[Objective]The spatial dynamic response of a new desert highway subgrade structure by geocell reinforcement with aeolian sand is studied.[Methods]Based on the dynamic triaxial test,a field test via monitoring the resp...[Objective]The spatial dynamic response of a new desert highway subgrade structure by geocell reinforcement with aeolian sand is studied.[Methods]Based on the dynamic triaxial test,a field test via monitoring the response acceleration change is carried out.The attenuation law and dynamic response range of the response acceleration along the depth and horizontal directions of the subgrade are obtained for the geocell-reinforced subgrade structure.The mechanism of dynamic response of geocell-reinforced materials to aeolian sand subgrade is further discussed.[Results]The result show that both vehicle load and vehicle speed have a great influence on the response acceleration of the new aeolian sand subgrade.The response acceleration shows a nonlinear attenuation in the depth direction,and the attenuation rate gradually slows down with increasing depth.Meantime,the horizontal direction shows a variation of exponential decay.Therefore,an attenuation prediction model of response acceleration along the horizontal direction of aeolian sand subgrade is established.[Conclusion]Based on this field test condition,the most dominant dynamic response region of the subgrade is in a range of 1.2 m in depth and 2.5 m in horizontal.The reinforcement effect of geocell on aeolian sand increases the confining pressure level,and restricts the lateral displacement of soil.In addition,the generation of shear bands in the soil is inhibited by the reinforcement effect.This makes the energy dissipation of the subgrade soil more obvious.展开更多
As an advanced device for observing atmospheric winds,the spaceborne Doppler Asymmetric Spatial Heterodyne(DASH)interferometer also encounters challenges associated with phase distortion,par-ticularly in limb sounding...As an advanced device for observing atmospheric winds,the spaceborne Doppler Asymmetric Spatial Heterodyne(DASH)interferometer also encounters challenges associated with phase distortion,par-ticularly in limb sounding scenarios.This paper discusses interferogram modeling and phase distortion cor-rection techniques for spaceborne DASH interferometers.The modeling of phase distortion interferograms with and without Doppler shift for limb observation was conducted,and the effectiveness of the analytical expression was verified through numerical simulation.The simulation results indicate that errors propagate layer by layer while using the onion-peeling inversion algorithm to handle phase-distorted interferograms.In contrast,the phase distortion correction algorithm can achieve effective correction.This phase correction method can be successfully applied to correct phase distortions in the interferograms of the spaceborne DASH interferometer,providing a feasible solution to enhance its measurement accuracy.展开更多
By introducing noncanonical vortex pairs to partially coherent beams, spatial correlation singularity (SCS) and orbital angular momenta (OAM) of the resulting beams are studied using the Fraunhofer diffraction integra...By introducing noncanonical vortex pairs to partially coherent beams, spatial correlation singularity (SCS) and orbital angular momenta (OAM) of the resulting beams are studied using the Fraunhofer diffraction integral. The effect of noncanonical strength, off-axis distance and vortex sign on spatial correlation singularities in far field is stressed. Furthermore, far-field OAM spectra and densities are also investigated, and the OAM detection and crosstalk probabilities are discussed. The results show that the number of dislocations of SCS always equals the sum of absolute values of topological charges for canonical or noncanonical vortex pairs. Although the sum of the product of each OAM mode and its power weight equals the algebraic sum of topological charges for canonical vortex pairs, the relationship no longer holds in the noncanonical case except for opposite-charge vortex pairs. The changes of off-axis distance, noncanonical strength or coherence length can lead to a more dominant power in adjacent mode than that in center detection mode, which also indicates that crosstalk probabilities of adjacent modes exceed the center detection probability. This work may provide potential applications in OAM-based optical communication, imaging, sensing and computing.展开更多
This study contests the prevalent perception of graffiti writing,especially tagging and bombing,as meaningless vandalism.It contends that graffiti is a form of expression with intrinsic political implications.Leveragi...This study contests the prevalent perception of graffiti writing,especially tagging and bombing,as meaningless vandalism.It contends that graffiti is a form of expression with intrinsic political implications.Leveraging the notion of spatial justice and Jacques Ranciere's philosophy,I demonstrate how graffiti reclaims urban visibility against the commercial monopoly of visibility in public spaces and challenges the inequitable allocation of opportunities for self-expression in modern cities.Despite writers'common denial of political motives,their actions may be interpreted as manifestations of resistance within wider sociospatial conflicts.This study situates grffti within discussions of political art,spatial commodification,and everyday resistance,proposing a normative framework for viewing the art of the urban signature as an activity that redefines"the community that speaks."展开更多
Femtosecond laser processing is an important machining method for micro-optical components such as Fresnel zone plate(FZP).However,the low processing efficiency of the femtosecond laser restricts its application.Here,...Femtosecond laser processing is an important machining method for micro-optical components such as Fresnel zone plate(FZP).However,the low processing efficiency of the femtosecond laser restricts its application.Here,a femtosecond laser Bessel beam is proposed to process micro-FZP,which is modulated from a Gaussian beam to a Bessel annular beam.The processing time for FZP with an outer diameter of 60μm is reduced from 30 min to 1.5 min on an important semiconductor material gallium arsenide(GaAs),which significantly improves the processing efficiency.In the modulation process,a central ablation hole that has an adverse effect on the diffraction performance is produced,and the adverse effect is eliminated by superimposing the blazed grating hologram.Meanwhile,the FZP machined by spatial light modulator(SLM)has good morphology and higher diffraction efficiency,which provides a strong guarantee for the application of micro-FZP in computed tomography and solar photovoltaic cells.展开更多
Exploring the effective and efficient path of agricultural carbon emission reduction in Henan Province is of great significance to optimizing the strategic layout of China's agricultural emission reduction and car...Exploring the effective and efficient path of agricultural carbon emission reduction in Henan Province is of great significance to optimizing the strategic layout of China's agricultural emission reduction and carbon sequestration.Accordingly,the agricultural carbon emissions of each county were measured scientifically and then the spatial measurement model was utilized to clarify the spatial and temporal evolution trend and spatial effect mechanism of agricultural carbon emissions based on the county data of Henan Province from 2010 to 2020.The results showed that:(1)in 2020,the total agricultural carbon emissions were 134.7274 million tons,with the high distribution in the southeast and low distribution in the northwest;(2)the spatial dependence of agricultural carbon emissions showed a four-stage trend of fluctuating down-continuing up-plummeting-fluctuating up again,and the spatial heterogeneity was dominated by low-low agglomeration,followed by high-low agglomeration;(3)there was an inverted U curve relationship between the level of agricultural economic development and agricultural carbon emissions.The increase in the level of agricultural mechanization and urbanization rate significantly reduced agricultural carbon emissions.The opposite was true for the financial support for agriculture,the income level of rural residents and the structure of the agricultural industry;(4)in terms of spatial spillover effects,the increase in the level of agricultural development in neighbor counties first increased and then decreased agricultural carbon emissions in Henan Province.The mechanization level and urbanization rate of neighbor counties reduced agricultural carbon emissions in Henan Province,and the opposite was true for the income level of rural residents and the scale utilization of agricultural land.展开更多
Jamming suppression is traditionally achieved through the use of spatial filters based on array signal processing theory.In order to achieve better jamming suppression performance,many studies have applied blind sourc...Jamming suppression is traditionally achieved through the use of spatial filters based on array signal processing theory.In order to achieve better jamming suppression performance,many studies have applied blind source separation(BSS)to jamming suppression.BSS can achieve the separation and extraction of the individual source signals from the mixed signal received by the array.This paper proposes a perspective to recognize BSS as spatial band-pass filters(SBPFs)for jamming suppression applications.The theoretical derivation indicates that the processing of mixed signals by BSS can be perceived as the application of a set of SBPFs that gate the source signals at various angles.Simulations are performed using radar jamming suppression as an example.The simulation results suggest that BSS and SBPFs produce approximately the same effects.Simulation results are consistent with theoretical derivation results.展开更多
地学数据具有结构复杂、多尺度、数据量大的特点.将多源地学数据库集成在同一操作平台与数据库中进行分析使用,使用传统的空间数据储存方法有一定的难度.采用大型数据库系统Oracle 9 i Spatial构建地学空间数据库方法,提供了建立空间数...地学数据具有结构复杂、多尺度、数据量大的特点.将多源地学数据库集成在同一操作平台与数据库中进行分析使用,使用传统的空间数据储存方法有一定的难度.采用大型数据库系统Oracle 9 i Spatial构建地学空间数据库方法,提供了建立空间数据库的实例与应用程序访问空间数据库方法.实践表明,采用Oracle Spatial构建多源地学空间数据库具有空间数据格式统一、数据安全性高、数据存储量大的优点.展开更多
文摘[Objective]The spatial dynamic response of a new desert highway subgrade structure by geocell reinforcement with aeolian sand is studied.[Methods]Based on the dynamic triaxial test,a field test via monitoring the response acceleration change is carried out.The attenuation law and dynamic response range of the response acceleration along the depth and horizontal directions of the subgrade are obtained for the geocell-reinforced subgrade structure.The mechanism of dynamic response of geocell-reinforced materials to aeolian sand subgrade is further discussed.[Results]The result show that both vehicle load and vehicle speed have a great influence on the response acceleration of the new aeolian sand subgrade.The response acceleration shows a nonlinear attenuation in the depth direction,and the attenuation rate gradually slows down with increasing depth.Meantime,the horizontal direction shows a variation of exponential decay.Therefore,an attenuation prediction model of response acceleration along the horizontal direction of aeolian sand subgrade is established.[Conclusion]Based on this field test condition,the most dominant dynamic response region of the subgrade is in a range of 1.2 m in depth and 2.5 m in horizontal.The reinforcement effect of geocell on aeolian sand increases the confining pressure level,and restricts the lateral displacement of soil.In addition,the generation of shear bands in the soil is inhibited by the reinforcement effect.This makes the energy dissipation of the subgrade soil more obvious.
文摘As an advanced device for observing atmospheric winds,the spaceborne Doppler Asymmetric Spatial Heterodyne(DASH)interferometer also encounters challenges associated with phase distortion,par-ticularly in limb sounding scenarios.This paper discusses interferogram modeling and phase distortion cor-rection techniques for spaceborne DASH interferometers.The modeling of phase distortion interferograms with and without Doppler shift for limb observation was conducted,and the effectiveness of the analytical expression was verified through numerical simulation.The simulation results indicate that errors propagate layer by layer while using the onion-peeling inversion algorithm to handle phase-distorted interferograms.In contrast,the phase distortion correction algorithm can achieve effective correction.This phase correction method can be successfully applied to correct phase distortions in the interferograms of the spaceborne DASH interferometer,providing a feasible solution to enhance its measurement accuracy.
文摘By introducing noncanonical vortex pairs to partially coherent beams, spatial correlation singularity (SCS) and orbital angular momenta (OAM) of the resulting beams are studied using the Fraunhofer diffraction integral. The effect of noncanonical strength, off-axis distance and vortex sign on spatial correlation singularities in far field is stressed. Furthermore, far-field OAM spectra and densities are also investigated, and the OAM detection and crosstalk probabilities are discussed. The results show that the number of dislocations of SCS always equals the sum of absolute values of topological charges for canonical or noncanonical vortex pairs. Although the sum of the product of each OAM mode and its power weight equals the algebraic sum of topological charges for canonical vortex pairs, the relationship no longer holds in the noncanonical case except for opposite-charge vortex pairs. The changes of off-axis distance, noncanonical strength or coherence length can lead to a more dominant power in adjacent mode than that in center detection mode, which also indicates that crosstalk probabilities of adjacent modes exceed the center detection probability. This work may provide potential applications in OAM-based optical communication, imaging, sensing and computing.
文摘This study contests the prevalent perception of graffiti writing,especially tagging and bombing,as meaningless vandalism.It contends that graffiti is a form of expression with intrinsic political implications.Leveraging the notion of spatial justice and Jacques Ranciere's philosophy,I demonstrate how graffiti reclaims urban visibility against the commercial monopoly of visibility in public spaces and challenges the inequitable allocation of opportunities for self-expression in modern cities.Despite writers'common denial of political motives,their actions may be interpreted as manifestations of resistance within wider sociospatial conflicts.This study situates grffti within discussions of political art,spatial commodification,and everyday resistance,proposing a normative framework for viewing the art of the urban signature as an activity that redefines"the community that speaks."
基金Projects(51875584,51875585,51975590)supported by the National Natural Science Foundation of China。
文摘Femtosecond laser processing is an important machining method for micro-optical components such as Fresnel zone plate(FZP).However,the low processing efficiency of the femtosecond laser restricts its application.Here,a femtosecond laser Bessel beam is proposed to process micro-FZP,which is modulated from a Gaussian beam to a Bessel annular beam.The processing time for FZP with an outer diameter of 60μm is reduced from 30 min to 1.5 min on an important semiconductor material gallium arsenide(GaAs),which significantly improves the processing efficiency.In the modulation process,a central ablation hole that has an adverse effect on the diffraction performance is produced,and the adverse effect is eliminated by superimposing the blazed grating hologram.Meanwhile,the FZP machined by spatial light modulator(SLM)has good morphology and higher diffraction efficiency,which provides a strong guarantee for the application of micro-FZP in computed tomography and solar photovoltaic cells.
基金Supported by the Humanities and Social Sciences Planning Program of the Ministry of Education(23YJA790027)。
文摘Exploring the effective and efficient path of agricultural carbon emission reduction in Henan Province is of great significance to optimizing the strategic layout of China's agricultural emission reduction and carbon sequestration.Accordingly,the agricultural carbon emissions of each county were measured scientifically and then the spatial measurement model was utilized to clarify the spatial and temporal evolution trend and spatial effect mechanism of agricultural carbon emissions based on the county data of Henan Province from 2010 to 2020.The results showed that:(1)in 2020,the total agricultural carbon emissions were 134.7274 million tons,with the high distribution in the southeast and low distribution in the northwest;(2)the spatial dependence of agricultural carbon emissions showed a four-stage trend of fluctuating down-continuing up-plummeting-fluctuating up again,and the spatial heterogeneity was dominated by low-low agglomeration,followed by high-low agglomeration;(3)there was an inverted U curve relationship between the level of agricultural economic development and agricultural carbon emissions.The increase in the level of agricultural mechanization and urbanization rate significantly reduced agricultural carbon emissions.The opposite was true for the financial support for agriculture,the income level of rural residents and the structure of the agricultural industry;(4)in terms of spatial spillover effects,the increase in the level of agricultural development in neighbor counties first increased and then decreased agricultural carbon emissions in Henan Province.The mechanization level and urbanization rate of neighbor counties reduced agricultural carbon emissions in Henan Province,and the opposite was true for the income level of rural residents and the scale utilization of agricultural land.
基金supported by the National Natural Science Foundation of China(6237104662201048)the Natural Science Foundation of Chongqing,China(cstc2020jcyj-msxmX0260).
文摘Jamming suppression is traditionally achieved through the use of spatial filters based on array signal processing theory.In order to achieve better jamming suppression performance,many studies have applied blind source separation(BSS)to jamming suppression.BSS can achieve the separation and extraction of the individual source signals from the mixed signal received by the array.This paper proposes a perspective to recognize BSS as spatial band-pass filters(SBPFs)for jamming suppression applications.The theoretical derivation indicates that the processing of mixed signals by BSS can be perceived as the application of a set of SBPFs that gate the source signals at various angles.Simulations are performed using radar jamming suppression as an example.The simulation results suggest that BSS and SBPFs produce approximately the same effects.Simulation results are consistent with theoretical derivation results.
文摘地学数据具有结构复杂、多尺度、数据量大的特点.将多源地学数据库集成在同一操作平台与数据库中进行分析使用,使用传统的空间数据储存方法有一定的难度.采用大型数据库系统Oracle 9 i Spatial构建地学空间数据库方法,提供了建立空间数据库的实例与应用程序访问空间数据库方法.实践表明,采用Oracle Spatial构建多源地学空间数据库具有空间数据格式统一、数据安全性高、数据存储量大的优点.
