Coulomb Control of Polygonal Linkages

Equilibria of polygonal linkage with respect to Coulomb potential of point charges placed at the vertices of linkage are considered. It is proved that any convex configuration of a quadrilateral linkage is the point of global minimum of Coulomb potential for appropriate values of charges of vertices. Similar problems are treated for the equilateral pentagonal linkage. Some corollaries and applications in the spirit of control theory are also presented.     

Linkages between oil price shocks and stock returns revisited

In this paper, we revisit the debate on the relationship between oil price shocks and stock market returns by replicating the quantile-on-quantile (QQ) regression model for the US stock market in Sim and Zhou (2015, Journal of Banking and Finance), and extending it to 15 countries. The classification of these countries as oil importers or oil exporters depends on their net position in crude oil trade. Our results indicate that the main finding by Sim and Zhou (2015) that large negative oil price shocks can bolster stock returns when markets are performing well is only partially supported by the three largest oil importers in our sample – China, Japan and India – during the period 1988:1–2007:12. However, when extending the study to more recent data (period 1988:1–2016:12), we find that China and India experience higher returns when markets perform well and there is a large positive oil price shock. Also, large positive oil price shocks often lead to higher stock market returns when markets perform well for both oil exporting countries – Canada, Russia, Norway – and moderately oil dependent countries – such as Malaysia, Philippines and Thailand. In most cases large negative oil price shocks depress further already poorly performing markets, as in Sim and Zhou (2015). These findings highlight that the relationship between the distributions of oil price shocks and stock market returns is not stable over time in most countries studied. Furthermore, the asymmetric effect between positive and negative oil price shocks observed in the US market by Sim and Zhou (2015) is less evident in most countries for both the baseline and extended periods.     

Linkages among energy, agriculture and environment in rural India

The interconnections between energy, agriculture and environment in rural India are analyzed in this paper using a systems perspective. Rural areas of developing countries use biomass for fuel, fodder, fertilizer and other purposes, and it is necessary to understand the fuel-fodder–fertilizer relationships for optimal biomass allocation. The allocation is explored using a linear programming model. First, the model is validated by simulating it using data for the year 1990–1991. The model is then applied for the year 2000, and several scenarios are generated to obtain answers to various policy questions. The results show that it is necessary to increase fertilizer consumption, to increase efficiencies of cooking stoves, to improve livestock feed, and/or to decrease population growth for maximizing the revenue generated in the rural system of India. It shows that when the prices of fertilizers increase, a large increase in kerosene requirements can be expected. It also points to the necessity to increase kerosene consumption to reduce emissions (due to non-commercial fuels) and soil fertility loss. For example, the carbon dioxide emissions associated with the scenarios range from 137.50 to 62.50 million tons (in carbon equivalent terms) for the high and low cases, respectively. Correspondingly, kerosene consumption ranges from 0.18 to 15.49 kilotons (kT).     

Energy for sustainable development in India: Linkages and strategic direction

In recent times the two major international endorsements of the elements of sustainable development the Millennium Development Goals (MDGs) and the World Summit on Sustainable Development (WSSD), have recognized universal access to energy as an important goal. In India, with a population of over a 1000 million people, it is estimated that a mere 43.5% of the households have access to electricity. The choices that the country makes towards energizing the remaining population will have a significant impact on other Sustainable Development parameters such as agriculture, water, health, and even biodiversity. India has set itself a target, going beyond the MDGs, of energizing all households by the year 2012. In view of the differentiated responsibilities of the various ministries to the Government of India, the strategy for reaching this target may not address itself to the larger development goals.     

折线形坝轴线重力坝地震动力反应分析

以某折线形坝轴线碾压混凝土重力坝为工程背景,基于有限元软件ADINA进行重力坝全坝段三维有限元时程动力分析,研究了该重力坝的抗震性能,确定了坝体抗震的薄弱部位。结果表明,该折线布置重力坝的动力反应规律与一般重力坝基本相同,但左岸转折后的岸坡坝段横河向动力反应较大,转折处楔形坝段上游面出现较为显著的坝轴线方向拉应力,应采取一定的抗震措施确保转折处楔形坝段的抗震安全性。     

电渗过程中电极与土体间电荷积累问题研究

电渗过程中的电荷积累现象是电极和土体界面间存在电压降的主要原因,将电荷积累区域视为一特殊电容器,模拟了土与电极界面间的电容效应,推导了界面电容与土体电阻串联后土体中的电压降、电容间距和孔隙水压力,通过圆柱形电极和电极板试验,验证了界面电容假设的合理性,同时指出随着电渗的进行,电荷积累增多,电压降增大,且圆柱形电极形成的电容大于电极板形成的电容。     

撒多水电站~#3机组主轴折线的调整

由于加工、运输、现场装配等原因,立式水轮机组主轴轴线很容易产生折线,导致水导轴承处的摆度不在规范之内。通过对撒多水电站#3机组主轴进行盘车,发现该轴线形成了折线,且水导轴承处的摆度值不在规定范围之内。利用现场所得盘车数据,计算得出水轮机轴和发电机轴的连接法兰处的刮削值,通过刮削该法兰,使联轴后的上导、下导和水导处的摆度值满足现行规范要求,并对卡环进行了刮削处理,减小了水导处的摆度值,达到了减小该机组震动的目的。     

Unstructured Polygonal Finite-Volume Solutions of Radiative Heat Transfer in a Complex Axisymmetric Enclosure

Radiative heat transfer in a complex axisymmetric enclosure with participating medium is investigated by using the finite-volume method (FVM). In particular, an implementation of the unstructured polygonal meshes is adopted by connecting each center point of the unstructured triangular meshes rather than joining the centroids of the triangular elements to the midpoints of the corresponding sides to form a polygonal element. Also, typical considerations regarding application of the present polygonal mesh system to axisymmetric radiation are discussed. After a mathematical formulation and corresponding discretization equation for the radiative transfer equation (RTE) are derived, the final discretization equation is introduced with the conventional finite-volume approach by using the directional weights. For validation and comparison, three test examples with complex axisymmetric geometries have been accomplished. The present study shows that not only is the method flexible in treating radiative problems with complex geometries, it is also accurate and efficient for the analysis of axisymmetric radiative heat transfer.     

不同施工顺序对深厚覆盖层坝基折线型防渗墙应力变形的影响

鉴于施工顺序对防渗墙应力变形影响很大,以折线型防渗墙为例,运用有限元模拟了两种防渗墙的施工顺序,对比分析了竣工期和蓄水期的防渗墙应力变形规律。结果表明,防渗墙在转折处存在一定的拉应力;推迟防渗墙施工能够有效减小防渗墙大主应力、竣工期顺河向位移量,但将增大蓄水后防渗墙的顺河向位移量。     

含蜡原油凝点和倾点的实验研究

凝点、倾点是以温度表征原油低温流动性的条件性指标,是影响管输安全性和经济性的关键因素。中国一直以凝点作为控制原油输送温度的一个重要参数,而国际上普遍采用倾点。着重对含蜡原油凝点和倾点进行对比实验研究。     

Performance Analysis of a Heat Pipe Heat Exchanger Under Different Fluid Charges

An experimental study was conducted on the effects of the amount of working fluid on the performance of a two-row copper-R134a heat pipe heat exchanger at the air side. The heat pipe heat exchanger operates in the horizontal configuration, and five different fluid charges were studied to cover the underload and overload cases. Moreover, the calculated outlet temperature of the evaporator side, obtained from the heat exchanger simulation, was compared with the experimental results. Based on the present study, it was found that the optimum performance of the copper-R134a heat pipe heat exchanger can be achieved at a fluid charge slightly exceeding the amount required to saturate the wick.     

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窗外朔风凛冽。冰冻已三尺。中国的北方正值数九隆冬——这本正常。然而,本“无”冬天的南国却屡遭寒流的侵袭;在遥远的太平洋彼岸,在欧美,同样不能幸免。全球正无可奈何地接受着因地球生态环境的进一步恶化而导致的极端天气的惩罚。     

开水锅炉沸点的一种测控方法

利用时间和温度的关系测控开水锅炉的沸点,取得了良好的效果。     

积极运用需求侧管理降低电费支出--对两家工业企业优化用电方式降低电费成本的剖析

对两家工业企业用电费用过高进行了详细分析,并提出了优化用电方式,提高电效,降低单位电价、节省电费开支的办法.     

倒闸操作的危险点分析及异常处理

针对倒母线操作中的危险点,分析了倒母线操作中的技术关键点及注意事项,提出了相应的防范措施。实际应用表明,防范措施有效。     

蒸汽蓄热器设计要点及案例分析

为提高蒸汽蓄热器设计质量,从基本结构和工作原理入手,对其设计选型过程中涉及的诸如蓄热容积、蓄热量、喷头数量以及充、放热特性等参数进行分析.在此基础上,对闪蒸量为54 t/h的蒸汽蓄热器进行设计计算,所得结果可供特殊试验目的用蒸汽蓄热器的设计作参考.     

点聚焦太阳炉设计方法与研制实践

从聚光原理、光学计算、硬件设计,到安装与调试,详细介绍了点聚焦太阳炉的研制过程。根据当地用户的需求和太阳能资源,通过自行设计的光学软件,计算出典型日一次反光定日镜在二次聚光器截光口平面上的照射情况、二次聚光器的最佳焦距以及焦平面焦点处的峰值热功率。模块化设计的一次反光定日镜,不仅降低了制造成本,提高了生产效率,简化了一次反光定日镜的整体支架,同时给运输和安装带来了方便。单元反光镜反光面采用12点支撑,为定日镜的单元镜面调平创造了条件。同样采用模块化设计的二次聚光器,有利于制造成本的降低,方便运输和现场安装。反光镜单元面型可调,大大增强了点聚焦太阳炉参数的适应性。通过样机研制,验证了设计方法的可行性。     

Point source in weak shear flow

This note is an analytic study of the temperature field due to a point heat source placed in a two-dimensional shear flow. The governing three-dimensional equation is perturbed using a small shear parameter. The resulting successive partial differential equations are further reduced into ordinary differential equations by utilizing a proper mixture of Cartesian and polar coordinate variables. The results show the isotherms are skewed towards the lower velocity regions. In certain cases a second temperature maximum may appear on downstream planes perpendicular to the flow.