博后经历对科研人员成长影响的定量研究          下载免费PDF全文

徐芳  周建中  刘文斌  李晓轩 《科研管理》2016,37(7):117-125

本研究以中国大陆科研人员为研究对象,选取免疫学和管理科学与工程两个学科领域为案例,采集科研人员的CV(Curriculum Vitae)数据,通过生存分析(Survival Analyses)方法研究不同因素,特别是博士后经历对不同类型学科领域科研人员职业生涯发展的作用与影响。Kaplan-Meier分析表明,对免疫学科而言,有过博士后经历的在进入副教授阶段的生存风险较高,即存活时间较短能较快晋升到副教授阶段,但在进入教授阶段则是相反,生存风险较低即存活时间较长从而延缓其晋升到教授阶段。对管理科学和工程学科而言,有过博士后经历的在进入副教授和教授阶段都是生存风险较低从而延缓其职业生涯的发展。COX比例风险回归分析表明,对免疫学科而言,性别、单位性质、博士毕业国别对其成长有显著影响,对管理科学与工程而言,单位性质以及流动频次对其成长有显著影响。最后本文对研究结果的原因进行了分析和讨论,并提出了下一步研究的设想。  相似文献   

Defect in mitochondrial functions in damaged human mitral valve     

Santosh Shinde  Pawan Kumar  Kaushala Mishra  Neela Patil 《Indian journal of clinical biochemistry : IJCB》2006,21(2):156-160

Mitochondrial diseases are a heterogeneous group of disorders in which a primary mitochondrial dysfunction is proven by morphological, biochemical, and genetic examinations. The mitral valve has important function in the regulation of blood flow from one chamber to another. Often, the mitral valve becomes abnormal with age, in Rheumatic fever or it is abnormal from birth (Congenital) or it can be destroyed by infection i.e. bacterial endocarditis and needs replacement. Myocardial function depends on energy produced by mitochondria and in any of these disease conditions, mitochondrial functions and enzyme activities may be impaired. With this in view, we analyzed the relationship between preoperative clinical conditions (as per New York heart Association) and extent of mitochondrial enzyme activities in damaged Human mitral valve in two types of heart disease such as Rheumatic Heart Disease (RHD) and Bacterial Endocarditis (BE). Thirty nine Patients undergoing cardiopulmonary bypass (CPB) for routine valvular heart surgery were included in the study. Controls included 11 normal porcine mitral valve samples without any evidence of heart disease. Mitochondrial enzymes like cytochrome oxidase (COX), succinate dehydrogenase (SDH), malate dehydrogenase (MDH), citrate synthase (CS) and ATPase were determined. Mitochondrial COX, SDH, CS and Total ATPase activities were significantly decreased in disease condition like BE and RHD when compared with control (P<0.001). On the other hand as per New York Heart Association (NYHA) preoperative clinical classification, all the mitochondrial enzymes were significantly (p<0.05) impaired in class IV as compared with NYHA class I, II and III. Present study shows that impairment in the mitochondrial enzymes activities are more pronounced in bacterial endocarditis (BE). It also indicates that damage to mitochondrial enzymes are most pronounced in NYHA class IV.  相似文献   

Negative Valve Overlap Mode of HCCI Operation Using Gasoline and Diesel Blended Fuels     

钟绍华  陈永东  Miroslaw Lech Wyszynski  徐宏明 《天津大学学报(英文版)》2007,13(6)

The negative valve overlap (NVO) strategy of HCCI operation was experimentally investigated on a gasoline HCCI engine operated with variable valve timing in association with the addition of diesel fuel. The experimental results show that, by using gasoline and diesel blended fuels, the required NVO interval for suitable HCCI combustion under a given engine speed and a moderate compression ratio condition could be reduced, and the HCCI combustion region was extended remarkably without substantial increase in NOx emissions under a given inlet and exhaust valve timing due to the improvement of charge ignitability. In addition, the possible scale of NVO was extended. A substantial increase in the lean limit of excess air ratio and the upper limit of load range can be achieved because of higher volumetric efficiency, resulting from the decrease in the required NVO and the presence of less residual gases in cylinder.  相似文献   

论美国妇女选举权实现后存在的问题及原因   总被引：2，自引：0，他引：2  

张华 《商丘职业技术学院学报》2008,7(4):29-31

美国国会通过第19条宪法修正案后,美国妇女获得了和男人一样的选举权。但是,美国妇女选举权的获得并没有从根本上改变她们的社会和经济地位,妇女的“黄金时代”并未到来。她们在选举、就业和工资待遇等方面仍受到严重的歧视,这其中存在很多问题和原因。  相似文献   

溢流阀的特性及应用     

李青虹 《三明学院学报》2004,21(2):29-32

对溢流阀的特性及分类进行了介绍,并阐述了溢流阀在液压系统中多种功能的具体应用。  相似文献   

水压轴向柱塞马达配流盘的研究     

聂松林  李壮云  杨曙东 《上海大学学报(英文版)》2002,6(1):73-78

This paper has introduced the developments of water hydraulic axial piston equipments.According to the effects of physicochemical properties of water on water hydraulic components,a novel valve plate for water hydraulic axial motor has been put forward,whose moment exerted by the fluid field between valve plate and bearing plate is balanced entirely.The material screening experiment of valve plate is done on the test rig.Through numerical simulation the effects of some geometry parameters on the performance of water hydraulic motor have been studied.The silencing grooves on the valve plate in water hydraulic motor can reduce the pressure shock and the occurrence of cavitation effectively.It is evident that the appropriate structure should change the wear status between matching paris and reduces the wear and specific pressure of the matching pairs.The specimen with the new type valve plate is used in a tool system.  相似文献   

一体化停水自闭式水阀创新设计     

王品越 《河北职业技术学院学报》2011,(4)

通过对现有停水自闭式水阀的现状及存在的主要问题进行分析,介绍了一体化停水自闭式水阀的工作原理及该水阀的创新点,并对该机构的使用前景进行了描述,对当今停水自闭式水阀的设计提供了一种新颖、实用的方法。  相似文献   

一体化停水自闭式水阀创新设计     

王品越 《廊坊师范学院学报(自然科学版)》2011,11(4):61-62

通过对现有停水自闭式水阀的现状及存在的主要问题进行分析,介绍了一体化停水自闭式水阀的工作原理及该水阀的创新点,并对该机构的使用前景进行了描述,对当今停水自闭式水阀的设计提供了一种新颖、实用的方法。  相似文献   

基于CFD的电动截止阀内流道数值模拟及改进设计     

周明健  唐铃凤  王玉勤 《巢湖学院学报》2011,(6):75-79

电动截止阀是流体输送的重要元件.阀的传统设计方法很少从流体角度对其流道进行设计,其流阻系数比较大,容易造成局部压力损失.流体介质通过阀口时,流动方向发生变化,可能产生诸如局部涡流、空化、水锤和死水区等水流现象及湍流脉动噪声,对阀体有很强的破坏性,降低阀的使用寿命.基于RAN-S方程组和RNG k-ε湍流模型,利用CFD技术对全开启状态下的电动截止阀的内流道进行三维的湍流数值模拟,获得其总压图、速度矢量图、湍动能强度图.通过数值模拟,可以直观地显示阀的内流道中流体的流动过程.改变进出口段流道的长度、曲率以及阀杆在流道中的布局等,进出口的压力差相对于未改进前减少30%左右,速度突变区域明显缩小,局部涡流现象消失,湍动能强度也降低了15%左右.  相似文献   

基于MCS-51单片机的远程浴室控制系统设计     

汤怀 《廊坊师范学院学报(自然科学版)》2012,12(4):40-42,45

给出了一种可进行远程控制的浴室控制器方案,浴室控制器主要由单片机、A/D转换器和电磁阀组成,设计了单片机与PC机之间的串行通信电路等。设计以MCS-51单片机作为系统控制单元,结合系统硬件电路设计和软件设计实现对电磁阀和A/D转换器的控制,从而实现对水温及浴池放水时间的控制。  相似文献