离心叶轮的有限元分析

运用大型通用有限元分析软件ANSYS8.0,对离心叶轮内流场三维紊流进行了分析.获得了叶轮内流场压力分布,确定了叶轮结构分析中液体作用于叶片上的载荷.在此基础上对叶轮结构进行了有限元分析,准确直观地得到了叶轮各处的应力和应变值,为叶轮的强度计算和设计提供了可靠依据.     

离心压缩机叶轮防共振逆向设计方法研究

离心式压缩机叶轮的逆向工程是设计压缩机叶轮的一个重要途径,逆向设计的压缩机叶轮的性能和稳定性对于压缩机的设计有着重要意义。针对压缩机的稳定性,对美国某增压机叶轮进行了逆向工程,并利用SAFT图法对离心叶轮的稳定性进行了分析,结果表明,SAFT图法能更好地判断叶轮的共振点,对叶轮的设计操作有着重要意义。同时,针对叶轮分析的模态阵型数据进行了分析,初步总结出了离心叶轮的共振规律,为共振判定以及计算提供了参考。     

整体叶轮CAD/CAM技术应用研究与实现

讨论了整体叶轮这一典型复杂零件的CAD/CAM技术问题.通过对整体叶轮加工工艺的分析,利用UG软件实现了叶轮的建模与五轴编程,解决了叶轮CAD/CAM过程中的诸多关键技术问题,在MIKRON UCP710高速加工中心上成功地加工出了合格的整体叶轮.     

航空发动机压气机叶轮外罩振动特性研究

通过噪声测试得到了三维频谱图,对噪声信号进行了分析,得到了叶轮外罩可能存在的激励频率,给出了基于噪声测试的叶轮外罩共振评估方法。对离心叶轮和叶轮外罩进行了有限元分析,给出了叶轮外罩与离心叶轮耦合共振的评估方法。结果表明:噪声测试频谱分析所得频率成分包含了转子叶片通过频率和不确定性激励频率,通过有限元分析可以考虑离心叶轮大小叶片与叶轮外罩的耦合共振作用。试验与有限元分析相结合对叶轮外罩进行振动评估的方法可以较全面地考虑可能存在的多种形式的激励频率。     

双吸叶轮熔模铸造制壳工艺改进

双吸叶轮结构复杂,试生产过程中容易出现变形缺陷,通过改进制壳流程,有效地降低了双吸叶轮流道模壳的缺陷,降低了流道变形,成功地铸造出质量合格的双吸叶轮铸件。     

空调用贯流风机叶轮几何建模的参数化

根据几何关系,建立了空调用贯流风机叶轮的三维数学模型,实现了空调用贯流风机叶轮几何建模的参数化.其成果极大地缩短了空调用贯流风机叶轮CFD分析的前处理时间.     

离心泵叶轮上水力径向力的分析

对离心泵叶轮和蜗壳这间的水力相互作用进行了理论分析。考虑了叶轮叶片不能准确地引导流体流过叶轮，而且对蜗壳中的流动进行了准一维处理，理论模型确定了叶轮出口的流量扰动和合力。用该模型计算了叶轮上水力作用力扰动、压力分布和径向力；并给出了理论计算结果和实验研究结果的比较。     

基于ANSYS的压气机叶轮振动特性有限元仿真分析

车用涡轮增压器的压气机叶轮常常因为振动而导致破坏,对压气机叶轮进行模态分析是避免叶轮与激振频率发生共振的常用手段,能有效避免因发生共振而导致的叶轮破坏问题。利用AN-SYS软件,采用子结构分析方法对压气机叶轮的中低阶固有频率进行了数值仿真计算,获得了不同转速和不同节径时的频率,并根据计算结果绘制了Campbell图,找出了与压气机叶轮固有频率产生共振的转速,为压气机叶轮的优化设计提供了依据,同时说明采用子结构分析的方法可以较精确地获得整体模型的低阶固有频率解。     

基于Kriging近似模型的轨道主冷叶轮多目标遗传优化

为最大限度地减小叶轮质量,通过反求模型和网格密度精度的分析,对叶轮结构进行数值计算,并构造了拉丁超立方试验设计模型和Kriging近似模型,得到叶轮结构的采样空间和高精度的近似模型用来代替数值分析,提出了轨道轴流风机叶轮结构多目标遗传优化方法。采用该方法分析了主要技术参数对叶轮结构受力的灵敏性,并找出了对叶轮结构应力影响最大的参数。叶轮结构通过优化后,质量减小了31.7%,大大节省了材料的成本,最大应力值也由初始方案的21.5MPa变为16.5MPa,有效地提高了叶轮的力学性能。优化后通过滑环引电器和动静态应变测试系统对风机叶轮进行动静态试验,并设计了叶轮旋转机械的工艺工装和试验方案,试验结果与计算结果十分吻合,且动应力相对很小,因此,叶轮具有良好的力学和振动性能,在工程应用中具有较高的价值。     

PT检测技术在水泵叶轮上的应用

扼要地介绍了水泵及叶轮部件在火电厂发电的重要性,为确保叶轮关键部件在水泵运行中安全稳定,对叶轮采用着色渗透(简称PT)探伤及磁粉(MT)探伤两种无损检测方法进行了分析,得出用PT探伤优于MT探伤,并对叶轮进行PT探伤操作过程进行了重点阐述,通过PT探伤可发现水泵叶轮在运行状态下难以发现的细小缺陷,从而避免了由于叶轮叶片裂纹导致的水泵不能工作及对火电生产产生不良影响,确保火电生产的稳定运行。     

A system for wear prediction in lubricated sliding contacts

A system of analysis is developed to predict the rate of wear in sliding contacts. The essence of the approach is the proposal that the rate of wear can be predicted only in probabilistic terms. Therefore, the estimation of the probability of wear, which can be regarded as synonymous with the probability of surface asperity contacts, precedes the calculation of the wear rate. Further, recognising the fact that wear takes place within the actual area of contact, it is argued that this area consists of plastic and elastic contacts between asperities which, in turn, have different shear strengths and contribute differently to the wear process. In the case of lubricated contact, a frictional film defect represents the influence of a lubricant on the wear process. Moreover, as in this type of contact the load is supported by both lubricating film and contacting asperities, a special procedure is provided to estimate the load supported by the asperities, because it is only that part of the load which contributes to the wear. The catastrophic form of wear in lubricated contacts, that is termed ‘scuffing’, is also considered, and the probability of scuffing, under a given set of operating conditions, is estimated. The predictive system has been tested and its predictions are compared with available experimental results.     

Histochemical and ultrahistochemical localization of heavy metals in calf organs

Cadmium, zinc, selenium, and copper were administered, singly or in combination, orally or subcutaneously. Experiment I included 32 calves of both sexes; six received Cd (two groups), Zn, Cd, and Zn, and Cd and Se (two groups) and one group was a control. In Experiment II (21 bulls), three were given Cd, Cd, and Cu, and Cd and Zn, respectively, and one group was a control. For light microscopy, in Experiment I the highest amounts of silver granules were present in the samples of liver, small intestine, and vesicular gland of all the exposed groups; in Experiment II the most affected organs were liver, kidney, and small intestine. For electron microscopy, in Experiment I, after administration of Cd and Zn, the highest amounts of granules were seen in the cytoplasm of hepatocytes and cells of the proximal and distal renal tubules and the lowest amounts were found in glandular cells of the pancreas. Administration of Cd and Se resulted in the presence of large numbers of granules in the nuclei and nucleoli of spermatogonies. In Experiment II, ingestion of Cd and Zn in feed led to the appearance of highest amounts of granules in the nucleoli, nuclei, and cytoplasm of cells in testes, kidneys, and pancreas. Following Cd intake, the highest accumulation of granules was observed in the nucleoli of hepatocytes and cells of the proximal and distal renal tubules. Combined Cd and Cu produced the highest number of granules in cells of the proximal and distal renal tubules and in the nucleoli and nuclei of germinal epithelium.     

Immunohistochemical distribution of enkephalin, substance P, and somatostatin in the brainstem of the leopard frog, Rana pipiens

The brainstems of frogs contain many of the neurochemicals that are found in mammals. However, the clustering of nuclei near the ventricles makes it difficult to distinguish individual cell groups. We addressed this problem by combining immunohistochemistry with tract tracing and an analysis of cell morphology to localize neuropeptides within the brainstem of Rana pipiens. We injected a retrograde tracer, Fluoro-Gold, into the spinal cord, and, in the same frog, processed adjacent sections for immunohistochemical location of antibodies to the neuropeptides enkephalin (ENK), substance P (SP), and somatostatin (SOM). SOM+ cells were more widespread than cells containing immunoreactivity (ir) to the other substances. Most reticular nuclei in frog brainstem contained ir to at least one of these chemicals. Cells with SOM ir were found in nucleus (n.) reticularis pontis oralis, n. reticularis magnocellularis, n. reticularis paragigantocellularis, n. reticularis dorsalis, the optic tectum, n. interpeduncularis, and n. solitarius. ENK-containing cell bodies were found in n. reticularis pontis oralis, n. reticularis dorsalis, the nucleus of the solitary tract, and the tectum. The midbrain contained most of the SP+ cells. Six nonreticular nuclei (griseum centrale rhombencephali, n. isthmi, n. profundus mesencephali, n. interpeduncularis, torus semicircularis laminaris, and the tectum) contained ir to one or more of the substances but did not project to the spinal cord. The descending tract of V, and the rubrospinal, reticulospinal, and solitary tracts contained all three peptides as did the n. profundus mesencephali, n. isthmi, and specific tectal layers. Because the distribution of neurochemicals within the frog brainstem is similar to that of amniotes, our results emphasize the large amount of conservation of structure, biochemistry, and possibly function that has occurred in the brainstem, and especially in the phylogenetically old reticular formation.     

双列调心凹面滚子轴承接触载荷分析

在考虑滚子与套圈、滚子与保持架以及保持架与引导套圈作用力的条件下,建立双列调心凹面滚子轴承动力学模型.以某双列调心凹面滚子轴承为研究对象,与静力学分析模型滚子最大接触载荷计算结果对比,验证了模型的正确性.并分析了工况条件(轴向载荷、径向载荷、倾覆力矩、转速)和结构参数(滚子数量、滚子长度、径向游隙)对滚子最大接触载荷的...     

Localization of sarcoglycan, neuronal nitric oxide synthase, beta-dystroglycan, and dystrophin molecules in normal skeletal myofiber: triple immunogold labeling electron microscopy.

In order to investigate the mode of existence of the sarcoglycan complex, neuronal nitric oxide synthase (nNOS), beta-dystroglycan, and dystrophin in the normal skeletal myofiber, we examined the ultrastructural localization and mutual spatial relationship of nNOS, beta-dystroglycan, dystrophin, and the individual components of the sarcoglycan complex by using triple immunogold labeling electron microscopy. Each molecule of alpha-, beta-, gamma- and delta-sarcoglycans is located intracellularly or extracellularly near the muscle plasma membrane mostly in accordance with the sarcoglycan antigenic sites against which the antibodies were generated. The association of different two and/or three sarcoglycan molecules out of alpha-, beta-, gamma- and delta-sarcoglycan molecules was frequently observed. Each molecule of nNOS, beta-dystroglycan, and dystrophin was ultrastructurally noted along the cell surface of normal skeletal myofibers. Moreover, the close relation of a sarcoglycan molecule with beta-dystroglycan and dystrophin, and the association of nNOS with dystrophin were also confirmed ultrastructurally. Thus, this study demonstrated that the constituting molecules of the sarcoglycan complex, nNOS, beta-dystroglycan, and dystrophin existed in the form of a cluster at the normal muscle plasma membrane. The association of nNOS with dystrophin and its associated glycoproteins may form a macromolecular signaling complex at the muscle plasma membrane.     

浅析空调净化系统的日常维护

在查看国内外文献、读书和实践的基础上,对空调净化系统各个部分的清洁消毒和维护进行讨论,包括高、中、初效过滤器的清洁更换、管道的清洁、仪表的校验、阀门的检查以及整个系统的消毒灭菌等,着重阐述其清洁消毒和维护的重要性,期望能够得到企业的重视。     

网格曲面上的样条曲线阵列

提出一种流形网格曲面上曲线阵列复制方法,达到曲线重用与再设计的目的。网格曲面上的曲线用测地B样条表示,使对曲线的操作可以转换为对曲线控制顶点的操作;引入离散指数映射理论将给定的源曲线控制顶点映射到切空间,获得它们的法坐标,按照曲线阵列前后控制顶点法坐标保持不变的原则,建立曲线阵列前后控制顶点的对应关系,实现曲线的有规律多重复制。法坐标很好地保持了控制顶点之间的测地距离和相对位置关系,因而也保证了曲线阵列重用过程中的形状保持性。将曲线阵列时的位置与形状分开处理,使曲线生成仅与其所在的局部区域有关而与曲面的整体大小无关,既便于保证曲线的形状保持性,也减少了计算量。试验结果表明,所介绍方法健壮、有效,能满足曲面上曲线的交互设计要求。     

Effects of polydatin on the proliferation,migration, and invasion of ovarian cancer

To investigate the effects of polydatin on the proliferation, migration, and invasion of ovarian cancer, the change of proliferative ability, migration ability, and invasive ability of human ovarian cancer cell OVCAR-3, A2780, and HO-8910 was detected by using polydatin and up-regulating PI3K. The anticancer activity and mechanism of polydatin in ovarian cancer were analyzed. Polydatin could effectively inhibit the proliferation, migration, and invasion of OVCAR-3, A2780, and HO-8910, and inhibit the expression of PI3K protein. After the expression level of PI3K protein was up-regulated, the inhibitory effect of polydatin on the proliferative ability, migration ability, and invasive ability of OVCAR-3, A2780, and HO-8910 significantly decreased, suggesting that PI3K was the target of polydatin. Therefore, we concluded that polydatin could inhibit the proliferation, migration, and invasion of ovarian cancer cells by inhibiting the expression of PI3K protein, which provides an experimental basis for polydatin in the treatment of ovarian cancer.     

Sperm ultrastructure and spermatogenesis in the lizard, <i>Tropidurus itambere</i>

Spermatogenesis, with emphasis on spermiogenesis, is described for the lizard, Tropidurus itambere, using light microscopy, phase contrast and epifluorescence, as well as scanning and transmission electron microscopy. Cellular differentiation involves events of chromatin condensation, nuclear elongation and the formation of structural complexes, such as the acrosomal and axonemal ones. Other new characteristics, exclusive for this species, include various aspects of the subacrosomal granule, the insertion of the proacrosomal vesicle and the development of these structures to participate in the acrosomal complex. Radial projections occur just above the nuclear shoulders, which have been recognized already from the beginning of cellular elongation. The development of the midpiece, the dense bodies, formation of the flagellum and elimination of residual cytoplasm result in the final characterization of the mature spermatozoon. Comparisons between Tropiduridae and other lizard families are made.     

Future directions of fundamental research in additive tribochemistry

This paper reviews briefly the present state of fundamental research, in tribochemistry of load-carrying additives, including oiliness agents, organolsulphur, organochlorine, organophosphorus, organic borates and organometallic compounds. The emphasis is on the weak areas of investigation. It is revealed that the least understood mechanisms, such as the effect of additives on fretting wear, additive-material compatibility, the efficacy of antifatigue additives and the action of water-based fluid additives in metalworking, are the concern of overlapping spheres of learning. A cooperative effort by chemists, metallurgists and mechanical engineers would help overcome the difficulties posed by problems in areas beyond individual expertises. Some research projects for the future are also suggested.