In order to predict the long-term rutting of asphalt pavement, the effective temperature for pavement rutting is calculated using the numerical simulation method. The transient temperature field of asphalt pavement wa...In order to predict the long-term rutting of asphalt pavement, the effective temperature for pavement rutting is calculated using the numerical simulation method. The transient temperature field of asphalt pavement was simulated based on actual meteorological data of Nanjing. 24-hour rutting development under a transient temperature field was calculated in each month. The rutting depth accumulated under the static temperature field was also estimated and the relationship between constant temperature parameters was analyzed. Then the effective temperature for pavement rutting was determined based on the rutting equivalence principle. The results show that the monthly effective temperature is above 40 t in July and August, while in June and September it ranges from 30 to 40 Rutting development can be ignored when the monthly effective temperature is less than 30 t. The yearly effective temperature for rutting in Nanjing is around 38. 5 t. The long-term rutting prediction model based on the effective temperature can reflect the influences of meteorological factors and traffic time distribution.展开更多
Based on the equivalence principle of deflection and stress, the concentrated vehicle load which acts on the center of continuously reinforced concrete pavement (CRCP) is translated into the equivalent half-wave sin...Based on the equivalence principle of deflection and stress, the concentrated vehicle load which acts on the center of continuously reinforced concrete pavement (CRCP) is translated into the equivalent half-wave sine load by the Fourier transform. On the basis of this transform and the small deflection theory of elastic thin plates, the deflection and stress formulae of CRCP under the concentrated vehicle load with a hollow foundation are put forward. The sensitivity of parameters is analyzed. The results show that maximum deflection is directly proportional to the concentrated vehicle load and the slab width, and inversely proportional to the lateral bending stiffness and slab thickness. The effects of slab width and thickness are significant with regard to maximum deflection. Maximum stress is directly proportional to the concentrated vehicle load and the slab width as well as inversely proportional to slab thickness. The effect of slab thickness is significant with regard to maximum stress. According to the calculation results, the most effective measure to reduce maximum deflection and stress is to increase slab thickness.展开更多
In order to solve the no-wait flowshop scheduling problem to minimize the maximum lateness,three job-block-based neighborhoods are proposed,among which the block exchange neighborhood have a size of O(n4)while the b...In order to solve the no-wait flowshop scheduling problem to minimize the maximum lateness,three job-block-based neighborhoods are proposed,among which the block exchange neighborhood have a size of O(n4)while the block swap and the simplified block exchange neighborhoods have a size of O(n3).With larger sizes than the existing neighborhoods,the proposed neighborhoods can enhance the solution quality of local search algorithms.Speedup properties for the neighborhoods are developed,which can evaluate a neighbor in constant time and explore the neighborhoods in time proportional to their proposed sizes. Unlike the dominance-rule-based speedup method,the proposed speedups are applicable to any machine number.Three neighborhoods and the union of block swap and the simplified block exchange neighborhoods are compared in the tabu search.Computational results on benchmark instances show that three tabu search algorithms with O(n3)neighborhoods outperform the existing algorithms and the tabu search algorithm with the union has the best performance among all the tested algorithms.展开更多
Datong-Qinhuangdao line, as the first electrified double-track heavy-haul line dedicated to coal transport in China, extends from Datong in the west, and reaches Qinhuangdao in the east, opened to traffic in December,...Datong-Qinhuangdao line, as the first electrified double-track heavy-haul line dedicated to coal transport in China, extends from Datong in the west, and reaches Qinhuangdao in the east, opened to traffic in December, 1992, totaling 653 km with the designed annual traffic volume of 1×108 t. In order to meet the demands of national economic development, the transport capacity of the line must be enhanced greatly. Depending on independent innovation, MOR, for the first time in the world,realizes the integration between GSM-R and Locotrol, the integration between 800 MHz digital radio and Locotrol, and the integration between a single set of Locotrol and SS4 locomotive. Meanwhile, CR develops equipment portfolio for heavy-haul through combining 2 high power locomotives of HXD series (means harmony) with controllable EOT. Relying on integration and innovation, it succeeds in operating 20 kt-level combined heavy-haul train on Datong-Qinhuangdao line, which tripled the annual traffic volume of the line from 1×108 t in 2002 to 3×108 t in 2007.展开更多
An electrical equivalent circuit model for lithium-ion batteries used for hybrid electric vehicles (HEV) is presented. The model has two RC networks characterizing battery activation and concentration polarization p...An electrical equivalent circuit model for lithium-ion batteries used for hybrid electric vehicles (HEV) is presented. The model has two RC networks characterizing battery activation and concentration polarization process. The parameters of the model are identified using combined experimental and extended Kalman filter (EKF) recursive methods. The open-circuit voltage and ohmic resistance of the battery are directly measured and calculated from experimental measurements, respectively. The rest of the coupled dynamic parameters, i.e. the RC network parameters, are estimated using the EKF method. Experimental and simulation results are presented to demonstrate the efficacy of the proposed circuit model and parameter identification techniques for simulating battery dynamics.展开更多
This work deals with super-harmonic responses and the stabilities of a gear transmission system of a high-speed train under the stick-slip oscillation of the wheel-set.The dynamic model of the system is developed with...This work deals with super-harmonic responses and the stabilities of a gear transmission system of a high-speed train under the stick-slip oscillation of the wheel-set.The dynamic model of the system is developed with consideration on the factors including the time-varying system stiffness,the transmission error,the tooth backlash and the self-excited excitation of the wheel-set.The frequency-response equation of the system at super-harmonic resonance is obtained by the multiple scales method,and the stabilities of the system are analyzed using the perturbation theory.Complex nonlinear behaviors of the system including multi-valued solutions,jump phenomenon,hardening stiffness are found.The effects of the equivalent damping and the loads of the system under the stick-slip oscillation are analyzed.It shows that the change of the load can obviously influence the resonance frequency of the system and have little effect on the steady-state response amplitude of the system.The damping of the system has a negative effect,opposite to the load.The synthetic damping of the system composed of meshing damping and equivalent damping may be less than zero when the wheel-set has a large slippage,and the system loses its stability owing to the Hopf bifurcation.Analytical results are validated by numerical simulations.展开更多
Rather than parking at nearby hourly parking lots, many passenger-picking-up vehicles prefer to idle at terminals and/or drive cycling around terminal facilities. As a result, extra vehicle emissions may be produced i...Rather than parking at nearby hourly parking lots, many passenger-picking-up vehicles prefer to idle at terminals and/or drive cycling around terminal facilities. As a result, extra vehicle emissions may be produced in an airport area. Even though there are limited studies on such emissions at airports, these estimations were normally based on the date emission models, which might cause bias in emission estimations. This paper proposes an approach to employ the floating car method and Global Positioning System (GPS) to record speeds and acceleration rates of idling and cycling vehicles at airport terminals. The tests were conducted under different time periods and traffic demands with different waiting time. The speeds and acceleration rates are synthesized to yield Vehicle Specific Power's (VSP) and Operational Mode (OM) distributions. Utilizing the Environmental Protection Agency (EPA) emission estimation model Motor Vehicle Emission Simulator (MOVES), pollutants and green house gas emission indexes (e.g. NOx, CO, CO2 and HC) and fuel consumptions can be easily estimated. As an illustration of the proposed approach, the research team collected GPS data at a terminal in Houston William Hobby Airport (HOU), and calculated the VSP distributions and OM distributions. Emissions of passenger-picking-up vehicles around these congested airport terminals.展开更多
Duralumin alloys have been utilized as structural components and parts for aircrafts, train-cars and so forth. Their high specific strength was attractive to those applications; however, their little corrosion resista...Duralumin alloys have been utilized as structural components and parts for aircrafts, train-cars and so forth. Their high specific strength was attractive to those applications; however, their little corrosion resistance and low wear endurance became a fatal demerit in practical applications. In order to overcome these issues of high strength aluminum alloys, high density plasma nitriding is proposed as an effective surface treatment for duralumin. This process has a capability to control the RF- and DC-plasmas independently for nitriding. This enables us to temporally control and describe the plasma state by in-situ plasma diagnosis. This plasma diagnosis was instrumented to search for optimum processing condition to plasma nitriding the duralumin alloys of type A2011. Both type A2011 aluminum alloy plates and pipes were employed to describe the inner nitriding behavior for hardening the duralumin alloys by the present plasma nitriding.展开更多
Vibration behaviors of bogie hunting motion contain key information that dominates the dynamic performance of rail vehicles,in which the eigenvalue of each mode reflects the damping ratio and the natural frequency.Thi...Vibration behaviors of bogie hunting motion contain key information that dominates the dynamic performance of rail vehicles,in which the eigenvalue of each mode reflects the damping ratio and the natural frequency.This paper focuses on the root loci curves of bogie hunting motion,starting from a rigid bogie,then to a bogie with flexible primary suspension.With regard to the rigid bogie,analytical formulas for the eigenvalues,the critical speed as well as the corresponding hunting frequency are derived and verified.While for the flexible bogie,the root loci curves are calculated numerically.The study shows that both free rigid bogie and free wheelset are dynamically unstable at any speed.The critical speed increases with diminished wheel-rail conicity,track gauge,and wheelset and bogie inertia,and with increased wheelbase and wheel radius.The dominating factors such as the stiffness of the primary suspension and the wheel-rail conicity should be optimized for a practical design.The influences of the damping coefficients and the variations of creep coefficients are negligible.The motor suspension affects the root loci curves and the critical speed significantly.Both inappropriate motor suspension design and rigidly suspended motor reduce the critical speed.The increase of critical speed by a motor suspension can only be achieved when the lower natural frequency of the motor-bogie frame-wheelsets system coincides with or is close to the hunting frequency.Special care should be taken for the design of motor suspension,the first is to avoid the decreased damping ratio in a certain speed range below the critical speed and the second is that the variations of parameters should not induce the rapid reduction of the critical speed.The main feature of the present study is that the root loci curves,which are derived as analytical formulas or calculated numerically,are used to study the vibrational behaviors of bogie hunting motion.Both the influencing laws of the dominating parameters and the principles regarding the motor suspension are significant for the stability design of modem railway vehicles which may use innovative structures/materials as well as modem control and monitoring technologies.展开更多
Aiming to enhance the luminescence yield of carbon nanotubes, we introduce a new class of hybrid nanoplasmonic colloidal systems (π-hybrids). Nanotubes dispersed in gold nanorod colloidal suspensions yield hybrid s...Aiming to enhance the luminescence yield of carbon nanotubes, we introduce a new class of hybrid nanoplasmonic colloidal systems (π-hybrids). Nanotubes dispersed in gold nanorod colloidal suspensions yield hybrid structures exhibiting enhanced luminescence up to a factor of 20. The novelty of the proposed enhancement mechanism relies on including metal proximity effects in addition to its localized surface plasmons. This simple, robust and flexible technique enhances the luminescence of nanotubes with chiralities whose enhancement has never reported before, for example the (8,4) tube.展开更多
基金The National Natural Science Foundation of China(No.51378121)the Fok Ying Tung Education Foundation(No.141076)the Scientific Innovation Research of College Graduates in Jiangsu Province(No.KYLX_0164)
文摘In order to predict the long-term rutting of asphalt pavement, the effective temperature for pavement rutting is calculated using the numerical simulation method. The transient temperature field of asphalt pavement was simulated based on actual meteorological data of Nanjing. 24-hour rutting development under a transient temperature field was calculated in each month. The rutting depth accumulated under the static temperature field was also estimated and the relationship between constant temperature parameters was analyzed. Then the effective temperature for pavement rutting was determined based on the rutting equivalence principle. The results show that the monthly effective temperature is above 40 t in July and August, while in June and September it ranges from 30 to 40 Rutting development can be ignored when the monthly effective temperature is less than 30 t. The yearly effective temperature for rutting in Nanjing is around 38. 5 t. The long-term rutting prediction model based on the effective temperature can reflect the influences of meteorological factors and traffic time distribution.
基金The Science Foundation of Ministry of Transport of the People's Republic of China(No.200731822301-7)
文摘Based on the equivalence principle of deflection and stress, the concentrated vehicle load which acts on the center of continuously reinforced concrete pavement (CRCP) is translated into the equivalent half-wave sine load by the Fourier transform. On the basis of this transform and the small deflection theory of elastic thin plates, the deflection and stress formulae of CRCP under the concentrated vehicle load with a hollow foundation are put forward. The sensitivity of parameters is analyzed. The results show that maximum deflection is directly proportional to the concentrated vehicle load and the slab width, and inversely proportional to the lateral bending stiffness and slab thickness. The effects of slab width and thickness are significant with regard to maximum deflection. Maximum stress is directly proportional to the concentrated vehicle load and the slab width as well as inversely proportional to slab thickness. The effect of slab thickness is significant with regard to maximum stress. According to the calculation results, the most effective measure to reduce maximum deflection and stress is to increase slab thickness.
基金The National Natural Science Foundation of China(No.60672092,60504029,60873236)the National High Technology Researchand Development Program of China(863 Program)(No.2008AA04Z103)
文摘In order to solve the no-wait flowshop scheduling problem to minimize the maximum lateness,three job-block-based neighborhoods are proposed,among which the block exchange neighborhood have a size of O(n4)while the block swap and the simplified block exchange neighborhoods have a size of O(n3).With larger sizes than the existing neighborhoods,the proposed neighborhoods can enhance the solution quality of local search algorithms.Speedup properties for the neighborhoods are developed,which can evaluate a neighbor in constant time and explore the neighborhoods in time proportional to their proposed sizes. Unlike the dominance-rule-based speedup method,the proposed speedups are applicable to any machine number.Three neighborhoods and the union of block swap and the simplified block exchange neighborhoods are compared in the tabu search.Computational results on benchmark instances show that three tabu search algorithms with O(n3)neighborhoods outperform the existing algorithms and the tabu search algorithm with the union has the best performance among all the tested algorithms.
文摘Datong-Qinhuangdao line, as the first electrified double-track heavy-haul line dedicated to coal transport in China, extends from Datong in the west, and reaches Qinhuangdao in the east, opened to traffic in December, 1992, totaling 653 km with the designed annual traffic volume of 1×108 t. In order to meet the demands of national economic development, the transport capacity of the line must be enhanced greatly. Depending on independent innovation, MOR, for the first time in the world,realizes the integration between GSM-R and Locotrol, the integration between 800 MHz digital radio and Locotrol, and the integration between a single set of Locotrol and SS4 locomotive. Meanwhile, CR develops equipment portfolio for heavy-haul through combining 2 high power locomotives of HXD series (means harmony) with controllable EOT. Relying on integration and innovation, it succeeds in operating 20 kt-level combined heavy-haul train on Datong-Qinhuangdao line, which tripled the annual traffic volume of the line from 1×108 t in 2002 to 3×108 t in 2007.
文摘An electrical equivalent circuit model for lithium-ion batteries used for hybrid electric vehicles (HEV) is presented. The model has two RC networks characterizing battery activation and concentration polarization process. The parameters of the model are identified using combined experimental and extended Kalman filter (EKF) recursive methods. The open-circuit voltage and ohmic resistance of the battery are directly measured and calculated from experimental measurements, respectively. The rest of the coupled dynamic parameters, i.e. the RC network parameters, are estimated using the EKF method. Experimental and simulation results are presented to demonstrate the efficacy of the proposed circuit model and parameter identification techniques for simulating battery dynamics.
基金Project(U1234208)supported by the National Natural Science Foundation of ChinaProject(2016YFB1200401)supported by the National Key Research and Development Program of China
文摘This work deals with super-harmonic responses and the stabilities of a gear transmission system of a high-speed train under the stick-slip oscillation of the wheel-set.The dynamic model of the system is developed with consideration on the factors including the time-varying system stiffness,the transmission error,the tooth backlash and the self-excited excitation of the wheel-set.The frequency-response equation of the system at super-harmonic resonance is obtained by the multiple scales method,and the stabilities of the system are analyzed using the perturbation theory.Complex nonlinear behaviors of the system including multi-valued solutions,jump phenomenon,hardening stiffness are found.The effects of the equivalent damping and the loads of the system under the stick-slip oscillation are analyzed.It shows that the change of the load can obviously influence the resonance frequency of the system and have little effect on the steady-state response amplitude of the system.The damping of the system has a negative effect,opposite to the load.The synthetic damping of the system composed of meshing damping and equivalent damping may be less than zero when the wheel-set has a large slippage,and the system loses its stability owing to the Hopf bifurcation.Analytical results are validated by numerical simulations.
文摘Rather than parking at nearby hourly parking lots, many passenger-picking-up vehicles prefer to idle at terminals and/or drive cycling around terminal facilities. As a result, extra vehicle emissions may be produced in an airport area. Even though there are limited studies on such emissions at airports, these estimations were normally based on the date emission models, which might cause bias in emission estimations. This paper proposes an approach to employ the floating car method and Global Positioning System (GPS) to record speeds and acceleration rates of idling and cycling vehicles at airport terminals. The tests were conducted under different time periods and traffic demands with different waiting time. The speeds and acceleration rates are synthesized to yield Vehicle Specific Power's (VSP) and Operational Mode (OM) distributions. Utilizing the Environmental Protection Agency (EPA) emission estimation model Motor Vehicle Emission Simulator (MOVES), pollutants and green house gas emission indexes (e.g. NOx, CO, CO2 and HC) and fuel consumptions can be easily estimated. As an illustration of the proposed approach, the research team collected GPS data at a terminal in Houston William Hobby Airport (HOU), and calculated the VSP distributions and OM distributions. Emissions of passenger-picking-up vehicles around these congested airport terminals.
文摘Duralumin alloys have been utilized as structural components and parts for aircrafts, train-cars and so forth. Their high specific strength was attractive to those applications; however, their little corrosion resistance and low wear endurance became a fatal demerit in practical applications. In order to overcome these issues of high strength aluminum alloys, high density plasma nitriding is proposed as an effective surface treatment for duralumin. This process has a capability to control the RF- and DC-plasmas independently for nitriding. This enables us to temporally control and describe the plasma state by in-situ plasma diagnosis. This plasma diagnosis was instrumented to search for optimum processing condition to plasma nitriding the duralumin alloys of type A2011. Both type A2011 aluminum alloy plates and pipes were employed to describe the inner nitriding behavior for hardening the duralumin alloys by the present plasma nitriding.
基金supported by the National Natural Science Foundation of China(Grant Nos.51805452,and 51935002)the Independent Research Project of State Key Laboratory of Traction Power(Grant No.2020TPL-T02).
文摘Vibration behaviors of bogie hunting motion contain key information that dominates the dynamic performance of rail vehicles,in which the eigenvalue of each mode reflects the damping ratio and the natural frequency.This paper focuses on the root loci curves of bogie hunting motion,starting from a rigid bogie,then to a bogie with flexible primary suspension.With regard to the rigid bogie,analytical formulas for the eigenvalues,the critical speed as well as the corresponding hunting frequency are derived and verified.While for the flexible bogie,the root loci curves are calculated numerically.The study shows that both free rigid bogie and free wheelset are dynamically unstable at any speed.The critical speed increases with diminished wheel-rail conicity,track gauge,and wheelset and bogie inertia,and with increased wheelbase and wheel radius.The dominating factors such as the stiffness of the primary suspension and the wheel-rail conicity should be optimized for a practical design.The influences of the damping coefficients and the variations of creep coefficients are negligible.The motor suspension affects the root loci curves and the critical speed significantly.Both inappropriate motor suspension design and rigidly suspended motor reduce the critical speed.The increase of critical speed by a motor suspension can only be achieved when the lower natural frequency of the motor-bogie frame-wheelsets system coincides with or is close to the hunting frequency.Special care should be taken for the design of motor suspension,the first is to avoid the decreased damping ratio in a certain speed range below the critical speed and the second is that the variations of parameters should not induce the rapid reduction of the critical speed.The main feature of the present study is that the root loci curves,which are derived as analytical formulas or calculated numerically,are used to study the vibrational behaviors of bogie hunting motion.Both the influencing laws of the dominating parameters and the principles regarding the motor suspension are significant for the stability design of modem railway vehicles which may use innovative structures/materials as well as modem control and monitoring technologies.
文摘Aiming to enhance the luminescence yield of carbon nanotubes, we introduce a new class of hybrid nanoplasmonic colloidal systems (π-hybrids). Nanotubes dispersed in gold nanorod colloidal suspensions yield hybrid structures exhibiting enhanced luminescence up to a factor of 20. The novelty of the proposed enhancement mechanism relies on including metal proximity effects in addition to its localized surface plasmons. This simple, robust and flexible technique enhances the luminescence of nanotubes with chiralities whose enhancement has never reported before, for example the (8,4) tube.