Physical Sciences and Mathematics Commons^™

Toward A Whole-Landscape Approach For Sustainable Land Use In The Tropics, R. Defries, C. Rosenzweig

United States National Aeronautics and Space Administration: Publications

Increasing food production and mitigating climate change are two primary but seemingly contradictory objectives for tropical landscapes. This special feature examines synergies and trade-offs among these objectives. Four themes emerge from the papers: the important roles of both forest and agriculture sectors for climate mitigation in tropical countries; the minor contribution from deforestation-related agricultural expansion to overall food production at global and continental scales; the opportunities for synergies between improved food production and reductions in greenhouse gas emissions through diversion of agricultural expansion to already-cleared lands, improved soil, crop, and livestock management, and agroforestry; and the need for targeted policy …

Toward Establishing A Realistic Benchmark For Airframe Noise Research: Issues And Challenges, Mehdi R. Khorrami

United States National Aeronautics and Space Administration: Publications

The availability of realistic benchmark configurations is essential to enable the validation of current Computational Aeroacoustic (CAA) methodologies and to further the development of new ideas and concepts that will foster the technologies of the next generation of CAA tools. The selection of a real-world configuration, the subsequent design and fabrication of an appropriate model for testing, and the acquisition of the necessarily comprehensive aeroacoustic data base are critical steps that demand great care and attention. In this paper, a brief account of the nose landing-gear configuration, being proposed jointly by NASA and the Gulfstream Aerospace Company as an airframe …

Remote Sensing Of Phytoplankton Pigment Distribution In The United States Northeast Coast, Xiaoju Pan, Antonio Mannino, Mary E. Russ, Stanford B. Hooker, Lawrence Harding

United States National Aeronautics and Space Administration: Publications

Phytoplankton pigments constitute many more compounds than chlorophyll a that can be applied to study phytoplankton diversity, populations, and primary production. In this study, field measurements were applied to develop ocean color satellite algorithms of phytoplankton pigments from in-water radiometry measurements. The match-up comparisons showed that the satellite-derived pigments from our algorithms agree reasonably well (e.g. 30–55% of uncertainty for SeaWiFS and 37–50% for MODIS-Aqua) to field data, with better agreement (e.g. 30–38% of uncertainty for SeaWiFS and 39–44% for MODIS-Aqua) for pigments abundant in diatoms. The seasonal and spatial variations of satellite-derived phytoplankton biomarker pigments, such as fucoxanthin, which …

The Carbon Budget Of California, Christopher Potter

United States National Aeronautics and Space Administration: Publications

The carbon budget of a region can be defined as the sum of annual fluxes of carbon dioxide (CO₂₎ and methane (CH₄) greenhouse gases (GHGs) into and out of the regional surface coverage area. According to the state government’s recent inventory, California’s carbon budget is presently dominated by 115 MMTCE per year in fossil fuel emissions of CO₂ (>85% of total annual GHG emissions) to meet energy and transportation requirements. Other notable (non-ecosystem) sources of carbon GHG emissions in 2004 were from cement- and lime-making industries (7%), livestock-based agriculture (5%), and waste treatment activities (2%). …

Thermal Expansion Of Vacuum Plasma Sprayed Coatings, S.V. Raj, A. Palczer

United States National Aeronautics and Space Administration: Publications

Metallic Cu–8%Cr, Cu–26%Cr, Cu–8%Cr–1%Al, NiAl and NiCrAlY monolithic coatings were fabricated by

vacuum plasma spray deposition processes for thermal expansion property measurements between 293

and 1223 K. The corrected thermal expansion, (∆L/L₀)_thermal, varies with the absolute temperature, T, as

( ∆L ) = A(T-293)³ + B(T-293)² + C(T -293) + D

(L₀)_thermal

where A, B, C and D are regression constants. Excellent reproducibility was observed for all of the

coatings except for data obtained on the Cu–8%Cr and Cu–26%Cr coatings in the first heat-up …

Test Method Variability In Slow Crack Growth Properties Of Sealing Glasses, J. Salem, R. Tandon

United States National Aeronautics and Space Administration: Publications

The crack growth properties of several sealing glasses were measured by using constant stress rate testing in ~2% and 95% RH (relative humidity). Crack growth parameters measured in high humidity are systematically smaller (n and B) than those measured in low humidity, and crack velocities for dry environments are ~100 x lower than for wet environments. The crack velocity is very sensitivity to small changes in RH at low RH. Biaxial and uniaxial stress states produced similar parameters. Confidence intervals on crack growth parameters that were estimated from propagation of errors solutions were comparable to those from Monte …

Evaluation Of Shortwave Infrared Atmospheric Correction For Ocean Color Remote Sensing Of Chesapeake Bay, P. Jeremy Werdell, Bryan A. Franz, Sean W. Bailey

United States National Aeronautics and Space Administration: Publications

The NASA Moderate Resolution Imaging Spectroradiometer onboard the Aqua platform (MODIS-Aqua) provides a viable data stream for operational water quality monitoring of Chesapeake Bay. Marine geophysical products from MODIS-Aqua depend on the efficacy of the atmospheric correction process, which can be problematic in coastal environments. The operational atmospheric correction algorithm for MODISAqua requires an assumption of negligible near-infrared water-leaving radiance, nL_w(NIR). This assumption progressively degrades with increasing turbidity and, as such, methods exist to account for non-negligible nL_w(NIR) within the atmospheric correction process or to use alternate radiometric bands where the assumption is satisfied, such as …

Development And Evaluation Of A Cloud-Gap-Filled Modis Daily Snow-Cover Product, Dorothy K. Hall, George A. Riggs, James L. Foster, Sujay V. Kumar

United States National Aeronautics and Space Administration: Publications

The utility of the Moderate Resolution Imaging Spectroradiometer (MODIS) snow-cover products is limited by cloud cover which causes gaps in the daily snow-cover map products. Wedescribe a cloud-gap-filled (CGF) daily snow-covermap using a simple algorithmto track cloud persistence, to account for the uncertainty created by the age of the snow observation. Developed from the 0.05° resolution climate-modeling grid daily snow-cover product,MOD10C1, each grid cell of the CGFmap provides a cloud-persistence count (CPC) that tellswhether the current or a prior day was used to make the snow decision. Percentage of grid cells “observable” is shown to increase dramatically when prior days …

Automation For Task Analysis Of Next Generation Air Traffic Management Systems, Maricel Medina, Lance Sherry, Michael Feary

United States National Aeronautics and Space Administration: Publications

The increasing span of control of Air Traffic Control enterprise automation (e.g. Flight Schedule Monitor, Departure Flow Management), along with lean-processes and pay-for-performance business models, has placed increased emphasis on operator training time and error rates. There are two traditional approaches to the design of human–computer interaction (HCI) to minimize training time and reduce error rates: (1) experimental user testing provides the most accurate assessment of training time and error rates, but occurs too late in the development cycle and is cost prohibitive, (2) manual review methods (e.g. cognitive walk through) can be used earlier in the development cycle, but …

Coupled Neutron Transport For Hzetrn, T.C. Slaba, S.R. Blattnig, S.K. Aghara, L.W. Townsend, T. Handler, T.A. Gabriel, L.S. Pinsky, B. Reddell

United States National Aeronautics and Space Administration: Publications

Exposure estimates inside space vehicles, surface habitats, and high altitude aircrafts exposed to space radiation are highly influenced by secondary neutron production. The deterministic transport code HZETRN has been identified as a reliable and efficient tool for such studies, but improvements to the underlying transport models and numerical methods are still necessary. In this paper, the forward– backward (FB) and directionally coupled forward–backward (DC) neutron transport models are derived, numerical methods for the FB model are reviewed, and a computationally efficient numerical solution is presented for the DC model. Both models are compared to the Monte Carlo codes HETC-HEDS, FLUKA, …

High-Order Finite Difference Methods With Subcell Resolution For Hyperbolic Conservation Laws With Stiff Reaction Terms: Preliminary Results, W. Wang, C.-W. Shu, Helen Yee, Bjorn Sjögreen

United States National Aeronautics and Space Administration: Publications

The motivation for this research stems from the high-speed chemical reacting flows which have stiff reaction terms, where the chemical time scales are often much smaller than the fluid dynamics time scales. It is usually too expensive to resolve all the spatial/ temporal scales if we are only interested in the main flow. On the other hand, insufficient spatial/temporal resolution will cause the speed of propagation of discontinuities to be incorrectly predicted for many numerical methods. This numerical phenomenon was first observed by Colella et al. (1986). Then LeVeque & Yee (1990) showed that a similar spurious propagation phenomenon can …

High-Order Simulation Of Hypersonic Nonequilibrium Flows On Overset Grids, A. Lani, Bjorn Sjögreen, Helen Yee

United States National Aeronautics and Space Administration: Publications

The time-accurate unsteady 3D compressible flow solver ADPDIS3D is supported by a grant from the Department of Energy (DOE) SciDAC program through the Science Application Partnership (SAP) initiative. The objective of this grant is to develop, implement and validate this variable high-order 3-D multiblock overlapping (overset) grid solver for turbulence with strong shocks and density variations. ADPDIS3D includes capabilities for both direct numerical simulation (DNS), resolving all scales of the flow fields, and large eddy simulation (LES) modeling the small turbulent scales. One of the unique features of the code is the ability to perform DNS and LES computations in …