A case study is presented of a regional development model for valley economies in the mountain areas of Beijing, China. The nature and framework of the valley economy model are described and the development of the mod...A case study is presented of a regional development model for valley economies in the mountain areas of Beijing, China. The nature and framework of the valley economy model are described and the development of the model, which is specific to the mountain areas of Beijing, is analyzed. Five different valley economy models applied in the Beijing mountain areas are compared. The major purpose of the valley economy model is to develop the regional economy, including the selection of appropriate industries, the allocation of industrial space, the establishment of supply chains and the integration of various industries. Pilot experiments using the valley economy model have been conducted in seven counties(districts) in Beijing: Pinggu, Huairou, Changping, Mentougou, and Fangshan districts, and Yanqing and Miyun counties. Five models for developing the Beijing mountain areas have been explored, including: creative cultural industries, characteristic industry clusters, the promotion of large tourist areas, natural scenic tourism and folk cultural tourism. Each model has its own unique features and potential to help in the regional development of mountain areas.展开更多
In desert areas in Hexi region,11 barchan dunes,6 chains of barchan dunes,6 pyramid dunes,6 parabolic dunes and 6 accumulated sand-belts were chosen to study their movement speed based on images obtained by Google Ear...In desert areas in Hexi region,11 barchan dunes,6 chains of barchan dunes,6 pyramid dunes,6 parabolic dunes and 6 accumulated sand-belts were chosen to study their movement speed based on images obtained by Google Earth in various periods.The results show that among the dunes,the movement of the barchan dunes was the fastest,followed by the chains of barchan dunes,and only the tops of the pyramid dunes swayed,while the parabolic dunes and accumulated sand-belts hardly moved forward.The higher the barchan dunes(or the chains of barchan dunes) were,the slower the movement was.On the contrary,the higher the pyramid dunes were,the faster the swing was.There was a positive correlation between the movement speed of the barchan dunes and the average wind speed of sandstorms.展开更多
To improve the comfortable physical environment for square in severe cold regions' rural areas. This paper applies the methods of questionnaires,field testing and statistical analysis to compare and analyze two di...To improve the comfortable physical environment for square in severe cold regions' rural areas. This paper applies the methods of questionnaires,field testing and statistical analysis to compare and analyze two different square cases of Qingyunpu in Liaoning Province,and conclude the main factors which affect the physical environmental comfort. The improvement strategies for physical environment of rural square are put forward from the aspects of site selection,road position,orientation,landscape design,and ground pavement material selection,aiming to provide the design basis for the physical environment of square in severe cold regions' rural areas.展开更多
Gully erosion is the frequent and main form of soil erosion in the black soil area of the northeastern China, which is one of the most important commodity grain production bases in China. It is encroaching upon the fe...Gully erosion is the frequent and main form of soil erosion in the black soil area of the northeastern China, which is one of the most important commodity grain production bases in China. It is encroaching upon the fertile farmland there. Regionalization of gully erosion can reveal the spatial distribution and regularity of the development of gully erosion. Based on the eco-geographical regional background features of the black soil area, this study combined the regionalization with influencing factors of the development of gully erosion. GIS spatial analysis, geostatistical analysis, spatial statistics, reclassification, debris polygon processing and map algebra methods were employed. As a result, the black soil area was divided into 12 subregions. The field survey data on type, length, volume and other characteristics indicators of gully erosion were used to calibrate the results. Then the features of every subregion, such as where the gully erosion is, how serious it is, and why it happens and develops, were expounded. The result is not only an essential prerequisite for gully erosion surveys and monitoring, but also an important basis for gully erosion prevention.展开更多
It is not clear how HPV infection is prevalent among Uygur women in Xinjiang Uygur Autonomous Region, China and whether the distribution of HPV infection is related with cervical intraepithelial neoplasia (CIN) inci...It is not clear how HPV infection is prevalent among Uygur women in Xinjiang Uygur Autonomous Region, China and whether the distribution of HPV infection is related with cervical intraepithelial neoplasia (CIN) incidence among them. A study including 883 Uygur women were conducted from 2006 to 2007 in Hetian Prefecture, Xinjiang Uygur Autonomous Region, China.展开更多
IEEE has set up in October 2004 the IEEE802.22 Working Group—Wireless Regional Area Network (WRAN) Task Force to work out air interface standard based on Cognitive Radio (CR) technologies. The standard includes Physi...IEEE has set up in October 2004 the IEEE802.22 Working Group—Wireless Regional Area Network (WRAN) Task Force to work out air interface standard based on Cognitive Radio (CR) technologies. The standard includes Physical Layer (PHY) and Media Access Control (MAC),to use the already allocated fallow spectrums to broadcast TV in a non-interference way. The WRAN employs CR technologies to sense and estimate the television frequencies and use the technologies of dynamic spectrum management to find and then allocate idle spectrums. The CR technologies are representing one of the major trends for future wireless communications. This article on WRANs and CR technologies will be divided into two issues. In this issue,WRANs and IEEE 802.22,CR technologies are introduced. And the second part in the next issue will analyze the applications of CR technologies.展开更多
IEEE has set up in October 2004 the IEEE802.22 Working Group-Wireless Regional Area Network (WRAN) Task Force to work out air interface standard based on Cognitive Radio (CR) technologies. The standard includes Physic...IEEE has set up in October 2004 the IEEE802.22 Working Group-Wireless Regional Area Network (WRAN) Task Force to work out air interface standard based on Cognitive Radio (CR) technologies. The standard includes Physical Layer (PHY) and Media Access Control (MAC), utilizig the vacant spectrum bands already allocated to broadcast TV without interference.. The WRAN employs CR technologies to sense and estimate the television signals and use the technologies of dynamic spectrum management to find and then allocate vacant spectrums. The CR technologies are representing one of the major trends for future wireless communications. This article on WRANs and CR technologies will be divided into two issues. In this issue, WRANs and IEEE 802.22, CR technologies are introduced. And the second part in the next issue will analyze the applications of CR technologies.展开更多
BACKGROUND: Previous studies reported that frontal-temporal-parietal-occipital pathological changes and diseased range in the right cerebral hemisphere were closely correlated with neglect. But studies on the correlat...BACKGROUND: Previous studies reported that frontal-temporal-parietal-occipital pathological changes and diseased range in the right cerebral hemisphere were closely correlated with neglect. But studies on the correlation of neglect with diseased region and area in patients who suffer from initial attack of single focus of cerebral infarction (CI) in left and right cerebral hemispheres are few. OBJECTIVE: To observe the status of neglect in patients who suffer from single focus of CI in cerebral hemisphere, and analyze the correlation of neglect with diseased region and area of CI. DESIGN: Case analysis. SETTING: Treatment Center for Cardiocerebrovascular Disease, Second Hospital of Xiamen city; Department of Neurology, First Hospital Affiliated to Baotou Medical College. PARTICIPANTS: All the CI patients hospitalized in the Department of Neurology, First Hospital Affiliated to Baotou Medical College from June 1998 to May 2001 were retrieved. Inclusive criteria: ① Patients who suffered from initial attack of CI, which was confirmed by skull CT or MRI within 24 hours after onset and presented single focus in cerebral hemisphere. ② be conscious and could cooperate in the examination. ③ did not receive formal education, but could do accounts and some simple writing and reading. ④Patients with homonymous hemianopia were excluded through the examination of perimeter. ⑤ Informed consents were obtained from all the patients. Among 67 patients who met the inclusive criteria, 33 suffered from CI in the left cerebral hemisphere and 34 in the right cerebral hemisphere. METHODS: ① Patients received neglect supplement examination and Chinese aphasia examination within 2.5 to 3 months after the attack of CI . The diagnostic criteria of neglect in the tests of line cancellation, line bisection and copying the figures were as follows: In the line cancellation test based on the method of Albert, patients who could not cancel one or more lines were regarded as abnormal. In the line bisection test based on the method of Peter, patients who left deviated 1.16% or right deviated 2.51% were regarded as abnormal. In the test of copying the figures, round-shape, square, cruciform and other shapes were asked to be copied, defect appeared in the figure was regarded as abnormal. The diagnostic criteria of aphasia were according to the diagnostic method of Chinese aphasia examination and type identification flow-sheet of aphasia. Infarct area was calculated based on Palisino formula: infarct area=π/6×the longest diameter of infarct area×the widest diameter of infarct area×the number of CT positive layer. ② Chi-square test was used for comparing the difference of measurement data. MAIN OUTCOME MEASURES: Diseased region and area of CI and their correlations with neglect. RESULTS: Sixty-seven patients were involved in result analysis. ① The correlation of the occurrence of neglect with the diseased regions of CI: Neglect was not found in 33 patients with CI in left cerebral hemisphere, but was found in 7 of 34 patients with CI in right cerebral hemisphere. The diseased regions involved right temporoparietal region, temporal-parietal-occipital region, frontal-temporal-parietal region, frontal-temporal-parietal-occipital region, temporoparietal basal nucleus, basal nucleus and dorsal caudate putamen. ②The correlation of the occurrence of neglect with diseased area: infarct area ≤ 30 cm3 was found in 2 patients with neglect (12.5%), infarct area at 31 to 60 cm3 in 1 patient with neglect (14.3%),infarct area ≥ 61 cm3 in 4 patients with neglect (36.4%). There was no significant difference in infarct area among groups (P > 0.05). CONCLUSION: ① Right cerebral hemisphere takes advantage in spatial attention. ② Neglect is more possibly caused by the combined pathological changes in temporal and parietal lobe. Temporal and parietal lobes may not cause neglect independently, but the occurrence of neglect is not directly correlated with infarct area.展开更多
In the stability study of the regional structures in the area of the Longyang Gorge Hydroelectrical Power Station, a model of the current stress-deformation field of the area was constructed based on analyses of avail...In the stability study of the regional structures in the area of the Longyang Gorge Hydroelectrical Power Station, a model of the current stress-deformation field of the area was constructed based on analyses of available data of regional surveys and historical earthquakes and field investigations of active faults and ancient earthquakes. This model was examined and verified by physical and mathematical simulation experiments, and quantitative relations and data were obtained.展开更多
The formation of rice distribution is based on certain natural ecological conditions and social economic environments. In China, rice cropping is distributed in a vast area extending across 5 tempera ture belts, the n...The formation of rice distribution is based on certain natural ecological conditions and social economic environments. In China, rice cropping is distributed in a vast area extending across 5 tempera ture belts, the northernmost of rice growing area in the world being in China. Distribution of rice cropping is characterized by a gradual decrease from south to north, from large and concentrated regions in Southeast to small and separated areas in Northwest. Natural conditions in rice regions differ in China with a varied topography, high in the west and low in the east. Rice fields in the west are mostly distributed on flatlands on plains, valleys among mountains, tablelands in river valleys, yellow-soil plains and basins in low valleys, alluvial plains, plains in river valleys, while those in the east are mainly distributed on alluvial plains, hilly areas among low mountains, coastal plains, along rivers and lakes and in basins among mountains.展开更多
This paper summarizes principles and measures of comprehensive division of mountainous areas, as well as clarifies meaning, structure, function and path established for the map and file information visibility system (...This paper summarizes principles and measures of comprehensive division of mountainous areas, as well as clarifies meaning, structure, function and path established for the map and file information visibility system (MFIVS). And then, taking Huaihua City of Hunan Province as an example, and based on the MFIVS means, concrete attempts on regionalization are carried out. The result is relatively objective and accurate, which illuminates that the method is a comprehensive one with the characteristics of concision, applicability and effectiveness.展开更多
Topography, especially altitude, will influence the way, process and characteristics of land cover changes in mountainous area, simultaneously, the vertical difference of land cover changes will affect soil quality an...Topography, especially altitude, will influence the way, process and characteristics of land cover changes in mountainous area, simultaneously, the vertical difference of land cover changes will affect soil quality and regional ecological environment. Therefore, the gradient relationship analysis between land cover changes and altitude is very important for regional sustainability. This study investigated land cover dynamics based on land cover data from a typical mountainous area in the Guizhou-Guangxi karst mountain area, China, in 2000 and 2010, then explored the relationship between altitude and land cover change and analyzed different drivers of land cover change at different altitudes. Our findings are as follows. 1) From 2000 to 2010, the total area of land cover transition was 7167.04 km^2 or 2.8% of the region. The increasing area of build-up land(926.23 km^2) was larger than that of forest(859.38 km^2), suggesting that the urban construction speed was higher than that of reforestation. 2) Intensity of land cover transition in northwestern Guizhou-Guangxi karst mountain area was much larger than that of southeast part and their transition trend was also significantly different, which was consistent with regional population and economy. 3) Human activity was the most dramatic at altitudes between 0–500 m. For 500–1000 m, grassland mainly converted to forest and build-up land. Area of land cover transition was the greatest between 1000–1500 m, while above 1500 m, the transition of grassland was the most obvious. 4) The drivers of land cover change varied. Land cover change was positively correlated with gross domestic product and population density but was inversely related to relief amplitude. There were correlations between land cover change and distance to roads and rivers, and their correlations varied with altitude. By revealing patterns and causes of land cover changes in different altitudes, we hope to understand the vertical dependence of land cover changes, so as to improve land productivity and protect land ecological environment scientifically.展开更多
The IEEE 802.22 standard based on wireless Cognitive Radio (CR) is an optimal solution to resolve the inefficient spectrum utility problem. In this paper, we focus on the spectrum allocation in IEEE 802.22 mesh networ...The IEEE 802.22 standard based on wireless Cognitive Radio (CR) is an optimal solution to resolve the inefficient spectrum utility problem. In this paper, we focus on the spectrum allocation in IEEE 802.22 mesh networks and propose a new graph-theory algorithm. The algorithm aims at two objectives: one is the sum of the allocated channel bandwidth is maximum, and the other is the number of users can be active simultaneity is maximum. In this proposed algorithm, the topology of network was modeled as a general graph and could be transformed into a weighted complete bipartite-graph by three processes. The simulations show that the presented algorithm can improve the performance of spectrum allocation.展开更多
This article focuses on the regional advantages to develop international logistics aiming at Southeast Asia in Yunnan province and intends to prove that it's of great significance to develop this kind of internationa...This article focuses on the regional advantages to develop international logistics aiming at Southeast Asia in Yunnan province and intends to prove that it's of great significance to develop this kind of international logistics. Further, it analyzes the status quo, market demand and problems existing in Yunnan's international logistics and puts forward proposals as how to develop international logistics aiming at Southeast Asia in Yunnan province.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.4120112941125005)+2 种基金the Hunan Provincial Natural Science Foundation of China(Grant No.12JJ3037)the Hunan Provincial Philosophy and Social Sciences Foundation of China(Grant No.11JD06)the Hengyang Normal University Youth Foundation in Hunan Province of China(Grant No.11A27)
文摘A case study is presented of a regional development model for valley economies in the mountain areas of Beijing, China. The nature and framework of the valley economy model are described and the development of the model, which is specific to the mountain areas of Beijing, is analyzed. Five different valley economy models applied in the Beijing mountain areas are compared. The major purpose of the valley economy model is to develop the regional economy, including the selection of appropriate industries, the allocation of industrial space, the establishment of supply chains and the integration of various industries. Pilot experiments using the valley economy model have been conducted in seven counties(districts) in Beijing: Pinggu, Huairou, Changping, Mentougou, and Fangshan districts, and Yanqing and Miyun counties. Five models for developing the Beijing mountain areas have been explored, including: creative cultural industries, characteristic industry clusters, the promotion of large tourist areas, natural scenic tourism and folk cultural tourism. Each model has its own unique features and potential to help in the regional development of mountain areas.
基金Sponsored by Major State Basic Research Development Program(973 Program)(2014CB460611)National Natural Science Foundation of China(41261102)
文摘In desert areas in Hexi region,11 barchan dunes,6 chains of barchan dunes,6 pyramid dunes,6 parabolic dunes and 6 accumulated sand-belts were chosen to study their movement speed based on images obtained by Google Earth in various periods.The results show that among the dunes,the movement of the barchan dunes was the fastest,followed by the chains of barchan dunes,and only the tops of the pyramid dunes swayed,while the parabolic dunes and accumulated sand-belts hardly moved forward.The higher the barchan dunes(or the chains of barchan dunes) were,the slower the movement was.On the contrary,the higher the pyramid dunes were,the faster the swing was.There was a positive correlation between the movement speed of the barchan dunes and the average wind speed of sandstorms.
基金Sponsored by the National Project of Scientific and Technical Supporting Programs Funded by Ministry of Science & Technology of China (Grant No.2013BAJ12B02)the National Natural Science Foundation of Heilongjiang (Grant No.E201316)the Fundamental Research Funds for the Central Universities (Grant No.HIT.KISTP.201419)
文摘To improve the comfortable physical environment for square in severe cold regions' rural areas. This paper applies the methods of questionnaires,field testing and statistical analysis to compare and analyze two different square cases of Qingyunpu in Liaoning Province,and conclude the main factors which affect the physical environmental comfort. The improvement strategies for physical environment of rural square are put forward from the aspects of site selection,road position,orientation,landscape design,and ground pavement material selection,aiming to provide the design basis for the physical environment of square in severe cold regions' rural areas.
基金Under the auspices of National Natural Science Foundation of China(No.41301467,41271416)Special Foundation of National Science and Technology Basic Work of China(No.2013FY112800)
文摘Gully erosion is the frequent and main form of soil erosion in the black soil area of the northeastern China, which is one of the most important commodity grain production bases in China. It is encroaching upon the fertile farmland there. Regionalization of gully erosion can reveal the spatial distribution and regularity of the development of gully erosion. Based on the eco-geographical regional background features of the black soil area, this study combined the regionalization with influencing factors of the development of gully erosion. GIS spatial analysis, geostatistical analysis, spatial statistics, reclassification, debris polygon processing and map algebra methods were employed. As a result, the black soil area was divided into 12 subregions. The field survey data on type, length, volume and other characteristics indicators of gully erosion were used to calibrate the results. Then the features of every subregion, such as where the gully erosion is, how serious it is, and why it happens and develops, were expounded. The result is not only an essential prerequisite for gully erosion surveys and monitoring, but also an important basis for gully erosion prevention.
文摘It is not clear how HPV infection is prevalent among Uygur women in Xinjiang Uygur Autonomous Region, China and whether the distribution of HPV infection is related with cervical intraepithelial neoplasia (CIN) incidence among them. A study including 883 Uygur women were conducted from 2006 to 2007 in Hetian Prefecture, Xinjiang Uygur Autonomous Region, China.
文摘IEEE has set up in October 2004 the IEEE802.22 Working Group—Wireless Regional Area Network (WRAN) Task Force to work out air interface standard based on Cognitive Radio (CR) technologies. The standard includes Physical Layer (PHY) and Media Access Control (MAC),to use the already allocated fallow spectrums to broadcast TV in a non-interference way. The WRAN employs CR technologies to sense and estimate the television frequencies and use the technologies of dynamic spectrum management to find and then allocate idle spectrums. The CR technologies are representing one of the major trends for future wireless communications. This article on WRANs and CR technologies will be divided into two issues. In this issue,WRANs and IEEE 802.22,CR technologies are introduced. And the second part in the next issue will analyze the applications of CR technologies.
基金Key Project of Chinese Ministry of Education(No.206055)
文摘IEEE has set up in October 2004 the IEEE802.22 Working Group-Wireless Regional Area Network (WRAN) Task Force to work out air interface standard based on Cognitive Radio (CR) technologies. The standard includes Physical Layer (PHY) and Media Access Control (MAC), utilizig the vacant spectrum bands already allocated to broadcast TV without interference.. The WRAN employs CR technologies to sense and estimate the television signals and use the technologies of dynamic spectrum management to find and then allocate vacant spectrums. The CR technologies are representing one of the major trends for future wireless communications. This article on WRANs and CR technologies will be divided into two issues. In this issue, WRANs and IEEE 802.22, CR technologies are introduced. And the second part in the next issue will analyze the applications of CR technologies.
基金the Natural Science Foundation of Nei Monggol Autonomous Region, No. 980204
文摘BACKGROUND: Previous studies reported that frontal-temporal-parietal-occipital pathological changes and diseased range in the right cerebral hemisphere were closely correlated with neglect. But studies on the correlation of neglect with diseased region and area in patients who suffer from initial attack of single focus of cerebral infarction (CI) in left and right cerebral hemispheres are few. OBJECTIVE: To observe the status of neglect in patients who suffer from single focus of CI in cerebral hemisphere, and analyze the correlation of neglect with diseased region and area of CI. DESIGN: Case analysis. SETTING: Treatment Center for Cardiocerebrovascular Disease, Second Hospital of Xiamen city; Department of Neurology, First Hospital Affiliated to Baotou Medical College. PARTICIPANTS: All the CI patients hospitalized in the Department of Neurology, First Hospital Affiliated to Baotou Medical College from June 1998 to May 2001 were retrieved. Inclusive criteria: ① Patients who suffered from initial attack of CI, which was confirmed by skull CT or MRI within 24 hours after onset and presented single focus in cerebral hemisphere. ② be conscious and could cooperate in the examination. ③ did not receive formal education, but could do accounts and some simple writing and reading. ④Patients with homonymous hemianopia were excluded through the examination of perimeter. ⑤ Informed consents were obtained from all the patients. Among 67 patients who met the inclusive criteria, 33 suffered from CI in the left cerebral hemisphere and 34 in the right cerebral hemisphere. METHODS: ① Patients received neglect supplement examination and Chinese aphasia examination within 2.5 to 3 months after the attack of CI . The diagnostic criteria of neglect in the tests of line cancellation, line bisection and copying the figures were as follows: In the line cancellation test based on the method of Albert, patients who could not cancel one or more lines were regarded as abnormal. In the line bisection test based on the method of Peter, patients who left deviated 1.16% or right deviated 2.51% were regarded as abnormal. In the test of copying the figures, round-shape, square, cruciform and other shapes were asked to be copied, defect appeared in the figure was regarded as abnormal. The diagnostic criteria of aphasia were according to the diagnostic method of Chinese aphasia examination and type identification flow-sheet of aphasia. Infarct area was calculated based on Palisino formula: infarct area=π/6×the longest diameter of infarct area×the widest diameter of infarct area×the number of CT positive layer. ② Chi-square test was used for comparing the difference of measurement data. MAIN OUTCOME MEASURES: Diseased region and area of CI and their correlations with neglect. RESULTS: Sixty-seven patients were involved in result analysis. ① The correlation of the occurrence of neglect with the diseased regions of CI: Neglect was not found in 33 patients with CI in left cerebral hemisphere, but was found in 7 of 34 patients with CI in right cerebral hemisphere. The diseased regions involved right temporoparietal region, temporal-parietal-occipital region, frontal-temporal-parietal region, frontal-temporal-parietal-occipital region, temporoparietal basal nucleus, basal nucleus and dorsal caudate putamen. ②The correlation of the occurrence of neglect with diseased area: infarct area ≤ 30 cm3 was found in 2 patients with neglect (12.5%), infarct area at 31 to 60 cm3 in 1 patient with neglect (14.3%),infarct area ≥ 61 cm3 in 4 patients with neglect (36.4%). There was no significant difference in infarct area among groups (P > 0.05). CONCLUSION: ① Right cerebral hemisphere takes advantage in spatial attention. ② Neglect is more possibly caused by the combined pathological changes in temporal and parietal lobe. Temporal and parietal lobes may not cause neglect independently, but the occurrence of neglect is not directly correlated with infarct area.
文摘In the stability study of the regional structures in the area of the Longyang Gorge Hydroelectrical Power Station, a model of the current stress-deformation field of the area was constructed based on analyses of available data of regional surveys and historical earthquakes and field investigations of active faults and ancient earthquakes. This model was examined and verified by physical and mathematical simulation experiments, and quantitative relations and data were obtained.
文摘The formation of rice distribution is based on certain natural ecological conditions and social economic environments. In China, rice cropping is distributed in a vast area extending across 5 tempera ture belts, the northernmost of rice growing area in the world being in China. Distribution of rice cropping is characterized by a gradual decrease from south to north, from large and concentrated regions in Southeast to small and separated areas in Northwest. Natural conditions in rice regions differ in China with a varied topography, high in the west and low in the east. Rice fields in the west are mostly distributed on flatlands on plains, valleys among mountains, tablelands in river valleys, yellow-soil plains and basins in low valleys, alluvial plains, plains in river valleys, while those in the east are mainly distributed on alluvial plains, hilly areas among low mountains, coastal plains, along rivers and lakes and in basins among mountains.
基金1998 Guangxi Education Department foundation item and 1999 Hunan SSUO key research project.
文摘This paper summarizes principles and measures of comprehensive division of mountainous areas, as well as clarifies meaning, structure, function and path established for the map and file information visibility system (MFIVS). And then, taking Huaihua City of Hunan Province as an example, and based on the MFIVS means, concrete attempts on regionalization are carried out. The result is relatively objective and accurate, which illuminates that the method is a comprehensive one with the characteristics of concision, applicability and effectiveness.
基金supported by the National Key Basic Research Program of China (973Program, 2015CB452706)the youth talent team program of the Institute of Mountain Hazards and Environment, CAS (SDSQB-2015-01)+1 种基金the National Natural Science Foundation of China (41401198 and 41571527)the Youth Innovation Promotion Association, CAS(No. 2016332)
文摘Topography, especially altitude, will influence the way, process and characteristics of land cover changes in mountainous area, simultaneously, the vertical difference of land cover changes will affect soil quality and regional ecological environment. Therefore, the gradient relationship analysis between land cover changes and altitude is very important for regional sustainability. This study investigated land cover dynamics based on land cover data from a typical mountainous area in the Guizhou-Guangxi karst mountain area, China, in 2000 and 2010, then explored the relationship between altitude and land cover change and analyzed different drivers of land cover change at different altitudes. Our findings are as follows. 1) From 2000 to 2010, the total area of land cover transition was 7167.04 km^2 or 2.8% of the region. The increasing area of build-up land(926.23 km^2) was larger than that of forest(859.38 km^2), suggesting that the urban construction speed was higher than that of reforestation. 2) Intensity of land cover transition in northwestern Guizhou-Guangxi karst mountain area was much larger than that of southeast part and their transition trend was also significantly different, which was consistent with regional population and economy. 3) Human activity was the most dramatic at altitudes between 0–500 m. For 500–1000 m, grassland mainly converted to forest and build-up land. Area of land cover transition was the greatest between 1000–1500 m, while above 1500 m, the transition of grassland was the most obvious. 4) The drivers of land cover change varied. Land cover change was positively correlated with gross domestic product and population density but was inversely related to relief amplitude. There were correlations between land cover change and distance to roads and rivers, and their correlations varied with altitude. By revealing patterns and causes of land cover changes in different altitudes, we hope to understand the vertical dependence of land cover changes, so as to improve land productivity and protect land ecological environment scientifically.
文摘The IEEE 802.22 standard based on wireless Cognitive Radio (CR) is an optimal solution to resolve the inefficient spectrum utility problem. In this paper, we focus on the spectrum allocation in IEEE 802.22 mesh networks and propose a new graph-theory algorithm. The algorithm aims at two objectives: one is the sum of the allocated channel bandwidth is maximum, and the other is the number of users can be active simultaneity is maximum. In this proposed algorithm, the topology of network was modeled as a general graph and could be transformed into a weighted complete bipartite-graph by three processes. The simulations show that the presented algorithm can improve the performance of spectrum allocation.
文摘This article focuses on the regional advantages to develop international logistics aiming at Southeast Asia in Yunnan province and intends to prove that it's of great significance to develop this kind of international logistics. Further, it analyzes the status quo, market demand and problems existing in Yunnan's international logistics and puts forward proposals as how to develop international logistics aiming at Southeast Asia in Yunnan province.