Three types of chemically and functionally different thermoplastic polymers have been chosen for evaluation with the fly ash derived filler: high density polyethylene (HDPE), thermoplastic elastomer (TPE) and polyethylene terephthalate (PET). The selections were based on volumes consumed in commercial and recycled products. The reference filler selected for comparison was 3 {micro}m calcium carbonate, a material which is commonly used with all three types of polymers. A procedure to prepare filled polymers has been developed and the polymer/filler blends have been prepared. Selected samples of filled polymers were subjected to SEM analysis to verify that the fly ash derived filler and the calcium carbonate were well dispersed. Material taken from a utility ash pond was classified using a novel combination of hydraulic and lamellar classifiers to produce an ultra-fine ash product. This product was dried and used in a series of tests to determine its potential as a filler in plastics. The general properties of the ultra-fine ash from several runs are as follows: D{sub 50}: 3-5 {micro}m; Specific gravity: {approx}2.41; Loss on ignition: 2-3%; Carbon content: 1-2%; Color: dark grey on content: 1-2%; and Morphology: spherical. The addition of fillers increased the modulus of the HDPE composite, but decreased …

Equipment wear is a major concern in the mineral processing industry, which dramatically increases the maintenance cost and adversely affects plant operation efficiency. In this research, novel surface treatment technologies, High Density Infrared (HDI) and Laser Surface Engineering (LSE) surface coating processes were developed for the surface enhancement of selected mineral processing equipment. Microstructural and mechanical properties of the coated specimens were characterized. Laboratory-simulated wear tests were conducted to evaluate the tribological performance of the coated components. Test results indicate that the wear resistance of ASTM A36 (raw coal screen section) and can be significantly increased by applying HDI and LSE coating processes. Field testing has been performed using a LSE-treated screen panel and it showed a 2 times improvement of the service life.

The objectives of our research were to develop the first automated radiochemical process analyzer including sample pretreatment methodoology, and to initiate work on new detection approaches, especially using modified diode detectors.

A generalization of Richardson-Gaudin models to the rank-2 SO(5) and SO(3,2) algebras is used to describe systems of two kinds of fermions or bosons interacting through a pairing force. They are applied to the proton-neutron neutron isovector pairing model and to the Interacting Boson Model 2, in the transition from vibration to gamma-soft nuclei, respectively. In both cases, the integrals of motion and their eigenvalues are obtained.

The CFEST (Coupled Flow, Energy, and Solute Transport) simulator described in this User’s Guide is a three-dimensional finite-element model used to evaluate groundwater flow and solute mass transport. Confined and unconfined aquifer systems, as well as constant and variable density fluid flows can be represented with CFEST. For unconfined aquifers, the model uses a moving boundary for the water table, deforming the numerical mesh so that the uppermost nodes are always at the water table. For solute transport, changes in concentra¬tion of a single dissolved chemical constituent are computed for advective and hydrodynamic transport, linear sorption represented by a retardation factor, and radioactive decay. Although several thermal parameters described in this User’s Guide are required inputs, thermal transport has not yet been fully implemented in the simulator. Once fully implemented, transport of thermal energy in the groundwater and solid matrix of the aquifer can also be used to model aquifer thermal regimes. The CFEST simulator is written in the FORTRAN 77 language, following American National Standards Institute (ANSI) standards. Execution of the CFEST simulator is controlled through three required text input files. These input file use a structured format of associated groups of input data. Example input data lines are …

The Savannah River National Laboratory (SRNL) uses the Lagrangian Particle Dispersion Model (LPDM) in conjunction with the Regional Atmospheric Modeling System as an operational tool for emergency response consequence assessments for the Savannah River Site (SRS). The LPDM is an advanced stochastic atmospheric transport model used to transport and disperse passive tracers subject to the meteorological field generated by RAMS from sources of varying number and shape. The Atmospheric Technologies Group (ATG) of the SRNL is undertaking the task of reviewing documentation and code for LPDM Quality Assurance (QA). The LPDM QA task will include a model technical description, computer coding descriptions, model applications, and configuration control. This report provides a comprehensive technical description of the LPDM model.

Steady-state analyses of generic PBPK models for volatile organic chemical (VOC) exposure and risk assessment have been undertaken and applied for nearly two decades now. Chiu and White's paper on this subject adds little new to this earlier work. Their dismissive claim that ''Similar analyses have been done for specific chemicals and for inhalation'' is misleading, because some of this earlier work did indeed focus on ''generic'' PBPK models generally applicable to VOC exposure by multiple routes. In particular, the earliest of these previous studies developed steady-state solutions for generic PBPK models including respiratory and 1-compartment oral routes of exposure, and further specified how to add injection and dermal exposure routes. Chiu and White included a 2-compartment oral pathway and a lung compartment in an otherwise identical generic PBPK model, but did not consider other exposure pathways such as dermal uptake. Each of the earlier studies first presented a steady-state solution to a generic, multiroute PBPK model, and only then applied the generic solution to a problem or illustration involving a specific compound--i.e., the same approach used later by Chiu and White. For example, the earlier study included a simple, intuitive expression for low-dose metabolized fraction f*{sub m} of any …

Gallium nitride (GaN) is the III-V semiconductor used to produce blue light-emitting diodes (LEDs) and blue and ultraviolet solid-state lasers. To be useful in electronic devices, GaN must be doped with elements that function either as electron donors or as acceptors to turn it into either an n-type semiconductor or a p-type semiconductor. It has been found that GaN can easily be grown with n-conductivity, even up to large concentrations of donors--in the few 10{sup 19}cm{sup -3} range. However, p-doping, the doping of the structure with atoms that provide electron sinks or holes, is not well understood and remains extremely difficult. The only efficient p-type dopant is Mg, but it is found that the free hole concentration is limited to 2 x 10{sup 18}cm{sup -3}, even when Mg concentrations are pushed into the low 10{sup 19}cm{sup -3} range. This saturation effect could place a limit on further development of GaN based devices. Further increase of the Mg concentration, up to 1 x 10{sup 20}cm{sup -3} leads to a decrease of the free hole concentration and an increase in defects. While low- to medium-brightness GaN light-emitting diodes (LEDs) are remarkably tolerant of crystal defects, blue and UV GaN lasers are much …