A fractal geometric boundary with natural wall features is introduced into a hybrid lattice-Boltzmann-method(LBM)multiphase model. The physical model of cavitation bubble collapse near the irregular geometric wall is ...A fractal geometric boundary with natural wall features is introduced into a hybrid lattice-Boltzmann-method(LBM)multiphase model. The physical model of cavitation bubble collapse near the irregular geometric wall is established to study the thermodynamic characteristics of the bubble collapse. Due to the lack of periodicity, symmetry, spatial uniformity and obvious correlation in the LBM simulation of the bubble collapse near the fractal wall, the morphological analysis based on Minkowski functional is introduced into the thermodynamic investigation of cavitation bubble so as to analyze and obtain the effective information. The results show that the Minkowski functional method can employed to study the temperature information in complex physical fields hierarchically and quantitatively. The high/low temperature region of the cavitation flow is explored, and thermal effect between irregular and fractal geometric wall and cavitation bubble can be revealed. It illustrates that LBM and morphological analysis complement each other, and morphological analysis can also be used as an optional and potential tool in research field of complex multiphase flows.展开更多
This study discusses the optimal link toll,which maximizes social surplus under a user equilibrium condition,with imperfect substitution assumption for route choice in a transportation network with many nodes and link...This study discusses the optimal link toll,which maximizes social surplus under a user equilibrium condition,with imperfect substitution assumption for route choice in a transportation network with many nodes and links,as well as taking into account the welfare cost of funds procurement.In contrast to previous studies,this study formulates optimal link tolls,taking into account the marginal cost of public funds(MCF),which is the marginal welfare loss of taxpayers due to a marginal tax raise.The formula for optimal tolls on links is derived from the following conditions.One is MCF classified into two,not taking into account funding(MCF equal to-1)and pricing for funding(MCF does not equal-1).Another is tolls classified into two,pricing on all links(full link pricing),and pricing on a specific link(partial link pricing).Following the above conditions,this study succeeds in deriving the formula for optimal tolls on a full network with many links and nodes.Furthermore,this study indicates two calculation methods:one is to solve analytically or numerically for when the functional form of link flow demand is known.When the functional form is unknown,such as a perfect substitution case,it is necessary to carry out iteration until convergence:with the traffic assignment given the price level and with a change in price level based on the traffic assignment.展开更多
Seoul Metro is Seoul’s leading metro company, transporting up to 3 billion people annually. However, future ridership is expected to plummet due to an aging and shrinking population with one of the fastest declining ...Seoul Metro is Seoul’s leading metro company, transporting up to 3 billion people annually. However, future ridership is expected to plummet due to an aging and shrinking population with one of the fastest declining total fertility rates in the world. The COVID-19 pandemic in 2019 accelerated this phenomenon. On the contrary, the e-commerce and home delivery industries have developed significantly since COVID-19. Seoul’s current logistics infrastructure cannot handle it. Under the inflection point of declining passenger transportation demand and increasing urban logistics demand, urban rail operators need new growth engines. Therefore, it is necessary to consider the introduction of an UULS (underground urban logistics system) that transports parcels instead of passengers through urban railways. If the UULS becomes a reality, it can be expected to secure scarce logistics land in cities, protect the environment and prevent traffic congestion by operating eco-friendly mass urban transportation, and acquire new revenue sources for urban rail operators. The UULS’s B/C ratio is 1.32. The sensitivity analysis shows that the ratio is above 1 in most cases where the unit cost of transportation is not significantly reduced.展开更多
Tunnels are vital in connecting crucial transportation hubs as transportation infrastructure evolves.Variations in tunnel design standards and driving conditions across different levels directly impact driver visual p...Tunnels are vital in connecting crucial transportation hubs as transportation infrastructure evolves.Variations in tunnel design standards and driving conditions across different levels directly impact driver visual perception and traffic safety.This study employs a Gaussian hybrid clustering machine learning model to explore driver gaze patterns in highway tunnels and exits.By utilizing contour coefficients,the optimal number of classification clusters is determined.Analysis of driver visual behavior across tunnel levels,focusing on gaze point distribution,gaze duration,and sweep speed,was conducted.Findings indicate freeway tunnel exits exhibit three distinct fixation point categories aligning with Gaussian distribution,while highway tunnels display four such characteristics.Notably,in both tunnel types,65%of driver gaze is concentrated on the near area ahead of their lane.Differences emerge in highway tunnels due to oncoming traffic,leading to 13.47%more fixation points and 0.9%increased fixation time in the right lane compared to regular highway tunnel conditions.Moreover,scanning speeds predominantly fall within the 0.25-0.3 range,accounting for 75.47%and 31.14%of the total sweep speed.展开更多
Imputation of missing data has long been an important topic and an essential application for intelligent transportation systems(ITS)in the real world.As a state-of-the-art generative model,the diffusion model has prov...Imputation of missing data has long been an important topic and an essential application for intelligent transportation systems(ITS)in the real world.As a state-of-the-art generative model,the diffusion model has proven highly successful in image generation,speech generation,time series modelling etc.and now opens a new avenue for traffic data imputation.In this paper,we propose a conditional diffusion model,called the implicit-explicit diffusion model,for traffic data imputation.This model exploits both the implicit and explicit feature of the data simultaneously.More specifically,we design two types of feature extraction modules,one to capture the implicit dependencies hidden in the raw data at multiple time scales and the other to obtain the long-term temporal dependencies of the time series.This approach not only inherits the advantages of the diffusion model for estimating missing data,but also takes into account the multiscale correlation inherent in traffic data.To illustrate the performance of the model,extensive experiments are conducted on three real-world time series datasets using different missing rates.The experimental results demonstrate that the model improves imputation accuracy and generalization capability.展开更多
The uninterrupted operation of the quay crane(QC)ensures that the large container ship can depart port within laytime,which effectively reduces the handling cost for the container terminal and ship owners.The QC waiti...The uninterrupted operation of the quay crane(QC)ensures that the large container ship can depart port within laytime,which effectively reduces the handling cost for the container terminal and ship owners.The QC waiting caused by automated guided vehicles(AGVs)delay in the uncertain environment can be alleviated by dynamic scheduling optimization.A dynamic scheduling process is introduced in this paper to solve the AGV scheduling and path planning problems,in which the scheduling scheme determines the starting and ending nodes of paths,and the choice of paths between nodes affects the scheduling of subsequent AGVs.This work proposes a two-stage mixed integer optimization model to minimize the transportation cost of AGVs under the constraint of laytime.A dynamic optimization algorithm,including the improved rule-based heuristic algorithm and the integration of the Dijkstra algorithm and the Q-Learning algorithm,is designed to solve the optimal AGV scheduling and path schemes.A new conflict avoidance strategy based on graph theory is also proposed to reduce the probability of path conflicts between AGVs.Numerical experiments are conducted to demonstrate the effectiveness of the proposed model and algorithm over existing methods.展开更多
We studied the problem of bifurcation and chaos in a 4-side fixed rectangular thin plate in electromagnetic and me-chanical fields.Based on the basic nonlinear electro-magneto-elastic motion equations for a rectangula...We studied the problem of bifurcation and chaos in a 4-side fixed rectangular thin plate in electromagnetic and me-chanical fields.Based on the basic nonlinear electro-magneto-elastic motion equations for a rectangular thin plate and the ex-pressions of electromagnetic forces,the vibration equations are derived for the mechanical loading in a steady transverse magnetic field.Using the Melnikov function method,the criteria are obtained for chaos motion to exist as demonstrated by the Smale horseshoe mapping.The vibration equations are solved numerically by a fourth-order Runge-Kutta method.Its bifurcation dia-gram,Lyapunov exponent diagram,displacement wave diagram,phase diagram and Poincare section diagram are obtained.展开更多
We propose a simplified human regular mobility model to simulate an individual's daily travel with three sequential activities:commuting to workplace,going to do leisure activities and returning home.With the assu...We propose a simplified human regular mobility model to simulate an individual's daily travel with three sequential activities:commuting to workplace,going to do leisure activities and returning home.With the assumption that the individual has a constant travel speed and inferior limit of time at home and in work,we prove that the daily moving area of an individual is an ellipse,and finally obtain an exact solution of the gyration radius.The analytical solution captures the empirical observation well.展开更多
Based on a self-developed hydrodynamic cavitation device with different geometric parameters for circular multi-orifice plates,turbulence characteristics of cavitating flow behind multi-orifice plates,including the ef...Based on a self-developed hydrodynamic cavitation device with different geometric parameters for circular multi-orifice plates,turbulence characteristics of cavitating flow behind multi-orifice plates,including the effects of orifice number and orifice layout on longitudinal velocity,turbulence intensity,and Reynolds stress,were measured with the particle image velocimetry(PIV)technique.Flow regimes of the cavitating flow were also observed with high-speed photography.The experimental results showed the following:(1)high-velocity multiple cavitating jets occurred behind the multi-orifice plates,and the cavitating flow fields were characterized by topological structures;(2)the longitudinal velocity at each cross-section exhibited a sawtooth-like distribution close to the multi-orifice plate,and each sawtooth indicated one jet issuing from one orifice;(3)there were similar magnitudes and forms for the longitudinal and vertical turbulence intensities at the same cross-section;(4)the variation in amplitude of Reynolds stress increased with an increase in orifice number;and(5)the cavitation clouds in the flow fields became denser with the increase in orifice number,and the clouds generated by the staggered layout of orifices were greater in number than those generated by the checkerboard-type one for the same orifice number.The experimental results can be used to analyze the mechanism of killing pathogenic microorganisms through hydrodynamic cavitation.展开更多
Studies in transportation planning routinely use data in which location attributes are an important source of information.Thus,using spatial attributes in urban travel forecasting models seems reasonable.The main obje...Studies in transportation planning routinely use data in which location attributes are an important source of information.Thus,using spatial attributes in urban travel forecasting models seems reasonable.The main objective of this paper is to estimate transit trip production using Factorial Kriging with External Drift(FKED)through an aggregated data case study of Traffic Analysis Zones in São Paulo city,Brazil.The method consists of a sequential application of Principal Components Analysis(PCA)and Kriging with External Drift(KED).The traditional Linear Regression(LR)model was adopted with the aim of validating the proposed method.The results show that PCA summarizes and combines 23 socioeconomic variables using 4 components.The first component is introduced in KED,as secondary information,to estimate transit trip production by public transport in geographic coordinates where there is no prior knowledge of the values.Cross-validation for the FKED model presented high values of the correlation coefficient between estimated and observed values.Moreover,low error values were observed.The accuracy of the LR model was similar to FKED.However,the proposed method is able to map the transit trip production in several geographical coordinates of non-sampled values.展开更多
This work correlated the detailed work zone location and time data from the Wis LCS system with the five-min inductive loop detector data. One-sample percentile value test and two-sample Kolmogorov-Smirnov(K-S) test w...This work correlated the detailed work zone location and time data from the Wis LCS system with the five-min inductive loop detector data. One-sample percentile value test and two-sample Kolmogorov-Smirnov(K-S) test were applied to compare the speed and flow characteristics between work zone and non-work zone conditions. Furthermore, we analyzed the mobility characteristics of freeway work zones within the urban area of Milwaukee, WI, USA. More than 50% of investigated work zones have experienced speed reduction and 15%-30% is necessary reduced volumes. Speed reduction was more significant within and at the downstream of work zones than at the upstream.展开更多
The main objective of this study is to analyze work travel-related behavior through a set of variables relative to socio-economic class, urban environment and travel characteristics. The Principal Component Analysis w...The main objective of this study is to analyze work travel-related behavior through a set of variables relative to socio-economic class, urban environment and travel characteristics. The Principal Component Analysis was applied in a sample consisting of workers of the S?o Paulo Metropolitan Area, based on the origin-destination home interview survey, carried out in 1997, in order to: 1) examine the interdependence between travel patterns and a set of socioeconomic and urban environment variables;2) determine if the original database can be synthetized on components. The results enabled to observe relations between the individual’s socio-economic class and car usage, characteristics of urban environment and destination choices, as well as age and non-motorized travel mode choice. It is then concluded that the database can be adequately summarized in three components for subsequent analysis: 1) urban environment;2) socio-economic class;and 3) family structure.展开更多
In this report, we reviewed the differences in the ecosystem services of coastal and inland areas surrounding 39 Sake breweries in Chiba Prefecture by investigating environmental variables (e.g., location, altitude, s...In this report, we reviewed the differences in the ecosystem services of coastal and inland areas surrounding 39 Sake breweries in Chiba Prefecture by investigating environmental variables (e.g., location, altitude, soil, and hardness of preparation water). The Sake breweries were located in three distinct environments: the coastal vicinity, the river plains region, and the plateau/ mountainous region. The hardness of the preparation water and the soil types in the coastal vicinity were compared with those of the river plains and the plateau/mountainous region. Strong hard and hard water sources were observed in 70% or more of the breweries in the coastal vicinity, and sand dune regosol, coarse particle brown lowland soil, and coarse particle grey soil were more prevalent along the coast than inland. Most of the Sake brewery wells in the coastal vicinity were approximately 5 - 10 munderground, and there were no great differences in the number of Sake breweries in each well depth class in the river plains and the plateau/mountains region. We analysed environmental factors (distance from the sea, soil type, water hardness and preparation water collection depth) using a principal component analysis. This analysis revealed the existence of three main environments: the coastal vicinity, the river plains and the plateau/mountainous region. We conclude that the decrease in altitude between the inland Sake breweries and those along the coast is accompanied by a corresponding increase in the hardness of preparation water (from soft water to strong hard or hard water) and shifts in soil composition from gley soil, grey lowland soil, brown forest soil, and andosol to sand dune regosol, coarse particle brown lowland soil, and coarse particle grey soil.展开更多
China ranks first in the world as the number of smokers. The environmental pollution and recycling problems of waste cigarette butts are becoming more and more serious. How to make better reuse of waste cigarette butt...China ranks first in the world as the number of smokers. The environmental pollution and recycling problems of waste cigarette butts are becoming more and more serious. How to make better reuse of waste cigarette butts has been taken action by some countries and regions in the world. In order to study the utilization value of the cigarette butt in road performance, this test takes No. 70 matrix bitumen and waste tobacco as raw material. The optimum amount of the content of the cigarette butt in the experiment is further determined based on the test performance of the modified asphalt mixture and the modified bitumen mixture is prepared by the addition method. The performance indexes of modified bituminous mixture with different dosages were tested and studied. Combined with production and economic realities, the optimum cigarette butt content of modified asphalt mixture is determined to make the road performance optimal. This paper focuses on the determination of the best bituminous content of the bituminous mixture. Through the toxicity test of the leachate published abroad to reflect the pollution of the cigarette butt to the environment and analyze the harm to the environment, combined with the development of global reusing technology and the economic benefits brought by cigarette butts, the prospect of the utilization of waste cigarette butts is forecasted.展开更多
The objective of this study is to estimate the vehicle kilometer traveled（VKT） and on-road emissions using the traffic volume in urban. We estimated two VKT; one is based on registered vehicles and the other is base...The objective of this study is to estimate the vehicle kilometer traveled（VKT） and on-road emissions using the traffic volume in urban. We estimated two VKT; one is based on registered vehicles and the other is based on traffic volumes. VKT for registered vehicles was 2.11 times greater than that of the applied traffic volumes because each VKT estimation method is different. Therefore, we had to define the inner VKT is moved VKT inner in urban to compare two values. Also, we focused on freight modes because these are discharged much air pollutant emissions. From analysis results, we found middle and large trucks registered in other regions traveled to target city in order to carry freight, target city has included many industrial and logistics areas. Freight is transferred through the harbors,large logistics centers, or via locations before being moved to the final destination. During this process, most freight is moved by middle and large trucks, and trailers rather than small trucks for freight import and export. Therefore, these trucks from other areas are inflow more than registered vehicles. Most emissions from diesel trucks had been overestimated in comparison to VKT from applied traffic volumes in target city. From these findings, VKT is essential based on traffic volume and travel speed on road links in order to estimate accurately the emissions of diesel trucks in target city. Our findings support the estimation of the effect of on-road emissions on urban air quality in Korea.展开更多
With the rapid growth of vehicle population and vehicle miles traveled, automobile emission has become a severe issue in the metropolitan cities of China. There are policies that concentrate on the management of emiss...With the rapid growth of vehicle population and vehicle miles traveled, automobile emission has become a severe issue in the metropolitan cities of China. There are policies that concentrate on the management of emission sources. However, improving the operation of the transportation system through apps on mobile devices, especially navigation apps, may have a unique role in promoting urban air quality. Real-time traveler information can not only help travelers avoid traffic congestion, hut also advise them to adjust their departure time, mode, or route, or even to cancel trips. Will such changes in personal travel patterns have a significant impact in decreasing emissions？ If so, to what extent will they impact urban air quality？ The aim of this study is to determine how urban traffic emission is affected by the use of navigation apps. With this work, we attempt to answer the question of whether the real-time traffic information provided by navigation apps can help to improve urban air quality. Some of these findings may provide references for the formulation of urban traffic and environmental policies.展开更多
The optimum design for flexible pavement structure is studied by using themethod of mathematical programming.The mathematical model is founded on the basisof“Design Code of Highway Flexible Pavement”issued by the Mi...The optimum design for flexible pavement structure is studied by using themethod of mathematical programming.The mathematical model is founded on the basisof“Design Code of Highway Flexible Pavement”issued by the Ministry of Communica-tions of China.The objective function is the cost of pavement structure.The optimal solu-tions of the mathematical model were searched successfully by flexiplex tolerance method.The relevant program has been developed on DPS-8 and IBM-PC computers.And thecalculated results show good convergence and accuracy for engineering applications.展开更多
Urban barriers are often a consequence of the unplanned expansion of transport infrastructures,housing growth nearby existing transport infrastructures,and the vehicular traffic itself.This process,also known as“comm...Urban barriers are often a consequence of the unplanned expansion of transport infrastructures,housing growth nearby existing transport infrastructures,and the vehicular traffic itself.This process,also known as“community severance”,is a problem that affects the travel patterns of the population and causes negative impacts to adjacent communities,but it is not easy to assess.As an alternative to the costly technologies and restricted-access data sometimes used to analyze urban barriers,we propose an analytical approach that assesses community severance levels by classifying the quality of Pedestrian Crossings on Urban Streets(the PeCUS index).Additionally,the approach is used to identify possible inequities nearby the different classification groups regarding demographic data.We used the chi-square(χ^(2))test of independence and the standardized Pearson residuals to indicate deficits and excesses of residents regarding the demographic characteristics studied surrounding the urban streets.We found the following evidences of associations:residents with low-income or those aged up to 19 tend to live close to the worst crossings,whereas residents with permanent mobility constraints or the elderly tend to live near the crossings with the best classifications.Therefore,the study shows that the assessment of community severance by the analysis of the PeCUS index is feasible.Moreover,it reveals that the distribution of residents surrounding the distinct classes of quality of crossings is equitable for vulnerable social groups,except for low-income or young residents.展开更多
In this paper the use of lime stabilized subgrade for low volume roads in two regions with high mountains and different frost penetration conditions in Türkiye was investigated in terms of design,performance,and ...In this paper the use of lime stabilized subgrade for low volume roads in two regions with high mountains and different frost penetration conditions in Türkiye was investigated in terms of design,performance,and cost.Pavements on unstabilized and stabilized subgrade were designed for two regions(Izmir and Van),covering all climate variations.The resilient modulus of the lime stabilized subgrade with different soil pulverization levels for non-freezing and freezing conditions were taken from a previous laboratory study.Frost effects were considered in pavement design using two different approaches,including limited subgrade frost penetration method and reduced subgrade strength method.Detailed application and evaluation were performed for all steps.Lime stabilized subgrades significantly reduced the thickness of base courses,and the benefit of lime stabilization was highly dependent on soil pulverization level.A detailed cost analysis on the unstabilized and stabilized cases found that the use of lime stabilization in the subgrade provided significant initial cost savings.Comparative analysis by using the AASHTO(1993)method and KENPAVE software,and quantity effect of soil pulverization level on the performance of low volume roads from a service life perspective,show that subgrade resilient modulus can be estimated.It is also possible to make correct performance estimation in the field.The results of the study show that lime stabilization is a good solution for low volume roads in the mountainous regions of Türkiye.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos. 11874140 and 12174085)Basic Science (Natural Science) Research Project for the Universities of Jiangsu Province (Grant No. 23KJD140002)the Natural Science Foundation of Nantong (Grant No. JC2023081)。
文摘A fractal geometric boundary with natural wall features is introduced into a hybrid lattice-Boltzmann-method(LBM)multiphase model. The physical model of cavitation bubble collapse near the irregular geometric wall is established to study the thermodynamic characteristics of the bubble collapse. Due to the lack of periodicity, symmetry, spatial uniformity and obvious correlation in the LBM simulation of the bubble collapse near the fractal wall, the morphological analysis based on Minkowski functional is introduced into the thermodynamic investigation of cavitation bubble so as to analyze and obtain the effective information. The results show that the Minkowski functional method can employed to study the temperature information in complex physical fields hierarchically and quantitatively. The high/low temperature region of the cavitation flow is explored, and thermal effect between irregular and fractal geometric wall and cavitation bubble can be revealed. It illustrates that LBM and morphological analysis complement each other, and morphological analysis can also be used as an optional and potential tool in research field of complex multiphase flows.
文摘This study discusses the optimal link toll,which maximizes social surplus under a user equilibrium condition,with imperfect substitution assumption for route choice in a transportation network with many nodes and links,as well as taking into account the welfare cost of funds procurement.In contrast to previous studies,this study formulates optimal link tolls,taking into account the marginal cost of public funds(MCF),which is the marginal welfare loss of taxpayers due to a marginal tax raise.The formula for optimal tolls on links is derived from the following conditions.One is MCF classified into two,not taking into account funding(MCF equal to-1)and pricing for funding(MCF does not equal-1).Another is tolls classified into two,pricing on all links(full link pricing),and pricing on a specific link(partial link pricing).Following the above conditions,this study succeeds in deriving the formula for optimal tolls on a full network with many links and nodes.Furthermore,this study indicates two calculation methods:one is to solve analytically or numerically for when the functional form of link flow demand is known.When the functional form is unknown,such as a perfect substitution case,it is necessary to carry out iteration until convergence:with the traffic assignment given the price level and with a change in price level based on the traffic assignment.
基金the Ministry of Land,Infrastructure and Transport and Korea Agency for Infrastructure Technology Advancement(22HCLP-C163194-02)。
文摘Seoul Metro is Seoul’s leading metro company, transporting up to 3 billion people annually. However, future ridership is expected to plummet due to an aging and shrinking population with one of the fastest declining total fertility rates in the world. The COVID-19 pandemic in 2019 accelerated this phenomenon. On the contrary, the e-commerce and home delivery industries have developed significantly since COVID-19. Seoul’s current logistics infrastructure cannot handle it. Under the inflection point of declining passenger transportation demand and increasing urban logistics demand, urban rail operators need new growth engines. Therefore, it is necessary to consider the introduction of an UULS (underground urban logistics system) that transports parcels instead of passengers through urban railways. If the UULS becomes a reality, it can be expected to secure scarce logistics land in cities, protect the environment and prevent traffic congestion by operating eco-friendly mass urban transportation, and acquire new revenue sources for urban rail operators. The UULS’s B/C ratio is 1.32. The sensitivity analysis shows that the ratio is above 1 in most cases where the unit cost of transportation is not significantly reduced.
基金supported by the National Natural Science Foundation of China(52302437)the Cangzhou Science and Technology Plan Project(213101011)+1 种基金the Science and Technology Program Projects of Shandong Provincial Department of Transportation(2024B28)the Doctoral Scientific Research Start-up Foundation of Shandong University of Technology(422049).
文摘Tunnels are vital in connecting crucial transportation hubs as transportation infrastructure evolves.Variations in tunnel design standards and driving conditions across different levels directly impact driver visual perception and traffic safety.This study employs a Gaussian hybrid clustering machine learning model to explore driver gaze patterns in highway tunnels and exits.By utilizing contour coefficients,the optimal number of classification clusters is determined.Analysis of driver visual behavior across tunnel levels,focusing on gaze point distribution,gaze duration,and sweep speed,was conducted.Findings indicate freeway tunnel exits exhibit three distinct fixation point categories aligning with Gaussian distribution,while highway tunnels display four such characteristics.Notably,in both tunnel types,65%of driver gaze is concentrated on the near area ahead of their lane.Differences emerge in highway tunnels due to oncoming traffic,leading to 13.47%more fixation points and 0.9%increased fixation time in the right lane compared to regular highway tunnel conditions.Moreover,scanning speeds predominantly fall within the 0.25-0.3 range,accounting for 75.47%and 31.14%of the total sweep speed.
基金partially supported by the National Natural Science Foundation of China(62271485)the SDHS Science and Technology Project(HS2023B044)
文摘Imputation of missing data has long been an important topic and an essential application for intelligent transportation systems(ITS)in the real world.As a state-of-the-art generative model,the diffusion model has proven highly successful in image generation,speech generation,time series modelling etc.and now opens a new avenue for traffic data imputation.In this paper,we propose a conditional diffusion model,called the implicit-explicit diffusion model,for traffic data imputation.This model exploits both the implicit and explicit feature of the data simultaneously.More specifically,we design two types of feature extraction modules,one to capture the implicit dependencies hidden in the raw data at multiple time scales and the other to obtain the long-term temporal dependencies of the time series.This approach not only inherits the advantages of the diffusion model for estimating missing data,but also takes into account the multiscale correlation inherent in traffic data.To illustrate the performance of the model,extensive experiments are conducted on three real-world time series datasets using different missing rates.The experimental results demonstrate that the model improves imputation accuracy and generalization capability.
基金supported in part by the National Natural Science Foundation of China(61473053)the Science and Technology Innovation Foundation of Dalian,China(2020JJ26GX033)。
文摘The uninterrupted operation of the quay crane(QC)ensures that the large container ship can depart port within laytime,which effectively reduces the handling cost for the container terminal and ship owners.The QC waiting caused by automated guided vehicles(AGVs)delay in the uncertain environment can be alleviated by dynamic scheduling optimization.A dynamic scheduling process is introduced in this paper to solve the AGV scheduling and path planning problems,in which the scheduling scheme determines the starting and ending nodes of paths,and the choice of paths between nodes affects the scheduling of subsequent AGVs.This work proposes a two-stage mixed integer optimization model to minimize the transportation cost of AGVs under the constraint of laytime.A dynamic optimization algorithm,including the improved rule-based heuristic algorithm and the integration of the Dijkstra algorithm and the Q-Learning algorithm,is designed to solve the optimal AGV scheduling and path schemes.A new conflict avoidance strategy based on graph theory is also proposed to reduce the probability of path conflicts between AGVs.Numerical experiments are conducted to demonstrate the effectiveness of the proposed model and algorithm over existing methods.
基金Project(No. A2006000190)supported by the Natural Science Foundation of Hebei Province,China
文摘We studied the problem of bifurcation and chaos in a 4-side fixed rectangular thin plate in electromagnetic and me-chanical fields.Based on the basic nonlinear electro-magneto-elastic motion equations for a rectangular thin plate and the ex-pressions of electromagnetic forces,the vibration equations are derived for the mechanical loading in a steady transverse magnetic field.Using the Melnikov function method,the criteria are obtained for chaos motion to exist as demonstrated by the Smale horseshoe mapping.The vibration equations are solved numerically by a fourth-order Runge-Kutta method.Its bifurcation dia-gram,Lyapunov exponent diagram,displacement wave diagram,phase diagram and Poincare section diagram are obtained.
基金Supported by the National Natural Science Foundation of China under Grant Nos 91024026,10975126,70871082 and 70971089the Specialized Research Fund for the Doctoral Program of Higher Education of China under Grant No 20093402110032the Research Foundation of Hebei Educational Committee under Grant No Z2009139.
文摘We propose a simplified human regular mobility model to simulate an individual's daily travel with three sequential activities:commuting to workplace,going to do leisure activities and returning home.With the assumption that the individual has a constant travel speed and inferior limit of time at home and in work,we prove that the daily moving area of an individual is an ellipse,and finally obtain an exact solution of the gyration radius.The analytical solution captures the empirical observation well.
基金supported by the National Natural Science Foundation of China(Grant No.51479177).
文摘Based on a self-developed hydrodynamic cavitation device with different geometric parameters for circular multi-orifice plates,turbulence characteristics of cavitating flow behind multi-orifice plates,including the effects of orifice number and orifice layout on longitudinal velocity,turbulence intensity,and Reynolds stress,were measured with the particle image velocimetry(PIV)technique.Flow regimes of the cavitating flow were also observed with high-speed photography.The experimental results showed the following:(1)high-velocity multiple cavitating jets occurred behind the multi-orifice plates,and the cavitating flow fields were characterized by topological structures;(2)the longitudinal velocity at each cross-section exhibited a sawtooth-like distribution close to the multi-orifice plate,and each sawtooth indicated one jet issuing from one orifice;(3)there were similar magnitudes and forms for the longitudinal and vertical turbulence intensities at the same cross-section;(4)the variation in amplitude of Reynolds stress increased with an increase in orifice number;and(5)the cavitation clouds in the flow fields became denser with the increase in orifice number,and the clouds generated by the staggered layout of orifices were greater in number than those generated by the checkerboard-type one for the same orifice number.The experimental results can be used to analyze the mechanism of killing pathogenic microorganisms through hydrodynamic cavitation.
基金This research was sponsored by the National Counsel of Technological and Scientific Development(CNPq,Brazil),the Coordination for the Improvement of Higher Education Personnel(CAPES,Brazil),the State of São Paulo Research Foundation(FAPESP-2013/25035-1,Brazil).
文摘Studies in transportation planning routinely use data in which location attributes are an important source of information.Thus,using spatial attributes in urban travel forecasting models seems reasonable.The main objective of this paper is to estimate transit trip production using Factorial Kriging with External Drift(FKED)through an aggregated data case study of Traffic Analysis Zones in São Paulo city,Brazil.The method consists of a sequential application of Principal Components Analysis(PCA)and Kriging with External Drift(KED).The traditional Linear Regression(LR)model was adopted with the aim of validating the proposed method.The results show that PCA summarizes and combines 23 socioeconomic variables using 4 components.The first component is introduced in KED,as secondary information,to estimate transit trip production by public transport in geographic coordinates where there is no prior knowledge of the values.Cross-validation for the FKED model presented high values of the correlation coefficient between estimated and observed values.Moreover,low error values were observed.The accuracy of the LR model was similar to FKED.However,the proposed method is able to map the transit trip production in several geographical coordinates of non-sampled values.
基金Project(61620106002)supported by the National Natural Science Foundation of ChinaProject(2016YFB0100906)supported by the National Key R&D Program in China+1 种基金Project(2015364X16030)supported by the Information Technology Research Project of Ministry of Transport of ChinaProject(2242015K42132)supported by the Fundamental Sciences of Southeast University,China
文摘This work correlated the detailed work zone location and time data from the Wis LCS system with the five-min inductive loop detector data. One-sample percentile value test and two-sample Kolmogorov-Smirnov(K-S) test were applied to compare the speed and flow characteristics between work zone and non-work zone conditions. Furthermore, we analyzed the mobility characteristics of freeway work zones within the urban area of Milwaukee, WI, USA. More than 50% of investigated work zones have experienced speed reduction and 15%-30% is necessary reduced volumes. Speed reduction was more significant within and at the downstream of work zones than at the upstream.
文摘The main objective of this study is to analyze work travel-related behavior through a set of variables relative to socio-economic class, urban environment and travel characteristics. The Principal Component Analysis was applied in a sample consisting of workers of the S?o Paulo Metropolitan Area, based on the origin-destination home interview survey, carried out in 1997, in order to: 1) examine the interdependence between travel patterns and a set of socioeconomic and urban environment variables;2) determine if the original database can be synthetized on components. The results enabled to observe relations between the individual’s socio-economic class and car usage, characteristics of urban environment and destination choices, as well as age and non-motorized travel mode choice. It is then concluded that the database can be adequately summarized in three components for subsequent analysis: 1) urban environment;2) socio-economic class;and 3) family structure.
文摘In this report, we reviewed the differences in the ecosystem services of coastal and inland areas surrounding 39 Sake breweries in Chiba Prefecture by investigating environmental variables (e.g., location, altitude, soil, and hardness of preparation water). The Sake breweries were located in three distinct environments: the coastal vicinity, the river plains region, and the plateau/ mountainous region. The hardness of the preparation water and the soil types in the coastal vicinity were compared with those of the river plains and the plateau/mountainous region. Strong hard and hard water sources were observed in 70% or more of the breweries in the coastal vicinity, and sand dune regosol, coarse particle brown lowland soil, and coarse particle grey soil were more prevalent along the coast than inland. Most of the Sake brewery wells in the coastal vicinity were approximately 5 - 10 munderground, and there were no great differences in the number of Sake breweries in each well depth class in the river plains and the plateau/mountains region. We analysed environmental factors (distance from the sea, soil type, water hardness and preparation water collection depth) using a principal component analysis. This analysis revealed the existence of three main environments: the coastal vicinity, the river plains and the plateau/mountainous region. We conclude that the decrease in altitude between the inland Sake breweries and those along the coast is accompanied by a corresponding increase in the hardness of preparation water (from soft water to strong hard or hard water) and shifts in soil composition from gley soil, grey lowland soil, brown forest soil, and andosol to sand dune regosol, coarse particle brown lowland soil, and coarse particle grey soil.
文摘China ranks first in the world as the number of smokers. The environmental pollution and recycling problems of waste cigarette butts are becoming more and more serious. How to make better reuse of waste cigarette butts has been taken action by some countries and regions in the world. In order to study the utilization value of the cigarette butt in road performance, this test takes No. 70 matrix bitumen and waste tobacco as raw material. The optimum amount of the content of the cigarette butt in the experiment is further determined based on the test performance of the modified asphalt mixture and the modified bitumen mixture is prepared by the addition method. The performance indexes of modified bituminous mixture with different dosages were tested and studied. Combined with production and economic realities, the optimum cigarette butt content of modified asphalt mixture is determined to make the road performance optimal. This paper focuses on the determination of the best bituminous content of the bituminous mixture. Through the toxicity test of the leachate published abroad to reflect the pollution of the cigarette butt to the environment and analyze the harm to the environment, combined with the development of global reusing technology and the economic benefits brought by cigarette butts, the prospect of the utilization of waste cigarette butts is forecasted.
基金supported by the Korea Transport Institute,Republic of Koreasupported by Technology Development to evaluate GHG Emissions Indices of Mobiles and Municipal Sustainability(Transport logistics project 14TLRP-CO84940-01) commissioned from KAIA
文摘The objective of this study is to estimate the vehicle kilometer traveled（VKT） and on-road emissions using the traffic volume in urban. We estimated two VKT; one is based on registered vehicles and the other is based on traffic volumes. VKT for registered vehicles was 2.11 times greater than that of the applied traffic volumes because each VKT estimation method is different. Therefore, we had to define the inner VKT is moved VKT inner in urban to compare two values. Also, we focused on freight modes because these are discharged much air pollutant emissions. From analysis results, we found middle and large trucks registered in other regions traveled to target city in order to carry freight, target city has included many industrial and logistics areas. Freight is transferred through the harbors,large logistics centers, or via locations before being moved to the final destination. During this process, most freight is moved by middle and large trucks, and trailers rather than small trucks for freight import and export. Therefore, these trucks from other areas are inflow more than registered vehicles. Most emissions from diesel trucks had been overestimated in comparison to VKT from applied traffic volumes in target city. From these findings, VKT is essential based on traffic volume and travel speed on road links in order to estimate accurately the emissions of diesel trucks in target city. Our findings support the estimation of the effect of on-road emissions on urban air quality in Korea.
文摘With the rapid growth of vehicle population and vehicle miles traveled, automobile emission has become a severe issue in the metropolitan cities of China. There are policies that concentrate on the management of emission sources. However, improving the operation of the transportation system through apps on mobile devices, especially navigation apps, may have a unique role in promoting urban air quality. Real-time traveler information can not only help travelers avoid traffic congestion, hut also advise them to adjust their departure time, mode, or route, or even to cancel trips. Will such changes in personal travel patterns have a significant impact in decreasing emissions？ If so, to what extent will they impact urban air quality？ The aim of this study is to determine how urban traffic emission is affected by the use of navigation apps. With this work, we attempt to answer the question of whether the real-time traffic information provided by navigation apps can help to improve urban air quality. Some of these findings may provide references for the formulation of urban traffic and environmental policies.
文摘The optimum design for flexible pavement structure is studied by using themethod of mathematical programming.The mathematical model is founded on the basisof“Design Code of Highway Flexible Pavement”issued by the Ministry of Communica-tions of China.The objective function is the cost of pavement structure.The optimal solu-tions of the mathematical model were searched successfully by flexiplex tolerance method.The relevant program has been developed on DPS-8 and IBM-PC computers.And thecalculated results show good convergence and accuracy for engineering applications.
基金This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior-Brasil(CAPES)-Finance Code[001].
文摘Urban barriers are often a consequence of the unplanned expansion of transport infrastructures,housing growth nearby existing transport infrastructures,and the vehicular traffic itself.This process,also known as“community severance”,is a problem that affects the travel patterns of the population and causes negative impacts to adjacent communities,but it is not easy to assess.As an alternative to the costly technologies and restricted-access data sometimes used to analyze urban barriers,we propose an analytical approach that assesses community severance levels by classifying the quality of Pedestrian Crossings on Urban Streets(the PeCUS index).Additionally,the approach is used to identify possible inequities nearby the different classification groups regarding demographic data.We used the chi-square(χ^(2))test of independence and the standardized Pearson residuals to indicate deficits and excesses of residents regarding the demographic characteristics studied surrounding the urban streets.We found the following evidences of associations:residents with low-income or those aged up to 19 tend to live close to the worst crossings,whereas residents with permanent mobility constraints or the elderly tend to live near the crossings with the best classifications.Therefore,the study shows that the assessment of community severance by the analysis of the PeCUS index is feasible.Moreover,it reveals that the distribution of residents surrounding the distinct classes of quality of crossings is equitable for vulnerable social groups,except for low-income or young residents.
基金a joint venture project between Istanbul University and the Turkish General Directorate of Highways by project number KGM-ARGE/2012-25funded by Istanbul University-Cerrahpasa Scientific Research Projects under Project No:ACIP 54739。
文摘In this paper the use of lime stabilized subgrade for low volume roads in two regions with high mountains and different frost penetration conditions in Türkiye was investigated in terms of design,performance,and cost.Pavements on unstabilized and stabilized subgrade were designed for two regions(Izmir and Van),covering all climate variations.The resilient modulus of the lime stabilized subgrade with different soil pulverization levels for non-freezing and freezing conditions were taken from a previous laboratory study.Frost effects were considered in pavement design using two different approaches,including limited subgrade frost penetration method and reduced subgrade strength method.Detailed application and evaluation were performed for all steps.Lime stabilized subgrades significantly reduced the thickness of base courses,and the benefit of lime stabilization was highly dependent on soil pulverization level.A detailed cost analysis on the unstabilized and stabilized cases found that the use of lime stabilization in the subgrade provided significant initial cost savings.Comparative analysis by using the AASHTO(1993)method and KENPAVE software,and quantity effect of soil pulverization level on the performance of low volume roads from a service life perspective,show that subgrade resilient modulus can be estimated.It is also possible to make correct performance estimation in the field.The results of the study show that lime stabilization is a good solution for low volume roads in the mountainous regions of Türkiye.
