Publications

Abstract not provided.

Abstract not provided.

In 1989 BNL was added to the EPAs National Priorities List. The site is divided into seven operable units (OU). OU-I includes the former landfill area. The field task site is noted as the AOC 2C Glass Holes location. Beginning in the 1960s and continuing into the 1980s, BNL disposed of laboratory waste (glassware, chemicals and animal carcasses) in numerous shallow pits. The drivers for remediating the pits are; historical records that indicate hazardous materials may have been disposed of in the pits; ground water contamination down gradient of the pits; a test excavation of one of the glass holes that unearthed laboratory glass bottles with unidentified liquids still contained; and the fact that BNL rests atop an EPA designated sole-source aquifer. The specific site chosen for this demonstration was pit G-11. The requirements that lead to choosing this pit were; a well characterized pit and a relatively isolated pit where our construction operations would not impact on adjacent pits. The glass holes area, including pit G-11, was comprehensively surveyed using a suite of geophysical techniques (e.g., EM-31, EM-61, GPR). Prior to stabilizing the waste form a subsurface barrier was constructed to contain the entire waste pit. The pit contents were then stabilized using a cement grout applied via jet grouting. The stabilization was performed to make removal of the waste from the pit easier and safer in terms of worker exposure. The grouting process would mix and masticate the waste and grout and form a single monolithic waste form. This large monolith would then be subdivided into smaller 4 foot by 4 foot by 10-12 foot block using a demolition grout. The smaller blocks would then be easily removed from the site and disposed of in a CERCLA waste site.

This is the final report of an LDRD program entitled 'Scanning Probe-Based Processes for Nanometer-Scale Device Fabrication'. This program intends to expand Sandia's expertise in scanning-probe based fabrication and characterization of nanostructures. Our object is to achieve an order of magnitude decrease in feature size compared to conventional fabrication technology. We are exploring approaches to nanostructure fabrication and characterization using scanning probe-based (STM, AFM). We also are developing numerical simulations of localized electric field and emission current to explore mechanisms and characterize limits to processing techniques. We emphasize novel fabrication processes and characterization of physical, chemical and electronic effects in nanostructures.

The process of manufacturing the MC4277 Neutron Tube requires the evacuation of the device through a 4.76 mm (.1875 in.) OD copper tube. Eight tubes are simultaneously evacuated and then baked out. When the process is completed, the tubes must be separated from the system without compromising the ultra-high vacuum in the tube and the system. Previously, a manual pinch-off tool was used. This procedure required up to 3 operators with a high probability of creating defective seals or destroyed tubes. Two new identical robotic systems were built to allow a single operator to consistently produce good tubes with perfect seals. These systems have the added capability of partially pinching off tubes at jaw displacements repeatable to *0.05 mm (kO.002 in.). Both systems have operated flawlessly since their installation in January and March, 1998. A detailed description of these systems is given in this report.

The elevation change data measured at the Weeks Island SPR site over the last 16+ years has been studied and analyzed. The subsidence rate is not constant with time and while the subsidence rate may have increased slightly during the past several years, recently the rate has increased more dramatically. The most recent increase comes at a time when the Strategic Petroleum Reserve (SPR) storage mine had been emptied of oil and was in the process of being refilled with brine. Damage to surface structures that has been observed during the past 12-18 months is attributed to the continued subsidence and dtierential subsidence across structures. The recent greater subsidence rates were unanticipated according to analysis results and will be used to aid further subsidence model development.

This work considers the problem of planning optimal paths for a mobile robot traversing complex terrain. In addition to the existing obstacles, locations in the terrain where the slope is too steep for the mobile robot to navigate safely without tipping over become mathematically equivalent to extra obstacles. To solve the optimal path problem, the authors use a dynamic programming approach. The dynamic programming approach utilized herein does not suffer the difficulties associated with spurious local minima that the artificial potential field approaches do. In fact, a globally optimal solution is guaranteed to be found if a feasible solution exists. The method is demonstrated on several complex examples including very complex terrains.

One of our primary goals was to determine how well a laser Doppler vibrometer (LDV) could measure the structural dynamic response of a wind turbine that was parked in the field. We performed a series of preliminary tests in the lab to determine the basic limitations of the LDV for this application. We then instrumented an installed parked horizontal axis wind turbine with accelerometers to determine the natural frequencies, damping, and mode shapes of the wind turbine and rotor as a baseline for the LDV and our other tests. We also wanted to determine if LDV modal information could be obtained from a naturally (wind) excited wind turbine. We compared concurrently obtained accelerometer and LDV data in an attempt to assess the quality of the LDV data. Our test results indicate the LDV can be successfully used in the field environment of an installed wind turbine, but with a few restrictions. We were successful in obtaining modal information from a naturally (wind) excited wind turbine in the field, but the data analysis requires a large number of averaged data sets to obtain reasonable results. An ultimate goal of this continuing project is to develop a technique that will monitor the health of a structure, detect damage, and hopefully predict an impending component failure.

As the technology for horizontal axis wind turbines (HAWT) development matures, more novel techniques are required for the capture of additional amounts of energy, alleviation of loads and control of the rotor. One such technique employs the use of an adaptive blade that could sense the wind velocity or rotational speed in some fashion and accordingly modify its aerodynamic configuration to meet a desired objective. This could be achieved in either an active or passive manner, although the passive approach is much more attractive due to its simplicity and economy. As an example, a blade design might employ coupling between bending and/or extension, and twisting so that, as it bends and extends due to the action of the aerodynamic and inertial loads, it also twists modifying the aerodynamic performance in some way. These performance modifications also have associated aeroelastic effects, including effects on aeroelastic instability. To address the scope and magnitude of these effects a tool has been developed for investigating classical flutter and divergence of HAWT blades. As a starting point, an adaptive version of the uniform Combined Experiment Blade will be investigated. Flutter and divergence airspeeds will be reported as a function of the strength of the coupling and also be compared to those of generic blade counterparts.

The NWTC (National Wind Technology Center) Variable-Speed Test Bed turbine is a three-bladed, 10-meter, downwind machine that can be run in either fixed-speed or variable-speed mode. In the variable-speed mode, the generator torque is regulated, using a discrete-stepped load bank to maximize the turbine`s power coefficient. At rated power, a second control loop that uses blade pitch to maintain rotor speed essentially as before, i.e., using the load bank to maintain either generator power or (optionally) generator torque. In this paper, the authors will use this turbine to study the effect of variable-speed operation on blade damage. Using time-series data obtained from blade flap and edge strain gauges, the load spectrum for the turbine is developed using rainflow counting techniques. Miner`s rule is then used to determine the damage rates for variable-speed and fixed-speed operation. The results illustrate that the controller algorithm used with this turbine introduces relatively large load cycles into the blade that significantly reduce its service lifetime, while power production is only marginally increased.

We demonstrate that tilted planar ferroelectric domain boundaries create tilted second harmonic beams in nonphase-matched second harmonic generation, and that the tilt of the boundary can be deduced from the harmonic direction.

A resolution study, employing a 3D nonlinear optimization technique, has been undertaken to study the viability of magnetotelluric (MT) measurements to detect and characterize buried facilities that make weapons of mass destruction. A significant advantage of the MT method is that no active source is required because the method employs passive field emissions. Thus measurements can be carried out covertly. Findings indicate it is possible to image WMD facilities, including depth of burial and lateral extent if a sufficient number of measurements are taken on the perimeter of the facility. Moreover if a station measurement can be made directly over the facility then the resolution is improved accordingly. In all cases it was not possible to image the base of the facility with any confidence as well as provide any precise inferences on the facility electrical conductivity. This later finding, however, is really not that critical since knowledge of facility geometry is far more important than knowledge of its conductivity. For the WMD problem it is recommended that MT measurements be made solely with the magnetic field ratios. In this context it would then be possible to deploy with far greater ease small coils about a suspected facility and would allow for the measurements to be conducted in a more covert manner. Before testing such a measurement system in the field, however, it would be necessary to carry out a similar resolution analysis as was done with MT measurements based on electric and magnetic fields. This is necessary to determine sensitivity of the proposed measurement to underground facilities along with needed data coverage and quality. Such a study is indispensable in producing useful reconstructions of underground facilities.

Proton implantation in GaN is found to reduce the free carrier density through two mechanisms - first, by creating electron and hole traps at around Ec-0.8eV and Ev+0.9eV that lead to compensation in both n- and p-type material, and second, by leading to formation of (AH)O complexes, where A is any acceptor (Mg, Ca, Zn, Be, Cd). The former mechanism is usefid in creating high resistivity regions for device isolation, whereas the latter produces unintentional acceptor passivation that is detrimental to device performance. The strong affinity of hydrogen for acceptors leads to markedly different redistribution behavior for implanted in n- and p-GaN due to the chemical reaction to form neutral complexes in the latter. The acceptors may be reactivated by simple annealing at 2600{degrees}C, or by electron injection at 25-150{degrees}C that produces debonding of the (AH) centers. Implanted hydrogen is also strongly attracted to regions of strain in heterostructure samples during annealing, leading to pile-up at epi-epi and epi-substrate interfaces. II? spectroscopy shows that implanted hydrogen also decorates VG, defects in undoped and n-GaN.

Since their invention in the mid-1960's, surface acoustic wave (SAW) devices have become popular for a wide variety of applications. SAW devices represent a low-cost and compact method of achieving a variety of electronic signal processing functions at high frequencies, such as RF filters for TV or mobile wireless communications [1]. SAW devices also provide a convenient platform in chemical sensing applications, achieving extremely high sensitivity to vapor phase analytes in part-per-billion concentrations [2]. Although the SAW acoustic mode can be created on virtually any crystalline substrate, the development of SAW technology has historically focused on the use of piezoelectric materials, such as various orientations of either quartz or lithium niobate, allowing the devices to be fabricated simply and inexpensively. However, the III-V compound semiconductors, and GaAs in particular, are also piezoelectric as a result of their partially covalent bonding and support the SAW acoustic mode, allowing for the convenient fabrication of SAW devices. In addition, GaAs microelectronics has, in the past decade, matured commercially in numerous RF wireless technologies. In fact, GaAs was recognized long ago as a potential candidate for the monolithic integration of SAW devices with microelectronics, to achieve compact RF signal processing functions [3]. The details of design and fabrication of SAW devices can be found in a variety of references [1].

A large-scale field demonstration comparing and contrasting final landfill cover designs has been constructed and is currently being monitored. Four alternative cover designs and two conventional designs (a RCRA Subtitle `D' Soil Cover and a RCRA Subtitle `C' Compacted Clay Cover) were constructed side-by-side for direct comparison. The demonstration is intended to evaluate the various cover designs based on their respective water balance performance, ease and reliability of construction, and cost. This paper provides an overview of the construction costs of each cover design.

The role of the inert gas additive (He, Ar, Xe) to C12 Inductively Coupled Plasmas for dry etching of GaAs and GaSb was examined through the effect on etch rate, surface roughness and near-surface stoichiometry. The etch rates for both materials go through a maximum with Clz 0/0 in each type of discharge (C12/'He, C12/Ar, C12/Xc), reflecting the need to have efficient ion-assisted resorption of the etch products. Etch yields initially increase strongly with source power as the chlorine neutral density increases, but decrease again at high powers as the etching becomes reactant-limited. The etched surfaces are generally smoother with Ax or Xe addition, and maintain their stoichiometry.

Dual control volume grand canonical molecular dynamics (DCV-GCMD) is a boundary-driven non-equilibrium molecular dynamics technique for simulating gradient driven diffusion in multi-component systems. Two control volumes are established at opposite ends of the simulation box. Constant temperature and chemical potential of diffusing species are imposed in the control volumes. This results in stable chemical potential gradients and steady-state diffusion fluxes in the region between the control volumes. We present results and detailed analysis for a new constant-pressure variant of the DCV-GCMD method in which one of the diffusing species for which a steady-state diffusion flux exists does not have to be inserted or deIeted. Constant temperature, pressure and chemical potential of all diffusing species except one are imposed in the control volumes. The constant-pressure method can be applied to situations in which insertion and deletion of large molecules would be prohibitively difficult. As an exampIe, we used the method to shnulate diffusion in a biruuy mixture of spherical particles with a 2:1 size ratio. Steady-state diffusion fluxes of both diffbsi.ng species were established. The constant-pressure diffision coefficients agreed closely with the results of the standard constant-volume calculations. In addition, we show how the concentration, chemical potential and flux profiles can be used to calculate kwd binary and Maxwell-Stefim diffusion coefficients. In the case of the 2:1 size ratio mixture, we found that the binary dlffision coefficients were asymmetric and composition dependent, whereas the Maxwell-Stefan diffision coefficients changed very little with composition and were symmetric. This last result verified that the Gibbs-Duhem relation was satisfied locally, thus validating the assumption of local equilibrium.

The fundamental difficulties incorporating experimentally obtained-boundary disorientation distributions (BMD) into 3D microstructural models are discussed. An algorithm is described which overcomes these difficulties. The boundary misorientations are treated as a statistical ensemble which is evolved toward the desired BMD using a Monte Carlo method. The application of this algorithm to a number complex arbitrary BMDs shows that the approach is effective for both conserved and non-conserved textures. The algorithm is successfully used to create the BMDs observed in deformation microstructure containing both incidental dislocation boundaries (IDBs) and geometrically necessary boundaries (GNBs).

The effects of solute dragon grain growth kinetics were studied in two dimensional (2-D) computer simulations by using a diffuse-interface field model. It is shown that, in the low velocity / low driving force regime, the velocity of a grain boundary motion departs from a linear relation with driving force (curvature) with solute drag. The nonlinear relation of migration velocity and driving force comes from the dependence of grain boundary energy and width on the curvature. The growth exponent m of power growth law for a polycrystalline system is affected by the segregation of solutes to grain boundaries. With the solute drag, the growth exponent m can take any value between 2 and 3 depending on the ratio of lattice diffusion to grain boundary mobility. The grain size and topological distributions are unaffected by solute drag, which are the same as those in a pure system.

The nucleation and growth of cracks at critical interfaces can degrade electrical and mechanical performance of electronic assemblies. Sandia National Laboratories is working to develop a fracture mechanics-based approach for assessing the reliability of components containing interfaces and subjected to thermal/mechanical fatigue. Models are being developed to predict the nucleation of a crack-like flaw in the vicinity of an interface, the path of crack propagation (along interface or into substrate), and the conditions for crack propagation. In addition, interfacial fracture toughness data are being generated to support model development. This paper summarizes an experimental study aimed at measuring the fracture toughness of epoxy-to-substrate interfaces that are representative of those found in bonded and encapsulated electronic components.

A phase-field model for grain growth is briefly described. In this model, a poly-crystalline microstructure is represented by multiple structural order parameter fields whose temporal and spatial evolutions follow the time-dependent Ginzburg-Landau (TDGL) equations. Results from phase-field simulations of two-dimensional (2D) grain growth will be summarized and preliminary results on three-dimensional (3D) grain growth will be presented. The physical interpretation of the structural order parameter fields and the efficient and accurate semi-implicit Fourier spectral method for solving the TDGL equations will be briefly discussed.

The research summarized in this paper is part of a multiyear effort focused on evaluating the viability of wavelet bases for the solution of partial differential equations. The primary objective for this work has been to establish a foundation for hierarchical/wavelet simulation methods based upon numerical performance, computational efficiency, and the ability to exploit the hierarchical adaptive nature of wavelets. This work has demonstrated that hierarchical bases can be effective for problems with a dominant elliptic character. However, the strict enforcement of orthogonality in the usual L 2 sense is less desirable than orthogonality in the energy norm. This conclusion has led to the development of a multi-scale lineax finite element based on a hierarchical change-of-basis. This work considers the numerical and computational performance of the hierarchical Schauder basis in a Galerkin context. A unique row-column lumping procedure is developed with multi-scale solution strategies for 1-D and 2-D elliptic partial differential equations.

An attempt is made to identify preferred values for the work functions of the rare earth elements by correlating the atomic chemical potential with the work function of the bulk elements. Trends in the alkali and alkali earth metal are evaluated in the same context. Strong linear correlation between the two quantities is observed within the IA, 11A, and IIIB (Se, Y, La) groups. Within the lanthanide series the nature of the correlation between the metallic radius and the work function suggests a dependence on the total angular momentum.

Advanced rechargeable lithium-ion batteries are presently being developed and commercialized worldwide for use in consumer electronics, military and space applications. At Sandia National Laboratories we have used different electrochemical techniques such as impedance and charge/discharge at ambient and subambient temperatures to probe the various electrochemical processes that are occurring in Li-ion cell. The purpose of this study is to identify the component that reduces the cell performance at subambient temperatures. Our impedance data suggest that while the variation in the electrolyte resistance between room temperature and {minus}20 C is negligible the anode electrolyte interfacial resistance increases by an order of magnitude in the same temperature regime. We believe that the solid electrolyte interface (SEI) layer on the carbon anode may be responsible for the increase in cell impedance. We have also evaluated the cells in hybrid mode with capacitors. High-current operation in the hybrid mode allowed fill usage of the Li-ion cell capacity at 25 C and showed a factor of 5 improvement in delivered capacity at {minus}20 C.

Silver/glass mirrors have excellent optical properties but need a method of support in order to be used in concentrating solar thermal systems. In collaboration with the Cummins dish/Stirling development program, they started investigating sandwich construction as a way to integrate silver/glass mirrors into solar optical elements. In sandwich construction, membranes such as sheet metal or plastic are bonded to the front and back of a core (like a sandwich). For solar optical elements, a glass mirror is bonded to one of the membranes. This type of construction has the advantages of a high strength-to-weight ratio, and reasonable material and manufacturing cost. The inherent stiffness of sandwich construction mirror panels also facilitates large panels. This can have cost advantages for both the amount of hardware required as well as reduced installation and alignment costs. In addition, by incorporating the panels into the support structure reductions in the amount of structural support required are potentially possible.

A 30-kVA Trace Technologies hybrid power processor was specified and tested at the Sandia inverter test facility. Trace Technologies involving the control system, in response to suggestions made modifications, primarily by Sandia and Arizona Public Service (APS) personnel. The modifications should make the inverter more universally applicable and less site-specific so that it can be applied in various sites with minimal field interaction required from the design engineer. The project emphasized the importance of battery management, generator selection, and site load management to the performance and reliability of hybrid power systems.

We describe Chemical Solution Deposition (CSD) processes by which Strontium Bismuth Tantalate (SBT) thin films can be prepared at temperatures as low as 550 C. In this paper, we will present strategies used to optimize the properties of the films including solution chemistry, film composition, the nature of the substrate (or bottom electrode) used, and the thermal processing cycle. Under suitable conditions, {approximately} 1700 {angstrom} films can be prepared which have a large switchable polarization (2P{sub r} > 10{micro}C/cm{sup 2}), and an operating voltage, defined as the voltage at which 0.80 x 2P{sub r} max is switched, 2.0V. We also describe an all-alkoxide route to SBT films from which SBT can be crystallized at 550 C.

Stirling-cycle engines have been identified as a promising technology for the conversion of concentrated solar energy into usable electrical power. In previous experimented work, we have demonstrated that a heat pipe receiver can significantly improve system performance-over a directly-illuminated heater head. The design and operating conditions of a heat pipe receiver differ significantly from typical laboratory heat pipes. New wick structures have been developed to exploit the characteristics of the solar generation system. Typically, these wick structures allow vapor generation within the wick. Conventional heat pipe models do not handle this enhancement yet it can more than double the performance of the wick. In this study, I develop a steady-state model of a boiling-enhanced wick for a solar heat pipe receiver. The model is used for design-point calculations and is written in FORTRAN90. Some limited comparisons have been made with actual test data.

Commercial microchips work well in their intended environments. However, generic microchips will not fimction correctly if exposed to sufficient amounts of ionizing radiation, the kind that satellites encounter in outer space. Modern CMOS circuits must overcome three specific concerns from ionizing radiation: total-dose, single-event, and dose-rate effects. Minority-carrier devices such as bipolar transistors, optical receivers, and solar cells must also deal with recombination-generation centers caused by displacement damage, which are not major concerns for majority-carrier CMOS devices. There are ways to make the chips themselves more resistant to radiation. This extra protection, called radiation hardening, has been called both a science and an art. Radiation hardening requires both changing the designs of the chips and altering the ways that the chips are manufactured.

We investigated the interaction of dissolved actinides Th, U, Np Zgpu, and Am, with a pure and a mixed culture of halophilic bactezia isolated from the Waste Isolation H.Iot Plant repository under anaerobic conditions to evaluate their potentiaI transport as biocolloids from the waste site. The sizes of the bacterial cells studied ranged from ().54 x 0.48 pm to 7.7 x 0.67pm Using sequential mimofiltration, we determined the ~~ation of actinides with fi-ee-living (mobile) bacterial cells suspended in a fluid medium containing. NaCl or M=W12 brine, at various phaes of their growth cycIes. The number of suspended kcteria rangy-d born 106 to 109 cells ml-*. Tine amount of actinide associatd with the wspend~ cell fraction (cakzdated & mol cell-*) was very Iow: Th, 10-*2; U, 10-1s - 10-lS; - ~ Np, 1o-15- 10-19; Pu, 10-ls -10-21 ; and h, 10-1* - 10-*9 ; and it varied with the bacteihl - CUIture studied. l%e differe&es in the asswiation are amibuted to the extent of bioamxmdation and biosorption by the bacteria pH, the compo&on of the brine, and the speziation and bioavaiIability of the actinides.

The search for a photonic crystal to confine optical waves in all three dimensions (3D) has proven to be a formidable task. It evolves from an early theoretical suggestion [1,2], a brief skepticism [3-5] and triumph in developing the mm-wave [6-8] and infrared 3D photonic crystals [9]. Yet, the challenge remains, as the ultimate goal for optoelectronic applications is to realize a 3D crystal at X=1.5 pm communication wavelengths. Operating at visible and near infrared wavelengths, X=1-2 pm, a photonic crystal may enhance the spontaneous emission rate [1, 10] and give rise to a semiconductor lasers with a zero lasing threshold[11, 12]. Another important application is optically switching, routing and interconnecting light [13,14] with an ultrafast transmission speed of terabits per second. A photonic crystal may also serve as a platform for integrating an all-optical circuitry with multiple photonic components, such as waveguides and switches, built on one chip [15]. In this Letter, we report on the successful fabrication of a working 3D crystal operating at optical L The minimum feature size of the 3D structure is 180 nanometers. The 3D crystal is free from defects over the entire 6-inch silicon wafer and has an absolute photonic band gap centered at A.-1.6 pm. Our data provides the first conclusive evidence for the existence of a full 3D photonic band gap in optical A. This development will pave the way to tinier, cheaper, more effective waveguides, optical switches and lasers.

The effects of the additive noble gases He, Ar and Xe on chlorine-based Inductively Coupled Plasma etching of InP, InSb, InGaP and InGaAs were studied as a function of source power, chuck power and discharge composition. The etch rates of all materials with C12/He and C12/Xe are greater than with C12/Ar. Etch rates in excess of 4.8 pndmin for InP and InSb with C12/He or C12/Xe, 0.9 pndmin for InGaP with C12/Xe, and 3.8 prdmin for InGaAs with Clz/Xe were obtained at 750 W ICP power, 250 W rf power, - 1570 C12 and 5 mTorr. All three plasma chemistries produced smooth morphologies for the etched InGaP surfaces, while the etched surface of InP showed rough morphology under all conditions.

Constraints on assembly plans vary depending on product, assembly facility, assembly volume, and many other factors. Assembly costs and other measures to optimize vary just as widely. To be effective, computer-aided assembly planning systems must allow users to express the plan selection criteria that appIy to their products and production environments. We begin this article by surveying the types of user criteria, both constraints and quality measures, that have been accepted by assembly planning systems to date. The survey is organized along several dimensions, including strategic vs. tactical criteria; manufacturing requirements VS. requirements of the automated planning process itself and the information needed to assess compliance with each criterion. The latter strongly influences the efficiency of planning. We then focus on constraints. We describe a framework to support a wide variety of user constraints for intuitive and efficient assembly planning. Our framework expresses all constraints on a sequencing level, specifying orders and conditions on part mating operations in a number of ways. Constraints are implemented as simple procedures that either accept or reject assembly operations proposed by the planner. For efficiency, some constraints are supplemented with special-purpose modifications to the planner's algorithms. Fast replanning enables an interactive plan-view-constrain-replan cycle that aids in constraint discovery and documentation. We describe an implementation of the framework in a computer-aided assembly planning system and experiments applying the system to a number of complex assemblies, including one with 472 parts.

A 2-D finite element code has been developed for the solution of arbitrary geometry cable SGEMP and box IEMP problems. The quasi- static electric field equations with radiation- induced charge deposition and radiation-induced conductivity y are numerically solved on a triangular mesh. Multiple regions of different dielectric materials and multiple conductors are permitted.

As any structure ages, its structural characteristics will also change. The goal of this work was to determine if modal response data fkom a wind turbine could be used in the detection of damage. The input stimuli to the wind turbine were from traditional modal hammer input and natural wind excitation. The structural response data was acquired using accelerometers mounted on the rotor of a parked and undamaged horizontal-axis wind turbine. The bolts at the root of one of the three blades were then loosened to simulate a damaged blade. The structural response data of the rotor was again recorded. The undamaged and damage-simulated datasets were compared using existing darnage detection algorithms. Also, a novel algorithm for combining the results of different damage detection algorithms was utilized in the assessment of the data. This paper summarizes the code development and discusses some preliminary damage detection results.

The use of a digital infrared as a non-destructive evaluation thermography camera (NDE) tool was ex- plored in two separate wind turbine blade fatigue tests. The fwst test was a fatigue test of part of a 13.1 meter wood-epoxy-composite blade. The second test was on a 4.25 meter pultruded fiber glass blade section driven at several mechanical resonant frequencies. The digital infrared camera can produce images of either the static temperature distribution on the surface of the specimen, or the dynamic temperature distribution that is in phase with a specific frequency on a vibrating specimen. The dynamic temperature distribution (due to thermoplastic effects) gives a measure of the sum of the principal stresses at each point on the surface. In the wood- epoxy-composite blade fatigue test, the point of ultimate failure was detected long before failure occurred. The mode shapes obtained with the digital infrared camera, from the resonant blade tests, were in very good agree- ment with the finite-element calculations. In addition, the static temperature images of the resonating blade showed two areas that contained cracks. Close-up dy- namic inf%red images of these areas showed the crack structure that agreed with subsequent dye-penetrant analysis.

We have completed and exercised a communication framework called CHI (CLOS to HTML Interface) by which agents can communicate with humans. CHI follows HTTP (HyperText Transfer Protocol) and produces HTML (HyperText Markup Language) for use by WWW (World-Wide Web) browsers. CHI enables the rapid and dynamic construction of interface mechanisms. The essence of CHI is automatic registration of dynamically generated interface elements to named objects in the agent's internal environment. The agent can access information in these objects at will. State is preserved, so an agent can pursue branching interaction sequences, activate failure recovery behaviors, and otherwise act opportunistically to maintain a conversation. The CHI mechanism remains transparent in multi-agent, multi-user environments because of automatically generated unique identifiers built into the CHI mechanism. In this paper we discuss design, language, implementation, and extension issues, and, by way of illustration, examine the use of the general CHI/HCHI mechanism in a specific international electronic commerce system. We conclude that the CHI mechanism is an effective, efficient, and extensible means of the agent/human communication.

We have successfully developed a method for fabricating scandate-based thermionic emitters in thin film form. The primary goal of our effort is to develop thin film emitters that exhibit low work fimction, high intrinsic electron emissivity, minimum thermal activation properties and that can be readily incorporated into a microgap converter. Our approach has been to incorporate BaSrO into a SqOq matrix using rf sputtering to produce thin films. Diode testing has shown the resulting films to be electron emissive at temperatures as low as 900 K with current densities of 0.1 mA.cm-2 at 1100 K and saturation voltages. We calculate an approximate maximum work function of 1.8 eV and an apparent emission constant (Richardson's constant, A*) of 36 mA.cm-2.K-2. Film compositional and structural analysis shows that a significant surface and subsurface alkaline earth hydroxide phase can form and probably explains the limited utilization and stability of Ba and its surface complexes. The flexibility inherent in sputter deposition suggests alternate strategies for eliminating undesirable phases and optimizing thin film emitter properties.

The Video Scanning Hartmann Optical Tester (VSHOT) is a laser ray-trace tool for measuring the slope error of solar concentrator mirrors. The VSHOT measurements made on two, 8.5-m diameter, Distal II dishes represent its first use on a concentrator installed and operating in the field. A number of valuable lessons were learned regarding the use of the VSHOT for outdoor testing. The two dishes were found to have overall figure-of-merit RMS slope errors from an ideal parabola of 2.99 and 3.18 milliradians. The VSHOT measurements compare well qualitatively with distant observer photographs made using a colored concentric ring target.

We report on our work on the double electron layer tunneling transistor (DELTT), based on the gate-control of two-dimensional -- two-dimensional (2D-2D) tunneling in a double quantum well heterostructure. While previous quantum transistors have typically required tiny laterally-defined features, by contrast the DELTT is entirely planar and can be reliably fabricated in large numbers. We use a novel epoxy-bond-and-stop-etch (EBASE) flip-chip process, whereby submicron gating on opposite sides of semiconductor epitaxial layers as thin as 0.24 microns can be achieved. Because both electron layers in the DELTT are 2D, the resonant tunneling features are unusually sharp, and can be easily modulated with one or more surface gates. We demonstrate DELTTs with peak-to-valley ratios in the source-drain I-V curve of order 20:1 below 1 K. Both the height and position of the resonant current peak can be controlled by gate voltage over a wide range. DELTTs with larger subband energy offsets ({approximately} 21 meV) exhibit characteristics that are nearly as good at 77 K, in good agreement with our theoretical calculations. Using these devices, we also demonstrate bistable memories operating at 77 K. Finally, we briefly discuss the prospects for room temperature operation, increases in gain, and high-speed.

Numerical codes have become indispensable for designing underground structures and interpretating the behavior of geologic systems. Because of the complexities of geologic systems, however, code calculations often are associated with large quantitative uncertainties. This papers presents three examples to demonstrate the value of laboratory(or bench scale) experiments to evaluate the predictive capabilities of such codes with five major conclusions: Laboratory or bench-scale experiments are a very cost-effective, controlled means of evaluating and validating numerical codes, not instead of but before or at least concurrent with the implementation of in situ studies. The design of good laboratory validation tests must identifj what aspects of a code are to be scrutinized in order to optimize the size, geometry, boundary conditions, and duration of the experiments. The design of good and sometimes difficult numerical analyses and sensitivity studies. Laboratory validation tests must involve: Good validation experiments will generate independent data sets to identify the combined effect of constitutive models, model generalizations, material parameters, and numerical algorithms. Successfid validations of numerical codes mandate a close collaboration between experimentalists and analysts drawing from the full gamut of observations, measurements, and mathematical results.

Highly crystalline, size-selected silicon (Si) nanocrystals in the size range 2-10 nm were grown in inverse micelles and their optical absorption and photoluminescence (PL) properties were studied. High resolution TEM and electron diffraction results show that these nanocrystals retain their cubic diamond stuctures down to sizes {approximately}4 nm in diameter, and optical absorption data suggest that this structure and bulk-like properties are retained down to the smallest sizes produced ({approximately}1.8 nm diameter containing about 150 Si atoms). High pressure liquid chromatography techniques with on-line optical and electrical diagnostics were developed to purify and separate the clusters into pure, monodisperse populations. The optical absorption revealed features associated with both the indirect and direct bandgap transitions, and these transitions exhibited different quantum confinement effects. The indirect bandgap shifts from 1.1 eV in the bulk to {approximately}2.1 eV for nanocrystals {approximately}2 nm in diameter and the direct transition at r(l_"X - r15) blue shifts by 0.4 eV from its 3.4 eV bulk value over the same size range. Tailorable, visible, room temperature PL in the range 700-350 nm (1.8 - 3.5 eV) was observed from these nanocrystals. The most intense PL was in the violet region of the spectrum ({approximately}400 nm) and is attributed to direct electron-hole recombination. Other less intense PL peaks are attributed to surface state and to indirect bandgap recombination. The results are compared to earlier work on Si clusters grown by other techniques and to the predictions of various model calculations. Currently, the wide variations in the theoretical predictions of the various models along with considerable uncertainties in experimental size determination for clusters less than 3-4 nm, make it difficult to select among competing models.

Rectangular trench profiles are modeled with analytic etch rates determined from measured ion distribution functions. The pattern transfer step for this plasma etch is for trilayer lithography. Argon and chlorine angular ion energy distribution functions measured by a spherical collector ring analyzer are fit to a sum of drifting Maxwellian velocity distribution functions with anisotropic temperatures. The fit of the model ion distribution functions by a simulated annealing optimization procedure converges adequately for only two drifting Maxwellians. The etch rates are proportional to analytic expressions for the ion energy flux. Numerical computation of the etch profiles by integration of the characteristic equations for profile points and connection of the profiles points is efficient.

In this paper we report absolute intensities of vacuum ultraviolet and near ultraviolet emission lines (4.8 eV to 18 eV ) for aluminum etching discharges in an inductively coupled plasma reactor. We report line intensities as a function of wafer type, pressure, gas mixture and rf excitation level. IrI a standard aluminum etching mixture containing C12 and BC13 almost all the light emitted at energies exceeding 8.8 eV was due to neutral atomic chlorine. Optical trapping of the WV radiation in the discharge complicates calculations of VUV fluxes to the wafer. However, we see total photon fluxes to the wailer at energies above 8.8 eV on the order of 4 x 1014 photons/cm2sec with anon- reactive wafer and 0.7 x 10 `4 photons/cm2sec with a reactive wtier. The maj ority of the radiation observed was between 8.9 and 9.3 eV. At these energies, the photons have enough energy to create electron-hole pairs in Si02, but may penetrate up to a micron into the Si02 before being absorbed. Relevance of these measurements to vacuum-W photon-induced darnage of Si02 during etching is discussed.

To examine the forces of acid-base adhesive interactions at the molecular level, we utilize the scanning probe Interracial Force Microscope (IFM). Unlike cantilever-based atomic force microscopes, the EM is a non-compliant, mechanically stable probe that provides a complete adhesive profile without jump-to-contact. In this way, we are able to quantitatively measure the work of adhesion and bond energies at well-defined, nanometer-scale single asperity contacts. In particular, we will discuss the displacement-controlled adhesive forces between self-assembled monolayer of functionalized alkanethiols strongly bound to a gold substrate and a similarly functionalized tip. We also discuss a method utilizing decoupled lateral and normal force sensors to simultaneously observe the onset of both friction and chemical bond formation. Measurements show that friction can be directly attributed to bond formation and rupture well before repulsive contact.

To probe directly the analyte/film interactions that characterize molecular recognition in gas sensors, we recorded changes to the in-situ surface vibrational spectra of specifically fictionalized surface acoustic wave (SAW) devices concurrently with analyte exposure and SAW measurement of the extent of sorption. Fourier-lmnsform infrared external- reflectance spectra (FTIR-ERS) were collected from operating 97-MH2 SAW delay lines during exposure to a range of analytes as they interacted with thin-film coatings previously shown to be selective: cyclodextrins for chiral recognition, Ni-camphorates for Lewis bases such as pyridine and organophosphonates, and phthalocyanines for aromatic compounds. In most cases where specific chemical interactions-metal coordination, "cage" compound inclusion, or z stacking-were expected, analyte dosing caused distinctive changes in the IR spectr~ together with anomalously large SAW sensor responses. In contrast, control experiments involving the physisorption of the same analytes by conventional organic polymers did not cause similar changes in the IR spectra, and the SAW responses were smaller. For a given conventional polymer, the partition coefficients (or SAW sensor signals) roughly followed the analyte fraction of saturation vapor pressure. These SAW/FTIR results support earlier conclusions derived from thickness-shear mode resonator data.

Patterning the group-IH nitrides has been challenging due to their strong bond energies and relatively inert chemical nature as compared to other compound semiconductors. Plasma etch processes have been used almost exclusively to pattern these films. The use of high-density plasma etch systems, including inductively coupled plasmas (ICP), has resulted in relatively high etch rates (often greater than 1.0 pmhnin) with anisotropic profiles and smooth etch morphologies. However, the etch mechanism is often dominated by high ion bombardment energies which can minimize etch selectivity. The use of an ICP-generated BCl~/C12 pkyma has yielded a highly versatile GaN etch process with rates ranging from 100 to 8000 A/rnin making this plasma chemistry a prime candidate for optimization of etch selectivity. In this study, we will report ICP etch rates and selectivities for GaN, AIN, and InN as a function of BCl~/Clz flow ratios, cathode rf-power, and ICP-source power. GaN:InN and GaN:AIN etch selectivities were typically less than 7:1 and showed the strongest dependence on flow ratio. This trend maybe attributed to faster GaN etch rates observed at higher concentrations of atomic Cl which was monitored using optical emission spectroscopy (OES). ~E~~~~f:~ INTRODUCTION DEC j 4898 Etch selectivi

Abstract not provided.

At the 1995 IEEE Symposium on Assembly and Task Planning, Sandia National Laboratories introduced the Archimedes 2 Software Tool [2]. The system was described as a second-generation assembly planning system that allowed preliminmy application of awembly planning for industry, while solidly supporting further research in planning techniques. Sandia has worked closely with indust~ and academia over the last four years. The results of these working relationships have bridged a gap for the next generation in assembly planning. Zke goal of this paper is to share Sandia 's technological advancements in assembly planning over the last four years and the impact these advancements have made on the manufacturing communip.

When a product concept emerges, the manufacturing engineer is asked to sketch out a production strategy and estimate its cost. The engineer is given an initial product design, along with a schedule of expected production volumes. The engineer then determines the best approach to manufacturing the product, comparing a variey of alternative production strategies. The engineer must consider capital cost, operating cost, lead-time, and other issues in an attempt to maximize pro$ts. After making these basic choices and sketching the design of overall production, the engineer produces estimates of the required capital, operating costs, and production capacity. 177is process may iterate as the product design is refined in order to improve its pe~ormance or manufacturability. The focus of this paper is on the development of computer tools to aid manufacturing engineers in their decision-making processes. This computer sof~are tool provides aj?amework in which accurate cost estimates can be seamlessly derivedfiom design requirements at the start of any engineering project. Z+e result is faster cycle times through first-pass success; lower ll~e cycie cost due to requirements-driven design and accurate cost estimates derived early in the process.