The authors report laser-induced damage threshold measurements on pure and multilayer dielectrics and gold-coated optics at 1053 and 526 nm for pulse durations, {tau}, ranging from 140 fs to 1 ns. Damage thresholds of gold coatings are limited to 500 mJ/cm{sup 2} in the subpicosecond range for 1053-nm pulses. In dielectrics, qualitative differences in the morphology of damage and a departure from the diffusion-dominated {tau}1/2 scaling indicate that damage results from plasma formation and ablation for {tau}{le}10 ps and from conventional melting and boiling for {tau}>50 ps. A theoretical model based on electron production via multiphoton ionization, Joule heating, and collisional (avalanche) ionization is in quantitative agreement with both the pulsewidth and wavelength scaling of experimental results.

Three-dimensional transient finite element analysis is performed on unstructured grids. A trend toward running larger analysis problems, combined with a desire for interactive animation of analysis results, demands efficient visualization techniques. This paper discusses a set of data structures and algorithms for visualizing transient analysis results on unstructured grids and introduces some modifications in order to better support large grids. In particular, an element grouping approach is used to reduce the amount of memory needed for external surface determination and to speed up ``point in element`` tests. The techniques described lend themselves to visualization of analyses carried out in parallel on a massively parallel computer (MPC).

This overview presents current research at Sandia National Laboratories in the Virtual Reality and Intelligent Simulation Lab. Into an existing distributed VR environment which we have been developing, and which provides shared immersion for multiple users, we are adding virtual actor support. The virtual actor support we are adding to this environment is intended to provide semi-autonomous actors, with oversight and high-level guiding control by a director/user, and to allow the overall action to be driven by a scenario. We present an overview of the environment into which our virtual actors will be added in Section 3, and discuss the direction of the Virtual Actor research itself in Section 4. We will briefly review related work in Section 2. First however we need to place the research in the context of what motivates it. The motivation for our construction of this environment, and the line of research associated with it, is based on a long-term program of providing support, through simulation, for situational training, by which we mean a type of training in which students learn to handle multiple situations or scenarios. In these situations, the student may encounter events ranging from the routine occurance to the rare emergency. Indeed, …

Previous papers have described a general method for visualizing vector fields that involves drawing many small ``glyphs`` to represent the field. This paper shows how to improve the speed of the algorithm by utilizing hardware support for line drawing and extends the technique from regular to unstructured grids. The new approach can be used to visualize vector fields at arbitrary surfaces within regular and unstructured grids. Applications of the algorithm include interactive visualization of transient electromagnetic fields and visualization of velocity fields in fluid flow problems.

We report tests of a refuelable zinc/air battery of modular, bipolar-cell design, intended for fleet electric busses and vans. The stack consists of twelve 250-cm{sup 2} cells built of two units: (1) a copper-clad glass-reinforced epoxy board supporting anode and cathode current collectors, and (2) polymer frame providing for air- and electrolyte distribution and zinc fuel storage. The stack was refueled in 4 min. by a hydraulic transfer of zinc particles entrained in solution flow.

This conference covers four main topics: (1) Southeastern Labor Market and its Impact on Corporate/Industry Development; (2) New Issues for Science and Technology in the Year 2000 and Beyond; (3) The Role of Academia in Developing the Labor Force of the Southeast; and (4) K-12 Education: Challenges for the 21st Century.

A spectroscopic analysis is made of electrons and photons from the standpoint of physical realism. In this conceptual framework, moving particles are portrayed as localized entities which are surrounded by ``empty`` waves. A spectroscopic model for the electron Stands as a guide for a somewhat similar, but in essential respects radically different, model for the photon. This leads in turn to a model for the ``zeron``. the quantum of the empty wave. The properties of these quanta mandate new basis states, and hence an extension of our customary framework for dealing with them. The zeron wave field of a photon differs in one important respect from the standard formalism for an electromagnetic wave. The vacuum state emerges as more than just a passive bystander. Its polarization properties provide wave stabilization, particle probability distributions, and orbit quantization. Questions with regard to special relativity are discussed.

Compressed Natural Gas (CNG) has favorable characteristics as a vehicular fuel, in terms of fuel economy as well as emissions. Using CNG as a fuel in a series hybrid vehicle has the potential of resulting in very high fuel economy (between 26 and 30 km/liter, 60 to 70 mpg) and very low emissions (substantially lower than Federal Tier II or CARB ULEV). This paper uses a vehicle evaluation code and an optimizer to find a set of vehicle parameters that result in optimum vehicle fuel economy. The vehicle evaluation code used in this analysis estimates vehicle power performance, including engine efficiency and power, generator efficiency, energy storage device efficiency and state-of-charge, and motor and transmission efficiencies. Eight vehicle parameters are selected as free variables for the optimization. The optimum vehicle must also meet two perfect requirements: accelerate to 97 km/h in less than 10 s, and climb an infinitely long hill with a 6% slope at 97 km/h with a 272 kg (600 lb.) payload. The optimizer used in this work was originally developed in the magnetic fusion energy program, and has been used to optimize complex systems, such as magnetic and inertial fusion devices, neutron sources, and mil guns. …

At the Fernald Environmental Restoration Management Corporation (FERMCO), our product is a clean site. We measure productivity by our progress in taking down buildings and dispositioning hazardous waste. To those ends, Quality and Safety work together to ensure that productivity is gained in the safest way possible. The Plant 7 deconstruction is an example of how this teamwork has increased productivity at the site.

A method for managing safety in a research and development environment is described which involves both the subject matter experts and the researchers in development of safety policy and implementation planning. This method has been used effectively at LLNL to maximize safety benefits while minimizing the costs of the safety program and aggravation to the researcher. A product of this effort is the establishment of an effective safety culture as the line organizations work with the subject matter experts to develop and implement the safety program.

Lithium metal can be electrolytically refined from aqueous solutions of its compounds by partial reduction to form a lithium amalgam, followed by reduction of the amalgam to liquid lithium in a molten salt cell at 225 C. A bipolar cell (with a continuous, amalgam electrode circulating between the aqueous and salt cells) was designed, constructed and successfully tested on the bench scale, as a proof of principle of an efficient, safe and low-temperature alternative to existing processes.

We present a comprehensive performance evaluation of our molecular dynamics code SPaSM on the CM-5 in order to devise optimization strategies for the CM-5, T3D, and RISC workstations. In this analysis, we focus on the effective use of the SPARC microprocessor by performing measurements of instruction set utilization, cache effects, memory access patterns, and pipeline stall cycles. We then show that we can account for more than 99% of observed execution time of our program. Optimization strategies are devised and we show that our highly optimized ANSI C program running only on the SPARC microprocessor of the CM-5 is only twice as slow as our Gordon-Bell prize winning code that utilized the CM-5 vector units. On the CM-5E, we show that this optimized code run faster than the vector unit version. We then apply these techniques to the Cray T3D and measure resulting speedups. Finally, we show that simple optimization strategies are effective on a wide variety of high performance RISC workstations.

The ultimate objective of this work has been to develop a nonthermal plasma process to reduce NO{sub x} in diesel exhaust gas. A secondary objective has been to study the possibility of particulate matter (soot) reduction by the same technique. The early work revealed a fundamental difficulty with this NO{sub x} reduction approach in the gas environment of the diesel engine exhaust. These observations necessitated a thorough study of the unfavorable chemistry in the hope that knowledge of the chemical mechanism would offer an opportunity to make the approach useful for NO{sub x} reduction. Whereas fundamental understanding of the mechanism has been obtained, the authors have not found any measure that would make the approach meet its original objective.

This paper describes efforts to model hybrid poplar and switchgrass production costs and supply curves. Estimates of the full economic cost of producing switchgrass bales and hybrid poplar chips in six US regions are presented. Average production costs vary by region and yield, ranging from $US 25 to $62/dry ton for switchgrass bales and $US 30 to $86/dry ton for poplar chips. Biomass prices are generally lower for switchgrass than for hybrid poplar, and are higher in the Lake States and Corn Belt than for other regions. Estimated national biomass supply curves are also presented. Assuming average US yields of 5 dry ton/acre/year, approximately 300 million dry tons of switchgrass could be supplied nationally at farm-gate prices of less than $30/dry ton. Approximately 250 million dry tons of woody crops can be potentially supplied nationally at farm-gate prices of less than $40/dry ton. This is enough biomass to produce 24 to 33 billion gallons of ethanol at a feedstock price of $0.36 to $0.63/gal (depending on conversion efficiency), or 600 billion kWh at a price of $0.04 to $0.05/kWh.

The possibility of using an induction linac for phase rotation, or equivalently flattening the head to tail mean energy sweep, of a muon bunch in the production region of a {mu}{sup +} {minus} {mu}{sup {minus}} is examined. Axial spreading of an accelerating bunch is analyzed and the form of appropriate induction cell voltage waveforms is derived. A set of parametric equations for the induction accelerator structure is given and specific solutions are presented which demonstrate the technological feasibility of the induction linac approach to phase rotation.

A novel method of fabricating three-dimensional silicon micro electromechanical systems (MEMS) is presented, using selectivity thin film deposited Au-Si eutectic bond pads. Utilizing this process, complicated structures such as microgrippers and microchannels are fabricated. Bond strengths are higher than the silicon fracture strength and the bond areas can be localized and aligned to the processed wafer. The process and the applications are described in this paper.

From mechanics and macroscopic viewpoints, the sensitivity of the flow stress of a material to the strain rate, i.e. the strain rate sensitivity (m), governs the development of neck formation and therefore has a strong influence on the tensile ductility and hence formability of materials. Values of strain rate sensitivity range from unity, for the case of Newtonian viscous materials, to less than 0.1 for some dispersion strengthened alloys. Intermediate values of m = 0.5 are associated with classical superplastic materials which contain very fine grain sizes following specialized processing. An overview is given of the influence of strain rate sensitivity on tensile ductility and of the various materials groups that can exhibit high values of strain rate sensitivity. Recent examples of enhanced formability (or extended tensile ductility) in specific regimes between m = 1 and m = 0.3 are described, and potential areas for commercial exploitation are noted. These examples include: internal stress superplasticity, superplastic ceramics, superplastic intermetallics, superplastic laminated composites, superplastic behavior over six orders of magnitude of strain rate in a range of aluminum-based alloys and composites, and enhanced ductility in Al-Mg alloys that require no special processing for microstructural development.

This paper discusses a project performed to recover wet records discovered in January 1995 at the Fernald Environmental Management Project (FEMP). This paper discusses the emergency and record recovery phases of the project, the technical options considered for records recovery, and special measures which were required due to radiological contamination of the records. Also, the root causes and lessons learned from the incident, and path forward for future records management operations at Fernald, are discussed.

A model-based approach is proposed to solve the oceanic internal wave signal processing problem that is based on state-space representations of the normal-mode vertical velocity and plane wave horizontal velocity propagation models. It is shown that these representations can be utilized to spatially propagate the modal (depth) vertical velocity functions given the basic parameters (wave numbers, Brunt-Vaisala frequency profile etc.) developed from the solution of the associated boundary value problem as well as the horizontal velocity components. These models are then generalized to the stochastic case where an approximate Gauss-Markov theory applies. The resulting Gauss-Markov representation, in principle, allows the inclusion of stochastic phenomena such as noise and modeling errors in a consistent manner. Based on this framework, investigations are made of model-based solutions to the signal enhancement problem for internal waves. In particular, a processor is designed that allows in situ recursive estimation of the required velocity functions. Finally, it is shown that the associated residual or so-called innovation sequence that ensues from the recursive nature of this formulation can be employed to monitor the model`s fit to the data.