We investigate the chaotic and regular spatial structures of Bose–Einstein condensates(BECs)with a spatially modulated atom-atom interaction and without an external trapping potential.A BEC with a spatially modulated...We investigate the chaotic and regular spatial structures of Bose–Einstein condensates(BECs)with a spatially modulated atom-atom interaction and without an external trapping potential.A BEC with a spatially modulated atom-atom interaction is equivalent to being constrained by a nonlinear optical lattice.Theoretical analyses show the existence of a steady atomic current in the BEC with a spatially varying phase.Under perturbative conditions,the Melnikov chaos criteria of BECs with a spatially varying phase and a constant one are theoretically obtained,respectively.When the perturbative conditions cannot be satisfied,for a repulsive BEC with a spatially varying phase,numerical simulations demonstrate that changing the initial condition can eliminate the chaotic spatial structure and then the system transitions into a biperiodic spatial structure.Increasing the chemical potential can result in a transition from the biperiodic spatial structure to a single-periodic spatial structure.For an attractive BEC with a spatially varying phase,numerical simulations show that decreasing the chemical potential can lead to a high atomic density,but when the wave number of the laser inducing the optical Feshbach resonance exceeds a critical value,the atomic density falls back to a finite range.Regardless of whether the BEC has a spatially varying phase or a constant one,modulating the laser wave number can effectively suppress the chaotic spatial structure in the BEC and then force it into a regular spatial structure.展开更多
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
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
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
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
Under the background of China's rapid urbanization, study on comparative analysis of the spatial structure of urban agglomerations between China and the US can provide the policy proposals of space optimization fo...Under the background of China's rapid urbanization, study on comparative analysis of the spatial structure of urban agglomerations between China and the US can provide the policy proposals of space optimization for the Chinese government. Taking the Beijing-Tianjin-Hebei(BTH) and Boswash as study area, we mapped the subpixel-level impervious surface coverage of the BTH and Boswash, respectively, from 1972 to 2011. Further, landscape metrics, gravitational model and spatial analysis were used to analyze the differences of the spatial structures between the BTH and Boswash. The results showed that(1) the area of the impervious surface increased rapidly in the BTH, while those remained stable in the Boswash.(2) The spatial structure of the BTH experienced different periods including isolated cities stage, dual-core cities stage, group cities stage and network-style cities stage, while those of the Boswash was more stable, and its spatial pattern showed a "point-axis" structure.(3) The spatial pattern of high-high assembling regions of the impervious surface exhibited a "standing pancake" feature in the BTH, while those showed a "multi-center, local aggregation and global discrete" feature in the Boswash.(4) All the percentages of the impervious surface of ecological, living, and production land of the BTH were higher than those of the Boswash. At last, from the perspective of space optimization of urban agglomeration, the development proposals for the BTH were proposed.展开更多
The swelling behavior and stability in solid electrolyte interphase(SEI)have been proved to determine the battery cycle life.A high swollen,unstable SEI shows a high permeability to electrolyte,which results in the ra...The swelling behavior and stability in solid electrolyte interphase(SEI)have been proved to determine the battery cycle life.A high swollen,unstable SEI shows a high permeability to electrolyte,which results in the rapid battery performance degradation.Here,we customize two SEIs with different spatial structures(bilayer and mosaic)by simply regulating the proportion of additive fluoroethylene carbonate.Surprisingly,due to the uniform distribution of dense inorganic nano-crystals in the inner,the bilayer SEI exhibits low-swelling and excellent mechanical properties,so the undesirable side reactions of the electrolyte are effectively suppressed.In addition,we put forward the growth rate of swelling ratio(GSR)as a key indicator to reveal the swelling change in SEI.The GSR of bilayer SEI merely increases from1.73 to 3.16 after the 300th cycle,which enables the corresponding graphite‖Li battery to achieve longer cycle stability.The capacity retention is improved by 47.5% after 300 cycles at 0.5 C.The correlation among SEI spatial structure,swelling behavior,and battery performance provides a new direction for electrolyte optimization and interphase structure design of high energy density batteries.展开更多
An appropriate spatial structure of a power battery supply network is crucial for the specialization and scale development of key components in new energy vehicles, accelerating the transformation and upgrade of the i...An appropriate spatial structure of a power battery supply network is crucial for the specialization and scale development of key components in new energy vehicles, accelerating the transformation and upgrade of the industry. This paper investigates the cooperative relationships among supply chain enterprises from the perspective of complex networks.Employing methodologies such as the gravity model and Moran's I analysis, it explores the spatial structural characteristics and correlation patterns of the power battery supply network in China and discusses the influencing factors using the quadratic assignment procedure,revealing the mechanisms behind the differences in the spatial distributions of the power battery supply network. The results indicate that the distribution of power battery enterprises is densely concentrated in the eastern and southern regions, whereas the western region has a sparse distribution. The spatial supply network consists of a four-tier linkage system, encompassing 135 prefecture-level cities, with Chongqing, Shanghai, Nanjing, and other cities particularly prominent. Overall, the degree of agglomeration is low, with coastal cities dominating the landscape and inland cities serving as complementary regions. Most areas are characterized as insignificant or low-high regions, and the regional linkage effect of core cities is not pronounced. There is a notable lack of significance and high spatial heterogeneity.Four types of factors—spatial factors, market factors, agglomeration economies, and innovation levels—jointly influence and shape the spatial structure of the power battery supply network.展开更多
Traditional deconvolution methods based on single-channel inversion do not consider the spatial structural relation between channels,and hence,they yield high-resolution results with the existing transverse inconsiste...Traditional deconvolution methods based on single-channel inversion do not consider the spatial structural relation between channels,and hence,they yield high-resolution results with the existing transverse inconsistency or discontinuity.Therefore,in this study,the local dip angle was used to obtain the structural information and construct the spatial structurally constraint operator.This operator is then introduced into multichannel deconvolution as a regularization operator to improve the resolution and maintain the transverse continuity of seismic data.Model tests and actual seismic data processing have demonstrated the effectiveness and practicability of this method.展开更多
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
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
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
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
With the increment of the complexity of structural systems and the span of spatial structures, the interactions between parts of the structures, especially between some flexible substructures, become too complex to be...With the increment of the complexity of structural systems and the span of spatial structures, the interactions between parts of the structures, especially between some flexible substructures, become too complex to be analyzed clearly. In this paper, taking an actual gymnasium of a long-span spatial steel-cable-membrane hybrid structure as the calculation model, the static and dynamic analyses of the hybrid structures are performed by employing the global analysis of the whole hybrid structure and the substructural analysis of the truss arch substructure, the cable-membrane substructure, etc. In addition, the comparison of stresses and displacements of structural members in the global and substructural analyses is made. The numerical results show that serious errors exist in the substructural analysis of the hybrid structure, and the global analysis is necessary for the hybrid structure under the excitation of static loads and seismic loads.展开更多
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
A distance measure that infers to indicate the evolutionary relationship of protein structures has been developed based on spatial preference factors of residues. The spatial preference factor is a reflection of the e...A distance measure that infers to indicate the evolutionary relationship of protein structures has been developed based on spatial preference factors of residues. The spatial preference factor is a reflection of the environment of residues in tertiary structure. Compared with the phyletic relationships derived from sequence homologies and three-dimensional structures, we find that the two lines of evolution are similar in general. This approach is applied to a group of glins here.展开更多
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
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
Regional CO_(2) emissions are closely related to their territorial function, which is the major role a region plays in sustainable processes on the earth's surface. Given that China is implementing a top-down emis...Regional CO_(2) emissions are closely related to their territorial function, which is the major role a region plays in sustainable processes on the earth's surface. Given that China is implementing a top-down emission allocation quota strategy, studying the impact of a territorial function on emissions addresses the research gap from a spatial integration dimension.By investigating the effects of three basic functional territories(urbanization zones(UZ), food security zones(FSZ), and ecological security zones(ESZ)), horizontal spatial structure and vertical combinations of functional territories on CO_(2) emission patterns in China, we found that functional territory patterns were highly coupled with the spatial distribution of CO_(2) emissions, with a ratio of CO_(2) emissions from UZ–FSZ–ESZ was stable at around 5:2:1 from 2000 to 2017. Spatially, CO_(2) emissions in FSZ and ESZ were 1.06–2.12 times higher than the average value within 200 km from the UZ. As territorial function combination increased with spatial upscaling, the emission characteristics attributable to functional territories became indistinct. The findings above can provide a basis for the long-term prediction of CO_(2) emissions from spatial dimension, support scientific guidance for inter-zone cooperation and classified management of carbon emissions with the major function oriented zones as impetus.展开更多
基金Projects supported by the Natural Science Foundation of Hunan Province(2016JJ6020)the Scientific Research Fund of Hunan Provincial Education Department(18A436)the Scientific Research Fund of Hunan First normal University(XYS13N16)。
文摘We investigate the chaotic and regular spatial structures of Bose–Einstein condensates(BECs)with a spatially modulated atom-atom interaction and without an external trapping potential.A BEC with a spatially modulated atom-atom interaction is equivalent to being constrained by a nonlinear optical lattice.Theoretical analyses show the existence of a steady atomic current in the BEC with a spatially varying phase.Under perturbative conditions,the Melnikov chaos criteria of BECs with a spatially varying phase and a constant one are theoretically obtained,respectively.When the perturbative conditions cannot be satisfied,for a repulsive BEC with a spatially varying phase,numerical simulations demonstrate that changing the initial condition can eliminate the chaotic spatial structure and then the system transitions into a biperiodic spatial structure.Increasing the chemical potential can result in a transition from the biperiodic spatial structure to a single-periodic spatial structure.For an attractive BEC with a spatially varying phase,numerical simulations show that decreasing the chemical potential can lead to a high atomic density,but when the wave number of the laser inducing the optical Feshbach resonance exceeds a critical value,the atomic density falls back to a finite range.Regardless of whether the BEC has a spatially varying phase or a constant one,modulating the laser wave number can effectively suppress the chaotic spatial structure in the BEC and then force it into a regular spatial structure.
基金financially supported by the research special fund of public service sector from the Ministry of Land and Resources (No. 201111008)
文摘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.
基金The National Natural Science Foundation of China under contract Nos 50479053 and 10672034the Program for the Changjiang Scholars and the Innovative Research Team in the University of Chinathe Shanxi Province Natural Science Foundation for Young Scholar of China under contract No.2011021025-1
文摘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.
基金National Natural Science Foundation of China under Grant Nos.51738007,51808099the Fundamental Research Funds for the Central Universities under Grant No.DUT20RC(3)005。
文摘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.
文摘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.
基金National Natural Science Foundation of China,No.41671339
文摘Under the background of China's rapid urbanization, study on comparative analysis of the spatial structure of urban agglomerations between China and the US can provide the policy proposals of space optimization for the Chinese government. Taking the Beijing-Tianjin-Hebei(BTH) and Boswash as study area, we mapped the subpixel-level impervious surface coverage of the BTH and Boswash, respectively, from 1972 to 2011. Further, landscape metrics, gravitational model and spatial analysis were used to analyze the differences of the spatial structures between the BTH and Boswash. The results showed that(1) the area of the impervious surface increased rapidly in the BTH, while those remained stable in the Boswash.(2) The spatial structure of the BTH experienced different periods including isolated cities stage, dual-core cities stage, group cities stage and network-style cities stage, while those of the Boswash was more stable, and its spatial pattern showed a "point-axis" structure.(3) The spatial pattern of high-high assembling regions of the impervious surface exhibited a "standing pancake" feature in the BTH, while those showed a "multi-center, local aggregation and global discrete" feature in the Boswash.(4) All the percentages of the impervious surface of ecological, living, and production land of the BTH were higher than those of the Boswash. At last, from the perspective of space optimization of urban agglomeration, the development proposals for the BTH were proposed.
基金supported by the National Natural Science Foundation of China(22369011)the Gansu Key Research and Development Program(23YFGA0053 and 24YFGA025)the Hongliu Outstanding Youth Talent Support Program of Lanzhou University of Technology and Postgraduate research exploration project of Lanzhou University of Technology(256017)。
文摘The swelling behavior and stability in solid electrolyte interphase(SEI)have been proved to determine the battery cycle life.A high swollen,unstable SEI shows a high permeability to electrolyte,which results in the rapid battery performance degradation.Here,we customize two SEIs with different spatial structures(bilayer and mosaic)by simply regulating the proportion of additive fluoroethylene carbonate.Surprisingly,due to the uniform distribution of dense inorganic nano-crystals in the inner,the bilayer SEI exhibits low-swelling and excellent mechanical properties,so the undesirable side reactions of the electrolyte are effectively suppressed.In addition,we put forward the growth rate of swelling ratio(GSR)as a key indicator to reveal the swelling change in SEI.The GSR of bilayer SEI merely increases from1.73 to 3.16 after the 300th cycle,which enables the corresponding graphite‖Li battery to achieve longer cycle stability.The capacity retention is improved by 47.5% after 300 cycles at 0.5 C.The correlation among SEI spatial structure,swelling behavior,and battery performance provides a new direction for electrolyte optimization and interphase structure design of high energy density batteries.
基金Humanities and Social Sciences Project of the Ministry of Education of China,No.23YJCZH195Scientific Research Program funded by the Shaanxi Provincial Education Department,No.20JK0358, No.21JK0908+2 种基金Natural Science Basic Research Program of Shaanxi,No.2024JC-YBQN-0738, No.2023-JC-QN-0560Shaanxi Provincial Education Science Planning Project,No.SGH23Y2484China Logistics Society&China Federation of Logistics and Purchasing Research Fund,No.2023CSLKT3-220。
文摘An appropriate spatial structure of a power battery supply network is crucial for the specialization and scale development of key components in new energy vehicles, accelerating the transformation and upgrade of the industry. This paper investigates the cooperative relationships among supply chain enterprises from the perspective of complex networks.Employing methodologies such as the gravity model and Moran's I analysis, it explores the spatial structural characteristics and correlation patterns of the power battery supply network in China and discusses the influencing factors using the quadratic assignment procedure,revealing the mechanisms behind the differences in the spatial distributions of the power battery supply network. The results indicate that the distribution of power battery enterprises is densely concentrated in the eastern and southern regions, whereas the western region has a sparse distribution. The spatial supply network consists of a four-tier linkage system, encompassing 135 prefecture-level cities, with Chongqing, Shanghai, Nanjing, and other cities particularly prominent. Overall, the degree of agglomeration is low, with coastal cities dominating the landscape and inland cities serving as complementary regions. Most areas are characterized as insignificant or low-high regions, and the regional linkage effect of core cities is not pronounced. There is a notable lack of significance and high spatial heterogeneity.Four types of factors—spatial factors, market factors, agglomeration economies, and innovation levels—jointly influence and shape the spatial structure of the power battery supply network.
基金supported by the basic and forward-looking project(No.2023YQX302)。
文摘Traditional deconvolution methods based on single-channel inversion do not consider the spatial structural relation between channels,and hence,they yield high-resolution results with the existing transverse inconsistency or discontinuity.Therefore,in this study,the local dip angle was used to obtain the structural information and construct the spatial structurally constraint operator.This operator is then introduced into multichannel deconvolution as a regularization operator to improve the resolution and maintain the transverse continuity of seismic data.Model tests and actual seismic data processing have demonstrated the effectiveness and practicability of this method.
基金National Natural Science Foundation of China Under Grand No.50778006Funding Project for Academic Human Resources Development in Institutions of Higher Learning Under the Jurisdiction of Beijing Municipality
文摘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.
文摘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.
基金Supported by:National Science Fund for Distinguished Young Scholars of China Under Grant No. 50425824the National Natural Science Foundation of China Under Grant No.50578109,90715034 and 90715032
文摘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.
基金financially supported by the Innovation Foundation for Doctoral Program of Forestry Engineering of Northeast Forestry University,grant number:LYGC202117the China Scholarship Council(CSC),grant number:202306600046+1 种基金the Research and Development Plan of Applied Technology in Heilongjiang Province of China,grant number:GA19C006Research and Demonstration on Functional Improvement Technology of Forest Ecological Security Barrier in Heilongjiang Province,grant number:GA21C030。
文摘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.
文摘With the increment of the complexity of structural systems and the span of spatial structures, the interactions between parts of the structures, especially between some flexible substructures, become too complex to be analyzed clearly. In this paper, taking an actual gymnasium of a long-span spatial steel-cable-membrane hybrid structure as the calculation model, the static and dynamic analyses of the hybrid structures are performed by employing the global analysis of the whole hybrid structure and the substructural analysis of the truss arch substructure, the cable-membrane substructure, etc. In addition, the comparison of stresses and displacements of structural members in the global and substructural analyses is made. The numerical results show that serious errors exist in the substructural analysis of the hybrid structure, and the global analysis is necessary for the hybrid structure under the excitation of static loads and seismic loads.
文摘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.
文摘A distance measure that infers to indicate the evolutionary relationship of protein structures has been developed based on spatial preference factors of residues. The spatial preference factor is a reflection of the environment of residues in tertiary structure. Compared with the phyletic relationships derived from sequence homologies and three-dimensional structures, we find that the two lines of evolution are similar in general. This approach is applied to a group of glins here.
基金funded by The Guangdong Province General Universities Young Innovative Talent Project(Grant No.2023WQNCX122)The Zhuhai Philosophy and Social Science Planning Project(Grant No.2023YBB049)。
文摘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.
文摘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.
基金National Natural Science Foundation of China,No.42230510。
文摘Regional CO_(2) emissions are closely related to their territorial function, which is the major role a region plays in sustainable processes on the earth's surface. Given that China is implementing a top-down emission allocation quota strategy, studying the impact of a territorial function on emissions addresses the research gap from a spatial integration dimension.By investigating the effects of three basic functional territories(urbanization zones(UZ), food security zones(FSZ), and ecological security zones(ESZ)), horizontal spatial structure and vertical combinations of functional territories on CO_(2) emission patterns in China, we found that functional territory patterns were highly coupled with the spatial distribution of CO_(2) emissions, with a ratio of CO_(2) emissions from UZ–FSZ–ESZ was stable at around 5:2:1 from 2000 to 2017. Spatially, CO_(2) emissions in FSZ and ESZ were 1.06–2.12 times higher than the average value within 200 km from the UZ. As territorial function combination increased with spatial upscaling, the emission characteristics attributable to functional territories became indistinct. The findings above can provide a basis for the long-term prediction of CO_(2) emissions from spatial dimension, support scientific guidance for inter-zone cooperation and classified management of carbon emissions with the major function oriented zones as impetus.
