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At least 343 records · Page 19

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NASA NTRS1976

LACIE performance predictor FOC users manual

The LACIE Performance Predictor (LPP) is a computer simulation of the LACIE process for predicting worldwide wheat production. The simulation provides for the introduction of various errors into the system and provides estimates based on these errors, thus allowing the user to determine the impact of selected error sources. The FOC LPP simulates the acquisition of the sample segment data by the LANDSAT Satellite (DAPTS), the classification of the agricultural area within the sample segment (CAMS), the estimation of the wheat yield (YES), and the production estimation and aggregation (CAS). These elements include data acquisition characteristics, environmental conditions, classification algorithms, the LACIE aggregation and data adjustment procedures. The operational structure for simulating these elements consists of the following key programs: (1) LACIE Utility Maintenance Process, (2) System Error Executive, (3) Ephemeris Generator, (4) Access Generator, (5) Acquisition Selector, (6) LACIE Error Model (LEM), and (7) Post Processor.

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NASA NTRS1976

An Atlas of extraterrestrial particles collected with NASA U-2 aircraft, 1974 - 1976

Extraterrestrial particles collected during U-2 flights in the stratosphere were divided into four groups: chondritic, iron-sulfur--nickel, mafic silicates, and others. The chondritic aggregates are typically composed of Fe, Mg, Si, C, S, Ca, and Ni. Detectable levels of He-4 implanted from the solar wind occur in some. Olivine, spinel, and possibly pyrrhotite and a hydrated layered-lattice silicate were identified. The chondritic ablation particles contain no sulfur and appear to have been melted. Magnetite, olivine, and pyroxene were identified. The iron-sulfur-nickel type particles resemble meteoritic iron sulfide with a small amount of nickel, and contain magnetite and troilite. The mafic silicate type particles are iron magnesium silicate grains with clumps of chondritic aggregate particles adhering to their surfaces. Olivine and possibly pyrrhotite and pyroxene were identified. Most of the iron-nickel type particles are spherules and include taenite and wustite. The other type particles include nickel-iron mounds on spheroidal glassy-like grains having chondritic-like elemental abundances.

Brownlee, D. E.↗

NASA NTRS1975

A digital computer simulation and study of a direct-energy-transfer power-conditioning system

An investigation of the behavior of the power-conditioning system as a whole is a necessity to ensure the integrity of the aggregate system in the case of space applications. An approach for conducting such an investigation is considered. A description is given of the application of a general digital analog simulator program to the study of an aggregate power-conditioning system which is being developed for use on the International Ultraviolet Explorer spacecraft. The function of the direct energy transfer system studied involves a coupling of a solar array through a main distribution bus to the spacecraft electrical loads.

Burns, W. W., III↗

NASA NTRS1980

Equilibrium swelling of elastomers in solvents

Two proposed empirical equations, developed from Eilers-VanDijk equation to characterize relative modulus of filled elastomers as function of filler content, describe: (1) equilibrium swelling for cases where fillers are composed of permanent aggregates of primary particles; and (2) equilibrium swelling when filler material is composed of non-aggregated particles.

Fedors, R. F.↗

NASA NTRS1978

Traveling wave tube circuit

A traveling wave tube (TWT) has a slow wave structure (SWS) which is severed into two or more sections. A signal path, connects the end of an SWS section to the beginning of the following SWS section. The signal path comprises an impedance matching coupler (IMC), followed by an isolator, a variable phase shifter, and a second IMC. The aggregate band pass characteristic of the components in the signal path is chosen to reject, or strongly attenuate, all frequencies outside the desired operating frequency range of the TWT and yet pass, with minimal attenuation in the forward direction, all frequencies within the desired operating frequency range. The isolator is chosen to reject, or strongly attenuate, waves, of all frequencies, which propagate in the backward direction. The aggregate phase shift characteristic of the components in the signal path is chosen to apply signal power to the beginning of the following SWS section with the phase angle yielding maximum efficiency.

Connolly, D. J.↗

NASA NTRS1978

Heat and moisture flow in concrete as a function of temperature

Due to temperature, reactors in operation cause heat and moisture flows in the thick walled prestressed pressure vessels. These flows were studied in three beams of concrete made with crushed limestone aggregate, and in three beams made of crushed gravel/sand aggregate. The flow phenomena were related to the structural development of the concrete by determining the amount of non-evaporatable water, the total porosity, and the pore size distribution. Local temperature and moisture conditions also influenced the technical properties. Compressive strength, changes in length due to shrinkage and contraction, thermal expansion, and thermal conductivity were determined.

Hundt, J.↗

NASA NTRS1979

The value of improved telecommunications service to hospitals: A preliminary assessment

In view of the rapid rate of development of domestic telecommunication services and the emphasis on private networks, it was sought to determine if hospitals had major requirements which could be aggregated and served by such networks. The value of the information transfer services judged to be most promising over the next twenty years was evaluated, based on expenditures and activity levels in five hospitals and one management services firm and the judgement of their senior staff. An implicit assumption is that services will become affordable once the hospital industry aggregates its requirements. A methodology to evaluate the value of telecommunication services in a hospital was developed and tested.

Potter, J. G.↗

NASA NTRS1978

The chaotic solar nebula - Evidence for episodic condensation in several distinct zones

Abundances of rare earth elements in Allende inclusions are considered along with the rim sequence on coarse-grained chondrules. It is found that in at least several zones the nebula went through episodes of condensation and gas/grain separation. Four separate zones are required to make the two types of fine-grained aggregates and the two types of coarse-grained chondrules. Other types of inclusions in Allende, such as the olivine aggregates, may well require additional condensation zones. All of these conclusions are based on data from one meteorite. Although the details of the gas/grain separation mechanism in these zones is not well understood, it is clear that a single monotonic-cooling condensation sequence followed by isolation of grains from gas cannot account for the observations.

Boynton, W. V.↗

NASA NTRS1978

Chemical and structural studies of 'Brownlee' particles

Several techniques were applied to the study of small particles (around 10 microns) collected in the upper atmosphere by U-2 aircraft. The major element chemistry of roughly 1/3 of the particles is similar to that of chondritic meteorites, although considerable variation of element ratios is observed from particle to particle, and even within a given particle. All particles of 'chondritic' composition are polycrystalline aggregates. About half have fully re-entrant structures; the remaining ones have more compact structures ranging from platey to spherical morphologies. Micro-crystallites with various internal structures are observed in the size range from less than 100 A to several microns. Although tracks are clearly observed in transmission electron microscope examination of terrestrial analog crystals, no tracks of solar flare origin have yet been identified in the U-2 particles. Induced fission track analysis of one aggregate shows that the U concentration is less than 15 ppbm, lending support to the extraterrestrial origin hypothesis.

Flynn, G. J.↗

NASA NTRS1980

Occurrence and mineral chemistry of high pressure phases, Portrillo basalt, southcentral New Mexico

Inclusions of clinopyroxenite, kaersutiteclinopyroxenite, kaersutite-rich inclusions, wehrlite and olivine-clinopyroxenite together with megacrysts of feldspar, kaersutite and spinel are found loose on the flanks of cinder cones, as inclusions within lava flows and within the cores of volcanic bombs in the Quaternary alkali-olivine basalt of the West Potrillo Mountains, southcentral New Mexico. Based on petrological and geochemical evidence the megacysts are interpreted to be phenocrysts which formed at great depth rather that xenocrysts of larger crystal aggregates. These large crystals are believed to have formed as stable phases at high temperature and pressure and have partially reacted with the basalt to produce subhedral to anhedral crystal boundaries. It can be demonstrated that the mafic and ultramafic crystal aggregates were derived from an alkali-basalt source rock generated in the mantle. The inclusions are believed to represent a cumulus body or bodies injected within the lower crust or upper mantle.

Hoffer, J. M.↗

NASA NTRS1979

Forest Classification and Inventory System using Landsat, digital terrain, and ground sample data

Accurate timber inventory data for cost-effective forest management is the primary goal of a Forest Classification and Inventory System (FOCIS) designed to provide estimates of timber volume by species aggregated by compartments, townships, or other spatial management units. FOCIS uses Landsat spectral data, including a synthesized texture channel, and Forest Service ground sample data to produce timber volume-homogeneous classes through a two-step unsupervised clustering process. Registered digital terrain data, including derived slope angle and slope aspect channels, are used to predict species proportions through a trend surface model, again using ground sample data for model calibration. In the final stage of FOCIS, volume estimates and predicted species proportions are merged and aggregated to yield timber volumes by species within management areas.

Strahler, A. H.↗

NASA NTRS1980

A new method of efficient heat transfer and storage at very high temperatures

A unique, high temperature (1000-2000 K) continuously operating capacitive heat exchanger system is described. The system transfers heat from a combustion or solar furnace to a working gas by means of a circulating high temperature molten refractory. A uniform aggregate of beads of a glass-like refractory is injected into the furnace volume. The aggregate is melted and piped to a heat exchanger where it is sprayed through a counter-flowing, high pressure working gas. The refractory droplets transfer their heat to the gas, undergoing a phase change into the solid bead state. The resulting high temperature gas is used to drive a suitable high efficiency heat engine. The solidified refractory beads are delivered back to the furnace and melted to continue the cycle. This approach avoids the important temperature limitations of conventional tube-type heat exchangers, giving rise to the potential of converting heat energy into useful work at considerably higher efficiencies than currently attainable and of storing energy at high thermodynamic potential.

Shaw, D.↗

NASA NTRS1981

Interplanetary dust in the transmission electron microscope - Diverse materials from the early solar system

An analytical electron microscope study of dispersed interplanetary dust aggregates collected in the earth's stratosphere shows that, in spite of their similarities, the aggregates exhibit significant differences in composition, internal morphology, and mineralogy. Of 11 chondritic particles examined, two consist mostly of a noncrystalline chondritic material with an atomic S/Fe ratio equal to or greater than 2 in places, one consists of submicron metal and reduced silicate 'microchondrules' and sulfide grains embedded in a carbonaceous matrix, and another consists of submicron magnetic-decorated unequilibrated silicate and sulfide grains with thick low-Z coatings. Although the particles are unmetamorphosed by criteria commonly applied for chondritic meteorites, the presence of reduced chemistries and the ubiquity of mafic, instead of hydrated, silicates confirm that they are not simply C1 or C2 chondrite matrix material. The observations indicate that portions of some particles have not been significantly altered by thermal or radiation processes since their assembly, and that the particles probably contain fine debris from diverse processes in the early solar system.

Fraundorf, P.↗

NASA NTRS1980

AgRISTARS: Foreign commodity production forecasting. Minutes of the annual formal project manager's review, including preliminary technical review reports of FY80 experiments

The U.S./Canada wheat/barley exploratory experiment is discussed with emphasis on labeling, machine processing using P1A, and the crop calendar. Classification and the simulated aggregation test used in the U.S. corn/soybean exploratory experiment are also considered. Topics covered regarding the foreign commodity production forecasting project include: (1) the acquisition, handling, and processing of both U.S. and foreign agricultural data, as well as meteorological data. The accuracy assessment methodology, multicrop sampling and aggregation technology development, frame development, the yield project interface, and classification for area estimation are also examined.

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NASA NTRS1981

US corn and soybeans exploratory experiment

The results from the U.S. corn/soybeans exploratory experiment which was completed during FY 1980 are summarized. The experiment consisted of two parts: the classification procedures verification test and the simulated aggregation test. Evaluations of labeling, proportion estimation, and aggregation procedures are presented.

Carnes, J. G.↗

NASA NTRS1982

Fluid models and simulations of biological cell phenomena

The dynamics of coated droplets are examined within the context of biofluids. Of specific interest is the manner in which the shape of a droplet, the motion within it as well as that of aggregates of droplets can be controlled by the modulation of surface properties and the extent to which such fluid phenomena are an intrinsic part of cellular processes. From the standpoint of biology, an objective is to elucidate some of the general dynamical features that affect the disposition of an entire cell, cell colonies and tissues. Conventionally averaged field variables of continuum mechanics are used to describe the overall global effects which result from the myriad of small scale molecular interactions. An attempt is made to establish cause and effect relationships from correct dynamical laws of motion rather than by what may have been unnecessary invocation of metabolic or life processes. Several topics are discussed where there are strong analogies droplets and cells including: encapsulated droplets/cell membranes; droplet shape/cell shape; adhesion and spread of a droplet/cell motility and adhesion; and oams and multiphase flows/cell aggregates and tissues. Evidence is presented to show that certain concepts of continuum theory such as suface tension, surface free energy, contact angle, bending moments, etc. are relevant and applicable to the study of cell biology.

Greenspan, H. P.↗

NASA NTRS1979

Flocculation of colloidal sols: Diffusion-controlled vs agitation-induced flocculation

A proposal for carrying out flocculation experiments in microgravity is presented. These experiments might allow a correlation between theory and experiment. First, all particles, whether single primary particles or aggregates of primary particles would not settle or cream at any agitation rate, or even in the absence of agitation. This failure to separate would keep all aggregates active, still serving as centers for diffusion-controlled flocculation. Keeping all particles suspended would allow the possibility of determining the total number of particles as a function of time from beginning to end of flocculation. Finally, the experiments would allow a definite separation diffusion-controlled and agitation-induced flocculation by studying diffusion-controlled flocculation with and without agitation.

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NASA NTRS1979

Some potential blood flow experiments for space

Blood is a colloidal suspension of cells, predominantly erythrocytes, (red cells) in an aqueous solution called plasma. Because the red cells are more dense than the plasma, and because they tend to aggregate, erythrocyte sedimentation can be significant when the shear stresses in flowing blood are small. This behavior, coupled with equipment restrictions, has prevented certain definitive fluid mechanical studies from being performed with blood in ground-based experiments. Among such experiments, which could be satisfactorily performed in a microgravity environment, are the following: (1) studies of blood flow in small tubes, to obtain pressure-flow rate relationships, to determine if increased red cell aggregation can be an aid to blood circulation, and to determine vessel entrance lengths, and (2) studies of blood flow through vessel junctions (bifurcations), to obtain information on cell distribution in downstream vessels of (arterial) bifurcations, and to test flow models of stratified convergent blood flows downstream from (venous) bifurcations.

Cokelet, G. R.↗