Publications

This report describes the results of experiments performed to determine the viability of titanium dioxide photocatalysis towards the treatment of water contaminated with different metal-EDTA complexes. Both the PB-EDTA and Ni-EDTA complexes were chosen for study, as they represent respectively metals that are and are not capable of photodeposition onto the TiO{sub 2} catalyst during the photoreaction. Batch reactions were carried out in a jacketed glass pot reactor using 300 ml of 50m g/l metal chelated with an equimolar amount of EDTA and 0.1wt% of TiO{sub 2} in the solution. The UV source used was a 100 W low-pressure Hg spot lamp. The two systems were studied using Degussa P-25 titanium dioxide, and Aldrich titanium dioxide loaded with Pt and Au. Around 80% removal of the Ni-EDTA complex was attained after 120 min using both catalysts with no photodeposition of Ni onto the catalyst. However, pH precipitation treatment of the reacted solutions indicated that the Ni was still complexed, probably to complexing agents that were EDTA oxidation products. Apparent zero-order kinetics was observed in the P-25 catalyst reaction, whereas apparent first-order kinetics was observed in the metal-loaded TiO{sub 2} catalyst. In contrast the Pb-EDTA complex was completely removed in 10 min using both catalysts. Also, complete Pb deposition onto the catalyst was attained in 30 min for both catalysts. The Pb deposition seemed to first require the degradation of the complex. Total organic carbon was reduced in the Ni-EDTA system 15--21% using both catalysts, and about 33% in the Pb-EDTA system using both catalysts. No reduction of either metal or metal complex was observed when no catalyst was present and the other conditions held constant.

Borehole-to-surface electromagnetic (EM) methods are an attractive alternative to Surface-based EM methods for a variety of environmental and engineering applications. They have improved sensitivity to the subsurface resistivity distribution because of the closer proximity to the area of interest offered by the borehole for the source or the receiver. For the borehole-to-surface measurements the source is in the borehole and the receivers are on the surface. On the other hand, for the surface-to-borehole methods, the source is on the surface and the receiver is in a borehole. The surface-to-borehole method has an added advantage since measurements are often more accurate due to the lower noise environment for the receiver. For these methods, the source can be a grounded electric dipole or a vertical magnetic dipole source. An added benefit of these techniques is field measurements are made using a variety of arrays where the system is tailored to the application and where one can take advantage of some new imaging methods. In this short paper the authors describe the application of the borehole-to-surface method, discuss benefits and shortcomings, and give two field examples where they have been used for underground imaging. The examples were the monitoring of a salt water flooding of an oil well and the characterization of a fuel oil spill.

The authors performed an X-ray diffraction study of tetrahedral-coordinated-amorphous carbon (a-tC) films prepared by pulsed laser deposition (PLD). Samples properties were analyzed as a function of laser energy and thickness. For all thicknesses and laser energies, films were made up of clusters with a basic unit size of 7 - 11 nm. Thicker films, as well as films prepared at higher laser densities exhibit larger clusters, in the tens of nanometers. The clusters are not readily observable by AFM, which may indicate the presence of a flat (graphitized) top film surface.

The structural evaluation test unit is roughly equivalent to a 1/3 scale model of a high level waste rail cask. The test unit was designed to just meet the requirements of NRC Regulatory Guide 7.6 when subjected to a 9 m (30 ft) free drop resulting in an impact velocity of 13.4 m/s (30 mph) onto an unyielding target in the end-on orientation. The test unit was then subjected to impacts with higher velocities to determine the amount of built-in conservatism in this design approach. Test impacts of 13.4, 20.1 and 26.8 m/s (30, 45, and 60 mph) were performed. This paper will describe the design, testing, and comparison of measured strains and deformations to the equivalent analytical predictions.

A Discrete element computer program named DMC (Distinct Motion Code) has been developed for modeling rock blasting. This program employs explicit time integration and uses spherical or cylindrical elements which are represented as circles in 2-D. DMC calculations have been compared with measurements on bench blasts in the field with relatively good comparison. Structural rock mass characteristics have a significant impact on any blast and DMC has not, until now, included these effects. This paper discusses a recently added DMC capability for treating joints and bedding planes in bench blast simulations. Material strength is treated in DMC by creating links between spheres to hold them together. The links can be broken based on any criterion; simple tension, compression and shear are currently employed. Joint sets are treated in DMC by defining the dip of each set toward or away from the bench face along with the joint spacing. Strength links that cross joint planes can have their strength properties modified or they can be deleted. Modification of the link patterns based on joint sets creates distinct blocks of spheres outlined by the intersecting joints. These blocks of spheres move together as a solid unit unless stress and strain conditions within the block indicate that links should be broken. Simulations using this capability show some blocks remaining intact throughout the blast and some being partially or completely broken. When this occurs, the joint pattern is shown to influence the characteristics of the blast. Upon completion of this capability both rock breakage and motion will be modeled during the same simulation. Much work remains to be done on this concept making this paper a progress report on the development of this new capability.

Hydrogen is found to readily diffuse into InGaN, InAlN and InGaAlN epitaxial layers during plasma exposures at 170-250{degree}C for 40 sec-30 min. The diffusivity of hydrogen is > 10{sup -11} cm{sup 2} {center_dot} s{sup -1} at 170{degree}C, and the native donor species are passivated by association with the hydrogen. Reactivation of these species occurs at 450-500{degree}C, but the hydrogen remains in the material until {ge} 800{degree}C.

Pb(Zr,Ti)O{sub 3} (PZT) thin films are being developed for use in optical and electronic memory devices. To study ferroelectric switching behavior, the authors have produced relatively untextured PZT thin films on Si substrates. They have developed a method for using X-ray diffraction to observe domain switching in situ. This study involved the use of a micro-diffractometer to monitor the switching behavior in relatively small (0.7 mm diameter) electroded areas. Diffraction analyses were done while DC voltages were applied and removed, representing several places in the hysteresis loop. In particular, the authors were looking for relative intensity changes in the [h00],[00l] diffraction peaks as a function of position in the hysteresis loop. This study indicates that the 90{degrees} domain switching exhibited by bulk ferroelectrics, is very limited in films on Si when grain sizes are less than about 1{mu}m.

Increasingly constrained budgets in the defense community, both DoD and DOE, have created a need to emphasize affordability in the development of future weapons systems and components. Increased use of commercially compatible components will play an important role, but there will always remain a need for specialized production, especially at the system level. We will present on-going work at Sandia National Laboratories (referred to from here as Sandia) aimed at insuring the affordability of low-volume, defence-specific systems.

The 6.4 MeV p({sup l5}N,{alpha}{gamma}){sup 12}C resonant nuclear reaction has been used to investigate the role of hydrogen as a contributing factor in the formation of stress-induced voids in very large scale integrated circuit metallizations. Hydrogen profiles were measured from a series of layered structures consisting of aluminum-copper alloy metallizations deposited on borophosphosilicate glass and capped with a variety of commercial passivation materials in order to examine differences in the concentrations and depth distributions of hydrogen within the layered structures.

Accident source terms, source term probabilities, consequences, and risks are developed for ship collisions that might occur in US ports during the shipment of spent fuel from foreign research reactors to the United States.

Increasing computational speed has led to the development and use of sophisticated numerical methods in radioactive material (RAM) transportation container design. The design of a RAM container often involves a complex coupling of structural, thermal, and radioactive shielding analyses. Sandia National Laboratories has integrated automatic mesh generation, explicit structural finite element analysis, transient thermal finite element analysis, and numerical optimization techniques into a unified RAM container design tool to increase the efficiency of both the design process and the resultant design through coupled analyses. Although development of this technique has progressed significantly, inaccurate numerical gradients due to design space nonsmoothness and excessive computational time have hampered successful implementation of numerical optimization as a ``black box`` design tool. This paper presents the details of analysis tool integration, simplified model development, constraint boundary nonsmoothness difficulties, and numerical optimization results for a lightweight composite-overpack Type B RAM package subject to dynamic crush and fuel fire accident condition constraints.

The possibility of a collision with the earth and need for detection of asteroids and comets is briefly discussed.

An historical look at software systems reveals a progression of thinking about protection and risk management. In this paper, three generations are defined. For each, we examine the prevalent views of risk, risk assessment, and risk mitigation. We also examine prevalent strategies for assurance. Many gaps exist in current knowledge of how to manage and assess risks in software systems. This paper presents a new perspective which enables comprehensive risk-based design and evaluation of systems, spanning a range of surety concerns (including correctness and safety, in addition to traditional security concerns), and addressing multiple system aspects. We believe this to be a new and unique multidisciplinary approach which transcends both traditional security approaches and traditional risk analysis methods. It facilitates a risk analysis completely tailored to the system at hand, instantiating its threats, its barriers, and its needs for risk reduction.

Etch rates for binary nitrides in ECR Cl{sub 2}/CH{sub 4}/H{sub 2}/Ar are reported as a function of temperature, rf-bias, microwave power, pressure and relative gas proportions. GaN etch rates remain relatively constant from 30 to 125{degrees}C and then increase to a maximum of 2340 {angstrom}-min{sup {minus}1} at 170{degrees}C. The AlN etch rate decreases throughout the temperature range studied with a maximum of 960 {angstrom}-min{sup {minus}1} at 30{degrees}C. When CH{sub 4} is removed from the plasma chemistry, the GaN and InN etch rates are slightly lower, with less dramatic changes with temperature. The surface composition of the III-V nitrides remains unchanged over the temperatures studied. The GaN and InN rates increase significantly with rf power, and the fastest rates for all three binaries are obtained at 2 mTorr. Surface morphology is smooth for GaN over a wide range of conditions, whereas InN surfaces are more sensitive to plasma parameters.

In a light-water reactor core melt accident, if the reactor pressure vessel (RPV) fails while the reactor coolant system (RCS) at high pressure, the expulsion of molten core debris may pressurize the reactor containment building (RCB) beyond its failure pressure. A failure in the bottom head of the RPV, followed by melt expulsion and blowdown of the RCS, will entrain molten core debris in the high-velocity steam blowdown gas. This chain of events is called a high-pressure melt ejection (HPME). Four mechanisms may cause a rapid increase in pressure and temperature in the reactor containment: (1) blowdown of the RCS, (2) efficient debris-to-gas heat transfer, (3) exothermic metal-steam and metal-oxygen reactions, and (4) hydrogen combustion. These processes, which lead to increased loads on the containment building, are collectively referred to as direct containment heating (DCH). It is necessary to understand factors that enhance or mitigate DCH because the pressure load imposed on the RCB may lead to early failure of the containment.

In this paper, a massively parallel implementation of the boundary element method to study particle transport in Stokes flow is discussed. The numerical algorithm couples the quasistatic Stokes equations for the fluid with kinematic and equilibrium equations for the particles. The formation and assembly of the discretized boundary element equations is based on the torus-wrap mapping as opposed to the more traditional row- or column-wrap mappings. The equation set is solved using a block Jacobi iteration method. Results are shown for an example application problem, which requires solving a dense system of 6240 equations more than 1200 times.

Poly (1, 4 bis(triethoxysilyl)benzene) (PTESB), a representative of a new type of organic-inorganic hybrid polysilsesquioxane material, was characterized by fluorescence spectroscopy for both microenvironmental polarity and solvent accessibility. A dansyl fluorescent molecule was incorporated into the bulk as well as onto the surface of both PTESB and silica materials. Information about the microenvironment polarity and accessibility of PTESB to various organic solvents was determined and compared to that of silica gel. This study found that both the bulk and surface of PTESB are less polar than that of the silica material. The silica material is accessible to polar solvents and water, while YMB is accessible to polar solvents but not to water. The hydrophobicity of PTESB differentiates these new materials from silica gel.

By developing an approximation to the first integral of the Poisson equation, one can obtain solutions for the voltage-current characteristics of a radio-frequency (rf) plasma sheath that are valid over the whole range of inertial response of the ions to an imposed rf voltage or current-specified conditions. The theory adequately reproduces the time-dependent voltage-current characteristics of the two extreme cases corresponding to the Lieberman rf sheath theory and the Metze-Ernie-Oskam theory. Contained within the approximation is a time constant which controls the amount of ion response to the rf electric field. A prescription is given for determining this ion relaxation time constant, which also determines the time-dependent ion impact energy on the electrode surface.

Organometallic and hydride compounds are widely used as precursors for the epitaxial growth of GaAs and other compound semiconductors. These precursors are most commonly used to perform organometallic vapor phase epitaxy (OMVPE) and also in related deposition techniques such as atomic layer epitaxy (ALE) and metalorganic molecular beam epitaxy (MOMBE). We have investigated the surface chemical properties of these precursors on GaAs(100) using a variety of surface science diagnostics. Results have shed light on the mechanisms of precursor decomposition which lead to film growth and carbon doping. For instance, kinetics of trimethylgallium (TMGa) decomposition on the Ga-rich and As-rich surfaces, measured by TPD, are in semiquantitative agreement with ALE results; indicating that the dominant growth mechanism during ALE is heterogeneous. Furthermore, there is no compelling evidence for the production of methane (CH{sub 4}) on the GaAs surface when TMGa and arsine (AsH{sub 3}) are coadsorbed.

This paper describes a new optical interconnect architecture and the integrated optoelectronic circuit technology for implementing a parallel, reconfigurable, multiprocessor network. The technology consists of monolithic array`s of optoelectronic switches that integrate vertical-cavity surface-emitting lasers with three-terminal heterojunction phototransistors, which effectively combined the functions of an optical transceiver and an optical spatial routing switch. These switches have demonstrated optical switching at 200 Mb/s, and electrical-to-optical data conversion at > 500 Mb/s, with a small-signal electrical-to-optical modulation bandwidth of {approximately} 4 GHz.

Bimodal space reactor systems provide both thermal propulsion for the spacecraft orbital transfer and electrical power to the spacecraft bus once it is on station. These systems have the potential to increase both the available payload in high energy orbits and the available power to that payload. These increased mass and power capabilities can be used to either reduce mission cost by permitting the use of smaller launch vehicles or to provide increased mission performance from the current launch vehicle. A major barrier to the deployment of these bimodal systems has been the cost associated with their development. This paper describes a bimodal reactor system with performance potential to permit more than 70% of the instrumented payload of the Titan IV/Centaur to be launched from the Atlas IIAS. The development cost is minimized by basing the design on existing component technologies.

Sandia Laboratories has developed a thin film diamond substrate technology to meet the requirements for high power and high density circuits. Processes were developed to metallize, photopattern, laser process, and, package diamond thin film networks which were later assembled into high power multichip modules (MCMS) to test for effectiveness at removing heat. Diamond clearly demonstrated improvement in heat transfer during 20 Watt, strip heating experiments with junction-to-ambient temperature increases of less than 24 C compared to 126 C and 265 C for the aluminum nitride and ceramic versions, respectively.

Accurate finite-element simulation of 3-D nonlinear heat transfer in complex systems may require meshes composed of tens of thousands of finite elements and hours of CPU time on today`s fastest computers. To treat applications in which thousands of calculations may be necessary such as for risk assessment or design of high-temperature manufacturing processes, methods are needed which can solve these problems far more efficiently and maintain an acceptably high degree of accuracy. For this purpose, we developed the Thermal Evaluation and Matching Program for Risk Applications (TEMPRA). The primary differentiator between TEMPRA and comparable codes is its numerical formulation, which is designed to be unconditionally stable even with very large time steps, to afford good accuracy even with relatively coarse meshing, and to facilitate benchmarking/calibration through the use of adjustable parameters. Analysis for a sample problem shows that TEMPRA can obtain temperature response solutions with errors of less than 10% using approximately 1/1000 of the computer time required by a typical finite element code.

Prosperity Games are an outgrowth and adaptation of move/countermove and seminar War Games. Prosperity Games are simulations that explore complex issues in a variety of areas including economics, politics, sociology, environment, education and research. These issues can be examined from a variety of perspectives ranging from a global, macroeconomic and geopolitical viewpoint down to the details of customer/supplier/market interactions in specific industries. All Prosperity Games are unique in that both the game format and the player contributions vary from game to game. This report documents the Prosperity Game conducted under the sponsorship of the Electronics Subcommittee of the Civilian Industrial Technology Committee (under the National Science and Technology Council), and the Electronics Partnership Project. Players were drawn from the electronics industry, from government, national laboratories, and universities, and from Japan and Austria. The primary objectives of this game were: To connect the technical and non-technical (i.e., policy) issues that were developed in the roadmap-making endeavor of the National Electronics Manufacturing Initiative (NENI);to provide energy, enthusiasm and people to help the roadmap succeed; and to provide insight into high-leverage public and private investments. The deliberations and recommendations of these teams provide valuable insights as to the views of this diverse group of decision makers concerning policy changes, foreign competition, the robustness of strategic thinking and planning, and the development, delivery and commercialization of new technologies.

The transmission of mechanical power is often accomplished through the use of gearing. The recently developed surface micromachined microengine provides us with an actuator which is suitable for driving surface micromachined geared systems. In this paper we will present aspects of the microengine as they relate to the driving of geared mechanisms, issues relating to the design of micro gear mechanisms, and details of a design of a microengine-driven geared shutter mechanism.