Publications

A vibration test method has been proposed where control is accomplished using extremal control of the force and acceleration at the input to a test item. This proposal is examined with several examples. The method does limit the acceleration input at frequencies where the test item responses tend to be unrealistically large. However, the method's application is not straightforward and care must be taken in the application of the method. 9 refs., 16 figs.

The microstructure, mechanical properties and fracture characteristics of a pulsed Nd:YAG laser weld in a rapid solidification/powder metallurgy (RS/PM) Al-8 wt % Fe-2.3 wt % Mo alloy have been investigated. Results showed the high power density but low total energy input associated with pulsed Nd:YAG laser welding to promote extremely rapid fusion zone (FZ) cooling rates in the vicinity of 10/sup 5//degree/C/s. The weld FZ microstructure consisted primarily of submicron-sized spherical dispersoids in a matrix of fine dendritic-alpha aluminum. A dispersoid-coarsened heat-affected zone (HAZ) was also observed in the boundary between successive, overlapping melt zones. Transverse-weld tensile testing found fracture to occur in the unaffected base metal indicating 100% weld joint efficiency. Longitudinal-weld bend ductility testing revealed fracture initiation and propagation to be associated with the HAZ between successive melt zones at a bend ductility level only marginally below that of the base metal. 12 refs., 7 figs.

A good many words have been spoken and written (some by the present authors) about factoring very large numbers. Therefore, the thrust of this paper is a discussion of how the quadratic sieve algorithm has been adapted to work on a 1024-processor hypercube at Sandia National Laboratories. A brief description of the hypercube, an NCUBE/ten, its idiosyncrasies and its power, as well as some comparisons of timings between numbers factored on the CRAY and on the hypercube, are included. 6 refs., 1 tab.

PBFA II is the first pulsed power accelerator designed and built specifically to produce light ions for driving targets in Sandia National Laboratories inertial confinement fusion program. Recent progress in ion beam generation and focusing has been excellent. Record ion beam intensities have been obtained. Development of an extensive array of diagnostics and advances in the theory of ion diodes have had a major impact on this progress. A summary of recent progress and the present status of the PBFA-II light ion beam fusion program is given. 40 refs., 4 figs.

Amorphous metal foil-wound inductors have been tested as ferromagnetic saturable inductive elements for pulsed-power (multi-terawatt) switching modules in the inertial confinement fusion program at Sandia National Laboratories. In simulated capacitor testing premature dielectric breakdown of thin polyethylene terephthalate film insulation in the inductor windings occurs at considerably below 2500 V. This appears to be due to inadvertant dielectric damage from micro-spikes on the amorphous foil surface. Electron micrographs and dielectric breakdown data illustrate that electrophoretically-applied dielectric coatings, deposited from organic aqueous colloid dispersions, can be used to provide insulating coatings on the foil which provide a 240% improvement (6000 V) in the breakdown strength of wound amorphous foil inductors. The theory and operation of a dedicated electrophoretic continuous coating system is described. The machine was constructed and successfully applied for dielectric coating of amorphous metal foil. Additional possible applications exist for practical dielectric coating of metallic films or foils used in various commercial wound-type capacitor structures. 7 refs., 9 figs.

The influence of coal structure on primary conversions and oil yields in thermolytic extraction with different H-donor and non-H-donor solvents and in dry catalytic hydrogenation has been investigated. Pre-soaking of coal/H-donor solvent slurries at 250/degree/C increased conversions and the level of hydrogen transfer at short contact times (SCT, less than or equal to 10 min), demonstrating studies, prior removal of THF-extractable material (mobile phase) from one bituminous coal actually gave rise to higher conversions to pyridine-solubles for non-donor polynuclear aromatic compounds (PAC), such as naphthalene, phenanthrene and pyrene. These findings highlight the difficulties in relating primary conversions to coal characteristics. In contrast, oil yields have been found to increase broadly with decreasing rank in both H-donor solvent extraction with a process solvent and dry catalytic hydrogenation. However, in SCT tetralin extraction where poor physical contact between coal and solvent exists, neither total conversion nor oil yield correlates with rank. 23 refs., 1 fig., 3 tabs.

We first discuss the progress in linear optics, in particular, the formulation and application of geometrical-optics approximation and its generalization. We then discuss the progress in non-linear optics, in particular, the enhancement of a first-order Freedericksz transition and intrinsic optical bistability in homeotropic and parallel oriented nematic liquid crystal cells. Finally, we discuss the liquid crystal alignment and surface effects on field-induced Freedericksz transition. 50 refs.

Thin silicon nitride (Si/sub 3/N/sub 4/) films are widely used as a dielectric in metal-nitride-oxide-silicon (MNOS) structures for radiation hard non-volatile memories. The retention of charge in these devices depends, among other things, on the chemistry of the films. It has been reported that charge transport in MNOS structures can be reduced by replacing the Si/sub 3/N/sub 4/ film by a silicon oxynitride (SiO/sub x/N/sub y/) film. In order to understand the relationship between chemistry and retention of charge, it is necessary to have a technique that can determine the chemistry of the films as a function of depth. This can be accomplished with Auger electron spectroscopy by using fingerprint spectra for each of the elements and compounds present in the sample. By using classical least-squares techniques, a unique combination of the standard spectra can be found that best fits the unknown spectrum. When this method is repeated for each spectrum in a depth profile, a chemical state depth profile is obtained. The use of this technique to profile oxynitride films where the SiO/sub 2/ content varies between 0 and 12 atomic percent is presented. 6 refs., 7 figs.

The dramatic improvement in silicon concentrator cell efficiency recently demonstrated in university laboratories has had a significant influence on concentrator technology development. This paper briefly describes concentrator field experience, economics, current technology paths, and concludes with a detailed summary of concentrator cell performance. 29 refs., 2 figs., 3 tabs.

When a technology such as solar energy enters the everyday world, the documentation about it must also become part of the technology transfer. The challenge in creating publications about technical subjects for semi-technical people or for popular use is to be both accurate and interesting. The process of creating this documentation should begin by carefully defining the audience and aiming the publication at it. To a large extent, the audience determines both the content and the language that will be used. 2 refs.

In this work, compaction-induced combustion in packed beds of nitrocellulose-based ball propellants is modeled using a multiphase mixture description. This model is applied to conditions simulating low-velocity impact experiments of Sandusky, et. al. (NSWC). A two- stage combustion model is used whereby compressive reaction begins at the compaction front. Subsequent energy release is delayed following an induction rate law based on time-to-reaction experimental data. Given conditions of sufficient energy release and heat transfer, grain burning is initiated when granular surface temperatures exceed decomposition conditions. Numerical solutions of the one-dimensional multiphase conservation equations are obtained using an adaptive finite element method and calculations are compared to experiments investigating various impact loading conditions on the ball propellants TS3659 and WC140. 11 refs., 12 figs., 1 tab.

A study was performed to evaluate the performance of equivalent drag area single parachute systems and cluster parachute systems during the early inflation and initial deceleration phase. Analytical work showed that the cluster system could exhibit better performance during this unsteady aerodynamic phase due to a significant decrease in the apparent mass of air influenced by the parachutes. Two test programs have been performed in support of these assumptions. The first compared systems with parachute drag areas of approximately 750 ft/sup 2/ and a payload of 2400 lbs. The cluster system exhibited increased performance and less susceptibility to parachute collapse due to wake recontact. The second series compared systems with parachute drag areas of approximately 260 ft/sup 2/ with a payload of 800 lbs. The advantages of the cluster system were less apparent but performance was moderately improved. 4 refs., 7 figs.

Time stepping algorithms are often used to solve parabolic and hyperbolic differential equations numerically. These algorithms are generally regarded as sequential in time; that is, the solution on a time level must be known before the computation of the solution at subsequent time levels can start. While this remains true in principle, we demonstrate that it is possible for processors to perform useful work on many time levels simultaneously. Specifically, it is possible for a processor assigned to a ''later'' time level to compute a very good initial guess for the solution based on approximations to the solutions on ''previous'' time levels, thus reducing the time required for solution. The reduction in the solution time can be measured as parallel speedup. We demonstrate two parallel time stepping algorithms that can be used for both linear and nonlinear problems. We compare the two algorithms and discuss their performance in terms of parameters associated with classical time stepping algorithms. 4 refs., 5 tabs.

A general representation approach is described which employs a hierarchy of holes and notches. A matching procedure is also described which allows non-ideal image hierarchies to be matched to class representations. The representation and matching methods are demonstrated on a set of handgun photographs. Examples of handguns which are different in detail are shown to exhibit the same class characteristics, while other similarly shaped objects are correctly distinguished from the handgun class. 6 refs., 8 figs.

The activities involved in establishing an integrated CIM database at Sandia National Laboratories (SNL) are centered around the development of information engineering techniques. Several information engineering techniques were investigated including: top-down/bottom-up, data flow, entity-attribute and binary models. Most of the techniques were rejected because they did not capture all of the required information or they captured information that was not needed in the development of the CIM database. All current modeling activity is required for database development. This paper describes the modeling methodology utilized, the information engineering practices being developed, and a distributed database implementation at SNL. 10 refs., 12 figs.

This paper describes the migration path a company goes through as it moves up the data management learning curve. This migration path is based on four distinct roles for data management in CIM. The first two sections review the justification for CIM and data management. The first section describes the changing competitive environment manufacturers face and how CIM addresses the problems this situation creates. The second section identifies the two key characteristics of a database management system and the benefits provided. The third section identifies and discusses the four roles for data management in CIM. These four roles and their variations provide snapshots of where a company is on the data management learning curve. The fourth section describes the migration path a company goes through as it moves up the learning curve. Although there are similarities, there are some significant differences between this learning curve and the one experienced by MIS as it adopted data management technology. 3 refs.

The fire risk scoping study was sponsored by the US Nuclear Regulatory Commission and performed at Sandia National Laboratories. The study was initiated as a result of previous USNRC-sponsored fire research efforts that had identified certain fire risk issues that had not been addressed in previously completed commercial nuclear power plant fire risk analyses. The specific objectives of this study were: (1) to review and requantify fire risk scenarios from four fire probabilistic risk assessments in light of updated data bases made available as a result of USNRC-sponsored Fire Protection Research Program and updated computer fire modeling capabilities, (2) to identify potentially significant fire risk issues that have not been previously addressed in a fire risk context and to quantify the potential impact of those identified fire risk issues where possible, and (3) to review current fire regulations and plant implementation practices for relevance to the identified unaddressed fire risk issues. 9 refs., 3 tabs.

We are currently investigating a solar-driven photocatalytic process that promises to destroy low concentrations of hazardous organic molecules in large volumes of contaminated groundwater or industrial waste streams. Preliminary results of laboratory-scale screening tests using a model compound, salicylic acid, and titanium dioxide catalyst have shown that no measurable reaction occurs without both uv light and catalyst; no measurable volatilization of the salicylic acid occurs at room temperature; salicylic acid destruction rates depend on catalyst supplier and concentration and on uv light intensity; and some intermediates are being formed and subsequently destroyed. Observed reaction rates are consistent with those observed in an initial pilot-scale solar test of a falling-film reactor, although further testing will be required to quantify the comparison. 10 refs., 5 figs.

The Simplified Analytical Model of Penetration with Lateral Loading (SAMPLL) computer code developed at Sandia National Laboratories has been modified to allow additional penetration capabilities. The new capabilities include the ability to model penetration by other than cylindrical penetrators (flares, tapers, and boattails) and the ability to calculate penetration/perforation of multiple layers of different materials. Additionally, updated soil and rock empirical equations have been added to the model. A broader range of problems can now be modeled more accurately with the modified SAMPLL. 7 refs., 6 figs.

Article VII, paragraphs 8 and 14, of the inspection protocol of the INF Treaty between the US and the USSR provides for the use of radiation detection devices as a verification tool. That is, the Treaty allows the parties to measure the radiation from the radioactive components of nuclear weapons in order to verify that the inspected party is complying with the Treaty. This is the only verification provision in the Treaty that addresses the nuclear components of the relevant weapon systems. Acceptance of and confidence in such measurements is a significant development and similar measurements may be needed for verification of future treaties.

A novel technique is presented for segmenting seismic waveforms. The method produces waveform segments which closely correspond to explosion and earthquake signal onsets as well as additional structure of interest. Noise spikes or glitches are also successfully isolated. The approach uses threshold parameters obtained from human segmentation judgment tests and requires only simple, time domain calculations. 6 refs., 3 figs.

Semiconductor detectors for high energy physics applications offer the potential to obtain accurate particle spacial resolution and on-line data reduction. A significant disadvantage of semiconductor detectors and their associated circuitry however, is their sensitivity to radiation. Fortunately, a sufficient understanding of radiation effects on semiconductor devices exists that some classes of radiation tolerant semiconductor detectors are possible. 11 refs., 11 figs.

The Design Assistance Center (DAC) has developed a database of design, performance, and operating experience for remote photovoltaic (PV) systems. The DAC uses this database to assist potential users in evaluating PV for their specific applications and to accelerate the acceptance of PV as a viable power option for remote applications. 12 refs., 1 fig., 1 tab.

Strong coupling models for the electronic structure of La{sub 2}CuO{sub 4} are derived in two successive stages of renormalization. First, a three-band Hubbard model is derived using a constrained density functional approach. Second, exact diagonalization studies of finite clusters within the three band Hubbard model are used to select and map the low energy spectra onto effective one-band Hamiltonians. At each stage, some observables are calculated and found to be in quantitative agreement with experiment. The final results suggest the following models to be adequate descriptions of the low energy scale dynamics: (1) a spin 1/2 Heisenberg model for the insulating case with nearest neighbor J{approx}130 meV; (2) a t -- t' -- J'' model with nearly identical parameters for the electron and hole doped cases. 14 refs., 2 figs., 1 tab.

A high intensity acoustic test facility has been designed and is under construction at Sandia National Laboratories in Albuquerque, NM. The chamber is designed to provide an acoustic environment of 154dB (re 20 {mu}Pa) overall sound pressure level over the bandwidth of 50 Hz to 10,000 Hz. The chamber has a volume of 16,000 cubic feet with interior dimensions of 21.6 ft {times} 24.6 ft {times} 30 ft. The construction of the chamber should be complete by the summer of 1990. This paper discusses the design goals and constraints of the facility. The construction characteristics are discussed in detail, as are the acoustic performance design characteristics. The authors hope that this work will help others in designing acoustic chambers. 12 refs., 6 figs.