Spectrofluorometric imaging microscopy is demonstrated in a confocal microscope using a supercontinuum laser as an excitation source and a custom-built prism spectrometer for detection. This microscope system provides confocal imaging with spectrally resolved fluorescence excitation and detection from 450 to 700 nm. The supercontinuum laser provides a broad spectrum light source and is coupled with an acousto-optic tunable filter to provide continuously tunable fluorescence excitation with a 1-nm bandwidth. Eight different excitation wavelengths can be simultaneously selected. The prism spectrometer provides spectrally resolved detection with sensitivity comparable to a standard confocal system. This new microscope system enables optimal access to a multitude of fluorophores and provides fluorescence excitation and emission spectra for each location in a 3D confocal image. The speed of the spectral scans is suitable for spectrofluorometric imaging of live cells. Effects of chromatic aberration are modest and do not significantly limit the spatial resolution of the confocal measurements.
New low-temperature combustion (LTC) strategies can reduce both NOx and soot emissions from compression-ignition engines, but unburned hydrocarbon (UHC) emissions typically increase. Incylinder UHC evolution can be marked by formaldehyde, an intermediate species in the combustion process. Formaldehyde is formed during the first stage of ignition of diesel-like fuels, and it persists along with UHC in regions that do not achieve complete combustion. During the second stage of ignition, fuel and formaldehyde are largely consumed as OH radicals become prominent. The appearance of OH therefore indicates second-stage ignition and relatively complete combustion of fuel. Simultaneous planar laser-induced fluorescence (PLIF) images of formaldehyde and OH are acquired for two LTC conditions with different ignition delays, using neat n-heptane fuel. For both cases, formaldehyde PLIF is initially observed throughout the jet. Later, OH PLIF first appears downstream in the jet, where formaldehyde and UHC are locally consumed. For the shorter ignition-delay condition, OH PLIF quickly appears upstream locally where formaldehyde PLIF decreases, marking second-stage ignition and consumption of formaldehyde and UHC. For the longer ignition-delay condition, however, OH PLIF does not appear upstream, even late in combustion. Rather, formaldehyde PLIF, and therefore UHCs, persist near the injector late in combustion, indicating that regions near the injector do not achieve complete combustion, and may contribute to UHC emissions for the longer ignition delay condition.
As the amount of real time data collected during drilling continues to rise, sophisticated methods for analyzing and displaying data are needed to make sense out of large volumes of data. This paper describes a novel use of the concepts of computational geometry to analyze and display data from a downhole drilling data tool. The use of a mathematical transformation called a convex hull allows one to create a boundary around a set (cloud) of data points. This is most easily visualized in two dimensions as putting a rubber band around the set of points. Imagine that the rubber band is such that it will be tightly stretched when it is around all the points, so that certain points in the data cloud dictate the resulting outline. A convex hull software routine, the best known of which is the"qhull" program from the University of Minnesota, fits line segments around a cloud of points in up to nine dimensions. Utilizing the convex hull output one can calculate the volume in 3-D or area in 2-D described by data clouds. The result is used as an indicator of bit and drill string behavior. Copyright 2007, Society of Petroleum Engineers.
This report contains the results of a research effort on advanced robot locomotion. The majority of this work focuses on walking robots. Walking robot applications include delivery of special payloads to unique locations that require human locomotion to exo-skeleton human assistance applications. A walking robot could step over obstacles and move through narrow openings that a wheeled or tracked vehicle could not overcome. It could pick up and manipulate objects in ways that a standard robot gripper could not. Most importantly, a walking robot would be able to rapidly perform these tasks through an intuitive user interface that mimics natural human motion. The largest obstacle arises in emulating stability and balance control naturally present in humans but needed for bipedal locomotion in a robot. A tracked robot is bulky and limited, but a wide wheel base assures passive stability. Human bipedal motion is so common that it is taken for granted, but bipedal motion requires active balance and stability control for which the analysis is non-trivial. This report contains an extensive literature study on the state-of-the-art of legged robotics, and it additionally provides the analysis, simulation, and hardware verification of two variants of a proto-type leg design.
Over the years, researchers have been investigating large-scale pool fores, both experimentally and numerically, because of the risk they pose during transport accidents. In the course of developing and validating computational models, researchers have come to realize that knowledge of the soot concentration, temperature and optical properties within fires is required to quantify the amount of heat transferred. In turn, such knowledge may help in understanding the dynamics of fires, particularly large accidental ones.
A shear test was used to investigate the effect of shielding gas (Argon, Nitrogen and air) on the mechanical properties of laser spot welds in Fe-28Ni-17Co alloy (Kovar). The load vs. displacement curves obtained, while superficially resembling those of a standard tensile test, were quite non-reproducible, and obscured the differences due to process conditions. Fractographic examination of the samples and analysis of the testing conditions led to significant conclusions about how to correctly interpret the shear test results, which in turn enabled a determination of the real effects of the change in shielding gas. Several different types of fracture morphology were noted, depending upon how the fracture surface developed relative to the original weld. This resulted in the disparate nature of the load-displacement curves. The results of the shear testing, fractography and metallography will be used to support interpretation of the differences found with respect to porosity formation, strength and work hardening behavior.
Collection of Technical Papers - AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference
Robertson, Lawrence M.; Lane, Steven A.; Ingram, Brea R.; Hansen, Eric J.; Babuska, Vit B.; Goodding, James; Mimovich, Mark; Mehle, Gregory; Coombs, Doug; Ardelean, Emil V.
A top level overview of the effect cables have on the dynamic response of precision structures is presented. The focus of this paper is on precision, low-damping, low-first modal frequency space structures where cables are not implicitly designed to be in the load path. The paper presents the top-level, Phase I results which include pathfinder tests, an industry/government/academia survey, modeling and testing of individual cable bundles, and modeling and testing of cables on a simple structure. The end goal is to discover a set of practical approaches for updating well defined dynamical models of cableless structures. Knowledge of the cable type, position and tie-down method is assumed to be known. Simulation sensitivity analysis of the effect cables have on a precision structure has also been completed. Each section of the paper will focus on the details of each area.
Collection of Technical Papers - AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference
Ardelean, Emil V.; Goodding, James C.; Mehle, Gregory; Coombs, Douglas M.; Babuska, Vit B.; Robertson, Lawrence M.; Lane, Steven A.; Ingram, Brea R.; Hansen, Eric J.
This paper presents experimental results and modeling aspects for electrical power and signal cable harnesses used for space applications. Dynamics of large precision structures can be significantly influenced by subsystems such as electrical cables and harnesses as the structural mass of those structures tends to become smaller, and the quantity of attached cables continues to increase largely due to the ever increasing complexity of such structures. Contributions of cables to structural dynamic responses were observed but never studied, except for a low scale research effort conducted at the Air Force Research Laboratory, Space Vehicles Directorate (AFRL/VSSV). General observations were that at low frequencies cables have a mass loading effect while at higher frequencies they have a dissipative effect. The cables studied here adhere to space industry practices, identified through an extensive industry survey. Experimental procedures for extracting structural properties of the cables were developed. The structural properties of the cables extracted from the extensive experimental database that is being created can be used for numerical modeling of cabled structures. Explicit methods for analytical modeling of electrical cables attached to a structure in general are yet to be developed and the goal of this effort is to advance the state of the art in modeling cable harnesses mounted on lightweight spacecraft structures.
Signal and power harnesses on spacecraft buses and payloads can alter structural dynamics, as has been noted in previous flight programs. The community, however, has never undertaken a thorough study to understand the impact of harness dynamics on spacecraft structures. The Air Force Research Laboratory is leading a test and analysis program to develop fundamental knowledge of how spacecraft harnesses impact dynamics and develop tools that structural designers could use to achieve accurate predictions of cable-dressed structures. The work described in this paper involved a beam under simulated free boundary conditions that served as a validation test bed for model development.
Current published models for predicting squeeze film damping (SFD), which are based on different assumptions, give widely different results in the free-molecule regime. The work presented here provides experimental data for validating SFD models in that regime. The test device was an almost rectangular micro plate supported by beam springs. The structure was base-excited. The rigid plate oscillated vertically while staying parallel to the substrate. The velocities of the plate and of the substrate were measured with a laser Doppler vibrometer and a microscope. The damping ratio was calculated by performing modal analysis of the frequency response functions. The test structures were contained in a vacuum chamber with air pressures controlled to provide a five-order-of-magnitude range of Knudsen numbers. The damping coefficients from the measurements were compared with predictions from various published models. The results show that the continuum-base Reynolds equation predicts squeeze-film damping accurately if used with correct boundary conditions. The accuracy of molecular-based models depends heavily on the assumptions used in developing the models.
Full-waveform seismic reflection responses of an isolated porous sandstone layer are simulated with three-dimensional (3D) isotropic poroelastic and isotropic elastic finite-difference (FD) numerical algorithms. When the pore-filling fluid is brine water with realistic viscosity, there is about a ∼10% difference in synthetic seismograms observed in an AVO recording geometry. These preliminary results suggest that equivalent elastic medium modeling is adequate for general interpretive purposes, but more refined investigations (such as AVO waveform analysis) should account for poroelastic wave propagation effects.
Visual simultaneous localization and mapping (VSLAM) is the problem of using video input to reconstruct the 3D world and the path of the camera in an 'on-line' manner. Since the data is processed in real time, one does not have access to all of the data at once. (Contrast this with structure from motion (SFM), which is usually formulated as an 'off-line' process on all the data seen, and is not time dependent.) A VSLAM solution is useful for mobile robot navigation or as an assistant for humans exploring an unknown environment. This report documents the design and implementation of a VSLAM system that consists of a small inertial measurement unit (IMU) and camera. The approach is based on a modified Extended Kalman Filter. This research was performed under a Laboratory Directed Research and Development (LDRD) effort.
Materials Science and Technology Conference and Exhibition, MS and T'07 - "Exploring Structure, Processing, and Applications Across Multiple Materials Systems"
Review of High Pressure Science and Technology/Koatsuryoku No Kagaku To Gijutsu
Asay, James R.
The ability to study material response during isentropic compression has been a grand challenge of the scientific community for several decades. However, development of precision techniques for producing isentropic compression at high pressures has been limited. The revolutionary advance for using planar magnetic loading on the Z accelerator accelerated this goal by enabling quasi-isentropic studies on macroscopically sized materials to over 5 Mbar. In addition, the accelerator is easily configured to launch flyer plates to velocities more than four times higher than possible with conventional launchers, thus allowing shock compression studies in the laboratory to pressures exceeding 20 Mbar.
An experimental apparatus is described that measures gas-surface thermal accommodation coefficients from the pressure dependence of the conductive heat flux between parallel plates separated by a gas-filled gap. Heat flux between the plates is inferred from measurements of temperature drop between the plate surface and an adjacent temperature-controlled water bath. Thermal accommodation coefficients are determined from the pressure dependence of the heat flux at a fixed plate separation. The apparatus is designed to conduct tests with a variety of gases in contact with interchangeable, well-characterized surfaces of various materials (e.g., metals, ceramics, semiconductors) with various surface finishes (e.g., smooth, rough). Experiments are reported for three gases (argon, nitrogen, and helium) in contact with pairs of 304 stainless steel plates prepared with one of two finishes: lathe-machined or mirror-polished. For argon and nitrogen, the measured accommodation coefficients for machined and polished plates are near unity and independent of finish to within experimental uncertainty. For helium, the accommodation coefficients are much lower and show a slight variation with surface roughness. Two different methods are used to determine the accommodation coefficient from experimental data: the Sherman-Lees formula and the GTR formula. These approaches yield values of 0.87 and 0.94 for argon, 0.80 and 0.86 for nitrogen, 0.36 and 0.38 for helium with the machined finish, and 0.40 and 0.42 for helium with the polished finish, respectively, with an uncertainty of ±0.02. The GTR values for argon and nitrogen are generally in better agreement with the results of other investigators than the Sherman-Lees values are, and both helium results are in reasonable agreement with values in the literature.
The convergence behavior of the Direct Simulation Monte Carlo (DSMC) method is investigated for transient flows. Two types of flows are considered: a Couette-like flow, in which an initial velocity profile decays in time, and a Fourier-like flow, in which an initial temperature profile decays in time. DSMC results are presented for hard-sphere argon with Knudsen numbers in the range 0.01-0.4. Low-Knudsen-number DSMC results are compared with Navier-Stokes results. The DSMC discretization errors from finite time step and finite cell size (in the limit of infinite number of computational molecules per cell) are compared with the predictions of Green-Kubo theory for conditions in this regime.
By using a radio frequency (RF) audio distortion measurement test setup, communication devices can be evaluated for degradation caused by electromagnetic interference (EMI) from active vehicle components. This measurement technique can be used to determine the performance of a radio receiver under a variety of conditions. The test setup consists of making measurements on a baseband audio signal that is sent to the device under test (receiver) via over-the-air RF transmissions. Once a baseline is established, active components on the vehicle can be powered on to determine their contribution to the receiver's degradation. The degradation measured is a result of distortion caused by conducted, radiated, and/or coupled EMI from active components into the receiver's passband.
The electrical, thermal, and mechanical responses of surface micromachined (SMM) 2-beam actuators have been simulated using the Calagio code, a coupled physics analysis tool. The present analysis, unlike previous analyses, includes the surrounding air in the computational domain so that heat losses from the beams onto the silicon substrate will be accurately modeled. This setup is essential because the existing 'shape factor' correlations have difficulty capturing the threedimensional geometric effect of the heat loss in the shuttle at the center that connects the bent beams. In addition, results from the present analysis reveal that because the local heat flux can be extremely high, a significant temperature jump can occur across the air-structure interfaces.
Boundary layer transition continues to be a critical factor in hypersonic fight vehicle design. Measurements of transition during hypersonic flight testing provide valuable data for the development and verification of transition prediction techniques. A summary of transition measurement techniques used on vehicles flown by Sandia National Laboratories is presented, including sample flight data to illustrate the type of transition indication obtained from each measurement technique. SHARP-B2, a ballistic vehicle flown by Sandia for NASA, is used as a case study to illustrate how transition is determined for a flight vehicle and to illustrate some of the difficulties associated with these types of measurements.
IRMMW-THz2007 - Conference Digest of the Joint 32nd International Conference on Infrared and Millimetre Waves, and 15th International Conference on Terahertz Electronics
This paper presents heterodyne mixer measurements at 2.9 THz using quantum cascade lasers (QCLs) as sources. The linewidth of the laser was explored by biasing it to run in dual mode operation and observing the linewidth of the beat note. In addition the frequency of the QCL is determined by beating it against a deuterated methanol line from a molecular gas laser.
Prior HCCI optical engine experiments utilizing laser-induced fluorescence (LIF) measurements of stratified fuel-air mixtures have demonstrated the utility of probability density function (PDF) statistics for correlating mixture preparation with combustion. However, PDF statistics neglect all spatial details of in-cylinder fuel distribution. The current computational paper examines the effects of spatial fuel distribution on combustion using a novel combination of a 3-D CFD model with a 1-D linear-eddy model of turbulent mixing. In the simulations, the spatial coarseness of initial fuel distribution prior to the start of heat release is varied while keeping PDF statistics constant. Several cases are run, and as the initial mixture is made coarser, combustion phasing monotonically advances due to high local equivalence ratios that persist longer. The effect of turbulent mixing is more complex. For the case where the length scale of the initial distribution matches the integral length scale of turbulence, turbulent mixing leads to moderation of peak heat-release rate. The randomness of turbulence is captured in the simulation, and for the above case, cycle-to-cycle variation of the combustion is evident. In contrast, when the initial fuel distribution is significantly finer or coarser than the turbulence length scale, turbulent mixing does not affect combustion for two different reasons. For fine distributions, molecular diffusion alone homogenizes the fuel-air mixture prior to ignition, so turbulence adds nothing. For initial distributions that are coarse compared to the turbulence length scale, diffusion and turbulence are both ineffective at mixing, so again turbulence has a minimal effect on combustion.
Cyclic ethers, like tetrahydrofuran (THF), are formed during the autoignition of alkanes and subsequently influence their combustion chemistry. To learn more about the oxidation chemistry of these ether intermediates, a fuel-rich THF flame (π = 1.75) has been studied using the versatile technique of flame-sampling Molecular Beam Mass Spectrometry (MBMS) in combination with single-photon ionization. Several cyclic intermediates which are potentially formed by dehydrogenation of the fuel are identified by their ionization energies. Ethylene, propene, ketene and formaldehyde are major stable decomposition products of THF and their mole fraction profiles are presented. Detected oxygenated species include ethenol, acetaldehyde and propanal. Despite the fuel-rich conditions, the concentrations of benzene and other aromatic hydrocarbons are near the detection limit.
Western States Section/Combustion Institute Fall Meeting 2007
Lignell, D.O.; Hewson, J.C.; Chen, J.H.
Modelling soot formation in turbulent nonpremixed combustion is a difficult problem. Unlike most gaseous combustion species, soot lacks a strong state relationship with the mixture fraction due to unsteady formation rates which overlap transport timescales, and strong differential diffusion between gaseous species and soot. The conditional moment closure model (CMC) has recently been applied to the problem of turbulent soot formation. A challenge in CMC modelling is the treatment of differential diffusion. Three-dimensional direct numerical simulation (DNS) of a nonpremixed ethylene jet flame with soot formation has been performed for the first time, using a nineteen species reduced ethylene mechanism and a four-step, three-moment, semi-empirical soot model. The DNS provides full resolution of the turbulent flow field and is used to perform a-priori analysis of a new CMC model derived from the joint scalar PDF transport equation. Unlike other approaches, this CMC model does not require additional transport equations to treat differentially diffusing species. A budget of the terms of the CMC equation for both gaseous species and soot is presented. In particular, exact expressions for unclosed terms are compared to typical closure models for scalar dissipation, cross dissipation, differential diffusion, and reactive source terms.
Western States Section/Combustion Institute Fall Meeting 2007
Lignell, D.O.; Chen, J.H.; Lu, T.; Law, C.K.
Direct numerical simulation of a nonpremixed, turbulent, ethylene jet flame is performed to investigate fundamental mechanisms of extinction and reignition processes. A reduced ethylene mechanism consisting of nineteen transported and ten quasi-steady state species, with 167 reactions was used, along with mixture averaged transport properties. The flow configuration is a temporally-evolving slot jet at a Reynolds number of 5,120. Extreme extinction of the nonpremixed flame occurs, followed by a period of intense turbulent scalar mixing between reactants and quenched products in which less than 2stratified mixture with nonhomogeneous composition and temperature. Various modes of reignition are analyzed-autoignition, edge flame propagation, and premixed flame propagation-by monitoring Takeno's flame index [H. Yamashitia, M. Shimada, and T. Takeno, Proc. Combust. Inst., 26 (1996) 27-34], homogeneous ignition delay times by sampling the mixture prior to reignition, and the turbulent displacement speed of the reaction front. The dominant reignition mechanism is found to be premixed flame propagation commencing from a few high temperature flame kernels which survive near global extinction.
Lecture Notes in Computational Science and Engineering
Phipps, Eric; Casey, Richard; Guckenheimer, John
Periodic processes are ubiquitous in biological systems, yet modeling these processes with high fidelity as periodic orbits of dynamical systems is challenging. Moreover, mathematical models of biological processes frequently contain many poorly-known parameters. This paper describes techniques for computing periodic orbits in systems of hybrid differential-algebraic equations and parameter estimation methods for fitting these orbits to data. These techniques make extensive use of automatic differentiation to evaluate derivatives accurately and efficiently for time integration, parameter sensitivities, root finding and optimization. The resulting algorithms allow periodic orbits to be computed to high accuracy using coarse discretizations. Derivative computations are carried out using a new automatic differentiation package called ADMC++ that provides derivatives and Taylor series coefficients of matrix-valued functions written in the MATLAB programming language. The algorithms are applied to a periodic orbit problem in rigid-body dynamics and a parameter estimation problem in neural oscillations.
Many large-scale computations involve a mesh and first (or sometimes higher) partial derivatives of functions of mesh elements. In principle, automatic differentiation (AD) can provide the requisite partials more efficiently and accurately than conventional finite-difference approximations. AD requires source-code modifications, which may be little more than changes to declarations. Such simple changes can easily give improved results, e.g., when Jacobian-vector products are used iteratively to solve nonlinear equations. When gradients are required (say, for optimization) and the problem involves many variables, "backward" AD in theory is very efficient, but when carried out automatically and straightforwardly, may use a prohibitive amount of memory. In this case, applying AD separately to each element function and manually assembling the gradient pieces - semiautomatic differentiation - can deliver gradients efficiently and accurately. This paper concerns on-going work; it compares several implementations of backward AD, describes a simple operator-overloading implementation specialized for gradient computations, and compares the implementations on some mesh-optimization examples. Ideas from the specialized implementation could be used in fully general source-to-source translators for C and C++.
Nanometric aluminum (123nm, spherical) was mixed with two different sieve-cut sizes of HMX (106-150 μm and 212-300 μm), and a series of gas gun tests were conducted to compare reactive wave development in pure HMX to that of aluminized HMX. In the absence of added metal, 4-mm-thick, low-density (68% of theoretical maximum density) pressings of the 106-150 μm HMX respond to modest shock loading by developing distinctive reactive waves that exhibit both temporal and meso-scale spatial fluctuations. Similar pressings of Al/HMX containing 10% aluminum (by mass) show an initial suppression of the usual wave growth seen in HMX samples. The suppression is then followed by an induction period where it is hypothesized that a phase change in the aluminum may occur. Data from VISAR, line-ORVIS, and 2-color pyrometry are given and discussed, and numerical modeling of inert sucrose is used to aid the explanation of the resulting data.
Simulations of a low-speed square cylinder wake and a supersonic axisymmetric base wake are performed using the detached eddy simulation model. A reduced-dissipation form of a shock-capturing flux scheme is employed to mitigate the effects of dissipative error in regions of smooth flow. The reduced-dissipation scheme is demonstrated on a two-dimensional square cylinder wake problem, showing a marked improvement in accuracy for a given grid resolution. The results for simulations on three grids of increasing resolution for the three-dimensional square cylinder wake are compared with experimental data and to other computational studies. The comparisons of mean flow and global flow quantities to experimental data are favorable, whereas the results for second order statistics hi the wake are mixed and do not always improve with increasing spatial resolution. Comparisons to large eddy simulation are also generally favorable, suggesting detached eddy simulation provides an adequate subgrid scale model. Predictions of base drag and centerline wake velocity for the supersonic wake are also good, given sufficient grid refinement. These cases add to the validation library for detached eddy simulation and support its use as an engineering analysis tool for accurate prediction of global flow quantities and mean flow properties.
In order to better understand how the US natural gas network might respond to disruptions, a model was created that represents the network on a regional basis. Natural gas storage for each region is represented as a stock. Transmission between each region is represented as a flow, as is natural gas production, importation, and consumption. Various disruption scenarios were run to test the robustness of the network. The system as modeled proved robust to a variety of disruption scenarios. However, a weakness of the system is that production shortfalls or interruptions cannot be replaced, and demand must therefore be reduced by the amount of the shortfall.
An oxidation treatment, often termed "pre-oxidation", is performed on austenitic stainless steel prior to joining to alkali barium silicate glass to produce hermetic seals. The resulting thin oxide acts as a transitional layer and a source of Cr and other elements which diffuse into the glass during the subsequent bonding process. Pre-oxidation is performed in a low pO2 atmosphere to avoid iron oxide formation and the final oxide is composed of Cr2O3, MnCr2O4 spinel, and SiO2. Significant heat-to-heat variations in the oxidation behavior of 304L stainless steel have been observed, which result in inconsistent glass-to-metal (GTM) seal behavior. The objectives of this work were to characterize the stainless steel pre-oxidized layer and the glass/oxide/304L interface region after glass sealing. The 304L oxidation kinetics were determined by thermogravimetric (TG) analysis and the glass/metal seals characteristics were studied using sessile drop tests, in which wetting angles were measured and glass adhesion was analyzed. The pre-oxidized layers and glass/metal interface regions were characterized using metallography, focused ion beam (FIB) sectioning, scanning and transmission electron microscopy, and electron probe microanalysis (EPMA). The results show that poor glass sealing behavior is associated with a more continuous layer of SiO 2 at the metal/oxide interface.
Many systems can be approximated as linear with coefficients that vary periodically with time. For example, an anisotropic shaft rotating at constant speed on anisotropic bearings can be modeled as periodically time varying (PTV). Similar models can be obtained for wind turbines, some mechanisms, etc... However, the vast majority of modal analysis algorithms and techniques apply only to linear time invariant (LTI) systems. In this paper, two methods are demonstrated by which the free response of a periodically time varying system can be exactly parameterized by an LTI system. The parameters of the LTI representation can then be identified using standard techniques. The analysis techniques are demonstrated on a simple system, representing a rotor mounted on an anisotropic, flexible shaft, supported by anisotropic bearings. They are then applied to synthetic response data for a system with parameters that vary only weakly with time, as might be encountered when attempting to detect small cracks in a rotating shaft. These examples demonstrate the methods' ability to characterize the anisotropy of the shaft, even when both the shaft and supports are anisotropic.
This paper presents a new method for the analysis of sinusoidal aquifer test data that extends current analytical techniques to include the analysis of pressure responses in multi-layer aquifers. The multi-layer sinusoidal solution is applied to data from a series of sinusoidal aquifer tests conducted in the two-layered Culebra dolomite at the Waste Isolation Pilot Plant near Carlsbad, NM. In addition to the multilayered solution, a summary of available sinusoidal solutions is provided along with tools to pre-process sinusoidal response data.
Gaussian processes are used as emulators for expensive computer simulations. Recently, Gaussian processes have also been used to model the "error field" or "code discrepancy" between a computer simulation code and experimental data, and the delta term between two levels of computer simulation (multi-fidelity codes). This work presents the use of Gaussian process models to approximate error or delta fields, and examines how one calculates the parameters governing the process. In multi-fidelity modeling, the delta term is used to correct a lower fidelity model to match or approximate a higher fidelity model. The terms governing the Gaussian process (e.g., the parameters of the covariance matrix) are updated using a Bayesian approach. We have found that use of Gaussian process models requires a good understanding of the method itself and an understanding of the problem in enough detail to identify reasonable covariance parameters. The methods are not "black-box" methods that can be used without some statistical understanding. However, Gaussian processes offer the ability to account for uncertainties in prediction. This approach can help reduce the number of high-fidelity function evaluations necessary in multi-fidelity optimization.
Forces generated by a static magnetic field interacting with eddy currents can provide a novel method of vibration damping. This paper discusses an experiment performed to validate modeling [3] for a case where a static magnetic field penetrates a thin sheet of conducting, non-magnetic material. When the thin sheet experiences motion, the penetrating magnetic field generates eddy currents within the sheet. These eddy currents then interact with the static field, creating magnetic forces that act on the sheet, providing damping to the sheet motion. In the presented experiment, the sheet was supported by cantilever springs attached to a frame, then excited with a vibratory shaker. The recorded motions of the sheet and the frame were used to characterize the effect of the eddy current damping.
Multiple references are often used to excite a structure in modal testing programs. This is necessary to excite all the modes and to extract accurate mode shapes when closely spaced roots are present. An algorithm known as SMAC (Synthesize Modes And Correlate), based on principles of modal filtering, has been in development for several years. This extraction technique calculates reciprocal modal vectors based on frequency response function (FRF) measurements. SMAC was developed to accurately extract modes from structures with moderately damped modes and/or high modal density. In the past SMAC has only worked with single reference data. This paper presents an extension of SMAC to work with multiple reference data. If roots are truly perfectly repeated, the mode shapes extracted by any method will be a linear combination of the "true" shapes. However, most closely spaced roots are not perfectly repeated but have some small difference in frequency and/or damping. SMAC exploits these very small differences. The multi-reference capability of SMAC begins with an evaluation of the MMIF (Multivariate Mode Indicator Function) or CMIF (Complex Mode Indicator Function) from the starting frequency list to determine which roots are likely repeated. Several seed roots are scattered in the region of the suspected multiple roots and convergence is obtained. Mode shapes are then created from each of the references individually. The final set of mode shapes are selected based on one of three different selection techniques. Each of these is presented in this paper. SMAC has long included synthesis of FRFs and MIFs from the roots and residues to check extraction quality against the original data, but the capability to include residual effects has been minimal. Its capabilities for including residual vectors to account for out-of-band modes have now been greatly enhanced. The ability to resynthesize FRFs and mode indicator functions from the final mode shapes and residual information has also been developed. Examples are provided utilizing the SMAC package on multi-reference experimental data from two different systems.
A finite element (FE) model of a shell-payload structure is to be used to predict structural dynamic acceleration response to untestable blast environments. To understand the confidence level of these predictions, the model will be validated using test data from a blast tube experiment. The first step in validating the structural response is to validate the loading. A computational fluid dynamics (CFD) code, Saccara, was used to provide the blast tube pressure loading to the FE model. This paper describes the validation of the CFD pressure loading and its uncertainty quantification with respect to experimental pressure data obtained from geometrical mock-up structures instrumented with pressure gages in multiple nominal blast tube tests. A systematic validation approach was used from the uncertainty quantification group at Sandia National Labs. Significant effort was applied to distill the pressure loading to a small number of validation metrics important to obtaining valid final response which is in terms of acceleration shock response spectrum. Uncertainty in the pressure loading amplitude is quantified so that it can be applied to the validation blast tube test on the shell payload structure which has significant acceleration instrumentation but only a few pressure gages.
International SAMPE Symposium and Exhibition (Proceedings)
Crane, Nathan B.; Wilkes, Jan; Sachs, Emanuel; Allen, Samuel M.
This work reports on the densification of iron nanoparticles by slow drying followed by pressureless sintering. In contrast, most previous work has used high heating rates to both dry and density the nanoparticle suspension in a single step. Laser heating has been required to achieve high densities by this approach. The slow drying/pressureless sintering approach is shown to be sensitive to reactions between the particles, the stabilizing ligands, the atmosphere, and the substrate. The sintering rate of iron nanoparticles and the final composition of the deposits are significantly impacted by these interactions. However, in both the cases studied, the nanoparticles densify under pressureless sintering. When the iron nanoparticle colloid is dried in a porous steel skeleton, it is shown to increase high-temperature strength and reduce the sintering shrinkage.
Oxygen-fuel fired glass melting furnaces have successfully reduced NO x and particulate emissions and improved the furnace energy efficiency relative to the more conventional air-fuel fired technology. However, full optimisation of the oxygen/fuel approach (particularly with respect to crown refractory corrosion) is unlikely to be achieved until there is improved understanding of the effects of furnace operating conditions on alkali vaporization, batch carryover, and the formation of gaseous air pollutants in operating furnaces. In this investigation, continuous online measurements of alkali concentration (by laser induced breakdown spectroscopy) were coupled with measurements of the flue gas composition in the exhaust of an oxygen/natural gas fired container glass furnace. The burner stoichiometry was purposefully varied while maintaining normal glass production. The data demonstrate that alkali vaporization and SO2 release increase as the oxygen concentration in the exhaust decreases. NOx emissions showed a direct correlation with the flow rate of infiltrated air into the combustion space. The extent of batch carryover was primarily affected by variations in the furnace differential pressure. The furnace temperature did not vary significantly during the measurement campaign, so no clear correlation could be obtained between the available measurements of furnace temperature and alkali vaporization.
Techniques to ensure shock data quality and to recognize bad data are discussed in this paper. For certain shock environments, acceleration response up to ten kHz is desired for structural model validation purposes. The validity and uncertainty associated with the experimental data need to be known in order to use it effectively in model validation. In some cases the frequency content of impulsive or pyrotechnic loading or metal to metal contact of joints in the structure may excite accelerometer resonances at hundreds of kHz. The piezoresistive accelerometers often used to measure such events can provide unreliable data depending on the level and frequency content of the shock. The filtered acceleration time history may not reveal that the data are unreliable. Some data validity considerations include accelerometer mounting systems, sampling rates, band-edge settings, peak acceleration specifications, signal conditioning bandwidth, accelerometer mounted resonance and signal processing checks. One approach for uncertainty quantification of the sensors, signal conditioning and data acquisition system is also explained.
Proceedings of the 11th International High Level Radioactive Waste Management Conference, IHLRWM
James, Scott C.; Dickinson, Jesse E.; Mehl, Steffen W.; Hill, Mary C.; Leake, Stanley A.; Zyvoloski, George A.; Eddebbarh, Al A.
A flexible, robust method for linking grids of locally refined ground-water flow models constructed with different numerical methods is needed to address a variety of hydrologic problems. This work outlines and tests a new ghost-node model-linking method for a refined "child" model that is contained within a larger and coarser "parent" model that is based on the iterative method of Steffen W. Mehl and Mary C. Hill (2002, Advances in Water Res., 25, p. 497-511; 2004, Advances in Water Res., 27, p. 899-912). The method is applicable to steady-state solutions for ground-water flow. Tests are presented for a homogeneous two-dimensional system that has matching grids (parent cells border an integer number of child cells) or nonmatching grids. The coupled grids are simulated by using the finite-difference and finite-element models MODFLOW and FEHM, respectively. The simulations require no alteration of the MODFLOW or FEHM models and are executed using a batch file on Windows operating systems. Results indicate that when the grids are matched spatially so that nodes and child-cell boundaries are aligned, the new coupling technique has error nearly equal to that when coupling two MODFLOW models. When the grids are nonmatching, model accuracy is slightly increased compared to that for matching-grid cases. Overall, results indicate that the ghost-node technique is a viable means to couple distinct models because the overall head and flow errors relative to the analytical solution are less than if only the regional coarse-grid model was used to simulate flow in the child model's domain.
A discussion on an active gas imager that can potentially improve system performance and reliability in Smart Leak Detection and Repair covers conventional single-wavelength imaging; differential imaging; methane detection; modification for detecting fugitive emissions relevant to refineries and chemical plants; and system description. This is an abstract of a paper presented at the AWMA's 99th Annual Conference and Exhibition (New Orleans, LA 6/20-23/2006).
The RADTRAN Loss of Shielding (LOS) Model was benchmarked using MicroShield 6.20®. This analysis considers an intact spent fuel truck cask as well as a set of damaged truck casks. Ratios of dose rates are calculated for casks with a loss of lead shielding to those of intact casks, and are then compared to ratios generated by the LOS model. LOS Model results were considered verified if two main constraints were satisfied. First, the dose rate profiles for both the LOS and MicroShield 6.20® calculations must have the same general shape and behavior. Additionally, the largest factor difference between any two points of the dose rate profiles may not exceed an order of magnitude. Reasonable agreement is shown for large-fraction LOS scenarios; however the differences in results are not satisfactory for cases with small fractions of slump.
A wide variety of MicroElectroMechanical Systems (MEMS) are fabricated using existing novel technologies. State-of-the art integrated circuit (IC) fabrication methods are used for the fabrication of these MEMS. The fabrication of these structures requires many process steps that include deposition, patterning, etching, and CMP. The use of CMP enables the fabrication of complex, multi-level MEMS. Similar to IC fabrication, there are concerns about non-uniformity, erosion and dishing after CMP, but because of the thickness of the materials, CMP processing issues are amplified. Unlike ICs, there is no transistor basic building block so processing must be technology specific and process development is driven by the device/system performance requirements, which are very specific to the application.
When a micro cantilever beam is excited by base shaking, electrostatic force makes the tip displacement response nonlinear with respect to the base acceleration input. This paper derives a single-degree-of-freedom model for the deflection in a micro cantilever due to electrostatic voltage for this excitation. The tip deflection due to electrostatic force is derived first as part of the total tip deflection, and then in terms of an equivalent base excitation. The relationship between electrostatic deflection and equivalent base excitation is determined numerically, but can be represented accurately by a simple curve-fit function.
Electroslag Remelting (ESR) is a complex process used to produce high quality specialty alloy materials. The quality can be directly correlated to variances in melt rate and immersion depth. Conventional ESR furnaces control these quantities using two independent control loops using proportional changes in current for melt rate and driving the electrode up and down to match a voltage set point for immersion depth. However it is well known that the control loops are highly coupled, i.e. changing the current to account for melt rate deviations changes the voltage depth relationship and vice verse. In addition the noise in measurements of the ESR process can be considerable, forcing conventional controllers to use highly damped responses. A new model-based controller has been developed to embody the coupling and improve responsiveness by using estimates from a reduced-order linear ESR model and the typical process measurements to control melt rate and immersion depth simultaneously. Kalman filtering is used to optimally combine the model estimates of eight process states and the measurements of voltage, current, position and mass to estimate the instantaneous melt rate and immersion depth. Several ESR melts under steady state and transient conditions were conducted to evaluate the performance of the new controller. This paper will discuss the design of the new ESR model and controller and will present experimental results demonstrating its much improved control and responsiveness. While this controller was developed for the ESR process, the effectiveness of model-based control in managing such a complex process with relatively simple equations suggests the approach could be employed for many other processes as well.
This paper 1 develops a novel control system design methodology that uniquely combines: concepts from thermodynamic exergy and entropy; Hamiltonian systems; Lyapunov's direct method and Lyapunov optimal analysis; electric AC power concepts; and power flow analysis. Relationships are derived between exergy/entropy and Lyapunov optimal functions for Hamiltonian systems. The methodology is demonstrated with two fundamental numerical simulation examples: 1) a Duffing oscillator/Coulomb friction nonlinear model that employs PID regulator control and 2) a van der Pol nonlinear oscillator system. The control system performances and/or appropriately identified terms are partitioned and evaluated based on exergy generation and exergy dissipation terms. This novel nonlinear control methodology results in both necessary and sufficient conditions for stability of nonlinear systems.
A series of pressurized sulfuric acid decomposition tests are being performed to (1) obtain data on the fraction of sulfuric acid catalytically converted to sulfur dioxide, oxygen, and water as a function of temperature and pressure, (2) demonstrate real-time measurements of acid conversion for use as process control in the Sulfur-Iodine (SI) thermochemical cycle, and (3) obtain multiple measurements of conversion as a function of temperature within a single experiment. Acid conversion data are presented at pressures of 6 and 11 bars in the temperature range of 750 - 875 °C. The design for an acid decomposer section with heat and mass recovery of undecomposed acid using a direct contact heat exchanger are presented.
Acoustic wave propagation in a three-dimensional atmosphere that is spatially heterogeneous, time-varying, and/or moving is accurately simulated with a numerical algorithm recently developed under the DOD Common High Performance Computing Software Support Initiative (CHSSI). Sound waves within such a dynamic environment are mathematically described by a set of four, coupled, first-order partial differential equations governing small-amplitude fluctuations in pressure and particle velocity. The system is rigorously derived from fundamental principles of continuum mechanics, ideal-fluid constitutive relations, and reasonable assumptions that the ambient atmospheric motion is adiabatic and divergence-free. An explicit, finite-difference time-domain (FDTD) numerical scheme is used to solve the system for both pressure and particle velocity wavefields. Dependent variables are stored on staggered spatial and temporal grids, and centered FDTD operators possess 2nd-order and 4th-order space/time accuracy. We first present results of a test that shows the accuracy of our algorithm by comparison with analytic formulations. We then present a contrast and comparison of the sound character at a series of distances from a point source activated with a causal source. We are able to investigate the effects of turbulence, complex meteorology (including wind effects), a topographically variable ground surface, and a partially reflective ground surface.
A series of pressurized sulfuric acid decomposition tests are being performed to (1) obtain data on the fraction of sulfuric acid catalytically converted to sulfur dioxide, oxygen, and water as a function of temperature and pressure, (2) demonstrate real-time measurements of acid conversion for use as process control in the Sulfur-Iodine (SI) thermochemical cycle, and (3) obtain multiple measurements of conversion as a function of temperature within a single experiment. Acid conversion data are presented at pressures of 6 and 11 bars in the temperature range of 750 - 875 °C. The design for an acid decomposer section with heat and mass recovery of undecomposed acid using a direct contact heat exchanger are presented.
Advances in Powder Metallurgy and Particulate Materials - 2006, Proceedings of the 2006 International Conference on Powder Metallurgy and Particulate Materials, PowderMet 2006
Laser Engineered Net-shaping (LENS®) can directly manufacture near net shape metallic components from CAD files. The thermal history associated with LENS® process, which involves numerous reheating cycles, is critical to the microstructural evolution and mechanical properties of the LENS® fabricated parts. In this paper, the surface morphology of as-atomized PH13-8Mo steel powder is characterized; Variation of the height of deposited materials with process parameters is measured; Microhardness and tensile tests are carried out to evaluate the mechanical performance of LENS® deposited PH13-8Mo components; Microstructural analysis is conducted using OM, SEM, TEM to understand the microstructural evolution of the LENS® deposited PH13-8Mo samples; The thermal history and its effects on microstructural evolution and resultant mechanical properties is studied in order to understand the relationship between processing parameter, microstructure and mechanical properties of the LENS® fabricated PH13-8Mo components.
The heat output of the radioactive waste proposed to be emplaced at Yucca Mountain will strongly affect the thermal-hydrological (TH) conditions in and near the geologic repository for thousands of years. Recent computational fluid dynamics (CFD) analysis has demonstrated that the emplacement tunnels (drifts) will act as important conduits for gas flows driven by natural convection. As a result, vapor generated from boiling/evaporation of formation water near elevated-temperature sections of the drifts may effectively be transported to cooler end sections (where no waste is emplaced), would condense there, and subsequently drain into underlying rock units. To study these processes, we have developed a new simulation method that couples existing tools for simulating TH conditions in the fractured formation with modules that approximate natural convection in heated emplacement drifts. The new method is applied to evaluate the future TH conditions at Yucca Mountain in a three-dimensional model domain comprising a representative emplacement drift and the surrounding fractured rock.
IEEE Antennas and Propagation Society, AP-S International Symposium (Digest)
Feldner, Lucas M.; Rodenbeck, Christopher T.; Christodoulou, Christos G.
A tunable electrically small PIFA-as-a-package antenna for miniature wireless device applications has been developed using conventional printed circuit board processing techniques and commercial-off-the-shelf surface mount switches. The design is scalable to any frequency and form factor, while enabling adaptive tuning of the characteristically narrow band resonance of electrically small antennas. Our UHF prototype measures less than 2" (.08λ) on its longest side and provides approximately - 9dBi of gain from 419-472 MHz. Simulated and measured results will be discussed in the presentation.
The effects of diameter on detonation velocity of packed granular beds of HNS (2,2',4,4',6,6'-hexanitrostilbene) and CL-20 (2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane, HNIW) will be discussed. Due to the novel nature of the diagnostic technique utilized here, a thorough discussion of the experimental method is provided. The dimension at which finite diameter effects occur was characterized by conducting simultaneous streak camera and framing camera measurements on miniature rate sticks similar in concept to traditional rate sticks. A significant difference between historical rate sticks and those discussed here comes in the form of how they were produced. A femtosecond laser was used to generate precision miniature rate sticks down to diameters of 187 μm. Finally, we will discuss the somewhat unexpected result of nano particulate generation of energetic materials due to the laser machining process.
Encapsulation of high voltage transformers can be a difficult undertaking. Stresses arise due to the coefficient of thermal expansion (CTE) mismatch of the components. Due to the viscoelastic nature of the encapsulation, these stresses can change over time. Excessive tensile stress in the ceramic cores results in cracks which can affect the performance of the transformer. The transformer that is the subject of this paper performed well after manufacturing and an initial thermal cycle; four years later however, the same transformer failed during the heat-up portion of a similar thermal cycle. X-rays revealed a large crack in the ceramic core. This paper summarizes the elastic and nonlinear viscoelastic finite element modeling that was done in support of the failure investigation and redesign of the transformer. In both the elastic and viscoelastic finite element models, the maximum principal tensile stresses at the low temperature condition of the thermal cycle exceeded the estimated ultimate tensile strength of the core material. At room temperature, the models predicted that the maximum principal tensile stresses were sufficiently high to produce subcritical crack growth in the core material. The viscoelastic model indicated that the core could experience a significant increase in stress due to physical aging of the encapsulation. Modeling stresses compared well to the cracks found in the failed transformer. The final design utilized a silicone coating applied to the interior surfaces of the cores. The coating acts as a stress relief layer that decouples the high CTE encapsulation from the ceramic core. The addition of the silicone coating resulted in a significant stress reduction. X-rays of transformers made with the silicone coating reveal no cracks in the cores.
A new approach to explosive sample preparation is described in which microelectronics-related processing techniques are utilized. Fused silica and alumina substrates were prepared utilizing laser machining. Films of PETN were deposited into channels within the substrates by physical vapor deposition. Four distinct explosive behaviors were observed with high-speed framing photography by driving the films with a donor explosive. Initiation at hot spots was directly observed, followed by either energy dissipation leading to failure, or growth to a detonation. Unsteady behavior in velocity and structure was observed as reactive waves failed due to decreasing channel width. Mesoscale simulations were performed to assist in experiment development and understanding. We have demonstrated the ability to pattern these films of explosives and preliminary mesoscale simulations of arrays of voids showed effects dependent on void size and that detonation would not develop with voids below a certain size. Future work involves experimentation on deposited films with regular patterned porosity to elucidate mesoscale explosive behavior.
Future energy systems based on gasification of coal or biomass for co-production of electrical power and gaseous or liquid fuels may require gas turbine operation on unusual fuel mixtures. In addition, global climate change concerns may dictate the production of a CO2 product stream for end-use or sequestration, with potential impacts on the oxidizer used in the gas turbine. In this study the operation at atmospheric pressure of a small, optically accessible swirl-stabilized premixed combustor, burning fuels ranging from pure methane to conventional and H2-rich and H2-lean syngas mixtures is investigated. Both air and CO2-diluted oxygen are used as the oxidizers. CO and NOx emissions for these flames have been determined over the full range of stoichiometrics from the lean blow-off limit to slightly rich conditions (φ ∼ 1.03). The presence of hydrogen in the syngas fuel mixtures results in more compact, higher temperature flames, resulting in increased flame stability and higher NOx emissions. The lean blowoff limit and the lean stoichiometry at which CO emissions become significant both decrease with increasing H2 content in the syngas. For the investigated mixtures, CO emissions near the stoichiometric point do not become significant until (φ > 0.95. At this stoichiometric limit, where dilute-oxygen power systems would preferably operate, CO emissions rise more rapidly for combustion in O2-CO2 mixtures than for combustion in air.
A mesoscale dimensional artifact based on silicon bulk micromachining fabrication has been developed with the intention of evaluating the artifact both on a high precision Coordinate Measuring Machine (CMM), and on a video-probe based measuring system. A high accuracy touch-probe based CMM can achieve accuracies that are as good as the 2-D repeatability of video-probe systems. While video-probe based systems are commonly used to inspect mesoscale mechanical components, a video-probe system's certified accuracy is generally much worse than its repeatability. By using a hybrid artifact where the same features can be extracted by both a touch-probe and a video-probe, the accuracy of video-probe systems can be improved. In order to use the micromachined device as a calibration artifact, it is important to understand the uncertainty present in the touch-probe measurements. An uncertainty analysis is presented to show the potential accuracy of the measurement of these artifacts on a high precision CMM.
This paper describes a high-rel transformer design and the design iterations required to meet the severe environments of military grade transformers. It describes a method of reducing the mechanical stress caused when a ferrite pot core is encapsulated in a rigid epoxy. Stresses are due to differences in coefficient of thermal expansion between the two materials. The mechanical design optimization of a small flyback transformer designed to charge an energy storage capacitor up to 6 kV from a low voltage source is described. The basic design uses a 2616 manganese zinc ferrite pot core. The goal was to eliminate the core cracking problem. The purpose for writing and presenting this paper is to document a proven process that evolved out of necessity, and to present to the industry a method which reduces stresses on the core, eliminates cracking of the core and provides the insulation necessary for small high voltage transformers.
Organic polymer materials are used frequently in structures and transportation systems. Polymer materials may provide fuel for a fire or be damaged catastrophically due to an incident heat flux. Modeling the response of such structures and systems in fire environments has important applications in safety and vulnerability analyses. The decomposition chemistry of the organic polymer materials is an important factor in many analyses. To provide input to numerical models for hazard and vulnerability analyses, the thermal decomposition chemistry of organic polymers is being experimentally investigated using TGA-FTIR, GC-FTIR, infrared microprobe (IRMP), and DSC Both TGA-FTIR and DSC experiments are done with unconfined and partially confined samples. Unconfined samples are used to examine initial decomposition reactions. Partially confined samples are used to examine reversible and secondary reactions. This paper discusses phenomena pertinent to using the aforementioned techniques to develop rate expressions for polymer decomposition reactions, and a specific example illustrating development of rate expressions for decomposition of PMMA is given.
Decomposition of PGN (Poly Glycidyl Nitrate) has been investigated using TJump/ FTIR (Fourier Transform Infrared Spectroscopy) and STMBMS (Simultaneous Thermogravimetric Modulated Beam Mass Spectrometry) in an effort to understand the effects of hydroxyl end-modification and isocyanate curing of PGN. T-Jump/FTIR allows real-time determination and quantification of decomposition gas products as samples are heated very fast (20°C/s) to simulate deflagration conditions. Our results identify decomposition gas products including: CH2O, H2O, CO2, CO, N2O, NO, NO2, HCN and HONO. PGN deflagration kinetic rates relative to CO2 formation and preliminary results on the effects of hydroxyl end-capping are presented. Slow heating, STMBS experiments aid in discerning possible mechanistic pathways by temporally separating decomposition gas products as they evolve. These results show that thermal decomposition of PGN is controlled by a three step reaction process: (I) decomposition of the CH2-ONO2 functional moiety, (II) reactions of initial low-molecular-weight species with each other, and (III) reactions of lowmolecular-weight species with the polymer backbone. While this work focuses only on ncured PGN prepolymer, future results will include the effects of isocyanate curing on standard and end-modified PGN.
The development of tools and techniques for security testing and performance testing of Process Control Systems (PCS) is needed since those systems are vulnerable to the same classes of threats as other networked computer systems. In practice, security testing is difficult to perform on operational PCS because it introduces an unacceptable risk of disruption to the critical systems (e.g., power grids) that they control. In addition, the hardware used in PCS is often expensive, making full-scale mockup systems for live experiments impractical. A more flexible approach to these problems can be provided through test beds that provide the proper mix of real, emulated, and virtual elements to model large, complex systems such as critical infrastructures. This paper describes a "Virtual Control System Environment" that addresses these issues.
Removable polymer coatings were evaluated as a means to suppress dehydration of Alodine chromate conversion coatings during thermal aging and thereby retain the corrosion protection afforded by Alodine. Two types of polymer coatings were applied to Alodine-treated panels of aluminum alloys 7075-T73 and 6061-T6 that were subsequently aged for 15 to 50 hours at temperatures between 135 F to 200 F. The corrosion resistance of the thermally aged panels was evaluated, after stripping the polymer coatings, by exposure to a standard salt-fog corrosion test and the extent of pitting of the polymer-coated and untreated panels compared. Removable polymer coatings mitigated the loss of corrosion resistance due to thermal aging experienced by the untreated alloys. An epoxide coating was more effective than a fluorosilicone coating as a dehydration barrier.
TufFoam™ is a TDI-free, water-blown, closed-cell, rigid polyurethane foam (PU) initially formulated as an electronics encapsulant to mitigate the effects of harsh mechanical environments. Because it contains no TDI, the handling hazards and chemical sensitization associated with exposure during processing of common, commercial PU foams are obviated. The mechanical properties of TufFoam™ have been found to be comparable or superior to conventional TDI-based foams. Beyond its original intent, it has since found use in a variety of additional applications, including as a structural material and as a thermal and electrical insulating material. TufFoam™ constituents are commercially available in commodity quantities and batch processing schedules have been developed for its preparation at densities ranging from 0.03 to 0.70 g/cc (2 to 40 pcf). TufFoam™ has a uniform, fine cell structure over the entire range of density explored. Its Tg is somewhat dependant on the cure temperature, but is approximately 127°C when cured at 65°C. The coefficient of thermal expansion (CTE) is 7x10 -5 °C -1. TufFoam™ is electrically insulating with a volume resistivity of 3x10 17 ohm-cm at a density of 0.1 g/cc.
Frictional contact results in surface and subsurface damage that could influence the performance, aging, and reliability of moving mechanical assemblies. Changes in surface roughness, hardness, grain size and texture often occur during the initial run-in period, resulting in the evolution of subsurface layers with characteristic microstructural features that are different from those of the bulk. The objective of this LDRD funded research was to model friction-induced microstructures. In order to accomplish this objective, novel experimental techniques were developed to make friction measurements on single crystal surfaces along specific crystallographic surfaces. Focused ion beam techniques were used to prepare cross-sections of wear scars, and electron backscattered diffraction (EBSD) and TEM to understand the deformation, orientation changes, and recrystallization that are associated with sliding wear. The extent of subsurface deformation and the coefficient of friction were strongly dependent on the crystal orientation. These experimental observations and insights were used to develop and validate phenomenological models. A phenomenological model was developed to elucidate the relationships between deformation, microstructure formation, and friction during wear. The contact mechanics problem was described by well-known mathematical solutions for the stresses during sliding friction. Crystal plasticity theory was used to describe the evolution of dislocation content in the worn material, which in turn provided an estimate of the characteristic microstructural feature size as a function of the imposed strain. An analysis of grain boundary sliding in ultra-fine-grained material provided a mechanism for lubrication, and model predictions of the contribution of grain boundary sliding (relative to plastic deformation) to lubrication were in good qualitative agreement with experimental evidence. A nanomechanics-based approach has been developed for characterizing the mechanical response of wear surfaces. Coatings are often required to mitigate friction and wear. Amongst other factors, plastic deformation of the substrate determines the coating-substrate interface reliability. Finite element modeling has been applied to predict the plastic deformation for the specific case of diamond-like carbon (DLC) coated Ni alloy substrates.
Electroluminescence from self-assembled InAs quantum dots in cascade-like unipolar heterostructures is demonstrated. Initial results show weak luminescence signals in the mid-infrared from such structures, though more recent designs exhibit significantly stronger luminescence with improved designs of the active region of these devices. Further studies of mid-infrared emitting quantum dot structures have shown anisotropically polarized emission at multiple wavelengths. A qualitative explanation of such luminescence is developed and used to understand the growth morphology of buried quantum dots grown on AlAs layers. Finally, a novel design for future mid-infrared quantum dot emitters, intended to increase excited state scattering times and, at the same time, more efficiently extract carriers from the lowest states of our quantum dots, is presented,.
Genetic expression and control pathways can be successfully modeled as electrical circuits. To tackle large multicellular and genome scale simulations, the massively-parallel, electronic circuit simulator, Xyce™ [11], was adapted to address biological problems. Unique to this bio-circuit simulator is the ability to simulate not just one or a set of genetic circuits in a cell, but many cells and their internal circuits interacting through a common environment. Additionally, the circuit simulator Xyce can couple to the optimization and uncertainty analysis framework Dakota [2] allowing one to find viable parameter spaces for normal cell functionality and required parameter ranges for unknown or difficult to measure biological constants. Using such tools, we investigate the Drosophila sp. segmental differentiation network's stability as a function of initial conditions.
The probability of a laser caused ocular injury, to the aircrew of an undetected aircraft entering the exclusion zone about the AURA LIDAR airborne platform with the possible violation of the Laser Hazard Zone boundary, was investigated and quantified for risk analysis and management.
Dargaville, Tim R.; Elliott, Julie M.; Jones, Gary D.; Celina, Mathias C.
Piezoelectric polymers based on polyvinylidene fluoride (PVDF) are of interest as smart materials for novel space-based telescope applications. Dimensional adjustments of adaptive thin polymer films are achieved via controlled charge deposition. Predicting their long-term performance requires a detailed understanding of the piezoelectric property changes that develop during space environmental exposure. The overall materials performance is governed by a combination of chemical and physical degradation processes occurring in low Earth orbit as established by our past laboratory-based materials performance experiments (see report SAND 2005-6846). Molecular changes are primarily induced via radiative damage, and physical damage from temperature and atomic oxygen exposure is evident as depoling, loss of orientation and surface erosion. The current project extension has allowed us to design and fabricate small experimental units to be exposed to low Earth orbit environments as part of the Materials International Space Station Experiments program. The space exposure of these piezoelectric polymers will verify the observed trends and their degradation pathways, and provide feedback on using piezoelectric polymer films in space. This will be the first time that PVDF-based adaptive polymer films will be operated and exposed to combined atomic oxygen, solar UV and temperature variations in an actual space environment. The experiments are designed to be fully autonomous, involving cyclic application of excitation voltages, sensitive film position sensors and remote data logging. This mission will provide critically needed feedback on the long-term performance and degradation of such materials, and ultimately the feasibility of large adaptive and low weight optical systems utilizing these polymers in space.
Four Well-Characterized Open Pool fires were conducted by Fire Science and Technology Department. The focus of the Well-Characterized Open Pool fire series was to provide environmental information for open pool fires on a physics first principal basis. The experiments measured the burning rate of liquid fuel in an open pool and the resultant heat flux to a weapon-sized object and the surrounding environment with well-characterized boundary and initial conditions. Results presented in this report include a general description of test observation (pre- and post-test), wind measurements, fire plume topology, average fuel recession and heat release rates, and incident heat flux to the pool and to the calorimeters. As expected, results of the experiments show a strong correlation between wind conditions, fuel vaporization (mass loss) rate, and incident heat flux to the fuel and ground surface and calorimeters. Numerical fire simulations using both temporally- and spatially-dependant wind boundary conditions were performed using the Vulcan fire code. Comparisons of data to simulation predictions showed similar trends; however, simulation-predicted incident heat fluxes were lower than measured.
This report examines the localization of time harmonic high frequency modal fields in two dimensional cavities along periodic paths between opposing sides of the cavity. The cases where these orbits lead to unstable localized modes are known as scars. This paper examines the enhancements for these unstable orbits when the opposing mirrors are both convex and concave. In the latter case the construction includes the treatment of interior foci.
Establishing a Cartesian coordinate reference system for an existing Compact Antenna Range using the parabolic reflector is presented. A SMX (Spatial Metrix Corporation) M/N 4000 laser-based coordinate measuring system established absolute coordinates for the facility. Electric field characteristics with positional movement correction are evaluated. Feed Horn relocation for alignment with the reflector axis is also described. Reference points are established for follow-on non-laser alignments utilizing a theodolite.
Recent amendments to the Safe Drinking Water Act emphasize efforts toward safeguarding our nation's water supplies against attack and contamination. Specifically, the Public Health Security and Bioterrorism Preparedness and Response Act of 2002 established requirements for each community water system serving more than 3300 people to conduct an assessment of the vulnerability of its system to a terrorist attack or other intentional acts. Integral to evaluating system vulnerability is the threat assessment, which is the process by which the credibility of a threat is quantified. Unfortunately, full probabilistic assessment is generally not feasible, as there is insufficient experience and/or data to quantify the associated probabilities. For this reason, an alternative approach is proposed based on Markov Latent Effects (MLE) modeling, which provides a framework for quantifying imprecise subjective metrics through possibilistic or fuzzy mathematics. Here, an MLE model for water systems is developed and demonstrated to determine threat assessments for different scenarios identified by the assailant, asset, and means. Scenario assailants include terrorists, insiders, and vandals. Assets include a water treatment plant, water storage tank, node, pipeline, well, and a pump station. Means used in attacks include contamination (onsite chemicals, biological and chemical), explosives and vandalism. Results demonstrated highest threats are vandalism events and least likely events are those performed by a terrorist.
Three dimensional finite element analyses were performed to evaluate the structural integrity of the caverns located at the Bayou Choctaw (BC) site which is considered a candidate for expansion. Fifteen active and nine abandoned caverns exist at BC, with a total cavern volume of some 164 MMB. A 3D model allowing control of each cavern individually was constructed because the location and depth of caverns and the date of excavation are irregular. The total cavern volume has practical interest, as this void space affects total creep closure in the BC salt mass. Operations including both cavern workover, where wellhead pressures are temporarily reduced to atmospheric, and cavern enlargement due to leaching during oil drawdowns that use water to displace the oil from the caverns, were modeled to account for as many as the five future oil drawdowns in the six SPR caverns. The impacts on cavern stability, underground creep closure, surface subsidence, infrastructure, and well integrity were quantified.
Monroe, Justin; Tang, Zhong; Gu, Xuehong; Dong, Junhang; Weinkauf, Donald; Nenoff, Tina M.
Hydrogen production from biomass has been paid more attention for years. Processes suggested for production of hydrogen from biomass are often involved in high-temperature pyrolysis[1-2], catalytic steam reforming [3] or enzymatic biosynthesis[4]. These strategies, however, encounter problems of high consumption of energy, low catalyst efficiency and very limited productivity. Group VIII metals such as Pt, Ni and Ru are more likely to be effective catalysts for reforming of oxygenated hydrocarbons (the main component in biomass), and among which, only Pt and Pd show both high activities and high selectivity for production of H 2[5-7]. Although lots of catalysts have been screened for this aqueous-phase reforming, the catalysts with high loadings noble metal such as platinum has to be used even when conducting at low feed concentration of 1 wt%[8]. Therefore, highly active catalytic materials need to be developed in order to render the process practical.
Understanding the role of emotional states is critical for predicting the kind of decisions people will make in risky situations. Currently, there is little understanding as to how emotion influences decision-making in situations such as terrorist attacks, natural disasters, pandemics, and combat. To help address this, we used behavioral and neuroimaging methods to examine how emotion states and traits influence decisions. Specifically, this study used a wheel of fortune behavioral task and functional magnetic resonance imaging (fMRI) to examine the effects of emotional states and traits on decision-making pertaining to the degree of risk people are willing to make in specific situations. The behavioral results are reported here. The neural data requires additional time to analyze and will be reported at a future date. Biases caused by emotion states and traits were found regarding the likelihood of making risky decisions. The behavioral results will help provide a solid empirical foundation for modeling the effects of emotion on decision in risky situations.
Public mediated resource planning is quickly becoming the norm rather than the exception. Unfortunately, supporting tools are lacking that interactively engage the public in the decision-making process and integrate over the myriad values that influence water policy. In the pages of this report we document the first steps toward developing a specialized decision framework to meet this need; specifically, a modular and generic resource-planning ''toolbox''. The technical challenge lies in the integration of the disparate systems of hydrology, ecology, climate, demographics, economics, policy and law, each of which influence the supply and demand for water. Specifically, these systems, their associated processes, and most importantly the constitutive relations that link them must be identified, abstracted, and quantified. For this reason, the toolbox forms a collection of process modules and constitutive relations that the analyst can ''swap'' in and out to model the physical and social systems unique to their problem. This toolbox with all of its modules is developed within the common computational platform of system dynamics linked to a Geographical Information System (GIS). Development of this resource-planning toolbox represents an important foundational element of the proposed interagency center for Computer Aided Dispute Resolution (CADRe). The Center's mission is to manage water conflict through the application of computer-aided collaborative decision-making methods. The Center will promote the use of decision-support technologies within collaborative stakeholder processes to help stakeholders find common ground and create mutually beneficial water management solutions. The Center will also serve to develop new methods and technologies to help federal, state and local water managers find innovative and balanced solutions to the nation's most vexing water problems. The toolbox is an important step toward achieving the technology development goals of this center.
Control of nanoparticle size is crucial to the development of nanotechnology. At this point in time, no general, rational synthetic strategy for controlling nanocrystal diameters and producing narrow diameter distributions has emerged. This is a reflection of a poor understanding of the mechanisms for nanocrystal growth. Based on previous studies of bismuth and gold nanoparticle growth, this work clearly establishes two new synthetic approaches to controlled growth of colloidal Pt nanocrystals, both based on aggregative-growth mechanisms, which afford narrow size distributions and size control over a wide and relevant size regime. The first new method is a phase transfer process, where growth is controlled by varying ligand stabilizer concentrations. The second method involves rapid reduction of a molecular platinum precursor in the presence of a polymer stabilizer. At present the size control is empirical, and incompletely understood and incompletely developed. However, the new synthetic pathways are amenable to kinetic study and analysis, establishing that a quantitative, rational control of sizes and size distributions can be achieved.
The goal of this project was to develop a risk analysis meta tool--a tool that enables security analysts both to combine and analyze data from multiple other risk assessment tools on demand. Our approach was based on the innovative self-assembling software technology under development by the project team. This technology provides a mechanism for the user to specify his intentions at a very high level (e.g., equations or English-like text), and then the code self-assembles itself, taking care of the implementation details. The first version of the meta tool focused specifically in importing and analyzing data from Joint Conflict and Tactical Simulation (JCATS) force-on-force simulation. We discuss the problem, our approach, technical risk, and accomplishments on this project, and outline next steps to be addressed with follow-on funding.
Nonlinear FM (NLFM) waveforms offer a radar matched filter output with inherently low range sidelobes. This yields a 1-2 dB advantage in Signal-to-Noise Ratio over the output of a Linear FM (LFM) waveform with equivalent sidelobe filtering. This report presents details of processing NLFM waveforms in both range and Doppler dimensions, with special emphasis on compensating intra-pulse Doppler, often cited as a weakness of NLFM waveforms.
DEDICOM is a linear algebra model for analyzing intrinsically asymmetric relationships, such as trade among nations or the exchange of emails among individuals. DEDICOM decomposes a complex pattern of observed relations among objects into a sum of simpler patterns of inferred relations among latent components of the objects. Three-way DEDICOM is a higher-order extension of the model that incorporates a third mode of the data, such as time, giving it stronger uniqueness properties and consequently enhancing interpretability of solutions. In this paper, we present algorithms for computing these decompositions on large, sparse data as well as a variant for computing an asymmetric nonnegative factorization. When we apply these techniques to adjacency arrays arising from directed graphs with edges labeled by time, we obtain a smaller graph on latent semantic dimensions and gain additional information about their changing relationships over time. We demonstrate these techniques on the Enron email corpus to learn about the social networks and their transient behavior. The mixture of roles assigned to individuals by DEDICOM showed strong correspondence with known job classifications and revealed the patterns of communication between these roles. Changes in the communication pattern over time, e.g., between top executives and the legal department, were also apparent in the solutions.
Electronic components such as bipolar junction transistors (BJTs) are damaged when they are exposed to radiation and, as a result, their performance can significantly degrade. In certain environments the radiation consists of short, high flux pulses of neutrons. Electronics components have traditionally been tested against short neutron pulses in pulsed nuclear reactors. These reactors are becoming less and less available; many of them were shut down permanently in the past few years. Therefore, new methods using radiation sources other than pulsed nuclear reactors needed to be developed. Neutrons affect semiconductors such as Si by causing atomic displacements of Si atoms. The recoiled Si atom creates a collision cascade which leads to displacements in Si. Since heavy ions create similar cascades in Si we can use them to create similar damage to what neutrons create. This LDRD successfully developed a new technique using easily available particle accelerators to provide an alternative to pulsed nuclear reactors to study the displacement damage and subsequent transient annealing that occurs in various transistor devices and potentially qualify them against radiation effects caused by pulsed neutrons.
This one year LDRD addressed the problem of rapid characterization of bacterial spores such as those from the genus Bacillus, the group that contains pathogenic spores such as B. anthracis. In this effort we addressed the feasibility of using a proteomics based approach to spore characterization using a subset of conserved spore proteins known as the small acid soluble proteins or SASPs. We proposed developing techniques that built on our previous expertise in microseparations to rapidly characterize or identify spores. An alternative SASP extraction method was developed that was amenable to both the subsequent fluorescent labeling required for laser-induced fluorescence detection and the low ionic strength requirements for isoelectric focusing. For the microseparations, both capillary isoelectric focusing and chip gel electrophoresis were employed. A variety of methods were evaluated to improve the molecular weight resolution for the SASPs, which are in a molecular weight range that is not well resolved by the current methods. Isoelectric focusing was optimized and employed to resolve the SASPs using UV absorbance detection. Proteomic signatures of native wild type Bacillus spores and clones genetically engineered to produce altered SASP patterns were assessed by slab gel electrophoresis, capillary isoelectric focusing with absorbance detection as well as microchip based gel electrophoresis employing sensitive laser-induced fluorescence detection.
We define a new diagnostic method where computationally-intensive numerical solutions are used as an integral part of making difficult, non-contact, nanometer-scale measurements. The limited scope of this report comprises most of a due diligence investigation into implementing the new diagnostic for measuring dynamic operation of Sandia's RF Ohmic Switch. Our results are all positive, providing insight into how this switch deforms during normal operation. Future work should contribute important measurements on a variety of operating MEMS devices, with insights that are complimentary to those from measurements made using interferometry and laser Doppler methods. More generally, the work opens up a broad front of possibility where exploiting massive high-performance computers enable new measurements.
This report summarizes our findings during the study of a novel system that yields multi-colored materials as products. This system is quite unusual as it leads to multi-chromic behavior in single crystals, where one would expect that only a single color would exist. We have speculated that these novel solids might play a role in materials applications such as non-linear optics, liquid crystal displays, piezoelectric devices, and other similar applications. The system examined consisted of a main-group alkyl compound (a p block element such as gallium or aluminum) complexed with various organic di-imines. The di-imines had substituents of two types--either alkyl or aromatic groups attached to the nitrogen atoms. We observed that single crystals, characterized by X-ray crystallography, were obtained in most cases. Our research during January-July, 2006, was geared towards understanding the factors leading to the multi-chromic nature of the complexes. The main possibilities put forth initially considered (a) the chiral nature of the main group metal, (b) possible reduction of the metal to a lower-valent, radical state, (c) the nature of the ligand(s) attached to the main group metal, and (d) possible degradation products of the ligand leading to highly-colored products. The work carried out indicates that the most likely explanation considered involves degradation of the aromatic ligands (a combination of (c) and (d)), as the experiments performed can clearly rule out (a) and (b).
Traditional cluster monitoring approaches consider nodes in singleton, using manufacturer-specified extreme limits as thresholds for failure ''prediction''. We have developed a tool, OVIS, for monitoring and analysis of large computational platforms which, instead, uses a statistical approach to characterize single device behaviors from those of a large number of statistically similar devices. Baseline capabilities of OVIS include the visual display of deterministic information about state variables (e.g., temperature, CPU utilization, fan speed) and their aggregate statistics. Visual consideration of the cluster as a comparative ensemble, rather than as singleton nodes, is an easy and useful method for tuning cluster configuration and determining effects of real-time changes.
Monitoring programs for nuclear-waste repositories are now conceived as an exercise in performance confirmation: the purpose of the monitoring program is to provide objective evidence that the repository system is functioning as expected. However, monitoring is still largely seen as being entirely focused on the near-repository environment, with the aim of verifying predictions made about such things as temperature or rock mass behavior that are relevant to the designed functioning of the repository. A more comprehensive approach comes from recognizing that the repository is embedded in a larger natural system that may be affected by factors in addition to the repository. At some current or prospective repository sites, various human activities that are amenable to monitoring might potentially (or actually) affect the natural system. Observing these anthropogenically induced changes in the natural system and being able to simulate them accurately using the models already constructed for repository performance assessment provide an additional opportunity for performance confirmation. Water-level changes induced by oil and gas exploration and/or potash mining activities near the Waste Isolation Pilot Plant site provided an opportunity to confirm important features of the groundwater model used in performance assessment calculations. Repository programs should evaluate the potential for ongoing or future human activities to affect the systems in which their repositories are situated and provide an opportunity for performance confirmation.
Legacy plutonium-bearing materials are stored in shipping containers at the Savannah River Site (SRS) until their final disposition can be determined. This material has been stabilized and is maintained per the DOE’s standard for long-term storage of Pu-containing materials, DOE-STD-3013. As a part of its ongoing storage mission, Washington Savannah River Company’s (WSRC) Nuclear Materials Management (NMM) organization is tasked with a surveillance program that will ensure these materials have remained in their expected condition over the several years of storage. Information from this program will be used by multiple entities to further validate the safe storage of Pu-bearing materials per DOE-STD-3013. Part of the program entails cutting open selected 3013 containers and sampling the materials inside. These samples will then be analyzed by Savannah River National Laboratory (SRNL). The remaining material not used for samples will then be repackaged in non-3013 containers to be placed back into shipping packages for storage until disposition at SRS. These repackaged materials will be stored per the requirements of DOE’s Criteria for Interim Safe Storage of Plutonium Bearing Materials (ISSC).
The emission from a radiating source embedded in a photonic lattice is investigated. The photonic lattice spectrum was found to deviate from the blackbody distribution, with intracavity emission suppressed at certain frequencies and significantly enhanced at others. For rapid population relaxation, where the photonic lattice and blackbody populations are described by the same thermal distribution, it was found that the enhancement does not result in output intensities exceeding those of the blackbody. However, for slow population relaxation, the photonic lattice population has a greater tendency to deviate from thermal equilibrium, resulting in output intensities exceeding those of the blackbody.
In recent years, several researchers have constructed novel neural network models based on lattice algebra. Because of computational similarities to operations in the system of image morphology, these models are often called morphological neural networks. One neural model that has been successfully applied to many pattern recognition problems is the single-layer morphological perceptron with dendritic structure (SLMP). In this model, the fundamental computations are performed at dendrites connected to the body of a single neuron. Current training algorithms for the SLMP work by enclosing the target patterns in a set of hyperboxes orthogonal to the axes of the data space. This work introduces an alternate model of the SLMP, dubbed the synoptic morphological perceptron (SMP). In this model, each dendrite has one or more synapses that receive connections from inputs. The SMP can learn any region of space determined by an arbitrary configuration of hyperplanes, and is not restricted to forming hyperboxes during training. Thus, it represents a more general form of the morphological perceptron than previous architectures.
Link, Anthony; Chowdhury, Enam A.; Morrison, John T.; Ovchinnikov, Vladimir M.; Offermann, Dustin; Van Woerkom, Linn; Freeman, Richard R.; Pasley, John; Shipton, Erik; Beg, Farhat; Rambo, Patrick K.; Schwarz, Jens S.; Geissel, Matthias G.; Edens, Aaron E.; Porter, John L.
In optical firing sets, laser light is used to supply power to electronics (to charge capacitors, for example), to trigger electronics (such as vacuum switches), or in some cases, initiate explosives directly. Since MEMS devices combine electronics with electro-mechanical actuators, one can integrate safe and arm logic alongside the actuators to provide all functions in a single miniature package. We propose using MEMS-activated mirrors to make or break optical paths as part of the safe and arm architecture in an optical firing set. In the safe mode, a miniature (∼1 mm diameter) mirror is oriented to prevent completion of the optical path. To arm the firing set, the MEMS mirrors are deflected into the proper orientation thereby completing the optical path required for system functionality (e.g., light from a miniature laser completes the path to an optically triggered switch). The optical properties (i.e. damage threshold, reflectivity, transmission, absorption and scatter) of the miniature mirrors are critical to this application. Since Si is a strong absorber at the wavelengths under consideration (800 to 1064 nm), high-reflectivity, high-damage-threshold, dielectric coatings must be applied to the MEMS devices. In this paper we present conceptual MEMS-activated mirror architectures for performing arming and safing functions in an optical firing set and report test data which shows that dielectric coatings applied to MEMS-mirrors can withstand the prerequisite laser pulse irradiance. The measured optical damage threshold of polysilicon membranes with high-reflectivity multilayer dielectric coatings is ∼ 4 GW/cm 2, clearly demonstrating the feasibility of using coated MEMS mirrors in firing sets.
The LIGA microfabrication technique offers a unique method for fabricating 3-dimensional photonic lattices based on the Iowa State "logpile" structure. These structures represent the [111] orientation of the [100] logpile structures previously demonstrated by Sandia National Laboratories, The novelty to this approach is the single step process that does not require any alignment. The mask and substrate are fixed to one another and exposed twice from different angles using a synchrotron light source. The first exposure patterns the resist at an angle of 45 degrees normal to the substrate with a rotation of 8 degrees. The second exposure requires a 180 degree rotation about the normal of the mask and substrate. The resulting pattern is a vertically oriented logpile pattern that is rotated slightly off axis. The exposed PMMA is developed in a single step to produce an inverse lattice structure. This mold is filled with electroplated gold and stripped away to create a usable gold photonic crystal. Tilted logpiles demonstrate band characteristics very similar to those observed from [100] logpiles. Reflectivity tests show a band edge around 5 μm and compare well with numerical simulations.
The optical transfer of power is becoming important for military and industrial applications. The powering of electrical circuitry, sensors and actuators over optical fiber offers immunity from RF, EMI, voltage breakdown, lightning and high voltage hazards. Optical power transfer is being employed in industries such as electric power, communications, remote sensing, and aerospace. In this paper we address issues associated with the illumination of Series Connected Photovoltaic Arrays (SCPA). SCPAs are extremely sensitive to the uniformity of illumination. The performance of a photovoltaic array is dominated by the least illuminated cell. We introduce an analytical model that predicts the performance of a photovoltaic array for an arbitrary illumination. Experimental data on array performance is presented, and general issues associated with the problem of producing uniform illumination are discussed.
The use of photosensitive materials for the development of integrated, refractive-index structures supporting telecom, remote sensing, and varied optical beam manipulation applications is well established. Our investigations of photosensitive phenomena in polysilanes, however, have been motivated by the desire to configure, or program, the photonic device function immediately prior to use. Such an operational mode imposes requirements on wavelength sensitivity, incident fluence and environmental conditions that are not typical of more conventional applications of photosensitive material. The present paper focuses on our efforts to understand and manipulate photosensitivity in polysilane thin films under different excitation wavelengths, local atmospheric compositions and thermal history in this context. We find that the photoresponse can be influenced through the control of such optical exposure conditions, thereby influencing the magnitude of the photoinduced refractive-index change attained.
A decision was made early in the Tri-Lab Usage Model process, that the collection of the user requirements be separated from the document describing capabilities of the user environment. The purpose in developing the requirements as a separate document was to allow the requirements to take on a higher-level view of user requirements for ASC platforms in general. In other words, a separate ASC user requirement document could capture requirements in a way that was not focused on ''how'' the requirements would be fulfilled. The intent of doing this was to create a set of user requirements that were not linked to any particular computational platform. The idea was that user requirements would endure from one ASC platform user environment to another. The hope was that capturing the requirements in this way would assist in creating stable user environments even though the particular platforms would be evolving and changing. In order to clearly make the separation, the Tri-lab S&CS program decided to create a new title for the requirements. The user requirements became known as the ASC Computational Environment (ACE) Requirements.
A very general and robust approach to solving continuous-variable optimization problems involving uncertainty in the objective function is through the use of ordinal optimization. At each step in the optimization problem, improvement is based only on a relative ranking of the uncertainty effects on local design alternatives, rather than on precise quantification of the effects. One simply asks ''Is that alternative better or worse than this one?'' -not ''HOW MUCH better or worse is that alternative to this one?'' The answer to the latter question requires precise characterization of the uncertainty--with the corresponding sampling/integration expense for precise resolution. However, in this report we demonstrate correct decision-making in a continuous-variable probabilistic optimization problem despite extreme vagueness in the statistical characterization of the design options. We present a new adaptive ordinal method for probabilistic optimization in which the trade-off between computational expense and vagueness in the uncertainty characterization can be conveniently managed in various phases of the optimization problem to make cost-effective stepping decisions in the design space. Spatial correlation of uncertainty in the continuous-variable design space is exploited to dramatically increase method efficiency. Under many circumstances the method appears to have favorable robustness and cost-scaling properties relative to other probabilistic optimization methods, and uniquely has mechanisms for quantifying and controlling error likelihood in design-space stepping decisions. The method is asymptotically convergent to the true probabilistic optimum, so could be useful as a reference standard against which the efficiency and robustness of other methods can be compared--analogous to the role that Monte Carlo simulation plays in uncertainty propagation.
Thermal properties of niobium-modified PZT95/5(1.8Nb) and PSZT ceramics used for the ferroelectric power supply have been studied from -100 C to 375 C. Within this temperature range, these materials exhibit ferroelectric-ferroelectric and ferroelectric-paraelectric phase transformations. The thermal expansion coefficient, heat capacity, and thermal diffusivity of different phases were measured. Thermal conductivity and Grueneisen constant were calculated at several selected temperatures between -60 C and 100 C. Results show that thermal properties of these two solid solutions are very similar. Phase transformations in these ceramics possess first order transformation characteristics including thermal hysteresis, transformational strain, and enthalpy change. The thermal strain in the high temperature rhombohedral phase region is extremely anisotropic. The heat capacity for both materials approaches to 3R (or 5.938 cal/(g-mole*K)) near room temperature. The thermal diffusivity and the thermal conductivity are quite low in comparison to common oxide ceramics, and are comparable to amorphous silicate glass. Furthermore, the thermal conductivity of these materials between -60 C and 100 C becomes independent of temperature and is sensitive to the structural phase transformation. These phenomena suggest that the phonon mean free path governing the thermal conductivity in this temperature range is limited by the lattice dimensions, which is in good agreement with calculated values. Effects of small compositional changes and density/porosity variations in these ceramics on their thermal properties are also discussed. The implications of these transformation characteristics and unusual thermal properties are important in guiding processing and handling procedures for these materials.
A procedure for extending the size of a Latin hypercube sample (LHS) with rank correlated variables is described and illustrated. The extension procedure starts with an LHS of size m and associated rank correlation matrix C and constructs a new LHS of size 2m that contains the elements of the original LHS and has a rank correlation matrix that is close to the original rank correlation matrix C. The procedure is intended for use in conjunction with uncertainty and sensitivity analysis of computationally demanding models in which it is important to make efficient use of a necessarily limited number of model evaluations.
Atmospheric pressure chemical vapor deposition (APCVD) of tin oxide is a very important manufacturing technique used in the production of low-emissivity glass. It is also the primary method used to provide wear-resistant coatings on glass containers. The complexity of these systems, which involve chemical reactions in both the gas phase and on the deposition surface, as well as complex fluid dynamics, makes process optimization and design of new coating reactors a very difficult task. In 2001 the U.S. Dept. of Energy Industrial Technologies Program Glass Industry of the Future Team funded a project to address the need for more accurate data concerning the tin oxide APCVD process. This report presents a case study of on-line APCVD using organometallic precursors, which are the primary reactants used in industrial coating processes. Research staff at Sandia National Laboratories in Livermore, CA, and the PPG Industries Glass Technology Center in Pittsburgh, PA collaborated to produce this work. In this report, we describe a detailed investigation of the factors controlling the growth of tin oxide films. The report begins with a discussion of the basic elements of the deposition chemistry, including gas-phase thermochemistry of tin species and mechanisms of chemical reactions involved in the decomposition of tin precursors. These results provide the basis for experimental investigations in which tin oxide growth rates were measured as a function of all major process variables. The experiments focused on growth from monobutyltintrichloride (MBTC) since this is one of the two primary precursors used industrially. There are almost no reliable growth-rate data available for this precursor. Robust models describing the growth rate as a function of these variables are derived from modeling of these data. Finally, the results are used to conduct computational fluid dynamic simulations of both pilot- and full-scale coating reactors. As a result, general conclusions are reached concerning the factors affecting the growth rate in on-line APCVD reactors. In addition, a substantial body of data was generated that can be used to model many different industrial tin oxide coating processes. These data include the most extensive compilation of thermochemistry for gas-phase tin-containing species as well as kinetic expressions describing tin oxide growth rates over a wide range of temperatures, pressures, and reactant concentrations.
Laser Engineered Net Shaping{trademark} (LENS{reg_sign}) is a unique, layer additive, metal manufacturing technique that offers the ability to create fully dense metal features and components directly from a computer solid model. LENS offers opportunities to repair and modify components by adding features to existing geometry, refilling holes, repairing weld lips, and many other potential applications. The material deposited has good mechanical properties with strengths typically slightly higher that wrought material due to grain refinement from a quickly cooling weld pool. The result is a material with properties similar to cold worked material, but without the loss in ductility traditionally seen with such treatments. Furthermore, 304L LENS material exhibits good corrosion resistance and hydrogen compatibility. This report gives a background of the LENS process including materials analysis addressing the requirements of a number of different applications. Suggestions are given to aid both the product engineer and the process engineer in the successful utilization of LENS for their applications. The results of testing on interface strength, machinability, weldability, corrosion resistance, geometric effects, heat treatment, and repair strategy testing are all included. Finally, the qualification of the LENS process is briefly discussed to give the user confidence in selecting LENS as the process of choice for high rigor applications. The testing showed LENS components to have capability in repair/modification applications requiring complex castings (W80-3 D-Bottle bracket), thin wall parts requiring metal to be rebuilt onto the part (W87 Firing Set Housing and Y-12 Test Rings), the filling of counterbores for use in reservoir reclamation welding (SRNL hydrogen compatibility study) and the repair of surface defects on pressure vessels (SRNL gas bottle repair). The material is machinable, as testing has shown that LENS deposited material machines similar to that of welded metal. Tool wear is slightly higher in LENS material than in wrought material, but not so much that one would be concerned with increased tooling cost. The LENS process achieved process qualification for the AY1E0125 D-Bottle Bracket from the W80-3 LEP program, and in the effort, also underwent testing in weapons environments. These tests included structural dynamic response testing and drop testing. The LENS deposited parts were compared in these tests with conventionally machined parts and showed equivalency to such an extent that the parts were accepted for use in parallel path subsystem-level weapon environment testing. The evaluation of LENS has shown that the process can be a viable option when either complete metal parts are needed or existing metal parts require modification or repair. The LENS Qualification Technology Investment team successfully investigated new applications for the LENS process and showed that it has great applicability across the Nuclear Weapons Complex as well as in other high rigor applications.
The LENS Qualification team had the goal of performing a process qualification for the Laser Engineered Net Shaping{trademark}(LENS{reg_sign}) process. Process Qualification requires that a part be selected for process demonstration. The AY1E0125 D-Bottle Bracket from the W80-3 was selected for this work. The repeatability of the LENS process was baselined to determine process parameters. Six D-Bottle brackets were deposited using LENS, machined to final dimensions, and tested in comparison to conventionally processed brackets. The tests, taken from ES1E0003, included a mass analysis and structural dynamic testing including free-free and assembly-level modal tests, and Haversine shock tests. The LENS brackets performed with very similar characteristics to the conventionally processed brackets. Based on the results of the testing, it was concluded that the performance of the brackets made them eligible for parallel path testing in subsystem level tests. The testing results and process rigor qualified the LENS process as detailed in EER200638525A.
The purpose of this project is to develop tools to model and simulate the processes of self-assembly and growth in biological systems from the molecular to the continuum length scales. The model biological system chosen for the study is the tendon fiber which is composed mainly of Type I collagen fibrils. The macroscopic processes of self-assembly and growth at the fiber scale arise from microscopic processes at the fibrillar and molecular length scales. At these nano-scopic length scales, we employed molecular modeling and simulation method to characterize the mechanical behavior and stability of the collagen triple helix and the collagen fibril. To obtain the physical parameters governing mass transport in the tendon fiber we performed direct numerical simulations of fluid flow and solute transport through an idealized fibrillar microstructure. At the continuum scale, we developed a mixture theory approach for modeling the coupled processes of mechanical deformation, transport, and species inter-conversion involved in growth. In the mixture theory approach, the microstructure of the tissue is represented by the species concentration and transport and material parameters, obtained from fibril and molecular scale calculations, while the mechanical deformation, transport, and growth processes are governed by balance laws and constitutive relations developed within a thermodynamically consistent framework.
Laser Engineered Net Shaping{trademark} (LENS{reg_sign}) is a layer additive manufacturing process that creates fully dense metal components using a laser, metal powder, and a computer solid model. This process has previously been utilized in research settings to create metal components and new material alloys. The ''Qualification of LENS for the Repair and Modification of Metal NWC Components'' project team has completed a Technology Investment project to investigate the use of LENS for repair of high rigor components. The team submitted components from four NWC sites for repair or modification using the LENS process. These components were then evaluated for their compatibility to high rigor weapons applications. The repairs included hole filling, replacement of weld lips, addition of step joints, and repair of surface flaws and gouges. The parts were evaluated for mechanical properties, corrosion resistance, weldability, and hydrogen compatibility. This document is a record of the LENS processing of each of these component types and includes process parameters, build strategies, and lessons learned. Through this project, the LENS process was shown to successfully repair or modify metal NWC components.
Due to increasing concerns over the buildup of long-lived transuranic isotopes in spent nuclear fuel waste, attention has been given in recent years to technologies that can burn up these species. The separation and transmutation of transuranics is part of a solution to decreasing the volume and heat load of nuclear waste significantly to increase the repository capacity. A fusion neutron source can be used for transmutation as an alternative to fast reactor systems. Sandia National Laboratories is investigating the use of a Z-Pinch fusion driver for this application. This report summarizes the initial design and engineering issues of this ''In-Zinerator'' concept. Relatively modest fusion requirements on the order of 20 MW can be used to drive a sub-critical, actinide-bearing, fluid blanket. The fluid fuel eliminates the need for expensive fuel fabrication and allows for continuous refueling and removal of fission products. This reactor has the capability of burning up 1,280 kg of actinides per year while at the same time producing 3,000 MWth. The report discusses the baseline design, engineering issues, modeling results, safety issues, and fuel cycle impact.
A major portion of the Wireless Networking Project at Sandia National Laboratories over the last few years has been to examine IEEE 802.11 wireless networking for possible use at Sandia and if practical, introduce this technology. This project team deployed 802.11a, b, and g Wireless Local Area Networking at Sandia. This report examines the basics of wireless networking and captures key results from project tests and experiments. It also records project members thoughts and designs on wireless LAN architecture and security issues. It documents some of the actions and milestones of this project, including pilot and production deployment of wireless networking equipment, and captures the team's rationale behind some of the decisions made. Finally, the report examines lessons learned, future directions, and conclusions.
Microsystems pose unparalleled opportunity in the realm of real-time sample analysis for multiple applications, including Homeland Security monitoring devices, environmental monitoring, and biomedical diagnostics. The need for a universal means of processing, separating, and delivering a sample within these devices is a critical need if these systems are to receive widespread implementation in the industry and government sectors. Efficient particle separation and enrichment techniques are critical for a range of analytical functions including pathogen detection, sample preparation, high-throughput particle sorting, and biomedical diagnostics. Previously, using insulator-based dielectrophoresis (iDEP) in microfluidic glass devices, we demonstrated simultaneous particle separation and concentration. As an alternative to glass, we evaluate the performance of similar iDEP structures produced in polymer-based microdevices and their enhancement through dynamic surface coatings. There are numerous processing and operational advantages that motivate our transition to polymers such as the availability of numerous innate chemical compositions for tailoring performance, mechanical robustness, economy of scale, and ease of thermoforming and mass manufacturing. The polymer chips we have evaluated are fabricated through an injection molding process of the commercially available cyclic olefin copolymer Zeonor{reg_sign}. We demonstrate that the polymer devices achieve the same performance metrics as glass devices. Additionally, we show that the nonionic block copolymer surfactant Pluronic F127 has a strong interaction with the cyclic olefin copolymer at very low concentrations, positively impacting performance by decreasing the magnitude of the applied electric field necessary to achieve particle trapping. The presence of these dynamic surface coatings, therefore, lowers the power required to operate such devices and minimizes Joule heating. The results of this study demonstrate that polymeric microfluidic devices with surfactant coatings for insulator-based dielectrophoresis provide an affordable engineering strategy for selective particle enrichment and sorting.
We have investigated a novel emulsion interfacial filter that is applicable for a wide range of materials, from nano-particles to cells and bacteria. This technology uses the interface between the two immiscible phases as the active surface area for adsorption of targeted materials. We showed that emulsion interfaces can effectively collect and trap materials from aqueous solution. We tested two aqueous systems, a bovine serum albumin (BSA) solution and coal bed methane produced water (CBMPW). Using a pendant drop technique to monitor the interfacial tension, we demonstrated that materials in both samples were adsorbed to the liquid-liquid interface, and did not readily desorb. A prototype system was built to test the emulsion interfacial filter concept. For the BSA system, a protein assay showed a progressive decrease in the residual BSA concentration as the sample was processed. Based on the initial prototype operation, we propose an improved system design.