Unidirectional two-lane freeway is a typical and the simplest form of freeway. The traffic flow char- acteristics including safety condition on two-lane freeway is of great significance in planning, design, and manage...Unidirectional two-lane freeway is a typical and the simplest form of freeway. The traffic flow char- acteristics including safety condition on two-lane freeway is of great significance in planning, design, and manage- ment of a freeway. Many previous traffic flow models are able to figure out flow characteristics such as speed, den- sity, delay, and so forth. These models, however, have great difficulty in reflecting safety condition of vehicles. Besides, for the cellular automation, one of the most widely used microscopic traffic simulation models, its discreteness in both time and space can possibly cause inaccuracy or big errors in simulation results. In this paper, a micro-simula- tion model of two-lane freeway vehicles is proposed to evaluate characteristics of traffic flow, including safety condition. The model is also discrete in time but continu- ous in space, and it divides drivers into several groups on the basis of their preferences for overtaking, which makes the simulation more aligned with real situations. Partial test is conducted in this study and results of delay, speed, volume, and density indicate the preliminary validity of our model, based on which the proposed safety coefficient evaluates safety condition under different flow levels. It is found that the results of this evaluation coincide with daily experience of drivers, providing ground for effectiveness of the safety coefficient.展开更多
This paper investigates the traffic accidents＇ trends and causes in Dubai. For this purpose, the traffic accident statistics for years 2003 to 2012 are used to examine the trends of different types of accidents and t...This paper investigates the traffic accidents＇ trends and causes in Dubai. For this purpose, the traffic accident statistics for years 2003 to 2012 are used to examine the trends of different types of accidents and the causes of these accidents. Also, the paper determines the most common types of accidents over the study period and identifies some of the causes for these accidents. Furthermore, the paper shows the impact of the new traffic law amendments, which were issued in 2008, on the accident rates and trends. The results showed that the implementation of the traffic law amendments did not have major impact in year 2008. However, there was a significant effect of these amendments in the following years. Also, lack of awareness of traffic laws and regulations in Dubai has been proven to be one of the major causes of accidents. Finally, the paper provides some recommendations to reduce the traffic accident rates, in order to achieve the Dubai Police Department 2020 strategic goal to have zero fatalities.展开更多
As the transport sector is a major source of greenhouse gas emissions, the effect of urbanization on transport CO2 emissions in developing cities has become a key issue under global climate change. Examining the case ...As the transport sector is a major source of greenhouse gas emissions, the effect of urbanization on transport CO2 emissions in developing cities has become a key issue under global climate change. Examining the case of Xi＇an, this paper aims to explore the spatial distribution of commuting CO2 emissions and influencing factors in the new, urban industry zones and city centers considering Xi＇an＇s transition from a monocentric to a polycentric city in the process of urbanization. Based on household survey data from 1501 respondents, there are obvious differences in commuting CO2 emissions between new industry zones and city centers： City centers feature lower household emissions of 2.86 kg CO2 per week, whereas new industry zones generally have higher household emissions of 3.20 kg CO2 per week. Contrary to previous research results, not all new industry zones have high levels of CO2 emissions; with the rapid development of various types of industries, even a minimum level of household emissions of 2.53 kg CO2 per week is possible. The uneven distribution of commuting CO2 emissions is not uniformly affected by spatial parameters such as job-housing balance, residential density, employment density, and land use diversity. Optimum combination of the spatial parameters and travel pattern along with corresponding transport infrastructure construction may be an appropriate path to reduction and control of emissions from commuting.展开更多
To improve the level of active traffic management,a short-term traffic flow prediction model is proposed by combining phase space reconstruction(PSR)and extreme gradient boosting(XGBoost)algorithms.Firstly,the traditi...To improve the level of active traffic management,a short-term traffic flow prediction model is proposed by combining phase space reconstruction(PSR)and extreme gradient boosting(XGBoost)algorithms.Firstly,the traditional data preprocessing method is improved.The new method uses hierarchical clustering to determine the traffic flow state and fills in missing and abnormal data according to different traffic flow states.Secondly,one-dimensional data are mapped into a multidimensional data matrix through PSR,and the time series complex network is used to verify the data reconstruction effect.Finally,the multidimensional data matrix is inputted into the XGBoost model to predict future traffic flow parameters.The experimental results show that the mean square error,average absolute error,and average absolute percentage error of the prediction results of the PSR-XGBoost model are 5.399%,1.632%,and 6.278%,respectively,and the required running time is 17.35 s.Compared with mathematical-statistical models and other machine learning models,the PSR-XGBoost model has clear advantages in multiple predictive indicators,proving its feasibility and superiority in short-term traffic flow prediction.展开更多
Boron nitride nanotubes （BN-NTs） with pure hexagonal BN phase have been synthesized by heating ball-milled boron powders in flowing ammonia gas at a temperature of 1200℃. The as-synthesized products were characteri...Boron nitride nanotubes （BN-NTs） with pure hexagonal BN phase have been synthesized by heating ball-milled boron powders in flowing ammonia gas at a temperature of 1200℃. The as-synthesized products were characterized by X-ray powder diffraction, transmission electron microscopy, high-resolution transmission electron microscopy, and electron energy loss spectroscopy （EELS）. The diameters of nanotubes are in the rage of 40-120nm and the lengths are more than 10μm. EELS result identifies that the ratio of boron and nitrogen is almost 1：1 The growth temperature is a crucial growth parameter in controlling the structure and crystalline of BN-NTs. The nanotubes grown at 1100℃ possesses of a bamboo-like structure, while as the temperature increased to 1200℃, most of the nanotubes exhibited a cylindrical structure. In addition, changing the heating time can control the size of the nanotubes. The gas atmosphere has influence on the yield of BN-NTs during heating process. When heating atmosphere was replaced by nitrogen, the yield of nanotubes was remarkably decreased.展开更多
Aiming at the defects in previous research and based on porous pelletmodel,the kinetics model of organic matter degradation in FBBR has been estab-lished.By means of synthesis phenolic wastewater treatment experiment,...Aiming at the defects in previous research and based on porous pelletmodel,the kinetics model of organic matter degradation in FBBR has been estab-lished.By means of synthesis phenolic wastewater treatment experiment,the reliabil-ity of the model is tested and the result shows that the precision is satistactory.De-pending on the model,the paper analyses in detail the mechanism of organic matterdegradation and the effect of biofilm thickness on reactor performance in FBBR.Theresearch result indicates that high efficiency of FBBR lies in high value of ηX and thebiofilm thickness is a significant factor affecting η,X and reactor performance.展开更多
This paper discusses two urgent problems that need to be solved in fully automatic operation(FAO)for urban rail transit.The first is the analysis of safety in FAO,while another is the analysis of efficiency in FAO.Fir...This paper discusses two urgent problems that need to be solved in fully automatic operation(FAO)for urban rail transit.The first is the analysis of safety in FAO,while another is the analysis of efficiency in FAO.Firstly,this paper establishes an operational safety evaluation index system from the perspective of operation for the unique or typical risk sources of the FAO system,and uses the analytic hierarchy process(AHP)to evaluate the indicators,analyzes various factors that affect the safe operation of FAO,and provides safety management recommendations for FAO lines operation to maintain the FAO system specifically.Secondly,taking the Yanfang Line as an example,this paper uses OpenTrack software to analyze the efficiency of FAO operation,and conducts simulation calculations for key links such as the mainline tracking interval,train entry and exit,and return limit interval.The fault impact surface of the FAO trains is simulated and discussed to verify whether FAO can meet the long-term operation requirements of Yanfang Line.Finally,this paper compares the simulation data of FAO on the Yanfang Line with manual operation(MO)to verify the advantages of FAO and guide the engineering construction of subsequent fully automated driving lines.展开更多
The symbiotic FM radio data system(SRDS)is a radio data system that a specially designed OFDM signal co-lives with FM signal,which enables a significantly higher data rate than existing radio data systems.The cyclic p...The symbiotic FM radio data system(SRDS)is a radio data system that a specially designed OFDM signal co-lives with FM signal,which enables a significantly higher data rate than existing radio data systems.The cyclic prefix of the OFDM symbol has the same length as the OFDM body,which enables the analytic separation of the co-channel OFDM and FM signal at receiver side,utilizing the fact that the OFDM body and prefix is equal.In this work,we show that the OFDM body and prefix cannot be viewed as equal when there is sufficient carrier frequency offset(CFO).Thus,we propose a two-step CFO estimation algorithm for FM and SRDS hybrid signal.The first step estimates the coarse CFO by exploring the characteristics of the FM signal.Once the coarse CFO is removed,the residual CFO is small enough for FM and OFDM separation.The second step fine estimates CFO from the OFDM-only signal using its repeated PN structure after the separation.Detailed mathematical equations are formulated and simulation results are given.The results show that the proposed algorithm works fine with the simulation setup and has a final residual CFO less than 3.9Hz.展开更多
Redesign of motorized and non-motorized transport in cities and sustainable mobility possibilities and utilization of already occupied areas for motorized and non-motorized transport in cities. Reserved area for publi...Redesign of motorized and non-motorized transport in cities and sustainable mobility possibilities and utilization of already occupied areas for motorized and non-motorized transport in cities. Reserved area for public transport may be the redesign much more to take advantage of without taking up new space in cities. Redesigned solutions shown in the work of public mass transport and the redesign of non-motorized transport, bicycle and pedestrian paths point to the improved use and safety of movement of passengers, cyclists and pedestrians. This paper presents five redesigned concept designs as improving existing forms of transport and movement of cyclists and pedestrians in cities. Redesigned conceptual designs of motorized and non-motorized transport in cities should serve as ideas for the growing problems of urban development in the segment of insufficient surface for pedestrians and cyclists, as well as sustainable mobility transport people in the city.展开更多
Demand-responsive transportation has been introduced in many cities around the world.However,whether it is applicable in the railway is still questionable,an exploration of passenger choice behavior between demandresp...Demand-responsive transportation has been introduced in many cities around the world.However,whether it is applicable in the railway is still questionable,an exploration of passenger choice behavior between demandresponsive trains and pre-scheduled trains is pivotal in addressing this issue.To delve into passengers’choice preferences when facing demand-responsive trains and to dissect the feasibility of implementing demandresponsive service in high-speed railways,the stated preference survey method is employed to investigate travel intention of passengers.Based on the survey data obtained in China,the heterogeneity of passengers is analyzed from three aspects:personal socio-economic characteristics,travel characteristics,and travel mode choice.Considering the situation that demand-responsive train cannot operate,the risk attributes are considered.To bolster the appeal of demand-responsive trains,personalized service product attributes are added.Mixed Logit mode,which takes into account the heterogeneous travel choice behavior of passengers,is developed,and Maximum Likelihood Estimation and the Monte Carlo method are used to calibrate model parameters.The willingness to pay in terms of different factors of passengers is determined.The results indicate that early arrival deviation time,late arrival deviation time,demand response time,and success rate of ticket purchase remarkable influence passengers’decision regarding demand-responsive train,with only the success rate of ticket purchase positively impacting train choice.Moreover,the significant difference in train ticket price is observed solely in the self-funded long distance scenario,while demand-responsive trains are found to be particularly appealing in self-funded short distance scenario.Through the Willingness To Pay(WTP)analysis,it is discovered that by shortening demand response time,enhancing the success rate of ticket purchase,and minimizing the deviation times of early arrival and late arrival of trains,the attractiveness of the demand-responsive train to passengers under three travel scenarios can be augmented.This study provides profound insights into the possibility of railway enterprises operating demand-responsive trains.展开更多
Due to errors in vehicle dynamics modeling,uncertainty in model parameters,and disturbances from curvature,the performance of the path tracking controller is poor or even unstable under high-speed and large-curvature ...Due to errors in vehicle dynamics modeling,uncertainty in model parameters,and disturbances from curvature,the performance of the path tracking controller is poor or even unstable under high-speed and large-curvature conditions.Therefore,a path tracking robust control strategy based on force-driven H_(∞)and MPC is proposed.To fully exploit the nonlinear dynamics characteristics of tires,a force-driven state space model of a path tracking system based on a linear time-varying tire model is established;the H_(∞)and MPC methods are used to design a robust controller.Considering disturbance and system state constraints,the robust control constraint model based on LMI is established.Finally,the proposed controller is validated through joint simulations using CarSim and MATLAB.The results show that the maximum lateral deviation is reduced by 17.07%,and the maximum course angle deviation is reduced by 13.04%under large curvature disturbance conditions.The maximum lateral deviation is reduced by 27.85%,and the maximum course angle deviation is reduced by 31.17%under conditions of uncertain road adhesion coefficients.Based on the controller’s performance,the proposed controller effectively mitigates modeling errors,parameter uncertainties,and curvature disturbances.展开更多
Connected and autonomous vehicle formation(CAVF)technology is considerably important for improving transportation efficiency,optimizing traffic flow,and reduc-ing energy consumption.Despite the extensive research con-...Connected and autonomous vehicle formation(CAVF)technology is considerably important for improving transportation efficiency,optimizing traffic flow,and reduc-ing energy consumption.Despite the extensive research con-ducted on trajectory tracking control and other aspects of CAVF,the quality of the extant literature varies consider-ably,and research content remains scattered.To better pro-mote the sustainable and healthy development of the CAVF field,this paper employs the mapping knowledge domain(MKD)methodology to comprehensively review and visual-ize the current research status in this domain.Based on this review,research themes,hotspots,research challenges,and future development directions are proposed.The findings suggest that the research on CAVF can be categorized into three primary developmental stages.China and the United States are the primary countries conducting CAVF research.There is a positive correlation between economic develop-ment and the generation of scientific research outcomes.Re-search institutions are predominantly concentrated in univer-sities.The field exhibits significant interdisciplinary and inte-gration characteristics,forming key research personnel and teams.It is expected that future research will concentrate on topics such as deep learning,trajectory optimization,energy management strategy,mixed vehicle platoon,and other re-lated subjects.Research on cognition-driven intelligent for-mation decision-making mechanisms,resilience-oriented for-mation safety assurance systems,multiobjective collabora-tive formation optimization strategies,and digital twin-driven formation system validation platforms represents key future development directions.展开更多
Objective: To study the epidemiological characteristics and preventive methods of road traffic crashes in a mountain city in western China through sampling investigation of traffic crashes in different regions of Chon...Objective: To study the epidemiological characteristics and preventive methods of road traffic crashes in a mountain city in western China through sampling investigation of traffic crashes in different regions of Chongqing city in recent years. Methods: Two police teams of traffic management in downtown, two teams in suburb, one team in county and one freeway team were randomly selected, and road traffic crashes between 1988 and 1997 were investigated and analyzed. Results: A total of 13121 road traffic crashes with 6201 crashes with casualties were analyzed. The incidence of crashes was higher in May, June and July, and on Friday and Wednesday and at 8:00-12:00 and 14:00-18:00 within a day. Casualties were 44.0% in pedestrians and 42.5% in passengers of total casualties. The deaths and severe injuries in pedestrians were 59.1% of total deaths and 56.4% of total severe injuries. The age of drivers and passengers were mainly at 18-30 years, followed by 31-40 years. People over 60 years old accounted for 24.1% of total pedestrian casualty. Head injury was the most common reason for deaths. The main reasons for these crashes were improper driving and violating traffic laws. Violating traffic laws by pedestrian was one of the main reasons for pedestrian casualty. Conclusions: The crashes are related to the characteristics of geography, climate, society activity of people, and the sense of traffic safety, the basic traffic construction and management in Chongqing. The traffic casualty of pedestrian is a big problem in Chongqing. To prevent and decrease road traffic injuries effective methods should be worked out and propaganda on traffic safety and traffic management should be strengthened according to different characteristics of different regions. To strengthen the first aid and treatment of cranium-brain injury and chest-back injury is also helpful in decreasing traffic deaths.展开更多
A lane-level intersection map is a cornerstone in high-definition(HD) traffic network maps for autonomous driving and high-precision intelligent transportation systems applications such as traffic management and contr...A lane-level intersection map is a cornerstone in high-definition(HD) traffic network maps for autonomous driving and high-precision intelligent transportation systems applications such as traffic management and control, and traffic accident evaluation and prevention. Mapping an HD intersection is time-consuming, labor-intensive, and expensive with conventional methods. In this paper, we used a low-channel roadside light detection and range sensor(LiDAR) to automatically and dynamically generate a lane-level intersection, including the signal phases, geometry, layout, and lane directions. First, a mathematical model was proposed to describe the topology and detail of a lane-level intersection. Second, continuous and discontinuous traffic object trajectories were extracted to identify the signal phases and times. Third, the layout, geometry, and lane direction were identified using the convex hull detection algorithm for trajectories. Fourth, a sliding window algorithm was presented to detect the lane marking and extract the lane, and the virtual lane connecting the inbound and outbound of the intersection were generated using the vehicle trajectories within the intersection and considering the traffic rules. In the field experiment, the mean absolute estimation error is 2 s for signal phase and time identification. The lane marking identification Precision and Recall are96% and 94.12%, respectively. Compared with the satellite-based,MMS-based, and crowdsourcing-based lane mapping methods,the average lane location deviation is 0.2 m and the update period is less than one hour by the proposed method with low-channel roadside LiDAR.展开更多
It was found that the cheap waste polyethylene film and polypropylenefilm are good modifying agents for the oxidized asphalt of high paraffin content,andthe polyvinyl chloride is not suited to be a modifying agent.The...It was found that the cheap waste polyethylene film and polypropylenefilm are good modifying agents for the oxidized asphalt of high paraffin content,andthe polyvinyl chloride is not suited to be a modifying agent.The modified asphalt isbetter than the original asphalt in high and low temperature properties.展开更多
In this paper, after analyzing the predicaments that Chinese traditional logistics enterprises face while launching modem logistics services, the theory of reforming Chinese traditional logistics enterprises with Busi...In this paper, after analyzing the predicaments that Chinese traditional logistics enterprises face while launching modem logistics services, the theory of reforming Chinese traditional logistics enterprises with Business Process Reengineering （BPR） is put forward. Then the basic implementation principles are discussed, and the steps of BPR are also analyzed for Chinese logistics enterprises. Moreover, five relevant measures of ensuring the success of BPR for them are concept reengineering, system reengineering, organization reengineering, culture reengineering and technology reengineering.展开更多
It is interesting that despite its long-term and widespread use in China,relatively little is known about the operational characteristics of a variable approach lane(VAL)in real world.Using one month of inductive-loop...It is interesting that despite its long-term and widespread use in China,relatively little is known about the operational characteristics of a variable approach lane(VAL)in real world.Using one month of inductive-loop detector data at ten dynamic approaches(intersection approaches with dynamic lane assignment)from different intersections in Hangzhou,China,this paper presents the results of a study materializing the flow characteristics of variable approach lanes by comparing them with adjacent normal-flow lanes under various operating conditions.The effectiveness of the results was examined in a case-control analysis by integrating 12 fixed approaches(without variable lane)as benchmark.It was found that the difference or similarity of flow rate between the variable lane and the normally-flowing lane differs under a variety of traffic volume,time-of-day,modeof-operation,and overhead lane-use guidance sign(OHS)location conditions.The study also revealed that while naturally there may be a difference in the flow rates between referencing lanes at fixed approaches,the flow difference percentage(FDP)at dynamic approaches is significantly higher.展开更多
The dispersion of vehicular paths is a common phenomenon in the inner area of signalized intersections due to heterogeneous driver behavior and interactions.This study aims to develop an explainable neural network-bas...The dispersion of vehicular paths is a common phenomenon in the inner area of signalized intersections due to heterogeneous driver behavior and interactions.This study aims to develop an explainable neural network-based model to describe the vehicle path dispersion by exploring the relationship between the path dispersion and external factors.A backpropagation neural network model was established to analyze the effects of external factors on the dispersion of through and left-turn paths based on real trajectory data collected from 20 intersections in Shanghai,China.Twelve influencing factors in varying geometric,traffic,signalization,and traffic management conditions were considered.The predictive power and transferability of the model were verified by applying the trained model on the four new intersections.The contributions of the influencing factors on the path dispersion were explored based on the neural interpretation diagram,relative importance of influencing factors,and sensitivity analysis to offer explanatory insights for the proposed model.The results show that the mean absolute percentage errors of the path dispersion models for the through and left-turn movements are only 14.67%and 17.65%,respectively.The through path dispersion is primarily influenced by the number of exit lanes,the offset degree between the approach and exit lanes,and the traffic saturation degree on the through lane.In contrast,the path dispersion of the left turn is mainly affected by the number of exit lanes,the left-turn angle,and the setting of guide lines.展开更多
Highway on-ramp merging locations are vulnerable to traffic collisions inflicting fatal or serious injuries to drivers.Although numerous studies have uncovered the major contributing factors to crashes at on-ramp merg...Highway on-ramp merging locations are vulnerable to traffic collisions inflicting fatal or serious injuries to drivers.Although numerous studies have uncovered the major contributing factors to crashes at on-ramp merging areas,none of these studies have focused on fatal/severe-injury crashes.This paper aims to provide an in-depth and systematic investigation on critical contributing factors of the high-severity crashes at highway merging areas.As part of the analysis,support vector machines(SVM)and random forest(RF)models were developed for a 10-year data set of crashes at more than 250 merging locations in Texas,United States,using 23 different crash attributes describing each incident to predict highseverity crashes.A sensitivity analysis was conducted to quantify the marginal effects of each contributing factor.The results indicate that there is an increased likelihood of fatal/severe-injury crashes when the number of highway lanes is high,and the number of lanes on the frontage roads/connector roads is low(<4).Likewise,presence of heavy vehicles seems to affect the occurrence of fatal injury crashes at merging areas.Additionally,longer ramp lengths,presence of auxiliary lanes,and the proximity of exit ramps are found to increase the likelihood of high severity crashes.These findings,either new or consistent with previous studies are helpful in enriching the literature of on-ramp related highway safety studies.展开更多
文摘Unidirectional two-lane freeway is a typical and the simplest form of freeway. The traffic flow char- acteristics including safety condition on two-lane freeway is of great significance in planning, design, and manage- ment of a freeway. Many previous traffic flow models are able to figure out flow characteristics such as speed, den- sity, delay, and so forth. These models, however, have great difficulty in reflecting safety condition of vehicles. Besides, for the cellular automation, one of the most widely used microscopic traffic simulation models, its discreteness in both time and space can possibly cause inaccuracy or big errors in simulation results. In this paper, a micro-simula- tion model of two-lane freeway vehicles is proposed to evaluate characteristics of traffic flow, including safety condition. The model is also discrete in time but continu- ous in space, and it divides drivers into several groups on the basis of their preferences for overtaking, which makes the simulation more aligned with real situations. Partial test is conducted in this study and results of delay, speed, volume, and density indicate the preliminary validity of our model, based on which the proposed safety coefficient evaluates safety condition under different flow levels. It is found that the results of this evaluation coincide with daily experience of drivers, providing ground for effectiveness of the safety coefficient.
文摘This paper investigates the traffic accidents＇ trends and causes in Dubai. For this purpose, the traffic accident statistics for years 2003 to 2012 are used to examine the trends of different types of accidents and the causes of these accidents. Also, the paper determines the most common types of accidents over the study period and identifies some of the causes for these accidents. Furthermore, the paper shows the impact of the new traffic law amendments, which were issued in 2008, on the accident rates and trends. The results showed that the implementation of the traffic law amendments did not have major impact in year 2008. However, there was a significant effect of these amendments in the following years. Also, lack of awareness of traffic laws and regulations in Dubai has been proven to be one of the major causes of accidents. Finally, the paper provides some recommendations to reduce the traffic accident rates, in order to achieve the Dubai Police Department 2020 strategic goal to have zero fatalities.
基金funded by National Natural Science Foundation of China(51178055)Asia Pacific Network for Global Change Research(1094801)
文摘As the transport sector is a major source of greenhouse gas emissions, the effect of urbanization on transport CO2 emissions in developing cities has become a key issue under global climate change. Examining the case of Xi＇an, this paper aims to explore the spatial distribution of commuting CO2 emissions and influencing factors in the new, urban industry zones and city centers considering Xi＇an＇s transition from a monocentric to a polycentric city in the process of urbanization. Based on household survey data from 1501 respondents, there are obvious differences in commuting CO2 emissions between new industry zones and city centers： City centers feature lower household emissions of 2.86 kg CO2 per week, whereas new industry zones generally have higher household emissions of 3.20 kg CO2 per week. Contrary to previous research results, not all new industry zones have high levels of CO2 emissions; with the rapid development of various types of industries, even a minimum level of household emissions of 2.53 kg CO2 per week is possible. The uneven distribution of commuting CO2 emissions is not uniformly affected by spatial parameters such as job-housing balance, residential density, employment density, and land use diversity. Optimum combination of the spatial parameters and travel pattern along with corresponding transport infrastructure construction may be an appropriate path to reduction and control of emissions from commuting.
基金The National Natural Science Foundation of China (No.71771019, 71871130, 71971125)the Science and Technology Special Project of Shandong Provincial Public Security Department (No. 37000000015900920210010001,37000000015900920210012001)。
文摘To improve the level of active traffic management,a short-term traffic flow prediction model is proposed by combining phase space reconstruction(PSR)and extreme gradient boosting(XGBoost)algorithms.Firstly,the traditional data preprocessing method is improved.The new method uses hierarchical clustering to determine the traffic flow state and fills in missing and abnormal data according to different traffic flow states.Secondly,one-dimensional data are mapped into a multidimensional data matrix through PSR,and the time series complex network is used to verify the data reconstruction effect.Finally,the multidimensional data matrix is inputted into the XGBoost model to predict future traffic flow parameters.The experimental results show that the mean square error,average absolute error,and average absolute percentage error of the prediction results of the PSR-XGBoost model are 5.399%,1.632%,and 6.278%,respectively,and the required running time is 17.35 s.Compared with mathematical-statistical models and other machine learning models,the PSR-XGBoost model has clear advantages in multiple predictive indicators,proving its feasibility and superiority in short-term traffic flow prediction.
基金Supported by the National Natural Science Foundation of China （No.20171007）.
文摘Boron nitride nanotubes （BN-NTs） with pure hexagonal BN phase have been synthesized by heating ball-milled boron powders in flowing ammonia gas at a temperature of 1200℃. The as-synthesized products were characterized by X-ray powder diffraction, transmission electron microscopy, high-resolution transmission electron microscopy, and electron energy loss spectroscopy （EELS）. The diameters of nanotubes are in the rage of 40-120nm and the lengths are more than 10μm. EELS result identifies that the ratio of boron and nitrogen is almost 1：1 The growth temperature is a crucial growth parameter in controlling the structure and crystalline of BN-NTs. The nanotubes grown at 1100℃ possesses of a bamboo-like structure, while as the temperature increased to 1200℃, most of the nanotubes exhibited a cylindrical structure. In addition, changing the heating time can control the size of the nanotubes. The gas atmosphere has influence on the yield of BN-NTs during heating process. When heating atmosphere was replaced by nitrogen, the yield of nanotubes was remarkably decreased.
基金The project supported by National Natural Science Foundation of China.
文摘Aiming at the defects in previous research and based on porous pelletmodel,the kinetics model of organic matter degradation in FBBR has been estab-lished.By means of synthesis phenolic wastewater treatment experiment,the reliabil-ity of the model is tested and the result shows that the precision is satistactory.De-pending on the model,the paper analyses in detail the mechanism of organic matterdegradation and the effect of biofilm thickness on reactor performance in FBBR.Theresearch result indicates that high efficiency of FBBR lies in high value of ηX and thebiofilm thickness is a significant factor affecting η,X and reactor performance.
文摘This paper discusses two urgent problems that need to be solved in fully automatic operation(FAO)for urban rail transit.The first is the analysis of safety in FAO,while another is the analysis of efficiency in FAO.Firstly,this paper establishes an operational safety evaluation index system from the perspective of operation for the unique or typical risk sources of the FAO system,and uses the analytic hierarchy process(AHP)to evaluate the indicators,analyzes various factors that affect the safe operation of FAO,and provides safety management recommendations for FAO lines operation to maintain the FAO system specifically.Secondly,taking the Yanfang Line as an example,this paper uses OpenTrack software to analyze the efficiency of FAO operation,and conducts simulation calculations for key links such as the mainline tracking interval,train entry and exit,and return limit interval.The fault impact surface of the FAO trains is simulated and discussed to verify whether FAO can meet the long-term operation requirements of Yanfang Line.Finally,this paper compares the simulation data of FAO on the Yanfang Line with manual operation(MO)to verify the advantages of FAO and guide the engineering construction of subsequent fully automated driving lines.
基金supported by the National Natural Science Foundation of China (Grant No.61671264)Basic scientific research project of Beijing University of Posts and Telecommunications (Grant No. 2019RC02)National Key R&D Program of China(Grant No.2018YFE0101000)
文摘The symbiotic FM radio data system(SRDS)is a radio data system that a specially designed OFDM signal co-lives with FM signal,which enables a significantly higher data rate than existing radio data systems.The cyclic prefix of the OFDM symbol has the same length as the OFDM body,which enables the analytic separation of the co-channel OFDM and FM signal at receiver side,utilizing the fact that the OFDM body and prefix is equal.In this work,we show that the OFDM body and prefix cannot be viewed as equal when there is sufficient carrier frequency offset(CFO).Thus,we propose a two-step CFO estimation algorithm for FM and SRDS hybrid signal.The first step estimates the coarse CFO by exploring the characteristics of the FM signal.Once the coarse CFO is removed,the residual CFO is small enough for FM and OFDM separation.The second step fine estimates CFO from the OFDM-only signal using its repeated PN structure after the separation.Detailed mathematical equations are formulated and simulation results are given.The results show that the proposed algorithm works fine with the simulation setup and has a final residual CFO less than 3.9Hz.
文摘Redesign of motorized and non-motorized transport in cities and sustainable mobility possibilities and utilization of already occupied areas for motorized and non-motorized transport in cities. Reserved area for public transport may be the redesign much more to take advantage of without taking up new space in cities. Redesigned solutions shown in the work of public mass transport and the redesign of non-motorized transport, bicycle and pedestrian paths point to the improved use and safety of movement of passengers, cyclists and pedestrians. This paper presents five redesigned concept designs as improving existing forms of transport and movement of cyclists and pedestrians in cities. Redesigned conceptual designs of motorized and non-motorized transport in cities should serve as ideas for the growing problems of urban development in the segment of insufficient surface for pedestrians and cyclists, as well as sustainable mobility transport people in the city.
基金supported by the National Natural Science Foundation of China(No.72471023,71971019)the Fundamental Research Funds for the Central Universities(No.2024QYBS025).
文摘Demand-responsive transportation has been introduced in many cities around the world.However,whether it is applicable in the railway is still questionable,an exploration of passenger choice behavior between demandresponsive trains and pre-scheduled trains is pivotal in addressing this issue.To delve into passengers’choice preferences when facing demand-responsive trains and to dissect the feasibility of implementing demandresponsive service in high-speed railways,the stated preference survey method is employed to investigate travel intention of passengers.Based on the survey data obtained in China,the heterogeneity of passengers is analyzed from three aspects:personal socio-economic characteristics,travel characteristics,and travel mode choice.Considering the situation that demand-responsive train cannot operate,the risk attributes are considered.To bolster the appeal of demand-responsive trains,personalized service product attributes are added.Mixed Logit mode,which takes into account the heterogeneous travel choice behavior of passengers,is developed,and Maximum Likelihood Estimation and the Monte Carlo method are used to calibrate model parameters.The willingness to pay in terms of different factors of passengers is determined.The results indicate that early arrival deviation time,late arrival deviation time,demand response time,and success rate of ticket purchase remarkable influence passengers’decision regarding demand-responsive train,with only the success rate of ticket purchase positively impacting train choice.Moreover,the significant difference in train ticket price is observed solely in the self-funded long distance scenario,while demand-responsive trains are found to be particularly appealing in self-funded short distance scenario.Through the Willingness To Pay(WTP)analysis,it is discovered that by shortening demand response time,enhancing the success rate of ticket purchase,and minimizing the deviation times of early arrival and late arrival of trains,the attractiveness of the demand-responsive train to passengers under three travel scenarios can be augmented.This study provides profound insights into the possibility of railway enterprises operating demand-responsive trains.
基金Supported by Qinghai University Youth Research Fund,China(Grant No.2023-QGY-15)。
文摘Due to errors in vehicle dynamics modeling,uncertainty in model parameters,and disturbances from curvature,the performance of the path tracking controller is poor or even unstable under high-speed and large-curvature conditions.Therefore,a path tracking robust control strategy based on force-driven H_(∞)and MPC is proposed.To fully exploit the nonlinear dynamics characteristics of tires,a force-driven state space model of a path tracking system based on a linear time-varying tire model is established;the H_(∞)and MPC methods are used to design a robust controller.Considering disturbance and system state constraints,the robust control constraint model based on LMI is established.Finally,the proposed controller is validated through joint simulations using CarSim and MATLAB.The results show that the maximum lateral deviation is reduced by 17.07%,and the maximum course angle deviation is reduced by 13.04%under large curvature disturbance conditions.The maximum lateral deviation is reduced by 27.85%,and the maximum course angle deviation is reduced by 31.17%under conditions of uncertain road adhesion coefficients.Based on the controller’s performance,the proposed controller effectively mitigates modeling errors,parameter uncertainties,and curvature disturbances.
基金The National Natural Science Foundation of China (No. 52302373, 52472317)the Natural Science Foundation of Beijing (No. L231023)the Beijing Nova Program (No. 20230484443)。
文摘Connected and autonomous vehicle formation(CAVF)technology is considerably important for improving transportation efficiency,optimizing traffic flow,and reduc-ing energy consumption.Despite the extensive research con-ducted on trajectory tracking control and other aspects of CAVF,the quality of the extant literature varies consider-ably,and research content remains scattered.To better pro-mote the sustainable and healthy development of the CAVF field,this paper employs the mapping knowledge domain(MKD)methodology to comprehensively review and visual-ize the current research status in this domain.Based on this review,research themes,hotspots,research challenges,and future development directions are proposed.The findings suggest that the research on CAVF can be categorized into three primary developmental stages.China and the United States are the primary countries conducting CAVF research.There is a positive correlation between economic develop-ment and the generation of scientific research outcomes.Re-search institutions are predominantly concentrated in univer-sities.The field exhibits significant interdisciplinary and inte-gration characteristics,forming key research personnel and teams.It is expected that future research will concentrate on topics such as deep learning,trajectory optimization,energy management strategy,mixed vehicle platoon,and other re-lated subjects.Research on cognition-driven intelligent for-mation decision-making mechanisms,resilience-oriented for-mation safety assurance systems,multiobjective collabora-tive formation optimization strategies,and digital twin-driven formation system validation platforms represents key future development directions.
文摘Objective: To study the epidemiological characteristics and preventive methods of road traffic crashes in a mountain city in western China through sampling investigation of traffic crashes in different regions of Chongqing city in recent years. Methods: Two police teams of traffic management in downtown, two teams in suburb, one team in county and one freeway team were randomly selected, and road traffic crashes between 1988 and 1997 were investigated and analyzed. Results: A total of 13121 road traffic crashes with 6201 crashes with casualties were analyzed. The incidence of crashes was higher in May, June and July, and on Friday and Wednesday and at 8:00-12:00 and 14:00-18:00 within a day. Casualties were 44.0% in pedestrians and 42.5% in passengers of total casualties. The deaths and severe injuries in pedestrians were 59.1% of total deaths and 56.4% of total severe injuries. The age of drivers and passengers were mainly at 18-30 years, followed by 31-40 years. People over 60 years old accounted for 24.1% of total pedestrian casualty. Head injury was the most common reason for deaths. The main reasons for these crashes were improper driving and violating traffic laws. Violating traffic laws by pedestrian was one of the main reasons for pedestrian casualty. Conclusions: The crashes are related to the characteristics of geography, climate, society activity of people, and the sense of traffic safety, the basic traffic construction and management in Chongqing. The traffic casualty of pedestrian is a big problem in Chongqing. To prevent and decrease road traffic injuries effective methods should be worked out and propaganda on traffic safety and traffic management should be strengthened according to different characteristics of different regions. To strengthen the first aid and treatment of cranium-brain injury and chest-back injury is also helpful in decreasing traffic deaths.
基金supported in part by the Scientific Research Project of the Education Department of Jilin Province (JJKH20221020KJ)the National Natural Science Foundation of China (51408257)the Graduate Innovation Fund of Jilin University (101832020CX150)。
文摘A lane-level intersection map is a cornerstone in high-definition(HD) traffic network maps for autonomous driving and high-precision intelligent transportation systems applications such as traffic management and control, and traffic accident evaluation and prevention. Mapping an HD intersection is time-consuming, labor-intensive, and expensive with conventional methods. In this paper, we used a low-channel roadside light detection and range sensor(LiDAR) to automatically and dynamically generate a lane-level intersection, including the signal phases, geometry, layout, and lane directions. First, a mathematical model was proposed to describe the topology and detail of a lane-level intersection. Second, continuous and discontinuous traffic object trajectories were extracted to identify the signal phases and times. Third, the layout, geometry, and lane direction were identified using the convex hull detection algorithm for trajectories. Fourth, a sliding window algorithm was presented to detect the lane marking and extract the lane, and the virtual lane connecting the inbound and outbound of the intersection were generated using the vehicle trajectories within the intersection and considering the traffic rules. In the field experiment, the mean absolute estimation error is 2 s for signal phase and time identification. The lane marking identification Precision and Recall are96% and 94.12%, respectively. Compared with the satellite-based,MMS-based, and crowdsourcing-based lane mapping methods,the average lane location deviation is 0.2 m and the update period is less than one hour by the proposed method with low-channel roadside LiDAR.
文摘It was found that the cheap waste polyethylene film and polypropylenefilm are good modifying agents for the oxidized asphalt of high paraffin content,andthe polyvinyl chloride is not suited to be a modifying agent.The modified asphalt isbetter than the original asphalt in high and low temperature properties.
文摘In this paper, after analyzing the predicaments that Chinese traditional logistics enterprises face while launching modem logistics services, the theory of reforming Chinese traditional logistics enterprises with Business Process Reengineering （BPR） is put forward. Then the basic implementation principles are discussed, and the steps of BPR are also analyzed for Chinese logistics enterprises. Moreover, five relevant measures of ensuring the success of BPR for them are concept reengineering, system reengineering, organization reengineering, culture reengineering and technology reengineering.
基金supported by“Pioneer”and“Leading Goose”R&D Program of Zhejiang Province of China(No.2022C01042)the Natural Science Foundation of Zhejiang Province of China(Nos.LGF21E080002 and LR23E080002)+1 种基金the National Natural Science Foundation of China(No.72361137006)the Alibaba-Zhejiang University Joint Research Institute of Frontier Technologies.
文摘It is interesting that despite its long-term and widespread use in China,relatively little is known about the operational characteristics of a variable approach lane(VAL)in real world.Using one month of inductive-loop detector data at ten dynamic approaches(intersection approaches with dynamic lane assignment)from different intersections in Hangzhou,China,this paper presents the results of a study materializing the flow characteristics of variable approach lanes by comparing them with adjacent normal-flow lanes under various operating conditions.The effectiveness of the results was examined in a case-control analysis by integrating 12 fixed approaches(without variable lane)as benchmark.It was found that the difference or similarity of flow rate between the variable lane and the normally-flowing lane differs under a variety of traffic volume,time-of-day,modeof-operation,and overhead lane-use guidance sign(OHS)location conditions.The study also revealed that while naturally there may be a difference in the flow rates between referencing lanes at fixed approaches,the flow difference percentage(FDP)at dynamic approaches is significantly higher.
基金supported by grants from the National Natural Science Foundation of China(71971140 and 52122215)the Shanghai Pujiang Program(21PJC085)the Shanghai Shuguang Program(22SG45).
文摘The dispersion of vehicular paths is a common phenomenon in the inner area of signalized intersections due to heterogeneous driver behavior and interactions.This study aims to develop an explainable neural network-based model to describe the vehicle path dispersion by exploring the relationship between the path dispersion and external factors.A backpropagation neural network model was established to analyze the effects of external factors on the dispersion of through and left-turn paths based on real trajectory data collected from 20 intersections in Shanghai,China.Twelve influencing factors in varying geometric,traffic,signalization,and traffic management conditions were considered.The predictive power and transferability of the model were verified by applying the trained model on the four new intersections.The contributions of the influencing factors on the path dispersion were explored based on the neural interpretation diagram,relative importance of influencing factors,and sensitivity analysis to offer explanatory insights for the proposed model.The results show that the mean absolute percentage errors of the path dispersion models for the through and left-turn movements are only 14.67%and 17.65%,respectively.The through path dispersion is primarily influenced by the number of exit lanes,the offset degree between the approach and exit lanes,and the traffic saturation degree on the through lane.In contrast,the path dispersion of the left turn is mainly affected by the number of exit lanes,the left-turn angle,and the setting of guide lines.
基金the Scientific and Technological Developing Project of Jilin Province(grant no.20240402076GH)is partly supporting this work。
文摘Highway on-ramp merging locations are vulnerable to traffic collisions inflicting fatal or serious injuries to drivers.Although numerous studies have uncovered the major contributing factors to crashes at on-ramp merging areas,none of these studies have focused on fatal/severe-injury crashes.This paper aims to provide an in-depth and systematic investigation on critical contributing factors of the high-severity crashes at highway merging areas.As part of the analysis,support vector machines(SVM)and random forest(RF)models were developed for a 10-year data set of crashes at more than 250 merging locations in Texas,United States,using 23 different crash attributes describing each incident to predict highseverity crashes.A sensitivity analysis was conducted to quantify the marginal effects of each contributing factor.The results indicate that there is an increased likelihood of fatal/severe-injury crashes when the number of highway lanes is high,and the number of lanes on the frontage roads/connector roads is low(<4).Likewise,presence of heavy vehicles seems to affect the occurrence of fatal injury crashes at merging areas.Additionally,longer ramp lengths,presence of auxiliary lanes,and the proximity of exit ramps are found to increase the likelihood of high severity crashes.These findings,either new or consistent with previous studies are helpful in enriching the literature of on-ramp related highway safety studies.
