Publications

We create mobile surface vacancies on vicinal Si(001) by bombarding the surface with 300 eV Xe ions at a substrate temperature of 465{degrees}C. The vacancies preferentially annihilate at the rough steps retracting them with respect to their smooth neighbors. This process leads to a bimodal terrace width distribution. The retraction of the rough steps due to the vacancy annihilation is in competition with the healing process by which the surface tries to maintain its equilibrium configuration of equally spaced steps. As the two competing processes balance, the surface reaches steady state and subsequent removal of surface atoms is manifest as simple step flow.

The purpose of publishing the minutes of this workshop is to document the content of the presentations and the direction of the discussions at the workshop as a means of fostering collaborative research and development on chromate replacements throughout the defense, automotive, aerospace, and packaging industries. The goal of the workshop was to bring together coating researchers, developers, and users from a variety of industries to discuss new coating ideas, testing methods, and coating preparation techniques from the perspective not only of end user, but also from the perspective of coating supplier, developer, and researcher. To this end, we succeeded because of the wide-ranging interests of attendees present in the more than 60 workshop registrants. It is our hope that future workshops, not only this one but others like it throughout government and industry, can benefit from the recorded minutes of our meeting and use them as a starting point for future discussions of the directions for chromate replacements in light metal finishing.

The multiphase, multicomponent, non-isothermal simulator M2NOTS was tested against several one-dimensional experiments. The experiments represented limiting conditions of soil venting processes: (1) a through-flow condition in which air flows through the contaminated region, and (2) a bypass-flow condition in which air is channeled around (rather than through) the contaminated region. Predictions using M2NOTS of changing in situ compositions and effluent concentrations for toluene and o-xylene mixtures were compared to the observed results for each condition. Results showed that M2NOTS was able to capture the salient trends and features of multicomponent through-flow and bypass-flow venting processes.

We identify a general framework for search called bootstrap search, which is defined as global search using only a local search procedure along with some memory for learning intermediate subgoals. We present a simple algorithm for bootstrap search, and provide some initial theory on their performance. In our theoretical analysis, we develop a random digraph problem model and use it to make some performance predictions and comparisons. We also use it to provide some techniques for approximating the optimal resource bound on the local search to achieve the best global search. We validate our theoretical results with empirical demonstration on the 15-puzzle. We show how to reduce the cost of a global search by 2 orders of magnitude using bootstrap search. We also demonstrate a natural but not widely recognized connection between search costs and the lognormal distribution. To further illustrate our algorithm`s generality and effectiveness, we also apply it to robot path planning, and demonstrate a phenomenon of over-learning.

The original DAMP (DAta Manipulation Program) was written by Mark Hedemann of Sandia National Laboratories and used the CA-DISSPLA{trademark} (available from Computer Associates International, Inc., Garden City, NY) graphics package as its engine. It was used to plot, modify, and otherwise manipulate the one-dimensional data waveforms (data vs time) from a wide variety of accelerators. With the waning of CA-DISSPLA and the increasing popularity of UNIX{reg_sign}-based workstations, a replacement was needed. This package uses the IDL{reg_sign} software, available from Research Systems Incorporated in Boulder, Colorado, as the engine, and creates a set of widgets to manipulate the data in a manner similar to the original DAMP. IDL is currently supported on a wide variety of UNIX platforms such as IBM{reg_sign} workstations, Hewlett Packard workstations, SUN{reg_sign} workstations, Microsoft{reg_sign} Windows{trademark} computers, Macintosh{reg_sign} computers and Digital Equipment Corporation VMS{reg_sign} systems. Thus, this program should be portable across many platforms. We have verified operation, albeit with some IDL bugs, on IBM UNIX platforms, DEC Alpha systems, HP 9000/7OO series workstations, and Macintosh computers, both regular and PowerPC{trademark} versions.

This report documents an exploratory research work, funded by the Laboratory Directed Research and Development (LDRD) office at Sandia National Laboratories, to develop an advanced, general purpose, robust compressible flow solver for handling large, complex, chemically reacting gas dynamics problems. The deliverable of this project, a computer program called PINCA (Parallel INtegrated Computer Analysis) will run on massively parallel computers such as the Intel/Gamma and Intel/Paragon. With the development of this parallel compressible flow solver, engineers will be better able to address large three-dimensional scientific arid engineering problems involving multi-component gas mixtures with finite rate chemistry. These problems occur in high temperature industrial processes, combustion, and hypersonic: reentry of space-crafts.

Utilizing unique properties of a recently developed set of attitude parameters, the modified Rodrigues parameters, we develop feedforward/feedback type control laws that globally control a spacecraft undergoing large nonlinear motions, using three or more reaction wheels. The method is suitable for tracking given smooth reference trajectories that spline smoothly into a target slate or pure spin motion; these reference trajectories may be exact or approximate solutions of the system equations of motion. In particular, we illustrate the ideas using both near-minimum-time and near-minimum fuel rotations about Euler`s principal rotation axis, with parameterization of the sharpness of the control switching for each class of reference maneuvers. Lyapunov stability theory is used to prove rigorous stability of closed loop motion in the end game, and qualified Lyapunov stability during the large nonlinear path tracking portion of the closed loop tracking error dynamics. The methodology is illustrated by designing example control laws for a prototype landmark tracking spacecraft; simulations are reported that show this approach to be attractive for practical applications. The inputs to the reference trajectory are designed with user-controlled sharpness of all control switches, to enhance the trackability of the reference maneuvers in the presence of structural flexibility.

With the recent completion of the documentation of the results from the Grand Gulf Nuclear Power Plant Low Power and Shutdown (LP and S) project funded by the US Nuclear Regulatory Commission (NRC), detailed probabilistic risk assessment (PRA) information from a boiling water reactor (BWR) for a specific time period in LP and S conditions became available for examination. This report contains observations and insights extracted from an examination of: (1) results in the LP and S documentation; (2) the specific models and assumptions used in the LP and S analyses; (3) selected results from the full-power analysis; (4) the experience of the analysts who performed the original LP and S study; and (5) results from sensitivity calculations performed as part of this project to help determine the impact that model assumptions and data values had on the results from the original LP and S analysis. Specifically, this study makes observations on and develops insights from the estimates of core damage frequency and aggregate risk (early fatalities and total latent cancer fatalities) associated with operations during plant operational state (POS) 5 (i.e., basically cold shutdown as defined by Technical Specifications) during a refueling outage for traditional internal events. A discussion of similarities and differences between full power accidents and accidents during LP and S conditions is provided. As part of this discussion, core damage frequency and risks results are presented on a per hour and per calendar year basis, allowing alternative perspectives on both the core damage frequency and risk associated with these two operational states.

Feasibility of ceramic joining using a high energy (10 MeV) electron beam. The experiments used refractory metals as bonding materials in buried interfaces between Si{sub 3}N{sub 4} pieces. Because the heat capacity of the metal bonding layer is much lower than the ceramic, the metal reaches much higher temperatures than the adjoining ceramic. Using the right combination of beam parameters allows the metal to be melted without causing the adjoining ceramics to melt or decompose. Beam energy deposition and thermal simulations were performed to guide the experiments. Joints were shear tested and interfaces between the metal and the ceramic were examined to identify the bonding mechanism. Specimens joined by electron beams were compared to specimens produced by hot-pressing. Similar reactions occurred using both processes. Reactions between the metal and ceramic produced silicides that bond the metal to the ceramic. The molybdenum silicide reaction products appeared to be more brittle than the platinum silicides. Si{sub 3}N{sub 4} was also joined to Si{sub 3} N{sub 4} directly. The bonding appears to have been produced by the flow of intergranular glass into the interface. Shear strength was similar to the metal bonded specimens. Bend specimens Of Si{sub 3}N{sub 4} were exposed to electron beams with similar parameters to those used in joining experiments to determine how beam exposure degrades the strength. Damage was macroscopic in nature with craters being tonned by material ablation, and cracking occurring due to excessive thermal stresses. Si was also observed on the surface indicating the Si{sub 3}N{sub 4} was decomposing. Bend strength after exposure was 62% of the asreceived strength. No obvious microstructural differences were observed in the material close to the damaged region compared to material in regions far away from the damage.

Design criteria for carbon-based Ultracapacitors have been determined for specified energy and power requirements, using the geometry of the components and such material properties as density, porosity and conductivity as parameters, while also considering chemical compatibility. This analysis shows that the weights of active and inactive components of the capacitor structure must be carefully balanced for maximum energy and power density. When applied to nonaqueous electrolytes, the design rules for a 5 Wh/kg device call for porous carbon with a specific capacitance of about 30 F/cm{sup 3}. This performance is not achievable with pure, electrostatic double layer capacitance. Double layer capacitance is only 5 to 30% of that observed in aqueous electrolyte. Tests also showed that nonaqeous elcctrolytes have a diminished capability to access micropores in activated carbon, in one case yielding a capacitance of less than 1 F/cm{sup 3} for carbon that had 100 F/cm{sup 3} in aqueous electrolyte. With negative results on nonaqueous electrolytes dominating the present study, the obvious conclusion is to concentrate on aqueous systems. Only aqueous double layer capacitors offer adequate electrostatic charging characteristics which is the basis for high power performance. There arc many opportunities for further advancing aqueous double layer capacitors, one being the use of highly activated carbon films, as opposed to powders, fibers and foams. While the manufacture of carbon films is still costly, and while the energy and power density of the resulting devices may not meet the optimistic goals that have been proposed, this technology could produce true double layer capacitors with significantly improved performance and large commercial potential.

In robotics, path planning refers to finding a short. collision-free path from an initial robot configuration to a desired configuratioin. It has to be fast to support real-time task-level robot programming. Unfortunately, current planning techniques are still too slow to be effective, as they often require several minutes, if not hours of computation. To remedy this situation, we present and analyze a learning algorithm that uses past experience to increase future performance. The algorithm relies on an existing path planner to provide solutions to difficult tasks. From these solutions, an evolving sparse network of useful robot configurations is learned to support faster planning. More generally, the algorithm provides a speedup-learning framework in which a slow but capable planner may be improved both cost-wise and capability-wise by a faster but less capable planner coupled with experience. The basic algorithm is suitable for stationary environments, and can be extended to accommodate changing environments with on-demand experience repair and object-attached experience abstraction. To analyze the algorithm, we characterize the situations in which the adaptive planner is useful, provide quantitative bounds to predict its behavior, and confirm our theoretical results with experiments in path planning of manipulators. Our algorithm and analysis are sufficiently, general that they may also be applied to other planning domains in which experience is useful.

System identification for the purpose of robust control design involves estimating a nominal model of a physical system and the uncertainty bounds of that nominal model via the use of experimentally measured input/output data. Although many algorithms have been developed to identify nominal models, little effort has been directed towards identifying uncertainty bounds. Therefore, in this document, a discussion of both nominal model identification and bounded output multiplicative uncertainty identification will be presented. This document is divided into several sections. Background information relevant to system identification and control design will be presented. A derivation of eigensystem realization type algorithms will be presented. An algorithm will be developed for calculating the maximum singular value of output multiplicative uncertainty from measured data. An application will be given involving the identification of a complex system with aliased dynamics, feedback control, and exogenous noise disturbances. And, finally, a short discussion of results will be presented.

Russian scientists and engineers have drilled the deepest holes in the world. It is recognized that this experience has given them an expertise in drilling superdeep holes, as well as other aspects of drilling, completions, and geophysics. More and more US oil and gas companies are vigorously expanding their exploration and development into Russia. It is important for them to identify and use Russian technology in drilling, completion, logging, and reservoir characterization to the extent possible, in order to both reduce drilling costs and help support the Russian economy. While these US companies are interested in becoming involved in and/or sponsoring research in Russia, they have been unsure as to which scientists and institutes are working on problems of interest. It was also important to determine in which areas Russian technology is farther advanced than in the West. Such technology could then be commercialized as part of the Industrial Partnering Program. In order to develop a clear understanding of these issues, two Sandia engineers with drilling and completions expertise and a geophysicist with expertise in reservoir analysis traveled to Russia to meet with Russian scientists and engineers to discuss their technologies and areas of interest. This report contains a summary of the information obtained during the visit.

Natural disasters cause billions of dollars of damage and thousands Of deaths globally each year. While the magnitude is clear, the exact costs (in damage and fatalities) are difficult to clearly identify. This document reports on the results of a survey of data on the costs associated with significant natural disasters. There is an impressive amount of work and effort going into natural disaster research, mitigation, and relief. However, despite this effort, there are surprisingly few consistent and reliable data available regarding the effects of natural disasters. Even lacking consistent and complete data, it is clear that the damage and fatalities from natural disasters are increasing, both in the United States, and globally. Projections using the available data suggest that, in the United States alone, the costs of natural disasters between 1995 and 2010 will be in the range of $90 billion (94$) and 5000 lives.

Open demonstrations of technologies developed by the Office of Technology Development`s (QTD`s) Mixed Waste Landfill Integrated Demonstration (MWLID) should facilitate regulatory acceptance and speed the transfer and commercialization of these technologies. The purpose of the present project is to identify the environmental restoration needs of hazardous waste and/or mixed waste landfill owners within a 25-mile radius of Sandia National Laboratories (SNL). Most municipal landfills that operated prior to the mid-1980s accepted household/commercial hazardous waste and medical waste that included low-level radioactive waste. The locations of hazardous and/or mixed waste landfills within the State of New Mexico were. identified using federal, state, municipal and Native American tribal environmental records. The records reviewed included the US Environmental Protection Agency (EPA) Superfund Program CERCLIS Event/Site listing (which includes tribal records), the New Mexico Environment Department (NMED), Solid Waste Bureau mixed waste landfill database, and the City of Albuquerque Environmental Health Department landfill database. Tribal envirorunental records are controlled by each tribal government, so each tribal environmental officer and governor was contacted to obtain release of specific site data beyond what is available in the CERCLIS listings.

Radiation testing of photonic components is not new, however component level testing to date has not completely addressed quantities which are important to system behavior. One characteristic that is of particular importance for optical processing systems is the frequency response. In this report, we present the analysis of data from an experiment designed to provide a preliminary understanding of the effects of radiation on the frequency response of acousto-optic devices. The goal of the analysis is to describe possible physical mechanisms responsible for the radiation effects and to discuss the effects on signal processing functionality. The experiment discussed in this report was designed by Sandia National Laboratories and performed by Sandia and Phillips Laboratory personnel at White Sands Missile Range (WSMR). In the experiment, a TeO{sub 2} slow shear wave acousto-optic cell was exposed to radiation from the WSMR linear accelerator. The TeO{sub 2} cell was placed in an experimental configuration which allowed swept frequency diffracted power measurements to be taken during radiation exposure and recovery. A series of exposures was performed. Each exposure consisted of between 1 to 800, 1{mu}sec radiation pulses (yielding exposures of 2.25 kRad(Si) to 913 kRad(Si)), followed by recovery time. At low total and cumulative doses, the bandshape of the frequency response (i.e. diffracted power vs. frequency) remained almost identical during and after radiation. At the higher exposures, however, the amplitude and width of the frequency response changed as the radiation continued, but returned to the original shape slowly after the radiation stopped and recovery proceeded. It is interesting to note that the location of the Bragg degeneracy does not change significantly with radiation. In this report, we discuss these effects from the perspective of anisotropic Bragg diffraction and momentum mismatch, and we discuss the effect on the signal processing functionality.

The following annotated bibliography lists documents prepared by the Department of Energy (DOE), and predecessor agencies, to meet the requirements of the National Environmental Policy Act (NEPA) for activities and facilities at Sandia National Laboratories sites. For each NEPA document summary information and a brief discussion of content is provided. This information may be used to reduce the amount of time or cost associated with NEPA compliance for future Sandia National Laboratories projects. This summary may be used to identify model documents, documents to use as sources of information, or documents from which to tier additional NEPA documents.

An aqueous-based process that uses electrophoresis to attract powdered lubricant in suspension to a charged target was developed. The deposition process yields coatings with low friction, complies with environmental safety regulations, requires minimal equipment, and has several advantages over processes involving organic binders or vacuum techniques. This work focuses on development of the deposition process, includes an analysis of the friction coefficient of the material in sliding contact with stainless steel under a range of conditions, and a functional evaluation of coating performance in a precision mechanical device application. Results show that solid lubricant films with friction coefficients as low as 0.03 can be produced. A 0.03 friction coefficient is superior to solid lubricants with binder systems and is comparable to friction coefficients generated with more costly vacuum techniques.

The work involves research leading to an optically triggered switch for a high power laser pulse. The switch uses a semiconductor heterostructure whose optical properties are modified by a low power laser trigger such as a laser diode. Potential applications include optical control of pulsed power systems, control of medical lasers and implementation of security features in optical warhead architectures.

formulation to satisfy velocity boundary conditions for the vorticity form of the incompressible, viscous fluid momentum equations is presented. The tangential and normal components of the velocity boundary condition are satisfied simultaneously by creating vorticity adjacent to boundaries. The newly created vorticity is determined using a kinematical formulation which is a generalization of Helmholtz` decomposition of a vector field. Though it has not been generally recognized, these formulations resolve the over-specification issue associated with creating voracity to satisfy velocity boundary conditions. The generalized decomposition has not been widely used, apparently due to a lack of a useful physical interpretation. An analysis is presented which shows that the generalized decomposition has a relatively simple physical interpretation which facilitates its numerical implementation. The implementation of the generalized decomposition is discussed in detail. As an example the flow in a two-dimensional lid-driven cavity is simulated. The solution technique is based on a Lagrangian transport algorithm in the hydrocode ALEGRA. ALEGRA`s Lagrangian transport algorithm has been modified to solve the vorticity transport equation and the generalized decomposition, thus providing a new, accurate method to simulate incompressible flows. This numerical implementation and the new boundary condition formulation allow vorticity-based formulations to be used in a wider range of engineering problems.

A series of tests investigating dynamic pulse buckling of a cylindrical shell under axial impact is compared to several 2D and 3D finite element simulations of the event. The purpose of the work is to investigate the performance of various analysis codes and element types on a problem which is applicable to radioactive material transport packages, and ultimately to develop a benchmark problem to qualify finite element analysis codes for the transport package design industry. Four axial impact tests were performed on 4 in-diameter, 8 in-long, 304 L stainless steel cylinders with a 3/16 in wall thickness. The cylinders were struck by a 597 lb mass with an impact velocity ranging from 42.2 to 45.1 ft/sec. During the impact event, a buckle formed at each end of the cylinder, and one of the two buckles became unstable and collapsed. The instability occurred at the top of the cylinder in three tests and at the bottom in one test. Numerical simulations of the test were performed using the following codes and element types: PRONTO2D with axisymmetric four-node quadrilaterals; PRONTO3D with both four-node shells and eight-node hexahedrons; and ABAQUS/Explicit with axisymmetric two-node shells and four-node quadrilaterals, and 3D four-node shells and eight-node hexahedrons. All of the calculations are compared to the tests with respect to deformed shape and impact load history. As in the tests, the location of the instability is not consistent in all of the calculations. However, the calculations show good agreement with impact load measurements with the exception of an initial load spike which is proven to be the dynamic response of the load cell to the impact. Finally, the PRONIT02D calculation is compared to the tests with respect to strain and acceleration histories. Accelerometer data exhibited good qualitative agreement with the calculations. The strain comparisons show that measurements are very sensitive to gage placement.

EN-7, EN-8, and EN-9 are polyurethane systems that are used in numerous applications in the Department of Energy complex. These systems contain high levels of toluene diisocyanate (TDI). Currently, TDI is being treated as a suspect human carcinogen within the Department of Energy complex. This report documents the results of a material characterization study of three polyurethane systems that contain low levels of free (potentially airborne) TDI. The characterization has been accomplished by performing a set of statistically designed experiments. The purpose of these experiments is to explore the effects of formulation and cure schedule on various material properties. In general, the material properties (pot life, glass transition temperature, hardness, and tear strength) were relatively insensitive to variation in the cure schedule. On the other hand, variation in curative level had measurable effects on material properties for the polyurethane systems studied. Furthermore, the material properties of the three low-free-TDI polyurethane systems were found to be comparable or superior (for certain curative levels) to commonly-used polyurethane systems. Thus, these low-free-TDI systems appear to be viable candidates for applications where a polyurethane is needed.

A disposal planning process was established by the Department of Energy (DOE) Mixed Low-Level Waste (MLLW) Disposal Workgroup. The process, jointly developed with the States, includes three steps: site-screening, site-evaluation, and configuration study. As a result of the screening process, 28 sites have been eliminated from further consideration for MLLW disposal and 4 sites have been assigned a lower priority for evaluation. Currently 16 sites are being evaluated by the DOE for their potential strengths and weaknesses as MLLW disposal sites. The results of the evaluation will provide a general idea of the technical capability of the 16 disposal sites; the results can also be used to identify which treated MLLW streams can be disposed on-site and which should be disposed of off-site. The information will then serve as the basis for a disposal configuration study, which includes analysis of both technical as well as non-technical issues, that will lead to the ultimate decision on MLLW disposal site locations.

Infrared absorption spectra of borophosphosilicate glass (BPSG) thin films were collected to develop a rapid classification method for determining if the films are within the desired specifications. Classification of samples into good and bad categories was performed using principal component analysis applied to the spectra. Mahalanobis distances were used as the classification metric. The highest overall percentage of correct classification of samples based upon their spectra was 91.6%.

The interaction of cesium at the (0001) and (1{bar 1}02) surfaces of sapphire has been investigated using a variety of surface analytical techniques. Reflection mass spectrometric measurements yield initial Cs adsorption probabilities of 0.9 and 0.85 for the unreconstructed (0001) and (1{bar 1}02) surfaces, respectively. The adsorption probability decreases dramatically for these surfaces at critical Cs coverages of 2.O {times} 10{sup 14} and 3.4 {times} 10{sup 14} atoms/cm{sup 2}, respectively. Thermally induced reconstruction of the (0001) surface to form an oxygen deficient surface results in a decrease in the initial probability and capacity for Cs adsorption. Low energy electron diffraction (LEED) demonstrates that an intermediate, mixed domain surface yields an initial adsorption probability of 0.5 while a ({radical}31 {times} {radical}31) R {plus_minus} 9{degree} reconstructed surface yields a value of 0.27. Thermal desorption mass spectrometry (TDMS) shows that surface reconstruction eliminates the high binding energy states of Cs (2.7 eV/atom), consistent with the observed changes in adsorption probability. In contrast, reconstruction of the (1{bar 1}02) surface produces only minor changes in Cs adsorption. X-ray photoelectron spectroscopy (XPS) indicates that no formal reductive/oxidative chemistry takes place at the interface. We interpret the facile adsorption and strong binding of Cs on sapphire to result from Cs interacting with coordinatively unsaturated oxygen.