Biomass feedstocks contain roughly 15-30% lignin, a substance that can not be converted to fermentable sugars. Hence, most schemes for producing biofuels assume that the lignin coproduct will be utilized as boiler fuel. Yet, the chemical structure of lignin suggests that it will make an excellent high value fuel additive, if it can be broken down into smaller compounds. From Fiscal year 1997 through Fiscal year 2001, Sandia National Laboratories participated in a cooperative effort with the National Renewable Energy Laboratory and the University of Utah to develop and scale a base catalyzed depolymerization (BCD) process for lignin conversion. SNL's primary role in the effort was to perform kinetic studies, examine the reaction chemistry, and to develop alternate BCD catalyst systems. This report summarizes the work performed at Sandia during Fiscal Year 1999 through Fiscal Year 2001 with aqueous systems. Work with alcohol based systems is summarized in part 1 of this report. Our study of lignin depolymerization by aqueous NaOH showed that the primary factor governing the extent of lignin conversion is the NaOH:lignin ratio. NaOH concentration is at best a secondary issue. The maximum lignin conversion is achieved at NaOH:lignin mole ratios of 1.5-2. This is consistent with acidic compounds in the depolymerized lignin neutralizing the base catalyst. The addition of CaO to NaOH improves the reaction kinetics, but not the degree of lignin conversion. The combination of Na{sub 2}CO{sub 3} and CaO offers a cost saving alternative to NaOH that performs identically to NaOH on a per Na basis. A process where CaO is regenerated from CaCO{sub 3} could offer further advantages, as could recovering the Na as Na{sub 2}CO{sub 3} or NaHCO{sub 3} by neutralization of the product solution with CO2. Model compound studies show that two types of reactions involving methoxy substituents on the aromatic ring occur: methyl group migration between phenolic groups (making and breaking ether bonds) and the loss of methyl/methoxy groups from the aromatic ring (destruction of ether linkages). The migration reactions are significantly faster than the demethylation reactions, but ultimately demethylation processes predominates.
Islanding, the supply of energy to a disconnected portion of the grid, is a phenomenon that could result in personnel hazard, interfere with reclosure, or damage hardware. Considerable effort has been expended on the development of IEEE 929, a document that defines unacceptable islanding and a method for evaluating energy sources. The worst expected loads for an islanded inverter are defined in IEEE 929 as being composed of passive resistance, inductance, and capacitance. However, a controversy continues concerning the possibility that a capacitively compensated, single-phase induction motor with a very lightly damped mechanical load having a large rotational inertia would be a significantly more difficult load to shed during an island. This report documents the result of a study that shows such a motor is not a more severe case, simply a special case of the RLC network.
We discuss application of the FETI-DP linear solver within the Salinas finite element application. An overview of Salinas and of the FETI-DP solver is presented. We discuss scalability of the software on ASCI-red, Cplant and ASCI-white. Options for solution of the coarse grid problem that results from the FETI problem are evaluated. The finite element software and solver are seen to be numerically and cpu scalable on each of these platforms. In addition, the software is very robust and can be used on a large variety of finite element models.
The magnetically excited flexural plate wave (mag-FPW) device has great promise as a versatile sensor platform. FPW's can have better sensitivity at lower operating frequencies than surface acoustic wave (SAW) devices. Lower operating frequency (< 1 MHz for the FPW versus several hundred MHz to a few GHz for the SAW device) simplifies the control electronics and makes integration of sensor with electronics easier. Magnetic rather than piezoelectric excitation of the FPW greatly simplifies the device structure and processing by eliminating the need for piezoelectric thin films, also simplifying integration issues. The versatile mag-FPW resonator structure can potentially be configured to fulfill a number of critical functions in an autonomous sensored system. As a physical sensor, the device can be extremely sensitive to temperature, fluid flow, strain, acceleration and vibration. By coating the membrane with self-assembled monolayers (SAMs), or polymer films with selective absorption properties (originally developed for SAW sensors), the mass sensitivity of the FPW allows it to be used as biological or chemical sensors. Yet another critical need in autonomous sensor systems is the ability to pump fluid. FPW structures can be configured as micro-pumps. This report describes work done to develop mag-FPW devices as physical, chemical, and acoustic sensors, and as micro-pumps for both liquid and gas-phase analytes to enable new integrated sensing platform.
This report describes the results of the FY01 Level 1 Peer Reviews for the Verification and Validation (V&V) Program at Sandia National Laboratories. V&V peer review at Sandia is intended to assess the ASCI (Accelerated Strategic Computing Initiative) code team V&V planning process and execution. The Level 1 Peer Review process is conducted in accordance with the process defined in SAND2000-3099. V&V Plans are developed in accordance with the guidelines defined in SAND2000-3 101. The peer review process and process for improving the Guidelines are necessarily synchronized and form parts of a larger quality improvement process supporting the ASCI V&V program at Sandia. During FY00 a prototype of the process was conducted for two code teams and their V&V Plans and the process and guidelines updated based on the prototype. In FY01, Level 1 Peer Reviews were conducted on an additional eleven code teams and their respective V&V Plans. This report summarizes the results from those peer reviews, including recommendations from the panels that conducted the reviews.
The Controlatron Software Suite is a custom built application to perform automated testing of Controlatron neutron tubes. The software package was designed to allowing users to design tests and to run a series of test suites on a tube. The data is output to ASCII files of a pre-defined format for data analysis and viewing with the Controlatron Data Viewer Application. This manual discusses the operation of the Controlatron Test Suite Software and a brief discussion of state machine theory, as state machine is the functional basis of the software.
Electrical connectors corrode. Even our best SA and MC connectors finished with 50 to 100 microinches of gold over 50 to 100 microinches of nickel corrode. This work started because some, but not all, lots of connectors held in KC stores for a decade had been destroyed by pore corrosion (chemical corrosion). We have identified a MIL-L-87177 lubricant that absolutely stops chemical corrosion on SA connectors, even in the most severe environments. For commercial connectors which typically have thinner plating thicknesses, not only does the lubricant significantly retard effects of chemical corrosion, but also it greatly prolongs the fretting life. This report highlights the initial development history and use of the lubricant at Bell Labs and AT&T, and the Battelle studies and the USAF experience that lead to its deployment to stop dangerous connector corrosion on the F-16. We report the Sandia, HFM&T and Battelle development work, connector qualification, and material compatibility studies that demonstrate its usefulness and safety on JTA and WR systems. We will be applying MIL-L-87177 Connector Lubricant to all new connectors that go into KC stores. We recommend that it be applied to connectors on newly built cables and equipment as well as material that recycles through manufacturing locations from the field.
This document summarizes research of reactively deposited metal hydride thin films and their properties. Reactive deposition processes are of interest, because desired stoichiometric phases are created in a one-step process. In general, this allows for better control of film stress compared with two-step processes that react hydrogen with pre-deposited metal films. Films grown by reactive methods potentially have improved mechanical integrity, performance and aging characteristics. The two reactive deposition techniques described in this report are reactive sputter deposition and reactive deposition involving electron-beam evaporation. Erbium hydride thin films are the main focus of this work. ErH{sub x} films are grown by ion beam sputtering erbium in the presence of hydrogen. Substrates include a Al{sub 2}O{sub 3} {l_brace}0001{r_brace}, a Al{sub 2}O{sub 3} {l_brace}1120{r_brace}, Si{l_brace}001{r_brace} having a native oxide, and polycrystalline molybdenum substrates. Scandium dideuteride films are also studied. ScD{sub x} is grown by evaporating scandium in the presence of molecular deuterium. Substrates used for scandium deuteride growth include single crystal sapphire and molybdenum-alumina cermet. Ultra-high vacuum methods are employed in all experiments to ensure the growth of high purity films, because both erbium and scandium have a strong affinity for oxygen. Film microstructure, phase, composition and stress are evaluated using a number of thin film and surface analytical techniques. In particular, we present evidence for a new erbium hydride phase, cubic erbium trihydride. This phase develops in films having a large in-plane compressive stress independent of substrate material. Erbium hydride thin films form with a strong <111> out-of-plane texture on all substrate materials. A moderate in-plane texture is also found; this crystallographic alignment forms as a result of the substrate/target geometry and not epitaxy. Multi-beam optical sensors (MOSS) are used for in-situ analysis of erbium hydride and scandium hydride film stress. These instruments probe the evolution of film stress during all stages of deposition and cooldown. Erbium hydride thin film stress is investigated for different growth conditions including temperature and sputter gas, and properties such as thermal expansion coefficient are measured. The in-situ stress measurement technique is further developed to make it suitable for manufacturing systems. New features added to this technique include the ability to monitor multiple substrates during a single deposition and a rapidly switched, tiltable mirror that accounts for small differences in sample alignment on a platen.
The transboundary nature of water resources demands a transboundary approach to their monitoring and management. However, transboundary water projects raise a challenging set of problems related to communication issues, and standardization of sampling, analysis and data management methods. This manual addresses those challenges and provides the information and guidance needed to perform the Navruz Project, a cooperative, transboundary, river monitoring project involving rivers and institutions in Kazakhstan, Kyrgyzstan, Tajikistan, and Uzbekistan facilitated by Sandia National Laboratories in the U.S. The Navruz Project focuses on waterborne radionuclides and metals because of their importance to public health and nuclear materials proliferation concerns in the region. This manual provides guidelines for participants on sample and data collection, field equipment operations and procedures, sample handling, laboratory analysis, and data management. Also included are descriptions of rivers, sampling sites and parameters on which data are collected. Data obtained in this project are shared among all participating countries and the public through an internet web site, and are available for use in further studies and in regional transboundary water resource management efforts. Overall, the project addresses three main goals: to help increase capabilities in Central Asian nations for sustainable water resources management; to provide a scientific basis for supporting nuclear transparency and non-proliferation in the region; and to help reduce the threat of conflict in Central Asia over water resources, proliferation concerns, or other factors.
A suite of laboratory triaxial compression and triaxial steady-state creep tests provide quasi-static elastic constants and damage criteria for bedded rock salt and dolomite extracted from Cavern Well No.1 of the Tioga field in northern Pennsylvania. The elastic constants, quasi-static damage criteria, and creep parameters of host rocks provides information for evaluating a proposed cavern field for gas storage near Tioga, Pennsylvania. The Young's modulus of the dolomite was determined to be 6.4 ({+-}1.0) x 10{sup 6} psi, with a Poisson's ratio of 0.26 ({+-}0.04). The elastic Young's modulus was obtained from the slope of the unloading-reloading portion of the stress-strain plots as 7.8 ({+-}0.9) x 10{sup 6} psi. The damage criterion of the dolomite based on the peak load was determined to be J{sub 2}{sup 0.5} (psi) = 3113 + 0.34 I{sub 1} (psi) where I{sub 1} and J{sub 2} are first and second invariants respectively. Using the dilation limit as a threshold level for damage, the damage criterion was conservatively estimated as J{sub 2}{sup 0.5} (psi) = 2614 + 0.30 I{sub 1} (psi). The Young's modulus of the rock salt, which will host the storage cavern, was determined to be 2.4 ({+-}0.65) x 10{sup 6} psi, with a Poisson's ratio of 0.24 ({+-}0.07). The elastic Young's modulus was determined to be 5.0 ({+-}0.46) x 10{sup 6} psi. Unlike the dolomite specimens under triaxial compression, rock salt specimens did not show shear failure with peak axial load. Instead, most specimens showed distinct dilatancy as an indication of internal damage. Based on dilation limit, the damage criterion for the rock salt was estimated as J{sub 2}{sup 0.5} (psi) = 704 + 0.17 I{sub 1} (psi). In order to determine the time dependent deformation of the rock salt, we conducted five triaxial creep tests. The creep deformation of the Tioga rock salt was modeled based on the following three-parameter power law as {var_epsilon}{sub s} = 1.2 x 10{sup -17} {sigma}{sup 4.75} exp(-6161/T), where {var_epsilon}{sub s} is the steady state strain rate in s{sup -1}, {sigma} is the applied axial stress difference in psi, and T is the temperature in Kelvin.
The DAKOTA (Design Analysis Kit for Optimization and Terascale Applications) toolkit provides a flexible and extensible interface between simulation codes and iterative analysis methods. DAKOTA contains algorithms for optimization with gradient and nongradient-based methods; uncertainty quantification with sampling, analytic reliability, and stochastic finite element methods; parameter estimation with nonlinear least squares methods; and sensitivity analysis with design of experiments and parameter study methods. These capabilities may be used on their own or as components within advanced strategies such as surrogate-based optimization, mixed integer nonlinear programming, or optimization under uncertainty. By employing object-oriented design to implement abstractions of the key components required for iterative systems analyses, the DAKOTA toolkit provides a flexible and extensible problem-solving environment for design and performance analysis of computational models on high performance computers. This report serves as a developers manual for the DAKOTA software and describes the DAKOTA class hierarchies and their interrelationships. It derives directly from annotation of the actual source code and provides detailed class documentation, including all member functions and attributes.
The DAKOTA (Design Analysis Kit for Optimization and Terascale Applications) toolkit provides a flexible and extensible interface between simulation codes and iterative analysis methods. DAKOTA contains algorithms for optimization with gradient and nongradient-based methods; uncertainty quantification with sampling, analytic reliability, and stochastic finite element methods; parameter estimation with nonlinear least squares methods; and sensitivity analysis with design of experiments and parameter study methods. These capabilities may be used on their own or as components within advanced strategies such as surrogate-based optimization, mixed integer nonlinear programming, or optimization under uncertainty. By employing object-oriented design to implement abstractions of the key components required for iterative systems analyses, the DAKOTA toolkit provides a flexible and extensible problem-solving environment for design and performance analysis of computational models on high performance computers. This report serves as a user's manual for the DAKOTA software and provides capability overviews and procedures for software execution, as well as a variety of example studies.
This report describes Umbra's High Level Architecture HLA library. This library serves as an interface to the Defense Simulation and Modeling Office's (DMSO) Run Time Infrastructure Next Generation Version 1.3 (RTI NG1.3) software library and enables Umbra-based models to be federated into HLA environments. The Umbra library was built to enable the modeling of robots for military and security system concept evaluation. A first application provides component technologies that ideally fit the US Army JPSD's Joint Virtual Battlespace (JVB) simulation framework for Objective Force concept analysis. In addition to describing the Umbra HLA library, the report describes general issues of integrating Umbra with RTI code and outlines ways of building models to support particular HLA simulation frameworks like the JVB.
Supervisory Control and Data Acquisition (SCADA) systems are a part of the nation's critical infrastructure that is especially vulnerable to attack or disruption. Sandia National Laboratories is developing a high-security SCADA specification to increase the national security posture of the U.S. Because SCADA security is an international problem and is shaped by foreign and multinational interests, Sandia is working to develop a standards-based solution through committees such as the IEC TC 57 WG 15, the IEEE Substation Committee, and the IEEE P1547-related activity on communications and controls. The accepted standards are anticipated to take the form of a Common Criteria Protection Profile. This report provides the status of work completed and discusses several challenges ahead.
This report details some proof-of-principle experiments we conducted under a small, one year ($100K) grant from the Strategic Environmental Research and Development Program (SERDP) under the SERDP Exploratory Development (SEED) effort. Our chemiresistor technology had been developed over the last few years for detecting volatile organic compounds (VOCs) in the air, but these sensors had never been used to detect VOCs in water. In this project we tried several different configurations of the chemiresistors to find the best method for water detection. To test the effect of direct immersion of the (non-water soluble) chemiresistors in contaminated water, we constructed a fixture that allowed liquid water to pass over the chemiresistor polymer without touching the electrical leads used to measure the electrical resistance of the chemiresistor. In subsequent experiments we designed and fabricated probes that protected the chemiresistor and electronics behind GORE-TEX{reg_sign} membranes that allowed the vapor from the VOCs and the water to reach a submerged chemiresistor without allowing the liquids to touch the chemiresistor. We also designed a vapor flow-through system that allowed the headspace vapor from contaminated water to be forced past a dry chemiresistor array. All the methods demonstrated that VOCs in a high enough concentration in water can be detected by chemiresistors, but the last method of vapor phase exposure to a dry chemiresistor gave the fastest and most repeatable measurements of contamination. Answers to questions posed by SERDP reviewers subsequent to a presentation of this material are contained in the appendix.
The computer vision field has undergone a revolution of sorts in the past five years. Moore's law has driven real-time image processing from the domain of dedicated, expensive hardware, to the domain of commercial off-the-shelf computers. This thesis describes their work on the design, analysis and implementation of a Real-Time Shape from Silhouette Sensor (RT S{sup 3}). The system produces time-varying volumetric data at real-time rates (10-30Hz). The data is in the form of binary volumetric images. Until recently, using this technique in a real-time system was impractical due to the computational burden. In this thesis they review the previous work in the field, and derive the mathematics behind volumetric calibration, silhouette extraction, and shape-from-silhouette. For the sensor implementation, they use four color camera/framegrabber pairs and a single high-end Pentium III computer. The color cameras were configured to observe a common volume. This hardware uses the RT S{sup 3} software to track volumetric motion. Two types of shape-from-silhouette algorithms were implemented and their relative performance was compared. They have also explored an application of this sensor to markerless motion tracking. In his recent review of work done in motion tracking Gavrila states that results of markerless vision based 3D tracking are still limited. The method proposed in this paper not only expands upon the previous work but will also attempt to overcome these limitations.
Dempster-Shafer theory offers an alternative to traditional probabilistic theory for the mathematical representation of uncertainty. The significant innovation of this framework is that it allows for the allocation of a probability mass to sets or intervals. Dempster-Shafer theory does not require an assumption regarding the probability of the individual constituents of the set or interval. This is a potentially valuable tool for the evaluation of risk and reliability in engineering applications when it is not possible to obtain a precise measurement from experiments, or when knowledge is obtained from expert elicitation. An important aspect of this theory is the combination of evidence obtained from multiple sources and the modeling of conflict between them. This report surveys a number of possible combination rules for Dempster-Shafer structures and provides examples of the implementation of these rules for discrete and interval-valued data.
Critical infrastructures underpin the domestic security, health, safety and economic well being of the United States. They are large, widely dispersed, mostly privately owned systems operated under a mixture of federal, state and local government departments, laws and regulations. While there currently are enormous pressures to secure all aspects of all critical infrastructures immediately, budget realities limit available options. The purpose of this study is to provide a clear framework for systematically analyzing and prioritizing resources to most effectively secure US critical infrastructures from terrorist threats. It is a scalable framework (based on the interplay of consequences, threats and vulnerabilities) that can be applied at the highest national level, the component level of an individual infrastructure, or anywhere in between. This study also provides a set of key findings and a recommended approach for framework application. In addition, this study develops three laptop computer-based tools to assist with framework implementation-a Risk Assessment Credibility Tool, a Notional Risk Prioritization Tool, and a County Prioritization tool. This study's tools and insights are based on Sandia National Laboratories' many years of experience in risk, consequence, threat and vulnerability assessments, both in defense- and critical infrastructure-related areas.
In October 2000, the personnel responsible for administration of the corporate computers managed by the Scientific Computing Department assembled to reengineer the process of creating and deleting users' computer accounts. Using the Carnegie Mellon Software Engineering Institute (SEI) Capability Maturity Model (CMM) for quality improvement process, the team performed the reengineering by way of process modeling, defining and measuring the maturity of the processes, per SEI and CMM practices. The computers residing in the classified environment are bound by security requirements of the Secure Classified Network (SCN) Security Plan. These security requirements delimited the scope of the project, specifically mandating validation of all user accounts on the central corporate computer systems. System administrators, in addition to their assigned responsibilities, were spending valuable hours performing the additional tacit responsibility of tracking user accountability for user-generated data. For example, in cases where the data originator was no longer an employee, the administrators were forced to spend considerable time and effort determining the appropriate management personnel to assume ownership or disposition of the former owner's data files. In order to prevent this sort of problem from occurring and to have a defined procedure in the event of an anomaly, the computer account management procedure was thoroughly reengineered, as detailed in this document. An automated procedure is now in place that is initiated and supplied data by central corporate processes certifying the integrity, timeliness and authentication of account holders and their management. Automated scripts identify when an account is about to expire, to preempt the problem of data becoming ''orphaned'' without a responsible ''owner'' on the system. The automated account-management procedure currently operates on and provides a standard process for all of the computers maintained by the Scientific Computing Department.
Computational techniques for the evaluation of steady plane subsonic flows represented by Chaplygin series in the hodograph plane are presented. These techniques are utilized to examine the properties of the free surface wall jet solution. This solution is a prototype for the shaped charge jet, a problem which is particularly difficult to compute properly using general purpose finite element or finite difference continuum mechanics codes. The shaped charge jet is a classic validation problem for models involving high explosives and material strength. Therefore, the problem studied in this report represents a useful verification problem associated with shaped charge jet modeling.
Superresolution concepts offer the potential of resolution beyond the classical limit. This great promise has not generally been realized. In this study we investigate the potential application of superresolution concepts to synthetic aperture radar. The analytical basis for superresolution theory is discussed. In a previous report the application of the concept to synthetic aperture radar was investigated as an operator inversion problem. Generally, the operator inversion problem is ill posed. This work treats the problem from the standpoint of regularization. Both the operator inversion approach and the regularization approach show that the ability to superresolve SAR imagery is severely limited by system noise.
A technical review is presented of experiment activities and state of knowledge on air-borne, radiation source terms resulting from explosive sabotage attacks on spent reactor fuel subassemblies in shielded casks. Current assumptions about the behavior of irradiated fuel are largely based on a limited number of experimental results involving unirradiated, depleted uranium dioxide ''surrogate'' fuel. The behavior of irradiated nuclear fuel subjected to explosive conditions could be different from the behavior of the surrogate fuel, depending on the assumptions made by the evaluator. Available data indicate that these potential differences could result in errors, and possible orders-of-magnitude overestimates of aerosol dispersion and potential health effects from sabotage attacks. Furthermore, it is suggested that the current assumptions used in arriving at existing regulations for the transportation and storage of spent fuel in the U.S. are overly conservative. This, in turn, has led to potentially higher-than-needed operating expenses for those activities. A confirmatory experimental program is needed to develop a realistic correlation between source terms of irradiated fuel and unirradiated fuel. The motivations for performing the confirmatory experimental program are also presented.
This document describes a proactive plan for assessing and controlling sources of risk for the ASCI (Accelerated Strategic Computing Initiative) V&V program at Sandia National Laboratories. It offers a graded approach for identifying, analyzing, prioritizing, responding to, and monitoring risks.
The goal of this project was to develop a device that uses electric fields to grasp and possibly levitate LIGA parts. This non-contact form of grasping would solve many of the problems associated with grasping parts that are only a few microns in dimensions. Scaling laws show that for parts this size, electrostatic and electromagnetic forces are dominant over gravitational forces. This is why micro-parts often stick to mechanical tweezers. If these forces can be controlled under feedback control, the parts could be levitated, possibly even rotated in air. In this project, we designed, fabricated, and tested several grippers that use electrostatic and electromagnetic fields to grasp and release metal LIGA parts. The eventual use of this tool will be to assemble metal and non-metal LIGA parts into small electromechanical systems.
Photovoltaic inverters are the most mature of any DER inverter, and their mean time to first failure (MTFF) is about five years. This is an unacceptable MTFF and will inhibit the rapid expansion of PV. With all DER technologies, (solar, wind, fuel cells, and microturbines) the inverter is still an immature product that will result in reliability problems in fielded systems. The increasing need for all of these technologies to have a reliable inverter provides a unique opportunity to address these needs with focused R&D development projects. The requirements for these inverters are so similar that modular designs with universal features are obviously the best solution for a ''next generation'' inverter. A ''next generation'' inverter will have improved performance, higher reliability, and improved profitability. Sandia National Laboratories has estimated that the development of a ''next generation'' inverter could require approximately 20 man-years of work over an 18- to 24-month time frame, and that a government-industry partnership will greatly improve the chances of success.
The synthesis and characterization of soluble and processable high molecular weight polysilsesquioxanes with carboxylate functionalities was discussed. It was found that the tert-butyl functionality in these polymers was eliminated to give carboxylic acids functionalized polysilsesquioxane or methyltin carboxylatosilsesquioxane gels. The analysis showed that the polysilsesquioxane binds and removes tin through gelation.
The Boeing Company fabricated the Solar Two receiver as a subcontractor for the Solar Two project. The receiver absorbed sunlight reflected from the heliostat field. A molten-nitrate-salt heat transfer fluid was pumped from a storage tank at grade level, heated from 290 to 565 C by the receiver mounted on top of a tower, then flowed back down into another storage tank. To make electricity, the hot salt was pumped through a steam generator to produce steam that powered a conventional Rankine steam turbine/generator. This evaluation identifies the most significant Solar Two receiver system lessons learned from the Mechanical Design, Instrumentation and Control, Panel Fabrication, Site Construction, Receiver System Operation, and Management from the perspective of the receiver designer/manufacturer. The lessons learned on the receiver system described here consist of two parts: the Problem and one or more identified Solutions. The appendix summarizes an inspection of the advanced receiver panel developed by Boeing that was installed and operated in the Solar Two receiver.
Polycrystalline silicon (polysilicon) surface micromachining is a new technology for building micrometer ({micro}m) scale mechanical devices on silicon wafers using techniques and process tools borrowed from the manufacture of integrated circuits. Sandia National Laboratories has invested a significant effort in demonstrating the viability of polysilicon surface micromachining and has developed the Sandia Ultraplanar Micromachining Technology (SUMMiT V{trademark} ) process, which consists of five structural levels of polysilicon. A major advantage of polysilicon surface micromachining over other micromachining methods is that thousands to millions of thin film mechanical devices can be built on multiple wafers in a single fabrication lot and will operate without post-processing assembly. However, if thin film mechanical or surface properties do not lie within certain tightly set bounds, micromachined devices will fail and yield will be low. This results in high fabrication costs to attain a certain number of working devices. An important factor in determining the yield of devices in this parallel-processing method is the uniformity of these properties across a wafer and from wafer to wafer. No metrology tool exists that can routinely and accurately quantify such properties. Such a tool would enable micromachining process engineers to understand trends and thereby improve yield of micromachined devices. In this LDRD project, we demonstrated the feasibility of and made significant progress towards automatically mapping mechanical and surface properties of thin films across a wafer. The MEMS parametrics measurement team has implemented a subset of this platform, and approximately 30 wafer lots have been characterized. While more remains to be done to achieve routine characterization of all these properties, we have demonstrated the essential technologies. These include: (1) well-understood test structures fabricated side-by-side with MEMS devices, (2) well-developed analysis methods, (3) new metrologies (i.e., long working distance interferometry) and (4) a hardware/software platform that integrates (1), (2) and (3). In this report, we summarize the major focus areas of our LDRD project. We describe the contents of several articles that provide the details of our approach. We also describe hardware and software innovations we made to realize a fully automatic wafer prober system for MEMS mechanical and surface property characterization across wafers and from wafer-lot to wafer-lot.
This report documents measurements in inductively driven plasmas containing SF{sub 6}/Argon gas mixtures. The data in this report is presented in a series of appendices with a minimum of interpretation. During the course of this work we investigated: the electron and negative ion density using microwave interferometry and laser photodetachment; the optical emission; plasma species using mass spectrometry, and the ion energy distributions at the surface of the rf biased electrode in several configurations. The goal of this work was to assemble a consistent set of data to understand the important chemical mechanisms in SF{sub 6} based processing of materials and to validate models of the gas and surface processes.
This report presents general concepts in a broadly applicable methodology for validation of Accelerated Strategic Computing Initiative (ASCI) codes for Defense Programs applications at Sandia National Laboratories. The concepts are defined and analyzed within the context of their relative roles in an experimental validation process. Examples of applying the proposed methodology to three existing experimental validation activities are provided in appendices, using an appraisal technique recommended in this report.
LOCA, the Library of Continuation Algorithms, is a software library for performing stability analysis of large-scale applications. LOCA enables the tracking of solution branches as a function of a system parameter, the direct tracking of bifurcation points, and, when linked with the ARPACK library, a linear stability analysis capability. It is designed to be easy to implement around codes that already use Newton's method to converge to steady-state solutions. The algorithms are chosen to work for large problems, such as those that arise from discretizations of partial differential equations, and to run on distributed memory parallel machines. This manual presents LOCA's continuation and bifurcation analysis algorithms, and instructions on how to implement LOCA with an application code. The LOCA code is being made publicly available at www.cs.sandia.gov/loca.
Three-dimensional finite element analyses simulate the mechanical response of enlarging existing caverns at the Strategic Petroleum Reserve (SPR). The caverns are located in Gulf Coast salt domes and are enlarged by leaching during oil drawdowns as fresh water is injected to displace the crude oil from the caverns. The current criteria adopted by the SPR limits cavern usage to 5 drawdowns (leaches). As a base case, 5 leaches were modeled over a 25 year period to roughly double the volume of a 19 cavern field. Thirteen additional leaches where then simulated until caverns approached coalescence. The cavern field approximated the geometries and geologic properties found at the West Hackberry site. This enabled comparisons are data collected over nearly 20 years to analysis predictions. The analyses closely predicted the measured surface subsidence and cavern closure rates as inferred from historic well head pressures. This provided the necessary assurance that the model displacements, strains, and stresses are accurate. However, the cavern field has not yet experienced the large scale drawdowns being simulated. Should they occur in the future, code predictions should be validated with actual field behavior at that time. The simulations were performed using JAS3D, a three dimensional finite element analysis code for nonlinear quasi-static solids. The results examine the impacts of leaching and cavern workovers, where internal cavern pressures are reduced, on surface subsidence, well integrity, and cavern stability. The results suggest that the current limit of 5 oil drawdowns may be extended with some mitigative action required on the wells and later on to surface structure due to subsidence strains. The predicted stress state in the salt shows damage to start occurring after 15 drawdowns with significant failure occurring at the 16th drawdown, well beyond the current limit of 5 drawdowns.
This report addresses the effects of spectrum loading on lifetime and residual strength of a typical fiberglass laminate configuration used in wind turbine blade construction. Over 1100 tests have been run on laboratory specimens under a variety of load sequences. Repeated block loading at two or more load levels, either tensile-tensile, compressive-compressive, or reversing, as well as more random standard spectra have been studied. Data have been obtained for residual strength at various stages of the lifetime. Several lifetime prediction theories have been applied to the results. The repeated block loading data show lifetimes that are usually shorter than predicted by the most widely used linear damage accumulation theory, Miner's sum. Actual lifetimes are in the range of 10 to 20 percent of predicted lifetime in many cases. Linear and nonlinear residual strength models tend to fit the data better than Miner's sum, with the nonlinear providing a better fit of the two. Direct tests of residual strength at various fractions of the lifetime are consistent with the residual strength models. Load sequencing effects are found to be insignificant. The more a spectrum deviates from constant amplitude, the more sensitive predictions are to the damage law used. The nonlinear model provided improved correlation with test data for a modified standard wind turbine spectrum. When a single, relatively high load cycle was removed, all models provided similar, though somewhat non-conservative correlation with the experimental results. Predictions for the full spectrum, including tensile and compressive loads were slightly non-conservative relative to the experimental data, and accurately captured the trend with varying maximum load. The nonlinear residual strength based prediction with a power law S-N curve extrapolation provided the best fit to the data in most cases. The selection of the constant amplitude fatigue regression model becomes important at the lower stress, higher cycle loading cases. The residual strength models may provide a more accurate estimate of blade lifetime than Miner's rule for some loads spectra. They have the added advantage of providing an estimate of current blade strength throughout the service life.
The final report for a Laboratory Directed Research and Development project entitled, Molecular Simulation of Reacting Systems is presented. It describes efforts to incorporate chemical reaction events into the LAMMPS massively parallel molecular dynamics code. This was accomplished using a scheme in which several classes of reactions are allowed to occur in a probabilistic fashion at specified times during the MD simulation. Three classes of reaction were implemented: addition, chain transfer and scission. A fully parallel implementation was achieved using a checkerboarding scheme, which avoids conflicts due to reactions occurring on neighboring processors. The observed chemical evolution is independent of the number of processors used. The code was applied to two test applications: irreversible linear polymerization and thermal degradation chemistry.
Military test and training ranges generate scrap materials from targets and ordnance debris. These materials are routinely removed from the range for recycling; however, energetic material residues in this range scrap has presented a significant safety hazard to operations personnel and damaged recycling equipment. The Strategic Environmental Research and Development Program (SERDP) sought proof of concept evaluations for monitoring technologies to identify energetic residues among range scrap. Sandia National Laboratories teamed with Nomadics, Inc. to evaluate the Nomadics FIDO vapor sensor for application to this problem. Laboratory tests were completed that determined the vapor-sensing threshold to be 10 to 20 ppt for TNT and 150 to 200 ppt for DNT. Field tests with the FIDO demonstrated the proof of concept that energetic material residues can be identified with vapor sensing in enclosed scrap bins. Items such as low order detonation debris, demolition block granules, and unused 81-mm mortars were detected quickly and with minimum effort. Conceptual designs for field-screening scrap for energetic material residues include handheld vapor sensing systems, batch scrap sensing systems, continuous conveyor sensing systems and a hot gas decontamination verification system.
A physics-based understanding of material aging mechanisms helps to increase reliability when predicting the lifetime of mechanical and electrical components. This report examines in detail the mechanisms of atmospheric copper sulfidation and evaluates new methods of parallel experimentation for high-throughput corrosion analysis. Often our knowledge of aging mechanisms is limited because coupled chemical reactions and physical processes are involved that depend on complex interactions with the environment and component functionality. Atmospheric corrosion is one of the most complex aging phenomena and it has profound consequences for the nation's economy and safety. Therefore, copper sulfidation was used as a test-case to examine the utility of parallel experimentation. Through the use of parallel and conventional experimentation, we measured: (1) the sulfidation rate as a function of humidity, light, temperature and O{sub 2} concentration; (2) the primary moving species in solid state transport; (3) the diffusivity of Cu vacancies through Cu{sub 2}S; (4) the sulfidation activation energies as a function of relative humidity (RH); (5) the sulfidation induction times at low humidities; and (6) the effect of light on the sulfidation rate. Also, the importance of various sulfidation mechanisms was determined as a function of RH and sulfide thickness. Different models for sulfidation-reactor geometries and the sulfidation reaction process are presented.