Case Studies on the Implementation of Balanced Mix Design and Performance Tests for Asphalt Mixtures: California Department of Transportation (Caltrans)

The primary objective of this overall effort was to identify and put forth positive practices used by SHAs when implementing BMD and performance testing of asphalt mixtures. To accomplish this objective, information was collected through site visits and other means with seven key agencies. California Department of Transportation (Caltrans) graciously agreed to host a virtual site visit

Case Studies on the Implementation of Balanced Mix Design and Performance Tests for Asphalt Mixtures: Texas Department of Transportation (TxDOT)

The primary objective of this overall effort was to identify and put forth positive practices used by SHAs when implementing BMD and performance testing of asphalt mixtures. To accomplish this objective, information was collected through site visits and other means with seven key agencies. Texas Department of Transportation (TxDOT) graciously agreed to host a virtual site visit

Two interacting diffusing particles on low-dimensional discrete structures

In this paper we study the motion of two particles diffusing on low-dimensional discrete structures in presence of a hard-core repulsive interaction. We show that the problem can be mapped in two decoupled problems of single particles diffusing on different graphs by a transformation we call 'diffusion graph transform'. This technique is applied to study two specific cases: the narrow comb and the ladder lattice. We focus on the determination of the long time probabilities for the contact between particles and their reciprocal crossing. We also obtain the mean square dispersion of the particles in the case of the narrow comb lattice. The case of a sticking potential and of 'vicious' particles are discussed.Comment: 9 pages, 6 postscript figures, to appear in 'Journal of Physics A',-January 200

Case Studies on the Implementation of Balanced Mix Design and Performance Tests for Asphalt Mixtures: Virginia Department of Transportation (VDOT)

The primary objective of this overall effort was to identify and put forth positive practices used by SHAs when implementing BMD and performance testing of asphalt mixtures. To accomplish this objective, information was collected through site visits and other means with seven key agencies. Virginia Department of Transportation (VDOT) graciously agreed to host a virtual site visit

Case Studies on the Implementation of Balanced Mix Design and Performance Tests for Asphalt Mixtures: Illinois Department of Transportation (IDOT)

The primary objective of this overall effort was to identify and put forth positive practices used by SHAs when implementing BMD and performance testing of asphalt mixtures. To accomplish this objective, information was collected through site visits and other means with seven key agencies. Illinois Department of Transportation (IDOT) graciously agreed to host a virtual site visit

Positive Practices, Lessons Learned, and Challenges When Implementing Balanced Design of Asphalt Mixtures: Site Visits

Virtual site visits and interviews of seven key State Departments of Transportation (DOTs), along with material producers, consultants and paving contractors that serviced the agencies were conducted to learn more regarding the details of Balanced Mix Design (BMD) and performance tests implementation efforts. Successful practices documented from these virtual site visits were collected and synthesized into an overall process of implementing BMD as part of mix design approval and quality assurance (QA). This process comprises eight major tasks that are meant to present and summarize the activities that a State DOT may need to undertake to implement a BMD program depending on its organizational structure, staffing level, workspace, annual asphalt tonnage, as well as industry experiences and practices. Examples of positive practices, lessons learned, and challenges from States for the various tasks are presented. A list of research and deployment topics identified during the virtual site visits are also summarized

Case Studies on the Implementation of Balanced Mix Design and Performance Tests for Asphalt Mixtures: Maine Department of Transportation (MaineDOT)

The primary objective of this overall effort was to identify and put forth positive practices used by SHAs when implementing BMD and performance testing of asphalt mixtures. To accomplish this objective, information was collected through site visits and other means with seven key agencies. Maine Department of Transportation (MaineDOT) graciously agreed to host a virtual site visit

Ions Adsorbed at Amorphous Solid/Solution Interfaces Form Wigner Crystal-like Structures.

When a surface is immersed in a solution, it usually acquires a charge, which attracts counterions and repels co-ions to form an electrical double layer. The ions directly adsorbed to the surface are referred to as the Stern layer. The structure of the Stern layer normal to the interface was described decades ago, but the lateral organization within the Stern layer has received scant attention. This is because instrumental limitations have prevented visualization of the ion arrangements except for atypical, model, crystalline surfaces. Here, we use high-resolution amplitude modulated atomic force microscopy (AFM) to visualize the lateral structure of Stern layer ions adsorbed to polycrystalline gold, and amorphous silica and gallium nitride (GaN). For all three substrates, when the density of ions in the layer exceeds a system-dependent threshold, correlation effects induce the formation of close packed structures akin to Wigner crystals. Depending on the surface and the ions, the Wigner crystal-like structure can be hexagonally close packed, cubic, or worm-like. The influence of the electrolyte concentration, species, and valence, as well as the surface type and charge, on the Stern layer structures is described. When the system parameters are changed to reduce the Stern layer ion surface excess below the threshold value, Wigner crystal-like structures do not form and the Stern layer is unstructured. For gold surfaces, molecular dynamics (MD) simulations reveal that when sufficient potential is applied to the surface, ion clusters form with dimensions similar to the Wigner crystal-like structures in the AFM images. The lateral Stern layer structures presented, and in particular the Wigner crystal-like structures, will influence diverse applications in chemistry, energy storage, environmental science, nanotechnology, biology, and medicine

Radial Migration in Disk Galaxies I: Transient Spiral Structure and Dynamics

We seek to understand the origin of radial migration in spiral galaxies by analyzing in detail the structure and evolution of an idealized, isolated galactic disk. To understand the redistribution of stars, we characterize the time-evolution of properties of spirals that spontaneously form in the disk. Our models unambiguously show that in such disks, single spirals are unlikely, but that a number of transient patterns may coexist in the disk. However, we also show that while spirals are transient in amplitude, at any given time the disk favors patterns of certain pattern speeds. Using several runs with different numerical parameters we show that the properties of spirals that occur spontaneously in the disk do not sensitively depend on resolution. The existence of multiple transient patterns has large implications for the orbits of stars in the disk, and we therefore examine the resonant scattering mechanisms that profoundly alter angular momenta of individual stars. We confirm that the corotation scattering mechanism described by Sellwood & Binney (2002) is responsible for the largest angular momentum changes in our simulations.Comment: accepted to MNRAS; substantial additions to Section 4 dealing with the radial mixing proces