Investigation of Durability and Performance of High Friction Surface Treatment

The Indiana Department of Transportation (INDOT) completed a total of 25 high friction surface treatment (HFST) projects across the state in 2018. This research study attempted to investigate the durability and performance of HFST in terms of its HFST-pavement system integrity and surface friction performance. Laboratory tests were conducted to determine the physical and mechanical properties of epoxy-bauxite mortar. Field inspections were carried out to identify site conditions and common early HFST distresses. Cyclic loading test and finite element method (FEM) analysis were performed to evaluate the bonding strength between HFST and existing pavement, in particular chip seal with different pretreatments such as vacuum sweeping, shotblasting, and scarification milling. Both surface friction and texture tests were undertaken periodically (generally once every 6 months) to evaluate the surface friction performance of HFST. Crash records over a 5-year period, i.e., 3 years before installation and 2 years after installation, were examined to determine the safety performance of HFST, crash modification factor (CMF) in particular. It was found that HFST epoxy-bauxite mortar has a coefficient of thermal expansion (CTE) significantly higher than those of hot mix asphalt (HMA) mixtures and Portland cement concrete (PCC), and good cracking resistance. The most common early HFST distresses in Indiana are reflective cracking, surface wrinkling, aggregate loss, and delamination. Vacuum sweeping is the optimal method for pretreating existing pavements, chip seal in particular. Chip seal in good condition is structurally capable of providing a sound base for HFST. On two-lane highway curves, HFST is capable of reducing the total vehicle crash by 30%, injury crash by 50%, and wet weather crash by 44%, and providing a CMF of 0.584 in Indiana. Great variability may arise in the results of friction tests on horizontal curves by the use of locked wheel skid tester (LWST) due both to the nature of vehicle dynamics and to the operation of test vehicle. Texture testing, however, is capable of providing continuous texture measurements that can be used to calculate a texture height parameter, i.e., mean profile depth (MPD), not only for evaluating friction performance but also implementing quality control (QC) and quality assurance (QA) plans for HFST

Image-Based Road Pavement Macrotexture Determination

Pavement macrotexture contributes greatly to road surface friction, which in turn plays a significant role in reducing road incidents. Conventional methods for macrotexture measurement techniques (e.g., the sand patch method, the outflow method, and laser measuring) are either expensive, time-consuming, or of poor repeatability. This thesis aims to develop and evaluate affordable and convenient alternative approaches to determine pavement macrotexture. The proposed solution is based on multi-view smartphone images collected in situ over the pavement. Computer vision techniques are then applied to create high resolution three-dimensional (3D) models of the pavement. The thesis develops the analytics to determine two primary macrotexture metrics: mean profile depth and aggregation loss. Experiments with 790 images over 25 spots of three State Roads and 6 spots of the INDOT test site demonstrated that the image-based method can yield reliable results comparable to conventional laser texture scanner results. Moreover, based on experiments with 280 images over 7 sample plates with different aggregate loss percentage, the newly developed analytics were proven to enable estimation of the aggregation loss, which is largely compromised in the laser scanning technique and conventional MPD calculation approach. The root mean square height based on the captured images was verified in this thesis as a more comprehensive metric for macrotexture evaluation. It is expected that the developed approach and analytics can be adopted for practical use at a large scale

Practice and Experience of French Foreign Language Education Reform——Taking the Report Suggestions for Improving Foreign Language Proficiency: Dare to Express the New World as an Example 法国中小学外语教育改革实践与经验——以《提高外语水平的建议：敢于表达新世界》报告为例

2018年9月,法国发布外语教育政策及教学实践改革建议报告《提高外语水平的建议:敢于表达新世界》。报告一方面总结法国外语教育环境、改革历史及特点,另一方面根据调研结果及国内外学生外语能力测试结果,提出教育政策改革建议,涉及英语地位、课程类型、教师培训、教育技术等。文章对该报告反映的法国外语教育改革思路和方法进行研究,以期对中国外语教育政策制定提供参考

Practice and Experience of French Foreign Language Education Reform——Taking the Report Suggestions for Improving Foreign Language Proficiency: Dare to Express the New World as an Example 法国中小学外语教育改革实践与经验——以《提高外语水平的建议：敢于表达新世界》报告为例

International audience2018年9月,法国发布外语教育政策及教学实践改革建议报告《提高外语水平的建议:敢于表达新世界》。报告一方面总结法国外语教育环境、改革历史及特点,另一方面根据调研结果及国内外学生外语能力测试结果,提出教育政策改革建议,涉及英语地位、课程类型、教师培训、教育技术等。文章对该报告反映的法国外语教育改革思路和方法进行研究,以期对中国外语教育政策制定提供参考

Simulation and quantitative analysis of fluorescence intensity distribution based on the Monte Carlo method

The Monte Carlo method is a versatile simulation algorithm to model the propagation of photons inside the biological tissues. It has been applied to the reconstruction of the fluorescence molecular tomography (FMT). However, such method suffers from low computational efficiency, and the time consumption is not desirable. One way to solve this problem is to introduce a priori knowledge which will facilitate iterative convergence. We presented an in vivo simulation environment for fluorescence molecular tomography (ISEFMT) using the Monte Carlo method to simulate the photon distribution of fluorescent objects and their sectional view in any direction quantitatively. A series of simulation experiments were carried out on different phantoms each with two fluorescent volumes to investigate the relationship among fluorescence intensity distribution and the excitation photon number, the locations and sizes of the fluorescence volumes, and the anisotropy coefficient. A significant principle was discovered, that along the direction of the excitation light, the fluorescent volume near the excitation point will provide shelter effect so that the energy of the fluorescent volume farther away from the excitation point is relatively lower. Through quantitative analysis, it was discovered that both the photon energy distribution on every cross section and the fluorescence intensity distributed in the two volumes exhibit exponential relationships. The two maximum positions in this distribution correspond to the centers of fluorescent volumes. Finally, we also explored the effect of the phantom coefficients on the exponential rule, and found out that the exponential rule still exists, only the coefficient of the exponential rule changed. Such results can be utilized in locating the positions of multiple fluorescent volumes in complicated FMT reconstruction involving multiple fluorescent volumes. Thus, a priori knowledge can be generalized, which would accelerate the reconstruction of FMT and even other images

Maneuverability and Hydrodynamics of a Tethered Underwater Robot Based on Mixing Grid Technique

The maneuverability and hydrodynamic performance of the tethered underwater robot in a uniform flow field is investigated. In this research, a tethered underwater robot symmetrically installed with NACA66 hydrofoils and Ka 4-70/19A ducted propellers around its main body is first constructed. The method of overlapping grid combined with sliding mesh is applied in the numerical simulations, and the principle of relative motion is adopted to describe the hydrodynamic responses of the tethered underwater robot during the robot manipulation. The reliability of the CFD methods applied in this research is verified by experimental results, and the comparison between numerical and experimental ones shows that there is very little difference being found. The numerical results indicate that computational cost due to the research’s large-scale domain can be effectively reduced by the adopted numerical methods, hydrofoils’ control effect is greatly influenced by the towing speeds, and thrusts issued from the ducted propellers are related to the tethered underwater robot’s position and towing speed