China's food security has a great influence on the world,and has always been the top priority in China.In recent years,as the concept of food security is evolving into one of nutrition security and the importance ...China's food security has a great influence on the world,and has always been the top priority in China.In recent years,as the concept of food security is evolving into one of nutrition security and the importance of food diversity is increasing,research based on nutrition security and broad food systems are increasingly needed in today’s China.Thus,not only grain for human consumption,but also animal foods have been integrated into the Food Equivalent,which is used to analyze China’s current agriculture system and reveal the water resource distribution.The results indicated that the average animal food consumption has risen by 78.6%,and now China’s daily supply of animal food per capita has reached about 50%of that in the USA and 80%of that in the South Korea.So there exist an obvious disparity in animal food supply between China and these two countries.It is impossible for the China’s current agricultural system to achieve the level in the USA.Under China’s current agricultural system,the consumption proportion of feed grain had surpassed the consumption of food grain,increased sharply from 33%in 1992 to 67%in 2011.However,the growth potential of total grain output is approaching an upper limit,so the continued growth of feed grain demand exerts great pressure on the China’s food supply.The discordance of the spatial distribution of water resource and virtual water revealed that China’s current agriculture system had a low efficiency in being able to achieve food and nutrition security.China’s current“grain farming”cannot meet the demand of increasing nutrition and appropriate resource utilization.The implementation of grassland agriculture appears feasible and necessary for saving feed grain,providing a large number of high-quality animal foods and appropriate water resource utilization.展开更多
A new approach in combination of the effective medium theory with the equivalent unit in numerical simulation was developed to study the effective thermal conductivity of porous ceramics. The finite element method was...A new approach in combination of the effective medium theory with the equivalent unit in numerical simulation was developed to study the effective thermal conductivity of porous ceramics. The finite element method was used to simulate the heat transfer process which enables to acquire accurate results through highly complicated modeling and intensive computation. An alternative approach to mesh the material into small cells was also presented. The effective medium theory accounts for the effective thermal conductivity of cells while the equivalent unit is subsequently applied in numerical simulation to analyze the effective thermal conductivity of the porous ceramics. A new expression for the effective thermal conductivity, allowing for some structure factors such as volume fraction of pores and thermal conductivity, was put forward, and the results of its application was proved to be close to those of the mathematical simulation.展开更多
To explore the distribution of food demand and the projected trend in future food demand in China, this paper analyzed the change in current(1998–2012) percapita demand for grain, grain-consuming and herbivorous live...To explore the distribution of food demand and the projected trend in future food demand in China, this paper analyzed the change in current(1998–2012) percapita demand for grain, grain-consuming and herbivorous livestock products, and predicted the food demand in 2020 The results indicated that in 1998–2012, the national percapita consumption of grain ration declined by about36.66%, and the per-capita consumption of grain-consuming and herbivorous livestock products increased by about 48% and 34.09%, respectively. The grain-consuming livestock products have become the primary source of both calories and protein for consumers. The proportion of herbivorous livestock products in consumer diets has increased steadily and there has been huge potential in substituting beef and mutton for pork in this dynamic market. The demand for food in different regions of China is highly variable, which is important for planning grassland agriculture development and ensuring food safety. The demand for grain, and grain-consuming and herbivorous livestock products will increase by about3.3%, 20% and 14% respectively by 2020. Based on the food demand and trend in the development of grassland agriculture, the 31 regions in China are divided into three priority groups for grassland agriculture development.展开更多
The abdomen of a honeybee is a blueprint for bioinspired mechanical design because of its movement flexibility and compactness.However,the abdominal muscles closely related to the movement flexibility mechanism have n...The abdomen of a honeybee is a blueprint for bioinspired mechanical design because of its movement flexibility and compactness.However,the abdominal muscles closely related to the movement flexibility mechanism have not been fully identified,limiting the potential biological advantage of their use in bionic mechanism design.In this study,we reveal the muscle distribution of the complete muscular driving unit in a honeybee abdomen using stereoscopy and scanning electron microscopy,and the muscle distribution was effectively verified using X-ray tomography.A novel equivalent unit mechanism(EUM)was then proposed and the kinematic analysis indicated that the extension ratio,bending angle,and swing angle of the EUM reached 9.36%,1.22°,and 4.43°,respectively.The deformation ability of the EUM was consistent with the movement of the abdomen,confirming the movement flexibility.This work may provide a new perspective for distributed bionic mechanism design.展开更多
This paper proposes a new eddy current method, named equivalent unit method （EUM）, for the thickness measurement of the top copper film ofmultilayer interconnects in the chemical mechanical polishing （CMP） process...This paper proposes a new eddy current method, named equivalent unit method （EUM）, for the thickness measurement of the top copper film ofmultilayer interconnects in the chemical mechanical polishing （CMP） process, which is an important step in the integrated circuit （IC） manufacturing. The influence of the underneath circuit layers on the eddy current is modeled and treated as an equivalent film thickness. By subtracting this equivalent film component, the accuracy of the thickness measure- ment of the top copper layer with an eddy current sensor is improved and the absolute error is 3 nm for sampler measurement.展开更多
基金supported by the key consultative project“Ecological security of grassland and food security in China”by Chinese Academy of Engineering(2012-ZD-7)Program for Changjiang Scholars and Innovative Research Team in University(IRT13019).
文摘China's food security has a great influence on the world,and has always been the top priority in China.In recent years,as the concept of food security is evolving into one of nutrition security and the importance of food diversity is increasing,research based on nutrition security and broad food systems are increasingly needed in today’s China.Thus,not only grain for human consumption,but also animal foods have been integrated into the Food Equivalent,which is used to analyze China’s current agriculture system and reveal the water resource distribution.The results indicated that the average animal food consumption has risen by 78.6%,and now China’s daily supply of animal food per capita has reached about 50%of that in the USA and 80%of that in the South Korea.So there exist an obvious disparity in animal food supply between China and these two countries.It is impossible for the China’s current agricultural system to achieve the level in the USA.Under China’s current agricultural system,the consumption proportion of feed grain had surpassed the consumption of food grain,increased sharply from 33%in 1992 to 67%in 2011.However,the growth potential of total grain output is approaching an upper limit,so the continued growth of feed grain demand exerts great pressure on the China’s food supply.The discordance of the spatial distribution of water resource and virtual water revealed that China’s current agriculture system had a low efficiency in being able to achieve food and nutrition security.China’s current“grain farming”cannot meet the demand of increasing nutrition and appropriate resource utilization.The implementation of grassland agriculture appears feasible and necessary for saving feed grain,providing a large number of high-quality animal foods and appropriate water resource utilization.
文摘A new approach in combination of the effective medium theory with the equivalent unit in numerical simulation was developed to study the effective thermal conductivity of porous ceramics. The finite element method was used to simulate the heat transfer process which enables to acquire accurate results through highly complicated modeling and intensive computation. An alternative approach to mesh the material into small cells was also presented. The effective medium theory accounts for the effective thermal conductivity of cells while the equivalent unit is subsequently applied in numerical simulation to analyze the effective thermal conductivity of the porous ceramics. A new expression for the effective thermal conductivity, allowing for some structure factors such as volume fraction of pores and thermal conductivity, was put forward, and the results of its application was proved to be close to those of the mathematical simulation.
基金supported by the key project "Study of the Dynamic Market Equilibrium in Substituting Beef and Mutton for Pork" by the State Key Laboratory of Grassland Agroecosystems (SKLGAE201502)Program for Changjiang Scholars and Innovative Research Team in University (IRT13019)
文摘To explore the distribution of food demand and the projected trend in future food demand in China, this paper analyzed the change in current(1998–2012) percapita demand for grain, grain-consuming and herbivorous livestock products, and predicted the food demand in 2020 The results indicated that in 1998–2012, the national percapita consumption of grain ration declined by about36.66%, and the per-capita consumption of grain-consuming and herbivorous livestock products increased by about 48% and 34.09%, respectively. The grain-consuming livestock products have become the primary source of both calories and protein for consumers. The proportion of herbivorous livestock products in consumer diets has increased steadily and there has been huge potential in substituting beef and mutton for pork in this dynamic market. The demand for food in different regions of China is highly variable, which is important for planning grassland agriculture development and ensuring food safety. The demand for grain, and grain-consuming and herbivorous livestock products will increase by about3.3%, 20% and 14% respectively by 2020. Based on the food demand and trend in the development of grassland agriculture, the 31 regions in China are divided into three priority groups for grassland agriculture development.
基金We thank Mr.Yanfei Hu,Mr.Chenzhou Wang,and Ms.Chenguang Zhao,Center of Biomedical Analysis in Tsinghua University,for microstructure observation experiments about honeybee abdomen.This work was supported by the National Natural Science Foundations of China(Grant No.51475258 and 51805293)the Beijing Natural Science Foundation(Grant No.3184050)the free exploration project of State Key Laboratory of Tribology,Tsinghua University(SKLT2020B04).
文摘The abdomen of a honeybee is a blueprint for bioinspired mechanical design because of its movement flexibility and compactness.However,the abdominal muscles closely related to the movement flexibility mechanism have not been fully identified,limiting the potential biological advantage of their use in bionic mechanism design.In this study,we reveal the muscle distribution of the complete muscular driving unit in a honeybee abdomen using stereoscopy and scanning electron microscopy,and the muscle distribution was effectively verified using X-ray tomography.A novel equivalent unit mechanism(EUM)was then proposed and the kinematic analysis indicated that the extension ratio,bending angle,and swing angle of the EUM reached 9.36%,1.22°,and 4.43°,respectively.The deformation ability of the EUM was consistent with the movement of the abdomen,confirming the movement flexibility.This work may provide a new perspective for distributed bionic mechanism design.
文摘This paper proposes a new eddy current method, named equivalent unit method （EUM）, for the thickness measurement of the top copper film ofmultilayer interconnects in the chemical mechanical polishing （CMP） process, which is an important step in the integrated circuit （IC） manufacturing. The influence of the underneath circuit layers on the eddy current is modeled and treated as an equivalent film thickness. By subtracting this equivalent film component, the accuracy of the thickness measure- ment of the top copper layer with an eddy current sensor is improved and the absolute error is 3 nm for sampler measurement.
