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At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Baroclinic instability with variable static stability - A design study for a spherical atmospheric model experiment

The effect of a radially-variable, dielectric body force, analogous to gravity on baroclinic instability for the design of a spherical, synoptic-scale, atmospheric model experiment in a Spacelab flight is investigated. Exact solutions are examined for quasi-geostrophic baroclinic instability in which the rotational Froude number is a linear function of the height. Flow in a rotating rectilinear channel with a vertically variable body force without horizontal shear of the basic state is also discussed.

Giere, A. C.↗
DOE OSTI2015

The nutrition transition in Colombia over a decade: a novel household classification system of anthropometric measures

Background: Overweight and underweight increase the risk of metabolic impairments and chronic disease. Interventions at the household level require the diagnosis of nutritional status among family members. The aim of this study was to describe the prevalence and patterns of various anthropometric typologies over a decade in Colombia using a novel approach that considers all children in the household as well as the mother. This approach also allows identifying a dual burden of malnutrition within a household, where one child may be overweight and another one undernourished. Methods: This study used data from the Demographic and Health Survey and the Colombian National Nutrition Survey [2000 n = 2,876, 2005 n = 8,598, and 2010 n = 11,349]. Four mutually exclusive household (HH) anthropometric typologies - normal, undernourished, overweight/obese, and dual burden - were created. Anthropometric information of height-for-age Z-scores (HAZ) and body-mass-index-forage Z-scores (BMIz) in children under the age of 5 y, and on body mass index (BMI) in mothers, 18–49 y was used. Results: Prevalence of overweight/obese HHs increased between 2000 (38.2%) and 2010 (43.1%) (p < 0.05), while undernourished and dual burden HHs significantly decreased between 2005 (13.7% and 10.6%, respectively) and 2010 (3.5% and 5.1%, respectively) (p < 0.05). A greater increase of overweight/obesity was observed for the lowest quintile of wealth index (WI), with an increase of almost 10% between 2000 and 2010, compared to 2% and 4% for the fourth and highest WI, respectively. Although in 2010 there is still a higher prevalence of overweight/obesity HHs in urban areas (43.7%), the prevalence of overweight/obesity HHs in rural areas increased sharply between 2000 (34.3%) and 2010 (41.6%) (p < 0.05). Conclusion: The observed prevalence of dual burden households was not different from the expected prevalence. Results from this study indicate that although overweight/obesity continues to be more prevalent among high-income Colombian households, it is growing at a faster pace among the most economically disadvantaged.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

Characterization and Development of the Male Shoulder Shield in an Introduced Wild Pig Population

A sample of 721 males from an introduced wild pig population in western South Carolina was examined to better describe the unique structure known as the shoulder shield in this species. The shield initially developed as early as 9-12 months of age, and then increased to be found in all adults (36 months of age or older). Growth of the structure began in the central lateral shoulder region and increased to cover an area extending from the posterior neck back to the anterior hips, and from the middorsum down to the proximal margin of the exposed portion of the front leg. The shield dimensions (i.e., length, height and thickness) increased with age, physical size, and body mass of the boar. The thickness varied seasonally, being greatest during the annual peak of conception. The thickness was also positively correlated with the animal’s body condition, implying a potential for a nutritional influence affecting that dimension, and possibly also an energy storage function. Injuries indicative of male-male fighting were primarily found on portions of the body covered by the shield. This corroborates the function of this structure as being protective in such male-male aggressive encounters in this species.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1988

Hypersonic, stratified gas flows past an obstacle - Direct simulation Monte Carlo calculations

Monte Carlo particle dynamics are presently used to study the interaction of a stratified gas that impinges hypersonically on a solid body, whose size is comparable to the gas scale height. Attention is given to the results of these computations for two representative cases, where the obstacle adopted is a short, uniform cylindrical pipe whose upstream end is fully open, facing directly into the flow, while the downstream end is covered by a flat circular endplate containing an 'orifice' at its center. The cases are those of a completely closed and a fully open orifice; together, these bound the full range of obstructed hypersonic, stratified gas flows of interest.

Roberts, William W., Jr.↗
NASA NTRSDate not supplied

Lunar Surface Crater Thermal Effects on Lander Radiator Performance

Lunar surface craters smaller than the spatial resolution of surface meshes used in typical Lunar surface thermal models (10 to 60 meters per pixel) may impact the accuracy of thermal model extrema predictions. The goal of this study is to investigate the thermal sensitivity of representative lander systems with realistic thermal surface orientations in bare and cratered terrain environments at relevant Artemis mission locations. This thermal analysis task investigates the impact of lunar surface craters on lander radiator performance by comparing heat rejection capability results between bare and cratered terrain environments. This study examines external body-mounted lander radiator thermal performance across varying lander heights (5.5m, 20m, 50m) and radiator orientations (horizontal, 45º tilted, and vertical) at two representative Artemis mission latitudes (-89.5ºS and -82.5ºS), spanning from the Shackleton Connecting Ridge to Mons Mouton Plateau.

Lunar Surface↗
NASA NTRS2016

Bubbles on Enceladus

Saturn’s icy moon, Enceladus, ejects frozen particles consisting of water and salts indicative of a subsurface ocean. Believed to originate from hydrothermal reactions near the core, the subsequent pressure drop generates boiling liquids that erupt and expand out of the tiger stripes. The purpose of this research is to simulate the ongoing geyser activity of Enceladus in the lab and to explore the concentrations of biomass which could exist in geyser bubbles as compared to ejected particles. We tested variance of intensity of light absorbed from the bubbles at different heights of the simulated plume. Anazodye, Allura Red, is a complex organic that will act as a tracer molecule allowing for quantitative analysis of light absorption through a spectrophotometer. Theazodye in combination with water is ejected from a water chamber using compressed air to simulate bubbles forming and a jet erupting from a body of water. Samples were taken of the bubbles at varying heights of the simulated plume as analogs to the Enceladus geysers. This research will provide quantitative analog information on rising bubbles from the ocean of Enceladus which can be applied directly to the practical concern of measuring biomass in the plume.

tiger stripes↗
NASA NTRS2001

Lumbar spine disc height and curvature responses to an axial load generated by a compression device compatible with magnetic resonance imaging

STUDY DESIGN: Axial load-dependent changes in the lumbar spine of supine healthy volunteers were examined using a compression device compatible with magnetic resonance imaging. OBJECTIVE: To test two hypotheses: Axial loading of 50% body weight from shoulder to feet in supine posture 1) simulates the upright lumbar spine alignment and 2) decreases disc height significantly. SUMMARY OF BACKGROUND DATA: Axial compression on the lumbar spine has significantly narrowed the lumbar dural sac in patients with sciatica, neurogenic claudication or both. METHODS: Using a device compatible with magnetic resonance imaging, the lumbar spine of eight young volunteers, ages 22 to 36 years, was axially compressed with a force equivalent to 50% of body weight, approximating the normal load on the lumbar spine in upright posture. Sagittal lumbar magnetic resonance imaging was performed to measure intervertebral angle and disc height before and during compression. RESULTS: Each intervertebral angle before and during compression was as follows: T12-L1 (-0.8 degrees +/- 2.5 degrees and -1.5 degrees +/- 2.6 degrees ), L1-L2 (0.7 degrees +/- 1.4 degrees and 3.3 degrees +/- 2.9 degrees ), L2-L3 (4.7 degrees +/- 3.5 degrees and 7.3 degrees +/- 6 degrees ), L3-L4 (7.9 degrees +/- 2.4 degrees and 11.1 degrees +/- 4.6 degrees ), L4-L5 (14.3 degrees +/- 3.3 degrees and 14.9 degrees +/- 1.7 degrees ), L5-S1 (25.8 degrees +/- 5.2 degrees and 20.8 degrees +/- 6 degrees ), and L1-S1 (53.4 degrees +/- 11.9 degrees and 57.3 degrees +/- 16.7 degrees ). Negative values reflect kyphosis, and positive values reflect lordosis. A significant difference between values before and during compression was obtained at L3-L4 and L5-S1. There was a significant decrease in disc height only at L4-L5 during compression. CONCLUSIONS: The axial force of 50% body weight in supine posture simulates the upright lumbar spine morphologically. No change in intervertebral angle occurred at L4-L5. However, disc height at L4-L5 decreased significantly during compression.

Non-NASA Center↗
NASA NTRS1939

Resistance of Transparent Plastics to Impact

The problem of developing a windshield for aircraft which will withstand the effect of bird impacts during flight is a difficult one, as an estimate of the striking energy will indicate. If the average speed of the airplane is considered to be about 200 miles per hour and that of the bird about 70 miles per hour, the speed of the bird relative to the airplane may be as great as 400 feet per second. If a 4-pound bird is involved, a maximum impact energy of approximately 10,000 foot-pounds must be dissipated. To obtain this energy in a drop test in the Washington Monument, it would be necessary to drop a 20-pound weight down the 500-foot shaft. For both theoretical and practical reasons, it is necessary to keep the mass and speed more nearly like those to be encountered. However, to get an impact of about 10,000 foot-pounds with a 4-pound falling body, it would be necessary to drop it from a height of approximately one-half mile, neglecting air resistance. These facts will indicate some of the experimental obstacles in the way of simulating bird impacts against aircraft windshields.

Axilrod, Benjamin M↗
NASA NTRS1982

Response Characteristics of a Linear Rotorcraft Vibration Model

A fully coupled vibration model, consisting of a rotor with only flapping degrees of freedom plus pylon and fuselage pitching motion, was used in a parametric study undertaken to investigate the response characteristics of a simplified helicopter. Among the parameters studied were uncoupled body frequency, blade stiffness, hinge offset, advance ratio, and mast height. Results from the harmonic balance solution of the equations of motion show how each of these quantities affects the response of the model. The results also indicate that there is a potential for reducing vibration response through the judicious definition of the design parameters.

Kunz, Donald L.↗
NASA NTRS2009

Preliminary Results of the Effect of Spinal Elongation in Microgravity on Seated Height

The Constellation Program is designing a new vehicle for future space travel to the International Space Station and to the Moon and beyond. One major accommodation and design issue that needs to be addressed with the current seat layout design is spinal elongation. Spinal elongation is the spinal growth that occurs due to straightening of the spinal curve and expansion of the inter-verbal discs in microgravity. Spinal elongation is critical to the design of the seats, seat layout, suit fit, and crew accommodation because of the implications it can have on the a safe return of the crewmembers or during the mission. Inadequate clearance between crewmembers and/or between crewmember hardware interfaces may potentially result in injury during the mission or upon returning to earth. Therefore, design requirements need to be determined that will allow for the elongation of the spine. The current requirement as specified in the Human Systems Integration Requirement (HSIR) document states that a 3% increase in standing height must be accommodated. However, it cannot be assumed that the amount of standing height growth is equivalent to the amount of spinal elongation because of the variation in body proportions between the lower body and torso. Thus, the purpose of this study was to determine the amount of spinal elongation for a seated posture for 6 Shuttle and 7 ISS missions. Crewmembers seated heights were collected before, during, and after spaceflight to determine the change in seated height and the amount of spinal growth that occurs due to microgravity. The changes in seated height will provide the designers with a design requirement that will allow for change in spinal growth for a seated posture. Preliminary results have shown that increase in seated height is greater than the 3% increase currently stated in the requirement.

Rajulu, Sudhakar↗
NASA NTRS1986

Lidar measurements of thermal structure

Rayleigh backscatter observations at 532 nm and 355 nm of relative atmospheric density above Aberystwyth on a total of 93 nights between Dec. 1982 and Feb. 1985 were used to derive the height variation of temperature in the upper stratosphere and mesosphere. Preliminary results for height up to about 25 km were also obtained from observations of Raman backscattering from nitrogen molecules. Comparisons were carried out for stratospheric heights with satellite borne measurements; good agreement was found between equivalent black body temperatures derived from the lidar observations and those obtained from nadir measurements in three channels of the stratosphere sounder units on NOAA satellites; the lidar based atmospheric temperatures have shown general agreement with but a greater degree of structure than the limb sounding measurements obtained using the SAMS experiment on the NOAA-7 satellite. In summer, stratospheric and mesospheric temperatures showed a smooth height variation similar to that of the CIRA model atmosphere. In contrast, the winter data showed a great variability with height, and marked temperature changes both from night to night and within a given night.

Jenkins, D. B.↗
NASA NTRS2002

Solar particle event organ doses and dose equivalents for interplanetary crews: variations due to body size

Proper assessments of spacecraft shielding requirements and concomitant estimates of risk to critical body organs of spacecraft crews from energetic space radiation require accurate, quantitative methods of characterizing the compositional changes in these radiation fields as they pass through the spacecraft and overlying tissue. When estimating astronaut radiation organ doses and dose equivalents it is customary to use the Computerized Anatomical Man (CAM) model of human geometry to account for body self-shielding. Usually, the distribution for the 50th percentile man (175 cm height; 70 kg mass) is used. Most male members of the U.S. astronaut corps are taller and nearly all have heights that deviate from the 175 cm mean. In this work, estimates of critical organ doses and dose equivalents for interplanetary crews exposed to an event similar to the October 1989 solar particle event are presented for male body sizes that vary from the 5th to the 95th percentiles. Overall the results suggest that calculations of organ dose and dose equivalent may vary by as much as approximately 15% as body size is varied from the 5th to the 95th percentile in the population used to derive the CAM model data. c2002 Published by Elsevier Science Ltd on behalf of COSPAR.

NASA Discipline Radiation Health↗
NASA NTRS2003

Gender not a factor for altitude decompression sickness risk

INTRODUCTION: Early, retrospective reports of the incidence of altitude decompression sickness (DCS) during altitude chamber training exposures indicated that women were more susceptible than men. We hypothesized that a controlled, prospective study would show no significant difference. METHODS: We conducted 25 altitude chamber decompression exposure profiles. A total of 291 human subjects, 197 men and 94 women, underwent 961 exposures to simulated altitude for up to 8 h, using zero to 4 h of preoxygenation. Throughout the exposures, subjects breathed 100% oxygen, rested or performed mild or strenuous exercise, and were monitored for precordial venous gas emboli (VGE) and DCS symptoms. RESULTS: No significant differences in DCS incidence were observed between men (49.5%) and women (45.3%). However, VGE occurred at significantly higher rates among men than women under the same exposure conditions, 69.3% and 55.0% respectively. Women using hormonal contraception showed significantly greater susceptibility to DCS than those not using hormonal contraception during the latter two weeks of the menstrual cycle. Significantly higher DCS incidence was observed in the heaviest men, in women with the highest body fat, and in subjects with the highest body mass indices and lowest levels of fitness. CONCLUSION: No differences in altitude DCS incidence were observed between the sexes under our test conditions, although men developed VGE more often than women. Age and height showed no significant influence on DCS incidence, but persons of either sex with higher body mass index and lower physical fitness developed DCS more frequently.

NASA Discipline Environmental Health↗
NASA NTRS2002

From Milk to Bones, Moving Calcium Through the Body: Calcium Kinetics During Space Flight

Did you know that when astronauts are in space, their height increases about two inches? This happens because the weightlessness of space allows the spine, usually compressed in Earth's gravity, to expand. While this change is relatively harmless, other more serious things can happen with extended stays in weightlessness, notably bone loss. From previous experiments, scientists have observed that astronauts lose bone mass at a rate of about one percent per month during flight. Scientists know that bone is a dynamic tissue - continually being made and repaired by specialized bone cells throughout life. Certain cells produce new bone, while other cells are responsible for removing and replacing old bone. Research on the mechanisms of bone metabolism and the effects of space flight on its formation and repair are part of the exciting studies that will be performed during STS-107. Calcium plays a central role because 1) it gives strength and structure to bone and 2) all types of cells require it to function normally. Ninety-nine percent of calcium in the body is stored in the skeleton. However, calcium may be released, or resorbed, from bone to provide for other tissues when you are not eating. To better understand how and why weightlessness induces bone loss, astronauts will participate in a study of calcium kinetics - that is, the movement of calcium through the body, including absorption from food, and its role in the formation and breakdown of bone.

Scott Smith↗
DOE OSTI2015

A mathematical model of the passage of an asteroid-comet body through the Earth’s atmosphere

In the paper, a mathematical model and a numerical algorithm are proposed for modeling the complex of phenomena which accompany the passage of a friable asteroid-comet body through the Earth’s atmosphere: the material ablation, the dissociation of molecules, and the radiation. The proposed model is constructed on the basis of the Navier-Stokes equations for viscous heat-conducting gas with an additional equation for the motion and propagation of a friable lumpy-dust material in air. The energy equation is modified for the relation between two its kinds: the usual energy of the translation of molecules (which defines the temperature and pressure) and the combined energy of their rotation, oscillation, electronic excitation, dissociation, and radiation. For the mathematical model of atmosphere, the distribution of density, pressure, and temperature in height is taken as for the standard atmosphere. An asteroid-comet body is taken initially as a round body consisting of a friable lumpy-dust material with corresponding density and significant viscosity which far exceed those for the atmosphere gas. A numerical algorithm is proposed for solving the initial-boundary problem for the extended system of Navier-Stokes equations. The algorithm is the combination of the semi-Lagrangian approximation for Lagrange transport derivatives and the conforming finite element method for other terms. The implementation of these approaches is illustrated by a numerical example.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS2002

Computational Modeling of Vortex Generators for Turbomachinery

In this work computational models were developed and used to investigate applications of vortex generators (VGs) to turbomachinery. The work was aimed at increasing the efficiency of compressor components designed for the NASA Ultra Efficient Engine Technology (UEET) program. Initial calculations were used to investigate the physical behavior of VGs. A parametric study of the effects of VG height was done using 3-D calculations of isolated VGs. A body force model was developed to simulate the effects of VGs without requiring complicated grids. The model was calibrated using 2-D calculations of the VG vanes and was validated using the 3-D results. Then three applications of VGs to a compressor rotor and stator were investigated: 1) The results of the 3-D calculations were used to simulate the use of small casing VGs used to generate rotor preswirl or counterswirl. Computed performance maps were used to evaluate the effects of VGs. 2) The body force model was used to simulate large part-span splitters on the casing ahead of the stator. Computed loss buckets showed the effects of the VGs. 3) The body force model was also used to investigate the use of tiny VGs on the stator suction surface for controlling secondary flows. Near-surface particle traces and exit loss profiles were used to evaluate the effects of the VGs.

Chima, R. V.↗
NASA NTRS2023

Understanding Volume Estimation Uncertainty of Lakes and Wetlands Using Satellites and Citizen Science

We studied variations in the volume of water stored in small lakes and wetlands using satellite remote sensing and lake water height data contributed by citizen scientists. A total of 94 water bodies across the globe were studied using satellite data in the optical and microwave wavelengths from Landsat 8, Sentinel-1, and Sentinel-2. The uncertainty in volume estimation as a function of geography and geophysical factors, such as cloud cover, precipitation, and water surface temperature, was studied. The key finding that emerged from this global study is that uncertainty is highest in regions with a distinct precipitation season, such as in the monsoon dominated South Asia or the Pacific Northwestern region of the USA. This uncertainty is further compounded when small lakes and wetlands are seasonal with alternating land use as a water body and agricultural land, such as the wetlands of Northeastern Bangladesh. On an average, 45% of studied lakes could be estimated of their volume change with a statistical significant uncertainty that is less than the expected volume in South Asia. In North America, this statistically significant uncertainty in volume estimation was found to be around 50% in lakes eastward of the 108th meridian with lowest uncertainty found in lakes along the East coast of the USA. The article provides a baseline for understanding the current state of the art in estimating volumetric change of lakes and wetlands using citizen science in anticipation of the recently launched Surface Water and Ocean Topography Mission.

Shahzaib Khan↗
NASA NTRS2023

Increasing the Payload Capacity of Soft Robot Arms by Localized Stiffening

Soft robot arms offer safety and adaptability due to their passive compliance, but this compliance typically limits their payload capacity and prevents them from performing many tasks. This paper presents a model-based design approach to effectively increase the payload capacity of soft robot arms. The proposed approach uses localized body stiffening to decrease the compliance at the end effector without sacrificing the robot’s range of motion. This approach is validated on both a simulated and a real soft robot arm, where experiments show that increasing the stiffness of localized regions of their bodies reduces the compliance at the end effector and increases the height to which the arm can lift a payload. By increasing the payload capacity of soft robot arms, this approach has the potential to improve their efficacy in a variety of tasks including object manipulation and exploration of cluttered environments.

Daniel Bruder↗