Affected by external environmental factors and evolution of dam performance, dam seepage behavior shows nonlinear time-varying characteristics. In this study, to predict and evaluate the long-term development trend an...Affected by external environmental factors and evolution of dam performance, dam seepage behavior shows nonlinear time-varying characteristics. In this study, to predict and evaluate the long-term development trend and short-term fluctuation of the dam seepage behavior, two monitoring models were developed, one for the base flow effect and one for daily variation of dam seepage elements. In the first model, to avoid the influence of the time lag effect on the evaluation of seepage variation with the time effect component of seepage elements, the base values of the seepage element and the reservoir water level were extracted using the wavelet multi-resolution analysis method, and the time effect component was separated by the established base flow effect monitoring model. For the development of the daily variation monitoring model for dam seepage elements, all the previous factors, of which the measured time series prior to the dam seepage element monitoring time may have certain influence on the monitored results, were considered. Those factors that were positively correlated with the analyzed seepage element were initially considered to be the support vector machine(SVM) model input factors, and then the SVM kernel function-based sensitivity analysis was performed to optimize the input factor set and establish the optimized daily variation SVM model. The efficiency and rationality of the two models were verified by case studies of the water level of two piezometric tubes buried under the slope of a concrete gravity dam.Sensitivity analysis of the optimized SVM model shows that the influences of the daily variation of the upstream reservoir water level and rainfall on the daily variation of piezometric tube water level are processes subject to normal distribution.展开更多
In order to study the effect of time lag and stress loading rates on rock deformation,the conventional stepped stress loading mode was changed into a continuous mode to investigate the effect of effective pressure on ...In order to study the effect of time lag and stress loading rates on rock deformation,the conventional stepped stress loading mode was changed into a continuous mode to investigate the effect of effective pressure on permeability and porosity.The time lag effect of rock deformation illustrating the relationship between changes in permeability and steady time was studied.Permeability reduction ratios were measured under different stress loading rates which were achieved by different pump rate settings.The results show that permeability and porosity gradually decrease with increases in effective pressure.Permeability at high effective pressure attains stability quickly.Steady times at low effective pressure are very long.Reduction in permeability at lower stress loading rates is small,while,in contrast,it is large at high stress loading rates.展开更多
The objective of this paper is to identify time lag effect in the relationship between supply chain management and financial performance.We hypothesize that firms with higher supply chain management capability are ass...The objective of this paper is to identify time lag effect in the relationship between supply chain management and financial performance.We hypothesize that firms with higher supply chain management capability are associated with higher financial performance and the impact would last longer.In addition,we introduce two contextual variables,ownership and market orientation,to detect the moderating effect of ownership structure and organizational culture,respectively.We use firm-level empirical data from 1,131 public Chinese manufacturing firms for the 2010–2019 period to investigate the effect and the result shows that there is a two-year time lag effect in the relationship,which means the positive impact of current supply chain management would last for three years.Furthermore,we find evidence that supply chain management in non-state-owned firms is more efficient and its positive financial impact would last longer than that in state-owned enterprises.Finally,we indicate that market-orientation can’t moderate the relationship between supply chain management and financial performance.展开更多
冠气温差能够间接监测作物水分变化规律,而冠层温度与大气温度之间存在的时滞效应会影响监测效果,为探明两者之间的时滞效应变化规律及影响因素,本研究以拔节期至乳熟期的冬小麦为研究对象,利用红外温度传感器连续监测灌溉上限分别为田...冠气温差能够间接监测作物水分变化规律,而冠层温度与大气温度之间存在的时滞效应会影响监测效果,为探明两者之间的时滞效应变化规律及影响因素,本研究以拔节期至乳熟期的冬小麦为研究对象,利用红外温度传感器连续监测灌溉上限分别为田间持水率的95%(T1)、80%(T2)、65%(T3)和50%(T4)4个不同灌溉处理的冠层温度,并同步获取短波净辐射(Short-wave net radiation,R_(S))、大气温度(Atmospheric temperature,T_(A))、相对湿度(Relative humidity,R_(H))等气象数据。利用错位相关法计算冠层温度与大气温度之间的时滞时间(Time lag,TL),分析其在不同生育期和不同灌溉条件下变化规律,并采用相关性分析法探究气象因子(R_(S)、T_(A)、R_(H))变化率和日均值与时滞时间的相关性,最后通过通径分析探讨气象因子(R_(S)、T_(A)、R_(H))、土壤含水率(Soil moisture content,SMC)以及叶面积指数(Leaf area index,LAI)对时滞时间的共同影响。结果表明:不同生育期和不同灌溉条件下冬小麦冠层温度变化均提前于大气温度;在不同灌溉处理下,T1、T2和T3处理的时滞时间高于T4处理,且在不同生育期下,时滞时间呈现先减少再增加的趋势。短波净辐射变化率(Change rate of short-wave net radiation,R_(SCR))、大气温度变化率(Change rate of atmospheric temperature,T_(ACR))和相对湿度变化率(Change rate of relative humidity,R_(HCR))与时滞时间的相关性均高于对应日均值与时滞时间的相关性;同时,R_(SCR)与时滞时间的相关程度最高(相关系数R为0.718~0.806),TACR次之(R为0.582~0.661),RHCR最低(R为-0.534~-0.570)。利用通径分析发现,时滞时间主要受R_(SCR)、SMC以及LAI共同影响,但在不同灌溉条件下影响时滞时间的主要因素存在差异,其中T1、T2和T3处理主要受R_(SCR)和LAI影响,而T4主要受R_(SCR)和SMC影响。研究可为利用冠气温差信息监测作物水分变化进一步提供理论依据。展开更多
基金supported by the National Natural Science Foundation of China(Grant No.51709021)the Open Foundation of the State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering(Grant No.2016491111)
文摘Affected by external environmental factors and evolution of dam performance, dam seepage behavior shows nonlinear time-varying characteristics. In this study, to predict and evaluate the long-term development trend and short-term fluctuation of the dam seepage behavior, two monitoring models were developed, one for the base flow effect and one for daily variation of dam seepage elements. In the first model, to avoid the influence of the time lag effect on the evaluation of seepage variation with the time effect component of seepage elements, the base values of the seepage element and the reservoir water level were extracted using the wavelet multi-resolution analysis method, and the time effect component was separated by the established base flow effect monitoring model. For the development of the daily variation monitoring model for dam seepage elements, all the previous factors, of which the measured time series prior to the dam seepage element monitoring time may have certain influence on the monitored results, were considered. Those factors that were positively correlated with the analyzed seepage element were initially considered to be the support vector machine(SVM) model input factors, and then the SVM kernel function-based sensitivity analysis was performed to optimize the input factor set and establish the optimized daily variation SVM model. The efficiency and rationality of the two models were verified by case studies of the water level of two piezometric tubes buried under the slope of a concrete gravity dam.Sensitivity analysis of the optimized SVM model shows that the influences of the daily variation of the upstream reservoir water level and rainfall on the daily variation of piezometric tube water level are processes subject to normal distribution.
基金Projects 2008ZX05009-004 supported by the National Key Sci-Tech Major Special Item2006CB705805 by the National Basic Research Program of Chinasupported by the National Basic Research Program of China and "enhanced oil recovery basic theory for low permeability reservoirs" under grant 2002CCA00700
文摘In order to study the effect of time lag and stress loading rates on rock deformation,the conventional stepped stress loading mode was changed into a continuous mode to investigate the effect of effective pressure on permeability and porosity.The time lag effect of rock deformation illustrating the relationship between changes in permeability and steady time was studied.Permeability reduction ratios were measured under different stress loading rates which were achieved by different pump rate settings.The results show that permeability and porosity gradually decrease with increases in effective pressure.Permeability at high effective pressure attains stability quickly.Steady times at low effective pressure are very long.Reduction in permeability at lower stress loading rates is small,while,in contrast,it is large at high stress loading rates.
基金This work was supported by the National Natural Science Foundation of China(NSFC),under Grant 71871114.
文摘The objective of this paper is to identify time lag effect in the relationship between supply chain management and financial performance.We hypothesize that firms with higher supply chain management capability are associated with higher financial performance and the impact would last longer.In addition,we introduce two contextual variables,ownership and market orientation,to detect the moderating effect of ownership structure and organizational culture,respectively.We use firm-level empirical data from 1,131 public Chinese manufacturing firms for the 2010–2019 period to investigate the effect and the result shows that there is a two-year time lag effect in the relationship,which means the positive impact of current supply chain management would last for three years.Furthermore,we find evidence that supply chain management in non-state-owned firms is more efficient and its positive financial impact would last longer than that in state-owned enterprises.Finally,we indicate that market-orientation can’t moderate the relationship between supply chain management and financial performance.
文摘目的:探讨“冬病夏治”全方配伍和无白芥子配伍延胡索乙素在模型家兔“肺俞”穴皮下药代动力学特征及药代动力学-药效动力学(PK-PD)模型的相关性。方法:支气管哮喘模型家兔随机分成延胡索单方组、缺白芥子组、全方组,微透析技术收集14 h穴位皮下透析液,液相色谱-质谱法(Liquid Chromatography Mass Spectrometry,LCMS)法检测方中君药延胡索主要成分延胡索乙素浓度,获得药代动力学参数;酶联免疫吸附试验(ELISA)法检测对应时间点模型动物血清中IgE水平,获得药效学参数;对药动学、药效学参数进行PK-PD模型拟合。结果:白芥子配伍后的药峰浓度(C_(max))、药时曲线下面积(AUC_(0-t))、平均滞留时间(MRT_(0-t))均显著增加(P<0.01,P<0.01,P<0.05),达峰时间(T_(max))提前(P<0.01);“浓度-时间-效应”三维曲线表明,方中有白芥子配伍时,药效出现更快、消退更慢,起效时间晚于峰浓度,具有一定滞后性。结论:动力学参数、PK-PD模型结果表明,白芥子配伍能够改变“方中君药”——延胡索的主要成分延胡索乙素穴位局部的皮下分布,促进方中君药有效成分快速吸收,延长滞留时间,在方剂中起到主药、改善其他药物分布的“双重”作用。
文摘冠气温差能够间接监测作物水分变化规律,而冠层温度与大气温度之间存在的时滞效应会影响监测效果,为探明两者之间的时滞效应变化规律及影响因素,本研究以拔节期至乳熟期的冬小麦为研究对象,利用红外温度传感器连续监测灌溉上限分别为田间持水率的95%(T1)、80%(T2)、65%(T3)和50%(T4)4个不同灌溉处理的冠层温度,并同步获取短波净辐射(Short-wave net radiation,R_(S))、大气温度(Atmospheric temperature,T_(A))、相对湿度(Relative humidity,R_(H))等气象数据。利用错位相关法计算冠层温度与大气温度之间的时滞时间(Time lag,TL),分析其在不同生育期和不同灌溉条件下变化规律,并采用相关性分析法探究气象因子(R_(S)、T_(A)、R_(H))变化率和日均值与时滞时间的相关性,最后通过通径分析探讨气象因子(R_(S)、T_(A)、R_(H))、土壤含水率(Soil moisture content,SMC)以及叶面积指数(Leaf area index,LAI)对时滞时间的共同影响。结果表明:不同生育期和不同灌溉条件下冬小麦冠层温度变化均提前于大气温度;在不同灌溉处理下,T1、T2和T3处理的时滞时间高于T4处理,且在不同生育期下,时滞时间呈现先减少再增加的趋势。短波净辐射变化率(Change rate of short-wave net radiation,R_(SCR))、大气温度变化率(Change rate of atmospheric temperature,T_(ACR))和相对湿度变化率(Change rate of relative humidity,R_(HCR))与时滞时间的相关性均高于对应日均值与时滞时间的相关性;同时,R_(SCR)与时滞时间的相关程度最高(相关系数R为0.718~0.806),TACR次之(R为0.582~0.661),RHCR最低(R为-0.534~-0.570)。利用通径分析发现,时滞时间主要受R_(SCR)、SMC以及LAI共同影响,但在不同灌溉条件下影响时滞时间的主要因素存在差异,其中T1、T2和T3处理主要受R_(SCR)和LAI影响,而T4主要受R_(SCR)和SMC影响。研究可为利用冠气温差信息监测作物水分变化进一步提供理论依据。
