共查询到19条相似文献，搜索用时 247 毫秒
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曲柄摇杆机构中若摇杆为主动件,曲柄为从动件,当摇杆处于左右两个极限位置时,连杆与曲柄处于共线的位置,摇杆经连杆传递到曲柄上的作用力,刚好通过曲柄的回转中心,无法使曲柄转动,出现顶死现象。机构的这个位置称为死点位置。对传动机构来说,死点位置是不利的。怎样通过死点位置保证机构继续正常运转？方法一：利用从动曲柄本身的质量或附加一转动惯性大的飞轮;方法二：增设辅助构件;方法三：采用多组机构错列。 相似文献
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提出了一种改变两角度差调节滑块行程的平面双曲柄六杆滑块机构,列出其速度和加速度矢量运动学方程,在此基础上利用MATLAB／Simulink软件包对该机构进行运动学仿真。通过仿真可得到滑块和连杆的运动规律,为机构的设计、制造和应用提供了科学的依据。 相似文献
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在生产生活中,有很多安装及维修等工作需要爬杆作业,冬季温差昼夜明显,使水泥杆塔结了一层冰或者霜,人工爬杆无法实现。设计一款爬杆机器人由曲柄滑块机构、并联盘形凸轮机构、移动凸轮机构以及上下机械手爪等组成,通过弹簧的预紧力来实现机器人手爪对杆的抱紧,通过曲柄滑块机构、凸轮机构等实现攀爬动作,同时机器人只需一个驱动源就能带动整个机器人的运动,能攀爬变直径的杆,工作简单可靠,运动灵活,可以广泛应用于很多爬杆作业。 相似文献
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采用Eclipse RCP和SWT,利用Java语言采用面向对象的设计方法,以曲柄滑块机构的运动仿真为例,实现了仿真建模、仿真系统设计、仿真结果输出和仿真数据采集等功能,从而为独立的和跨平台应用的仿真系统设计与实现提供一种高效、快捷的方法。 相似文献
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抽油泵抽油是当前国内外石油开采中应用最广泛的机械采油技术,我国85％以上的油井都是采用抽油泵抽油开采的。抽油泵作为机械采油的主要设备,在油田开发生产中占重要地位,而由于抽油泵结构及特定工作环境,使得抽油泵出现各类故障。本文主要针对抽油泵上部与油杆连接部分存在的问题,设计改进了抽油泵滑杆;在现场取得了较好的效果,使抽油泵滑杆的故障率大为降低,取得了很好的经济效益。 相似文献
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T.K. Gaisser 《Journal of The Franklin Institute》1974,298(4):271-287
Cosmic ray extensive air shower observations can give clues about the properties of high-energy particle interactions above 1015eV, in addition to giving information about the primary cosmic ray spectrum at these energies. A brief review of recent high energy accelerator data and its theoretical interpretation is given to explain the necessity for obtaining information from cosmic rays about hadronic interactions beyond machine energies. In particular, it is shown that recent measurements of the energy dependence of total cross-sections and of production cross-sections suggest some sort of threshold behavior in the 1000 GeV region. Studies at higher energies are required to understand the nature of this behavior. The use of air shower data for this purpose is illustrated by comparing shower size us depth measurements with the expectations of various models of strong interactions. 相似文献
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A new and systematic approach for the analysis and simulation of a non-circular chainwheel in a bicycle drive system is presented. The proposed leg-bicycle model is based on a five-bar linkage and explicit expressions for the kinematics and kinetics are derived. The generated shape of the chainwheel is smoothed to an ellipse, for practical reasons. The performance of this elliptical chainwheel is assessed by comparing the joint moments, leg angular accelerations, crank angular velocities, crank angular accelerations and output forces with those of a conventional circular chainwheel. The results suggest combining the elliptical and circular chainwheels into a single unit, in order to accommodate a wide range of pedalling speeds. At low speeds, the elliptical chainwheel is engaged, but as the speed increases, a switch over to the circular chainwheel is recommended. 相似文献
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介绍了气流磨的特点,重点研究了渐缩型喷嘴设计的主要参数,对喷嘴的喷气速度、工质流量及喷嘴几何参数进行了研究,得到了喷嘴设计过程中的关键参数对粉碎性能的影响,为进一步将气流粉碎应用到煤炭提供了依据。 相似文献
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C. G. Hebert S. J. R. Staton T. Q. Hudson S. J. Hart C. Lopez-Mariscal A. Terray 《Biomicrofluidics》2015,9(2)
The ability to confine flows and focus particle streams has become an integral component of the design of microfluidic systems for the analysis of a wide range of samples. Presented here is the implementation of a 3D microfluidic nozzle capable of both focusing particles as well as dynamically positioning those particles in selected flow lamina within the downstream analysis channel. Through the independent adjustment of the three sheath inlet flows, the nozzle controlled the size of a focused stream for 6, 10, and 15 μm polystyrene microparticles. Additional flow adjustment allowed the nozzle to dynamically position the focused particle stream to a specific area within the downstream channel. This unique ability provides additional capability and sample flexibility to the system. In order to gain insight into the fluidic behavior of the system, experimental conditions and results were duplicated within 4.75 μm using a COMSOL Multiphysics® model to elucidate the structure, direction, proportion, and fate of fluid lamina throughout the nozzle region. The COMSOL Multiphysics model showed that the position and distribution of particles upon entering the nozzle have negligible influence over its focusing ability, extending the experimental results into a wider range of particle sizes and system flow rates. These results are promising for the application of this design to allow for a relatively simple, fast, fully fluidically controlled nozzle for selective particle focusing and positioning for further particle analysis and sorting. 相似文献
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This paper reports the improvement of rectification effects in diffuser∕nozzle structures with viscoelastic fluids. Since rectification in a diffuser∕nozzle structure with Newtonian fluids is caused by inertial effects, micropumps based on this concept require a relatively high Reynolds numbers and high pumping frequencies. In applications with relatively low Reynolds numbers, anisotropic behavior can be achieved with viscoelastic effects. In our investigations, a solution of dilute polyethylene oxide was used as the viscoelastic fluid. A microfluidic device was fabricated in silicon using deep reactive ion etching. The microfluidic device consists of access ports for pressure measurement, and a series of ten diffuser∕nozzle structures. Measurements were carried out for diffuser∕nozzle structures with opening angles ranging from 15° to 60°. Flow visualization, pressure drop and diodicity of de-ionized water and the viscoelastic fluid were compared and discussed. The improvement of diodicity promises a simple pumping concept at low Reynolds numbers for lab-on-a-chip applications. 相似文献
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近年来,团购网站犹如雨后春笋不断涌现,“团购”活动影响着人们生活,成为人们关注和讨论的热点问题。文章对中国团购网站的现状、存在的问题以及团购网站的发展前景进行分析和探讨。 相似文献
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A procedure is described for determining the characteristics of adiabatic flow through a rocket nozzle with and without composition change. The method of calculation is illustrated for the expansion of pure hydrogen gas from a chamber temperature of 306° K. and a pressure of 20.42 atm. to atmospheric pressure.The study indicates that the exhaust velocity and temperature are highest for flow where complete equilibrium is reached at each temperature with respect to the reaction Flow with composition change requires a nozzle exit to nozzle throat area ratio somewhat greater than that determined for adiabatic flow without composition change for the same ratio of chamber pressure to exit pressure.The residence time in a given temperature range is computed as a function of gas temperature for the two types of flow. The results of this calculation may be used to determine the minimum required reaction rates which allow composition changes during flow through the nozzle. 相似文献