双心室心脏泵内部流动非定常数值模拟

为了研究某新型离心式双心室人工心脏泵内部血液流动特性,采用CFD技术对泵设计工况下的内部流场进行数值模拟分析,获得了该心脏泵内部速度、湍流动能和切应力分布规律,同时得到了泵进口流量、作用在不同过流部件的轴向力和径向力变化情况,并对蜗壳处的压力脉动进行分析.研究结果表明:该型双心室心脏泵内部流场没有出现明显的流动死水区,满足心脏泵的抗血栓要求;泵内压力和切应力分布规律相似,整体分布均匀,满足抗溶血性能的要求;由于心脏泵的整体设计为对称结构,很好地平衡了左右叶轮的轴向力;较小的泵整体结构的径向力和转矩有利于心脏泵抵御瞬态的径向负荷;左右两泵蜗壳处的压力脉动呈现明显的正弦周期性变化规律,均含有6个波峰和6个波谷,且各监测点处压力脉动的主频为叶片通过频率,这是由于叶轮和蜗壳的动静干涉作用.     

Postnatal development of canine axial globe length measured by B-scan ultrasonography

OBJECTIVE: The objectives of this study were to document the development of axial globe length (AGL) in normal mesocephalic cross-bred dogs between 2 and 52 weeks of age, to determine a relationship between AGL and age, and derive an equation to predict AGL in normal mesocephalic cross-bred dogs. ANIMALS STUDIED AND PROCEDURE: The AGL of twenty normal mesocephalic cross-bred dogs was measured at 12 time points from 2 to 52 weeks of age using B-scan ultrasonography. RESULTS: The mean (+/- SEM) AGL increased from 12.65 mm (+/- 0.18) at 2 weeks of age to 19.52 mm (+/- 0.18) at 52 weeks of age. The correlation between AGL and age was evaluated by fitting possible variables to a regression pattern. A linear model of natural logarithmic-transformed value of AGL (mm) and age (week) was established. Side (left or right eye) and gender did not correlate with development of AGL. CONCLUSIONS: A reverse transformation of the formula can be used to predict AGL in mesocephalic cross-bred dogs: AGL = 10.847 * age in weeks 0.1653.     

隙控式全射流喷头性能特点及与摇臂式喷头的比较研究

研制了一种新型旋转式喷头——隙控式全射流喷头,介绍了其结构形式及工作原理。首次对二种PX10型号的全射流喷头及一种PY210摇臂式喷头的水力性能进行了对比试验及分析。研究表明：隙控式全射流喷头的流量大于试验用PY2摇臂式喷头8％左右,射程比摇臂式喷头的射程明显加大,最大增幅达到31％。全射流喷头水量分布均匀性与摇臂式喷头相当,但末端雨滴直径小于摇臂式喷头。由于其独特的射流元件及反向机构,全射流喷头结构简单,性能优良,价格低廉,具有显著的节能效果及良好的市场前景。     

新疆野苹果小吉丁虫防治试验

采用林间试验,在苹果小吉丁虫幼虫期对受害野苹果树进行不同施药方式和施药浓度的组合处理,探究16%虫线清乳油对野苹果小吉丁虫化学防治效果。试验结果表明,采用打孔注药和输液法施药方式在30 d后校正防效均达到90%以上;采用输液法及施药浓度为1倍稀释时,在整个防治期内校正防效均高于其它处理。对返青率进行比较分析时发现,对于野苹果树生长,最适合的施药浓度为2倍稀释。因此,在虫害防治前期采用1倍稀释浓度、防治后期采用2倍稀释浓度进行施药防治的效果较好。     

叶轮背叶片对离心泵轴向力影响的试验及分析

为了研究叶轮背叶片对离心泵轴向力特性的影响规律,以降速后的IS80-50-315型离心泵为研究对象,通过改变背叶片的宽度和数目,共设计出13种叶轮背叶片方案,并经过试验测试获得背叶片宽度和数目对泵性能、泵腔内液体压力及轴向力的影响规律.研究表明,当背叶片数目不变时,随着背叶片宽度的增大,试验泵的扬程和轴功率均增大,泵的效率逐渐降低;当背叶片宽度和数目增大到一定值时,轴向力的方向会发生改变,这将影响整机运行的稳定性.从平衡离心泵轴向力的角度出发,分析得出背叶片宽度t=3.5 mm、数目Z=5为最佳方案,此时轴向力方向为正、变化幅度较小.对比分析3种背叶片数目下,背叶片端部和泵盖的间隙δ与轴向力系数c_F关系曲线,得出间隙δ越小,背叶片平衡轴向力效果越显著.该研究成果为工程实践中背叶片的设计提供了理论依据.     

CFRP加固冷弯薄壁C型钢长构件的轴压承载力

为了研究CFRP加固冷弯薄壁C型钢长构件的承载能力,对腹板和翼缘均粘贴CFRP的试件进行了轴心受压加载试验。7根长度均为1 400 mm的试件,其中1根为未加固的控制试件,其余6根封闭缠绕外贴50 mm宽CFRP间距为50、100、150 mm 3种情况,层数为1层和2层。试验结果表明,在轴心荷载作用下的破坏模式为整体弯扭失稳,与控制试件相比,加固后试件的稳定极限承载力均有不同程度的提高;当CFRP间距与腹板高度的比值小于1时,加固效果较理想,且2层CFRP的加固效果好于1层。最后,采用有限元对模型进行数值模拟,对比试验数据和数值模拟结果,二者吻合较好。     

气门二次调整法在多缸V型发动机中的应用

正确的气门间隙对发动机正常运转、保持良好的性能是非常重要的。由于发动机的各气缸分布不同,做功的间隔角不同,使其气门间隙的调整各有差异。为此,结合多缸V型发动机曲轴配角、做功间隔角以及发火顺序等基本工况和原理,通过实例分析,探讨了二次调整法在多缸V型发动机气门间隙调整中的应用。     

梁非线性动力分析中剪力和轴力的相互影响

考虑梁的几何非线性动力问题，研究了其动力分析的中剪力和轴力相互影响的重要性，提出了剪力和轴力的相互影响是考虑系统非线性影响的关键。     

变形轴中心孔最佳位置的确定

以往生产中只能凭直观或用外圆打表测量方法来确定变形轴中心孔最佳位置，这既不方便又不准确．经分析与计算，得出变形轴中心孔最佳位置为０．３５Ｌ．     

Variation in clearance and ingestion rates by larvae of the black-lip pearl oyster (Pinctada margaritifera, L.) feeding on various microalgae

Clearance rate (CR) and ingestion rate (IR) of different sizes (89, 125 and 188 μm shell length) of Pinctada margaritifera larvae were determined when feeding on various microalgae. The microalgae tested were the diatoms, Chaetoceros muelleri and C. simplex, and flagellates, Tahitian Isochrysis aff. galbana, Pavlova lutheri and P. salina at 5 or 10 cells μL^–1. Both CR and IR of microalgae tested in this study increased with increasing larval size; but at all larval sizes, diatoms resulted in lower CR and IR. Of the microalgae tested, P. margaritifera larvae showed greatest CR and IR with the two Pavlova spp. Maximum CR for P. salina was 10.5, 21.2 and 29.7 μL h^–1 for larvae with shell lengths of 89, 125 and 188 μm, respectively. The highest IR values for P. margaritifera larvae with shell lengths of 89, 125 and 188 μm were 8.7, 81.0 and 165.7 cells·larva^–1 h^–1, respectively. CR and IR of P. salina were approximately five times higher than those recorded for C. muelleri and C. simplex.