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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
NASA NTRS1998

Vision Algorithms to Determine Shape and Distance for Manipulation of Unmodeled Objects

This paper discusses the development of a robotic system for general use in an unstructured environment. This is illustrated through pick and place of randomly positioned, un-modeled objects. There are many applications for this project, including rock collection for the Mars Surveyor Program. This system is demonstrated with a Puma560 robot, Barrett hand, Cognex vision system, and Cimetrix simulation and control, all running on a PC. The demonstration consists of two processes: vision system and robotics. The vision system determines the size and location of the unknown objects. The robotics part consists of moving the robot to the object, configuring the hand based on the information from the vision system, then performing the pick/place operation. This work enhances and is a part of the Low Cost Virtual Collaborative Environment which provides remote simulation and control of equipment.

Montes, Leticia↗
NASA NTRS2000

Synthesis and Properties of Phenylethynyl-Terminated, Star-Branched, Phenylquinoxaline Oligomers

The primary objective of this work was to prepare readily melt and solution processable phenylquinoxaline (PQ) oligomers that could be thermally crosslinked to solvent-resistant resins. Thus, a mixture of 2-(4-hydroxyphenyl)-3-phenyl-6-fluoroquinoxaline and 3-(4-hydroxyphenyl)-2-phenyl-6-fluoroquinoxaline (HPFQ) was used to prepare star-branched PQ oligomers end-capped with 4-fluoro-4-phenylethynylbenzophenone (FPEB). 1,1,1-Tris(4-hydroxyphenyl)ethane (THPE) was used as the branching unit. The oligomer number-average molecular weights (M (bar) (sub n) S) as determined by size exclusion chromatography (SEC) were close to the calculated values of 2922, 4698, 6474, and 13,578 g/mol, and their intrinsic viscosities ranged from 0.16 to 0.57 dl/g (m-cresol at 30 C). The oligomers, which were quite soluble in common organic solvents, had glass transition temperatures (T (sub g) S) that ranged from 181 to 233 C (DSC, DELTA T = 20 C/min). They also underwent an exothermic cure with maxima from 377 to 443 C. The T (sub g) S of the cured oligomers ranged from 259 to 284 C depending on the oligomer M (bar) (sub n) and the curing conditions. The oligomers had low melt viscosities, e.g. an oligomer (SPQ-46) with an M (bar) (sub n) of 4816 g/mol (SEC) had a melt viscosity of 150 Pa s at 348 C. A cured thin film of SPQ-46, which was insoluble in common organic solvents, had a room temperature (RT) tensile strength of 100 MPa, a RT modulus of 2358 MPa, and a RT elongation of 5.9%. A cured sample of SPQ-46 displayed a RT titanium-titanium lap shear tensile strength of 35.2 MPa. SPQ-46/carbon fiber(IM-7) composites, were prepared that displayed a RT flexural strength of 1902 MPa, a RT modulus of 1.38 GPa and a RT open hole compressive strength of 433 MPa.

Ooi, I. H.↗
NASA NTRS1999

Dynamic Light Scattering of Diabetic Vitreopathy

Diabetes induces pathology throughout the body via nonenzymatic glycation of proteins. Vitreous, which is replete with type 11 collagen, undergoes significant changes in diabetes. The resultant diabetic vitreopathy plays an important role in diabetic retinopathy. Detecting these molecular changes could provide insight into diabetic eye disease as well as molecular effects elsewhere in the body. Human eyes were obtained at autopsy and studied in the fresh, unfixed state. Sclera, choroid, and retina were dissected off the vitreous for dark-field slit microscopy and dynamic light scattering (DLS). For the former, the entire vitreous was exposed. For the latter, only a window at the equator was dissected in some specimens, and the anterior segment was removed leaving the posterior lens capsule intact in others. DLS was performed to determine particle sizes at multiple sites 0.5 mm apart, spanning the globe at the equator (window dissections) and along the antero-posterior axis. Dark-field slit microscopy in diabetic subjects detected findings typical of age-related vitreous degeneration, but at much younger ages than nondiabetic controls. Noninvasive DLS measurements found a greater heterogeneity and larger particle sizes in vitreous of subjects with diabetes as compared to age-matched controls. DLS can detect and quantify the early molecular effects that cause vitreous collagen fibrils to cross-link and aggregate. This could provide valuable insight into ocular and systemic effects of hyperglycemia, because the molecular changes in diabetic vitreopathy could serve as an index of such effects throughout the body. In addition to the diagnostic implications, this methodology could provide a rapid, reproducible way to monitor the response to therapy with novel agents intended to prevent the complications of diabetes on a molecular level.

Sebag, J.↗
NASA NTRS2001

Current Induced Forces on Adsorbates at Conducting Carbon Nanotubes

The problem addressed is force on an impurity due to electric current. In order to determine the size and direction of the force, as well as its dependence on the voltage, LCAO (Linear Combination of Atomic Orbitals) and the Green's Function approach were implemented. The resultant induced mean force was directed outwards in addition to a smaller component in the electron flow direction. At low bias, force is larger for larger radius, and crosses over the opposite trend when increasing the bias. The crossover current is approximately inversely proportional to the radius.

Mingo, N.↗
NASA NTRS2001

A Procedure for Determining the Nature of Mercury's Core

We review past assertions that the determinations of the four parameters, C(20), C(22), theta, phi, are sufficient to determine the size and state of Mercury's core. C(20) and C(22) are gravitational harmonics, theta is Mercury's obliquity and phi is the amplitude of the forced, 88 day period libration in longitude. The upcoming MESSENGER orbiter mission to Mercury with onboard instrumentation capable of measuring these four parameters, and the possibility of precision measurements of Mercury's spin geometry with radar interferometry techniques make a reexamination of this proposal particularly relevant. The two necessary conditions on the core-mantle interaction for the experiment to work are: 1. The core must not follow the 88 day physical librations of the mantle. 2. The core must follow the mantle on the time scale of the 250,000 year precession of the spin in Cassini state 1. We shall assume these two conditions are satisfied to develop the method and later establish the constraints on the core viscosity for which they are satisfied. Proposed mechanisms of core mantle coupling other than a viscous coupling do not frustrate the first condition. The physical libration of the mantle about the mean resonant angular velocity arises from the periodically reversing torque on the permanent deformation as Mercury rotates relative to the Sun. Additional information is contained in the original extended abstract.

Peale, S. J.↗
NASA NTRS2002

Optical Scattering Characterization for the Glennan Microsystems Microscale Particulate Classifier

Small sensors that are tolerant to mechanically and thermally harsh environments present the possibility for in-situ particle characterization in propulsion, industrial, and planetary science applications. Under a continuing grant from the Glennan Microsystems Initiative to the Microgravity Fluids Physics Branch of the NASA-Glenn Research Center, a Microscale Particle Classifier (MiPAC) instrument is being developed. The MiPAC instrument will be capable of determining the size distribution of airborne particles from about 1 nm to 30 micrometers, and will provide partial information as to the concentration, charge state, shape, and structure of the particles, while being an order of magnitude smaller in size and lighter in weight than presently commercially available instruments. The portion of the instrument that will characterize the nm-range particles will employ electrical mobility techniques and is being developed under a separate grant to Prof. David Pui of the University of Minnesota. The portion of the instrument that will characterize the micrometer-size particles such as dirt, pollens, spores, molds, soot, and combustion aerosols will use light scattering techniques. The development of data analysis techniques to be employed in the light scattering portion of the instrument is covered by this grant.

Lock, James A.↗
NASA NTRS2002

The Evolution of Dust in the Multiphase Interstellar Medium

Interstellar dust has a profound effect on the structure and evolution of the interstellar medium (ISM) and on the processes by which stars form from it. Dust obscures regions of star formation from view, and the uncertain quantities of elements in dust makes it difficult to measure accurately the abundances of the elements in low density regions. Despite the central importance of dust in astrophysics, we cannot answer some of the most basic questions about it: Why is it that most of the refractory elements are in dust grains? What determines the sizes of interstellar grains? In our theoretical investigations we have addressed these questions by studying the destruction of interstellar grains. We describe here the investigations that we have completed to date. As part of our original proposal we proposed additional projects that have not been completed. We are requesting a no-cost extension to carry out those investigations and describe those in our request.

Slavin, J.↗
NASA NTRS1994

Small Business Innovations

A Small Business Innovation Research (SBIR) contract resulted in a series of commercially available lasers, which have application in fiber optic communications, difference frequency generation, fiber optic sensing and general laboratory use. Developed under a Small Business Innovation Research (SBIR) contract, the Phase Doppler Particles Analyzer is a non-disruptive, highly accurate laser-based method of determining particle size, number density, trajectory, turbulence and other information about particles passing through a measurement probe volume. The system consists of an optical transmitter and receiver, signal processor and computer with data acquisition and analysis software. A variety of systems are offered for applications including spray characterization for paint, and agricultural and other sprays. The Microsizer, a related product, is used in medical equipment manufacturing and analysis of contained flows. High frequency components and subsystems produced by Millitech Corporation are marketed for both research and commercial use. These systems, which operate in the upper portion of the millimeter wave, resulted from a number of Small Business Innovation Research (SBIR) projects. By developing very high performance mixers and multipliers, the company has advanced the state of the art in sensitive receiver technology. Components are used in receivers and transceivers for monitoring chlorine monoxides, ozone, in plasma characterization and in material properties characterization.

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NASA NTRS2001

New Interstellar Dust Models Consistent with Interstellar Extinction, Emission and Abundances Constraints

We present new interstellar dust models that are consistent with both, the FUV to near-IR extinction and infrared (IR) emission measurements from the diffuse interstellar medium. The models are characterized by different dust compositions and abundances. The problem we solve consists of determining the size distribution of the various dust components of the model. This problem is a typical ill-posed inversion problem which we solve using the regularization approach. We reproduce the Li Draine (2001, ApJ, 554, 778) results, however their model requires an excessive amount of interstellar silicon (48 ppM of hydrogen compared to the 36 ppM available for an ISM of solar composition) to be locked up in dust. We found that dust models consisting of PAHs, amorphous silicate, graphite, and composite grains made up from silicates, organic refractory, and water ice, provide an improved fit to the extinction and IR emission measurements, while still requiring a subsolar amount of silicon to be in the dust. This research was supported by NASA Astrophysical Theory Program NRA 99-OSS-01.

Zubko, V.↗
NASA NTRS2002

Novel Directional Solidification Processing of Hypermonotectic Alloys

A model has been developed that determines the size of Liquid (sub 11) droplets generated during application of ultrasonic energy (as a function of amplitude) to immiscible alloys. The initial results are in accordance with experimental results based on Succinonitrile - Glycerol "alloys" and pure tin dispersions. Future work will take into account the importance of other effects, e.g., thermo-vibrational convection, sound attenuation, viscosity variations, and compositional changes.

Kaukler, William↗
NASA NTRS2003

Modeling Tetragonal Lysozyme Crystal Growth Rates

Tetragonal lysozyme 110 face crystal growth rates, measured over 5 orders of magnitude in range, can be described using a model where growth occurs by 2D nucleation on the crystal surface for solution supersaturations of c/c(sub eq) less than or equal to 7 +/- 2. Based upon the model, the step energy per unit length, beta was estimated to be approx. 5.3 +/- 0.4 x 10(exp -7) erg/mol-cm, which for a step height of 56 A corresponds to barrier of approx. 7 +/- 1 k(sub B)T at 300 K. For supersaturations of c/c(sub eq) > 8, the model emphasizing crystal growth by 2D nucleation not only could not predict, but also consistently overestimated, the highest observable crystal growth rates. Kinetic roughening is hypothesized to occur at a cross-over supersaturation of c/c(sub eq) > 8, where crystal growth is postulated to occur by a different process such as adsorption. Under this assumption, all growth rate data indicated that a kinetic roughening transition and subsequent crystal growth by adsorption for all solution conditions, varying in buffer pH, temperature and precipitant concentration, occurs for c/c(sub eq)(T, pH, NaCl) in the range between 5 and 10, with an energy barrier for adsorption estimated to be approx. 20 k(sub B)T at 300 K. Based upon these and other estimates, we determined the size of the critical surface nucleate, at the crossover supersaturation and higher concentrations, to range from 4 to 10 molecules.

Gorti, Sridhar↗
NASA NTRS2003

Light Absorbing Particle (LAP) Measurements in the Lower Stratosphere

This viewgraph presentation covers the capabilities and design of the Single Particle Soot Photometer (SP-2), and reviews its role on the Sage III Ozone Loss Validation Experiment (SOLVE II) field campaign during 2003. On SOLVE II the SP-2 was carried into the Arctic onboard a DC-8 aircraft, in order to determine the size distribution of light-absorbing and non light-absorbing particles in the stratosphere. Graphs and tables relate some of the results from SOLVE II.

Baumgardner, D.↗
NASA NTRS2003

The Evolution of Dust in the Multiphase Interstellar Medium

Interstellar dust has a profound effect on the structure and evolution of the interstellar medium (ISM) and on the processes by which stars form from it. Dust obscures regions of star formation from view, and the uncertain quantities of elements in dust makes it difficult to measure accurately the abundances of the elements in low density regions. Despite the central importance of dust in astrophysics, we cannot answer some of the most basic questions about it: Why is it that most of the refractory elements are in dust grains? What determines the sizes of interstellar grains? It has been the goal of our proposed theoretical investigations to address these questions by studying the destruction of interstellar grains, and to develop observational diagnostics that can test the models we develop.

Oliversen, Ronald J.↗
NASA NTRS2003

Disaster Response and Preparedness Application: Emergency Environmental Response Tool (EERT)

In 2000, the National Aeronautics and Space Administration (NASA) Environmental Office at the John C. Stennis Space Center (SSC) developed an Environmental Geographic Information Systems (EGIS) database. NASA had previously developed a GIS database at SSC to assist in the NASA Environmental Office's management of the Center. This GIS became the basis for the NASA-wide EGIS project, which was proposed after the applicability of the SSC database was demonstrated. Since its completion, the SSC EGIS has aided the Environmental Office with noise pollution modeling, land cover assessment, wetlands delineation, environmental hazards mapping, and critical habitat delineation for protected species. At SSC, facility management and safety officers are responsible for ensuring the physical security of the facilities, staff, and equipment as well as for responding to environmental emergencies, such as accidental releases of hazardous materials. All phases of emergency management (planning, mitigation, preparedness, and response) depend on data reliability and system interoperability from a variety of sources to determine the size and scope of the emergency operation. Because geospatial data are now available for all NASA facilities, it was suggested that this data could be incorporated into a computerized management information program to assist facility managers. The idea was that the information system could improve both the effectiveness and the efficiency of managing and controlling actions associated with disaster, homeland security, and other activities. It was decided to use SSC as a pilot site to demonstrate the efficacy of having a baseline, computerized management information system that ultimately was referred to as the Emergency Environmental Response Tool (EERT).

Smoot, James↗
NASA NTRS2003

A High Efficiency DC Bus Regulator/RPC for Spacecraft Applications

DC bus voltage regulation may be required in future high powered spacecraft due to the length of the busses or because they are not generated at precise voltage levels. In these cases the regulation range is often only a few percent increase or decrease, but conventional DC voltage regulators switch all the power passing through them, and this level of power switched determines the size and losses in the regulator. A recently developed concept used a low power DC-DC converter in series with the bs to raise or lower the bus voltage over a small range. This partial power processing technique combines the small size and power losses of the low power converter with the ability to regulate, (over a small range) a high power bus. The Series Connected Buck Boost Regulator (SCBBR) described herein provides bus regulation with an efficiency of 98%. The circuit also provides bus switching and overcurrent limiting functions of a Remote Power Controller (RPC). This paper described the circuit design and performance of a breadboard SCBBR configured as a bus voltage regulator providing plus of minus 40% voltage regulation range, bus switching, and overload limiting.

Birchenough, Arthur G.↗
NASA NTRS2001

Timber Management of NASA's John C. Stennis Space Station

John C. Stennis Space Center occupies over 48560 hectares or just over 120000 acres in southwestern Mississippi and southeastern Louisiana near border of the two states. This area includes the Stennis Fee Area, which is the Center itself and the Acoustic Buffer Zone (ABZ) surrounding the Center. The ABZ is owned by several government, public and private entities and managed accordingly. The Fee Area and ABZ include wetlands, pine woodlands and areas of mixed floral species. The included maps detail the delineation of land in and around the Stennis Space Center. Areas owned by the federal government are divided into three stands to facilitate timber management. The stands are classified by species, density and average size to determine several timber in management issues including the schedule for controlled burns, economic viability of stands, and the creation of low impact recreational areas such as scenic trails or bike paths.

Carr, Hugh↗
NASA NTRS2004

X-Ray Emission from the Halo of M31

Our goal was to use short (10 ksec) observations of selected fields in the halo of M31, to determine the size and characteristics of its X-ray population and to study the connection between globular clusters and X-ray sources. The program of observations has yet to be successfully completed. We received acceptable data from just 2 of the 5 approved fields. Nevertheless, the results were intriguing and we have submitted a paper based on this data to Nature. We find that the X-ray source density is significantly enhanced in the vicinity of one GC, providing the first observational evidence supporting the ejection hypothesis. We also find additional X-ray sources, including some which are very soft, in large enough numbers to suggest that not all could have been formed in GCs. That is, some must be descended from the same primordial halo population that produced any compact stars comprising part of the halo's dark matter. Extrapolating fiom the X-ray source population, we estimate that stellar remnants and dim old stars in the halo could comprise as much as 25% of the estimated mass (approx. 10(exp 12) Solar Mass) of the halo. These results suggest that the other approved fields should be observed soon and also provide strong motivation for the future XMM-Newton programs.

Mushotzky, Richard↗
NASA NTRS2003

Evolution of Local Microstructures: Spatial Instabilities in Coarsening Clusters

Diffusion-limited capillarity-driven coarsening of precipitates is an important and intensively studied phenomenon. The classic coarsening theory developed by Lifshitz and Syozov and Wagner (LSW theory) is limited to infinitesimally small volume fractions, V(sub nu), therefore neglects all direct interparticle interactions. This work uses modeling and holographic imaging to compare coarsening rates in "high" volume fraction versus low volume fraction microstructures by observing mixed-dimensional droplets (spherical caps on a surface coarsening by two-dimensional diffusion) during ground-based investigations. The method involves filling a cell with selected homogeneous parent phase, and cooling below the consolute temperature to the isopycnic temperature in the two-phase region of a monotectic system. A microgravity holographic experiment is required for three-dimensional observations to minimize sedimentation during long-term coarsening. Determination of sizes and positions of the many droplets in the holographic images requires automation. We have developed software for automated data analysis, and demonstrated good agreement between regenerated maps and scaled photographs of the original holograms for mixed dimensional coarsening. The results of these experiments were presented in a formal microgravity Science Concept Review (SCR) on December 18, 2000.

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