P<0.05)。结论在重症吸入性肺炎患者中应用俯卧位机械通气效果显著,能够有效地改善患者血流动力学、血气分析指标,值得临床上广泛推广。

关键词： 内燃机   汽轮机   燃气轮机   水轮机   风力机   电动机   流体传动装置  

摘要： 本文介绍了动力机械的相关定义及选用因素,同时重点阐述了内燃机、汽轮机、燃气轮机、水轮机、风力机、电动机及流体传动装置之间的相互区别并进行对比,同时明确了其具体应用领域。为相关领域工作人员提供了必要的理论依据。

关键词： Comfort analysis   Finite elements models   Frequency response function (FRF)   Pillars   Tuned mass damper  

摘要： Yacht designers and builders are continuously looking for new solutions to reduce construction costs and to improve the quality and innovation of their vessels. In the case of superyachts over 30 m in length, performances are no longer a primary goal and the efforts of technical offices are mostly addressed on other aspects related to the aesthetic impact of the project and to the on board comfort. From this point of view, vibrations and noise represent a difficult issues to deal with for designers, both in the initial phase of the project, when it is necessary to have preliminary information about the response of the structure not yet defined, and during construction, in case some critical behaviors arose in any part of the structure. In this paper, the dynamic behavior of a 40 m motor yacht is investigated. The Vibration Velocity Spectra obtained by the numerical model of the yacht are compared with the value of level limits imposed by the 1SO6954:1984. Different structural solutions are investigate to improve the comfort level in same area not in compliance with the rule.