The great spatial and temporal variability in hydrological conditions and nitrogen（N）processing introduces large uncertainties to the identification of N sources and quantifying N cycles in plain river network regio...The great spatial and temporal variability in hydrological conditions and nitrogen（N）processing introduces large uncertainties to the identification of N sources and quantifying N cycles in plain river network regions. By combining isotopic data with chemical and hydrologic measurements, we determined the relative importance of N sources and biogeochemical N processes in the Taige River in the East Plain Region of China. The river was polluted more seriously by anthropogenic inputs in winter than in summer. Manure and urban sewage effluent were the main nitrate（NO-3） sources, with the nitrification of N-containing organic materials serving as another important source of NO-3. In the downstream, with minor variations in hydrological conditions, nitrification played a more important role than assimilation for the decreasing ammonium（NH＋4-N） concentrations.The N isotopic enrichment factors（ε） during NH＋4utilization ranged from- 13.88‰ in March to- 29.00‰ in July. The ratio of the increase in δ^18O and δ^15N of river NO-3in the downstream was 1.04 in January and 0.92 in March. This ratio indicated that NO-3assimilation by phytoplankton was responsible for the increasing δ^15N and δ^18O values of NO-3in winter. The relationships between δ^15N of particulate organic nitrogen and isotopic compositions of dissolved inorganic nitrogen indicated that the phytoplankton in the Taige River probably utilized NH＋4preferentially and mainly in summer, while in winter, NO-3assimilation by phytoplankton was dominant.展开更多
Under the background of constructing harmonious economic society, how to realize the coordinated development of regions in the course of region integration is a key problem. According to the relevant theory of enterpr...Under the background of constructing harmonious economic society, how to realize the coordinated development of regions in the course of region integration is a key problem. According to the relevant theory of enterprise gene reconfiguration and enterprise value network construction, we analyzed the problems in the merging course between the value network construction and region economic growth. Finally, we put forward the basic path of coordinated development of regions.展开更多
This paper studies pinning-controlled synchronization of complex networks with bounded or unbounded synchronized regions. To study a state-feedback pinning-controlled network with N nodes, it first converts the contro...This paper studies pinning-controlled synchronization of complex networks with bounded or unbounded synchronized regions. To study a state-feedback pinning-controlled network with N nodes, it first converts the controlled network to an extended network of N＋1 nodes without controls. It is shown that the controlled synchronizability of the given network is determined by the real part of the smallest nonzero eigenvalue of the coupling matrix of its extended network when the synchronized region is unbounded; but it is determined by the ratio of the real parts of the largest and the smallest nonzero eigenvalues of the coupling matrix when the synchronized region is bounded. Both theoretical analysis and numerical simulation show that the portion of controlled nodes has no critical values when the synchronized region is unbounded, but it has a critical value when the synchronized region is bounded. In the former case, therefore, it is possible to control the network to achieve synchronization by pinning only one node. In the latter case, the network can achieve controlled synchronization only when the portion of controlled nodes is larger than the critical value.展开更多
Ground military target recognition plays a crucial role in unmanned equipment and grasping the battlefield dynamics for military applications, but is disturbed by low-resolution and noisyrepresentation. In this paper,...Ground military target recognition plays a crucial role in unmanned equipment and grasping the battlefield dynamics for military applications, but is disturbed by low-resolution and noisyrepresentation. In this paper, a recognition method, involving a novel visual attention mechanismbased Gabor region proposal sub-network(Gabor RPN) and improved refinement generative adversarial sub-network(GAN), is proposed. Novel central-peripheral rivalry 3D color Gabor filters are proposed to simulate retinal structures and taken as feature extraction convolutional kernels in low-level layer to improve the recognition accuracy and framework training efficiency in Gabor RPN. Improved refinement GAN is used to solve the problem of blurry target classification, involving a generator to directly generate large high-resolution images from small blurry ones and a discriminator to distinguish not only real images vs. fake images but also the class of targets. A special recognition dataset for ground military target, named Ground Military Target Dataset(GMTD), is constructed. Experiments performed on the GMTD dataset effectively demonstrate that our method can achieve better energy-saving and recognition results when low-resolution and noisy-representation targets are involved, thus ensuring this algorithm a good engineering application prospect.展开更多
This paper addresses an interesting security problem in wireless ad hoc networks: the dynamic group key agreement key establishment. For secure group communication in an ad hoc network, a group key shared by all group...This paper addresses an interesting security problem in wireless ad hoc networks: the dynamic group key agreement key establishment. For secure group communication in an ad hoc network, a group key shared by all group members is required. This group key should be updated when there are membership changes (when the new member joins or current member leaves) in the group. In this paper, we propose a novel, secure, scalable and efficient region-based group key agreement protocol for ad hoc networks. This is implemented by a two-level structure and a new scheme of group key update. The idea is to divide the group into subgroups, each maintaining its subgroup keys using group elliptic curve diffie-hellman (GECDH) Protocol and links with other subgroups in a tree structure using tree-based group elliptic curve diffie-hellman (TGECDH) protocol. By introducing region-based approach, messages and key updates will be limited within subgroup and outer group;hence computation load is distributed to many hosts. Both theoretical analysis and experimental results show that this Region-based key agreement protocol performs well for the key establishment problem in ad hoc network in terms of memory cost, computation cost and communication cost.展开更多
In a given district, the accessibility of any point should be the synthetically evaluation of the internal and external accessibilities. Using MapX component and Delphi, the author presents an information system to ca...In a given district, the accessibility of any point should be the synthetically evaluation of the internal and external accessibilities. Using MapX component and Delphi, the author presents an information system to calculate and analyze regional accessibility according to the shortest travel time, generating thus a mark diffusing figure. Based on land traffic network, this paper assesses the present and the future regional accessibilities of sixteen major cities in the Yangtze River Delta. The result shows that the regional accessibility of the Yangtze River Delta presents a fan with Shanghai as its core. The top two most accessible cities are Shanghai and Jiaxing, and the bottom two ones are Taizhou （Zhejiang province） and Nantong With the construction of Sutong Bridge, Hangzhouwan Bridge and Zhoushan Bridge, the regional internal accessibility of all cities will be improved. Especially for Shaoxing, Ningbo and Taizhou （Jiangsu province）, the regional internal accessibility will be decreased by one hour, and other cities will be shortened by about 25 minutes averagely. As the construction of Yangkou Harbor in Nantong, the regional external accessibility of the harbor cities in Jiangsu province will be speeded up by about one hour.展开更多
A statistical correlation method is used to study the effect of instability of the calculation datum （ used in traditional method of indirect adjustment） on calculated gravity results, using data recorded by Longmen...A statistical correlation method is used to study the effect of instability of the calculation datum （ used in traditional method of indirect adjustment） on calculated gravity results, using data recorded by Longmen Mountain regional gravity network during 1996 -2007. The result shows that when this effect is corrected, anomalous gravity changes before the 2008 Wenchuan Ms8. 0 earthquake become obvious and characteristically distinctive. Thus the datum-stability problem must be considered when processing and analyzing data recorded by a regional gravity network.展开更多
In this paper, authors describe the characters and the present situation of computer region network, Moreover, authors put forward the method to plan and de sign ration ally the computer regional network system depend...In this paper, authors describe the characters and the present situation of computer region network, Moreover, authors put forward the method to plan and de sign ration ally the computer regional network system depending on the actual situa tion, in order to share the resources of software and hardware resources of the net work in best way and get higher efficiency of information management.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 Physical La...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
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 L...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
BeiDou navigation satellite system with global coverage(BDS-3)has been fully operational since July 2020,currently providing the positioning,navigation and timing service together with regional BDS-2.In addition to th...BeiDou navigation satellite system with global coverage(BDS-3)has been fully operational since July 2020,currently providing the positioning,navigation and timing service together with regional BDS-2.In addition to the legacy signals of B1I and B3I,the BDS-3 also transmits several new signals such as BIC,B2a and B2b,which brings new opportunities for rapid ambiguity resolution(AR)of BDS precise point positioning(PPP).In this contribution,a multi-frequency(MF)rapid PPP-AR method with regional network augmentation was proposed.Firstly,BDS five-frequency observations were introduced into uncombined double-differenced models to retrieve regional augmentation corrections at the server.Thereafter,a cascade PPP-AR strategy using extra-wide-lane,wide-lane and narrow-lane ambiguity was employed at the user.Once ambiguities were fixed to integers,the phase correction accuracy could reach about 3 cm on average overall BDS frequencies in the network with inter-station distances of 100-200 km.Subsequently,the statistical results of seven-day simulated kinematic experiments showed that over 99% of epochs on average realized PPP-AR.Correspondingly,the positioning accuracy of the MF fixed solution reached 1.8,1.9,4.7 cm in the east,north and up components,respectively,improving by 5-15% compared with the dual-frequency scheme.Moreover,several vehicle-borne experiments under different urban scenarios were also conducted.Under an open-sky or a relatively open highway scene,the BDS-MF scheme similarly exhibited good performance,and over 98% of epochs achieved rapid PPP-AR with a positioning accuracy better than 3 cm.More encouragingly,for this BDS-challenged experiment with an average satellite number of 8.6,although only 72.06% of epochs were available due to serious signal blockages caused by overpass,tunnels or tall buildings,the horizontal positioning accuracy could still remain 7 cm on average.展开更多
There are put forward in this paper the principle of using artificial neural networks to determine the featureswhich reflect seismotectonics and seismicity of the potential focal regions and the method to divide quant...There are put forward in this paper the principle of using artificial neural networks to determine the featureswhich reflect seismotectonics and seismicity of the potential focal regions and the method to divide quantitativelythe potential focal regions. The calculation of the actual data of North China area shows that it may fully reveal the relations between the potential focal regions and their controling characteristics by the method, of which the principle is concise and convenient to apply, the calculated results reasonable, the division in a meticulous way and the achievement practicable.展开更多
Network RTK (Real-Time Kinematic) is a technology that is based on GPS (Global Positioning System) or more gener-ally on GNSS (Global Navigation Satellite System) measurements to achieve centimeter-level accuracy posi...Network RTK (Real-Time Kinematic) is a technology that is based on GPS (Global Positioning System) or more gener-ally on GNSS (Global Navigation Satellite System) measurements to achieve centimeter-level accuracy positioning in real-time. Reference station placement is an important problem in the design and deployment of network RTK systems as it directly affects the quality of the positioning service and the cost of the network RTK systems. This paper identifies a new reference station placement for network RTK, namely QoS-aware regional network RTK reference station placement problem, and proposes an algorithm for the new reference station placement problem. The algorithm can always produce a reference station placement solution that completely covers the region of network RTK.展开更多
This paper attempts to integrate urban development and ecological conservation by applying and syncretizing the “urban region” concept from landscape ecology and the “city-region” concept from socioeconomics. Firs...This paper attempts to integrate urban development and ecological conservation by applying and syncretizing the “urban region” concept from landscape ecology and the “city-region” concept from socioeconomics. First, various concepts pertaining to regions are discussed and then, the integration of ecological conservation and urban development on a regional scale is introduced. Subsequently, the Greater Pearl River Delta, in China, is used as a case study area and landscape ecology’s “urban region” concept is applied to produce a landscape spatial arrangement framework for an urban region. This framework is achieved through the following steps: conceiving the study area as a region that consists of two urban regions, arranging ecological conservation landscapes by establishing a regional ecological network within the urban-region rings;and formulating an urban development strategy using central place theory. The resulting landscape spatial arrangement solution includes natural protection areas that cover half of the study area, several key strategic urbanizing locations, and suggestions for the strict protection of certain agricultural land-use areas. We believe that this framework facilitates a feasible exploration of land-use planning on a regional scale, although more in-depth studies are required to refine this approach.展开更多
In an era of rising trade protectionism and frequent antiglobalization events,strengthening regional economic connections has important practical significance for resisting external economic shocks,improving economic ...In an era of rising trade protectionism and frequent antiglobalization events,strengthening regional economic connections has important practical significance for resisting external economic shocks,improving economic resilience,and promoting regional economic development.Based on input-output analysis,value-added decomposition,and network analysis,this paper uses long-term,multiregional input-output data to measure the spatiotemporal patterns of Asian production networks(APNs)and the influence of the Belt and Road Initiative(BRI).The results demonstrate that Asian countries account for a high and growing proportion,with a weak ability to capture value in global production networks(GPNs).The BRI has significantly strengthened production cooperation among Asian nations,promoting participation and strengthening abilities to capture value in GPNs.The continuous stability and strengthening of internal cooperation of APNs improves resilience from external shocks.Inside APNs,the proportions of East Asia and Southeast Asia show an overall downward trend,while South,West,and Central Asia show an increasing trend.China has also replaced Japan as the largest participant,and the rise of South Asian countries,led by India,has transformed APNs from a binary to a triple structure.In addition,China’s upstream degree index increased significantly,whereas Japan experienced the largest decline,causing a level of high-end vacancy in APNs.We propose that the most urgent task for the Asian countries to enhance APNs is to achieve stratified development and build more complete production circles.展开更多
Event region detection is the important application for wireless sensor networks（WSNs）, where the existing faulty sensors would lead to drastic deterioration of network quality of service.Considering single-moment n...Event region detection is the important application for wireless sensor networks（WSNs）, where the existing faulty sensors would lead to drastic deterioration of network quality of service.Considering single-moment nodes fault-tolerance, a novel distributed fault-tolerant detection algorithm named distributed fault-tolerance based on weighted distance（DFWD） is proposed, which exploits the spatial correlation among sensor nodes and their redundant information.In sensor networks, neighborhood sensor nodes will be endowed with different relative weights respectively according to the distances between them and the central node.Having syncretized the weighted information of dual-neighborhood nodes appropriately, it is reasonable to decide the ultimate status of the central sensor node.Simultaneously, readings of faulty sensors would be corrected during this process.Simulation results demonstrate that the DFWD has a higher fault detection accuracy compared with other algorithms, and when the sensor fault probability is 10%, the DFWD can still correct more than 91% faulty sensor nodes, which significantly improves the performance of the whole sensor network.展开更多
基金supported by the Mega-projects of Science Research for Water Environment Improvement (No. 2012ZX07101)
文摘The great spatial and temporal variability in hydrological conditions and nitrogen（N）processing introduces large uncertainties to the identification of N sources and quantifying N cycles in plain river network regions. By combining isotopic data with chemical and hydrologic measurements, we determined the relative importance of N sources and biogeochemical N processes in the Taige River in the East Plain Region of China. The river was polluted more seriously by anthropogenic inputs in winter than in summer. Manure and urban sewage effluent were the main nitrate（NO-3） sources, with the nitrification of N-containing organic materials serving as another important source of NO-3. In the downstream, with minor variations in hydrological conditions, nitrification played a more important role than assimilation for the decreasing ammonium（NH＋4-N） concentrations.The N isotopic enrichment factors（ε） during NH＋4utilization ranged from- 13.88‰ in March to- 29.00‰ in July. The ratio of the increase in δ^18O and δ^15N of river NO-3in the downstream was 1.04 in January and 0.92 in March. This ratio indicated that NO-3assimilation by phytoplankton was responsible for the increasing δ^15N and δ^18O values of NO-3in winter. The relationships between δ^15N of particulate organic nitrogen and isotopic compositions of dissolved inorganic nitrogen indicated that the phytoplankton in the Taige River probably utilized NH＋4preferentially and mainly in summer, while in winter, NO-3assimilation by phytoplankton was dominant.
文摘Under the background of constructing harmonious economic society, how to realize the coordinated development of regions in the course of region integration is a key problem. According to the relevant theory of enterprise gene reconfiguration and enterprise value network construction, we analyzed the problems in the merging course between the value network construction and region economic growth. Finally, we put forward the basic path of coordinated development of regions.
基金supported by the National Natural Science Foundation of China (Grant No 10647001)the Guangxi Natural Science Foundation (Grant No 0728042)+1 种基金the Program for Excellent Talents in Guangxi Higher Education Institutions (Grant No RC2007006)the NSFC-HK Joint Research Scheme (Grant No N-CityU107/07)
文摘This paper studies pinning-controlled synchronization of complex networks with bounded or unbounded synchronized regions. To study a state-feedback pinning-controlled network with N nodes, it first converts the controlled network to an extended network of N＋1 nodes without controls. It is shown that the controlled synchronizability of the given network is determined by the real part of the smallest nonzero eigenvalue of the coupling matrix of its extended network when the synchronized region is unbounded; but it is determined by the ratio of the real parts of the largest and the smallest nonzero eigenvalues of the coupling matrix when the synchronized region is bounded. Both theoretical analysis and numerical simulation show that the portion of controlled nodes has no critical values when the synchronized region is unbounded, but it has a critical value when the synchronized region is bounded. In the former case, therefore, it is possible to control the network to achieve synchronization by pinning only one node. In the latter case, the network can achieve controlled synchronization only when the portion of controlled nodes is larger than the critical value.
基金the National Key Research and Development Program of China(No.2016YFC0802904)National Natural Science Foundation of China(No.61671470)Natural Science Foundation of Jiangsu Province(BK20161470).
文摘Ground military target recognition plays a crucial role in unmanned equipment and grasping the battlefield dynamics for military applications, but is disturbed by low-resolution and noisyrepresentation. In this paper, a recognition method, involving a novel visual attention mechanismbased Gabor region proposal sub-network(Gabor RPN) and improved refinement generative adversarial sub-network(GAN), is proposed. Novel central-peripheral rivalry 3D color Gabor filters are proposed to simulate retinal structures and taken as feature extraction convolutional kernels in low-level layer to improve the recognition accuracy and framework training efficiency in Gabor RPN. Improved refinement GAN is used to solve the problem of blurry target classification, involving a generator to directly generate large high-resolution images from small blurry ones and a discriminator to distinguish not only real images vs. fake images but also the class of targets. A special recognition dataset for ground military target, named Ground Military Target Dataset(GMTD), is constructed. Experiments performed on the GMTD dataset effectively demonstrate that our method can achieve better energy-saving and recognition results when low-resolution and noisy-representation targets are involved, thus ensuring this algorithm a good engineering application prospect.
文摘This paper addresses an interesting security problem in wireless ad hoc networks: the dynamic group key agreement key establishment. For secure group communication in an ad hoc network, a group key shared by all group members is required. This group key should be updated when there are membership changes (when the new member joins or current member leaves) in the group. In this paper, we propose a novel, secure, scalable and efficient region-based group key agreement protocol for ad hoc networks. This is implemented by a two-level structure and a new scheme of group key update. The idea is to divide the group into subgroups, each maintaining its subgroup keys using group elliptic curve diffie-hellman (GECDH) Protocol and links with other subgroups in a tree structure using tree-based group elliptic curve diffie-hellman (TGECDH) protocol. By introducing region-based approach, messages and key updates will be limited within subgroup and outer group;hence computation load is distributed to many hosts. Both theoretical analysis and experimental results show that this Region-based key agreement protocol performs well for the key establishment problem in ad hoc network in terms of memory cost, computation cost and communication cost.
基金National Natural Science Foundation of China, No.40371044 No.70573053
文摘In a given district, the accessibility of any point should be the synthetically evaluation of the internal and external accessibilities. Using MapX component and Delphi, the author presents an information system to calculate and analyze regional accessibility according to the shortest travel time, generating thus a mark diffusing figure. Based on land traffic network, this paper assesses the present and the future regional accessibilities of sixteen major cities in the Yangtze River Delta. The result shows that the regional accessibility of the Yangtze River Delta presents a fan with Shanghai as its core. The top two most accessible cities are Shanghai and Jiaxing, and the bottom two ones are Taizhou （Zhejiang province） and Nantong With the construction of Sutong Bridge, Hangzhouwan Bridge and Zhoushan Bridge, the regional internal accessibility of all cities will be improved. Especially for Shaoxing, Ningbo and Taizhou （Jiangsu province）, the regional internal accessibility will be decreased by one hour, and other cities will be shortened by about 25 minutes averagely. As the construction of Yangkou Harbor in Nantong, the regional external accessibility of the harbor cities in Jiangsu province will be speeded up by about one hour.
基金supported by the Eathquake Science Join Foundation( A07030)
文摘A statistical correlation method is used to study the effect of instability of the calculation datum （ used in traditional method of indirect adjustment） on calculated gravity results, using data recorded by Longmen Mountain regional gravity network during 1996 -2007. The result shows that when this effect is corrected, anomalous gravity changes before the 2008 Wenchuan Ms8. 0 earthquake become obvious and characteristically distinctive. Thus the datum-stability problem must be considered when processing and analyzing data recorded by a regional gravity network.
文摘In this paper, authors describe the characters and the present situation of computer region network, Moreover, authors put forward the method to plan and de sign ration ally the computer regional network system depending on the actual situa tion, in order to share the resources of software and hardware resources of the net work in best way and get higher efficiency of information management.
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.
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supported by the National Natural Science Foundation of China[Grant 41774030,Grant 41974027 and Grant 41974029]the Hubei Province Natural Science Foundation of China[Grant 2018CFA081]+1 种基金the frontier project of basic application from Wuhan science and technology bureau[Grant 2019010701011395]the Sino-German mobility programme[Grant No.M-0054].
文摘BeiDou navigation satellite system with global coverage(BDS-3)has been fully operational since July 2020,currently providing the positioning,navigation and timing service together with regional BDS-2.In addition to the legacy signals of B1I and B3I,the BDS-3 also transmits several new signals such as BIC,B2a and B2b,which brings new opportunities for rapid ambiguity resolution(AR)of BDS precise point positioning(PPP).In this contribution,a multi-frequency(MF)rapid PPP-AR method with regional network augmentation was proposed.Firstly,BDS five-frequency observations were introduced into uncombined double-differenced models to retrieve regional augmentation corrections at the server.Thereafter,a cascade PPP-AR strategy using extra-wide-lane,wide-lane and narrow-lane ambiguity was employed at the user.Once ambiguities were fixed to integers,the phase correction accuracy could reach about 3 cm on average overall BDS frequencies in the network with inter-station distances of 100-200 km.Subsequently,the statistical results of seven-day simulated kinematic experiments showed that over 99% of epochs on average realized PPP-AR.Correspondingly,the positioning accuracy of the MF fixed solution reached 1.8,1.9,4.7 cm in the east,north and up components,respectively,improving by 5-15% compared with the dual-frequency scheme.Moreover,several vehicle-borne experiments under different urban scenarios were also conducted.Under an open-sky or a relatively open highway scene,the BDS-MF scheme similarly exhibited good performance,and over 98% of epochs achieved rapid PPP-AR with a positioning accuracy better than 3 cm.More encouragingly,for this BDS-challenged experiment with an average satellite number of 8.6,although only 72.06% of epochs were available due to serious signal blockages caused by overpass,tunnels or tall buildings,the horizontal positioning accuracy could still remain 7 cm on average.
文摘There are put forward in this paper the principle of using artificial neural networks to determine the featureswhich reflect seismotectonics and seismicity of the potential focal regions and the method to divide quantitativelythe potential focal regions. The calculation of the actual data of North China area shows that it may fully reveal the relations between the potential focal regions and their controling characteristics by the method, of which the principle is concise and convenient to apply, the calculated results reasonable, the division in a meticulous way and the achievement practicable.
文摘Network RTK (Real-Time Kinematic) is a technology that is based on GPS (Global Positioning System) or more gener-ally on GNSS (Global Navigation Satellite System) measurements to achieve centimeter-level accuracy positioning in real-time. Reference station placement is an important problem in the design and deployment of network RTK systems as it directly affects the quality of the positioning service and the cost of the network RTK systems. This paper identifies a new reference station placement for network RTK, namely QoS-aware regional network RTK reference station placement problem, and proposes an algorithm for the new reference station placement problem. The algorithm can always produce a reference station placement solution that completely covers the region of network RTK.
文摘This paper attempts to integrate urban development and ecological conservation by applying and syncretizing the “urban region” concept from landscape ecology and the “city-region” concept from socioeconomics. First, various concepts pertaining to regions are discussed and then, the integration of ecological conservation and urban development on a regional scale is introduced. Subsequently, the Greater Pearl River Delta, in China, is used as a case study area and landscape ecology’s “urban region” concept is applied to produce a landscape spatial arrangement framework for an urban region. This framework is achieved through the following steps: conceiving the study area as a region that consists of two urban regions, arranging ecological conservation landscapes by establishing a regional ecological network within the urban-region rings;and formulating an urban development strategy using central place theory. The resulting landscape spatial arrangement solution includes natural protection areas that cover half of the study area, several key strategic urbanizing locations, and suggestions for the strict protection of certain agricultural land-use areas. We believe that this framework facilitates a feasible exploration of land-use planning on a regional scale, although more in-depth studies are required to refine this approach.
基金Under the auspices of National Natural Science Foundation of China(No.42201188)。
文摘In an era of rising trade protectionism and frequent antiglobalization events,strengthening regional economic connections has important practical significance for resisting external economic shocks,improving economic resilience,and promoting regional economic development.Based on input-output analysis,value-added decomposition,and network analysis,this paper uses long-term,multiregional input-output data to measure the spatiotemporal patterns of Asian production networks(APNs)and the influence of the Belt and Road Initiative(BRI).The results demonstrate that Asian countries account for a high and growing proportion,with a weak ability to capture value in global production networks(GPNs).The BRI has significantly strengthened production cooperation among Asian nations,promoting participation and strengthening abilities to capture value in GPNs.The continuous stability and strengthening of internal cooperation of APNs improves resilience from external shocks.Inside APNs,the proportions of East Asia and Southeast Asia show an overall downward trend,while South,West,and Central Asia show an increasing trend.China has also replaced Japan as the largest participant,and the rise of South Asian countries,led by India,has transformed APNs from a binary to a triple structure.In addition,China’s upstream degree index increased significantly,whereas Japan experienced the largest decline,causing a level of high-end vacancy in APNs.We propose that the most urgent task for the Asian countries to enhance APNs is to achieve stratified development and build more complete production circles.
基金supported by the National Science Foundation for Outstanding Young Scientists (60425310)the Science Foundation for Post-doctoral Scientists of Central South University (2008)
文摘Event region detection is the important application for wireless sensor networks（WSNs）, where the existing faulty sensors would lead to drastic deterioration of network quality of service.Considering single-moment nodes fault-tolerance, a novel distributed fault-tolerant detection algorithm named distributed fault-tolerance based on weighted distance（DFWD） is proposed, which exploits the spatial correlation among sensor nodes and their redundant information.In sensor networks, neighborhood sensor nodes will be endowed with different relative weights respectively according to the distances between them and the central node.Having syncretized the weighted information of dual-neighborhood nodes appropriately, it is reasonable to decide the ultimate status of the central sensor node.Simultaneously, readings of faulty sensors would be corrected during this process.Simulation results demonstrate that the DFWD has a higher fault detection accuracy compared with other algorithms, and when the sensor fault probability is 10%, the DFWD can still correct more than 91% faulty sensor nodes, which significantly improves the performance of the whole sensor network.
