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1.
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
2.
Around
the design of air flow and distribution about the laminated air conditioning in summer in
the powerhouse of Sanxia hydropower station, the system division, air flow pattern, air
supply state and volume etc have been analyzed separately. Based on the existing domestic
achievements, the relative calculation model has been established and the application
method has been explored. From this the program named as AFDC/LACS has been compiled with
language FORTRAN77 and the calculation on the airflow and distribution of the place
mentioned above has been done with several design conditions. Thus some batches of the
technical parameters have been provided to plan the test conditions in the heat simulated
test.. 相似文献
3.
银杏树体茎流变化及其对环境因子的响应 总被引：2，自引：1，他引：2
为了动态地掌握银杏的蒸腾耗水规律，并揭示其生态、生理作用机理，采用热扩散式液流探针（TDP）监测银杏树体不同生长阶段的茎流变化，并通过气象站同步测定环境因子参数。结果表明：在典型的晴天、多云、阴雨天气下，银杏树干茎流的日变化差异显著，日累积茎流通量为晴天>多云天气>阴雨天气；银杏茎流的季节变化趋势呈现为先上升后下降的态势，在新梢生长期的蒸腾耗水量最大，日耗水量可达23L左右。在叶速生期、新梢生长期和叶黄期银杏日蒸腾耗水量的波动明显，其中以新梢生长期最为显著，日间差异最大可达20L。以各阶段日均耗水量来估算，12年生银杏年耗水量大约为2580L；银杏在年生长周期中茎流通量的变化趋势与气温、土壤湿度、土壤温度、相对湿度、光合有效辐射以及降雨量的季节变化趋势基本一致，逐步回归分析表明银杏年生长周期中大气温度是茎流最为主要的影响因子，回归方程达到极显著水平。 相似文献
4.
气象要素对浅层土壤水分影响的灰色关联分析 总被引：2，自引：2，他引：0
为深入研究呼和浩特市土默特左旗作物生长期,气象要素对土壤水分的影响,利用2012年4—9月土默特左旗气象站连续观测的有关数据,采用灰色关联分析方法,分析有降水天气和无降水天气条件下,日平均风速、日平均地面温度、日平均气温、日平均相对湿度4个气象要素对日10 cm土壤水分的影响。结果表明,有降水天气,各气象因素重要性排序为：日平均风速＞日平均相对湿度＞日平均气温＞日平均地面温度;无降水天气,各气象因素重要性排序为：日平均相对湿度＞日平均风速＞日平均气温＞日平均地面温度。研究表明,不同天气条件下,同一气象因素可能对同一层土壤水分的影响程度不同。因此,关注土壤水分的变化,应根据天气条件的不同,进一步深入细致的研究影响的主要因素及影响程度,以便更好地掌握土壤水分变化的规律,有效利用土壤水分资源。 相似文献
5.
The influence of initial internal structure of coal sample on gas flow characteristic 总被引：1，自引：0，他引：1
Three kinds of coal samples with different components are chosen as study objects.Density calculation and SEM are adopted to study their internal structures,and a self made triaxial gas seepage instrument is used to study their internal gas flow characteristics.The results show that internal structures of coal samples made of different particle size coal powders under identical external conditions are various,and nonlinearity is presented on the influence caused by fabric.Gas flow characteristic is complex in complete stress strain process,generally it firstly increases and then decreases,initial gas flow velocity is lower than the one after the failure of coal sample,and obvious hysteretic nature of gas flow characteristic is showed.The influence of gas flow characteristic caused by initial internal structure of coal sample is nonlinear and the stress sensitivity is high on the influence of gas flow characteristic caused by initial internal structure.The more complex the initial internal structure of the coal sample is,the lower the axial tress sensitivity is,and the higher the confining pressure sensitivity is. 相似文献
6.
In order to analyze the reason why the Spiral Up-flow Reactor system has excellent removal effect of COD, N and P, the authors use PHOENICS, a computational fluid dynamics program, to investigate the hydraulic characteristics and flow model of the anaerobic part of Spiral uP-flow reactor. The result shows that the fluid in the reactor unit flowed upward by the spiral way, and that flow pattern was combined by plug flow and complete-mix flow, and that the percentage of plug flow was about sixty-five percent. Spiral Up-flow Reactor units the Characteristics of PFR and CSTR, which makes it work well. 相似文献
7.
Tests are carried out on the filtration and organized forms of pure water flow and pond water flow using two kinds of flow channel porous ceramic membrane. Results show that for the two kinds of porous ceramic membranes, their removal efficiency of turbidity degree, chroma, CODMn and UV254 are nearly the same. The filtering quality of fan-channel porous ceramic membrane is better than that of circular-channel porous ceramic membrane, and the filtration flux of the former is 1.45 times the flux of the latter. 相似文献
8.
为掌握适合鱼类生长的水流条件,对国内外现有的鱼类在不同水流条件下的行为特征及生理代谢进行了系统性的回顾,分析了水流对水质的影响,对比了不同鱼类受水流刺激导致的行为上的差异,并从鱼类生理代谢角度分析了水流对鱼类的影响。结果表明：鱼类能够承受的最大流速一般与体长(Body length, BL)有关,较低的水流速度(<0.5 bl/s)对鱼类无显著性影响,较高的水流速度(>2 bl/s)对鱼类的行为、存活率和生理代谢产生较大的负面影响,而中等的水流速度(0.5～2 bl/s)适合鱼类的生长,能够提高鱼体免疫力,增强鱼体抗氧化水平。针对当前鱼类耐受流速的研究进行展望,从实验角度进行优化,以期获得更加准确的生长-流速曲线。 相似文献
9.
Chen Jingqiu 《保鲜与加工》1988,(6)
The Bicharacteristics-Method for unsteady, compressible and inviscid flow has been developed in four . dimensional time-space. A new shock-tracing has been presented. A successful numerical solution for reflexion and focusing of a shock has been made. 相似文献
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12.
ZHANG Fu- ren 《保鲜与加工》2007,(2):103-109
Through analysis on the process of unsteady leakage of gas pipeline,the calculating model of unsteady leakage rate has been established.According to the variable characteristic of unsteady leakage ratio,based on the differential equation of on-flow diffusion,and combining the relevant original and boundary conditions,the diffusion model of unsteady leakage of gas pipeline has been established.Based on the practical application,all of the dangerous areas have been discussed and analyzed.The damaging and destroying areas have been calculated under definite conditions.This will provide safety standards and references for confirming and formulating the safety distance for the important buildings(school etc.) apart from the long high-pressure gas pipeline and main gas pipeline in city.At the same time,this will provide guarantee for reducing the dangerous degree,when accidents happened. 相似文献
13.
渗透系数是控制地下水流动的重要参数,对渗透系数的空间分布规律进行研究具有重要的意义。基于Gardner模型获取了一维稳态流非饱和土渗透系数沿垂直分布模型,该模型用指数函数描述,受饱和渗透系数和无量纲的深度与流动率等因素的控制;该模型表明一维稳态流条件下均质典型土类的渗透系数其沿垂直方向变化趋势主要受比流量与饱和渗流系数的负数值二者之间的相对大小影响。分别采用泰勒级数方法和以地下水位处及地表处的渗透系数作为控制条件方法对一维稳态流非饱和土渗透系数沿垂直分布模型进行线性近似简化。采用泰勒级数方法获取的简化模型其计算误差随无量纲的深度增大而增大。简化后的模型具有形式简单、参数少等特点。通过算例对比简化模型与原模型的差异,计算结果表明:采用以地下水位处及地表处的渗透系数作为控制条件的方法进行线性近似简化的模型计算误差比采用泰勒级数方法获得的线性近似简化模型的计算误差小。 相似文献
14.
Tongkou power station is an all-round hydro project,where the mixed exploitation mode is adopted with mainly for power generation.Integrated with the model test result,the duct discharge capacity and flow coefficient in various discharge hole are discussed,the influence of duct shape on inlet pressure,energy dissipation and tail water is analyzed,the improvement measures on conveyer way pressure and energy dissipation are put forward too.The achievements of this study have been adopted by the designers. 相似文献
15.
应用臭氧—活性炭联用技术处理食品厂废水的探究 总被引：3，自引：0，他引：3
采用臭氧—活性炭联用技术对食品厂废水进行处理,并对臭氧处理时间,臭氧浓度,处理水的流量等因素进行不同水平单因素实验,以找出最佳实验条件,同时结合实际问题,采用L9(34)正交表进行3因素3水平实验,最终得出臭氧—活性炭联用技术处理食品厂污水的最佳工艺条件为:臭氧处理时间为30min,臭氧质量浓度为9.6mg/L,水流量为0.8m3/h。在最佳工艺条件下,臭氧—活性炭结合工艺对COD的去除率为89.8%,对UV254的去除率为97.3%,达到了农田灌溉水质(水作和旱作的灌溉)标准,基本达到蔬菜灌溉用水的标准。 相似文献
16.
Large amounts of wastewater containing heavy metal ions are discharged into the surrounding,which can't be degraded but only be changed in their forms or transported,diluted and accumulated in the human organisms,so it has serious impact on the health of living things.In order to dispose the wastewater containing many kinds of heavy metal ions,in this experiment,ferrite was adopted to deal with the wastewater containing irons,taking the wastewater of Yunnan Chihong zinc & germanium Co,Ltd as the raw materials.The result shows that the temperature,stirring rate and pH all affected the effect of treatment.A best condition for treatment of the waste water containing heavy metal treatment has been obtained by this experiment. 相似文献
17.
Use of diploid self incompatible rose genotypes as a tool for gene flow analyses in roses 总被引：1，自引：0，他引：1
A diploid rose genotype previously found to be self incompatible in greenhouse pollination experiments was analyzed in order to investigate the capacity to self fertilize under field conditions. A subset of 36 plants from open pollinations were analyzed by means of AFLP markers. All plants were found to be the result of outcrossing events, thereby demonstrating the utility of these kinds of rose genotypes as effective pollen sinks for future gene flow analyses under field conditions. Furthermore, it was demonstrated that isolation distances of 250 m from large rose plantations are insufficient to prevent gene flow between populations. 相似文献
18.
《Soil Technology》1988,1(4):373-382
For surface water quality modelling all contributing discharges, each with different loads of dissolved matter have to be considered separately. Apart from physical and (bio)chemical interactions, water quality is the result of all inputs, both in volume and mass. For this reason dynamic modelling of water quality is possible only when the processes leading to the temporal variability for each different type of input can be modelled as well.In the Netherlands almost all inland watersheds discharge considerable amounts of groundwater. During storm events however, surface runoff is an important factor even in these flat areas. Other discharge sources to be modelled are channel precipitation and effluent discharges.A dynamic one-dimensional numeric discharge model has been developed for a catchment area in the central part of the Netherlands, with distinct subareas where infiltration or seepage is dominant. Model output is dayly discharge of the three most important discharge components (groundwater discharge, overland flow and channel precipitation) and total catchment outflow.From these components groundwater discharge has been calculated using recorded levels of groundwater and surface water. Because precipitation volumes per day can be computed from meteorological data and surface water area, and effluent discharges usually are well known, overland flow discharge modelling was possible. 相似文献
19.
The transient flow fields of gallgladder bile in vivo are calculated by finite element methods. Computer tomograph, ultrasound B and contrast radiography are applied to determine the moving boundary conditions, The penalty formulation and moving triangle elements have been successfully adopted and be flow fields for axisymmetric Newtonian bile flow have been obtained. The results show that there exists obvions reverse flow at the cross section (Perpendicular to Center axis) and thus forms axisymmetric vartexes inside a contracting gallbladder in vivo,Which well agree with the previous prediction. 相似文献
20.
NPV have been widely applied. A majority of the existing calculating methods of cash flow are the static method or the expectation method. It is more reasonable to regard future cash flow as random variable which has certain probability distribution, which shifts with time. But the research about it has been introduced rarely. Through introducing some kinds of existing methods and considering the feature of Markov method, a dynamic method which is used in solved the distributing of indeterminate feature cash flow is showed. So a new kind of dynamic calculation method about NPV is obtained. The method is applied in the calculation to future cash flow of the certain highway investment project of China. The result shows that this method is feasible, effective. 相似文献