共查询到20条相似文献，搜索用时 15 毫秒
1.
In order to optimize design and operation, it is necessary to calculate accurately hydraulic characteristics large central air-conditioning systems. Simplified Model can not be applied to hydraulic calculation of large pipe network topological structure for its large calculation error. Taking into account the regulating characteristics of terminal branch temperature regulating valve, a direct-return chilled water system is studied, an accurate mathematical model of pipe network hydraulic characteristics has been established and a computer logic algorithm with virtual flow has been given. A direct-return pipe network with ten AHU branches is used as simulation calculation object, the pipe network supply-return water pressure difference is calculated, and also the temperature regulating valve opening and actual flow of each branch are calculated in the condition of different supply-return water pressure difference. The calculated results accord with the natural characteristics of high pressure difference unbalanced for direct-return pipe network. The calculation method can ensure calculation convergence. 相似文献
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In this paper,the reliability calculation models of water delivery pipeline system with setting up communicating tubes are studied by net decomposition method.The calculation results show that the reliability of water delivery pipeline system may be lowered or increased with increment of the communicating tube number,and the influence of reliability variety of tubulation of delivery main pipeline and T branch pipe is a sensitive factor influencing the reliability of the system.Therefore,the research results have the important leading meaning to the design,the choice of subassembly,the construction installation,maintenance management of the water delivery pipeline system,and looking for path with the biggest reliability of the system. 相似文献
3.
Pressure-Dependent Analysis of Water Supply Network Damaged by Earthquake Based on Emitter Model 总被引：2，自引：0，他引：2
When the water supply network suffered earthquake damages, pipeline leaks and bursts may occur. In the period in post-earthquake emergency rescue and repair, the network is supplying water with additional outflow of damages (leaks and breaks), which result in pressure deficient. According to the frictional head loss along the break pipeline, a model with additional emitter at the endpoint of the disconnect pipeline was proposed to simulate the break, which simplifies the modeling of breaks. The pressure-dependent demand relationship was adopted in the process of pressure-deficient hydraulic simulation to avoid node negative pressure. Meanwhile a backtracking and line search procedure was utilized to control the iteration step of pipeline network nonlinear equations, which ensure the global convergence of the hydraulic simulation. The effectiveness of the proposed method was verified by a case study. 相似文献
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There are two main problems in the kinematic analysisof slewing mechanism on hydraulic excavator driven by variable displace-ment pumps with total hp-control when the excavator works and it'spumps get into variable displacement state as well.The first is how todetermine the oil flow in the hydraulic system according to the sum ofthe instantaneous pressure existing both in the slewing motor and in theworking cylinder.The second is how to calculate the driving torqueacting on the mechanism according to the instantaneous pressure existingin the motor.At pressent,the methods used for the kinematic analysisof the mechanism are based upon the assumption of the mechanism to bedriven by the fixed displacement pumps or by the variable displacementpumps with individual constant hp-control.But in these ways,theproblems mentioned above cannot be solved.This paper,on the basisof the variable displacement characteristic of the pumps with totalconstant hp-control,analyses the general kinematic pattern of the slewingmechanism in detail,presents the mathematical model and the numericalmethod used for it's kinematic analysis and establishes the the basis forevaluating it's design. 相似文献
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It is helpful for energy efftciency to use distributed pumps instead of valves to regulate hydraulic balance in a district heating system (DHS). A new scheme of distributed pump-system is presented based on performance comparison of hydraulic regime and power saving of single-heat-source dendritic pipeline networks with regulating valves and/or distributed pumps. Supposing that the new scheme was employed in multi-sources looped-pipe network, theoretical analysis and case study were carried out to evaluate off-design performances including hydraulic self-regulation, supply water temperature stability and power-saving potential. The results indicated that the proposed scheme would contribute to minimizing power consumption, retarding water temperature change, and would be convenient to adjust the quality and quantity independently in the looped-pipe heat supply networks. 相似文献
6.
Branch -like pipeline is a common structure in gas transmission pipeline. In the light of the constituent properties of natural gas branch - like pipeline system, the system can be divided into fundamental constituent units. This paper presents a realistic unsteady flow model consisting of simple models of pipeline units and connecting conditions, boundary conditions and initial condition associated with units by using system analysis method. The solutions in wide sense are obtained by theory of functional analysis and operator series method, Such a method has the properties of both analytical solution and numerical solution methods. When the divided pipeline unit is larger, an intuitive approximate analytical solution may be obtained; while the one is smaller, a more accurate numerical solution may be acquired. Based on this, a general computer program has been developed for this model and solutions have been used successfully in a local natural gas transmission network in Sichuan. It is proved that the model and algorithm proposed in this paper are of the advantages of convenient calculation, high precision, time saving and wide application range by way of analysis and application. 相似文献
7.
When large damage, such as rupture and leakage, occurs in buried pipeline, a steel pipeline extrusion throttle device is applied to crush the pipeline and block the oil flow quickly in a short time. An extrusion model under uniformly distributed radial load is established based on the theory of plastic deformation and the principle of virtual work. The pipeline plastic deformation is analyzed and computed and the pipeline extruding load is obtained. The extrusion of X60 steel tube of 325 mm diameter and 6 mm thickness loaded by indenter of 18 mm width is examined. The load-deformation curve of pipeline extrusion is obtained. The results of the comparison between experimental data and theoretical data show that the model is in good agreement with the experiment. This model can be used to calculate the extruding load of pipelines of different sizes and provide the theoretical and practical reference for urgent repair of pipeline leakage. 相似文献
8.
This paper presents a construction method of square magicsquare and twofold magic square,and describes how to change the cons-truction into a pair of magic square Latin squares.As soon as a pair ofmagic square is constructed,the square and twofold magic square can bewritten.Then the number of the same order twofold magic square willbe infinite if it exists. 相似文献
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A new method to calculate electric values of unsymmetrical open conductorfaults in power systems with variable structures and parameters is proposed. All the fault componentsof nodal voltage or branch current and the equivalent parameters of open port for each sequence net-work can be obtained rapidly. The method presented here is much more understandable in contrast tothose available, and meanwhile the amount of calculations is greatly reduced. Its effectiveness hasbeen verified by numerical examples. 相似文献
11.
Zhang Chuanfu 《保鲜与加工》1990,(1)
The determination of structural parameters of hydraulic lock is interrelated to the speed ratio, the load sustained and its hydraulic working condition. In this paper, main problems and calculation method of matching operation are discussed with illustrating examples. 相似文献
12.
为了研究甘蓝型油菜各农艺性状之间的相互关系,提高油菜新品种的选育效率,对229份DH纯系材料进行农艺性状（包括株高、分枝高度、一次分枝数、主花序长度、主花序角果数、单株经济学产量和单株生物学产量等）的相关性和主成分分析。结果表明,株高、分枝高度、主花序长度、单株生物学产量和单株经济学产量等5个性状偏向于父本,而一次分枝数和主花序角果数偏向于母本。相关性分析显示,株高、分枝高度、主花序角果数、单株经济学产量和单株生物学产量之间均呈现极显著正相关,一次分枝数与株高和分枝高度之间呈负相关。主成分分析可将农艺性状综合为株高因子、一次分枝数因子、主花序角果数因子和分枝高度因子,累计贡献率达90.0%,基本涵盖了农艺性状的全部信息。 相似文献
13.
In this paper, taking the hydraulic mechanism of auto unloading truck as an example, the author discussed mainly how to analyze the movement of mechanism by the optimization method. 相似文献
14.
为了更好地利用花生种质资源进行育种工作,对300份花生种质资源在江淮区域的农艺性状数据进行数理统计,并结合SPSS 20.0软件进行相关性与聚类分析。结果表明:供试花生种质8个农艺性状中,有效分枝数与单株结果数极显著正相关;主茎高与单株生产力极显著负相关;主茎高与单株结果数显著负相关。采用Ward法在平方欧式距离D2=4时,将供试种质材料划分为三大类群。同一类型的种质其地理来源有不同,同一地理来源的种质其类型有不同,同一类型或者同一地理来源的花生种质亲缘关系非最近。江淮区域花生种质资源的农艺性状具有丰富的遗传多样性,本研究结果为江淮区域花生育种工作提供参考。 相似文献
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Equivalent linear system method is the main method of nonlinear structural system random response analysis. While it would generate big error when the results of equivalent linear system method are used to analyze the structural dynamic reliability. Through minimum mean square error principle, general nonlinear system was converted to equivalent Duffing nonlinear system, based on which the structural dynamic reliability was analyzed. The accurate steady state analytic solution of Duffing nonlinear system can be worked out by FPK equation, so it is not only convenient but also accurate to analyze structural dynamic reliability by using the equivalent nonlinear system method. It is also shown that the analysis results of equivalent nonlinear system method presented here is reliable and the calculation accuracy is higher than equivalent linear system method apparently through the example analysis. 相似文献
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Luxikou River is one of shallow waterway in middle reach of Yangtze River.The navigational channal changes with the fluvial process of river. In the meanwhile,the shoals exist at the entrance of Zhigang and Zhonggang branch. It's difficult to maintain the waterway. The depth of waterway is kept upon 3.2 meters,and the carrying capacity of tank barge must be decreaed to pass through.For the demands of constructing the main channel of Yangtze River,the measements for stabilizing and improving must be carried out as soon as possible. 相似文献
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摘要：一直以来,大规格树木的修剪是我们园林绿化美化环节中一个相对薄弱的环节,各地的修剪按以往经验和主观意识进行,缺乏统一的理论依据。近些年来,随着北京地区城市绿化美化进一步发展的需求,对成形的大规格树木进行修剪并制定出一个比较科学合理的方法是摆在我们面前急需解决的问题。本文以国槐、油松、银杏三种树木作为研究对象,对大规格树木的修剪进行探讨,目的在于找出规律及相对合理的理论依据,为今后大规格树木修剪制定操作规范提供帮助。 相似文献
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为了验证AutoCAD在测量苹果砧木枝条解剖结构中的应用,以2年生Y-1苹果矮化砧木植株为试材,实例介绍了用AutoCAD软件测量解剖结构组织长度及面积的方法,通过分别用IPE法和AutoCAD法测量了精确1mm和1mm2台尺的长度,苹果砧木Y-1 1年生枝各组织厚度、不同部位导管及筛管面积,比较了2种方法的精确度及对苹果砧木枝条解剖结构各组织测量值的差异显著性。结果表明,和IPE法相比,AutoCAD法测量精确度较高,且用2种方法测量苹果砧木Y-1 1年生枝横断面各组织厚度及面积的测量值差异不显著。得出,用AutoCAD软件对苹果砧木1年生枝横断面各组织厚度和面积进行测量比用IPE软件更精确、便捷,功能强大,提出用AutoCAD软件测量苹果砧木枝条解剖结构各组织长度与面积是一种值得推荐的方法,可在其他植物组织解剖结构的显微测量中推广应用。 相似文献
20.
对来自于中国黄淮海大豆产区、北方大豆产区和南方大豆产区的316个大豆品种的主要农艺性状进行了鉴定和比较。结果表明,育成品种的分枝数、分枝荚数、单株总荚数明显不及农家品种,而其它性状如主茎荚数、单株粒重、单株粒数和百粒重优于农家品种。以育成品种和农家品种分别所作的相关分析表明,主茎荚数、分枝荚数、单株总荚数均与单株粒数和单株粒重呈显著的正相关;主茎节数与株高、主茎荚数、单株总荚数、单株粒重、单株粒数呈显著正相关;分枝数与分枝荚数、单株总荚数、单株粒数和单株粒重呈极显著或非显著正相关,但与主茎荚数呈负向显著相关;单株粒数与单株粒重显著正相关,百粒重与单株粒重正向显著相关,与单株粒数负相关显著。通过比较和分析,就百粒重、生育期和株高筛选出一些具有极端值的品种,可以用作品种选育的亲本和大豆分子育种如转基因受体或分子标记作图群体的遗传材料。 相似文献