The impact of inputs on farm production growth was evaluated by analyzing the economic data of the upper and middle parts of the Yellow River basin, China for the period of 1980-1999. Descriptive statistics were emplo...The impact of inputs on farm production growth was evaluated by analyzing the economic data of the upper and middle parts of the Yellow River basin, China for the period of 1980-1999. Descriptive statistics were employed to characterize the temporal trends and spatial patterns in farm production and five pertinent inputs of cultivated cropland, irrigation ratio, agricultural labor, machinery power and chemical fertilizer. Stochastic frontier production function was applied to quantify the dependence of the farm production on these inputs. The growth of farm production was decomposed to reflect the contributions by input growths and change in total factor productivity.. The change in total factor productivity was further decomposed into the changes in technology and in technical efficiency. The gross value of farm production in the region of study increased by 1.6 fold during 1980-1999. Among the five selected farm inputs, machinery power and chemical fertilizer increased by 1.8 and 2.8 fold, respectively. The increases in cultivated cropland, irrigated cropland, and agricultural labor were all less than 0.16 fold. The growth in the farm production was primarily contributed by the increase in the total factor productivity during 1980-1985, and by input growths after 1985. More than 80% of the contributions by input growths were attributed to the increased application of fertilizer and machinery. In the change of total factor productivity, the technology change dominated over the technical efficiency change in the study period except in the period of 1985-1990, implying that institution and investment played important roles in farm production growth. There was a decreasing trend in the technical efficiency in the region of study, indicating a potential to increase farm production by improving the technical efficiency in farm activities. Given the limited natural resources in the basin, the results of this study suggested that, for a sustainable growth of farm production in the area, efforts should be directed to technology progress and improvement in technical efficiency in the use of available resources.展开更多
A two-dimensional numerical model,which is configured on the basis of Princeton ocean model（POM）,is used to study the effect of Stokes production（SP） of the turbulent kinetic energy on a density profile and Ekman ...A two-dimensional numerical model,which is configured on the basis of Princeton ocean model（POM）,is used to study the effect of Stokes production（SP） of the turbulent kinetic energy on a density profile and Ekman transport in an idealized shelf region in summer.The energy input from SP is parameterized and included into the Mellor-Yamada turbulence closure submodel.Results reveal that the intensity of wind-driven upwelling fronts near the sea surface is weakened by the SP-associated turbulent kinetic energy input.The vertical eddy viscosity coefficient in the surface boundary layer is enhanced greatly owing to the impact of SP,which decreases the alongshore velocity and changes the distribution of upwelling.In addition,the SP-induced mixing easily suppresses the strong stratification and significantly increases the depth of the upper mixed layer（ML） under strong winds.展开更多
基金support was partially provided by the University of Connecticut Research Foundation,Storrs Agricultural Experiment Station,Chinese Academy of Sciences Outstanding Overseas Chinese Scholars Award,and the National Natural Science Foundation of China(40671071).
文摘The impact of inputs on farm production growth was evaluated by analyzing the economic data of the upper and middle parts of the Yellow River basin, China for the period of 1980-1999. Descriptive statistics were employed to characterize the temporal trends and spatial patterns in farm production and five pertinent inputs of cultivated cropland, irrigation ratio, agricultural labor, machinery power and chemical fertilizer. Stochastic frontier production function was applied to quantify the dependence of the farm production on these inputs. The growth of farm production was decomposed to reflect the contributions by input growths and change in total factor productivity.. The change in total factor productivity was further decomposed into the changes in technology and in technical efficiency. The gross value of farm production in the region of study increased by 1.6 fold during 1980-1999. Among the five selected farm inputs, machinery power and chemical fertilizer increased by 1.8 and 2.8 fold, respectively. The increases in cultivated cropland, irrigated cropland, and agricultural labor were all less than 0.16 fold. The growth in the farm production was primarily contributed by the increase in the total factor productivity during 1980-1985, and by input growths after 1985. More than 80% of the contributions by input growths were attributed to the increased application of fertilizer and machinery. In the change of total factor productivity, the technology change dominated over the technical efficiency change in the study period except in the period of 1985-1990, implying that institution and investment played important roles in farm production growth. There was a decreasing trend in the technical efficiency in the region of study, indicating a potential to increase farm production by improving the technical efficiency in farm activities. Given the limited natural resources in the basin, the results of this study suggested that, for a sustainable growth of farm production in the area, efforts should be directed to technology progress and improvement in technical efficiency in the use of available resources.
基金The National Basic Research Program of China under contract No.2013CB430304the National Natural Science Foundation of China under contract Nos 41030854+2 种基金4110600541176003 and 41206178the National Science and Technology Support Program of China under contract No.2011BAC03B02-01
文摘A two-dimensional numerical model,which is configured on the basis of Princeton ocean model（POM）,is used to study the effect of Stokes production（SP） of the turbulent kinetic energy on a density profile and Ekman transport in an idealized shelf region in summer.The energy input from SP is parameterized and included into the Mellor-Yamada turbulence closure submodel.Results reveal that the intensity of wind-driven upwelling fronts near the sea surface is weakened by the SP-associated turbulent kinetic energy input.The vertical eddy viscosity coefficient in the surface boundary layer is enhanced greatly owing to the impact of SP,which decreases the alongshore velocity and changes the distribution of upwelling.In addition,the SP-induced mixing easily suppresses the strong stratification and significantly increases the depth of the upper mixed layer（ML） under strong winds.
