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Results 81801–81900 of 96,771

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Hydrodynamic effects on coalescence

Grillet, Anne M.; Brooks, Carlton F.; De Boer, Maarten P.; Bourdon, Christopher B.; Gorby, Allen D.

The goal of this project was to design, build and test novel diagnostics to probe the effect of hydrodynamic forces on coalescence dynamics. Our investigation focused on how a drop coalesces onto a flat surface which is analogous to two drops coalescing, but more amenable to precise experimental measurements. We designed and built a flow cell to create an axisymmetric compression flow which brings a drop onto a flat surface. A computer-controlled system manipulates the flow to steer the drop and maintain a symmetric flow. Particle image velocimetry was performed to confirm that the control system was delivering a well conditioned flow. To examine the dynamics of the coalescence, we implemented an interferometry capability to measure the drainage of the thin film between the drop and the surface during the coalescence process. A semi-automated analysis routine was developed which converts the dynamic interferogram series into drop shape evolution data.

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TYPE SAND Report YEAR 2006
DOIOSTI

A tunable electrochromic fabry-perot filter for adaptive optics applications

Kammler, Daniel K.; Ambrosini, Andrea A.; Yelton, William G.; Verley, Jason V.; Heller, Edwin J.; Sweatt, W.C.

The potential for electrochromic (EC) materials to be incorporated into a Fabry-Perot (FP) filter to allow modest amounts of tuning was evaluated by both experimental methods and modeling. A combination of chemical vapor deposition (CVD), physical vapor deposition (PVD), and electrochemical methods was used to produce an ECFP film stack consisting of an EC WO{sub 3}/Ta{sub 2}O{sub 5}/NiO{sub x}H{sub y} film stack (with indium-tin-oxide electrodes) sandwiched between two Si{sub 3}N{sub 4}/SiO{sub 2} dielectric reflector stacks. A process to produce a NiO{sub x}H{sub y} charge storage layer that freed the EC stack from dependence on atmospheric humidity and allowed construction of this complex EC-FP stack was developed. The refractive index (n) and extinction coefficient (k) for each layer in the EC-FP film stack was measured between 300 and 1700 nm. A prototype EC-FP filter was produced that had a transmission at 500 nm of 36%, and a FWHM of 10 nm. A general modeling approach that takes into account the desired pass band location, pass band width, required transmission and EC optical constants in order to estimate the maximum tuning from an EC-FP filter was developed. Modeling shows that minor thickness changes in the prototype stack developed in this project should yield a filter with a transmission at 600 nm of 33% and a FWHM of 9.6 nm, which could be tuned to 598 nm with a FWHM of 12.1 nm and a transmission of 16%. Additional modeling shows that if the EC WO{sub 3} absorption centers were optimized, then a shift from 600 nm to 598 nm could be made with a FWHM of 11.3 nm and a transmission of 20%. If (at 600 nm) the FWHM is decreased to 1 nm and transmission maintained at a reasonable level (e.g. 30%), only fractions of a nm of tuning would be possible with the film stack considered in this study. These tradeoffs may improve at other wavelengths or with EC materials different than those considered here. Finally, based on our limited investigation and material set, the severe absorption associated with the refractive index change suggests that incorporating EC materials into phase correcting spatial light modulators (SLMS) would allow for only negligible phase correction before transmission losses became too severe. However, we would like to emphasize that other EC materials may allow sufficient phase correction with limited absorption, which could make this approach attractive.

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TYPE SAND Report YEAR 2006
DOIOSTI

A Risk-Based System Analysis Framework for Geological Carbon Sequestration

Kobos, Peter H.

The purpose of this project was to characterize existing carbon capture and sequestration technologies at a high level, develop an analytical framework to help assess the technologies, and implement the framework in a system dynamics model. The first year of this project succeeded in characterizing existing technologies to help focus the analysis on power plants. The assessment also helped determine which technologies are largely accepted by the carbon capture research community as relatively proven technologies, discuss the salient performance metrics, and assess the associated economics. With this information, an analytical framework was developed to assess the technologies from a systems view perspective. With this framework, the Carbon Sequestration and Risk Model (CSR) was developed to assess performance and economic risk issues as they relate to global atmospheric CO2 concentration goals and single plant scale projects to characterize the economics of these systems.

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TYPE SAND Report YEAR 2006
DOIOSTIDOIOSTI

1- and 2-frame monochromatic x-ray imaging of NIF-like capsules on Z and future higher-energy higher-resolution 2- & 4-frame x-radiography plans for ZR

Bennett, Guy R.; Campbell, David V.; Claus, Liam D.; Foresi, James S.; Johnson, Drew J.; Jones, Michael J.; Keller, Keith L.; Leifeste, Gordon T.; McPherson, Leroy A.; Mulville, Thomas D.; Neely, Kelly A.; Sinars, Daniel S.; Herrmann, Mark H.; Rambo, Patrick K.; Rovang, Dean C.; Ruggles, Larry R.; Simpson, Walter W.; Speas, Christopher S.; Wenger, D.F.; Smith, Ian C.; Cuneo, M.E.; Adams, Richard G.; Atherton, B.W.; Barnard, Wilson J.; Beutler, David E.; Burr, Robert A.

Abstract not provided.

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TYPE Conference YEAR 2006
OSTI

Accelerating DSMC data extraction

Piekos, Edward S.; Gallis, Michail A.

In many direct simulation Monte Carlo (DSMC) simulations, the majority of computation time is consumed after the flowfield reaches a steady state. This situation occurs when the desired output quantities are small compared to the background fluctuations. For example, gas flows in many microelectromechanical systems (MEMS) have mean speeds more than two orders of magnitude smaller than the thermal speeds of the molecules themselves. The current solution to this problem is to collect sufficient samples to achieve the desired resolution. This can be an arduous process because the error is inversely proportional to the square root of the number of samples so we must, for example, quadruple the samples to cut the error in half. This work is intended to improve this situation by employing more advanced techniques, from fields other than solely statistics, for determining the output quantities. Our strategy centers on exploiting information neglected by current techniques, which collect moments in each cell without regard to one another, values in neighboring cells, nor their evolution in time. Unlike many previous acceleration techniques that modify the method itself, the techniques examined in this work strictly post-process so they may be applied to any DSMC code without affecting its fidelity or generality. Many potential methods are drawn from successful applications in a diverse range of areas, from ultrasound imaging to financial market analysis. The most promising methods exploit relationships between variables in space, which always exist in DSMC due to the absence of shocks. Disparate techniques were shown to produce similar error reductions, suggesting that the results shown in this report may be typical of what is possible using these methods. Sample count reduction factors of approximately three to five were found to be typical, although factors exceeding ten were shown on some variables under some techniques.

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TYPE SAND Report YEAR 2006
DOIOSTI

Studies of the laser-induced fluorescence of explosives and explosive compositions

Schmitt, Randal L.; Thorne, Lawrence R.; Hargis, Philip J.; Parmeter, John E.

Continuing use of explosives by terrorists throughout the world has led to great interest in explosives detection technology, especially in technologies that have potential for standoff detection. This LDRD was undertaken in order to investigate the possible detection of explosive particulates at safe standoff distances in an attempt to identify vehicles that might contain large vehicle bombs (LVBs). The explosives investigated have included the common homogeneous or molecular explosives, 2,4,6-trinitrotoluene (TNT), pentaerythritol tetranitrate (PETN), cyclonite or hexogen (RDX), octogen (HMX), and the heterogeneous explosive, ammonium nitrate/fuel oil (ANFO), and its components. We have investigated standard excited/dispersed fluorescence, laser-excited prompt and delayed dispersed fluorescence using excitation wavelengths of 266 and 355 nm, the effects of polarization of the laser excitation light, and fluorescence imaging microscopy using 365- and 470-nm excitation. The four nitro-based, homogeneous explosives (TNT, PETN, RDX, and HMX) exhibit virtually no native fluorescence, but do exhibit quenching effects of varying magnitude when adsorbed on fluorescing surfaces. Ammonium nitrate and fuel oil mixtures fluoresce primarily due to the fuel oil, and, in some cases, due to the presence of hydrophobic coatings on ammonium nitrate prill or impurities in the ammonium nitrate itself. Pure ammonium nitrate shows no detectable fluorescence. These results are of scientific interest, but they provide little hope for the use of UV-excited fluorescence as a technique to perform safe standoff detection of adsorbed explosive particulates under real-world conditions with a useful degree of reliability.

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TYPE SAND Report YEAR 2006
DOIOSTI
Results 81801–81900 of 96,771
Results 81801–81900 of 96,771