A comprehensive analysis on the change of the total grain production and the temporal and spatial change of three main crops production（including wheat,maize and rice）,as well as the transfer trace of the center gra...A comprehensive analysis on the change of the total grain production and the temporal and spatial change of three main crops production（including wheat,maize and rice）,as well as the transfer trace of the center gravity of grain production in China were analyzed to reveal the overall developing trend of the grain production,explore the reasons and finally propose the corresponding suggestions and strategies to cope with the situation.展开更多
On-orbit servicing, such as spacecraft maintenance, on-orbit assembly, refueling, and de-orbiting, can reduce the cost of space missions, improve the performance of spacecraft, and extend its life span. The relative s...On-orbit servicing, such as spacecraft maintenance, on-orbit assembly, refueling, and de-orbiting, can reduce the cost of space missions, improve the performance of spacecraft, and extend its life span. The relative state between the servicing and target spacecraft is vital for on-orbit servicing missions, especially the final approaching stage. The major challenge of this stage is that the observed features of the target are incomplete or are constantly changing due to the short distance and limited Field of View (FOV) of camera. Different from cooperative spacecraft, non-cooperative target does not have artificial feature markers. Therefore, contour features, including triangle supports of solar array, docking ring, and corner points of the spacecraft body, are used as the measuring features. To overcome the drawback of FOV limitation and imaging ambiguity of the camera, a "selfie stick" structure and a self-calibration strategy were implemented, ensuring that part of the contour features could be observed precisely when the two spacecraft approached each other. The observed features were constantly changing as the relative distance shortened. It was difficult to build a unified measurement model for different types of features, including points, line segments, and circle. Therefore, dual quaternion was implemented to model the relative dynamics and measuring features. With the consideration of state uncertainty of the target, a fuzzy adaptive strong tracking filter( FASTF) combining fuzzy logic adaptive controller (FLAC) with strong tracking filter(STF) was designed to robustly estimate the relative states between the servicing spacecraft and the target. Finally, the effectiveness of the strategy was verified by mathematical simulation. The achievement of this research provides a theoretical and technical foundation for future on-orbit servicing missions.展开更多
According to the complex adaptive systems theory, tourist destinations may be regarded as complex adaptive systems formed by multiple adaptive agent interactions and composed of an agent system, tourist attraction sub...According to the complex adaptive systems theory, tourist destinations may be regarded as complex adaptive systems formed by multiple adaptive agent interactions and composed of an agent system, tourist attraction subsystem, tourist service facility subsystem, and external environment system. This paper explores the spatial evolutionary progress of the Southern Anhui tourist area. The period 1979 to 1990 comprised the formation stage of spatial agglomerates, during which tourist attractions centering on Huangshan Scenic Area and Jiuhuashan Scenic Area were gradually exploited and formed scale agglomeration;tourism spatial structure began to show the characteristics of agglomeration development, and Gini indexes of the number of tourists and tourism revenue increased significantly from 0.26 to 0.29, and from 0.33 to 0.35, respectively. From 1991 to 2008, the system experienced a growth stage in which Huangshan Scenic Area and Jiuhuashan Scenic Area were further developed with improved tourist service facilities. Rapid development of Xidi-Hongcun Scenic Area and establishment of Fantawild Tourist Area promoted the formation of more spatial agglomerates with larger scales;Gini indexes of the number of tourists and tourism revenue presented fluctuating changes, reaching low points of 0.15 and 0.25 in 2000 and 0.12 and 0.22 in 2007, respectively. From 2009 to the present day, the system has remained in a blowout-development stage, during which non-linear interactions among agents are strengthened;various emerging development factors generate cultural tourism, vacation tourism, rural tourism and other new tourism products jointly with traditional development factors. New tourism products form a large number of new spatial agglomerates that are interconnected, accelerating the spatial flow of tourists and tourism revenue and reducing the differences in tourism development levels within the region;Gini indexes of the number of tourists and tourism revenue declined steadily from 0.17 and 0.23 in 2009 to 0.12 and 0.15 in 2016.展开更多
This study aims to extend the multivariate adaptive regression splines(MARS)-Monte Carlo simulation(MCS) method for reliability analysis of slopes in spatially variable soils. This approach is used to explore the infl...This study aims to extend the multivariate adaptive regression splines(MARS)-Monte Carlo simulation(MCS) method for reliability analysis of slopes in spatially variable soils. This approach is used to explore the influences of the multiscale spatial variability of soil properties on the probability of failure(P_f) of the slopes. In the proposed approach, the relationship between the factor of safety and the soil strength parameters characterized with spatial variability is approximated by the MARS, with the aid of Karhunen-Loeve expansion. MCS is subsequently performed on the established MARS model to evaluate Pf.Finally, a nominally homogeneous cohesive-frictional slope and a heterogeneous cohesive slope, which are both characterized with different spatial variabilities, are utilized to illustrate the proposed approach.Results showed that the proposed approach can estimate the P_f of the slopes efficiently in spatially variable soils with sufficient accuracy. Moreover, the approach is relatively robust to the influence of different statistics of soil properties, thereby making it an effective and practical tool for addressing slope reliability problems concerning time-consuming deterministic stability models with low levels of P_f.Furthermore, disregarding the multiscale spatial variability of soil properties can overestimate or underestimate the P_f. Although the difference is small in general, the multiscale spatial variability of the soil properties must still be considered in the reliability analysis of heterogeneous slopes, especially for those highly related to cost effective and accurate designs.展开更多
Confocal laser scanning microscopy(CLSM) has emerged as one of the most advanced fluorescence cell imaging techniques in the field of biomedicine. However, fluorescence cell imaging is limited by spatial blur and addi...Confocal laser scanning microscopy(CLSM) has emerged as one of the most advanced fluorescence cell imaging techniques in the field of biomedicine. However, fluorescence cell imaging is limited by spatial blur and additive white noise induced by the excitation light. In this paper, a spatially adaptive high-order total variation(SA-HOTV) model for weak fluorescence image restoration is proposed to conduct image restoration. The method consists of two steps: optimizing the deconvolution model of the fluorescence image by the generalized Lagrange equation and alternating direction method of multipliers(ADMM); using spatially adaptive parameters to balance the image fidelity and the staircase effect. Finally, an comparison of SA-HOTV model and Richardson-Lucy model with total variation(RL-TV model) indicates that the proposed method can preserve the image details ultimately,reduce the staircase effect substantially and further upgrade the quality of the restored weak fluorescence image.展开更多
This study focused on spatial analysis to identify the changes in adaptability over the last five decades.The features influencing adaptability were selected from the reference study.An appropriate method was used to ...This study focused on spatial analysis to identify the changes in adaptability over the last five decades.The features influencing adaptability were selected from the reference study.An appropriate method was used to analyse these features through spatial analysis.Six distinctive typologies of rural houses were selected from six regions.Unlike the traditional houses,the contemporary houses in the same area reflected a different character.Urban houses built since the early and mid-20th century were compared with contemporary houses.After analysing the openness,generality,flexibility,depth,typicality,construction technique,involvement of end-users,and the feedback from the inhabitants,the study identified a significant decrease in contemporary houses'adaptability.Spatial analysis was used to quantify the different features and comparison between traditional and contemporary houses.Though the adaptability had been reduced over time,the latest houses started to achieve better flexibility in some features due to government policy and implementation of statutory building regulations.Further recommendations were provided to enhance the residential architecture's adaptability in future.The study samples were selected from different regions of Bangladesh.Still,the result and policy recommendations can be helpful for other countries,especially with high population density and a developing economy.展开更多
In recent years, MIMO technology has emerged as one of the technical breakthroughs in the field of wireless communications. Two famous MIMO techniques have become investigated thoroughly throughout the literature;Spat...In recent years, MIMO technology has emerged as one of the technical breakthroughs in the field of wireless communications. Two famous MIMO techniques have become investigated thoroughly throughout the literature;Spatial Multiplexing, and Space Time Block Coding. On one hand, Spatial Multiplexing offers high data rates. On the other hand, Space Time Block Coding presents transmission fidelity. This imposes a fundamental tradeoff between capacity and reliability. Adaptive MIMO Switching schemes have been proposed to select the MIMO scheme that best fits the channel conditions. However, the switching schemes presented in the literature directly switch between the MIMO endpoints. In this paper, an adaptive MIMO system that incrementally switches from multiplexing towards diversity is proposed. The proposed scheme is referred to as incremental diversity and can be set to operate in two different modes;Rate-Adaptive, and Energy-Conservative Incremental Diversity. Results indicate that the proposed incremental diversity framework achieves transmission reliability offered by MIMO diversity, while maintaining a gradual increase in spectral efficiency (in the Rate-Adaptive mode) or a reduction in required number of received symbols (in the Energy-Conservative mode) with increase in the SNR.展开更多
Drought severely threatens food security, and its detrimental effects will be exacerbated by climate change in many parts of the world. Rice production is water-consuming and particularly vulnerable to drought stress....Drought severely threatens food security, and its detrimental effects will be exacerbated by climate change in many parts of the world. Rice production is water-consuming and particularly vulnerable to drought stress. Upland rice is a special rice ecotype that specifically adapts to dryland mainly due to its robust root system. However, the molecular and developmental mechanism underlying this adaption has remained elusive. In this study, by comparing the root development between upland and irrigated rice phenotypically and cytologically, we identified key developmental phenotypes that distinguish upland rice from irrigated rice. We further generated spatial transcriptomic atlases for coleoptilar nodes and root tips to explore their molecular differences in crown root formation and development, uncovering promising genes for enhancing rice drought resistance. Among the identified genes, HMGB1, a transcriptional regulator, functions as a key factor that facilitates root elongation and thickening in upland rice and thereby enhances drought resistance. In summary, our study uncovers spatially resolved transcriptomic features in roots of upland rice that contribute to its adaptation to dryland conditions, providing valuable genetic resources for breeding drought-resilient rice.展开更多
Scientifically assessing the suitability,safety and resilience of urban development is the premise for high-quality regional development in China.Here we developed a high-precision coupling model for comprehensive ass...Scientifically assessing the suitability,safety and resilience of urban development is the premise for high-quality regional development in China.Here we developed a high-precision coupling model for comprehensive assessing the spatially explicit adaptation,and livability and safety of urban development,based on urban expansion and nine types of natural disaster risks data in 1990–2020.Through remote sensing and big data mining methods,we revealed spatial differentiation characteristics of urban development's spatial adaptation and livability safety levels over the past three decades,diagnosing the expansion status of cities at varying potential safety risk levels.The results indicate that urban development was primarily concentrated in medium to high suitability level areas(83.23%,5.23×10^(4)km^(2))from 1990 to 2020,with 14.46%of urban expansion occurring in the lowest suitability areas,predominantly in the eastern coastal and western regions.From the safety aspect,urban development predominantly occurred in areas with medium to highest safety levels(49%),yet 13%of urban expansion areas exhibit relatively high safety risks.In the eastern coastal regions,the primary threat is water-related risks,with urban expansion in these risk areas accounting for 62%of total expansion.The western region is mainly threatened by geological earthquake risks,with urban expansion area in these risk zones exceeding by more than four times of that in the eastern,central,and northeastern regions.The central region is primarily at risk from high-temperature disaster,while the northeastern region faces risks from low-temperature and snow-related disasters.Overall,urban development in China over the past three decades has displayed a pattern of the highsuitability and high-expansion in the eastern regions,medium-suitability and medium-speed expansion in the central region,lowsuitability and low-expansion in the western region,and the high-suitability and slow-expansion in the northeastern region.This study provides scientific guidance for the“Beautiful China”initiative,facilitating the precise adaptation of high-quality regional development and resilient urban safety,and promoting the coordinated development of differentiated regional socioeconomic and ecological systems.展开更多
The behind-armor debris(BAD) formed by the perforation of an EFP is the main damage factor for the secondary destruction to the behind-armor components.Aiming at investigating the BAD caused by EFP,flash X-ray radiogr...The behind-armor debris(BAD) formed by the perforation of an EFP is the main damage factor for the secondary destruction to the behind-armor components.Aiming at investigating the BAD caused by EFP,flash X-ray radiography combined with an experimental witness plate test method was used,and the FEM-SPH adaptive conversion algorithm in LS-DYNA software was erployed to model the perforation process.The simulation results of the debris cloud shape and number of debris were in good agreement with the flash X-ray radiographs and perforated holes on the witness plate,respectlvely.Threedimensional numerical simulations of EFP's penetration under various impact conditions were conducted.The results show that,an ellipsoidal debris cloud,with the major-to-minor axis radio(a/b)smaller than that caused by shaped charge jets,was formed behind the target.With the increase of target thickness(h) and decrease of impact velocity(v_0) and obliquity(θ),the value of a/b decreases.The number of debris ejected from target is significantly higher than that from EFP.Based on the statistical analysis of the spatial distribution of the BAD,An engineering calculation model was established considering the influence of h,v_0 and θ.The model can with reasonable accuracy predict the quantity and velocity distribution characteristics of BAD formed by EFP.展开更多
The technique of adaptive tree mesh is an effective way to reduce computational cost through automatic adjustment of cell size according to necessity. In the present study, the 2D numerical N-S solver based on the ada...The technique of adaptive tree mesh is an effective way to reduce computational cost through automatic adjustment of cell size according to necessity. In the present study, the 2D numerical N-S solver based on the adaptive quadtree mesh system was extended to a 3D one, in which a spatially adaptive oetree mesh system and multiple particle level set method were adopted for the convenience to deal with the air-water-structure multiple-medium coexisting domain. The stretching process of a dumbbell was simulated and the results indicate that the meshes are well adaptable to the free surface. The collapsing process of water column impinging a circle cylinder was simulated and from the results, it can be seen that the processes of fluid splitting and merging are properly simulated. The interaction of second-order Stokes waves with a square cylinder was simulated and the obtained drag force is consistent with the result by the Morison＇s wave force formula with the coefficient values of the stable drag component and the inertial force component bein~ set as 2.54.展开更多
The performance the quaternion-Capon（ Q-Capon） beamformer degraded when suppressing the interferences that are coherent with the signal of interest（ SOI）. To tackle the problem,the spatial smoothing technique is a...The performance the quaternion-Capon（ Q-Capon） beamformer degraded when suppressing the interferences that are coherent with the signal of interest（ SOI）. To tackle the problem,the spatial smoothing technique is adopted in quaternion domain to decorrelate the interferences by using linearly and uniformly spaced two-component electromagnetic vector-sensors. By averaging several translational invariant subarray quaternion covariance matrices,the quaternion spatial smoothing is performed to prevent the SOI cancellation phenomena caused by the presence of coherent interferences. It is demonstrated that the quaternion spatial smoothing Q-Capon beamformer can suppress the coherent interferences remarkably while the computational cost is lower than the complex domain long vector spatial smoothing counterpart. Theoretical analyses and simulation results validate the efficacy of the spatially smoothed Q-Capon beamformer in terms of coherent interference suppression capability.展开更多
Generalized Space Shift Keying(GSSK)modulation is a low-complexity spatial nmltiplexing technique for nmltiple-antenna wireless systems.However,effective transmit antenna combinations have to be preselected,and there ...Generalized Space Shift Keying(GSSK)modulation is a low-complexity spatial nmltiplexing technique for nmltiple-antenna wireless systems.However,effective transmit antenna combinations have to be preselected,and there exist redundant antenna combinations which are not used in GSSK.In this paper,a novel adaptive mapping scheme for GSSK modulation,named as Adaptive Mapping Generalized Space Shift Keying(AMGSSK),is presented.Compared with GSSK,the antenna combinations are updated adaptively according to the Channel State Inforrmtion(CSI)in the proposed AMGSSK system,and the perfonrance of average Symbol Error Rate(SER)is reduced considerably.In the proposed scheme,two algorithrrs for selecting the optimum antenna combinations are described.The SER perfonmnce of AMGSSK is analyzed theoretically,and validated by Monte Carlo sinmlation.It is shown that the proposed AMGSSK scheme has good perfonmnce in SER and spectral efficiency.展开更多
The idea behind this work is developing an adaptive method for the environmental assessment of buildings, to configure different versions according to the variables affecting them (spatial, temporal and associated wit...The idea behind this work is developing an adaptive method for the environmental assessment of buildings, to configure different versions according to the variables affecting them (spatial, temporal and associated with building characteristics) to suit different evaluated projects. This method may be applied using an electronic tool, which is in a development stage. Amending different assessment versions of the adaptive method is done by including the variables effect, according to set of steps, such as modifying the formulation of the assessment items, adjusting their estimation weights, and amending their achievement evaluation levels and their returned scores. When using the adaptive method, the assessment result of a building using a certain version differs from the results using other versions, even in the same country, so configuring an appropriate version due to the variables affecting the assessment helps getting more accurate results than the ones currently provided. The main goal of that research is to introduce the adaptive method that is proposed to ensure a fairer assessment results from the perspective of Green Architecture, and allow a more credible and accuracy of results comparison according to the environmental performance of buildings. The researcher analyzed the different main features she used in developing the adaptive method, the Comparative aspects between it and the current assessment methods, and the expected reached advantages from its usage. The paper arrived to the importance of adapting the environmental assessment of buildings according to the different affecting variables, and recommended developing the adaptive method and its tool to the stage of application to benefit its advantages.展开更多
基金Supported by National Scientific and Technological Supporting Project(2006BAD20B05)~~
文摘A comprehensive analysis on the change of the total grain production and the temporal and spatial change of three main crops production（including wheat,maize and rice）,as well as the transfer trace of the center gravity of grain production in China were analyzed to reveal the overall developing trend of the grain production,explore the reasons and finally propose the corresponding suggestions and strategies to cope with the situation.
基金Sponsored by the National Natural Science Foundation of China(Grant No.61973153)
文摘On-orbit servicing, such as spacecraft maintenance, on-orbit assembly, refueling, and de-orbiting, can reduce the cost of space missions, improve the performance of spacecraft, and extend its life span. The relative state between the servicing and target spacecraft is vital for on-orbit servicing missions, especially the final approaching stage. The major challenge of this stage is that the observed features of the target are incomplete or are constantly changing due to the short distance and limited Field of View (FOV) of camera. Different from cooperative spacecraft, non-cooperative target does not have artificial feature markers. Therefore, contour features, including triangle supports of solar array, docking ring, and corner points of the spacecraft body, are used as the measuring features. To overcome the drawback of FOV limitation and imaging ambiguity of the camera, a "selfie stick" structure and a self-calibration strategy were implemented, ensuring that part of the contour features could be observed precisely when the two spacecraft approached each other. The observed features were constantly changing as the relative distance shortened. It was difficult to build a unified measurement model for different types of features, including points, line segments, and circle. Therefore, dual quaternion was implemented to model the relative dynamics and measuring features. With the consideration of state uncertainty of the target, a fuzzy adaptive strong tracking filter( FASTF) combining fuzzy logic adaptive controller (FLAC) with strong tracking filter(STF) was designed to robustly estimate the relative states between the servicing spacecraft and the target. Finally, the effectiveness of the strategy was verified by mathematical simulation. The achievement of this research provides a theoretical and technical foundation for future on-orbit servicing missions.
基金National Natural Science Foundation of China,No.51278239
文摘According to the complex adaptive systems theory, tourist destinations may be regarded as complex adaptive systems formed by multiple adaptive agent interactions and composed of an agent system, tourist attraction subsystem, tourist service facility subsystem, and external environment system. This paper explores the spatial evolutionary progress of the Southern Anhui tourist area. The period 1979 to 1990 comprised the formation stage of spatial agglomerates, during which tourist attractions centering on Huangshan Scenic Area and Jiuhuashan Scenic Area were gradually exploited and formed scale agglomeration;tourism spatial structure began to show the characteristics of agglomeration development, and Gini indexes of the number of tourists and tourism revenue increased significantly from 0.26 to 0.29, and from 0.33 to 0.35, respectively. From 1991 to 2008, the system experienced a growth stage in which Huangshan Scenic Area and Jiuhuashan Scenic Area were further developed with improved tourist service facilities. Rapid development of Xidi-Hongcun Scenic Area and establishment of Fantawild Tourist Area promoted the formation of more spatial agglomerates with larger scales;Gini indexes of the number of tourists and tourism revenue presented fluctuating changes, reaching low points of 0.15 and 0.25 in 2000 and 0.12 and 0.22 in 2007, respectively. From 2009 to the present day, the system has remained in a blowout-development stage, during which non-linear interactions among agents are strengthened;various emerging development factors generate cultural tourism, vacation tourism, rural tourism and other new tourism products jointly with traditional development factors. New tourism products form a large number of new spatial agglomerates that are interconnected, accelerating the spatial flow of tourists and tourism revenue and reducing the differences in tourism development levels within the region;Gini indexes of the number of tourists and tourism revenue declined steadily from 0.17 and 0.23 in 2009 to 0.12 and 0.15 in 2016.
基金supported by The Hong Kong Polytechnic University through the project RU3Ythe Research Grant Council through the project PolyU 5128/13E+1 种基金National Natural Science Foundation of China(Grant No.51778313)Cooperative Innovation Center of Engineering Construction and Safety in Shangdong Blue Economic Zone
文摘This study aims to extend the multivariate adaptive regression splines(MARS)-Monte Carlo simulation(MCS) method for reliability analysis of slopes in spatially variable soils. This approach is used to explore the influences of the multiscale spatial variability of soil properties on the probability of failure(P_f) of the slopes. In the proposed approach, the relationship between the factor of safety and the soil strength parameters characterized with spatial variability is approximated by the MARS, with the aid of Karhunen-Loeve expansion. MCS is subsequently performed on the established MARS model to evaluate Pf.Finally, a nominally homogeneous cohesive-frictional slope and a heterogeneous cohesive slope, which are both characterized with different spatial variabilities, are utilized to illustrate the proposed approach.Results showed that the proposed approach can estimate the P_f of the slopes efficiently in spatially variable soils with sufficient accuracy. Moreover, the approach is relatively robust to the influence of different statistics of soil properties, thereby making it an effective and practical tool for addressing slope reliability problems concerning time-consuming deterministic stability models with low levels of P_f.Furthermore, disregarding the multiscale spatial variability of soil properties can overestimate or underestimate the P_f. Although the difference is small in general, the multiscale spatial variability of the soil properties must still be considered in the reliability analysis of heterogeneous slopes, especially for those highly related to cost effective and accurate designs.
基金the National Natural Science Foundation of China(Nos.51605302 and 51675329)
文摘Confocal laser scanning microscopy(CLSM) has emerged as one of the most advanced fluorescence cell imaging techniques in the field of biomedicine. However, fluorescence cell imaging is limited by spatial blur and additive white noise induced by the excitation light. In this paper, a spatially adaptive high-order total variation(SA-HOTV) model for weak fluorescence image restoration is proposed to conduct image restoration. The method consists of two steps: optimizing the deconvolution model of the fluorescence image by the generalized Lagrange equation and alternating direction method of multipliers(ADMM); using spatially adaptive parameters to balance the image fidelity and the staircase effect. Finally, an comparison of SA-HOTV model and Richardson-Lucy model with total variation(RL-TV model) indicates that the proposed method can preserve the image details ultimately,reduce the staircase effect substantially and further upgrade the quality of the restored weak fluorescence image.
文摘This study focused on spatial analysis to identify the changes in adaptability over the last five decades.The features influencing adaptability were selected from the reference study.An appropriate method was used to analyse these features through spatial analysis.Six distinctive typologies of rural houses were selected from six regions.Unlike the traditional houses,the contemporary houses in the same area reflected a different character.Urban houses built since the early and mid-20th century were compared with contemporary houses.After analysing the openness,generality,flexibility,depth,typicality,construction technique,involvement of end-users,and the feedback from the inhabitants,the study identified a significant decrease in contemporary houses'adaptability.Spatial analysis was used to quantify the different features and comparison between traditional and contemporary houses.Though the adaptability had been reduced over time,the latest houses started to achieve better flexibility in some features due to government policy and implementation of statutory building regulations.Further recommendations were provided to enhance the residential architecture's adaptability in future.The study samples were selected from different regions of Bangladesh.Still,the result and policy recommendations can be helpful for other countries,especially with high population density and a developing economy.
文摘In recent years, MIMO technology has emerged as one of the technical breakthroughs in the field of wireless communications. Two famous MIMO techniques have become investigated thoroughly throughout the literature;Spatial Multiplexing, and Space Time Block Coding. On one hand, Spatial Multiplexing offers high data rates. On the other hand, Space Time Block Coding presents transmission fidelity. This imposes a fundamental tradeoff between capacity and reliability. Adaptive MIMO Switching schemes have been proposed to select the MIMO scheme that best fits the channel conditions. However, the switching schemes presented in the literature directly switch between the MIMO endpoints. In this paper, an adaptive MIMO system that incrementally switches from multiplexing towards diversity is proposed. The proposed scheme is referred to as incremental diversity and can be set to operate in two different modes;Rate-Adaptive, and Energy-Conservative Incremental Diversity. Results indicate that the proposed incremental diversity framework achieves transmission reliability offered by MIMO diversity, while maintaining a gradual increase in spectral efficiency (in the Rate-Adaptive mode) or a reduction in required number of received symbols (in the Energy-Conservative mode) with increase in the SNR.
基金supported by Biological Breeding-National Scinece and Tecnology Major Project(2023ZD04073)the National Natural Science Foundation of China(32070563 and 32470307)+3 种基金the Shenzhen Science and Technology Program(KQTD20230301092839007,KJZD20230921114607016)the Guangdong Laboratory of Lingnan Morden Agriculture(AGIS-ZDXM202203)the Fundamental Research Funds for the Central Universities(2662023SKPY002)Guangdong Provincial Key Laboratory of core collection of crop genetic resources research and application,BGl-Shenzhen,Shenzhen 518120,China(NO.2011A091000047).
文摘Drought severely threatens food security, and its detrimental effects will be exacerbated by climate change in many parts of the world. Rice production is water-consuming and particularly vulnerable to drought stress. Upland rice is a special rice ecotype that specifically adapts to dryland mainly due to its robust root system. However, the molecular and developmental mechanism underlying this adaption has remained elusive. In this study, by comparing the root development between upland and irrigated rice phenotypically and cytologically, we identified key developmental phenotypes that distinguish upland rice from irrigated rice. We further generated spatial transcriptomic atlases for coleoptilar nodes and root tips to explore their molecular differences in crown root formation and development, uncovering promising genes for enhancing rice drought resistance. Among the identified genes, HMGB1, a transcriptional regulator, functions as a key factor that facilitates root elongation and thickening in upland rice and thereby enhances drought resistance. In summary, our study uncovers spatially resolved transcriptomic features in roots of upland rice that contribute to its adaptation to dryland conditions, providing valuable genetic resources for breeding drought-resilient rice.
基金supported by the National Key Research and Development Program of China(Grant No.2022YFC3800101)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDA23100201)。
文摘Scientifically assessing the suitability,safety and resilience of urban development is the premise for high-quality regional development in China.Here we developed a high-precision coupling model for comprehensive assessing the spatially explicit adaptation,and livability and safety of urban development,based on urban expansion and nine types of natural disaster risks data in 1990–2020.Through remote sensing and big data mining methods,we revealed spatial differentiation characteristics of urban development's spatial adaptation and livability safety levels over the past three decades,diagnosing the expansion status of cities at varying potential safety risk levels.The results indicate that urban development was primarily concentrated in medium to high suitability level areas(83.23%,5.23×10^(4)km^(2))from 1990 to 2020,with 14.46%of urban expansion occurring in the lowest suitability areas,predominantly in the eastern coastal and western regions.From the safety aspect,urban development predominantly occurred in areas with medium to highest safety levels(49%),yet 13%of urban expansion areas exhibit relatively high safety risks.In the eastern coastal regions,the primary threat is water-related risks,with urban expansion in these risk areas accounting for 62%of total expansion.The western region is mainly threatened by geological earthquake risks,with urban expansion area in these risk zones exceeding by more than four times of that in the eastern,central,and northeastern regions.The central region is primarily at risk from high-temperature disaster,while the northeastern region faces risks from low-temperature and snow-related disasters.Overall,urban development in China over the past three decades has displayed a pattern of the highsuitability and high-expansion in the eastern regions,medium-suitability and medium-speed expansion in the central region,lowsuitability and low-expansion in the western region,and the high-suitability and slow-expansion in the northeastern region.This study provides scientific guidance for the“Beautiful China”initiative,facilitating the precise adaptation of high-quality regional development and resilient urban safety,and promoting the coordinated development of differentiated regional socioeconomic and ecological systems.
基金supported by National Natural Science Foundation of China(Grant no.11872123)。
文摘The behind-armor debris(BAD) formed by the perforation of an EFP is the main damage factor for the secondary destruction to the behind-armor components.Aiming at investigating the BAD caused by EFP,flash X-ray radiography combined with an experimental witness plate test method was used,and the FEM-SPH adaptive conversion algorithm in LS-DYNA software was erployed to model the perforation process.The simulation results of the debris cloud shape and number of debris were in good agreement with the flash X-ray radiographs and perforated holes on the witness plate,respectlvely.Threedimensional numerical simulations of EFP's penetration under various impact conditions were conducted.The results show that,an ellipsoidal debris cloud,with the major-to-minor axis radio(a/b)smaller than that caused by shaped charge jets,was formed behind the target.With the increase of target thickness(h) and decrease of impact velocity(v_0) and obliquity(θ),the value of a/b decreases.The number of debris ejected from target is significantly higher than that from EFP.Based on the statistical analysis of the spatial distribution of the BAD,An engineering calculation model was established considering the influence of h,v_0 and θ.The model can with reasonable accuracy predict the quantity and velocity distribution characteristics of BAD formed by EFP.
基金Supported by the National Natural Science Foundation of China(No.51379143 and No.51109018)the Foundation for Innovative Research Groups of the National Natural Science Foundation of China(No.51021004)+1 种基金the Open Foundation of Key Laboratory of Water-Sediment Science and Water Disaster Prevention of Hunan Province(No.2014SS01)the Open Foundation of State Key Laboratory of Hydraulic Engineering Simulation and Safety(No.HSSKLTJU-201208)
文摘The technique of adaptive tree mesh is an effective way to reduce computational cost through automatic adjustment of cell size according to necessity. In the present study, the 2D numerical N-S solver based on the adaptive quadtree mesh system was extended to a 3D one, in which a spatially adaptive oetree mesh system and multiple particle level set method were adopted for the convenience to deal with the air-water-structure multiple-medium coexisting domain. The stretching process of a dumbbell was simulated and the results indicate that the meshes are well adaptable to the free surface. The collapsing process of water column impinging a circle cylinder was simulated and from the results, it can be seen that the processes of fluid splitting and merging are properly simulated. The interaction of second-order Stokes waves with a square cylinder was simulated and the obtained drag force is consistent with the result by the Morison＇s wave force formula with the coefficient values of the stable drag component and the inertial force component bein~ set as 2.54.
基金Supported by the National Natural Science Foundation of China(61331019)
文摘The performance the quaternion-Capon（ Q-Capon） beamformer degraded when suppressing the interferences that are coherent with the signal of interest（ SOI）. To tackle the problem,the spatial smoothing technique is adopted in quaternion domain to decorrelate the interferences by using linearly and uniformly spaced two-component electromagnetic vector-sensors. By averaging several translational invariant subarray quaternion covariance matrices,the quaternion spatial smoothing is performed to prevent the SOI cancellation phenomena caused by the presence of coherent interferences. It is demonstrated that the quaternion spatial smoothing Q-Capon beamformer can suppress the coherent interferences remarkably while the computational cost is lower than the complex domain long vector spatial smoothing counterpart. Theoretical analyses and simulation results validate the efficacy of the spatially smoothed Q-Capon beamformer in terms of coherent interference suppression capability.
基金supported partially by the National Key Basic Research Program of China under Grant No.2007CB310605the Science and Technology Development Fund of Tianjin Colleges and Universities under Grant No.20080708the Research Fund of Tianjin University of Technology and Education under Grants No.KJ09-012,No.KJ10-06
文摘Generalized Space Shift Keying(GSSK)modulation is a low-complexity spatial nmltiplexing technique for nmltiple-antenna wireless systems.However,effective transmit antenna combinations have to be preselected,and there exist redundant antenna combinations which are not used in GSSK.In this paper,a novel adaptive mapping scheme for GSSK modulation,named as Adaptive Mapping Generalized Space Shift Keying(AMGSSK),is presented.Compared with GSSK,the antenna combinations are updated adaptively according to the Channel State Inforrmtion(CSI)in the proposed AMGSSK system,and the perfonrance of average Symbol Error Rate(SER)is reduced considerably.In the proposed scheme,two algorithrrs for selecting the optimum antenna combinations are described.The SER perfonmnce of AMGSSK is analyzed theoretically,and validated by Monte Carlo sinmlation.It is shown that the proposed AMGSSK scheme has good perfonmnce in SER and spectral efficiency.
文摘The idea behind this work is developing an adaptive method for the environmental assessment of buildings, to configure different versions according to the variables affecting them (spatial, temporal and associated with building characteristics) to suit different evaluated projects. This method may be applied using an electronic tool, which is in a development stage. Amending different assessment versions of the adaptive method is done by including the variables effect, according to set of steps, such as modifying the formulation of the assessment items, adjusting their estimation weights, and amending their achievement evaluation levels and their returned scores. When using the adaptive method, the assessment result of a building using a certain version differs from the results using other versions, even in the same country, so configuring an appropriate version due to the variables affecting the assessment helps getting more accurate results than the ones currently provided. The main goal of that research is to introduce the adaptive method that is proposed to ensure a fairer assessment results from the perspective of Green Architecture, and allow a more credible and accuracy of results comparison according to the environmental performance of buildings. The researcher analyzed the different main features she used in developing the adaptive method, the Comparative aspects between it and the current assessment methods, and the expected reached advantages from its usage. The paper arrived to the importance of adapting the environmental assessment of buildings according to the different affecting variables, and recommended developing the adaptive method and its tool to the stage of application to benefit its advantages.
