关键词： 多体动力学   机械工程   技术应用  

摘要： 随着科技的不断进步,很多新的科学技术都被研发和应用,多体动力学也作为一项高科技技术广泛的应用在机械工程领域。机械工程领域的很多设备设计和产品研发都需要应用多体系统系统学的相关知识。据此,重点阐述了多提动力学在机械工程领域的具体应用,希望为同行提供一些参考。

关键词： 动力电池包   复杂系统安全   精细化模型   评价方法  

摘要： 动力电池包是一个复杂系统综合体,对复杂系统而言仅考虑组件的可靠安全性并不能保证其系统的安全性,迫切需要从系统层面分析评价动力电池包的安全性。运用复杂系统安全理论结合电动汽车实际工况,提出基于整体精细化模型可量化、层次化的动力电池包系统安全性评价。保证单体锂电池模型精细化的情况下,从正碰、侧碰、振动冲击三种常见工况对动力电池包进行仿真分析,采用层次分析(AHP)和模糊综合评价(FCE)相结合的方法对影响动力电池包系统安全的关键因素指标进行综合性安全评价。结果表明动力电池包系统安全性等级较低,安全性能较差。所提方法可为动力电池包正向结构设计和系统安全改善等工作提供参考。

关键词： 废荧光粉   稀土元素   机械活化   酸浸   动力学  

摘要： 针对废荧光粉进行机械活化预处理以提高其反应活性,实现其中金属钇(Y)在盐酸溶液中的高效浸出。通过浸出实验,考察了浸出温度以及盐酸初始浓度对废荧光粉中钇浸出效果的影响。废荧光粉经机械活化预处理后,在较低的温度和盐酸初始浓度条件下,钇浸出速率均显著提高。在球磨转速550 r·min-1、球料比41:1、球磨时间60 min条件下,经机械活化预处理后,废荧光粉的表观活化能和反应级数由原始样品的41.9 kJ·mol-1和0.69降至10.9 kJ·mol-1和0.23。

关键词： 机械波   弹性粒子   半波损失  

摘要： 本文利用粒子化的概念,在机械波传输界面上,分析了半波损失的产生机制。在几种常见的边界条件下,分别从波和粒子的角度,对比分析了入射波、反射波和透射波之间在分界面上的相位变化。结合初学者更为熟悉的动量守恒定律和能量守恒定律,用粒子的碰撞模型,定性分析了机械波在传输界面上的相位变化,对半波损失的概念给出了一种直观、简洁的解释。从约束方程来看,本文所采用的粒子化的经典动力学的方法,与利用波函数边界条件的分析方法,本质上是一致的,都是动量守恒定律和能量守恒定律的普适性在波动现象这一物理过程中的体现。

关键词： 机械动力学   分子动力学   微机械  

摘要： 微机械是传统的宏观机械动力学与纳米技术的结合,具有节能、环保、能耗小等特点。微机械由于尺寸小,其动力学行为是宏观机械动力学基于纳米技术的应用,是微机械的理论基础,因此有必要讨论其微机械状态下的动力学行为与研究。介绍了微机械动力学的研究现状,研究内容以及尚存在的问题,提出了未来的发展趋势。

关键词： Grain boundaries  

摘要： The effect of pre-deformation on the precipitation behavior of the beta-Mn phase while aging at 600 degrees C was investigated in Fe-30Mn-9Al-1C (wt pct) steel. The accelerated precipitation and growth of the beta-Mn phase along the grain boundaries and deformation bands are ascribed to variations in the microstructure and storage energy. The precipitation kinetics of the beta-Mn phase can be restrained using the Johnson-Mehl-Avrami model. The high storage energy level resulting from the pre-deformation facilitates the nucleation of the -Mn phase. The characteristics of the grain boundaries and deformation bands as a channel for rapid diffusion of the solute atoms is beneficial for the growth of the beta-Mn phase. In addition, the existence of intergranular kappa-carbides causes the beta-Mn phase to precipitate earlier than alpha-ferrite during the aging treatment. Finally, the precipitation of the beta-Mn phase increases the hardness but dramatically reduces the plasticity. (C) The Minerals, Metals & Materials Society and ASM International 2019

关键词： Ice nanotube   Carbon nanotube   Aqueous environment   Buckling   Molecular dynamics simulations  

摘要： In this article, molecular dynamics (MD) simulations are utilized to investigate the buckling behavior of carbon nanotubes (CNTs) containing ice nanotubes in the vacuum and aqueous environment. The obtained results show that unlike the critical strain, the critical buckling load of CNT containing ice nanotube is higher than that of pure CNT in the vacuum. It is also indicated that the sensitivity of critical budding load and the critical strain of CNT containing ice nanotube to the variation of length decreases when the nanostructure is subjected to the aqueous environment. Additionally, it is observed that the calculated critical budding load and the critical strain of CNTs filled with ice nanotubes in the aqueous environment are respectively larger and smaller than those obtained in the vacuum. It is further observed that CNTs lose their symmetric buckling mode shape as they are filled with ice nanotubes in the vacuum. The results of these simulations can be used as a benchmark for further studies in designing novel potential applications such as proton electronic-based nanoelectromechanical systems (NEMS). (C) 2019 Elsevier Inc. All rights reserved.

关键词： autophagy   cardiac resynchronization therapy   heart failure   mitochondria   mitochondrial calcium uniporter  

摘要： The mechanism of cardiac resynchronization therapy (CRT) remains unclear. In this study, mitochondria calcium uniporter (MCU), dynamin-related protein-1 (DNM1L/Drp1) and their relationship with autophagy in heart failure (HF) and CRT are investigated. Thirteen male beagle's dogs were divided into three groups (sham, HF, CRT). Animals received left bundle branch (LBB) ablation followed by either 8-week rapid atrial pacing or 4-week rapid atrial pacing and 4-week biventricular pacing. Cardiac function was evaluated by echocardiography. Differentially expressed genes (DEGs) were detected by microarray analysis. General morphological changes, mitochondria! ultrastructure, autophagosomes and mitophagosomes were investigated. The cardiomyocyte stretching was adopted to imitate the mechanical effect of CRT. Cells were divided into three groups (control, angiotensin-II and angiotensin-II + stretching). MCU, DNM1L/Drp1 and autophagy markers were detected by western blots or immunofluorescence. In the present study, CRT could correct cardiac dysfunction, decrease cardiomyocyte's size, alleviate cardiac fibrosis, promote the formation of autophagosome and mitigate mitochondrial injury. CRT significantly influenced gene expression profile, especially down-regulating MCU and up-regulating DNM1L/Drp1. Cell stretching reversed the angiotensin-II induced changes of MCU and DNM1L/Drp1 and partly restored autophagy. CRT's mechanical effects down-regulated MCU, up-regulated DNM1L/Drp1 and subsequently enhanced autophagy. Besides, the mechanical stretching prevented the angiotensin-II-induced cellular enlargement.

关键词： Ablation   Cardiomyopathy   Mechanical bradycardia   Postextrasystolic potentiation   Premature ventricular contraction  

摘要： BACKGROUND The relationships between hemodynamic consequences of premature ventricular contractions (PVCs) and development of premature ventricular contraction-induced cardiomyopathy (PVC-CM) have not been investigated. OBJECTIVE The purpose of this study was to correlate concealed mechanical bradycardia and/or postextrasystolic potentiation (PEP) to PVC-CM. METHODS Invasive arterial pressure measurements from 17 patients with PVC-CM and 16 controls with frequent PVCs were retrospectively analyzed. PVCs were considered efficient (ejecting PVCs) when generating a measurable systolic arterial pressure. PEP was defined by a systolic arterial pressure of the post-PVC beat >= 5 mm Hg higher than the preceding sinus beat. Every PVC was analyzed for 10 minutes before ablation, and the electromechanical index (EMi = number of ejecting PVCs/total PVC) and postextrasystolic potentiation index (PEPi = number of PVCs with PEP/total PVC) were calculated. RESULTS EMi was 29% +/- 31% in PVC-CM and 78% +/- 20% in controls (P <.0001). PEPi was 41% +/- 28% in PVC-CM and 14% +/- 10 % in controls (P = .001). There was no control in groups of low EMi or high PEPi. EMi and PEPi were not significantly correlated to left ventricular dimensions or function in PVC-CM patients. PVC coupling interval was related to both ejecting PVCs and PEP. CONCLUSION Patients with PVC-CM more often display nonejecting PVCs and PEP compared to controls.