Single crystals of R{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7-{delta}}, (R=Y, Eu and Gd), have been irradiated with 0.4--1.0 MeV electrons in directions near the c-axis. An incident threshold electron energy for producing flux pinning defects has been found. In-situ TEM studies found no visible defects induced by electron irradiation. This means that point defects or small clusters ({le} 20 {Angstrom}) are responsible for the extra pinning. A consistent interpretation of the data suggests that the most likely pinning defect is the displacement of a Cu atom from the CuO{sub 2} planes.

The Energy Systems Modernization Office at Pacific Northwest Laboratory is developing and applying the Federal Energy Decision Screening (FEDS) system for federal installations in cooperation with the servicing utility(s). In the process, we conduct an installation-wide, fuel-blind energy-efficiency resource assessment, identify the most life-cycle cost-effective technologies, work with the servicing utility to develop a program to implement energy conservation projects and technologies, evaluate rates and rate structures, and contribute to the design and implementation of an energy savings verification procedure to evaluate the impact of installed technologies. Fort Lewis was identified as a site for a pilot program which would result in a model approach to apply to other federal installations. Fort Lewis, a large (population 35,000) military installation in Tacoma, Washington, purchases electricity through Tacoma Public Utilities (TPU). TPU in turn purchases electricity through the Bonneville Power Administration. Fort Lewis has an annual electric load of about 195,000 megawatt-hours (MWh)([approximately]40 MW). An energy conservation supply curve for the Fort was developed showing the amount of electric energy savings that can be achieved at different prices for energy saved. From these data, a proposal was prepared for acquiring approximately 43,000 kilowatt-hours of annual cost-effective electric energy savings. This proposal identified …

In this paper we describe a solution strategy to determine the natural frequencies of piezoelectric crystals subject to moderate changes in temperature and a variety of boundary constraints. The finite element equations governing piezoelectricity are derived based upon a Galerkin formulation of the problem. Suitable assumptions are made to linearize the steady-state (static) problem leading to an iteration scheme that can be used to refine the solution and include non-linear geometric effects caused by deformation. The eigenvalue problem is cast in this perturbed state to allow more accurate prediction of resonant frequencies.

Article on direct evidence for the amorphous silicon phase in visible photoluminescent porous silicon.

Article on the utilization of cyanide as a nitrogenous substrate by Pseudomonas fluorescens NCIMB 11764 and evidence for multiple pathways of metabolic conversion.

The electron quantum yields from barium cathodes excited by excimer laser radiation at 193, 248, 308, and 351 nm have been determined. Experiments with different cathode surface preparation techniques reveal that deposition of barium film a few microns thick on a clean copper surface under moderate vacuum conditions achieves relatively high quantum efficiencies. Quantum yields measured from surfaces prepared in this manner are 2.3 x 10{sup -3} at 193 nm, 7.6 x 10{sup - 4} at 248 nm, 6.1 x 10{sup -4} at 308 nm, and 4.0 x 10{sup -4} at 351 nm. Other preparation techniques, such as laser cleaning of a solid barium surface, produced quantum yields that were at least an order of magnitude lower than these values.

Cobalt foils and stainless steel samples were analyzed for induced {sup 6O}Co activity with both an ultra-low background germanium gamma-ray spectrometer and with a large NaI(Tl) multidimensional spectrometer, both of which use electronic anticoincidence shielding to reduce background counts resulting from cosmic rays. Aluminum samples were analyzed for {sup 22}Na. The results, in addition to the relative sensitivities and precisions afforded by the two methods, are presented.

Because environmental problems are growing and resources for dealing with them are shrinking, the environmental movement is witnessing an evolutionary shift toward greater emphasis on the use of risk assessment and management tools in setting environmental standards, determining levels of cleanup and deciding environmental program funding priorities. This change has important ramifications for the Department of Energy (DOE) and its national laboratories in terms of the costs of weapons facilities cleanup, the types of cleanup technology that will be emphasized and the way the DOE programs will be run. Other Federal agencies responsible for cleanup operations [e.g., the Environmental Protection Agency (EPA) and the Department of Defense (DOD)] will be similarly affected. This paper defines risk management and risk assessment and explains why these concepts will be of growing importance in the 1990s. It also defines other relevant terms. The paper develops a rationale for why risk assessment and management will be of increasing importance in environmental decision-making in the 1990s and beyond.

Titrations of acidic solutions in waters from the tuff and carbonate aquifers at Yucca Mountain were simulated using the geochemical codes PHREEQE and EQ3/6. The simulations tested pH stability of the waters in the presence of different minerals and in their absence. Two acidic solutions, 10{sup {minus}4} HCl and 10{sup {minus}4}M UO{sub 2}(NO{sub 3}){sub 2}, were titrated in to the water. Little pH and/or compositional change resulted in the groundwater when the HCl solution was titrated, but significant pH and CO{sub 2} fugacity changes were observed when UO{sub 2}(NO{sub 3}){sub 2} was titrated. Water interactions with alkali feldspar, quartz or cristobalite, and Ca-smectite buffered the pH and compositional changes in the carbonate water and decreased the magnitude of pH and compositional changes when small volumes of UO{sub 2}(NO{sub 3}){sub 2} added to the tuffaceous waters.

To adequately manage the low level nuclear waste (LLW) repository in Area 5 of the Nevada Test Site (NTS), a knowledge of the water table under the site is paramount. The estimated thickness of the arid intermountain basin alluvium is roughly 900 feet. Very little reliable water table data for Area 5 currently exists. The Special Projects Section of the Reynolds Electrical & Engineering Co., Inc. Waste Management Department is currently formulating a long-range drilling and sampling plan in support of a Resource Conservation Recovery Act (RCRA) Part B permit waiver for groundwater monitoring and liner systems. An estimate of the water table under the LLW repository, called the Radioactive Waste Management Site (RWMS) in Area 5, is needed for the drilling and sampling plan. Very old water table elevation estimates at about a dozen widely scattered test drill holes, as well as water wells, are available from declassified US Geological Survey, Lawrence Livermore National Laboratory, and Los Alamos National Laboratory drilling logs. A three-dimensional steady-state water-flow equation for estimating the water table elevation under a thick, very dry vadose zone is developed using the Dupuit assumption. A prescribed positive vertical downward infiltration/evaporation condition is assumed at the atmosphere/soil interface. …

Assessing the suitability of Yucca Mtn., NV as a potential repository for high-level nuclear waste requires the means to simulate ion-exchange behavior of zeolites. Vanselow and Gapon convention cation-exchange models have been added to geochemical modeling codes EQ3NR/EQ6, allowing exchange to be modeled for up to three exchangers or a single exchanger with three independent sites. Solid-solution models that are numerically equivalent to the ion-exchange models were derived and also implemented in the code. The Gapon model is inconsistent with experimental adsorption isotherms of trace components in clinoptilolite. A one-site Vanselow model can describe adsorption of Cs or Sr on clinoptilolite, but a two-site Vanselow exchange model is necessary to describe K contents of natural clinoptilolites.

The Superconducting Super Collider`s Medium Energy Booster Abort (MEBA) kicker modulator will supply a current pulse to the abort magnets which deflect the proton beam from the MEB ring into a designated beam stop. The abort kicker will be used extensively during testing of the Low Energy Booster (LEB) and the MEB rings. When the Collider is in full operation, the MEBA kicker modulator will abort the MEB beam in the event of a malfunction during the filling process. The modulator must generate a 14-{mu}s wide pulse with a rise time of less than 1 {mu}s, including the delay and jitter times. It must also be able to deliver a current pulse to the magnet proportional to the beam energy at any time during ramp-up of the accelerator. Tracking the beam energy, which increases from 12 GeV at injection to 200 GeV at extraction, requires the modulator to operate over a wide range of voltages (4 kV to 80 kV). A vacuum spark gap and a thyratron have been chosen for test and evaluation as candidate switches for the abort modulator. Modulator design, switching time delay, jitter and pre-fire data are presented.

Computational Integrated Photonics (CIP) is the area of computational physics that treats the propagation of light in optical fibers and in integrated optical circuits. The purpose of integrated photonics simulation is to develop the computational tools that will support the design of photonic and optoelectronic integrated devices. CIP has, in general, two thrusts: (1) predictive models of photonic device behavior that can be used reliably to enhance significantly the speed with which designs axe optimized for development applications, and (2) to further our ability to describe the linear and nonlinear processes that occur - and can be exploited - in real photonic devices. Experimental integrated optics has been around for over a decade with much of the work during this period. centered on proof-of-principle devices that could be described using simple analytic and numerical models. Recent advances in material growths, photolithography, and device complexity have conspired to reduce significantly the number of devices that can be designed with simple models and to increase dramatically the interest in CIP. In the area of device design, CIP is viewed as critical to understanding device behavior and to optimization. In the area of propagation physics, CIP is an important tool in the study …