Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Directional Effect”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 757 records · Page 42
All sourcesNASA NTRSDOE OSTI
NASA NTRS2019

Gravity as a Continuum: Effects of Altered Gravity on Drosophila Melanogaster Immunity

The impact of spaceflight on immune function is undoubtedly a critical focus in the area of space biology and human health research. Heat shock proteins (Hsp) are an evolutionarily conserved family of proteins that are expressed in response to cellular and physiological stressors, experienced during radiation exposure, confinement, circadian rhythm disruption, and altered gravity (hypergravity experienced at launch/landing and microgravity experienced in-flight). In particular, Hsp70 aids in the folding of proteins, facilitates the movement of proteins across the membranes during signal transductions and can stimulate innate immunity. Since Hsp70 is induced during cellular stress, and can act as a stimulator for innate immunity, we sought to address how a loss of Hsp70 affects immunity, under the stress-inducing model of acute and chronic hypergravity. Moreover, the effects of gravity as a continuum on the induction of Hsps and key immune genes were also assessed to determine if increased cellular stress, via increased gravity (g)-force, contributes to immune dysfunctions. For this, wildtype (W1118) and Hsp70 deficient (Hsp70null) Drosophila melanogaster were subjected to simulated hypergravity at increasing levels of g-force (1.2g, 3g, and 5g) for acute (1hr) and chronic (7-day) timepoints and were compared to 0g 'non-hypergravity' controls. Following simulation, whole bodies were sex-segregated, RNA was isolated and quantitative (q)PCR was performed to determine differential immune gene expression profiles. Further, functional output of hemocytes were assessed by a phagocytosis assay. Collectively, these studies evaluated the effects of Hsp70 in the context of immunity during acute and chronic hypergravity. Indeed, relevance for this work can directly translate to acute effects of launch/landing gravitational forces upon liftoff (~1.7g) and entry (~3.4g) that astronauts experience. In addition, the effects of chronic cellular stress is directly relevant to the immune health of astronauts on long duration missions, as well. Thus, as we approach the goal of returning to the Moon and landing the first humans on Mars, an evaluation of gravity as a continuum and the stress-inducing effects of altered gravity experienced during spaceflight on astronaut immunity and health are necessary.

Olivieri, Joe↗
NASA NTRS2001

Effects of Minor Alloying Additions on the Microstructure, Toughness, and Creep Strength of Directionally Solidified NiAl-31Cr-3Mo

A study of the effects of small (0.25 to 1.0 at%) fifth element additions to the structure and mechanical properties of directionally solidified (DS) NiAl-31Cr-3Mo has been undertaken. Essentially all the additions changed the as-DS'ed microstructure from lamellar eutectic grains to cells and, in some cases, introduced NiAl dendrites and/or third phases. In general the alloying additions did not improve strength or toughness over that possessed by the base composition; only Hf and, perhaps Ti, gave a minor increase in elevated temperature creep resistance. The lack of improvement in creep properties is probably due to inability to precipitation harden NiAl.

Whittenberger, J. D.↗
NASA NTRS2019

The Effect of Redox Conditions on Seismic Waves in Iron-Bearing Olivine: Implications for Understanding Planetary Interiros Through Seismilogy

Seismic data, inclusive of velocities and attenuation, can be utilized to elucidate the physical state of planetary interiors]. However, numerous micromechanical factors have been either experimentally demonstrated, or theoretically considered, to affect the propagation and dissipation of seismic energy within crystalline solids - including, but not limited to, changes in grain size, temperature, melt fraction, pressure and dislocation density. Thus, observed variations in seismic wave speeds and attenuation may be used to ultimately ‘map’ variations in physical properties, such as those listed above, within planetary bodies. But, in order to complete a successful inversion of seismic data into representations of physical properties, a first requirement is to obtain a fundamental laboratory based understanding of how each of these possible factors individually influences seismic waves. Here we conduct an experimental study with the initial objective to further understand one of the most commonly invoked, yet least studied, mechanisms that could alter intrinsic seismic wave attenuation: water content (occurring as chemically-bound hydroxyl). The historical basis for determining the effect of water on seismic properties was established predominantly through analogy with large-strain creep experiments conducted on olivine under water-saturated conditions. While these deformation experiments routinely demonstrate a weakening of olivine in the presence of water, they represent a fundamentally different deformation regime in comparison to the microstrains experienced due to a passing seismic wave. Thus, in order to directly assess the effects of water on seismic properties, small-strain experiments are required. Substantially modified seismic properties in the presence of water have been observed previously at low strains and low frequencies, but only in a single exploratory study conducted under water-saturated conditions. Thus, to properly test the theoretical predictions we conducted a systematic study of the seismic properties of olivine using low-frequency torsional oscillation on aggregates containing varying concentrations of bound hydroxyl, for the first time at under saturated conditions.

Cline, C. J., II↗
NASA NTRS1999

Propulsion System Airframe Integration Issues and Aerodynamic Database Development for the Hyper-X Flight Research Vehicle

NASA's Hyper-X Research Vehicle will provide a unique opportunity to obtain data on an operational airframe integrated scramjet propulsion system at true flight conditions. The airframe integrated nature of the scramjet engine with the Hyper-X vehicle results in a strong coupling effect between the propulsion system operation and the airframe s basic aerodynamic characteristics. Comments on general airframe integrated scramjet propulsion system effects on vehicle aerodynamic performance, stability, and control are provided, followed by examples specific to the Hyper-X research vehicle. An overview is provided of the current activities associated with the development of the Hyper-X aerodynamic database, including wind tunnel test activities and parallel CFD analysis efforts. A brief summary of the Hyper-X aerodynamic characteristics is provided, including the direct and indirect effects of the airframe integrated scramjet propulsion system operation on the basic airframe stability and control characteristics.

Engelund, Walter C.↗
NASA NTRS2002

Inhibition of the active lymph pump by flow in rat mesenteric lymphatics and thoracic duct

There are only a few reports of the influence of imposed flow on an active lymph pump under conditions of controlled intraluminal pressure. Thus, the mechanisms are not clearly defined. Rat mesenteric lymphatics and thoracic ducts were isolated, cannulated and pressurized. Input and output pressures were adjusted to impose various flows. Lymphatic systolic and diastolic diameters were measured and used to determine contraction frequency and pump flow indices. Imposed flow inhibited the active lymph pump in both mesenteric lymphatics and in the thoracic duct. The active pump of the thoracic duct appeared more sensitive to flow than did the active pump of the mesenteric lymphatics. Imposed flow reduced the frequency and amplitude of the contractions and accordingly the active pump flow. Flow-induced inhibition of the active lymph pump followed two temporal patterns. The first pattern was a rapidly developing inhibition of contraction frequency. Upon imposition of flow, the contraction frequency immediately fell and then partially recovered over time during continued flow. This effect was dependent on the magnitude of imposed flow, but did not depend on the direction of flow. The effect also depended upon the rate of change in the direction of flow. The second pattern was a slowly developing reduction of the amplitude of the lymphatic contractions, which increased over time during continued flow. The inhibition of contraction amplitude was dependent on the direction of the imposed flow, but independent of the magnitude of flow. Nitric oxide was partly but not completely responsible for the influence of flow on the mesenteric lymph pump. Exposure to NO mimicked the effects of flow, and inhibition of the NO synthase by N (G)-monomethyl-L-arginine attenuated but did not completely abolish the effects of flow.

NASA Discipline Musculoskeletal↗
NASA NTRS2022

Light in Ecological Settings: Entrainment, Circadian Disruption, and Interventions

Light is the predominant signal for the human circadian clock to synchronize to the solar 24-h day through an active process called entrainment. Modern light profiles are characterized by exposure to both natural daylight and artificial lighting. A mismatch between these self-selected light profiles and the solar day-night alternation can disrupt the circadian system, resulting in acute and chronic effects for health and safety. In this chapter, we describe (i) how entrainment works in the real world, illustrating the major role of light for this process; (ii) ways in which the circadian system can be disrupted by (external) factors such as irregular sleep, shift work, daylight saving time, and longitudinal position in a time zone; and (iii) how field studies have used light interventions to reduce direct and indirect effects of circadian disruption in ecological settings.

light interventions↗
NASA NTRS1977

The tilt effect for Saturn's rings

Multiple-scattering computations are carried out to explain the variation of the observed brightness of the A and B rings of Saturn with declination of the earth and sun. These computations are performed by a doubling scheme for a homogeneous plane-parallel scattering medium. A range of choices is tested for the phase function, albedo for single scattering, and optical depth of both the rings. Isotropic scattering and several other simple phase functions are ruled out, and it is found that the phase function must be moderately peaked in both the forward and backward directions. The tilt effect can be explained by multiple scattering in a homogeneous layer, but, for ring B, this requires a single-scattering albedo in excess of 0.8. The brightest part of ring B must have an optical depth greater than 0.9. It is found that the tilt effect for ring A can be reproduced by particles having the same properties as those in ring B with the optical depth for the A ring in the range 0.4 to 0.6.

Esposito, L. W.↗
NASA NTRS1988

Space station induced electromagnetic effects

Several mechanisms which can cause electric (E) and magnetic (B) field contaminations of the Space Station environment are identified. The level of E and B fields generated by some of them such as the motion of the vehicle across the ambient magnetic field B(0) and the 20-kHz leakage currents and charges can be controlled by proper design considerations. On the other hand, there are some mechanisms which are inherent to the interaction of large vehicles with the plasma and probably their contributions to E and B fields cannot be controlled; these include plasma waves in the wake and ram directions and the effects of the volume current generated by the ionization of neutrals. The interaction of high-voltage solar arrays with plasma is yet another rich source of E and B fields and it is probably uncontrollable. Wherever possible, quantitative estimates of E and B are given. A set of recommendations is included for further study in areas where indepth knowledge is seriously lacking.

Singh, N.↗
NASA NTRS1993

LDEF Space Plasma-High Voltage Drainage Experiment post-flight results

The Space Plasma-High Voltage Drainage Experiment (SP-HVDE) was comprised of two identical experimental trays. With one tray located on the leading (ram facing, B10) edge and the other located on the trailing (wake facing, D4) edge of the Long Duration Exposure Facility (LDEF), it was possible to directly compare the effects of ram and wake spacecraft environments on charged dielectric materials. Six arrays of Kapton dielectric samples of 2 mil, 3 mil, and 5 mil thicknesses maintained at +/- 300, +/- 500, and +/- 1000 voltage bias formed the experimental matrix of each tray. In addition, each tray carried two solar cell strings, one biased at +300 volts and the other at -300 volts, to study current leakage from High Voltage Solar Arrays (HVSA). The SP-HVDE provides the first direct, long-term, in-flight measurements of average leakage current through dielectric materials under electric stress. The experiment also yields information on the long term stability of the bulk dielectric properties of such materials. Data and findings of the SP-HVDE are an extension of those from shorter term flight experiments such as the PIX-1 (Plasma Interaction Experiment) and PIX-2 and are therefore valuable in the design and evaluation of long-lived space systems with high voltage systems exposed to the low earth orbital environment. A summary of the SP-HVDE post flight analysis final report delivered to the LDEF Project Office under contract to the National Aeronautics and Space Administration is presented.

Yaung, J. Y.↗
NASA NTRS1993

Optical characterization of LDEF contaminant film

Dark brown molecular film deposits were found at numerous locations on the Long Duration Exposure Facility (LDEF) and have been documented in great detail by several investigators. The exact deposition mechanism for these deposits is as yet unknown, although direct and scattered atomic oxygen, and solar radiation interacting with materials outgassing products have all been implicated in the formation process. Specimens of the brown molecular film were taken from below the flange of the experimental tray located at position D10 on the LDEF. The tray was one of two, comprising the same experiment, the other being located on the wake facing side of the LDEF satellite at position B4. Having access to both trays, we were able to directly compare the effect that orientation with respect to the atomic oxygen flux vector had on the formation of the brown molecular film deposits. The film is thickest on surfaces facing toward the exterior, i.e. the tray corner, as can be seen by comparing the lee and wake aspects of the rivets. The patterns appear to be aligned not with the velocity vector but with the corner of the tray suggesting that flux to the surface is due to scattered atomic oxygen rather than direct ram impingement. The role of scattered flux is further supported by more faint plume patterns on the sides of the tray. The angle of these plumes is strongly aligned with the ram direction but the outline of the deposit implies that incident atoms are scattered by collisions with the edges of the opening resulting in a directed, but diffuse, flux of atomic oxygen to the surface. Spectral reflectance measurements in the 2 to 10 micron (4000 to 1000 wavenumbers) spectral range are presented for the film in the 'as deposited' condition and for the free standing film. The material was analyzed by FTIR (Fourier Transform Infrared) microspectroscopy using gold as the reference standard. The 'as deposited' specimen was on an aluminum rivet taken from beneath the tray flange while the free film was obtained by chipping some of the material from the rivet. The transmission spectrum over the 2 to 10 micron range for the free film is presented. This spectrum appears to be essentially the same as that presented by Crutcher et.al. for films formed at vent sites which faced into the ram direction and suggested to originate from urethanes and silicones used on the LDEF. Banks et. al. state that silicones, when exposed to atomic oxygen, release polymeric scission fragments which deposit on surfaces and form a glassy, dark contaminant layer upon further atomic oxygen exposure and solar irradiation.

Blakkolb, Brian K.↗
NASA NTRS2011

East Asian Studies of Tropospheric Aerosols and their Impact on Regional Climate (EAST -AIRC): An overview

As the most populated region of the world, Asia is a major source of aerosols with potential large impact over vast downstream areas, Papers published in this special section describe the variety of aerosols observed in China and their effects and interactions with the regional climate as part of the East Asian Study of Tropospheric Aerosols and their Impact on Regional Climate (EAST-AIRC), The majority of the papers are based on analyses of observations made under three field projects, namely, the Atmospheric Radiation Measurements (ARM) Mobile Facility mission in China (AMF-China), the East Asian Study of Tropospheric Aerosols: An International Regional Experiment (EAST-AIRE), and the Atmospheric Aerosols of China and their Climate Effects (AACCE), The former two are U,S,-China collaborative projects, and the latter is a part of the China's National Basic Research program (or often referred to as "973 project"), Routine meteorological data of China are also employed in some studies, The wealth of general and speCIalized measurements lead to extensive and close-up investigations of the optical, physical, and chemical properties of anthropogenic, natural, and mixed aerosols; their sources, formation, and transport mechanisms; horizontal, vertical, and temporal variations; direct and indirect effects; and interactions with the East Asian monsoon system, Particular efforts are made to advance our understanding of the mixing and interaction between dust and anthropogenic pollutants during transport. Several modeling studies were carried out to simulate aerosol impact on radiation budget, temperature, precipitation, wind and atmospheric circulation, fog, etc, In addition, impacts of the Asian monsoon system on aerosol loading are also simulated.

Zhangqing, Li↗
NASA NTRS1980

An implicit algorithm for the transonic full-potential equation in conservative form

A fast, implicit approximate factorization algorithm for the solution of the conservative full-potential equation for transonic flow in two and three dimensions is presented. Stability in supersonic regions is maintained by the use of an upwind evaluation of the density coefficient along all coordinate directions, providing an effective upwind difference of the streamwise terms for any orientation of the velocity vector and thereby enhancing the reliability of the algorithm. The algorithm is shown to provide rapid convergence for the computation of certain difficult two-dimensional test cases, including cases with fishtail shock patterns, demonstrating the reliability and efficiency of the procedure. Surface pressure coefficient distributions obtained by the present method are also found to be in good agreement with those computed by successive-line overrelaxation and a hybrid direct-solver/successive-line overrelaxation scheme, with significant reductions in CPU time required. A three-dimensional solution for a swept wing mounted between parallel walls is also presented which demonstrates the high convergence rate of the algorithm in three dimensions as well as two.

Holst, T.↗
NASA NTRS1986

Noise radiation directivity from a wind-tunnel inlet with inlet vanes and duct wall linings

The acoustic radiation patterns from a 1/15th scale model of the Ames 80- by 120-Ft Wind Tunnel test section and inlet have been measured with a noise source installed in the test section. Data were acquired without airflow in the duct. Sound-absorbent inlet vanes oriented parallel to each other, or splayed with a variable incidence relative to the duct long axis, were evaluated along with duct wall linings. Results show that splayed vans tend to spread the sound to greater angles than those measured with the open inlet. Parallel vanes narrowed the high-frequency radiation pattern. Duct wall linings had a strong effect on acoustic directivity by attenuating wall reflections. Vane insertion loss was measured. Directivity results are compared with existing data from square ducts. Two prediction methods for duct radiation directivity are described: one is an empirical method based on the test data, and the other is a analytical method based on ray acoustics.

Soderman, P. T.↗
NASA NTRS1987

Ductility and fracture in B2 FeAl alloys

The mechanical behavior of B2FeAl alloys was studied. Stoichiometric Fe-50Al exhibits totally brittle behavior while iron-rich Fe-40Al yields and displays about 3% total strain. This change in behavior results from large decreases in the yield strength with iron-rich deviations from stoichiometry while the fracture stress remains essentially constant. Single crystal studies show that these yield strength decreases are directly related to decreases in the critical resolved shear stress for a group of zone axes /111/ set of (110) planes slip. This behavior is rationalized in terms of the decrease in antiphase boundary energy with decreasing aluminum content. The addition of boron results in improvements in the mechanical behavior of alloys on the iron-rich side of stoichiometry. These improvements are increased brittle fracture stresses of near-stoichiometric alloys, and enhanced ductility of up to 6% in Fe-40Al. These effects were attributed to increased grain boundary adhesion as reflected by changes in fracture mode from intergranular to transgranular failure. The increases in yield strength, which are observed in both polycrystals and single crystals, result from the quenching in of large numbers of thermal vacancies. Hall-Petch plots show that the cooling rate effects are a direct result of changes in the Hall-Petch intercept/lattice resistance flow.

Crimp, Martin A.↗
NASA NTRS2018

Recent Developments in the Code RITRACKS (Relativistic Ion Tracks)

The code RITRACKS (Relativistic Ion Tracks) was developed to simulate detailed stochastic radiation track structures of ions of different types and energies. Many new capabilities were added to the code during the recent years. Several options were added to specify the times at which the tracks appear in the irradiated volume, allowing the simulation of dose-rate effects. The code has been used to simulate energy deposition in several targets: spherical, ellipsoidal and cylindrical. More recently, density changes as well as a spherical shell were implemented for spherical targets, in order to simulate energy deposition in walled tissue equivalent proportional counters. RITRACKS is used as a part of the new program BDSTracks (Biological Damage by Stochastic Tracks) to simulate several types of chromosome aberrations in various irradiation conditions. The simulation of damage to various DNA structures (linear and chromatin fiber) by direct and indirect effects has been improved and is ongoing. Many improvements were also made to the graphic user interface (GUI), including the addition of several labels allowing changes of units. A new GUI has been added to display the electron ejection vectors. The parallel calculation capabilities, notably the pre- and post-simulation processing on Windows and Linux machines have been reviewed to make them more portable between different systems. The calculation part is currently maintained in an Atlassian Stash® repository for code tracking and possibly future collaboration.

Plante, Ianik↗
NASA NTRS2008

Initial Results from the Variable Intensity Sonic Boom Propagation Database

An extensive sonic boom propagation database with low- to normal-intensity booms (overpressures of 0.08 lbf/sq ft to 2.20 lbf/sq ft) was collected for propagation code validation, and initial results and flight research techniques are presented. Several arrays of microphones were used, including a 10 m tall tower to measure shock wave directionality and the effect of height above ground on acoustic level. A sailplane was employed to measure sonic booms above and within the atmospheric turbulent boundary layer, and the sailplane was positioned to intercept the shock waves between the supersonic airplane and the ground sensors. Sailplane and ground-level sonic boom recordings were used to generate atmospheric turbulence filter functions showing excellent agreement with ground measurements. The sonic boom prediction software PCBoom4 was employed as a preflight planning tool using preflight weather data. The measured data of shock wave directionality, arrival time, and overpressure gave excellent agreement with the PCBoom4-calculated results using the measured aircraft and atmospheric data as inputs. C-weighted acoustic levels generally decreased with increasing height above the ground. A-weighted and perceived levels usually were at a minimum for a height where the elevated microphone pressure rise time history was the straightest, which is a result of incident and ground-reflected shock waves interacting.

Haering, Edward A., Jr.↗
NASA NTRS1980

Aero-optical characterization of aircraft optical turrets by holography, interferometry and shadowgraph

Density variations in the aircraft boundary layer, turret wakes and shock waves create distortion of an optical wavefront through associated refractive index variations. Such effects can be observed directly through optical flow visualization. The application of holographic interferometry, wave shearing interferometry, and laser shadowgraph to observe and quantify such effects is described. Examples of the results from five different wind tunnel tests are presented. The examples show that diagnostics have provided valuable qualitiative and quantitiative data. These include (1) wake dimensions, (2) optical strength of the flow field, (3) turbulence characterization, (4) shock location, and (5) direct observation of areo-optical effects.

Trolinger, J. D.↗
NASA NTRS2009

Case Studies of Aerosol Remote Sensing in the Vicinity of Clouds

Studying the spatial variability of aerosol properties in the vicinity of clouds is essential to our ability to determine aerosol direct and indirect effects on climate. In this paper, we describe aerosol observations collected near cloud edges by an airborne Sun photometer over dark ocean waters. Focusing on case studies of aerosol measurements near eight cloud edges within a dissipating stratiform cloud deck, we compare the airborne Sun photometer observations to retrievals of aerosol properties using the standard Moderate Resolution Imaging Spectroradiometer (MODIS) aerosol algorithm applied to 500-m-resolution MODIS spectral reflectances. We find a persistent, spectrally neutral increase in the Sun photometer-derived aerosol optical depth (AOD) of up to 10% (0.015) in the 2-km distances closest to the edges of several distinct clouds. At midvisible wavelengths, the MODIS AOD retrievals show similar increases toward cloud edges, although a larger increase in AOD is found in the MODIS along-scan direction. At shortwave infrared (SWIR) wavelengths (1240-2130 nm), the MODIS-derived AOD increases near cloud edges are of the order of 0.03 and as such three times as large as the Sun photometer-derived values. Hence, in contrast to recently discussed bluing of aerosols near cloud edges, i.e., a preferential apparent increase in the visible reflectances of clear-sky pixels due to 3-D radiative transfer effects in the vicinity of clouds, we find a reddening of aerosols in the MODIS 500-m-resolution aerosol retrievals near clouds. This reddening in our study can be traced to larger absolute increases in SWIR reflectances when compared to visible reflectances near clouds, which in turn seem to stem from larger electronic cross talk in the MODIS SWIR bands (5-7). We note that the lack of bluing in our MODIS observations is likely due to the small geometric and optical thicknesses of the clouds considered.

Redemann, Jens↗