A novel approach to simulating the dominant dynamic processes present during concentrated energy beam welding of metals is presented. A model for transient behavior of the front keyhole wall is developed. It is assumed that keyhole propagation is dominated by evaporation recoil-driven melt expulsion from the beam interaction zone. Results from the model show keyhole instabilities consistent with experimental observations of metal welding, metal cutting and ice welding.

Accurate estimation of the depth of partial-thickness burns and the early prediction of a need for surgical intervention are difficult. A non-invasive technique utilizing the difference in thermal relaxation time between burned and normal skin may be useful in this regard. In practice, a thermal camera would record the skin's response to heating or cooling by a small amount-roughly 5 C for a short duration. The thermal stimulus would be provided by a heat lamp, hot or cold air, or other means. Processing of the thermal transients would reveal areas that returned to equilibrium at different rates, which should correspond to different burn depths. In deeper thickness burns, the outside layer of skin is further removed from the constant-temperature region maintained through blood flow. Deeper thickness areas should thus return to equilibrium more slowly than other areas. Since the technique only records changes in the skin's temperature, it is not sensitive to room temperature, the burn's location, or the state of the patient. Preliminary results are presented for analysis of a simulated burn, formed by applying a patch of biosynthetic wound dressing on top of normal skin tissue.

The relationships between the extent of interfacial bonding, energy dissipation mechanisms, and fracture toughness in a glassy adhesive/inorganic solid joint are not well understood. We address this subject with a model system involving an epoxy adhesive on a polished silicon wafer containing its native oxide. The extent of interfacial bonding, and the wetting behavior of the epoxy, is varied continuously using self-assembling monolayers (SAMs) of octadecyltrichlorosilane (ODTS). The epoxy interacts strongly with the bare silicon oxide surface, but forms only a very weak interface with the methylated tails of the ODTS monolayer. We examine the fracture behavior of such joints as a function of the coverage of ODTS in the napkin-ring geometry. Various characterization methods are applied to the ODTS-coated surface before application of the epoxy, and to both surfaces after fracture. The fracture data are discussed with respect to the wetting of the liquid epoxy on the ODTS-coated substrates, the locus of failure, and the energy dissipation mechanisms. Our goal is to understand how energy is dissipated during fracture as a function of interface strength.

We have been working for many years to develop improved methods for predicting the lifetimes of polymers exposed to air environments and have recently turned our attention to seal materials. This paper describes an extensive study on a butyl material using elevated temperature compression stress-relaxation (CSR) techniques in combination with conventional oven aging exposures. The results initially indicated important synergistic effects when mechanical strain is combined with oven aging, as well as complex, non-Arrhenius behavior of the CSR results. By combining modeling and experiments, we show that diffusion-limited oxidation (DLO) anomalies dominate traditional CSR experiments. A new CSR approach allows us to eliminate DLO effects and recover Arrhenius behavior. Furthermore, the resulting CSR activation energy (E{sub a}) from 125 C to 70 C is identical to the activation energies for the tensile elongation and for the oxygen consumption rate of unstrained material over similar temperature ranges. This strongly suggests that the same underlying oxidation reactions determine both the unstrained and strained degradation rates. We therefore utilize our ultrasensitive oxygen consumption rate approach down to 23 C to show that the CSR E{sub a} likely remains unchanged when extrapolated below 70 C, allowing very confident room temperature lifetime predictions for the …

The Warden ASP project has progressed from the initial planning stage to construction of an injection plant. An ASP chemical system was designed based on laboratory evaluations that included interfacial tension, mobility requirements, rock-alkali interaction, fluid capabilities, and core tests. Field cores were obtained from the Permian No. 5 and No. 6 sands on the Warden lease in Sho-Vel-Tum oil field. A separate tank battery for the pilot pattern area was installed, and a field tracer test is currently being evaluated. Tracer test results to date indicate that there is no major fracturing in the No. 5 sand. There is indication, however, of some channeling through high permeability sand. The field injection plant was designed, and construction is in progress. Several variations of injection plant design have been evaluated. Some plant design details, such as alkali storage, were found to be dependent on the availability of use equipment and project budget. The surfactant storage facility design was shown to be dependent on surfactant rheology.

Several months ago, a report called PNNL-11895, ''Spent Fuel Dissolution Rates as a Function of Burnup and Water Chemistry'', by W. J. Gray dated June 1998 was mailed out. Unfortunately, an error was discovered in this document. The technetium (Tc) data in Figures 5 to 8, pages 21 to 24, are incorrect. Replacement figures, which show the corrected Tc data, are presented. No other data in the report was affected by this error.

A method of separating ultra-fine particulate from an aqueous suspension such as a process stream or a waste stream. The method involves the addition of alkali silicate and an organic gelling agent to a volume of liquid, from the respective process or waste stream, to form a gel. The gel then undergoes syneresis to remove water and soluble salts from the gel-containing the particulate, thus, forming a silica monolith. The silica monolith is then sintered to form a hard, nonporous waste form.

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