Hurricane Ida ferociously affected many south-eastern and eastern parts of the United States,making it one of the strongest hurricanes in recent years.Advanced forecast and warning tool has been used to track the path...Hurricane Ida ferociously affected many south-eastern and eastern parts of the United States,making it one of the strongest hurricanes in recent years.Advanced forecast and warning tool has been used to track the path of the ex-Hurricane,Ida,as it left New Orleans on its way towards the northeast,accurately predicting significant supercell development above New York City on September 01,2021.This advanced method accurately detected the area with the highest possible level of convective instability with 24-h lead time and even Level 5,devised in the categorical outlooks legend of the system.Therefore,an extreme level implied a very high probability of the local-scale hazard occurring above the NYC.Cloud model output fields(updrafts and downdrafts,wind shear,near-surface convergence,the vertical component of relative vorticity)show the rapid development of a strong supercell storm with rotating updrafts and a mesocyclone.The characteristic hook-shaped echo signature visible in the reflectivity patterns indicates a signal for a highly precipitable(HP)supercell with the possibility of tornado initiation.Open boundary conditions represent a good basis for simulating a tornado that evolved from a supercell storm,initialized with initial data obtained from a real-time simulation in the period when the bow echo and tornado-like signature occurred.Тhe modeled results agree well with the observations.展开更多
Hindukush is an active subduction zone where at least one earthquake occurs on daily basis.For seismic hazard studies,it is important to develop a local magnitude scale using the data of local seismic network.We have ...Hindukush is an active subduction zone where at least one earthquake occurs on daily basis.For seismic hazard studies,it is important to develop a local magnitude scale using the data of local seismic network.We have computed local magnitude scale for Hindukush earthquakes using data from local network belonging to Center for Earthquake Studies(CES)for a period of three years,i.e.2015–2017.A total of 26,365 seismic records pertaining to 2,683 earthquakes with magnitude 2.0 and greater,was used with hypocentral distance less than 600 km.Magnitude scale developed by using this data comes to be M_(L)=logA+0.929logr+0.00298r-1.84.The magnitude determined through formulated relation was compared with that of standard relation for Southern California and relation developed by the same authors for local network for Northern Punjab.It was observed that Hindukush region has high attenuation as compared to that of Southern California and Northern Punjab which implies that Hindukush is tectonically more disturbed as compared to the said regions,hence,seismically more active as well.We have calculated station correction factors for our network.Station correction factors do not show any pattern which probably owes to the geological and tectonic complexity of this structure.Standard deviation and variance of magnitude residuals for CES network determined using Hutton and Boore scale and scale developed in this study were compared,it showed that a variance reduction of 44.1%was achieved.Average of magnitude residuals for different distance ranges was almost zero which showed that our magnitude scale was stable for all distances up to 600 km.Newly developed magnitude scale will help in homogenization of earthquake catalog.It has been observed that b-value of CES catalog decreases when magnitude is calculated by using newly developed magnitude scale.展开更多
Due to the heterogeneity of the structure on a scale-free network, making the betweennesses of all nodes become homogeneous by reassigning the weights of nodes or edges is very difficult. In order to take advantage of...Due to the heterogeneity of the structure on a scale-free network, making the betweennesses of all nodes become homogeneous by reassigning the weights of nodes or edges is very difficult. In order to take advantage of the important effect of high degree nodes on the shortest path communication and preferentially deliver packets by them to increase the probability to destination, an adaptive local routing strategy on a scale-free network is proposed, in which the node adjusts the forwarding probability with the dynamical traffic load （packet queue length） and the degree distribution of neighbouring nodes. The critical queue length of a node is set to be proportional to its degree, and the node with high degree has a larger critical queue length to store and forward more packets. When the queue length of a high degree node is shorter than its critical queue length, it has a higher probability to forward packets. After higher degree nodes are saturated （whose queue lengths are longer than their critical queue lengths）, more packets will be delivered by the lower degree nodes around them. The adaptive local routing strategy increases the probability of a packet finding its destination quickly, and improves the transmission capacity on the scale-free network by reducing routing hops. The simulation results show that the transmission capacity of the adaptive local routing strategy is larger than that of three previous local routing strategies.展开更多
The spatial scale(?shing grid) of ?sheries research af fects the observed spatial patterns of?sheries resources such as catch-per-unit-ef fort(CPUE) and ?shing ef fort. We examined the scale impact of high value(HH) c...The spatial scale(?shing grid) of ?sheries research af fects the observed spatial patterns of?sheries resources such as catch-per-unit-ef fort(CPUE) and ?shing ef fort. We examined the scale impact of high value(HH) clusters of the annual ?shing ef fort for Dosidicus gigas of fshore Peru from 2009 to 2012.For a multi-scale analysis, the original commercial ?shery data were tessellated to twelve spatial scales from 6′ to 72′ with an interval of 6′. Under these spatial scales, D. gigas clusters were identi?ed using the Anselin Local Moran's I. Statistics including the number of points, mean CPUE, standard deviation(SD),skewness, kurtosis, area and centroid were calculated for these HH clusters. We found that the z-score of global Moran's I and the number of points for HH clusters follow a power law scaling relationship from2009 to 2012. The mean ef fort and its SD also follow a power law scaling relationship from 2009 to 2012.The skewness follows a linear scaling relationship in 2010 and 2011 but ?uctuates with spatial scale in2009 and 2012; kurtosis follows a logarithmic scale relationship in 2009, 2011 and 2012 but a linear scale relationship in 2010. Cluster area follows a power law scaling relationship in 2010 and 2012, a linear scaling relationship in 2009, and a quadratic scaling relationship in 2011. Based on the peaks of Moran's I indices and the multi-scale analysis, we conclude that the optimum scales are 12′ in 2009 ? 2011 and 6′ in 2012, while the coarsest allowable scales are 48′ in 2009, 2010 and 2012, and 60′ in 2011. Our research provides the best spatial scales for conducting spatial analysis of this pelagic species, and provides a better understanding of scaling behavior for the ?shing ef fort of D. gigas in the of fshore Peruvian waters.展开更多
It is a challenging topic to develop an efficient algorithm for large scale classification problems in many applications of machine learning. In this paper, a hierarchical clustering and fixed- layer local learning （...It is a challenging topic to develop an efficient algorithm for large scale classification problems in many applications of machine learning. In this paper, a hierarchical clustering and fixed- layer local learning （HCFLL） based support vector machine（SVM） algorithm is proposed to deal with this problem. Firstly, HCFLL hierarchically dusters a given dataset into a modified clustering feature tree based on the ideas of unsupervised clustering and supervised clustering. Then it locally trains SVM on each labeled subtree at a fixed-layer of the tree. The experimental results show that compared with the existing popular algorithms such as core vector machine and decision.tree support vector machine, HCFLL can significantly improve the training and testing speeds with comparable testing accuracy.展开更多
Developing ecological scale breeding of local chickens with natural conditions, such as forest lands, grass lands, orchards and mulberry fields, not only can improve the quality of poultry products and the production ...Developing ecological scale breeding of local chickens with natural conditions, such as forest lands, grass lands, orchards and mulberry fields, not only can improve the quality of poultry products and the production benefits of chicken breeding, but also can develop and use local chicken germplasm effectively and promote their breed protection and industrialization. From integration and application of breed selection, breeding management, nutrient regulation, grass planting and grazing, a new ecological scale breeding technique of local chickens is proposed.展开更多
The traditional description of atomic-scale friction, as investigated in Friction force microscopy, in terms of mechanical stick-slip instabilities appears so successful that it obscures the actual mechanisms of frict...The traditional description of atomic-scale friction, as investigated in Friction force microscopy, in terms of mechanical stick-slip instabilities appears so successful that it obscures the actual mechanisms of frictional energy dissipation. More sophisticated theoretical approach, which takes into account damping explicitly, reveals the existence of some hidden, unexplained problems, like the universal nearly-critical damping and unexpectedly high value of the dissipation rate. In this paper, we combine analysis in the framework of nonequilibrium statistical mechanics with simple atomistic modeling to show that the hidden problems of atomic scale friction find their origin in the nontrivial character of energy dissipation that is non-local and dominated by memory effects, which have not been addressed before in the context of dry, atomic-scale friction.展开更多
Tree species respond to climate change at multiple scales,such as species physiological response at fine scale and species distribution (quantified by percent area) at broader spatial scale.At a given spatial scale,sp...Tree species respond to climate change at multiple scales,such as species physiological response at fine scale and species distribution (quantified by percent area) at broader spatial scale.At a given spatial scale,species physiological response and distribution can be correlated positively or negatively.The consistency of such correlation relationships at different spatial scales determines whether species responses derived from local scales can be extrapo-lated to broader spatial scales.In this study,we used a coupled modeling approach that coupled a plot-level ecosystem process model (LINKAGES) with a spatially explicit landscape model (LANDIS).We investigated species physio-logical responses and distribution responses to climate warming at the local,zonal and landscape scales respectively,and examined how species physiological response and distribution correlated at each corresponding scale and whether the correlations were consistent among these scales.The results indicate that for zonal and warming-sensitive species,the correlations between species physiological response and distribution are consistent at these spatial scales,and therefore the research results of vegetation response to climate warming at the local scale can be extrapolated to the zonal and landscape scales.By contrast,for zonal and warming-insensitive species the correlations among different spatial scales are consistent at some spatial scales but at other scales.The results also suggest that the results of azonal species at the local scale near their distribution boundaries can not be extrapolated simply to broader scales due to stronger responses to climate warming in those boundary regions.展开更多
We examined the scale impacts on spatial hot and cold spots of CPUE for Ommastrephes bartramii in the northwest Pacific Ocean. The original fishery data were tessellated to 18 spatial scales from 5′×5′ to 90′&...We examined the scale impacts on spatial hot and cold spots of CPUE for Ommastrephes bartramii in the northwest Pacific Ocean. The original fishery data were tessellated to 18 spatial scales from 5′×5′ to 90′×90′ with a scale interval of 5′ to identify the local clusters. The changes in location, boundaries, and statistics regarding the Getis-Ord Gi＊ hot and cold spots in response to the spatial scales were analyzed in detail. Several statistics including Min, mean, Max, SD, CV, skewness, kurtosis, first quartile（Q1）, median, third quartile（Q3）, area and centroid were calculated for spatial hot and cold spots. Scaling impacts were examined for the selected statistics using linear, logarithmic, exponential, power law and polynomial functions. Clear scaling relations were identified for Max, SD and kurtosis for both hot and cold spots. For the remaining statistics, either a difference of scale impacts was found between the two clusters, or no clear scaling relation was identified. Spatial scales coarser than 30′ are not recommended to identify the local spatial patterns of fisheries because the boundary and locations of hot and cold spots at a coarser scale are significantly different from those at the original scale.展开更多
Oasis is a special geographic landscape among the vast desert/Gobi in Northwest China (NWC). The surface sensitive heat flux and latent heat flux at Zhangye Oasis during 1 to 11 August 1991 are simulated using the NCA...Oasis is a special geographic landscape among the vast desert/Gobi in Northwest China (NWC). The surface sensitive heat flux and latent heat flux at Zhangye Oasis during 1 to 11 August 1991 are simulated using the NCAR nonhydrostatic mesoscale model MM5 Version 3. The horizontal grid resolution is set as 1km. By comparing the simulation results with HEIFE observations, it is proved that the model can be used to simulate the surface energy and water mass exchange of arid and semiarid regions in NWC. Based on the above results, the influence of different oasis scales on the local atmospheric field near the ground surface, and the critical scale of oasis maintenance, in NWC are studied dynamically. The following conclusion is obtained: the local thermal circulation between the oasis and the desert/Gobi is formed in the oasis downstream if the oasis scale is larger than 4 km. This local thermal circulation between the oasis and the desert adjacent to the oasis helps to conserve water vapor over the oasis. At the same time, it transfers the abundant water vapor from the oasis into the desert/Gobi near to the oasis to supply relatively plentiful water vapor for desert crops to grow on the fringe of the oasis. So, it is advantageous for oasis extension. However, if the scale of the oasis is smaller than 4 km, it is not easy for the local thermal circulation between the oasis and the desert/Gobi to take shape. This study provides a new standpoint for oasis maintenance and development.展开更多
By using Doppler weather radar data,the meso-scale characteristics of extremely heavy rainstorm process which happened suddenly in Jieyang urban area on July 31,2008 were analyzed.The results showed that the radar ech...By using Doppler weather radar data,the meso-scale characteristics of extremely heavy rainstorm process which happened suddenly in Jieyang urban area on July 31,2008 were analyzed.The results showed that the radar echo only needed 20 minutes from the generation to the strong echo which quickly strengthened above 50 dBz.The storm center went down south and went up north near Jieyang City all the time.The component which moved eastward was very tiny,and the heavy precipitation echo stagnated.In this heavy precipitation process,the characteristics types of radial velocity which were favorable to the generation and development of heavy precipitation echo appeared alternately each other.The radial velocity's characteristics types were the first type headwind zone,the second type headwind zone,meso-scale convergence type and cyclonic convergence and so on.Thus,this heavy precipitation process which broke the record happened.The analyses showed that the headwind zone which developed vigorously and the convergence which had influx and outflux airflow in the vertical direction of headwind zone made obvious contributions to the precipitation.展开更多
Localization of sensor nodes is crucial in Wireless Sensor Network because of applications like surveillance, tracking, navigation etc. Various optimization techniques for localization have been proposed in literature...Localization of sensor nodes is crucial in Wireless Sensor Network because of applications like surveillance, tracking, navigation etc. Various optimization techniques for localization have been proposed in literature by different researchers. In this paper, we propose a two phase hybrid approach for localization using Multidi- mensional Scaling and trilateration, namely, MDS with refinement using trilateration. Trilateration refines the estimated locations obtained by the MDS algorithm and hence acts as a post optimizer which improves the accuracy of the estimated positions of sensor nodes. Through extensive simulations, we have shown that the proposed algorithm is more robust to noise than previous approaches and provides higher accuracy for estimating the positions of sensor nodes.展开更多
A closed,trans-scale formulation of damage evolution based on the statistical mi- crodamage mechanics is summarized in this paper.The dynamic function of damage bridges the mesoscopic and macroscopic evolution of dama...A closed,trans-scale formulation of damage evolution based on the statistical mi- crodamage mechanics is summarized in this paper.The dynamic function of damage bridges the mesoscopic and macroscopic evolution of damage.The spallation in an aluminium plate is studied with this formulation.It is found that the damage evolution is governed by several dimensionless parameters, i.e.,imposed Deborah numbers De~* and De,Mach number M and damage number S.In particular, the most critical mode of the macroscopic damage evolution,i.e.,the damage localization,is deter- mined by Deborah number De~*.Deborah number De~* reflects the coupling and competition between the macroscopic loading and the microdamage growth.Therefore,our results reveal the multi-scale nature of spallation.In fact,the damage localization results from the nonlinearity of the microdamage growth.In addition,the dependence of the damage rate on imposed Deborah numbers De~* and De, Mach number M and damage number S is discussed.展开更多
文摘Hurricane Ida ferociously affected many south-eastern and eastern parts of the United States,making it one of the strongest hurricanes in recent years.Advanced forecast and warning tool has been used to track the path of the ex-Hurricane,Ida,as it left New Orleans on its way towards the northeast,accurately predicting significant supercell development above New York City on September 01,2021.This advanced method accurately detected the area with the highest possible level of convective instability with 24-h lead time and even Level 5,devised in the categorical outlooks legend of the system.Therefore,an extreme level implied a very high probability of the local-scale hazard occurring above the NYC.Cloud model output fields(updrafts and downdrafts,wind shear,near-surface convergence,the vertical component of relative vorticity)show the rapid development of a strong supercell storm with rotating updrafts and a mesocyclone.The characteristic hook-shaped echo signature visible in the reflectivity patterns indicates a signal for a highly precipitable(HP)supercell with the possibility of tornado initiation.Open boundary conditions represent a good basis for simulating a tornado that evolved from a supercell storm,initialized with initial data obtained from a real-time simulation in the period when the bow echo and tornado-like signature occurred.Тhe modeled results agree well with the observations.
文摘Hindukush is an active subduction zone where at least one earthquake occurs on daily basis.For seismic hazard studies,it is important to develop a local magnitude scale using the data of local seismic network.We have computed local magnitude scale for Hindukush earthquakes using data from local network belonging to Center for Earthquake Studies(CES)for a period of three years,i.e.2015–2017.A total of 26,365 seismic records pertaining to 2,683 earthquakes with magnitude 2.0 and greater,was used with hypocentral distance less than 600 km.Magnitude scale developed by using this data comes to be M_(L)=logA+0.929logr+0.00298r-1.84.The magnitude determined through formulated relation was compared with that of standard relation for Southern California and relation developed by the same authors for local network for Northern Punjab.It was observed that Hindukush region has high attenuation as compared to that of Southern California and Northern Punjab which implies that Hindukush is tectonically more disturbed as compared to the said regions,hence,seismically more active as well.We have calculated station correction factors for our network.Station correction factors do not show any pattern which probably owes to the geological and tectonic complexity of this structure.Standard deviation and variance of magnitude residuals for CES network determined using Hutton and Boore scale and scale developed in this study were compared,it showed that a variance reduction of 44.1%was achieved.Average of magnitude residuals for different distance ranges was almost zero which showed that our magnitude scale was stable for all distances up to 600 km.Newly developed magnitude scale will help in homogenization of earthquake catalog.It has been observed that b-value of CES catalog decreases when magnitude is calculated by using newly developed magnitude scale.
基金Project supported in part by the National Natural Science Foundation of China (Grant Nos. 60872011 and 60502017)the State Key Development Program for Basic Research of China (Grant Nos. 2009CB320504 and 2010CB731800)Program for New Century Excellent Talents in University
文摘Due to the heterogeneity of the structure on a scale-free network, making the betweennesses of all nodes become homogeneous by reassigning the weights of nodes or edges is very difficult. In order to take advantage of the important effect of high degree nodes on the shortest path communication and preferentially deliver packets by them to increase the probability to destination, an adaptive local routing strategy on a scale-free network is proposed, in which the node adjusts the forwarding probability with the dynamical traffic load （packet queue length） and the degree distribution of neighbouring nodes. The critical queue length of a node is set to be proportional to its degree, and the node with high degree has a larger critical queue length to store and forward more packets. When the queue length of a high degree node is shorter than its critical queue length, it has a higher probability to forward packets. After higher degree nodes are saturated （whose queue lengths are longer than their critical queue lengths）, more packets will be delivered by the lower degree nodes around them. The adaptive local routing strategy increases the probability of a packet finding its destination quickly, and improves the transmission capacity on the scale-free network by reducing routing hops. The simulation results show that the transmission capacity of the adaptive local routing strategy is larger than that of three previous local routing strategies.
基金Supported by the National Natural Science Foundation of China(No.41406146)the Laboratory for Marine Fisheries Science and Food Production Processes at Qingdao National Laboratory for Marine Science and Technology of China(No.2017-1A02)the Shanghai Universities First-class Disciplines Project-Fisheries(A)
文摘The spatial scale(?shing grid) of ?sheries research af fects the observed spatial patterns of?sheries resources such as catch-per-unit-ef fort(CPUE) and ?shing ef fort. We examined the scale impact of high value(HH) clusters of the annual ?shing ef fort for Dosidicus gigas of fshore Peru from 2009 to 2012.For a multi-scale analysis, the original commercial ?shery data were tessellated to twelve spatial scales from 6′ to 72′ with an interval of 6′. Under these spatial scales, D. gigas clusters were identi?ed using the Anselin Local Moran's I. Statistics including the number of points, mean CPUE, standard deviation(SD),skewness, kurtosis, area and centroid were calculated for these HH clusters. We found that the z-score of global Moran's I and the number of points for HH clusters follow a power law scaling relationship from2009 to 2012. The mean ef fort and its SD also follow a power law scaling relationship from 2009 to 2012.The skewness follows a linear scaling relationship in 2010 and 2011 but ?uctuates with spatial scale in2009 and 2012; kurtosis follows a logarithmic scale relationship in 2009, 2011 and 2012 but a linear scale relationship in 2010. Cluster area follows a power law scaling relationship in 2010 and 2012, a linear scaling relationship in 2009, and a quadratic scaling relationship in 2011. Based on the peaks of Moran's I indices and the multi-scale analysis, we conclude that the optimum scales are 12′ in 2009 ? 2011 and 6′ in 2012, while the coarsest allowable scales are 48′ in 2009, 2010 and 2012, and 60′ in 2011. Our research provides the best spatial scales for conducting spatial analysis of this pelagic species, and provides a better understanding of scaling behavior for the ?shing ef fort of D. gigas in the of fshore Peruvian waters.
基金National Natural Science Foundation of China ( No. 61070033 )Fundamental Research Funds for the Central Universities,China( No. 2012ZM0061)
文摘It is a challenging topic to develop an efficient algorithm for large scale classification problems in many applications of machine learning. In this paper, a hierarchical clustering and fixed- layer local learning （HCFLL） based support vector machine（SVM） algorithm is proposed to deal with this problem. Firstly, HCFLL hierarchically dusters a given dataset into a modified clustering feature tree based on the ideas of unsupervised clustering and supervised clustering. Then it locally trains SVM on each labeled subtree at a fixed-layer of the tree. The experimental results show that compared with the existing popular algorithms such as core vector machine and decision.tree support vector machine, HCFLL can significantly improve the training and testing speeds with comparable testing accuracy.
基金Supported by Three New Agricultural Project in Jiangsu Province(SXGC[2013]234)
文摘Developing ecological scale breeding of local chickens with natural conditions, such as forest lands, grass lands, orchards and mulberry fields, not only can improve the quality of poultry products and the production benefits of chicken breeding, but also can develop and use local chicken germplasm effectively and promote their breed protection and industrialization. From integration and application of breed selection, breeding management, nutrient regulation, grass planting and grazing, a new ecological scale breeding technique of local chickens is proposed.
文摘The traditional description of atomic-scale friction, as investigated in Friction force microscopy, in terms of mechanical stick-slip instabilities appears so successful that it obscures the actual mechanisms of frictional energy dissipation. More sophisticated theoretical approach, which takes into account damping explicitly, reveals the existence of some hidden, unexplained problems, like the universal nearly-critical damping and unexpectedly high value of the dissipation rate. In this paper, we combine analysis in the framework of nonequilibrium statistical mechanics with simple atomistic modeling to show that the hidden problems of atomic scale friction find their origin in the nontrivial character of energy dissipation that is non-local and dominated by memory effects, which have not been addressed before in the context of dry, atomic-scale friction.
基金Under the auspices of International Partnership Program of Chinese Academy of Sciences (No.KZCX2-YW-T06)Key Direction in Knowledge Innovation Programs of Chinese Academy of Sciences (No.KZCX2-YW-444)Major State Basic Research Development Program of China (No.2009CB421101)
文摘Tree species respond to climate change at multiple scales,such as species physiological response at fine scale and species distribution (quantified by percent area) at broader spatial scale.At a given spatial scale,species physiological response and distribution can be correlated positively or negatively.The consistency of such correlation relationships at different spatial scales determines whether species responses derived from local scales can be extrapo-lated to broader spatial scales.In this study,we used a coupled modeling approach that coupled a plot-level ecosystem process model (LINKAGES) with a spatially explicit landscape model (LANDIS).We investigated species physio-logical responses and distribution responses to climate warming at the local,zonal and landscape scales respectively,and examined how species physiological response and distribution correlated at each corresponding scale and whether the correlations were consistent among these scales.The results indicate that for zonal and warming-sensitive species,the correlations between species physiological response and distribution are consistent at these spatial scales,and therefore the research results of vegetation response to climate warming at the local scale can be extrapolated to the zonal and landscape scales.By contrast,for zonal and warming-insensitive species the correlations among different spatial scales are consistent at some spatial scales but at other scales.The results also suggest that the results of azonal species at the local scale near their distribution boundaries can not be extrapolated simply to broader scales due to stronger responses to climate warming in those boundary regions.
基金The National Natural Science Foundation of China under contract No.41406146the Open Fund from Laboratory for Marine Fisheries Science and Food Production Processes at Qingdao National Laboratory for Marine Science and Technology of China under contract No.2017-1A02Shanghai Universities First-class Disciplines Project-Fisheries(A)
文摘We examined the scale impacts on spatial hot and cold spots of CPUE for Ommastrephes bartramii in the northwest Pacific Ocean. The original fishery data were tessellated to 18 spatial scales from 5′×5′ to 90′×90′ with a scale interval of 5′ to identify the local clusters. The changes in location, boundaries, and statistics regarding the Getis-Ord Gi＊ hot and cold spots in response to the spatial scales were analyzed in detail. Several statistics including Min, mean, Max, SD, CV, skewness, kurtosis, first quartile（Q1）, median, third quartile（Q3）, area and centroid were calculated for spatial hot and cold spots. Scaling impacts were examined for the selected statistics using linear, logarithmic, exponential, power law and polynomial functions. Clear scaling relations were identified for Max, SD and kurtosis for both hot and cold spots. For the remaining statistics, either a difference of scale impacts was found between the two clusters, or no clear scaling relation was identified. Spatial scales coarser than 30′ are not recommended to identify the local spatial patterns of fisheries because the boundary and locations of hot and cold spots at a coarser scale are significantly different from those at the original scale.
基金supported by the National Natural Science Foundation of China under Grant Nos.40233035,and 40075022the Innovative Project of the Chinese Academy Sciences (No.KZCX3-SW-329).
文摘Oasis is a special geographic landscape among the vast desert/Gobi in Northwest China (NWC). The surface sensitive heat flux and latent heat flux at Zhangye Oasis during 1 to 11 August 1991 are simulated using the NCAR nonhydrostatic mesoscale model MM5 Version 3. The horizontal grid resolution is set as 1km. By comparing the simulation results with HEIFE observations, it is proved that the model can be used to simulate the surface energy and water mass exchange of arid and semiarid regions in NWC. Based on the above results, the influence of different oasis scales on the local atmospheric field near the ground surface, and the critical scale of oasis maintenance, in NWC are studied dynamically. The following conclusion is obtained: the local thermal circulation between the oasis and the desert/Gobi is formed in the oasis downstream if the oasis scale is larger than 4 km. This local thermal circulation between the oasis and the desert adjacent to the oasis helps to conserve water vapor over the oasis. At the same time, it transfers the abundant water vapor from the oasis into the desert/Gobi near to the oasis to supply relatively plentiful water vapor for desert crops to grow on the fringe of the oasis. So, it is advantageous for oasis extension. However, if the scale of the oasis is smaller than 4 km, it is not easy for the local thermal circulation between the oasis and the desert/Gobi to take shape. This study provides a new standpoint for oasis maintenance and development.
基金Supported by The State Natural Science Fund Project(40875025, 40875030,40775033)Shanghai Natural Science Fund Project (08ZR1422900)
文摘By using Doppler weather radar data,the meso-scale characteristics of extremely heavy rainstorm process which happened suddenly in Jieyang urban area on July 31,2008 were analyzed.The results showed that the radar echo only needed 20 minutes from the generation to the strong echo which quickly strengthened above 50 dBz.The storm center went down south and went up north near Jieyang City all the time.The component which moved eastward was very tiny,and the heavy precipitation echo stagnated.In this heavy precipitation process,the characteristics types of radial velocity which were favorable to the generation and development of heavy precipitation echo appeared alternately each other.The radial velocity's characteristics types were the first type headwind zone,the second type headwind zone,meso-scale convergence type and cyclonic convergence and so on.Thus,this heavy precipitation process which broke the record happened.The analyses showed that the headwind zone which developed vigorously and the convergence which had influx and outflux airflow in the vertical direction of headwind zone made obvious contributions to the precipitation.
文摘Localization of sensor nodes is crucial in Wireless Sensor Network because of applications like surveillance, tracking, navigation etc. Various optimization techniques for localization have been proposed in literature by different researchers. In this paper, we propose a two phase hybrid approach for localization using Multidi- mensional Scaling and trilateration, namely, MDS with refinement using trilateration. Trilateration refines the estimated locations obtained by the MDS algorithm and hence acts as a post optimizer which improves the accuracy of the estimated positions of sensor nodes. Through extensive simulations, we have shown that the proposed algorithm is more robust to noise than previous approaches and provides higher accuracy for estimating the positions of sensor nodes.
基金The project supported by the National Natural Science Foundation of China (10172084,10232040,10232050,10372012,10302029) and the Special Funds for Major State Research Project (G200077305)
文摘A closed,trans-scale formulation of damage evolution based on the statistical mi- crodamage mechanics is summarized in this paper.The dynamic function of damage bridges the mesoscopic and macroscopic evolution of damage.The spallation in an aluminium plate is studied with this formulation.It is found that the damage evolution is governed by several dimensionless parameters, i.e.,imposed Deborah numbers De~* and De,Mach number M and damage number S.In particular, the most critical mode of the macroscopic damage evolution,i.e.,the damage localization,is deter- mined by Deborah number De~*.Deborah number De~* reflects the coupling and competition between the macroscopic loading and the microdamage growth.Therefore,our results reveal the multi-scale nature of spallation.In fact,the damage localization results from the nonlinearity of the microdamage growth.In addition,the dependence of the damage rate on imposed Deborah numbers De~* and De, Mach number M and damage number S is discussed.
