The reduction of TE-scattering by a conducting cylinder with multiple surface impedance loads is investigated. Synthesis procedures are developed to find the optimal loading which result in zero scattering in the desi...The reduction of TE-scattering by a conducting cylinder with multiple surface impedance loads is investigated. Synthesis procedures are developed to find the optimal loading which result in zero scattering in the desired directions or at several frequencies. Numerical results of these procedures are presented. The theoretical predictions are confirmed with an experiment. The proposed synthesis procedure is completely general and can be applied to arbitrarily shaped conducting bodies.展开更多
With the increasing traffic demand, the closely built three or more tunnels with large section play a significant role in the tunnel construction. However, the interaction among tunnels has important influences on the...With the increasing traffic demand, the closely built three or more tunnels with large section play a significant role in the tunnel construction. However, the interaction among tunnels has important influences on the security and economy of tunnel engineering, and the calculation of pressure from the surrounding rock during the excavation is one of the problems that need to be solved urgently. Based on the practical engineering of three tunnels, the load model of three tunnels was proposed in consideration of the interaction and excavation sequence between tunnels. In comparison with the load model of single tunnel, the construction mechanical characteristics of the three tunnels were analyzed. The results show that the rock pressure of three tunnels calculated by the current tunnel design code is not reliable, and the interaction force increases with the spacing between tunnels.展开更多
The influence of enlarged section parameters on pressure transients of high-speed train passing through a tunnel was investigated by numerical simulation.The calculation results obtained by the structured and unstruct...The influence of enlarged section parameters on pressure transients of high-speed train passing through a tunnel was investigated by numerical simulation.The calculation results obtained by the structured and unstructured grid and the experimental results of smooth wall tunnel were verified.Numerical simulation studies were conducted on three tunnel enlarged section parameters,the enlarged section distribution along circumferential direction,the enlarged section area and the enlarged section distribution along tunnel length direction.The calculation results show that the influence of the different enlarged section distributions along tunnel circumferential direction on pressure transients in the tunnel is basically consistent.There is an optimal enlarged section area for the minimum value of the pressure variation amplitude and the average pressure variation in the tunnel.The law of the pressure variation amplitude and the average pressure variation of the enlarged section distribution along tunnel length direction are obtained.展开更多
The exact radar cross-section （RCS） measurement is difficult when the scattering of targets is low. Ful polarimetric cali-bration is one technique that offers the potential for improving the accuracy of RCS measurem...The exact radar cross-section （RCS） measurement is difficult when the scattering of targets is low. Ful polarimetric cali-bration is one technique that offers the potential for improving the accuracy of RCS measurements. There are numerous polarimetric calibration algorithms. Some complex expressions in these algo-rithms cannot be easily used in an engineering practice. A radar polarimetric coefficients matrix （RPCM） with a simpler expression is presented for the monostatic radar polarization scattering matrix （PSM） measurement. Using a rhombic dihedral corner reflector and a metal ic sphere, the RPCM can be obtained by solving a set of equations, which can be used to find the true PSM for any target. An example for the PSM of a metal ic dish shows that the proposed method obviously improves the accuracy of cross-polarized RCS measurements.展开更多
The stability control of surrounding rock for large or super-large section chamber is a difficult technical problem in deep mining condition.Based on the in-site geological conditions of Longgu coal mine,this paper us...The stability control of surrounding rock for large or super-large section chamber is a difficult technical problem in deep mining condition.Based on the in-site geological conditions of Longgu coal mine,this paper used the dynamic module of FLAC3D to study the response characteristics of deep super-large section chamber under dynamic and static combined loading condition.Results showed that under the static loading condition,the maximum vertical stress,deformation and failure range are large,where the stress concentration coefficient is 1.64.The maximum roof-to-floor and two-sides deformations are 54.6 mm and 53.1 mm,respectively.Then,under the dynamic and static combined loading condition:(1)The influence of dynamic load frequency on the two-sides is more obvious;(2)The dynamic load amplitude has the greatest influence on the stress concentration degree,and the plastic failure tends to develop to the deeper;(3)With the dynamic load source distance increase,the response of surrounding rock is gradually attenuated.On this basis,empirical equations for each dynamic load conditions were obtained by using regression analysis method,and all correlation coefficients are greater than 0.99.This research provided reference for the supporting design of deep super-large section chamber under same or similar conditions.展开更多
Based on the vehicle track coupling dynamics theory, a new spatial dynamic numerical model of vehicle track subgrade coupling system was established considering the interaction among different structural layers in the...Based on the vehicle track coupling dynamics theory, a new spatial dynamic numerical model of vehicle track subgrade coupling system was established considering the interaction among different structural layers in the subgrade system. The dynamic responses of the coupled system were analyzed when the speed of train was 350 km/h and the transition was filled with graded broken stones mixed with 5% cement. The results indicate that the setting form of bridge-approach embankment section has little effect on the dynamic responses, thus designers can choose it on account of the practical circumstances. Because the location about 5 m from the bridge abutment has the greatest deformation, the stiffness within 0 5 m zone behind the abutment should be specially designed. The results of the study from vehicle track dynamics show that the maximum allowable track deflection angle should be 0.09% and the coefficient of subgrade reaction(K30) is greater than 190 MPa within the 0 5 m zone behind the abutment and greater than 150 MPa in other zones.展开更多
The Qaidam Basin,located in the northern margin of the Qinghai-Tibet Plateau,is a large Mesozoic -Cenozoic basin,and bears huge thick Cenozoic strata.The geologic events of the Indian-Eurasian plate-plate collision si...The Qaidam Basin,located in the northern margin of the Qinghai-Tibet Plateau,is a large Mesozoic -Cenozoic basin,and bears huge thick Cenozoic strata.The geologic events of the Indian-Eurasian plate-plate collision since～55 Ma have been well recorded.Based on the latest progress in high-resolution stratigraphy,a technique of balanced section was applied to six pieces of northeast-southwest geologic seismic profiles in the central and eastern of the Qaidam Basin to reconstruct the crustal shortening deformation history during the Cenozoic collision. The results show that the Qaidam Basin began展开更多
Casting-cold extrusion technology was presented to fabricate alttminum/copper clad composite, and copper tubes with different sketch sections were designed. The technology of aluminum/copper clad composite fabricated ...Casting-cold extrusion technology was presented to fabricate alttminum/copper clad composite, and copper tubes with different sketch sections were designed. The technology of aluminum/copper clad composite fabricated by casting-cold extrusion was simulated by DEFORM software using tubes with four arc grooves. The stress and strain in different deformation zones were analyzed. The groove size reduces gradually and the groove shape drives to triangle during the extrusion procedure. The maximum values of equivalent effective stress and radial stress appear in groove zones, and the maximum equivalent effective strain firstly is obtained also in groove zones. The grain size in groove zones is less than that in other zones. The experimental results are consistent with simulation results, which prove that the copper tubes with sketch section are favorable to the metallurgy bond of boundary interface between aluminum and copper.展开更多
Based on transient temperature field theory of heat conduction, the solar temperature field calculation model of U-shape sectioned high-speed railway cable-stayed bridge under actions of concrete beams and ballast was...Based on transient temperature field theory of heat conduction, the solar temperature field calculation model of U-shape sectioned high-speed railway cable-stayed bridge under actions of concrete beams and ballast was established. Using parametric programming language, finite element calculation modules considering climate conditions, bridge site, structure dimension and material thermophysical properties were compiled. Six standard day cycles with the strongest yearly radiation among the bridge sites were selected for sectional solar temperature field calculation and temperature distributions under different temperature-sensitive parameters were compared. The results show that under the influence of sunshine, U-shape section of the beam shows obvious nonlinear distribution characteristics and the maximum cross-section temperature difference is more than 21℃; the ballast significantly reduces sunshine temperature difference of the beam and temperature peak of the bottom margin lags with the increase of ballast thickness; the maximum cross-section vertical temperature gradient appears in summer while large transverse temperature difference appears in winter.展开更多
A number of geological cross\|sections from the western Himalayan foothills are based on field,seismic reflection,and well data of the Oil & Natural Gas Corporation India.These cross\|sections have been described ...A number of geological cross\|sections from the western Himalayan foothills are based on field,seismic reflection,and well data of the Oil & Natural Gas Corporation India.These cross\|sections have been described by two contradictory interpretations.The first interpretation that depicts a prominent basal decollement above the pre\|Tertiary sequence is used for palinspastic reconstruction,using line length balancing,and determination of total shortening in the area.The second interpretation reveals a large variation in the thickness of individual stratigraphic horizons and a number of flower structures.These flower structures never cut the Himalayan thrusts but terminate below them.Away from the thrusts,the faults cut the younger Siwalik molasse (Middle Miocene—Pleistocene)and even reach to the surface as strike slip faults.Apart from the presence of strike slip faults,the other constraints for restoration of the section is oblique ramp structure at the Kangra Reentrant (or Punjab Reentrant).The oblique ramp was formed as a normal fault during the tensional regime in the region and later reactivated as thrust fault during the Tertiary Himalayan orogeny.These features reveal that the assumption of plane strain deformation is not valid for the region.Furthermore,the amount of extension during pre\|Tertiary rifting and layer parallel shortening during the Tertiary compressional phase is still unknown hence balancing of the sections is problematic.展开更多
Geological studies indicate that Qinghai\|Tibet plateau crust has shortened at least 2500km and the thickness was increased to 60～70km in the past 45Ma. Different researchers advocate different views to explain the s...Geological studies indicate that Qinghai\|Tibet plateau crust has shortened at least 2500km and the thickness was increased to 60～70km in the past 45Ma. Different researchers advocate different views to explain the shortening according to their studies.( Tapponnier,1977;Chang et al,1986;England et al,1986;Murphy,1997;Y.Pan,1999),however it is still unresolved on how much shortening in upper crustal especially in Qiangtang terrain.Qiangtang terrain is located in the center of Qinghai\|Tibet plateau, the tectonic deformation has been resulted from intracontinental convergence and collision of India plate with Eurasian plate.The deformation style of Qiangtang terrain shows east\|west\|trending folds and thrusts which formed in the shallow tectonic level during collisional\|intracontinental period. The folds type is characterized by nonpenetrative\|foliation parallel fold, the hinges have the same trend with the thrusts. These traits are favourable for restoring the balanced cross\|section and measuring the shortening. The balanced reconstruction is based on line balancing on three different stratigraphic sections (A,B and C)across the Northern Qiangtang basin in the area between 85°E and 87°E.The sections are all north\|south\|trending in accordance with the moving direction of thrusts.展开更多
Due to the variation of the blade cross-section, the deformation stress and strain of the workpiece keep changing during the rolling process and the conventional rolling theory is no longer valid. The complexity and d...Due to the variation of the blade cross-section, the deformation stress and strain of the workpiece keep changing during the rolling process and the conventional rolling theory is no longer valid. The complexity and diversity of the blade cross-section determine it impossible to establish an universal theoretical model for the rolling process. Finite element analysis(FEA) provides a perspective solution to the prediction. The FEA software DEFORM was applied to discovering the deformation, stress, strain and velocity field of the variable cross-section workpiece, and the effects of friction coefficient and rolling speed during the rolling process. which indicates that the average rolling force at friction coefficient of 0.4 is 6.5% higher than that at 0.12, and the rolling velocity has less effect on the equivalent stress and strain distribution, which would confer instructive significance on the theoretical study as well as the engineering practice.展开更多
In order to reduce the traffic pressure of urban arterial road with the rational utilization of the branch road,the vehicle meeting behavior on the branch road without divided lane was described,and the cellular autom...In order to reduce the traffic pressure of urban arterial road with the rational utilization of the branch road,the vehicle meeting behavior on the branch road without divided lane was described,and the cellular automation (CA) model was put forward by introducing meeting behavior to reflect the relation between safe meeting speed and road width.The numerical simulation results depict several relation curves between road section capacity,speed and road width under different directional distributions of traffic flow,as well as the curves between the major and minor direction saturation flow,speed and road width.These relation characteristics indicate that except the one-way road section capacity and speed remaining unchanged,other road section capacities and speeds under different directional distributions increase with the increase of road width.On narrow road,the two-way traffic capacity and speed are less than those of one-way traffic;on wide road,the two-way traffic capacity doubles that of one-way traffic,but their speeds are almost the same.As the directional distribution moves to an even distribution of 50/50,the major direction saturation flows and speeds as well as the minor direction speeds tend to decease,while the minor direction saturation flow tends to increase.展开更多
文摘The reduction of TE-scattering by a conducting cylinder with multiple surface impedance loads is investigated. Synthesis procedures are developed to find the optimal loading which result in zero scattering in the desired directions or at several frequencies. Numerical results of these procedures are presented. The theoretical predictions are confirmed with an experiment. The proposed synthesis procedure is completely general and can be applied to arbitrarily shaped conducting bodies.
基金Project(2011CB01380) supported by the National Basic Research Program of ChinaProject(51178468) supported by the National Natural Science Foundation of ChinaProject(2011G013-B) supported by Science and Technology Development of Railways Department in China
文摘With the increasing traffic demand, the closely built three or more tunnels with large section play a significant role in the tunnel construction. However, the interaction among tunnels has important influences on the security and economy of tunnel engineering, and the calculation of pressure from the surrounding rock during the excavation is one of the problems that need to be solved urgently. Based on the practical engineering of three tunnels, the load model of three tunnels was proposed in consideration of the interaction and excavation sequence between tunnels. In comparison with the load model of single tunnel, the construction mechanical characteristics of the three tunnels were analyzed. The results show that the rock pressure of three tunnels calculated by the current tunnel design code is not reliable, and the interaction force increases with the spacing between tunnels.
基金Project (2016YFB1200602-11) supported by National Key R&D Plan of China
文摘The influence of enlarged section parameters on pressure transients of high-speed train passing through a tunnel was investigated by numerical simulation.The calculation results obtained by the structured and unstructured grid and the experimental results of smooth wall tunnel were verified.Numerical simulation studies were conducted on three tunnel enlarged section parameters,the enlarged section distribution along circumferential direction,the enlarged section area and the enlarged section distribution along tunnel length direction.The calculation results show that the influence of the different enlarged section distributions along tunnel circumferential direction on pressure transients in the tunnel is basically consistent.There is an optimal enlarged section area for the minimum value of the pressure variation amplitude and the average pressure variation in the tunnel.The law of the pressure variation amplitude and the average pressure variation of the enlarged section distribution along tunnel length direction are obtained.
基金supported by the National Basic Research Program of China(973 Program)(2010CB731905)
文摘The exact radar cross-section （RCS） measurement is difficult when the scattering of targets is low. Ful polarimetric cali-bration is one technique that offers the potential for improving the accuracy of RCS measurements. There are numerous polarimetric calibration algorithms. Some complex expressions in these algo-rithms cannot be easily used in an engineering practice. A radar polarimetric coefficients matrix （RPCM） with a simpler expression is presented for the monostatic radar polarization scattering matrix （PSM） measurement. Using a rhombic dihedral corner reflector and a metal ic sphere, the RPCM can be obtained by solving a set of equations, which can be used to find the true PSM for any target. An example for the PSM of a metal ic dish shows that the proposed method obviously improves the accuracy of cross-polarized RCS measurements.
基金Project(2018YFC0604703)supported by the National Key R&D Program of ChinaProjects(51804181,51874190)supported by the National Natural Science Foundation of China+3 种基金Project(ZR2018QEE002)supported by the Shandong Province Natural Science Fund,ChinaProject(ZR2018ZA0603)supported by the Major Program of Shandong Province Natural Science Foundation,ChinaProject(2019GSF116003)supported by the Key R&D Project of Shandong Province,ChinaProject(SDKDYC190234)supported by the Shandong University of Science and Technology,Graduate Student Technology Innovation Project,China。
文摘The stability control of surrounding rock for large or super-large section chamber is a difficult technical problem in deep mining condition.Based on the in-site geological conditions of Longgu coal mine,this paper used the dynamic module of FLAC3D to study the response characteristics of deep super-large section chamber under dynamic and static combined loading condition.Results showed that under the static loading condition,the maximum vertical stress,deformation and failure range are large,where the stress concentration coefficient is 1.64.The maximum roof-to-floor and two-sides deformations are 54.6 mm and 53.1 mm,respectively.Then,under the dynamic and static combined loading condition:(1)The influence of dynamic load frequency on the two-sides is more obvious;(2)The dynamic load amplitude has the greatest influence on the stress concentration degree,and the plastic failure tends to develop to the deeper;(3)With the dynamic load source distance increase,the response of surrounding rock is gradually attenuated.On this basis,empirical equations for each dynamic load conditions were obtained by using regression analysis method,and all correlation coefficients are greater than 0.99.This research provided reference for the supporting design of deep super-large section chamber under same or similar conditions.
基金Project(41030742) supported by the National Natural Science Foundation of ChinaProject(2009G010-c) supported by the Technological Research and Development Programs of the Ministry of Railways,China
文摘Based on the vehicle track coupling dynamics theory, a new spatial dynamic numerical model of vehicle track subgrade coupling system was established considering the interaction among different structural layers in the subgrade system. The dynamic responses of the coupled system were analyzed when the speed of train was 350 km/h and the transition was filled with graded broken stones mixed with 5% cement. The results indicate that the setting form of bridge-approach embankment section has little effect on the dynamic responses, thus designers can choose it on account of the practical circumstances. Because the location about 5 m from the bridge abutment has the greatest deformation, the stiffness within 0 5 m zone behind the abutment should be specially designed. The results of the study from vehicle track dynamics show that the maximum allowable track deflection angle should be 0.09% and the coefficient of subgrade reaction(K30) is greater than 190 MPa within the 0 5 m zone behind the abutment and greater than 150 MPa in other zones.
文摘The Qaidam Basin,located in the northern margin of the Qinghai-Tibet Plateau,is a large Mesozoic -Cenozoic basin,and bears huge thick Cenozoic strata.The geologic events of the Indian-Eurasian plate-plate collision since～55 Ma have been well recorded.Based on the latest progress in high-resolution stratigraphy,a technique of balanced section was applied to six pieces of northeast-southwest geologic seismic profiles in the central and eastern of the Qaidam Basin to reconstruct the crustal shortening deformation history during the Cenozoic collision. The results show that the Qaidam Basin began
文摘Casting-cold extrusion technology was presented to fabricate alttminum/copper clad composite, and copper tubes with different sketch sections were designed. The technology of aluminum/copper clad composite fabricated by casting-cold extrusion was simulated by DEFORM software using tubes with four arc grooves. The stress and strain in different deformation zones were analyzed. The groove size reduces gradually and the groove shape drives to triangle during the extrusion procedure. The maximum values of equivalent effective stress and radial stress appear in groove zones, and the maximum equivalent effective strain firstly is obtained also in groove zones. The grain size in groove zones is less than that in other zones. The experimental results are consistent with simulation results, which prove that the copper tubes with sketch section are favorable to the metallurgy bond of boundary interface between aluminum and copper.
基金Project(51378503)supported by the National Natural Science Foundation of ChinaProject(2010G018-A-3)supported by Technology Research and Development Program of the Ministry of Railways,China
文摘Based on transient temperature field theory of heat conduction, the solar temperature field calculation model of U-shape sectioned high-speed railway cable-stayed bridge under actions of concrete beams and ballast was established. Using parametric programming language, finite element calculation modules considering climate conditions, bridge site, structure dimension and material thermophysical properties were compiled. Six standard day cycles with the strongest yearly radiation among the bridge sites were selected for sectional solar temperature field calculation and temperature distributions under different temperature-sensitive parameters were compared. The results show that under the influence of sunshine, U-shape section of the beam shows obvious nonlinear distribution characteristics and the maximum cross-section temperature difference is more than 21℃; the ballast significantly reduces sunshine temperature difference of the beam and temperature peak of the bottom margin lags with the increase of ballast thickness; the maximum cross-section vertical temperature gradient appears in summer while large transverse temperature difference appears in winter.
文摘A number of geological cross\|sections from the western Himalayan foothills are based on field,seismic reflection,and well data of the Oil & Natural Gas Corporation India.These cross\|sections have been described by two contradictory interpretations.The first interpretation that depicts a prominent basal decollement above the pre\|Tertiary sequence is used for palinspastic reconstruction,using line length balancing,and determination of total shortening in the area.The second interpretation reveals a large variation in the thickness of individual stratigraphic horizons and a number of flower structures.These flower structures never cut the Himalayan thrusts but terminate below them.Away from the thrusts,the faults cut the younger Siwalik molasse (Middle Miocene—Pleistocene)and even reach to the surface as strike slip faults.Apart from the presence of strike slip faults,the other constraints for restoration of the section is oblique ramp structure at the Kangra Reentrant (or Punjab Reentrant).The oblique ramp was formed as a normal fault during the tensional regime in the region and later reactivated as thrust fault during the Tertiary Himalayan orogeny.These features reveal that the assumption of plane strain deformation is not valid for the region.Furthermore,the amount of extension during pre\|Tertiary rifting and layer parallel shortening during the Tertiary compressional phase is still unknown hence balancing of the sections is problematic.
文摘Geological studies indicate that Qinghai\|Tibet plateau crust has shortened at least 2500km and the thickness was increased to 60～70km in the past 45Ma. Different researchers advocate different views to explain the shortening according to their studies.( Tapponnier,1977;Chang et al,1986;England et al,1986;Murphy,1997;Y.Pan,1999),however it is still unresolved on how much shortening in upper crustal especially in Qiangtang terrain.Qiangtang terrain is located in the center of Qinghai\|Tibet plateau, the tectonic deformation has been resulted from intracontinental convergence and collision of India plate with Eurasian plate.The deformation style of Qiangtang terrain shows east\|west\|trending folds and thrusts which formed in the shallow tectonic level during collisional\|intracontinental period. The folds type is characterized by nonpenetrative\|foliation parallel fold, the hinges have the same trend with the thrusts. These traits are favourable for restoring the balanced cross\|section and measuring the shortening. The balanced reconstruction is based on line balancing on three different stratigraphic sections (A,B and C)across the Northern Qiangtang basin in the area between 85°E and 87°E.The sections are all north\|south\|trending in accordance with the moving direction of thrusts.
基金Project(F12-256-1-00)supported by the Key Laboratory Program of Shenyang City,ChinaProject(N090403006)supported by the Seed Cultivation Fund,ChinaProject supported by the Research Innovation Fund for Young Teachers,China
文摘Due to the variation of the blade cross-section, the deformation stress and strain of the workpiece keep changing during the rolling process and the conventional rolling theory is no longer valid. The complexity and diversity of the blade cross-section determine it impossible to establish an universal theoretical model for the rolling process. Finite element analysis(FEA) provides a perspective solution to the prediction. The FEA software DEFORM was applied to discovering the deformation, stress, strain and velocity field of the variable cross-section workpiece, and the effects of friction coefficient and rolling speed during the rolling process. which indicates that the average rolling force at friction coefficient of 0.4 is 6.5% higher than that at 0.12, and the rolling velocity has less effect on the equivalent stress and strain distribution, which would confer instructive significance on the theoretical study as well as the engineering practice.
基金Project(71171200) supported by the National Natural Science Foundation of China
文摘In order to reduce the traffic pressure of urban arterial road with the rational utilization of the branch road,the vehicle meeting behavior on the branch road without divided lane was described,and the cellular automation (CA) model was put forward by introducing meeting behavior to reflect the relation between safe meeting speed and road width.The numerical simulation results depict several relation curves between road section capacity,speed and road width under different directional distributions of traffic flow,as well as the curves between the major and minor direction saturation flow,speed and road width.These relation characteristics indicate that except the one-way road section capacity and speed remaining unchanged,other road section capacities and speeds under different directional distributions increase with the increase of road width.On narrow road,the two-way traffic capacity and speed are less than those of one-way traffic;on wide road,the two-way traffic capacity doubles that of one-way traffic,but their speeds are almost the same.As the directional distribution moves to an even distribution of 50/50,the major direction saturation flows and speeds as well as the minor direction speeds tend to decease,while the minor direction saturation flow tends to increase.
