We present a theory for transforming the system-theory-based realization models into the corresponding physical coordinate-based structural models. The theory has been implemented into computational procedure and applied to several example problems. Our results show that the present transformation theory yields an objective model basis possessing a unique set of structural parameters from an infinite set of equivalent system realization models. For proportionally damped systems, the transformation directly and systematicaly yields the normal modes and modal damping. Moreover, when nonproportional damping is present, the relative magnitude and phase of the damped mode shapes are separately characterized, and a corrective transformation is then employed to capture the undamped normal modes and nondiagonal modal damping matrix.
A tunable, high-accelerating-gradient cavity has been designed for use in the rf system of the Low Energy Booster (LEB) at the Superconducting Super Collider (SSC). Details of the cavity design are discussed along with low level, swept frequency, and high pwoer test results.
Three potential methods for measuring the surface tritium content of the TFTR vacuum vessel are described, each based on a different technique for measuring the in situ beta emission from tritium. These methods should be able to provide both a local and a global assessment of the tritium content within the top [approx] 1[mu]m of the inner wall surface.
The Robotic All-Terrain Lunar Exploration Rover (RATLER) is a four wheeled all-wheel-drive dual-body vehicle. A uniquely simple method of chassis articulation is employed which allows all four wheels to remain in contact with the ground, even while climbing over step-like obstacles as large as 1.3 wheel diameters. The RATLER design concept began at Sandia National Laboratories in late 1991 with a series of small, proof-of-principle, working scale models. The models proved the viability of the concept for high mobility through mechanical simplicity, and eventually received internal funding at Sandia National Laboratories for full scale, proof-of-concept prototype development. Whereas the proof-of-principle models demonstrated the mechanical design's capabilities for mobility, the full scale proof-of-concept design currently under development is intended to support field operations for experiments in telerobotics, autonomous robotic operations, telerobotic field geology, and advanced man-machine interface concepts. The development program's current status is described, including an outline of the program's work over the past year, recent accomplishments, and plans for follow-on development work.
This paper describes a collision avoidance system using Whole Arm Proximity (WHAP) sensors on a PUMA 560 robot arm. The capacitance-based sensors generate electric fields which can completely encompass the robot arm and detect obstacles as they approach from any direction. The directional obstacle information gathered by the WHAP sensors together with the sensor geometry and robot configuration is used to scale the commanded joint velocities of the robot. A linearized relationship between the WHAP sensor reading and the distance from the obstacle allows direct transformation of perturbations in WHAP readings to perturbations in joint velocities. The WHAP reading is used to directly reduce the component of the command input velocity along the normal axis of the sensor, allowing graceful reductions in speed as the arm approaches the obstacle. By scaling only the component of the velocity vector in the direction of the nearest obstacles, the control system restricts motion in the direction of obstacles while permitting unconstrained motion in other directions.
The computational fluid dynamics code FIDAP (Fluid Dynamics International) is used to perform simulations of the steady laminar flow of an incompressible fluid in a three-dimensional rectangular cavity. Although most previous studies have considered a 'lid-driven' cavity, where a uniform horizontal velocity is imposed on the cavity lid, the flow in the channel above the cavity is explicitly included in the computational domain in these simulations. Simulations are performed for various Reynolds numbers in the range 0 ≤ Re ≤ 1000 and are compared to corresponding two-dimensional results. The three-dimensional flows are seen to exhibit a smooth topology change around Re ≈ 35.
Detection of air-borne environmental contaminants, such as organic solvents, requires unambiguous compound identification and sensitivity to concentrations below those permitted by regulating agencies. One promising detection approach uses a pulsed supersonic molecular beam vacuum expansion in combination with fluorescence signal spectral analysis to identify species in a chemical mixture. This report describes the use and performance of the ultraviolet excitation molecular beam fluorometer.
We have studied a singly-resonant KTP ring OPO pumped by nanosecond pulses from a frequency-doubled NdYAG laser. We present measurements of the temporal and spatial intensity profiles of the incident pump beam and OPO output beams, including the depleted pump, as well as the output energy as a function of pump laser energy. These measurements have been carried out for both injection-seeded and unseeded operation of the OPO The results of these measurements have been compared to the output of a computer model.
The Telemanaged Mobile Security Station (TMSS) was developed at Sandia National Laboratories to investigate the role of mobile robotics in exterior perimeter security systems. A major feature of the system is its capability to perform autonomous patrols of the security site's network of roads. Perimeter security sites are well known, structured environments; the locations of the roads, buildings, and fences are relatively static. A security robot has the advantage of being able to learn its new environment prior to autonomous travel. The TMSS robot combines information from a microwave beacon system and on-board dead reckoning sensors to determine its location within the site. The operator is required to teleoperate the robot in a teach mode over all desired paths before autonomous operations can commence. During this teach phase, TMSS stores points from its position location system at two meter intervals. This map data base is used for planning paths and for reference during path following. Details of the position location and path following systems will be described along with system performance and recommendations for future enhancements.
A method was developed for applying an inorganic conversion coating on that is procedurally similar to chromate conversion coating methods; this method, however does not use or involve hazardous/toxic chemicals. The coating forms by precipitation involving Al{sup 3+} Li{sup +}, OH{sup {minus}}, CO{sub 3}{sup 2}{minus}, and possibly other anions. This polycrystalline coating is continuous, conformal and persistent in aggressive environments. Coating thicknesses range from several tenths to ten micrometers. Although the outer portions of the coating are porous, the pores do not penetrate to the substrate interface. These coatings do not match the levels of performance offered by commercially available chromate conversion coatings, but are capable of meeting many of the corrosion resistance, electrical resistivity, and paint adhesion requirements established in MIL-C-5541E ``Chemical Conversion Coatings on Aluminum and Aluminum Alloys.`` In this paper, methods for producing the talc coating on aluminum alloys 1100 and 6061-T6 are described and compared to traditional chromate conversion coating methods. Resulting coating structure and composition are described. Performance data for the talc coatings in MIL-C-5541E required tests are presented along with data commercial chromate-based coatings.
Fluorescence depolarization studies of polysilane chains in solution have shown that energy transfer along the polymer chains occurs for only a very short time relative to the excited state lifetime and only over short distances before the excited states become trapped in long, low-energy segments. However, in solid films we have shown in previous work that excitons are highly mobile throughout their 600 ps lifetime at room temperature, presumably because energy transfer among neighboring, parallel chain segments becomes possible. In this paper we report that the exciton-exciton annihilation rate constant decreases by only a factor of five between room temperature and 12 K, showing that the excitons do not become trapped even at low temperatures.
Analog-to-digital converters are frequently modeled as a linear polynomial plus a random process. The parameters of the linear polynomial are the familiar gain and offset of the analog-to-digital converter. The output of the random process is uniformly distributed on plus or minus the least significant bit of the analog-to-digital converter. In this paper, the transfer function of an analog-to-digital converter is modeled as a nonlinear polynomial plus a random process. This model can explain the generation of harmonics by the analog-to-digital converter, but the simpler linear model cannot. The parameters of the nonlinear polynomial are estimated from the response to the analog-to-digital converter to a sine wave. The model parameters are used to estimate the nonlinear part of the transfer function of the analog-to-digital converter.
The blast-induced movement and final location of geologic layers that may cause environmental problems can be predicted using discrete element methods. This prediction capability can be used by mine operators to locate the material in the muck pile during excavation which would allow encapsulation to prevent groundwater infiltration.
In support of the Department of Energy`s Dismantlement Program, the Optoelectronics Characterization and Sensor Development Department 2231 at Sandia National Laboratories/New Mexico has developed an in situ nonintrusive Optoelectronic Inventory System (OIS) that has the potential for application wherever periodic inventory of selected material is desired. Using a network of fiber-optic links, the OIS retrieves and stores inventory signatures from data storage devices (which are permanently attached to material storage containers) while inherently providing electromagnetic pulse immunity and electrical noise isolation. Photovoltaic cells (located within the storage facility) convert laser diode optic power from a laser driver to electrical energy. When powered and triggered, the data storage devices sequentially output their digital inventory signatures through light-emitting diode/photo diode data links for retrieval and storage in a mobile data acquisition system. An item`s exact location is determined through fiber-optic network and software design. The OIS provides an on-demand method for obtaining acceptable inventory reports while eliminating the need for human presence inside the material storage facility. By using modularization and prefabricated construction with mature technologies and components, an OIS installation with virtually unlimited capacity can be tailored to the customer`s requirements.
Time-resolved velocity interferometry measurements have been made on boron carbide and silicon carbide ceramics to assess dynamic equation-of-state and strength properties of these materials. Hugoniot precursor characteristics, and post-yield shock and release wave properties, indicated markedly different dynamic strength and flow behavior for the two carbides.
To investigate the feasibility of producing a compact, efficient blue laser source, pumped-cavity second harmonic generation of diode lasers was explored. It is desirable to have such lasers to increase optical disk storage density, for color displays and for under-the-sea green-blue optical signal transmission. Based on assumed cavity losses, a cavity was designed and numerical analysis predicted an overall conversion efficiency to the second harmonic wavelength of 76% from a 75 mW diode laser. The diode laser used in these experiments had a single longitudinal and a single transverse mode output at 860 nm. The best conversion efficiency obtained (26%) was less than optimum due to the 2.5% single-pass linear losses associated with the cavity. However, calculations based on these higher losses are in good agreement with the experimentally determined values. In additions, a factor of 1.65 increase in the second harmonic output power is anticipated by reducing the input mirror reflectivity to better impedance-match the cavity. With this relatively low second harmonic conversion, the power to light conversion is 7.8%.
A series of explosive tests were performed to establish containment integrity data for commonly used handling and storage containers of energetic materials at Sandia National Laboratories, Albuquerque, N.M. The tests consisted of two phases: (1) each container was tested for explosive integrity and propagation, and (2) the data were used to evaluate a nominal donor-receptor test matrix for verifying the confinement integrity of a typical explosives service locker.
This study is a comparison of hydraulic fracture models run using test data from the GRI Staged Field Experiment No. 3. Models compared include 2D, pseudo-3D, and 3D codes, run on up to eight different cases. Documented in this comparison are the differences in length, height, width, pressure, and efficiency. The purpose of this study is to provide the completions engineer with a practical comparison of the available models so that rational decisions can be made as to which model is optimal for a given application.
Synthetic Aperture Radar (SAR) from an airborne platform has been proposed for imaging targets beneath the earth`s surface. The propagation of the radar`s energy within the ground, however, is much different than in the earth`s atmosphere. The result is signal refraction, echo delay, propagation losses, dispersion, and volumetric scattering. These all combine to make SAR image formation from an airborne platform much more challenging than a surface imaging counterpart. This report treats the ground as a lossy dispersive half-space, and presents a model for the radar echo based on measurable parameters. The model is then used to explore various imaging schemes, and image properties. Dynamic range is discussed, as is the impact of loss on dynamic range. Modified window functions are proposed to mitigate effects of sidelobes of shallow targets overwhelming deeper targets.
This report is divided into: budget, capital equipment requests, general programmatic overview and institutional issues, DOE center of excellence for synthesis and processing of advanced materials, industrial interactions and technology transfer, and research program summaries (new proposals, existing programs). Ceramics, semiconductors, superconductors, interfaces, CVD, tailored surfaces, adhesion, growth and epitaxy, boron-rich solids, nanoclusters, etc. are covered.