To understand the high strain rate deformation mechanism and determine the grain size,strain rate and porosity dependent yield strength of nanocrystalline materials,a new mechanical model based on the deformation mech...To understand the high strain rate deformation mechanism and determine the grain size,strain rate and porosity dependent yield strength of nanocrystalline materials,a new mechanical model based on the deformation mechanism of nanocrystalline materials under high strain rate loading was developed.As a first step of the research,the yield behavior of the nanocrystalline materials under high strain rate loading was mainly concerned in the model and uniform deformation was assumed for simplification.Nanocrystalline materials were treated as composites consisting of grain interior phase and grain boundary phase,and grain interior and grain boundary deformation mechanisms under high strain rate loading were analyzed,then Voigt model was applied to coupling grain boundary constitutive relation with mechanical model for grain interior phase to describe the overall yield mechanical behavior of nanocrystalline materials.The predictions by the developed model on the yield strength of nanocrysatlline materials at high strain rates show good agreements with various experimental data.Further discussion was presented for calculation results and relative experimental observations.展开更多
The objective of this study is to analyze a chemostat model of very simple type with the Haldane expression of growth rate and a variable yield coefficient. The proposed modified model is analyzed qualitatively and qu...The objective of this study is to analyze a chemostat model of very simple type with the Haldane expression of growth rate and a variable yield coefficient. The proposed modified model is analyzed qualitatively and quantitatively. Analytic conditions for stability and optimality are determined for washout and no washout equilibrium solutions. One of the main focuses of the study is to determine parameter values for which Hopf Bifurcations occur in a bioreactor. It has been shown that the maximum stable non-washout equilibrium exits at a residence time under suitable parameter values. Hopf bifurcation is observed at three different conditions of the parameters.展开更多
The Pacific saury(Cololabis saira)is one of the major harvested species in the temperate waters of the northwestern Pacific Ocean(NPO).The Catch-MSY model uses catch data and basic life history information to estimate...The Pacific saury(Cololabis saira)is one of the major harvested species in the temperate waters of the northwestern Pacific Ocean(NPO).The Catch-MSY model uses catch data and basic life history information to estimate the Maximum Sustainable Yield(MSY)for data-limited fisheries.Since there is considerable uncertainty in the current status of the Pacific saury stock in the NPO,the Catch-MSY model was used in this study to estimate MSY on the basis of catch data and life history information from the North Pacific Fisheries Commission(NPFC).During the process,17 scenarios,according to different prior distributions of the intrinsic rate of increase(r)and carrying capacity(K),were set for sensitivity analysis.Moreover,the influence of different catch time series and different process errors were taken into account.The results show the following:(1)there was a strong negative correlation relationship between ln(r)and ln(K);the MSY increases with an increase in the lower limit of r;(2)The time series of catch data had a limited impact on the assessment results,whereas the results of the model were sensitive to the annual catch in the first and last years;(3)The estimated MSYs of the Pacific saury were 47.37×10^4 t(41.57×10^4 t to 53.17×10^4 t)in scenario S1A and 47.53×10^4 t(41.79×10^4 t to 53.27×10^4 t)in scenario S1B.Given the uncertainty of the Catch-MSY model,maintaining a management target between 50×10^4 t and 70×10^4 t was a better management regulation.This study shows that the Catch-MSY model is a useful choice for estimating the MSY of data-limited species such as the Pacific saury.展开更多
Based on theoretical analysis of crop risk and premium rate setting,we take the case of premium rate setting of insurance on cotton yield in Shache County,Shaya County and Aksu City of Xinjiang.Using parametric method...Based on theoretical analysis of crop risk and premium rate setting,we take the case of premium rate setting of insurance on cotton yield in Shache County,Shaya County and Aksu City of Xinjiang.Using parametric methods and insurance actuarial technique,we select the optimal model for risk fitting of cotton yield in three areas;compare the premium rate calculated accurately under four risk distribution assumptions of cotton yield,and the rational premium rate,to analyze the impact of risk distribution of crop yield on premium rate setting.The empirical results show that the Logistic distribution is the optimal distribution for risk fitting of cotton yield in three areas;the rational net premium rate of cotton insurance in three areas is 7.62%,6.32% and 4.96%,respectively;there are errors in premium rate setting under assumptions of normal distribution,normalized skew distribution and Weibull distribution,ranging from 0.2 percentage points to 8 percentage points.Thus,it indicates that the selection of risk distribution model of yield directly affects the accuracy of premium rate setting of crops,and the key to accurate premium rate setting of crops lies in correct selection of risk distribution model of yield.展开更多
Different ratios of NPK were adopted in this research to study its effects on the objective traits of 2 early forage-rice varieties, and to obtain the optimum ratio to further improve the application technique in theo...Different ratios of NPK were adopted in this research to study its effects on the objective traits of 2 early forage-rice varieties, and to obtain the optimum ratio to further improve the application technique in theory. At the same time, the possibility of increasing yield and protein content in the grain through cultivation technique was also studied. The conclusions were：展开更多
Most fisheries in China do not have maximum sustainable yield（MSY） estimates due to limited and poor data.Therefore, finding a common method to estimate MSY or total allowable catch（TAC） for fishery management is ...Most fisheries in China do not have maximum sustainable yield（MSY） estimates due to limited and poor data.Therefore, finding a common method to estimate MSY or total allowable catch（TAC） for fishery management is necessary. MSYs of three important fisheries in the East China Sea were evaluated through a catch-based model.Estimates for intrinsic rate of increase（r） and five levels of process error were considered. Results showed hairtail Trichiurus japonicas（Temminck and Schlegel） and small yellow croaker Larimichthys polyactis（Bleeker） fisheries experienced overfishing from the mid-1990 s to the early 2000 s, and the suggested TACs were 55.8×10^4 t and9.06×10^4 t, respectively. Decades of overfishing in wintering and spawning grounds of large yellow croaker Larimichthys crocea（Richardson） caused the fishery＇s collapse in the 1980 s, and it has not recovered until today.The Catch–MSY model generated similar estimated MSYs with other methods and may be a useful choice for the assessment of regional stocks in China.展开更多
Delay-difference models are intermediate between simple surplus-production models and complicated age-structured models. Such intermediate models are more efficient and require less data than age-structured models. In...Delay-difference models are intermediate between simple surplus-production models and complicated age-structured models. Such intermediate models are more efficient and require less data than age-structured models. In this study, a delay-differ- ence model was applied to fit catch and catch per unit effort （CPUE） data （1975-2011） of the southern Atlantic albacore （Thunnus alalunga） stock. The proposed delay-difference model captures annual fluctuations in predicted CPUE data better than Fox model. In a Monte Carlo simulation, white noises （CVs） were superimposed on the observed CPUE data at four levels. Relative estimate error was then calculated to compare the estimated results with the true values of parameters a and fl in Ricker stock-recruitment model and the catchability coefficient q. a is more sensitive to CV than fl and q. We also calculated an 80% percentile confidence interval of the maximum sustainable yield （MSY, 21756 t to 23408 t; median 22490 t） with the delay-difference model. The yield of the southern Atlantic albacore stock in 2011 was 24122t, and the estimated ratios of catch against MSY for the past seven years were approxi- mately 1.0. We suggest that care should be taken to protect the albacore fishery in the southern Atlantic Ocean. The proposed de- lay-difference model provides a good fit to the data of southern Atlantic albacore stock and may be a useful choice for the assessment of regional albacore stock.展开更多
基金Project(10502025) supported by the National Natural Science Foundation of ChinaProject(101005) supported by Fok Ying Tong Education FoundationProject(BK2007528) supported by the Natural Science Foundation of Jiangsu Province,China
文摘To understand the high strain rate deformation mechanism and determine the grain size,strain rate and porosity dependent yield strength of nanocrystalline materials,a new mechanical model based on the deformation mechanism of nanocrystalline materials under high strain rate loading was developed.As a first step of the research,the yield behavior of the nanocrystalline materials under high strain rate loading was mainly concerned in the model and uniform deformation was assumed for simplification.Nanocrystalline materials were treated as composites consisting of grain interior phase and grain boundary phase,and grain interior and grain boundary deformation mechanisms under high strain rate loading were analyzed,then Voigt model was applied to coupling grain boundary constitutive relation with mechanical model for grain interior phase to describe the overall yield mechanical behavior of nanocrystalline materials.The predictions by the developed model on the yield strength of nanocrysatlline materials at high strain rates show good agreements with various experimental data.Further discussion was presented for calculation results and relative experimental observations.
文摘The objective of this study is to analyze a chemostat model of very simple type with the Haldane expression of growth rate and a variable yield coefficient. The proposed modified model is analyzed qualitatively and quantitatively. Analytic conditions for stability and optimality are determined for washout and no washout equilibrium solutions. One of the main focuses of the study is to determine parameter values for which Hopf Bifurcations occur in a bioreactor. It has been shown that the maximum stable non-washout equilibrium exits at a residence time under suitable parameter values. Hopf bifurcation is observed at three different conditions of the parameters.
基金Supported by the National Sci-Tech Support Plan“Fishing Technology and New Resources in Oceanic Fisheries”(No.2013BAD13B05)。
文摘The Pacific saury(Cololabis saira)is one of the major harvested species in the temperate waters of the northwestern Pacific Ocean(NPO).The Catch-MSY model uses catch data and basic life history information to estimate the Maximum Sustainable Yield(MSY)for data-limited fisheries.Since there is considerable uncertainty in the current status of the Pacific saury stock in the NPO,the Catch-MSY model was used in this study to estimate MSY on the basis of catch data and life history information from the North Pacific Fisheries Commission(NPFC).During the process,17 scenarios,according to different prior distributions of the intrinsic rate of increase(r)and carrying capacity(K),were set for sensitivity analysis.Moreover,the influence of different catch time series and different process errors were taken into account.The results show the following:(1)there was a strong negative correlation relationship between ln(r)and ln(K);the MSY increases with an increase in the lower limit of r;(2)The time series of catch data had a limited impact on the assessment results,whereas the results of the model were sensitive to the annual catch in the first and last years;(3)The estimated MSYs of the Pacific saury were 47.37×10^4 t(41.57×10^4 t to 53.17×10^4 t)in scenario S1A and 47.53×10^4 t(41.79×10^4 t to 53.27×10^4 t)in scenario S1B.Given the uncertainty of the Catch-MSY model,maintaining a management target between 50×10^4 t and 70×10^4 t was a better management regulation.This study shows that the Catch-MSY model is a useful choice for estimating the MSY of data-limited species such as the Pacific saury.
基金Supported by International Cooperation Project of China's Agricultural Insurance (DelPHE ACIC)
文摘Based on theoretical analysis of crop risk and premium rate setting,we take the case of premium rate setting of insurance on cotton yield in Shache County,Shaya County and Aksu City of Xinjiang.Using parametric methods and insurance actuarial technique,we select the optimal model for risk fitting of cotton yield in three areas;compare the premium rate calculated accurately under four risk distribution assumptions of cotton yield,and the rational premium rate,to analyze the impact of risk distribution of crop yield on premium rate setting.The empirical results show that the Logistic distribution is the optimal distribution for risk fitting of cotton yield in three areas;the rational net premium rate of cotton insurance in three areas is 7.62%,6.32% and 4.96%,respectively;there are errors in premium rate setting under assumptions of normal distribution,normalized skew distribution and Weibull distribution,ranging from 0.2 percentage points to 8 percentage points.Thus,it indicates that the selection of risk distribution model of yield directly affects the accuracy of premium rate setting of crops,and the key to accurate premium rate setting of crops lies in correct selection of risk distribution model of yield.
文摘Different ratios of NPK were adopted in this research to study its effects on the objective traits of 2 early forage-rice varieties, and to obtain the optimum ratio to further improve the application technique in theory. At the same time, the possibility of increasing yield and protein content in the grain through cultivation technique was also studied. The conclusions were：
基金The National Natural Science Foundation of China under contract No.31602157the Special Fund for Agroscientific Research in the Public Interest under contract No.201403008the Central Public-interest Scientific Institution Basal Research Fund of South China Sea Fisheries Research Institute under contract No.2016TS06
文摘Most fisheries in China do not have maximum sustainable yield（MSY） estimates due to limited and poor data.Therefore, finding a common method to estimate MSY or total allowable catch（TAC） for fishery management is necessary. MSYs of three important fisheries in the East China Sea were evaluated through a catch-based model.Estimates for intrinsic rate of increase（r） and five levels of process error were considered. Results showed hairtail Trichiurus japonicas（Temminck and Schlegel） and small yellow croaker Larimichthys polyactis（Bleeker） fisheries experienced overfishing from the mid-1990 s to the early 2000 s, and the suggested TACs were 55.8×10^4 t and9.06×10^4 t, respectively. Decades of overfishing in wintering and spawning grounds of large yellow croaker Larimichthys crocea（Richardson） caused the fishery＇s collapse in the 1980 s, and it has not recovered until today.The Catch–MSY model generated similar estimated MSYs with other methods and may be a useful choice for the assessment of regional stocks in China.
基金supported by the Fundamental Research Funds for the Central Universities of China (Grant No. 201022001)
文摘Delay-difference models are intermediate between simple surplus-production models and complicated age-structured models. Such intermediate models are more efficient and require less data than age-structured models. In this study, a delay-differ- ence model was applied to fit catch and catch per unit effort （CPUE） data （1975-2011） of the southern Atlantic albacore （Thunnus alalunga） stock. The proposed delay-difference model captures annual fluctuations in predicted CPUE data better than Fox model. In a Monte Carlo simulation, white noises （CVs） were superimposed on the observed CPUE data at four levels. Relative estimate error was then calculated to compare the estimated results with the true values of parameters a and fl in Ricker stock-recruitment model and the catchability coefficient q. a is more sensitive to CV than fl and q. We also calculated an 80% percentile confidence interval of the maximum sustainable yield （MSY, 21756 t to 23408 t; median 22490 t） with the delay-difference model. The yield of the southern Atlantic albacore stock in 2011 was 24122t, and the estimated ratios of catch against MSY for the past seven years were approxi- mately 1.0. We suggest that care should be taken to protect the albacore fishery in the southern Atlantic Ocean. The proposed de- lay-difference model provides a good fit to the data of southern Atlantic albacore stock and may be a useful choice for the assessment of regional albacore stock.
