The ^(12)C+^(12)C fusion is one of the most important reactions in modern nuclear astrophysics.The trend and magnitude of the reaction rate within the Gamow window strongly influence various astrophysical processes.Ho...The ^(12)C+^(12)C fusion is one of the most important reactions in modern nuclear astrophysics.The trend and magnitude of the reaction rate within the Gamow window strongly influence various astrophysical processes.However,direct measurement of this reaction is extremely difficult,which makes it necessary to develop indirect methods.In this study,the ^(23)Na+p reaction system was used to study the compound nucleus ^(24)Mg.We employed a thick-target inverse kinematics method combined with theγ-charged-particle coincidence technique to measure the proton andα exit channels of ^(24)Mg.Technical details of the ^(23)Na+p thick-target inverse kinematics experiment and analysis are presented herein.展开更多
Due to the diversity of work requirements and environment,the number of degrees of freedom(DOFs)and the complexity of structure of industrial robots are constantly increasing.It is difficult to establish the accurate ...Due to the diversity of work requirements and environment,the number of degrees of freedom(DOFs)and the complexity of structure of industrial robots are constantly increasing.It is difficult to establish the accurate dynamical model of industrial robots,which greatly hinders the realization of a stable,fast and accurate trajectory tracking control.Therefore,the general expression of the constraint relation in the explicit dynamic equation of the multi-DOF industrial robot is derived on the basis of solving the Jacobian matrix and Hessian matrix by using the kinematic influence coefficients method.Moreover,an explicit dynamic equation with general constraint relation expression is established based on the Udwadia-Kalaba theory.The problem of increasing the time of establishing constraint relationship when the multi-DOF industrial robots complete complex task constraints is solved.With the SCARA robot as the research object,the simulation results show that the proposed method can provide a new idea for industrial robot system modeling with complex constraints.展开更多
First the kinematic principle of singularity is proved, that is theintersecting point of three normal planes of three velocities at three non-collinear points in arigid body lying in the plane determined by the three ...First the kinematic principle of singularity is proved, that is theintersecting point of three normal planes of three velocities at three non-collinear points in arigid body lying in the plane determined by the three corresponding points. It is a sufficient andnecessary condition that the velocities of three non-collinear points in a rigid body can determinea screw motion of the body. Based on this principle, a simple and direct new method to distinguishthe singularity of the parallel manipulator is derived. With this new kinematic method, the 3-RPSparallel manipulator is studied. Its singularity loci are obtained for some orientations for thefirst time and verified with Grassmann line geometry and screw theory and the force Jacobian matrix.展开更多
A rigorous back analysis of shear strength parameters of landslide slip was presented. Kinematical element method was adopted to determine factor of safety and critical failure surface, which overcomes the disadvantag...A rigorous back analysis of shear strength parameters of landslide slip was presented. Kinematical element method was adopted to determine factor of safety and critical failure surface, which overcomes the disadvantage of limit equilibrium method. The theoretical relationship between the combination of shear strength parameters and stability state was studied. The results show that the location of critical slip surface, F/tan f and F/c depend only on the value of c/tan f. The failure surface moves towards the inside of slope as c/tan f increases. According to the information involving factor of safety and critical failure surface in a specific cross-section, strength parameters can be back calculated based on the above findings. Three examples were given for demonstrating the validity of the present method. The shear strength parameters obtained by back analysis are almost consistent with their correct solutions or test results.展开更多
The HY-2 satellite carrying a satellite-borne GPS receiver is the first Chinese radar altimeter satellite, whose radial orbit determination precision must reach the centimeter level. Now HY-2 is in the test phase so t...The HY-2 satellite carrying a satellite-borne GPS receiver is the first Chinese radar altimeter satellite, whose radial orbit determination precision must reach the centimeter level. Now HY-2 is in the test phase so that the observations are not openly released. In order to study the precise orbit determination precision and procedure for HY-2 based on the satellite- borne GPS technique, the satellite-borne GPS data are simulated in this paper. The HY-2 satellite-borne GPS antenna can receive at least seven GPS satellites each epoch, which can validate the GPS receiver and antenna design. What＇s more, the precise orbit determination processing flow is given and precise orbit determination experiments are conducted using the HY-2-borne GPS data with both the reduced-dynamic method and the kinematic geometry method. With the 1 and 3 mm phase data random errors, the radial orbit determination precision can achieve the centimeter level using these two methods and the kinematic orbit accuracy is slightly lower than that of the reduced-dynamic orbit. The earth gravity field model is an important factor which seriously affects the precise orbit determination of altimeter satellites. The reduced-dynamic orbit determination experiments are made with different earth gravity field models, such as EIGEN2, EGM96, TEG4, and GEMT3. Using a large number of high precision satellite-bome GPS data, the HY-2 precise orbit determination can reach the centimeter level with commonly used earth gravity field models up to above 50 degrees and orders.展开更多
A CFD-based Numerical Virtual Flight(NVF)simulator is presented,which integrates an unsteady flow solver on moving hybrid grids,a Rigid-Body Dynamics(RBD)solver and a module of the Flight Control System(FCS).A techni...A CFD-based Numerical Virtual Flight(NVF)simulator is presented,which integrates an unsteady flow solver on moving hybrid grids,a Rigid-Body Dynamics(RBD)solver and a module of the Flight Control System(FCS).A technique of dynamic hybrid grids is developed to control the active control surfaces with body morphing,with a technique of parallel unstructured dynamic overlapping grids generating proper moving grids over the deflecting control surfaces(e.g.the afterbody rudders of a missile).For the flow/kinematic coupled problems,the 6 Degree-Of-Freedom(DOF)equations are solved by an explicit or implicit method coupled with the URANS CFD solver.The module of the control law is explicitly coupled into the NVF simulator and then improved by the simulation of the pitching maneuver process of a maneuverable missile model.A nonlinear dynamic inversion method is then implemented to design the control law for the pitching process of the maneuverable missile model.Simulations and analysis of the pitching maneuver process are carried out by the NVF simulator to improve the flight control law.Higher control response performance is obtained by adjusting the gain factors and adding an integrator into the control loop.展开更多
Faster response to orientation varying is one of the outstanding abilities of a parallel kinematic machine（PKM）.It enables such a system to act as a reconfgurable module employed to machine large components effcient...Faster response to orientation varying is one of the outstanding abilities of a parallel kinematic machine（PKM）.It enables such a system to act as a reconfgurable module employed to machine large components effciently.The stiffness formulation and analysis are the beforehand key tasks for its parameters design.A novel PKM with four degrees of freedom（DOFs）is proposed in this paper.The topology behind it is 2PUS-2PRS parallel mechanism.Its semianalytical stiffness model is frstly obtained,where the generalized Jacobian matrix of 2PUS-2PRS is formulated with the help of the screw theory and the stiffness coeffcients of complicated components are estimated by integrating fnite element analysis and numerical ftting.Under the help of the model,it is predicted that the property of system stiffness distributes within the given workspace,which features symmetry about a certain plane and is also verifed by performing fnite element analysis of the virtual prototype.Furthermore,key parameters affecting the system stiffness are identifed through sensitivity analysis.These provide insights for further optimization design of this PKM.展开更多
This article discusses the physical and kinematical characteristics of planetary nebulae accompanying PG 1159 central stars.The study is based on the parallax and proper motion measurements recently offered by the Gai...This article discusses the physical and kinematical characteristics of planetary nebulae accompanying PG 1159 central stars.The study is based on the parallax and proper motion measurements recently offered by the Gaia space mission.Two approaches were used to investigate the kinematical properties of the sample.The results revealed that most of the studied nebulae arise from progenitor stars in the mass range 0.9-1.75 M⊙.Furthermore,they tend to live within the Galactic thick disk and move with an average peculiar velocity of 61.7±19.2 km s^(-1) at a mean vertical height of 469±79 pc.The locations of the PG 1159 stars on the H-R diagram indicate that they have an average final stellar mass and evolutionary age of 0.58±0.08 M⊙and 25.5±5.3×103 yr,respectively.We found a good agreement between the mean evolutionary age of the PG 1159 stars and the mean dynamical age of their companion planetary nebulae(28.0±6.4×103 yr).展开更多
We present an efficient, robust computational method for modeling the Newtonian dynamics for rotation curve analysis of thin-disk galaxies. With appropriate mathematical treatments, the apparent numerical difficulties...We present an efficient, robust computational method for modeling the Newtonian dynamics for rotation curve analysis of thin-disk galaxies. With appropriate mathematical treatments, the apparent numerical difficulties associated with singularities in computing elliptic integrals are completely removed. Using a boundary element discretization procedure, the governing equations are transformed into a linear algebra matrix equation that can be solved by straightforward Gauss elimination in one step without further iterations. The numerical code implemented according to our algorithm can accurately determine the surface mass density distribution in a disk galaxy from a measured rotation curve （or vice versa）. For a disk galaxy with a typical flat rotation curve, our modeling results show that the surface mass density monotonically decreases from the galactic center toward the periphery, according to Newtonian dynamics. In a large portion of the galaxy, the surface mass density follows an approximately exponential law of decay with respect to the galactic radial coordinate. Yet the radial scale length for the surface mass density seems to be generally larger than that of the measured brightness distribution, suggesting an increasing mass-tolight ratio with the radial distance in a disk galaxy. In a nondimensionalized form, our mathematical system contains a dimensionless parameter which we call the ＂galactic rotation number＂ that represents the gross ratio of centrifugal force and gravitational force. The value of this galactic rotation number is determined as part of the numerial solution. Through a systematic computational analysis, we have illustrated that the galactic rotation number remains within 4-10% of 1.70 for a wide variety of rotation curves. This implies that the total mass in a disk galaxy is proportional to V02 Rg, with V0 denoting the characteristic rotation velocity （such as the ＂flat＂ value in a typical ro- tation curve） and Rg the radius of the galactic disk. The predicted total galactic mass of the Milky Way is in good agreement with the star-count data.展开更多
This paper presents multicolor optical photometry of the nearby galaxy cluster Abell 119 （z = 0.0442） with the Beijing-Arizona-Taiwan-Connecticut system of 15 intermediate bands. Within the BATC field of view of 58...This paper presents multicolor optical photometry of the nearby galaxy cluster Abell 119 （z = 0.0442） with the Beijing-Arizona-Taiwan-Connecticut system of 15 intermediate bands. Within the BATC field of view of 58＇× 58＇, there are 368 galaxies with known spectroscopic redshifts, including 238 member galaxies （called sample I）. Based on the spectral energy distributions of 1376 galaxies brighter than iBATC ---- 19.5, the photometric redshift technique and the color-magnitude relation of early-type galaxies are applied to select faint member galaxies. As a result, 117 faint galaxies were selected as new member galaxies. Combined with sample I, an enlarged sample （called sample II） of 355 member galaxies is obtained. Spatial distribution and localized velocity structure for two samples demonstrate that A119 is a dynami- cally complex cluster with at least three prominent substructures in the central region within 1 Mpc. A large velocity dispersion for the central clump indicates a merging along the line of sight. No significant evidence for morphology or luminosity segrega- tions is found in either sample. With the PEGASE evolutionary synthesis model, the environmental effect on the properties of star formation is confirmed. Faint galaxies in the low-density region tend to have longer time scales of star formation, smaller mean stellar ages, and lower metallicities in their interstellar medium, which is in agreement with the context of the hierarchical cosmological scenario.展开更多
We enhance the Syer ＆ Tremaine made-to-measure （M2M） particle method of stellar dynamical modelling to model simultaneously both kinematic data and absorption line strength data, thus creating a ＇chemo-M2M＇ model...We enhance the Syer ＆ Tremaine made-to-measure （M2M） particle method of stellar dynamical modelling to model simultaneously both kinematic data and absorption line strength data, thus creating a ＇chemo-M2M＇ modelling scheme. We apply the enhanced method to four galaxies （NGC 1248, NGC 3838, NGC 4452, NGC 4551） observed using the SAURON integral-field spectrograph as part of the ATLAS3D programme. We are able to reproduce successfully the 2D line strength data achieving mean X2 per bin values of ≈ 1 with 〉 95% of particles having converged weights. Because M2M uses a 3D particle system, we are also able to examine the underlying 3D line strength distributions. The extent to which these dis- tributions are plausible representations of real galaxies requires further consideration. Overall, we consider the modelling exercise to be a promising first step in developing a ＇chemo-M2M＇ modelling system and in understanding some of the issues to be addressed. While the made-to-measure techniques developed have been applied to absorption line strength data, they are in fact general and may be of value in modelling other aspects of galaxies.展开更多
Pavement horizontal curve is designed to serve as a transition between straight segments, and its presence may cause a series of driving-related safety issues to motorists and drivers. As is recognized that traditiona...Pavement horizontal curve is designed to serve as a transition between straight segments, and its presence may cause a series of driving-related safety issues to motorists and drivers. As is recognized that traditional methods for curve geometry investigation are time consuming, labor intensive, and inaccurate, this study attempts to develop a method that can automatically conduct horizontal curve identification and measurement at network level. The digital highway data vehicle （DHDV） was utilized for data collection, in which three Euler angles, driving speed, and acceleration of survey vehicle were measured with an inertial measurement unit （IMU）. The 3D profiling data used for cross slope calibration was obtained with PaveVision3D Ultra technology at 1 mm resolution. In this study, the curve identification was based on the variation of heading angle, and the curve radius was calculated with ki- nematic method, geometry method, and lateral acceleration method. In order to verify the accuracy of the three methods, the analysis of variance （ANOVA） test was applied by using the control variable of curve radius measured by field test. Based on the measured curve radius, a curve safety analysis model was used to predict the crash rates and safe driving speeds at horizontal curves. Finally, a case study on 4.35 km road segment demonstrated that the proposed method could efficiently conduct network level analysis.展开更多
基金supported by the National Key Research and Development Project (No. 2022YFA1602301)the National Natural Science Foundation of China (Nos. U2267205, 12275361, 12125509, 12222514, 11961141003, and 12005304)+2 种基金the CAST Young Talent Support Planthe CNNC Science Fund for Talented Young Scholarsthe Continuous-Support Basic Scientific Research Project
文摘The ^(12)C+^(12)C fusion is one of the most important reactions in modern nuclear astrophysics.The trend and magnitude of the reaction rate within the Gamow window strongly influence various astrophysical processes.However,direct measurement of this reaction is extremely difficult,which makes it necessary to develop indirect methods.In this study,the ^(23)Na+p reaction system was used to study the compound nucleus ^(24)Mg.We employed a thick-target inverse kinematics method combined with theγ-charged-particle coincidence technique to measure the proton andα exit channels of ^(24)Mg.Technical details of the ^(23)Na+p thick-target inverse kinematics experiment and analysis are presented herein.
基金the Beijing Municipal Scienceand Technology Project (No.KM202111417006)the Academic Research Projects of Beijing Union University (Nos.ZK10202305 and ZK80202004)the Beijing Municipal Science and Technology Project (No.KM202111417005)。
文摘Due to the diversity of work requirements and environment,the number of degrees of freedom(DOFs)and the complexity of structure of industrial robots are constantly increasing.It is difficult to establish the accurate dynamical model of industrial robots,which greatly hinders the realization of a stable,fast and accurate trajectory tracking control.Therefore,the general expression of the constraint relation in the explicit dynamic equation of the multi-DOF industrial robot is derived on the basis of solving the Jacobian matrix and Hessian matrix by using the kinematic influence coefficients method.Moreover,an explicit dynamic equation with general constraint relation expression is established based on the Udwadia-Kalaba theory.The problem of increasing the time of establishing constraint relationship when the multi-DOF industrial robots complete complex task constraints is solved.With the SCARA robot as the research object,the simulation results show that the proposed method can provide a new idea for industrial robot system modeling with complex constraints.
基金This project is supported by National Natural Science Foundation of China (No.50275129).
文摘First the kinematic principle of singularity is proved, that is theintersecting point of three normal planes of three velocities at three non-collinear points in arigid body lying in the plane determined by the three corresponding points. It is a sufficient andnecessary condition that the velocities of three non-collinear points in a rigid body can determinea screw motion of the body. Based on this principle, a simple and direct new method to distinguishthe singularity of the parallel manipulator is derived. With this new kinematic method, the 3-RPSparallel manipulator is studied. Its singularity loci are obtained for some orientations for thefirst time and verified with Grassmann line geometry and screw theory and the force Jacobian matrix.
基金Project(51174228)supported by the National Natural Science Foundation of ChinaProject(CX2012B069)supported by Hunan Provincial Innovation Foundation for PostgraduateProject(201003)supported by Transportation Science and Technology Projects of Hunan Province,China
文摘A rigorous back analysis of shear strength parameters of landslide slip was presented. Kinematical element method was adopted to determine factor of safety and critical failure surface, which overcomes the disadvantage of limit equilibrium method. The theoretical relationship between the combination of shear strength parameters and stability state was studied. The results show that the location of critical slip surface, F/tan f and F/c depend only on the value of c/tan f. The failure surface moves towards the inside of slope as c/tan f increases. According to the information involving factor of safety and critical failure surface in a specific cross-section, strength parameters can be back calculated based on the above findings. Three examples were given for demonstrating the validity of the present method. The shear strength parameters obtained by back analysis are almost consistent with their correct solutions or test results.
基金supported partially by the National Natural Science Foundation of China (Nos. 40974004 and 40974016)Key Laboratory of Dynamic Geodesy of CAS, China (No. L09-01) R&I Team Support Program and the Graduate Science and Technology Foundation of SDUST, China (No. YCA110403)
文摘The HY-2 satellite carrying a satellite-borne GPS receiver is the first Chinese radar altimeter satellite, whose radial orbit determination precision must reach the centimeter level. Now HY-2 is in the test phase so that the observations are not openly released. In order to study the precise orbit determination precision and procedure for HY-2 based on the satellite- borne GPS technique, the satellite-borne GPS data are simulated in this paper. The HY-2 satellite-borne GPS antenna can receive at least seven GPS satellites each epoch, which can validate the GPS receiver and antenna design. What＇s more, the precise orbit determination processing flow is given and precise orbit determination experiments are conducted using the HY-2-borne GPS data with both the reduced-dynamic method and the kinematic geometry method. With the 1 and 3 mm phase data random errors, the radial orbit determination precision can achieve the centimeter level using these two methods and the kinematic orbit accuracy is slightly lower than that of the reduced-dynamic orbit. The earth gravity field model is an important factor which seriously affects the precise orbit determination of altimeter satellites. The reduced-dynamic orbit determination experiments are made with different earth gravity field models, such as EIGEN2, EGM96, TEG4, and GEMT3. Using a large number of high precision satellite-bome GPS data, the HY-2 precise orbit determination can reach the centimeter level with commonly used earth gravity field models up to above 50 degrees and orders.
基金supported by The Shaanxi Province Industrial Research Projects(2012K10-10)2015GY068 project categories:Industrial Technology Research of Shaanxi Province project name:The key technology research on coal sampling manipulator full face high speed sampling
基金supported partially by National Key Research and Development Program (No. 2016YFB0200701)National Natural Science Foundation of China (Nos. 11532016 and 11672324)
文摘A CFD-based Numerical Virtual Flight(NVF)simulator is presented,which integrates an unsteady flow solver on moving hybrid grids,a Rigid-Body Dynamics(RBD)solver and a module of the Flight Control System(FCS).A technique of dynamic hybrid grids is developed to control the active control surfaces with body morphing,with a technique of parallel unstructured dynamic overlapping grids generating proper moving grids over the deflecting control surfaces(e.g.the afterbody rudders of a missile).For the flow/kinematic coupled problems,the 6 Degree-Of-Freedom(DOF)equations are solved by an explicit or implicit method coupled with the URANS CFD solver.The module of the control law is explicitly coupled into the NVF simulator and then improved by the simulation of the pitching maneuver process of a maneuverable missile model.A nonlinear dynamic inversion method is then implemented to design the control law for the pitching process of the maneuverable missile model.Simulations and analysis of the pitching maneuver process are carried out by the NVF simulator to improve the flight control law.Higher control response performance is obtained by adjusting the gain factors and adding an integrator into the control loop.
基金supported by the National Natural Science Foundation of China (Nos.51075295 and 51005164)Tianjin Research Program of Application Foundation and Advanced Technology (No.11JCYBJC05600)
文摘Faster response to orientation varying is one of the outstanding abilities of a parallel kinematic machine（PKM）.It enables such a system to act as a reconfgurable module employed to machine large components effciently.The stiffness formulation and analysis are the beforehand key tasks for its parameters design.A novel PKM with four degrees of freedom（DOFs）is proposed in this paper.The topology behind it is 2PUS-2PRS parallel mechanism.Its semianalytical stiffness model is frstly obtained,where the generalized Jacobian matrix of 2PUS-2PRS is formulated with the help of the screw theory and the stiffness coeffcients of complicated components are estimated by integrating fnite element analysis and numerical ftting.Under the help of the model,it is predicted that the property of system stiffness distributes within the given workspace,which features symmetry about a certain plane and is also verifed by performing fnite element analysis of the virtual prototype.Furthermore,key parameters affecting the system stiffness are identifed through sensitivity analysis.These provide insights for further optimization design of this PKM.
文摘This article discusses the physical and kinematical characteristics of planetary nebulae accompanying PG 1159 central stars.The study is based on the parallax and proper motion measurements recently offered by the Gaia space mission.Two approaches were used to investigate the kinematical properties of the sample.The results revealed that most of the studied nebulae arise from progenitor stars in the mass range 0.9-1.75 M⊙.Furthermore,they tend to live within the Galactic thick disk and move with an average peculiar velocity of 61.7±19.2 km s^(-1) at a mean vertical height of 469±79 pc.The locations of the PG 1159 stars on the H-R diagram indicate that they have an average final stellar mass and evolutionary age of 0.58±0.08 M⊙and 25.5±5.3×103 yr,respectively.We found a good agreement between the mean evolutionary age of the PG 1159 stars and the mean dynamical age of their companion planetary nebulae(28.0±6.4×103 yr).
文摘We present an efficient, robust computational method for modeling the Newtonian dynamics for rotation curve analysis of thin-disk galaxies. With appropriate mathematical treatments, the apparent numerical difficulties associated with singularities in computing elliptic integrals are completely removed. Using a boundary element discretization procedure, the governing equations are transformed into a linear algebra matrix equation that can be solved by straightforward Gauss elimination in one step without further iterations. The numerical code implemented according to our algorithm can accurately determine the surface mass density distribution in a disk galaxy from a measured rotation curve （or vice versa）. For a disk galaxy with a typical flat rotation curve, our modeling results show that the surface mass density monotonically decreases from the galactic center toward the periphery, according to Newtonian dynamics. In a large portion of the galaxy, the surface mass density follows an approximately exponential law of decay with respect to the galactic radial coordinate. Yet the radial scale length for the surface mass density seems to be generally larger than that of the measured brightness distribution, suggesting an increasing mass-tolight ratio with the radial distance in a disk galaxy. In a nondimensionalized form, our mathematical system contains a dimensionless parameter which we call the ＂galactic rotation number＂ that represents the gross ratio of centrifugal force and gravitational force. The value of this galactic rotation number is determined as part of the numerial solution. Through a systematic computational analysis, we have illustrated that the galactic rotation number remains within 4-10% of 1.70 for a wide variety of rotation curves. This implies that the total mass in a disk galaxy is proportional to V02 Rg, with V0 denoting the characteristic rotation velocity （such as the ＂flat＂ value in a typical ro- tation curve） and Rg the radius of the galactic disk. The predicted total galactic mass of the Milky Way is in good agreement with the star-count data.
基金funded by the National Natural Science Foundation of China (Grant Nos. 11173016, 10873016, 11073032, 11003021 and 10803007)the National Basic Research Program of China (973 Program Grant No. 2007CB815403)
文摘This paper presents multicolor optical photometry of the nearby galaxy cluster Abell 119 （z = 0.0442） with the Beijing-Arizona-Taiwan-Connecticut system of 15 intermediate bands. Within the BATC field of view of 58＇× 58＇, there are 368 galaxies with known spectroscopic redshifts, including 238 member galaxies （called sample I）. Based on the spectral energy distributions of 1376 galaxies brighter than iBATC ---- 19.5, the photometric redshift technique and the color-magnitude relation of early-type galaxies are applied to select faint member galaxies. As a result, 117 faint galaxies were selected as new member galaxies. Combined with sample I, an enlarged sample （called sample II） of 355 member galaxies is obtained. Spatial distribution and localized velocity structure for two samples demonstrate that A119 is a dynami- cally complex cluster with at least three prominent substructures in the central region within 1 Mpc. A large velocity dispersion for the central clump indicates a merging along the line of sight. No significant evidence for morphology or luminosity segrega- tions is found in either sample. With the PEGASE evolutionary synthesis model, the environmental effect on the properties of star formation is confirmed. Faint galaxies in the low-density region tend to have longer time scales of star formation, smaller mean stellar ages, and lower metallicities in their interstellar medium, which is in agreement with the context of the hierarchical cosmological scenario.
基金supported by the Strategic Priority Research Program“The Emergence of Cosmological Structures”of the Chinese Academy of Sciences(Grant No.XDB09000000)by the National Natural Science Foundation of China(NSFC,Grant Nos.11333003 and 11390372).
文摘We enhance the Syer ＆ Tremaine made-to-measure （M2M） particle method of stellar dynamical modelling to model simultaneously both kinematic data and absorption line strength data, thus creating a ＇chemo-M2M＇ modelling scheme. We apply the enhanced method to four galaxies （NGC 1248, NGC 3838, NGC 4452, NGC 4551） observed using the SAURON integral-field spectrograph as part of the ATLAS3D programme. We are able to reproduce successfully the 2D line strength data achieving mean X2 per bin values of ≈ 1 with 〉 95% of particles having converged weights. Because M2M uses a 3D particle system, we are also able to examine the underlying 3D line strength distributions. The extent to which these dis- tributions are plausible representations of real galaxies requires further consideration. Overall, we consider the modelling exercise to be a promising first step in developing a ＇chemo-M2M＇ modelling system and in understanding some of the issues to be addressed. While the made-to-measure techniques developed have been applied to absorption line strength data, they are in fact general and may be of value in modelling other aspects of galaxies.
文摘Pavement horizontal curve is designed to serve as a transition between straight segments, and its presence may cause a series of driving-related safety issues to motorists and drivers. As is recognized that traditional methods for curve geometry investigation are time consuming, labor intensive, and inaccurate, this study attempts to develop a method that can automatically conduct horizontal curve identification and measurement at network level. The digital highway data vehicle （DHDV） was utilized for data collection, in which three Euler angles, driving speed, and acceleration of survey vehicle were measured with an inertial measurement unit （IMU）. The 3D profiling data used for cross slope calibration was obtained with PaveVision3D Ultra technology at 1 mm resolution. In this study, the curve identification was based on the variation of heading angle, and the curve radius was calculated with ki- nematic method, geometry method, and lateral acceleration method. In order to verify the accuracy of the three methods, the analysis of variance （ANOVA） test was applied by using the control variable of curve radius measured by field test. Based on the measured curve radius, a curve safety analysis model was used to predict the crash rates and safe driving speeds at horizontal curves. Finally, a case study on 4.35 km road segment demonstrated that the proposed method could efficiently conduct network level analysis.
