共查询到20条相似文献,搜索用时 62 毫秒
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Megias-Alguacil D Keller T Lutz K Barlow AP Ettlin DA 《The Review of scientific instruments》2008,79(1):014301
We present the design, construction, and performance of a novel multi-injector gas jet delivery capable of operating in a magnetic resonance imaging environment. This apparatus is computer controlled and built with two separate pneumatic circuits enabling gas jet applications at variable sites through four independently activated injectors. Gas jet delivery is fully controllable in terms of pressure, flow rate, gas temperature, application time, and duration of interstimulus interval. We characterized these parameters, considering effects such as pressure drop by flow transport, transient effects, and delays in activation. The system offers new possibilities for use in various biomedical contexts such as, e.g., quantitative sensory testing or dental hypersensitivity assessment. 相似文献
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通过调研国内关于落震试验装置的研究资料及深空探测着陆器对地面落震试验的要求,设计了一种可以实现星表着陆缓冲装置全工况落震的试验系统,采用三维建模软件对该试验系统进行了结构设计,并开发了配套的试验方法。该试验系统包括台架系统、提升系统、水平框架系统、姿态控制系统、锁止释放系统和高速摄像机6个部分,考虑可搭载的缩比原理样机最大质量和极端落震工况,采用有限元方法完成了试验系统的结构力学性能校核,结果显示其强度和刚度满足要求,验证了所设计的落震试验系统的实际可行性与操作安全性。 相似文献
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Mott PH Twigg JN Roland DF Schrader HS Pathak JA Roland CM 《The Review of scientific instruments》2007,78(4):045105
A novel high-speed tensile test instrument is described, capable of measuring the mechanical response of elastomers at strain rates ranging from 10 to 1600 s(-1) for strains through failure. The device employs a drop weight that engages levers to stretch a sample on a horizontal track. To improve dynamic equilibrium, a common problem in high speed testing, equal and opposite loading was applied to each end of the sample. Demonstrative results are reported for two elastomers at strain rates to 588 s(-1) with maximum strains of 4.3. At the higher strain rates, there is a substantial inertial contribution to the measured force, an effect unaccounted for in prior works using the drop weight technique. The strain rates were essentially constant over most of the strain range and fill a three-decade gap in the data from existing methods. 相似文献
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研制一种适合对各种液压孔口或缝隙进行高低温流体力学试验的新型试验装置,运用该装置对具有不同几何参数的液压阻尼孔进行在-50~80℃宽温度范围内的流动特性试验,研究以普通抗磨液压油HM46和低温抗凝减振器油TITAN SAF 5045为工质及其温度变化时对液压阻尼孔流量-压力特性曲线、幂指数和流量系数的影响,研究表明,在低温条件下,液压阻尼孔的流量系数均因油液黏度增大、流动性变差而呈线性下降的趋势,从宏观上看,HM46通过液压阻尼孔时的流动稳定性较差,其对应流量系数的下降幅度明显大于TITAN SAF 5045对应的下降幅度,厚壁小孔流量系数的下降幅度明显大于薄壁小孔对应的下降幅度。研究所获得的新型试验装置、试验数据分析方法和具体理论公式为深入研究和优化现代液压元件在宽温度范围内的动态性能提供新型试验平台与理论基础。 相似文献
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This paper presents the design, construction, and testing of a two-wheeled low-cost mobile robot platform that has high survivability when subjected to large impact forces and general rough handling. The design of the drive transmission system and integrated suspension system is developed, along with general equations of motion describing their dynamics. Analyses were conducted to insure stability of the various subsystems and optimize parameters for the desired vibration characteristics. Equations of motion were also developed to describe the rocking chassis phenomenon inherent to the two-wheeled design. A flywheel compensation scheme which helps eliminate the rocking chassis problem is also outlined. An impact analysis combining theory and empirical data was used to predict the survivability threshold. Finally, three series of experiments were conducted, with the first two followed by design improvements. In contrast to currently available commercial robots, our new design employs a flexible mechanical platform capable of absorbing energy during high load impacts. This design was substantiated during the final tests when the robot survived a third story drop without any damage. 相似文献
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Tor Syverud 《Tribology International》2001,34(12)
This paper describes an experimental investigation with a rig for measuring the surface temperatures and pressures in single bore journal bearings. The test bearing was equipped with small bores, where the pressure was altered by means of a vacuum pump. The whole bearing arrangement can also be operated at different ambient pressures ranging from atmospheric down to −0.06 MPa. Oil temperatures at inlet and outlet are also measured. Experiments show a considerable drop in the temperature of oil undergoing a drop in pressure. The overall temperature level of the bearing system did not seem to affect the magnitude of the temperature drop. Experiments where the bearing system was operated at sub-ambient pressures revealed an increased temperature drop in the cavitation zone. Pressures higher than ambient were measured within the cavitation zone while the bearing was operated at sub-atmospheric pressure. The higher pressures are believed to be caused by evaporation of oil. It is therefore proposed that the temperature drop observed in the cavitation zone of journal bearings is primarily caused by evaporation of oil. However, isentropic decompression of the gases in the oil is also believed to play a role. 相似文献
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测定表面张力装置的改进 总被引:3,自引:0,他引:3
介绍了滴体积法表面张力测量装置的发展。经作者改进后的测量装置十分简便,可能随意控制液滴的下落速度,测量精度达0.1mN/m,消除了人为误差,数据重视性好。 相似文献
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电磁轴承转子系统中高速不平衡转子跌落过程的非线性动力学 总被引:3,自引:1,他引:2
对高速不平衡刚性转子在应急情况下跌落在保持轴承内的非线性动力学进行了研究, 数值分析了转子的瞬态响应,给出了跌落过程中转子在保持轴承中的轨迹、滑动涡动阶段的速度和功率损耗。探讨了诸如轴承间隙、摩擦系数、恢复系数、不平衡量和跌落初始条件对转子跌落行为的影响 相似文献
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根据GJB4225-2001的规定,要求被试榴弹在车载装卸(模拟高度3m)或装船海运(模拟高度12m)期间意外跌落安全。为了考核被试榴弹跌落是否安全,需要一种装置来模拟榴弹任意姿态、自由跌落的试验要求。设计了一套适合榴弹跌落的试验装置:拉伸弹簧预紧系统实现了在夹持过程中可靠性和安全性的保证,旋转刻度盘实现了多角度的跌落控制,激光传感器完成对跌落高度关键数据的测量。通过ADAMAS和MATLAB联合仿真及场地试验,证明该系统满足榴弹任意姿态跌落且得到稳定可靠的试验数据。 相似文献
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We have developed a novel flow chamber which imposes a controlled axisymmetric stagnation flow to enable the study of external flow effects on coalescence dynamics. This system allows for the first time the precise positioning of a drop in a three dimensional flow and additionally enforces a highly symmetric flow around the drop. We focus on the study of a single drop approaching a stationary flat plane as this is analogous to two drops approaching each other. A single drop is created and then guided along the unsteady center line of a stagnation flow. The real time computer control algorithm analyzes video images of the drop in two orthogonal planes and manipulates flow restricting valves along the four outlets of the flow. We demonstrate using particle image velocimetry that the computer control not only controls the drop position but also ensures a symmetric flow inside the flow chamber. This chamber will enable a detailed investigation of the drainage of the thin film between the drop and the lower surface in order to probe the effect of external flow on coalescence. 相似文献
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光纤、电容液滴传感器的设计研究 总被引:2,自引:1,他引:2
光纤、电容液滴分析技术是利用光纤和电容测试技术制成特殊的液滴传感器,获取经过液滴的光强信号随液滴生长变化的规律以及有关液滴体积的信息。文中将具体介绍光纤、电容液滴传感器的工作原理、电容液滴传感器的数学模型和液滴滴头的结构设计,同时给出由传感器获取的与液滴生长过程相关的光纤信号和液滴体积信号。 相似文献
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等效焓降法是基于热力学的热功转换原理。本文用等效焓降的方法分析了热力系统加装烟气换热器的节能效果。论证了锅炉余热的热经济性效果,并以600MW机组为例,对凝结水返回系统不同位置的四种方案进行了比较。最后通过定量计算得出加装烟气余热换热器对热力系统节能的重要作用。对工程实践有重要的指导意义。 相似文献
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利用二维正方晶格介质柱型光子晶体(PC),设计了一款由4个线性渐变型微腔和异质结构光子晶体反射器组成的多信道下路滤波器。利用平面波展开法(PWE)以及二维时域有限差分法(2D-FDTD)分析了该异质结构滤波器的工作机制,并进一步探究了微腔参考面与异质结界面之间距离对下路效率的影响。研究表明,滤波器中的异质结反射器可以实现接近100%的反射,从而大幅度地提高了三端口滤波器的滤波效率。设计的多信道滤波器各个通道都能有效地实现下路滤波功能,其信道间隔为10nm,滤波效率均在90%以上,透射谱半高宽均在0.54nm以下,实现了较高的品质因子特性。该滤波器尺寸只有15.15μm×13.91μm,且滤波效率很高,适于在波分复用系统中进行复用与解复用,在未来光路集成应用中具有良好的应用前景。 相似文献
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Afaqul Zafer Sanjay Yadav Arif Sanjid Lalit Kumar Raman Kumar Sharma 《Journal of Mechanical Science and Technology》2017,31(8):3769-3775
The calibration of a pressure transducer that works in dynamic conditions is an unavoidable challenge. To address this challenge, an experimental setup has been designed and developed to simultaneously generate and calibrate the dynamic pressure. The system mainly comprises a pressure chamber that accommodates a step pressure generator and test chamber with a quick open valve and pressure sensor under calibration. Accordingly, an aperiodic type of step pressure generator with a quick open valve is particularly designed. This instrument can generate a positive step pressure with a rise time of up to 11 ms and a negative step pressure with a fall time of up to 12 ms within a working pressure range from the atmospheric pressure to 200 MPa. The volume ratio of the test chamber to the pressure chamber and its effect on pressure drop is critical in such systems. The effect of volume ratio on the dynamic performance parameters, namely, rise/fall time, is explored and inferences for optimizing these parameters are derived. A mathematical model for pressure drop in the test chamber has been developed and validated to precisely determine the magnitude of the step pressure input. Lastly, the experimental study of the effect of volume ratio on pressure drop has been conducted to diminish the pressure drop, thereby minimizing the uncertainty. 相似文献