1,541 research outputs found
Dynamic Constellation Tasking and Management
Responsive orbits have gained much attention in recent years and many AFIT theses have addressed this topic. Specifically, the following topics have been studied: phasing within an orbit, adjusting time of arrival, avoidance, and maneuver detection. This thesis seeks to determine the feasibility of maneuvering satellites from circular (600 km) orbits to eccentric (600 km by 175 km) orbits in order to collect high resolution images for Earth surveillance. Coverage is calculated for multiple 6-satellite constellations. Perturbations for the subject orbits are analyzed and compared to simulation results
Glucose-fructose likely improves gastrointestinal comfort and endurance running performance relative to glucose-only
This study aimed to determine whether glucose-fructose (GF) ingestion, relative to glucose-only, would alter performance, metabolism, gastrointestinal (GI) symptoms, and psychological affect during prolonged running. On two occasions, 20 runners (14 men) completed a 120-min submaximal run followed by a 4-mile time trial (TT). Participants consumed glucose-only (G) or GF (1.2:1 ratio) beverages, which supplied ~1.3 g/min of carbohydrate. Substrate use, blood lactate, psychological affect [Feeling Scale (FS)], and GI distress were measured. Differences between conditions were assessed using magnitude-based inferential statistics. Participants completed the TT 1.9% (−1.9; −4.2, 0.4) faster with GF, representing a likely benefit. FS ratings were possibly higher and GI symptoms were possibly-to-likely lower with GF during the submaximal period and TT. Effect sizes for GI distress and FS ratings were relatively small (Cohen’s d = ~0.2 to 0.4). GF resulted in possibly higher fat oxidation during the submaximal period. No clear differences in lactate were observed. In conclusion, GF ingestion – compared with glucose-only – likely improves TT performance after 2 h of submaximal running, and GI distress and psychological affect are likely mechanisms. These results apply to runners consuming fluid at 500– 600 mL/h and carbohydrate at 1.0–1.3 g/min during running at 60–70% VO2peak
Glucose-fructose likely improves gastrointestinal comfort and endurance running performance relative to glucose-only
This study aimed to determine whether glucose-fructose (GF) ingestion, relative to glucose-only, would alter performance, metabolism, gastrointestinal (GI) symptoms, and psychological affect during prolonged running. On two occasions, 20 runners (14 men) completed a 120-min submaximal run followed by a 4-mile time trial (TT). Participants consumed glucose-only (G) or GF (1.2:1 ratio) beverages, which supplied ~1.3 g/min of carbohydrate. Substrate use, blood lactate, psychological affect [Feeling Scale (FS)], and GI distress were measured. Differences between conditions were assessed using magnitude-based inferential statistics. Participants completed the TT 1.9% (−1.9; −4.2, 0.4) faster with GF, representing a likely benefit. FS ratings were possibly higher and GI symptoms were possibly-to-likely lower with GF during the submaximal period and TT. Effect sizes for GI distress and FS ratings were relatively small (Cohen’s d = ~0.2 to 0.4). GF resulted in possibly higher fat oxidation during the submaximal period. No clear differences in lactate were observed. In conclusion, GF ingestion – compared with glucose-only – likely improves TT performance after 2 h of submaximal running, and GI distress and psychological affect are likely mechanisms. These results apply to runners consuming fluid at 500– 600 mL/h and carbohydrate at 1.0–1.3 g/min during running at 60–70% VO2peak
Estimating global warming potential for agricultural landscapes with minimal field data and cost
Greenhouse gas (GHG) emissions from agriculture comprise 10-12% of anthropocentric global emissions; and 76% of the agricultural emissions are generated in the developing world. Landscape GHG accounting is an effective way to efficiently develop baseline emissions and appropriate mitigation approaches. In a 9,736-hectare case study area dominated by rice and wheat in the Karnal district of Haryana state, India, the authors used a low-cost landscape agricultural GHG accounting method with limited fieldwork, remote sensing, and biogeochemical modeling. We used the DeNitrification-DeComposition (DNDC) model software to simulate crop growth and carbon and nitrogen cycling to estimate net GHG emissions, with information based on the mapping of cropping patterns over time using multi- resolution and multi-temporal optical remote sensing imagery. We estimated a mean net emission of 78,620 tCO2e/yr (tons of carbon dioxide equivalents per year) with a 95% confidence interval of 51,212-106,028 tCO2e/yr based on uncertainties in our crop mapping and soil data. A modeling sensitivity analysis showed soil clay fraction, soil organic carbon fraction, soil density, and nitrogen amendments to be among the most sensitive factors, and therefore critical to capture in field surveys. We recommend a multi-phase approach to increase efficiency and reduce cost in GHG accounting. Field campaigns and aspects of remote sensing image characteristics can be optimized for targeted landscapes through solid background research. An appropriate modeling approach can be selected based on crop and soil characteristics. Soil data in developing world landscapes remain a significant source of uncertainty for studies like these and should remain a key research and data development effort
Modeling and predicting the shape of the far-infrared to submillimeter emission in ultra-compact HII regions and cold clumps
Dust properties are very likely affected by the environment in which dust
grains evolve. For instance, some analyses of cold clumps (7 K- 17 K) indicate
that the aggregation process is favored in dense environments. However,
studying warm (30 K-40 K) dust emission at long wavelength (300
m) has been limited because it is difficult to combine far
infared-to-millimeter (FIR-to-mm) spectral coverage and high angular resolution
for observations of warm dust grains. Using Herschel data from 70 to 500
m, which are part of the Herschel infrared Galactic (Hi-GAL) survey
combined with 1.1 mm data from the Bolocam Galactic Plane Survey (BGPS), we
compared emission in two types of environments: ultra-compact HII (UCHII)
regions, and cold molecular clumps (denoted as cold clumps). With this
comparison we tested dust emission models in the FIR-to-mm domain that
reproduce emission in the diffuse medium, in these two environments (UCHII
regions and cold clumps). We also investigated their ability to predict the
dust emission in our Galaxy. We determined the emission spectra in twelve UCHII
regions and twelve cold clumps, and derived the dust temperature (T) using the
recent two-level system (TLS) model with three sets of parameters and the
so-called T- (temperature-dust emissvity index) phenomenological models,
with set to 1.5, 2 and 2.5. We tested the applicability of the TLS
model in warm regions for the first time. This analysis indicates distinct
trends in the dust emission between cold and warm environments that are visible
through changes in the dust emissivity index. However, with the use of standard
parameters, the TLS model is able to reproduce the spectral behavior observed
in cold and warm regions, from the change of the dust temperature alone,
whereas a T- model requires to be known.Comment: Accepted for publication in A&A. 19 pages, 8 figures, 7 table
Plasma Physics
Contains reports on six research projects.United States Atomic Energy Commission (Contract AT(30-1)-1842
Development of rotorcraft interior noise control concepts. Phase 3: Development of noise control concepts
The goal of this research is the understanding of helicopter internal noise mechanisms and the development, design, and testing of noise control concepts which will produce significant reductions in the acoustic environment to which passengers are exposed. The Phase 3 effort involved the identification and evaluation of current and advanced treatment concepts, including isolation of structure-borne paths. In addition, a plan was devised for the full-scale evaluation of an isolation concept. Specific objectives were as follows: (1) identification and characterization of various noise control concepts; (2) implementation of noise control concepts within the S-76 SEA (statistical energy analysis) model; (3) definition and evaluation of a preliminary acoustic isolation design to reduce structure-borne transmission of acoustic frequency main gearbox gear clash vibrations into the airframe; (4) formulation of a plan for the full-scale validation of the isolation concept; and (5) prediction of the cabin noise environment with various noise control concepts installed
The Land Conservation Plan for New Hampshire\u27s Coastal Watershed
Spanning 990 square miles and 46 towns, New Hampshire’s coastal watersheds harbor exceptional and irreplaceable natural, cultural, recreational and scenic resources (Figure 1). To advance the long-term protection of these resources, the State of New Hampshire, acting through the NH Coastal Program and the NH Estuaries Project, sought to develop a comprehensive, science-based land conservation plan for our coastal watersheds. The State engaged a partnership of The Nature Conservancy, Society for the Protection of New Hampshire Forests, Rockingham Planning Commission, and Strafford Regional Planning Commission to develop the plan. The New Hampshire Charitable Foundation’s Piscataqua Region supported this effort as a regional approach to setting land conservation priorities and strategies, and provided substantial matching funds. Southeastern New Hampshire is changing before our eyes. The region’s forests, wildlife habitat, clean water, and scenic vistas are increasingly threatened by sprawling development, roads, and other irreversible land use changes. Over the past 36 years, in Rockingham and Strafford Counties, an average of 2,230 acres per year has been converted from undeveloped land to a developed condition. And there is no indication that the pace of development will slow in the foreseeable future. The two Counties are projected to add more than 100,000 new residents from 2000 to 2025, and land values continue to rise steeply. With this conversion comes the loss of important natural resource values provided by undeveloped land, especially for plant and wildlife habitat, clean water, and other “ecological services.” To ensure a healthy environment into the future, it is essential that communities identify, retain, and protect the remaining undeveloped lands and waters that support the most important of these natural resource values and functions. Fortunately, it is not too late to protect the essential natural resources of Great Bay, Hampton Harbor, and the many important watersheds feeding into New Hampshire’s coastline. Thanks to the foresight and dedicated efforts of communities, citizens, conservation organizations and public agencies, more than nine percent of our coastal watersheds are permanently conserved. Many municipalities and communities have embraced land conservation through open space bonds, master plans, and local ordinances. New federal funds, such as the Coastal and Estuarine Land Conservation program, are available for conservation in the coastal watersheds. These protected lands and waters form the basis of a network of conservation areas that will help to safeguard our most critical natural resources over time. Now, more than ever, coastal New Hampshire communities need to ensure that they are making smart, enduring conservation investments in land protection and other effective local and regional strategies to have the greatest and most long-lasting beneficial impact on coastal Now, more than ever, coastal New Hampshire communities need to ensure that they are making smart, enduring conservation investments in land protection and other effective local and regional strategies to have the greatest and most long-lasting beneficial impact on coasta
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