为研究渠道水生植被特征对渠内水力特性影响,设计了渠道模型试验,探讨了植被生长间距、入渠流量等因素影响下渠道水位、流速变化。试验表明,入渠流量对渠内断面水位变化特征影响较小,但植被生长间距特征会改变渠内断面水位变化,在间距为...为研究渠道水生植被特征对渠内水力特性影响,设计了渠道模型试验,探讨了植被生长间距、入渠流量等因素影响下渠道水位、流速变化。试验表明,入渠流量对渠内断面水位变化特征影响较小,但植被生长间距特征会改变渠内断面水位变化,在间距为10~15、20~30、35~40 mm 3个区段具有不同的水位变化趋势。入渠流量愈大,则水位愈高;但植被生长间距愈大,则渠内水位愈低。当植被生长间距不超过25 mm时,渠内流速变化具有增、降阶段,而在间距为30~40 mm时流速较稳定。植被生长间距愈大,则流速愈高。研究认为渠内水生植被应控制其分布密度与间距,以降低水生植被对渠内动水势能的影响。展开更多
Two opposing intellectual traditions and their contem-porary developments regarding the relations among population, available resources, and quality of life as reflected in economic growth are reviewed. What is at iss...Two opposing intellectual traditions and their contem-porary developments regarding the relations among population, available resources, and quality of life as reflected in economic growth are reviewed. What is at issue is whether population growth is detrimental to or beneficial for economic development. Neither of the extreme views gives a complete picture of the interplay among population, resources, and quality of life. Following previous literature on the topic, this paper establishes a more balanced approach that considers the function linking population and quality of life not constant but variable and regards the limitedness of resources as not absolute but relative to regions and societies. The proposed approach is more flexible in better explaining the relation between population and economic growth. China is examined as a case in point to shed light on the interaction of population growth, economic development, and available resources, and its recent post-economic reform experiences showcase the appropriateness of the synthetic approach.展开更多
This study introduces space, transportation, and money into an economic growth model. Growth theory neglects the importance of transportation on economic growth and transportation economics fails to properly explain h...This study introduces space, transportation, and money into an economic growth model. Growth theory neglects the importance of transportation on economic growth and transportation economics fails to properly explain how changes in transportation conditions (such as technological improvement, infrastructure investment, and oil prices) affect long-term economic growth. By proposing a growth model with transportations, we try to explain effects of transportation on economic growth. Our model describes dynamic interactions among capital accumulation, travel time, housing, residential distribution, amenity, and endogenous time distribution among work, travel, and leisure. The study examines effects of inflation policy, transportation conditions, and other conditions on long-term economic growth and economic geography. The paper demonstrates a way to integrating some important models in the literature in economic growth theory, urban economics, and transportation research so that the significance of transportation systems upon economies can be properly analyzed.展开更多
In this study, the microstructure evolution of rapidly solidified ASP30 high-speed steel particles was predicted using a simulation method based on the cellular automaton-finite element （CAFE） model. The dendritic g...In this study, the microstructure evolution of rapidly solidified ASP30 high-speed steel particles was predicted using a simulation method based on the cellular automaton-finite element （CAFE） model. The dendritic growth kinetics, in view of the characteristics of ASP30 steel, were calculated and combined with macro heat transfer calculations by user-defined functions （UDFs） to simulate the microstructure of gas-atomized particles. The relationship among particle diameter, undercooling, and the convection heat transfer coefficient was also inves- tigated to provide cooling conditions for simulations. The simulated results indicated that a columnar grain microstructure was observed in small particles, whereas an equiaxed microstructure was observed in large particles. In addition, the morphologies and microstructures of gas-atomized ASP30 steel particles were also investigated experimentally using scanning electron microscopy （SEM）. The experimental re- suits showed that four major types ofmicrostructures were formed： dendritic, equiaxed, mixed, and multi-droplet microstructures. The simu- lated results and the available experimental data are in good agreement.展开更多
The management of fertilization in maize plants is a preponderant factor in the search for higher yields and obtaining quality seeds. In this sense, the study of nitrogen (N) management is predominant in improving the...The management of fertilization in maize plants is a preponderant factor in the search for higher yields and obtaining quality seeds. In this sense, the study of nitrogen (N) management is predominant in improving the efficiency of its application. The objective of this study was to evaluate the growth, partition assimilation and vigor expression of maize seeds submitted at different doses of nitrogen applied at sowing. The treatments were constituted by different doses of nitrogen fertilization at sowing, being: 25%, 50%, 75% and 100% of the recommended dose for the crop, according to the recommendation of nitrogen fertilization. The plants were collected at regular intervals of 21 days after sowing until the end of the growth cycle. For the analysis of growth and partition of dry matter between the organs, the accumulation of dry matter and leaf area was measured. The experimental design was randomized blocks in a 4 × 7 factorial scheme (four N rates at sowing and seven collection times with three replications). The maize plants under the influence of nitrogen fertilization at sowing presented differential growth and distinct responses in the assimilated partition between their structures, with the intensity dependent on the dose used. Plants grown using 75% of the recommended dose of N at sowing had a higher relative growth rate, with more pronounced effects compared to the other doses. The expression of maize seed vigor increases to an increase of 82.5% N at sowing.展开更多
文摘为研究渠道水生植被特征对渠内水力特性影响,设计了渠道模型试验,探讨了植被生长间距、入渠流量等因素影响下渠道水位、流速变化。试验表明,入渠流量对渠内断面水位变化特征影响较小,但植被生长间距特征会改变渠内断面水位变化,在间距为10~15、20~30、35~40 mm 3个区段具有不同的水位变化趋势。入渠流量愈大,则水位愈高;但植被生长间距愈大,则渠内水位愈低。当植被生长间距不超过25 mm时,渠内流速变化具有增、降阶段,而在间距为30~40 mm时流速较稳定。植被生长间距愈大,则流速愈高。研究认为渠内水生植被应控制其分布密度与间距,以降低水生植被对渠内动水势能的影响。
文摘Two opposing intellectual traditions and their contem-porary developments regarding the relations among population, available resources, and quality of life as reflected in economic growth are reviewed. What is at issue is whether population growth is detrimental to or beneficial for economic development. Neither of the extreme views gives a complete picture of the interplay among population, resources, and quality of life. Following previous literature on the topic, this paper establishes a more balanced approach that considers the function linking population and quality of life not constant but variable and regards the limitedness of resources as not absolute but relative to regions and societies. The proposed approach is more flexible in better explaining the relation between population and economic growth. China is examined as a case in point to shed light on the interaction of population growth, economic development, and available resources, and its recent post-economic reform experiences showcase the appropriateness of the synthetic approach.
文摘This study introduces space, transportation, and money into an economic growth model. Growth theory neglects the importance of transportation on economic growth and transportation economics fails to properly explain how changes in transportation conditions (such as technological improvement, infrastructure investment, and oil prices) affect long-term economic growth. By proposing a growth model with transportations, we try to explain effects of transportation on economic growth. Our model describes dynamic interactions among capital accumulation, travel time, housing, residential distribution, amenity, and endogenous time distribution among work, travel, and leisure. The study examines effects of inflation policy, transportation conditions, and other conditions on long-term economic growth and economic geography. The paper demonstrates a way to integrating some important models in the literature in economic growth theory, urban economics, and transportation research so that the significance of transportation systems upon economies can be properly analyzed.
基金the National Basic Research Program of China (No. 2011CB012902) for their continuing support to this research
文摘In this study, the microstructure evolution of rapidly solidified ASP30 high-speed steel particles was predicted using a simulation method based on the cellular automaton-finite element （CAFE） model. The dendritic growth kinetics, in view of the characteristics of ASP30 steel, were calculated and combined with macro heat transfer calculations by user-defined functions （UDFs） to simulate the microstructure of gas-atomized particles. The relationship among particle diameter, undercooling, and the convection heat transfer coefficient was also inves- tigated to provide cooling conditions for simulations. The simulated results indicated that a columnar grain microstructure was observed in small particles, whereas an equiaxed microstructure was observed in large particles. In addition, the morphologies and microstructures of gas-atomized ASP30 steel particles were also investigated experimentally using scanning electron microscopy （SEM）. The experimental re- suits showed that four major types ofmicrostructures were formed： dendritic, equiaxed, mixed, and multi-droplet microstructures. The simu- lated results and the available experimental data are in good agreement.
文摘The management of fertilization in maize plants is a preponderant factor in the search for higher yields and obtaining quality seeds. In this sense, the study of nitrogen (N) management is predominant in improving the efficiency of its application. The objective of this study was to evaluate the growth, partition assimilation and vigor expression of maize seeds submitted at different doses of nitrogen applied at sowing. The treatments were constituted by different doses of nitrogen fertilization at sowing, being: 25%, 50%, 75% and 100% of the recommended dose for the crop, according to the recommendation of nitrogen fertilization. The plants were collected at regular intervals of 21 days after sowing until the end of the growth cycle. For the analysis of growth and partition of dry matter between the organs, the accumulation of dry matter and leaf area was measured. The experimental design was randomized blocks in a 4 × 7 factorial scheme (four N rates at sowing and seven collection times with three replications). The maize plants under the influence of nitrogen fertilization at sowing presented differential growth and distinct responses in the assimilated partition between their structures, with the intensity dependent on the dose used. Plants grown using 75% of the recommended dose of N at sowing had a higher relative growth rate, with more pronounced effects compared to the other doses. The expression of maize seed vigor increases to an increase of 82.5% N at sowing.
