Rasmussen D.J.,National Oceanic and Atmospheric Administration |
Fiore A.M.,National Oceanic and Atmospheric Administration |
Naik V.,High Performance Technologies Inc. |
Horowitz L.W.,National Oceanic and Atmospheric Administration |
And 2 more authors.
Atmospheric Environment | Year: 2012
We use long-term, coincident O 3 and temperature measurements at the regionally representative US Environmental Protection Agency Clean Air Status and Trends Network (CASTNet) over the eastern US from 1988 through 2009 to characterize the surface O 3 response to year-to-year fluctuations in weather, for the purpose of evaluating global chemistry-climate models. We first produce a monthly climatology for each site over all available years, defined as the slope of the best-fit line (m O3-T) between monthly average values of maximum daily 8-hour average (MDA8) O 3 and monthly average values of daily maximum surface temperature (T max). Applying two distinct statistical approaches to aggregate the site-specific measurements to the regional scale, we find that summer time m O3-T is 3-6ppbK -1 (r=0.5-0.8) over the Northeast, 3-4ppbK -1 (r=0.5-0.9) over the Great Lakes, and 3-6ppbK -1 (r=0.2-0.8) over the Mid-Atlantic. The Geophysical Fluid Dynamics Laboratory (GFDL) Atmospheric Model version 3 (AM3) global chemistry-climate model generally captures the seasonal variations in correlation coefficients and m O3-T despite biases in both monthly mean summertime MDA8 O 3 (up to-+10 to-+30ppb) and daily T max (up to-+5K) over the eastern US. During summer, GFDL AM3 reproduces m O3-T over the Northeast (m O3-T=2-6ppbK -1; r=0.6-0.9), but underestimates m O3-T by 4ppbK -1 over the Mid-Atlantic, in part due to excessively warm temperatures above which O 3 production saturates in the model. Combining T max biases in GFDL AM3 with an observation-based m O3-T estimate of 3ppbK -1implies that temperature biases could explain up to 5-15ppb of the MDA8 O 3 bias in August and September though correcting for excessively cool temperatures would worsen the O 3 bias in June. We underscore the need for long-term, coincident measurements of air pollution and meteorological variables to develop process-level constraints for evaluating chemistry-climate models used to project air quality responses to climate change. © 2011.
Guo H.,National Oceanic and Atmospheric Administration |
Golaz J.-C.,National Oceanic and Atmospheric Administration |
Donner L.J.,National Oceanic and Atmospheric Administration |
Ginoux P.,National Oceanic and Atmospheric Administration |
Hemler R.S.,High Performance Technologies Inc.
Journal of Climate | Year: 2014
A unified turbulence and cloud parameterization based on multivariate probability density functions (PDFs) has been incorporated into the GFDL atmospheric general circulation model (AM3). This PDFbased parameterization not only predicts subgrid variations in vertical velocity, temperature, and total water, which bridge subgrid-scale processes (e.g., aerosol activation and cloud microphysics) and grid-scale dynamic and thermodynamic fields, but also unifies the treatment of planetary boundary layer (PBL), shallow convection, and cloud macrophysics. This parameterization is called the Cloud Layers Unified by Binormals (CLUBB) parameterization. With the incorporation of CLUBB in AM3, coupled with a two-moment cloud microphysical scheme, AM3-CLUBB allows for a more physically based and self-consistent treatment of aerosol activation, cloud micro- and macrophysics, PBL, and shallow convection. The configuration and performance of AM3-CLUBB are described. Cloud and radiation fields, as well as most basic climate features, are modeled realistically. Relative to AM3, AM3-CLUBB improves the simulation of coastal stratocumulus, a longstanding deficiency in GFDL models, and their seasonal cycle, especially at higher horizontal resolution, but global skill scores deteriorate slightly. Through sensitivity experiments, it is shown that 1) the two-moment cloud microphysics helps relieve the deficiency of coastal stratocumulus, 2) using the CLUBB subgrid cloud water variability in the cloud microphysics has a considerable positive impact on global cloudiness, and 3) the impact of adjusting CLUBB parameters is to improve the overall agreement between model and observations. © 2014 American Meteorological Society.
Briones A.M.,University of Dayton |
Sekar B.,Air Force Research Lab |
Thornburg H.J.,High Performance Technologies Inc.
41st AIAA Fluid Dynamics Conference and Exhibit | Year: 2011
The Ultra-Compact Combustor (UCC) that operates as an Inter-turbine Burner (ITB) situated in between the high and low pressure turbine stages is modeled with the Trapped Vortex Combustor (TVC) with a single vane containing a notch and with various protuberance designs and arrays, located in the vane and in the TVC. The steady threedimensional governing equations of continuity, momentum, energy, turbulence, and species in Eulerian reference frame as well as the C12H23 liquid-fuel droplet trajectory, and heat and mass exchange with the continuum phase in a Lagrangian frame were solved using FLUENT. Turbulence was modeled using the Realizable k-ε RANS governing equations. The density varied with pressure and the turbulence model included production of turbulent kinetic energy by mean velocity gradients and consumption also accounted for dilation dissipation. Turbulence-chemistry interaction was modeled using the eddy-dissipation model. Temperature- and species-dependent thermodynamic and transport properties were considered. This paper discusses the flow/flame structure, exit temperature profiles, and global performance parameters of the various UCC/ITB/TVC. Liquid fuel is injected in the cavity as a conical spray of droplets that evaporates and boils almost immediately after injection within the TVC cavity. A turbulent triple flame is attached to the leading edge of the TVC cavity containing a nonpremixed reaction zone (NPRZ) sandwiched by a rich premixed (RPRZ) and lean premixed reaction zone (LPRZ). When adding a vane with notch the triple flame spreads in the transverse direction attaching itself to the trailing edge of this notch. At a given streamwise location the velocity magnitude downstream of the vane is nonuniform for the vane containing notch configurations, whereas it is uniform for that configuration without vane and notch. The combustion flow field is characterized by alternating high- and low-temperature regions with intensified transverse vorticity. High temperature regions are obtained in the vane suction side and not on the vane compression side. This leads to a non-uniform averaged exit temperature distribution in the spanwise direction. Two possible solutions can be envisioned to improve the non-uniform spanwise temperature distribution. A guide vane with appropriate curvature could be used downstream of a curved vane and/or the separation distance between vanes can be reduced to allow overlapping of the high-temperature regions. At the exit plane, the temperature increases from lean to richer mixtures, it reaches a peak near stoichiometric and then it decreases again for rich mixtures. For the configuration without vane with notch, the maximum exit temperature T≈2500 K peaks in the rich mixture. For the other configurations containing vane with notch, the maximum temperature increases to T≈2700 K and shifts to a more stoichiometric mixture. Future studies of UCC/ITB/TVC could take advantage of mixture fraction models, which would reduce the computational cost due to the reduction on the number of species being solved without compromising accuracy. Moreover, none of the configurations studied exhibit a desired transverse exit temperature profile. However, it is learned that as the averaged transverse temperature gradient decreases the maximum transverse average temperature (T) peaks closer to the bottom wall. This fact should be taken into account in the future design of UCC/ITB/TVC, which desired T peaks above the mid-height of the gas turbine vane blade. Furthermore, for all the configurations the total pressure losses do not exceed 5% and the combustion efficiency varies from 66 % to 97 %. The vane leading edge dimples (VLED) are promising in further reducing total pressure losses (q) and drag coefficient (CD), while enhancing fuel/air mixing, combustion efficiency (η), and pattern factor (PF). In addition, q increases nearly quadratically with CD and decreases somewhat linearly with mixing deviation (σ). Mixing improves linearly with lowering PF and with increasing η. The latter also increases quadratically with decreasing PF. © 2011 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.
Zhang S.,High Performance Technologies Inc.
2012 Symposium on Photonics and Optoelectronics, SOPO 2012 | Year: 2012
the 3D integration and packaging of semiconductor devices has gone through a paradigm shift over the last decade. The 3D technology outperforms conventional semiconductor assembling methods in density, cost, and performance simultaneously. This paper summarizes characteristics,platforms, approaches, and trends in 3D semiconductor optoelectronics. © 2012 IEEE.
Dungan K.E.,High Performance Technologies Inc. |
Potter L.C.,Ohio State University
IEEE Journal on Selected Topics in Signal Processing | Year: 2011
We present a fast, scalable method to simultaneously register and classify vehicles in circular synthetic aperture radar imagery. The method is robust to occlusions and partial matches. Images are represented as a set of attributed scattering centers that are mapped to local sets, which are invariant to rigid transformations. Similarity between local sets is measured using a method called pyramid match hashing, which applies a pyramid match kernel to compare sets and a Hamming distance to compare hash codes generated from those sets. By preprocessing a database into binary hash codes, we are able to quickly find the nearest neighbor of a query among a large number of records. To demonstrate the algorithm, we simulated X-band scattering from ten civilian vehicles placed throughout a large scene, varying elevation angles in the 35°-59° range. We achieved better than 98% classification performance. Similar performance is demonstrated for a seven class task using airborne radar measurements. © 2010 IEEE.
Hellberg C.S.,Center for Computational Materials Science |
Andersen K.E.,High Performance Technologies Inc. |
Li H.,Shenzhen New Degree Technology Co. |
Ryan P.J.,Argonne National Laboratory |
Woicik J.C.,U.S. National Institute of Standards and Technology
Physical Review Letters | Year: 2012
The epitaxial deposition of oxides on silicon opens the possibility of incorporating their diverse properties into silicon-device technology. Deposition of SrTiO 3 on silicon was first reported over a decade ago, but growing the coherent, lattice-matched films that are critical for many applications has been difficult for thicknesses beyond 5 unit cells. Using a combination of density functional calculations and x-ray diffraction measurements, we determine the atomic structure of coherent SrTiO 3 films on silicon, finding that the Sr concentration at the interface varies with the film thickness. The structures with the lowest computed energies best match the x-ray diffraction. During growth, Sr diffuses from the interface to the surface of the film; the increasing difficulty of Sr diffusion with film thickness may cause the disorder seen in thicker films. The identification of this unique thickness-dependent interfacial structure opens the possibility of modifying the interface to improve the thickness and quality of metal oxide films on silicon. © 2012 American Physical Society.
Wen Y.H.,Air Force Research Lab |
Wen Y.H.,UES, Inc. |
Lill J.V.,High Performance Technologies Inc. |
Chen S.L.,CompuTherm LLC |
Simmons J.P.,Air Force Research Lab
Acta Materialia | Year: 2010
A ternary phase-field model was developed that is linked directly to commercial CALPHAD software to provide quantitative thermodynamic driving forces. A recently available diffusion mobility database for ordered phases is also implemented to give a better description of the diffusion behavior in alloys. Because the targeted application of this model is the study of precipitation in Ni-based superalloys, a Ni-Al-Cr model alloy was constructed. A detailed description of this model is given in the paper. We have considered the misfit effects of the partitioning of the two solute elements. Transformation rules of the dual representation of the γ + γ′ microstructure by CALPHAD and by the phase field are established and the link with commercial CALPHAD software is described. Proof-of-concept tests were performed to evaluate the model and the results demonstrate that the model can qualitatively reproduce observed γ′ precipitation behavior. Uphill diffusion of Al is observed in a few diffusion couples, showing the significant influence of Cr on the chemical potential of Al. Possible applications of this model are discussed. © 2009 Acta Materialia Inc.
Ziegeler S.B.,High Performance Technologies Inc. |
Dykes J.D.,U.S. Navy |
Shriver J.F.,U.S. Navy
Journal of Atmospheric and Oceanic Technology | Year: 2012
A common problem with modern numerical oceanographic models is spatial displacement, including misplacement and misshapenness of ocean circulation features. Traditional error metrics, such as least squares methods, are ineffective in many such cases; for example, only small errors in the location of a frontal pattern are translated to large differences in least squares of intensities. Such problems are common in meteorological forecast verification as well, so the application of spatial error metrics have been a recently popular topic there. Spatial error metrics separate model error into a displacement component and an intensity component, providing a more reliable assessment of model biases and a more descriptive portrayal of numerical model prediction skill. The application of spatial error metrics to oceanographic models has been sparse, and further advances for both meteorology and oceanography exist in the medical imaging field. These advances are presented, along with modifications necessary for oceanographic model output. Standard methods and options for those methods in the literature are explored, and where the best arrangements of options are unclear, comparison studies are conducted. These trials require the reproduction of synthetic displacements in conjunction with synthetic intensity perturbations across 480 Navy Coastal Ocean Model (NCOM) temperature fields from various regions of the globe throughout 2009. Study results revealed the success of certain approaches novel to both meteorology and oceanography, including B-spline transforms and mutual information. That, combined with other common methods, such as quasi-Newton optimization and land masking, could best recover the synthetic displacements under various synthetic intensity changes. © 2012 American Meteorological Society.
Agency: Department of Homeland Security | Branch: | Program: SBIR | Phase: Phase II | Award Amount: 749.93K | Year: 2009
Many government agencies share the need to determine the best courses of action that diminish the long range threat, vulnerability or impact from a potential event that affects our domestic population or infrastructure. We propose to develop a functional prototype of the Current Event - Future Outcome (CEFO) software we described in Phase I, which will leverage the existing wealth of domain-specific and integrated models from many sources, along with innovative techniques drawn from probabilistic risk assessment, decision theory, and statistical analysis. We will reuse and customize software from other sources to create a workflow platform that can accommodate various existing infrastructure models. We will develop user-friendly interfaces in creating this prototype. We will collaborate with another government agency to demonstrate the effectiveness of the prototype by modeling a regional infrastructure scenario of interest. This will demonstrate that CEFO can provide useful understanding of the complex interrelationships between actions and effects in an interconnected domestic infrastructure. The demonstration will show how the software enables government planners to easily apply systems dynamics methodologies to analyze the impact of events, and potential responsive actions as they relate to the physical, economic, or social infrastructure.