期刊文献+
共找到54,480篇文章
< 1 2 250 >
每页显示 20 50 100
Permeability Prediction Using Hydraulic Flow Units: Baltim North Gas Field, Nile Delta, Egypt 认领
1
作者 Abdel Moktader A. El Sayed Samy Zayed Nahla A. El Sayed 《地球科学国际期刊(英文)》 2021年第2期57-76,共20页
168 core samples data of two production wells in the Baltim North field were used to identify the complex discrepancies in reservoir pore geometry which governing the Abu Madi reservoir fluid flow properties. Permeabi... 168 core samples data of two production wells in the Baltim North field were used to identify the complex discrepancies in reservoir pore geometry which governing the Abu Madi reservoir fluid flow properties. Permeability prediction from well logs is significant goal when the core data is rarely available in most cases because<span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> of</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> its expensive cost. The hydraulic flow unit approach was used to classify reservoir rocks according to its pore aperture size in the cored wells. The predicted permeability was calculated from core porosity and core permeability relationship for each flow unit. The difference between Neutron porosity and Density porosity was recognized to distinguish different hydraulic flow units. The higher difference indicates higher quality flow unit and vice versa. For model’s verification the predicted permeability was plotted against the laboratory measured permeability in all studied wells and shows highly matching.</span></span></span> 展开更多
关键词 PERMEABILITY Hydraulic Flow Units Pore Throat (r35) Baltim Gas Field EGYPT
在线阅读 免费下载
Analysis of Rolling Contact Bearings Test Data by the Bımodal Method 认领
2
作者 Yaakov Meged 《材料物理与化学进展(英文)》 2021年第1期1-6,共6页
Lieblein J. and Zelen A. conducted a study of the fatigue life of deep groove ball bearings. This study was based on data of 4948 bearings as obtained from 5 companies and 213 test groups. Among these data is a detail... Lieblein J. and Zelen A. conducted a study of the fatigue life of deep groove ball bearings. This study was based on data of 4948 bearings as obtained from 5 companies and 213 test groups. Among these data is a detailed test report #3183, lot 73, consisting of 23 failed bearings. This report states that the Weibull slope of this group is 2.23, meaning that this distribution is mono sloped. These test data were plotted by the author on a bilinear scale plane, of endurance life versus bearing number and proved to be distinctly bi sloped. This basic difference prompted a wide study resulting in several new findings and set the grounds for a new analysis method. 展开更多
关键词 Bimodal Fatigue Mechanism Deep Groove Ball Bearings Mechanical Mode Hydraulic Mode Relative Intensity Cavitation Erosion
在线阅读 免费下载
甘蔗收获机切割器仿形机构研究现状与发展趋势 认领
3
作者 夏鼎宽 何冯光 +3 位作者 邓干然 李国杰 李玲 覃双眉 《现代农业装备》 2021年第1期15-20,共6页
切割器是甘蔗收割机的重要工作部件之一。本文论述了国内外甘蔗切割器的研究状况和仿形技术的应用情况,对比了两种仿形机构模式的优缺点,针对蔗叶杂草等干扰传感器信号收集困难的问题,提出选用超声波传感器作为测距元件的方案,为甘蔗切... 切割器是甘蔗收割机的重要工作部件之一。本文论述了国内外甘蔗切割器的研究状况和仿形技术的应用情况,对比了两种仿形机构模式的优缺点,针对蔗叶杂草等干扰传感器信号收集困难的问题,提出选用超声波传感器作为测距元件的方案,为甘蔗切割器仿形机构设计方案的选定提供了依据。 展开更多
关键词 甘蔗 切割器 仿形 液压
在线阅读 下载PDF
小型液压压力机的设计 认领
4
作者 徐林锋 陈巨源 《液压气动与密封》 2021年第4期81-83,共3页
为解决实际生产制造过程中人力挤压安装某些零部件困难且存在安全隐患的问题,专门设计了一款适用于各种需要挤压、折弯等组装工序的小型液压压力机。压力机是一种结构精巧,用途广泛,生产效率高的专用设备,其设计制造相对较为复杂,成本... 为解决实际生产制造过程中人力挤压安装某些零部件困难且存在安全隐患的问题,专门设计了一款适用于各种需要挤压、折弯等组装工序的小型液压压力机。压力机是一种结构精巧,用途广泛,生产效率高的专用设备,其设计制造相对较为复杂,成本较高。新设计的小型液压压力机结构简单,制造简单,操作方便,成本低廉,目前已成功应用于公司的组装生产制造过程中,有效提高了衬套、轴承等零部件的压入工序和液压油管的折弯工序的工作效率。 展开更多
关键词 小型 液压 压力机 设计
在线阅读 下载PDF
刮板输送机液压自动调高电缆槽的设计 认领
5
作者 王艳丽 《煤矿机械》 北大核心 2021年第3期8-10,共3页
在某些采煤工作面,巷道高度存在落差,固定高度的刮板输送机电缆槽无法满足开采需要,需要更换不同高度电缆槽;同时大采高工作面由于电缆槽挡板过高,电缆槽常采用一体式或者上下两部分可拆分结构,在设备发生故障时,需将电缆槽或上半部分... 在某些采煤工作面,巷道高度存在落差,固定高度的刮板输送机电缆槽无法满足开采需要,需要更换不同高度电缆槽;同时大采高工作面由于电缆槽挡板过高,电缆槽常采用一体式或者上下两部分可拆分结构,在设备发生故障时,需将电缆槽或上半部分电缆槽拆下,在井下维修时存在安全隐患,修理时间长。设计一种液压自动调高电缆槽,活挡板、电缆槽两部分使用液压连接,需要调整挡板高度时,通过液压自动调节高度,实现存在不高落差工作面的开采,同时实现无需拆卸电缆槽进行检修,降低安全生产隐患。 展开更多
关键词 检修电缆槽 自动调高电缆槽 大采高工作面 液压
Advantages of employing multilevel monitoring wells for design of tunnels subjected to multi-aquifer alluvial 认领
6
作者 Mohsen GOLIAN Ebrahim SHARIFI TESHNIZI +6 位作者 Hamed TAVASOLI ROSTAMI Homayoon KATIBEH Mario PARISE Masoud MAHDAD Habib SAADAT Mehdi ABBASI Mahshid EBAD ARDESTANI 《山地科学学报:英文版》 SCIE CSCD 2021年第1期219-232,共14页
For tunnels being excavated through multiple knowledge of the aquifers’hydraulic head becomes essential for determining groundwater inflow into the tunnel and analyzing its stability,specifically using multilevel mon... For tunnels being excavated through multiple knowledge of the aquifers’hydraulic head becomes essential for determining groundwater inflow into the tunnel and analyzing its stability,specifically using multilevel monitoring systems.In the multi-aquifer alluvial section of the Glas tunnel(Iran),since the hydraulic head calculations were based on the data obtained from single-piezometer boreholes,the excavation risk was assessed to be at high level and the tunnel seemed to be unstable,thus an incorrect conclusion was derived from the misleading data.To take cost mitigation measures into account,it was necessary to calculate the hydraulic head at tunnel level accurately.By installing nested and clustered wells the mean hydraulic head was measured to be 70 m,significantly different from the 90 m previously determined by boreholes.Considering the updated value,the groundwater inflow and bulkhead load,formerly calculated as 0.65 m3/s and 9.5 bars,were determined to be 0.49 m3/s and 7.5 bars,respectively. 展开更多
关键词 Nested wells Clustered wells Hydraulic head Pumping test Mechanized tunneling Iran
Aquifer hydraulic conductivity prediction via coupling model of MCMC-ANN 认领
7
作者 GUI Chun-lei WANG Zhen-xing +1 位作者 MA Rong ZUO Xue-feng 《地下水科学与工程:英文版》 2021年第1期1-11,共11页
Grain-size distribution data,as a substitute for measuring hydraulic conductivity(K),has often been used to get K value indirectly.With grain-size distribution data of 150 sets of samples being input data,this study c... Grain-size distribution data,as a substitute for measuring hydraulic conductivity(K),has often been used to get K value indirectly.With grain-size distribution data of 150 sets of samples being input data,this study combined the Artificial Neural Network technology(ANN)and Markov Chain Monte Carlo method(MCMC),which replaced the Monte Carlo method(MC)of Generalized Likelihood Uncertainty Estimation(GLUE),to establish the GLUE-ANN model for hydraulic conductivity prediction and uncertainty analysis.By means of applying the GLUE-ANN model to a typical piedmont region and central region of North China Plain,and being compared with actually measured values of hydraulic conductivity,the relative error ranges are between 1.55%and 23.53%and between 14.08%and 27.22%respectively,the accuracy of which can meet the requirements of groundwater resources assessment.The global best parameter gained through posterior distribution test indicates that the GLUEANN model,which has satisfying sampling efficiency and optimization capability,is able to reasonably reflect the uncertainty of hydrogeological parameters.Furthermore,the influence of stochastic observation error(SOE)in grain-size analysis upon prediction of hydraulic conductivity was discussed,and it is believed that the influence can not be neglected. 展开更多
关键词 Grain-size distribution Hydraulic conductivity ANN GLUE MCMC Stochastic Observation Error(SOE)
在线阅读 下载PDF
Prediction criteria for groundwater potential zones in Kemuning District,Indonesia using the integration of geoelectrical and physical parameters 认领
8
作者 Juandi Muhammad Nur Islami 《地下水科学与工程:英文版》 2021年第1期12-19,共8页
The presence of groundwater is strongly related to its geological and geohydrological conditions.It is,however,important to study the groundwater potential in an area before it is utilized to provide clean water.Werne... The presence of groundwater is strongly related to its geological and geohydrological conditions.It is,however,important to study the groundwater potential in an area before it is utilized to provide clean water.Werner-Schlumberger’s method was used to analyze the groundwater potential while hydraulic properties such as soil porosity and hydraulic conductivity were used to determine the quality and ability of the soil to allow water’s movement in the aquifer.The results show that the aquifer in the Sekara and Kemuning Muda is at a depth of more than 6 meters below the ground level with moderate groundwater potential.It is also found that the aquifer at depths of over 60 m have high groundwater potential.Moreover,soil porosity in Kemuning is found to be average while the ability to conduct water was moderate.This makes it possible for some surface water to seep into the soil while the remaining flows to the rivers and ditches. 展开更多
关键词 Geoelectrics GROUNDWATER Hydraulic property Aquifer Werner-Schlumberger’s configuration
在线阅读 下载PDF
基于混合动力液压挖掘机系统优化设计的研究 认领
9
作者 董丽娟 朱哲煜 《内燃机与配件》 2021年第1期55-56,共2页
本文分析了我国对混合动力的液压挖掘机系统的研究情况,以此探讨工程机械中采用混合动力技术能否有效适用,在此基础上对液压挖掘机系统优化设计中混合动力技术的具体应用进行了相应的探讨,明确了基于混合动力液压挖掘机系统在串联和并... 本文分析了我国对混合动力的液压挖掘机系统的研究情况,以此探讨工程机械中采用混合动力技术能否有效适用,在此基础上对液压挖掘机系统优化设计中混合动力技术的具体应用进行了相应的探讨,明确了基于混合动力液压挖掘机系统在串联和并联两种方式上的运行原理,同时评价并对比了串联和并联两种方式下混合动力液压挖掘机系统的性能、经济性及其节能效果。 展开更多
关键词 混合动力 液压 挖掘机 优化设计
在线阅读 下载PDF
液压长抽芯注射模设计 认领
10
作者 褚建忠 《模具制造》 2021年第3期43-46,共4页
根据长抽芯结构的塑件在模具结构方面的要求,设计了基于液压动力的长抽芯注射模,分析了模具在抽芯运动、顶出运动、冷却系统等方面存在的问题,对相关的机构分别进行了创新设计。该项技术不但实现了长抽芯塑件的自动生产,而且提升了塑件... 根据长抽芯结构的塑件在模具结构方面的要求,设计了基于液压动力的长抽芯注射模,分析了模具在抽芯运动、顶出运动、冷却系统等方面存在的问题,对相关的机构分别进行了创新设计。该项技术不但实现了长抽芯塑件的自动生产,而且提升了塑件的质量稳定性。 展开更多
关键词 液压 长抽芯 注射模
在线阅读 下载PDF
Battery Management for the Electric Hydraulic Pump System of a Lifting Trolley 认领
11
作者 Wen-Ning Chuang Min-Wei Hung 《机械工程与自动化:英文版》 2021年第1期17-20,共4页
This study proposed a battery management approach for the electric hydraulic pump system of a lifting trolley.The pump system was powered by two 12-V lead-acid batteries in series.Because direct measurement of the act... This study proposed a battery management approach for the electric hydraulic pump system of a lifting trolley.The pump system was powered by two 12-V lead-acid batteries in series.Because direct measurement of the actual battery state of charge is unlikely,it has mostly been determined through estimation based on the measured open-circuit voltage.A discharge current will result in a voltage drop and hence a lower voltage during discharge;however,the battery voltage will return to the original open-circuit voltage once the discharge stops.The operating current of the electric hydraulic pump system employed in this study was associated with three factors:the lifting height,lifting load,and battery state of charge.The operating current remained constant during the first half of the lifting phase and increased gradually with the lifting height in the second half.The operating current peaked when the lifting height reached the maximum.The power management approach for the electric hydraulic pump system featured the following basic functions:overcharge protection,overdischarge protection,short-circuit protection,overload protection,and an operating timer established in accordance with the system’s operating current variation.According to the manufacturer-defined maximum lifting load and lifting height of the lifting trolley,this study conducted experiments to obtain the maximum required operating time.An operating time greater than the maximum required operating time indicates the occurrence of an unexpected event,discharge should be stopped until the fault is resolved. 展开更多
关键词 Battery management lead-acid battery electric hydraulic pump system.
在线阅读 下载PDF
大鼠循经低流阻通道的发现 认领
12
作者 宋晓晶 张维波 +4 位作者 贾术永 王广军 王淑友 李宏彦 熊枫 《世界针灸杂志:英文版》 CSCD 2021年第1期22-29,共8页
Background:Continuous and porous low hydraulic resistance channels(LHRCs)are important structures of meridians in traditional Chinese medicine(TCM).In this study,based on the previous research on LHRCs along meridian ... Background:Continuous and porous low hydraulic resistance channels(LHRCs)are important structures of meridians in traditional Chinese medicine(TCM).In this study,based on the previous research on LHRCs along meridian paths(LHRCMs)in mini-pig,we aimed to detect the low hydraulic resistance point(LHRP)and display the LHRCMs in rats.Methods:A technique for measuring interstitial hydraulic resistance(Rh)in rats was established to detect and measure the Rh along the conception vessel(CV)in TCM,and Alcian Blue(AB)solution was injected into the LHRP along the CV.The interstitial fluid pressure(IFP)of the LHRP was measured before and after AB injection.Then,the distribution characteristics of the AB solution were investigated to explore the relationship between AB tracks and meridian paths in TCM.Results:The positions of the LHRPs coincided with the low impedance points(LIPs)of the rat skin along the CV.The Rh value along the CV(10.37,1.26,×106dyne s cm-5)was significantly lower than that in the non-meridian area(19.13±1.37,×106dyne s cm-5,P<0.01).After AB injection,the IFP of the LHRP was 2.52 mmHg,which was higher than that before AB injection.The AB tracks(ABT)along the CV,spleen meridian,and kidney meridian appeared in one or two directions,with single or multiple paths and uneven thickness and length.The appearance rate was 73.33%.Conclusions:LHRCMs existed not only in minipigs but also in rats.The LHRCMs could be observed after AB injection into the LHRP in the subcutaneous connective tissues of rats. 展开更多
关键词 Low hydraulic resistance channels MERIDIAN Alcain blue Track along meridians Rat
Groundwater contaminant source identification based on QS-ILUES 认领
13
作者 LIU Jin-bing JIANG Si-min +3 位作者 ZHOU Nian-qing CAI Yi CHENG Lu WANG Zhi-yuan 《地下水科学与工程:英文版》 2021年第1期73-82,共10页
When groundwater pollution occurs,to come up with an efficient remediation plan,it is particularly important to collect information of contaminant source(location and source strength)and hydraulic conductivity field o... When groundwater pollution occurs,to come up with an efficient remediation plan,it is particularly important to collect information of contaminant source(location and source strength)and hydraulic conductivity field of the site accurately and quickly.However,the information can not be obtained by direct observation,and can only be derived from limited measurement data.Data assimilation of observations such as head and concentration is often used to estimate parameters of contaminant source.As for hydraulic conductivity field,especially for complex non-Gaussian field,it can be directly estimated by geostatistics method based on limited hard data,while the accuracy is often not high.Better estimation of hydraulic conductivity can be achieved by solving inverse groundwater problem.Therefore,in this study,the multi-point geostatistics method Quick Sampling(QS)is proposed and introduced for the first time and combined with the iterative local updating ensemble smoother(ILUES)to develop a new data assimilation framework QS-ILUES.It helps to solve the contaminant source parameters and non-Gaussian hydraulic conductivity field simultaneously by assimilating hydraulic head and pollutant concentration data.While the pilot points are utilized to reduce the dimension of hydraulic conductivity field,the influence of pilot points’layout and the ensemble size of ILUES algorithm on the inverse simulation results are further explored. 展开更多
关键词 Inverse groundwater problem Data assimilation Multi-point Geostatistics Quick Sampling Non-Gaussian hydraulic conductivity field
在线阅读 下载PDF
Study on anisotropy of Longmaxi shale using hydraulic fracturing experiment 认领
14
作者 Hongyu ZHAI Xu CHANG +2 位作者 Wei ZHU Xinglin LEI Ziqiu XUE 《中国科学:地球科学英文版》 SCIE EI CSCD 2021年第2期260-277,共18页
Hydraulic fracturing reservoir reconstruction technology is crucial in the development of shale gas exploitation techniques.Large quantities of high-pressure fluids injected into shale reservoirs significantly alter c... Hydraulic fracturing reservoir reconstruction technology is crucial in the development of shale gas exploitation techniques.Large quantities of high-pressure fluids injected into shale reservoirs significantly alter compressional(P)and shear(S)wave velocities,rock mechanical parameters,and anisotropic characteristics.In this study,differentiated hydraulic fracturing petrophysical experiments were carried out on Longmaxi Formation shale under pseudo-triaxial stress loading conditions.The effects of stress loading methods,and water-rock physical and chemical reactions on P-and S-wave velocities and rock mechanical parameters were compared.The experimental results showed that isotropic stress loading may increase the P-and Swave velocities and Young’s modulus of dry shale kldnsample.Furthermore,it may lead to a weakening of the corresponding anisotropy.In contrast,differential stress loading was able to improve the anisotropy of Young’s modulus and accelerate the decrease in the compressive strength of shale in the vertical bedding direction.The water-rock physical and chemical reactions prompted by hydraulic fracturing was found to"soften"shale samples and reduce Young’s modulus.The influence of this"soften"effect on the compressional and shear wave velocities of shale was negligible,whilst there was a significant decrease in the anisotropy characteristics of Thomsen parameters,Young’s modulus,and Poisson’s ratio.The negative linear relationship between the Poisson’s ratios of the shale samples was also observed to lose sensitivity to stress loading,as a result of the"soften"effect of fracturing fluid on shale.The results of this study provide a reliable reference point and data support for future research on the mechanical properties of Longmaxi shale rocks. 展开更多
关键词 Longmaxi shale Anisotropic parameters Hydraulic fracturing experiment
Cause analysis and solutions of water blocking damage in cracked/non-cracked tight sandstone gas reservoirs 认领
15
作者 Jie Wang Fu-Jian Zhou 《石油科学:英文版》 SCIE CAS CSCD 2021年第1期219-233,共15页
After hydraulic fracturing treatment,a reduction in permeability caused by the invasion of fracturing fluids is an inevitable problem,which is called water blocking damage.Therefore,it is important to mitigate and eli... After hydraulic fracturing treatment,a reduction in permeability caused by the invasion of fracturing fluids is an inevitable problem,which is called water blocking damage.Therefore,it is important to mitigate and eliminate water blocking damage to improve the flow capacities of formation fluids and flowback rates of the fracturing fluid.However,the steady-state core flow method cannot quickly and accurately evaluate the effects of chemical agents in enhancing the fluid flow capacities in tight reservoirs.This paper introduces a time-saving and accurate method,pressure transmission test(PTT),which can quickly and quantitatively evaluate the liquid flow capacities and gas-drive flowback rates of a new nanoemulsion.Furthermore,scanning electron microscopy(SEM)was used to analyze the damage mechanism of different fluids and the adsorption of chemical agents on the rock surface.Parallel core flow experiments were used to evaluate the effects of the nanoemulsion on enhancing flowback rates in heterogeneous tight reservoirs.Experimental results show that the water blocking damage mechanisms differ in matrices and fractures.The main channels for gas channeling are fractures in cracked cores and pores in non-cracked cores.Cracked cores suffer less damage from water blocking than non-cracked cores,but have a lower potential to reduce water saturation.The PTT and SEM results show that the permeability reduction in tight sandstones caused by invasion of external fluids can be list as guar gum fracturing fluid>slickwater>brine.Parallel core flow experiments show that for low-permeability heterogenous s andstone reservoirs with a certain permeability ratio,the nanoemulsion can not only reduce reverse gas channeling degree,but also increase the flowback rate of the fracturing fluid.The nanoemulsion system provides a new solution to mitigate and eliminate water blocking damage caused by fracturing fluids in tight sandstone gas reservoirs. 展开更多
关键词 Hydraulic fracturing Water blocking damage NANOEMULSION Pressure transmission test Liquid flow capacity Flowback rate
Experimental study of multi-timescale crack blunting in hydraulic fracture 认领
16
作者 Jing-Nan Dong Guang-Jie Yuan +4 位作者 Xiang-Yang Wang Mian Chen Yan Jin Chao Zeng Musharraf Zaman 《石油科学:英文版》 SCIE CAS CSCD 2021年第1期234-244,共11页
Hydraulic fracture is important in unconventional oil and gas exploration.During the propagation of the hydraulic fracture,the crack tip is blunted due to the development of the process zone in the near-tip area.In th... Hydraulic fracture is important in unconventional oil and gas exploration.During the propagation of the hydraulic fracture,the crack tip is blunted due to the development of the process zone in the near-tip area.In this study,the blunting of the hydraulic fracture in polymethyl methacrylate specimens due to multi-timescale stress concentration is investigated.The ratio of the initiation toughness to the arrest toughness of the blunted hydraulic fracture is measured using both the dynamic and the static methods.Results show that a hydraulic fracture can be blunted with the time span of stress concentration from 1 ms to 600 s.It is also shown that the blunting of hydraulic fracture is a highly localized process.The morphology of the blunted crack depends on the stress distribution in the vicinity of the crack tip. 展开更多
关键词 Hydraulic fracture Crack blunting Crack tip morphology
1LFT-555型液压翻转栅条犁的设计与试验 认领
17
作者 雷智高 郑炫 +2 位作者 汤智辉 杨怀君 孟祥金 《农机化研究》 北大核心 2021年第2期174-179,共6页
针对当前农业生产需求及147kW以上拖拉机配套液压翻转犁依赖进口的现状,研制了1LFT-555型液压翻转栅条犁。该机翻转可靠性高,操作简单,主犁体采用栅条式结构,翻垡覆盖效果好,耕作阻力小。田间试验结果表明:该机和不同功率及多种轮距的... 针对当前农业生产需求及147kW以上拖拉机配套液压翻转犁依赖进口的现状,研制了1LFT-555型液压翻转栅条犁。该机翻转可靠性高,操作简单,主犁体采用栅条式结构,翻垡覆盖效果好,耕作阻力小。田间试验结果表明:该机和不同功率及多种轮距的拖拉机配套使用,作业速度可达10.8km/h,犁耕作业效果好,在棉花地和水稻地的耕深稳定性系数及耕宽稳定性系数均达到了95%以上,在棉花地的碎土率也达到了90%以上。该机各项性能指标达到国家有关标准的要求,为147kW以上拖拉机提供了配套犁耕机具。 展开更多
关键词 犁体 翻转犁 液压 栅条
在线阅读 下载PDF
Functionality analysis of an urban water supply network after strong earthquakes 认领
18
作者 Li Jichao Shang Qingxue +2 位作者 Hou Guanjie Li Quanwang Wang Tao 《地震工程与工程振动:英文版》 SCIE EI CSCD 2021年第2期291-302,共12页
An urban water supply network(WSN)is a crucial lifeline system that helps to maintain the normal functioning of modern society.However,the hydraulic analysis of a significantly damaged WSN that suffers from pipe break... An urban water supply network(WSN)is a crucial lifeline system that helps to maintain the normal functioning of modern society.However,the hydraulic analysis of a significantly damaged WSN that suffers from pipe breaks or leaks remains challenging.In this paper,a probability-based framework is proposed to assess the functionality of WSNs in the aftermath of powerful earthquakes.The serviceability of the WSN is quantified by using a comprehensive index that considers nodal water flow and nodal pressure.This index includes a coefficient that reflects the relative importance of these two parameters.The demand reduction(DR)method,which reduces the water flow of nodes while preventing the negative pressure of nodes,is proposed.The difference between the negative pressure elimination(NPE)method and the DR method is discussed by using the example of a WSN in a medium-sized city in China.The functionality values of the WSN are 0.76 and 0.99 when nodal pressure and nodal demands are used respectively as the index of system serviceability at an intensity level that would pertain to an earthquake considered to occur at a maximum level.When the intensity of ground motion is as high as 0.4 g,the DR method requires fewer samples than the NPE method to obtain accurate results.The NPE method eliminates most of the pipes,which may be unrealistic. 展开更多
关键词 water supply network system serviceability hydraulic analysis negative pressure elimination benchmark city
在线阅读 下载PDF
Rock brittleness indices and their applications to different fields of rock engineering:A review 认领
19
作者 Fanzhen Meng Louis Ngai Yuen Wong Hui Zhou 《岩石力学与岩土工程学报:英文版》 SCIE CSCD 2021年第1期221-247,共27页
Brittleness is an important parameter controlling the mechanical behavior and failure characteristics of rocks under loading and unloading conditions,such as fracability,cutability,drillability and rockburst proneness... Brittleness is an important parameter controlling the mechanical behavior and failure characteristics of rocks under loading and unloading conditions,such as fracability,cutability,drillability and rockburst proneness.As such,it is of high practical value to correctly evaluate rock brittleness.However,the definition and measurement method of rock brittleness have been very diverse and not yet been standardized.In this paper,the definitions of rock brittleness are firstly reviewed,and several representative definitions of rock brittleness are identified and briefly discussed.The development and role of rock brittleness in different fields of rock engineering are also studied.Eighty brittleness indices publicly available in rock mechanics literature are compiled,and the measurement method,applicability and limitations of some indices are discussed.The results show that(1)the large number of brittleness indices and brittleness definitions is attributed to the different foci on the rock behavior when it breaks;(2)indices developed in one field usually are not directly applicable to other fields;and(3)the term“brittleness”is sometimes misused,and many empirically-obtained brittleness indices,which lack theoretical basis,fail to truly reflect rock brittleness.On the basis of this review,three measurement methods are identified,i.e.(1)elastic deformation before fracture,(2)shape of post-peak stressestrain curves,and(3)methods based on fracture mechanics theory,which have the potential to be further refined and unified to become the standard measurement methods of rock brittleness.It is highly beneficial for the rock mechanics community to develop a robust definition of rock brittleness.This study will undoubtedly provide a comprehensive timely reference for selecting an appropriate brittleness index for their applications,and will also pave the way for the development of a standard definition and measurement method of rock brittleness in the long term. 展开更多
关键词 Rock brittleness Practical applicability Hydraulic fracturing Rockburst proneness Crack propagation Fragmentation efficiency
在线阅读 下载PDF
Drought stress,mercuric chloride,andβ-mercaptoethanol effects on hydraulic characteristics of three cultivars of wolfberry(Lycium chinense) 认领
20
作者 Shengrong Xu Ruili Ma +3 位作者 Enhe Zhang Yuan Chen Qi Wang Qinglin Liu 《林业研究:英文版》 SCIE CAS CSCD 2021年第1期233-240,共8页
In order to further understand the effects of drought stress on hydraulic characteristics and the relationship between hydraulic conductivity and aquaporins or water channels of root systems of three wolfberry cultiva... In order to further understand the effects of drought stress on hydraulic characteristics and the relationship between hydraulic conductivity and aquaporins or water channels of root systems of three wolfberry cultivars(Lycium chinense Mill.),hydraulic conductivity of 2-yearold pot-grown seedlings was measured under drought stress,rewatering,and treatment with exogenous mercuric chloride andβ-mercaptoethanol.Under moderate and severe drought stress levels,the most significant decrease of hydraulic conductivity was 37.3%and 24.0%,respectively,in the‘Ningqi 5’cultivar compared with the nonstressed control.After rewatering,the rate of recovery in specific conductivity was most rapid in the‘Mengqi 1’cultivar,at 0.058 and 0.072 kg MPa^-1 m^-2 s^-1 h^-1 under moderate and severe drought stress levels,respectively.The‘Mengqi 1’cultivar had the highest recovery degree of hydraulic conductivity under two concentrations ofβ-ME(500 or 1000 lmol L^-1),reaching 82.4%and 88.5%,respectively,of the initial conductivity.The adaptive capacity of hydraulic conductivity in the‘Ningqi 5’cultivar was weaker than in the‘Ningqi 1’and‘Mengqi 1’cultivars under drought stress.The recovery capacity of hydraulic conductivity in‘Mengqi 1’cultivar was stronger than the‘Ningqi 1’and‘Ningqi 5’cultivars after rewatering.Aquaporins of the‘Ningqi 1’cultivar root systems had the highest binding affinity with mercuric chloride,which was the most likely cause in the decrease in hydraulic conductivity,whereas aquaporins of‘Mengqi 1’root systems had the weakest binding affinity.The inhibitory effect of mercuric chloride was readily eliminated byβ-mercaptoethanol in the‘Mengqi 1’cultivar.The hydraulic characteristics of this cultivar were more sensitive to drought,mercuric chloride andβ-mercaptoethanol than the other cultivars. 展开更多
关键词 β-Mercaptoethanol AQUAPORINS Hydraulic conductivity Mercuric chloride Wolfberry(Lycium chinense)
在线阅读 下载PDF
上一页 1 2 250 下一页 到第
使用帮助 返回顶部 意见反馈