Rising sea levels threaten the sustainability of coastal wetlands around the globe. The ability of coastal marshes to maintain their position in the intertidal zone depends on the accumulation of both organic and inor...Rising sea levels threaten the sustainability of coastal wetlands around the globe. The ability of coastal marshes to maintain their position in the intertidal zone depends on the accumulation of both organic and inorganic materials, and vegetation is important in these processes. To study the effects of vegetation type on surface elevation change, we measured surface accretion and elevation change from 2011 to 2016 using rod surface elevation table and feldspar marker horizon method (RSET-MH) in two Phragmites and two Suaeda marshes in the Liaohe River Delta. The Phragmites marshes exhibited higher rates of surface accretion and elevation change than the Suaeda marshes. The two Phragmites marsh sites had average surface elevation change rates at 8.78 mm/yr and 9.26 mm/yr and surface accretion rates at 17.56 mm/yr and 17.88 mm/yr, respectively. At the same time, the two Suaeda marsh sites had average surface elevation change rates at 5.77 mmJyr and 5.91 mm/yr and surface accretion rates at 13.42 mm/yr and 14.38 mm/yr, respectively. The elevation change rates in both the Phragmites marshes and the Suaeda marshes in the Liaohe River Delta could keep pace and even continue to gain elevation relative to averaged sea level rise in the Bohai Sea reported by the 2016 State Oceanic Administration, Peo- ple's Republic of China projection (2.4-5.5 mm/yr) in current situations. Our data suggest that vegetation is important in the accretionary processes and vegetation type could regulate the wetland surface elevation. However, the vulnerability of coastal wetlands in the Liaohe River Delta need further assessment considering the accelerated sea level rise, the high rate of subsidence, and the declining sediment delivery, especially for the Suaeda marshes.展开更多
The vibrational state-selected population transfer from a highly vibrationally excited level to the ground level is of great importance in the preparation of ultra-cold molecules. By using the time-dependent quantum-w...The vibrational state-selected population transfer from a highly vibrationally excited level to the ground level is of great importance in the preparation of ultra-cold molecules. By using the time-dependent quantum-wave-packet method, the population transfer dynamics is investigated theoretically for the HF molecule. A double-E-type laser scheme is proposed to transfer the population from the |v=16〉 level to the ground vibrational level |v=0〉 on the ground electronic state. The scheme consists of two steps: The first step is to transfer the population from |v=16〉 to |v=7〉 via an intermediate level |v=11〉, and the second one is to transfer the population from |v=7〉 to |v=0〉 via |v=3〉. In each step, three vibrational levels form a E-type population transfer path under the action of two temporally overlapped laser pulses. The maximal population-transfer efficiency is obtained by optimizing the laser inten- sities, frequencies, and relative delays. Cases for the pulses in intuitive and counterintuitive sequences are both calculated and compared. It is found that for both cases the population can be efficiently (over 90%) transferred from the |v=-16〉 level to the |v=0〉 level.展开更多
Interdecadal and interannuat variations of saline-alkali land area in Qian'an County, Jilin Province, China were comprehensively analyzed in this paper by means of satellite remote sensing interpretation, field flux ...Interdecadal and interannuat variations of saline-alkali land area in Qian'an County, Jilin Province, China were comprehensively analyzed in this paper by means of satellite remote sensing interpretation, field flux observations and regional climate diagnosis. The results show that on the interannual scale, the impact of climate factors accounts for 71.6% of the total variation of the saline-alkali land area, and that of human activities accounts for 28.4%. Therefore the impact of climate factors is obviously greater than that of human activities. On the interdecadal scale, the impact of climate factors on the increase of the saline-alkali land area accounts for 43.2%, and that of human activities accounts for 56.8%. The impact of human activities on the variation of saline-alkali land area is very clear on the interdecadal scale, and the negative impact of human activities on the environment should not be negligible. Besides, changes in the area of heavy saline-alkali land have some indication for development of saline-alkali land in Qian'an County.展开更多
For the last two decades the world has undergone a population explosion which has been accompanied by a speeding up of urbanization and land use for industrial and agricultural products. These involve a vast increase ...For the last two decades the world has undergone a population explosion which has been accompanied by a speeding up of urbanization and land use for industrial and agricultural products. These involve a vast increase in the discharge of pollutants into very different receiving water bodies, and have had adverse effects on the various components of the environment. For a long time, human has concerned a little of the natural environment. It is obvious that this variation in surface temperature of the earth increases the level of sea due to snowmelt. So climate change is manifested by many phenomena: floods, droughts, fires, tornadoes, cyclones, earthquakes, volcanic eruptions, diseases etc.. The statement today is dramatic. Entire regions were devastated and many rivers and lakes have become polluted around the world. Pollution has it nature which is hard to be absorbed. Where did the different pollutants come from? What are the risks to the aquatic environment? To prevent and combat the general decline of these ecosystems, it is important to distinguish and determine the effects of different sources of pollution and any changes that may suffer the physical environment. The climate depends primarily on changes in earth orbit parameters, which affect the solar radiation received by the earth surface. Therefore, human participates strongly to these changes, for example, pollution is the main reason to argue the greenhouse effect, an increase of anthropogenic carbon dioxide (CO2) into the atmosphere, which promotes global warming to the planet. These modifications are already applied in order to ensure durable development in water resources by controlling discharges into streams to preserve water resources for future generations and to ensure reconciliation between man-climate and environment.展开更多
According to the epicenter distance and the site classification, the 404 groups of earthquake recordings of the main shock of the Chi-Chi, Taiwan China earthquake in 1999 are catalogued. Based on these data, we analyz...According to the epicenter distance and the site classification, the 404 groups of earthquake recordings of the main shock of the Chi-Chi, Taiwan China earthquake in 1999 are catalogued. Based on these data, we analyze the statistical features of duration, PGA, envelopes and the response spectra ratio of the horizontal and vertical components of the acceleration recordings. The results of these analyses show that the effect of site classification on the acceleration of various components is obvious; furthermore, fault direction also has certain effects on the characteristics of the horizontal components of ground motion. The detailed research results are as follows: ( 1 ) the duration of the horizontal components of acceleration records increases with the softening of the site; (2) the direction of fault slip has some effects on PGA's attenuation features; (3) the average envelopes of acceleration records at different distances and site dames are basically single peak functions of time and the envelopes of horizontal and vertical components of ground motion are obviously different; (4) with the same epicenter distance, EW/NS response spectrum ratios tend to approximate 1.0 as the site becomes softer and the period shorter. V/H response spectrum ratios in short periods (〈 0. 1s) increase with the softening of site, however, V/H ratios within the long-period range ( 〉 characteristic period) decrease with the softening of the site, and the decrease of V/EW ratio speeds up relatively.展开更多
Radiation affects the environment and local human activity in any location of the earth's surface. Due to this fact, the aim of this study was to monitor the ionizing radiation and rain intensity using portable devic...Radiation affects the environment and local human activity in any location of the earth's surface. Due to this fact, the aim of this study was to monitor the ionizing radiation and rain intensity using portable devices. During May 23 to October 2, 2015, it was made measures the intensity of gamma radiation from 30 keV to 10.0 MeV at a height of 25 meters in Sao Jos6 dos Campos city, SP, Brazil. It was used a crystal of sodium iodide scintillator 3 - 3 inches coupled to a photomultiplier and associated electronic. The measurements were made continually with minute's interval throughout the period and it was monitored rain intensity every minute at the same height of the tower. In this job, it was possible to correlate rain-radiation and it was observed which gamma radiation has a directly proportional relationship with rain and visible frequency of 1 day.展开更多
This study uses DEM (Digital Elevation Model) data and remote sensing maps of the study area in 1993, 1999, and 2009 to analyze the slope gradient change of land use patterns in Qiandongnan Prefecture, Guizhou provi...This study uses DEM (Digital Elevation Model) data and remote sensing maps of the study area in 1993, 1999, and 2009 to analyze the slope gradient change of land use patterns in Qiandongnan Prefecture, Guizhou province, China. The land use data were classified into five types, forest, farmland, grassland, water and built-up, the slope gradients were divided into four grades. Indices for analyzing land use features were defined by their proportions, transformation matrixes, land use degree and changes The results showed that all land use types can be found at every gradient. Generally, with the slope degree increased, the area of forest being augmented as well, while the area of the other land use types (farmland, grassland and build-up) declined. Moreover, a mass of farmland were shifted from other land use types from o° to 25°, while a quantity of forest were transformed from the other land use types on 〉 25° from 2993 to 2009. In terms of land use degree and changes, the area of farmland and buildup land use types decreased when slope degree increased. Finally, we calculated the five landscape pattern metrics: Patch Density (PD) value, Largest Patch Index (LPI), Shannon's Diversity Index (SHDI), Area-Weighted Mean Shape Index (AWMSI) and Contagion Index (CONTAG). The results of metricsanalysis showed that PD values, SHDI values and CONTA values had a similar variation trend, that is, they decreased when slope degree increased. There was no obvious variation trend on LPI value.展开更多
Over the last 30 years, environmental philosophers and ecological researchers have turned their attention to the possibilities of narratives: the stories people tell about their lives in conjunction with the human an...Over the last 30 years, environmental philosophers and ecological researchers have turned their attention to the possibilities of narratives: the stories people tell about their lives in conjunction with the human and non-human agents they live with. An interest in narrative environmental ethics reflects a re-evaluation of canonical ecophilosophical texts. Works such as Paul W. Taylor's Respect for Nature suggest an essentialist view of environmental ethics in which predetermined principles are imposed on places and situations. On the other hand, Aldo Leopold's A Sand County Almanac combines first-person prose with science-based explanations of the "biotic pyramid" towards the development of a land ethic. Examples, such as Leopold's, of narrative ethics are thought to offer relational, place-based, non-authoritative, and non-anthropocentric models. This article examines three critical components of environmental narratives: self, context, and tradition. In order for environmental narratives to advance ecological ethics, they must be accompanied by the tradition of natural science (geology, ecology, and evolution) to provide the "sponsoring ground" for ethical concern and action. The role of natural science as a tradition--and indeed one of many--in narrative ethics provides the basis for ecological selfhood in the context of place. These assertions will be supported by an analysis of the environmental narratives of Karen Warren and Jim Cheney. However, in the temporally expansive and ecologically conscious poetic narratives of John Kinsella we find an environmental ethics deeply rooted in the material realities of place.展开更多
Abstract: The Bogota Savannah was great Lake Humboldt 20,000 years ago. In the early 20th century, there were 50,000 ha of wetlands in Bogotá, but now this area has reduced to around 800 ha, due principally to h...Abstract: The Bogota Savannah was great Lake Humboldt 20,000 years ago. In the early 20th century, there were 50,000 ha of wetlands in Bogotá, but now this area has reduced to around 800 ha, due principally to human activities like industry, city-planning expansion, and agriculture. Actually, there are 13 wetlands and two lakes in Bogotá. SW (Salitre wetland) is an aquatic area that contains migratory and resident bird's species. Around this wetland, there are some urbanization and recreational areas that affect this natural habitat. Due to city-planning expansion, the city government wanted to build a great area to perform massive public events on the Salitre area. From June 2009 to June 2010, the researchers have made bird monitoring and recorded the SW as a very important habitat for birds; they demonstrated that this site offered them food and protection. Migratory species like Dendroica striata, Porzana carolina, Porphyrio martinica, Actitis macularia, Piranga rubra, Contopus cooperi and Contopus virens, inhabit this area. Most of the birds in SW use the area primarily for feeding and roosting, and the authors have recorded presence of eggs and chicks. In this way, the authors have demonstrated that this area is very important for migratory and resident birds. Currently, SW is in process to be officially designated as a wetland after many efforts. However, conservation and educational efforts should be taken into consideration for the protection and conservation of this wetland.展开更多
The hypersonic long-run scramjet test tunnel is one of the key ground facilities for the studies of ramjet/scramjet and hypersonic thermal management.Due to the significantly large heat loading,the nozzle of the tunne...The hypersonic long-run scramjet test tunnel is one of the key ground facilities for the studies of ramjet/scramjet and hypersonic thermal management.Due to the significantly large heat loading,the nozzle of the tunnel facility demands effective cooling protection.In this work,the two-dimensional,three-dimensional and axisymmetric Mach 6.5 nozzles at an inlet total temperature of 1840 K and a total pressure of 6.4 MPa were studied with main focuses on the properties of aerodynamic heating of nozzles.The present work aims to provide insights into the design of an effective cooling system for the nozzle and other components of the hypersonic long-run wind tunnel.展开更多
We obtain an inequality in Sm×R and Hm×R which is similar to DDVV conjecture.As an application,we show that a minimal submanifold in H m×R with nonnegative scalar curvature must be a surface of the type...We obtain an inequality in Sm×R and Hm×R which is similar to DDVV conjecture.As an application,we show that a minimal submanifold in H m×R with nonnegative scalar curvature must be a surface of the type γ×R,where γ is a geodesic in H m.In addition,we get a pinching theorem in Sm×R.展开更多
Modeling and analyzing dynamic changes of land thermal radiance scenes play an important role in thermal remote sensing. In this paper, the diurnal variation of ground surface thermal scene is mainly discussed. Firstl...Modeling and analyzing dynamic changes of land thermal radiance scenes play an important role in thermal remote sensing. In this paper, the diurnal variation of ground surface thermal scene is mainly discussed. Firstly, based on the land surface energy balance equation, the diurnal variation of land surface temperatures (LSTs) over bare land covers were simulated by an analyt- ical thermal model with second harmonic terms, and the diurnal LST variation of vegetation canopy was simulated using the Cupid model. Secondly, normalized difference vegetation index (NDVI), normalized difference water index (NDWI), and ratio resident-area index (RRI) were used to evaluate the endmember abundance of four land cover types including vegetation, bare soil, impervious and water area, which were calculated from IKONOS visible and near infrared (VNIR) bands. Finally, the thermal radiance scenes at various times and view angles were modeled based on the linear-energy-mixing hypothesis. The re- suits showed that the simulated daily LST variations for vegetated and bare surfaces are correlated with the measured values with a maximum standard deviation of 2.7℃, that land thermal radiant textures with high-resolution are restored from the lin- ear-energy-mixing method, and that the information abundance of the scene are related to the distribution of land cover, the imaging time, and the view angle.展开更多
The problem of task assignment for multiple cooperating unmanned aerial vehicle(UAV) teams is considered. Multiple UAVs forming several small teams are needed to perform attack tasks on a set of predetermined ground t...The problem of task assignment for multiple cooperating unmanned aerial vehicle(UAV) teams is considered. Multiple UAVs forming several small teams are needed to perform attack tasks on a set of predetermined ground targets. A hierarchical task assignment method is presented to address the problem. It breaks the original problem down to three levels of sub-problems: target clustering, cluster allocation and target assignment. The first two sub-problems are centrally solved by using clustering algorithms and integer linear programming, respectively, and the third sub-problem is solved in a distributed and parallel manner, using a mixed integer linear programming model and an improved ant colony algorithm. The proposed hierarchical method can reduce the computational complexity of the task assignment problem considerably, especially when the number of tasks or the number of UAVs is large. Experimental results show that this method is feasible and more efficient than non-hierarchical methods.展开更多
The use of landscape covariates to variability of soil properties in similar estimate soil properties is not suitable topographic and vegetation conditions. for the areas of low relief due to the high A new method wa...The use of landscape covariates to variability of soil properties in similar estimate soil properties is not suitable topographic and vegetation conditions. for the areas of low relief due to the high A new method was implemented to map regional soil texture (in terms of sand, silt and clay contents) by hypothesizing that the change in the land surface diurnal temperature difference (DTD) is related to soil texture in case of a relatively homogeneous rainfall input. To examine this hypothesis, the DTDs from moderate resolution imagine spectroradiometer (MODIS) during a selected time period, i.e., after a heavy rainfall between autumn harvest and autumn sowing, were classified using fuzzy-c-means (FCM) clustering. Six classes were generated, and for each class, the sand (〉 0.05 mm), silt (0.002-0.05 mm) and clay (〈 0.002 mm) contents at the location of maximum membership value were considered as the typical values of that class. A weighted average model was then used to digitally map soil texture. The results showed that the predicted map quite accurately reflected the regional soil variation. A validation dataset produced estimates of error for the predicted maps of sand, silt and clay contents at root mean of squared error values of 8.4%, 7.8% and 2.3%, respectively, which is satisfactory in a practical context. This study thus provided a methodology that can help improve the accuracy and efficiency of soil texture mapping in plain areas using easily available data sources.展开更多
基金Under the auspices of National Key Research and Development Program of China(No.2016YFA0602303)National Natural Science Foundation of China(No.41501105,41620104005)Open Fund of the State Environmental Protection Key Laboratory of Wetland Ecology and Vegetation Restoration in Northeast Normal University(No.130028627)
文摘Rising sea levels threaten the sustainability of coastal wetlands around the globe. The ability of coastal marshes to maintain their position in the intertidal zone depends on the accumulation of both organic and inorganic materials, and vegetation is important in these processes. To study the effects of vegetation type on surface elevation change, we measured surface accretion and elevation change from 2011 to 2016 using rod surface elevation table and feldspar marker horizon method (RSET-MH) in two Phragmites and two Suaeda marshes in the Liaohe River Delta. The Phragmites marshes exhibited higher rates of surface accretion and elevation change than the Suaeda marshes. The two Phragmites marsh sites had average surface elevation change rates at 8.78 mm/yr and 9.26 mm/yr and surface accretion rates at 17.56 mm/yr and 17.88 mm/yr, respectively. At the same time, the two Suaeda marsh sites had average surface elevation change rates at 5.77 mmJyr and 5.91 mm/yr and surface accretion rates at 13.42 mm/yr and 14.38 mm/yr, respectively. The elevation change rates in both the Phragmites marshes and the Suaeda marshes in the Liaohe River Delta could keep pace and even continue to gain elevation relative to averaged sea level rise in the Bohai Sea reported by the 2016 State Oceanic Administration, Peo- ple's Republic of China projection (2.4-5.5 mm/yr) in current situations. Our data suggest that vegetation is important in the accretionary processes and vegetation type could regulate the wetland surface elevation. However, the vulnerability of coastal wetlands in the Liaohe River Delta need further assessment considering the accelerated sea level rise, the high rate of subsidence, and the declining sediment delivery, especially for the Suaeda marshes.
基金Li-hang Li thanks Dr. Yin Huang for assistance. The project is supported by the Specialized Research Fund for the Doctoral Program of Higher Education (No.20130041120053), SRF for ROCS, SEM, the Sci- ence and Technology Research Funds of the Depart- ment of Education of Liaoning Province (L2013014), the National Magnetic Confinement Fusion Science Pro- gram (No.2013GB109005), the Fundamental Research Funds for the Central Universities (DUT12RC(3)60), and the NationM Natural Science Foundation of China (No.21473018, No.10974024, and No.11274056).
文摘The vibrational state-selected population transfer from a highly vibrationally excited level to the ground level is of great importance in the preparation of ultra-cold molecules. By using the time-dependent quantum-wave-packet method, the population transfer dynamics is investigated theoretically for the HF molecule. A double-E-type laser scheme is proposed to transfer the population from the |v=16〉 level to the ground vibrational level |v=0〉 on the ground electronic state. The scheme consists of two steps: The first step is to transfer the population from |v=16〉 to |v=7〉 via an intermediate level |v=11〉, and the second one is to transfer the population from |v=7〉 to |v=0〉 via |v=3〉. In each step, three vibrational levels form a E-type population transfer path under the action of two temporally overlapped laser pulses. The maximal population-transfer efficiency is obtained by optimizing the laser inten- sities, frequencies, and relative delays. Cases for the pulses in intuitive and counterintuitive sequences are both calculated and compared. It is found that for both cases the population can be efficiently (over 90%) transferred from the |v=-16〉 level to the |v=0〉 level.
基金Under the auspices of National Key Technology R&D Program of China (No. 2007BAC29B01)Major State Basic Research Development Program of China (973 Program) (No. 2006CB400500)+1 种基金National Natural Science Foundation of China (No.40575047, 40705036, 40975055)Key Program of Jilin Provincial Science & Technology Department (No. 20020417)
文摘Interdecadal and interannuat variations of saline-alkali land area in Qian'an County, Jilin Province, China were comprehensively analyzed in this paper by means of satellite remote sensing interpretation, field flux observations and regional climate diagnosis. The results show that on the interannual scale, the impact of climate factors accounts for 71.6% of the total variation of the saline-alkali land area, and that of human activities accounts for 28.4%. Therefore the impact of climate factors is obviously greater than that of human activities. On the interdecadal scale, the impact of climate factors on the increase of the saline-alkali land area accounts for 43.2%, and that of human activities accounts for 56.8%. The impact of human activities on the variation of saline-alkali land area is very clear on the interdecadal scale, and the negative impact of human activities on the environment should not be negligible. Besides, changes in the area of heavy saline-alkali land have some indication for development of saline-alkali land in Qian'an County.
文摘For the last two decades the world has undergone a population explosion which has been accompanied by a speeding up of urbanization and land use for industrial and agricultural products. These involve a vast increase in the discharge of pollutants into very different receiving water bodies, and have had adverse effects on the various components of the environment. For a long time, human has concerned a little of the natural environment. It is obvious that this variation in surface temperature of the earth increases the level of sea due to snowmelt. So climate change is manifested by many phenomena: floods, droughts, fires, tornadoes, cyclones, earthquakes, volcanic eruptions, diseases etc.. The statement today is dramatic. Entire regions were devastated and many rivers and lakes have become polluted around the world. Pollution has it nature which is hard to be absorbed. Where did the different pollutants come from? What are the risks to the aquatic environment? To prevent and combat the general decline of these ecosystems, it is important to distinguish and determine the effects of different sources of pollution and any changes that may suffer the physical environment. The climate depends primarily on changes in earth orbit parameters, which affect the solar radiation received by the earth surface. Therefore, human participates strongly to these changes, for example, pollution is the main reason to argue the greenhouse effect, an increase of anthropogenic carbon dioxide (CO2) into the atmosphere, which promotes global warming to the planet. These modifications are already applied in order to ensure durable development in water resources by controlling discharges into streams to preserve water resources for future generations and to ensure reconciliation between man-climate and environment.
基金The research was funded by the National NaturalSciences Foundation of China with Grant Number :50408005 and 50578004
文摘According to the epicenter distance and the site classification, the 404 groups of earthquake recordings of the main shock of the Chi-Chi, Taiwan China earthquake in 1999 are catalogued. Based on these data, we analyze the statistical features of duration, PGA, envelopes and the response spectra ratio of the horizontal and vertical components of the acceleration recordings. The results of these analyses show that the effect of site classification on the acceleration of various components is obvious; furthermore, fault direction also has certain effects on the characteristics of the horizontal components of ground motion. The detailed research results are as follows: ( 1 ) the duration of the horizontal components of acceleration records increases with the softening of the site; (2) the direction of fault slip has some effects on PGA's attenuation features; (3) the average envelopes of acceleration records at different distances and site dames are basically single peak functions of time and the envelopes of horizontal and vertical components of ground motion are obviously different; (4) with the same epicenter distance, EW/NS response spectrum ratios tend to approximate 1.0 as the site becomes softer and the period shorter. V/H response spectrum ratios in short periods (〈 0. 1s) increase with the softening of site, however, V/H ratios within the long-period range ( 〉 characteristic period) decrease with the softening of the site, and the decrease of V/EW ratio speeds up relatively.
文摘Radiation affects the environment and local human activity in any location of the earth's surface. Due to this fact, the aim of this study was to monitor the ionizing radiation and rain intensity using portable devices. During May 23 to October 2, 2015, it was made measures the intensity of gamma radiation from 30 keV to 10.0 MeV at a height of 25 meters in Sao Jos6 dos Campos city, SP, Brazil. It was used a crystal of sodium iodide scintillator 3 - 3 inches coupled to a photomultiplier and associated electronic. The measurements were made continually with minute's interval throughout the period and it was monitored rain intensity every minute at the same height of the tower. In this job, it was possible to correlate rain-radiation and it was observed which gamma radiation has a directly proportional relationship with rain and visible frequency of 1 day.
基金supported by the National Natural Science Foundation of China (Grant No. 31370480)111 Project (B08044)Minzu University of China (MUC98507-08)
文摘This study uses DEM (Digital Elevation Model) data and remote sensing maps of the study area in 1993, 1999, and 2009 to analyze the slope gradient change of land use patterns in Qiandongnan Prefecture, Guizhou province, China. The land use data were classified into five types, forest, farmland, grassland, water and built-up, the slope gradients were divided into four grades. Indices for analyzing land use features were defined by their proportions, transformation matrixes, land use degree and changes The results showed that all land use types can be found at every gradient. Generally, with the slope degree increased, the area of forest being augmented as well, while the area of the other land use types (farmland, grassland and build-up) declined. Moreover, a mass of farmland were shifted from other land use types from o° to 25°, while a quantity of forest were transformed from the other land use types on 〉 25° from 2993 to 2009. In terms of land use degree and changes, the area of farmland and buildup land use types decreased when slope degree increased. Finally, we calculated the five landscape pattern metrics: Patch Density (PD) value, Largest Patch Index (LPI), Shannon's Diversity Index (SHDI), Area-Weighted Mean Shape Index (AWMSI) and Contagion Index (CONTAG). The results of metricsanalysis showed that PD values, SHDI values and CONTA values had a similar variation trend, that is, they decreased when slope degree increased. There was no obvious variation trend on LPI value.
文摘Over the last 30 years, environmental philosophers and ecological researchers have turned their attention to the possibilities of narratives: the stories people tell about their lives in conjunction with the human and non-human agents they live with. An interest in narrative environmental ethics reflects a re-evaluation of canonical ecophilosophical texts. Works such as Paul W. Taylor's Respect for Nature suggest an essentialist view of environmental ethics in which predetermined principles are imposed on places and situations. On the other hand, Aldo Leopold's A Sand County Almanac combines first-person prose with science-based explanations of the "biotic pyramid" towards the development of a land ethic. Examples, such as Leopold's, of narrative ethics are thought to offer relational, place-based, non-authoritative, and non-anthropocentric models. This article examines three critical components of environmental narratives: self, context, and tradition. In order for environmental narratives to advance ecological ethics, they must be accompanied by the tradition of natural science (geology, ecology, and evolution) to provide the "sponsoring ground" for ethical concern and action. The role of natural science as a tradition--and indeed one of many--in narrative ethics provides the basis for ecological selfhood in the context of place. These assertions will be supported by an analysis of the environmental narratives of Karen Warren and Jim Cheney. However, in the temporally expansive and ecologically conscious poetic narratives of John Kinsella we find an environmental ethics deeply rooted in the material realities of place.
文摘Abstract: The Bogota Savannah was great Lake Humboldt 20,000 years ago. In the early 20th century, there were 50,000 ha of wetlands in Bogotá, but now this area has reduced to around 800 ha, due principally to human activities like industry, city-planning expansion, and agriculture. Actually, there are 13 wetlands and two lakes in Bogotá. SW (Salitre wetland) is an aquatic area that contains migratory and resident bird's species. Around this wetland, there are some urbanization and recreational areas that affect this natural habitat. Due to city-planning expansion, the city government wanted to build a great area to perform massive public events on the Salitre area. From June 2009 to June 2010, the researchers have made bird monitoring and recorded the SW as a very important habitat for birds; they demonstrated that this site offered them food and protection. Migratory species like Dendroica striata, Porzana carolina, Porphyrio martinica, Actitis macularia, Piranga rubra, Contopus cooperi and Contopus virens, inhabit this area. Most of the birds in SW use the area primarily for feeding and roosting, and the authors have recorded presence of eggs and chicks. In this way, the authors have demonstrated that this area is very important for migratory and resident birds. Currently, SW is in process to be officially designated as a wetland after many efforts. However, conservation and educational efforts should be taken into consideration for the protection and conservation of this wetland.
基金supported by the National Natural Science Foundation of China(Grant Nos.11202218 and 11172309)
文摘The hypersonic long-run scramjet test tunnel is one of the key ground facilities for the studies of ramjet/scramjet and hypersonic thermal management.Due to the significantly large heat loading,the nozzle of the tunnel facility demands effective cooling protection.In this work,the two-dimensional,three-dimensional and axisymmetric Mach 6.5 nozzles at an inlet total temperature of 1840 K and a total pressure of 6.4 MPa were studied with main focuses on the properties of aerodynamic heating of nozzles.The present work aims to provide insights into the design of an effective cooling system for the nozzle and other components of the hypersonic long-run wind tunnel.
基金supported by National Natural Science Foundation of China (Grant No.10871149)Research Fund for the Doctoral Program of Higher Education of China (Grant No. 200804860046)
文摘We obtain an inequality in Sm×R and Hm×R which is similar to DDVV conjecture.As an application,we show that a minimal submanifold in H m×R with nonnegative scalar curvature must be a surface of the type γ×R,where γ is a geodesic in H m.In addition,we get a pinching theorem in Sm×R.
基金supported by the 12th and the 11th Five-Year Plan of Civil Aerospace Technology Advanced Research Projects (Grant Nos.O6K00100KJ,Y1K0030044)the China International Science and Technology Cooperation Program (Grant No. 2010DFA21880)
文摘Modeling and analyzing dynamic changes of land thermal radiance scenes play an important role in thermal remote sensing. In this paper, the diurnal variation of ground surface thermal scene is mainly discussed. Firstly, based on the land surface energy balance equation, the diurnal variation of land surface temperatures (LSTs) over bare land covers were simulated by an analyt- ical thermal model with second harmonic terms, and the diurnal LST variation of vegetation canopy was simulated using the Cupid model. Secondly, normalized difference vegetation index (NDVI), normalized difference water index (NDWI), and ratio resident-area index (RRI) were used to evaluate the endmember abundance of four land cover types including vegetation, bare soil, impervious and water area, which were calculated from IKONOS visible and near infrared (VNIR) bands. Finally, the thermal radiance scenes at various times and view angles were modeled based on the linear-energy-mixing hypothesis. The re- suits showed that the simulated daily LST variations for vegetated and bare surfaces are correlated with the measured values with a maximum standard deviation of 2.7℃, that land thermal radiant textures with high-resolution are restored from the lin- ear-energy-mixing method, and that the information abundance of the scene are related to the distribution of land cover, the imaging time, and the view angle.
基金supported by the National Natural Science Foundation of China(7147205871401048)the Fundamental Research Funds for the Central Universities(2012HGZY0009)
文摘The problem of task assignment for multiple cooperating unmanned aerial vehicle(UAV) teams is considered. Multiple UAVs forming several small teams are needed to perform attack tasks on a set of predetermined ground targets. A hierarchical task assignment method is presented to address the problem. It breaks the original problem down to three levels of sub-problems: target clustering, cluster allocation and target assignment. The first two sub-problems are centrally solved by using clustering algorithms and integer linear programming, respectively, and the third sub-problem is solved in a distributed and parallel manner, using a mixed integer linear programming model and an improved ant colony algorithm. The proposed hierarchical method can reduce the computational complexity of the task assignment problem considerably, especially when the number of tasks or the number of UAVs is large. Experimental results show that this method is feasible and more efficient than non-hierarchical methods.
基金Supported by the Basic Research Program of Jiangsu Province,China (No. BK2008058)the Knowledge Innovation Program of Chinese Academy of Sciences (No. KZCX2-YW-409)
文摘The use of landscape covariates to variability of soil properties in similar estimate soil properties is not suitable topographic and vegetation conditions. for the areas of low relief due to the high A new method was implemented to map regional soil texture (in terms of sand, silt and clay contents) by hypothesizing that the change in the land surface diurnal temperature difference (DTD) is related to soil texture in case of a relatively homogeneous rainfall input. To examine this hypothesis, the DTDs from moderate resolution imagine spectroradiometer (MODIS) during a selected time period, i.e., after a heavy rainfall between autumn harvest and autumn sowing, were classified using fuzzy-c-means (FCM) clustering. Six classes were generated, and for each class, the sand (〉 0.05 mm), silt (0.002-0.05 mm) and clay (〈 0.002 mm) contents at the location of maximum membership value were considered as the typical values of that class. A weighted average model was then used to digitally map soil texture. The results showed that the predicted map quite accurately reflected the regional soil variation. A validation dataset produced estimates of error for the predicted maps of sand, silt and clay contents at root mean of squared error values of 8.4%, 7.8% and 2.3%, respectively, which is satisfactory in a practical context. This study thus provided a methodology that can help improve the accuracy and efficiency of soil texture mapping in plain areas using easily available data sources.