共查询到19条相似文献,搜索用时 125 毫秒
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能量守恒定律是自然界普遍存在的定律之一,本文通过内能概念,利用能量守恒定律从微观上解释蒸气压缩式制冷的各个过程,从而为我们理解蒸气压缩式制冷原理提供了一个新思路。 相似文献
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物体的动量比起物体的速度,更能全面地反映物体的运动状态;动量定理和动量守恒定律比起牛顿运动定律,具有更大的普遍性和独立性。本文介绍了动量的概念、动量定理和动量守恒定律;应用动量定理和动量守恒定律求解了典型例题,解题后有说明,点评了本题的重点、难点或解题方法,画龙点睛。 相似文献
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综述了高分子介质中机械能变热能、声能变热能、辐射能变热能、电能变热能、电能变辐射能、机械能变电能、辐射能变化学能、声能变化学能、机械能变化学能等能量转换的研究近况,并介绍了它们在不同领域的应用前景。 相似文献
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基于无碳小车的越障要求,设计一辆无碳小车,在设计、工艺、成本分析和工程管理等方面进行优化设计,通过给予一定的重力势能,依据能量转换的原理,将重力势能转换为动能等机械能来驱动小车行进。 相似文献
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引风机是依靠输入的机械能,提高气体压力并排送气体的机械,它是~种从动的流体机械。引风机广泛用于工厂、矿井、隧道、冷却塔、车辆、船舶和建筑物的通风、排尘和冷却,锅炉和工业炉窑的通风和引风等,其能耗较大,因此,对引风机进行节能改造具有很大的经济效益,文章介绍了变频器的调速原理和其优点,分析了变频调速于引风机节能改造中的应用。 相似文献
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给定一重力势能,根据能量转换原理,设计一种可将该绿色能源重力势能转换为机械能并可用来驱动小车行走的装置。通过不同的条件进行一定的附加设计,达到特定目的。 相似文献
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液压泵是液压系统的动力源,也称“动力元件”,它能将原动机(电动机、内燃机等)输入的机械能转换为液压能,用以驱动液压系统中的执行元件。在每个液压系统中,液压油泵是不可或缺的动力设备,液压泵的应用范围比较广,从大的工程机械到小液压工具都离不开液压泵,所以了解液压油泵的工作原理及常见故障是每个工程人员不可缺少的知识。本文就从液压泵的种类、工作原理及常出现的故障进行论述,为工程人员更好的了解液压系统提供基础知识。 相似文献
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Hypervelocity penetration modeling: momentum vs. energy and energy transfer mechanisms 总被引:1,自引:0,他引:1
James D. Walker 《International Journal of Impact Engineering》2001,26(1-10):809-822
Analytic penetration modeling usually relies on either a momentum balance or an energy-rate balance to predict depth of penetration by a penetrator based on initial geometry and impact velocity. In recent years, fairly sophisticated models of penetration have arisen that develop the three-dimensional flow field within a target. Based on the flow field and constitutive assumptions, it is then possible to derive a momentum or an energy-rate balance. This paper examines the use of assumed flow fields within a target created by impact and then examines the resulting predicted behavior based on either momentum conservation or energy conservation. It is shown that for the energy-rate balance to work, the details of the energy transfer mechanisms must be included in the model. In particular, how the projectile energy is initially transferred into target kinetic energy and elastic compression energy must be included. As impact velocity increases, more and more energy during the penetration event is temporarily deposited within the target as elastic compression and target kinetic energy. This energy will be dissipated by the target at a later time, but at the time of penetration it is this transfer of energy that defines the forces acting on the projectile. Thus, for an energy rate balance approach to successfully model penetration, it must include the transfer of energy into kinetic energy within the target and the storage of energy by elastic compression. Understanding the role of energy dissipation in the target clarifies the various terms in analytic models and identifies their origin in terms of the fundamental physics. Understanding the modes of energy transfer also assists in understanding the hypervelocity result that penetration depth only slowly increases with increasing velocity even though the kinetic energy increases as the square of the velocity. 相似文献
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Lee PC Edwards NP 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2008,55(2):293-296
The three-dimensional equations of linear viscopiezoelectricity and an accompanying electromechanical energy theorem are deduced, by the quasielectrostatic approximation, from the equations of viscoelectromagnetism and a generalized Poynting's theorem, respectively. For a viscopiezoelectric solid of volume V and bounding surface S, the internal energy, kinetic energy, and electric enthalpy densities as well as the variation of work done over S and the variation of energy dissipation in V are defined. A variational principle in terms of the defined functions is presented. It is shown that, from the principle, the equations of viscopiezoelectricity in V and the natural boundary conditions on S are obtained. 相似文献
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建筑爆破倒塌过程的摄影测量分析(Ⅱ)——后坐及能量转化分析 总被引:2,自引:1,他引:1
通过前文"建筑爆破倒塌过程的摄影测量分析(Ⅰ)——运动过程分析"中搭建的摄影测量系统,根据图像处理原理以及非量测用摄影机采集到的一系列建筑物倒塌过程的图片的特点——摄影的坐标定位相同,编写图像批处理程序,对建筑物倒塌过程的运动轨迹进行测量。根据摄影测量分析获得的建筑物倒塌过程中的姿态及力学参数,对建筑物爆破拆除过程中后坐现象的形成过程和机理进行了分析,并探讨了建筑物倒塌过程中的势能、动能和机械能的变化和转化的过程。 相似文献
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Hossein Ali Sepiani Asdollah Ghazavi 《International Journal of Mechanics and Materials in Design》2009,5(2):111-122
This paper presents a theoretical study of the in-plane behavior of Smart Shape Memory Alloy Woven Composites (SSMAWC) under
biaxial loading by developing an integrated micromechanical constitutive model. The model studied in this research is established
on the geometric parameters of fibers, metal layers, unit cell, the material constants of composite constituents, and the
orientation of fibers, in which the fibers in one direction are SMA ones. The Helmholtz free energy of a Shape Memory Alloy,
in 3-Dimensional and 1-Dimensional applications is derived. Using mechanical energy of matrix and elastic yarns, the constitutive
relations are developed with the use of strain energy approach and energy variation theorem. The kinetic relations of SMA
depicted by Brinson is coupled with the final governing equation of the composite to predict the stress history in smart shape
memory alloy woven composites. The deflection of the structure, subjected to uniform biaxial loading is studied numerically.
It is found that the effect of Shape Memory Effect (SME) of the SMA wires on the behavior of plain woven flexible fabric composite
is significant. 相似文献
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Pascal Jung Sigrid Leyendecker Joachim Linn Michael Ortiz 《International journal for numerical methods in engineering》2011,85(1):31-60
A theory of discrete Cosserat rods is formulated in the language of discrete Lagrangian mechanics. By exploiting Kirchhoff's kinetic analogy, the potential energy density of a rod is a function on the tangent bundle of the configuration manifold and thus formally corresponds to the Lagrangian function of a dynamical system. The equilibrium equations are derived from a variational principle using a formulation that involves null‐space matrices. In this formulation, no Lagrange multipliers are necessary to enforce orthonormality of the directors. Noether's theorem relates first integrals of the equilibrium equations to Lie group actions on the configuration bundle, so‐called symmetries. The symmetries relevant for rod mechanics are frame‐indifference, isotropy, and uniformity. We show that a completely analogous and self‐contained theory of discrete rods can be formulated in which the arc‐length is a discrete variable ab initio. In this formulation, the potential energy density is defined directly on pairs of points along the arc‐length of the rod, in analogy to Veselov's discrete reformulation of Lagrangian mechanics. A discrete version of Noether's theorem then identifies exact first integrals of the discrete equilibrium equations. These exact conservation properties confer the discrete solutions accuracy and robustness, as demonstrated by selected examples of application. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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为研究水下近场非接触爆炸载荷作用下固支方板的破口现象,根据能量守恒原理,假设冲击波能完全转化为结构的初始动能,进而转化为结构的塑性变形能。通过假设变形模式,建立塑性变形能与平板转角之间关系,进而求解平板转角。平板在中间出现破口后,裂纹向外扩展,呈现花瓣状,满足环向应变等于开裂应变条件时裂纹终止,破口达到最大。根据转角大小,可以求解破口尺寸。与通用有限元软件ABAQUS/EXPLICIT计算结果对比,两者吻合较好。工程上,可以利用本文建立的计算方法估算破口大小。 相似文献
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Mauro M. Doria 《Journal of Superconductivity and Novel Magnetism》2009,22(3):235-238
Average quantities can be determined in many-body physics by the virial theorem even in cases when knowledge about the interaction
among particles is not complete. Starting from the virial theorem for superconductivity we obtain an expression for the magnetization
of two periodic systems, the infinitely extended film of arbitrary thickness under a perpendicular applied field and the bulk
superconductor. We show that the kinetic energy of the condensate can be directly retrieved from the magnetization for a large
κ type II superconductor or near the upper critical field, in the pinning free (reversible) regime. Isofield kinetic energy
lines for low- and high-T
c
compounds have striking differences near the critical transition that clearly indicate for the latter case the presence of
a unique superconducting condensate below and above the mean field critical temperature.
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