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杨源 《内蒙古科技与经济》2014,(13):64-64
某公司凝汽器抽真空水环真空泵运行中发生叶轮叶片断裂的故障,经分析,认为凝汽器真空泵在系统设计上存在缺陷,造成泵的入口负压过高并引发叶轮气蚀,导致叶轮叶片产生裂纹甚至断裂。经过技术改造后,水泵噪音、振动明显降低,问题得到彻底解决。 相似文献
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本文主要介绍了利用激光和声音测量的方法,对某型离心叶轮叶片进行振动特性分析。详细分析了利用激光传感器和声压传感器在固有频率测试中的不同作用,并总结出某型离心叶轮叶片固有频率测量的最佳方案。 相似文献
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基于全三维雷诺时均N-S方程和标准k-ε两方程湍流模型,采用多重参考系模型(MRF)和壁面函数法,利用FLUENT软件对应用于中比转速冲压焊接多级离心泵的扭曲式叶轮、圆柱式叶轮和堵塞式叶轮进行内部流场的数值模拟,得到了三种叶轮的内部流动特征。结果表明:扭曲式叶轮具有抗气蚀性能强,无明显的分流层现象,较好的水力性能等特点,在三种叶片中最适宜采用扭曲式叶片,为中比转速冲压焊接多级泵的叶轮设计选型提供了依据。 相似文献
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在叶轮设计和改型时,必须进行整体叶轮强度的分析,否则将会威胁叶轮的安全运行,或难以满足所需性能的基本要求。本文对料渣泵工程陶瓷叶轮最薄弱部位轮毂和叶片的受力和强度进行了理论分析,并通过有限元仿真软件ANSYS对叶轮工作时在流体反作用力下的强度进行了仿真。 相似文献
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大型离心压缩机是一种非常重要的工业装备,具有科技含量高、应用前景优良等特点。在离心压缩机当中,叶轮叶片是核心部件,其可靠性能够对离心压缩机性能的稳定性产生重要影响。本课题笔者重点对大型离心压缩机叶轮叶片疲劳可靠性进行了探究,希望以此使大型离心压缩机更具应用价值。 相似文献
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在大斜度井弯曲井眼中,钻杆受井眼约束,管柱产生大挠度,管柱的变形属于大变形;钻杆在这种工况下是一个大挠度、大变形、大位移,小应变的几何非线性问题。并对弯曲井眼中的钻杆承受轴向压力、轴向拉力进行分析。 相似文献
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Casikar V Mujica E Mongelli M Aliaga J Lopez N Smith C Bartholomew F 《Indian journal of clinical biochemistry : IJCB》2010,25(3):311-314
Andean Indians have used coca leaves (Erythroxylon coca and related species) for centuries to enhance physical performance. The benefits and disadvantages of using coca leaf have
been a subject of many political debates. The aim of this study was to investigate the effects of chewing coca leaves on biochemical
and physiological parameters. Cutaneous microdialysis catheters were used to estimate systemic biochemical changes. We subjected
10 healthy adult males (local residents) in Cajamarca (Peru, altitude 2700 m) to a standardised exercise routine on a stationary
cycle ergometer. The blood pressure, oxygen saturation (digital), pulse, VO2 max and ECG (Holter monitor) were recorded before
the exercise. Cutaneous microdialysis catheters were introduced in the forearm. The subjects were given to chew 8 g of coca
leaves with a small amount of lime. They were then placed on the cycle ergometer for 20 min. Blood pressure, oxygen saturation,
pulse, ECG and VO2 max were recorded. Pyruvate, glucose, lactate, glycerol and glutamate levels were estimated. Oxygen saturation,
blood pressure, and pulse rate did not show any significant changes between the two groups. Glucose levels showed hyperglycaemic
response. Glycerol, Lactate and Pyruvate increased. Glutamate remained unchanged. Similar changes were not seen in the controls.
These results suggest that coca leaves have blocked the glycolytic pathway of glucose oxidation resulting in accumulation
of glucose and pyruvate. The energy requirement for exercise is being met with beta-oxidation of fatty acids. The glycerol
released was also getting accumulated since its pathway for oxidation was blocked. These experimental findings suggest that
chewing coca leaves is beneficial during exercise and that the effects are felt over a prolonged period of sustained physical
activity. 相似文献
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本文用201种禾本科植物幼苗的60个形态和解剖性状进行了聚类分析，将禾本科植物分为四个大类(一级聚合单位)—狐茅类(Festucoid)、黍类(Panicoid)，竹类(Bambusoid)和画眉草类(Eragrostidoid)。这四类基本上与分类系统中的亚科相吻合，只是芦竹亚科植物的幼苗分散聚到了其它类中。推测芦竹亚科是一个比较原始的类群，狐茅亚科、黍亚科和画眉草亚科可能是在芦竹亚科的基础上进化而来的。 除个别种外，大多数同属的种在较低的聚合水平上聚在一起，超族在亚聚合单位中基本上能够反映出来。 研究证明禾本科植物的幼苗性状在禾本科植物分类中具有重要的分类学意义。 相似文献
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Combined static stress experiments are discribed in which thin walled tubes of a nickel-chrome-molybdenum steel are subjected to combined axial tension and internal pressure, and to combined axial compression and internal pressure. The axial loading was applied by means of a 30 ton hydraulic testing machine and the internal pressure by a pendulum dynamometer and pump. Tangential strains were measured by two newly developed hydraulic lateral extensometers, one of which was used in the axial tension experiments and the other in the axial compression tests. These extensometers possess the advantage over previous types for this work in that they measure accurately the average of the tangential strains over a considerable length of the tubes instead of at a single cross-section. Axial strains were measured with a Martens extensometer. Additional torsion tests are described. The experimental results checked well with the recently suggested constant energy of distortion theory of strength. 相似文献
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The radial and axial motions of electrons in the betatron are described by means of a potential function of forces. Previously reported conditions of equilibrium, stability and damping of oscillations are derived for the region of parabolic variation of the potential. Extension of the analysis to, non-parabolic regions gives an account of the injection in conventional instruments in better agreement with experiment, particularly in regard to higher voltages of injection.Space charge limitations are discussed with the help of the Laplacian of the potential of forces.By means of an additional radial electric field electrons can be introduced as in the magnetron, without any asymmetry inherent in the conventional betatron circumferential injector. The analysis of the conditions of equilibrium and stability, greatly facilitated in this case by the notion of potential, shows that no substantial improvement in space charge limitations can be expected and that the required variations between the flux linking the electron orbits and the magnetic and electric fields at the orbits are difficult to realize on account of their complexity and narrow tolerances. The X-ray output of a small experimental double yoke instrument was measured by a phototube multiplier viewing an irradiated fluorescent screen and gave evidence of multiple group electron capture. 相似文献
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为了解和掌握叶片处理段工艺参数与切丝含水率的相关关系,采用一元线性回归分析方法对叶片处理段工艺参数松散回潮累计加水量、叶片加料累计加水量、叶片处理段加水总量及贮叶时间与切丝含水率的相关性进行了分析,描述了叶片处理工艺参数与切丝含水率的相关性,建立叶片处理工艺参数与切丝含水率均值的一元线性方程。结果表明,松散回潮累计加水量及叶片处理段累计加水量与切丝含水率均值相关性较强,一元线性回归方程较为显著;叶片加料加水累计量及贮叶时间与切丝含水率均值不具有相关性;贮叶时间对烟片加料含水率与切丝含水率的差值相关性较强,一元线性回归方程较为显著;叶片加料出口含水率与切丝含水率相关性较强。 相似文献
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银杏叶生胚珠的发现及其系统意义 总被引：1，自引：0，他引：1
本文报道银杏的短枝叶缘着生胚珠的返祖现象，井结合银杏目的发展史对其系统意义进行了讨论，认为银杏胚珠的叶生性支持了”胚珠由边缘位置(种子蕨亚纲)到次生性顶生位置(银杏目等)转变”的说法。并指出，银杏的”营养叶”具有”孢子叶”的性质；同时支持了顶枝学说。 相似文献
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空间光学遥感器的计算机辅助热分析方法 总被引：4，自引：0，他引：4
介绍了一套空间光学遥感器的计算机辅助热分析方法 ,包括热平衡计算、热弹性分析、热光学分析、热光学灵敏度分析以及热设计方案评价等。热平衡计算用来预示遥感器的温度分布 ,热弹性分析用来计算热致变形和面型变化 ,热光学分析讨论热致位移和面型变化对成像质量的影响 ,热光学灵敏度分析则讨论不同形式的温差变化对成像质量影响的敏感程度。通过上述分析 ,能够弄清空间热环境对遥感器温度分布以及温度分布对成像质量的影响 ,进而提出热控制指标、制定合理的热设计方案。在工程任务的实际应用中表明该方法是可行的 相似文献