A new approach to the fabrication of porous, amorphous inorganic membranes using organic pore templates was investigated. The pore templates were a new family of hybrid organic-inorganic monomers. As background for membrane work, the monomers were polymerized by sol-gel techniques to make crosslinked polymers. Molecular modeling was used to create computer simulations of the materials and provide insight into their composites, were then converted into porous silicas using low temperature oxygen plasma techniques. A select few of the monomers were copolymerized with silica monomers to form non-porous thin films on mesoporous substrates. The films were converted into porous silica thin films with thermal oxidations and the resulting membranes were tested for gas selectivities and flux.
Sandia National Laboratories is developing a system that uses robots to package pits at Pantex in the AT-400A pit storage and transportation container. This report will give an overview of the AT-400A packaging process, and the parts of the overall AT-400A packaging operation that will be performed robotically. The process employed to move from development in the laboratory at Sandia to production use at Pantex will be described. Finally, important technology components being developed for and incorporated into the robotic system will be described. 7 refs., 9 figs.
In 1973 Mr. W. Athey of the Environmental Protection Agency wrote a computer program called SECPOP which calculated population estimates. Since that time, two things have changed which suggested the need for updating the original program - more recent population censuses and the widespread use of personal computers (PCs). The revised computer program uses the 1990 and 1992 Population Census information and runs on current PCs as {open_quotes}SECPOP90.{close_quotes} SECPOP90 consists of two parts: site and regional. The site provides population and economic data estimates for any location within the continental United States. Siting analysis is relatively fast running. The regional portion assesses site availability for different siting policy decisions; i.e., the impact of available sites given specific population density criteria within the continental United States. Regional analysis is slow. This report compares the SECPOP90 population estimates and the nuclear power reactor licensee-provided information. Although the source, and therefore the accuracy, of the licensee information is unknown, this comparison suggests SECPOP90 makes reasonable estimates. Given the total uncertainty in any current calculation of severe accidents, including the potential offsite consequences, the uncertainty within SECPOP90 population estimates is expected to be insignificant. 12 refs., 55 figs., 7 tabs.
Experimental results are presented for bulk and mechanical properties measurements on specimens of the Paintbrush tuff recovered from the USW NRG-6 and USW NRG-7/7A borehole at Yucca Mountain, Nevada. Measurements have been performed on five thermal/mechanical units: TCw, PTn, TSw2, and TSw3. The following bulk properties are reported for each specimen: dry bulk density, saturated bulk density, average grain density and porosity. Confined compression to failure tests were performed on selected specimens recovered from the boreholes at confining pressures of 5 and 10 MPa. In addition, compressional and shear wave velocities were measured on the specimens prior to testing. Measurements were conducted under drained conditions at room temperature on nominally water saturated specimens. The nominal strain rate for the experiments was 10{sup -5} s{sup -1}.
The major results from SNL`s Conceptual Model Development and Validation Task (WBS 1.2.5.4.6) as developed through exploration of small scale processes were synthesized in Glass et al. to give guidance to Performance Assessment on improving conceptual models for isothermal flow in unsaturated, fractured rock. There, pressure saturation and relative permeability curves for single fractures were proposed to be a function of both fracture orientation within the gravity field and initial conditions. We refer the reader to Glass et al. for a discussion of the implications of this behavior for Performance Assessment. The scientific research we report here substantiates this proposed behavior. We address the modeling of phase structure within fractures under natural gradient conditions relevant to unsaturated flow through fractures. This phase structure underlies the calculation of effective properties for individual fractures and hence fracture networks as required for Performance Assessment. Standard Percolation (SP) and Invasion Percolation (IP) approaches have been recently proposed to model the underlying phase saturation structures within the individual fractures during conditions of two-phase flow. Subsequent analysis of these structures yields effective two-phase pressure-saturation and relative permeability relations for the fracture. However, both of these approaches yield structures that are at odds with physical reality as we see in experiments and thus effective properties calculated from these structures are in error. Here we develop and evaluate a Modified Invasion Percolation (MIP) approach to better model quasi-static immiscible displacement in fractures. The effects of gravity, contact angle, local aperature field geometry, and local in-plane interfacial curvature between phases are included in the calculation of invasion pressure for individual sites in a discretized aperture field.
The purpose of this laboratory-directed research and development (LDRD) project was to develop and assess novel low-permittivity dielectric materials for applications as interlevel dielectrics (ILDs) in Si-based microelectronics. There were three classes of materials investigated: (1) novel covalently-bonded ceramics containing carbon, boron, and/or nitrogen, (2) fluorinated SiO{sub 2} (SiOF), and (3) plasma polymerized fluorocarbon (PPFC). The specific advantages and disadvantages for each potential low k ILD material were evaluated. It was discovered that highly energetic deposition processes are required for the formation of thermally and environmentally stable carbon or boron nitride ceramics, and the resulting films may have many potentially valuable applications, such as diffusion barriers, tribological coatings, micro-sensor materials, etc. The films are not suitable as low k ILDs, however, because the highly energetic deposition process leads to films with high atomic density, and this leads to high dielectric constants. SiOF shows a promise as low k ILD material for near-term applications, but special passivation or encapsulation strategies may be required in order to reduce two instability problems that the authors have discovered: moisture absorption and thermal instability of the SiOF/Al interface. PPFC films offer promise for even lower dielectric constant ILDs than SiOF, but it will be necessary to develop new strategies to passivate the free radicals in the films generated during deposition. These free radicals lead to increase in dielectric loss over time when the films are exposed to room ambient conditions.
The Virtual Collaborative Environment (VCE) and Distributed Collaborative Workbench (DCW) are new technologies that make it possible for diverse users to synthesize and share mechatronic, sensor, and information resources. Using these technologies, university researchers, manufacturers, design firms, and others can directly access and reconfigure systems located throughout the world. The architecture for implementing VCE and DCW has been developed based on the proposed National Information Infrastructure or Information Highway and a tool kit of Sandia-developed software. Further enhancements to the VCE and DCW technologies will facilitate access to other mechatronic resources. This report describes characteristics of VCE and DCW and also includes background information about the evolution of these technologies.
The authors developed and implemented a highly parallel computational algorithm for solution of the inverse scattering problem generated when an integrated circuit is illuminated by laser. The method was used as part of a system to measure diffraction grating line widths on specially fabricated test wafers and the results of the computational analysis were compared with more traditional line-width measurement techniques. The authors found they were able to measure the line width of singly periodic and doubly periodic diffraction gratings (i.e. 2D and 3D gratings respectively) with accuracy comparable to the best available experimental techniques. They demonstrated that their parallel code is highly scalable, achieving a scaled parallel efficiency of 90% or more on typical problems running on 1024 processors. They also made substantial improvements to the algorithmics and their original implementation of Rigorous Coupled Waveform Analysis, the underlying computational technique. These resulted in computational speed-ups of two orders of magnitude in some test problems. By combining these algorithmic improvements with parallelism the authors achieve speedups of between a few thousand and hundreds of thousands over the original engineering code. This made the laser diffraction measurement technique practical.
This report presents a microsimulation model of a transition economy. Transition is defined as the process of moving from a state-enterprise economy to a market economy. The emphasis is on growing a market economy starting from basic microprinciples. The model described in this report extends and modifies the capabilities of Aspen, a new agent-based model that is being developed at Sandia National Laboratories on a massively parallel Paragon computer. Aspen is significantly different from traditional models of the economy. Aspen`s emphasis on disequilibrium growth paths, its analysis based on evolution and emergent behavior rather than on a mechanistic view of society, and its use of learning algorithms to simulate the behavior of some agents rather than an assumption of perfect rationality make this model well-suited for analyzing economic variables of interest from transition economies. Preliminary results from several runs of the model are included.
A Monte Carlo algorithm is used to determine the apparent spatial blurring of a terrestrial 1.07 micron optical point source due to cloud scattering as seen from space. The virtual image of a point source over a virtual source plane area 22.4 x 22.4 square kilometers arising from cloud scattering was determined for stratus clouds (NASA cloud number 5) and altostratus clouds optical source arises from photon scattering by cloud water droplets. Displacement of the virtual source is due to the apparent illumination of the cloud top region directly about the actual source which when viewed at a nonzero look angle gives a projected displacement of the apparent source relative to the actual source. These features are quantified by an analysis of the Monte Carlo computational results.
Unlike silicon microelectronics, photonics packaging has proven to be low yield and expensive. One approach to make photonics packaging practical for low cost applications is the use of {open_quotes}smart{close_quotes} packages. {open_quotes}Smart{close_quotes} in this context means the ability of the package to actuate a mechanical change based on either a measurement taken by the package itself or by an input signal based on an external measurement. One avenue of smart photonics packaging, the use of polysilicon micromechanical devices integrated with photonic waveguides, was investigated in this research (LDRD 3505.340). The integration of optical components with polysilicon surface micromechanical actuation mechanisms shows significant promise for signal switching, fiber alignment, and optical sensing applications. The optical and stress properties of the oxides and nitrides considered for optical waveguides and how they are integrated with micromechanical devices were investigated.
This report describes the design features of series connected photovoltaic arrays which will be required to charge capacitors to relatively high (400V) voltages in time periods on the order of 1 microsecond. The factors which determine the array voltage and the capacitor charge time are given. Individual element junction designs, along with an interconnect scheme, and a semiconductor process to realize them are presented. Finally, the input laser optical required to meet the requirements is determined.
The response of a variety of sucker rod couplings to an applied axial load was simulated using axisymmetric finite element models. The calculations investigated three sucker rod sizes and various combinations of the slimhole, Spiralock, and Flexbar modifications to the coupling. In addition, the effect of various make-ups (assembly tightness) on the performance of coupling was investigated. An axial load was applied to the sucker rod ranging from {minus}5 ksi to 40 ksi, encompassing three load cycles identified on a modified Goodman diagram as acceptable for indefinite service life of the sucker rods. The simulations of the various coupling geometries and make-ups were evaluated with respect to how well they accomplish the two primary objectives of preloading threaded couplings: (1) to lock the threaded coupling together so that it will not loosen and eventually uncouple, and (2) to improve the fatigue resistance of the threaded connection by reducing the stress amplitude in the coupling when subjected to cyclic loading. Perhaps the most significant finding in this study was the characterization of the coupling parameters which affect two stress measures. The mean hydrostatic stress, which determines the permissible effective alternating stress, is a function of the coupling make-up. Whereas, the alternating effective stress is a function of the relative stiffnesses of the pin and box sections of the coupling and, as long as the coupling does not separate, is unaffected by the amount of circumferential displacement applied during make-up. The results of this study suggest approaches for improving the fatigue resistance of sucker rod couplings.
Experimental results are presented for 24 thermal expansion experiments performed on 5 welded specimens of the Paintbrush tuff recovered from borehole USW SD-12 at Yucca Mountain, Nevada. The thermal expansion experiments were performed at constant confining pressures between 1 and 30 MPa. On three specimens, the highest confining pressure measurements were performed first to inhibit thermally induced damage which might occur at lower confining pressures. At each confining pressure two complete thermal cycles were performed. The specimens were heated (to a nominal temperature of 250 C) and cooled at the nominal rate of 0.319 C per minute. The change in specimen length as a function of temperature was measured with two linear variable displacement transducers mounted on endcaps secured to the specimen. The strain increases with increasing temperature and the strain vs temperature curves are concave upward. On cooling, there is hysteresis at the higher temperatures at all confining pressures. The first heating/cooling cycle is anomalous; hysteresis is pronounced, and a permanent shortening of the specimen is observed at the termination of the cycle. The magnitude of the effect was similar for all five specimens regardless of whether the first cycle was carried out at the highest or lowest confining pressure. For subsequent cycles at all confining pressures, no permanent strain develops, and the strain versus temperature curves re very similar. The mean coefficients of thermal expansion ({alpha}) range from 7.9 to 10.8{sup {minus}6} C{sup {minus}1} at temperatures below 100 C, to 14.2 to 20.6 x 10{sup {minus}6} C{sup {minus}1} at temperatures approaching 250 C. The effect of confining pressure on thermal expansion is small. For temperatures above 175 C, the mean coefficients of thermal expansion decreases by 10--12% as the pressure increases from 1 to 30 MPa.
Shipboard fires both in the same ship hold and in an adjacent hold aboard a break-bulk cargo ship are simulated with a commercial finite-volume computational fluid mechanics code. The fire models and modeling techniques are described and discussed. Temperatures and heat fluxes to a simulated materials package are calculated and compared to experimental values. The overall accuracy of the calculations is assessed.
This report documents a preliminary evaluation of the ability of the greater confinement disposal boreholes at the Nevada Test Site to provide long-term isolation of radionuclides from the disposal of vitrified byproduct material. The byproduct material is essentially concentrated residue from processing uranium ore that contains a complex mixture of radionuclides, many of which are long-lived and present in concentrations greater than 100,000 picoCuries per gram. This material has been stored in three silos at the fernald Environmental Management Project since the early 1950s and will be vitrified into 6,000 yd{sup 3} (4,580 m{sup 3}) of glass gems prior to disposal. This report documents Sandia National Laboratories` preliminary evaluation for disposal of the byproduct material and includes: the selection of quantitative performance objectives; a conceptual model of the disposal system and the waste; results of the modeling; identified issues, and activities necessary to complete a full performance assessment.
The Alternative Landfill Cover Demonstration is a large scale field test that compares the performance of various landfill cover designs in dry environments. An important component of the comparison is the change in the moisture content of the soils throughout the different cover test plots. Time Domain Reflectometry (TDR) is the primary method for the measurement of the volumetric moisture content. Each of the covers is composed of layers of varying types and densities of soils. The probes are therefore calibrated to calculate the volumetric moisture content in each of the different soils in order to gain the optimum performance of the TDR system. The demonstration plots are constructed in two phases; a different probe is used in each phase. The probe that is used in Phase 1 is calibrated for the following soils: compacted native soil, uncompacted native soil, compacted native soil mixed with 6% sodium bentonite by weight, and sand. The probe that is used in Phase 2 is calibrated for the following soils: compacted native soil, uncompacted native soil, and sand. In addition, the probes are calibrated for the varying cable lengths of the TDR probes. The resulting empirically derived equations allow for the calculation of in-situ volumetric moisture content of all of the varying soils throughout the cover test plots in the demonstration.
The state-of-the-art in Lagrangian methods for the grid-free simulation of three-dimensional, incompressible, high Reynolds number, internal and/or external flows is surveyed. Specifically, vortex and velicity (or impulse) element methods are introduced. The relative merits of various available techniques and the outstanding challenges in simulating the processes of convection and diffusion, as well as in satisfying the wall boundary conditions are discussed individually. Issues regarding the stretch and solenoidality of vorticity are also discussed. A potentially successful algorithm for simulating the flow around a parachute is proposed as well.
A methodology for the evaluation of complex electromagnetics problems is presented. The methodology reduces the computational requirements for the analysis of large scale computational electromagnetics problems by hybridizing the method of moments and physical optics techniques. The target model is based on triangular facets and the incident field source by its system response function. Data which can be obtained from the analysis are radar cross section, power spectral density, and range profiles.
Surface-micromachined silicon inertial sensors are limited to relatively high-G applications in part because of the fundamental limitations on proof mass imposed by the manufacturing technology. At the same time, traditional micromolding technologies such as LIGA do not lend themselves to integration with electronics, a capability which is equally necessary for high-performance inertial sensors. The silicon micromolding processes described in this report promise to offer both larger proof masses and integrability with on-chip electronics. In Sandia`s silicon micromolding process, the proof mass is formed using a mold which is first recessed into the substrate using a deep silicon trench etch, then lined with a sacrificial or etch-stop layer, and filled with mechanical polysilicon. Since the mold is recessed into the substrate, the whole micromechanical structure can be formed, planarized, and integrated with standard silicon microelectronic circuits before the release etch. In addition, unlike surface-micromachined parts, the thickness of the molded parts is limited by the depth of the trench etch (typically 10--50 {micro}m) rather than the thickness of deposited polysilicon (typically 2 {micro}m). The fact that the high-aspect-ratio section of the device is embedded in the substrate enables the monolithic integration of high-aspect-ratio parts with surface-micromachined mechanical parts, and, in the future, also electronics. The authors anticipate that such an integrated mold/surface micromachining/electronics process will offer versatile high-aspect-ratio micromachined structures that can be batch-fabricated and monolithically integrated into complex microelectromechanical systems including high-performance inertial sensing systems.
Discharge capacitors were designed based on materials with antiferroelectric (AFE) to ferroelectric (FE) field enforced transitions that had 10 times the capacitance of relaxor ferroelectric or state of the art BaTiO{sub 3} materials in the voltage range of interest. Nonlinear RLC circuit analysis was used to show that the AFE to FE materials have potentially more than 2 times the peak discharge current density capability of the BaTiO{sub 3} or lead magnesium niobate (PMN) based relaxor materials. Both lead lanthanum zirconium tin titanate (PLZST) AFE to FE field enforced phase transition materials and PMN based relaxor materials were fabricated and characterized for Sandia`s pulse discharge capacitor applications. An outstanding feature of the PLZST materials is that there are high field regimes where the dielectric constant increases substantially, by a factor of 20 or more, with applied field. Specifically, these materials have a low field dielectric constant of 1,000, but an effective dielectric constant of 23,000 in the electric field range corresponding to the FE to AFE transition during discharge. Lead magnesium niobate (PMN) based relaxor materials were also investigated in this project because of their high dielectric constants. While the PMN based ceramics had a low field dielectric constant of 25,000, at a field corresponding to half the charging voltage, approximately 13 kV/cm, the dielectric constant decreases to approximately 7,500.
The flow behavior of liquid metals at solid interfaces is critically important to successful welding, brazing, soldering and the synthesis of metal/ceramic composites. Continuum flow models frequently fail to reliably predict wetting behavior because they are based upon bulk fluid properties, rather than microscopic flow processes at the actual solid/liquid interface. Improved understanding of interfacial liquid flow is hindered by the paucity of experimental measurements at this microscopic level. This report describes a new approach, Acoustic Wave Damping (AWD), to measuring viscoelastic properties of liquid metal layers in the nanometer thickness regime. The AWD experiment measures the frequency response of a quartz crystal microbalance in contact with a viscoelastic layer. An equivalent circuit model and continuum acoustic theory relate this electrical response to mechanical energy storage and dissipative loss. For viscoelastic layers of known thickness and density, a quantitative complex shear modulus can be determined from the AWD data. Studies of self-assembled monolayers (SAMs) demonstrate sensitivity to monolayer structure and bonding. Molecular dynamics simulations relate these atomistic properties to the ensemble response. AWD measurements of ultra-thin liquid indium layers reveal metastable undercooling for 10--50 nm thick indium layers. Continued refinement of the AWD technique and the addition of complementary interface characterization techniques will enable definitive studies of ultra-thin molten metals.
The on-site inspection provisions in many current and proposed arms control agreements require extensive preparation and training on the part of both the Inspection Teams (inspectors) and Inspected Parties (host). Current training techniques include table-top inspections and practice inspections. The Augmented Computer Exercise for Inspection Training (ACE-IT), an interactive computer training tool, increases the utility of table-top inspections. ACE-IT has been designed to provide training for challenge inspections under the Chemical Weapons Convention (CWC); however, this training tool can be modified for other inspection regimes. Although ACE-IT provides training from notification of an inspection through post-inspection activities, the primary emphasis of ACE-IT is in the inspection itself--particularly with the concept of managed access. ACE-IT also demonstrates how inspection provisions impact compliance determination and the protection of sensitive information. This User`s Guide describes the use of the ACE-IT training software.
The on-site inspection provisions in many current and proposed arms control agreements require extensive preparation and training on the part of both the Inspection Teams (inspectors) and Inspected Parties (host). Current training techniques include table-top inspections and practice inspections. The Augmented Computer Exercise for Inspection Training (ACE-IT), an interactive computer training tool, increases the utility of table-top inspections. ACE-IT has been designed to provide training for challenge inspections under the Chemical Weapons Convention (CWC); however, this training tool can be modified for other inspection regimes. Although ACE-IT provides training from notification of an inspection through post-inspection activities, the primary emphasis of ACE-IT is in the inspection itself--particularly with the concept of managed access. ACE-IT also demonstrates how inspection provisions impact compliance determination and the protection of sensitive information. This Technical Manual describes many of the technical aspects of the ACE-IT training software.
The on-site inspection provisions in many current and proposed arms control agreements require extensive preparation and training on the part of both the Inspected Party and the Inspection Team. Current training techniques include table-top inspections and practice inspections. The Augmented Computer Exercise for Inspection Training (ACE-IT), an interactive computer training tool, increases the utility of table-top inspections. ACE-IT has been designed to provide training for a hypothetical challenge inspection under the Chemical Weapons Convention (CWC); however, this training tool can be modified for other inspection regimes. Although ACE-IT provides training from notification of an inspection through post-inspection activities, the primary emphasis of ACE-IT is in the inspection itself--particularly with the concept of managed access. ACE-IT also demonstrates how inspection provisions impact compliance determination and the protection of sensitive information. The Exercise Manual supplements the ACE-IT software by providing general information on on-site inspections and detailed information for the CWC challenge inspection exercise. The detailed information includes the pre-inspection briefing, maps, list of sensitive items, medical records, and shipping records.