Calculation Method of Hydraulic Characteristics for Direct-Return Chilled Water System

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.     

Analysis of a New Distributed-Pump Scheme Applied in District Heating Network

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.     

Discussion on the Hydraulic Calculation Method of Loop Heating Pipe Network

The authors definitely make out the concept of loop main pipeline, supplying main pipeline and ramiform branch line, as well as the order of their hydraulic calculation. Then they puts forward the principia of how to study out the direction of loop main pipeline and presents the method of making flux initial distribution. The matrix of loop main pipeline hydraulic square dispersion is set up. The node referenced pressure is defined and the equation of how to calculate it is deduced. A software is developed to calculate the loop main pipeline hydraulic square dispersion. The method of calculating ramiform branch margin impetus is given.     

Effect of Initial Hydraulic Gradient on Consolidation of Sand drained Ground Improved by Vacuum Preloading

Because of the existence of initial hydraulic gradient in clay, non Darcy equation with initial hydraulic gradient was modified with classical consolidation theories of sand drained ground.And the approximate solution in the instance of vacuum preloading was presented.Based on this, the effect of initial hydraulic gradient on the seepage front, the pore water pressure and the average degree of consolidation were investigated.It was found that the spread of vacuum pressure was delayed because of initial hydraulic gradient, resulting in the dissipation of pore water pressure and the speed of soil layer consolidation.The hysteresis became more and more evident with the increase of initial hydraulic gradient.In addition, initial hydraulic gradient also caused some residual pore water pressure which could not reach vacuum pressure.Thus, the ultimate average degree of consolidation was less than 100%, which decreased with the increase of initial hydraulic gradient.     

Calculation of Fatigue Reliable Life of Natural Gas Pipeline

Various defects and cracks may be produced in the welding process in natural gas pipeline.Under variable pressure of natural gas,the cracks will be propagated it may lead to break and invalidity.The effect of internal surface cracks are more serious.It has been researched that the propagation along radial direction of internel surface cracks in the natural gas pipeline.The fatig life of pipeline has been calculated.On the other hand,considering the size of cracks, pressure of gas and character of material are random variable,and by using reliability method,the fatig reliable life of pipeline has been determined.This method has some practical value in design, working and overhaul of pipeline.     

The Effect of Short Warm Breaks during Chilling on Photosynthesis and the Activity of Antioxidant Enzymes in Plants Sensitive to Chilling

The effect of short warm breaks (from 15 min to 5 h) during chilling of three chilling-sensitive species (tomato, maize and soybean) was investigated. Injuries, intensity of net photosynthesis and antioxidant enzyme activity were measured. Throughout chilling treatment, plants were warmed by transferring them during the last few hours of the light phase from chilling temperature (5 °C for tomato and maize, 2 °C for soybean) to 20 °C. After warming, seedlings were moved back to chilling conditions. Warm breaks of 5 h almost entirely prevented the appearance of injuries, as measured by changes in leakage of electrolytes and tissue water content, during 12 days of chilling. Even a 15-min warm break ensured a significant decrease in injuries in chilled maize seedlings compared to continuously chilled seedlings. Inhibition of gas exchange and fluorescence in seedlings of two maize genotypes differing in chilling resistance was, to a small extent, prevented by 1-h warm breaks, while 4-h warm breaks reduced inhibition significantly. The length of the warm break (1 or 4 h) had no influence on changes in SOD activity compared to continuously chilled plants, but warm breaks of 4 h produced a significant increase in CAT activity. The possible influence of an alternative pathway in preventing injuries is discussed.     

Assessment of two parameter estimation techniques for the estimation of soil hydraulic characteristics

When Richard's flow equation was solved numerically two parameter estimation procedures were assessed for their applicability in the estimation of parameters of soil hydraulic characteristics, the water retention and hydraulic conductivity functions, and saturated hydraulic conductivity. The estimation procedures assessed were Taylor expansion and Marquardt (1963). The model simulated soil water content and pressure head profiles, obtained with the optimized estimates for the parameters from either method, agreed close with the corresponding measured profiles. Similar trends were observed for the water retention curve. The unsaturated hydraulic conductivities calculated, using the measured values in water content and pressure head agreed with those obtained using the established hydraulic conductivity functions. The results show that the techniques developed in this study were satisfactory to predict sufficiently accurate the hydraulic characteristics required to describe unsaturated flow of water in soil. The techniques appear promising, becuase the auxilliary information, soil water content, required for the estimation of hydraulic characteristics was minimal and relatively easy to collect.     

剪根与水分胁迫对小麦单根和细胞导水率及TaPIP基因表达的影响

剪去小麦部分根系能瞬间打破其水分平衡,研究根系导水特性对剪根的响应有助于解释静水压对作物根系吸水的调节机制。通过对苗期小麦(Triticum aestivum)剪根与水分胁迫处理,用压力探针技术测定单根和细胞两种尺度上的根导水特性变化,以及根中TaPIP1;2和TaPIP2;5的转录调节变化。结果显示,剪根处理或水分胁迫处理使叶片蒸腾速率和气孔导度均显著低于对照,而单根导水率和细胞导水率均与对照无显著差异。剪根处理的叶片蒸腾速率、气孔导度、叶水势、单根导水率和细胞导水率均显著高于水分胁迫处理,而剪根且水分胁迫处理的各参数均显著低于其他处理。各处理的单根导水率与细胞导水率显著正相关。各处理根中TaPIP1;2和TaPIP2;5相对mRNA含量的变化规律与单根和细胞导水率的变化规律相似。剪根处理显著上调了TaPIP1;2和TaPIP2;5转录,水分胁迫处理显著下调了其转录,但TaPIP1;2和TaPIP2;5在剪根且水分胁迫处理中的转录水平最低。这些结果表明,小麦的根导水特性在单根尺度和细胞尺度上具有一致性;剪根短期内能够增加小麦幼苗的水分敏感性。推测TaPIP1;2和TaPIP2;5参与了静水压对小麦根导水特性的调节过程。     

Character of Coalbed Methane Enrichment Controlled by Hydrological Geology in Libi Gorge Anticlines

The drain character and hydraulic linking are studied by analyzing the property of water-bearing and water-resisting, groundwater flowing and hydrochemistry character in Libi Gorge anticline. According this, the character of methane enrichment controlled by hydrological geology in the region is researched. It is indicated that Libi Gorge belongs to block anticline gas pool sealed by water pressure. In shallow layers, the water-bearing layers are controlled obviously by atmospheric water. The groundwater flows actively, drains nearby, but has no influence on the coalbed methane; in middle layers, the coal-bearing layers contain water weakly and the water flows slowly. The water has a roof and bottom enclosed effect on gas in water network ; in deep layers, the layers contain water weakly. The groundwater stops running and has a bottom enclosed effect on gas in water network. The most of faults are pressure faults, upper of them is water guiding, lower of them resisting. They enclose the gas by pressure. In addition, it is important for thickening rock character to enclose the gas.     

农业生产突发事件危害度评价研究

农业生产污染突发事件时有发生,致使农田土壤、农用水域、农区大气等受到污染,农业生产受到损害。为了及时采取适当的措施处置突发事件,必须首先对农业生产突发事件危害度进行评价,目前对农业生态系统突发事件的定量评价仍处于摸索研究阶段。此文通过构建农业生产突发事件的评价指标,采用层次分析法和模糊数学建立四类突发事件（病虫害、过量使用农业投入品、危化品泄露、气象自然灾害）的危害度评价模型,综合评价突发事件危害度,该模型考虑了农业生产突发事件的爆发性和处置有效性,能为突发事件的及时决策和实时处理提供技术支持。     

地震时城市供水管网连通可靠性分析

在分析地震条件下管线功能函数及极限状态方程基础上,对城市供水管单元体进行震害预测。以供水管网系统作为边权的有向网络图,通过基于神经网络的Monte Carlo方法,模拟各管线运行状态及其破坏状态。结合图论理论,分析供水管网的管线连通可靠性。     

Experimental Analysis on Power Consumption of Chilled Water Pump by Constant Pressure Difference Method with Bypass Valve

The power consumption of frequency conversion chilled water pump of an office building regulated by constant pressure difference method with bypass valve is studied experimentally. A model of power consumption of chilled water pump is proposed. The effects of pressure difference set point of bypass valve on instantaneous and annual power consumption of chilled water pump are analyzed. The simulation results are validated experimentally, which shows that there is a maximum water flow rate which increases with the increase of the pressure difference set point of bypass valve at equilibrium state. There are three pressure operation regions of the bypass valve: under pressure region, constant pressure region and over pressure region. The power consumption of frequency conversion chilled water pump is affected by the pressure difference set point of bypass valve significantly, and it would be minimized as the pressure difference set point of bypass valve is equal to the pressure difference between supply water and return water of the farthest user.     

Application the hydraulic fracturing technology in the highn pressure and low permeability mine

To solve the gas drainage problem of the high gas and low permeability mine, based on the features of the high pressure water, the hydraulic fracturing technology is proposed to improve the gas drainage rate. According to the first strength theory, through analyzing the stress around the borehole, the broken mechanism of the coal under high pressure is studied and the function of critical value is obtained. In addition, based on the coal features of the tenth mine of the Pingdingshan, the fracturing pressure is calculated and the hydraulic fracturing parameter is optimized. The equipment of the hydraulic fracturing technology is developed and applied successfully in the mine. And it is found that the gas drainage flux and concentration are improved with more than 5 times.     

4个品系橡胶树实生苗叶片及根系对水分胁迫的反应

运用聚乙二醇(PEG6000)模拟水分胁迫的方法,研究了水分胁迫对不同品系橡胶树根系水流导度（Lpr）、根系活力和叶片水分饱和亏缺变化的影响。结果表明：水分胁迫对橡胶树根系水力学导度、根系活力和叶片水分饱和亏缺产生明显影响,随着水分胁迫时间的延长,根系水力学导度逐渐下降,根系活力呈现先增加后下降,叶片水分饱和亏缺逐渐增加的趋势。从橡胶树根系水导与根系活力在水分胁迫下的下降程度和叶片维持水分平衡的能力来看,GT1对水分胁迫的抵御与适应能力相对较强,其次是PR107﹥RRIM600,PB86忍耐水分胁迫最弱。     

Analysis of the Medium Pressure Range in Urban Gas Transmission and Distribution System

According to the analysis of technology and economy about the gas supply with the medium pressure in gas pipeline network of urban gas transmission and distribution system,a more economical and feasible pressure value is obtained.     

负水头灌溉对温室番茄植株蒸腾规律影响的研究

利用Flow32茎流计分别测定负水头灌溉和常规灌溉方式下的番茄植株蒸腾速率,探讨负水头灌溉方式对番茄植株蒸腾影响及植株蒸腾速率与太阳辐射强度之间的关系,同时分析了负水头灌溉下植株一天不同时刻耗水量差异和负水头灌溉对水分利用效率的影响。试验结果表明,负水头灌溉下的番茄植株蒸腾速率要大于常规漫灌,但有着相同的变化趋势,植株的蒸腾速率主要受太阳辐射强度的影响;负水头灌溉方式能为作物适时适量提供水分,且有效地减少无效地表蒸发和地下深层渗漏,提高了作物的水分利用效率。     

Characteristics of Filling Process and Factors of Differential-pressure Cast for Thin-wall Castings

Filling process of differential-pressure cast for thin-wall castings of aluminum alloy is simulated with the hydraulic simulation method. The effects on filling fluid pattern was taken by the figure and amount of the ingate and the wall width of castings are researched. It is shown that the wall width of castings has obvious effect on critical pressure increase rate and critical filling rate, the thinner the wall width of castings is, the bigger the critical pressure increase rate and critical filling rate are; but the figure and the amount of the ingate has no obvious effect on the stationarety of filling. On the basis mentioned above, it is carried out that numeric simulation of filling process of differential-pressure cast and the process design of defferential -pressure cast to some large-scale thin-wall cabin-shape parts, and the result showes that are the smooth and stepwise filling,and the project of differential pressure cast is instituted by the process parameters, which is provide by the hydraulic simulation method. It provides the reference for the produce of this kind of castings.     

The application of TDR in laboratory column experiments

An automated TDR system was used together with an automated tensiometer system in laboratory column experiments for the measurement of unsaturated hydraulic properties of soils. The laboratory experiments were a stationary flux (sprinkling infiltrometer) carried out with different fluxes, and a transient (evaporation) method. Simultaneous measurements of water content and pressure head give the water retention characteristic and enable the application of the instantaneous profile analysis for calculating the hydraulic conductivity. This direct analysis is compared with the traditional analysis methods normally used for the laboratory experiments. The application of automated measurement techniques and the use of TDR increases the speed of the measurements, generates more data points and requires less assumptions in the data analysis. Moreover, TDR measurements give insight in the flow process, including effects of hysteresis and heterogeneity within a sample. Performing the sprinkling infiltrometer and evaporation experiments on the same sample enables the determination of the unsaturated hydraulic conductivity at pressure heads ranging from −0.01 m to −6 m.     

Numerical simulation of one-dimensional dam-break: A decoupled scheme with WENO reconstruction

Based on the reconstruction of interface variables with the fifth-order WENO, a high resolution scheme is proposed and the performance of capturing dam break waves is analyzed. With the part is linearized through Roe average, one dimensional shallow water equation is directly and decoupled solved, the velocity distribution and depth distribution are obtained. Numerical simulation shows that the decoupled schemes with WENO5 reconstruction has higher resolution and it shows the movement of dam-break.     

Analysis on rock cross-cut coal uncovering using high pressure water jet slotting in close distance seam group

Safe production and procedures at the driving face are restricted in mines of Guizhou province by the long periods required for rock cross-cut coal uncovering in high gas coal seam group. A new method is proposed to solve this problem using high pressure water jet slotting in penetration boreholes. This is proposed to increase the gas desorption rate and reduce drilling hole, which will shorten the cycle of rock cross-cut coal uncovering. Numerical simulation is used to compare the pressure relief effects of different slotting methods in penetration boreholes. The results show that the pressure relief effect of slotting all coal seams is more ideal. Field application indicates that high pressure water jet slotting has good effect of the pressure relief in coal seam group. The drilling number is reduced by 30, the drilling length is shortened by 610 m and the standard time of gas pre-pumping decreases by 39 days.