The Liupan Mountains is located in the southern Ningxia Hui Autonomous Region of China, which forms an important dividing line between landforms and bio-geographic regions. The populated part of the Liupan Mountains r...The Liupan Mountains is located in the southern Ningxia Hui Autonomous Region of China, which forms an important dividing line between landforms and bio-geographic regions. The populated part of the Liupan Mountains region has suffered tremendous ecological damages over time due to population pressure, excessive demand and inappropriate use of agricultural land resources. In this paper, datasets of land use between 1990 and 2000 were obtained from Landsat TM imagery, and then spatial models were used to characterize landscape conditions. Also, the relationship between the population density and land use/cover change (LUCC) was analyzed. Results indicate that cropland, forestland, and urban areas have increased by 44,186ha, 9001ha and 1550ha, respectively while the grassland area has appreciably decreased by 54,025ha in the study period. The decrease in grassland was most notable. Of the grassland lost, 49.4% was converted into cropland. The largest annual land conversion rate in the study area was less than 2%. These changes are attributed to industrial and agricultural development and population growth. To improve the eco-economic conditions in the study region, population control, urbanization and development of an ecological friendly agriculture were suggested.展开更多
Previous soil-disc force prediction models have considered spherical and concave blades, as used on disc ploughs and harrows, with many simplifying assumptions. This study proposes an approach applying the fundamental...Previous soil-disc force prediction models have considered spherical and concave blades, as used on disc ploughs and harrows, with many simplifying assumptions. This study proposes an approach applying the fundamental equation of earth moving mechanics for calculating the soil passive reaction acting on a rotating fiat disc blade as used on a zero-till single disc seeder. The study considers the effects of disc variable depth of cut, sweep and tilt angles, free rotation and a scrubbing reaction at the beveled edge. This paper outlines the modeling approach and prediction results for a fixed circular blade operating at 90° sweep angle over a range of speeds and at two tilt angles. To account for the varying depth across the circular disc shape width, elemental wide blade force reactions acting on wide blade segments of elemental width were integrated across the disc working width. By including inertia forces due to speed as well as additional bulldozing forces due to the loose soil accumulation in front of the blade the draught and upward vertical forces acting on the vertical disc blade were predicted with a deviation of 6%-19% and 1.5%-14% from measured data, respectively. The model was able to predict the effect of increasing the tilt angle from 0° to 20° on reducing both draught and upward vertical forces. Further development and validation of the model will be described in subsequent papers, reflecting a step by step approach of increasing complexity to model a disc blade as used on a zero-till single disc seeding system.展开更多
China is the largest developing country in the world and a well-known agricultural country. China＇s urbanization is a subject of great interest, one that has attracted the attention of people throughout the world. Wh...China is the largest developing country in the world and a well-known agricultural country. China＇s urbanization is a subject of great interest, one that has attracted the attention of people throughout the world. Whereas a handful of studies have assessed various aspects of urbanization（urban expansion, urban transition, urban-rural relationships, the spatial changes in urban and rural areas, motivations for sustaining rural places）, little is known of how to retain the indigenous character of rural areas in terms of landscape design. In this paper, the authors set out to contribute to this significant gap. They used Chengdu City and Five Golden Flowers（FGF） village in Chengdu＇s suburbs as case studies. A detailed description of the application of Ebenezer Howard＇s Garden City vision in Chengdu City was made; the Garden City vision was the key premise for FGF＇s ecotourism industry and successful conservation of landscapes with indigenous character. An analysis of the post-ecotourism landscape in FGF was accomplished using a typology method. Finally a set of landscape design methods for retaining indigenous character was proposed. The main conclusion of this paper was as follows： rural ecotourism can contribute to maintaining the indigenous character of rapidly urbanizing rural landscapes with the use of appropriate inheritance and renovation ways. The findings here may provide useful information for decision making by urban planners and policy-makers.展开更多
基金Under the auspices of the National Key Science and Technology Support Program of China (No. 2006BCA01A07-2)National Natural Science Foundation of China (No. 40671153)+1 种基金Hunan Land Resource Bureau Program (No. 2007-15)Hunan Educa-tion Bureau Program (No. 08C348)
文摘The Liupan Mountains is located in the southern Ningxia Hui Autonomous Region of China, which forms an important dividing line between landforms and bio-geographic regions. The populated part of the Liupan Mountains region has suffered tremendous ecological damages over time due to population pressure, excessive demand and inappropriate use of agricultural land resources. In this paper, datasets of land use between 1990 and 2000 were obtained from Landsat TM imagery, and then spatial models were used to characterize landscape conditions. Also, the relationship between the population density and land use/cover change (LUCC) was analyzed. Results indicate that cropland, forestland, and urban areas have increased by 44,186ha, 9001ha and 1550ha, respectively while the grassland area has appreciably decreased by 54,025ha in the study period. The decrease in grassland was most notable. Of the grassland lost, 49.4% was converted into cropland. The largest annual land conversion rate in the study area was less than 2%. These changes are attributed to industrial and agricultural development and population growth. To improve the eco-economic conditions in the study region, population control, urbanization and development of an ecological friendly agriculture were suggested.
文摘Previous soil-disc force prediction models have considered spherical and concave blades, as used on disc ploughs and harrows, with many simplifying assumptions. This study proposes an approach applying the fundamental equation of earth moving mechanics for calculating the soil passive reaction acting on a rotating fiat disc blade as used on a zero-till single disc seeder. The study considers the effects of disc variable depth of cut, sweep and tilt angles, free rotation and a scrubbing reaction at the beveled edge. This paper outlines the modeling approach and prediction results for a fixed circular blade operating at 90° sweep angle over a range of speeds and at two tilt angles. To account for the varying depth across the circular disc shape width, elemental wide blade force reactions acting on wide blade segments of elemental width were integrated across the disc working width. By including inertia forces due to speed as well as additional bulldozing forces due to the loose soil accumulation in front of the blade the draught and upward vertical forces acting on the vertical disc blade were predicted with a deviation of 6%-19% and 1.5%-14% from measured data, respectively. The model was able to predict the effect of increasing the tilt angle from 0° to 20° on reducing both draught and upward vertical forces. Further development and validation of the model will be described in subsequent papers, reflecting a step by step approach of increasing complexity to model a disc blade as used on a zero-till single disc seeding system.
基金National 12th Five-year Science and Technology Support Project of China(2012BAJ24B05)
文摘China is the largest developing country in the world and a well-known agricultural country. China＇s urbanization is a subject of great interest, one that has attracted the attention of people throughout the world. Whereas a handful of studies have assessed various aspects of urbanization（urban expansion, urban transition, urban-rural relationships, the spatial changes in urban and rural areas, motivations for sustaining rural places）, little is known of how to retain the indigenous character of rural areas in terms of landscape design. In this paper, the authors set out to contribute to this significant gap. They used Chengdu City and Five Golden Flowers（FGF） village in Chengdu＇s suburbs as case studies. A detailed description of the application of Ebenezer Howard＇s Garden City vision in Chengdu City was made; the Garden City vision was the key premise for FGF＇s ecotourism industry and successful conservation of landscapes with indigenous character. An analysis of the post-ecotourism landscape in FGF was accomplished using a typology method. Finally a set of landscape design methods for retaining indigenous character was proposed. The main conclusion of this paper was as follows： rural ecotourism can contribute to maintaining the indigenous character of rapidly urbanizing rural landscapes with the use of appropriate inheritance and renovation ways. The findings here may provide useful information for decision making by urban planners and policy-makers.
