Application of gray-tone difference matrix-based features of pavement macrotexture in skid resistance evaluation

This paper presents a method to characterize asphalt pavement macrotexture using the gray-tone difference matrix （GTDM）and discusses the potentials of the GTDM indicators for skid resistance evaluation.There are 37 field sites included in the data collection,which cover 6 types of asphalt pavement surfaces. The mean profile depth derived from 3-D macrotexture measurements （MPD3 ） has a significant relationship with the mean texture depth （MTD ）,which can be described by a logarithm model with R2 of 0.962.There is no significant linear relationship between the friction coefficient at a speed of 60 km/h （DFT60 ）and macrotexture indicators.A nonlinear model with British pendulum number （BPN ） incorporated can relate DFT60 to MTD or indicator fcon .A comparison with MTD shows that GTDM-based fcon has a potential to be a macrotexture indicator for skid resistance evaluation,which describes the general height difference and the average local height difference of pavement macrotexture. A relatively high fcon is helpful for improving asphalt pavement skid resistance.

Treatment outcomes and adverse drug reactions among patients with drug-resistant tuberculosis receiving all-oral,long-term regimens:First record viewing report from Pakistan

Objective:To assess the effectiveness and adverse drug reactions of all-oral regimens for patients with multidrug-resistant tuberculosis.Methods:This retrospective study was conducted at 10 Programmatic Management of Drug Resistant Tuberculosis sites in Punjab province of Pakistan.Patients receiving treatment for drug resistant tuberculosis from July 2019 to December 2020 with at least interim result i.e.6th month culture conversion or final outcomes(cured,complete,lost to follow-up,failure,death)available,were included in the study.Data was extracted from electronic data management system.For the reporting and management of adverse drug events,active tuberculosis drug safety monitoring and management was implemented across all sites.All the data was analyzed using SPSS version 22.Results:Out of 947 drug resistant tuberculosis patients included in this study,579(68%)of the patients had final outcomes available.Of these,384(67.9%)successfully completed their treatment.Out of 368(32%)patients who had their interim results available,all had their 6th month culture negative.Combining new medications was thought to result in serious adverse outcomes such as QT prolongation.However,this study did not record any severe adverse events among patients.Conclusions:All-oral regimens formulation guided by overall treatment effectiveness resulted in treatment outcomes comparable to those obtained with traditional injectable treatment.

Evaluation of surface textures and skid resistance of pervious concrete pavement

Surface textures had long been recognized as primary factors to provide the skid resistance on pavements; however, no measurement of skid resistance on pervious concrete pavement with various surface texture parameters had been made. Fractal geometry was introduced in the present work to accurately simulate transect contour curves of pervious concrete specimens through fractal interpolation. It is proved that its fractal dimension (D) can be adopted to measure the skid resistance on pervious concrete pavement, overcoming the shortcomings of both macrotexture depth (DT ) and British portable pendulum number (NBP). Combined with Fujikawa-Koike tire/road contact model, the optimization method of all surface textures was recommended for designing and constructing excellently skid-resistant and noise-absorptive pervious concrete pavement. In addition, evaluating of the abrasion process and attenuation of the surface textures on concrete pavement slabs was also the focus of this work based on accelerated abrasion test. Results show that the surface textures on pervious concrete pavement slabs is extremely durable, compared to those on conventional grooved or exposed aggregate concrete pavement slabs.

Influence of rainfall on skid resistance performance and driving safety conditions of asphalt pavements

To study the influence of rainfall on pavement skid-resistance performance and driving safety,the water film thickness(WFT)concept considering the longitudinal and transverse slopes of the pavement was utilized based on the total discharge formulation and turbulence theory of slope flow.Using experimental data measured using the British pendulum test under varying WFT levels,a model for calculating the skid resistance,namely the British pendulum number(BPN),was formulated and used to quantitatively evaluate the effects of rainfall intensity,transverse,and longitudinal slopes on the computed BPN.The study results reveal that skid resistance is linearly proportional to the pavement transverse slope and inversely proportional to the rainfall intensity and the pavement longitudinal slope.In particular,rainfall intensity,along with pavement texture depth,exhibited a significant impact on the tire-pavement friction and skid-resistance performance.The results further indicate that driving safety under wet weather is predominantly governed by skid resistance and visibility.The BPN and sideway force coefficient(SFC60)values for new asphalt pavements under different rainfall intensities are provided along with some modification to the stopping sight distance(SSD)criteria.Safe driving speed limits are also determined using a safe-driving model to develop the appropriate speed limit strategies.The overall study results provide some insights,methodology approach,and reference data for the evaluation of pavement skid-resistance performance and driving safety conditions under different pavement slopes and rainfall intensities.

Pavement Friction and Skid Resistance Measurement Methods: A Literature Review

Driving safety is of significance in the automobile industry and transportation systems. Pavement skid resistance has long been recognized as the most important parameter in reducing traffic accidents especially in wet conditions. The knowledge of the friction coefficient and skid resistance is very valuable information for safety enhancement of roads. Thus, it is important to find proper methods for measuring skid resistance and frictional properties of the pavement surface. There is a wide range of measurement methods and devices for measuring skid resistance. This paper presents a review on the research studies that have been done on characterization of the frictional properties of the pavement surface and discussed methods used for measurement and evaluation of texture characteristics and the strengths and weaknesses of these methods. Finally, some ideas have been suggested to develop new methods for better and proper measurement of skid resistance.

Influence of Thin Water Film on Skid Resistance

Most of past researches on the skid resistance/road wetness relationship deal with thick water depths （〉 1 mm）. Questions remain as to the variation of skid resistance with thin water films and the transition between the dry state and the so-called ＂damp＂ or ＂humid＂ state at which the skid resistance drop can be as high as 30%-40%. This paper deals with a theoretical and experimental assessment of the friction-water depth relationship. The main objective is to estimate local water depths trapped between the tire and the road asperities and to define a so-called ＂critical＂ water depth which can be used to detect risky situations for road users. Tests are performed in laboratory. It was found that the friction-water depth curves have an inverse-S shape and present an initial constant-friction part before decreasing to a minimum value. A ＂critical＂ water depth, defined as the water depth above which the friction coefficient collapses significantly, is determined from surface texture on critical water depth is discussed. observed friction-water depth curves. Influence of test speed and

Determination and prediction of pavement skid resistance–connecting research and practice

Adequate pavement skid resistance is a key requirement for safe road operations.Unfortunately,the measurement and prediction of the skid resistance property of an in-service road pavement,or pavement mixture specimens in the laboratory,is a highly challenging process from both theoretical and practical points of view.For more than 60 years,owing to the lack of theoretical solutions to the complex tire-fluid-pavement interaction problem,the practice of pavement skid resistance determination and prediction has essentially been derived from experimental and field observed data.The rapid development of efficient numerical computational techniques and high-power computing facilities in the last two decades made it possible for researchers to numerically solve the tire-fluidpavement interaction problem.It enables the numerical evaluation and prediction of high-speed wet skid resistance,and the determination of the tire-pavement kinetic friction coefficient in the evaluation of low-speed skid resistance.This paper presents a state-of-the-art review of the research development of theoretical mechanistic approaches in the determination and prediction of pavement skid resistance.It covers the following main aspects of the subject matter:(i)mechanisms of skid resistance generation in dry,wetted(i.e.,damp),wet and flooded pavements;(ii)theoretical evaluation of pavement skid resistance in dry,wetted,wet and flooded states;(iii)theoretical approaches in pavement skid resistance prediction;and(iv)concepts of representing the skid resistance state of pavement.The capability of finite element simulation approach for wet skid resistance evaluation with good accuracy is explained.Also highlighted is the practical significance of the Concept of Skid Resistance State.Areas of practical applications of the concept,coupled with the simulation model,are introduced.They include applications in driving safety analysis,road safety design and control,design of paving mixtures,safety maintenance and management of pavements,and harmonization of skid resistance measurements and predictions.

Investigation of the Skid Resistance at Accident Occurred at Urban Intersections

Skid resistance of road surface plays an important role on urban traffic accidents. It is thought that reduction of surface microtexture leads to reduced skid resistance. Hence, it affects driving safety negatively and may cause traffic accidents, This paper is about the effect of skid resistance and intersection safety. Urban four leg signalized intersections were selected from Isparta city. The surface frictional properties were measured and it was tried to find critical skid resistance value with the help of British Pendulum Tester. Macro texture values of the intersections were determined with Sand Patch test and concluded that surface macro texture contributes to skid resistance. An analysis technique based on probabili theory has been used. This method is used for expounding the interaction between skid resistance-intersection and accident rates. After the study results are evaluated, it is understood that pavement roughness is very important for urban intersection safety measures.

Effects of Aerobic Exercise Combined with Resistance Training on Patients with Myocardial Ischemia Caused by Coronary Heart Disease

Objective:To explore the clinical effect of long-term aerobic exercise combined with resistance training in patients with myocardial ischemia caused by coronary heart disease and its influence on cardiac function, exercise endurance and quality of life. Methods:100 patients with myocardial ischemia caused by coronary heart disease from January 2017 to January 2019 were randomly divided into control group (n = 50 cases) and observation group (n = 50 cases). The control group was given resistance training, while the observation group was combined with long-term aerobic exercise on the basis of the control group. The two groups were treated for 3 months. The cardiac function, exercise endurance and quality of life were compared between the two groups. Results:The levels of IVST (8.20+1.32) mm, LVDD (46.43+4.13) mm and LVSD (32.59+3.15) mm in the observation group were lower than those in the control group at 3 months after treatment. The level of LVEF (67.49+5.77)% in the observation group was higher than that in the control group at 3 months after treatment. The difference between the two groups was significant (P<0.05). The ET (55.42+2.9) in the observation group was higher than that in the control group (P<0.05). 2) The levels of ng/L and TXB2 (93.23 + 6.26) ng/L were significantly lower than those of the control group, and the difference between the two groups was statistically significant (P<0.05). The 6-minute walking distance (561.25 +43.64) m and the quality of life score (95.31 +6.39) in the observation group were higher than those in the control group 3 months after treatment, and the difference between the two groups was statistically significant (P<0.05). Conclusions:Long-term aerobic exercise combined with resistance training can improve cardiac function, exercise tolerance and quality of life in patients with myocardial ischemia caused by coronary heart disease, which is worthy of popularization and application.

The mechanisms,evaluation and estimation of anti-skid performance of snowy and icy pavement:A review

The anti-skid performance of snowy and icy pavements is a popular research topic among road workers.Snow and ice are pollutants on a road surface.They significantly reduce the skid resistance of pavements,and thus,cause traffic accidents.Pertinent research progress on the skid resistance of snowy and icy pavements was reviewed and summarized in this work.The formation and classification of snowy and icy pavements were described on the basis of the state of snow and ice.The friction mechanisms between tires and snowy and icy pavements were revealed.Measurement methods and their applicability to the skid resistance of snowy and icy pavements were summarized.Factors that affect the skid resistance of pavements were discussed from the perspectives of pavement,environment,and vehicle.In addition,models of snowy and icy pavement resistance were classified into experience,mechanical,and numerical models.The advantages and disadvantages of these models were then compared and analyzed.Some suggestions regarding snowy and icy pavements were presented in accordance with the aforementioned information,including the development of efficient testing tools,the quantification of skid resistance under the coupling effects of multiple factors,the establishment of unified evaluation standards,and the development of more effective skid resistance models.

Use of Wehner-Schulze machine to evaluate pavement skid resistance:A review

Pavement skid resistance plays a crucial role in ensuring road safety and avoiding accidents.In the past,the laboratory evaluation of the skid resistance was carried out by studying only the coarse aggregates of the wearing course.To overcome this drawback,the Wehner-Schulze(WS)machine was developed in Germany in the 1960s.This equipment,composed of a polishing unit and a measuring unit,has great potential in predicting pavement skid resistance and its evolution over time,but is still little known in the pavement community(especially outside Europe).For these reasons,there is a need of a comprehensive review of the existing technical-scientific literature concerning the use of the WS machine.Specifically,this paper focuses on the main factors affecting the skid resistance in WS tests,the correlation of WS data with other laboratory test methods and with field skid resistance/polishing,and the available prediction models that have been validated through WS measurements.The critical analysis of the existing literature highlights that it is possible to correlate WS data with typical skid resistance field measurements as well as WS polishing with traffic polishing,but further efforts are needed in this regard.Future work should focus especially on open-graded mixtures and innovative asphalt mixtures(e.g.,containing recycled materials and additives).From the perspective of pavement management,based on a theoretical background,the WS test results could be used as starting point for simplified prediction models of the in-situ skid resistance.

锚杆倒肋式风机基础受力性能的数值模拟

为了解决风机基础施工成本高、施工难度大等问题,提出了一种新型锚杆倒肋式风机基础。利用有限元分析软件ABAQUS对该新型风机基础与传统梁板式风机基础在极端运行荷载工况下的混凝土应力、钢筋应力、基础位移以及基础倾斜率进行数值模拟分析,并进一步讨论二者的混凝土用量、钢筋用量、土方开挖量。结果表明,锚杆的添加以及倒肋的结构设计使锚杆倒肋式风机基础的受力性能、经济性等方面明显优于传统梁板式风机基础,具有较好的应用前景。

国产官能化溶聚丁苯橡胶BF2055M混炼胶性能研究

官能化溶聚丁苯橡胶(SSBR)在绿色高性能轮胎领域应用广泛,且牌号众多,选择三种在国内轮胎行业应用较多的进口官能化SSBR与国产官能化SSBR BF2055M进行综合性能比较。实验结果表明,SSBR BF2055M与进口SSBR相比,具有良好的白炭黑分散性、与白炭黑的亲和性、加工安全性,硫化速率快;硫化胶的定伸应力大、回弹性好、拉伸强度较高、压缩温升较低;具有更好的高抗湿滑性能和低滚动阻力性能的平衡性,能够给轮胎提供更好的驾驶安全性和节油性,适用于城市路面的四季胎。在胎面胶的配方开发上建议复配天然橡胶以提高硫化胶的耐磨性。

基于胎-面间接触力学特性的沥青路面抗滑模型研究

为了进一步表征沥青路面抗滑性能,通过对轮胎与路面间接触力学特性的分析,构建了沥青路面抗滑模型;以AC-13、GAC-13和UTAC-10的沥青混合料作为研究对象,采用激光纹理测量仪获取路面纹理三维信息,并开展压力胶片等相关试验获取模型中各参数值;通过模型结果与摆值的相关性分析验证模型的有效性,并探索模型中黏附摩擦作用和咬合作用对路面抗滑作用的贡献情况。结果显示:模型结果与摆值的相关性达0.9881,表明此模型能很好地表征沥青路面抗滑性能。各路面的黏附摩擦作用系数在0.3~0.4范围内均大于咬合作用系数(0.1~0.25范围内),表明道路运营初期时路面抗滑作用主要来源于黏附摩擦作用。此外,咬合作用系数高意味着在抗滑性能衰减中后期或者存在水等不利条件下路面具有更好的抗滑潜能。

热拌极薄抗滑磨耗层在高速公路抗滑性能提升中的应用

为研究热拌极薄抗滑磨耗层在高速公路养护中的应用,提升路面抗滑性能,论文结合实际工程,介绍了热拌极薄抗滑磨耗层工程特性,详细阐述了热拌极薄抗滑磨耗层原材料及配合比设计,重点对热拌极薄抗滑磨耗层施工技术要点进行研究。结果表明:公路养护中采取热拌极薄磨耗层技术进行处理,其路面抗滑性能得到有效提高,并节约养护成本。

基于复合分形的路面抗滑随机森林评估模型

路面抗滑性能直接影响着道路交通安全,而基于路表纹理特征的路面抗滑性能评估方法目前存在着可解释性差、准确度不高的问题.该研究使用精度为0.05 mm的便携式三维激光表面分析仪采集了185组路面纹理数据,通过动态摩擦因数测试仪获得了相应路段0~80 km/h速度范围内的路面摩擦数据,构建了综合表征路面纹理空间、横剖、深度方向复杂度的复合分形维数指标,建立了10 km/h和70 km/h速度下的路面抗滑性能随机森林评估模型.研究结果表明:复合分形维数具备独立描述纹理复杂程度的能力,但与路面动态摩擦因数之间不存在线性关系;复合分形维数对70 km/h速度下动态摩擦因数预估的准确度为0.78,可用于评价轮胎橡胶快速滑动状态下的路面抗滑性能;复合分形指标中的空间、横剖、表层、浅层、深层剖面分形特征共同影响着路面抗滑性能,在进行路面纹理形貌评价时,应从多种空间视角下进行纹理特征综合分析.

基于表面纹理特征的沥青混合料抗滑性能评价方法研究

针对AC、SMA、PAC三种沥青混合料,采用车辙板试件开展车轮磨耗试验,在不同磨耗阶段提取三种混合料的表面纹理,并测量磨耗区域的摩擦系数.通过数字图像方法对表面纹理进行提取和分析,建立等效点密度、等效面积密度和等效夹角等量化评价指标.结果表明:在车轮磨耗作用下,前1 000次磨耗对等效点密度、等效面积密度的影响最为显著,与摩擦系数的变化规律一致.

广东省沥青路面长期抗滑性能预测模型

根据广东省高速公路沥青路面的抗滑指标、集料特性和混合料级配,以及交通量大数据,分析了不同类型沥青路面抗滑指标横向力系数(sideway force coefficient,SFC)的影响因素,确定了影响SFC的关键因素.以集料特性、级配参数,以及交通参数等关键因素为输入变量建立了沥青路面抗滑指标SFC的预测模型1通过单因素方差分析检验了模型的显著性,并将预测值与实测值进行比较检验预测模型的可靠性.结果表明:沥青路面的抗滑指标SFC稳定值与累积货车轴次CNAT、集料PSV、混合料级配参数λ、κ等参数具有显著相关性.构建的沥青路面抗滑性能预测模型精度较高,能够满足工程应用的要求.

足尺试验环道路面摆值变化趋势预测

路面抗滑性能是路面使用性能的重要指标之一,是行车安全性的重要保障.依托RIOHTrack足尺试验环道的检测数据,选用足尺试验环道STR2、STR4、STR9和STR164种结构的357组路面抗滑性能检测数据,采用路面温度、累计标准轴载作用次数和路面磨耗次数3个主要影响因素作为自变量,路面摆值(BPN)指标作为因变量,选用300组检测数据作为训练样本,其余57组数据作为验证样本,构建了BPN的显示化和隐式化预测模型.基于温度对沥青路面抗滑性能具备一定影响范围的假定,构建了路面摆值的显示化预测模型,其模型的相关系数(R^(2))为0.625,模型预测平均相对误差为10.227%.同时,采用不同的隐含层神经元和训练函数,构建了BP神经网络预测模型(隐式化预测模型),模型的BPN预测值和真实值基本吻合,变化趋势一致,平均相对误差为4.484%.研究提高了路面抗滑性能指标预测的有效性和准确性,不同预测模型具备不同的应用前景,为路面抗滑性能的预测分析提供了参考和依据.

基于MTLBO和ELM的沥青路面抗滑性能预测

针对沥青路面抗滑性能预测在精度和可靠性方面的不足,本文提出了基于改进教学优化算法(Modified Teaching-Learning-Based Optimization,MTLBO)和极限学习机(Extreme Learning Machine,ELM)的沥青路面抗滑性能预测模型.首先,利用MMLS3载荷模拟器对6块路面试样进行模拟加载,达到每个加载周期后,利用高精度激光扫描仪和摆式仪分别对路面试样的宏观纹理和抗滑性能表征指标摆值(British Pendulum Number,BPN)进行采集,提取与抗滑性能相关的纹理指标.其次,鉴于ELM训练过程时间短且具有良好的模型泛化能力,本文利用ELM预测沥青路面BPN的变化趋势.为了提高ELM的全局搜索能力和预测结果的准确性,引入MTLBO对ELM输入层和隐藏层之间的权重(ω_(i))和偏置(b_(i))进行优化,从而更好地反映路面BPN与纹理指标之间的非线性映射关系.最后,以均方根误差(Root Mean Square Error,RMSE)和预测样本复相关系数(R^(2))作为评价指标,与现有的支持向量机(Support Vector Machines,SVM)、ELM、基于教学优化的极限学习机(TLBO-ELM)3种方法进行比较,本文所提出的基于改进教学优化的极限学习机(MTLBO-ELM)预测结果的均方根误差分别降低了1.80%,1.50%,1.07%.