离心泵浮动叶轮轴向间隙的液体流动分析及轴向力计算

为了研究浮动叶轮轴向间隙变化对其液体泄漏量及压力、液体作用在不锈钢盘上轴向力的影响规律,将径向和轴向的间隙液体流动分别简化为平行平板间粘性层流运动和轴对称二维粘性层流运动,基于液体通过径向和轴向的间隙泄漏量相等,推导出了计算轴向间隙的液体泄漏量及压力、液体作用在不锈钢盘上轴向力的数学表达式。并通过设计实例计算,绘制出了轴向间隙的液体泄漏量和液体作用在不锈钢盘上轴向力与轴向间隙变化的关系曲线,从控制一定泄漏量并减少轴向力的角度出发,分析得出轴向间隙取0.4～0.8mm较为适宜。并在平衡腔内不安装不锈钢盘和石墨盘条件下,计算出了平衡腔内液体作用在叶轮上轴向力。通过比较分析,浮动叶轮有明显减少轴向力的效果。     

A Single‐Blood‐Sample Method Using Inulin for Estimating Feline Glomerular Filtration Rate

Background

Application of a multisample method using inulin to estimate glomerular filtration rate (GFR) in cats is cumbersome.

Objectives

To establish a simplified procedure to estimate GFR in cats, a single‐blood‐sample method using inulin was compared with a conventional 3‐sample method.

Animals

Nine cats including 6 clinically healthy cats and 3 cats with spontaneous chronic kidney disease.

Methods

Retrospective study. Inulin was administered as an intravenous bolus at 50 mg/kg to cats, and blood was collected at 60, 90, and 120 minutes later for the 3‐sample method. Serum inulin concentrations were colorimetrically determined by an autoanalyzer method. The GFR in the single‐blood‐sample method was calculated from the dose injected, serum concentration, sampling time, and estimated volume of distribution on the basis of the data of the 3‐sample method.

Results

An excellent correlation was observed (r = 0.99, P = .0001) between GFR values estimated by the single‐blood‐sample and 3‐sample methods.

Conclusions and Clinical Importance

The single‐blood‐sample method using inulin provides a practicable and ethical alternative for estimating glomerular filtration rate in cats.     

顶隙柱塞在非道路国Ⅱ排放柴油机中的研究及应用

对顶隙柱塞的工作原理进行分析,对我公司现生产的顶隙柱塞和普通柱塞的喷油提前特性进行了对比分析,并在某一非道路国Ⅱ排放发动机上进行性能及排放试验。试验结果表明,顶隙柱塞能够满足非道路国Ⅱ排放柴油机的性能和排放要求,具有推广价值。     

Changes in renal clearance and renal tubular function in albino mice under the influence of Dichlorvos

It is known that organophosphate pesticides and their metabolites are generally eliminated through urine and are likely to affect nephrons. Despite the widespread application of Dichlorvos only limited studies appear to have been done on its toxicity to kidney. Intraperitoneal administration of 400 μg/kg Dichlorvos in mice exhibited maximum reduction in total protein concentration of kidney after exposure to 120 h (52-fold decrease, t-test, P < 0.001). Variations in renal clearance and percent reabsorption of acid phosphatase, alkaline phosphatase and nonspecific esterase enzymes were significant at P < 0.01 and at P < 0.001 (2-way ANOVA), respectively. Maximum significant increase in renal contents of Na⁺ and Ca⁺⁺ was induced by 200 μg/kg dose after 120 and 240 h exposure (P < 0.001), while significantly highest retention of K⁺ and Cl⁻ ions was caused by 400 μg/kg dose after 24 and 72 h exposure (P < 0.01). Histopathological changes in glomeruli, PCTs, DCTs and CTs along with altered renal tubular function and renal clearance of enzymes and various ions indicate the development of acute renal disturbances under the influence of Dichlorvos.     

考虑混合间隙的空间并联机构非线性动力学特性分析

为了掌握同时考虑球面副间隙和三维转动副间隙的空间并联机构的非线性动力学特性,研究考虑混合间隙的空间并联机构多体系统动力学特性分析方法。首先以4-UPS/RPU空间并联机构为研究对象,建立三维转动副间隙和球面副间隙的模型,推导同时考虑球面副间隙和三维转动副间隙的4-UPS/RPU空间并联机构动力学方程;然后利用龙格库塔法对动力学方程进行数值求解,分析不同间隙类型、间隙、驱动速度和摩擦因数对并联机构动力学响应的影响,通过ADAMS虚拟样机仿真验证动力学模型和数值计算的正确性;最后利用相轨迹图、庞加莱映射图和分岔图等分析考虑混合间隙的4-UPS/RPU并联机构的非线性特性。该研究为考虑混合运动副间隙的空间并联机构动力学建模和非线性动力学特性分析提供了依据。     

间隙尺寸对水翼叶顶旋涡空化流动影响的试验研究

采用试验方法对不同间隙尺寸的水翼叶顶旋涡空化流动进行研究.试验在闭式空化水洞中进行,应用高速全流场显示技术对旋涡空化形态进行观测,采用图像处理技术对结果进行处理,并对比分析间隙尺寸分别为0.5和2.0 mm的2种工况下间隙空化流动的发展规律.研究结果表明:随着空化数的减小,叶顶空化流动可以分为涡空化初生阶段、间隙内部附着空化发展阶段和剪切层空化发展阶段3个典型阶段;在涡空化初生阶段,大间隙工况下涡空化沿流动方向延伸距离大于小间隙工况;在间隙内部附着空化发展阶段,随着空化数的降低,大间隙工况下附着空化的初生和发展均领先于小间隙工况;在剪切层空化发展阶段,大间隙工况下剪切层空化形态趋于稳定时对应的空化数大于小间隙工况,并且其向下游延伸距离大于小间隙工况.     

口环间隙对诱导轮离心泵空化流动和性能的影响

为了研究口环间隙对前置诱导轮离心泵空化性能的影响,基于RNG k-ε湍流模型和Rayleigh-Plesset方程均相流空化模型,以前置诱导轮离心泵为研究对象,选取口环间隙为0.15,0.25,0.40和0.60 mm这4种方案对其进行空化流动数值计算,并与试验结果对比分析.研究结果表明,口环间隙大小对诱导轮离心泵的外特性和空化性能影响较大,随着口环间隙的增大,总扬程效率和叶轮扬程效率均减小,与口环间隙为0.15 mm时相比,总扬程效率和叶轮扬程效率分别降低了0.60%和4.21%,效率分别下降了6.50%和9.32%;而口环间隙的增大使得诱导轮扬程和效率均增加,分别增大了29.86%和28.40%.另外,随着口环间隙的增大,空化性能曲线出现波动现象,间隙越大,波动越明显;离心泵主叶轮工作面靠近前盖板出现云状空泡分布,空化不稳定,间隙越大,空化越不稳定,临界空化数越大.经分析,引起空化不稳定性的因素可能有: 口环间隙出口处泄漏高压流体对主流的冲击;口环附近空化的发生以及诱导轮空化引起叶片出口液流角的变化.     

桉叶抗氧化物的提取与抗氧化性质研究

以广林9号桉叶粉为材料,通过单因素和正交实验,确定最佳提取条件为50％乙醇、料液比1：20、50℃提取1h;抗氧化稳定性研究表明：光照、空气和温度对提取物抗氧化活性均有较大的影响,而pH值对其影响较小;对酚类物质的含量进行测定,表明提取物中酚类物质的含量与抗氧化效果成正相关;以有机溶剂对上述提取物进行萃取,抗氧化效果为正丁醇萃取物〉乙酸乙酯萃取物〉水萃取物〉石油醚萃取物;然后比较了不同浓度乙醇作为洗脱剂对正丁醇萃取物分离的影响,以50％和70％乙醇洗脱成分活性最强。     

隙控式全射流喷头运转动力学分析

针对隙控式全射流喷头在恶劣工作条件下出现的附壁力小、驱动力矩小等不足,研究了获得射流元件的最大附壁驱动力矩和减小摩擦阻力矩的方法,对射流元件进行优化设计,以保证喷头的正常运转．分析了隙控式全射流喷头的转动驱动力矩和摩擦阻力矩,喷头转动驱动力矩由射流附壁时与射流元件侧壁产生的驱动力矩,射流与出口盖板的作用力矩组成,喷头的摩擦阻力矩由空心轴端面摩擦阻力矩,空心轴与轴套间的摩擦力矩,密封机构摩擦阻力矩组成．根据动量守恒方程推导出附壁射流中心线方程,得到中心线附壁点距离及附壁冲角的计算公式．推导了理论状态下,附壁力矩最大值与结构尺寸之间的关系．由刚体转动定律计算出全射流喷头的力矩公式及全射流喷头步进角度公式．