Corrosion is a primary cause of the slippage of friction⁃type high⁃strength bolted(FHSB)T⁃stub connections.This paper attempts to quantify the residual capacity of FHSB T⁃stub connections with corroded nuts.Firstly,co...Corrosion is a primary cause of the slippage of friction⁃type high⁃strength bolted(FHSB)T⁃stub connections.This paper attempts to quantify the residual capacity of FHSB T⁃stub connections with corroded nuts.Firstly,corrosion simulation tests were conducted on 48 manually cut nuts to find out the relationship between the damage degree of nut section and the residual clamping force(RCF)of bolt.Then,static load tests were carried out on 24 FHSB T⁃stub connections with nuts of different degrees of damage to obtain the failure modes.By finite⁃element(FE)models,a comparative analysis was performed on the initial friction load(IFL)and ultimate strength(US)of each connection with corroded nuts.Finally,the parameters of 96 FE models for FHSB T⁃stub connections were analyzed and used to derive the calculation formulas for the degree of damage for each nut and the IFL and US of each connection.The results show that the RCF decay of a bolt is a quadratic function of the equivalent radius loss ratio and the shear failure after nut corrosion;the IFL of each connection had a clear linear correlation with the RCF of the corresponding bolts,and the correlation depends on the applied load and static friction on connecting plate interface induced by the clamping force;the static friction had little impact on the US of the connection;the proposed IFL and US formulas can effectively derive the residual anti⁃slip capacity of FHSB T⁃stub connections from the degree of damage of the corroded nut section.The research results provide a scientific basis for the replacement and maintenance of corroded bolts of FHSB T⁃stub connections.展开更多
The potential of microbial mediated iron plaque reduction, and associated arsenic (As) mobility were examined by iron reducing bacteria enriched from As contaminated paddy soil. To our knowledge, this is the first t...The potential of microbial mediated iron plaque reduction, and associated arsenic (As) mobility were examined by iron reducing bacteria enriched from As contaminated paddy soil. To our knowledge, this is the first time to report the impact of microbial iron plaque reduction on As mobility. Iron reduction occurred during the inoculation of iron reducing enrichment culture in the treatments with iron plaque and ferrihydrite as the electron acceptors, respectively. The Fe(II) concentration with the treatment of anthraquinone-2, 6-disulfonic acid (AQDS) and iron reducing bacteria increased much faster than the control. Arsenic released from iron plaque with the iron reduction, and a significant correlation between Fe(II) and total As in culture was observed. However, compared with control, the increasing rate of As was inhibited by iron reducing bacteria especially in the presence of AQDS. In addition, the concentrations of As(III) and As(V) in abiotic treatments were higher than those in the biotic treatments at day 30. These results indicated that both microbial and chemical reductions of iron plaque caused As release from iron plaque to aqueous phase, however, microbial iron reduction induced the formation of more crystalline iron minerals, leading to As sequestration. In addition, the presence of AQDS in solution can accelerate the iron reduction, the As release from iron plaque and subsequently the As retention in the crystalline iron mineral. Thus, our results suggested that it is possible to remediate As contaminated soils by utilizing iron reducing bacteria and AQDS.展开更多
Road traffic is the main factor causing the decline in amphibian populations worldwide. The proper design of an amphibian tunnel is one of the most efficient measures to mitigate the negative impacts of road traffic o...Road traffic is the main factor causing the decline in amphibian populations worldwide. The proper design of an amphibian tunnel is one of the most efficient measures to mitigate the negative impacts of road traffic on amphibians. However, no study has investigated the effectiveness of amphibian tunnels under semi-controlled conditions in Asian amphibians. Here, we selected two representative amphibian species, the Chinese brown frog, Rana chensinensis, and the Asiatic toad, Bufo gargarizans, which suffer the most severe road mortality along the roads in Northeast China. We placed experimental arrays of culverts of various sizes(diameters of 1.5, 1, and 0.5 m for circular culverts; side lengths of 1.5, 1, and 0.5 m for box culverts), and substrate type(soil, concrete, and metal) to examine the preferences of both species during the migratory season between May and September in 2016 and 2017. The results revealed that the Chinese brown frog preferred mid-and large-sized culverts as well as soil culverts. We concluded that culverts with a side length ≥ 1 m, lined with soil, and accompanied by a ≥ 0.4 m high guide drift fence and ≤ 45° gradient on the roadside ditch wall would best facilitate road crossings for both species and likely for other amphibian species in Northeast China.展开更多
Nowadays validation of anti-lock braking systems(ABS) relies mainly on a large amount of road tests.An alternative means with higher efficiency is employing the hardware-in-the-loop simulation(HILS) system to subs...Nowadays validation of anti-lock braking systems(ABS) relies mainly on a large amount of road tests.An alternative means with higher efficiency is employing the hardware-in-the-loop simulation(HILS) system to substitute part of road tests for designing,testing,and tuning electronic control units(ECUs) of ABS.Most HILS systems for ABS use expensive digital signal processor hardware and special purpose software,and some fail-safe functions with regard to wheel speeds cannot be evaluated since artificial wheel speed signals are usually provided.In this paper,a low-cost ABS HILS test bench is developed and used for validating the anti-lock braking performance and tuning control parameters of ABS controllers.Another important merit of the proposed test bench is that it can comprehensively evaluate the fail-safe functions with regard to wheel speed signals since real tone rings and sensors are integrated in the bench.A 5-DOF vehicle model with consideration of longitudinal load transfer is used to calculate tire forces,wheel speeds and vehicle speed.Each of the four real-time wheel speed signal generators consists of a servo motor plus a ring gear,which has sufficient dynamic response ability to emulate the rapid changes of the wheel speeds under strict braking conditions of very slippery roads.The simulation of braking tests under different road adhesion coefficients using the HILS test bench is run,and results show that it can evaluate the anti-lock braking performance of ABS and partly the fail-safe functions.This HILS system can also be used in such applications as durability test,benchmarking and comparison between different ECUs.The test bench developed not only has a relatively low cost,but also can be used to validate the wheel speed-related ECU design and all its fail-safe functions,and a rapid testing and proving platform with a high efficiency for research and development of the automotive ABS is therefore provided.展开更多
Vegetation in slopes can effectively improve slope stability.However,it is difficult to estimate the effects of vegetation on slope stability because of variations in plant species and environmental conditions.Moreove...Vegetation in slopes can effectively improve slope stability.However,it is difficult to estimate the effects of vegetation on slope stability because of variations in plant species and environmental conditions.Moreover,influences of plant growth on slope stability change with time,resulting in changes in the safety factor.This study was conducted to evaluate the stability of vegetated slopes with time and investigate the effects of different layouts of plant species on slope stability.Here,we used a plant growth model and slope stability analysis to build an evaluation model.To accomplish this,one species of tree,shrub and grass was chosen to set six layout patterns.A slope with no vegetation served as a control.The safety factors of the seven slopes were then calculated using the developed evaluation model and differences in the safety factors of slopes were compared and discussed.The slope vegetated with Platycladus orientalis reached the most stable state at the age of 60 years.Shrub slope(Vitex negundo)had the maximum safety factor after 20 years.Overall,the safety factor of vegetated slopes increased from 12.1%to 49.6% compared to the slope with no vegetation.When wind force was considered,the safety factor value of the slope changed from 3.5%to 43.5%.Vegetation mixtures of trees and grasses resulted in the best slope stability.Planting grasses on slopes can improve slope stability of trees to a greater degree than that of slopes with shrubs in the early stage of growth.展开更多
Looking at all the indeterminate factors as a whole and regarding activity durations as independent random variables, the traditional stochastic network planning models ignore the inevitable relationship and dependenc...Looking at all the indeterminate factors as a whole and regarding activity durations as independent random variables, the traditional stochastic network planning models ignore the inevitable relationship and dependence among activity durations when more than one activity is possibly affected by the same indeterminate factors. On this basis of analysis of indeterminate effect factors of durations, the effect factors-based stochastic network planning (EFBSNP) model is proposed, which emphasizes on the effects of not only logistic and organizational relationships, but also the dependent relationships, due to indeterminate factors among activity durations on the project period. By virtue of indeterminate factor analysis the model extracts and describes the quantitatively indeterminate effect factors, and then takes into account the indeterminate factors effect schedule by using the Monte Carlo simulation technique. The method is flexible enough to deal with effect factors and is coincident with practice. A software has been developed to simplify the model-based calculation, in VisualStudio.NET language. Finally, a case study is included to demonstrate the applicability of the proposed model and comparison is made with some advantages over the existing models.展开更多
Based on the nondestructive test data of operating railway tunnels in China, this paper summarizes the basic characteristics of the complex contact behavior between the rock mass and lining structure. The contact mode...Based on the nondestructive test data of operating railway tunnels in China, this paper summarizes the basic characteristics of the complex contact behavior between the rock mass and lining structure. The contact modes are classified into dense contact, local non-contact, and loose contact. Subsequently, the corresponding mechanical model for each contact mode is developed according to its mechanical characteristics using the complex variable method. In the proposed mechanical model, a special algorithm is introduced to detect whether the local non-contact zone is re-contacted. Besides, a novel conformal mapping method is also proposed to accurately calculate the mechanical response of the concrete lining. Finally, the accuracy of the proposed method is verified by comparing it with the finite element method(FEM). Several parameter investigations are conducted to analyze the effects of different contact modes on the rock-lining interaction. The results show that:(i) the height of the local noncontact area does not have a significant effect on the contact stress distribution if no re-contact occurs;(ii) backfill grouting can reduce the local stress concentration caused by poor contact modes;and(iii) reducing the friction coefficient of the interface can lead to a more uniform distribution of internal forces in the concrete lining.展开更多
This review summarizes and analyzes the basic information of various types of road transport natural disaster emergencies,refers to various types of road transport emergency plans,and combines the actual needs of road...This review summarizes and analyzes the basic information of various types of road transport natural disaster emergencies,refers to various types of road transport emergency plans,and combines the actual needs of road transport emergency rescue with national emergency related laws.It also proposes the classification criteria and grading standard for the emergencies of road transport natural disasters based on the classification and grading standard of the regulations,which provide a basis to take reasonable and effective disposal measures in the emergency response of road transport emergencies under natural disaster conditions.展开更多
Occupational health management of liquid chemical transport wharf is still in its infancy,to grasp the occupational health status of employees in the industry and improve the occupational health management level of em...Occupational health management of liquid chemical transport wharf is still in its infancy,to grasp the occupational health status of employees in the industry and improve the occupational health management level of employees,taking the liquid chemical transport wharf of an enterprise as the investigation object,according to the relevant domestic occupations.Hygiene standards,using the combination of on-site occupational hygiene survey and workplace occupational hazard factors detection,identify the occupational hazard factors of the wharf and detect the degree of hazard.The survey results show that the overall occupational health of the wharf is basically good,but the noise index is slightly exceeded.It is suggested to further improve the occupational health management level of the wharf by improving the protection technology and strengthening the administrative management.展开更多
To achieve complete poverty alleviation,the improvement of infrastructure and living conditions is fundamental.Promoting the flow of factors through infrastructure investment,thereby reducing the income gap among resi...To achieve complete poverty alleviation,the improvement of infrastructure and living conditions is fundamental.Promoting the flow of factors through infrastructure investment,thereby reducing the income gap among residents,has become an important focus of poverty alleviation.Because of the high amount of investment in transportation infrastructure,greater attention has been paid to the income distribution effect it brings,but few studies have analysed the effect of rural highways on the income gap of farmers.Based on the panel data pertaining to 30 provinces in China from 1993 to 2013,this paper uses a fixed-effect model to test the impact of rural highways supply on the income gap of farmers.The empirical results show that:(1)The effect of Chinese rural highways on the farmers'income gap among provinces is"U-shaped".(2)Chinese national and provincial trunk highways are helpful in narrowing the farmers'income gap among provinces.(3)The level of education,household productive fixed assets investment,level of urbanization,and level of regional economic development have multiple effects on the farmers'income gap among provinces.Then,based on the empirical analysis,the paper analyzes the mechanism of rural highways affecting the income gap of farmers from a theoretical perspective and focuses on the causes of the"U-shaped"relationship between rural highways supply and farmers'income gap.展开更多
The results brought out in the trials of slope protection along Qinghai-Tibet Highway are presented in this paper. The trials were carried out simultaneously at 5 sites in Qinghai-Tibet Plateau from 2000 to 2002. Alti...The results brought out in the trials of slope protection along Qinghai-Tibet Highway are presented in this paper. The trials were carried out simultaneously at 5 sites in Qinghai-Tibet Plateau from 2000 to 2002. Altitudes at the experimental sites range between (4 240) m and (5 040) m. 4 sites are in permafrost area, and 1 site is in seasonally frozen ground. According to the trials of slope protection, vegetation is preferred to protect slopes along Qinghai-Tibet Highway. Road-GoodR, a chemical stabilizer, is proved as a good material for slope protection, and soil engineering system, combined with vegetative component and grade stabilization structures is proved as the best slope protection measure in these areas. The results showed that high-altitude areas at an altitude lower than (5 040) m, annual average temperatures higher than (-5.6) ℃ and annual rainfall more than 262\^2 mm, slopes can be protected using vegetative components.\;Trials for plant species selection proved that cold resistant grasses, Elymus nutans and Elymus sibiricus can be used for vegetation recovery along Qinghai-Tibet Highway. The results demonstrated that high-altitude areas at an altitude lower than (5 040) m, annual average temperatures higher than (-5.6) ℃ and annual rainfall more than 262\^2 mm, could be replanted. Hydroseeding proved to be a good planting technique, and mulch materials benefited vegetation recovery in such area.\;The experiment also proved that planting could improve slope stability, protect the ecological environment, and improve the roadside landscape.展开更多
At the turn of this century, China began the largest road and bridge development in the world, which has virtuously interacted with the social and economic development and has elevated the engineering technology to wo...At the turn of this century, China began the largest road and bridge development in the world, which has virtuously interacted with the social and economic development and has elevated the engineering technology to world-class level. Surveying the development of world transportation, and comparing the road and bridge construction efforts of Europe, U.S.A, Japan and China, general experiences of success can be derived as follows: It is greatly beneficial to give priority to transportation for economic development; it takes national strategy and social action to build up a transportation network; demand and innovation are the driving forces to upgrade road and bridge technology; management innovation and quality assurance can greatly improve development caliber. While rationally acknowledging China’s transportation infrastructure achievements, we should reflect on issues with Chinese characteristics that have affected quality and efficiency, expose all construction practices that violate scientific law, overall management defects in road and bridge construction and maintenance, and search for new ways to strengthen social management and the creation of a healthy soft environment.展开更多
Transportation is a basic service industry concerned with people’s livelihood and well-being. China has unveiled guidelines on improving China’s strength in transportation. By 2035, an accessible travel service syst...Transportation is a basic service industry concerned with people’s livelihood and well-being. China has unveiled guidelines on improving China’s strength in transportation. By 2035, an accessible travel service system should basically be built, according to the guidelines jointly released by the Communist Party of China Central Committee and the State Council. It is of great practical significance to accelerate the construction of an accessible transportation environment in the new era, which can improve the equalization of public services and promote the safe, convenient, and comfortable travel of the disabled and the elderly. In line with the development status of transportation in China, and through an analysis on the requirements for building a country with a strong transportation network, this paper proposes the framework and content for the establishment of an accessible transportation system in China.展开更多
In this article, we put forward a new approach to estimate multiple conditional regression quantiles simultaneously. Unlike the double summation method in most of the literatures, our proposed model allows continuous ...In this article, we put forward a new approach to estimate multiple conditional regression quantiles simultaneously. Unlike the double summation method in most of the literatures, our proposed model allows continuous variety for the quantile level over(0,1). As a result, all the quantile curves can be obtained via a 2-dimensional surface simultaneously. Most importantly, the proposed minimizing criterion can be readily transformed to a linear programming problem. We use tensor product bi-linear quantile smoothing B-splines tofit it. The asymptotic property of the estimator is derived and a real data set is analyzed to demonstrate the proposed method.展开更多
Road-deposited sediments(RDS)accumulated on road surfaces are an important environmental medium that often provides transport for heavy metals.In order to understand the characteristics of heavy metals in RDS,we inves...Road-deposited sediments(RDS)accumulated on road surfaces are an important environmental medium that often provides transport for heavy metals.In order to understand the characteristics of heavy metals in RDS,we investigated the size distribution and heavy metal(i.e.Cd,Cr,Cu,Ni,Pb and Zn)concentrations in RDS and road runoff in typical expressways of suburban and rural area in China.The results demonstrated that RDS particles from all impervious expressway surfaces were predominantly coarse particles(>250μm,58.4%±3.8%)and the RDS on all expressways contained more heavy metals than background soils.Furthermore,the concentrations of Cd,Cr,Cu,Ni,Pb and Zn increased with traffic volume,suggesting that these heavy metals are mainly derived from traffic activities.Moreover,it is found that although heavy metals were concentrated in fine grain fractions,the total loading is highest for the coarsest particles due to their large mass percentage.Additionally,it reveals that the heavy metal concentrations in road runoff of suburban expressway are higher than that in urban expressway.Our findings enhance the understanding of expressway pollution,and imply that for controlling runoff pollution from RDS,transportation agencies should be concerned with both fine and coarse particles and take cleaning methods into account.展开更多
Electric Taxis(ETs)are the most favored alternatives to Gasoline Taxis(GTs)in cities that aim to reduce environmental pollution.How to develop a reasonable scale on which GTs are substituted by ETs remains a challenge...Electric Taxis(ETs)are the most favored alternatives to Gasoline Taxis(GTs)in cities that aim to reduce environmental pollution.How to develop a reasonable scale on which GTs are substituted by ETs remains a challenge to governments due to the dynamics and complexity of the taxi system.To address this challenge,this paper develops a discrete-event-based simulation framework to simulate participants in the system and estimate the results under different substitution scales,which are helpful to understanding the status changing law of entities under different substitution scales,such as the operating indices of ETs,the unsatisfied travel requirements of passengers,and the usage state of charging facilities.The framework abstracts the behavioral process of ETs into three elements,namely,entity,behavior,and event.The entities are constructed from the information derived from the trajectory data.The behaviors are defined by rules following behavioral logic under anxiety psychology,which is caused by the limited range of ETs.The events are triggered based on rules from reality.With the help of this framework,a multi-objective optimization model is developed to obtain the optimal substitution scale of GTs in the case study area of Zhengzhou City.Overall,the approach could provide a practical tool to address this challenge,which could support further studies of the effect of ETs on urban taxis.展开更多
文摘Corrosion is a primary cause of the slippage of friction⁃type high⁃strength bolted(FHSB)T⁃stub connections.This paper attempts to quantify the residual capacity of FHSB T⁃stub connections with corroded nuts.Firstly,corrosion simulation tests were conducted on 48 manually cut nuts to find out the relationship between the damage degree of nut section and the residual clamping force(RCF)of bolt.Then,static load tests were carried out on 24 FHSB T⁃stub connections with nuts of different degrees of damage to obtain the failure modes.By finite⁃element(FE)models,a comparative analysis was performed on the initial friction load(IFL)and ultimate strength(US)of each connection with corroded nuts.Finally,the parameters of 96 FE models for FHSB T⁃stub connections were analyzed and used to derive the calculation formulas for the degree of damage for each nut and the IFL and US of each connection.The results show that the RCF decay of a bolt is a quadratic function of the equivalent radius loss ratio and the shear failure after nut corrosion;the IFL of each connection had a clear linear correlation with the RCF of the corresponding bolts,and the correlation depends on the applied load and static friction on connecting plate interface induced by the clamping force;the static friction had little impact on the US of the connection;the proposed IFL and US formulas can effectively derive the residual anti⁃slip capacity of FHSB T⁃stub connections from the degree of damage of the corroded nut section.The research results provide a scientific basis for the replacement and maintenance of corroded bolts of FHSB T⁃stub connections.
基金supported by the Knowledge Innovation Program of Chinese Academy of Sciences(No. KZCX1-YW-06-03)
文摘The potential of microbial mediated iron plaque reduction, and associated arsenic (As) mobility were examined by iron reducing bacteria enriched from As contaminated paddy soil. To our knowledge, this is the first time to report the impact of microbial iron plaque reduction on As mobility. Iron reduction occurred during the inoculation of iron reducing enrichment culture in the treatments with iron plaque and ferrihydrite as the electron acceptors, respectively. The Fe(II) concentration with the treatment of anthraquinone-2, 6-disulfonic acid (AQDS) and iron reducing bacteria increased much faster than the control. Arsenic released from iron plaque with the iron reduction, and a significant correlation between Fe(II) and total As in culture was observed. However, compared with control, the increasing rate of As was inhibited by iron reducing bacteria especially in the presence of AQDS. In addition, the concentrations of As(III) and As(V) in abiotic treatments were higher than those in the biotic treatments at day 30. These results indicated that both microbial and chemical reductions of iron plaque caused As release from iron plaque to aqueous phase, however, microbial iron reduction induced the formation of more crystalline iron minerals, leading to As sequestration. In addition, the presence of AQDS in solution can accelerate the iron reduction, the As release from iron plaque and subsequently the As retention in the crystalline iron mineral. Thus, our results suggested that it is possible to remediate As contaminated soils by utilizing iron reducing bacteria and AQDS.
基金funded by the National Natural Science Foundation of China (Grant No. 51508250)the Science and Technology Project of Department of Transportation of Jilin Province (Grant No. 2018-1-14)+1 种基金the Basic Research Program of the Centric Level, Scientific Research Institutes (Grant No. 20180615)the World Wild Fund for Nature Project (Grant No. P03516)
文摘Road traffic is the main factor causing the decline in amphibian populations worldwide. The proper design of an amphibian tunnel is one of the most efficient measures to mitigate the negative impacts of road traffic on amphibians. However, no study has investigated the effectiveness of amphibian tunnels under semi-controlled conditions in Asian amphibians. Here, we selected two representative amphibian species, the Chinese brown frog, Rana chensinensis, and the Asiatic toad, Bufo gargarizans, which suffer the most severe road mortality along the roads in Northeast China. We placed experimental arrays of culverts of various sizes(diameters of 1.5, 1, and 0.5 m for circular culverts; side lengths of 1.5, 1, and 0.5 m for box culverts), and substrate type(soil, concrete, and metal) to examine the preferences of both species during the migratory season between May and September in 2016 and 2017. The results revealed that the Chinese brown frog preferred mid-and large-sized culverts as well as soil culverts. We concluded that culverts with a side length ≥ 1 m, lined with soil, and accompanied by a ≥ 0.4 m high guide drift fence and ≤ 45° gradient on the roadside ditch wall would best facilitate road crossings for both species and likely for other amphibian species in Northeast China.
基金supported by National Natural Science Foundation of China(Grant No.50908008)National Hi-tech Research and Development Program of China(863Program,Grant No.2009AA11Z216)
文摘Nowadays validation of anti-lock braking systems(ABS) relies mainly on a large amount of road tests.An alternative means with higher efficiency is employing the hardware-in-the-loop simulation(HILS) system to substitute part of road tests for designing,testing,and tuning electronic control units(ECUs) of ABS.Most HILS systems for ABS use expensive digital signal processor hardware and special purpose software,and some fail-safe functions with regard to wheel speeds cannot be evaluated since artificial wheel speed signals are usually provided.In this paper,a low-cost ABS HILS test bench is developed and used for validating the anti-lock braking performance and tuning control parameters of ABS controllers.Another important merit of the proposed test bench is that it can comprehensively evaluate the fail-safe functions with regard to wheel speed signals since real tone rings and sensors are integrated in the bench.A 5-DOF vehicle model with consideration of longitudinal load transfer is used to calculate tire forces,wheel speeds and vehicle speed.Each of the four real-time wheel speed signal generators consists of a servo motor plus a ring gear,which has sufficient dynamic response ability to emulate the rapid changes of the wheel speeds under strict braking conditions of very slippery roads.The simulation of braking tests under different road adhesion coefficients using the HILS test bench is run,and results show that it can evaluate the anti-lock braking performance of ABS and partly the fail-safe functions.This HILS system can also be used in such applications as durability test,benchmarking and comparison between different ECUs.The test bench developed not only has a relatively low cost,but also can be used to validate the wheel speed-related ECU design and all its fail-safe functions,and a rapid testing and proving platform with a high efficiency for research and development of the automotive ABS is therefore provided.
基金supported by the Traffic Science and Technology Projects in Shandong Province(NO.2017JHKY2)the Operating Expenses for Basic Research Project of the Central Public Welfare Institute(NO.20160630Y)。
文摘Vegetation in slopes can effectively improve slope stability.However,it is difficult to estimate the effects of vegetation on slope stability because of variations in plant species and environmental conditions.Moreover,influences of plant growth on slope stability change with time,resulting in changes in the safety factor.This study was conducted to evaluate the stability of vegetated slopes with time and investigate the effects of different layouts of plant species on slope stability.Here,we used a plant growth model and slope stability analysis to build an evaluation model.To accomplish this,one species of tree,shrub and grass was chosen to set six layout patterns.A slope with no vegetation served as a control.The safety factors of the seven slopes were then calculated using the developed evaluation model and differences in the safety factors of slopes were compared and discussed.The slope vegetated with Platycladus orientalis reached the most stable state at the age of 60 years.Shrub slope(Vitex negundo)had the maximum safety factor after 20 years.Overall,the safety factor of vegetated slopes increased from 12.1%to 49.6% compared to the slope with no vegetation.When wind force was considered,the safety factor value of the slope changed from 3.5%to 43.5%.Vegetation mixtures of trees and grasses resulted in the best slope stability.Planting grasses on slopes can improve slope stability of trees to a greater degree than that of slopes with shrubs in the early stage of growth.
文摘Looking at all the indeterminate factors as a whole and regarding activity durations as independent random variables, the traditional stochastic network planning models ignore the inevitable relationship and dependence among activity durations when more than one activity is possibly affected by the same indeterminate factors. On this basis of analysis of indeterminate effect factors of durations, the effect factors-based stochastic network planning (EFBSNP) model is proposed, which emphasizes on the effects of not only logistic and organizational relationships, but also the dependent relationships, due to indeterminate factors among activity durations on the project period. By virtue of indeterminate factor analysis the model extracts and describes the quantitatively indeterminate effect factors, and then takes into account the indeterminate factors effect schedule by using the Monte Carlo simulation technique. The method is flexible enough to deal with effect factors and is coincident with practice. A software has been developed to simplify the model-based calculation, in VisualStudio.NET language. Finally, a case study is included to demonstrate the applicability of the proposed model and comparison is made with some advantages over the existing models.
基金supported by the National Natural Science Foundation of China (Grant Nos. 51738002 and 52108376)Fundamental Research Funds for the Central Universities (Grant No. 2021CZ111)
文摘Based on the nondestructive test data of operating railway tunnels in China, this paper summarizes the basic characteristics of the complex contact behavior between the rock mass and lining structure. The contact modes are classified into dense contact, local non-contact, and loose contact. Subsequently, the corresponding mechanical model for each contact mode is developed according to its mechanical characteristics using the complex variable method. In the proposed mechanical model, a special algorithm is introduced to detect whether the local non-contact zone is re-contacted. Besides, a novel conformal mapping method is also proposed to accurately calculate the mechanical response of the concrete lining. Finally, the accuracy of the proposed method is verified by comparing it with the finite element method(FEM). Several parameter investigations are conducted to analyze the effects of different contact modes on the rock-lining interaction. The results show that:(i) the height of the local noncontact area does not have a significant effect on the contact stress distribution if no re-contact occurs;(ii) backfill grouting can reduce the local stress concentration caused by poor contact modes;and(iii) reducing the friction coefficient of the interface can lead to a more uniform distribution of internal forces in the concrete lining.
文摘This review summarizes and analyzes the basic information of various types of road transport natural disaster emergencies,refers to various types of road transport emergency plans,and combines the actual needs of road transport emergency rescue with national emergency related laws.It also proposes the classification criteria and grading standard for the emergencies of road transport natural disasters based on the classification and grading standard of the regulations,which provide a basis to take reasonable and effective disposal measures in the emergency response of road transport emergencies under natural disaster conditions.
文摘Occupational health management of liquid chemical transport wharf is still in its infancy,to grasp the occupational health status of employees in the industry and improve the occupational health management level of employees,taking the liquid chemical transport wharf of an enterprise as the investigation object,according to the relevant domestic occupations.Hygiene standards,using the combination of on-site occupational hygiene survey and workplace occupational hazard factors detection,identify the occupational hazard factors of the wharf and detect the degree of hazard.The survey results show that the overall occupational health of the wharf is basically good,but the noise index is slightly exceeded.It is suggested to further improve the occupational health management level of the wharf by improving the protection technology and strengthening the administrative management.
基金supports from the Transport Strategic Planning Policy Foundation of the Ministry of Transport of China(2019-4-1)the Humanities and Social Sciences Project Funded by the Ministry of Education of China(20YJC790005)。
文摘To achieve complete poverty alleviation,the improvement of infrastructure and living conditions is fundamental.Promoting the flow of factors through infrastructure investment,thereby reducing the income gap among residents,has become an important focus of poverty alleviation.Because of the high amount of investment in transportation infrastructure,greater attention has been paid to the income distribution effect it brings,but few studies have analysed the effect of rural highways on the income gap of farmers.Based on the panel data pertaining to 30 provinces in China from 1993 to 2013,this paper uses a fixed-effect model to test the impact of rural highways supply on the income gap of farmers.The empirical results show that:(1)The effect of Chinese rural highways on the farmers'income gap among provinces is"U-shaped".(2)Chinese national and provincial trunk highways are helpful in narrowing the farmers'income gap among provinces.(3)The level of education,household productive fixed assets investment,level of urbanization,and level of regional economic development have multiple effects on the farmers'income gap among provinces.Then,based on the empirical analysis,the paper analyzes the mechanism of rural highways affecting the income gap of farmers from a theoretical perspective and focuses on the causes of the"U-shaped"relationship between rural highways supply and farmers'income gap.
文摘The results brought out in the trials of slope protection along Qinghai-Tibet Highway are presented in this paper. The trials were carried out simultaneously at 5 sites in Qinghai-Tibet Plateau from 2000 to 2002. Altitudes at the experimental sites range between (4 240) m and (5 040) m. 4 sites are in permafrost area, and 1 site is in seasonally frozen ground. According to the trials of slope protection, vegetation is preferred to protect slopes along Qinghai-Tibet Highway. Road-GoodR, a chemical stabilizer, is proved as a good material for slope protection, and soil engineering system, combined with vegetative component and grade stabilization structures is proved as the best slope protection measure in these areas. The results showed that high-altitude areas at an altitude lower than (5 040) m, annual average temperatures higher than (-5.6) ℃ and annual rainfall more than 262\^2 mm, slopes can be protected using vegetative components.\;Trials for plant species selection proved that cold resistant grasses, Elymus nutans and Elymus sibiricus can be used for vegetation recovery along Qinghai-Tibet Highway. The results demonstrated that high-altitude areas at an altitude lower than (5 040) m, annual average temperatures higher than (-5.6) ℃ and annual rainfall more than 262\^2 mm, could be replanted. Hydroseeding proved to be a good planting technique, and mulch materials benefited vegetation recovery in such area.\;The experiment also proved that planting could improve slope stability, protect the ecological environment, and improve the roadside landscape.
文摘At the turn of this century, China began the largest road and bridge development in the world, which has virtuously interacted with the social and economic development and has elevated the engineering technology to world-class level. Surveying the development of world transportation, and comparing the road and bridge construction efforts of Europe, U.S.A, Japan and China, general experiences of success can be derived as follows: It is greatly beneficial to give priority to transportation for economic development; it takes national strategy and social action to build up a transportation network; demand and innovation are the driving forces to upgrade road and bridge technology; management innovation and quality assurance can greatly improve development caliber. While rationally acknowledging China’s transportation infrastructure achievements, we should reflect on issues with Chinese characteristics that have affected quality and efficiency, expose all construction practices that violate scientific law, overall management defects in road and bridge construction and maintenance, and search for new ways to strengthen social management and the creation of a healthy soft environment.
文摘Transportation is a basic service industry concerned with people’s livelihood and well-being. China has unveiled guidelines on improving China’s strength in transportation. By 2035, an accessible travel service system should basically be built, according to the guidelines jointly released by the Communist Party of China Central Committee and the State Council. It is of great practical significance to accelerate the construction of an accessible transportation environment in the new era, which can improve the equalization of public services and promote the safe, convenient, and comfortable travel of the disabled and the elderly. In line with the development status of transportation in China, and through an analysis on the requirements for building a country with a strong transportation network, this paper proposes the framework and content for the establishment of an accessible transportation system in China.
基金partially supported by the National Natural Science Foundation of China(No.11861042)the Fundamental Research Funds for the Central Universitiesthe Research Funds of Renmin University of China(No.18XNL012)。
文摘In this article, we put forward a new approach to estimate multiple conditional regression quantiles simultaneously. Unlike the double summation method in most of the literatures, our proposed model allows continuous variety for the quantile level over(0,1). As a result, all the quantile curves can be obtained via a 2-dimensional surface simultaneously. Most importantly, the proposed minimizing criterion can be readily transformed to a linear programming problem. We use tensor product bi-linear quantile smoothing B-splines tofit it. The asymptotic property of the estimator is derived and a real data set is analyzed to demonstrate the proposed method.
基金supported by Central Public-interest Scientific Institution Basal Research Fund (No.20160604)Con-struction&Technology Projects in Ministry of Transportation (No.2014316670070,No.20113186701290)Construction&Technology Projects in Department of Transportation of Jilin Province (No.2014-4-1-7).
文摘Road-deposited sediments(RDS)accumulated on road surfaces are an important environmental medium that often provides transport for heavy metals.In order to understand the characteristics of heavy metals in RDS,we investigated the size distribution and heavy metal(i.e.Cd,Cr,Cu,Ni,Pb and Zn)concentrations in RDS and road runoff in typical expressways of suburban and rural area in China.The results demonstrated that RDS particles from all impervious expressway surfaces were predominantly coarse particles(>250μm,58.4%±3.8%)and the RDS on all expressways contained more heavy metals than background soils.Furthermore,the concentrations of Cd,Cr,Cu,Ni,Pb and Zn increased with traffic volume,suggesting that these heavy metals are mainly derived from traffic activities.Moreover,it is found that although heavy metals were concentrated in fine grain fractions,the total loading is highest for the coarsest particles due to their large mass percentage.Additionally,it reveals that the heavy metal concentrations in road runoff of suburban expressway are higher than that in urban expressway.Our findings enhance the understanding of expressway pollution,and imply that for controlling runoff pollution from RDS,transportation agencies should be concerned with both fine and coarse particles and take cleaning methods into account.
基金supported in part by the National Natural Science Foundation of China[Grant 41771473]Fundamental Research Funds for the Central Universities[Grant 2042020kfxg24].
文摘Electric Taxis(ETs)are the most favored alternatives to Gasoline Taxis(GTs)in cities that aim to reduce environmental pollution.How to develop a reasonable scale on which GTs are substituted by ETs remains a challenge to governments due to the dynamics and complexity of the taxi system.To address this challenge,this paper develops a discrete-event-based simulation framework to simulate participants in the system and estimate the results under different substitution scales,which are helpful to understanding the status changing law of entities under different substitution scales,such as the operating indices of ETs,the unsatisfied travel requirements of passengers,and the usage state of charging facilities.The framework abstracts the behavioral process of ETs into three elements,namely,entity,behavior,and event.The entities are constructed from the information derived from the trajectory data.The behaviors are defined by rules following behavioral logic under anxiety psychology,which is caused by the limited range of ETs.The events are triggered based on rules from reality.With the help of this framework,a multi-objective optimization model is developed to obtain the optimal substitution scale of GTs in the case study area of Zhengzhou City.Overall,the approach could provide a practical tool to address this challenge,which could support further studies of the effect of ETs on urban taxis.
基金Project supported by the National Natural Science Foundation of China(Nos.51008007 and 51308266)the Science and Technology Project on Construction of Ministry of Transport of China(No.2013318J01100)