喷灌系统加压泵的优化选型

该文根据系统分析原理，分析了水泵优化选型问题的目标函数和约束条件，选用适合于水泵直接加压式喷灌工程特点的大系统层次分析优化研究方法，建立了数学模型、并探讨解决了具体计算方法，为喷灌工程规划设计提供了快速、准确地水泵优化选型方法     

直喷式柴油机燃烧压力波动的共鸣分析

基于直喷式柴油机燃烧气体高频压力波与声波在燃烧室内传播特征的相似性，利用有限元法计算并实验研究了燃烧压力波动的共鸣特性。结果表明，随着活塞的不断下行，燃烧空腔各阶模式的特征频率向低频方向移动。在燃烧室空腔内不同位置测得的信号频率及幅值有明显不同。有限元计算结果和实验结果较为吻合，反映了燃烧室内共鸣频率变化的规律。上述结果经过修正可以得到柴油机燃烧室内压力波动各阶模式的特征频率随燃烧过程的瞬态变化规律。     

提高转速与增压对内燃机主轴颈和曲柄销磨损的影响

根据摩擦学综合解析模型,提高转速与增加负荷(增加缸内压力)都将加速主轴颈和曲柄销的磨损。以四缸柴油机为模型,在其它条件基本不变的情况下,通过计算证明了结论的正确性。同时,定量给出了提高发动机转速比增加气缸压力对主轴颈和曲柄销的磨损影响大的结论。     

壁流式蜂窝陶瓷微粒过滤器压力损失公式的建立

分析了洁净壁流式蜂窝陶瓷过滤器(DPF)压力损失的机理，包括过滤壁上的透过压力损失、进口收缩压力损失、出口扩散压力损失以及进／出口流道内的摩擦阻力损失，建立了各类压力损失的相应公式及总压力损失公式。并通过数值计算确定了压力损失公式中相关待定系数。得到的压力损失公式能较准确地估算DPF在不同流量下的压力损失值。     

Evaluation of left ventricular diastolic dysfunction at the early stage of pressure overload-induced myocardial remodeling in rats

AIM: To investigate the evaluation method of left ventricular diastolic function and myocardial hypertrophy induced by pressure overload in rats.METHODS: Male Sprague-Dawley rats were subject to left ventricular pressure overload by transverse aortic constriction (TAC).Cardiac structure and diastolic function were evaluated by echocardiography, hemodynamic analysis and examination of hydroxyproline concentration in the myocardial tissues.RESULTS: Compared with the sham-operated controls, left ventricular wall dimension in diastole significantly increased in the rats 3 weeks after TAC .Left ventricular early diastolic posterior wall motion velocity (E') significantly decreased in the rats 3 weeks after TAC , and was much lower than that in the rats 6 weeks after TAC.Left ventricular mass to tibia length in TAC rats was much higher than that in sham-operated controls .The ratio of maximum rate of degression of left ventricular pressure (dp/dt_min) to left ventricular systolic pressure (dp/dt_min/LVSP) started to decrease in TAC rats in the 3rd week (48.9±5.9 vs 63.5±9.9) and significantly decreased in TAC rats in the 6th week as compared with sham-operated controls (35.4±4.0 vs 54.4±2.9, P<0.01).Sirius red-stained collagen in cardiac interstitium, especially around the blood vessels, was increased in TAC rats.Six weeks after TAC, a significant increase in the content of myocardial hydroxyproline was observed.CONCLUSION: The early diastolic posterior wall motion velocity (E') detected by tissue Doppler imaging is a sensitive indicator of diastolic dysfunction at the early stage of myocardial remodeling induced by pressure overload in rats.     

水力剥皮原理的研究及最佳剥皮方法设计准则的初探

本文利用复合材料力学的横观各向同性假设作为剥皮力学模型的理论基础,分析了几种情况下剥皮液力的求法。并提出了应该先用机械方法使树皮剥开裂纹后,利用压差效应实现水力的最佳剥皮。     

超高压对鲜牛奶杀菌效果研究

以新鲜牛奶为主要原料,通过双因素正交试验研究了超高压对新鲜牛奶的杀菌作用。结果表明:压力越高,杀菌效果越好;在同一压力下延长受压时间并不一定能提高灭菌效果。     

浮动叶轮平衡腔内液体泄漏量特性试验

用专用设备模拟浮动叶轮的运行工况,对叶轮后密封环前后压力进行了直接测量,得出了后密封环前后压力与泵扬程的试验曲线,据此计算得到了浮动叶轮平衡腔内液体泄漏量特性曲线.试验解决了浮动叶轮平衡腔内液体泄漏量和压力的计算问题.