Pulse width broadening at 351-nm was measured in two single fibers (core sizes 100 and 435 µm), and in a 32-m bundle of 19 each 50-µm-core fibers.

Aircraft and later missile radar early warning stations played an important role in the Cold War. They are associated with important technological, social, political, and military themes of the Cold War and are worthy of preservation. The scope and scale of these systems make physical preservation impractical, but the U.S. Air Force program of historical evaluation and documentation of these systems will provide valuable information to future generations studying this historic period.

We have studied the effects of temporal pulse width and target density on the deposition of thin films of YBaCuO. A 248nm excimer laser and an 825nm Ti-sapphire laser were used to conduct the experiments with pulse widths of 27 ns, 16 ns, and 150 fs, and target densities of 80% and 90%. Scanning electron microscope photomicrographs and profilometer traces show a striking difference between nanosecond and femtosecond laser irradiation. Shortening the pulse width reduced particulate formation, provided stoichiometry, and improved the film properties. Decreasing the target density raised the ablation rate, produced thicker but nonuniform films, and reduced particulate formation.

InGaAsN is a new semiconductor alloy system with the remarkable property that the inclusion of only 2% nitrogen reduces the bandgap by more than 30%. In order to help understand the physical origin of this extreme deviation from the typically observed nearly linear dependence of alloy properties on concentration, we have investigated the pressure dependence of state energies using both experimental and theoretical methods. the excited We report measurements of the low temperature photoluminescence of the material for pressures between ambient and 110 kbar. We also describe a simple, density- functional-theory-based approach to calculating the pressure dependence of low lying excitation energies for low concentration alloys. The theoretically predicted pressure dependence of the bandgap is in excellent agreement with the experimental data. Based on the results of our calculations, we suggest an explanation for the strongly non-linear pressure dependence of the bandgap that, surprisingly, does not involve a nitrogen impurity state.

Semiconductor microlasers are attractive components for micro-analysis systems because of their ability to emit coherent intense light from a small aperture. By using a surface-emitting semiconductor geometry, we were able to incorporate fluid flow inside a laser microcavity for the first time. This confers significant advantages for high throughput screening of cells, particulates and fluid analytes in a sensitive microdevice. In this paper we discuss the intracavity microfluidics and present preliminary results with flowing blood and brain cells.

The role of a wedge prism for strain sign determination and enhancing the sensitivity for sub-fringe changes is emphasized. The design and incorporation aspects for in-plane sensitive interferometers have been described in detail. Some experimental results dealing with stress determination by laser annealing and speckle corelation interferometry are presented. The prism can also be applied to produce standardized carrier fringes in spatial phase shifting interferometry.

A low energy electron microscope (LEEM) has been used to investigate the faceting of W(111) as induced by Pt. The atomically rough W(111) surface, when fully covered with a monolayer film of Pt and annealed to temperatures higher than {approximately} 750 K, experiences a significant morphological restructuring: the initially planar surface undergoes a faceting transition and forms three-sided pyramids with {211} faces. The experiments demonstrate the capability of LEEM for imaging both the fully and partially faceted surface. In addition, we have observed the formation of the facets in real time, when Pt is dosed onto the heated surface. We find that the transition from planar surface, to partially faceted surface, and to fully faceted surface proceeds through the nucleation and growth of spatially separated faceted regions.

This report summarizes some challenges associated with the use of computational science to predict the behavior of complex phenomena. As such, the document is a compendium of ideas that have been generated by various staff at Sandia. The report emphasizes key components of the use of computational to predict complex phenomena, including computational complexity and correctness of implementations, the nature of the comparison with data, the importance of uncertainty quantification in comprehending what the prediction is telling us, and the role of risk in making and using computational predictions. Both broad and more narrowly focused technical recommendations for research are given. Several computational problems are summarized that help to illustrate the issues we have emphasized. The tone of the report is informal, with virtually no mathematics. However, we have attempted to provide a useful bibliography that would assist the interested reader in pursuing the content of this report in greater depth.

We present experimental result of carrier speckle noise averaging by a novel approach to generate numerous identical correlation fringes with randomly different speckles. The surface under study is sprayed with a new dry paint or a layer each time for the repetitive experiments to generate randomly different surfaces of the carrier speckle patterns.

Saltstone Production and Disposal Facilities (Z-Area) are a part of the Defense Waste Processing Facilities (DWPF). Z-Area facilities are just one segment of an integrated waste management and disposal system located at the Savannah River Site (SRS). The bases for the Justification of Continuing Operations (JCO) of the Saltstone Production and Disposal Facilities (Z-Area) at SRS are provided.

The minimum expended energy for fracture is the free energy required to form two new surfaces. For intergranular fracture, the minimum surface formation energy is complicated by the rough fracture surface, with area greater than the specimen cross-section. We utilize network optimization algorithms (max-flow/min-cut) to determine the minimum surface formation energies and surfaces for intergranular fracture in 3D polycrystals. For equiaxed grains and uniform boundary strength, the minimum energy fracture area is independent of grain size and is 45% larger than the specimen cross-section, and intergranular fracture will occur when surface energy is less than 1.6 times the grain boundary energy. The 3D fracture area is larger than projected from 2D systems. In systems with microcracked boundaries, the fracture surface deviates to preferentially include microcracked boundaries, creating interlocking grain configurations. Two-dimensional percolation of microcracks occurs at about 80% microcracked boundaries.

We report magneto-exciton spectroscopy studies of (411)A and (100)-oriented GaAs/Al{sub 0.3}Ga{sub 0.7}As multiquantum well structures. The samples consisted of seven GaAs quantum wells with widths varying between 0.6 and 12nm, were grown on (411)A and (100)-oriented GaAs substrates. The exciton diamagnetic energy shifts and linewidths were measured between 0 and 14T at 1.4K The dependence of the exciton diamagnetic shifts with magnetic field were calculated using a variational approach and good agreement with experiment for both substrate orientations was found.

The interface between liquid hexadecane and the (010) surface of silicalite was studied by molecular dynamics. The structure of molecules in the interracial region is influenced by the presence of pore mouths on the silicalite surface. For this surface, whose pores are the entrances to straight channels, the concentration profile for partially absorbed molecules is peaked around 10 monomers inside the zeolite. No preference to enter or exit the zeolite based on absorption length is observed except for very small or very large absorption lengths. We also found no preferential conformation of the unabsorbed tails for partially absorbed molecules.

Cathodolurninescence (CL) characterization in a demountable vacuum chamber is an important benchmarking tool for flat-panel display phosphors and screens. The proper way to perform these measurements is to minimize the effects of secondary electrons, excite the phosphor/screen with a uniform beam profile, and maintain a clean vacuum environment. CL measurements are important for preliminary evaluation and lifetesting of phosphor powders and screens prior to incorporation into the FPD. A survey of many CL characterization systems currently in use revealed the myriad of spectroradiometers, colorimeters, electron guns, vacuum pumps, mass spectrometers, etc. that introduce many avenues for error that are often difficult to isolate. A preliminary round-robin experiment was coordinated by Sandia and invoIved five other research groups. The purpose of this experiment was to obtain an indication of equipment capabilities and instrument variations, as well as reliability and consistency of results. Each group was asked to measure the luminence (cd/m{sup 2}) and chromaticity coordinates of a Y{sub 3}Al{sub 2}Ga{sub 3}O{sub 12}: Tb pellet and calculate the luminous efficiency. Pellets were chosen in order to reduce errors associated with processing and handling of powders or screens. Some of the data reported in this experiment were in good agreement while others differed …

The linewidth enhancement factor in single quantum-well GRINSCH semiconductor lasers is investigated theoretically and experimentally. For thin wells a small linewidth enhancement factor is obtained which clamps with increasing carrier density, in contrast to the monotonous increase observed for thicker wells. Microscopic many-body calculations reproduce the experimental observations attributing the clamping to a subtle interplay between excitation dependent gain shifts and carrier population distributions.

In July 1993, the Delmarva Power and Light Company (now Conectiv, Inc.) was awarded a contract for the development of a Dispatchable Photovoltaic Peak Shaving System under the US Department of Energy PV:BONUS Program. The rationale for the dispatchable PV peak shaving system is based on the coincidence between the solar resource and the electrical load in question. Where poor coincidence exists, a PV array by itself does little to offset peak demands. However, with the addition of a relatively small amount of energy storage, the energy from the PV array can be managed and the value of the PV system increases substantially. In Phase 2, Delmarva Power continued the refinement of the system deployed in Phase 1. Four additional dispatchable PV peak shaving systems were installed for extended testing and evaluation at sites in Delaware, Maryland, Wisconsin and North Carolina. A second type of system that can be used to provide back-up power as well as peak shaving was also developed in Phase 2. This PV-UPS system used a packaging approach nearly identical to the PV peak shaving system, although there were significant differences in the design of the power electronics and control systems. Conceptually, the PV-UPS system builds …

Research Triangle Institute (RTI), Eastman Chemical Company, and Bechtel collectively are developing a novel three-step process for the synthesis of methyl methacrylate (MMA) from coal-derived syngas that consists of the steps of synthesis of a propionate, its condensation with formaldehyde to form methacrylic acid (MAA), and esterification of MAA with methanol to produce MMA. The research team has completed the research on the three-step methanol-based route to MMA. Under an extension to the original contract, we are currently evaluating a new DME-based process for MMA. The key research need for DME route is to develop catalysts for DME partial oxidation reactions and DME condensation reactions. Over the last quarter(Oct.-Dec./98), we have investigated the condensation between methyl propionate and formaldehyde (MP/HCHO=4.5/1) at various reaction temperatures(280-360EC) over 5%, 10%, and 20% Nb O /SiO catalysts. The conversion of HCHO increases with reaction 2 5 2 temperature and niobium loading. MMA+MAA selectivity goes through a maximum with the temperature over both 10% and 20% Nb O /SiO . The selectivities to MMA+MAA are 67.2%, 2 5 2 72.3%and 58.1% at 320EC over 5%, 10%, 20% Nb O /SiO , respectively. However, the 2 5 2 conversion of formaldehyde decreases rapidly with time on …

POW7 is designed for structural measurements on glasses and liquids. Figure 1 provides a schematic representation of POW7, and Table 1 gives the parameters for this instrument. The short incident flight path maintains the highest possible flux on sample to allow the counting statistics needed to effectively use isotope substitution in cases where the contrast is low. Emphasis is placed on using the shortest wavelengths practical to measure each Q in order to minimize inelasticity effects.

POW3 provides rapid data collection while maintaining reasonably good resolution. Figure 1 provides a schematic representation of POW3, and Table 1 gives the parameters for this instrument. This is a workhorse refinement instrument for structures of modest complexity. In addition, this instrument views a cold moderator to enable long-wavelength neutrons to be used to measure long d-spacings.

POW6 is optimized to provide the best possible resolution at 90{degree} scattering angle for diffraction from materials in special environments (cryostats, furnaces, pressure cells, etc.) and for precision strain distribution and deformation measurements. Figure 1 provides a schematic representation of POW6, and Table 1 gives the parameters for this instrument. The instrument also provides very good resolution in backscattering.

SCD1 is intended to satisfy most needs for small-unit-cell single-crystal diffraction. Figure 1 provides a schematic representation of SCD1, and Table 1 gives the parameters for this instrument. This instrument will provide much faster data collection than any existing time-of-flight single-crystal diffractometer. The goal is data collection times of 1 hour for a simple structure and 1 day for a medium-complexity structure.

Leading an audit team goes beyond performance of the duties outlined in any requirement or training course. Anyone can memorize the steps to begin and to complete an audit, but it takes leadership to capitalize on the strengths of each team member and to interact with the auditee. Leadership has been written about and studied for many years. Principles and ideas developed by Covey, Senge, Peters, Blanchard, Hersey, Drucker, Yuki and many, many more but they all come down to some basic issues. There is no magic formula. There are theories and models that when applied work in one situation. Some theories and methodologies work better than others depending on the situation. The presentation today looks at leadership from the perspective of the lead auditor, as he/she has to guide the audit process and deal with many personalities from the audit team to the people being interviewed, Each situation is different, each audit team is different, each audit is unique. The basic principles are applied but it takes understanding leadership to have a successful audit. Applying the Situational Leadership model will enable you to be a good and effective leader and capitalize on the strengths of each team member. It …

ERD approaches its mission with a vision of continuously exceeding customer needs and expectations and continuously improving. It's this vision of continuous improvement that drives the ERD pollution prevention program towards innovation.

The successful commercialization of MicroElectroMechanical Systems (MEMS) is an essential prerequisite for their implementation in many critical government applications. Several unique challenges must be overcome to achieve this widespread commercialization. Challenges associated with design realization and reliability assurance are discussed, along with approaches taken by Sandia to successfully overcome these challenges.