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  • 1
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    Institut und Museum für Geologie und Paläontologie der Universität Tübingen
    In:  Tübinger Geowissenschaftliche Abhandlungen A, 5 . Institut und Museum für Geologie und Paläontologie der Universität Tübingen, Tübingen, V, 135 pp.
    Publication Date: 2017-11-06
    Description: Der Einfluß lateralen Stresses auf die mechanische Diagenese von marinen Sedimenten kann mithilfe sedimentphysikalischer Daten quantifiziert werden. Beispielhaft wurde dies anhand von Daten aus dem Deep Sea Drilling Project (DSDP) und Ocean Drilling Project (ODP) für den Akkretionskeil des Barbados Ridge Complex durchgeführt. Die Untersuchung erfolgte in drei Schritten. (1) In einer statistischen Untersuchung der umfangreichen sedimentologischen und sedimentphysikalischen Datenbank des DSDP wurden tief enabhängige Funktionen der mechanischen Diagenese für eine Reihe von lithologischen Standardtypen definiert. Diese, als Referenzgröße zur Quantifizierung der tektonischen KonsoHdation in einem rezenten Akkretionskeil benötigten Funktionen, wurden in erster Linie für pelitische und psammitische Sedimente mit geringen Karbonatgehalten entwickelt. Zwei verschiedene Verfahren zur Auswahl von entsprechenden Datensätzen werden beschrieben und die Ergebnisse der statistischen Untersuchung mit den in der Literatur beschriebenen Funktionen verglichen. (2) Die entwickelten Typfunktionen wurden bei der Durchführung eines palinspastischen Rekonstruktionsverfahrens benutzt, mit dem die Entwicklung sedimentphysikalischer Parameter während der initialen Deformationsphase in rezenten Akkretionssystemen modelliert werden konnte. Diese Untersuchung basierte im wesentlichen auf sedimentphysikalischen Daten der DSDP- und ODP-Legs 78A und J 10 (Barbados Ridge Komplex, Kleine Antillen). Durch palinspastische Entzerrung der imbrikierten Schuppung und stratigraphische Rekonstruktion akkretierter "thrust slices" im untersuchten Bereich, entsprechender Relozierung der zugehörigen sedimentphysikalischen Daten und dekompaktive Anpassung an die rekonstruierte Position konnte ein synthetisches prä-akkretionäres Profil der ursprünglichen Porosität rechnerisch modelliert werden. (3) Der Vergleich dieses synthetischen Porositäts-Tiefen-Profils mit charakteristischen Referenzprofilen aus undeformierten Sequenzen unmittelbar vor der Deformationsf ront zeigt eine systematische, lithologisch bestimmte Divergenz. Durch Überarbeitung des Rekonstruktionsverfahrens mithilfe von Stress-PorositätsBeziehungen konnte der relative und absolute Einfluß der lateralen Stresskomponente auf die Konsolidation hemipelagischer Sedimente in diesem Teil des konvergenten Plattenrandes quantifiziert werden.
    Type: Report , NonPeerReviewed
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  • 2
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    National Technical Information Service, US Department of Commerce
    In:  National Technical Information Service, US Department of Commerce, Springfield, VA, USA, 11 pp.
    Publication Date: 2018-01-15
    Type: Report , NonPeerReviewed
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  • 3
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    Geological Society
    In:  In: Magmatism in the Ocean Basins. , ed. by Saunders, A. D. and Norry, M. J. Geological Society Special Publications, 42 . Geological Society, London, pp. 257-276.
    Publication Date: 2018-05-24
    Description: Combined Sr-Nd-Pb isotope and trace-element data for St Helena are interpreted in terms of changing thermal and chemical fluxes impinging on and interacting with the base of the lithosphere over a period of 6 Ma. The data reveal the existence of two geochemically distinct components in the St Helena source region: (i) a HIMU (high U/Pb) component which has extremely radiogenic lead isotopes (206Pb/204Pb 〉20.8) with 87Sr/86Sr and 143Nd/144Nd ratios displaced below the mantle array; (ii) a component with less radiogenic lead and strontium isotopic compositions and more radiogenic neodymium compositions. Coupled trace-element and isotope variations are evident during the activity of each volcano. During shield development an increase in incompatible-trace-element enrichment occurs. This is coupled to a decrease in 143Nd/144Nd, whilst strontium and lead isotope ratios become progressively more radiogenic with time. The time-dependent variations are thought to be consistent with high-level processes occurring at the base of, or within, the lithosphere. A decrease in the signature of the depleted component with time is shown to be the result of a decreasing thermal flux acting on the base of the lithosphere. As a consequence the degree of partial melting of the depleted component (which may reside in the lithosphere or asthenosphere) is reduced, increasing the signature of the HIMU component in the erupted magmas.
    Type: Book chapter , NonPeerReviewed
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  • 4
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    In:  (Doctoral thesis/PhD), Christian-Albrechts-Universität Kiel, Kiel, Germany, 277 pp
    Publication Date: 2018-05-23
    Type: Thesis , NonPeerReviewed
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  • 5
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    In:  (Doctoral thesis/PhD), Christian-Albrechts-Universität Kiel, Kiel, Germany, 145 pp
    Publication Date: 2018-05-29
    Description: Zur Ableitung der Bodenalbedo aus METEOSAT - Daten müssen verschiedene Korrekturen vorgenommen werden: a)eine Wolkenelimination, b) eine Atmosphären-, c) eine Winkelkorrektur und d) eine spektrale Korrektur. Zur Wolkenerkennung wurde ein Extremwertverfahren entwickelt, das gleichzeitig eine Minimierung des Atmosphäreneinflusses bewirkt. Nach Anwendung dieses Verfahrens muß nur noch ein kleiner Einfluß der Atmosphäre behandelt werden. Für die Korrekturen im wolkenfreien Fall wurde mit Strahlungstransportsimulationen ein synthetischer Datensatz bestehend aus gefilterter und ungefilterter Bodenalbedo, METEOSAT - Strahldichte, Gesamtwasserdampfgehalt, optischer Dicke der Atmosphäre und dem Anisotropiefaktor am Boden erzeugt. Die multivariate Analyse des Datensatzes ergab als Auswertemodell einen linearen Zusammenhang zwischen gefilterter Bodenalbedo (Bodenalbedo im METEOSAT - Kanal), METEOSAT - Strahldichte, Gesamtwasserdampfgehalt, optischer Dicke und Anisotropiefaktor am Boden. Unter Berücksichtigung realistischer Fehler der Eingangsgrößen kann hiermit eine kombinierte Atmosphären- und Anisotropiekorrektur erfolgen. Das breite Spektrum an Reflexionseigenschaften, das in der Analyse berücksichtigt wurde, sowie der nach der Anwendung des Extremwertverfahrens geringe Atmosphäreneinfluß bewirken, daß die Atmosphärenparameter verglichen mit dem Anisotropieverhalten der Oberfläche nur eine untergeordnete Rolle spielen. Die Analyse des Datensatzes ergab gleichfalls einen linearen Zusammenhang zwischen ungefilterter und gefilterter Bodenalbedo, wobei im wesentlichen das spektrale Reflexionsvermögen der Oberfläche und weniger die Atmosphäre bestimmend ist. Bei Berücksichtigung von Zusatzinformationen beträgt die Genauigkeit der solaren Bodenalbedo 0.04 bis zu einem Sonnenzenitwinkel von 66.45° und für die meisten Blickwinkelgeometrien. In der Anwendung konnte für den Januar und Juni 1983 11:30 UT gezeigt werden, daß die Bodenalbedo über Afrika bei hohem Sonnenstand mit genügender Genauigkeit auch ohne Zusatzinformationen abgeleitet werden kann. Der maximale Fehler im Juni beträgt 0.03 und im Januar 0.034. Im Vergleich mit ebenfalls aus Satellitendaten abgeleiteten Werten der Bodenalbedo anderer Autoren in der westafrikanischen Sahelzone lagen die hier abgeleiteten Werte etwas niedriger, in einigen Fällen stimmten sie innerhalb der angegebenen Fehlergrenzen überein. Vergleiche mit in-situ Messungen der Bodenalbedo in der Sahara über sechs verschiedenen Oberflächen ergab in zwei Fällen eine gute Übereinstimmung innerhalb der Fehlergrenzen, bei den anderen traten größere Differenzen auf.
    Type: Thesis , NonPeerReviewed
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  • 6
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    In:  (Doctoral thesis/PhD), Christian-Albrechts-Universität Kiel, Kiel, Germany, 204 pp
    Publication Date: 2018-05-29
    Type: Thesis , NonPeerReviewed
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  • 7
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    Taylor & Francis
    In:  International Geology Review, 31 (12). pp. 1251-1257.
    Publication Date: 2018-07-09
    Type: Article , PeerReviewed
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  • 8
    Publication Date: 2019-05-06
    Description: The ice-proximal environment of the Nordaustlandet tidewater ice cap, Svalbard Archipelago, is one of the best analogues for understanding glacial geologic processes of northern continental shelves during initial Pleistocene deglaciation. Investigations of the proglacial region in 1980–1983 showed that the sedimentary environment is dominated by numerous meltwater outflows which discharge sediment-laden water from subglacial meltwater streams during the summer. Two large, stable meltwater outflows were observed in embayments along the southern part of the ice front. Landsat images show that both outflows have been in approximately the same position since at least 1976. They are located at the intersection of glacial drainage basins and centered over depressions in the underlying bedrock. An “outflow valley” extending away from the ice front was observed in front of the western meltwater outflow. Sidescan sonar profiling along the glacier front showed a 200 m wide gap in acoustic reflection at the base of the western meltwater outflow, probably caused by meltwater effluence. Enhanced sediment accumulations in this region, observed as a ≈ 3 ms sediment drape in front of the outflow, and large arcuate ridges in the outflow valley, testify to the transport efficiency of the subglacial meltwater stream. Several mounds, up to about 25 m high and 200 m wide, are observed on sidescan and 3.5 kHz profiles directly in front of the outflow. Although samples from these structures are absent, they are most likely composed of sediment and are similar to beaded eskers observed in Pleistocene glacimarine sequences indicating locally very high sedimentation rates. Fine-grained components of the subglacial discharge incorporated in the buoyant meltwater plume are usually entrained in a westerly coastal current. Elevated suspended particulate material concentrations are observed within the coastal waters in a region extending about 15 km perpendicular to the glacier front and at least 60 km along the ice front extending into the northwestern Barents Sea.
    Type: Article , PeerReviewed
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  • 9
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    In:  Proceedings of the Ocean Drilling Program: Scientific Results, 105 . pp. 137-154.
    Publication Date: 2019-05-08
    Description: Authigenic carbonates were recovered in lower to middle Eocene claystones at Ocean Drilling Program Site 647 in the Labrador Sea. Detailed chemical, petrographic, and X-ray investigations reveal that these diagenetic carbonates have a complex mineralogical composition. At least five different carbonate phases are identified: calcium-rich rhodochrosite, rhodochrosite, manganosiderite, siderite, and calcite. Manganese carbonates are the dominant carbonate phases formed throughout the section. Textural analyses show two major generations of carbonate formation. Early cementation of micritic carbonate in burrow structures was followed by carbonate cementation forming microsparry to sparry crystals. At approximately 620 meters below seafloor (mbsf), three concretions of iron carbonates occur, which indicates a special pore-water chemistry. Thin section analyses from this level show (1) several generations of diagenetic carbonates, (2) widespread secondary cavity formation in burrow structures, and (3) various cement precipitations in voids. We suggest that this level represents a hiatus or highly condensed sequence, as indicated by (1) the low carbonate content in host sediments, (2) carbonate dissolution reflected by the high ratio of benthic to planktonic foraminifers, and (3) complex diagenetic alteration in the carbonate concretions. Iron and manganese enrichments observed in lithologic Unit IV may have been derived from a hydrothermal source at the adjacent, then active, Labrador Sea mid-ocean ridge. Authigenic smectites forming numerous pseudomorphs of siliceous microfossils are precipitated in burrow structures. We propose that diagenetic smectite formation from biogenic opal and iron oxyhydroxide (analogous to smectite formation in surface sediments of the East Pacific area) occurred in the Labrador Sea during the early and middle Eocene.
    Type: Article , NonPeerReviewed
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  • 10
    Publication Date: 2019-05-10
    Description: Ocean crustal carbon uptake during seafloor alteration at DSDP Sites 417A, 417D, and 418A exceeds the estimated loss of carbon during magmatic ridge outgassing. If these sites are representative for oceanic crust in general, 2.2–2.9 × 1012 moles of carbon are removed from the oceans per year as a net flux of carbon between the oceanic crust and seawater. Although most of this carbon occurs as calcium carbonate, this ocean crustal carbonate probably cannot be considered part of the marine calcium carbonate sink since much of the Ca in these carbonates must be derived from basalt alteration that is not balanced by a concomitant uptake of seawater Mg. Our present estimate cannot be satisfactorily applied to global carbon budgets, because of uncertainties in the bulk budget of ocean floor alteration and because of the uniqueness of our estimate. Yet, our data document that the formation of ocean crust provides a significant sink for carbon that should be included in models of the global cycling of carbon. Furthermore, magmatic outgassing during ocean crust emplacement and seafloor basalt alteration may provide a buffering mechanism for atmospheric carbon.
    Type: Article , PeerReviewed
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  • 11
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    In:  Proceedings of the Ocean Drilling Program: Scientific Results, 104 . pp. 739-744.
    Publication Date: 2019-05-10
    Description: Ice-rafted fossils of late Cretaceous and Tertiary age were detected in Pleistocene-Pliocene glacially influenced sediments of the Vdring Plateau, eastern Norwegian Sea. The ice-rafted associations contain frequent Inoceramus (Bivalvia) prisms and rare occurrences of both benthic and planktonic foraminifers of Miocene, Oligocene, and Maastrichtian to Campanian age. As source areas, shallow outcrops on the Norwegian Continental Shelf as well as the Greenland Shelf and the North and Baltic Seas have to be considered.
    Type: Article , NonPeerReviewed
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  • 12
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    In:  Proceedings of the Ocean Drilling Program: Scientific Results, 104 . pp. 681-696.
    Publication Date: 2019-05-10
    Description: Sites 642, 643, and 644 were investigated for planktonic foraminifers. Frequent occurrences of barren intervals caused by dissolution as well as low- diversity and long-ranging assemblages reduce the stratigraphic resolution of these records. Based on Neogloboquadrina species a local zonation, correlated with high-latitude North Atlantic schemes, is proposed for the middle Miocene to Quaternary and correlated with paleomagnetic records. The middle to late Miocene boundary is defined by the last appearance datum of Neogloboquadrina mayeri and the first appearance datum of Neogloboquadrina acostaensis. Late Miocene age is defined by a N. acostaensis zone, whereas latest Miocene to Pliocene zones are defined by dextral and sinistrally coiling Neogloboquadrina atlantica. The top of the Pliocene is characterized by dextral and sinistrally coiling Neogloboquadrina pachyderma. The Pleistocene is defined by a nearly monospecific assemblage of Neogloquadrina pachy derma in its sinistrally coiled and encrusted variety.
    Type: Article , NonPeerReviewed
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  • 13
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    In:  Other Sources
    Publication Date: 2019-01-25
    Description: The extension of Forth into the realm of parallel processing on the Massively Parallel Processor (MPP) is described. The extended language, MPP Parallel FORTH, is a derivative of Forth-83 with extensions designed by the author as philosophically similar to serial Forth as possible. The MPP hardware characteristics are discussed, as viewed by the Forth programmer, and then a description is presented of MPP Parallel FORTH along with a detailed example developed by the author showing how the bitonic sort is implemented in this language.
    Keywords: COMPUTER SYSTEMS
    Type: Inst. for Applied FORTH Research, Inc., The Journal of FORTH Application and Research, Volume 5, No. 4, 1989; p 459-468
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  • 14
    Publication Date: 2019-01-25
    Description: A novel system architecture, based on the object model, is the central structuring concept used in the Clouds distributed operating system. This architecture makes Clouds attractive over a wide class of machines and environments. Clouds is a native operating system, designed and implemented at Georgia Tech. and runs on a set of generated purpose computers connected via a local area network. The system architecture of Clouds is composed of a system-wide global set of persistent (long-lived) virtual address spaces, called objects that contain persistent data and code. The object concept is implemented at the operating system level, thus presenting a single level storage view to the user. Lightweight treads carry computational activity through the code stored in the objects. The persistent objects and threads gives rise to a programming environment composed of shared permanent memory, dispensing with the need for hardware-derived concepts such as the file systems and message systems. Though the hardware may be distributed and may have disks and networks, the Clouds provides the applications with a logically centralized system, based on a shared, structured, single level store. The current design of Clouds uses a minimalist philosophy with respect to both the kernel and the operating system. That is, the kernel and the operating system support a bare minimum of functionality. Clouds also adheres to the concept of separation of policy and mechanism. Most low-level operating system services are implemented above the kernel and most high level services are implemented at the user level. From the measured performance of using the kernel mechanisms, we are able to demonstrate that efficient implementations are feasible for the object model on commercially available hardware. Clouds provides a rich environment for conducting research in distributed systems. Some of the topics addressed in this paper include distributed programming environments, consistency of persistent data and fault-tolerance.
    Keywords: COMPUTER SYSTEMS
    Type: Maryland Univ., The 1989 Workshop on Operating Systems for Mission Critical Computing; 21 p
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  • 15
    Publication Date: 2019-01-25
    Description: The exact nature of the solar flare process is still somewhat a mystery. A key element to understanding flares if the relationship between the hard x rays emitted by the most energetic portions of the flare and the soft x rays from other areas and times. This relationship was studied by comparing hard x ray light curved from the Hard X-Ray Burst Spectrometer (HXRBS) with the soft x ray light curve and its derivation from the Bent Crystal Spectrometer (BCS) which is part of the X-Ray Polychrometer (XRP), these instruments being on the Solar Maximum Mission spacecraft (SMM). Data sample was taken from flares observed with the above instruments during 1980, the peak of the previous maximum of solar activity. Flares were chosen based on complete coverage of the event by several instruments. The HXRBS data covers the x ray spectrum from about 25 keV to about 440 keV in 15 spectral channels, while the BCS data used covers a region of the Spectrum around 3 angstroms including emission from the Ca XIX ion. Both sets of data were summed over their spectral ranges and plotted against time at a maximum time resolution of around 3 seconds. The most popular theory of flares holds that a beam of electrons produces the hard x rays by bremsstrahlung while the soft x rays are the thermal response to this energy deposition. The question is whether the rate of change of soft x ray emission might reflect the variability of the electron beam and hence the variability of the hard x rays. To address this, we took the time derivative of the soft x ray light curve and compared it to the hard flares, 12 of them showed very closed agreement between the soft x ray derivative and the hard x ray light curve. The other five did not show this behavior but were similar to each other in general soft x ray behavior. Efforts to determine basic differences between the two kinds of flares continue. In addition the behavior of soft x ray temperature of flares was examined.
    Keywords: SOLAR PHYSICS
    Type: Maryland Univ., The 1989 NASA-ASEE Summer Faculty Fellowship Program in Aeronautics and Research; p 38
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  • 16
    Publication Date: 2019-01-25
    Description: A user requirements analysis (URA) was undertaken to determine and appropriate public domain Geographic Information System (GIS) software package for potential integration with NASA's LAS (Land Analysis System) 5.0 image processing system. The necessity for a public domain system was underscored due to the perceived need for source code access and flexibility in tailoring the GIS system to the needs of a heterogenous group of end-users, and to specific constraints imposed by LAS and its user interface, Transportable Applications Executive (TAE). Subsequently, a review was conducted of a variety of public domain GIS candidates, including GRASS 3.0, MOSS, IEMIS, and two university-based packages, IDRISI and KBGIS. The review method was a modified version of the GIS evaluation process, development by the Federal Interagency Coordinating Committee on Digital Cartography. One IEMIS-derivative product, the ALBE (AirLand Battlefield Environment) GIS, emerged as the most promising candidate for integration with LAS. IEMIS (Integrated Emergency Management Information System) was developed by the Federal Emergency Management Agency (FEMA). ALBE GIS is currently under development at the Pacific Northwest Laboratory under contract with the U.S. Army Corps of Engineers' Engineering Topographic Laboratory (ETL). Accordingly, recommendations are offered with respect to a potential LAS/ALBE GIS linkage and with respect to further system enhancements, including coordination with the development of the Spatial Analysis and Modeling System (SAMS) GIS in Goddard's IDM (Intelligent Data Management) developments in Goddard's National Space Science Data Center.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Maryland Univ., The 1989 NASA-ASEE Summer Faculty Fellowship Program in Aeronautics and Research; p 37
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  • 17
    Publication Date: 2019-01-25
    Description: Two projects using remote sensing of phytoplankton chlorophyll concentrations in the Chesapeake Bay estuary were proposed. The first project used aircraft remote sensing with a compact radiometer system developed at NASA's Goddard Space Flight Center (GSFC), the Ocean Data Acquisition System (ODAS). ODAS includes three radiometers at 460, 490, and 520 nm, an infrared temperature sensor (PRT-5), Loran-C for navigation, and a data acquisition system using a PC and mass storage device. This instrument package can be flown in light aircraft at relatively low expense, permitting regular and frequent flights. Sixteen flights with ODAS were completed using the Virginia Institute of Marine Science's De Havilland 'Beaver'. The goal was to increase spatial and temporal resolution in assaying phytoplankton pigment concentrations in the Chesapeake. At present, analysis is underway of flight data collected between March and July 1989. The second project focused on satellite data gathered with the Nimbus-7 Coastal Zone Color Scanner (CZSC) between late 1978 and mid 1986. The problem in using CZSC data for the Chesapeake Bay is that the optical characteristics of this (and many) coastal and estuarine waters are distinct from those of the open ocean for which algorithms for computing pigment concentrations were developed. The successful use of CZCS data for the estuary requires development of site-specific algorithms and analytical approaches. Of principal importance in developing site-specific procedures is the availability of in-situ data on pigment concentrations. A significant data set was acquired from EPA's Chesapeake Bay Program in Annapolis, Maryland, and clear satellite scenes are being analyzed for which same-day sea truth measurements of pigment were obtained. Both the University of Miami and GSFC Seapak systems are being used in this effort. The main finding to date is an expected one, i.e., the algorithms developed for oceanic waters are inadequate to compute pigment concentrations for the Case 2 waters of the Chesapeake Bay. One reason is the overestimation of aerosol radiances by assuming that water-leaving radiance in Band 4 of CZCS (670 nm) is zero, an assumption that is invalid for the Bay. This prompted any attempts to iterative procedures for estimating the proportion of the Band 4 radiance that is actually attributable to aerosol by estimating the water-leaving component using optical data. A cruise on the Chesapeake the week of 7 August 1989 was conducted to collect additional optical data necessary to this task.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Maryland Univ., The 1989 NASA-ASEE Summer Faculty Fellowship Program in Aeronautics and Research; p 33
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  • 18
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    In:  Other Sources
    Publication Date: 2019-01-25
    Description: The GSFC Computer Network Environment provides a broadband RF cable between campus buildings and ethernet spines in buildings for the interlinking of Local Area Networks (LANs). This system provides terminal and computer linkage among host and user systems thereby providing E-mail services, file exchange capability, and certain distributed computing opportunities. The Environment is designed to be transparent and supports multiple protocols. Networking at Goddard has a short history and has been under coordinated control of a Network Steering Committee for slightly more than two years; network growth has been rapid with more than 1500 nodes currently addressed and greater expansion expected. A new RF cable system with a different topology is being installed during summer 1989; consideration of a fiber optics system for the future will begin soon. Summmer study was directed toward Network Steering Committee operation and planning plus consideration of Center Network Environment analysis and modeling. Biweekly Steering Committee meetings were attended to learn the background of the network and the concerns of those managing it. Suggestions for historical data gathering have been made to support future planning and modeling. Data Systems Dynamic Simulator, a simulation package developed at NASA and maintained at GSFC was studied as a possible modeling tool for the network environment. A modeling concept based on a hierarchical model was hypothesized for further development. Such a model would allow input of newly updated parameters and would provide an estimation of the behavior of the network.
    Keywords: COMPUTER SYSTEMS
    Type: Maryland Univ., The 1989 NASA-ASEE Summer Faculty Fellowship Program in Aeronautics and Research; p 32
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  • 19
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    In:  Other Sources
    Publication Date: 2019-01-25
    Description: The development of a reliable and reproducible GaAs process was initiated for applications in gate array logic. Gallium Arsenide is an extremely important material for high speed electronic applications in both digital and analog circuits since its electron mobility is 3 to 5 times that of silicon, this allows for faster switching times for devices fabricated with it. Unfortunately GaAs is an extremely difficult material to process with respect to silicon and since it includes the arsenic component GaAs can be quite dangerous (toxic) especially during some heating steps. The first stage of the research was directed at developing a simple process to produce GaAs MESFETs. The MESFET (MEtal Semiconductor Field Effect Transistor) is the most useful, practical and simple active device which can be fabricated in GaAs. It utilizes an ohmic source and drain contact separated by a Schottky gate. The gate width is typically a few microns. Several process steps were required to produce a good working device including ion implantation, photolithography, thermal annealing, and metal deposition. A process was designed to reduce the total number of steps to a minimum so as to reduce possible errors. The first run produced no good devices. The problem occurred during an aluminum etch step while defining the gate contacts. It was found that the chemical etchant attacked the GaAs causing trenching and subsequent severing of the active gate region from the rest of the device. Thus all devices appeared as open circuits. This problem is being corrected and since it was the last step in the process correction should be successful. The second planned stage involves the circuit assembly of the discrete MESFETs into logic gates for test and analysis. Finally the third stage is to incorporate the designed process with the tested circuit in a layout that would produce the gate array as a GaAs integrated circuit.
    Keywords: SOLID-STATE PHYSICS
    Type: Maryland Univ., The 1989 NASA-ASEE Summer Faculty Fellowship Program in Aeronautics and Research; p 31
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  • 20
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    In:  Other Sources
    Publication Date: 2019-01-25
    Description: Thermal control of future large, high power spacecraft will require a two-phase fluid central bus. The two-phase fluid reservoir is a critical component in the two-phase fluid bus. It both controls the saturation temperature and provides a space for volumetric changes. A dynamic reservoir simulation model does not currently exist, but it is needed to expedite efforts and reduce risk. During 1989 an effort was made to develop a simulation model of the transient performance of a two-phase fluid reservoir. As a beginning, a preliminary model was developed. It is based upon component mathematical models in lumped parametric form and build upon five component mathematical models for calculating dynamic responses of two-phase fluid reservoirs, primary feedback elements, controller commands, heater actuators, and reservoir heaters. As much as possible, the model took advantage of the available SINDA'85/FLUINT thermal/fluid integrator. Additional calculation logic and computer subroutines were developed to complete implementation of the model. The model is capable of simulating dynamic response of an equilibrium two-phase fluid reservoir. Modification of the model to include the liquid/vapor nonequilibrium is required for applications of the model to simulate performance of reservoir in which the liquid and vapor phases of the reservoir fluid are not in equilibrium. In addition, the model in its present form, needs to be refined in several respects. More empirical data are needed to guide the model development. The model may then be used to conduct a full parametric study of two-phase fluid reservoirs. More complexities in two-phaes flow regions in laboratory and flight conditions may have to be considered eventually if empirical data cannot be simulated satisfactorily. System with other components arrangement also need to be simulated if optimization is ever to be attained. The present model does, however, preliminarily demonstrates that such analyses are quite possible and offers a far less expensive method to understand the transient of a two-phase fluid reservoir system than a totally headware approach.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Maryland Univ., The 1989 NASA-ASEE Summer Faculty Fellowship Program in Aeronautics and Research; p 30
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  • 21
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    Publication Date: 2019-01-25
    Description: The objective of this study is two-fold: to investigate the absorption of hard x rays along a tangential path through the terrestrial atmosphere, and to locate, other than the use of imaging devices, the flare source of x ray emission in the sun. Observational data were taken with the Hard X Ray Burst Spectrometer (HXRBS) on board the Solar Maximum Mission satellite (SMM). The occultation event chosen for investigation is the flare on 14 October 1981. Night fell on SMM during the decaying phase of the flare. In about fifteen seconds, the x ray flux decreased to zero. The model for computing synthetic light curve, which is directly comparable to the observed curve, consists of two computing programs. One is a modified version of an existing code, which compute the coordinates of the tangent points of the SMM-sun lines. The other program computed the atmospheric densities along the angles (N to S and E to W) measured from the center of the sun. The various model also depends on the destination of the terrestrial atmosphere at geocentric positions of SMM and the sun, the mean atmospheric densities at different heights and latitudes, and the x ray absorption cross of nitrogen, oxygen, and argon. The optical length, at a given time and for a x ray energy, is computed with the two angular parameters. The fit of a particular synthetic light, curve, i.e., the exponentials of the optical lengths, to the observed eclipse curve, yields the desired angular parameters.
    Keywords: SOLAR PHYSICS
    Type: Maryland Univ., The 1989 NASA-ASEE Summer Faculty Fellowship Program in Aeronautics and Research; p 29
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  • 22
    Publication Date: 2019-01-25
    Description: The analog control system for positioning each link of the Robotics Research Corporation Model K-1607 robot manipulator was redesigned for computer control. In order to accomplish the redesign, a linearized model of the dynamic behavior of the robot was developed. The parameters of the model were determined by examination of the input-output data collected in closed-loop operation of the analog control system. The robot manipulator possesses seven degrees of freedom in its motion. The analog control system installed by the manufacturer of the robot attempts to control the positioning of each link without feedback from other links. Constraints on the design of a digital control system include: the robot cannot be disassembled for measurement of parameters; the digital control system must not include filtering operations if possible, because of lack of computer capability; and criteria of goodness of control system performing is lacking. The resulting design employs sampled-data position and velocity feedback. The criteria of the design permits the control system gain margin and phase margin, measured at the same frequencies, to be the same as that provided by the analog control system.
    Keywords: MECHANICAL ENGINEERING
    Type: Maryland Univ., The 1989 NASA-ASEE Summer Faculty Fellowship Program in Aeronautics and Research; p 28
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  • 23
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    Publication Date: 2019-01-25
    Description: Following preliminary investigations of the low frequency electric and magnetic fields that may exists in the Earth-ionospheric cavity, measurements were taken with state-of-the art spectrum analyzers. As a follow up to this activity, an investigation was initiated to determine sources and values for possible low frequency signal that would appear in the cavity. The lowest cavity resonance is estimated at about 8 Hz, but lower frequencies may be an important component of our electromagnetic environment. The potential field frequencies produced by the electron were investigated by a classical model that included possible cross coupling of the electric and gravitation fields. During this work, an interesting relationship was found that related the high frequency charge field with the extremely low frequency of the gravitation field. The results of numerical calculations were surprisingly accurate and this area of investigation is continuing. The work toward continued development of a standardized monitoring facility is continuing with the potential of installing the prototype at West Virginia State College early in 1990. This installation would be capable of real time monitoring of ELF signals in the Earth-ionoshpere cavity and would provide some directional information. A high gain, low noise, 1/f frequency corrected preamplifier was designed and tested for the ferrite core magnetic sensor. The potential application of a super conducting sensor for the ELF magnetic field detection is under investigation. It is hoped that a fully operational monitoring network could pinpoint the location of ELF signal sources and provide new information on where these signals originate and what causes them, assuming that they are natural in origin.
    Keywords: GEOPHYSICS
    Type: Maryland Univ., The 1989 NASA-ASEE Summer Faculty Fellowship Program in Aeronautics and Research; p 27
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  • 24
    Publication Date: 2019-01-25
    Description: Efforts were concentrated on the spectral resolution of the Airborne Oceanographic Lidar (AOL). This year's work was targeted towards the analysis of calibration techniques to enable the AOL to measure absolute radiances of both passive and active modes of operation. Absolute spectral calibration of the AOL is necessary in order to fully understand and monitor the sensitivity and stability of the total system. Calibration is also needed to obtain valid surface truth data, with which to improve the accuracy of satellite-borne oceanic color scanners. In particular, accurate measurements of oceanic chlorophyll concentrations rests upon reliable irradiance calibrations of both laser induced and solar induced chlorophyll fluoresence. An analysis was performed on the spectral calibration methods used by the AOL. The optical path of the instrumentation was examined to study how the radiance from a calibration sphere was influenced. Ray tracing analysis was performed, including the Cassegrain-telescope optics. It was determined that the calibration radiance was significantly effected by optical-defocusing, due to close positioning of the calibration sphere with respect to the telescope. Since the multi-mode usages of the AOL require varying altitudes and trajectories, a computational algorithm was developed to compensate for image distortions of the telescope optics. Secondary mirror blockage, secondary vignetting, and beam divergence was determined, in order to account for the actual amount of calibrated flux received at the spectral sensors.
    Keywords: OCEANOGRAPHY
    Type: Maryland Univ., The 1989 NASA-ASEE Summer Faculty Fellowship Program in Aeronautics and Research; p 23
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  • 25
    Publication Date: 2019-01-25
    Description: Using seven years of data from tha SAM 2 (Stratospheric Aerosol Measurement 2) and TOMS (Total Ozone Mapping Spectrometer) instruments, along with 70 mbar temperatures extracted from an NMC analysis, the effect of the austral spring polar stratospheric clouds (PSC) on the formation of total ozone miniholes is investigated. A total ozone minihole event is designated as the rapid decrease of more than 20 DU of total ozone over a time period of a day and a spatial extent of approximately 1000 by 1000 km. The severe decrease of total ozone during these minihole events could be explained in part by PSC being formed at altitudes of 10 to 24 km and preventing scattered UV radiation from ozone below the cloud from reaching the TOMS instrument. A result of the cloud's opaqueness is that the total ozone retrieval from TOMS data would underestimate the ozone column in the vicinity of the PSC. The approach to investigate the effect of PSC on total ozone was to use SAM 2 aerosol extinction values in conjunction with NMC stratospheric temperatures to determine if PSC are present during total ozone minihole events occurring during August and September, 1979 to 1986. The minihole events during these seven years were divided into two types: type 1, where the minihole region of 24 hour darkness from regions exposed to sunlight, and type 2, where the minihole occurred 5 to 10 degrees north of the terminator. The presence of PSC in a given region was ascertained by a maximum aerosol extinction greater than .006/km occurring with a temperature less than 189 K. It is found that PSC are consistently present with type 2 minihole events. This is contrasted with PSC rarely occurring in the same vicinity of type 2 miniholes. Also observed of that type 1 minihole events have minimum total ozone values which are on the average 3 to 10 DU smaller than type 2 miniholes. It can be concluded that care must be taken when trying to deduce a dynamical explanation of minihole events near the polar terminator and the role of PSC must be accounted for in type 1 minihole formation.
    Keywords: ENVIRONMENT POLLUTION
    Type: Maryland Univ., The 1989 NASA-ASEE Summer Faculty Fellowship Program in Aeronautics and Research; p 24
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  • 26
    Publication Date: 2019-01-25
    Description: Parameters were described for spatial database to facilitate drought monitoring and famine early warning in the African Sahel. The proposed system, referred to as the African Drought and Famine Information System (ADFIS) is ultimately recommended for implementation with the NASA/FEMA Spatial Analysis and Modeling System (SAMS), a GIS/Dymanic Modeling software package, currently under development. SAMS is derived from FEMA'S Integration Emergency Management Information System (IEMIS) and the Pacific Northwest Laborotory's/Engineering Topographic Laboratory's Airland Battlefield Environment (ALBE) GIS. SAMS is primarily intended for disaster planning and resource management applications with the developing countries. Sources of data for the system would include the Developing Economics Branch of the U.S. Dept. of Agriculture, the World Bank, Tulane University School of Public Health and Tropical Medicine's Famine Early Warning Systems (FEWS) Project, the USAID's Foreign Disaster Assistance Section, the World Resources Institute, the World Meterological Institute, the USGS, the UNFAO, UNICEF, and the United Nations Disaster Relief Organization (UNDRO). Satellite imagery would include decadal AVHRR imagery and Normalized Difference Vegetation Index (NDVI) values from 1981 to the present for the African continent and selected Landsat scenes for the Sudan pilot study. The system is initially conceived for the MicroVAX 2/GPX, running VMS. To facilitate comparative analysis, a global time-series database (1950 to 1987) is included for a basic set of 125 socio-economic variables per country per year. A more detailed database for the Sahelian countries includes soil type, water resources, agricultural production, agricultural import and export, food aid, and consumption. A pilot dataset for the Sudan with over 2,500 variables from the World Bank's ANDREX system, also includes epidemiological data on incidence of kwashiorkor, marasmus, other nutritional deficiencies, and synergistically-related infectious diseases.
    Keywords: DOCUMENTATION AND INFORMATION SCIENCE
    Type: Maryland Univ., The 1989 NASA-ASEE Summer Faculty Fellowship Program in Aeronautics and Research; p 36
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  • 27
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    Publication Date: 2019-01-25
    Description: NASA continuous communications systems growth has increased the demand for image transmission and storage. Research and analysis was conducted on various lossy and lossless advanced data compression techniques or approaches used to improve the efficiency of transmission and storage of high volume stellite image data such as pulse code modulation (PCM), differential PCM (DPCM), transform coding, hybrid coding, interframe coding, and adaptive technique. In this presentation, the fundamentals of image data compression utilizing two techniques which are pulse code modulation (PCM) and differential PCM (DPCM) are presented along with an application utilizing these two coding techniques.
    Keywords: COMPUTER PROGRAMMING AND SOFTWARE
    Type: Maryland Univ., The 1989 NASA-ASEE Summer Faculty Fellowship Program in Aeronautics and Research; p 20
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  • 28
    Publication Date: 2019-01-25
    Description: Interpretation of planetary observations and proper modeling of planetary atmospheres are critically upon accurate laboratory data for the chemical and physical properties of the constitutes of the atmospheres. It is important that these data are taken over the appropriate range of parameters such as temperature, pressure, and composition. Availability of accurate, laboratory data for vapor pressures and equilibrium constants of condensed species at low temperatures is essential for photochemical and cloud models of the atmospheres of the outer planets. In the absence of such data, modelers have no choice but to assume values based on an educated guess. In those cases where higher temperature data are available, a standard procedure is to extrapolate these points to the lower temperatures using the Clausius-Clapeyron equation. Last summer the vapor pressures of acetylene (C2H2) hydrogen cyanide (HCN), and cyanoacetylene (HC3N) was measured using two different methods. At the higher temperatures 1 torr and 10 torr capacitance manometers were used. To measure very low pressures, a technique was used which is based on the infrared absorption of thin film (TFIR). This summer the vapor pressure of acetylene was measured the TFIR method. The vapor pressure of hydrogen sulfide (H2S) was measured using capacitance manometers. Results for H2O agree with literature data over the common range of temperature. At the lower temperatures the data lie slightly below the values predicted by extrapolation of the Clausius-Clapeyron equation. Thin film infrared (TFIR) data for acetylene lie significantly below the values predicted by extrapolation. It is hoped to bridge the gap between the low end of the CM data and the upper end of the TFIR data in the future using a new spinning rotor gauge.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Maryland Univ., The 1989 NASA-ASEE Summer Faculty Fellowship Program in Aeronautics and Research; p 16-17
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  • 29
    Publication Date: 2019-01-25
    Description: A method for ocean fish production estimation was proposed for development. The method was to use data acquired with the Coastal Zone Color Scanner, and processed into chlorophyll concentrations by the GSFC ocean Sciences Division, in combination with fish production and primary production data acquired from different ocean areas. A linear relation exits between annual fish production and annual phytoplankton carbon production for a wide range of coastal ocean environments. The uses of several existing algorithms which relate primary production to CZCS chlorophyll data as input to the fish production regression model is proposed. A question relating phytoplankton production to CZCS chlorophyll was obtained by Eppley (1984) using chlorophyll data obtained from field samples, equivalent to chlorophyll data obtained from CZCS imagery, and primary production data obtained from ship-board observations on a wide variety of coastal and open ocean environments. This equation was modified with additional data and was successfully tested using CZCS data and field chlorophyll and phytoplankton production data obtained from northeastern North American continental shelf waters and Atlantic open ocean waters. The modified Eppley (1984) relation also estimated phytoplankton annual carbon production in the Sargasso Sea within the confidence limits of a mean value obtained from the Eppley (1984) equation for oceanic waters that provide about 90 percent of total ocean primary production. The modified Eppley production formula applied to CZCS chlorophyll data obtained from several northeastern North American coastal environments gave phytoplankton annual carbon production values similar to the values used in the fish production regression equation.
    Keywords: OCEANOGRAPHY
    Type: Maryland Univ., The 1989 NASA-ASEE Summer Faculty Fellowship Program in Aeronautics and Research; p 15
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  • 30
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    Publication Date: 2019-01-25
    Description: The goal was to complete the design of a prototype for a Transportable Telemetry Workstation (TTW). The Macintosh 2 is used to provide a low-cost system which can house real-time cards mounted on the NuBus inside the Macintosh 2 plus provide a standardized user interface on the Macintosh 2 console. Prior to a telemetry run, the user will be able to configure his real-time telemetry processing functions from the Macintosh 2 console. During a telemetry run, the real-time cards will store the telemetry data directly on a hard disk while permitting viewing of the data cards on the Macintosh 2 console on various selectable formats. The user will view the cards in terms of the functions they perform and the selectable paths through the cards, it is not required to become involved directly in hardware issue except in terms of the functional configuration of the system components. The TTW will accept telemetry data from an RS422 serial input data bus, pass it through a frame synchronizer card and on to a real time controller card via a telemetry backplane bus. The controller card will then route the data to a hard disk through a SCSI interface, and/or to a user interface on the Macintosh 2 console by way of the Macintosh 2 NuBus. The three major components to be designed, therefore, are the TTW Controller Card, the TTW Synchronizer Card, and the NuBus/Macintosh 2 User Interface. Design and prototyping of this state-of-the-art, transportable, low-cost, easy-to-use multiprocessor telemetry system is continuing. Other functions are planned for the future.
    Keywords: SPACE COMMUNICATIONS, SPACECRAFT COMMUNICATIONS, COMMAND AND TRACKING
    Type: Maryland Univ., The 1989 NASA-ASEE Summer Faculty Fellowship Program in Aeronautics and Research; p 14
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  • 31
    Publication Date: 2019-01-25
    Description: An analysis of LANDSAT Thematic Mapper (TM) data of the Pasterze Glacier and the Kleines Fleisskees in the Austrian Alps was undertaken and compared with meteorological data of nearby weather stations. Alpine or valley glaciers can be used to study regional and worldwide climate changes. Alpine glaciers respond relatively fast to a warming or cooling trend in temperature through an advance or a retreat of the terminus. In addition, the mass balance of the glacier is being affected. Last year two TM scenes of the Pasterze Glacier of Aug. 1984 and Aug. 1986 were used to study the difference in reflectance. This year, in addition to the scenes from last year, one MSS scene of Aug. 1976 and a TM scene from 1988 were examined for both the Pasterze Glacier and the Kleines Fleisskees. During the overpass of the LANDSAT on 6 Aug. 1988 ground truthing on the Pasterze Glacier was undertaken. The results indicate that there was considerable more reflectance in 1976 and 1984 than in 1986 and 1988. The climatological data of the weather stations Sonnblick and Rudolfshuette were examined and compared with the results found through the LANDSAT data. There were relations between the meteorological and LANDSAT data: the average temperature over the last 100 years showed an increase of .4 C, the snowfall was declining during the same time period but the overall precipitation did not reveal any significant change over the same period. With the use of an interactive image analysis computer, the LANDSAT scenes were studied. The terminus of the Pasterze Glacier retreated 348 m and the terminus of the Kleines Fleisskees 121 m since 1965. This approach using LANDSAT MSS and TM digital data in conjunction with meteorological data can be effectively used to monitor regional and worldwide climate changes.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Maryland Univ., The 1989 NASA-ASEE Summer Faculty Fellowship Program in Aeronautics and Research; p 12
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  • 32
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    Publication Date: 2019-01-25
    Description: Theoretical calculations are made of rocket performance of exotic fuels at various operating conditions such as chamber pressure, pressure ratios, and oxidizer-to-fuel ratios. By exotic fuels, it is meant using materials that may not normally be used as fuels here on Earth due to low performance. The majority of the work is currently being done on a VAX using the CET 86 program by Gordon and McBride. The CET 86 program will be installed on our IBM PS/2 Model 80 to reduce computer costs. The JPL Solid Propellant Theoretical Performance program for the IBM was also used, it handles solid fuels better than the CET 86 program. The CET 86 program by Gordon and McBride was set on the VAX and results were obtained for a number of the propellant combinations being analyzed. A sample of these results is included. Several programs were written to reduce the large amounts of data generated to include only the information needed, such as specific impulse, temperature, etc. This work involves analyzing propellants at various operating conditions and determining which will give acceptable performance and yet be easily storable for long periods of time and be readily available in space missions.
    Keywords: PROPELLANTS AND FUELS
    Type: NASA Space Engineering Research Center for Utilization of Local Planetary Resources; 2 p
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  • 33
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    Publication Date: 2019-01-25
    Description: Development of the data base for near-Earth resources was begun. Specific items accomplished were: (1) Definition of data base contents via discussions among the PSI staff and outside scientist such as Lucy McFadden and Mark Skyes; (2) Discussion/demonstration of dBase capabilities and possible organization of file(s) with L. Alvarez, Steward Observatory; (3) Data base entries for near-Earth asteroids consisting of data from the Russian ephemeris, a forthcoming review chapter for the Asteroids 2 book, and other literature; and (4) Development of a list of asteroid observers worldwide to be contacted during the coordinated phase of the project. A copy of the data base as it now exists is included.
    Keywords: DOCUMENTATION AND INFORMATION SCIENCE
    Type: Arizona Univ., NASA Space Engineering Research Center for Utilization of Local Planetary Resources; 1 p
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  • 34
    Publication Date: 2019-01-25
    Description: Determining the long-term number of people that the planet can support without irreversibly reducing its ability to support people in the future, i.e., the carrying capacity of the Earth, is an exceedingly complex problem. About all that is known for certain is that, with present and foreseeable technologies, the human population has already exceeded the capacity. The reduction in carrying capacity that can be expected to result from direct human impacts on resources and the environment and from our indirect impacts of the climate system is discussed. Global warming and modeling global change and food security are also discussed with respect to carrying capacity.
    Keywords: ENVIRONMENT POLLUTION
    Type: National Academy of Sciences - National Research Council, Global Change and Our Common Future. Papers from a Forum; p 19-27
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  • 35
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    Publication Date: 2019-01-25
    Description: This program is aimed at developing sensors and measurement systems capable of obtaining the data necessary for the verification of computational models of the structural behavior, the fatigue life, and the environmental conditions pertinent to advanced reusable space propulsion systems. One of the characteristics of measurement systems needed to verify codes is that the sensors must be nonintrusive or at least minimally intrusive so as not to significantly perturb the conditions being measured. This leads to a heavy emphasis on laser optical techniques and on thin-film sensors. Another characteristic of such instruments is that they must be highly accurate and produce very high spatial and temporal resolution of the parameter being measured. The measurement systems needed generally fall into a number of broad categories. First there are the measurements needed on the surfaces of components such as turbine blades and vanes. Some of the desired parameters are temperature, strain, and heat flux. Another broad category encompasses those measurements needed in the flow environment around these components. Here, the desired results are high resolution maps of such parameters as flow velocity, temperature, density, pressure, and species concentration. The remaining category deals with measurements necessary for monitoring the health of the engine. This category has loomed ever more important since the Challenger disaster. An optical method for determining the characteristics of the plume is presented. Holographic measurement of structural damage is also presented.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Structural Integrity and Durability of Reusable Space Propulsion Systems; p 81-82
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  • 36
    Publication Date: 2019-01-25
    Description: The response of mesospheric ozone and temperature to short term solar ultraviolet variations related the the 27 day rotation of the Sun has been recently detected from analysis of satellite measurements. A systematic depletion of ozone was detected near 70 km, which is attributed to solar Lyman alpha photodissociation of water vapor with subsequent catalytic destruction of O(x) by HO(x) and temperature feedback effects resulting from the unexpectedly strong temperature/UV response near 70 km. The nature of latitudinal and semiannual variations in the ozone/UV and temperature/UV response were isolated. Observed variations are compared to theoretical models.
    Keywords: GEOPHYSICS
    Type: International Council of Scientific Unions, Middle Atmosphere Program. Handbook for MAP, Volume 29. Part 1: Extended Abstracts, International Symposium on Solar Activity Forcing of the Middle Atmosphere. Part 2: MASH Workshop, Williamsburg, 1986; p 67
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  • 37
    Publication Date: 2019-01-25
    Description: There are given results of the numerical experiments on modelling the influence of solar activity on chemical composition and temperature of the middle atmosphere. The consideration is made for peculiarities of solar activity impact under different values of antropogenic pollution of the atmosphere with chlorofluorocarbons and other stuff.
    Keywords: GEOPHYSICS
    Type: International Council of Scientific Unions, Middle Atmosphere Program. Handbook for MAP, Volume 29. Part 1: Extended Abstracts, International Symposium on Solar Activity Forcing of the Middle Atmosphere. Part 2: MASH Workshop, Williamsburg, 1986; p 117
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  • 38
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    Publication Date: 2019-01-25
    Description: The properties of molecules derive in part from their structures. Because of the importance of understanding molecular structures various methodologies, ranging from first principles to empirical technique, were developed for computing the structure of molecules. For large molecules such as polymer model compounds, the structural information is difficult to comprehend by examining tabulated data. Therefore, a molecular graphics display system, called MOLDS, was developed to help interpret the data. MOLDS is a menu-driven program developed to run on the LADC SNS computer systems. This program can read a data file generated by the modeling programs or data can be entered using the keyboard. MOLDS has the following capabilities: draws the 3-D representation of a molecule using stick, ball and ball, or space filled model from Cartesian coordinates, draws different perspective views of the molecule; rotates the molecule on the X, Y, Z axis or about some arbitrary line in space, zooms in on a small area of the molecule in order to obtain a better view of a specific region; and makes hard copy representation of molecules on a graphic printer. In addition, MOLDS can be easily updated and readily adapted to run on most computer systems.
    Keywords: ATOMIC AND MOLECULAR PHYSICS
    Type: Old Dominion Univ., NASA/American Society for Engineering Educati; Old Dominion Univ.,
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  • 39
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    Publication Date: 2019-01-25
    Description: Future spacecraft such as the International Space Station result in flexible models with hundreds, or perhaps thousands of modes in a frequency range where the potential for control/structure interaction exists. This provides the analyst with a formidable model reduction problem at both the component and the system level. Approaches to normal modes as a structural representation, applicability of alternate structural representations and algorithms for selecting important modal degrees of freedom at both the component and the system level are discussed. Practical implementation of these techniques on a large scale model of the Space Station are presented.
    Keywords: COMPUTER PROGRAMMING AND SOFTWARE
    Type: Jet Propulsion Lab., California Inst. of Tech., Proceedings of the 3rd Annual Conference on Aerospace Computational Control, Volume 2; p 818
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  • 40
    Publication Date: 2019-01-25
    Description: A software package for large order controlled structure design is described and demonstrated. The primary program, called OPTICAN, uses both Pro-Matlab M-file routines and selected compiled FORTRAN routines linked into the Pro-Matlab structure. The program accepts structural model information in the form of state-space matrices and performs three basic design functions on the model: (1) open loop analyses; (2) closed loop reduced order controller synthesis; and (3) closed loop stability and performance assessment. The current controller synthesis methods which were implemented in this software are based on the Generalized Linear Quadratic Gaussian theory of Bernstein. In particular, a reduced order Optimal Projection synthesis algorithm based on a homotopy solution method was successfully applied to an experimental truss structure using a 58-state dynamic model. These results are presented and discussed. Current plans to expand the practical size of the design model to several hundred states and the intention to interface Pro-Matlab to a supercomputing environment are discussed.
    Keywords: COMPUTER PROGRAMMING AND SOFTWARE
    Type: Jet Propulsion Lab., California Inst. of Tech., Proceedings of the 3rd Annual Conference on Aerospace Computational Control, Volume 2; p 640
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  • 41
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    Publication Date: 2019-01-25
    Description: An overview of current research activities at UT Austin is presented to discuss certain technical issues in the following areas: (1) Computer-Aided Nonlinear Control Design: In this project, the describing function method is employed for the nonlinear control analysis and design of a flexible spacecraft equipped with pulse modulated reaction jets. INCA program has been enhanced to allow the numerical calculation of describing functions as well as the nonlinear limit cycle analysis capability in the frequency domain; (2) Robust Linear Quadratic Gaussian (LQG) Compensator Synthesis: Robust control design techniques and software tools are developed for flexible space structures with parameter uncertainty. In particular, an interactive, robust multivariable control design capability is being developed for INCA program; and (3) LQR-Based Autonomous Control System for the Space Station: In this project, real time implementation of LQR-based autonomous control system is investigated for the space station with time-varying inertias and with significant multibody dynamic interactions.
    Keywords: COMPUTER PROGRAMMING AND SOFTWARE
    Type: Jet Propulsion Lab., California Inst. of Tech., Proceedings of the 3rd Annual Conference on Aerospace Computational Control, Volume 2; p 599
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  • 42
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    In:  Other Sources
    Publication Date: 2019-01-25
    Description: An inverse Poisson integral technique was used to determine a gravity field on the geoid which, when continued by analytic free space methods to the topographic surface, agrees with the observed field. The computation is performed in three stages, each stage refining the previous solution using data at progressively increasing resolution (1 x 1 deg, 5 x 5', 5/8 x 5/8') from a decreasing area of integration. Reduction corrections are computed at 5/8 x 5/8' granularity by differencing the geoidal and surface values, smoothed by low-pass filtering and sub-sampled at 5' intervals. The 1 x 1 deg averages of the reduction corrections thus obtained for 172 1 x 1 deg squares in western North America are discussed. The 1 x 1 deg mean reduction corrections are predominantly positive, varying from -3 to +15 mgal, with values in excess of 5 mgal for 26 squares. Their mean and rms values are +2.4 and 3.6 mgal respectively and they correlate well with the mean terrain corrections. The mean and rms contributions from the three stages of computation are: 1 x 1 deg stage +0.15 and 0.7 mgal; 5 x 5' stage + 1.0 and 1.6 mgal; and 5/8 x 5/8' stage +1.3 and 1.8 mgal. These results reflect a tendency for the contributions to become larger and more systematically positive as the wavelengths involved become shorter. The results are discussed in terms of two mechanisms; the first is a tendency for the absolute values of both positive and negative anomalies to become larger when continued downwards and, the second, a non-linear rectification, due to the correlation between gravity anomaly and topographic height, which results in the values continued to a level surface being systematically more positive than those on the topography.
    Keywords: GEOPHYSICS
    Type: Ohio State Univ., Progress in the Determination of the Earth's Gravity Field; p 107
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  • 43
    Publication Date: 2019-01-25
    Description: Covariance Controllers assign specified matrix values to the state covariance. A number of robustness results are directly related to the covariance matrix. The conservatism in known upperbounds on the H infinity, L infinity, and L (sub 2) norms for stability and disturbance robustness of linear uncertain systems using covariance controllers is illustrated with examples. These results are illustrated for continuous and discrete time systems. **** ONLY 2 BLOCK MARKERS FOUND -- RETRY *****
    Keywords: NUMERICAL ANALYSIS
    Type: Jet Propulsion Lab., California Inst. of Tech., Proceedings of the 3rd Annual Conference on Aerospace Computational Control, Volume 2; p 636-637
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  • 44
    Publication Date: 2019-01-25
    Description: Morphological and spectrophotometric investigations have been extensively applied in the past years to various kinds of micron and/or submicron-sized grains formed by materials which are candidate to be present in space. The samples are produced in the laboratory and then characterized in their physio-chemical properties. Some of the most recent results obtained on various kinds of carbonaceous materials are reported. Main attention is devoted to spectroscopic results in the VUV and IR wavelength ranges, where many of the analyzed samples show typical fingerprints which can be identified also in astrophysical and cometary materials. The laboratory methodologies used so far are also critically discussed in order to point out capabilities and present limitations, in the view of possible application to returned comet samples. Suggestions are given to develop new techniques which should overcome some of the problems faced in the manipulation and analysis of micron solid samples.
    Keywords: ASTROPHYSICS
    Type: Lunar and Planetary Inst., Workshop on Analysis of Returned Comet Nucleus Samples; p 15
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  • 45
    Publication Date: 2019-01-25
    Description: A non-equilibrium mechanism that may produce substantial thermal and chemical processing of the outermost layer of cometary nuclei is proposed. If this phenomenon does occur, its effects will impact the interpretation of results from the CNSR and CRAF missions.
    Keywords: ASTROPHYSICS
    Type: Lunar and Planetary Inst., Workshop on Analysis of Returned Comet Nucleus Samples; p 12
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  • 46
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    In:  Other Sources
    Publication Date: 2019-01-25
    Description: Electron microscopy will be useful for characterization of inorganic dust grains in returned comet nucleus samples. The choice of instrument(s) will depend primarily on the nature of the samples, but ultimately a variety of electron-beam methods could be employed. Scanning and analytical (transmission) electron microscopy are the logical choise for morphological, mineralogical, and bulk chemical analyses of dust grains removed from ices. It may also be possible to examine unmelted ice/dust mixtures using an environmental scanning electron microscope equipped with a cryo-transfer unit and a cold stage. Electron microscopic observations of comet nuclei might include: (1) porosities of dust grains; (2) morphologies and microstructures of individual mineral grains; (3) relative abundances of olivine, pyroxene, and glass; and (4) the presence of phases that might have resulted from aqueous alteration (layer silicates, carbonates, sulfates).
    Keywords: ASTROPHYSICS
    Type: Lunar and Planetary Inst., Workshop on Analysis of Returned Comet Nucleus Samples; p 11
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  • 47
    Publication Date: 2019-01-25
    Description: Ices of various kinds (H2O, CO, CO2, CH4, NH3, CH3OH, etc.) comprise a volumetrically significant proportion of objects in the solar system (comets, outer planets, planetary rings, satellites) as well as in interstellar space (astrophysical ices). The refinement of analytical electron microscopy (AEM) procedures for storing, preparing and analyzing ices and other materials at cryogenic temperatures is discussed. These procedures will be essential to the successful analysis of returned comet nucleus samples.
    Keywords: ASTROPHYSICS
    Type: Lunar and Planetary Inst., Workshop on Analysis of Returned Comet Nucleus Samples; p 9-10
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  • 48
    facet.materialart.
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    In:  Other Sources
    Publication Date: 2019-01-25
    Description: It is thought that comets are an intimate mixture of ices and sub-micron to pebble sized silicates. Based on experience with carbonaceous chrondrites, part of the smallest grains are expected to be primary condensates carrying the unadulterated isotopic signature of their place of origin. In order to extract this information a grain-by-grain analysis will be necessary.
    Keywords: ASTROPHYSICS
    Type: Lunar and Planetary Inst., Workshop on Analysis of Returned Comet Nucleus Samples; p 8
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  • 49
    facet.materialart.
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    In:  Other Sources
    Publication Date: 2019-01-25
    Description: It is timely to consider the possible tectonic regimes on Venus both in terms of what is known about Venus and in terms of deformation mechanisms operative on the earth. Plate tectonic phenomena dominate tectonics on the earth. Horizontal displacements are associated with the creation of new crust at ridges and destruction of crust at trenches. The presence of plate tectonics on Venus is debated, but there is certainly no evidence for the trenches associated with subduction on the earth. An essential question is what kind of tectonics can be expected if there is no plate tectonics on Venus. Mars and the Moon are reference examples. Volcanic constructs appear to play a dominant role on Mars but their role on Venus is not clear. On single plate planets and satellites, tectonic structures are often associated with thermal stresses. Cooling of a planet leads to thermal contraction and surface compressive features. Delamination has been propsed for Venus by several authors. Delamination is associated with the subduction of the mantle lithosphere and possibly the lower crust but not the upper crust. The surface manifestations of delamination are unclear. There is some evidence that delamination is occurring beneath the Transverse Ranges in California. Delamination will certainly lead to lithospheric thinning and is likely to lead to uplift and crustal thinning.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Abstracts for the Venus Geoscience Tutorial and Venus Geologic Mapping Workshop; p 49
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  • 50
    facet.materialart.
    Unknown
    In:  Other Sources
    Publication Date: 2019-01-25
    Description: The putative paradigm that planets of the same size and mass have the same tectonic style led to the adaptation of the mechanisms of terrestrial plate tectonics as the a priori model of the way Venus should behave. Data acquired over the last decade by Pioneer Venus, Venera, and ground-based radar have modified this view sharply and have illuminated the lack of detailed understanding of the plate tectonic mechanism. For reference, terrestrial mechanisms are briefly reviewed. Venusian lithospheric divergence, hotspot model, and horizontal deformation theories are proposed and examined.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Abstracts for the Venus Geoscience Tutorial and Venus Geologic Mapping Workshop; p 33-34
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  • 51
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    In:  Other Sources
    Publication Date: 2019-01-25
    Description: The Archean Era of the Earth is not a direct analog of the present tectonics of Venus. In this regard, it is useful to review the state of the Archean Earth. Most significantly, the temperature of the adiabatic interior of the Earth was 200 to 300 C hotter than the current temperature. Preservation biases limit what can be learned from the Archean record. Archean oceanic crust, most of the planetary surface at any one time, has been nearly all subducted. More speculatively, the core of the Earth has probably cooled more slowly than the mantle. Thus the temperature contrast above the core-mantle boundary and the vigor of mantle plumes has increased with time on the Earth. The most obvious difference between Venus and the present Earth is the high surface temperature and hence a low effective viscosity of the lithosphere. In addition, the temperature contrast between the adiabatic interior and the surface, which drives convection, is less on Venus than on the Earth. It appears that the hot lithosphere enhanced tectonics on the early Venus significantly enough that its interior cooled faster than the Earth's. The best evidence for a cool interior of Venus comes from long wavelength gravity anomalies. The low interior temperatures retard seafloor spreading on Venus. The high surface temperatures on Venus enhance crustal deformation. That is, the lower crust may become ductile enough to permit significant flow between the upper crust and the mantle. There is thus some analogy to modern and ancient areas of high heat flow on the Earth. Archean crustal blocks typically remained stable for long intervals and thus overall are not good analogies to the deformation style on Venus.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Abstracts for the Venus Geoscience Tutorial and Venus Geologic Mapping Workshop; p 46
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  • 52
    Publication Date: 2019-01-25
    Description: The relations between the identification of dominant lunar landforms, craters, and radar images at three resolutions are investigated. Although the percentage of craters that can be identified is found to increase with diameter or relief for any given resolution, it is noted that craters have not been identified at all diameters and relief. It is shown that the relation between the percentage of identified craters and their dimensions depends on the size-frequency distributions of both diameters and relief, and that crater identification depends strongly on the resolution of the radar image.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Abstracts for the Venus Geoscience Tutorial and Venus Geologic Mapping Workshop; p 32
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  • 53
    facet.materialart.
    Unknown
    In:  Other Sources
    Publication Date: 2019-01-25
    Description: Venus is more similar to Earth than to any other planet. It has elevated regions associated with marginal fold and thrust belts, fracture zones that extend tens of thousands of kilometers, crustal swells and shields that are hundreds of kilometers in diameter and 1 to 2 km high, and sublinear accumulations of volcanic cones and domes that stretch for thousands of kilometers across the plains. The Venusian surface is, however, distinctly different from Earth's in that: (1) its elevated terrains cannot be distinguished from its low plains on a hypsometric curve; (2) trenches have not been found plainsward of the marginal belts; (3) fracture zones bear no resemblance to mid-oceanic ridges; and (4) some features, such as the ridge-belt zone near 210 deg E, seem to have no terrestrial analog. Various theories about tectonism on Venus and Earth of other authors are reviewed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Abstracts for the Venus Geoscience Tutorial and Venus Geologic Mapping Workshop; p 29
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  • 54
    facet.materialart.
    Unknown
    In:  Other Sources
    Publication Date: 2019-01-25
    Description: It is shown how crater size-density counts may be used to help constrain the history of the Venus atmosphere, based on the predictions of simple but reasonable models for crater production, surface erosion, and the effects of atmospheric drag and breakup on incident meteors in the Venus atmosphere. In particular, if the atmosphere is young, the old (uneroded) surfaces will have crater densities upward of 0.0001/sq km and a ratio of small (4 km) craters to large (128 km) craters near 1000. If the atmosphere is old and the breakup mechanism is dominant, absolute crater densities on Venus surfaces will be diminished by several orders of magnitude relative to the young atmosphere case. If atmospheric drag is dominant, the absolute crater density will be lowered by perhaps an order of magnitude relative to the young atmosphere case, and the ratio of small to large craters will be reduced to a value near 10 to the 1.5 power. Once a large fraction of Venus surface has been imaged at kilometer resolution, as the Venus Orbiting Imaging Radar project promises to do, it could be possible to make an early determination of the age of the Venus atmosphere.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Abstracts for the Venus Geoscience Tutorial and Venus Geologic Mapping Workshop; p 26
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  • 55
    facet.materialart.
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    In:  Other Sources
    Publication Date: 2019-01-25
    Description: The brightness of surface features on side looking radar images of Venus is determined by many factors: the angles of incidence and reflection, polarization, surface geometry and composition, and so forth. The contribution from surface properties themselves can only be deduced by combining several types of measurement. For instance, without additional information, it is impossible to distinguish the effects of changes in surface roughness from those in dielectric constant. In common with the Moon and Mars, the surface of Venus appears to scatter radar waves in two ways: small-scale surface inhomogeneities, i.e., those smaller than the incident wavelength, depolarize and scatter the energy over a wide range of angles. The Pioneer Venus radar mapper experiment made three overlapping sets of measurements of the equatorial region of Venus from 15 deg S latitude to 45 deg N; the backscatter cross section at a range of incidence angles, the shape and intensity of radar echoes from the nadir, and the microwave brightness temperature of the surface. These techniques developed during the analysis of Pioneer Venus data will be used during the Magellan mission to extract measurements of surface slopes and dielectric constants over all areas covered by the SAR and altimeter antennae, with a resolution of about 10 km. A knowledge of the mechanisms that govern surface scattering will also be useful in the analysis of higher resolution side looking radar images, particularly in distinguishing the effects of changing roughness from those caused by a long range surface tilt or changing dielectric constant.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Abstracts for the Venus Geoscience Tutorial and Venus Geologic Mapping Workshop; p 12
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  • 56
    Publication Date: 2019-01-25
    Description: The high sensitivity of imaging radars to slope at moderate to low incidence angles enhances the perception of linear topography on images. It reveals broad spatial patterns that are essential to landform mapping and interpretation. As radar responses are strongly directional, the ability to discriminate linear features on images varies with their orientation. Landforms that appear prominent on images where they are transverse to the illumination may be obscure to indistinguishable on images where they are parallel to it. Landform detection is also influenced by the spatial resolution in radar images. Seasat radar images of the Gran Desierto Dunes complex, Sonora, Mexico; the Appalachian Valley and Ridge Province; and accreted terranes in eastern interior Alaska were processed to simulate both Venera 15 and 16 images (1000 to 3000 km resolution) and image data expected from the Magellan mission (120 to 300 m resolution. The Gran Desierto Dunes are not discernable in the Venera simulation, whereas the higher resolution Magellan simulation shows dominant dune patterns produced from differential erosion of the rocks. The Magellan simulation also shows that fluvial processes have dominated erosion and exposure of the folds.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Abstracts for the Venus Geoscience Tutorial and Venus Geologic Mapping Workshop; p 11
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  • 57
    Publication Date: 2019-01-25
    Description: Observations of small terrestrial craters by Seasat synthetic aperture radar (SAR) at high resolution (approx. 25 m) and of comparatively large Venusian craters by Venera 15/16 images at low resolution (1000 to 2000 m) and shorter wavelength show similarities in the radar responses to crater morphology. At low incidence angles, the responses are dominated by large scale slope effects on the order of meters; consequently it is difficult to locate the precise position of crater rims on the images. Abrupt contrasts in radar response to changing slope (hence incidence angle) across a crater produce sharp tonal boundaries normal to the illumination. Crater morphology that is radially symmetrical appears on images to have bilateral symmetry parallel to the illumination vector. Craters are compressed in the distal sector and drawn out in the proximal sector. At higher incidence angles obtained with the viewing geometry of SIR-A, crater morphology appears less compressed on the images. At any radar incidence angle, the distortion of a crater outline is minimal across the medial sector, in a direction normal to the illumination. Radar bright halos surround some craters imaged by SIR-A and Venera 15 and 16. The brightness probably denotes the radar response to small scale surface roughness of the surrounding ejecta blankets. Similarities in the radar responses of small terrestrial impact craters and volcanic craters of comparable dimensions emphasize the difficulties in discriminating an impact origin from a volcanic origin in the images. Similar difficulties will probably apply in discriminating the origin of small Venusian craters, if they exist. Because of orbital considerations, the nominal incidence angel of Magellan radar at the center of the imaging swath will vary from about 45 deg at 10 deg N latitude to about 16 deg at the north pole and at 70 deg S latitude. Impact craters and comparable volcanic landforms will show bilateral symmetry parallel to the illumination vector and will appear increasingly compressed toward higher latitudes.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Abstracts for the Venus Geoscience Tutorial and Venus Geologic Mapping Workshop; p 10
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  • 58
    Publication Date: 2018-06-05
    Description: Some techniques for laboratory calibration and characterization of video cameras used with frame grabber boards are presented. A laser-illuminated displaced reticle technique (with camera lens removed) is used to determine the camera/grabber effective horizontal and vertical pixel spacing as well as the angle of non-perpendicularity of the axes. The principal point of autocollimation and point of symmetry are found by illuminating the camera with an unexpanded laser beam, either aligned with the sensor or lens. Lens distortion and the principal distance are determined from images of a calibration plate suitable aligned with the camera. Calibration and characterization results for several video cameras are presented. Differences between these laboratory techniques and test range and plumb line calibration are noted.
    Keywords: Instrumentation and Photography
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  • 59
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    Karlsruhe : Institut für Wasser- und Abfallwirtschaft
    In:  Handbuch Hydrologie Baden-Württemberg ; 6,2
    Publication Date: 1989
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  • 60
    Publication Date: 1989
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  • 61
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    München : Bayerisches Landesamt für Wasserwirtschaft
    In:  Informationsberichte / Bayerisches Landesamt für Wasserwirtschaft, No. 89,3
    Publication Date: 1989
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  • 62
    facet.materialart.
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    In:  Bau intern 3/1989
    Publication Date: 1989
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  • 63
    Publication Date: 1989
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  • 64
    Publication Date: 1989
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  • 65
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    Lelystad : Internationale Kommission für die Hydrologie des Rheingebietes
    In:  Bericht / Internationale Kommission für die Hydrologie des Rheingebietes, No. II-3
    Publication Date: 1989
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  • 66
    Publication Date: 1989
    Description: Analyse der Fichtenweiserflächen in Bayern anhand der Zuwachstrends. Bei 50% Nadelverlust 30% Zuwachsverlust KATASTER-BESCHREIBUNG: KATASTER-DETAIL:
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  • 67
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    In:  Pesquisa Antartica Brasileira (Brazilian Antarctic Research), 1 (1). pp. 1-10.
    Publication Date: 2017-01-04
    Type: Article , PeerReviewed
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  • 68
    Publication Date: 2016-06-17
    Description: In a midoceanic region of the northeast Atlantic, patches of freshly deposited phytodetritus were discovered on the sea floor at a 4500 m depth in July/August 1986. The color of phytodetritus was variable and was obviously related to the degree of degradation. Microscopic analyses showed the presence of planktonic organisms from the euphotic zone, e.g., cyanobacteria, small chlorophytes, diatoms, coccolithophorids, silicoflagellates, dinoflagellates, tintinnids, radiolarians, and foraminifers. Additionally, crustacean exuviae and a great number of small fecal pellets, “minipellets,” were found. Although bacteria were abundant in phytodetritus, their number was not as high as in the sediment. Phytodetrital aggregates also contained a considerable number of benthic organisms such as nematodes and special assemblages of benthic foraminifers. Pigment analyses and the high content of particulate organic carbon indicated that the phytodetritus was relatively undegraded. Concentrations of proteins, carbohydrates, chloroplastic pigments, total adenylates, and bacteria were found to be significantly higher in sediment surface samples when phytodetritus was present than in equivalent samples collected at the same stations in early spring prior to phytodetritus deposition. Only the electron transport system activity showed no significant difference between the two sets of samples, which may be caused by physiological stress during sampling (decompression, warming). The chemical data of phytodetritus samples displayed a great variability indicative of the heterogeneous nature of the detrital material. The gut contents of various megafauna (holothurians, asteroids, sipunculids, and actiniarians) included phytodetritus showing that the detrital material is utilized as a food source by a wide range of benthic organisms. Our data suggest that the detrital material is partly rapidly consumed and remineralized at the sediment surface and partly incorporated into the sediment. Incubations of phytodetritus under simulated in situ conditions and determination of the biological oxygen demand under surface water conditions showed that part of its organic matter can be biologically utilized. Based on the measured standing stock of phytodetritus, it is estimated that 0.3–3% of spring primary production sedimented to the deep-sea floor. Modes of aggregate formation in the surface waters, their sedimentation, and distribution on the seabed are discussed.
    Type: Article , PeerReviewed
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  • 69
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    Springer
    In:  , ed. by Sommer, U. Springer, Berlin, Germany, 369 pp. ISBN 3-540-51373-6
    Publication Date: 2012-02-28
    Type: Book , NonPeerReviewed
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  • 70
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    Association for the Sciences of Limnology and Oceanography
    In:  Limnology and Oceanography, 34 (7). pp. 1162-1173.
    Publication Date: 2018-06-25
    Description: The nutritional status of phytoplankton in a shallow, hypertrophic lake was analyzed by stoichiometry of seston and by enrichment bioassays during a 6-month period. Both methods suggested moderate and temporally interrupted nutrient limitation of reproductive rates. Nitrogen was the most frequently limiting nutrient, phosphorus was next, and silicate limitation of three diatom species occurred only once. The nutritional status of the most abundant individual species could be described by the Monod equation. The nutritional status of the entire phytoplankton assemblage could be described by a modified version of the Droop equation. In accordance with competition theory, phytoplankton species were arrayed along resource ratio gradients. These results are consistent with ecophysiological models derived from culture experiments.
    Type: Article , PeerReviewed
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  • 71
    Publication Date: 2016-06-21
    Type: Article , PeerReviewed
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  • 72
    Publication Date: 2018-06-11
    Description: The electro-optic switching properties of injection-coupled coherent 2-D grating-surface-emitting laser arrays with multiple gain sections and quantum well active layers are discussed and demonstrated. Within such an array of injection-coupled grating-surface-emitting lasers, a single gain section can be operated as intra-cavity saturable loss element that can modulate the output of the entire array. Experimental results demonstrate efficient sub-nanosecond switching of high power grading-surface-emitting laser arrays by using only one gain section as an intra-cavity loss modulator.
    Keywords: Optics
    Type: NASA-CR-186772 , NAS 1.26:186772
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  • 73
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    In:  CASI
    Publication Date: 2018-06-09
    Description: NBOD2, a program developed at Goddard Space Flight Center to solve equations of motion coupled N-body systems is used by E.I. DuPont de Nemours & Co. to model potential drugs as a series of elements. The program analyses the vibrational and static motions of independent components in drugs. Information generated from this process is used to design specific drugs to interact with enzymes in designated ways.
    Keywords: Life Sciences (General)
    Type: Spinoff 1989; 83
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  • 74
    facet.materialart.
    Unknown
    In:  CASI
    Publication Date: 2018-06-09
    Description: American Hospital Supply Corporation (AHSC), Baxter Healthcare Corporation's predecessor, used the NASA informational base on contamination control technology to improve industrial contamination control technology. When a study determined that microscopic body particles escaping through tiny "windows" in woven garments worn by workers were the greatest source of contamination, AHSC developed TYVEK. This non-woven material filters 99% of all particulate matter larger than half a micron. Baxter Healthcare added a polyimide coating which seals and ties down any loose fibers, providing greater durability. Stress points along seams have been minimized to make the garment almost tearproof. Micro-Clean 212 garments are individually packaged and disposable.
    Keywords: Environment Pollution
    Type: Spinoff 1989; 88-89
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  • 75
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    In:  CASI
    Publication Date: 2018-06-09
    Description: When Enerpro, Inc. president, Frank J. Bourbeau, attempted to file a patent on a system for synchronizing a wind generator to the electric utility grid, he discovered Marshall Space Flight Center's Frank Nola's power factor controller. Bourbeau advanced the technology and received a NASA license and a patent for his Auto Synchronous Controller (ASC). The ASC reduces generator "inrush current," which occurs when large generators are abruptly brought on line. It controls voltage so the generator is smoothly connected to the utility grid when it reaches its synchronous speed, protecting the components from inrush current damage. Generator efficiency is also increased in light winds by applying lower than rated voltage. Wind energy is utilized to drive turbines to generate electricity for utility companies.
    Keywords: Energy Production and Conversion
    Type: Spinoff 1989; 78-79
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  • 76
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    In:  CASI
    Publication Date: 2018-06-09
    Description: 001 is an integrated tool suited for automatically developing ultra reliable models, simulations and software systems. Developed and marketed by Hamilton Technologies, Inc. (HTI), it has been applied in engineering, manufacturing, banking and software tools development. The software provides the ability to simplify the complex. A system developed with 001 can be a prototype or fully developed with production quality code. It is free of interface errors, consistent, logically complete and has no data or control flow errors. Systems can be designed, developed and maintained with maximum productivity. Margaret Hamilton, President of Hamilton Technologies, also directed the research and development of USE.IT, an earlier product which was the first computer aided software engineering product in the industry to concentrate on automatically supporting the development of an ultrareliable system throughout its life cycle. Both products originated in NASA technology developed under a Johnson Space Center contract.
    Keywords: Computer Programming and Software
    Type: Spinoff 1989; 104-105
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  • 77
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    Unknown
    In:  CASI
    Publication Date: 2018-06-09
    Description: Amoco Laser Company, a subsidiary of Amoco Corporation, has developed microlasers for the commercial market based on a JPL concept for optical communications over interplanetary distances. Lasers emit narrow, intense beams of light or other radiation. The beams transmit communication signals, drill, cut or melt materials or remove diseased body tissue. The microlasers cover a broad portion of the spectrum, and performance is improved significantly. Current applications include medical instrumentation, color separation equipment, telecommunications, etc.
    Keywords: Lasers and Masers
    Type: Spinoff 1989; 110
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  • 78
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    Unknown
    In:  Other Sources
    Publication Date: 2019-01-25
    Description: The development of probabilistic structural analysis methodology consists of the following program elements: (1) composite load spectra models, (2) computational probabilistic structural analysis methods, and (3) probabilistic constitutive relationships. The development of the probabilistic structural analysis methodology is a joint program of NASA Lewis in-house and sponsored research. The objective of this session is to illustrate recent progress on the application of this methodology to determine the reliability of structural components for rocket propulsion systems. The session contains descriptions of and progress reports on the following specific activities: (1) The NESSUS computer code, (2) approximate methods, (3) advanced methods, (4) composite load spectra applications, (5) probabilistic fracture mechanisms, and (6) probability of failure and risk analysis. Collectively, the progress to date demonstrates that the structural durability of hot engine structural components can be effectively evaluated in a formal probabilistic/reliability framework.
    Keywords: STRUCTURAL MECHANICS
    Type: Structural Integrity and Durability of Reusable Space Propulsion Systems; p 137-138
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    In:  Other Sources
    Publication Date: 2019-01-25
    Description: According to results of Earth based observations and in situ measurements cometary nuclei are intensive sources of both the gaseous and the dusty matter. Investigations of the interaction between gas-dust cometary atmospheres and dust grains of the Zodiacal dust cloud reveals the presence of two principally possible mechanisms: meteor-like and explosive-type ones. The meteor-like mechanism is connected with bombardment of zodiacal dust particles by cometary molecules when the temperatures T = 2000 to 3000 K are developed. This mechanism can create over-saturated vapors of refractory elements (Fe, Si, C etc.) in cometary heads. The explosion-type mechanism is connected with high-velocity impacts between cometary and zodiacal dust particles resulting in the generation of high-temperature plasma (T = 10(exp 5) to 10(exp 7) K) and, hence, of x ray radiation and multicharged ions, i.e., with the processes not yet realized in the laboratory conditions.
    Keywords: ASTROPHYSICS
    Type: Lunar and Planetary Inst., Workshop on Analysis of Returned Comet Nucleus Samples; p 31
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    Publication Date: 2019-01-25
    Description: On the basis of the 2-D radiative-photochemical model of the ozone layer at heights 0 to 60 km in the Northern Hemisphere there are revealed and analyzed in detail the characteristic features of the season-altitude-latitude variations of ozone and temperature due to changes of the solar flux during the 11 year cycle, electron and proton precipitations.
    Keywords: ENVIRONMENT POLLUTION
    Type: International Council of Scientific Unions, Middle Atmosphere Program. Handbook for MAP, Volume 29. Part 1: Extended Abstracts, International Symposium on Solar Activity Forcing of the Middle Atmosphere. Part 2: MASH Workshop, Williamsburg, 1986; p 118
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  • 81
    Publication Date: 2019-01-25
    Description: A great variety of physical mechanisms of possibly solar induced variations in the middle atmosphere has been discussed in the literature during the last decades. The views which have been put forward are often controversial in their physical consequences. The reason may be the complexity and non-linearity of the atmospheric response to comparatively weak forcing resulting from solar activity. Therefore this review focuses on aspects which seem to indicate nonlinear processes in the development of solar induced variations. Results from observations and numerical simulations are discussed.
    Keywords: GEOPHYSICS
    Type: International Council of Scientific Unions, Middle Atmosphere Program. Handbook for MAP, Volume 29. Part 1: Extended Abstracts, International Symposium on Solar Activity Forcing of the Middle Atmosphere. Part 2: MASH Workshop, Williamsburg, 1986; p 116
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    Publication Date: 2019-01-25
    Description: The observations of the low-mass x ray binary, Cyg X-2, taken with the International Ultraviolet Explorer (IUE) in a campaign conducted in June and October of 1988 are reported. A direct relationship between the strength of the UV continuum and line emission and the placement of the x ray spectrum in one of three branches of the so-called Z-shaped curve is found by comparison with simultaneous x ray observations. All three previously known x ray spectral states are detected; the UV continuum and line emission increase monotonically along the Z with the least emission in the horizontal branch, and the most in the flaring branch. Emission lines due to HeII, CIV, NIII, NIV, NV, SiIV, and MgII are observed.
    Keywords: ASTRONOMY
    Type: Max-Planck-Inst. fuer Physik und Astrophysik, Observations of Cygnus X-2 at X Ray, UV, Optical and Radio Frequencies; p 46-88
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  • 83
    Publication Date: 2019-01-25
    Description: There is an evident need to discover a means of establishing reliable, implementable controls for systems that are plagued by nonlinear and, or uncertain, model dynamics. The development of a generic controller design tool for tough-to-control systems is reported. The method utilizes a moving grid, time infinite element based solution of the necessary conditions that describe an optimal controller for a system. The technique produces a discrete feedback controller. Real time laboratory experiments are now being conducted to demonstrate the viability of the method. The algorithm that results is being implemented in a microprocessor environment. Critical computational tasks are accomplished using a low cost, on-board, multiprocessor (INMOS T800 Transputers) and parallel processing. Progress to date validates the methodology presented. Applications of the technique to the control of highly flexible robotic appendages are suggested.
    Keywords: COMPUTER PROGRAMMING AND SOFTWARE
    Type: Jet Propulsion Lab., California Inst. of Tech., Proceedings of the 3rd Annual Conference on Aerospace Computational Control, Volume 2; p 714
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  • 84
    Publication Date: 2019-01-25
    Description: A paradigm for control law design for modern engineering systems is proposed: Minimize control law complexity subject to the achievement of a specified accuracy in the face of a specified level of uncertainty. Correspondingly, the overall goal is to make progress towards the development of a control law design methodology which supports this paradigm. Researchers achieve this goal by developing a general theory of optimal constrained-structure dynamic output feedback compensation, where here constrained-structure means that the dynamic-structure (e.g., dynamic order, pole locations, zero locations, etc.) of the output feedback compensation is constrained in some way. By applying this theory in an innovative fashion, where here the indicated iteration occurs over the choice of the compensator dynamic-structure, the paradigm stated above can, in principle, be realized. The optimal constrained-structure dynamic output feedback problem is formulated in general terms. An elegant method for reducing optimal constrained-structure dynamic output feedback problems to optimal static output feedback problems is then developed. This reduction procedure makes use of star products, linear fractional transformations, and linear fractional decompositions, and yields as a byproduct a complete characterization of the class of optimal constrained-structure dynamic output feedback problems which can be reduced to optimal static output feedback problems. Issues such as operational/physical constraints, operating-point variations, and processor throughput/memory limitations are considered, and it is shown how anti-windup/bumpless transfer, gain-scheduling, and digital processor implementation can be facilitated by constraining the controller dynamic-structure in an appropriate fashion.
    Keywords: COMPUTER PROGRAMMING AND SOFTWARE
    Type: Jet Propulsion Lab., California Inst. of Tech., Proceedings of the 3rd Annual Conference on Aerospace Computational Control, Volume 2; p 638-639
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