Publications

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This highly interactive workshop is designed to elicit from the participants a vision of an ideal future analytic environment for intelligence analysis, the components of such a system that are already in place or in development and the identification of needed future developments. It will cover processes and tools for enabling effective individual analysts, teams of analysts, computer mediated analysis teams and management of tasks and teams.

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Single bilayer membranes of l-palmitoyl-2-oleoyl-sn-glycero-3- phosphocholine (POPC) were formed on ordered nanocomposite and nanoporous silica thin films by fusion of small unilamellar vesicles. The structure of these membranes was investigated using neutron reflectivity. The underlying thin films were formed by evaporation induced self-assembly to obtain periodic arrangements of silica and surfactant molecules in the nanocomposite thin films, followed by photocalcination to oxidatively remove the organics and render the films nanoporous. We show that this platform affords homogeneous and continuous bilayer membranes that have promising applications as model membranes and sensors. © 2005 American Chemical Society.

Joint fuel Raman and filtered Rayleigh-scattering (FRS) imaging is demonstrated in a laminar methane-air diffusion flame. These experiments are, to our knowledge, the first reported extension of the FRS technique to nonpremixed combustion. This joint imaging approach allows for correction of the FRS images for the large variations in Rayleigh cross section that occur in diffusion flames and for a secondary measurement of fuel mole fraction. The temperature-dependent filtered Rayleigh cross sections are computed with a six-moment kinetic model for calculation of major-species Rayleigh-Brillouin line shapes and a flamelet-based model for physically judicious estimates of gas-phase chemical composition. Shot-averaged temperatures, fuel mole fractions, and fuel number densities from steady and vortex-strained diffusion flames stabilized on a Wolfhard-Parker slot burner are presented, and a detailed uncertainty analysis reveals that the FRS-measured temperatures are accurate to within ±4.5 to 6% of the local absolute temperature. © 2005 Optical Society of America.

An experiment was recently conducted in DIII-D in which 13C methane (13CH4) was injected from the upper divertor plenum into 22 identical lower single null divertor L-mode plasmas. Twenty-nine graphite tiles were subsequently removed and analyzed to determine the spatial distribution of 13C deposited on the main chamber wall and divertor. 13C coverage was mapped by ion beam analysis using the 13C(3He, p)15N nuclear reaction. This technique also measures deuterium, boron and 12C content in the near-surface region of the tiles. The measurements show the 13C is deposited mainly at the inner divertor. © 2004 Elsevier B.V. All rights reserved.

Far scrape-off layer (SOL) plasma parameters in DIII-D depend strongly on the discharge density and confinement regime. In L-mode, cross-field transport increases with the average discharge density and elevates the far SOL density, thus increasing plasma-wall contact. Far SOL density near the low field side (LFS) of the main chamber wall also increases with decreasing plasma current and with decreasing outer wall gap. In H-mode, between edge localized modes (ELMs), plasma-wall contact is weaker than in L-mode. During ELMs plasma fluxes to the LFS wall increase to, or above the L-mode levels. A large fraction of the net cross-field fluxes is convected through the SOL by large amplitude intermittent transport events. In high-density L-mode and during ELMs in H-mode, intermittent events propagate all the way to the LFS wall and may cause sputtering. © 2004 Elsevier B.V. All rights reserved.

Use of carbon in tokamaks leads to a major tritium retention issue due to co-deposition. To investigate this process a low power L-mode experiment was performed on DIII-D in which 13CH4 was puffed into the main vessel through the toroidally-symmetric pumping plenum at the top of lower single-null discharges. Subsequently, the 13C content of tiles taken from the vessel wall was measured. The interpretive OEDGE code was used to model the results. It was found that the 13C deposition pattern is controlled by: (a) source strength of 13C+, (b) Δrs, radial location of the 13C+ source, (c) D⊥, (d) M∥, the scrape-off layer parallel Mach number. Best agreement was found for (a) ∼50% conversion efficiency 13CH 4 → 13C+, (b) Δrs, ∼+3.5 cm (outboard of separatrix) near 13CH4 injection location, (c) D⊥ ∼ 0.3 m2/s, (d) M∥∼ 0.4 toward inside. © 2004 Elsevier B.V. All rights reserved.

Time-resolved measurements of deposition in current tokamaks are crucial to gain a predictive understanding of deposition with a view to mitigating tritium retention and deposition on diagnostic mirrors expected in next-step devices. Two quartz crystal microbalances have been installed on NSTX at a location 0.77 m outside the last closed flux surface. This configuration mimics a typical diagnostic window or mirror. The deposits were analyzed ex-situ and found to be dominantly carbon, oxygen and deuterium. A rear facing quartz crystal recorded deposition of lower sticking probability molecules at 10% of the rate of the front facing one. Time resolved measurements over a 4-week period with 497 discharges, recorded 29.2 μg/cm2 of deposition, however surprisingly, 15.9 μg/cm2 of material loss occurred at 7 discharges. The net deposited mass of 13.3 μg/cm2 matched the mass of 13.5 μg/cm2 measured independently by ion beam analysis. Monte Carlo modeling suggests that transient processes are likely to dominate the deposition. © 2004 Elsevier B.V. All rights reserved.

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) instruments are capable of saving an entire mass spectrum at each pixel of an image, allowing for retrospective analysis of masses that were not selected for analysis during data collection. These TOF-SIMS spectral images contain a wealth of information, but few tools are available to assist the analyst in visualizing the entire raw data set and as a result, most of the data are not analyzed. Automated, nonbiased, multivariate statistical analysis (MVSA) techniques are useful for converting the massive amount of data into a smaller number of chemical components (spectra and images) that are needed to fully describe the TOF-SIMS measurement. Many samples require two back-to-back TOF-SIMS measurements in order to fully characterize the sample, one measurement of the fraction of positively charged secondary ions (positive ion fraction) and one measurement of the fraction of negatively charged secondary ions (negative ion fraction). Each measurement then needs to be individually evaluated. In this paper, we report the first MVSA analysis of a concatenated TOF-SIMS date set comprising positive ion and negative ion spectral images collected on the same region of a sample. MVSA of concatenated data sets provides results that are intuitive and fully describe the sample. The analytical insight provided by MVSA of the concatenated data set was not obtained when either polarity data set was analyzed separately. © 2005 American Chemical Society.

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The spherical harmonics (P{sub n}) approximation to the transport equation for time dependent problems has previously been treated using Riemann solvers and explicit time integration. Here we present an implicit time integration method for the P n equations using Riemann solvers. Both first-order and high-resolution spatial discretization schemes are detailed. One facet of the high-resolution scheme is that a system of nonlinear equations must be solved at each time step. This nonlinearity is the result of slope reconstruction techniques necessary to avoid the introduction of artifical extrema in the numerical solution. Results are presented that show auspicious agreement with analytical solutions using time steps well beyond the CFL limit.

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Using a multi-cellular, pathway model approach, we investigate the Drosophila sp. segmental differentiation network's stability as a function of initial conditions. While this network's functionality has been investigated in the absence of noise, this is the first work to specifically investigate how natural systems respond to random errors or noise. Our findings agree with earlier results that the overall network is robust in the absence of noise. However, when one includes random initial perturbations in intracellular protein WG levels, the robustness of the system decreases dramatically. The effect of noise on the system is not linear, and appears to level out at high noise levels.

Virtual manufacturing enterprises (VMEs) are a current, viable, and strategic form of organization for business and other organizations. The perspectives described in this literature review are based upon a basic cluster analysis that identified and classified papers into homogenous subgroups with meaningful themes, or categories. These general themes are related to strategies for business organization and advanced information technologies, virtual industrial/manufacturing organizations/enterprises, frameworks supporting virtual manufacturing enterprises (VMEs), and information technology infrastructures for VMEs.

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Materials studies of high Al-content (> 30%) AlGaN epilayers and the performance of AlGaN-based LEDs with emission wavelengths shorter than 300 nm are reported. N-type AlGaN films with Al compositions greater than 30% reveal a reduction in conductivity with increasing Al composition. The reduction of threading dislocation density from the 1-5 x10{sup 10} cm{sup -2} range to the 6-9 x 10{sup 9}cm{sup -2} range results in an improvement of electrical conductivity and Al{sub 0.90}Ga{sub 0.10}N films with n= 1.6e17 cm-3 and f{acute Y}=20 cm2/Vs have been achieved. The design, fabrication and packaging of flip-chip bonded deep UV LEDs is described. Large area (1 mm x 1 mm) LED structures with interdigitated contacts demonstrate output powers of 2.25 mW at 297 nm and 1.3 mW at 276 nm when operated under DC current. 300 f{acute Y}m x 300 f{acute Y}m LEDs emitting at 295 nm and operated at 20 mA DC have demonstrated less than 50% drop in output power after more than 2400 hours of operation. Optimization of the electron block layer in 274 nm LED structures has enabled a significant reduction in deep level emission bands, and a peak quantum well to deep level ratio of 700:1 has been achieved for 300 f{acute Y}m x 300 f{acute Y}m LEDs operated at 100 mA DC. Shorter wavelength LED designs are described, and LEDs emitting at 260 nm, 254nm and 237 nm are reported.

We have locked the frequency of a 3 THz quantum cascade laser (QCL) to that of a far-infrared gas laser with a tunable microwave offset frequency. The locked QCL line shape is essentially Gaussian, with linewidths of 65 and 141 kHz at the -3 and -10 dB levels, respectively. The lock condition can be maintained indefinitely, without requiring temperature or bias current regulation of the QCL other than that provided by the lock error signal. The result demonstrates that a terahertz QCL can be frequency controlled with 1-part-in-108 accuracy, which is a factor of 100 better than that needed for a local oscillator in a heterodyne receiver for atmospheric and astronomic spectroscopy.

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Supercomputer architects strive to maximize the performance of scientific applications. Unfortunately, the large, unwieldy nature of most scientific applications has lead to the creation of artificial benchmarks, such as SPEC-FP, for architecture research. Given the impact that these benchmarks have on architecture research, this paper seeks an understanding of how they relate to real-world applications within the Department of Energy. Since the memory system has been found to be a particularly key issue for many applications, the focus of the paper is on the relationship between how the SPEC-FP benchmarks and DOE applications use the memory system. The results indicate that while the SPEC-FP suite is a well balanced suite, supercomputing applications typically demand more from the memory system and must perform more 'other work' (in the form of integer computations) along with the floating point operations. The SPEC-FP suite generally demonstrates slightly more temporal locality leading to somewhat lower bandwidth demands. The most striking result is the cumulative difference between the benchmarks and the applications in terms of the requirements to sustain the floating-point operation rate: the DOE applications require significantly more data from main memory (not cache) per FLOP and dramatically more integer instructions per FLOP.

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The introduction of new multifunctional materials provides the potential for expanding the realm of microsystems device design and applications. Titanium nitride is identified as an attractive candidate material for use in NEMS applications given its favorable electrical, mechanical and chemical properties thereby enabling its use in high frequency applications and in harsh environments. We demonstrate TiN NEMS structures and low temperature residual stress control of the TiN comprising those structures. Potential applications of TiN as a NEMS structural material are discussed, with particular emphasis on active nanophotonic devices.

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The Explosive Destruction System (EDS) is a transportable system designed to treat chemical munitions. The EDS is transported on an open trailer that provides a mounting surface for major system components and an operator's work platform. The trailer is towed by a prime mover. An explosive containment vessel contains the shock, munition fragments, and the chemical agent during the munition opening process, and then provides a vessel for the subsequent chemical treatment of the agent. A fragmentation suppression system houses the chemical munition and protects the containment vessel from high velocity fragments. An explosive accessing system uses shaped charges to cut the munition open and attack the burster. A firing system detonates the shaped charges. A chemical feed system supplies neutralizing reagents and water to the containment vessel. A waste handling system drains the treated effluent.

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It is essential to characterize the nonlinearity in scanning probe microscopes (SPMs) in order to acquire spatial measurements with high levels of accuracy. In this paper, a new characterization method is presented that combines a high-resolution image processing technique used by the experimental mechanics community known as Digital Image Correlation (DIC) with digital images from a standard type of SPM known as an atomic force microscope (AFM). The characterization results using this new method match those from the conventional method using micromachined calibration gratings. However, the new method uses the texture of a specimen surface and not a precisely micromachined calibration grating. As a consequence, the new characterization technique is a more direct method for measuring scanning errors that can be conducted in situ when imaging a specimen surface at any scale within the scanning range of the SPM. It also has the advantage of reconstructing the position error curve more continuously with less noise than the conventional method.

This is a speculative work meant to stimulate discussion about the role of subsumability in self-similar software structures for computational simulations. As in natural phenomena, self-similar features in framework structures allow the size and complexity of code to grow without bound and still maintain apparent coherence. As in crystal growth, the coherence may be maintained by the application of a repeated pattern, or patterns may, as in fluid mechanical turbulence, be scaled by size and nested. Examples of these kinds of patterns applied to component systems in particular will be given. Conclusions and questions for discussion will be drawn regarding the applicability of these ideas to component architectures, complexity, and scientific computing.

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The dimensionless extinction coefficient, K{sub e}, was measured for soot produced in 2 m JP-8 pool fires. Light extinction and gravimetric sampling measurements were performed simultaneously at 635 and 1310 nm wavelengths at three heights in the flame zone and in the overfire region. Measured average K{sub e} values of 8.4 {+-} 1.2 at 635 nm and 8.7 {+-} 1.1 at 1310 nm in the overfire region agree well with values from 8-10 recently reported for different fuels and flame conditions. The overfire K{sub e} values are also relatively independent of wavelength, in agreement with recent findings for JP-8 soot in smaller flames. K{sub e} was nearly constant at 635 nm for all sampling locations in the large fires. However, at 1310 nm, the overfire K{sub e} was higher than in the flame zone. Chemical analysis of physically sampled soot shows variations in carbon-to-hydrogen (C/H) ratio and polycyclic aromatic hydrocarbon (PAH) concentration that may account for the smaller K{sub e} values measured in the flame zone. Rayleigh-Debye-Gans theory of scattering for polydisperse fractal aggregate (RDG-PFA) was applied to measured aggregate fractal dimensions and found to under-predict the extinction coefficient by 17-30% at 635 nm using commonly accepted refractive indices of soot, and agreed well with the experiments using the more recently published refractive index of 1.99-0.89i. This study represents the first measurements of soot chemistry, morphology, and optical properties in the flame zone of large, fully-turbulent pool fires, and emphasizes the importance of accurate measurements of optical properties both in the flame zone and overfire regions for models of radiative transport and interpretation of laser-based diagnostics of soot volume fraction and temperature.

This paper compares several linear-theory-based models for droplet shattering employed for simulations of spray impingement on flat wall surface or a circular cylinder. Numerical simulations are conducted using a stochastic separated flow (SSF) technique that includes sub-models for droplet dynamics and impact. Results for spray impingement over a flat wall indicate that the linear theory applicable for a single droplet impact over-predicts the number of satellite (or secondary) droplets upon shattering when compared to experimental data. The causes for the observed discrepancies are discussed. Numerical simulation results for spray impingement over for a circular cylinder in cross flow are obtained and discussed.

Transportation of sensitive flight hardware requires information about the expected transportation environment as well as the actual transportation environment during the part's movement--typically vibration with superimposed intermittent shocks. Each data type has different sampling, processing, and specification requirements. Analyzing shock data requires high sampling rates and leads to large file sizes. A barrier to analyzing data has been the vast quantity of information acquired. Previous approaches have focused either on manually separating data or on selectively recording extreme data. The use of an automated approach allows for quickly verifying vibration and shock levels while retaining the robustness of the underlying data set. Further, the automated approach allows the environments engineer to select criteria for shock/vibration sorting, which removes the subjectivity associated with visual differentiation. This automated technique evaluated several vehicles over four different road conditions in the same time that one data set could have been processed using visual discrimination. Automated processing of satellite shipment vibration and shock data is made thoroughly and objectively vs. traditional shock and tilt indicators. The automated technique could also be useful in processing large amounts of on-orbit data for changes in vibration signature.

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