A new organocatalytic double annulation cascade involving scission/recombination of N-O bonds of nitrones is reported for the first time, and used to produce a range of hitherto unprecedented tricyclic bridged-fused b...A new organocatalytic double annulation cascade involving scission/recombination of N-O bonds of nitrones is reported for the first time, and used to produce a range of hitherto unprecedented tricyclic bridged-fused benzo[d]azepines bearing three stereogenic centers with moderate to good yields and complete diastereoselectivity. A quinine-catalyzed reaction of yne–allenone esters with nitrones worked well and provided a convergent and regioselective pathway to access these three-dimensional scaffolds from the planar conjugated system. Density functional theory(DFT) calculations have been applied to understand the key process for forming diradical intermediates.展开更多
Identification of variables that influence differences between predicted and observed cycling times for one cyclist commuting to Okanagan College (OC) was performed using principal components analysis. These data were...Identification of variables that influence differences between predicted and observed cycling times for one cyclist commuting to Okanagan College (OC) was performed using principal components analysis. These data were used to create a personalized predictive time algorithm, which was subsequently applied in an isochrone map format centered on OC. A 29% difference in the area within the 20-minute commuting time was estimated, suggesting that potential residential location choices made with inaccurate isochrone maps are inaccurate. A comparison with an isochron cycling map for Trinity College Dublin was made to emphasise differences in the impact/implications of this type of map in the promotion of sustainable transportation for a post-secondary institution. It is determined that these maps may misinform new community members as to areas of residential location choice.展开更多
To investigate the distribution characteristics and influencing factors of bicycle detour behavior,this study ac-curately identified detour behavior using global positioning system(GPS)track data from shared bicycles....To investigate the distribution characteristics and influencing factors of bicycle detour behavior,this study ac-curately identified detour behavior using global positioning system(GPS)track data from shared bicycles.Factors such as travel time,road conditions,public transportation facilities,and land use types were considered in constructing a detour behavior influence model based on the CatBoost machine learning algorithm.The interpretability of the machine learning framework was enhanced via Shapley additive explanations(SHAP),enabling an analysis of the impact of each factor on detour behavior.The results indicated that the CatBoost model effectively recognized detour behavior with high accuracy.The frequency of detour behavior increased with higher road levels,greater distances to crossing facilities,wider bike lanes,and an increased number of bus stops,subway stations,and leisure and entertainment facilities,while it decreased with a higher number of office commuting facilities.In addition,detour behavior was more prevalent on weekends,during off-peak hours,and under conditions involving physical central lane separation and physical bike lane separation.These findings offer a novel approach for identifying bicycle riding behaviors and analyzing their influencing factors,providing effective technical support for non-motorized traffic management and infrastructure optimization.展开更多
Two environmentalists using bamboo bicycles to promote green transportation.THE exhaust emissions generated by transporting the world’s population on a daily basis are one of the main sources of greenhouse gases.Vehi...Two environmentalists using bamboo bicycles to promote green transportation.THE exhaust emissions generated by transporting the world’s population on a daily basis are one of the main sources of greenhouse gases.Vehicles such as cars,subways,and motorcycles,all produce carbon emissions.展开更多
CHINA.Bicycle Output.China’s bicycle production saw solid growth last year,increasing by 0.4 percent year on year to reach 99.54 million units,said Zheng Xiaoling,spokesperson for the China Bicycle Association.
Designed and built by eight Dutch engineers,the worlds longest bicycle is 55.16 meters,roughly the same length as four double-decker buses.39-year-old Ivan Schalk had been thinking about building the world's longe...Designed and built by eight Dutch engineers,the worlds longest bicycle is 55.16 meters,roughly the same length as four double-decker buses.39-year-old Ivan Schalk had been thinking about building the world's longest bicycle since reading about it in The Guinness Book of Records when he was a child,but he only started this project in 2018,as a way to fill up his free time.展开更多
To reduce the risk of traffic accidents significantly caused by the speeding behavior of electric bicycles,this study focuses on the Beijing Yizhuang Economic and Tech-nological Development Zone.This work relies on hi...To reduce the risk of traffic accidents significantly caused by the speeding behavior of electric bicycles,this study focuses on the Beijing Yizhuang Economic and Tech-nological Development Zone.This work relies on high-precision shared electric bicycle Global Positioning System trajectory data,integrating a spatiotemporal analysis model and geographic information system(GIS)technol-ogy to explore the spatial and temporal variability law and formation mechanism of speeding behavior.Through data preprocessing,speeding events are identified,and weekday features are extracted.Four periods are identified:morning peak,midday minipeak,evening peak,and nighttime flat peak.Using the GIS platform,global spatial autocorrela-tion and local clustering analysis are conducted to identify the spatial clustering characteristics of speeding behaviors and hotspot areas.The coldspot and hotspot patterns of speeding events and the dynamic trajectories of their evolu-tion are analyzed using spatiotemporal cube technology.The results show that speeding behaviors are strongly corre-lated with the commuting peak in time and spatially concen-trated in the intersections of urban main roads,the periphery of commercial complexes,and industrial parks,with a dif-fusion tendency.The results of this study provide novel in-sights into the research and analysis of the spatial and tempo-ral characteristics of speeding risk behaviors of electric bi-cycles and effective technical support for nonmotorized traf-fic safety management.展开更多
Chiral aryl cyclohex-3-en ether scaffold is widely present in bioactive natural products and drugs.The exploitation of efficient and enantioselective methods for the construction of aryl cyclohex-3-en ether scaffold i...Chiral aryl cyclohex-3-en ether scaffold is widely present in bioactive natural products and drugs.The exploitation of efficient and enantioselective methods for the construction of aryl cyclohex-3-en ether scaffold is significant.Herein we disclose a chiral N,N’-dioxide/Lewis acid complex-catalyzed asymmetric inverse-electron-demand Diels-Alder(IEDDA)reaction using electron-deficient 3-carboalkoxyl-2-pyrones and less electron-enriched aryl enol ethers as reactants.A wide range of non-and 1,2-disubstituted acyclic aryl enol ethers are applicable to deliver diverse chiral bridged bicyclic lactones in high yields and stereoselectivities(up to 96%yield,>20:1 dr,97:3 er).The bridged bicyclic lactone core can be easily converted into chiral aryl cyclohex-3-en ether scaffold.Notably,DFT calculations revealed a stepwise and endo mechanism to explain the high enantioselectivity controlled by the cooperative effect of the steric factors and the dispersion interactions between ligands and enol ethers.展开更多
Aim To develop a concise method for the synthesis of bicyclic azasugar and thiosugar with novel scaffold. Methods The two primary hydroxyl groups of compound 1 were selectively protected with tosyl cloloride in pyridi...Aim To develop a concise method for the synthesis of bicyclic azasugar and thiosugar with novel scaffold. Methods The two primary hydroxyl groups of compound 1 were selectively protected with tosyl cloloride in pyridine, followed by ring-closure with sodium sulfide or primary amine to form the oxy-bridged bicyclic molecules in good yields. Results Two bicyclic azasugars and a thiosugar were produced from L-sorbose in several steps. Conclusion The described procedures provide an efficient method to synthesize bicyclic azasugar and thiosugar with novel scaffold as potential glycosidase inhibitors.展开更多
The bicyclic product containing a chromene skeleton and a propargylamine skeleton（C（22）H（22）N2O2） was synthesized from the double sites of terminal alkyne, piperazine derivative and formaldehyde via one-pot proc...The bicyclic product containing a chromene skeleton and a propargylamine skeleton（C（22）H（22）N2O2） was synthesized from the double sites of terminal alkyne, piperazine derivative and formaldehyde via one-pot procedure. Its structure was characterized by ^1H NMR, ^13C NMR, IR and H RMS, and further confirmed by single-crystal X-ray diffraction. It crystallizes in the monoclinic system, space group P21/n with a = 12.6571（14）, b = 11.3249（12）, c = 12.6571（14） A, β = 105.22°,V = 1750.6（3） A^3, Z = 4, R = 0.0568 and w R = 0.1444. The fluorescence of the product was discussed.展开更多
This paper investigates the passing events between electric bicycles and conventional bicycles and explores the relationships between passing events and traffic parameters in bicycle facilities.Three exclusive bicycle...This paper investigates the passing events between electric bicycles and conventional bicycles and explores the relationships between passing events and traffic parameters in bicycle facilities.Three exclusive bicycle paths in Nanjing, China,were observed with cameras.Then,the field data including vehicle number,velocity characteristics and passing event features were analyzed in detail.Data analysis and fitting reveal that the speed difference has little impact on the passing event number,as does the bicycle ratio.The Gaussian function can better describe the relationship between the passing event number and bicycle volume （density）.The valid use level of bicycle path width influences the inflexion of the passing events-density fitting curve.The conclusions can be applied for estimating the passing events in mixed bicycle flows and for choosing a suitable width of separate bicycle path.展开更多
PI novel caged bicyclic phosphate flame retardant tri(1-oxo-2,6,7-trioxa-1-phosphabicyclo [2.2.2] octane-methyl) phosphate (Trimer) was synthesized from 1-oxo-4-hydroxymethyl-2,6,7-trioxa-1-phosphabicyclo [2.2.2] octa...PI novel caged bicyclic phosphate flame retardant tri(1-oxo-2,6,7-trioxa-1-phosphabicyclo [2.2.2] octane-methyl) phosphate (Trimer) was synthesized from 1-oxo-4-hydroxymethyl-2,6,7-trioxa-1-phosphabicyclo [2.2.2] octane (PEPA) and phosphorus oxychloride in this paper. Its structure was characterized by elemental analysis. FTIR, H-1 NMR. P-31 NMR and X-ray diffraction analysis.展开更多
Mobile information and communication technologies(MICTs) have fully penetrated everyday life in smart societies;this has greatly compressed time, space, and distance, and consequently, reshaped residents’ travel beha...Mobile information and communication technologies(MICTs) have fully penetrated everyday life in smart societies;this has greatly compressed time, space, and distance, and consequently, reshaped residents’ travel behaviour patterns. As a new mode of shared mobility, the sharing bicycle offers a variety of options for the daily travel of urban residents. Extant studies have mainly examined the travel characteristics and influencing factors of public bicycles with piles, while the travel patterns for sharing bicycles and their driving mechanisms have been largely ignored. Using one week’s travel data for Mobike, this study investigated the spatial and temporal distribution patterns of sharing bicycle travel behaviours in the central urban area of Guangzhou, China;furthermore, it identified the influences of built environment density factors on sharing bicycle travel behaviours based on the geographically weighted regression method. Obvious morning and evening peaks were observed in the sharing bicycle travel patterns for both weekdays and weekends. The old urban area, which had a high degree of mixed function, dense road networks, and cycling-friendly built environments, was the main travel area that attracted sharing bicycles on both weekdays and weekends. Furthermore, factors including the point of interest(POI) for the density of public transport stations, the functional mixing degree, and the density of residential POIs significantly affected residents’ travel behaviours. These findings could enrich discourse regarding shared mobility with a Chinese case characterised by rapidly developing MICTs and also provide references to local authorities for improving slow traffic environments.展开更多
In this paper,we study the dynamics of an idealized benchmark bicycle moving on a surface of revolution.We employ symbolic manipulations to derive the contact constraint equations from an ordered process,and apply the...In this paper,we study the dynamics of an idealized benchmark bicycle moving on a surface of revolution.We employ symbolic manipulations to derive the contact constraint equations from an ordered process,and apply the Lagrangian equations of the first type to establish the nonlinear differential algebraic equations(DAEs),leaving nine coupled differential equations,six contact equations,two holonomic constraint equations and four nonholonomic constraint equations.We then present a complete description of hands-free circular motions,in which the time-dependent variables are eliminated through a rotation transformation.We find that the circular motions,similar to those of the bicycle moving on a horizontal surface,nominally fall into four solution families,characterized by four curves varying with the angular speed of the front wheel.Then,we numerically investigate how the topological profiles of these curves change with the parameter of the revolution surface.Furthermore,we directly linearize the nonlinear DAEs,from which a reduced linearized system is obtained by removing the dependent coordinates and counting the symmetries arising from cyclic coordinates.The stability of the circular motion is then analyzed according to the eigenvalues of the Jacobian matrix of the reduced linearized system around the equilibrium position.We find that a stable circular motion exists only if the curvature of the revolution surface is very small and it is limited in small sections of solution families.Finally,based on the numerical simulation of the original nonlinear DAEs system,we show that the stable circular motion is not asymptotically stable.展开更多
To determine how bus stop design influences mixed traffic operation near Chinese bus stops,a new theoretical method was developed by using additive-conflict-flows procedure.The procedure was extended from homogeneous ...To determine how bus stop design influences mixed traffic operation near Chinese bus stops,a new theoretical method was developed by using additive-conflict-flows procedure.The procedure was extended from homogeneous traffic flow to mixed traffic flow.Based on the procedure and queuing theory,car capacity and speed models were proposed for three types of bus stops including curbside,bus bay and bicycle detour.The effects of various combinations of bus stop type,traffic volume,bus dwell time,and berth number on traffic operations were investigated.The results indicate that traffic volume,bus dwell time and berth number have negative effects on traffic operations for any type of bus stops.For different types of bus stops,at car volumes above approximately 200 vehicles per hour,the bus bay and bicycle detour designs provide more benefits than the curbside design.As traffic volume increases,the benefit firstly increases in uncongested conditions and then decreases in congested conditions.It reaches the maximum at car volumes nearly 1 100 vehicles per hour.The results can be used to aid in the selection of a preferred bus stop design for a given traffic volume in developing countries.展开更多
Sesquiterpanes are ubiquitous components of crude oils and ancient sediments.Liquid saturated hydrocarbons from simulated pyrolysis experiments on immature organic-rich mudstone collected from the Lower Cretaceous Hes...Sesquiterpanes are ubiquitous components of crude oils and ancient sediments.Liquid saturated hydrocarbons from simulated pyrolysis experiments on immature organic-rich mudstone collected from the Lower Cretaceous Hesigewula Sag were analyzed by gas chromatography-mass spectrometry(GC-MS).C14 bicyclic sesquiterpanes,namely,8β(H)-drimane,8β(H)-homodrimane,and 8 a(H)-homodrimane were detected and identified on basis of their diagnostic fragment ions(m/z123,179,193,and 207),and previously published mass spectra data,and these bicyclic sesquiterpanes presented relatively regular characteristics in their thermal evolution.The ratios 8β(H)-drimane/8β(H)-homodrimane,8β(H)-homodrimane/8 a(H)-homodrimane,and 8β(H)-drimane/8 a(H)-homodrimane all show a clear upward trend with increasing temperature below the temperature turning point.Thus,all these ratios can be used as evolution indexes of source rocks in the immature-lowmaturity stage.However,the last two ratios may be more suitable than the first ratio as valid parameters for measuring the extent of thermal evolution of organic matter in the immature-low-maturity stage because their change amplitude with increasing temperature is more obvious.展开更多
The safety and the fatigue comfort were compared between a domestic and a Japanese postal bicycle. Firstly, the fatigue comfort of these two kinds of bicycles was evaluated by surface electromyographic signal (sEMG) e...The safety and the fatigue comfort were compared between a domestic and a Japanese postal bicycle. Firstly, the fatigue comfort of these two kinds of bicycles was evaluated by surface electromyographic signal (sEMG) experiment, in which human lower limb muscle groups were research objects, and the average EMG (AEMG) index and median frequency (MF) were chosen as the evaluation indexes. Secondly, the safety of these two kinds of bicycle frames was analyzed and compared by using the finite element analysis. The results show that the riding fatigue comfort of the Japanese postal bicycle is better, and the Japanese postal bicycle frame is more safe and reasonable although both the postal bicycles meet the requirement for strength. Finally, based on the above analysis, the frame structure and related parameters of the domestic postal bicycle were improved with reference to the Japanese postal bicycle and biomechanics theory.展开更多
基金financial support from the National Natural Science Foundation of China (Nos. 21871112 and 21971090)。
文摘A new organocatalytic double annulation cascade involving scission/recombination of N-O bonds of nitrones is reported for the first time, and used to produce a range of hitherto unprecedented tricyclic bridged-fused benzo[d]azepines bearing three stereogenic centers with moderate to good yields and complete diastereoselectivity. A quinine-catalyzed reaction of yne–allenone esters with nitrones worked well and provided a convergent and regioselective pathway to access these three-dimensional scaffolds from the planar conjugated system. Density functional theory(DFT) calculations have been applied to understand the key process for forming diradical intermediates.
文摘Identification of variables that influence differences between predicted and observed cycling times for one cyclist commuting to Okanagan College (OC) was performed using principal components analysis. These data were used to create a personalized predictive time algorithm, which was subsequently applied in an isochrone map format centered on OC. A 29% difference in the area within the 20-minute commuting time was estimated, suggesting that potential residential location choices made with inaccurate isochrone maps are inaccurate. A comparison with an isochron cycling map for Trinity College Dublin was made to emphasise differences in the impact/implications of this type of map in the promotion of sustainable transportation for a post-secondary institution. It is determined that these maps may misinform new community members as to areas of residential location choice.
基金The National Natural Science Foundation of China(No.52072012)。
文摘To investigate the distribution characteristics and influencing factors of bicycle detour behavior,this study ac-curately identified detour behavior using global positioning system(GPS)track data from shared bicycles.Factors such as travel time,road conditions,public transportation facilities,and land use types were considered in constructing a detour behavior influence model based on the CatBoost machine learning algorithm.The interpretability of the machine learning framework was enhanced via Shapley additive explanations(SHAP),enabling an analysis of the impact of each factor on detour behavior.The results indicated that the CatBoost model effectively recognized detour behavior with high accuracy.The frequency of detour behavior increased with higher road levels,greater distances to crossing facilities,wider bike lanes,and an increased number of bus stops,subway stations,and leisure and entertainment facilities,while it decreased with a higher number of office commuting facilities.In addition,detour behavior was more prevalent on weekends,during off-peak hours,and under conditions involving physical central lane separation and physical bike lane separation.These findings offer a novel approach for identifying bicycle riding behaviors and analyzing their influencing factors,providing effective technical support for non-motorized traffic management and infrastructure optimization.
文摘Two environmentalists using bamboo bicycles to promote green transportation.THE exhaust emissions generated by transporting the world’s population on a daily basis are one of the main sources of greenhouse gases.Vehicles such as cars,subways,and motorcycles,all produce carbon emissions.
文摘CHINA.Bicycle Output.China’s bicycle production saw solid growth last year,increasing by 0.4 percent year on year to reach 99.54 million units,said Zheng Xiaoling,spokesperson for the China Bicycle Association.
文摘Designed and built by eight Dutch engineers,the worlds longest bicycle is 55.16 meters,roughly the same length as four double-decker buses.39-year-old Ivan Schalk had been thinking about building the world's longest bicycle since reading about it in The Guinness Book of Records when he was a child,but he only started this project in 2018,as a way to fill up his free time.
基金The National Natural Science Foundation of China(No. 52072012)。
文摘To reduce the risk of traffic accidents significantly caused by the speeding behavior of electric bicycles,this study focuses on the Beijing Yizhuang Economic and Tech-nological Development Zone.This work relies on high-precision shared electric bicycle Global Positioning System trajectory data,integrating a spatiotemporal analysis model and geographic information system(GIS)technol-ogy to explore the spatial and temporal variability law and formation mechanism of speeding behavior.Through data preprocessing,speeding events are identified,and weekday features are extracted.Four periods are identified:morning peak,midday minipeak,evening peak,and nighttime flat peak.Using the GIS platform,global spatial autocorrela-tion and local clustering analysis are conducted to identify the spatial clustering characteristics of speeding behaviors and hotspot areas.The coldspot and hotspot patterns of speeding events and the dynamic trajectories of their evolu-tion are analyzed using spatiotemporal cube technology.The results show that speeding behaviors are strongly corre-lated with the commuting peak in time and spatially concen-trated in the intersections of urban main roads,the periphery of commercial complexes,and industrial parks,with a dif-fusion tendency.The results of this study provide novel in-sights into the research and analysis of the spatial and tempo-ral characteristics of speeding risk behaviors of electric bi-cycles and effective technical support for nonmotorized traf-fic safety management.
基金National Natural Science Foundation of China(Nos.22001177,22203023)Guangdong Pearl River Talent Program(no.2021QN020268)+3 种基金the Natural Science Foundation of Guangdong Province(Nos.2024A1515012381,2022A1515011859)Shenzhen Bay Laboratory Startup Fund(No.S201100003)Major Program of Shenzhen Bay Laboratory(No.S211101001-4)Shenzhen Bay Qihang Fellow Program(No.QH23001)for generous financial support.
文摘Chiral aryl cyclohex-3-en ether scaffold is widely present in bioactive natural products and drugs.The exploitation of efficient and enantioselective methods for the construction of aryl cyclohex-3-en ether scaffold is significant.Herein we disclose a chiral N,N’-dioxide/Lewis acid complex-catalyzed asymmetric inverse-electron-demand Diels-Alder(IEDDA)reaction using electron-deficient 3-carboalkoxyl-2-pyrones and less electron-enriched aryl enol ethers as reactants.A wide range of non-and 1,2-disubstituted acyclic aryl enol ethers are applicable to deliver diverse chiral bridged bicyclic lactones in high yields and stereoselectivities(up to 96%yield,>20:1 dr,97:3 er).The bridged bicyclic lactone core can be easily converted into chiral aryl cyclohex-3-en ether scaffold.Notably,DFT calculations revealed a stepwise and endo mechanism to explain the high enantioselectivity controlled by the cooperative effect of the steric factors and the dispersion interactions between ligands and enol ethers.
基金We thank the National Science Foundation of China(NSFC,N0.20372003)for financial support.
文摘Aim To develop a concise method for the synthesis of bicyclic azasugar and thiosugar with novel scaffold. Methods The two primary hydroxyl groups of compound 1 were selectively protected with tosyl cloloride in pyridine, followed by ring-closure with sodium sulfide or primary amine to form the oxy-bridged bicyclic molecules in good yields. Results Two bicyclic azasugars and a thiosugar were produced from L-sorbose in several steps. Conclusion The described procedures provide an efficient method to synthesize bicyclic azasugar and thiosugar with novel scaffold as potential glycosidase inhibitors.
基金supported by the Natural Science Foundation of Anhui Province Education Department(No.KJ2014A141)the National Natural Science Foundation of China(No.21171008)
文摘The bicyclic product containing a chromene skeleton and a propargylamine skeleton（C（22）H（22）N2O2） was synthesized from the double sites of terminal alkyne, piperazine derivative and formaldehyde via one-pot procedure. Its structure was characterized by ^1H NMR, ^13C NMR, IR and H RMS, and further confirmed by single-crystal X-ray diffraction. It crystallizes in the monoclinic system, space group P21/n with a = 12.6571（14）, b = 11.3249（12）, c = 12.6571（14） A, β = 105.22°,V = 1750.6（3） A^3, Z = 4, R = 0.0568 and w R = 0.1444. The fluorescence of the product was discussed.
基金The National Natural Science Foundation of China(No.51238008,51408322)
文摘This paper investigates the passing events between electric bicycles and conventional bicycles and explores the relationships between passing events and traffic parameters in bicycle facilities.Three exclusive bicycle paths in Nanjing, China,were observed with cameras.Then,the field data including vehicle number,velocity characteristics and passing event features were analyzed in detail.Data analysis and fitting reveal that the speed difference has little impact on the passing event number,as does the bicycle ratio.The Gaussian function can better describe the relationship between the passing event number and bicycle volume （density）.The valid use level of bicycle path width influences the inflexion of the passing events-density fitting curve.The conclusions can be applied for estimating the passing events in mixed bicycle flows and for choosing a suitable width of separate bicycle path.
文摘PI novel caged bicyclic phosphate flame retardant tri(1-oxo-2,6,7-trioxa-1-phosphabicyclo [2.2.2] octane-methyl) phosphate (Trimer) was synthesized from 1-oxo-4-hydroxymethyl-2,6,7-trioxa-1-phosphabicyclo [2.2.2] octane (PEPA) and phosphorus oxychloride in this paper. Its structure was characterized by elemental analysis. FTIR, H-1 NMR. P-31 NMR and X-ray diffraction analysis.
基金Under the auspices of National Natural Science Foundation of China(No.41801150,41571146,41801144)Natural Science Foundation of Guangdong Province(No.2018A030310392)+2 种基金Guangdong Planning Project of Philosophy and Social Science(No.GD17YGL01)Science and Technology Program of Guangzhou(No.201906010033)GDAS’(Guangdong Academy of Sciences)Project of Science and Technology Development(No.2020GDASYL-20200104007)。
文摘Mobile information and communication technologies(MICTs) have fully penetrated everyday life in smart societies;this has greatly compressed time, space, and distance, and consequently, reshaped residents’ travel behaviour patterns. As a new mode of shared mobility, the sharing bicycle offers a variety of options for the daily travel of urban residents. Extant studies have mainly examined the travel characteristics and influencing factors of public bicycles with piles, while the travel patterns for sharing bicycles and their driving mechanisms have been largely ignored. Using one week’s travel data for Mobike, this study investigated the spatial and temporal distribution patterns of sharing bicycle travel behaviours in the central urban area of Guangzhou, China;furthermore, it identified the influences of built environment density factors on sharing bicycle travel behaviours based on the geographically weighted regression method. Obvious morning and evening peaks were observed in the sharing bicycle travel patterns for both weekdays and weekends. The old urban area, which had a high degree of mixed function, dense road networks, and cycling-friendly built environments, was the main travel area that attracted sharing bicycles on both weekdays and weekends. Furthermore, factors including the point of interest(POI) for the density of public transport stations, the functional mixing degree, and the density of residential POIs significantly affected residents’ travel behaviours. These findings could enrich discourse regarding shared mobility with a Chinese case characterised by rapidly developing MICTs and also provide references to local authorities for improving slow traffic environments.
基金National Natural Science Foundation of China(Grants 11932001 and 11702002).
文摘In this paper,we study the dynamics of an idealized benchmark bicycle moving on a surface of revolution.We employ symbolic manipulations to derive the contact constraint equations from an ordered process,and apply the Lagrangian equations of the first type to establish the nonlinear differential algebraic equations(DAEs),leaving nine coupled differential equations,six contact equations,two holonomic constraint equations and four nonholonomic constraint equations.We then present a complete description of hands-free circular motions,in which the time-dependent variables are eliminated through a rotation transformation.We find that the circular motions,similar to those of the bicycle moving on a horizontal surface,nominally fall into four solution families,characterized by four curves varying with the angular speed of the front wheel.Then,we numerically investigate how the topological profiles of these curves change with the parameter of the revolution surface.Furthermore,we directly linearize the nonlinear DAEs,from which a reduced linearized system is obtained by removing the dependent coordinates and counting the symmetries arising from cyclic coordinates.The stability of the circular motion is then analyzed according to the eigenvalues of the Jacobian matrix of the reduced linearized system around the equilibrium position.We find that a stable circular motion exists only if the curvature of the revolution surface is very small and it is limited in small sections of solution families.Finally,based on the numerical simulation of the original nonlinear DAEs system,we show that the stable circular motion is not asymptotically stable.
基金Project(2012CB725400) supported by the National Basic Research Program of ChinaProjects(70901005, 71071016, 71131001) supported by the National Natural Science Foundation of ChinaProject(2011JBM055) supported by the Fundamental Research Funds for the Central Universities of China
文摘To determine how bus stop design influences mixed traffic operation near Chinese bus stops,a new theoretical method was developed by using additive-conflict-flows procedure.The procedure was extended from homogeneous traffic flow to mixed traffic flow.Based on the procedure and queuing theory,car capacity and speed models were proposed for three types of bus stops including curbside,bus bay and bicycle detour.The effects of various combinations of bus stop type,traffic volume,bus dwell time,and berth number on traffic operations were investigated.The results indicate that traffic volume,bus dwell time and berth number have negative effects on traffic operations for any type of bus stops.For different types of bus stops,at car volumes above approximately 200 vehicles per hour,the bus bay and bicycle detour designs provide more benefits than the curbside design.As traffic volume increases,the benefit firstly increases in uncongested conditions and then decreases in congested conditions.It reaches the maximum at car volumes nearly 1 100 vehicles per hour.The results can be used to aid in the selection of a preferred bus stop design for a given traffic volume in developing countries.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41672117 and 41503034)the Hubei Provincial Natural Science Foundation of China (Project No. 2017CFA027)+1 种基金the Open Subject of Shandong Provincial Key Laboratory of Depositional Mineralization & Sedimentary Mineral (Baojun Liu Geoscience Science Foundation) (DMSM2017084)the Open Subject of the State Key Laboratory of Petroleum Resources and Prospecting (PRP/open-1509)
文摘Sesquiterpanes are ubiquitous components of crude oils and ancient sediments.Liquid saturated hydrocarbons from simulated pyrolysis experiments on immature organic-rich mudstone collected from the Lower Cretaceous Hesigewula Sag were analyzed by gas chromatography-mass spectrometry(GC-MS).C14 bicyclic sesquiterpanes,namely,8β(H)-drimane,8β(H)-homodrimane,and 8 a(H)-homodrimane were detected and identified on basis of their diagnostic fragment ions(m/z123,179,193,and 207),and previously published mass spectra data,and these bicyclic sesquiterpanes presented relatively regular characteristics in their thermal evolution.The ratios 8β(H)-drimane/8β(H)-homodrimane,8β(H)-homodrimane/8 a(H)-homodrimane,and 8β(H)-drimane/8 a(H)-homodrimane all show a clear upward trend with increasing temperature below the temperature turning point.Thus,all these ratios can be used as evolution indexes of source rocks in the immature-lowmaturity stage.However,the last two ratios may be more suitable than the first ratio as valid parameters for measuring the extent of thermal evolution of organic matter in the immature-low-maturity stage because their change amplitude with increasing temperature is more obvious.
基金Supported by Special Fund Project for Technology Innovation of Tianjin (No.10FDZDGX00500)Tianjin Product Quality Inspection Technology Research Institute
文摘The safety and the fatigue comfort were compared between a domestic and a Japanese postal bicycle. Firstly, the fatigue comfort of these two kinds of bicycles was evaluated by surface electromyographic signal (sEMG) experiment, in which human lower limb muscle groups were research objects, and the average EMG (AEMG) index and median frequency (MF) were chosen as the evaluation indexes. Secondly, the safety of these two kinds of bicycle frames was analyzed and compared by using the finite element analysis. The results show that the riding fatigue comfort of the Japanese postal bicycle is better, and the Japanese postal bicycle frame is more safe and reasonable although both the postal bicycles meet the requirement for strength. Finally, based on the above analysis, the frame structure and related parameters of the domestic postal bicycle were improved with reference to the Japanese postal bicycle and biomechanics theory.
