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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS2014

The Fleet Application for Scheduling and Tracking (FAST) Management Website

The FAST application was designed to replace the paper and pen method of checking out and checking in GSA Vehicles at KSC. By innovating from a paper and pen based checkout system to a fully digital one, not only the resources wasted by printing the checkout forms have been reduced, but it also reduces significantly the time that users and fleet managers need to interact with the system as well as improving the record accuracy for each vehicle. The vehicle information is pulled from a centralized database server in the SPSDL. In an attempt to add a new feature to the FAST application, the author of this report (alongside the FAST developers) has been designing and developing the FAST Management Website. The GSA fleet managers had to rely on the FAST developers in order to add new vehicles, edit vehicles and previous transactions, or for generating vehicles reports. By providing an easy-to-use FAST Management Website portal, the GSA fleet managers are now able to easily move vehicles, edit records, and print reports.

Object-Oriented Programming↗
NASA NTRS1984

Fast-mode magnetohydrodynamic waves in coronal holes and the solar wind

Fast-mode MHD waves in the solar corona can propagate in any direction relative to the background magnetic field. In coronal holes, they refract into regions of low Alfven speed and are relatively difficult to damp. These characteristics lead to the possibility that fast-mode waves transport energy from magnetically closed coronal regions into coronal holes, that they are refracted into the central regions of coronal holes, and that they deposit most of their energy in the region of supersonic flow of high-speed solar wind streams emanating from coronal holes. To investigate whether this possibility might be realized and fast-mode waves might play a significant role in driving high-speed streams, a parameter study is carried out to examine the propagation and damping of fast-mode waves in various coronal hole models. This study indicates a broad range of coronal hole parameters for which fast-mode waves can play such a role and emphasizes the need for an improved knowledge of large-scale coronal magnetic structure, which is required before any firm conclusions can be drawn.

Fla, T.↗
NASA NTRS1982

Effect of disuse on sarcoplasmic reticulum in fast and slow skeletal muscle

The effect of 6 weeks of hindlimb immobilization on rat skeletal muscle sarcoplasmic reticulum (SR) was determined in the slow-twitch, type 1 soleus (SOL), the fast-twitch, type 2A deep region of the vastus lateralis (DVL), and the fast-twitch, type 2B superficial region of the vastus lateralis (SVL). Immobilization produced a significant decline in the Ca(2+) uptake rate (V sub max) of SR vesicles from the slow SOL, while the SR V sub max increased in the fast SVL and was unaltered in the DVL. Vesicles from the fast SVL and DVL also exhibited a higher total Ca(2+) uptake capacity following immobilization. An evaluation of the time course of the immobilization-mediated effect revealed an increased Ca(2+) uptake capacity in all three samples after 1 wk. In the SOL total Ca(2+) uptake returned to control level after 2 wk, while in the fast-twitch muscles the higher capacities were maintained. The Ca(2+)-stimulated SR ATPase activity was not altered in any of the muscle studies.

Kim, D. H.↗
NASA NTRS1981

A comparison of rat myosin from fast and slow skeletal muscle and the effect of disuse

Certain enzymatic and structural features of myosin, purified from rat skeletal muscles representative of the fast twitch glycolytic (type IIb), the fast twitch oxidative (type IIa), and the slow twitch oxidative (type I) fiber, were determined and the results were compared with the measured contractile properties. Good correlation was found between the shortening velocities and Ca(2+)-activated ATPase activity for each fiber type. Short term hind limb immobilization caused prolongation of contraction time and one-half relaxation time in the fast twitch muscles and a reduction of these contractile properties in slow twitch soleus. Furthermore, the increased maximum shortening velocity in the immobilized soleus could be correlated with increased Ca(2+)-ATPase, but no change was observed in the enzymatic activity of the fast twitch muscles. No alteration in light chain distribution with disuse was observed in any of the fiber types. The myosin from slow twitch soleus could be distinguished from fast twitch myosins on the basis of the pattern of peptides generated by proteolysis of the heavy chains. Six weeks of hind limb immobilization resulted in both an increased ATPase activity and an altered heavy chain primary structure in the slow twitch soleus muscle.

Unsworth, B. R.↗
NASA NTRS1986

Protein turnover in adipose tissue from fasted or diabetic rats

Protein synthesis and degradation in vitro were compared in epididymal fat pads from animals deprived of food for 48 h or treated 6 or 12 days prior with streptozotocin to induce diabetes. Although both fasting and diabetes led to depressed (-24 to -57 percent) protein synthesis, the diminution in protein degradation (-63 to -72 percent) was even greater, so that net in vitro protein balance improved dramatically. Insulin failed to inhibit protein degradation in fat pads of these rats as it does for fed animals. Although insulin stimulated protein synthesis in fat pads of fasted and 12 day diabetic rats, the absolute change was much smaller than that seen in the fed state. The inhibition of protein degradation by leucine also seems to be less in fasted animals, probably because leucine catabolism is slower in fasting. These results show that fasting and diabetes may improve protein balance in adipose tissue but diminish the regulatory effects of insulin.

Tischler, Marc E.↗
NASA NTRS1986

Reduction-oxidation state and protein degradation in skeletal muscle of fasted and refed rats

Redox state and protein degradation were measured in isolated muscles of fasted (up to 10 d) and refed (up to 4 d) 7- to 14-wk-old rats. Protein degradation in the extensor digitorum longus muscle, but not in the soleus muscle, was greater in the fasted rats than in weight-matched muscle from fed rats. The NAD couple was more oxidized in incubated and fresh extensor digitorum longus muscles and in some incubated soleus muscles of fasted rats than in weight-matched muscle from fed rats. In the extensor digitorum longus muscle of refed or prolonged fasted rats, protein degradation was slower and the NAD couple was more reduced than in the fed state. Therefore, oxidation of the NAD couple was associated with increased muscle breakdown during fasting, whereas reduction of the NAD couple was associated with muscle conservation and deposition.

Fagan, Julie M.↗
NASA NTRS1991

FAST - A multiprocessed environment for visualization of computational fluid dynamics

The paper presents the Flow Analysis Software Toolset (FAST) to be used for fluid-mechanics analysis. The design criteria for FAST including the minimization of the data path in the computational fluid-dynamics (CFD) process, consistent user interface, extensible software architecture, modularization, and the isolation of three-dimensional tasks from the application programmer are outlined. Each separate process communicates through the FAST Hub, while other modules such as FAST Central, NAS file input, CFD calculator, surface extractor and renderer, titler, tracer, and isolev might work together to generate the scene. An interprocess communication package making it possible for FAST to operate as a modular environment where resources could be shared among different machines as well as a single host is discussed.

Bancroft, Gordon V.↗
NASA NTRS1995

Development of Fast Algorithms Using Recursion, Nesting and Iterations for Computational Electromagnetics

In the first phase of our work, we have concentrated on laying the foundation to develop fast algorithms, including the use of recursive structure like the recursive aggregate interaction matrix algorithm (RAIMA), the nested equivalence principle algorithm (NEPAL), the ray-propagation fast multipole algorithm (RPFMA), and the multi-level fast multipole algorithm (MLFMA). We have also investigated the use of curvilinear patches to build a basic method of moments code where these acceleration techniques can be used later. In the second phase, which is mainly reported on here, we have concentrated on implementing three-dimensional NEPAL on a massively parallel machine, the Connection Machine CM-5, and have been able to obtain some 3D scattering results. In order to understand the parallelization of codes on the Connection Machine, we have also studied the parallelization of 3D finite-difference time-domain (FDTD) code with PML material absorbing boundary condition (ABC). We found that simple algorithms like the FDTD with material ABC can be parallelized very well allowing us to solve within a minute a problem of over a million nodes. In addition, we have studied the use of the fast multipole method and the ray-propagation fast multipole algorithm to expedite matrix-vector multiplication in a conjugate-gradient solution to integral equations of scattering. We find that these methods are faster than LU decomposition for one incident angle, but are slower than LU decomposition when many incident angles are needed as in the monostatic RCS calculations.

Chew, W. C.↗
NASA NTRS1995

Transition of slow shocks to fast shocks

As a CME pushes its way through preceding slower solar wind, large disturbances in the interaction region may evolve to form transient MHD shocks. The shocks can be slow shocks in the coronal space but they appear as fast shocks near 1 AU. We use a polytropic MHD model to study the transition of slow shocks to fast shocks in an interaction region sandwiched between a faster solar wind and a slower solar wind near the equatorial plane. The polytropic index controls the radial increase of Beta outside the interaction region. The transition process is attributed chiefly to the increase of Beta and theta to a lesser degree to the radial increase of the shock angle 0. Under the initial condition of small Beta and theta near 0.1 AU, the interaction region evolves to form a pair of slow shocks inside 0.15 AU. As the interaction region convects outward. the increases of B and theta cause a transition of the shock system between 0.15 and 0.3 AU from a slow shock pair to a double shock pair consisting of both slow and fast shocks. As the system moves outward, and Beta continue to increase, the fast shock grows stronger, and the slow shock becomes weaker. Eventually. the slow shocks fade away, and the shock system finally evolves to a pair of fast shocks. Parametric studies of the transition process are carried out for shocks formed over a wide range of disturbances.

Whang, Y. C.↗
NASA NTRS1997

FAST Spacecraft Battery Design and Performance

The Fast Auroral Snapshot (FAST) Explorer spacecraft is to study the physical processes that produce the aurora borealis and aurora australis. It is a unique plasma physics experiment that will take fundamental measurements of the magnetic and electrical fields. This investigation will add significantly to our understanding of the near-earth space environments and its effect. The FAST has a 1 year requirement and 3-year goal for its mission life in low earth orbit. The FAST power power system topology is a Direct Energy Transfer (DET) system based on the SAMPEX design. The FAST flight battery supplies power to the satellite during pre-launch operations, the launch phase, the eclipse periods for all mission phases, and when the load is about 50 watts.

Jung, David S.↗
NASA NTRS1999

FAST Observations of Acceleration Processes in the Cusp--Evidence for Parallel Electric Fields

The existence of precipitating keV ions in the Earth's cusp originating at the magnetosheath provide unique means to test our understanding of particle acceleration and parallel electric fields in the lower altitude acceleration region. On numerous occasions, the FAST (The Fast Auroral Snapshot) spacecraft has encountered the Earth's cusp regions near its apogee of 4175 km which are characterized by their signatures of dispersed keV ion injections. The FAST instruments also reveal a complex microphysics inherent to many, but not all, of the cusp regions encountered by the spacecraft, that include upgoing ion beams and conics, inverted-V electrons, upgoing electron beams, and spikey DC-coupled electric fields and plasma waves. Detailed inspection of the FAST data often show clear modulation of the precipitating magnetosheath ions that indicate that they are affected by local electric potentials. For example, the magnetosheath ion precipitation is sometimes abruptly shut off precisely in regions where downgoing localized inverted-V electrons are observed. Such observations support the existence of a localized process, such as parallel electric fields, above the spacecraft which accelerate the electrons downward and consequently impede the precipitating ion precipitation. Other acceleration events in the cusp are sometimes organized with an apparent cellular structure that suggests Alfven waves or other large-scale phenomena are controlling the localized potentials. We examine several cusp encounters by the FAST satellite where the modulation of energetic session on acceleration particle populations reveals evidence of localized acceleration, most likely by parallel electric fields.

Pfaff, R. F.. Jr.↗
NASA NTRS2000

Discrete and Diffuse Aurora During Varying Activity Levels: Simultaneous Fast and Polar UVI Observations

We examine simultaneous measurements of auroral electron precipitation obtained in-situ by the FAST spacecraft and remotely by Polar Ultraviolet Imagery (UVI) images for activity levels ranging from quiet to storm-time intervals. The incident energy flux measured by FAST and inferred from the UVI images agree well during quiescent periods, particularly in regions of discrete aurora in which the electron precipitation spectra are dominated by the component accelerated by a field-aligned potential. During magnetospheric substorms and active storm periods, such as those following Coronal Mass Ejection (CME) disturbances of the magnetosphere, the energy flux inferred from the UVI images generally exceeds that measured locally by FAST at the same location by as much as an order of magnitude. The auroral electrons during these active periods are dominated by diffuse precipitation which is observed up the to the highest energy channel of FAST (30 keV). These storm-time observations imply that a high energy component above 30 keV not observed by FAST may be contributing significantly to the total energy flux carried by the precipitating electrons. Observations suggest that as magnetospheric activity increases acceleration processes in the magnetosphere and pitch-angle diffusion by wave-particle interactions become more important than the ionospheric acceleration in producing the measured auroral energy fluxes.

Chua, D.↗
NASA NTRS2003

Body water handling in response to hypertonic-saline induced diuresis in fasting northern elephant seal pups (Mirounga angustirostris)

During natural fasting conditions in postweaned northern elephant seal (NES) (Mirounga angustirostris) pups, urinary water loss is minimized and percent total body water (TBW) is maintained constant. However, following infusion of hypertonic saline, glomerular filtration rate (GFR) and urine output increased in fasting pups. Therefore, we quantified the magnitude of the hypernatremia-induced diuresis relative to the animal's total body water (TBW) pool and the percentage of filtered water reabsorbed. Following a 24 h control period, naturally fasting NES pups (n=7) were infused (4 ml min(-1)) with hypertonic saline (16.7%) at a dose of 3 mmol NaCl kg(-1) body mass. Total body water was estimated prior to infusion by tritium dilution, GFR was estimated by standard creatinine clearance, and urine output (V) was measured for 24 h during the control and post infusion periods. Percentage of filtered water reabsorbed was calculated as (1-(V/GFR))x100. Twenty-four hours following the infusion, GFR (control: 69+/-12 ml min(-1) and post-infusion: 118+/-19 ml min(-1); mean+/-S.E.) increased 77+/-28% above control and the percentage of filtered water reabsorbed was decreased 0.4+/-0.1%. The increase in urine output (control: 218+/-47 ml d(-1) and post-infusion: 883+/-92 ml d(-1)) accounted for 1.7+/-0.2% of the pups' TBW. The hypernatremia-induced diuresis was accompanied by the loss of body water indicating the lack of water retention. Although the 77% increase in GFR was only associated with a 0.4% decrease in the percentage of filtered water reabsorbed, this decrease was significant enough to result in a 4-fold increase in urine output. Despite the observed diuresis, fasting NES pups appear to possess an efficient water recycling mechanism requiring only a small percentage of body water to excrete an excess salt load. This water recycling mechanism may allow pups to avoid negative perturbations in body water as they initiate feeding in a marine environment following the fast.

Non-NASA Center↗
NASA NTRS2012

A Fast and Efficient Version of the TwO-Moment Aerosol Sectional (TOMAS) Global Aerosol Microphysics Model

This study develops more computationally efficient versions of the TwO-Moment Aerosol Sectional (TOMAS) microphysics algorithms, collectively called Fast TOMAS. Several methods for speeding up the algorithm were attempted, but only reducing the number of size sections was adopted. Fast TOMAS models, coupled to the GISS GCM II-prime, require a new coagulation algorithm with less restrictive size resolution assumptions but only minor changes in other processes. Fast TOMAS models have been evaluated in a box model against analytical solutions of coagulation and condensation and in a 3-D model against the original TOMAS (TOMAS-30) model. Condensation and coagulation in the Fast TOMAS models agree well with the analytical solution but show slightly more bias than the TOMAS-30 box model. In the 3-D model, errors resulting from decreased size resolution in each process (i.e., emissions, cloud processing wet deposition, microphysics) are quantified in a series of model sensitivity simulations. Errors resulting from lower size resolution in condensation and coagulation, defined as the microphysics error, affect number and mass concentrations by only a few percent. The microphysics error in CN70CN100 (number concentrations of particles larger than 70100 nm diameter), proxies for cloud condensation nuclei, range from 5 to 5 in most regions. The largest errors are associated with decreasing the size resolution in the cloud processing wet deposition calculations, defined as cloud-processing error, and range from 20 to 15 in most regions for CN70CN100 concentrations. Overall, the Fast TOMAS models increase the computational speed by 2 to 3 times with only small numerical errors stemming from condensation and coagulation calculations when compared to TOMAS-30. The faster versions of the TOMAS model allow for the longer, multi-year simulations required to assess aerosol effects on cloud lifetime and precipitation.

Lee, Yunha↗
NASA NTRS2022

A Deep Learning Approach to Fast Radiative Transfer

Due to the sheer volume of data, leveraging satellite instrument observations effectively in a data assimilation context for numerical weather prediction or for remote sensing requires a radiative transfer model as an observation operator that is both fast and accurate at the same time. Physics-based line-by-line radiative transfer (RT) models fulfil the requirement for accuracy, but are too slow and too costly in computational terms for operational applications. Therefore, fast methods were developed to be able to perform fast RT calculations using techniques such as spectral sampling or pre-computed look-up tables. The operational fast models currently calculate the absorption and scattering coefficients from the pre-computed regression coefficients and atmospheric state and cloud profiles. As a novel solution to this problem, this work investigates a deep learning approach to replace the regression coefficients in the fast RT models. A selection of hidden-layer neural network configurations is trained against atmospheric transmittance profile data computed by an accurate line-by-line model and their performance is evaluated and their advantages and disadvantages are discussed.

Machine learning↗
NASA NTRS2022

On the Existence of Fast Modes in Compressible Magnetohydrodynamic Turbulence

We study the existence and properties of fast magnetosonic modes in 3D compressible MHD turbulence by carrying out a number of simulations with compressible and incompressible driving conditions. We use two approaches to determine the presence of fast modes: mode decomposition based on spatial variations only and spatio-temporal 4D fast Fourier transform (4D FFT) analysis of all fluctuations. The latter method enables us to quantify fluctuations that satisfy the dispersion relation of fast modes with finite frequency. Overall, we find that the fraction of fast modes identified via the spatio-temporal 4D FFT approach in total fluctuation power is either tiny with nearly incompressible driving or ∼2% with highly compressible driving. We discuss the implications of our results for understanding the compressible fluctuations in space and astrophysical plasmas.

Zhaoming Gan↗
NASA NTRS1973

Nonlinear interaction of a fast magnetogasdynamic shock with a tangential discontinuity

A basic problem, which is of considerable interest in geoastrophysical applications of magnetogasdynamics, is the nonlinear interaction of a fast shock (S sub f) with a tangential discontinuity (T). The problem is treated for an arbitrary S sub f interacting with an arbitrary T under the assumption that in the frame of reference in which S sub f and T are at rest, the flow is superfast on both sides of T, and that a steady flow develops. As a result of the nonlinear analysis a flow pattern is obtained consisting of the incident discontinuities S sub f 1 and T2 and a transmitted fast shock S sub f 3, the modified tangential discontinuity T4 and a reflected fast shock S sub f 5 or fast rarefaction wave R sub f 5. The results are discussed in terms of seven significant similarity parameters. In addition special cases like changes in magnetic field direction only, changes in desnity or velocity shear only etc. are discussed.

Neubauer, F. M.↗
NASA NTRS1974

Effect of fast neutron, gamma-ray and combined radiations on the thermal decomposition of ammonium perchlorate single crystals

The thermal decomposition kinetics have been determined for ammonium perchlorate crystals subjected to a fast neutron irradiation or to a fast neutron irradiation followed by a gamma-ray irradiation. Qualitatively, the radiation induced changes are similar to those obtained in this and in previous studies, with samples exposed only to gamma rays. The induction period is shortened and the rate constants, obtained from an Avrami-Erofeyev kinetic analysis, are modified. The acceleratory period constant increases and the decay period constant decreases. When compared on an equal deposited energy basis, the fast neutron induced changes are appreciably larger than the gamma-ray induced changes. Some, or all, of the fast neutron induced effects might be attributable to the introduction of localized regions of concentrated radiation damage ('spikes') by lattice atom recoils which become thermal decomposition sites when the crystals are heated.

Herley, P. J.↗