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  • AERODYNAMICS  (1,026)
  • EARTH RESOURCES AND REMOTE SENSING  (938)
  • 2005-2009
  • 1990-1994  (979)
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  • 1955-1959
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  • 2005-2009
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  • 1
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    In:  Other Sources
    Publication Date: 2011-08-24
    Description: The problem of the hypersonic double ellipse in rarefied flow is treated by a particle method using the collision model first described by McDonald (1988). In the approach used here, the computational overhead is reduced by using simple cubic cells. The problem of the definition of complex geometries is addressed by developing an algorithm to define the relation of a body surface to the network of cells.
    Keywords: AERODYNAMICS
    Type: In: Hypersonic flows for reentry problems. Vol. 2 (A93-42576 17-02); p. 912-923.
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  • 2
    Publication Date: 2011-08-24
    Description: Program LAURA (Langley Aerothermodynamic Upwind Relaxation Algorithm) is an upwind-biased, point-implicit relaxation algorithm for obtaining the numerical solution to the governing equations for 3D viscous hypersonic flows in chemical and thermal nonequilibrium. The algorithm is derived using a finite-volume formulation in which the inviscid components of flux across cell walls are described with a modified Roe's averaging and with second-order corrections based on Yee's Symmetric Total Variation Diminishing scheme. The code has been applied to Problem 8.2 of this workshop for the case of thermochemical nonequilibrium flow through a nozzle. Chemical reaction rates are defined with the model of Park (1987). Thermal nonequilibrium is modeled using a two-temperature approximation in which the vibrational energies of all molecules are assumed to be in equilibrium at a single temperature which is generally different from the translational-rotational temperature. Two grids were used to define the flow for the original problem, with a stagnation temperature of 6500 K. A third case with a stagnation temperature of 10,000 K is also presented. The solution domain includes the converging nozzle, subsonic flow domain in which the gas is substantially in thermochemical equilibrium and the diverging nozzle, hypersonic flow domain in which the gas is substantially in thermochemical nonequilibrium.
    Keywords: AERODYNAMICS
    Type: In: Hypersonic flows for reentry problems. Vol. 2 (A93-42576 17-02); p. 1145-1158.
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  • 3
    Publication Date: 2011-08-24
    Description: Solutions have been computed and results are presented for Problem 1, the case of Mach 9 transitional flow past a 7 deg half-angle cone at zero incidence. The solutions were computed using a code developed for the integration of the parabolized Navier-Stokes equations. The algorithm employed in the code is based on a Roe-type flux-difference-splitting scheme applied following a finite-volume approach. The basic algorithm has been modified to make it implicit and second-order accurate in the crossflow directions. Results are presented in terms of surface pressure and heat transfer as well as boundary layer profiles of pitot pressure, Mach number, and tangential velocity. The case was recalculated several times in an effort to determine sensitivities to such parameters as grid density, wall temperature, turbulence model parameters, as well as freestream expansion. Comparisons with the experimental data are presented and discussed.
    Keywords: AERODYNAMICS
    Type: In: Hypersonic flows for reentry problems. Vol. 2 (A93-42576 17-02); p. 75-91.
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  • 4
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    Publication Date: 2011-08-24
    Description: Detecting and imaging small wildfires with an Airborne Scanner is done against generally high background levels. The Airborne Scanner System used is a two-channel thermal IR scanner, with one channel selected for imaging the terrain and the other channel sensitive to hotter targets. If a relationship can be determined between the two channels that quantifies the background signal for hotter targets, then an algorithm can be determined that removes the background signal in that channel leaving only the fire signal. The relationship can be determined anywhere between various points in the signal processing of the radiometric data from the radiometric input to the quantized output of the system. As long as only linear operations are performed on the signal, the relationship will only depend on the system gain and offsets within the range of interest. The algorithm can be implemented either by using a look-up table or performing the calculation in the system computer. The current presentation will describe the algorithm, its derivation, and its implementation in the Firefly Wildfire Detection System by means of an off-the-shelf commercial scanner. Improvement over the previous algorithm used and the margin gained for improving the imaging of the terrain will be demonstrated.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: In: Infrared technology XVII; Proceedings of the Meeting, San Diego, CA, July 22-26, 1991 (A93-38376 15-35); p. 207-212.
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  • 5
    Publication Date: 2011-08-24
    Description: Airloads measured on a two-bladed helicopter rotor in flight, from the Tip Aerodynamic and Acoustic Test, are compared with calculations from a comprehensive helicopter analysis (CAMRAD/JA), and the pressures compared with calculations from a full-potential rotor code (FPR). The flight test results cover an advance ratio range from 0.19 to 0.38. The lowest speed case is characterized by the presence of significant blade-vortex interactions. Good correlation of peak-to-peak vortex-induced loads and the corresponding pressures is obtained. The results of the correlation for this two-bladed rotor are substantially similar to the results for three- and four-bladed rotors, concerning the tip vortex core size for best correlation, calculation of the peak-to-peak loads on the retreating side, and calculation of vortex-induced loads on inboard radial stations.
    Keywords: AERODYNAMICS
    Type: In: AHS and Royal Aeronautical Society, Technical Specialists' Meeting on Rotorcraft Acoustics(Fluid Dynamics, Philadelphia, PA, Oct. 15-17, 1991, Proceedings (A93-29401 10-71); 38 p.
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  • 6
    Publication Date: 2011-08-24
    Description: A new CFD potential code, FPX (eXtended Full-Potential), has been developed for application to both helicopters and tilt-rotors. The code solves the unsteady, three-dimensional full potential equation and is an extension of the rotor code, FPR. Both entropy and viscosity corrections are included to enhance the physical modeling capabilities. A number of efficiency related modifications have yielded a factor of two speed-up in the code. An axial flow capability has been added to treat tilt-rotor in forward flight (cruise mode). In order to employ streamwise periodicity and accurately solve for the propagation of acoustic signals in the tip region, an H-H topology has been added to the basic O-H grid system. Computations are performed for the XV-15 Standard and ATB blades at high-speed conditions. Comparisons are made for the blade aerodynamics and the induced fuselage cabin pressure for a range of Mach numbers. Grid generation, wake treatment, and far-field wall treatment are identified as problem areas with recommendations for future research.
    Keywords: AERODYNAMICS
    Type: In: AHS and Royal Aeronautical Society, Technical Specialists' Meeting on Rotorcraft Acoustics(Fluid Dynamics, Philadelphia, PA, Oct. 15-17, 1991, Proceedings (A93-29401 10-71); 15 p.
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  • 7
    Publication Date: 2011-08-24
    Description: A preliminary test/theory correlation evaluation is conducted for wake measurement test results obtained by LDV for a B360 helicopter rotor, at conditions critical to the understanding of wake-rollup and blade-vortex interaction phenomena. The LDV data were complemented by acoustic, blade pressure, rotor performance, and blade/control load measurements.
    Keywords: AERODYNAMICS
    Type: In: AHS and Royal Aeronautical Society, Technical Specialists' Meeting on Rotorcraft Acoustics(Fluid Dynamics, Philadelphia, PA, Oct. 15-17, 1991, Proceedings (A93-29401 10-71); 16 p.
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  • 8
    Publication Date: 2011-08-24
    Description: The size and complexity of AVIRIS data sets makes analysis difficult. We present a technique that allows the researcher to rapidly scan the full data set in image form in order to empirically find significant spatial patterns anywhere across the spectrum. Our approach takes advantage of the speed and power of computer graphics workstations to allow real-time, interactive data manipulation and display. Empirical data selection avoids the bias inherent in theoretical selection criteria, and allows discovery of unexpected relationships within the data set. Link Winds, a prototype data analysis system under development, provides the visualization tools used in this study. We are applying this approach to geological studies in the eastern Mojave Desert.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: In: Thematic Conference on Geologic Remote Sensing, 8th, Denver, CO, Apr. 29-May 2, 1991, Proceedings. Vol. 1 (A93-28978 10-43); p. 423-426.
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  • 9
    Publication Date: 2011-08-24
    Description: Current atmospheric correction models applied to imaging spectroscopy data include such methods as residual or scene average, flat field correction, regression method or empirical line algorithm, the continuum interpolated band ratio (CIBR) derivation and the LOWTRAN 7 method. Due to the limitations of using residual and flat field corrections on vegetated scenes, three methods will be compared: regression, CIBR derivation and LOWTRAN 7. Field-measured bright and dark targets taken at the time of the 13 April, 1989 AVIRIS overflight of Jasper Ridge, California were used to formulate the regression method atmospheric correction. Using this corrected scene as 'ground truth', the CIBR derivation and the LOWTRAN 7 method with both input models are compared on the vegetated Jasper Ridge scene. Although representing a qualitative approach, this is a first approximation and shows the need for more quantitative analysis.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: In: Thematic Conference on Geologic Remote Sensing, 8th, Denver, CO, Apr. 29-May 2, 1991, Proceedings. Vol. 1 (A93-28978 10-43); p. 413-421.
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  • 10
    Publication Date: 2011-08-24
    Description: This paper provides a guide for the acquisition, processing, and interpretation of Landsat Thematic Mapper (TM) imagery of desert terrains for use in regional exploration. Sun angle considerations, data quality cautions, noise suppression routines, band selections, data calibration, spectral enhancements, perceptual considerations of displays, and general interpretation guidelines are all discussed as components of an image-information extraction procedure.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: In: Thematic Conference on Geologic Remote Sensing, 8th, Denver, CO, Apr. 29-May 2, 1991, Proceedings. Vol. 1 (A93-28978 10-43); p. 277-285.
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  • 11
    Publication Date: 2011-08-24
    Description: Computations were made for those test cases of Problem 3 which were designated as laminar flows, viz., test cases 3.1, 3.2, 3.4, and 3.5. These test cases corresponded to flows over a flat plate and a compression ramp at high Mach number and at high Reynolds number. The computations over the compression ramps indicate a substantial streamwise extent of separation. Based on previous experience with separated laminar flows at high Mach numbers which indicated a substantial effect with spatial grid refinement, a series of computations with different grid sizes were performed. Also, for the flat plate, comparisons of the results for two different algorithms were made.
    Keywords: AERODYNAMICS
    Type: In: Hypersonic flows for reentry problems. Vol. 2 (A93-42576 17-02); p. 244-254.
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  • 12
    Publication Date: 2011-08-24
    Description: A development status evaluation is presented for CFD methods applicable to fuselage-integrated scramjet powerplant incorporating hypersonic vehicles; these methods are critically important due to the unavailability of experimental facilities for such elevated Mach number/high-enthalphy conditions. Advancements are required in algorithm robustness and speed, geometric flexibility, and the inclusion of more complete flow physics. The most serious deficiencies lie in turbulence modeling, the lack of complete transition-prediction methods, and combustion modeling.
    Keywords: AERODYNAMICS
    Type: In: Hypersonic flows for reentry problems. Vol. 1 (A93-42576 17-02); p. 55-71.
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  • 13
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    Publication Date: 2011-08-24
    Description: An overview is given of research activity on the application of computational fluid dynamics (CDF) for hypersonic propulsion systems. After the initial consideration of the highly integrated nature of air-breathing hypersonic engines and airframe, attention is directed toward computations carried out for the components of the engine. A generic inlet configuration is considered in order to demonstrate the highly three dimensional viscous flow behavior occurring within rectangular inlets. Reacting flow computations for simple jet injection as well as for more complex combustion chambers are then discussed in order to show the capability of viscous finite rate chemical reaction computer simulations. Finally, the nozzle flow fields are demonstrated, showing the existence of complex shear layers and shock structure in the exhaust plume. The general issues associated with code validation as well as the specific issue associated with the use of CFD for design are discussed. A prognosis for the success of CFD in the design of future propulsion systems is offered.
    Keywords: AERODYNAMICS
    Type: In: Hypersonic flows for reentry problems. Vol. 1 (A93-42576 17-02); p. 170-186.
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  • 14
    Publication Date: 2011-08-24
    Description: The NASA Thermal Infrared Multispectral Scanner (TIMS) has been successfully used for the remote identification of a variety of soil and aggregate deposits in vegetated areas of two states. Over three million cubic meters of gravel deposits were identified from the imagery during a two year period. Verification was accomplished by ground reconnaissance using drilling machinery and by ground instrumentation. The method has been used to differentiate between fine and coarse grained soils, and gravel deposits. The deposits were found to have been naturally sorted according to grain size by depositional processes, providing each deposit with distinct spectral qualities. It was found that the masking effects of relatively dense vegetation were largely overcome by using imagery acquired at higher altitudes above terrain than 9000 meters, due to loss of resolution of the finer detail. The mechanics of image resolution are discussed, a method of data analysis used is described, and sample spectral signatures are illustrated.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: In: Earth and atmospheric remote sensing; Proceedings of the Meeting, Orlando, FL, Apr. 2-4, 1991 (A93-24176 08-42); p. 358-369.
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  • 15
    Publication Date: 2011-08-24
    Description: Viewing terrain data from various remote sensors in three dimensions has proven to be a valuable tool for scientists in understanding a variety of problems. A technique is presented for using image pyramids in such visualization of large terrain data sets, providing up to two orders of magnitude performance enhancement over simpler techniques, while at the same time eliminating false high-frequency information, which causes animations to sparkle.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: International Journal of Imaging Systems and Technology (ISSN 0899-9457); p. 157-166.
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  • 16
    Publication Date: 2011-08-24
    Description: An evaluation was performed on SWIR (2000-2400 nm) data from two airborne remote sensing systems for discriminating and identifying alteration minerals at Cuprite, Nevada. The data were acquired by the NASA Airborne Visible/InfraRed Imaging Spectrometer (AVIRIS) and the GEOSCAN Mk II multispectral scanner. The evaluation involved comparison of processed imagery and image-derived spectra with existing alteration maps and laboratory spectra of rock samples from Cuprite. Results indicate that both the AVIRIS and GEOSCAN data permit the discrimination of areas of alunite, buddingtonite, kaolinite, and silicification using color composite images formed from three SWIR bands processed with either the decorrelation stretch or a log residual algorithm. The laboratory spectral features alunite, kaolinite and buddingtonite could be seen clearly only in the log residual processed AVIRIS data. However, this does not preclude their identification with the GEOSCAN data.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Geophysics (ISSN 0016-8033); 56; 9; p. 1432-1440.
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  • 17
    Publication Date: 2011-08-24
    Description: The present work describes the mission operations system (MOS) design process for remote-sensing missions. A MOS is defined as the system required to perform, monitor, and control an operation, encompassing personnel, hardware, software and/or documentation. Attention is given to telecommunications and remote-sensing instrumentation, MOS definition program phases and reviews, and MOS organization, management, and staffing. Also treated are the uplink and downlink processes, anomalies and contingency plans, the illustrative case of the MOS for the Magellan radar sensing mission, and a projection of future MOSs incorporating AI.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
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  • 18
    Publication Date: 2011-08-24
    Description: After detailing a technique for the estimation of the instantaneous emission of trace gases produced by biomass burning, using satellite imagery, attention is given to the recent discovery that burning results in significant enhancement of biogenic emissions of N2O, NO, and CH4. Biomass burning accordingly has an immediate and long-term impact on the production of atmospheric trace gases. It is presently demonstrated that satellite imagery of fires may be used to estimate combustion emissions, and could be used to estimate long-term postburn biogenic emission of trace gases to the atmosphere.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
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  • 19
    Publication Date: 2011-08-24
    Description: One of the largest forest fires ever recorded burned in the People's Republic of China (PRC) and the Soviet Union in May 1987. The fire covered over 1.0 million hectares in the PRC and almost 4 million hectares in the Soviet Union. The progress and areal extent of the fire were measured using satellite images analyzed in the imaging facilities at NASA-Langley and Forestry Canada. The analyses show the utility and value of satellite measurements to assess the areal extent and geographical distribution of fires, and have important implications for future measurements to be obtained from space platforms, such as the Earth Observing System.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
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  • 20
    Publication Date: 2011-08-24
    Description: A central artificial-viscosity and an upwind-biased difference method are contrived to solve the Euler equations for flowfields over typical spacecrafts. The spatial discretization is based on either nodal or cell-vertex formulation in the domain extending from free stream to the end of the vehicle. The outer boundary is treated as a bow shock in the first method but is placed in the free stream in the second, which captures both bow and internal shocks using an approximate Riemann solver based on high-order extrapolation to the cell face. These methods were tested for the Shuttle and Hermes orbiters at wind-tunnel conditions and angles of attack ranging from 0 to 60 deg. The artificial-viscosity method incorporated with a shock-fitting procedure shows smeared crossflow and wing-shock positions and required 15 percent more CPU per node than the upwind method. Greater flexibility and robustness is demonstrated by the latter on a fixed grid for all cases considered.
    Keywords: AERODYNAMICS
    Type: Computer Methods in Applied Mechanics and Engineering (ISSN 0045-7825); 87; 2-3,
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  • 21
    Publication Date: 2011-08-24
    Description: The application of remote sensing to ecological investigations is briefly discussed. Emphasis is given to the recruitment problem in marine population dynamics, the regional analysis of terrestrial ecosystems, and the monitoring of ecological changes. Impediments to the use of remote sensing data in ecology are addressed.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Ecology (ISSN 0012-9658); 72; 6, De
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  • 22
    Publication Date: 2011-08-24
    Description: Some of the most significant earth-viewing imagery obtained during Space Shuttle Columbia's flight STS-35, December 2-10, 1990, is reviewed with emphasis on observations of the Southern Hemisphere. In particular, attention is given to environmental observations in areas of Madagascar, Brazil, and Persian Gulf; observation of land resources (Namibia, offshore Australia); and observations of ocean islands (Phillipines, Indonesia, and Reunion). Some of the photographs are included.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Geocarto International (ISSN 1010-6049); 6; 4, De
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  • 23
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    Publication Date: 2005-08-04
    Description: Use of current space imaging systems and airborne platforms has direct use in survey design and site location when used in concert with a comprehensive GIS environment. Local conditions and site physical and chemical properties are key factors in successful applications. Conjoining of environmental constraints and site properties are present for the later prehistoric occupations in the Arkansas and Mississippi River areas. Direct linkages between comprehensive site databases and satellite images can be used to evaluate site distributions for research and management.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: NASA. Stennis Space Center, Applications of Space-Age Technology in Anthropology; p 237-250
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  • 24
    Publication Date: 2005-08-04
    Description: Creating rain forest reserves is vital given the global decline in biodiversity. Yet, the plants and animals that will be protected from untrammeled commercial exploitation within such reserves constitute essential resources for indigenous foragers and farmers. Balancing the needs of local subsistence level populations with the goals of national and international conservation agencies requires a thorough understanding of the mutual impacts that arise from the interaction of park and people. In the Ituri forest of Zaire, LANDSAT TM image analysis and GPS ground truth data were used to locate human settlements so that boundaries of the proposed Okapi Reserve could be chosen to minimize its impact on the subsistence practices of the local foragers and farmers. Using satellite imagery in conjunction with cultural information should help to ensure traditional resource exploitation rights of indigenous peoples whilst simultaneously protecting the largest contiguous area of undisturbed forest.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: NASA. Stennis Space Center, Applications of Space-Age Technology in Anthropology; p 181-193
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  • 25
    Publication Date: 2005-08-04
    Description: A wide variety of remote sensing instruments have been utilized to attempt to detect archaeological features under volcanic ash in Central America. Some techniques have not been successful, such as seismic refraction, for reasons that are not difficult to understand. Others have been very successful and provide optimism for archaeologists witnessing the destruction of unburied sites throughout Central America. The sudden burial of buildings, gardens, and footpaths by volcanic ash can preserve them extremely well providing a rich data base for understanding human life and culture at certain points in time.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: NASA. Stennis Space Center, Applications of Space-Age Technology in Anthropology; p 167-179
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  • 26
    Publication Date: 2005-08-04
    Description: The concept of integrating ecological perspectives on early man's settlement patterns with advanced remote sensing technologies shows promise for predictive site modeling. Early work with aerial imagery and ecosystem analysis is discussed with respect to the development of a major project in Maya archaeology supported by NASA and the National Geographic Society with technical support from the Mississippi State Remote Sensing Center. A preliminary site reconnaissance model will be developed for testing during the 1991 field season.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Applications of Space-Age Technology in Anthropology; p 121-136
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  • 27
    Publication Date: 2005-08-04
    Description: A Geographic Information System (GIS)-type analysis of archaeological site locations using a dBase III plus program and a desk top computer is presented. A previously developed model of site locations in the Sequatchie Valley of northeastern Alabama is tested against known site locations in another large survey area there. The model fails to account for site locations in the test area. A model is developed for the test area and indicates the site locations are indeed different. Whether this is due to differences in site locations on a sub-regional level, or to sample error in the original model is unknown.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: NASA. Stennis Space Center, Applications of Space-Age Technology in Anthropology; p 95-110
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  • 28
    Publication Date: 2005-08-04
    Description: Data recovered as the result of a recent field project designed to test a model of the distribution of protohistoric settlement in an unusual physiographic zone in eastern Mississippi are examined using GIS based techniques to manipulate soil and stream distance information. Significant patterning is derived. The generally thin soils and uniform substratum of the Black Prairie in combination with a distinctive settlement pattern offer a promising opportunity for the search for site specific characteristics within airborne imagery. Landsat TM data provide information on modern ground cover which is used as a mask to select areas in which a multivariate search for archaeological site signatures within a TIMS image is most likely to prove fruitful.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: NASA. Stennis Space Center, Applications of Space-Age Technology in Anthropology; p 111-120
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  • 29
    Publication Date: 2005-08-04
    Description: A Macro-geographical reconnaissance of the Western Peloponnesos adopts spectral signatures taken by Landsat-5 Thematic Mapper as a new instrument of archaeological survey in Greece. Ancient records indicate that indigenous resources contributed to the prosperity of the region. Natural resources and Ancient, Medieval, and Pre-modern Folklife in the Western Peloponnesos describes the principal lines of research. For a supervised classification of attested ancient resources, a variety of biophysical surface features were pinpointed: stone quarries, coal mines, forests of oak and silver fir, terracotta-producing clay beds, crops, and various wild but exploited shrubs such as flax.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: NASA. Stennis Space Center, Applications of Space-Age Technology in Anthropology; p 63-79
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  • 30
    Publication Date: 2006-06-13
    Description: In the TOPEX/POSEIDON project, several satellite positioning systems, such as Laser, Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS), and Global Positioning Satellite (GPS) (on an experimental basis), will be used to track the satellite and to provide accurate orbits. Unfortunately, these systems will provide their dedicated tracking-station coordinates and the satellite orbits in different reference frames. Each technique will use, de facto, a different reference frame. In fact, even for the same technique, each group, depending on the hypothesis used in its computation, will use a different reference frame. This problem is not new for geodesists and can be overcome, in large part, but could create trouble for other scientists when they compare or combine different coordinate data sets. The main purpose of this investigation is to determine a consistent terrestrial system for TOPEX/POSEIDON in which all the tracking-station coordinates, all the orbit ephemerides, and all the other station coordinates of specific interest (such as tide gauges) could be expressed. Another issue of this investigation is the provision of reliable information concerning the relationships between all the possible reference frames of interest for th TOPEX/POSEIDON project. To be more explicit, we plan to provide the possible transformation formula between the TOPEX/POSEIDON terrestrial reference frame and the Laser, DORIS, GPS, and other internationally recognized frames such as the International Terrestrial Reference Frame (ITRF).
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: JPL, TOPEX(Poseidon Science Investigations Plan; p 27-28
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  • 31
    Publication Date: 2006-06-13
    Description: Our program includes five research items: (1) determination of a precision geoid and gravity anomaly field; (2) precise leveling and detection of tidal changes of the sea surface and study of the role of the tide in the global energy exchange; (3) oceanic effect on the Earth's rotation and polar motion; (4) geological and geophysical interpretation of the altimetry gravity field; and (5) evaluation of the effectiveness of local tracking of TOPEX/POSEIDON by use of a laser tracker.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: JPL, TOPEX(Poseidon Science Investigations Plan; p 126-130
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  • 32
    Publication Date: 2011-08-24
    Description: Research requirements to an ultra-high-Reynolds-number liquid helium facility are reviewed. Aerodynamic research areas under consideration include wave vortex hazard reduction, vortex control and diagnostics for maneuvering fighter aircraft, and performance of high-lift devices.
    Keywords: AERODYNAMICS
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  • 33
    Publication Date: 2011-08-24
    Keywords: AERODYNAMICS
    Type: Journal of Spacecraft and Rockets (ISSN 0022-4650); 28; 628-635
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  • 34
    Publication Date: 2011-08-24
    Description: A model for estimating wheat yields on the farm level was developed, that integrates the Landsat TM data and agrometeorological information. Results obtained for a test site in southern Brasil for years of 1986 and 1987 show that the vegetation index derived from Landsat TM could account for the 60 to 40 percent wheat-yield variability observed between the two crop years. Compared to results using either the Landsat TM vegetation index or the agrometeorological data alone, the joint use of both types of data in a single model yielded a significant improvement.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: International Journal of Remote Sensing (ISSN 0143-1161); 12; 2477-248
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  • 35
    Publication Date: 2011-08-24
    Description: Airborne and satellite passive microwave measurements acquired simultaneously with ground measurements of depth, density, and stratigraphy of the snow in central and northern Alaska between March 11 and 19, 1988, are reported. A good correspondence in brightness temperature (TB) trends between the aircraft and satellite data was found. An expected inverse correlation between depth hoar thickness and TB was not found to be strong. A persistent TB minimum in both the aircraft and the satellite data was detected along the northern foothills of the Brooks Range. In an area located at about 68 deg 60 min N, 149 deg 20 min W, the TB as recorded from the aircraft microwave sensor dropped by 55 K. Satellite microwave measurements showed a TB decrease of up to 45 K at approximately the same location. An examination of microwave satellite data from 1978 to 1987 revealed that similar low late-winter values were found in approximately the same locations as those observed in March 1988.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Remote Sensing of Environment (ISSN 0034-4257); 38; 161-172
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  • 36
    Publication Date: 2011-08-24
    Description: A static aeroelastic analysis capability that calculates flexible air loads for generic configuration wings was developed. It was made possible by integrating a finite element structural analysis code (MSC/NASTRAN) and a panel code of aerodynamic analysis based on linear potential flow theory. The framework already built in MSC/NASTRAN was used, and the aerodynamic influence coefficient matrix was computed externally and inserted in the NASTRAN by means of a DMAP program. It was shown that deformation and flexible air loads of an oblique wing configuration including asymmetric wings can be calculated reliably by this code both in subsonic and supersonic speeds.
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft (ISSN 0021-8669); 28; 801
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  • 37
    Publication Date: 2011-08-24
    Keywords: AERODYNAMICS
    Type: AIAA Journal (ISSN 0001-1452); 29; 2054-206
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  • 38
    Publication Date: 2011-08-24
    Description: The Michigan Microwave Canopy Scattering Model (MIMICS) is used to model scatterometer data that were obtained during the August 1987 EOS (Earth Observing System) synergism study. During this experiment, truck-based scatterometers were used to measure radar backscatter from a walnut orchard in Fresno County, California. Multipolarized L- and X-band data were recorded for orchard plots for which dielectric and evapotranspiration characteristics were monitored. MIMICS is used to model a multiangle data set in which a single orchard plot was observed at varying impedance angles and a series of diurnal measurements in which backscatter from this same plot was measured continuously over several 24-h periods. MIMICS accounts for variations in canopy backscatter driven by changes in canopy state that occur diurnally as well as on longer time scales. L-band backscatter is dependent not only on properties of the vegetation but also on properties of the underlying soil surface. The behavior of the X-band backscatter is dominated by properties of the tree crowns.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: IEEE Transactions on Geoscience and Remote Sensing (ISSN 0196-2892); 29; 852-863
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  • 39
    Publication Date: 2011-08-24
    Description: A recent study of total-pressure probes for use in highly turbulent streams is extended herein by developing probe systems that measure time-averaged static or ambient pressure and turbulence intensity. Arrangements of tubular probes of circular and elliptical cross section are described that measure the pressure at orifices on the sides of the probes to obtain different responses to the cross-stream velocity fluctuations. When the measured data are combined to remove the effect of the presence of the probes on the local pressure, the time-averaged static pressure and the cross-stream components of turbulence intensity can be determined. If a system of total pressure tubes, as described in an accompanying paper, is added to the static pressure group to form a single cluster, redundant measurements are obtained that permit accuracy and consistency checks.
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft (ISSN 0021-8669); 28; 750-755
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  • 40
    Publication Date: 2011-08-24
    Keywords: AERODYNAMICS
    Type: AIAA Journal (ISSN 0001-1452); 29; 1836-184
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  • 41
    Publication Date: 2011-08-24
    Description: Flow over slender prolate spheroids at incidence is examined. The incidence angle is chosen high enough to cause streamwise separation of the flow in addition to crossflow separation generally observed at lower incidence angles. The freestream Mach number for the cases investigated here is subsonic, thus precluding the use of parabolized procedures. Laminar, transitional and turbulent flow cases are investigated.
    Keywords: AERODYNAMICS
    Type: Computers and Fluids (ISSN 0045-7930); 20; 3, 19
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  • 42
    Publication Date: 2011-08-24
    Keywords: AERODYNAMICS
    Type: Journal of Spacecraft and Rockets (ISSN 0022-4650); 28; 552-559
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  • 43
    Publication Date: 2011-08-24
    Keywords: AERODYNAMICS
    Type: Journal of Thermophysics and Heat Transfer (ISSN 0887-8722); 5; 456-462
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  • 44
    Publication Date: 2011-08-24
    Description: Airborne Visible/Infrared Imaging Spectrometer data covering the wavelength range between 2000 and 2400 nm are examined for their ability to display the diagnostic mineral absorption features of certain alteration minerals, employing various data processing techniques. The techniques may be separated into two broad categories: scene based techniques that use parameters derived from the data themselves, and correction techniques utilizing external information such as solar/atmospheric models. Results indicate that the data corrected utilizing the LOWTRAN 7 atmospheric transfer code constrained with local weather station data are the most effective at showing the diagnostic absorption features of the regions of known mineralogy and introduce the least number of artifacts into the data.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Photogrammetric Engineering and Remote Sensing (ISSN 0099-1112); 57; 1303-130
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  • 45
    Publication Date: 2011-08-19
    Description: The authors present the results of an experiment using the NASA/JPL DC-8 AIRSAR (aircraft synthetic-aperture radar) over a coniferous forest near Mt. Shasta (California) in 1989. Calibration devices were deployed in clearings and under the forest canopy and passes at 20, 40, and 55 deg incidence angles were made with the AIRSAR. A total of eight images at differing incidence angles have been processed and calibrated. The multipolarization, multifrequency data were examined, and it was found that the C-band cross section averaged over like and cross polarizations is the best parameter for distinguishing between two stands with differing forest biomass. The average cross section at P- and L-bands is useful only for smaller incidence angles. Parameters describing the polarization behavior of the scattering were primarily useful in identifying the dominant scattering mechanisms for forest backscatter. It was found that both branch scattering and ground/tree interactions are important at P-band. At L-band and C-bands, the return is primarily from the canopy. Comparison with model calculations verified this conclusion.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: IEEE Transactions on Geoscience and Remote Sensing (ISSN 0196-2892); 29; 444-450
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  • 46
    Publication Date: 2011-08-19
    Description: All orders of scattering are analyzed for two artifical canopies. The SHL canopy consists of Small Horizontal Leaves that are much smaller than the leaf-to-leaf spacing. The IHL canopy consists of Infinite Horizontal Layers, where each leaf is of infinite extent (a horizontal plane). Hemispheric leaf reflectances and transmittances independent of the direction of illumination lead to exact solutions for these models. Sunlight that penetrates to a given leaf area index level is much stronger in an SHL canopy than that in IHL; but the difference becomes muted when leaf transmittance is large. Multiple scattering enhances the hemispheric canopy reflectance more strongly in SHL than it does in IHL. The enhancement depends linearly on leaf transmittance in SHL and on the transmittance squared in IHL. Comparison with measured reflectances indicates that IHL model grossly underestimates multiple scattering in soybean canopies.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Applied Optics (ISSN 0003-6935); 30; 1562-156
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  • 47
    Publication Date: 2011-08-19
    Description: A spatially variable monthly, infrared cloud-threshold data base has been used to screen cloud-contaminated observations from radiances measured by the NOAA-9 AVHRR over Africa. Cloud-screening through a monthly average infrared threshold based on measured surface air temperature, which is geographically dependent, shows an improvement over using a seasonally and geographically independent thermal cloud threshold of 287 K. It is found that differences in cloud-screening for these two thresholds occur for cases of lower altitude clouds or subpixel clouds where the radiative temperature is higher than the 287 K infrared threshold, yet colder than the variable threshold developed by Stowe et al. (1988) for the Nimbus-7 global cloud climatology. The variable IR threshold is shown to be effective over persistently cloud-covered regions, such as the coastal region of the Gulf of Guinea, but may introduce some erroneous cloud identifications over mountains.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: International Journal of Remote Sensing (ISSN 0143-1161); 12; 1205-122
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  • 48
    Publication Date: 2011-08-19
    Description: In order to monitor the aerosol characteristics needed for atmospheric correction of remotely sensed data, a network of sun photometers was established in the Sahel region of Senegal, Mali, and Niger. Data analysis suggests that there is a high spatial variability of the aerosol optical thickness tau(a) in the western Sahel region. At a 67 percent confidence level the instantaneous values of tau(a) can be extrapolated approximately 270-400 km with an error tolerance of 50 percent. Spatial variability in the dry season is found to be of a similar magnitude. The ranges of variations in the NDVI in the Sahel region are shown to be approximately 0.02 and 0.01, respectively, due to commonly observed fluctuations in the aerosol optical thickness and aerosol size distribution.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: International Journal of Remote Sensing (ISSN 0143-1161); 12; 1147-116
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  • 49
    Publication Date: 2011-08-19
    Description: Images are presented that show the mean and coefficient of variation of nine years (1981-1989) of NOAA AVHRR normalized difference vegetation index (NDVI) data for the growing season (July-October) in Africa, north of the equator. The variation in the growing season NDVI is represented by the coefficient of variation image that shows the large variation in the Sahelian growing season between years. It is concluded that these images illustrate some aspects of the perspective being brought to regional and continental scale processes by coarse resolution satellite sensors and the potential of these sensors to provide consistent, long-term datasets.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: International Journal of Remote Sensing (ISSN 0143-1161); 12; 1133-113
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  • 50
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    Publication Date: 2011-08-19
    Keywords: AERODYNAMICS
    Type: AIAA Journal (ISSN 0001-1452); 29; 560-566
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  • 51
    Publication Date: 2011-08-19
    Description: NASA's Aeroassist Flight Experiment (AFE) vehicle will be deployed from the Space Shuttle Orbiter in 1994 to make a data-gethering aeropass through the upper atmosphere before returning to orbit for Shuttle pickup. An axisymmetric, chemically-reacting viscous shock-layer code is presently used to calculate AFE heating rates which automatically accounts for the viscous-inviscid interaction and entropy layer-swallowing effects which are ignored by the conventional boundary-layer methods. Results are presented for the stagnation-point heating of the current AFE baseline trajectory.
    Keywords: AERODYNAMICS
    Type: Journal of Spacecraft and Rockets (ISSN 0022-4650); 28; 125-128
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  • 52
    Publication Date: 2011-08-19
    Keywords: AERODYNAMICS
    Type: Journal of Spacecraft and Rockets (ISSN 0022-4650); 28; 9-15
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  • 53
    Publication Date: 2011-08-19
    Keywords: AERODYNAMICS
    Type: Journal of Spacecraft and Rockets (ISSN 0022-4650); 28; 31-39
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  • 54
    Publication Date: 2011-08-19
    Description: A new image enlargement and reconstruction routine, the digital image enlarging balanced reconstruction algorithm (DIEBRA), is described. Using a highly modified form of 'balanced' two-dimensional polynomial interpolation, this program enlarges digital imagery, creating synthetic high spatial resolution images. Statistical analysis shows the DIEBRA-generated imagery to be significantly closer to true high spatial resolution imagery at all frequencies than imagery generated by a cubic convolutional reconstruction filter.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: International Journal of Remote Sensing (ISSN 0143-1161); 12; 627-634
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  • 55
    Publication Date: 2011-08-19
    Description: Irrigated rice provides an ideal breeding habitat for Anopheles free-borni, the western malaria mosquito, throughout California. In a 1985 study, it was determined that early-season rice canopy development, as monitored using remotely sensed data, could be used to distinguish between high and low mosquito producing rice fields. This distinction could be made over two months prior to peak mosquito production. It was found that high-producing fields were located in an area characterized by a diversity of land use, including livestock pastures, whereas the low-producing fields were in an area devoted almost exclusively to the cultivation of rice. The ability to distinguish between high and low mosquito producing fields prior to peak mosquito production is important in terms of mosquito habitat surveillance and control.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: International Journal of Remote Sensing (ISSN 0143-1161); 12; 621-626
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  • 56
    Publication Date: 2011-08-19
    Description: Complete polarimetric signatures of a layer of random, nonspherical discrete scatterers overlying a homogeneous half space are studied with the first- and second-order solutions of the vector radiative transfer theory. Some of the salient features of the numerical results are as follows: (1) the inclusion of the nondiagonal extinction matrix in the vector radiative transfer theory accounts for an appreciable phase difference between vv and hh polarizations, particularly for aligned scatterers; (2) the ensemble-averaged scattered Stokes vector is generally partially polarized, with the degree of polarization less than unity; (3) there generally exists a pedestal in the copolarization return when plotted as a function of ellipticity and orientation angles, which may be due to heterogeneity of scattering objects and/or multiple scattering effects; and (4) multiple scattering effects generally enhance the pedestal in copolarization return, decrease the degree of polarization, affect phase difference, and also enhance the depolarization return.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: IEEE Transactions on Geoscience and Remote Sensing (ISSN 0196-2892); 29; 242-253
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  • 57
    Publication Date: 2011-08-19
    Description: An unstructured-grid, finite-volume method has been developed for simulating the inviscid flow over spacecrafts of realistic configuration. The grid generation is accomplished by a new technique on the basis of the advancing-front concept. This simple technique is shown to be equally as powerful for a complex multibody as for a single vehicle. Second- or third-order accuracy is obtained via an innovative interpolation procedure similar to the conventional MUSCL approach. This method has been applied to the Shuttle orbiter and a representative Shuttle launch vehicle consisting of the orbiter, the external tank, and the solid rocket boosters. A comparison is discussed between the present results and other results obtained from structured- and unstructured-grid methods.
    Keywords: AERODYNAMICS
    Type: Computers and Structures (ISSN 0045-7949); 39; 1-2,
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  • 58
    Publication Date: 2011-08-19
    Description: An evaluation of the polarization signatures obtained from the four Stokes parameters is reported for the atmosphere and a soybean canopy. The polarimeter design and operation are set forth, and the Stokes parameters' relationships are discussed. The canopy polarization was different from the sky at azimuths of 90 and 270 degrees, demonstrating a response that reflecting the sky polarization signatures across a plane parallel to the polarization axis and passing through a phase angle of about 90 degrees would produce. Classical behavior in terms of electromagnetic theory was found in the fourth Stokes parameter of the canopy which was obtained in the principal plane. Only the third Stokes parameter is demonstrated to be unambiguously affected in a comparison of sky polarization signatures and aerosol optical densities. The similarity between the sky at azimuth 180 degrees and the soybean canopy data at the principal plane is interesting considering the disparity of the subjects.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: International Journal of Remote Sensing (ISSN 0143-1161); 12; 1087-109
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  • 59
    Publication Date: 2011-08-19
    Description: Finite-difference approximations for steady-state compressible Navier-Stokes equations, whose two spatial dimensions are written in generalized curvilinear coordinates and strong conservation-law form, are presently solved by means of Newton's method in order to obtain a lifting-airfoil flow field under subsonic and transonnic conditions. In addition to ascertaining the computational requirements of an initial guess ensuring convergence and the degree of computational efficiency obtainable via the approximate Newton method's freezing of the Jacobian matrices, attention is given to the need for auxiliary methods assessing the temporal stability of steady-state solutions. It is demonstrated that nonunique solutions of the finite-difference equations are obtainable by Newton's method in conjunction with a continuation method.
    Keywords: AERODYNAMICS
    Type: Journal of Computational Physics (ISSN 0021-9991); 93; 108-127
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  • 60
    Publication Date: 2011-08-19
    Description: Measurements of radar backscatter from an artificial tree were made in the laboratory at 6 and 10 GHz at horizontal incidence. The system had a resolution cylinder 18 cm in diameter and 11 cm long, so about half of the tree (30.5 cm high) was within the beam. The mean returned power from the target with leaves was always higher than that from the target without leaves, as expected. The signal faded with an exponential distribution when the artificial tree was rotated about its trunk, with no angular trend apparent. When the leaves were present, tilted polarizations gave results favoring an angle corresponding with that of the branches. When leaves were absent, the trunk of the tree dominated the radar backscatter at all polarizations.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: International Journal of Remote Sensing (ISSN 0143-1161); 12; 401-417
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  • 61
    Publication Date: 2011-08-19
    Description: An 8-b quantization scheme to reduce the data volume for single-look complex scattering matrix data measured by polarimetric imaging radar systems is described. The scattering matrices are not symmetrized before compression, thereby retaining information about background noise and system effects. The data volume is reduced by a factor of 3.2. It is shown, with measured data, that the signal to quantization noise ratio for the compression scheme is more than 35 dB for the cross-polarized channels, and more than 45 dB for the copolarized channels.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: IEEE Transactions on Geoscience and Remote Sensing (ISSN 0196-2892); 29; 784-786
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  • 62
    Publication Date: 2011-08-19
    Keywords: AERODYNAMICS
    Type: Journal of Propulsion and Power (ISSN 0748-4658); 7; 626-634
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  • 63
    Publication Date: 2011-08-19
    Description: An engineering approach was used to include the nonlinear effects of thickness and camber in an analytical aeroelastic analysis of casecades in supersonic acial flow (supersonic leading-edge locus). A hybrid code using Lighthill's nonlinear piston theory and Lane's linear potential theory was developed to include these nonlinear effects. Lighthill's theory was used to calculate the unsteady pressures on the noninterference surface regions of the airfoils in cascade. Lane's theory was used to calculate the unsteady pressures on the remaining interference surface regions. Two airfoil profiles were investigated (a supersonic throughflow fan design and a NACA 66-206 airfoil with a sharp leading edge). Results show that compared with predictions of Lane's potential theory for flat plates, the inclusion of thickness (with or without camber) may increase or decrease the aeroelastic stability, depending on the airfoil geometry and operating conditions. When thickness effects are included in the aeroelastic analysis, inclusion of camber will influence the predicted stability in proportion to the magnitude of the added camber. The critical interblade phase angle, depending on the airfoil profile and operating conditions, may also be influenced by thickness and camber. Compared with predictions of Lane's linear potential theory, the inclusion of thickness and camber decreased the aerodynamic stiffness and increased the aerodynamic damping at Mach 2 and 2.95 for a cascade of supersonic throughflow fan airfoils oscillating 180 degrees out of phase at a reduced frequency of 0.1.
    Keywords: AERODYNAMICS
    Type: Journal of Propulsion and Power (ISSN 0748-4658); 7; 404-411
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  • 64
    Publication Date: 2011-08-19
    Description: An efficient and highly accurate algorithm based on a spectral collocation method is developed for numerical solution of the compressible, two-dimensional and axisymmetric boundary layer equations. The numerical method incorporates a fifth-order, fully implicit marching scheme in the streamwise (timelike) dimension and a spectral collocation method based on Chebyshev polynomial expansions in the wall-normal (spacelike) dimension. The spectral collocation algorithm is used to derive the nonsimilar mean velocity and temperature profiles in the boundary layer of a 'fuselage' (cylinder) in a high-speed (Mach 5) flow parallel to its axis. The stability of the flow is shown to be sensitive to the gradual streamwise evolution of the mean flow and it is concluded that the effects of transverse curvature on stability should not be ignored routinely.
    Keywords: AERODYNAMICS
    Type: International Journal for Numerical Methods in Fluids (ISSN 0271-2091); 13; 713-737
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  • 65
    Publication Date: 2011-08-19
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft (ISSN 0021-8669); 28; 609-617
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  • 66
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    Publication Date: 2011-08-19
    Description: This paper reviews the role of terrestrial hydrology in determining the coupling between the surface and atmosphere. Present experience with interactive numerical simulation is discussed and approaches to the inclusion of land hydrology in global climate models ae considered. At present, a wide range of answers as to expected changes in surface hydrology is given by nominally similar models. Studies of the effects of tropical deforestation and global warming illustrate this point.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Tellus, Series A-B: Special Issue (ISSN 0280-6495); 43A-B; 176-181
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  • 67
    Publication Date: 2011-08-19
    Description: Supersonic flows over a sharp and a flat-faced blunt fin mounted on a flat plate are simulated numerically. Several basic issues involved in the resultant three-dimensional steady flow separation are studied. Using the same number of grid points, different grid spacings are employed to investigate the effects of a grid resolution on the origin of the line of separation. Various shock strengths are used to study the so-called separation and unseparated boundary layer and to establish the existence or absence of secondary separation. The length of separation ahead of the flat-faced blunt fin, bifurcation of a horseshoe vortex, and the accessibility of a closed-type separation are investigated. The usual interpretation of the flow field from previous studies and new interpretations arising from the present simulation are discussed.
    Keywords: AERODYNAMICS
    Type: AIAA Journal (ISSN 0001-1452); 29; 1659-166
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  • 68
    Publication Date: 2011-08-19
    Keywords: AERODYNAMICS
    Type: AIAA Journal (ISSN 0001-1452); 29; 1573-158
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  • 69
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    Publication Date: 2011-08-19
    Description: The Vaisala-Brunt frequencies of atmospheric waves lie sufficiently near He-filled balloon buoyancy oscillation frequencies to cause a near-resonance condition, especially in the 11.6-24.4 km altitude range. This excitation will hold for such balloons irrespective of size and payload variations due to the independence of balloon buoyant frequencies from size. Vertical perturbations of approximately 5-min period should accordingly be anticipated by balloon flight-control system designers.
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft (ISSN 0021-8669); 28; 606-608
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  • 70
    Publication Date: 2011-08-19
    Description: Numerical solutions of the thin-layer approximation of the 3D Navier-Stokes equations are presented for flows around an ogive-cylinder body with and without a splitter plate. It is suggested that the presence of the splitter plate prevents the interaction between flows on either side of the symmetry plane. It is concluded that, as a result of the enforced symmetry, the antisymmetric mode of the convective instability near the apex of the body cannot be excited and, therefore, the vortices remain symmetric, staying low and parallel to the upper body surface. The antisymmetric mode of the absolute instability mechanism cannot be initiated, which suppresses the alternate shedding of vortices from the cylindrical portion of the body. High-frequency fluctuations of the shear layer are found to remain virtually unaffected by the presence of the splitter plate.
    Keywords: AERODYNAMICS
    Type: Physics of Fluids A (ISSN 0899-8213); 3; 2122-213
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  • 71
    Publication Date: 2011-08-19
    Description: A 10 x 13-km area in Quetico Provincial Park, Canada has been studied using a digital elevation model to separate different drainage classes and to examine the influence of site factors and lithology on vegetation. Landsat Thematic Mapper data have been classified into six forest classes of varying deciduous-coniferous cover through nPDF, a procedure based on probability density functions. It is shown that forests growing on mafic lithologies are enriched in deciduous species, compared to those growing on granites. Of the forest classes found on mafics, the highest coniferous component was on north facing slopes, and the highest deciduous component on south facing slopes. Granites showed no substantial variation between site classes. The digital elevation derived site data is considered to be an important tool in geobotanical investigations.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Photogrammetric Engineering and Remote Sensing (ISSN 0099-1112); 57; 1179-118
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  • 72
    Publication Date: 2011-08-19
    Description: Remotely acquired multispectral data are used to improve landslide hazard assessments at all scales of investigation. A vegetation map produced from automated interpretation of TM data is used in a GIS context to explore the effect of vegetation type on debris flow occurrence in preparation for inclusion in debris flow hazard modeling. Spectral vegetation indices map spatial patterns of grass senescence which are found to be correlated with soil thickness variations on hillslopes. Grassland senescence is delayed over deeper, wetter soils that are likely debris flow source areas. Prediction of actual soil depths using vegetation indices may be possible up to some limiting depth greater than the grass rooting zone. On forested earthflows, the slow slide movement disrupts the overhead timber canopy, exposes understory vegetation and soils, and alters site spectral characteristics. Both spectral and textural measures from broad band multispectral data are successful at detecting an earthflow within an undisturbed old-growth forest.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Photogrammetric Engineering and Remote Sensing (ISSN 0099-1112); 57; 1185-119
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  • 73
    Publication Date: 2011-08-19
    Keywords: AERODYNAMICS
    Type: AIAA Journal (ISSN 0001-1452); 29; 1355-136
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  • 74
    Publication Date: 2011-08-19
    Description: Data from polar-orbiting meteorological satellites have been used to determine the extent of the Sahara Desert and to document its interannual variation from 1980 to 1990. The Sahara Desert ranged from 8,633,000 square kilometers in 1980 to 9,982,000 square kilometers in 1984. The greatest annual north-south latitudinal movement of the southern Saharan boundary was 110 kilometers from 1984 to 1985 and resulted in a decrease in desert area of 724,000 square kilometers.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Science (ISSN 0036-8075); 253; 299-301
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  • 75
    Publication Date: 2011-08-19
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft (ISSN 0021-8669); 28; 517-525
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  • 76
    Publication Date: 2011-08-19
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft (ISSN 0021-8669); 28; 481-488
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  • 77
    Publication Date: 2011-08-19
    Description: Acquisition of ground truth data for use in microwave interaction modeling requires measurement of surface roughness sampled at intervals comparable to a fraction of the microwave wavelength and extensive enough to adequately represent the statistics of a surface unit. Sub-centimetric measurement accuracy is thus required over large areas, and existing techniques are usually inadequate. A technique is discussed for acquiring the necessary photogrammetric data using twin film cameras mounted on a helicopter. In an attempt to eliminate tedious data reduction, an automated technique was applied to the helicopter photographs, and results were compared to those produced by conventional stereogrammetry. Derived root-mean-square (RMS) roughness for the same stereo-pair was 7.5 cm for the automated technique versus 6.5 cm for the manual method. The principal source of error is probably due to vegetation in the scene, which affects the automated technique but is ignored by a human operator.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Photogrammetric Engineering and Remote Sensing (ISSN 0099-1112); 57; 1075-107
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  • 78
    Publication Date: 2011-08-19
    Keywords: AERODYNAMICS
    Type: AIAA Journal (ISSN 0001-1452); 29; 1250-125
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  • 79
    Publication Date: 2011-08-19
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft (ISSN 0021-8669); 28; 403-409
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  • 80
    Publication Date: 2011-08-19
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft (ISSN 0021-8669); 28; 456-462
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  • 81
    Publication Date: 2011-08-19
    Description: Improved algorithms for the solution of the three-dimensional, time-dependent Euler equations are presented for aerodynamic analysis involving unstructured dynamic meshes. The improvements have been developed recently to the spatial and temporal discretizations used by unstructured-grid flow solvers. The spatial discretization involves a flux-split approach that is naturally dissipative and captures shock waves sharply with at most one grid point within the shock structure. The temporal discretization involves either an explicit time-integration scheme using a multistage Runge-Kutta procedure or an implicit time-integration scheme using a Gauss-Seidel relaxation procedure, which is computationally efficient for either steady or unsteady flow problems. With the implicit Gauss-Seidel procedure, very large time steps may be used for rapid convergence to steady state, and the step size for unsteady cases may be selected for temporal accuracy rather than for numerical stability. Steady flow results are presented for both the NACA 0012 airfoil and the Office National d'Etudes et de Recherches Aerospatiales M6 wing to demonstrate applications of the new Euler solvers. The paper presents a description of the Euler solvers along with results and comparisons that assess the capability.
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft (ISSN 0021-8669); 28; 397-402
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  • 82
    Publication Date: 2011-08-19
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft (ISSN 0021-8669); 28; 374-380
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  • 83
    Publication Date: 2011-08-19
    Keywords: AERODYNAMICS
    Type: Journal of Thermophysics and Heat Transfer (ISSN 0887-8722); 5; 301-307
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  • 84
    Publication Date: 2011-08-19
    Keywords: AERODYNAMICS
    Type: AIAA Journal (ISSN 0001-1452); 29; 1108-111
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  • 85
    Publication Date: 2011-08-19
    Description: An extension is undertaken of a previous numerical study in order to improve current understanding of nonequilibrium flow effects over slender bodies. Upon extension of the parametric study to encompass smaller nose radii, the downstream influence of equilibrium nonequilibrium flow is found to be much smaller than for the larger nose radii. A comparison of individual stagnation nonequilibrium heating rates demonstrates that a relative comparison of the ratios was not indicative of the actual heating reduction.
    Keywords: AERODYNAMICS
    Type: Journal of Spacecraft and Rockets (ISSN 0022-4650); 28; 358-360
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  • 86
    Publication Date: 2011-08-19
    Keywords: AERODYNAMICS
    Type: Journal of Propulsion and Power (ISSN 0748-4658); 7; 452-461
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  • 87
    Publication Date: 2011-08-19
    Description: Hypersonic rarefied flow about the Aeroassist Flight Experiment vehicle has been investigated using a three-dimensional direct simulation Monte Carlo method. Calculations are performed for the transitional flows encountered during the vehicle's atmospheric entry for altitudes of 110 and 100 km with an entry velocity of 9.9 km/s. The simulations are performed using a five-species reacting gas model that account for rotational and vibrational internal energies. The solutions indicate that dissociation is important at altitudes of 110 km and below. Results are presented for surface pressures, convective heating, flowfield structure, and aerodynamic coefficient variations with altitude.
    Keywords: AERODYNAMICS
    Type: AIAA Journal (ISSN 0001-1452); 29; 52-57
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  • 88
    Publication Date: 2011-08-19
    Description: The mean flow structure upstream, around within, and in the near wake of a turbulent junction or horseshoe vortex is reported for an incompressible subsonic flow. Measurements of the primitive variables of velocity and pressure are reported on all surfaces bounding the region of the vortex flow and on three transverse and one streamwise plane within the flowfield itself for comparisons between the measured and any calculated flow variables. Detailed surface flow visualizations and some direct force measurements of surface shear stress are also available. The data is a highly detailed, coherent, self-consistent set offered to the computational fluid mechanics community as a standard test case for the evaluation of the capability of numerical solvers intended for predicting the flowfield in such a complex, separated, three-dimensional turbulent flow. This data base is available for copying to user supplied tapes or for transmission via BITNET, as well as in two National Technical Information Service (NTIS) reports.
    Keywords: AERODYNAMICS
    Type: AIAA Journal (ISSN 0001-1452); 29; 14
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  • 89
    Publication Date: 2011-08-19
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft (ISSN 0021-8669); 28; 175-180
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  • 90
    Publication Date: 2011-08-19
    Keywords: AERODYNAMICS
    Type: AIAA Journal (ISSN 0001-1452); 29; 667-675
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  • 91
    Publication Date: 2011-08-19
    Keywords: AERODYNAMICS
    Type: Journal of Propulsion and Power (ISSN 0748-4658); 7; 297-299
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  • 92
    Publication Date: 2011-08-19
    Description: High-temperature effects alter the physical and transport properties of a gas, air in particular, due to vibrational excitation and gas dissociation, and thus the chemical reactions have to be considered in order to compute the flow field. Linear stability of high-temperature boundary layers is investigated under the assumption of chemical equilibrium and this gas model is labeled here as real gas model. In this model, the system of stability equations remains of the same order as for the perfect gas and the effect of chemical reactions is introduced only through mean flow and gas property variations. Calculations are performed for Mach 10 and 15 boundary layers and the results indicate that real gas effects cause the first mode instability to stabilize while the second mode is made more unstable. It is also found that the second mode instability shifts to lower frequencies. There is a slight destabilizing influence of real gas on the Goertler instability as compared to the perfect gas results.
    Keywords: AERODYNAMICS
    Type: Physics of Fluids A (ISSN 0899-8213); 3; 803-821
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  • 93
    Publication Date: 2011-08-19
    Description: An overview of space flight STS-41 is presented, including personal observations and comments by the mission astronauts. The crew deployed the Ulysses spacecraft to study the polar regions of the sun and the interplanetary space above the poles. Environmental observations, including those of Lake Turkana, Lake Chad, biomass burning in Madagascar and Argentina, and circular features in Yucatan are described. Observations that include landforms and geology, continental sedimentation, desert landscapes, and river morphology are discussed.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Geocarto International (ISSN 1010-6049); 6; 69-80
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  • 94
    Publication Date: 2011-08-19
    Keywords: AERODYNAMICS
    Type: AIAA Journal (ISSN 0001-1452); 29; 1021-102
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  • 95
    Publication Date: 2011-08-19
    Description: An evaluation is conducted of the accuracy of the 'Preston tube' surface pitot-pressure skin friction measurement method relative to the already proven laser interferometer skin-friction meter in a swept shock wave/turbulent boundary-layer interaction. The Preston tube was used to estimate the total shear-stress distribution in a fin-generated swept shock-wave/turbulent boundary-layer interaction. The Keener-Hopkins calibration method using the isentropic relation to calculate the Preston-tube Mach number produces the best results.
    Keywords: AERODYNAMICS
    Type: AIAA Journal (ISSN 0001-1452); 29; 1007-100
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  • 96
    Publication Date: 2011-08-19
    Keywords: AERODYNAMICS
    Type: Journal of Thermophysics and Heat Transfer (ISSN 0887-8722); 5; 166-171
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  • 97
    Publication Date: 2011-08-19
    Description: The effects of soil optical properties on vegetation index imagery are analyzed with ground-based spectral measurements and both simulated and actual AVHRR data from the NOAA satellites. Soil effects on vegetation indices were divided into primary variations associated with the brightness of bare soils, secondary variations attributed to 'color' differences among bare soils, and soil-vegetation spectral mixing. Primary variations were attributed to shifts in the soil line owing to atmosphere or soil composition. Secondary soil variance was responsible for the Saharan desert 'artefact' areas of increased vegetation index response in AVHRR imagery.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: International Journal of Remote Sensing (ISSN 0143-1161); 12; 1223-124
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  • 98
    Publication Date: 2011-08-19
    Description: Variable atmospheric conditions have a significant impact on satellite monitoring of vegetation in the Sahelian zone of Africa. The effects of atmospheric O3, H2O, and aerosols on spectral, directional reflectances and derived measures, such as the normalized difference vegetation index are discussed using a sensitivity study. An atmospheric correction scheme is presented based on measurements of optical thicknesses from the ground and is applied to NOAA AVHRR data. The use of the reflectance of the ocean surface close to the terrestrial target to estimate atmospheric effects on terrestrial reflectance is also discussed.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: International Journal of Remote Sensing (ISSN 0143-1161); 12; 1189-120
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  • 99
    Publication Date: 2011-08-19
    Keywords: AERODYNAMICS
    Type: Journal of Spacecraft and Rockets (ISSN 0022-4650); 28; 16-22
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  • 100
    Publication Date: 2011-08-19
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft (ISSN 0021-8669); 28; 239-245
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