Multi-frictional disks are employed to transmit the torque in speeding wetclutch, and the oil thickness within frictional disks could be adjusted for practical outputspeeding. As oil combined with alpha-hydrocarbon or...Multi-frictional disks are employed to transmit the torque in speeding wetclutch, and the oil thickness within frictional disks could be adjusted for practical outputspeeding. As oil combined with alpha-hydrocarbon or polyester is getting widely used as lubricantand the speeding wet clutch works within hydrodynamic lubrication, mixture lubrication, boundarylubrication and contact situation, established the thermal analysis model for investigating thebehavior of frictional disks in speeding wet clutch, which covers the power-law fluid model,Patir-Cheng average flow model, GT asperity contact model, oil film inertia and heat effects, meanenergy equation, and heat conduction equation. The formulas in the model are deduced. The numeralcalculation and analysis for hydrodynamic lubrication and mixture lubrication are executed.Relationships and variations among transmitting torque, mean push pressure, output speed, and loadare presented. Thermal effect should be considered during the hydrodynamic lubrication and largertransmitting torque makes earlier entrance to mixture lubrication.展开更多
China is the main silk producer in the world, whose RSS (Raw Silk Standard)is widely approved in international trade. After entering WTO, China needs to revise the RSSaccording to the changes of silk industry and deve...China is the main silk producer in the world, whose RSS (Raw Silk Standard)is widely approved in international trade. After entering WTO, China needs to revise the RSSaccording to the changes of silk industry and develop advanced electronic testing system and improvetesting means, so as to promote the internationlization of the RSS. 1. The international standingof Chinese silk The silk consisting of 18 amino acids has the similar protein structure to people'sskin. It is enjoyed by most people for it' s comfortable, magnificent and noble features and ispraised to be the second skin for its unique effects on health and adjusting the body water. In the21st century, silk is the main international fashion as the representative of green products.展开更多
In recent years, the subcontracting production for foreign trade of the Xi’an Aviation Engine Company (XAEC), a foreign trade production base of China, has achieved rapid development. In 1994, the company’s export e...In recent years, the subcontracting production for foreign trade of the Xi’an Aviation Engine Company (XAEC), a foreign trade production base of China, has achieved rapid development. In 1994, the company’s export earnings from foreign trade made a breakthrough at US$11 million, and it was commended by the State Economic展开更多
To introduce foreign capital for the municipal highway construction is a great measure to meet the development of the socialist market economy and to reform the investment system for the municipal highway construction...To introduce foreign capital for the municipal highway construction is a great measure to meet the development of the socialist market economy and to reform the investment system for the municipal highway construction. The aim of the reform lies in taking the construction and management of the municipal highway facilities as an industry to operate, widening the investment channel of the municipal highway construction and gradually forming a benign cycle of investment-construc-展开更多
According to customs statistics, China’s exports of machinery and electric products in 1996 were worth US$ 48.21 billion, an increase of 9.9 percent over the preceding year, and 8.4 percent higher than the growth rat...According to customs statistics, China’s exports of machinery and electric products in 1996 were worth US$ 48.21 billion, an increase of 9.9 percent over the preceding year, and 8.4 percent higher than the growth rate of the nation’s total exports. The proportion of machinery and electric product exports in the nation’s total foreign trade volume\ increased from 29.5 percent in 1995 to 31.9 percent in 1996, a growth at 2.4 percent.展开更多
Housing isone of the necessities of humansfor existence and development.The Chinese government hasalways attached great importanceto housing construction;especially in recent years,thepriority development of housingco...Housing isone of the necessities of humansfor existence and development.The Chinese government hasalways attached great importanceto housing construction;especially in recent years,thepriority development of housingconstruction has been seen inthe real estate and propertiesindustry.Hou Jie,Minister ofConstruction,not long ago wrotean article summarizing theachievements made in this sectorand drawing a blueprint forspeedup of housing constructionand the improvement of livingconditions in the future.It willprovide a vast vista for thedevelopment of China’s buildingindustry and its internationalcooperation.展开更多
High-speed railways have the merits of high speed, high transport capacity, low consumption of energy, less pollution, less occupation of land, and greater safety. The development of high-speed railways is suitable fo...High-speed railways have the merits of high speed, high transport capacity, low consumption of energy, less pollution, less occupation of land, and greater safety. The development of high-speed railways is suitable for the national conditions in China.The authors suggest that, with the Hu-Ning (Shanghai-Nanjing) section of the Jing-Hu (Beijing-Shanghai) Railway as the starting point, a high-speed dedicated passenger railway line be built to realize the separate transportation of passengers and goods, thus easing the strain on transport in East China, accumulating experience for the future development of high-speed railways, and bringing along the development of high and new technology industries.展开更多
This paper discusses the urgency to further develop China’s space technological industry;analyzes the gaps between China and other advanced countries in space industry,including technological level,development scale,...This paper discusses the urgency to further develop China’s space technological industry;analyzes the gaps between China and other advanced countries in space industry,including technological level,development scale,application scope and investment;describes the current severe situation that the China’s space industry is faced with and proposes the overall objective,guiding principles and major tasks of China’s space technological sector in the Ninth-Five Year Plan and the coming decade.Finally,it proposes some policies and effective measures to speed up the development of China’s space industry to meet the challenge in the 21st century.展开更多
Speeding in a work zone needs to be tackled effectively to enhance work zone safety. This study evaluates the influence of three different work zone signs—speed photo enforced signs, dynamic speed display signs and r...Speeding in a work zone needs to be tackled effectively to enhance work zone safety. This study evaluates the influence of three different work zone signs—speed photo enforced signs, dynamic speed display signs and reduced speed limit signs—on driver speeding behavior using a medium-fidelity driving simulator. The speed photo enforced and reduced speed limit signs were placed at intervals before the start of the work zone and in the work zone. A virtual work zone network was built to replicate the Baltimore–Washington Parkway(MD-295). A total of 66 participants from different socioeconomic backgrounds participated in 264 driving simulation sessions. The speeds were measured over four phases: initial speed area, sign visible area, sign readable area and post sign area. An analysis of variance and post hoc analysis showed that the speed photo enforced sign was the most effective of the three signs. The second speed photo enforced sign within the work zone was more effective at reducing speed than the sign before the start of the work zone, especially in the post sign area. It was observed that female participants tend to slow down more when encountering a speed photo enforcement sign.展开更多
Over-speeding is a pivotal factor in fatal traffic crashes globally,necessitating robust speed management strategies to augment road safety.In 2021,the National Highway Traffic Safety Administration reported over 1200...Over-speeding is a pivotal factor in fatal traffic crashes globally,necessitating robust speed management strategies to augment road safety.In 2021,the National Highway Traffic Safety Administration reported over 12000 speed-related fatalities in the United States alone.Previous studies aggregated over-speeding tendencies;however,the extent of over-speeding has a significant implication on the crash outcome.This study delves into the prevalence and magnitude of over-speeding in various scenarios,utilizing data from traffic cameras in Edmonton,Canada,and employing a negative binomial statistical model for analysis.The model elucidates the significance and likelihood of over-speeding tenden-cies by incorporating temporal and built environment variables,i.e.,year,month,number of lanes,dwelling unit types,school-related,and open green space.Study results indicated that the aggregation of the over-speeding data tends to underestimate the influence of var-ious factors.Notably,the estimated impact of the posted speed limit for the disaggregated models is up to over two times that for the aggregated model.Further,the summer months exhibit a roughly 25%uptick in speed limit violations for aggregated models while about a 40%uptick in the speed limit violations for disaggregated approaches.Conversely,a dis-cernible decline in over-speeding tendencies is observed with camera enforcement,show-casing a 25%reduction over four years.Built environment variables presented mixed results,with one-unit dwellings associated with a 12%increase in over-speeding,while proximity to schools indicated a 10%decrease.These pivotal findings provide policymakers and practitioners with valuable insights to formulate targeted interventions and counter-measures to curtail speed limit violations and bolster overall road safety conditions.展开更多
Speeding likelihood is usually used to measure drivers'propensity of committing speeding.Albeit some studies have analyzed speeding likelihood,most of them are inadequate in considering spatial effects when analyz...Speeding likelihood is usually used to measure drivers'propensity of committing speeding.Albeit some studies have analyzed speeding likelihood,most of them are inadequate in considering spatial effects when analyzing speeding behaviors on urban road networks.This study aims to fill this knowledge gap by modeling speeding likelihood with spatial models and then evaluate the influence of contributing factors.The percent of speeding observations(PSO)is adopted to represent the speeding likelihood.The speeding behaviors and PSO of each floating car(i.e.,taxi)are extracted from the GPS trajectories in Chengdu,China.PSO is modeled by several Bayesian beta general linear models with spatial effects,namely the beta model,beta logit-normal model,beta intrinsic conditional autoregressive(ICAR)model,beta Besag-York-Molli e(BYM)model,and beta BYM2 model.Results show that the beta BYM2 model performs better than other models in terms of data-fitting.According to the estimates from the beta BYM2,spatial correlation is the main reason for the model variability.The roads with more lanes and roads linked by elevated roads are found to increase the speeding likelihood,while higher speed limits,intersection density,traffic congestion,and roadside parking are associated with lower speeding likelihood.These findings provide valuable insights for designing effective anti-speeding countermeasures on urban road networks.展开更多
Speeding is one of the most common aberrant driving behaviors among the driving population.Although research on speeding behavior among drivers has increased over the decades,little is known about the motivating facto...Speeding is one of the most common aberrant driving behaviors among the driving population.Although research on speeding behavior among drivers has increased over the decades,little is known about the motivating factors associated with speeding behavior among long-haul truck drivers(LHTDs),especially in developing nations like India.This study aims to develop a prediction model for speeding behavior and to identify the contributory factors and their influential patterns underlying speeding behavior among LHTDs in India.A cross-sectional study was conducted among LHTDs in Salem City,Tamil Nadu,India.The data were collected through face-to-face interviews using a questionnaire encompassing socio-demographic,work,vehicle,health-related lifestyle,and speeding-related characteristics.A total of 756 valid samples were collected and utilized for analysis purposes.While conventional statistical methods like binary logit technique lacked prediction capabilities,machine learning(ML)algorithms including decision tree(DT),random forest(RF),adaptive boosting(AdaBoost),and extreme gradient boosting(XGBoost)were employed to model speeding behavior among LHTDs.The analysis results showed that RF demonstrated superior performance in predicting speeding behavior over other competing algorithms with accuracy(0.80),F1 score(0.77),and AUROC(0.81).From the befitting RF model,the importance of factors contributing to speeding behavior among LHTDs was determined through the variable importance plot.Pressured delivery of goods,sleeping duration per day,age of truck,size of truck,monthly income,driving experience,driving duration per day,and age of the driver were identified as the eight topmost critical factors contributing to speeding behavior among LHTDs.Based on the developed RF model,the hidden relationships behind identified critical factors in relation to the speeding behavior were investigated using partial dependence plots(PDPs).The outcomes of this research will be useful for road safety authorities and Indian trucking industries to frame suitable policies and to introduce effective strategies for mitigating speeding behavior among LHTDs to promote road safety.展开更多
1 Authorities in Montgomery Township,Pennsylvania,have introduced wavy lane patterns on some streets in an effort to slow down traffic in the area.2 Driving along Grays Lane in Montgomery Township for the first time m...1 Authorities in Montgomery Township,Pennsylvania,have introduced wavy lane patterns on some streets in an effort to slow down traffic in the area.2 Driving along Grays Lane in Montgomery Township for the first time must be challenging.Thats because the regular lane patterns have been replaced by wavy and zig⁃zag lines that look like they were painted by a drunk.But they are wavy by design.According to Montgomery Township officials,the unusual patterns were thought as the best solution to discouraging speeding on some of the streets.Police sources told local media outlets that the“traffic⁃calming measures”were installed in response to numerous complaints about certain streets being used as“speedways”.展开更多
Microstructure,texture,and mechanical properties of the extruded Mg-2.49Nd-1.82Gd-0.2Zn-0.2Zr alloy were investigated at different extrusion temperatures(260 and 320℃),extrusion ratios(10:1,15:1,and 30:1),and extrusi...Microstructure,texture,and mechanical properties of the extruded Mg-2.49Nd-1.82Gd-0.2Zn-0.2Zr alloy were investigated at different extrusion temperatures(260 and 320℃),extrusion ratios(10:1,15:1,and 30:1),and extrusion speeds(3 and 6 mm/s).The experimental results exhibited that the grain sizes after extrusion were much finer than that of the homogenized alloy,and the second phase showed streamline distribution along the extrusion direction(ED).With extrusion temperature increased from 260 to 320℃,the microstructure,texture,and mechanical properties of alloys changed slightly.The dynamic recrystallization(DRX)degree and grain sizes enhanced as the extrusion ratio increased from 10:1 to 30:1,and the strength gradually decreased but elongation(EL)increased.With the extrusion speed increased from 3 to 6 mm/s,the grain sizes and DRX degree increased significantly,and the samples presented the typical<2111>-<1123>rare-earth(RE)textures.The alloy extruded at 260℃ with extrusion ratio of 10:1 and extrusion speed of 3 mm/s showed the tensile yield strength(TYS)of 213 MPa and EL of 30.6%.After quantitatively analyzing the contribution of strengthening mechanisms,it was found that the grain boundary strengthening and dislocation strengthening played major roles among strengthening contributions.These results provide some guidelines for enlarging the industrial application of extruded Mg-RE alloy.展开更多
The present research aimed to identify critical factors that affect speeding behavior.For that purpose,high-resolution smartphone data collected from a naturalistic driving experiment of 88 drivers were utilized,augme...The present research aimed to identify critical factors that affect speeding behavior.For that purpose,high-resolution smartphone data collected from a naturalistic driving experiment of 88 drivers were utilized,augmented with data from self-reported questionnaires.Using risk exposure and driving behavior indicators calculated from smartphone sensor data,as well as demographic characteristics and self-reported driving performance,statistical analysis was carried out for modelling the percentage of driving time over the speed limit,namely by means of generalized linear mixed-effects models.More precisely,an overall model was developed for all road environments,and additional separate models were developed for driving on urban and rural roads.The results from the interpretation of the estimated parameters of the models can be summarized as follows:the parameters of trip distance and mobile phone use while driving have been determined as statistically significant and positively correlated with the percentage of speeding time during a driver's trip.In the same context,male drivers and drivers in the age group of18-34 also increase the percentages of speeding instances while driving.Regarding driving behavior as stated on the questionnaire,it seems that low frequencies of self-declared speeding(never or rarely)are statistically significant and negatively correlated with the percentage of speeding time.It is expected that this research can provide considerable gains to society,since the stakeholders including policy makers and industry could rely on the results and recommendations regarding risk factors that appear to be critical for safe driving.展开更多
To reveal the rock burst mechanism,the stress and failure characteristics of coal-rock strata under different advancing speeds of mining working face were explored by theoretical analysis,simulation,and engineering mo...To reveal the rock burst mechanism,the stress and failure characteristics of coal-rock strata under different advancing speeds of mining working face were explored by theoretical analysis,simulation,and engineering monitoring.The relationship between energy accumulation and release was analyzed,and a reasonable mining speed according to specific projects was recommended.The theoretical analysis shows that as the mining speed increases from 4 to 15 m/d,the rheological coefficient of coal mass ranges from 0.9 to 0.4,and the elastic energy of coal mass accumulation varies from 100 to 900 kJ.Based on the simulation,there is a critical advancing speed,the iteration numbers of simulation are less than 15,000 per mining 10 m coal seam,the overburden structure is obvious,the abutment pressure in coal mass is large,and the accumulated energy is large,which is easy to cause strong rock burst.When the iteration number is greater than 15,000,the static force of coal mass increases slightly,but there is no obvious rock burst.Based on engineering monitoring,the mining speed of a mine is less than 8 m/d,and the periodic weighting distance is about 17 m;as the mining speed is greater than 10 m/d,and the periodic weighting distance is greater than 20 m;as the mining speed is 3-8 m/d,and the range of high stress in surrounding rock is 48 m;as the advancing speed is 8-12 m/d,and the high-stress range in surrounding rock is 80 m.Moreover,as the mining speed is less than 8 cut cycles,the micro seismic energy is less than 10,000 J;as the mining speed is 12 cut cycles,the microseismic energy is about 20,000 J.In summary,the advancing speed is positively correlated with the micro seismic event;as the mining speed increases,the accumulated elastic energy of surrounding rock is greater,which is easy to cause rock burst.The comprehensive analysis indicates the daily advance speed of the mine is not more than 12 cut cycles.展开更多
Switched Reluctance Motors(SRMs),outfitted with rugged construction,good speed range,high torque density,and rare earth-free nature that outweigh induction motors(IM)and permanent magnet synchronous motor(PMSM),afford...Switched Reluctance Motors(SRMs),outfitted with rugged construction,good speed range,high torque density,and rare earth-free nature that outweigh induction motors(IM)and permanent magnet synchronous motor(PMSM),afford a broad range of applications in the domain of electric vehicles(EVs).Standard copper magnetic wire and low-carbon steel laminations are used to construct SRMs,which give them high efficiency in the range of 85-95%.Despite SRM's desirable features over traditional motor-speed drives,high torque ripples and radial distortions constrain their deployment in EVs.Precise rotor position is imperative for effective management of the speed and torque of SRMs.This paper provides an illustrative compendium on review of the torque-speed control and ripple mitigation techniques using design enhancements and control methods for SRM drives for EV applications.The various schemes were evaluated on their performance metricsoperational speed range,control complexity,practical realization,need for pre-stored parameters(look-up tables of current,inductance and torque profiles)and motor controller memory requirements.The findings provide valuable insights into balancing the gains and trade-offs associated with EV applications.Furthermore,they pinpoint opportunities for enhancement by analyzing the cost and technical aspects of different SRM controllers.展开更多
When the proton exchange membrane fuel cell(PEMFC)system is running,there will be a condition that does not require power output for a short time.In order to achieve zero power output under low power consumption,it is...When the proton exchange membrane fuel cell(PEMFC)system is running,there will be a condition that does not require power output for a short time.In order to achieve zero power output under low power consumption,it is necessary to consider the diversity of control targets and the complexity of dynamic models,which brings the challenge of high-precision tracking control of the stack output power and cathode intake flow.For system idle speed control,a modelbased nonlinear control framework is constructed in this paper.Firstly,the nonlinear dynamic model of output power and cathode intake flow is derived.Secondly,a control scheme combining nonlinear extended Kalman filter observer and state feedback controller is designed.Finally,the control scheme is verified on the PEMFC experimental platform and compared with the proportion-integration-differentiation(PID)controller.The experimental results show that the control strategy proposed in this paper can realize the idle speed control of the fuel cell system and achieve the purpose of zero power output.Compared with PID controller,it has faster response speed and better system dynamics.展开更多
文摘Multi-frictional disks are employed to transmit the torque in speeding wetclutch, and the oil thickness within frictional disks could be adjusted for practical outputspeeding. As oil combined with alpha-hydrocarbon or polyester is getting widely used as lubricantand the speeding wet clutch works within hydrodynamic lubrication, mixture lubrication, boundarylubrication and contact situation, established the thermal analysis model for investigating thebehavior of frictional disks in speeding wet clutch, which covers the power-law fluid model,Patir-Cheng average flow model, GT asperity contact model, oil film inertia and heat effects, meanenergy equation, and heat conduction equation. The formulas in the model are deduced. The numeralcalculation and analysis for hydrodynamic lubrication and mixture lubrication are executed.Relationships and variations among transmitting torque, mean push pressure, output speed, and loadare presented. Thermal effect should be considered during the hydrodynamic lubrication and largertransmitting torque makes earlier entrance to mixture lubrication.
文摘China is the main silk producer in the world, whose RSS (Raw Silk Standard)is widely approved in international trade. After entering WTO, China needs to revise the RSSaccording to the changes of silk industry and develop advanced electronic testing system and improvetesting means, so as to promote the internationlization of the RSS. 1. The international standingof Chinese silk The silk consisting of 18 amino acids has the similar protein structure to people'sskin. It is enjoyed by most people for it' s comfortable, magnificent and noble features and ispraised to be the second skin for its unique effects on health and adjusting the body water. In the21st century, silk is the main international fashion as the representative of green products.
文摘In recent years, the subcontracting production for foreign trade of the Xi’an Aviation Engine Company (XAEC), a foreign trade production base of China, has achieved rapid development. In 1994, the company’s export earnings from foreign trade made a breakthrough at US$11 million, and it was commended by the State Economic
文摘To introduce foreign capital for the municipal highway construction is a great measure to meet the development of the socialist market economy and to reform the investment system for the municipal highway construction. The aim of the reform lies in taking the construction and management of the municipal highway facilities as an industry to operate, widening the investment channel of the municipal highway construction and gradually forming a benign cycle of investment-construc-
文摘According to customs statistics, China’s exports of machinery and electric products in 1996 were worth US$ 48.21 billion, an increase of 9.9 percent over the preceding year, and 8.4 percent higher than the growth rate of the nation’s total exports. The proportion of machinery and electric product exports in the nation’s total foreign trade volume\ increased from 29.5 percent in 1995 to 31.9 percent in 1996, a growth at 2.4 percent.
文摘Housing isone of the necessities of humansfor existence and development.The Chinese government hasalways attached great importanceto housing construction;especially in recent years,thepriority development of housingconstruction has been seen inthe real estate and propertiesindustry.Hou Jie,Minister ofConstruction,not long ago wrotean article summarizing theachievements made in this sectorand drawing a blueprint forspeedup of housing constructionand the improvement of livingconditions in the future.It willprovide a vast vista for thedevelopment of China’s buildingindustry and its internationalcooperation.
文摘High-speed railways have the merits of high speed, high transport capacity, low consumption of energy, less pollution, less occupation of land, and greater safety. The development of high-speed railways is suitable for the national conditions in China.The authors suggest that, with the Hu-Ning (Shanghai-Nanjing) section of the Jing-Hu (Beijing-Shanghai) Railway as the starting point, a high-speed dedicated passenger railway line be built to realize the separate transportation of passengers and goods, thus easing the strain on transport in East China, accumulating experience for the future development of high-speed railways, and bringing along the development of high and new technology industries.
文摘This paper discusses the urgency to further develop China’s space technological industry;analyzes the gaps between China and other advanced countries in space industry,including technological level,development scale,application scope and investment;describes the current severe situation that the China’s space industry is faced with and proposes the overall objective,guiding principles and major tasks of China’s space technological sector in the Ninth-Five Year Plan and the coming decade.Finally,it proposes some policies and effective measures to speed up the development of China’s space industry to meet the challenge in the 21st century.
基金the Maryland State Highway Association (SHA) for its funding support throughout the study
文摘Speeding in a work zone needs to be tackled effectively to enhance work zone safety. This study evaluates the influence of three different work zone signs—speed photo enforced signs, dynamic speed display signs and reduced speed limit signs—on driver speeding behavior using a medium-fidelity driving simulator. The speed photo enforced and reduced speed limit signs were placed at intervals before the start of the work zone and in the work zone. A virtual work zone network was built to replicate the Baltimore–Washington Parkway(MD-295). A total of 66 participants from different socioeconomic backgrounds participated in 264 driving simulation sessions. The speeds were measured over four phases: initial speed area, sign visible area, sign readable area and post sign area. An analysis of variance and post hoc analysis showed that the speed photo enforced sign was the most effective of the three signs. The second speed photo enforced sign within the work zone was more effective at reducing speed than the sign before the start of the work zone, especially in the post sign area. It was observed that female participants tend to slow down more when encountering a speed photo enforcement sign.
文摘Over-speeding is a pivotal factor in fatal traffic crashes globally,necessitating robust speed management strategies to augment road safety.In 2021,the National Highway Traffic Safety Administration reported over 12000 speed-related fatalities in the United States alone.Previous studies aggregated over-speeding tendencies;however,the extent of over-speeding has a significant implication on the crash outcome.This study delves into the prevalence and magnitude of over-speeding in various scenarios,utilizing data from traffic cameras in Edmonton,Canada,and employing a negative binomial statistical model for analysis.The model elucidates the significance and likelihood of over-speeding tenden-cies by incorporating temporal and built environment variables,i.e.,year,month,number of lanes,dwelling unit types,school-related,and open green space.Study results indicated that the aggregation of the over-speeding data tends to underestimate the influence of var-ious factors.Notably,the estimated impact of the posted speed limit for the disaggregated models is up to over two times that for the aggregated model.Further,the summer months exhibit a roughly 25%uptick in speed limit violations for aggregated models while about a 40%uptick in the speed limit violations for disaggregated approaches.Conversely,a dis-cernible decline in over-speeding tendencies is observed with camera enforcement,show-casing a 25%reduction over four years.Built environment variables presented mixed results,with one-unit dwellings associated with a 12%increase in over-speeding,while proximity to schools indicated a 10%decrease.These pivotal findings provide policymakers and practitioners with valuable insights to formulate targeted interventions and counter-measures to curtail speed limit violations and bolster overall road safety conditions.
基金supported by the Open Fund of Key Laboratory of Flight Techniques and Flight Safety(FZ2021KF05)the National Natural Science Foundation of China(71801182)+3 种基金the Fundamental Research Funds for the Central Universities(AUGA5710010222)the Opening Project of Intelligent Policing Key Laboratory of Sichuan Province(ZNJW2023KFZD001)the Natural Science Foundation of Heilongjiang Province of China(LH2022E074)the Smart Transportation Safety International Joint Lab Program。
文摘Speeding likelihood is usually used to measure drivers'propensity of committing speeding.Albeit some studies have analyzed speeding likelihood,most of them are inadequate in considering spatial effects when analyzing speeding behaviors on urban road networks.This study aims to fill this knowledge gap by modeling speeding likelihood with spatial models and then evaluate the influence of contributing factors.The percent of speeding observations(PSO)is adopted to represent the speeding likelihood.The speeding behaviors and PSO of each floating car(i.e.,taxi)are extracted from the GPS trajectories in Chengdu,China.PSO is modeled by several Bayesian beta general linear models with spatial effects,namely the beta model,beta logit-normal model,beta intrinsic conditional autoregressive(ICAR)model,beta Besag-York-Molli e(BYM)model,and beta BYM2 model.Results show that the beta BYM2 model performs better than other models in terms of data-fitting.According to the estimates from the beta BYM2,spatial correlation is the main reason for the model variability.The roads with more lanes and roads linked by elevated roads are found to increase the speeding likelihood,while higher speed limits,intersection density,traffic congestion,and roadside parking are associated with lower speeding likelihood.These findings provide valuable insights for designing effective anti-speeding countermeasures on urban road networks.
文摘Speeding is one of the most common aberrant driving behaviors among the driving population.Although research on speeding behavior among drivers has increased over the decades,little is known about the motivating factors associated with speeding behavior among long-haul truck drivers(LHTDs),especially in developing nations like India.This study aims to develop a prediction model for speeding behavior and to identify the contributory factors and their influential patterns underlying speeding behavior among LHTDs in India.A cross-sectional study was conducted among LHTDs in Salem City,Tamil Nadu,India.The data were collected through face-to-face interviews using a questionnaire encompassing socio-demographic,work,vehicle,health-related lifestyle,and speeding-related characteristics.A total of 756 valid samples were collected and utilized for analysis purposes.While conventional statistical methods like binary logit technique lacked prediction capabilities,machine learning(ML)algorithms including decision tree(DT),random forest(RF),adaptive boosting(AdaBoost),and extreme gradient boosting(XGBoost)were employed to model speeding behavior among LHTDs.The analysis results showed that RF demonstrated superior performance in predicting speeding behavior over other competing algorithms with accuracy(0.80),F1 score(0.77),and AUROC(0.81).From the befitting RF model,the importance of factors contributing to speeding behavior among LHTDs was determined through the variable importance plot.Pressured delivery of goods,sleeping duration per day,age of truck,size of truck,monthly income,driving experience,driving duration per day,and age of the driver were identified as the eight topmost critical factors contributing to speeding behavior among LHTDs.Based on the developed RF model,the hidden relationships behind identified critical factors in relation to the speeding behavior were investigated using partial dependence plots(PDPs).The outcomes of this research will be useful for road safety authorities and Indian trucking industries to frame suitable policies and to introduce effective strategies for mitigating speeding behavior among LHTDs to promote road safety.
文摘1 Authorities in Montgomery Township,Pennsylvania,have introduced wavy lane patterns on some streets in an effort to slow down traffic in the area.2 Driving along Grays Lane in Montgomery Township for the first time must be challenging.Thats because the regular lane patterns have been replaced by wavy and zig⁃zag lines that look like they were painted by a drunk.But they are wavy by design.According to Montgomery Township officials,the unusual patterns were thought as the best solution to discouraging speeding on some of the streets.Police sources told local media outlets that the“traffic⁃calming measures”were installed in response to numerous complaints about certain streets being used as“speedways”.
基金supported by the National Science and Technology Major Project,China(No.2019-VI-0004-0118)the National Natural Science Foundation of China(No.51771152)the National Key R&D Program of China(No.2018YFB1106800)。
文摘Microstructure,texture,and mechanical properties of the extruded Mg-2.49Nd-1.82Gd-0.2Zn-0.2Zr alloy were investigated at different extrusion temperatures(260 and 320℃),extrusion ratios(10:1,15:1,and 30:1),and extrusion speeds(3 and 6 mm/s).The experimental results exhibited that the grain sizes after extrusion were much finer than that of the homogenized alloy,and the second phase showed streamline distribution along the extrusion direction(ED).With extrusion temperature increased from 260 to 320℃,the microstructure,texture,and mechanical properties of alloys changed slightly.The dynamic recrystallization(DRX)degree and grain sizes enhanced as the extrusion ratio increased from 10:1 to 30:1,and the strength gradually decreased but elongation(EL)increased.With the extrusion speed increased from 3 to 6 mm/s,the grain sizes and DRX degree increased significantly,and the samples presented the typical<2111>-<1123>rare-earth(RE)textures.The alloy extruded at 260℃ with extrusion ratio of 10:1 and extrusion speed of 3 mm/s showed the tensile yield strength(TYS)of 213 MPa and EL of 30.6%.After quantitatively analyzing the contribution of strengthening mechanisms,it was found that the grain boundary strengthening and dislocation strengthening played major roles among strengthening contributions.These results provide some guidelines for enlarging the industrial application of extruded Mg-RE alloy.
基金co-financed by the European Union-European Regional Development Fund (ERDF)and Greek national funds through the Operational Program“Competitiveness,Entrepreneurship and Innovation” (EPAnEK)of the National Strategic Reference Framework (NSRF)-Research Funding Program:BeSmart-multi-modal driver behavior and safety support system on the basis of smartphone applications。
文摘The present research aimed to identify critical factors that affect speeding behavior.For that purpose,high-resolution smartphone data collected from a naturalistic driving experiment of 88 drivers were utilized,augmented with data from self-reported questionnaires.Using risk exposure and driving behavior indicators calculated from smartphone sensor data,as well as demographic characteristics and self-reported driving performance,statistical analysis was carried out for modelling the percentage of driving time over the speed limit,namely by means of generalized linear mixed-effects models.More precisely,an overall model was developed for all road environments,and additional separate models were developed for driving on urban and rural roads.The results from the interpretation of the estimated parameters of the models can be summarized as follows:the parameters of trip distance and mobile phone use while driving have been determined as statistically significant and positively correlated with the percentage of speeding time during a driver's trip.In the same context,male drivers and drivers in the age group of18-34 also increase the percentages of speeding instances while driving.Regarding driving behavior as stated on the questionnaire,it seems that low frequencies of self-declared speeding(never or rarely)are statistically significant and negatively correlated with the percentage of speeding time.It is expected that this research can provide considerable gains to society,since the stakeholders including policy makers and industry could rely on the results and recommendations regarding risk factors that appear to be critical for safe driving.
基金supported by the National Natural Science Foundation of China(52174109)Program for Innovative Research Team(in Science and Technology)in University of Henan Province(22IRTSTHN005)+1 种基金Key Research and Development Project of Henan Province(242102240029)Key Research Project of Institutions of Higher Education in Henan Province(24A580001).
文摘To reveal the rock burst mechanism,the stress and failure characteristics of coal-rock strata under different advancing speeds of mining working face were explored by theoretical analysis,simulation,and engineering monitoring.The relationship between energy accumulation and release was analyzed,and a reasonable mining speed according to specific projects was recommended.The theoretical analysis shows that as the mining speed increases from 4 to 15 m/d,the rheological coefficient of coal mass ranges from 0.9 to 0.4,and the elastic energy of coal mass accumulation varies from 100 to 900 kJ.Based on the simulation,there is a critical advancing speed,the iteration numbers of simulation are less than 15,000 per mining 10 m coal seam,the overburden structure is obvious,the abutment pressure in coal mass is large,and the accumulated energy is large,which is easy to cause strong rock burst.When the iteration number is greater than 15,000,the static force of coal mass increases slightly,but there is no obvious rock burst.Based on engineering monitoring,the mining speed of a mine is less than 8 m/d,and the periodic weighting distance is about 17 m;as the mining speed is greater than 10 m/d,and the periodic weighting distance is greater than 20 m;as the mining speed is 3-8 m/d,and the range of high stress in surrounding rock is 48 m;as the advancing speed is 8-12 m/d,and the high-stress range in surrounding rock is 80 m.Moreover,as the mining speed is less than 8 cut cycles,the micro seismic energy is less than 10,000 J;as the mining speed is 12 cut cycles,the microseismic energy is about 20,000 J.In summary,the advancing speed is positively correlated with the micro seismic event;as the mining speed increases,the accumulated elastic energy of surrounding rock is greater,which is easy to cause rock burst.The comprehensive analysis indicates the daily advance speed of the mine is not more than 12 cut cycles.
基金supported in part by the Universitat Politècnica de València under grant PAID-10-21supported through AMRITA Seed Grant(Proposal ID:ASG2022188)。
文摘Switched Reluctance Motors(SRMs),outfitted with rugged construction,good speed range,high torque density,and rare earth-free nature that outweigh induction motors(IM)and permanent magnet synchronous motor(PMSM),afford a broad range of applications in the domain of electric vehicles(EVs).Standard copper magnetic wire and low-carbon steel laminations are used to construct SRMs,which give them high efficiency in the range of 85-95%.Despite SRM's desirable features over traditional motor-speed drives,high torque ripples and radial distortions constrain their deployment in EVs.Precise rotor position is imperative for effective management of the speed and torque of SRMs.This paper provides an illustrative compendium on review of the torque-speed control and ripple mitigation techniques using design enhancements and control methods for SRM drives for EV applications.The various schemes were evaluated on their performance metricsoperational speed range,control complexity,practical realization,need for pre-stored parameters(look-up tables of current,inductance and torque profiles)and motor controller memory requirements.The findings provide valuable insights into balancing the gains and trade-offs associated with EV applications.Furthermore,they pinpoint opportunities for enhancement by analyzing the cost and technical aspects of different SRM controllers.
基金Supported by the Major Science and Technology Projects in Jilin Province and Changchun City(20220301010GX).
文摘When the proton exchange membrane fuel cell(PEMFC)system is running,there will be a condition that does not require power output for a short time.In order to achieve zero power output under low power consumption,it is necessary to consider the diversity of control targets and the complexity of dynamic models,which brings the challenge of high-precision tracking control of the stack output power and cathode intake flow.For system idle speed control,a modelbased nonlinear control framework is constructed in this paper.Firstly,the nonlinear dynamic model of output power and cathode intake flow is derived.Secondly,a control scheme combining nonlinear extended Kalman filter observer and state feedback controller is designed.Finally,the control scheme is verified on the PEMFC experimental platform and compared with the proportion-integration-differentiation(PID)controller.The experimental results show that the control strategy proposed in this paper can realize the idle speed control of the fuel cell system and achieve the purpose of zero power output.Compared with PID controller,it has faster response speed and better system dynamics.
