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Drivers of spatial structure in thinned forests
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作者 Zichun Wang Yaoxiang Li +4 位作者 Guangyu Wang Zheyu Zhang Ya Chen Xiaoli Liu Rundong Peng 《Forest Ecosystems》 SCIE CSCD 2024年第2期202-213,共12页
Background:As is widely known,an increasing number of forest areas were managed to preserve and enhance the health of forest ecosystems.However,previous research on forest management has often overlooked the importanc... Background:As is widely known,an increasing number of forest areas were managed to preserve and enhance the health of forest ecosystems.However,previous research on forest management has often overlooked the importance of structure-based.Aims:Our objectives were to define the direction of structure-based forest management.Subsequently,we investigated the relationships between forest structure and the regeneration,growth,and mortality of trees under different thinning treatments.Ultimately,the drivers of forest structural change were explored.Methods:On the basis of 92 sites selected from northeastern China,with different recovery time (from 1 to 15years) and different thinning intensities (0–59.9%) since the last thinning.Principal component analysis (PCA)identified relationships among factors determining forest spatial structure.The structural equation model (SEM)was used to analyze the driving factors behind the changes in forest spatial structure after thinning.Results:Light thinning (0–20%trees removed) promoted forest regeneration,and heavy thinning (over 35% of trees removed) facilitated forest growth.However,only moderate thinning (20%–35%trees removed) created a reasonable spatial structure.While dead trees were clustered,and they were hardly affected by thinning intensity.Additionally,thinning intensity,recovery time,and altitude indirectly improve the spatial structure of the forest by influencing diameter at breast height (DBH) and canopy area.Conclusion:Creating larger DBH and canopy area through thinning will promote the formation of complex forest structures,which cultivates healthy and stable forests. 展开更多
关键词 THINNING Natural secondary forest spatial structure Dynamic changes Growth factors Structural equation modeling
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Ultrafast dynamics of femtosecond laser-induced high spatial frequency periodic structures on silicon surfaces
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作者 Ruozhong Han Yuchan Zhang +6 位作者 Qilin Jiang Long Chen Kaiqiang Cao Shian Zhang Donghai Feng Zhenrong Sun Tianqing Jia 《Opto-Electronic Science》 2024年第3期33-46,共14页
Femtosecond laser-induced periodic surface structures(LIPSS)have been extensively studied over the past few decades.In particular,the period and groove width of high-spatial-frequency LIPSS(HSFL)is much smaller than t... Femtosecond laser-induced periodic surface structures(LIPSS)have been extensively studied over the past few decades.In particular,the period and groove width of high-spatial-frequency LIPSS(HSFL)is much smaller than the diffraction limit,making it a useful method for efficient nanomanufacturing.However,compared with the low-spatial-frequency LIPSS(LSFL),the structure size of the HSFL is smaller,and it is more easily submerged.Therefore,the formation mechanism of HSFL is complex and has always been a research hotspot in this field.In this study,regular LSFL with a period of 760 nm was fabricated in advance on a silicon surface with two-beam interference using an 800 nm,50 fs femtosecond laser.The ultrafast dynamics of HSFL formation on the silicon surface of prefabricated LSFL under single femtosecond laser pulse irradiation were observed and analyzed for the first time using collinear pump-probe imaging method.In general,the evolution of the surface structure undergoes five sequential stages:the LSFL begins to split,becomes uniform HSFL,degenerates into an irregular LSFL,undergoes secondary splitting into a weakly uniform HSFL,and evolves into an irregular LSFL or is submerged.The results indicate that the local enhancement of the submerged nanocavity,or the nanoplasma,in the prefabricated LSFL ridge led to the splitting of the LSFL,and the thermodynamic effect drove the homogenization of the splitting LSFL,which evolved into HSFL. 展开更多
关键词 laser-induced periodic surface structures(LIPSS) local field enhancement collinear pump-probe imaging silicon high spatial frequency periodic structures
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The Study on the Evolution of Urban Spatial Structure in Zhuhai City Based on Spatial Syntax
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作者 Weiqiang Zhou Fangting Liang 《Journal of Architectural Research and Development》 2024年第4期40-44,共5页
With the deepening of the Guangdong-Hong Kong-Macao Greater Bay Area strategy and the accelerated integration and development of the east and west sides of the Pearl River Estuary,Zhuhai’s hub position is becoming mo... With the deepening of the Guangdong-Hong Kong-Macao Greater Bay Area strategy and the accelerated integration and development of the east and west sides of the Pearl River Estuary,Zhuhai’s hub position is becoming more and more prominent.The city of Zhuhai has a dense water network and is divided into two urban areas,the east and the west,under the influence of the Mordor Gate waterway.Based on the theory of spatial syntax,this paper carries out an analytical study on the urban spatial structure of Zhuhai,identifies the distribution characteristics of urban POIs,and provides theoretical support for the urban development of Zhuhai. 展开更多
关键词 spatial syntax POI data Transport network Urban spatial structure
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A novel model to evaluate spatial structure in thinned conifer-broadleaved mixed natural forests
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作者 Hui Liu Xibin Dong +3 位作者 Yuan Meng Tong Gao Liangliang Mao Ran Gao 《Journal of Forestry Research》 SCIE CAS CSCD 2023年第6期1881-1898,共18页
In order to ensure the effective analysis and reconstruction of forests,it is key to ensure the quantitative description of their spatial structure.In this paper,a distance model for the optimal stand spatial structur... In order to ensure the effective analysis and reconstruction of forests,it is key to ensure the quantitative description of their spatial structure.In this paper,a distance model for the optimal stand spatial structure based on weighted Voronoi diagrams is proposed.In particular,we provide a novel methodological model for the comprehensive evaluation of the spatial structure of forest stands in natural mixed conifer-broadleaved forests and the formulation of management decision plans.The applicability of the rank evaluation and the optimal solution distance model are compared and assessed for different standard sample plots of natural mixed conifer-broadleaved forests.The effect of crown width on the spatial structure unit of the trees is observed to be higher than that of the diameter at breast height.Moreover,the influence of crown length is greater than that of tree height.There are nine possible spatial structure units determined by the weighted Voronoi diagram for the number of neighboring trees in the central tree,with an average intersection of neighboring crowns reaching 80%.The rank rating of natural forest sample plots is correlated with the optimal solution distance model,and their results are generally consistent for natural forests.However,the rank rating is not able to provide a quantitative assessment.The optimal solution distance model is observed to be more comprehensive than traditional methods for the evaluation of the spatial structure of forest stands.It can effectively reflect the trends in realistic stand spatial structure factors close to or far from the ideal structure point,and accurately assesses the forest spatial structure.The proposed optimal solution distance model improves the integrated evaluation of the spatial structure of forest stands and provides solid theoretical and technical support for sustainable forest management. 展开更多
关键词 Weighted Voronoi diagram Optimal distance model spatial structure quantifi cation Thinning intensity Conifer-broadleaved mixed natural forests
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Identifying the Spatial Structure of Black Hole and Tropical Cyclone Based on a Theoretical Analysis of Orthogonal Interaction
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作者 Weihong Qian 《Journal of Modern Physics》 CAS 2023年第6期933-952,共20页
Black holes are recognized by Newton’s gravitational theory and Einstein’s general relativity, but there is still a lack of understanding the spatial structure of events, especially the nature of event horizon. In t... Black holes are recognized by Newton’s gravitational theory and Einstein’s general relativity, but there is still a lack of understanding the spatial structure of events, especially the nature of event horizon. In this paper, a theoretical analysis is used to compare the structures of tropical cyclone in the atmosphere and black hole in the astronomy so that five results are: 1) Both of them share the similar spatial structure, with tropical cyclone and black hole having the outflow cloud shield and the horizon sphere in the central part, respectively, while four spiral material bands exist in the rotating plane around them;2) In theoretically, the energy density formed by the orthogonal interaction of the four spiral material bands is as times as the total kinetic energy of the head-on interaction;3) This region of high energy density can lead to the conversion from mass to energy and the creation of new physical states of matter, which is a black hole event;4) The outer horizon of a black hole is the outermost interface of events, or the orthogonal interaction interface of particles;5) High-speed plasma jets extended at the poles of the black hole are directly associated with the shear stress of orthogonal interaction. 展开更多
关键词 Black Hole Event Horizon Tropical Cyclone spatial structure Orthographic Interaction
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Evolution of the Spatial Distribution of Basic Infrastructures and Services in the Niakhar Area (Fatick), Senegal
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作者 Alphousseyni Ndonky Mouhamadou Moustapha Mbacké Ndour +1 位作者 Pape Boubou Sow Rosalie Diouf 《Journal of Geographic Information System》 2023年第6期611-628,共18页
Basic infrastructures and services present an important socio-economic and territorial equity issue, because the availability of these makes it possible to improve the living conditions of populations, makes territori... Basic infrastructures and services present an important socio-economic and territorial equity issue, because the availability of these makes it possible to improve the living conditions of populations, makes territories attractive and stimulates their development. The objective of our study has been achieved, so our results provided information on the rate of propagation of basic infrastructures and services, as well as the evolution of the forms of spatial distribution of the latter. The data used comes from the census and geolocation of basic infrastructures and services in the Niakhar area, carried out by the IRD in 2018. Centrographic measurements were used to describe the overall spatial distribution and the use of chi-square statistics confirmed the existence of a preferential direction of distribution. To verify the existence of a spatial structure of infrastructure and service seeding, the Ripley statistic is used. Our results can be useful for land use planning and spatial resource allocation policies. Indeed, the identification of different types of spatial aggregates and the highlighting of the preferred directions of the distribution of basic infrastructures and services, make it possible to correct disparities in the spatial distribution of basic resources. 展开更多
关键词 spatial structure spatial Disparities Ripley Statistic Centrographic Measurements
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Analysis of spatial distribution characteristics and driving factors of ethnicminority villages in China using geospatial technology and statistical models
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作者 SHAO Dandan ZOH Kyungjin 《Journal of Mountain Science》 SCIE CSCD 2024年第8期2770-2789,共20页
This study aims to reveal the spatial structural characteristics of 1,652 Ethnic-Minority Villages(EMV)in China and to analyze the mechanisms driving their spatial heterogeneity.EMV are a special type of settlement sp... This study aims to reveal the spatial structural characteristics of 1,652 Ethnic-Minority Villages(EMV)in China and to analyze the mechanisms driving their spatial heterogeneity.EMV are a special type of settlement space that preserve a large number of historical traces of the ethnic culture of ancient China.They are important carriers of China’s excellent traditional culture and are key to the implementation of rural revitalization strategies.In this study,1652 EMV in China were selected as the research subjects.The Nearest Neighbor Index,kernel density,and spatial autocorrelation index were employed to reveal the spatial structural characteristics of minority villages.Neural network models,spatial lag models,and geographical detectors were used to analyze the formation mechanism of spatial heterogeneity in EMV.The results indicate that:(1)EMV exhibit significant spatial differentiation characterized by“single-core with multiple surrounding sub-centers,”“polarization between east and west,”“decreasing quantity from southwest to east coast to northeast to northwest,”and“large dispersion with small agglomeration.”(2)EMV are mainly distributed in areas rich in intangible cultural heritage,with high vegetation coverage and low altitude,far from central cities,and having limited arable land and an underdeveloped economy and transportation,particularly in shaded or riverbank areas.(3)Distance from the nearest river(X3),distance from central cities(X8),national intangible cultural heritage(X9),and NDVI(X10)were the main driving factors affecting the spatial distribution of EMV,whereas elevation(X1)and GDP(X5)had the weakest influence.As EMV are a relatively unique territorial spatial unit,the identification of their spatial heterogeneity characteristics not only deepens the research content of settlement geography,but also involves the assessment,protection,and development of Minority Villages,which is of great significance for the inheritance and utilization of excellent ethnic cultures in the era. 展开更多
关键词 Ethnic-Minority Villages spatial structure Settlement geography Neural network model spatial econometric model GeoDetector
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Spatial structural characteristics of the Deda ancient landslide in the eastern Tibetan Plateau:Insights from Audio-frequency Magnetotellurics and the Microtremor Survey Method
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作者 Zhen-dong Qiu Chang-bao Guo +5 位作者 Yi-ying Zhang Zhi-hua Yang Rui-an Wu Yi-qiu Yan Wen-kai Chen Feng Jin 《China Geology》 CAS CSCD 2024年第2期188-202,共15页
It is of crucial importance to investigate the spatial structures of ancient landslides in the eastern Tibetan Plateau’s alpine canyons as they could provide valuable insights into the evolutionary history of the lan... It is of crucial importance to investigate the spatial structures of ancient landslides in the eastern Tibetan Plateau’s alpine canyons as they could provide valuable insights into the evolutionary history of the landslides and indicate the potential for future reactivation.This study examines the Deda ancient landslide,situated in the Chalong-ranbu fault zone,where creep deformation suggests a complex underground structure.By integrating remote sensing,field surveys,Audio-frequency Magnetotellurics(AMT),and Microtremor Survey Method(MSM)techniques,along with engineering geological drilling for validation,to uncover the landslide’s spatial feature s.The research indicates that a fault is developed in the upper part of the Deda ancient landslide,and the gully divides it into Deda landslide accumulation zoneⅠand Deda landslide accumulation zoneⅡin space.The distinctive geological characteristics detectable by MSM in the shallow subsurface and by AMT in deeper layers.The findings include the identification of two sliding zones in the Deda I landslide,the shallow sliding zone(DD-I-S1)depth is approximately 20 m,and the deep sliding zone(DD-I-S2)depth is 36.2-49.9 m.The sliding zone(DD-Ⅱ-S1)depth of the DedaⅡlandslide is 37.6-43.1 m.A novel MSM-based method for sliding zone identification is proposed,achieving less than 5%discrepancy in depth determination when compared with drilling data.These results provide a valuable reference for the spatial structural analysis of large-deepseated landslides in geologically complex regions like the eastern Tibetan Plateau. 展开更多
关键词 Ancient landslide Remote sensing Audio-frequency Magnetotellurics(AMT) Microtremor Survey Method(MSM) Geological drilling engineering spatial structure Tibetan Plateau Geological hazard survey engineering
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Seismic isolation analysis of FPS bearings in spatial lattice shell structures 被引量:14
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作者 Yong-Chul Kim Xue Suduo +2 位作者 Zhuang Peng Zhao Wei Li Chenghao 《Earthquake Engineering and Engineering Vibration》 SCIE EI CSCD 2010年第1期93-102,共10页
A theoretical model of a friction pendulum system (FPS) is introduced to examine its application for the seismic isolation of spatial lattice shell structures. An equation of motion of the lattice shell with FPS bea... A theoretical model of a friction pendulum system (FPS) is introduced to examine its application for the seismic isolation of spatial lattice shell structures. An equation of motion of the lattice shell with FPS bearings is developed. Then, seismic isolation studies are performed for both double-layer and single-layer lattice shell structures under different seismic input and design parameters of the FPS. The influence of frictional coefficients and radius of the FPS on seismic performance are discussed. Based on the study, some suggestions for seismic isolation design of lattice shells with FPS bearings are given and conclusions are made which could be helpful in the application of FPS. 展开更多
关键词 seismic isolation friction pendulum system spatial structure lattice shell parameter analysis
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Anomaly Models of Spatial Structures for Copper-Molybdenum Ore Deposits and their Application 被引量:11
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作者 MA Shengming ZHU Lixin +2 位作者 LIU Chongmin XI Mingjie TANG Shixin 《Acta Geologica Sinica(English Edition)》 SCIE CAS CSCD 2013年第3期843-857,共15页
This paper discusses the enrichment and depletion regularities for porphyry coppermolybdenum ore deposits in different regions and varied deposit genetic types in the same area, taking three porphyry copper-molybdenum... This paper discusses the enrichment and depletion regularities for porphyry coppermolybdenum ore deposits in different regions and varied deposit genetic types in the same area, taking three porphyry copper-molybdenum ore deposits (i.e., the Chengmenshan in Jiangxi, Wunugetushan in Inner Mongolia, Baishantang in Gansu) and two copper deposits in Gansu Province (the Huitongshan skarn deposit and Gongpoquan composite deposit) as case studies. The results show that porphyry Cu-Mo deposits or skarn copper deposits include both enrichment of the ore-forming elements and associated elements, and depletion of some lithophile dispersed elements, rare earth elements (REE) and some major elements. And the depleted elements vary with deposits, having generality and their own features. On a deposit scale, the positive anomalies of enriched elements and negative anomalies of depleted elements follow in a sequence to comprise regular anomaly models of spatial structures. The exploration in the Tongchang deposit in Jiangxi and Huitongshan deposit in Gansu suggests that anomaly models play a key role in the identification of mineral occurrences and deposits compared to one single enriched element anomaly. And the anomaly models exert a critical effect on the optimization of prospecting targets and their potential evaluation. 展开更多
关键词 copper-molybdenum deposits enrichment and depletion anomaly models of spatial structures case studies
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Spatial Structure,Hierarchy and Formation Mechanisms of Scientific Collaboration Networks:Evidence of the Belt and Road Regions 被引量:7
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作者 GU Weinan LIU Hui 《Chinese Geographical Science》 SCIE CSCD 2020年第6期959-975,共17页
Scientific collaboration has become an important part of the people-to-people exchanges in the Belt and Road initiative,and remarkable progress has been made since 2013.Taking the 65 countries along the Belt and Road(... Scientific collaboration has become an important part of the people-to-people exchanges in the Belt and Road initiative,and remarkable progress has been made since 2013.Taking the 65 countries along the Belt and Road(BRI countries)as the research areas and using collaborated Web of Science(WOS)core collection papers to construct an international scientific collaboration matrix,the paper explores the spatial structure,hierarchy and formation mechanisms of scientific collaboration networks of 65 countries along the Belt and Road.The results show that:1)Beyond the Belt and Road regions(BRI regions),Central&Eastern Europe,China and West Asia&North Africa have formed a situation in which they all have the most external links with other countries beyond BRI regions.China has the dominant role over other BRI countries in generating scientific links.The overall spatial structure has changed to a skeleton structure consisting of many dense regions,such as Europe,North America,East Asia and Oceania.2)Within the Belt and Road regions,Central&Eastern Europe has become the largest collaboration partner with other sub-regions in BRI countries.The spatial structure of scientific collaboration networks has transformed from the‘dual core’composed of China and the Central&Eastern Europe region,to the‘multi-polarization’composed of‘one zone and multi-points’.3)The hierarchical structure of scientific collaboration networks presents a typical‘core-periphery’structure,and changes from‘single core’to‘double cores’.4)Among the formation mechanisms of scientific collaboration networks,scientific research strength and social proximity play the most important roles,while geographical distance gradually weakens the hindrance to scientific collaboration. 展开更多
关键词 scientific collaboration networks spatial structure HIERARCHY formation mechanisms the Belt and Road regions
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An experimental study of the spatial structures of the instabilities of longshore currents on plane beaches 被引量:5
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作者 REN Chunping ZOU Zhili 《Acta Oceanologica Sinica》 SCIE CAS CSCD 2012年第6期32-45,共14页
A laboratory experiment on alongshore currents is conducted for two plane beaches with slopes 1:40 and 1:i00 to investigate the instability of alongshore currents. The dye release experiment is also performed synchr... A laboratory experiment on alongshore currents is conducted for two plane beaches with slopes 1:40 and 1:i00 to investigate the instability of alongshore currents. The dye release experiment is also performed synchronously in surf zone. Complicated and strongly unstable motions of alongshore currents are observed in the experiment. To examine the spatial and temporal variations of the shear instabilities of longshore clearly, dye batches are released in surf zone. The deformation of the dye patch is observed efficiently and effectively with charge coupled device (CCD) system. Some essential characteristics of the shear instability are validated from the results of image analyses of the temporal variation of the dye patch. The influences of alongshore currents, Stokes drift, large-scale vorticity and the shear instabilities on the transport of dye are analyzed using the collected images. The spatial structure of the instabilities of longshore currents is studied by analyzing collected images of the dye patch. And the phase velocity of the meandering movements is obtained through measuring the movement distances of the oscillations of dye patch in alongshore direction with time. The results suggest that the propagation speed of the shear instability is approximately 5070 7570 of maximum of mean alongshore currents for irregular and regular waves. The calculated propagation speed using a linear instability analysis theory is compared with the experimental results. The comparison shows agreements between them. 展开更多
关键词 alongshore currents shear instability spatial structures linear instability analysis
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Strength failure of spatial reticulated structures under multi-support excitation 被引量:5
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作者 Ye Jihong Zhang Zhiqiang Chu Ye 《Earthquake Engineering and Engineering Vibration》 SCIE EI CSCD 2011年第1期21-36,共16页
Under strong earthquakes, long-span spatial latticed structures may collapse due to dynamic instability or strength failure. The elasto-plastic dynamic behaviors of three spatial latticed structures, including two dou... Under strong earthquakes, long-span spatial latticed structures may collapse due to dynamic instability or strength failure. The elasto-plastic dynamic behaviors of three spatial latticed structures, including two double-layer cylindrical shells and one spherical shell constructed for the 2008 Olympic Games in Beijing, were quantitatively examined under multi-support excitation (MSE) and uniform support excitation (USE). In the numerical analyses, several important parameters were investigated such as the peak acceleration and displacement responses at key joints, the number and distribution of plastic members, and the deformation of the shell at the moment of collapse. Analysis results reveal the features and the failure mechanism of the spatial latticed structures under MSE and USE. In both scenarios, the double-layer reticulated shell collapses in the "overflow" mode, and the collapse is governed by the number of invalid plastic members rather than the total number of plastic members, beginning with damage to some of the local regions near the supports. By comparing the numbers and distributions of the plastic members under MSE to those under USE, it was observed that the plastic members spread more sufficiently and the internal forces are more uniform under MSE, especially in cases of lower apparent velocities in soils. Due to the effects of pseudo-static displacement, the stresses in the members near the supports under MSE are higher than those under USE. 展开更多
关键词 multiple support excitation (MSE) uniform support excitation (USE) ELASTOPLASTIC spatial latticed structure strength failure
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Spatial structure and seasonal changes of nekton assemblages in the Taiwan Strait 被引量:2
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作者 SONG Puqing LIN Longshan +1 位作者 LI Yuan ZHONG Zhihui 《Acta Oceanologica Sinica》 SCIE CAS CSCD 2016年第6期59-67,共9页
The Taiwan Strait is a transition zone between the East China Sea and the South China Sea with unique hydrology and a geographical environment that creates special marine community features.To analyze the spatial stru... The Taiwan Strait is a transition zone between the East China Sea and the South China Sea with unique hydrology and a geographical environment that creates special marine community features.To analyze the spatial structure and seasonal changes of the nekton assemblages in the Taiwan Strait,seasonal experimental trawl surveys were conducted during 2006-2007.The results showed that there were two assemblages in the area with different sets of species,and the average similarity within each group varies between 39.38% and 74.20%.By using multivariate statistical analysis and analyzing the distribution of dominant species,we found that the structures of the assemblages had obvious seasonal variation.The middle region from the Putian transect to the Xiamen transect could be considered a mixing area for the two assemblages.The analysis of the relationship between species assemblages and environmental factors indicated that temperature was the most important factor affecting the community structure in cold seasons,and 22.5°C and 17°C could be considered dividing lines for spring and winter,respectively.In warm seasons,the most important factor was water depth,but the relationship with depth was not as significant,with a correlation between 0.264 and 0.399.The seasonal changes of nekton assemblages basically reflected the dynamic currents in the Taiwan Strait.The south coastal assemblage extended to nearly the entire area of the Taiwan Strait along with a strong and intense warm current that shrinks in spring and winter when the southward intrusion of the cold Zhejiang-Fujian coastal current becomes stronger.The impact of shortterm and long-term environmental changes,such as extreme weather,global warming and human activity on nekton assemblages,had been recognized but need further research.Our study on nekton assemblages could be used as a baseline for measuring future changes. 展开更多
关键词 nekton assemblages species composition spatial structure transition zone Taiwan Strait
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Nonlinearity Modulating Intensities and Spatial Structures of Central Pacific and Eastern Pacific El Nio Events 被引量:2
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作者 Wansuo DUAN Chaoming HUANG Hui XU 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2017年第6期737-756,共20页
This paper compares data from linearized and nonlinear Zebiak-Cane model, as constrained by observed sea surface temperature anomaly (SSTA), in simulating central Pacific (CP) and eastern Pacific (EP) E1 Nino. T... This paper compares data from linearized and nonlinear Zebiak-Cane model, as constrained by observed sea surface temperature anomaly (SSTA), in simulating central Pacific (CP) and eastern Pacific (EP) E1 Nino. The difference between the temperature advections (determined by subtracting those of the linearized model from those of the nonlinear model), referred to here as the nonlinearly induced temperature advection change (NTA), is analyzed. The results demonstrate that the NTA records warming in the central equatorial Pacific during CP E1 Nino and makes fewer contributions to the structural distinctions of the CP E1 Nino, whereas it records warming in the eastern equatorial Pacific during EP E1 Nino, and thus significantly promotes EP E1 Nino during E1 Nino-type selection. The NTA for CP and EP E1 Nino varies in its amplitude, and is smaller in CP E1 Nino than it is in EP E1 Nino. These results demonstrate that CP E1 Nino are weakly modulated by small intensities of NTA, and may be controlled by weak nonlinearity; whereas, EP E1 Nino are significantly enhanced by large amplitudes of NTA, and are therefore likely to be modulated by relatively strong nonlinearity. These data could explain why CP E1 Nino are weaker than EP E1 Nino. Because the NTA for CP and EP E1 Nino differs in spatial structures and intensities, as well as their roles within different E1 Nino modes, the diversity of E1 Nino may be closely related to changes in the nonlinear characteristics of the tropical Pacific. 展开更多
关键词 E1 Nifio diversity NONLINEARITY INTENSITY spatial structures nonlinear temperature advection
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Trust-region based instantaneous optimal semi-active control of long-span spatially extended structures with MRF-04K damper 被引量:7
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作者 Lin Wei Li Zhongxian Ding Yang 《Earthquake Engineering and Engineering Vibration》 SCIE EI CSCD 2008年第4期447-464,共18页
In the field of civil engineering, magnetorheological fluid (MRF) damper-based semi-active control systems have received considerable attention for use in protecting structures from natural hazards such as strong ea... In the field of civil engineering, magnetorheological fluid (MRF) damper-based semi-active control systems have received considerable attention for use in protecting structures from natural hazards such as strong earthquakes and high winds. In this paper, the MRF damper-based semi-active control system is applied to a long-span spatially extended structure and its feasibility is discussed. Meanwhile, a _trust-region method based instantaneous optimal semi-active control algorithm (TIOC) is proposed to improve the performance of the semi-active control system in a multiple damper situation. The proposed TIOC describes the control process as a bounded constraint optimization problem, in which an optimal semi- active control force vector is solved by the trust-region method in every control step to minimize the structural responses. A numerical example of a railway station roof structure installed with MRF-04K dampers is presented. First, a modified Bouc- Wen model is utilized to describe the behavior of the selected MRF-04K damper. Then, two semi-active control systems, including the well-known clipped-optimal controller and the proposed TIOC controller, are considered. Based on the characteristics of the long-span spatially extended structure, the performance of the control system is evaluated under uniform earthquake excitation and travelling-wave excitation with different apparent velocities. The simulation results indicate that the MR fluid damper-based semi-active control systems have the potential to mitigate the responses of full-scale long-span spatially extended structures under earthquake hazards. The superiority of the proposed TIOC controller is demonstrated by comparing its control effectiveness with the clipped-optimal controller for several different cases. 展开更多
关键词 long-span spatially extended structure instantaneous optimal control semi-active control trust-regionmethod magnetorheological (MR) damper bounded constraint optimization modified Bouc-Wen model clipped-optimal control
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Study on Spatial Structure of Traditional Villages from the Perspective of Clanism 被引量:2
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作者 DENG Wei HE Yi HU Haiyan 《Journal of Landscape Research》 2014年第2期18-20,24,共4页
"China's deep-rooted family culture and the resulting family spirit is one of the basic characteristics of Chinese society that differs from western society," said by Chinese sociologist Fei Xiaotong. Ge... "China's deep-rooted family culture and the resulting family spirit is one of the basic characteristics of Chinese society that differs from western society," said by Chinese sociologist Fei Xiaotong. German sociologist Max Weber defi nes Chinese society as "family structure society"[1]. And sociologist Fei Zhengqing believes that the villages in China are organized by families. In sociological studies, the traditional villages are divided into three types: single-clan villages with only one dominating family, main-clan villages which are mainly composed of several families, and multi-clan villages where some coequal families live together[2]. The authors believe that traditional villages are organized social communities with kinship as a link. They are products of the family system. There is a close connection between a village's family composition and its space construction. Single-clan village is an introverted spatial organization mode entirely based on kinship, ancestral hall is located in the center and the whole spatial structure grows toward it. Main-clan village is a decentralized family aggregate based on the ties of blood as well as region. And the organization of its village space depends on temples and pavilions where families enshrine and worship ancestors and gods. It owns obvious features of collage and collaboration. M ulticlan village is a collaborative and extroverted complex spatial system led by relationship of colleagues, where large public buildings are taken as the core to organize commercial activities. Its form is similar to the form of small towns. Taking sociological term "family" as the starting point and cases of national historic cultural villages including Hong Village, Zhuge Village, Zoumatang Village, Suzhuang Village and Guoyu Village into further study, this article analyses the correlation between kinship composition and spatial form of villages, tries to reveal the essential structure of traditional space of villages and to provide a new perspective on spatial study as well as basis for preservation of traditional villages. 展开更多
关键词 CLAN Traditional village Clan structure spatial structure
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Study on urban spatial structure and morphology of Guangzhou-Foshan metropolitan coordinating region compared with Randstad,Netherlands 被引量:1
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作者 Bilin Chen Yimin Sun 《西部人居环境学刊》 2020年第S01期1-9,共9页
In recent years,regional integration of Chinese cities has gradually developed.Meanwhile,metropolitan areas and urban agglomerations have taken shape.On the one hand,the development of the metropolitan area has brough... In recent years,regional integration of Chinese cities has gradually developed.Meanwhile,metropolitan areas and urban agglomerations have taken shape.On the one hand,the development of the metropolitan area has brought about urban spatial expansion,as well as population and economic growth.On the other hand,it has led to problems such as the urban sprawl and suburbanization,increasing pressure on environmental resources,and the decline of urban central areas.Under this background,the Guangdong-Hong Kong-Macao Greater Bay Area Development Plan Outline proposes to accelerate the integration of Guangzhou-Foshan(Guang Fo)Metropolitan Coordinating Region(MCR),and to construct a networked space pattern driven by urban poles and shafts.Based on the academic research of Metropolitan Coordinating Region(MCR),as well as the theory of urban spatial structure and morphology,this study focus on urban spatial patterns and elements in different scales,from two individual cites(Guangzhou and Foshan),Guang Fo MCR,to Guangdong-Hong Kong-Macao(GHM)Greater Bay Area.With GIS and the mapping method,the spatial elements such as green space,water system,built-up area,road network,rail transit network and main pivot points of the Guang Fo MCR are classified,laid out individually and again overlaid in order to figure out the relationship of these elements.At the same time,through the comparative case study of the Randstad MCR in the Netherlands,the enlightenment of solving the development problem of MCR is hopefully to be obtained.As delta cities,the Guang Fo MCR is cut by the multi-channel water network,while the urban built-up area is concentrated in the middle of the MCR and spread out along the traffic corridor to the suburban district.The traffic structure of the Guang Fo MCR is characterized by the outward radiation of the central area of Guangzhou and Foshan.Simultaneously,the traffic connection between Guangzhou and Foshan is relatively weak.Compared with the polycentric spatial structure,which is called Decentralized Compact pattern of Randstad MCR,the Guang Fo MCR presents a city form with little hierarchy but homogeneity,and its urban space is disorderly spread.The bluegreen system of water and vegetation is fragmented because of the urban invasion in Guang Fo MCR,while the green heart in central Randstad is well preserved.As a result,it is well advised to explore a more resilient and ecological urban development in Guang Fo MCR. 展开更多
关键词 GuangFo MCR spatial structure Urban morphology TRAFFIC Land use Blue-green system
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Seismic response of large-span spatial structures under multi-support and multidimensional excitations including rotational components
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作者 Zhang Jie Li Hongnan Li Chao 《Earthquake Engineering and Engineering Vibration》 SCIE EI CSCD 2021年第1期141-159,共19页
To achieve rational and precise seismic response predictions of large span spatial structures(LSSSs),the inherent non-uniformity and multidimensionality characteristics of earthquake ground motions should be properly ... To achieve rational and precise seismic response predictions of large span spatial structures(LSSSs),the inherent non-uniformity and multidimensionality characteristics of earthquake ground motions should be properly taken into consideration.However,due to the limitations of available earthquake stations to record seismic rotational components,the effects of rocking and torsional earthquake components are commonly neglected in the seismic analyses of LSSSs.In this study,a newly developed method to extract the rocking and torsion components at any point along the area of a deployed dense array from the translational earthquake recordings is applied to obtain the rotational seismic inputs for a LSSS.The numerical model of an actual LSSS,the Dalian International Conference Center(DICC),is developed to study the influences of multi-support and multidimensional excitations on the seismic responses of LSSSs.The numerical results reveal that the non-uniformity and multidimensionality of ground motion input can considerably affect the dynamic response of the DICC.The specific degree of influence on the overall and local structural displacements,deformations and forces are comprehensively investigated and discussed. 展开更多
关键词 large-span spatial structures seismic responses multi-support MULTIDIMENSIONAL rotational components
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Spatial network structure of transportation carbon emission efficiency in China and its influencing factors
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作者 Haiqin Shao Zhaofeng Wang 《Chinese Journal of Population,Resources and Environment》 2021年第4期295-303,共9页
Grasping the spatial correlation structure of transportation carbon emission efficiency(TCEE)and its influencing factors is significant for promoting high-quality and coordinated development of the transportation indu... Grasping the spatial correlation structure of transportation carbon emission efficiency(TCEE)and its influencing factors is significant for promoting high-quality and coordinated development of the transportation industry and the relevant region.Based on the ideal point cross-efficiency(IPCE)model,the social network analysis method was employed herein to explore the spatial correlation network structure of China’s provincial TCEE and its influencing factors.The results obtained showed the following outcomes.(1)During the study period,China’s provincial TCEE formed a complex and multithreaded network association relationship,but its network association structure was still relatively loose and presented the hierarchical gradient characteristics of dense in the east and sparse in the west.(2)The correlation of China’s TCEE formed a block segmentation based on the regional boundaries,and its factional structure was relatively obvious.The eastern region was closely connected with the central region,and generally connected with the western and northeastern regions.The central region was mainly connected with the eastern and western regions,and relatively less connected with the northeastern region.Besides,the northeastern region was weakly connected with the western region.(3)Shanghai,Beijing,Zhejiang,Guangdong,Jiangsu,Tianjin,and other developed provinces were in the core leading position in the TCEE network,which significantly impacted the spatial correlation of TCEE.However,Heilongjiang,Jilin,Xinjiang,Qinghai,and other remote provinces in the northeast and northwest were at the absolute edge of the network,which weakly impacted the spatial correlation of TCEE.(4)Provincial distance,economic development-level difference,transportation intensity difference,and transportation structure difference had significant negative impacts on the spatial correlation network of China’s provincial TCEE.In contrast,the energy-saving technology level difference had a significant positive impact on it.The regression coefficients of transportation energy structure and environmental regulation differences were positive but insignificant;their response mechanism and effects need to be improved and enhanced. 展开更多
关键词 Transportation carbon emission efficiency spatial network structure Influencing factor Social network analysis
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