Journal of Traffic and Transportation Engineering-English Edition最新文献_第7页

Risk diagnosis model for high-speed rail safety operation in big-data environment 大数据环境下高铁安全运行风险诊断模型

IF 7.4 2区工程技术 Q1 ENGINEERING, CIVIL

Journal of Traffic and Transportation Engineering-English Edition

Pub Date : 2025-02-01 Epub Date: 2025-01-16 DOI: 10.1016/j.jtte.2023.03.003

Qizhou Hu, Xin Guan, Xiaoyu Wu

Aiming at the risk issue of high-speed rail (HSR) safety operation, big data technology and uncertain mathematical method are adopted to study it. Firstly, from the perspective of system science, the risk diagnosis mode of HSR safety operation is put forward, which mainly includes the operation environment diagnosis mode based on multivariate product, high-speed train diagnosis mode based on failure influence, staff diagnosis mode based on management conditions, track diagnosis mode based on probability safety, etc. And based on comprehensive analysis, the conventional risk diagnosis index system is constructed. Then the dynamic diagnosis index system based on principal component analysis is proposed, and the risk diagnosis model of HSR safety operation is established. The diagnosis model can quickly evaluate the operation situations of HSR, and the diagnosis results are conducive to grasping the situation of risk events quickly and accurately, so as to meet the timeliness requirements of emergency decision-making. Finally, to verify the effectiveness of this new model, the Beijing–Shanghai HSR is selected as a case study. The analysis results show that the diagnosis model can quickly diagnose the safety operation situation of HSR, simplify the evaluation process and improve the efficiency of the comprehensive evaluation of emergencies.

针对高铁安全运行的风险问题，采用大数据技术和不确定数学方法对其进行研究。首先，从系统科学的角度提出了高铁安全运行风险诊断模式，主要包括基于多变量乘积的运行环境诊断模式、基于故障影响的高铁列车诊断模式、基于管理条件的人员诊断模式、基于概率安全的轨道诊断模式等。在综合分析的基础上，构建了常规风险诊断指标体系。在此基础上，提出了基于主成分分析的动态诊断指标体系，建立了高铁安全运行风险诊断模型。该诊断模型可以快速评估高铁运行情况，诊断结果有利于快速准确地掌握风险事件的情况，从而满足应急决策的时效性要求。最后，以京沪高铁为例，验证了该模型的有效性。分析结果表明，该诊断模型能够快速诊断高铁安全运行状况，简化评价流程，提高突发事件综合评价效率。

{"title":"Risk diagnosis model for high-speed rail safety operation in big-data environment","authors":"Qizhou Hu, Xin Guan, Xiaoyu Wu","doi":"10.1016/j.jtte.2023.03.003","DOIUrl":"10.1016/j.jtte.2023.03.003","url":null,"abstract":"<div><div>Aiming at the risk issue of high-speed rail (HSR) safety operation, big data technology and uncertain mathematical method are adopted to study it. Firstly, from the perspective of system science, the risk diagnosis mode of HSR safety operation is put forward, which mainly includes the operation environment diagnosis mode based on multivariate product, high-speed train diagnosis mode based on failure influence, staff diagnosis mode based on management conditions, track diagnosis mode based on probability safety, etc. And based on comprehensive analysis, the conventional risk diagnosis index system is constructed. Then the dynamic diagnosis index system based on principal component analysis is proposed, and the risk diagnosis model of HSR safety operation is established. The diagnosis model can quickly evaluate the operation situations of HSR, and the diagnosis results are conducive to grasping the situation of risk events quickly and accurately, so as to meet the timeliness requirements of emergency decision-making. Finally, to verify the effectiveness of this new model, the Beijing–Shanghai HSR is selected as a case study. The analysis results show that the diagnosis model can quickly diagnose the safety operation situation of HSR, simplify the evaluation process and improve the efficiency of the comprehensive evaluation of emergencies.</div></div>","PeriodicalId":47239,"journal":{"name":"Journal of Traffic and Transportation Engineering-English Edition","volume":"12 1","pages":"Pages 12-22"},"PeriodicalIF":7.4,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143479334","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Using piezoelectric technology to harvest energy from pavement: A review 利用压电技术从路面获取能量：综述

IF 7.4 2区工程技术 Q1 ENGINEERING, CIVIL

Journal of Traffic and Transportation Engineering-English Edition

Pub Date : 2025-02-01 Epub Date: 2025-01-21 DOI: 10.1016/j.jtte.2024.11.002

Keliang Mou , Xiaoping Ji , Jie Liu , Haoyu Zhou , Haochen Tian , Xiaojuan Li , Honghui Liu

A key point in building a contemporary energy system is the search for sustainable and green energy. Many green energy sources exist in the road or pavement domain, such as solar, thermal, wind, and mechanical energy, etc. Under the repeated vehicle loads, stresses and strains are generated in the pavement, which can generate substantial mechanical energy. In recent two decades, there has been a growing scholarly preference for utilizing the piezoelectric effect to convert mechanical energy from pavement into electricity to supply low-power transportation facilities, pavement sensors, etc. This paper provides an in-depth review of state-of-the-art advances in road piezoelectric energy harvesters. The basic principle of piezoelectric energy harvesting and common piezoelectric materials were briefly introduced. The piezoelectric energy harvesters suitable for roads are thoroughly reviewed from five perspectives: structure, finite element analyses, protective packaging, management circuit, and application. Finally, the challenges faced by piezoelectric energy harvesters for pavements were summarized, and the potential research directions were also proposed. This review serves as a valuable reference for advancing road piezoelectric harvesting technology development.

构建当代能源体系的一个关键点是寻找可持续的绿色能源。许多绿色能源存在于道路或路面领域，如太阳能、热能、风能和机械能等。在车辆反复荷载作用下，路面会产生应力和应变，产生大量的机械能。近二十年来，越来越多的学者倾向于利用压电效应将路面的机械能转化为电能，为低功耗的交通设施、路面传感器等供电。本文对道路压电能量采集器的最新进展进行了深入的综述。简要介绍了压电能量收集的基本原理和常用的压电材料。从结构、有限元分析、防护封装、管理电路和应用五个方面对适用于道路的压电能量采集器进行了全面的综述。最后，总结了路面压电能量采集器面临的挑战，并提出了未来的研究方向。本文对推进道路压电采集技术的发展具有重要的参考价值。

{"title":"Using piezoelectric technology to harvest energy from pavement: A review","authors":"Keliang Mou , Xiaoping Ji , Jie Liu , Haoyu Zhou , Haochen Tian , Xiaojuan Li , Honghui Liu","doi":"10.1016/j.jtte.2024.11.002","DOIUrl":"10.1016/j.jtte.2024.11.002","url":null,"abstract":"<div><div>A key point in building a contemporary energy system is the search for sustainable and green energy. Many green energy sources exist in the road or pavement domain, such as solar, thermal, wind, and mechanical energy, etc. Under the repeated vehicle loads, stresses and strains are generated in the pavement, which can generate substantial mechanical energy. In recent two decades, there has been a growing scholarly preference for utilizing the piezoelectric effect to convert mechanical energy from pavement into electricity to supply low-power transportation facilities, pavement sensors, etc. This paper provides an in-depth review of state-of-the-art advances in road piezoelectric energy harvesters. The basic principle of piezoelectric energy harvesting and common piezoelectric materials were briefly introduced. The piezoelectric energy harvesters suitable for roads are thoroughly reviewed from five perspectives: structure, finite element analyses, protective packaging, management circuit, and application. Finally, the challenges faced by piezoelectric energy harvesters for pavements were summarized, and the potential research directions were also proposed. This review serves as a valuable reference for advancing road piezoelectric harvesting technology development.</div></div>","PeriodicalId":47239,"journal":{"name":"Journal of Traffic and Transportation Engineering-English Edition","volume":"12 1","pages":"Pages 68-86"},"PeriodicalIF":7.4,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143479338","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Prediction of remaining parking spaces based on EMD-LSTM-BiLSTM neural network 基于EMD-LSTM-BiLSTM神经网络的剩余车位预测

IF 7.4 2区工程技术 Q1 ENGINEERING, CIVIL

Journal of Traffic and Transportation Engineering-English Edition

Pub Date : 2025-02-01 Epub Date: 2025-01-11 DOI: 10.1016/j.jtte.2023.01.004

Changxi Ma, Xiaoting Huang, Ke Wang, Yongpeng Zhao

The traffic congestion caused by the mismatch between the demand of car owners and the supply of parking spaces has become one of the severe traffic problems in various places. It is important to predict the remaining parking space which can not only help the driver to plan their trips reasonably but also reduce the pressure on urban road traffic. To reduce the stochastic fluctuations of complex data and improve the predictability of parking spaces, a hybrid prediction model EMD-LSTM-BiLSTM is proposed, which is combined the adaptive ability of empirical mode decomposition (EMD) to process time series data and the advantage of long short-term memory network (LSTM) and bidirectional long short-term memory network (BiLSTM) to solve long-range dependencies. First, the EMD algorithm is employed to decompose the components of different scales in the time series and generate a series of mode functions with the same characteristic scale. Next, the construction, training, and prediction of the LSTM-BiLSTM neural network are completed in the deep learning framework of Keras. BiLSTM was built for proposing the bi-directional temporal features of the sequences, and LSTM was responsible for learning the output features, which effectively avoids large prediction errors. Finally, the performance of the model is verified by the actual parking data sets of different parking lots for parking space prediction. The proposed hybrid model is compared with a variety of current mainstream deep learning algorithms, and the effectiveness of the EMD-LSTM-BiLSTM method is validated. The results may provide some potential insights for parking prediction.

由于车主需求与停车位供给不匹配而导致的交通拥堵，已成为各地严重的交通问题之一。对剩余停车空间进行预测，不仅可以帮助驾驶员合理规划行程，而且可以减轻城市道路交通的压力。为了降低复杂数据的随机波动，提高停车位的可预测性，提出了一种混合预测模型EMD-LSTM-BiLSTM，该模型结合了经验模态分解（EMD）处理时间序列数据的自适应能力和长短期记忆网络（LSTM）和双向长短期记忆网络（BiLSTM）解决长期依赖关系的优势。首先，利用EMD算法对时间序列中不同尺度的分量进行分解，生成一系列具有相同特征尺度的模态函数。接下来，在Keras的深度学习框架中完成LSTM-BiLSTM神经网络的构建、训练和预测。BiLSTM用于提出序列的双向时间特征，LSTM负责学习输出特征，有效避免了较大的预测误差。最后，通过不同停车场的实际停车数据集对模型的性能进行验证，用于车位预测。将所提出的混合模型与当前多种主流深度学习算法进行比较，验证了EMD-LSTM-BiLSTM方法的有效性。研究结果可能为停车预测提供一些潜在的见解。

{"title":"Prediction of remaining parking spaces based on EMD-LSTM-BiLSTM neural network","authors":"Changxi Ma, Xiaoting Huang, Ke Wang, Yongpeng Zhao","doi":"10.1016/j.jtte.2023.01.004","DOIUrl":"10.1016/j.jtte.2023.01.004","url":null,"abstract":"<div><div>The traffic congestion caused by the mismatch between the demand of car owners and the supply of parking spaces has become one of the severe traffic problems in various places. It is important to predict the remaining parking space which can not only help the driver to plan their trips reasonably but also reduce the pressure on urban road traffic. To reduce the stochastic fluctuations of complex data and improve the predictability of parking spaces, a hybrid prediction model EMD-LSTM-BiLSTM is proposed, which is combined the adaptive ability of empirical mode decomposition (EMD) to process time series data and the advantage of long short-term memory network (LSTM) and bidirectional long short-term memory network (BiLSTM) to solve long-range dependencies. First, the EMD algorithm is employed to decompose the components of different scales in the time series and generate a series of mode functions with the same characteristic scale. Next, the construction, training, and prediction of the LSTM-BiLSTM neural network are completed in the deep learning framework of Keras. BiLSTM was built for proposing the bi-directional temporal features of the sequences, and LSTM was responsible for learning the output features, which effectively avoids large prediction errors. Finally, the performance of the model is verified by the actual parking data sets of different parking lots for parking space prediction. The proposed hybrid model is compared with a variety of current mainstream deep learning algorithms, and the effectiveness of the EMD-LSTM-BiLSTM method is validated. The results may provide some potential insights for parking prediction.</div></div>","PeriodicalId":47239,"journal":{"name":"Journal of Traffic and Transportation Engineering-English Edition","volume":"12 1","pages":"Pages 201-213"},"PeriodicalIF":7.4,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143479358","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

A comparison on the effects of coal fines and sand fouling on the shear behaviors of railway ballast using large scale direct shear tests 采用大型直剪试验比较了煤粉和砂土污染对铁路道砟剪切特性的影响

IF 7.4 2区工程技术 Q1 ENGINEERING, CIVIL

Journal of Traffic and Transportation Engineering-English Edition

Pub Date : 2025-02-01 Epub Date: 2025-01-11 DOI: 10.1016/j.jtte.2022.09.003

Xu Zhang , Shunying Ji , Yang Feng , Yongjun Li , Chunfa Zhao

Railway ballast is easily contaminated by different fouling material and the fouled ballast always causes the deterioration of railway track. Many previous studies focused on the effect of a certain kind of fouling material on ballast performance, but few studies compared the influence of different fouling material. This paper presents a series of direct shear tests on the clean ballast and the fouled ballast mixed with coal fines or sand to understand the effects of different fouling material. A unified empirical model is proposed to well capture the shear stress-displacement responses of the clean and fouled ballast. Empirical equations are also obtained to characterize the variation of the nonlinear shear strength envelope of the fouled ballast with the fouling content. Based on these equations, a simple method is proposed to predict the shear strength of the fouled ballast using the shear test results of clean ballast. The measured results demonstrate significant differences between the effects of coal fines and sand on the shear behaviors of ballast, to which particular attention should be paid in order to take targeted maintenance measures for the fouled ballast. The mechanisms for the different effects of coal fines and sand are also analyzed to understand the roles that various fouling material plays in the fouled ballast.

铁路道砟容易受到各种污垢物质的污染，其污染往往会导致铁路轨道的劣化。以往的研究多集中于某一种污垢材料对压载性能的影响，但比较不同污垢材料对压载性能影响的研究较少。本文通过对洁净压舱水和掺入煤粉或砂土的污染压舱水进行一系列直剪试验，了解不同污染物质对压舱水的影响。提出了一个统一的经验模型，可以很好地反映清洁和污染压舱物的剪切应力-位移响应。得到了污舱非线性抗剪强度包络线随污量变化的经验方程。在此基础上，提出了一种利用清洁压舱物剪切试验结果预测污染压舱物抗剪强度的简便方法。实测结果表明，煤粉与砂土对压舱物剪切特性的影响存在显著差异，应引起重视，对受污染的压舱物采取有针对性的维护措施。分析了煤粉和砂土对压舱物不同影响的机理，了解了不同污染物质在压舱物污染中的作用。

{"title":"A comparison on the effects of coal fines and sand fouling on the shear behaviors of railway ballast using large scale direct shear tests","authors":"Xu Zhang , Shunying Ji , Yang Feng , Yongjun Li , Chunfa Zhao","doi":"10.1016/j.jtte.2022.09.003","DOIUrl":"10.1016/j.jtte.2022.09.003","url":null,"abstract":"<div><div>Railway ballast is easily contaminated by different fouling material and the fouled ballast always causes the deterioration of railway track. Many previous studies focused on the effect of a certain kind of fouling material on ballast performance, but few studies compared the influence of different fouling material. This paper presents a series of direct shear tests on the clean ballast and the fouled ballast mixed with coal fines or sand to understand the effects of different fouling material. A unified empirical model is proposed to well capture the shear stress-displacement responses of the clean and fouled ballast. Empirical equations are also obtained to characterize the variation of the nonlinear shear strength envelope of the fouled ballast with the fouling content. Based on these equations, a simple method is proposed to predict the shear strength of the fouled ballast using the shear test results of clean ballast. The measured results demonstrate significant differences between the effects of coal fines and sand on the shear behaviors of ballast, to which particular attention should be paid in order to take targeted maintenance measures for the fouled ballast. The mechanisms for the different effects of coal fines and sand are also analyzed to understand the roles that various fouling material plays in the fouled ballast.</div></div>","PeriodicalId":47239,"journal":{"name":"Journal of Traffic and Transportation Engineering-English Edition","volume":"12 1","pages":"Pages 52-67"},"PeriodicalIF":7.4,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143479337","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Bayesian spatial modeling for speeding likelihood using floating car trajectories 基于浮动汽车轨迹的超速可能性贝叶斯空间建模

IF 7.4 2区工程技术 Q1 ENGINEERING, CIVIL

Journal of Traffic and Transportation Engineering-English Edition

Pub Date : 2025-02-01 Epub Date: 2025-01-11 DOI: 10.1016/j.jtte.2023.07.013

Haiyue Liu , Chaozhe Jiang , Chuanyun Fu , Yue Zhou , Chenyang Zhang , Zhiqiang Sun

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-Mollié (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.

超速可能性通常用来衡量司机超速的倾向。虽然有一些研究分析了超速可能性，但在分析城市路网超速行为时，大多没有考虑到空间效应。本研究旨在利用空间模型对超速似然进行建模，以填补这一知识空白，并评估各影响因素的影响。采用超速观测的百分比（PSO）来表示超速可能性。从成都市的GPS轨迹中提取了每辆浮动汽车（即出租车）的超速行为和PSO。PSO模型采用几种具有空间效应的贝叶斯β一般线性模型，即β模型、β logit-normal模型、β intrinsic conditional autoregressive （ICAR）模型、β besag - york - molli (BYM)模型和β BYM2模型。结果表明，beta BYM2模型在数据拟合方面优于其他模型。根据beta BYM2的估计，空间相关性是造成模式变异的主要原因。车道较多的道路和高架道路连接的道路增加了超速可能性，而较高的限速、交叉口密度、交通拥堵和路边停车与较低的超速可能性相关。这些发现为设计有效的城市道路网络反超速对策提供了有价值的见解。

{"title":"Bayesian spatial modeling for speeding likelihood using floating car trajectories","authors":"Haiyue Liu , Chaozhe Jiang , Chuanyun Fu , Yue Zhou , Chenyang Zhang , Zhiqiang Sun","doi":"10.1016/j.jtte.2023.07.013","DOIUrl":"10.1016/j.jtte.2023.07.013","url":null,"abstract":"<div><div>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-Mollié (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.</div></div>","PeriodicalId":47239,"journal":{"name":"Journal of Traffic and Transportation Engineering-English Edition","volume":"12 1","pages":"Pages 139-150"},"PeriodicalIF":7.4,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143479864","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Skid resistance performance and texture lateral distribution within the lanes of asphalt pavements 沥青路面车道内抗滑性能及纹理横向分布

IF 7.4 2区工程技术 Q1 ENGINEERING, CIVIL

Journal of Traffic and Transportation Engineering-English Edition

Pub Date : 2025-02-01 Epub Date: 2025-01-16 DOI: 10.1016/j.jtte.2021.03.010

Di Yun , Liqun Hu , Ulf Sandberg , Cheng Tang

The skid resistance and pavement texture can vary a lot for different lane paths, meaning that the lateral shift of the vehicle driving in the lane section can affect the safety significantly. On the other hand, a varying skid resistance across a lane section provides the opportunity to influence vehicles to run in lateral positions where the tire/road friction has not yet been reduced by wear; thus, improving safety. This measure would be useful only if the distribution of skid resistance and pavement texture in the lane sections are investigated at frequent intervals.

This study focused on four test sections on in-service urban roads. A friction measuring device known as the T2GO system was used to test the skid resistance performance of pavements for both dry and wet conditions. A high-precision 3D-scanner was used to capture the pavement macrotexture, and a microscope was employed to investigate the pavement abrasion. Subsequently, the effect of the lateral variation across the lane of friction and texture was discussed. The feasibility of displacing the vehicles to run in tracks with better skid resistance was explored in terms of the measured friction and the texture-dependent drainage capacity. The results indicated that driving closer to the lanes' right side means that better values of friction, texture, and drainage parameters of the unworn pavement surface can be utilized. A 0.3 m or more lateral displacement would create improved friction, in a range between 13% and 14% for 1.5 m track width and between 8% and 11% for 1.65 m track width. Furthermore, the results are useful in studying the vehicles' sideslip.

不同车道的路面结构和防滑性能差异很大，车辆在车道段行驶时的侧向位移对行车安全性影响较大。另一方面，不同路段的防滑阻力可以影响车辆在轮胎/路面摩擦尚未减少的横向位置行驶；从而提高安全性。只有在频繁地研究车道段的防滑性和路面纹理分布的情况下，这种措施才有用。本研究主要针对在役城市道路上的四个测试路段进行研究。一种被称为T2GO系统的摩擦测量装置被用来测试路面在干燥和潮湿条件下的抗滑性能。采用高精度三维扫描仪捕捉路面宏观纹理，并用显微镜观察路面磨损情况。在此基础上，讨论了摩擦和织构对横向变化的影响。根据实测的摩擦和纹理相关的排水能力，探讨了将车辆置换到具有较好防滑性的轨道上运行的可行性。结果表明，靠近车道右侧行驶意味着可以更好地利用未磨损路面的摩擦、纹理和排水参数值。0.3 m或更大的横向位移将改善摩擦力，在1.5 m轨道宽度下，摩擦力在13%至14%之间，在1.65 m轨道宽度下，摩擦力在8%至11%之间。此外，该结果对车辆侧滑的研究也有一定的参考价值。

{"title":"Skid resistance performance and texture lateral distribution within the lanes of asphalt pavements","authors":"Di Yun , Liqun Hu , Ulf Sandberg , Cheng Tang","doi":"10.1016/j.jtte.2021.03.010","DOIUrl":"10.1016/j.jtte.2021.03.010","url":null,"abstract":"<div><div>The skid resistance and pavement texture can vary a lot for different lane paths, meaning that the lateral shift of the vehicle driving in the lane section can affect the safety significantly. On the other hand, a varying skid resistance across a lane section provides the opportunity to influence vehicles to run in lateral positions where the tire/road friction has not yet been reduced by wear; thus, improving safety. This measure would be useful only if the distribution of skid resistance and pavement texture in the lane sections are investigated at frequent intervals.</div><div>This study focused on four test sections on in-service urban roads. A friction measuring device known as the T2GO system was used to test the skid resistance performance of pavements for both dry and wet conditions. A high-precision 3D-scanner was used to capture the pavement macrotexture, and a microscope was employed to investigate the pavement abrasion. Subsequently, the effect of the lateral variation across the lane of friction and texture was discussed. The feasibility of displacing the vehicles to run in tracks with better skid resistance was explored in terms of the measured friction and the texture-dependent drainage capacity. The results indicated that driving closer to the lanes' right side means that better values of friction, texture, and drainage parameters of the unworn pavement surface can be utilized. A 0.3 m or more lateral displacement would create improved friction, in a range between 13% and 14% for 1.5 m track width and between 8% and 11% for 1.65 m track width. Furthermore, the results are useful in studying the vehicles' sideslip.</div></div>","PeriodicalId":47239,"journal":{"name":"Journal of Traffic and Transportation Engineering-English Edition","volume":"12 1","pages":"Pages 87-107"},"PeriodicalIF":7.4,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143479339","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Study on interface shear strength between polyurethane treated and original Pisha sandstone under dry-wet cycles 干湿循环作用下聚氨酯处理与原皮沙砂岩界面抗剪强度研究

IF 7.4 2区工程技术 Q1 ENGINEERING, CIVIL

Journal of Traffic and Transportation Engineering-English Edition

Pub Date : 2025-02-01 Epub Date: 2025-01-11 DOI: 10.1016/j.jtte.2021.12.007

Wenbo Ma , Xuan Zhou , Jiaping Li , Yanli Chen , Yuyang Li , Caiqian Yang , Minke Ma , Jiale Long , Shuaicheng Guo

Currently, utilization of hydrophilic polyurethane (W-OH) materials for slope protection in arid areas has proved to be a cost-effective protocol. The treatment effect highly depends on the interfacial performance between the W-OH treated and the original sandstone. This study aims to investigate the corresponding shear strength and its long-term performance under dry-wet cycles under the arid environment. The results from the direct shear test indicate the interface shear strength increases with W-OH solution concentration and decreases with the increase of water content of the Pisha sandstone. Further investigations under dry-wet cycles indicate the interface cohesion is obviously weakened by the dry-wet cycles, while the influence on the internal friction angle is not obvious. The correlation between the degradation level and the dry-wet cycles can be well fitted with the inverted S-curve using two combined exponential functions. Furthermore, the ethylene-vinyl acetate (EVA) content is utilized to enhance the durability performance under dry-wet cycles. It is found the EVA can obviously improve the bonding property and the resistance to dry-wet cycles. This study’s results can serve as a solid base for the application of W-OH materials to resolve the soil erosion in the arid region.

目前，在干旱地区使用亲水聚氨酯（W-OH）材料进行边坡防护已被证明是一种具有成本效益的方案。处理效果在很大程度上取决于处理后的W-OH与原始砂岩之间的界面性能。本研究旨在研究干湿循环条件下相应的抗剪强度及其长期性能。直剪试验结果表明，界面抗剪强度随W-OH溶液浓度的增加而增大，随含水量的增加而减小。在干湿循环下的进一步研究表明，干湿循环明显削弱了界面黏聚力，而对内摩擦角的影响不明显。利用两个复合指数函数可以很好地拟合出退化程度与干湿循环之间的倒s曲线关系。此外，利用乙烯-醋酸乙烯酯（EVA）含量来提高干湿循环下的耐久性。结果表明，EVA能明显提高复合材料的粘接性能和抗干湿循环性能。本研究结果可为W-OH材料在干旱区土壤侵蚀治理中的应用提供坚实的基础。

{"title":"Study on interface shear strength between polyurethane treated and original Pisha sandstone under dry-wet cycles","authors":"Wenbo Ma , Xuan Zhou , Jiaping Li , Yanli Chen , Yuyang Li , Caiqian Yang , Minke Ma , Jiale Long , Shuaicheng Guo","doi":"10.1016/j.jtte.2021.12.007","DOIUrl":"10.1016/j.jtte.2021.12.007","url":null,"abstract":"<div><div>Currently, utilization of hydrophilic polyurethane (W-OH) materials for slope protection in arid areas has proved to be a cost-effective protocol. The treatment effect highly depends on the interfacial performance between the W-OH treated and the original sandstone. This study aims to investigate the corresponding shear strength and its long-term performance under dry-wet cycles under the arid environment. The results from the direct shear test indicate the interface shear strength increases with W-OH solution concentration and decreases with the increase of water content of the Pisha sandstone. Further investigations under dry-wet cycles indicate the interface cohesion is obviously weakened by the dry-wet cycles, while the influence on the internal friction angle is not obvious. The correlation between the degradation level and the dry-wet cycles can be well fitted with the inverted S-curve using two combined exponential functions. Furthermore, the ethylene-vinyl acetate (EVA) content is utilized to enhance the durability performance under dry-wet cycles. It is found the EVA can obviously improve the bonding property and the resistance to dry-wet cycles. This study’s results can serve as a solid base for the application of W-OH materials to resolve the soil erosion in the arid region.</div></div>","PeriodicalId":47239,"journal":{"name":"Journal of Traffic and Transportation Engineering-English Edition","volume":"12 1","pages":"Pages 108-122"},"PeriodicalIF":7.4,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143479340","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Comparative evaluation of alternative Bayesian semi-parametric spatial crash frequency models 不同贝叶斯半参数空间碰撞频率模型的比较评价

IF 7.4 2区工程技术 Q1 ENGINEERING, CIVIL

Journal of Traffic and Transportation Engineering-English Edition

Pub Date : 2025-02-01 Epub Date: 2025-01-16 DOI: 10.1016/j.jtte.2022.01.005

Gurdiljot Singh Gill , Wen Cheng , Mankirat Singh , Yihua Li

Albeit with the notable benefits associated with Dirichlet crash frequency models and spatial ones, there is little research dedicated to exploring their combined advantages. Such ensemble approach could be a viable alternative to existing models as it accounts for the unobserved heterogeneity by relaxing the constraints of specific distribution placed on the intercept while addressing the spatial correlations among roadway entities. To fill this gap, the authors aimed to develop Dirichlet semi-parametric models over the over-dispersed generalized linear model framework while also incorporating spatially structured random effects using a distance-based weight matrix.

Five models were developed which include four semi-parametric with flexible intercept and one parametric base model for comparison purposes. The four semi-parametric models entailed two models with a popular specification of stick-breaking Dirichlet process (DP) and two models with an alternative approach of Dirichlet distribution (DD), which are first applied in the field of traffic safety. All four models were estimated for mixture of points (discrete) and mixture of normals (continuous). The posterior density plots for the precision parameter justified the employment of the flexible Dirichlet approach to fit the crash data and supported the assumed prior for the precision parameter. All four Dirichlet models demonstrated the presence of distinct subpopulations suggesting that the intercepts of the models were not generated from a common distribution. The DP model based on mixture of normals illustrated better performance indicating its potential superiority to fit both in-sample and out-of-sample crash data. This finding indicated that the approach of continuous densities, unlike discrete points, may lend more flexibility to fit the data.

尽管Dirichlet碰撞频率模型和空间模型具有显著的优势，但很少有研究致力于探索它们的综合优势。这种集成方法可能是现有模型的可行替代方案，因为它通过放松放置在截距上的特定分布的约束来解释未观察到的异质性，同时解决道路实体之间的空间相关性。为了填补这一空白，作者旨在在过度分散的广义线性模型框架上开发Dirichlet半参数模型，同时还使用基于距离的权重矩阵结合空间结构随机效应。建立了五个模型，其中包括四个具有柔性截距的半参数模型和一个用于比较的参数基模型。这四种半参数模型包括两种最常用的掰棍狄利克雷过程（DP）规范模型和两种最早应用于交通安全领域的狄利克雷分布（DD）替代方法模型。对所有四种模型进行了点混合（离散）和法线混合（连续）的估计。精度参数的后验密度图证明了采用柔性狄利克雷方法拟合碰撞数据的合理性，并支持精度参数的假设先验。所有四个狄利克雷模型都显示了不同亚种群的存在，这表明模型的截距不是由一个共同分布产生的。基于混合法线的DP模型表现出更好的性能，表明它在拟合样本内和样本外崩溃数据方面具有潜在的优势。这一发现表明，连续密度的方法，不像离散点，可以提供更大的灵活性来拟合数据。

{"title":"Comparative evaluation of alternative Bayesian semi-parametric spatial crash frequency models","authors":"Gurdiljot Singh Gill , Wen Cheng , Mankirat Singh , Yihua Li","doi":"10.1016/j.jtte.2022.01.005","DOIUrl":"10.1016/j.jtte.2022.01.005","url":null,"abstract":"<div><div>Albeit with the notable benefits associated with Dirichlet crash frequency models and spatial ones, there is little research dedicated to exploring their combined advantages. Such ensemble approach could be a viable alternative to existing models as it accounts for the unobserved heterogeneity by relaxing the constraints of specific distribution placed on the intercept while addressing the spatial correlations among roadway entities. To fill this gap, the authors aimed to develop Dirichlet semi-parametric models over the over-dispersed generalized linear model framework while also incorporating spatially structured random effects using a distance-based weight matrix.</div><div>Five models were developed which include four semi-parametric with flexible intercept and one parametric base model for comparison purposes. The four semi-parametric models entailed two models with a popular specification of stick-breaking Dirichlet process (DP) and two models with an alternative approach of Dirichlet distribution (DD), which are first applied in the field of traffic safety. All four models were estimated for mixture of points (discrete) and mixture of normals (continuous). The posterior density plots for the precision parameter justified the employment of the flexible Dirichlet approach to fit the crash data and supported the assumed prior for the precision parameter. All four Dirichlet models demonstrated the presence of distinct subpopulations suggesting that the intercepts of the models were not generated from a common distribution. The DP model based on mixture of normals illustrated better performance indicating its potential superiority to fit both in-sample and out-of-sample crash data. This finding indicated that the approach of continuous densities, unlike discrete points, may lend more flexibility to fit the data.</div></div>","PeriodicalId":47239,"journal":{"name":"Journal of Traffic and Transportation Engineering-English Edition","volume":"12 1","pages":"Pages 151-166"},"PeriodicalIF":7.4,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143479865","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Empirical comparison of the effects of other party's vehicle type on motorcyclists' injury severity 对方车辆类型对摩托车手伤害严重程度影响的实证比较

IF 7.4 2区工程技术 Q1 ENGINEERING, CIVIL

Journal of Traffic and Transportation Engineering-English Edition

Pub Date : 2025-02-01 Epub Date: 2025-01-11 DOI: 10.1016/j.jtte.2023.11.007

Thanapong Champahom , Chamroeun Se , Wimon Laphrom , Duangdao Watthanaklang , Sajjakaj Jomnonkwao , Vatanavongs Ratanavaraha

This research explores the various factors influencing the severity of injuries motorcyclists sustain across different collision scenarios. The study considers the types of vehicles involved, including motorcycle (MC), cars, pickup trucks, vans, and trucks. The study is grounded in an analysis of road crashes in Thailand from 2016 to 2019. Recognizing the unique characteristics inherent in each collision type, the study categorizes crashes into six distinct models for a comprehensive analysis. Each model is constructed using the random parameter logit with unobserved heterogeneity in means. Notably, all models incorporate random parameters, with the exception of the MC vs. truck model. Despite some consistent factors across most models, there are noteworthy variations in parameters when comparing different vehicle types. In the context of single-motorcycle crashes, speed limit violation emerges as a critical factor. For the MC vs. MC model, crashes happening from midnight to early morning are significant. The presence of a passenger (pillion) is a key determinant in the MC vs. car model. Meanwhile, in the MC vs. pickup truck model, crashes occurring under poor light conditions from midnight to early morning are of particular importance. The MC vs. van model notably highlights the involvement of male riders. Lastly, the MC vs. truck model draws attention to crashes happening on weekends. By creating specific crash models for diverse vehicle types, this study enhances our understanding of motorcycle crashes. The findings provide valuable insights to inform the development of policies, the design of safety campaigns, the creation of training programs, and the evaluation of road safety.

本研究探讨了影响摩托车手在不同碰撞情况下受伤严重程度的各种因素。该研究考虑了所涉及的车辆类型，包括摩托车（MC）、汽车、皮卡、货车和卡车。该研究基于对泰国2016年至2019年道路交通事故的分析。认识到每种碰撞类型固有的独特特征，该研究将碰撞分为六种不同的模型进行全面分析。每个模型都是使用随机参数logit构建的，其中均值具有未观察到的异质性。值得注意的是，除了MC与卡车模型外，所有模型都包含随机参数。尽管在大多数车型中存在一些一致的因素，但在比较不同车型时，参数存在值得注意的差异。在单摩托车碰撞事故中，限速违规成为一个关键因素。对于MC vs MC模型，从午夜到清晨发生的崩溃是重要的。乘客（座席）的存在是MC与汽车模型的关键决定因素。与此同时，在MC与皮卡模型中，在午夜至凌晨光线不足的情况下发生的撞车事故尤为重要。MC vs. van模式特别强调了男性骑手的参与。最后，MC与卡车的模型引起了人们对周末发生的撞车事故的关注。通过建立不同车辆类型的特定碰撞模型，本研究增强了我们对摩托车碰撞的理解。研究结果为制定政策、设计安全运动、制定培训计划和评估道路安全提供了宝贵的见解。

{"title":"Empirical comparison of the effects of other party's vehicle type on motorcyclists' injury severity","authors":"Thanapong Champahom , Chamroeun Se , Wimon Laphrom , Duangdao Watthanaklang , Sajjakaj Jomnonkwao , Vatanavongs Ratanavaraha","doi":"10.1016/j.jtte.2023.11.007","DOIUrl":"10.1016/j.jtte.2023.11.007","url":null,"abstract":"<div><div>This research explores the various factors influencing the severity of injuries motorcyclists sustain across different collision scenarios. The study considers the types of vehicles involved, including motorcycle (MC), cars, pickup trucks, vans, and trucks. The study is grounded in an analysis of road crashes in Thailand from 2016 to 2019. Recognizing the unique characteristics inherent in each collision type, the study categorizes crashes into six distinct models for a comprehensive analysis. Each model is constructed using the random parameter logit with unobserved heterogeneity in means. Notably, all models incorporate random parameters, with the exception of the MC vs. truck model. Despite some consistent factors across most models, there are noteworthy variations in parameters when comparing different vehicle types. In the context of single-motorcycle crashes, speed limit violation emerges as a critical factor. For the MC vs. MC model, crashes happening from midnight to early morning are significant. The presence of a passenger (pillion) is a key determinant in the MC vs. car model. Meanwhile, in the MC vs. pickup truck model, crashes occurring under poor light conditions from midnight to early morning are of particular importance. The MC vs. van model notably highlights the involvement of male riders. Lastly, the MC vs. truck model draws attention to crashes happening on weekends. By creating specific crash models for diverse vehicle types, this study enhances our understanding of motorcycle crashes. The findings provide valuable insights to inform the development of policies, the design of safety campaigns, the creation of training programs, and the evaluation of road safety.</div></div>","PeriodicalId":47239,"journal":{"name":"Journal of Traffic and Transportation Engineering-English Edition","volume":"12 1","pages":"Pages 180-200"},"PeriodicalIF":7.4,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143479357","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Deformation properties of remolded loess compacted via vertical vibration compaction method 垂直振动压实法重塑黄土的变形特性

IF 7.4 2区工程技术 Q1 ENGINEERING, CIVIL

Journal of Traffic and Transportation Engineering-English Edition

Pub Date : 2025-02-01 Epub Date: 2025-01-16 DOI: 10.1016/j.jtte.2022.04.001

Yingjun Jiang , Kejia Yuan , Jiangtao Fan , Chenfan Bai , Wei Zhang , Jinshun Xue

To investigate the deformation properties of remolded loess subgrade under long-term cyclic dynamic loading, remolded loess specimens compacted via vertical vibration compaction method were produced and some factors influencing elastic strain and cumulative plastic strain, which include the number of vibration cycles, depth, and water content, have been investigated. A prediction model for cumulative plastic deformation was established. In addition, the collapsible deformation properties of remolded loess were investigated. Results indicate that the elastic strain and plastic strain are decreased with increasing vibration cycles and depth and finally tend to be stable when the number of vibration cycles is more than 2000 and the depth exceeds 2.5 m. The elastic strain and cumulative plastic strain of compacted loess are increased by 7.2% and 13.0%, respectively, when the water content increases by 1.0%. The cumulative plastic deformation of remolded loess follows a logarithmic distribution. The elastic deformation and cumulative plastic deformation of loess subgrade are far less than the demands for elastic deformation and post-construction settlement of subgrade. As the compaction coefficient and water content are increased by 1.0%, the collapsibility coefficient of compacted loess is decreased by an average of 13.7% and 14.5%. Such investigations can prevent subgrade diseases and ensure the safety of subgrade filled with loess soils.

为研究长期循环动力荷载作用下重塑黄土路基的变形特性，制作了竖向振动压实法压实的重塑黄土试样，研究了振动循环次数、深度、含水率等因素对重塑黄土弹性应变和累积塑性应变的影响。建立了累积塑性变形的预测模型。此外，还研究了重塑黄土的湿陷变形特性。结果表明：弹性应变和塑性应变随振动循环次数和深度的增加而减小，当振动循环次数超过2000次且深度超过2.5 m时趋于稳定；含水量每增加1.0%，压实黄土的弹性应变和累积塑性应变分别增加7.2%和13.0%。重塑黄土的累积塑性变形服从对数分布。黄土路基的弹性变形和累积塑性变形远远小于对路基弹性变形和工后沉降的要求。压实系数和含水率每增加1.0%，压实黄土的湿陷系数平均降低13.7%和14.5%。这样的调查可以预防路基病害，保证黄土填土路基的安全。

{"title":"Deformation properties of remolded loess compacted via vertical vibration compaction method","authors":"Yingjun Jiang , Kejia Yuan , Jiangtao Fan , Chenfan Bai , Wei Zhang , Jinshun Xue","doi":"10.1016/j.jtte.2022.04.001","DOIUrl":"10.1016/j.jtte.2022.04.001","url":null,"abstract":"<div><div>To investigate the deformation properties of remolded loess subgrade under long-term cyclic dynamic loading, remolded loess specimens compacted via vertical vibration compaction method were produced and some factors influencing elastic strain and cumulative plastic strain, which include the number of vibration cycles, depth, and water content, have been investigated. A prediction model for cumulative plastic deformation was established. In addition, the collapsible deformation properties of remolded loess were investigated. Results indicate that the elastic strain and plastic strain are decreased with increasing vibration cycles and depth and finally tend to be stable when the number of vibration cycles is more than 2000 and the depth exceeds 2.5 m. The elastic strain and cumulative plastic strain of compacted loess are increased by 7.2% and 13.0%, respectively, when the water content increases by 1.0%. The cumulative plastic deformation of remolded loess follows a logarithmic distribution. The elastic deformation and cumulative plastic deformation of loess subgrade are far less than the demands for elastic deformation and post-construction settlement of subgrade. As the compaction coefficient and water content are increased by 1.0%, the collapsibility coefficient of compacted loess is decreased by an average of 13.7% and 14.5%. Such investigations can prevent subgrade diseases and ensure the safety of subgrade filled with loess soils.</div></div>","PeriodicalId":47239,"journal":{"name":"Journal of Traffic and Transportation Engineering-English Edition","volume":"12 1","pages":"Pages 123-138"},"PeriodicalIF":7.4,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143479341","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0