以TK515井为例分析气举阀工作原理     

吴飞  周生福  张鹏  唐勇 《中国科技信息》2012,(8):157+164

本文以塔河油田TK515井为实例,详细介绍了气举阀气举工作原理。以套压发生突降为突破点对气举初期氮气推动环空液体向下移动的方式进行了分析。结合气举正常阶段各项施工参数对环空氮气气柱压力进行了估算。通过计算验证气举阀处环空压力大于波纹管预充填打开压力和油管内液柱压力后,环空流体可经阀孔和单流阀进入油管。  相似文献   

排球运动员步态支撑期的足底压力特征   总被引：1，自引：0，他引：1  

苍海  李翰君  高维纬 《沈阳体育学院学报》2012,31(1):84-87

通过测试得到排球运动员步态中足底压力的主要特征,并比较膝关节损伤运动员与无膝关节损伤运动员的足底压力特征,尝试分析膝关节损伤对足底压力产生的变化,为排球运动员正常步态数据提供可信的参考标准。选取北京体育大学竞技体育学院排球专项学生共48人(26男、22女)作为研究对象。运用FOOTSCAN足底压力分布测量系统和QUALISYS-MCU500红外运动测试系统的6个摄像头采集足底压力及步态基本运动学参数,测量被试者赤足状态下的步态。要求被试者以自己正常的步速行走,左右脚分别测试3次。将足部分为10个解剖分区:第L趾骨(T1)、第2-5趾骨(T2-T5)、第1跖骨(M1)、第2跖骨(M2)、第3跖骨(M3)、第4跖骨(M4)、第5跖骨(M5)、足中部(MF)、足跟内侧(HM)和足跟外侧(HL)。选取各个分区的接触开始时刻、接触结束时刻、最大压强时刻、接触时间作为时间指标。根据足底压力数据,男女排球运动员在步态支撑时期不同阶段的比例分别为:着地阶段(6.2%男,6.4%女)、前足接触阶段(5.5%男,6.6%女)、整足接触阶段(43.44%男,40.4%女)、离地阶段(42.9%男,46.5%女)。膝关节损伤运动员受伤腿足中部足底压强峰值明显低于未受伤腿。  相似文献   

普通高校毕业生就业压力状况研究   总被引：2，自引：0，他引：2  

邱桂平  张丽锦 《教育理论与实践》2009,(15)

通过自编问卷对普通高校毕业生就业压力状况进行的调查研究发现:普通高校毕业生有一定程度的就业压力,所调查的被试中接近1/3的学生处于较高的就业压力水平;毕业生就业压力存在显著的学科及性别差异,文科学生就业压力显著高于理工科学生(p<0.05),女生就业压力显著高于男生(p<0.01);不同类别大学生普遍将就业压力的原因归于社会就业现实状况不佳等外部因素,较少考虑个人主观因素。  相似文献   

Tennis serve performances at break points: Approaching practice patterns for coaching     

Dominik Meffert  Craig O’Shannessy  Philipp Born  Ralph Grambow  Tobias Vogt 《European Journal of Sport Science》2018,18(8):1151-1157

Tennis comprises specific match situations when winning the next point is crucial. These big points can decide about a win or loss and, thus, reasonably arouse mental stress. Break points (BPs) are considered as big points and the outcome is influenced by, among a variety of other factors, the serve, which is well accepted being one of the dominant strokes in Men’s tennis. In this study, we examined the serve behaviour for male players in the Wimbledon tournament 2016 to investigate the possible impacts of presumed mental stress within the situation of BPs, and further, if winning players perform better than losing players. A total of 28.843 points were analysed and divided into BP (n?=?2.035) and non-break points – referred to as regular points (RP; n?=?26.808).  相似文献   

挖方工程挡土结构土压力计算问题研究     

于林平  赵家臻  赵广会 《大连大学学报》2009,30(3):71-74

土压力是作用在挡土结构上的主要荷载,土压力计算是挡土结构设计的重要内容。本文以挖方工程挡土结构土压力计算问题为研究对象,推导了作为判断土压力计算条件重要依据的理论滑动面倾角的计算公式,并针对现行规范中土压力计算条件的判断方法不完全统一的现状,结合工程实例对比分析了不同判断方法及其土压力的计算问题,提出的判断挖方工程挡土结构土压力计算条件的新方法。  相似文献   

缓冲回路在钢卷运输车上的应用研究     

李溪平 《辽宁科技学院学报》2009,11(1):42-43

通过对冷轧厂钢卷运输车制动时产生故障的原因进行分析,阐述了在其液压系统中设置缓冲回路的必要性,并进一步对几种缓冲回路进行了研究,从而提出了比较可行的缓冲回路形式及制动压力的确定方法。  相似文献   

Stoichiometric evolutions of PH3 under high pressure: implication for high-Tc superconducting hydrides     

Ye Yuan  Yinwei Li  Guoyong Fang  Guangtao Liu  Cuiying Pei  Xin Li  Haiyan Zheng  Ke Yang  Lin Wang 《国家科学评论(英文版)》2019,6(3):524

The superconductivity of hydrides under high pressure has attracted a great deal of attention since the recent observation of the superconducting transition at 203 K in strongly compressed H₂S. It has been realized that the stoichiometry of hydrides might change under high pressure, which is crucial in understanding the superconducting mechanism. In this study, PH₃ was studied to understand its superconducting transition and stoichiometry under high pressure using Raman, IR and X-ray diffraction measurements, as well as theoretical calculations. PH₃ is stable below 11.7 GPa and then it starts to dehydrogenate through two dimerization processes at room temperature and pressures up to 25 GPa. Two resulting phosphorus hydrides, P₂H₄ and P₄H₆, were verified experimentally and can be recovered to ambient pressure. Under further compression above 35 GPa, the P₄H₆ directly decomposed into elemental phosphorus. Low temperature can greatly hinder polymerization/decomposition under high pressure and retains P₄H₆ up to at least 205 GPa. The superconductivity transition temperature of P₄H₆ is predicted to be 67 K at 200 GPa, which agrees with the reported result, suggesting that it might be responsible for superconductivity at higher pressures. Our results clearly show that P₂H₄ and P₄H₆ are the only stable P–H compounds between PH₃ and elemental phosphorus, which is helpful for shedding light on the superconducting mechanism.  相似文献   

High-temperature superconductivity in sulfur hydride evidenced by alternating-current magnetic susceptibility     

Xiaoli Huang  Xin Wang  Defang Duan  Bertil Sundqvist  Xin Li  Yanping Huang  Hongyu Yu  Fangfei Li  Qiang Zhou  Bingbing Liu  Tian Cui 《国家科学评论(英文版)》2019,6(4):713

  相似文献   

Li-ion battery material under high pressure: amorphization and enhanced conductivity of Li4Ti5O12     

Yanwei Huang  Yu He  Howard Sheng  Xia Lu  Haini Dong  Sudeshna Samanta  Hongliang Dong  Xifeng Li  Duck Young Kim  Ho-kwang Mao  Yuzi Liu  Heping Li  Hong Li  Lin Wang 《国家科学评论(英文版)》2019,6(2):239

Lithium titanium oxide (Li₄Ti₅O₁₂, LTO), a ‘zero-strain’ anode material for lithium-ion batteries, exhibits excellent cycling performance. However, its poor conductivity highly limits its applications. Here, the structural stability and conductivity of LTO were studied using in situ high-pressure measurements and first-principles calculations. LTO underwent a pressure-induced amorphization (PIA) at 26.9 GPa. The impedance spectroscopy revealed that the conductivity of LTO improved significantly after amorphization and that the conductivity of decompressed amorphous LTO increased by an order of magnitude compared with its starting phase. Furthermore, our calculations demonstrated that the different compressibility of the LiO₆ and TiO₆ octahedra in the structure was crucial for the PIA. The amorphous phase promotes Li⁺ diffusion and enhances its ionic conductivity by providing defects for ion migration. Our results not only provide an insight into the pressure depended structural properties of a spinel-like material, but also facilitate exploration of the interplay between PIA and conductivity.  相似文献   

On Hemingway''s In Another Country     

俞丽芳 《承德职业学院学报》2002,7(3)

歌颂勇气是海明威写作的主题.他笔下的人物总是勇敢,无畏,而且充满希望.小说<在异乡>充分表现了这一点.海明威用他独特的艺术技巧与风格,使主人公永远都不失其"重压下的优雅风度".  相似文献