某型内燃机闭环控制减振的仿真研究

内燃机自身的振动是重型军用车辆主要的振动和噪声源,对其进行有效的振动控制十分重要.但由于内燃机系统结构的复杂性,研究其振动和噪声控制比较困难.针对某型内燃机系统,采用Matlab软件的Simulink工具,建立了整个系统的动力学仿真模型,并分别对该模型进行简谐、白噪声信号扰动下的减振控制研究,控制方法采用闭环数字PI策略.系统输出转矩和转速的曲线结果表明减振具有明显的效果.     

蒸发冷却水质问题的分析研究

蒸发冷却空调是以水作为制冷剂,通过在西北地区的实际工程应用,发现存在着蒸发冷却器表面结水垢以及细菌滋生等水质问题.本文针对这两大问题,从产生的原因、条件以及环境等方面进行了分析;阐述了导致上述两大问题的关键原因,提出从补水、流失水比例、水系统的软化以及抗菌剂的填加等几个环节加强水质管理的措施;通过全面的分析和研究,认为蒸发冷却器不会产生军团病.     

对气体分析仪现状与发展的初步探讨

本文较详细地介绍了氩、氧、水分等几种分析仪器 ,阐述了它们的工作原理、优点、缺点及使用中应注意的问题     

Die Geschichte der Vakuumkühlung. The History of Vacuum Refrigeration

The use of the high evaporation enthalpy of water is one of the oldest technologies of refrigeration for food preservation used by the mankind. One could nearly celebrate the true 5000^th anniversary of this technology. Nowadays we call the refrigeration by evaporation from wet surfaces “adiabatic refrigeration”, it regulates, for instance, our body heat by evaporating sweat. After the introduction of some vacuum pumps into the experimental scientific works, 250 years ago, namely in Great Britan, the modern form of “artificial” refrigeration began its career, the evaporation of liquids under the absence of permanent gasses in vacuum. The vacuum refrigeration has been nearly abruptly stopped by the development of compression refrigeration processes, about 150 years ago. Only after world war 2, a reintroduction of vacuum refrigeration began again. Now, at the beginning of the 3. milennium, there are good chances for recovering terrain.     

Derivation of applied stress-crack opening displacement relationships for the evaluation of effective stress intensity factor range

Linear elastic fracture mechanics (LEFM) integrated with the interference of fracture surface asperities has been formulated. The asperities are considered to simulate the influence of the microstructures and possibly oxide debris. The applied stress/load-crack opening displacement (COD) relationships in several cases have been derived. In the original LEFM, the stress-COD relationship is represented by a straight line passing through the origin of the stress-COD plot. The insert of one asperity results in a deviation of the stress-COD response from the LEFM relationship, leading to the exhibition of an inflection point (first contact point, σ_op), a larger slope, and a residual COD. In the case of two asperities, the slope and the residual COD of the stress-COD relationship become further larger, and two inflection points emerge. A general stress-COD expression in the case of multiple asperities has been derived. The slope of the stress-COD equation, the residual COD, and the minimum COD all increase with increasing number of asperities for a given loading condition, resulting in a smaller ΔCOD and Δσ_eff. The number of the inflection points is the same as that of the asperities. To the authors' knowledge, this paper is the first to derive analytically an applied stress-COD curve with a gradual variation below σ_op, caused by the asperity-/roughness-, or oxide-induced crack closure.     

Structure, Phonon Vibration, and Spin Correlation of LaBa2Cu3−x Co x O y

Polycrystalline samples LaBa₂Cu_3?xCo _x O _y (0 ≤ x ≤ 1.0) were synthesized by solid state reaction method. The structure, phonon vibration, conduction, and spin correlation were investigated by means of X-ray diffraction, infrared spectra, resistivity, and electron spin resonance. It is found that there are orthorhombic–tetragonal and tetragonal–orthorhombic structural transitions with Co doping, and the conduction behavior changes from metallic to semiconducting. With the increase of Co content, the Cu(1)—O(1) phonon mode around 531 cm^?1 softens, the Cu(2)—O(2) phonon mode around 657 cm^?1 hardens, and the Cu(1)—O(4) mode around 583 cm^?1 is nearly unchanged. The Cu²⁺ spins tend to localize with Co doping. The changes in structure, phonon vibration, and spin correlation with Co doping are analyzed and discussed.