The phenomenology involved in severe accidents in nuclear reactors is highly complex.Currently,integrated analysis programs used for severe accident analysis heavily rely on custom empirical parameters,which introduce...The phenomenology involved in severe accidents in nuclear reactors is highly complex.Currently,integrated analysis programs used for severe accident analysis heavily rely on custom empirical parameters,which introduce considerable uncertainty.Therefore,in recent years,the field of severe accidents has shifted its focus toward applying uncertainty analysis methods to quantify uncertainty in safety assessment programs,known as“best estimate plus uncertainty(BEPU).”This approach aids in enhancing our comprehension of these programs and their further development and improvement.This study concentrates on a third-generation pressurized water reactor equipped with advanced active and passive mitigation strategies.Through an Integrated Severe Accident Analysis Program(ISAA),numerical modeling and uncertainty analysis were conducted on severe accidents resulting from large break loss of coolant accidents.Seventeen uncertainty parameters of the ISAA program were meticulously screened.Using Wilks'formula,the developed uncertainty program code,SAUP,was employed to carry out Latin hypercube sampling,while ISAA was employed to execute batch calculations.Statistical analysis was then conducted on two figures of merit,namely hydrogen generation and the release of fission products within the pressure vessel.Uncertainty calculations revealed that hydrogen production and the fraction of fission product released exhibited a normal distribution,ranging from 182.784 to 330.664 kg and from 15.6 to 84.3%,respectively.The ratio of hydrogen production to reactor thermal power fell within the range of 0.0578–0.105.A sensitivity analysis was performed for uncertain input parameters,revealing significant correlations between the failure temperature of the cladding oxide layer,maximum melt flow rate,size of the particulate debris,and porosity of the debris with both hydrogen generation and the release of fission products.展开更多
To improve the productivity of oil wells,perforation technology is usually used to improve the productivity of horizontal wells in oilfield exploitation.After the perforation operation,the perforation channel around t...To improve the productivity of oil wells,perforation technology is usually used to improve the productivity of horizontal wells in oilfield exploitation.After the perforation operation,the perforation channel around the wellbore will form a near-well high-permeability reservoir area with the penetration depth as the radius,that is,the formation has different permeability characteristics with the perforation depth as the dividing line.Generally,the permeability is measured by the permeability tester,but this approach has a high workload and limited application.In this paper,according to the reservoir characteristics of perforated horizontal wells,the reservoir is divided into two areas:the original reservoir area and the near-well high permeability reservoir area.Based on the theory of seepage mechanics and the formula of open hole productivity,the permeability calculation formula of near-well high permeability reservoir area with perforation parameters is deduced.According to the principle of seepage continuity,the seepage is regarded as the synthesis of two directions:the horizontal plane elliptic seepage field and the vertical plane radial seepage field,and the oil well productivity prediction model of the perforated horizontal well is established by partition.The model comparison demonstrates that the model is reasonable and feasible.To calculate and analyze the effect of oil well production and the law of influencing factors,actual production data of the oilfield are substituted into the oil well productivity formula.It can effectively guide the technical process design and effect prediction of perforated horizontal wells.展开更多
Gross primary productivity(GPP)of vegetation is an important constituent of the terrestrial carbon sinks and is significantly influenced by drought.Understanding the impact of droughts on different types of vegetation...Gross primary productivity(GPP)of vegetation is an important constituent of the terrestrial carbon sinks and is significantly influenced by drought.Understanding the impact of droughts on different types of vegetation GPP provides insight into the spatiotemporal variation of terrestrial carbon sinks,aiding efforts to mitigate the detrimental effects of climate change.In this study,we utilized the precipitation and temperature data from the Climatic Research Unit,the standardized precipitation evapotranspiration index(SPEI),the standardized precipitation index(SPI),and the simulated vegetation GPP using the eddy covariance-light use efficiency(EC-LUE)model to analyze the spatiotemporal change of GPP and its response to different drought indices in the Mongolian Plateau during 1982-2018.The main findings indicated that vegetation GPP decreased in 50.53% of the plateau,mainly in its northern and northeastern parts,while it increased in the remaining 49.47%area.Specifically,meadow steppe(78.92%)and deciduous forest(79.46%)witnessed a significant decrease in vegetation GPP,while alpine steppe(75.08%),cropland(76.27%),and sandy vegetation(87.88%)recovered well.Warming aridification areas accounted for 71.39% of the affected areas,while 28.53% of the areas underwent severe aridification,mainly located in the south and central regions.Notably,the warming aridification areas of desert steppe(92.68%)and sandy vegetation(90.24%)were significant.Climate warming was found to amplify the sensitivity of coniferous forest,deciduous forest,meadow steppe,and alpine steppe GPP to drought.Additionally,the drought sensitivity of vegetation GPP in the Mongolian Plateau gradually decreased as altitude increased.The cumulative effect of drought on vegetation GPP persisted for 3.00-8.00 months.The findings of this study will improve the understanding of how drought influences vegetation in arid and semi-arid areas.展开更多
Background:Process-based models are widely used to simulate forest productivity,but complex parameterization and calibration challenge the application and development of these models.Sensitivity analysis of numerous p...Background:Process-based models are widely used to simulate forest productivity,but complex parameterization and calibration challenge the application and development of these models.Sensitivity analysis of numerous parameters is an essential step in model calibration and carbon flux simulation.However,parameters are not dependent on each other,and the results of sensitivity analysis usually vary due to different forest types and regions.Hence,global and representative sensitivity analysis would provide reliable information for simple calibration.Methods:To determine the contributions of input parameters to gross primary productivity(GPP)and net primary productivity(NPP),regression analysis and extended Fourier amplitude sensitivity testing(EFAST)were conducted for Biome-BGCMuSo to calculate the sensitivity index of the parameters at four observation sites under climate gradient from ChinaFLUX.Results:Generally,GPP and NPP were highly sensitive to C:Nleaf(C:N of leaves),Wint(canopy water interception coefficient),k(canopy light extinction coefficient),FLNR(fraction of leaf N in Rubisco),MRpern(coefficient of linear relationship between tissue N and maintenance respiration),VPDf(vapor pressure deficit complete conductance reduction),and SLA1(canopy average specific leaf area in phenological phase 1)at all observation sites.Various sensitive parameters occurred at four observation sites within different climate zones.GPP and NPP were particularly sensitive to FLNR,SLA1 and Wint,and C:Nleaf in temperate,alpine and subtropical zones,respectively.Conclusions:The results indicated that sensitivity parameters of China's forest ecosystems change with climate gradient.We found that parameter calibration should be performed according to plant functional type(PFT),and more attention needs to be paid to the differences in climate and environment.These findings contribute to determining the target parameters in field experiments and model calibration.展开更多
Permeability sensitivity to stress experiments were conducted on standard core samples taken from Wen 23 Gas Storage at multi-cycle injection and production conditions of the gas storage to study the change pattern of...Permeability sensitivity to stress experiments were conducted on standard core samples taken from Wen 23 Gas Storage at multi-cycle injection and production conditions of the gas storage to study the change pattern of stress sensitivity of permeability.A method for calculating permeability under overburden pressure in the multi-cycle injection and production process was proposed,and the effect of stress sensitivity of reservoir permeability on gas well injectivity and productivity in UGS was analyzed.Retention rate of permeability decreased sharply first and then slowly with the increase of the UGS cycles.The stress sensitivity index of permeability decreased with the increase of cycle number of net stress variations in the increase process of net stress.The stress sensitivity index of permeability hardly changed with the increase of cycle number of net stress variations in the decrease process of net stress.With the increase of cycle number of net stress variation,the stress sensitivity index of permeability in the increase process of net stress approached that in the decrease process of net stress.The lower the reservoir permeability,the greater the irreversible permeability loss rate,the stronger the cyclic stress sensitivity,and the higher the stress sensitivity index of the reservoir,the stronger the reservoir stress sensitivity.The gas zones with permeability lower than 0.3’10-3 mm2 are not suitable as gas storage regions.Stress sensitivity of reservoir permeability has strong impact on gas well injectivity and productivity and mainly in the first few cycles.展开更多
Climate warming has prolonged the optimization of crop-growing seasons,shortened actual growth periods,and changed crop-planting boundaries.It also has boosted crop yields in certain regions while compromising crop qu...Climate warming has prolonged the optimization of crop-growing seasons,shortened actual growth periods,and changed crop-planting boundaries.It also has boosted crop yields in certain regions while compromising crop quality and affected the occurrence of meteorological disasters and pest diseases damage,which has resulted in reduction in grain yield.Crop production systems will evidence more sensitivity to climate change in future;for example,with an increase of 1°C in temperature,the average growth period will be shortened by 17 days for winter wheat and 7-8 days for maize and rice.Of course regional differences will exist.Climate change will threaten crop yield stability and affect crop quality.Vulnerability will be addressed in regard to extreme climatic events,which include reducing exposure and improving adaptive capacity,because the exposure of rain-fed agriculture is greater than that of irrigated agriculture.Therefore,we propose three suggestions to reduce the vulnerability of crop production systems to climate change.First,strengthen the evaluation capacity construction of sensitivity,which includes(1)refining and improving all types of evaluation indicator systems and models;(2)innovating and developing evaluation methods and tools;and(3)combining field observation and case studies,so that(1)the impact of climate change and sensitivity can be assessed scientifically;(2)uncertainty in the study can be identified and reduced;and(3)improved understanding of climate systems and their changes,climate change impact,and sensitivity will be achieved.Second,strengthen adaptive capacity construction for crop production systems,which includes(1)rebuilding existing farmland infrastructure to improve meteorological disaster defences;(2)adjusting agriculture structure and adopting new crop varieties with enhanced resistance;(3)popularizing water-saving technology and dry farming technology;and(4)further researching interdisciplinary theories and methods.Third,strengthen function construction for natural and social systems,which includes(1)popularizing innovative technology;(2)progressing agricultural insurance;and(3)improving energy efficiency and increasing carbon sequestration and emission reduction ability to maintain a favorable ecological environment.展开更多
This paper is concerned with the sensitivity of set-valued discrete systems. Firstly, this paper obtained the equivalence between <img src="Edit_7024f70b-0568-4ca8-a554-c0d05abc0df0.bmp" alt="" ...This paper is concerned with the sensitivity of set-valued discrete systems. Firstly, this paper obtained the equivalence between <img src="Edit_7024f70b-0568-4ca8-a554-c0d05abc0df0.bmp" alt="" />or <img src="Edit_95636a59-7d5d-4b6c-8bd5-f699dd9208df.bmp" alt="" /> and the product system <img src="Edit_c714caaf-0ed9-46bc-b3e1-b0223474a8f5.bmp" alt="" /> in sensitivity, infinite sensitivity, <em>F</em>-sensitivity, (<em>F</em><sub>1</sub>, <em>F</em><sub>2</sub>)-sensitivity. Then, the relation between (<em>X</em>, <em>f</em><sub>1,∞</sub>) or (<em>Y</em>, <em>g</em><sub>1,∞</sub>) and <img src="Edit_55b4ce47-89f3-4476-a8a8-4d4db5a4e8eb.bmp" alt="" /> in ergodic sensitivity is obtained. Where <img src="Edit_a99604c4-2f72-4e75-a998-8057b8790e03.bmp" alt="" /> is the set-valued dynamical system induced by a non-autonomous discrete dynamical system (<em>X</em>, <em>f</em><sub>1,∞</sub>).展开更多
This study shows that a decline in investment efficiency due to information asymmetry may not necessarily devalue a firm but may enhance its value instead.Firms base their investment decisions on both public and priva...This study shows that a decline in investment efficiency due to information asymmetry may not necessarily devalue a firm but may enhance its value instead.Firms base their investment decisions on both public and private information.However,effectively transmitting private information to investors in a competitive market is quite challenging,as it leads to stock prices inadequately reflecting a firm’s true value.Simultaneously,firms must invest to achieve their business objectives,which results in a deviation between a firm’s actual investment level and the market’s expected investment level,thereby reducing investment-q sensitivity.However,this deviation does not imply a waste of societal resources;instead,it improves a firm’s core competitiveness in the product market.We consider the future launch of new products as a proxy for firm private information.We find that(1)private information is negatively associated with investment-q sensitivity,and that the greater the sales of the new product,the lower the investment-q sensitivity;(2)the negative effect is more pronounced for firms with higher revenue volatility and ownership concentration than for those with lower revenue volatility and ownership concentration.This study helps us to further understand how to evaluate firm investment efficiency from the perspective of private information and provides empirical evidence of the costs of the new product launch process.展开更多
基金This work was supported financially by the National Natural Science Foundation of China(No.12375176).
文摘The phenomenology involved in severe accidents in nuclear reactors is highly complex.Currently,integrated analysis programs used for severe accident analysis heavily rely on custom empirical parameters,which introduce considerable uncertainty.Therefore,in recent years,the field of severe accidents has shifted its focus toward applying uncertainty analysis methods to quantify uncertainty in safety assessment programs,known as“best estimate plus uncertainty(BEPU).”This approach aids in enhancing our comprehension of these programs and their further development and improvement.This study concentrates on a third-generation pressurized water reactor equipped with advanced active and passive mitigation strategies.Through an Integrated Severe Accident Analysis Program(ISAA),numerical modeling and uncertainty analysis were conducted on severe accidents resulting from large break loss of coolant accidents.Seventeen uncertainty parameters of the ISAA program were meticulously screened.Using Wilks'formula,the developed uncertainty program code,SAUP,was employed to carry out Latin hypercube sampling,while ISAA was employed to execute batch calculations.Statistical analysis was then conducted on two figures of merit,namely hydrogen generation and the release of fission products within the pressure vessel.Uncertainty calculations revealed that hydrogen production and the fraction of fission product released exhibited a normal distribution,ranging from 182.784 to 330.664 kg and from 15.6 to 84.3%,respectively.The ratio of hydrogen production to reactor thermal power fell within the range of 0.0578–0.105.A sensitivity analysis was performed for uncertain input parameters,revealing significant correlations between the failure temperature of the cladding oxide layer,maximum melt flow rate,size of the particulate debris,and porosity of the debris with both hydrogen generation and the release of fission products.
文摘To improve the productivity of oil wells,perforation technology is usually used to improve the productivity of horizontal wells in oilfield exploitation.After the perforation operation,the perforation channel around the wellbore will form a near-well high-permeability reservoir area with the penetration depth as the radius,that is,the formation has different permeability characteristics with the perforation depth as the dividing line.Generally,the permeability is measured by the permeability tester,but this approach has a high workload and limited application.In this paper,according to the reservoir characteristics of perforated horizontal wells,the reservoir is divided into two areas:the original reservoir area and the near-well high permeability reservoir area.Based on the theory of seepage mechanics and the formula of open hole productivity,the permeability calculation formula of near-well high permeability reservoir area with perforation parameters is deduced.According to the principle of seepage continuity,the seepage is regarded as the synthesis of two directions:the horizontal plane elliptic seepage field and the vertical plane radial seepage field,and the oil well productivity prediction model of the perforated horizontal well is established by partition.The model comparison demonstrates that the model is reasonable and feasible.To calculate and analyze the effect of oil well production and the law of influencing factors,actual production data of the oilfield are substituted into the oil well productivity formula.It can effectively guide the technical process design and effect prediction of perforated horizontal wells.
基金jointly supported by the National Natural Science Foundation of China(42361024,42101030,42261079,and 41961058)the Talent Project of Science and Technology in Inner Mongolia of China(NJYT22027 and NJYT23019)the Fundamental Research Funds for the Inner Mongolia Normal University,China(2022JBBJ014 and 2022JBQN093)。
文摘Gross primary productivity(GPP)of vegetation is an important constituent of the terrestrial carbon sinks and is significantly influenced by drought.Understanding the impact of droughts on different types of vegetation GPP provides insight into the spatiotemporal variation of terrestrial carbon sinks,aiding efforts to mitigate the detrimental effects of climate change.In this study,we utilized the precipitation and temperature data from the Climatic Research Unit,the standardized precipitation evapotranspiration index(SPEI),the standardized precipitation index(SPI),and the simulated vegetation GPP using the eddy covariance-light use efficiency(EC-LUE)model to analyze the spatiotemporal change of GPP and its response to different drought indices in the Mongolian Plateau during 1982-2018.The main findings indicated that vegetation GPP decreased in 50.53% of the plateau,mainly in its northern and northeastern parts,while it increased in the remaining 49.47%area.Specifically,meadow steppe(78.92%)and deciduous forest(79.46%)witnessed a significant decrease in vegetation GPP,while alpine steppe(75.08%),cropland(76.27%),and sandy vegetation(87.88%)recovered well.Warming aridification areas accounted for 71.39% of the affected areas,while 28.53% of the areas underwent severe aridification,mainly located in the south and central regions.Notably,the warming aridification areas of desert steppe(92.68%)and sandy vegetation(90.24%)were significant.Climate warming was found to amplify the sensitivity of coniferous forest,deciduous forest,meadow steppe,and alpine steppe GPP to drought.Additionally,the drought sensitivity of vegetation GPP in the Mongolian Plateau gradually decreased as altitude increased.The cumulative effect of drought on vegetation GPP persisted for 3.00-8.00 months.The findings of this study will improve the understanding of how drought influences vegetation in arid and semi-arid areas.
基金This study was funded by the National Natural Science Foundation of China(grant number 41871279 and 41901364).
文摘Background:Process-based models are widely used to simulate forest productivity,but complex parameterization and calibration challenge the application and development of these models.Sensitivity analysis of numerous parameters is an essential step in model calibration and carbon flux simulation.However,parameters are not dependent on each other,and the results of sensitivity analysis usually vary due to different forest types and regions.Hence,global and representative sensitivity analysis would provide reliable information for simple calibration.Methods:To determine the contributions of input parameters to gross primary productivity(GPP)and net primary productivity(NPP),regression analysis and extended Fourier amplitude sensitivity testing(EFAST)were conducted for Biome-BGCMuSo to calculate the sensitivity index of the parameters at four observation sites under climate gradient from ChinaFLUX.Results:Generally,GPP and NPP were highly sensitive to C:Nleaf(C:N of leaves),Wint(canopy water interception coefficient),k(canopy light extinction coefficient),FLNR(fraction of leaf N in Rubisco),MRpern(coefficient of linear relationship between tissue N and maintenance respiration),VPDf(vapor pressure deficit complete conductance reduction),and SLA1(canopy average specific leaf area in phenological phase 1)at all observation sites.Various sensitive parameters occurred at four observation sites within different climate zones.GPP and NPP were particularly sensitive to FLNR,SLA1 and Wint,and C:Nleaf in temperate,alpine and subtropical zones,respectively.Conclusions:The results indicated that sensitivity parameters of China's forest ecosystems change with climate gradient.We found that parameter calibration should be performed according to plant functional type(PFT),and more attention needs to be paid to the differences in climate and environment.These findings contribute to determining the target parameters in field experiments and model calibration.
基金Supported by the Chongqing Technical Innovation and Application&Development Special Project(cstc2020jscx-msxmX0189)。
文摘Permeability sensitivity to stress experiments were conducted on standard core samples taken from Wen 23 Gas Storage at multi-cycle injection and production conditions of the gas storage to study the change pattern of stress sensitivity of permeability.A method for calculating permeability under overburden pressure in the multi-cycle injection and production process was proposed,and the effect of stress sensitivity of reservoir permeability on gas well injectivity and productivity in UGS was analyzed.Retention rate of permeability decreased sharply first and then slowly with the increase of the UGS cycles.The stress sensitivity index of permeability decreased with the increase of cycle number of net stress variations in the increase process of net stress.The stress sensitivity index of permeability hardly changed with the increase of cycle number of net stress variations in the decrease process of net stress.With the increase of cycle number of net stress variation,the stress sensitivity index of permeability in the increase process of net stress approached that in the decrease process of net stress.The lower the reservoir permeability,the greater the irreversible permeability loss rate,the stronger the cyclic stress sensitivity,and the higher the stress sensitivity index of the reservoir,the stronger the reservoir stress sensitivity.The gas zones with permeability lower than 0.3’10-3 mm2 are not suitable as gas storage regions.Stress sensitivity of reservoir permeability has strong impact on gas well injectivity and productivity and mainly in the first few cycles.
文摘Climate warming has prolonged the optimization of crop-growing seasons,shortened actual growth periods,and changed crop-planting boundaries.It also has boosted crop yields in certain regions while compromising crop quality and affected the occurrence of meteorological disasters and pest diseases damage,which has resulted in reduction in grain yield.Crop production systems will evidence more sensitivity to climate change in future;for example,with an increase of 1°C in temperature,the average growth period will be shortened by 17 days for winter wheat and 7-8 days for maize and rice.Of course regional differences will exist.Climate change will threaten crop yield stability and affect crop quality.Vulnerability will be addressed in regard to extreme climatic events,which include reducing exposure and improving adaptive capacity,because the exposure of rain-fed agriculture is greater than that of irrigated agriculture.Therefore,we propose three suggestions to reduce the vulnerability of crop production systems to climate change.First,strengthen the evaluation capacity construction of sensitivity,which includes(1)refining and improving all types of evaluation indicator systems and models;(2)innovating and developing evaluation methods and tools;and(3)combining field observation and case studies,so that(1)the impact of climate change and sensitivity can be assessed scientifically;(2)uncertainty in the study can be identified and reduced;and(3)improved understanding of climate systems and their changes,climate change impact,and sensitivity will be achieved.Second,strengthen adaptive capacity construction for crop production systems,which includes(1)rebuilding existing farmland infrastructure to improve meteorological disaster defences;(2)adjusting agriculture structure and adopting new crop varieties with enhanced resistance;(3)popularizing water-saving technology and dry farming technology;and(4)further researching interdisciplinary theories and methods.Third,strengthen function construction for natural and social systems,which includes(1)popularizing innovative technology;(2)progressing agricultural insurance;and(3)improving energy efficiency and increasing carbon sequestration and emission reduction ability to maintain a favorable ecological environment.
文摘This paper is concerned with the sensitivity of set-valued discrete systems. Firstly, this paper obtained the equivalence between <img src="Edit_7024f70b-0568-4ca8-a554-c0d05abc0df0.bmp" alt="" />or <img src="Edit_95636a59-7d5d-4b6c-8bd5-f699dd9208df.bmp" alt="" /> and the product system <img src="Edit_c714caaf-0ed9-46bc-b3e1-b0223474a8f5.bmp" alt="" /> in sensitivity, infinite sensitivity, <em>F</em>-sensitivity, (<em>F</em><sub>1</sub>, <em>F</em><sub>2</sub>)-sensitivity. Then, the relation between (<em>X</em>, <em>f</em><sub>1,∞</sub>) or (<em>Y</em>, <em>g</em><sub>1,∞</sub>) and <img src="Edit_55b4ce47-89f3-4476-a8a8-4d4db5a4e8eb.bmp" alt="" /> in ergodic sensitivity is obtained. Where <img src="Edit_a99604c4-2f72-4e75-a998-8057b8790e03.bmp" alt="" /> is the set-valued dynamical system induced by a non-autonomous discrete dynamical system (<em>X</em>, <em>f</em><sub>1,∞</sub>).
基金the National Science Foundation of China for its support(No.71632006)and(No.72072107).
文摘This study shows that a decline in investment efficiency due to information asymmetry may not necessarily devalue a firm but may enhance its value instead.Firms base their investment decisions on both public and private information.However,effectively transmitting private information to investors in a competitive market is quite challenging,as it leads to stock prices inadequately reflecting a firm’s true value.Simultaneously,firms must invest to achieve their business objectives,which results in a deviation between a firm’s actual investment level and the market’s expected investment level,thereby reducing investment-q sensitivity.However,this deviation does not imply a waste of societal resources;instead,it improves a firm’s core competitiveness in the product market.We consider the future launch of new products as a proxy for firm private information.We find that(1)private information is negatively associated with investment-q sensitivity,and that the greater the sales of the new product,the lower the investment-q sensitivity;(2)the negative effect is more pronounced for firms with higher revenue volatility and ownership concentration than for those with lower revenue volatility and ownership concentration.This study helps us to further understand how to evaluate firm investment efficiency from the perspective of private information and provides empirical evidence of the costs of the new product launch process.