Specific applications of image processing to surface flaw detection

An approach to detect surface flaws automatically through digital image processing techniques is investigated in this work. In addition, a novel pre-processing transducer applicable to this area is presented.The digitized image of the surface of a part to be inspected is obtained by means of a vidicon camera. The image is then properly segmented to separate the information-bearing objects from the background by means of a thresholding scheme. An analysis of the resulting binary image is then made by following the borders present.Objects on interest in the image can be located by means of template matching. The use of a hardware Number Theoretic Transform (NTT) convulutional filter is shown to provide processing times commensurate with industrial requirements.Results arer shown for 3 practical cases in which the system was used to detect surface flaws.To assist in the measurement of surface flaws a transducer is introduced which converts true surface-depth information into a gray level image for processing by the system.     

考虑板角脱空的公路隧道水泥路面设计方法

建立了公路隧道水泥混凝土路面结构在板角脱空下的三维有限元分析模型,计算了各种因素水平下的板角顶面拉应力和板底拉应力,并利用多元非线性回归技术得出了高强度基岩下的应力计算公式.基于此,提出以板底拉应力和板角顶面拉应力为控制指标的隧道水泥混凝土路面的设计方法,并通过实例进行了计算,对公路隧道工程设计人员进行路面结构设计时具有实际的参考价值.     

Mixed logit model-based driver injury severity investigations in single- and multi-vehicle crashes on rural two-lane highways

Crashes occurring on rural two-lane highways are more likely to result in severe driver incapacitating injuries and fatalities. In this study, mixed logit models are developed to analyze driver injury severities in single-vehicle (SV) and multi-vehicle (MV) crashes on rural two-lane highways in New Mexico from 2010 to 2011. A series of significant contributing factors in terms of driver behavior, weather conditions, environmental characteristics, roadway geometric features and traffic compositions, are identified and their impacts on injury severities are quantified for these two types of crashes, respectively. Elasticity analyses and transferability tests were conducted to better understand the models’ specification and generality. The research findings indicate that there are significant differences in causal attributes determining driver injury severities between SV and MV crashes. For example, more severe driver injuries and fatalities can be observed in MV crashes when motorcycles or trucks are involved. Dark lighting conditions and dusty weather conditions are found to significantly increase MV crash injury severities. However, SV crashes demonstrate different characteristics influencing driver injury severities. For example, the probability of having severe injury outcomes is higher when vans are identified in SV crashes. Drivers’ overtaking actions will significantly increase SV crash injury severities. Although some common attributes, such as alcohol impaired driving, are significant in both SV and MV crash severity models, their effects on different injury outcomes vary substantially. This study provides a better understanding of similarities and differences in significant contributing factors and their impacts on driver injury severities between SV and MV crashes on rural two-lane highways. It is also helpful to develop cost-effective solutions or appropriate injury prevention strategies for rural SV and MV crashes.     

基于聚类与自适应神经模糊推理的车速预测

针对道路交通系统的非线性和随机性特点,设计一种具有学习能力的车速预测方法。首先,对交通流历史特征数据采用模糊聚类的方法进行状态分类并确立模型结构。然后,建立交通流状态预测的自适应神经模糊系统,以实测交通流数据进行系统参数优化训练。最后,利用MATLAB进行系统的仿真及检测。检测的预测结果表明系统具有良好的应用性能。     

A Bayesian mixture model for short-term average link travel time estimation using large-scale limited information trip-based data

Accurate estimation and prediction of urban link travel times are important for urban traffic operations and management. This paper develops a Bayesian mixture model to estimate short-term average urban link travel times using large-scale trip-based data with partial information. Unlike typical GPS trajectory data, trip-based data from taxies or other sources provide limited trip level information, which only contains the trip origin and destination locations, trip travel times and distances, etc. The focus of this study is to develop a robust probabilistic short-term average link travel time estimation model and demonstrate the feasibility of estimating network conditions using large-scale trip level information. In the model, the path taken by each trip is considered as latent and modeled using a multinomial logit distribution. The observed trip data given the possible path set and the mean and variance of the average link travel times can thus be characterized using a finite mixture distribution. A transition model is also introduced to serve as an informative prior that captures the temporal and spatial dependencies of link travel times. A solution approach based on the expectation–maximization (EM) algorithm is proposed to solve the problem. The model is tested on estimating the mean and variance of the average link travel times for 30 min time intervals using a large-scale taxi trip dataset from New York City. More robust estimation results are obtained owing to the adoption of the Bayesian framework.     

Load transfer mechanism in pile group due to single tunnel advancement in stiff clay

Construction of tunnels in urban cities may induce excessive settlement and tilting of nearby existing pile foundations. Various studies reported in the literature have investigated the tunnel–soil–pile interaction by means of field monitoring, centrifuge and numerical modelling. However, the load transfer mechanism between piles in a group, the induced settlement and the tilting of a pile group due to tunnel advancement has not been investigated systematically and is not well understood. This study conducts three-dimensional, coupled-consolidation finite element analyses to investigate tunnelling effects on an existing 2 × 2 pile group. The construction of a 6 m diameter (D) tunnel in saturated stiff clay is simulated. Responses of the pile group located at a clear distance of 2.1 m (0.35D) from a tunnel constructed at three different cover-to-diameter-of-tunnel ratios (C/D) of 1.5, 2.5 and 3.5 are investigated. The computed results are compared to published data based on field monitoring. It is found that the most critical stage for settlement, tilting and induced bending moment of pile group due to tunnelling is when the tunnel face is close to the pile group rather than at the end of tunnel excavation. The depth of the tunnel relative to the pile group has a vital influence on the settlement, tilting of pile group and the load transfer mechanism between piles in pile group induced by tunnel excavation. Tunnelling near the mid-depth of the pile group (i.e. C/D = 1.5) induces the largest bending moment in the piles, but the settlement and tilting of the pile group are relatively small. Based on a settlement criterion, apparent loss of capacity of the pile group is 14% and 23% for tunnels constructed at depths of C/D = 1.5 and at both C/D = 2.5 and 3.5, respectively. The largest load redistribution between the front and rear piles in the group and the largest tilting of the pile cap towards the tunnel occurs when tunnel excavated at C/D = 2.5.     

Reliability-based robust geotechnical design using Monte Carlo simulation

Bulletin of Engineering Geology and the Environment - The reliability-based robust geotechnical design (RGD) approach provides an effective tool to deal with the uncertainty in the estimated...     

Investigation the influences of geotextile on reducing the thermal reflective cracking using XFEM

Abstract

A 3D extended finite element model (XFEM) was constructed to investigate the thermal reflective cracking propagation and anti-cracking characteristic of geotextile. Influence factors of tensile modulus and placement location of geotextile were analysed. A temperature cycling test in the material test system was utilised in this work to validate the XFEM. Thermal simulations were performed considering the influences of solar radiation, air convection and air radiation. It has been found that crack initiated and propagated as temperature declining in earlier cycle, and crack length being fixed because of no more severe temperature variation based on maximum principal stress criterion. Geotextile with high tensile modulus had a significant influence on reducing the crack propagation compared with low tensile modulus geotextile or unreinforced situation. Geotextile placing at the bottom of asphalt surface had the best crack resistance influence, and geotextile placed at one-fourth depth from asphalt course bottom was more efficient than placed at other locations in terms of anti-crack propagation.     

Safety evaluation of signalized intersections with left-turn waiting area in China

In recent years the metropolitans in China have seen the surging installations of the left-turn waiting area (LWA) at the signalized intersections. The design allows the left-turning vehicles to enter the intersection at the onset of the through green phase (of the same approach) and wait for the exclusive left-turn signal at the LWA. The LWA layout can effectively reduce the probability of stranded and queue overflow of the left-turn vehicles, but no study is conducted yet to assess the safety performance of the signalized intersections with LWA. The paper adopts the traffic conflict technique (represented by post-encroachment time), compares the discrepancy of conflict types between intersections with LWA and without, and develops the severity models to identify the contributing factors for the left-turn conflicts. Results demonstrate that the left-turn volume, driving outside the LWA, running red light, the presence of secondary conflicts, and the rear-end conflicts significantly increase the severities of traffic conflicts at the LWA. The findings serve to provide recommendations to revise the current design standard of the LWA (GB5768-2009) and consequently improve the safety operations of signalized intersections with LWA in China.     

Recycling of municipal solid waste incinerator ash in hot-mix asphalt concrete

This research investigated the use of incinerator ash as a partial replacement of fine aggregate in hot-mix asphalt concrete. Municipal solid waste (MSW) Incinerator ash was obtained from an incinerator facility at Sultan Qaboos University. Physical tests were performed on the incinerator ash to determine its gradation and specific gravity, as well as chemical composition of the leachate from the ash. MSW ash was used in the mixture of hot-mix asphalt with a percentage of up to 40% by total aggregate weight. Optimum mixtures were evaluated for moisture susceptibility and raveling potential. The results indicate the potential use of the MSW ash in asphalt concrete mixtures for surface and base course mixtures with percentages of 15 and 20 ash substitution, respectively.