单螺杆泵的合理选择研究

为合理选择单螺杆泵,将螺杆泵抽油井作为一个大的生产系统,把油层、套管、油管、井下螺杆泵机组和井口作为5个子系统,利用系统节点分析法,确定出泵的工作载荷,并根据油井的实际工作参数,对泵特性曲线进行换算。由油井工作参数和单螺杆泵输油特性曲线对比可知,单螺杆泵的特性曲线和油井工作参数配合最好的情况是:油井的工作点应位于泵特性曲线Q0-H0的下面,而且在高效区的开始处。实践证明,采用这种方法选泵,既能保证油井的产量,又能明显地提高单螺杆泵整套装置的效率,还能延长泵的使用寿命。     

单螺杆泵的性能评价指标及其影响因素分析

首先分析了单螺杆泵转子与定子截面骨线、等距曲线的方程,依据丁晴橡胶摩擦磨损理论,提出以过流面积、固定接触点最大综合曲率、流动接触点最小相对滑动速度、变幅系数作为单螺杆泵的性能评价指标体系,分析了结构参数对单螺杆泵性能指标的影响,发现设计时各性能指标不能同时最优,必须采用化设计理论对单螺杆泵结构进行优化设计。     

抽油机井无泵效问题的认识

抽油机井泵况是描述油井是否正常生产的重要资料。几年,因为无泵效造成抽油机井检泵率呈逐年上升趋势。本文通过总现场的工作经验,结合示功图、沉没度、产液量、含水、电流、压力等多生产数据,对可能产生无泵效的原因进行分析。使对无泵效井的检查处理有的放矢,同时提出针对无泵效问题的预防性措施。     

海上平台泵改造策略研究

在海上油田开发中,当新油田依托已建平台进行开发,即涉及到对原有设施进行能力的升级和改造。其中,对平台主要工艺泵的改造属于较为普遍和常见情况。本文将通过海上番禺4-2油田外输泵改造的实际案例,对平台泵改造的策略和措施提供借鉴及良好思路。     

化学工业用无密封泵的选择

文章通过介绍化工用泵的密封技术,分析有无密封泵的利弊,提出使用无密封泵的要求,从而使其能够更好地满足工业生产的需要。     

长距离输水泵站水泵泵型的选择

文章结合实际对长距离输水泵站水泵泵型的选择进行分析,比较了几种泵型的优缺点,为实践中长距离输水泵站的选择着重分析了单级双吸中开式离心泵干室式泵房布置和潜水排污离心泵湿室式泵房布置的方案,并分析了各自的适用奈件。     

螺杆泵的选择、使用中的问题研究

伴随着螺杆泵举升方式应用规模的日益扩大,常规地面驱动螺杆泵装置存在合理选用的问题:螺杆泵的合理选用、带泵电机的合理选用等。如果选用不当,会造成电机和螺杆泵的效率下降、能耗过大;存在安全隐患等问题。     

浅谈刀具合理几何参数的选择

刀具的几何参数的合理选择直接影响刀具寿命、加工质量、生产效率及加工成本,文章讨论了刀具的前角及前刀面形状、后角及后刀面、主偏角,副偏角及刀尖形状、刃倾角的合理选择原则。     

浅析液压系统中高压双泵保压的合理设计潜力

本文根据两种高压双泵保压设计方案,经过分析、对比,说明在设计上有降低制造成本、提高系统效率、延长系统使用寿命等方面的潜力与优势.     

东辛油田螺杆泵故障分析及改进

简要论述了东辛油田螺杆泵应用情况,针对生产过程中出现的主要问题,仔细分析了故障原因,并提出改进措施,现场应用效果良好。     

Street-lighting projects selection: A rational decision making approach

The study presented in this paper represents a new and fresh approach to the problem of efficiently and optimally allocating scarce resources in the provision of public services—namely, street-lighting. The methodology developed is aimed at introducing more systematic and rational thinking in a way which is both technically and politically feasible. To the best of the author's knowledge, the study presents, for the first time, a procedure for the comprehensive quantitative estimate of the utility accruing from street-lighting. The utility value derived from each street-lighting project depends upon several factors, some of which can be technically assessed and others estimated only by subjective values.

In order to deduce the subjective values, the Delphi method was employed. This method permits derivation of subjective values for groups of interviewees whose assessments may reasonably be assumed to be crucial in determining the relative values of the objectives of the utility function. Those components of the utility function representing subjective values were identified and estimated.

The conventional practice, whereby residents have no explicit say in the planning of the lighting system in their city, was abandoned. Residents' value judgements concerning the relative importance of the objectives to be gained by the lighting system were incorporated into the planning process. An optimization model based on an integer programming algorithm was employed because it permits periodic (e.g. annual) selection of a set of indivisible projects to be realized during a given period. This enables maximum economic and social utility to be derived, subject to budgetary and technological constraints.

The selection process was extended and deepened so as to render it sensitive to benefit from economies of scale and external economies. The optimization process was carried out with the use of an IBM-MPS X (an integer programming algorithm). The methodology was applied to a large and diverse quarter in the city of Jerusalem that is divided into seven semi-homogeneous neighborhoods—in terms of their physical as well as their socio-economic and demographic characteristics. This represents a very different approach when compared to the conventional way in which the planning design and installation of street-lighting projects are currently carried out.     

10kV配电变压器保护配置的特点及合理选用

10kV配电变压器的保护配置,主要有负荷开关、负荷开关加高压熔断器组合或断路器等。文章主要对10kV配电变压器的保护配置方式进行比较分析。     

Estimation and model selection based inference in single and multiple threshold models

This paper evaluates the properties of a joint and sequential estimation procedure for estimating the parameters of single and multiple threshold models. We initially proceed under the assumption that the number of regimes is known á priori but subsequently relax this assumption via the introduction of a model selection based procedure that allows the estimation of both the unknown parameters and their number to be performed jointly. Theoretical properties of the resulting estimators are derived and their finite sample properties investigated.     

Patterns of rational default

In this paper, we move closer to the interests of empirical research by providing the entire distribution of default’s severity, not just a summary total. The total price of a mortgage’s default option already provides a rough summary statistic of the unconditional expected severity of default, but as will be seen, distributions of severity are both disperse and skewed and so inadequately described by even their conditional means. The results make it clear that the likelihood of default and the likely magnitude of that default must be treated as separate phenomena.     

暖通空调节能减排与热泵技术应用研究

随着现代建筑向着舒适化的方向发展,中央空调系统已经成为现代建筑技术中的重要标志,但其能耗巨大的特点迫使人们寻找相应的节能减排技术,并积极寻找新的能源。     

Identification of rational expectations models

This paper deals with the problem of the identification of simultaneous Rational Expectations (RE) models. In the case of RE models with current expectations of the endogenous variables, the necessary and sufficient conditions for the global identification are derived explicitly in terms of the structural parameters and the linear homogenous identifying restrictions. It is shown that in the absence of a priori restrictions on the processes generating the exogenous variables and the disturbances, RE models and general distributed lag models are ‘observationally equivalent’. In the case of RE models with future expectations of the endogenous variables, a general solution that highlights the ‘non-uniqueness’ problem and from which other solutions such as forward or backward solutions can be obtained, is derived. It is shown that untestable and often quite arbitrary restrictions are needed if RE models with future expectations are to be identifiable. Certain order conditions similar to those obtained for the identification of RE models with current expectations are also derived for this case.     

浅谈电力变压器的分类与选用

电力变压器是电网中最重要的电气元件之一。变压器容量的科学配置和可靠运行,对用户供电的充裕度、经济性和可靠性有着关键性的影响。同时,变压器的选型、配置及运行容载比也从根本上影响着供电企业投资收益水平。文章从变压器历史分类、选用、参数选择与配置三个方面对变压器进行概括性论述,可为科学选配变压器提供理论参考。