Numerical forecasting surge in a piping of compressor shops of gas pipeline network

This paper presents a method of forecasting stable operation of gas compressor unit (GCU) centrifugal supercharger (CFS) installed on a piping of compressor shops servicing gas pipelines. The stability of superchargers operation is assessed in relation to the phenomenon of surge. Solution of this problem amounts to the development and numerical analysis of a set of ordinary differential equations. The set describes transmission of gas through a compressor shop as a fluid dynamics model with lumped parameters. The proposed method is oriented to wide application by specialists working in the gas industry. The practical application of this method can use all-purpose programming and mathematical software available to specialists of gas companies.     

Numerical simulation of a gas pipeline network using computational fluid dynamics simulators

This article describes numerical simulation of gas pipeline network operation using high-accuracy computational fluid dynamics (CFD) simulators of the modes of gas mixture transmission through long, multi-line pipeline systems (CFD-simulator). The approach used in CFD-simulators for modeling gas mixture transmission through long, branched, multi-section pipelines is based on tailoring the full system of fluid dynamics equations to conditions of unsteady, non-isothermal processes of the gas mixture flow. Identification, in a CFD-simulator, of safe parameters for gas transmission through compressor stations amounts to finding the interior points of admissible sets described by systems of nonlinear algebraic equalities and inequalities. Such systems of equalities and inequalities comprise a formal statement of technological, design, operational and other constraints to which operation of the network equipment is subject. To illustrate the practicability of the method of numerical simulation of a gas transmission network, we compare computation results and gas flow parameters measured on-site at the gas transmission enter-prise.     

对变分问题的灵密度分析

考虑变分问题的灵密度分析,利用扰动法推出边界值问题和流动方程,以此来获得偏导数（灵敏性）的目标函数的所有参数。主要考虑参数系变分问题的灵密度分析,当参数产生改变时,它相应的最优解是如何随之而改变的,为了问题简单,开始考虑有限维参数的变分问题,最后定理4给出灵密度分析的一个固定公式,这个结果利于直接通过原始的目标函数关于参数P分析灵密度。     

直埋供热管道双层折角的应力分析

针对直埋供热工程中管道折角处易发生应力集中和变形而导致管道破裂泄漏的问题,提出一种新型双层折角结构。通过有限元方法,对比新型双层折角与普通折角的应力最大值和应力分布,分析外套管壁厚、肋片高度、管土摩擦系数对双层折角应力最大值的影响。结果表明:新型双层折角能有效降低折角的应力最大值,且折角角度越大,应力值降低效果越好;新型双层折角能适用于各种土壤环境,即使管土摩擦系数较小,也能很好地保护折角。研究结果可为实际工程中直埋折角的强化和大角度折角的敷设提供参考。     

High-order lateral buckling analysis of submarine pipeline under thermal stress

It is of importance to study and predict the possible buckling of submarine pipeline under thermal stress in pipeline design.Since soil resistance is not strong enough to restrain the large deformation of pipeline,high-order buckling modes occur very easily.Analytical solutions to high-order buckling modes were obtained in this paper.The relationships between buckling temperature and the amplitude or the wavelength of buckling modes were established.Analytical solutions were obtained to predict the occurrence and consequence of in-service buckling of a heated pipeline in an oil field.The effects of temperature difference and properties of subsoil on buckling modes were investigated.The results show that buckling will occur once temperature difference exceeds safe temperature;high-order pipeline buckling occurs very easily;the larger the friction coefficients are,the safer the submarine pipeline will be.     

考虑能量方程影响的燃气管道流动特性分析

采用特征线法对高压燃气长输管道非稳态流动的数学模型进行了数值求解,考虑能量方程和城市用气规律,对燃气管网非稳态流动问题从理论上进行了分析,解决了由于忽略能量方程所带来的计算精度低的问题,编制出了用户负荷随时间变化时,压力、温度、流量沿管线分布的动态模拟程序,并给出了计算实例.     

关于凸分析问题的两个注记

指出凸分析问题的两个定理（凹规划定理和对偶定理）的证明中所存在的漏洞,并给出正确的证明．首先,将凸集的端子集的概念推广到一般集合的端集,再利用推广后的端集正确地证明了凹规划定理．其次,给出局部凸空间的一个引理,并利用这个引理证明了共轭函数的对偶定理．     

Numerical analysis of buried pipe characteristics

Voluminous statistical data on the breakage and leakage of pipelines occurring frequently in water supply and drainage engineering, were collected and analyzed to find the causes and solutions for the breakage and leakage. Then the original parameter method of foundation beam on elastic semi-infinite plane subgrade was applied to verify the statistical results. Numerical computational results showed that the performance of the original parameter method of foundation beam was satisfactory. Project supported by Zhejiang Province Science & Technology Foundation for Construction.     

多层柔性海底管道隆起屈曲有限元分析

由于海床不平整以及高温服役条件,多层海洋柔性管道容易发生隆起屈曲。利用大型商业有限元分析软件ANSYS,建立多层柔性管道有限元模型,分析管道内液体温度、压力及埋泥深度3种因素对多层柔性管道隆起屈曲程度的影响。分析结果表明:对于多层柔性管道,管道内液体温度越高,管道隆起高度越高;管道内输送的液体压力升高将限制管道的隆起;埋泥深度越深,越限制管道的隆起。研究工作和分析结果可为海底管道铺设提供理论依据和设计参考。     

浅析我国的法律移植问题

自改革开放以来,中国法律制度建设日趋完善.在这个发展过程中,法律移植起到了不可忽视的促进作用.本文对法律移植的意义、实质等进行探讨,在此基础上提出:在法律移植过程中应注意国外法与本国法之间的同构性和兼容性,做到有选择地移植;移植过来的法律还要面临一个"本土化"的过程;移植法律的同时必须注意植入与之相适应的法律精神、意识和观念.从而迅速缩小与发达国家的差距,促进我国法制的现代化.     

择校问题的理性分析

择校作为一个相对较新的事物,能够出现并且有很大的发展,说明有其存在的合理性。教育公平是择校问题出现的基础,成本和收益是家庭进行择校的重要依据,供给和需求是学校选择出现的重要原因。缓解择校问题,可以从促进学校的多样化、政府通过财政支持消除教育的不平等、转变教育管理机构职能等方面入手。     

《汉语语法分析问题》评介

吕叔湘先生是国内外享有盛名的语言学家,他也是近代汉语语法研究的创始人。本文主要是对吕叔湘的《汉语语法分析问题》进行介绍并对其结构特点进行剖析,同时指出其鲜明特点、价值地位及不足之处。     

泉州家族企业管理问题分析

我国民营企业是我国国民经济中一支重要支撑力量,家族式企业又是民营企业的重要组成部分。泉州民营经济的"泉州模式"是我国民营经济三大典范之一。研究泉州家族企业发展中的问题对加强和深化改革现代家族企业管理论具有重要的意义。     

西安市城区通风环境数值建模及分析

近年来,城市建筑的高度和密度不断增加,对城市通风环境产生了很大影响。针对西安市绕城高速以内区域,建立了城区建筑、道路等几何模型,在此基础上建立了城市风环境数值仿真模型。通过数值仿真,分析了在冬季主导风ENE风向下,区域风环境的现状,包括风速分布、通风能力等。研究表明,建筑布局、街道布局、建筑密度和风向会对区域风速分布及通风能力有明显影响。控制城市内十字路口处建筑高度及建立城市主导风向上通风廊道有利于城市内的通风。     

凝华结霜导热系数数值计算分析

用数值计算方法,验证了作者本人提出的水蒸汽凝华结霜过程中在冷壁面上形成的霜层的导热系数表达式,并将结果与前人的实验数据进行了比较分析,取得了较好的吻合性,增强了导热系数理论表达式的实用价值.     

An analysis of global problem issues in sixth-and seventh-grade textbooks

The study examines the extent to which the global issues of population growth, world hunger, air quality and atmosphere, and water resources were treated in sixth- and seventh-grade science textbooks. Ten textbooks were examined by five raters to determine the amount of content presented by different textbooks on global issues, the number of pages of content devoted to each issue, and the degree of depth in which issues were treated. Differences between grade levels were also explored. Of the 4,393 pages of content analyzed, less than 2 percent was devoted to these issues identified as the most serious human problems. No significant differences were found between textbook series. Significant differences were found in the number of pages of content presented on each issue. Most of the content fell into the categories of water resources, population growth, air quality, and atmosphere. The issue of war technology had the least amount of content. Distribution of content did not vary by grade level. Both levels addressed the issues of population growth, air quality, and water resources with a greater degree of depth than the issue of world hunger or war technology. The study concludes that the most widely used textbooks at the sixth- and seventh-grade levels avoid serious discussion of major global problems. And like the career indecision of a recent Miss America contestant, purchasers don't seem to be able to decide whether they want science textbooks to be “a brain surgeon or a movie actress.” Implications stemming from this dichotomy and its relationship to future science education curricular are also explored.     

技能大赛赛题风险问题分析及建议——以BG赛项为例

本文以2014年全国职业技能大赛BG赛项赛题涉嫌过度披露商业信息为例,介绍该赛题的主要内容,指出其存在的侵权风险,并分析产生原因,建议在严格遵守全国职业技能大赛赛项赛题管理办法和赛程的前提下,对真实的案例选取应该获得相关企业的授权,对没有获得授权的真实的案例应该进行改写,赛题须法律顾问审核等建议。     

一类热传导方程移动边界问题的数值求解

给出了数值求解具有多层区域热方程移动边界问题的算法,算法是基于有限差分格式的,给出处理界面条件和曲边的方法,分析并且给出了最佳的处理方案;最后用数值例子说明我们的方法具有较高的精度.