The American Society for Testing and Materials (ASTM) is an independent organization devoted to the development of standards.

American Society for Testing and Materials

The Environmental Protection Agency (EPA) provides access to information on a variety of topics related to the environment and strives to inform citizens of health risks. The EPA also has an extensive library network that consists of 26 libraries throughout the United States, which provide access to a plethora of information to EPA employees, scientists, and researchers. The EPA implemented a reorganization project to digitize their materials so they would be more accessible to a wider range of users, but this plan was drastically accelerated when the EPA was threatened with a budget cut. It chose to close and reduce the hours and services of some of their libraries. As a result, the agency was accused of denying users the “right to know” by making information unavailable, not providing an adequate strategic plan, and discarding vital materials. This case study explores the background of the digitization project, the practices implemented, and the critiques of the project.

/pdf/the-environmental-protection-agency-3gx4opzrjm.pdf

The Environmental Protection Agency

Artificial neural networks (ANNs) constitute a class of flexible nonlinear models designed to mimic biological neural systems. In this entry, we introduce ANN using familiar econometric terminology and provide an overview of ANN modeling approach and its implementation methods. † Correspondence: Chung-Ming Kuan, Institute of Economics, Academia Sinica, 128 Academia Road, Sec. 2, Taipei 115, Taiwan; ckuan@econ.sinica.edu.tw. †† I would like to express my sincere gratitude to the editor, Professor Steven Durlauf, for his patience and constructive comments on early drafts of this entry. I also thank Shih-Hsun Hsu and Yu-Lieh Huang for very helpful suggestions. The remaining errors are all mine.

Artificial neural networks

Highway Capacity Manual改訂の動向--テイラ-教授の講演より

Dynamics of structures

Emerging trends for high-speed rail track superstructures—ballastless track as an alternative to the ballasted track

In this paper, a simple method is introduced for the computational modelling of multiphase materials, and for the approximation of their mechanical response. The two-dimensional microstructures of ...

/pdf/mechanical-modelling-of-asphalt-concrete-using-grid-division-29mhmwgnte.pdf

Mechanical Modelling of Asphalt Concrete Using Grid Division

This study evaluated the performance effectivenss of sand mix interlayer in controlling reflective cracking in asphalt concrete (AC) overlaid existing jointed concrete pavement (JCP) using a three-dimentional finite element (FE) model. A cohesive zone model was incorporated into the FE model to characterize the fracture behavior of the AC overlay under transient vehicular loading. A limit state load approach was used to determine the resistance of the AC overlay to reflective cracking in terms of normalized axle load of an overload equivalent to an 80-kN single-axle load. The study concluded that the sand mix interlayer enhanced the fracture resistance of the AC overlay due to its relatively high fracture energy. A macro-crack level of reflective cracking was initiated in the wearing course in the AC overlay earlier than in the leveling binder, so-called crack jumping. The softer the sand mix, the tougher it may be, but it may cause shear rutting in the AC overlay. As the bearing capacity of the JCP becomes lower, more fractured area was developed in the AC overlay and the performance effectiveness of the sand mix interlayer was better.

Sand Mix Interlayer Retarding Reflective Cracking in Asphalt Concrete Overlay

Resilient characteristics of bottom ash

Researchers conducted eight large-scale laboratory tests to assess the combined impact of hot-mix asphalt (HMA) overlay mix and thickness on its performance to control reflective cracking. Bonding efficiency, flexibility, and stiffness of the HMA mix as well as overlay thickness significantly affect an overlay’s performance against reflective cracking. Researchers developed a generalized 3D finite-element model to predict an overlay’s reflective cracking potential and generated a database of 128 cases. They also developed a data-driven surrogate model to predict reflective cracking potential that engineers can easily use. Life-cycle cost analysis of overlay alternatives was performed using Illinois Department of Transportation’s unit prices from contracts between 2018 and 2019. The researchers identified optimal overlay configurations to control reflective cracking. An overlay composed of a 1.5 in (38.1 mm) SMA-9.5 or 1.25 in (31.8 mm) IL-9.5FG surface course and a 0.75 in (19.1 mm) IL-4.75 binder course had the lowest annual cost per mile among non-interstate projects. For interstate projects, an overlay composed of a 2 in (50.8 mm) SMA-12.5 surface course and a 2.25 in (57.2 mm) IL-19.0 binder course was the most cost-effective. The study concluded that to control reflective cracking and to reduce life-cycle cost, an overlay composed of an SMA-9.5 surface course and an IL-4.75 binder course is recommended for non-interstate projects. An IL-9.5FG surface course and an IL-4.75 binder course are suggested for low-volume and low-speed roads. For interstate projects, an overlay comprised of an SMA-12.5 surface course and an IL-19.0 binder course is recommended. A data-driven surrogate model may be used to design overlay thicknesses.

/pdf/optimized-hot-mix-asphalt-lift-configuration-for-performance-2uitihtm.pdf

Imad L. Al-Qadi

Papers

Emerging trends for high-speed rail track superstructures—ballastless track as an alternative to the ballasted track

Mechanical Modelling of Asphalt Concrete Using Grid Division

Sand Mix Interlayer Retarding Reflective Cracking in Asphalt Concrete Overlay

Resilient characteristics of bottom ash

Optimized Hot-Mix Asphalt Lift Configuration for Performance