Evaluation of Cracking Indices for Asphalt Mixtures Using SCB Tests at Different Temperatures and Loading Rates

In recent years, there has been a shift towards implementing performance based pavement specifications (PBPS) to increase reliability of asphalt concrete mixture specifications and enhance service lives of roadways. Several of the performance indices used in PBPS are based on the asphalt mixture fracture tests. There is an increasing need for a better understanding the effects of temperature and loading rate interdependency for fracture properties of asphalt mixtures. The goal of this study is to build upon previous work conducted during a Summer Undergraduate Research Program (SURF) project entitled, “Exploration of Temperature and Loading Rate Interdependency for Fracture Properties of Asphalt Mixtures,” as well as to incorporate ongoing research studies at the University of New Hampshire (UNH). There are many proposed fracture indices including Fracture Energy (Gf), Illinois Flexibility Index (FI), Toughness Index (TI), Nflex, and Fracture Strain Tolerance (FST). The objective of this study is to evaluate different fracture indices and their variations with changes in test temperature and loading rates. Results from Semi-Circular Bend (SCB) fracture tests on five asphalt mixtures (from Vermont and Virginia) are being evaluated. All mixtures represent same aggregate maximum sizes and consist of varying amounts of Reclaimed Asphalt Pavement (RAP). Conclusions will be drawn on the effectiveness of each fracture index to distinguish and appropriately rank mixtures as well as on the variations of these indices with changes in test temperature and loading rates. On basis of this study, use of crack mouth opening displacements for fracture index calculations is recommended obtain better distinction of cracking performances between mixtures

Active heat exchange system development for latent heat thermal energy storage

Various active heat exchange concepts were identified from among three generic categories: scrapers, agitators/vibrators and slurries. The more practical ones were given a more detailed technical evaluation and an economic comparison with a passive tube-shell design for a reference application. Two concepts selected for hardware development are a direct contact heat exchanger in which molten salt droplets are injected into a cooler counterflowing stream of liquid metal carrier fluid, and a rotating drum scraper in which molten salt is sprayed onto the circumference of a rotating drum, which contains the fluid heat sink in an internal annulus near the surface. A fixed scraper blade removes the solidified salt from the surface which has been nickel plated to decrease adhesion forces. Suitable phase change material (PCM) storage media with melting points in the temperature range of interest (250 C to 400 C) were investigated. The specific salt recommended for laboratory tests was a chloride eutectic (20.5KCl-24/5 NaCl-55.0MgCl 2% by wt.), with a nominal melting point of 385 C

Planar growth generates scale free networks

In this paper we introduce a model of spatial network growth in which nodes are placed at randomly selected locations on a unit square in $\mathbb{R}^2$, forming new connections to old nodes subject to the constraint that edges do not cross. The resulting network has a power law degree distribution, high clustering and the small world property. We argue that these characteristics are a consequence of the two defining features of the network formation procedure; growth and planarity conservation. We demonstrate that the model can be understood as a variant of random Apollonian growth and further propose a one parameter family of models with the Random Apollonian Network and the Deterministic Apollonian Network as extreme cases and our model as a midpoint between them. We then relax the planarity constraint by allowing edge crossings with some probability and find a smooth crossover from power law to exponential degree distributions when this probability is increased.Comment: 27 pages, 9 figure

Thermal Control Working Group report

The Thermal Control Working Group limited its evaluation to issues associated with Earth orbiting and planetary spacecraft with power levels up to 50 kW. It was concluded that the space station technology is a necessary precursor but does not meet S/C 2000 needs (life, high heat flux, long term cryogenics, and survivability). Additional basic and applied research are required (fluid/materials compatibility and two phase system modeling). Scaling, the key issue, must define accelerated life test criteria. The two phase systems require 0g to 1 g correlation. Additional ground test beds are required and combined space environment tests of materials

Table builder problem - confidentiality for linked tables

The aim of this project is to investigate solutions to the problem of improving access to detailed survey data, while ensuring no person or organisation is likely to be identified, or otherwise put at risk of having their data disclosed, and to link general findings back to the ABS Table Builder problem. We focussed on making contributions in two main areas, namely: 1. Identification of sensitive cells in a table, 2. Maximizing data utility and minimising information loss - ensuring the table provides useful information

Beyond Acute Lyme

Vermont has one of the highest rates of Lyme disease infection in the country. There is growing disagreement not only between the medical community and a growing patient population, but also within the medical community itself, around the issue of persistent syndromes that may or may not be related to a Lyme diagnosis. Many patients seek treatment for persistent symptoms outside of physician guidelines for either Post Treatment Lyme Disease or the contentious Chronic Lyme Disease via prolonged courses of IV antibiotics, colloidal silver infusions, electromagnetic frequency treatments, and more. Regardless of the debatable extent of spirochete carnage in vivo, there is a need for effective and compassionate communication between providers and concerned patients. The aim of this project is to nudge this inevitably ongoing conversation in a productive direction, and to create a broader shared awareness between populations at growing odds.https://scholarworks.uvm.edu/fmclerk/1572/thumbnail.jp

Thermal energy storage heat exchanger: Molten salt heat exchanger design for utility power plants

The use of thermal energy storage (TES) in the latent heat of molten salts as a means of conserving fossil fuels and lowering the cost of electric power was evaluated. Public utility systems provided electric power on demand. This demand is generally maximum during late weekday afternoons, with considerably lower overnight and weekend loads. Typically, the average demand is only 60% to 80% of peak load. As peak load increases, the present practice is to purchase power from other grid facilities or to bring older less efficient fossil-fuel plants on line which increase the cost of electric power. The widespread use of oil-fired boilers, gas turbine and diesel equipment to meet peaking loads depletes our oil-based energy resources. Heat exchangers utilizing molten salts can be used to level the energy consumption curve. The study begins with a demand analysis and the consideration of several existing modern fossil-fuel and nuclear power plants for use as models. Salts are evaluated for thermodynamic, economic, corrosive, and safety characteristics. Heat exchanger concepts are explored and heat exchanger designs are conceived. Finally, the economics of TES conversions in existing plants and new construction is analyzed. The study concluded that TES is feasible in electric power generation. Substantial data are presented for TES design, and reference material for further investigation of techniques is included