电驱离心式压缩机组冷态对中的影响因素     

蒲斌 《油气储运》2021,(3):319-325,351

电驱离心式压缩机组联轴器处的对中会影响机组的运行稳定性,因此需要在现场进行校验,并修正压缩机生产厂家的冷态对中数据,以确保冷态对中的准确性,提升对中质量。根据离心式压缩机组的结构及运行特点,分析机组冷态与正常运行状态时的差异,得出冷态对中的影响因素,并提出了计算和修正冷态对中数据的公式。从热膨胀、轴上升高度、顶升高度、工具挠度4个方面分析其对离心式压缩机组冷态对中的影响。在计算材料热膨胀数值的过程中,发现其具有明显的线性关系,据此简化了热膨胀数值的计算方式。通过状态监测工具得出转子轴中心的上升高度,并对冷态对中过程中的转子顶升高度进行修正,最终得出修正的冷态对中数据,对指导压缩机组开展冷态对中具有一定借鉴意义。  相似文献   

龙竹竹材吸湿膨胀特性研究     

孙照斌  田芸  曲保雪 《林业机械与木工设备》2006,34(9):7-9

对龙竹竹材的吸湿膨胀特性进行了测试和分析。结果表明,竹材各个方向上吸湿膨胀特性差异显著,且竹间部位和竹节部位的吸湿膨胀特性也有一定差异。  相似文献   

Cumulus Oophorus Expansion of Bovine Oocytes Cultured in vitro: A SEM and TEM Study     

J. Laurincík  J. Pivko  P. Kroslák 《Reproduction in domestic animals》1992,27(4):217-228

Bovine cumulus-oocyte complexes (COCs) were aspirated from antral follicles (3–6 mm in diameter). COCs with a compact multilayered cumulus investment were cultured for 9, 13 and 24 hours, respectively, and processed for scanning or transmission electron microscopy after different periods of culture including a 0 hour control group. In all 0 hour control COCs initial formation of cumulus cell projections, blebs and microvilli were observed. The start of cumulus-oocyte disconnection in cattle was observed after 9 hours of in vitro culture. These connections were almost completely discrupted after 13 hours, when a continuous production of extracellular matrix was observed. The full expansion of corona radiata cells was not observed even after 24 hours. Some cumulus oophorus cells were bound together with junctions of the zonula adherens type after 24 hours when extracellular matrix was found only in deeper layers. The full expansion of corona radiata cells was not the prerequisite for disconnection of cumulus-oocyte complex. Inhalt: Kumulus oophorus Expansion von in vitro kultivierten Rinderoozyten: Eine SEM und TEM Untersuchung Kumulus-Oozyten-Komplexe (COC) von Rindern wurden aus antralen Follikeln aspiriert (Durchmesser 3–6 mm). COC's mit kompakten mehrschichtigen Kumulus wurden für 9, 13 und 24 Stunden kultiviert und für die Scanner- oder Transmissionselektronenmikroskopie vorbereitet. Verschiedene Kulturzeiten incl. einer 0-Stundengruppe als Kontrolle wurden untersucht. In allen Kontroll COC's wurden beginnende Formationen yon Kumuluszellprojektionen, Bläschen und Mikrovilli beobachtet. Nach 9-stündiger in vitro Kultur begann die Lösung zwischen Kumulus und Oozyte. Die Verbindungen waren nach 13 Stunden vollständig unterbrochen, wobei eine kontinuierliche Produktion extrazellulärer Matrix beobachtet wurde. Eine vollständige Expansion der Corona radiata Zellen wurde auch nicht nach 24 Stunden beobachtet. Nach 24 Stunden waren einige Cumulus Oophorus Zellen über Verbindungen des Zonula adherens Typs verknüpft, wobei extrazelluläre Matrix nur in den tieferen Zellschichten gefunden wurde. Eine vollständige Kumulusexpansion ist keine Voraussetzung für die Auflösung des Kumulus-Oozyten-Komplexes.  相似文献   

Optimal cultivar mixtures in focal plant diseases     

F. van den Bosch 《European journal of plant pathology / European Foundation for Plant Pathology》1993,99(Z3):41-50

This paper deals with a study on the effects of mixtures of partially resistant cultivars in focus forming plant diseases. The focus expansion velocity in a mixture of two partially resistant cultivars depends on four parameters, the focus expansion velocity in a crop of cultivar 1 only and in a crop of cultivar 2 only, the net-reproduction in a crop of cultivar 1 and of cultivar 2, respectively. An explicit equation is developed for the damage of a cultivar mixture where the crop is infected by two physiological races of the pathogen. It is shown that cultivar mixtures exist where damage is smaller than in crops of either of the two cultivars only. A simple explicit formula is given on the basis of which it can be decided whether an optimal mixture exists for a given pathosystem.  相似文献   

The ex vivo expansion characteristic of endothelial progenitor cells     

LIU Chao  SUN Zong-quan  WU Yong-chao  CHEN Xin-zhong  FENG Jian-e 《园艺学报》2004,20(5):760-764

AIM: To explore the ex vivo expansion characteristics of the endothelial progenitor cells (EPCs). METHODS: CD34⁺ cells were selected from umbilical cord blood mononuclear cells (MNC) by MiniMACS system, expanded at the same conditions as that for total MNC, coincubation of CD34⁺ and CD34^- from the same donation for EPCs. In addition, we tested the effect of vessel endothelial growth factor (VEGF) and passage on cell differentiation, expansion kinetics and apoptosis. EPCs were determined and quantified by immunocytochemistry and flow cytometry. RESULTS: Coculture of CD34⁺ and CD34^-,total MNC led to a significant increase in the expansion of CD34⁺ cells compared with CD34 enrichment (P＜0.05). There was a trend toward decreased apoptosis in cultures when early passage was performed once the linear cord like structures appeared. There was no significant effect on apoptosis between with VEGF and without VEGF group (P＞0.05). These differentiated EPCs were stained positive for CD34⁺, von Willebrand factor (vWF), KDR, CD31 and incorporate acetylated low-density lipoprotein (LDL). CD34⁺ and AC133⁺cells accounted for 68.2%±6.3% (n=6) and 57.2%±9.8% (n=6) of attaching (AT) cells at day 7 of culture, respectively. CONCLUSIONS: Coculture of CD34⁺ and CD34^- or culture of MNC enhances ex vivo expansion of EPCs. Early passage decreases apoptosis rate, VEGF has no significant effect on ex vivo expansion of EPCs.  相似文献   

Quantifying canopy formation processes in fodder beet (Beta vulgaris subsp. vulgaris var. alba L.) crops     

《European Journal of Agronomy》2016

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长春市精明增长测评研究     

王光灿  刘兆顺  李淑杰  何有富  解小雨  于丽丽 《安徽农业科学》2014,(30):10738-10742

“精明增长”是由西方国家针对城市蔓延提出的一种全新的城市发展理念,它倡导高效、集约、紧凑的城市发展模式,对于解决我国城市化进程中面临的诸多问题具有现实意义.该研究从城市增长的数量、强度、效益、循环和建设水平5个方面选取了8个指标建立城市精明增长现状测评体系,对长春市的精明增长现状进行测评.结果表明,长春市城市扩展速度较快,土地利用的集约度与强度均有待提高,但就城市经济发展、道路和公共交通现状来说,符合精明增长的发展方向.  相似文献   

A Dynamic Model for Generation Expansion Planning and Algorithm     

Yang Xiutai Nie Duan 《保鲜与加工》1993,(4):6-10

This paper discusses the problem of long-range generation expansion planning. A dynamic model for long-range expansion planning is set up and an algorithm-a two-step programming is presented, which is used here in a case.  相似文献   

山西草地螟发生预测模糊近似推理模型     

鲁光球  张树堃  刘梅凤 《华北农学报》1988,(3)

模糊近似推理方法是模糊集理论应用前景十分广泛的一种方法.我们用此法为山西草地螟发生预测建立了一个模糊近似推理模型,初步试用效果满意.本文在模型的预报输出中引用了特征展开近似推理方法,大幅度地简化了运算过程;并且使得模型可以带入较多的因素.  相似文献   

多孔介质水分运动的随机数值分析     

李少龙  杨金忠  蔡树英 《灌溉排水学报》2006,25(2):4-7,11

采用van Genuchten-Mualem模型描述非饱和水力传导度和水分特征曲线,将模型中的3个参数作为随机场处理,联合运用Karhunen-Loeve展开和摄动方法,得到饱和非饱和水流的一个随机数值模型。应用该模型分析了介质随机参数的空间变异性对水头分布的影响,结果表明,水头标准差对介质参数的敏感程度由大到小依次为非饱和参数n、β、饱和水力传导度Ks,饱和带水头分布的变异性较非饱和带小。  相似文献