The need for a reliable, fast, wireless telemetry system in the drilling industry is great but the technical challenge to develop such a system is huge. A downhole wireless telemetry system based on Surface Area Modulation (SAM) has been developed which involves the introduction of an electrically insulated gap near the bottom of an otherwise conductive drillstring. The electrical resistance of this gap can be modulated to alter the electrical characteristics of a circuit involving a surface power supply, the sections of the drillstring above and below the gap, the earth, and a nearby return electrode. These changes alter the current in the circuit, which can be monitored at the surface with an ammeter. Downhole data are encoded and transmitted to the surface as a pattern of current oscillations. In a field test, the SAM system successfully transmitted downhole information from depths of 1,400 ft below the fluid level to the surface at a rate of 110 baud. Electrical insulation on the outside of the simulated drillstring was required to achieve this level of performance. Electrically insulated tubing improved the data transmission rate at a given depth by more than an order of magnitude, and increased the maximum depth from which successful data telemetry could be achieved by more than a factor of two.
This study examines ergonomic stressors associated with front-end process tool maintenance, relates them to decreased machine utilization, and proposes solution strategies to reduce their negative impact on productivity. Member company ergonomists observed technicians performing field maintenance tasks on seven different bottleneck tools and recorded ergonomic stressors using SEMaCheck, a graphics-based, integrated checklist developed by Sandia National Laboratories. The top ten stressors were prioritized according to a cost formula that accounted for difficulty, time, and potential errors. Estimates of additional time on a task caused by ergonomic stressors demonstrated that machine utilization could be increased from 6% to 25%. Optimal solution strategies were formulated based on redesign budget, stressor cost, and estimates of solution costs and benefits
The concept of ``progressive Lattice Sampling`` as a basis for generating successive finite element response surfaces that are increasingly effective in matching actual response functions is investigated here. The goal is optimal response surface generation, which achieves an adequate representation of system behavior over the relevant parameter space of a problem with a minimum of computational and user effort. Such is important in global optimization and in estimation of system probabilistic response, which are both made much more viable by replacing large complex computer models of system behavior by fast running accurate approximations. This paper outlines the methodology for Finite Element/Lattice Sampling (FE/LS) response surface generation and examines the effectiveness of progressively refined FE/LS response surfaces in decoupled Monte Carlo analysis of several model problems. The proposed method is in all cases more efficient (generally orders of magnitude more efficient) than direct Monte Carlo evaluation, with no appreciable loss of accuracy. Thus, when arriving at probabilities or distributions by Monte Carlo, it appears to be more efficient to expend computer model function evaluations on building a FE/LS response surface than to expend them in direct Monte Carlo sampling. Furthermore, the marginal efficiency of the FE/LS decoupled Monte Carlo approach increases as the size of the computer model increases, which is a very favorable property.
This report represents the completion of a three-year Laboratory-Directed Research and Development (LDRD) program to investigate sub-wavelength surface relief structures fabricated by direct-write e-beam technology as unique and very high-efficiency optical elements. A semiconductor layer with sub-wavelength sized etched openings or features can be considered as a layer with an effective index of refraction determined by the fraction of the surface filled with semiconductor relative to the fraction filled with air or other material. Such as a layer can be used to implement planar gradient-index lenses on a surface. Additionally, the nanometer-scale surface structures have diffractive properties that allow the direct manipulation of polarization and altering of the reflective properties of surfaces. With this technology a single direct-write mask and etch can be used to integrate a wide variety of optical functions into a device surface with high efficiencies; allowing for example, direct integration of polarizing optics into the surface with high efficiencies; allowing for example, direct integration of polarizing optics into the surfaces of devices, forming anti-reflection surfaces or fabricating high-efficiency, high-numerical aperture lenses, including integration inside vertical semiconductor laser cavities.
This report summarizes work on the development of high-speed vertical cavity surface emitting lasers (VCSELs) for multi-gigabit per second optical data communications applications (LDRD case number 3506.010). The program resulted in VCSELs that operate with an electrical bandwidth of 20 GHz along with a simultaneous conversion efficiency (DC to light) of about 20%. To achieve the large electrical bandwidth, conventional VCSELs were appropriately modified to reduce electrical parasitics and adapted for microwave probing for high-speed operation.
Micromachining technologies, or Micro-Electro-Mechanical Systems (MEMS), enable the develop of low-cost devices capable of sensing motion in a reliable and accurate manner. Sandia has developed a MEMS fabrication process for integrating both the micromechanical structures and microelectronics circuitry of surface micromachined sensors, such as silicon accelerometers, on the same chip. Integration of the micromechanical sensor elements with microelectronics provides substantial performance and reliability advantages for MEMS accelerometers. A design team at Sandia was assembled to develop a micromachined silicon accelerometer capable of surviving and measuring very high accelerations (up to 50,000 times the acceleration due to gravity). The Sandia integrated surface micromachining process was selected for fabrication of the sensor due to the extreme measurement sensitivity potential associated with integrated microelectronics. Very fine measurement sensitivity was required due to the very small accelerometer proof mass (< 200 {times} 10{sup {minus}9} gram) obtainable with this surface micromachining process. The small proof mass corresponded to small sensor deflections which required very sensitive electronics to enable accurate acceleration measurement over a range of 1,000 to 50,000 times the acceleration due to gravity. Several prototype sensors, based on a suspended plate mass configuration, were developed and the details of the design, modeling, fabrication and validation of the device will be presented in this paper. The device was analyzed using both conventional lumped parameter modeling techniques and finite element analysis tools. The device was tested and performed well over its design range (the device was tested over a range of a few thousand G to 46,000 G, where 1 G equals the acceleration due to gravity).
The intent and purpose of this work was to investigate and demonstrate cooperative behavior among a group of mobile robot machines. The specific goal of this work was to build a small swarm of identical machines and control them in such a way as to show a coordinated movement of the group in a flocking manner, similar to that observed in nature. Control of the swarm`s individual members and its overall configuration is available to the human user via a graphic man-machine interface running on a base station control computer. Any robot may be designated as the nominal leader through the interface tool, which then may be commanded to proceed to a particular geographic destination. The remainder of the flock follows the leader by maintaining their relative positions in formation, as specified by the human controller through the interface. The formation`s configuration can be altered manually through an interactive graphic-based tool. An alternative mode of control allows for teleoperation of one robot, with the flock following along as described above.
An autonomous mobile robotic capability is critical to developing remote work applications for hazardous environments. A few potential applications include humanitarian demining and ordnance neutralization, extraterrestrial science exploration, and hazardous waste cleanup. The ability of the remote platform to sense and maneuver within its environment is a basic technology requirement which is currently lacking. This enabling technology will open the door for force multiplication and cost effective solutions to remote operations. The ultimate goal of this work is to develop a mobile robotic platform that can identify and avoid local obstacles as it traverses from its current location to a specified destination. This goal directed autonomous navigation scheme uses the Global Positioning System (GPS) to identify the robot`s current coordinates in space and neural network processing of LADAR range images for local obstacle detection and avoidance. The initial year funding provided by this LDRD project has developed a small exterior mobile robotic development platform and a fieldable version of Sandia`s Scannerless Range Imager (SRI) system. The robotic testbed platform is based on the Surveillance And Reconnaissance ground Equipment (SARGE) robotic vehicle design recently developed for the US DoD. Contingent upon follow-on funding, future enhancements will develop neural network processing of the range map data to traverse unstructured exterior terrain while avoiding obstacles. The SRI will provide real-time range images to a neural network for autonomous guidance. Neural network processing of the range map data will allow real-time operation on a Pentium based embedded processor board.
The report is intended to address the need for data analysis in environmental sampling programs. Routine environmental sampling has been conducted at Sandia National Laboratories/New Mexico (SNL/NM) to ensure that site operations have not resulted in undue risk to the public and the environment. Over the years, large amounts of data have been accumulated. The richness of the data should be fully utilized to improve sampling design and prioritize sampling needs for a technically-sound, yet cost-effective sampling design. The report presents a methodology for analyzing environmental monitoring data and demonstrates the application by using SNL`s historical monitoring data. Recommendations for sampling design modification were derived based on the results of the analyses.
LUG and Sway brace ANalysis (LUGSAN) II is an analysis and database computer program that is designed to calculate store lug and sway brace loads for aircraft captive carriage. LUGSAN II combines the rigid body dynamics code, SWAY85, with a Macintosh Hypercard database to function both as an analysis and archival system. This report describes the LUGSAN II application program, which operates on the Macintosh System (Hypercard 2.2 or later) and includes function descriptions, layout examples, and sample sessions. Although this report is primarily a user`s manual, a brief overview of the LUGSAN II computer code is included with suggested resources for programmers.
Lost circulation, which is the loss of well drilling fluids to the formation while drilling, is a common problem encountered while drilling geothermal wells. The rapid detection of the loss of well drilling fluids is critical to the successful and cost-effective treatment of the wellbore to stop or minimize lost circulation. Sandia National Laboratories has developed an instrument to accurately measure the outflow rate of drilling fluids while drilling. This instrument, the Rolling Float Meter, has been under development at Sandia since 1991 and is now available for utilization by interested industry users. This report documents recent Rolling Float Meter design upgrades resulting from field testing and industry input, the effects of ongoing testing and evaluation both in the laboratory and in the field, and the final design package that is available to transfer this technology to industry users.
Two Monte Carlo programs, XITRAN and XMTRAN, were developed for calculating the emission of electrons from high-Z foils irradiated with x rays. XITRAN follows all individual elastic collisions of electrons with atoms, whereas XMTRAN uses the condensed-random-walk model. Both codes take into account photo-electrons, fluorescence radiation, and Auger electrons. Comparisons are made with an experiment by Dolan at Sandia Laboratories involving the backward and forward emission of electrons from a tantalum foil irradiated by 100-kV and 50-kV x-ray beams. There is good agreement between results from the XITRAN and XMTRAN codes. There emitted per incident x-ray photon, and in regard to the angular distribution of the emerging electrons. In regard to the electron energy spectra, there is fair agreement down to a spectral energy of 20 keV, whereas below 20 keV the calculated spectra lie considerably below the measurements.
This report is a user`s manual for GRAFLAB, which is a new database, analysis, and plotting package that has been written entirely in the MATLAB programming language. GRAFLAB is currently used for data reduction, analysis, and archival. GRAFLAB was written to replace GRAFAID, which is a FORTRAN database, analysis, and plotting package that runs on VAX/VMS.
In the present study we describe the development of an experimental fracture material property test method specific to dynamic fragmentation. Spherical test samples of the metals of interest are subjected to controlled impulsive stress loads by acceleration to high velocities with a light-gas launcher facility and subsequent normal impact on thin plates. Motion, deformation and fragmentation of the test samples are diagnosed with multiple flash radiography methods. The impact plate materials are selected to be transparent to the x-ray method so that only test metal material is imaged. Through a systematic series of such tests both strain-to-failure and fragmentation resistance properties are determined through this experimental method. Fragmentation property data for several steels, copper, aluminum, tantalum and titanium have been obtained to date. Aspects of the dynamic data have been analyzed with computational methods to achieve a better understanding of the processes leading to failure and fragmentation, and to test an existing computational fragmentation model.
Sandia has established a foundational technology in photonic integrated circuits (PICs) based on the (Al,Ga,In)As material system for optical communication, radar control and testing, and network switching applications at the important 1.3{mu}m/1.55{mu}m wavelengths. We investigated the optical, electrooptical, and microwave performance characteristics of the fundamental building-block PIC elements designed to be as simple and process-tolerant as possible, with particular emphasis placed on reducing optical insertion loss. Relatively conventional device array and circuit designs were built using these PIC elements: (1) to establish a baseline performance standard; (2) to assess the impact of epitaxial growth accuracy and uniformity, and of fabrication uniformity and yield; (3) to validate our theoretical and numerical models; and (4) to resolve the optical and microwave packaging issues associated with building fully packaged prototypes. Novel and more complex PIC designs and fabrication processes, viewed as higher payoff but higher risk, were explored in a parallel effort with the intention of meshing those advances into our baseline higher-yield capability as they mature. The application focus targeted the design and fabrication of packaged solitary modulators meeting the requirements of future wideband and high-speed analog and digital data links. Successfully prototyped devices are expected to feed into more complex PICs solving specific problems in high-performance communications, such as optical beamforming networks for phased array antennas.
The Waste Isolation Pilot Plant (WIPP) is being developed by the US Department of Energy for the geologic (deep underground) disposal of transuranic (TRU) waste. A Compliance Certification Application (CCA) of the WIPP (1) for such disposal was submitted to the US Environmental Protection Agency (EPA) in October, 1996, and is currently under review, with a decision anticipated in late 1997. An important component of the CCA is a performance assessment (PA) for the WIPP carried out by Sandia National Laboratories. The final outcome of the PA is a complementary cumulative distribution function (CCDF) for radionuclide releases from the WIPP to the accessible environment and an assessment of the confidence with which this CCDF can be estimated. This paper describes the computational process used to develop the CCDF. The results of uncertainty and sensitivity analysis are also presented.
The objective of the USNRC supported Lower Head Failure (LHF) Experiment Program at Sandia National Laboratories is to experimentally investigate and characterize the failure of the reactor pressure vessel (RPV) lower head due to the thermal and pressure loads of a severe accident. The experimental program is complemented by a modeling program focused on the development of a constitutive formulation for use in standard finite element structure mechanics codes. The problem is of importance because: lower head failure defines the initial conditions of all ex-vessel events; the inability of state-of-the-art models to simulate the result of the TMI-II accident (Stickler, et al. 1993); and TMI-II results suggest the possibility of in-vessel cooling, and creep deformation may be a precursor to water ingression leading to in-vessel cooling.
This paper presents an overview of several emerging nondestructive evaluation technologies that are being employed or considered for use to inspect commercial transport, commuter aircraft and military aircraft. An overview of the Federal Aviation Administration (FAA) Airworthiness Assurance NDI Validation Center (AANC) is described and how AANC teams with industry, universities, and other federal entities to assess these technologies.
Optimal response surface construction is being investigated as part of Sandia discretionary (LDRD) research into Analytic Nondeterministic Methods. The goal is to achieve an adequate representation of system behavior over the relevant parameter space of a problem with a minimum of computational and user effort. This is important in global optimization and in estimation of system probabilistic response, which are both made more viable by replacing large complex computer models with fast-running accurate and noiseless approximations. A Finite Element/Lattice Sampling (FE/LS) methodology for constructing progressively refined finite element response surfaces that reuse previous generations of samples is described here. Similar finite element implementations can be extended to N-dimensional problems and/or random fields and applied to other types of structured sampling paradigms, such as classical experimental design and Gauss, Lobatto, and Patterson sampling. Here the FE/LS model is applied in a ``decoupled`` Monte Carlo analysis of two sets of probability quantification test problems. The analytic test problems, spanning a large range of probabilities and very demanding failure region geometries, constitute a good testbed for comparing the performance of various nondeterministic analysis methods. In results here, FE/LS decoupled Monte Carlo analysis required orders of magnitude less computer time than direct Monte Carlo analysis, with no appreciable loss of accuracy. Thus, when arriving at probabilities or distributions by Monte Carlo, it appears to be more efficient to expend computer-model function evaluations on building a FE/LS response surface than to expend them in direct Monte Carlo sampling.
The single-event upset (SEU) responses of 16 Kbit to 1 Mbit SRAMs irradiated with low and high-energy heavy ions are reported. Standard low-energy heavy ion tests appear to be sufficiently conservative for technologies down to 0.5 {micro}m.
This paper presents preliminary analysis of a volcanic tuff repository containing a combination of low enrichment commercial spent nuclear fuels (SNF) and DOE-owned SNF packages. These SNFs were analyzed with respect to their criticality risks. Disposal of SNF packages containing significant fissile mass within a geologic repository must comply with current regulations relative to criticality safety during transportation and handling within operational facilities. However, once the repository is closed, the double contingency credits for criticality safety are subject to unremediable degradation, (e.g., water intrusion, continued presence of neutron absorbers in proximity to fissile material, and fissile material reconfiguration). The work presented in this paper focused on two attributes of criticality in a volcanic tuff repository for near-field and far-field scenarios: (1) scenario conditions necessary to have a criticality, and (2) consequences of a nuclear excursion that are components of risk. All criticality consequences are dependent upon eventual water intrusion into the repository and subsequent breach of the disposal package. Key criticality parameters necessary for a critical assembly are: (1) adequate thermal fissile mass, (2) adequate concentration of fissile material, (3) separation of neutron poison from fissile materials, and (4) sufficient neutron moderation (expressed in units of moderator to fissile atom ratios). Key results from this study indicated that the total energies released during a single excursion are minimal (comparable to those released in previous solution accidents), and the maximum frequency of occurrence is bounded by the saturation and temperature recycle times, thus resulting in small criticality risks.
This report represents the completion of a two years Laboratory Directed Research and Development (LDRD) program to investigate miniaturized systems for chemical detection and analysis. The future of advanced chemical detection and analysis is in miniature devices that are able to characterize increasingly complex samples, a laboratory on a chip. In this concept, chemical operations used to analyze complicated samples in a chemical laboratory sample handling, species separation, chemical derivitization and detection are incorporated into a miniature device. By using electrokinetic flow, this approach does not require pumps or valves, as fluids in microfabricated channels can be driven by externally applied voltages. This is ideal for sample handling in miniature devices. This project was to develop truly miniature on-chip optical systems based on Vertical Cavity Surface Emitting Lasers (VCSELs) and diffractive optics. These can be built into a complete system that also has on-chip electrokinetic fluid handling and chemical separation in a microfabricated column. The primary goal was the design and fabrication of an on-chip separation column with fluorescence sources and detectors that, using electrokinetic flow, can be used as the basis of an automated chemical analysis system. Secondary goals involved investigation of a dispersed fluorescence module that can be used to extend the versatility of the basic system and on chip, intracavity laser absorption as a high sensitivity detection technique.
Sandia National Laboratories is responsible for assuring that the US nuclear deterrent remains credible and that the one in a billion disaster of unintended nuclear detonation never occurs. Letting mistake-generated defects into the stockpile would undermine its mission. The current era of shrinking stockpiles is shrinking Sandia`s opportunities to discover and correct mistakes and fine tune processes over long production runs. In response, Sandia has chosen to develop and use a science-based, life cycle systems engineering practices that, in part, require understanding the design to manufacturing issues in enough detail to tune processes and eliminate mistakes before ever making a part. Defect prevention is a key area of concern that currently lacks sufficient theoretical understanding. This report is the result of a scoping study in the application of best-practice quality techniques that could address Sandia`s stockpile mission. The study provides detail on sources and control of mistakes, poka-yoke or mistake-proofing techniques, the Toyota Production system, and design theory in relation to manufacturing quality prediction. Scoping experiments are described and areas for future research are identified.
This report describes the numerical procedure used to implement the Green`s function method for solving the Poisson equation in two-dimensional Cartesian coordinates. The procedure can determine the solution to a problem with any or all of applied voltage boundary conditions, dielectric media, floating (insulated) conducting media, dielectric surface charging, periodic (reflective) boundary conditions, and volumetric space charge. The numerical solution is reasonably fast, and the dimension of the linear problem to be solved is that of the number of elements needed to represent the surfaces, not the whole computational volume. The method of solution is useful in the simulation of plasma particle motion in the vicinity of complex surface structures as found in microelectronics plasma processing applications. A FORTRAN implementation of this procedure is available from the author.
This paper presents a model for evaluating microcrack development and dilatant behavior of crystalline rocks. The model is developed within the concepts of continuum mechanics, with special emphasis on the development of internal boundaries in the continuum by utilizing fracture mechanics based cohesive zone models. The model is capable of describing the evolution from initial debonding through complete separation and subsequent void growth of an interface. An example problem of a rock salt specimen subjected to a high deviatoric load and low confinement is presented that predicts preferential opening of fractures oriented parallel with the maximum compressive stress axis.