Partition of unity based numerical manifold method can solve continuous and discontinuous problems in a unified framework with a two-cover system,i.e.,the mathematical cover and physical cover.However,renewal of the t...Partition of unity based numerical manifold method can solve continuous and discontinuous problems in a unified framework with a two-cover system,i.e.,the mathematical cover and physical cover.However,renewal of the topology of the two-cover system poses a challenge for multiple crack propagation problems and there are few references.In this study,a robust and efficient strategy is proposed to update the cover system of the numerical manifold method in simulation of multiple crack propagation problems.The proposed algorithm updates the cover system with a bottom-up process:1)identification of fractured manifold elements according to the previous and latest crack tip position;and 2)local topological update of the manifold elements,physical patches,block boundary loops,and non-persistent joint loops according to the scenario classification of the propagating crack.The proposed crack tracking strategy and classification of the renewal cases promote a robust and efficient cover renewal algorithm for multiple crack propagation analysis.Three crack propagation examples show that the proposed algorithm performs well in updating the cover system.This cover renewal methodology can be extended for numerical manifold method with polygonal mathematical covers.展开更多
To achieve durability of the embankment in southern China,a method to control the change of moisture content with the cushion and cover was proposed.A finite element model of cushion and cover considering different ma...To achieve durability of the embankment in southern China,a method to control the change of moisture content with the cushion and cover was proposed.A finite element model of cushion and cover considering different materials and thicknesses for a typical embankment was built,and 20 numerical analyses of transient seepage in the embankment were simulated.The results show that the sand cushion effectively blocks the effect of groundwater capillary rise and the minimum thickness of the sand cushion is 75 cm without considering the atmospheric environment.With the combination of sand cushion and clay cover,as the thickness of the clay cover increases,the duration time of the moisture content from the initial to relative equilibrium state increases,but the equilibrium moisture content is the same as that of the original embankment.Besides,with the combination of the sand cushion and sand cover,the moisture content inside the embankment remains the same,which is consistent with the optimum moisture content during construction.The combination of 75 cm sand cushion and 30 cm sand cover is a very effective method to block groundwater and atmospheric environment,and achieve the control of the humidity stability of the embankment in southern China.展开更多
In view of that existing opening technologies of front cover for rocket launch canister have disadvantages such as causing damage on the ground equipment,not being reused and easily broken.A novel reusable non-separat...In view of that existing opening technologies of front cover for rocket launch canister have disadvantages such as causing damage on the ground equipment,not being reused and easily broken.A novel reusable non-separation spring-driven opening scheme is proposed to achieve rapid and reliable opening of the front cover.The mathematical model of the opening process of the front cover is established by the rigid body dynamics theory.To establish a response surface model to optimize the opening scheme,three main influencing factors of the opening process are obtained through the designed experiments,including the pre-compression,the stiffness of the thrust spring,and the thrust spring force arm length.In addition,the prescribed kinematic law was taken as constraint,and the smaller thrust spring preliminary pressure and angular velocity was taken as optimization expectations.The results show that the opening scheme meets the design requirements on opening process well.It also shows that the optimized scheme can reduce the kinetic energy of the front cover,and the impact on the canister effectively,achieving a reliable and rapid opening of the front cover.展开更多
A novel algorithm named randomized binary gravita- tional search （RBGS） algorithm is proposed for the set covering problem （SCP）. It differs from previous SCP approaches because it does not work directly on the SC...A novel algorithm named randomized binary gravita- tional search （RBGS） algorithm is proposed for the set covering problem （SCP）. It differs from previous SCP approaches because it does not work directly on the SCP matrix. In the proposed algo- rithm, the solution of SCP is viewed as multi-dimension position of objects in the binary search space. All objects in the space attract each other by the gravity force, and this force causes a global movement of all objects towards the objects with heavier masses which correspond to good solutions. Computation results show that the proposed algorithm is very competitive. In addition, the proposed aigodthm is extended for SCP to solve the fault diagno- sis problem in graph-based systems.展开更多
The field spectroradiometer was used to measure spectra of different snow and snow-covered land surface objects in Beijing area.The result showed that for a pure snow spectrum,the snow reflectance peaks appeared from ...The field spectroradiometer was used to measure spectra of different snow and snow-covered land surface objects in Beijing area.The result showed that for a pure snow spectrum,the snow reflectance peaks appeared from visible to 800 nm band locations;there was an obvious absorption valley of snow spectrum near 1 030 nm wavelength.Compared with fresh snow,the reflection peaks of the old snow and melting snow showed different degrees of decline in the ranges of 300～1 300,1 700～1 800 and 2 200～2 300 nm,the lowest was from the compacted snow and frozen ice.For the vegetation and snow mixed spectral characteristics,it was indicated that the spectral reflectance increased for the snow-covered land types(including pine leaf with snow and pine leaf on snow background), due to the influence of snow background in the range of 350～1 300 nm.However, the spectrum reflectance of mixed pixel remained a vegetation spectral characteristic.In the end,based on the spectrum analysis of snow,vegetation,and mixed snow/vegetation pixels,the mixed spectral fitting equations were established,and the results showed that there was good correlation between spectral curves by simulation fitting and observed ones(correlation coefficient R2=0.950 9).展开更多
The Barekese reservoir provides 80 percent of the total public pipe borne water to the Kumasi metropolis and its environs.However,over the past two decades, the Barekese river basin has seen persistent degradation thr...The Barekese reservoir provides 80 percent of the total public pipe borne water to the Kumasi metropolis and its environs.However,over the past two decades, the Barekese river basin has seen persistent degradation through anthropogenic activities along its catchment area which also raises concern on the deteriorating water quality.The study examines展开更多
Grouting pile is a new soft soil foundation treatment method with characteristics such as no vibration, no noise, no soil compaction, light construction machines and quick construction velocity and so on. At present, ...Grouting pile is a new soft soil foundation treatment method with characteristics such as no vibration, no noise, no soil compaction, light construction machines and quick construction velocity and so on. At present, study on reinforcement mechanism and design calculation method of composite foundation of grouting pile is initially started without design specifications, so it is usually required to draw on design specifications of stump pile when designing composite foundation of grouting pile while grouting pile has its characteristics and difference although reinforcement mechanisms and construction processes of two types of piles are similar. Sedimentation formula of composite foundation of grouting pile with cover plate is educed and a suitable deformation mode is proposed by aiming to deformation characteristics of composite foundation of grouting pile with cover plate under embankment load on basis of relevant sedimentation theories of composite foundation by combination of characteristics of composite foundation of grouting pile. The sedimentation calculation formula of grouting pile with cover plate under embankment load is educed according to balance relation of force and displacement coordination conditions by elastic theory and sedimentation calculation model established is validated by sedimentation monitoring documents of one expressway in China.展开更多
The Covered Karst, which formed in subsoil environment and distributed in the Tibet Plateau and its eastern district, denuded on the ground surface in different degrees (forming stone pinnacles), but they had the good...The Covered Karst, which formed in subsoil environment and distributed in the Tibet Plateau and its eastern district, denuded on the ground surface in different degrees (forming stone pinnacles), but they had the good consistency in their characteristics. First, some kind of landform, such as stone pinnacles, rock well etc, kept the slippery rock surface. It was believed that they were resulted from the process in soil. Nearer the foot of rock the site was; more clear and integrated the form was. Second, the covered karst often associated with red weathering crust. Based on the character of the red weathering crust of the summit plane of Anduo Mountain, its forming environment was relatively humid and hot. Third, the best geomorphologic position, where the karst was bare, was not on the summit plane but on the slope.The baring degrees and later reworked characteristics of the covered karst made up of an integrated series. They could be divided into three kinds of districts according to their response to the Plateau uplift. (1) The western district, where the uplift was intensive, was mainly Tibet Plateau. For example, in Anduo Mountain, the covered karst was entirely denuded on the ground surface, and the rock surface was turned into mottled rock well because the frost weathering intensively reworked it. The red weathering crust was only kept in the bottom of rock, most of which was observed in the crack of limestone. The present karst process on the ground surface stopped. (2) The middle district, where the uplift degree was moderate, was mainly Yungui Plateau. The covered karst was partly denuded to form the stone pinnacles. Its part, which is baring, is changed to be aciculate and sharp\|pointed, and is active now. (3) The eastern district, where the uplift was weak, was mainly the northern part of Guangxi Province and the southern part of Hunan Province. The covered karst was entirely covered by soil and only observed in the section, which was excavated by human. The form of the covered karst generally had the typical character of the process below the soil.展开更多
Thirty one cases of the achalasia underwent myotomywith omentum covering and cardio-valvoplasty from 1983to 1988 at our hospital. Follow-up study, one to 4 yearspostoperatively, showed that 29 cases (93.5%) of themwit...Thirty one cases of the achalasia underwent myotomywith omentum covering and cardio-valvoplasty from 1983to 1988 at our hospital. Follow-up study, one to 4 yearspostoperatively, showed that 29 cases (93.5%) of themwith excellent results, only 2 cases(6.5%)showed slightdysphagia. The advantages of this procedure are as fol-lows: 1. relief of obstruction at lower end of esophagusand cardia preventing the recurrence of stenosis; 2. pre-vention of occurence of reflux esophagitis; 3. no altera-tion of normal anatomy of the esophagocardia region andno intervention of mucosa; 4. simplicity and safety ofthis procedure.展开更多
The cover image presents the inverse opal photonic crystals for photocatalytic hydrogen production.In article No.1803014,ZHANG et al.demonstrated that the CdS inverse opals with hierarchical porous structures could la...The cover image presents the inverse opal photonic crystals for photocatalytic hydrogen production.In article No.1803014,ZHANG et al.demonstrated that the CdS inverse opals with hierarchical porous structures could largely enhance the hydrogen production via multiple scattering and reflection of the induced mimic solar light.展开更多
This paper presents a new hybrid genetic algorithm for the vertex cover problems in which scan-repair and local improvement techniques are used for local optimization. With the hybrid approach, genetic algorithms are ...This paper presents a new hybrid genetic algorithm for the vertex cover problems in which scan-repair and local improvement techniques are used for local optimization. With the hybrid approach, genetic algorithms are used to perform global exploration in a population, while neighborhood search methods are used to perform local exploitation around the chromosomes. The experimental results indicate that hybrid genetic algorithms can obtain solutions of excellent quality to the problem instances with different sizes. The pure genetic algorithms are outperformed by the neighborhood search heuristics procedures combined with genetic algorithms.展开更多
This paper proposes a novel pair of induced IF covering approximation operators in an IF covering approximation space,and discusses some basic properties about definable IFSs.A measure is defined to describe the uncer...This paper proposes a novel pair of induced IF covering approximation operators in an IF covering approximation space,and discusses some basic properties about definable IFSs.A measure is defined to describe the uncertainty of IFSs in IF covering approximation spaces.Finally,we study the properties of reductions of an IF covering respectively based on induced IF covering approximation operators and IF covering approximation operators.展开更多
基金Project(51321065,51479191,11672360)supported by the National Natural Science Foundation of China。
文摘Partition of unity based numerical manifold method can solve continuous and discontinuous problems in a unified framework with a two-cover system,i.e.,the mathematical cover and physical cover.However,renewal of the topology of the two-cover system poses a challenge for multiple crack propagation problems and there are few references.In this study,a robust and efficient strategy is proposed to update the cover system of the numerical manifold method in simulation of multiple crack propagation problems.The proposed algorithm updates the cover system with a bottom-up process:1)identification of fractured manifold elements according to the previous and latest crack tip position;and 2)local topological update of the manifold elements,physical patches,block boundary loops,and non-persistent joint loops according to the scenario classification of the propagating crack.The proposed crack tracking strategy and classification of the renewal cases promote a robust and efficient cover renewal algorithm for multiple crack propagation analysis.Three crack propagation examples show that the proposed algorithm performs well in updating the cover system.This cover renewal methodology can be extended for numerical manifold method with polygonal mathematical covers.
基金Project(2017YFC0805307)supported by the National Key Research and Development Program of ChinaProjects(51838001,51878070,51878078,51911530215,51927814)supported by the National Natural Science Foundation of China+5 种基金Project(2018JJ1026)supported by the Excellent Youth Foundation of Natural Science Foundation of Hunan Province,ChinaProject(17A008)supported by the Key Project of Education Department of Hunan Province,ChinaProjects(kfj150103,kfj170106)supported by the Changsha University of Science&Technology via Key Project of Open Research Fund of National Engineering Laboratory of Highway Maintenance Technology,ChinaProject(kfj170404)supported by the Open Fund of Engineering Research Center of Catastrophic Prophylaxis and Treatment of Road and Traffic Safety of Ministry of Education(Changsha University of Science&Technology),ChinaProject(CX2018B527)supported by the Hunan Provincial Innovation Foundation for Postgraduate,ChinaProject(2018-025)supported by the Training Program for High-level Technical Personnel in Transportation Industry,China。
文摘To achieve durability of the embankment in southern China,a method to control the change of moisture content with the cushion and cover was proposed.A finite element model of cushion and cover considering different materials and thicknesses for a typical embankment was built,and 20 numerical analyses of transient seepage in the embankment were simulated.The results show that the sand cushion effectively blocks the effect of groundwater capillary rise and the minimum thickness of the sand cushion is 75 cm without considering the atmospheric environment.With the combination of sand cushion and clay cover,as the thickness of the clay cover increases,the duration time of the moisture content from the initial to relative equilibrium state increases,but the equilibrium moisture content is the same as that of the original embankment.Besides,with the combination of the sand cushion and sand cover,the moisture content inside the embankment remains the same,which is consistent with the optimum moisture content during construction.The combination of 75 cm sand cushion and 30 cm sand cover is a very effective method to block groundwater and atmospheric environment,and achieve the control of the humidity stability of the embankment in southern China.
文摘In view of that existing opening technologies of front cover for rocket launch canister have disadvantages such as causing damage on the ground equipment,not being reused and easily broken.A novel reusable non-separation spring-driven opening scheme is proposed to achieve rapid and reliable opening of the front cover.The mathematical model of the opening process of the front cover is established by the rigid body dynamics theory.To establish a response surface model to optimize the opening scheme,three main influencing factors of the opening process are obtained through the designed experiments,including the pre-compression,the stiffness of the thrust spring,and the thrust spring force arm length.In addition,the prescribed kinematic law was taken as constraint,and the smaller thrust spring preliminary pressure and angular velocity was taken as optimization expectations.The results show that the opening scheme meets the design requirements on opening process well.It also shows that the optimized scheme can reduce the kinetic energy of the front cover,and the impact on the canister effectively,achieving a reliable and rapid opening of the front cover.
基金supported by the National Natural Science Foundation of China (4100605850909096)
文摘A novel algorithm named randomized binary gravita- tional search （RBGS） algorithm is proposed for the set covering problem （SCP）. It differs from previous SCP approaches because it does not work directly on the SCP matrix. In the proposed algo- rithm, the solution of SCP is viewed as multi-dimension position of objects in the binary search space. All objects in the space attract each other by the gravity force, and this force causes a global movement of all objects towards the objects with heavier masses which correspond to good solutions. Computation results show that the proposed algorithm is very competitive. In addition, the proposed aigodthm is extended for SCP to solve the fault diagno- sis problem in graph-based systems.
基金National Natural Science Foundation of China(40771147)Global Change Research Projects of Key National Scientific Research Plan(2010CB951302)the Social Commonweal Meteorological Research Project(GYHY201106027)
文摘The field spectroradiometer was used to measure spectra of different snow and snow-covered land surface objects in Beijing area.The result showed that for a pure snow spectrum,the snow reflectance peaks appeared from visible to 800 nm band locations;there was an obvious absorption valley of snow spectrum near 1 030 nm wavelength.Compared with fresh snow,the reflection peaks of the old snow and melting snow showed different degrees of decline in the ranges of 300～1 300,1 700～1 800 and 2 200～2 300 nm,the lowest was from the compacted snow and frozen ice.For the vegetation and snow mixed spectral characteristics,it was indicated that the spectral reflectance increased for the snow-covered land types(including pine leaf with snow and pine leaf on snow background), due to the influence of snow background in the range of 350～1 300 nm.However, the spectrum reflectance of mixed pixel remained a vegetation spectral characteristic.In the end,based on the spectrum analysis of snow,vegetation,and mixed snow/vegetation pixels,the mixed spectral fitting equations were established,and the results showed that there was good correlation between spectral curves by simulation fitting and observed ones(correlation coefficient R2=0.950 9).
文摘The Barekese reservoir provides 80 percent of the total public pipe borne water to the Kumasi metropolis and its environs.However,over the past two decades, the Barekese river basin has seen persistent degradation through anthropogenic activities along its catchment area which also raises concern on the deteriorating water quality.The study examines
文摘Grouting pile is a new soft soil foundation treatment method with characteristics such as no vibration, no noise, no soil compaction, light construction machines and quick construction velocity and so on. At present, study on reinforcement mechanism and design calculation method of composite foundation of grouting pile is initially started without design specifications, so it is usually required to draw on design specifications of stump pile when designing composite foundation of grouting pile while grouting pile has its characteristics and difference although reinforcement mechanisms and construction processes of two types of piles are similar. Sedimentation formula of composite foundation of grouting pile with cover plate is educed and a suitable deformation mode is proposed by aiming to deformation characteristics of composite foundation of grouting pile with cover plate under embankment load on basis of relevant sedimentation theories of composite foundation by combination of characteristics of composite foundation of grouting pile. The sedimentation calculation formula of grouting pile with cover plate under embankment load is educed according to balance relation of force and displacement coordination conditions by elastic theory and sedimentation calculation model established is validated by sedimentation monitoring documents of one expressway in China.
文摘The Covered Karst, which formed in subsoil environment and distributed in the Tibet Plateau and its eastern district, denuded on the ground surface in different degrees (forming stone pinnacles), but they had the good consistency in their characteristics. First, some kind of landform, such as stone pinnacles, rock well etc, kept the slippery rock surface. It was believed that they were resulted from the process in soil. Nearer the foot of rock the site was; more clear and integrated the form was. Second, the covered karst often associated with red weathering crust. Based on the character of the red weathering crust of the summit plane of Anduo Mountain, its forming environment was relatively humid and hot. Third, the best geomorphologic position, where the karst was bare, was not on the summit plane but on the slope.The baring degrees and later reworked characteristics of the covered karst made up of an integrated series. They could be divided into three kinds of districts according to their response to the Plateau uplift. (1) The western district, where the uplift was intensive, was mainly Tibet Plateau. For example, in Anduo Mountain, the covered karst was entirely denuded on the ground surface, and the rock surface was turned into mottled rock well because the frost weathering intensively reworked it. The red weathering crust was only kept in the bottom of rock, most of which was observed in the crack of limestone. The present karst process on the ground surface stopped. (2) The middle district, where the uplift degree was moderate, was mainly Yungui Plateau. The covered karst was partly denuded to form the stone pinnacles. Its part, which is baring, is changed to be aciculate and sharp\|pointed, and is active now. (3) The eastern district, where the uplift was weak, was mainly the northern part of Guangxi Province and the southern part of Hunan Province. The covered karst was entirely covered by soil and only observed in the section, which was excavated by human. The form of the covered karst generally had the typical character of the process below the soil.
文摘Thirty one cases of the achalasia underwent myotomywith omentum covering and cardio-valvoplasty from 1983to 1988 at our hospital. Follow-up study, one to 4 yearspostoperatively, showed that 29 cases (93.5%) of themwith excellent results, only 2 cases(6.5%)showed slightdysphagia. The advantages of this procedure are as fol-lows: 1. relief of obstruction at lower end of esophagusand cardia preventing the recurrence of stenosis; 2. pre-vention of occurence of reflux esophagitis; 3. no altera-tion of normal anatomy of the esophagocardia region andno intervention of mucosa; 4. simplicity and safety ofthis procedure.
文摘The cover image presents the inverse opal photonic crystals for photocatalytic hydrogen production.In article No.1803014,ZHANG et al.demonstrated that the CdS inverse opals with hierarchical porous structures could largely enhance the hydrogen production via multiple scattering and reflection of the induced mimic solar light.
基金This project was supported by the National Natural Science Foundation of China the Open Project Foundation of Comput-er Software New Technique National Key Laboratory of Nanjing University.
文摘This paper presents a new hybrid genetic algorithm for the vertex cover problems in which scan-repair and local improvement techniques are used for local optimization. With the hybrid approach, genetic algorithms are used to perform global exploration in a population, while neighborhood search methods are used to perform local exploitation around the chromosomes. The experimental results indicate that hybrid genetic algorithms can obtain solutions of excellent quality to the problem instances with different sizes. The pure genetic algorithms are outperformed by the neighborhood search heuristics procedures combined with genetic algorithms.
基金supported by the National Natural Science Foundation of China(Nos.60773174 and 60963006)Hebei Province Science and Technology Research and Development Program(No.09276158).
文摘This paper proposes a novel pair of induced IF covering approximation operators in an IF covering approximation space,and discusses some basic properties about definable IFSs.A measure is defined to describe the uncertainty of IFSs in IF covering approximation spaces.Finally,we study the properties of reductions of an IF covering respectively based on induced IF covering approximation operators and IF covering approximation operators.
