To detect space gravitational waves in the extremely low-frequency band,the telescope and optic-al platform require high stability and reliability.However,the cantilevered design presents challenges,espe-cially in the...To detect space gravitational waves in the extremely low-frequency band,the telescope and optic-al platform require high stability and reliability.However,the cantilevered design presents challenges,espe-cially in the glass-metal hetero-bonding process.This study focuses on the analysis and experimental re-search of the bonding layer in the integrated structure.By optimizing the structural configuration and select-ing suitable bonding processes,the reliability of the telescope system is enhanced.The research indicates that using J-133 adhesive achieves the best performance,with a bonding layer thickness of 0.30 mm and a metal substrate surface roughness of Ra 0.8.These findings significantly enhance the reliability of the optical sys-tem while minimizing potential risks.展开更多
An adaptive robust attitude tracking control law based on switched nonlinear systems is presented for a variable structure near space vehicle （VSNSV） in the presence of uncertainties and disturbances. The adaptive f...An adaptive robust attitude tracking control law based on switched nonlinear systems is presented for a variable structure near space vehicle （VSNSV） in the presence of uncertainties and disturbances. The adaptive fuzzy systems are employed for approximating unknown functions in the flight dynamic model and their parameters are updated online. To improve the flight robust performance, robust controllers with adaptive gains are designed to compensate for the approximation errors and thus they have less design conservation. Moreover, a systematic procedure is developed for the synthesis of adaptive fuzzy dynamic surface control （DSC） approach. According to the common Lyapunov function theory, it is proved that all signals of the closed-loop system are uniformly ultimately bounded by the continuous controller. The simulation results demonstrate the effectiveness and robustness of the proposed control scheme.展开更多
Severe damage to steel space structures is rarely reported when compared to other structural systems damaged during past major earthquakes around the world. Two gymnasiums of steel space structures in downtown Lushan ...Severe damage to steel space structures is rarely reported when compared to other structural systems damaged during past major earthquakes around the world. Two gymnasiums of steel space structures in downtown Lushan County that were damaged during the 2013 M7.0 Lushan earthquake in China were investigated and the observations are summarized in this paper. Typical damage to these two steel space structures ranges from moderate to severe. Moderate damage includes global buckling and dislocation of bolted connections of truss members, and inelastic elongation of anchor bolts and sliding of pedestal plates of supports. Severe damage includes member fracture caused by local buckling, and fracture failure of anchor bolts and welds. The distribution of structural damage to these two structures is described in detail and future research opportunities are suggested.展开更多
Deployable space structure technology is an approach used in building spacecraft,especially when realizing deployment and folding functions.Once in orbit,the structures are released from the fairing,deployed,and posit...Deployable space structure technology is an approach used in building spacecraft,especially when realizing deployment and folding functions.Once in orbit,the structures are released from the fairing,deployed,and positioned.With the development of communication,remote-sensing,and navigation satellites,space-deployable structures have become cutting-edge research topics in space science and technology.This paper summarizes the current research status and development trend of spacedeployable structures in China,including large space mesh antennas,space solar arrays,and deployable structures and mechanisms for deep-space exploration.Critical technologies of space-deployable structures are addressed from the perspectives of deployable mechanisms,cable-membrane form-finding,dynamic analysis,reliable environmental adaptability analysis,and validation.Finally,future technology developments and trends are elucidated in the fields of mesh antennas,solar arrays,deployable mechanisms,and on-orbit adjustment,assembly,and construction.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
A switching disturbance rejection attitude control law is proposed for a near space vehicle(NSV) with variable structure.The multiple flight modes, system uncertainties and disturbances of the NSV are taken into accou...A switching disturbance rejection attitude control law is proposed for a near space vehicle(NSV) with variable structure.The multiple flight modes, system uncertainties and disturbances of the NSV are taken into account based on switched nonlinear systems. Compared with traditional backstepping design methods,the proposed method utilizes the added integrals of attitude angle and angular rate tracking errors to further decrease the tracking errors. Moreover, to reduce the computation complexity, a rapid convergent differentiator is employed to obtain the derivative of the virtual control command. Finally, for disturbance rejection, based on the idea from the extended state observer(ESO), two disturbance observers are designed by using non-smooth functions to estimate the disturbances in the switched nonlinear systems. All signals of the closed-loop system are proven to be uniformly ultimately bounded under the Lyapunov function framework. Simulation results demonstrate the effectiveness of the proposed control scheme.展开更多
Based on the transmitting theory of "smoke ring effect", the transient electromagnetism technique was used in coal mines to detect abnormal areas of aquiferous structures in both roofs and floors of coal sea...Based on the transmitting theory of "smoke ring effect", the transient electromagnetism technique was used in coal mines to detect abnormal areas of aquiferous structures in both roofs and floors of coal seams and in front of excavated roadways. Survey devices, working methods and techniques as well as data processing and interpretation are discussed systematically. In addition, the direction of mini-wireframe emission electromagnetic wave of the full space transient electromagnetism technique was verified by an underground borehole for water detection and drainage. The result indicates that this technique can detect both horizontal and vertical development rules of abnormal water bodies to a certain depth below the floor of coal seams and can also detect the abnormal, low resistance water bodies within a certain distance of roofs. Furthermore, it can detect such abnormal bodies in ahead of the excavated roadway front. Limited by the underground environment, the full space transient electromagnetism technique can detect to a depth of only 120 m or so.展开更多
A nonlinear dynamic modeling method for primary mirror of Flower-like Deployable Space Telescope(F-DST)undergoing large deployment motion is proposed in this paper.To ensure pointing accuracy and attitude stability of...A nonlinear dynamic modeling method for primary mirror of Flower-like Deployable Space Telescope(F-DST)undergoing large deployment motion is proposed in this paper.To ensure pointing accuracy and attitude stability of the paraboloidal primary mirror,the mirror is discretized into equal thickness shell elements by considering shell curvature.And the material nonlinear constitutive relation of flexible mirror is acquired using Absolute Nodal Coordinate Formulation(ANCF).Furthermore,the primary mirror of F-DST can be regarded as a clustered multi-body system,and its dynamic equations of elastic deformation and deployment motion are established by virtual work principle.Finally,the deployment motion of primary mirror by different driving conditions are simulated,the results show that the vibrations of mirrors that driven by elastic hinge device are more than that driven by servo motor.In addition,single sub-mirror deployment process will perturb the pointing accuracy of primary mirror,and the multiple sub-mirrors simultaneously deploying will seriously affect all the sub-mirrors surface accuracy because of the coupling effect.Thus,there are theoretical value and practical significance for the controlling surface accuracy and attitude accuracy of space telescope.展开更多
Let X be a Banach space, S(X) be the unit sphere of X, φ be a function: S(X)→ S(X *) such that φ(x)∈ x, and v φ(ε) =inf 1-12x+y: x,y∈S(X), and 〈φ(x), x-y 〉≥ε, 0≤ε≤2, whe...Let X be a Banach space, S(X) be the unit sphere of X, φ be a function: S(X)→ S(X *) such that φ(x)∈ x, and v φ(ε) =inf 1-12x+y: x,y∈S(X), and 〈φ(x), x-y 〉≥ε, 0≤ε≤2, where x is the set of norm 1 supporting functionals of S(X) at x. A geometric concept, modulus of V convexity V(ε)= sup {V φ(ε), for all φ: S(X)→S(X *)}, is introduced; the properties of V(ε) and the relationship between V(ε) and other geometric concepts are discussed. The main result is that V12>0 implies normal structure.展开更多
Organic matter(OM)and minerals are major particle components of lacustrine shales.The influence of OM and minerals on pore space and structure in organic-rich oil-prone shales containing a large range of total organic...Organic matter(OM)and minerals are major particle components of lacustrine shales.The influence of OM and minerals on pore space and structure in organic-rich oil-prone shales containing a large range of total organic carbon(TOC)contents is poorly understood.In this study,we investigated the variation in pore space and structure of low mature lacustrine shales in the Songliao Basin(NE China),based on a study of the mineralogy,petrography,geochemistry,and geophysical properties of shales.Different pore types make markedly different contributions to the mineral surface area(MSA)and pore volume(PV)of the shales.There exists a negative correlation between MSA/PV and TOC in mesopores(r^(2)=0.75/0.65)and macropores(r^(2)=0.74/0.68),and a positive correlation in micropores(r^(2)=0.59/0.64),which are associated with the variation of mineral and TOC contents.A positive relationship between the throat/pore ratio and TOC(r^(2)=0.82)shows an increase in throat radius and decrease in pore radius with increasing TOC content.This relationship is supported by the reduction in mean pore diameter(MPD)for large pores and increase in MPD for small pores.These variations are related to the decreased pores by quartz plus feldspar(Q+F)content,increased throats by clay minerals,an d enhanced pore-fill by OM.We propose that the variation of OM and minerals is a key control on the pore space and structure of low mature organic-rich oil-prone shales.展开更多
This paper presents the principle and mathematic model for the 3D depth map method based on space encoding images performed by modulating scanning structuredlight according to time sequences,and the synchro control ...This paper presents the principle and mathematic model for the 3D depth map method based on space encoding images performed by modulating scanning structuredlight according to time sequences,and the synchro control among the camera,laser diode modulation and scanning polyhedron.展开更多
The rural social space quality is an important indicator to measure the living standard and thinking ideas and so forth of rural residents in a certain region.In this paper,213 administrative villages in Longxi County...The rural social space quality is an important indicator to measure the living standard and thinking ideas and so forth of rural residents in a certain region.In this paper,213 administrative villages in Longxi County of the Loess Hilly Area,China are taken as evaluation units to construct the evaluation model of the rural social space quality.This paper deeply analyzed the variation patterns and their formation mechanism of the rural social space quality at a village scale,and proposed a governance model based on the rural social space quality.The results show that:(1)the social space quality levels of individual administrative villages show a gradually decreasing trend from the township seats to outward.The eastern part of Longxi County has a relatively high education level and living standard,and the western part has a relatively high population stability level and income level.(2)The rural social space quality is mainly in a ring structure,supplemented by the interlaced structure.The core area is the towns and their surrounding areas,while the transition area,marginal area,and other areas are expanded around the core area.(3)Social forces and spatial effects jointly shape the variation of the rural social space quality.Social organizations provide a driving force for the allocation of elements,and interweaving with the spatial effects lead to the differences in the social space quality.(4)The governance models of the rural social space quality are constructed based on the principles of retaining the rural“people”,optimizing the rural“land”,and developing the rural“industry”,so as to improve the rural centripetal force,core force,inner thrust,and source power.展开更多
Although many methods of spatial analysis have been developed for a better understanding and modelling of urban space analysis, there is still a need for exploration of new analytical techniques for modelling urban sp...Although many methods of spatial analysis have been developed for a better understanding and modelling of urban space analysis, there is still a need for exploration of new analytical techniques for modelling urban spaces. Space Syntax models the spatial configurations of urban spaces by using a connectivity graph representation. Such a configuration of space identifies patterns that can be used to study urban structures and human behaviors. This paper tries to present a new methodology to investigate the urban spatial structure by using Space Syntax with the GIS information including land use, buildings’ characteristics and practical evaluations of the potential of the Space Syntax approach with GIS and multivariate analysis technique. Finally we try to offer some recommendations that attempt to improve the identified problems faced in Kitakyushu, Japan.展开更多
The footpad structure of a deep space exploration lander is a critical system that makes the initial contact with the ground,and thereby plays a crucial role in determining the stability and energy absorption characte...The footpad structure of a deep space exploration lander is a critical system that makes the initial contact with the ground,and thereby plays a crucial role in determining the stability and energy absorption characteristics during the impact process.The conventional footpad is typically designed with an aluminum honeycomb structure that dissipates energy through plastic deformation.Nevertheless,its effectiveness in providing cushioning and energy absorption becomes significantly compromised when the structure is crushed,rendering it unusable for reusable landers in the future.This study presents a methodology for designing and evaluating structural energy absorption systems incorporating recoverable strain constraints of shape memory alloys(SMA).The topological configuration of the energy absorbing structure is derived using an equivalent static load method(ESL),and three lightweight footpad designs featuring honeycomb-like Ni-Ti shape memory alloys structures and having variable stiffness skins are proposed.To verify the accuracy of the numerical modelling,a honeycomb-like structure subjected to compression load is modeled and then compared with experimental results.Moreover,the influence of the configurations and thickness distribution of the proposed structures on their energy absorption performance is comprehensively evaluated using finite element simulations.The results demonstrate that the proposed design approach effectively regulates the strain threshold to maintain the SMA within the constraint of maximum recoverable strain,resulting in a structural energy absorption capacity of 362 J/kg with a crushing force efficiency greater than 63%.展开更多
It is proposed that the digital space structure consists of attachment space (denoted as 1) for rest mass and detachment space (denoted as 0) for kinetic energy. Attachment space attaches to object permanently with ze...It is proposed that the digital space structure consists of attachment space (denoted as 1) for rest mass and detachment space (denoted as 0) for kinetic energy. Attachment space attaches to object permanently with zero speed, and detachment space detaches from the object at the speed of light. The combination of attachment space and detachment space brings about the three structures: binary lattice space, miscible space, and binary partition space. Binary lattice space, (1 0)n, consists of repetitive units of alternative attachment space and detachment space. In miscible space, attachment space is miscible to detachment space without separation. Binary partition space, (1)n(0)n, consists of separated continuous phases of attachment space and detachment space. Binary lattice space, miscible space, and binary partition space constitute quantum mechanics, special relativity, and the extreme force fields, respectively. Through the detachment space, a higher dimensional particle in attachment space is sliced into infinitely surrounding a lower dimensional core attachment space, resulting in a particle surrounding by gauge field in the form of binary lattice space. The 10d particle can be sliced into 9d, 8d, 7d, 6d, 5d, and 4d particles equally by mass, corresponding to baryonic particle as 4d and dark matter as other 5 particles, so the ratio between baryonic matter and dark matter is 1 to 5, in agreement with the observed ratio. At extreme conditions, such as extremely low temperature, the gauge force field in the form of binary lattice space is transformed into the extreme force field in the form of binary partition space to explain extreme phenomena, such as superconductivity.展开更多
Granular computing is a very hot research field in recent years. In our previous work an algebraic quotient space model was proposed,where the quotient structure could not be deduced if the granulation was based on an...Granular computing is a very hot research field in recent years. In our previous work an algebraic quotient space model was proposed,where the quotient structure could not be deduced if the granulation was based on an equivalence relation. In this paper,definitions were given and formulas of the lower quotient congruence and upper quotient congruence were calculated to roughly represent the quotient structure. Then the accuracy and roughness were defined to measure the quotient structure in quantification. Finally,a numerical example was given to demonstrate that the rough representation and measuring methods are efficient and applicable. The work has greatly enriched the algebraic quotient space model and granular computing theory.展开更多
In this paper, an asymmetric array structure of space laser communication receiver is proposed. This structure can greatly reduce alignment requirement, and lighten the signal strength jitter caused by atmospheric tur...In this paper, an asymmetric array structure of space laser communication receiver is proposed. This structure can greatly reduce alignment requirement, and lighten the signal strength jitter caused by atmospheric turbulence. A prototype of the proposed structure is fabricated and a 2.5 Mbit/s on-off keying(OOK) modulated demonstration link over 40 m free space is built. This asymmetric array structure can effectively collect optical signal while rotating in a window angle of ±17°, and the bit error ratio(BER) keeps zero.展开更多
An approach to sequence planning for on-orbit assembly of large space truss structures in a multirobot environment is presented. A hierarchical representation of large space truss structures at the structural volume e...An approach to sequence planning for on-orbit assembly of large space truss structures in a multirobot environment is presented. A hierarchical representation of large space truss structures at the structural volume element level and strut level is adopted. The representation of connectivity matrix and directed graph is respectively presented at the strut level and SVE level. The multirobot environment that consists of autonomous space robots and struts is supposed. Then the multirobot serial assembly strategy,assembly states,assembly tasks and assembly sequences are described. The assembly sequence planning algorithms at the strut level and SVE level are respectively discussed. The results of the simulations show that this approach is feasible and efficient. Two extensions of this approach include more accurate assessment of the efficiency representation and improvements in planning algorithm. In the future,the assembly sequence planning of more large space truss structures and complex multirobot environments and assembly tasks will be considered.展开更多
In this paper, we present a highly efficient structure determination pipeline software suite(X^2 DF) that is based on the "Parameter space screening" method, by combining the popular crystallographic structu...In this paper, we present a highly efficient structure determination pipeline software suite(X^2 DF) that is based on the "Parameter space screening" method, by combining the popular crystallographic structure determination programs and high-performance parallel computing. The phasing method employed in X^2 DF is based on the single-wavelength anomalous diffraction(SAD) theory. In the X^2 DF, the choice of crystallographic software, the input parameters to this software and the results display layout, are all parameters which users can select and screen automatically. Users may submit multiple structure determination jobs each time, and each job uses a slightly different set of input parameters or programs. Upon completion, the results of the calculation performed can be displayed, harvested, and analyzed by using the graphical user interface(GUI) of the system. We have applied the X^2 DF successfully to many cases including the cases that the structure solutions fail to be yielded by using manual approaches.展开更多
In-space 3D printing is transforming the manufacturing paradigm of space structures from ground-based production to in-situ space manufacturing,effectively addressing the challenges of high costs,long response times,a...In-space 3D printing is transforming the manufacturing paradigm of space structures from ground-based production to in-situ space manufacturing,effectively addressing the challenges of high costs,long response times,and structural size limitations associated with traditional rocket launches.This technology enables rapid on-orbit emergency repairs and significantly expands the geometric dimensions of space structures.High-performance polymers and their composites are widely used in in-space 3D printing,yet their implementation faces complex challenges posed by extreme space environmental conditions and limited energy or resources.This paper reviews the state-of-the-art in 3D printing of polymer and composites for on-orbit structure manufacturing.Based on existing research activities,the review focuses on three key aspects including the impact of extreme space environments on forming process and performance,innovative design and manufacturing methods for space structures,and on-orbit recycling and remanufacturing of raw materials.Some experiments that have already been conducted on-orbit and simulated experiments completed on the ground are systematically analyzed to provide a more comprehensive understanding of the constraints and objectives for on-orbit structure manufacturing.Furthermore,several perspectives requiring further research in future are proposed to facilitate the development of new in-space 3D printing technologies and space structures,thereby supporting increasingly advanced space exploration activities.展开更多
文摘To detect space gravitational waves in the extremely low-frequency band,the telescope and optic-al platform require high stability and reliability.However,the cantilevered design presents challenges,espe-cially in the glass-metal hetero-bonding process.This study focuses on the analysis and experimental re-search of the bonding layer in the integrated structure.By optimizing the structural configuration and select-ing suitable bonding processes,the reliability of the telescope system is enhanced.The research indicates that using J-133 adhesive achieves the best performance,with a bonding layer thickness of 0.30 mm and a metal substrate surface roughness of Ra 0.8.These findings significantly enhance the reliability of the optical sys-tem while minimizing potential risks.
基金co-supported by National Natural Science Foundation of China (Nos. 91116017, 60974106 and 11102080)Funding for Outstanding Doctoral Dissertation in NUAA (No. BCXJ10-04)
文摘An adaptive robust attitude tracking control law based on switched nonlinear systems is presented for a variable structure near space vehicle （VSNSV） in the presence of uncertainties and disturbances. The adaptive fuzzy systems are employed for approximating unknown functions in the flight dynamic model and their parameters are updated online. To improve the flight robust performance, robust controllers with adaptive gains are designed to compensate for the approximation errors and thus they have less design conservation. Moreover, a systematic procedure is developed for the synthesis of adaptive fuzzy dynamic surface control （DSC） approach. According to the common Lyapunov function theory, it is proved that all signals of the closed-loop system are uniformly ultimately bounded by the continuous controller. The simulation results demonstrate the effectiveness and robustness of the proposed control scheme.
基金the National Science and Technology Supporting Program(2012BAK15B02)the National Natural Science Foundation Program(50938006)the special program for Science Field Investigation on Lushan M7.0 Earthquake from the China Earthquake Administration
文摘Severe damage to steel space structures is rarely reported when compared to other structural systems damaged during past major earthquakes around the world. Two gymnasiums of steel space structures in downtown Lushan County that were damaged during the 2013 M7.0 Lushan earthquake in China were investigated and the observations are summarized in this paper. Typical damage to these two steel space structures ranges from moderate to severe. Moderate damage includes global buckling and dislocation of bolted connections of truss members, and inelastic elongation of anchor bolts and sliding of pedestal plates of supports. Severe damage includes member fracture caused by local buckling, and fracture failure of anchor bolts and welds. The distribution of structural damage to these two structures is described in detail and future research opportunities are suggested.
基金financial support from the National Natural Science Foundation of China(11290154 and U20B2033)。
文摘Deployable space structure technology is an approach used in building spacecraft,especially when realizing deployment and folding functions.Once in orbit,the structures are released from the fairing,deployed,and positioned.With the development of communication,remote-sensing,and navigation satellites,space-deployable structures have become cutting-edge research topics in space science and technology.This paper summarizes the current research status and development trend of spacedeployable structures in China,including large space mesh antennas,space solar arrays,and deployable structures and mechanisms for deep-space exploration.Critical technologies of space-deployable structures are addressed from the perspectives of deployable mechanisms,cable-membrane form-finding,dynamic analysis,reliable environmental adaptability analysis,and validation.Finally,future technology developments and trends are elucidated in the fields of mesh antennas,solar arrays,deployable mechanisms,and on-orbit adjustment,assembly,and construction.
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.
基金supported by the National Natural Science Foundation of China(61374012)the Aeronautical Science Foundation of China(2016ZA51011)
文摘A switching disturbance rejection attitude control law is proposed for a near space vehicle(NSV) with variable structure.The multiple flight modes, system uncertainties and disturbances of the NSV are taken into account based on switched nonlinear systems. Compared with traditional backstepping design methods,the proposed method utilizes the added integrals of attitude angle and angular rate tracking errors to further decrease the tracking errors. Moreover, to reduce the computation complexity, a rapid convergent differentiator is employed to obtain the derivative of the virtual control command. Finally, for disturbance rejection, based on the idea from the extended state observer(ESO), two disturbance observers are designed by using non-smooth functions to estimate the disturbances in the switched nonlinear systems. All signals of the closed-loop system are proven to be uniformly ultimately bounded under the Lyapunov function framework. Simulation results demonstrate the effectiveness of the proposed control scheme.
文摘Based on the transmitting theory of "smoke ring effect", the transient electromagnetism technique was used in coal mines to detect abnormal areas of aquiferous structures in both roofs and floors of coal seams and in front of excavated roadways. Survey devices, working methods and techniques as well as data processing and interpretation are discussed systematically. In addition, the direction of mini-wireframe emission electromagnetic wave of the full space transient electromagnetism technique was verified by an underground borehole for water detection and drainage. The result indicates that this technique can detect both horizontal and vertical development rules of abnormal water bodies to a certain depth below the floor of coal seams and can also detect the abnormal, low resistance water bodies within a certain distance of roofs. Furthermore, it can detect such abnormal bodies in ahead of the excavated roadway front. Limited by the underground environment, the full space transient electromagnetism technique can detect to a depth of only 120 m or so.
基金based on Project 51575126 the National Natural Science Foundation of ChinaProjects 2013M541358 and 2015T80358 the China Postdoctoral Science Foundation。
文摘A nonlinear dynamic modeling method for primary mirror of Flower-like Deployable Space Telescope(F-DST)undergoing large deployment motion is proposed in this paper.To ensure pointing accuracy and attitude stability of the paraboloidal primary mirror,the mirror is discretized into equal thickness shell elements by considering shell curvature.And the material nonlinear constitutive relation of flexible mirror is acquired using Absolute Nodal Coordinate Formulation(ANCF).Furthermore,the primary mirror of F-DST can be regarded as a clustered multi-body system,and its dynamic equations of elastic deformation and deployment motion are established by virtual work principle.Finally,the deployment motion of primary mirror by different driving conditions are simulated,the results show that the vibrations of mirrors that driven by elastic hinge device are more than that driven by servo motor.In addition,single sub-mirror deployment process will perturb the pointing accuracy of primary mirror,and the multiple sub-mirrors simultaneously deploying will seriously affect all the sub-mirrors surface accuracy because of the coupling effect.Thus,there are theoretical value and practical significance for the controlling surface accuracy and attitude accuracy of space telescope.
文摘Let X be a Banach space, S(X) be the unit sphere of X, φ be a function: S(X)→ S(X *) such that φ(x)∈ x, and v φ(ε) =inf 1-12x+y: x,y∈S(X), and 〈φ(x), x-y 〉≥ε, 0≤ε≤2, where x is the set of norm 1 supporting functionals of S(X) at x. A geometric concept, modulus of V convexity V(ε)= sup {V φ(ε), for all φ: S(X)→S(X *)}, is introduced; the properties of V(ε) and the relationship between V(ε) and other geometric concepts are discussed. The main result is that V12>0 implies normal structure.
基金supported by the National Natural Science Foundation of China(Grant Nos.41772114,41402123)the CGS Research Fund of China(Grant Nos.J1901-33,J1803)the China Geological Survey(Grant No.DD20221817).
文摘Organic matter(OM)and minerals are major particle components of lacustrine shales.The influence of OM and minerals on pore space and structure in organic-rich oil-prone shales containing a large range of total organic carbon(TOC)contents is poorly understood.In this study,we investigated the variation in pore space and structure of low mature lacustrine shales in the Songliao Basin(NE China),based on a study of the mineralogy,petrography,geochemistry,and geophysical properties of shales.Different pore types make markedly different contributions to the mineral surface area(MSA)and pore volume(PV)of the shales.There exists a negative correlation between MSA/PV and TOC in mesopores(r^(2)=0.75/0.65)and macropores(r^(2)=0.74/0.68),and a positive correlation in micropores(r^(2)=0.59/0.64),which are associated with the variation of mineral and TOC contents.A positive relationship between the throat/pore ratio and TOC(r^(2)=0.82)shows an increase in throat radius and decrease in pore radius with increasing TOC content.This relationship is supported by the reduction in mean pore diameter(MPD)for large pores and increase in MPD for small pores.These variations are related to the decreased pores by quartz plus feldspar(Q+F)content,increased throats by clay minerals,an d enhanced pore-fill by OM.We propose that the variation of OM and minerals is a key control on the pore space and structure of low mature organic-rich oil-prone shales.
文摘This paper presents the principle and mathematic model for the 3D depth map method based on space encoding images performed by modulating scanning structuredlight according to time sequences,and the synchro control among the camera,laser diode modulation and scanning polyhedron.
基金National Natural Science Foundation of China,No.41961033Natural Science Foundation of Gansu Province,No.20JR5RA519The Graduate Research Funding Project of Northwest Normal University in 2021,No.2021KYZZ01039。
文摘The rural social space quality is an important indicator to measure the living standard and thinking ideas and so forth of rural residents in a certain region.In this paper,213 administrative villages in Longxi County of the Loess Hilly Area,China are taken as evaluation units to construct the evaluation model of the rural social space quality.This paper deeply analyzed the variation patterns and their formation mechanism of the rural social space quality at a village scale,and proposed a governance model based on the rural social space quality.The results show that:(1)the social space quality levels of individual administrative villages show a gradually decreasing trend from the township seats to outward.The eastern part of Longxi County has a relatively high education level and living standard,and the western part has a relatively high population stability level and income level.(2)The rural social space quality is mainly in a ring structure,supplemented by the interlaced structure.The core area is the towns and their surrounding areas,while the transition area,marginal area,and other areas are expanded around the core area.(3)Social forces and spatial effects jointly shape the variation of the rural social space quality.Social organizations provide a driving force for the allocation of elements,and interweaving with the spatial effects lead to the differences in the social space quality.(4)The governance models of the rural social space quality are constructed based on the principles of retaining the rural“people”,optimizing the rural“land”,and developing the rural“industry”,so as to improve the rural centripetal force,core force,inner thrust,and source power.
文摘Although many methods of spatial analysis have been developed for a better understanding and modelling of urban space analysis, there is still a need for exploration of new analytical techniques for modelling urban spaces. Space Syntax models the spatial configurations of urban spaces by using a connectivity graph representation. Such a configuration of space identifies patterns that can be used to study urban structures and human behaviors. This paper tries to present a new methodology to investigate the urban spatial structure by using Space Syntax with the GIS information including land use, buildings’ characteristics and practical evaluations of the potential of the Space Syntax approach with GIS and multivariate analysis technique. Finally we try to offer some recommendations that attempt to improve the identified problems faced in Kitakyushu, Japan.
基金Supported by Fundamental Research Funds for the Central Universities of China(Grant No.2021JBM021)National Natural Science Foundation of China(Grant Nos.52202431,52172353).
文摘The footpad structure of a deep space exploration lander is a critical system that makes the initial contact with the ground,and thereby plays a crucial role in determining the stability and energy absorption characteristics during the impact process.The conventional footpad is typically designed with an aluminum honeycomb structure that dissipates energy through plastic deformation.Nevertheless,its effectiveness in providing cushioning and energy absorption becomes significantly compromised when the structure is crushed,rendering it unusable for reusable landers in the future.This study presents a methodology for designing and evaluating structural energy absorption systems incorporating recoverable strain constraints of shape memory alloys(SMA).The topological configuration of the energy absorbing structure is derived using an equivalent static load method(ESL),and three lightweight footpad designs featuring honeycomb-like Ni-Ti shape memory alloys structures and having variable stiffness skins are proposed.To verify the accuracy of the numerical modelling,a honeycomb-like structure subjected to compression load is modeled and then compared with experimental results.Moreover,the influence of the configurations and thickness distribution of the proposed structures on their energy absorption performance is comprehensively evaluated using finite element simulations.The results demonstrate that the proposed design approach effectively regulates the strain threshold to maintain the SMA within the constraint of maximum recoverable strain,resulting in a structural energy absorption capacity of 362 J/kg with a crushing force efficiency greater than 63%.
文摘It is proposed that the digital space structure consists of attachment space (denoted as 1) for rest mass and detachment space (denoted as 0) for kinetic energy. Attachment space attaches to object permanently with zero speed, and detachment space detaches from the object at the speed of light. The combination of attachment space and detachment space brings about the three structures: binary lattice space, miscible space, and binary partition space. Binary lattice space, (1 0)n, consists of repetitive units of alternative attachment space and detachment space. In miscible space, attachment space is miscible to detachment space without separation. Binary partition space, (1)n(0)n, consists of separated continuous phases of attachment space and detachment space. Binary lattice space, miscible space, and binary partition space constitute quantum mechanics, special relativity, and the extreme force fields, respectively. Through the detachment space, a higher dimensional particle in attachment space is sliced into infinitely surrounding a lower dimensional core attachment space, resulting in a particle surrounding by gauge field in the form of binary lattice space. The 10d particle can be sliced into 9d, 8d, 7d, 6d, 5d, and 4d particles equally by mass, corresponding to baryonic particle as 4d and dark matter as other 5 particles, so the ratio between baryonic matter and dark matter is 1 to 5, in agreement with the observed ratio. At extreme conditions, such as extremely low temperature, the gauge force field in the form of binary lattice space is transformed into the extreme force field in the form of binary partition space to explain extreme phenomena, such as superconductivity.
基金Supported by the National Natural Science Foundation of China(No.61772031)the Special Energy Saving Foundation of Changsha,Hunan Province in 2017
文摘Granular computing is a very hot research field in recent years. In our previous work an algebraic quotient space model was proposed,where the quotient structure could not be deduced if the granulation was based on an equivalence relation. In this paper,definitions were given and formulas of the lower quotient congruence and upper quotient congruence were calculated to roughly represent the quotient structure. Then the accuracy and roughness were defined to measure the quotient structure in quantification. Finally,a numerical example was given to demonstrate that the rough representation and measuring methods are efficient and applicable. The work has greatly enriched the algebraic quotient space model and granular computing theory.
基金supported by the National Natural Science Foundation of China (Nos.61674142 and 62041502)。
文摘In this paper, an asymmetric array structure of space laser communication receiver is proposed. This structure can greatly reduce alignment requirement, and lighten the signal strength jitter caused by atmospheric turbulence. A prototype of the proposed structure is fabricated and a 2.5 Mbit/s on-off keying(OOK) modulated demonstration link over 40 m free space is built. This asymmetric array structure can effectively collect optical signal while rotating in a window angle of ±17°, and the bit error ratio(BER) keeps zero.
文摘An approach to sequence planning for on-orbit assembly of large space truss structures in a multirobot environment is presented. A hierarchical representation of large space truss structures at the structural volume element level and strut level is adopted. The representation of connectivity matrix and directed graph is respectively presented at the strut level and SVE level. The multirobot environment that consists of autonomous space robots and struts is supposed. Then the multirobot serial assembly strategy,assembly states,assembly tasks and assembly sequences are described. The assembly sequence planning algorithms at the strut level and SVE level are respectively discussed. The results of the simulations show that this approach is feasible and efficient. Two extensions of this approach include more accurate assessment of the efficiency representation and improvements in planning algorithm. In the future,the assembly sequence planning of more large space truss structures and complex multirobot environments and assembly tasks will be considered.
文摘In this paper, we present a highly efficient structure determination pipeline software suite(X^2 DF) that is based on the "Parameter space screening" method, by combining the popular crystallographic structure determination programs and high-performance parallel computing. The phasing method employed in X^2 DF is based on the single-wavelength anomalous diffraction(SAD) theory. In the X^2 DF, the choice of crystallographic software, the input parameters to this software and the results display layout, are all parameters which users can select and screen automatically. Users may submit multiple structure determination jobs each time, and each job uses a slightly different set of input parameters or programs. Upon completion, the results of the calculation performed can be displayed, harvested, and analyzed by using the graphical user interface(GUI) of the system. We have applied the X^2 DF successfully to many cases including the cases that the structure solutions fail to be yielded by using manual approaches.
基金supported by National Natural Science Foundation of China(Grant No.52205413)National Key Research and Development Program(Grant No.2022YFB3806101)+1 种基金K C Wong Education FoundationThe Youth Innovation Team of Shaanxi Universities。
文摘In-space 3D printing is transforming the manufacturing paradigm of space structures from ground-based production to in-situ space manufacturing,effectively addressing the challenges of high costs,long response times,and structural size limitations associated with traditional rocket launches.This technology enables rapid on-orbit emergency repairs and significantly expands the geometric dimensions of space structures.High-performance polymers and their composites are widely used in in-space 3D printing,yet their implementation faces complex challenges posed by extreme space environmental conditions and limited energy or resources.This paper reviews the state-of-the-art in 3D printing of polymer and composites for on-orbit structure manufacturing.Based on existing research activities,the review focuses on three key aspects including the impact of extreme space environments on forming process and performance,innovative design and manufacturing methods for space structures,and on-orbit recycling and remanufacturing of raw materials.Some experiments that have already been conducted on-orbit and simulated experiments completed on the ground are systematically analyzed to provide a more comprehensive understanding of the constraints and objectives for on-orbit structure manufacturing.Furthermore,several perspectives requiring further research in future are proposed to facilitate the development of new in-space 3D printing technologies and space structures,thereby supporting increasingly advanced space exploration activities.
