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  • 1
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    Peripheral vascular responses to heat stress after hindlimb suspension (2002)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: PURPOSE: The purpose of this study was to determine whether hindlimb suspension (which simulates the effects of microgravity) results in impaired hemodynamic responses to heat stress or alterations in mesenteric small artery sympathetic nerve innervation. METHODS: Over 28 d, 16 male Sprague-Dawley rats were hindlimb-suspended, and 13 control rats were housed in the same type of cage. After the treatment, mean arterial pressure (MAP), colonic temperature (Tcol), and superior mesenteric and iliac artery resistances (using Doppler flowmetry) were measured during heat stress [exposure to 42 degrees C until the endpoint of 80 mm Hg blood pressure was reached (75 +/- 9 min); endpoint Tcore = 43.6 +/- 0.2] while rats were anesthetized (sodium pentobarbital, 50 mg x kg(-1) BW). RESULTS: Hindlimb-suspended and control rats exhibited similar increases in Tcol, MAP, and superior mesenteric artery resistance, and similar decreases in iliac resistance during heat stress (endpoint was a fall in MAP below 80 mm Hg). Tyrosine hydroxylase immunostaining indicated similar sympathetic nerve innervation in small mesenteric arteries from both groups. CONCLUSION: Hindlimb suspension does not alter the hemodynamic or thermoregulatory responses to heat stress in the anesthetized rat or mesenteric sympathetic nerve innervation, suggesting that this sympathetic pathway is intact.
    Keywords: Aerospace Medicine
    Type: Medicine and science in sports and exercise (ISSN 0195-9131); Volume 34; 7; 1120-5
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  • 2
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    Design and Development of an Optical Path Difference Scan Mechanism for Fourier Transform Spectrometers using High Displacement RAINBOW Actuators (1997)
    In:  CASI
    Details
    Publication Date: 2018-06-05
    Description: A new piezoelectric drive mechanism has been developed for optical translation in space-based spectrometer systems. The mechanism utilizes a stack of RAINBOW high displacement piezoelectric actuators to move optical components weighing less than 250 grams through a one centimeter travel. The mechanism uses the direct motion of the piezoelectric devices, stacked such that the displacement of the individual RAINBOW actuators is additive. A prototype device has been built which utilizes 21 RAINBOWs to accomplish the necessary travel. The mechanism weighs approximately 0.6 kilograms and uses less than 2 Watts of power at a scanning frequency of 0.5 Hertz, significantly less power than that required by state-of-the-art motor systems.
    Keywords: Solid-State Physics
    Format: application/pdf
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  • 3
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    The ASAC Air Carrier Investment Model (Second Generation) (1997)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: To meet its objective of assisting the U.S. aviation industry with the technological challenges of the future, NASA must identify research areas that have the greatest potential for improving the operation of the air transportation system. To accomplish this, NASA is building an Aviation System Analysis Capability (ASAC). The ASAC differs from previous NASA modeling efforts in that the economic behavior of buyers and sellers in the air transportation and aviation industries is central to its conception. To link the economics of flight with the technology of flight, ASAC requires a parametrically based mode with extensions that link airline operations and investments in aircraft with aircraft characteristics. This model also must provide a mechanism for incorporating air travel demand and profitability factors into the airlines' investment decisions. Finally, the model must be flexible and capable of being incorporated into a wide-ranging suite of economic and technical models that are envisioned for ASAC. We describe a second-generation Air Carrier Investment Model that meets these requirements. The enhanced model incorporates econometric results from the supply and demand curves faced by U.S.-scheduled passenger air carriers. It uses detailed information about their fleets in 1995 to make predictions about future aircraft purchases. It enables analysts with the ability to project revenue passenger-miles flown, airline industry employment, airline operating profit margins, numbers and types of aircraft in the fleet, and changes in aircraft manufacturing employment under various user-defined scenarios.
    Keywords: Aeronautics (General)
    Type: NASA-CR-201678 , LMI-NS602T1 , NAS 1.26:201678
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  • 4
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    20-HETE pathway antagonists inhibit rat small mesenteric artery tone (2002)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: No abstract available
    Keywords: Life Sciences (General)
    Type: Microvascular research (ISSN 0026-2862); 64; 2; 349-352
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  • 5
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    Comparison of Direct Acoustic Impingement of Avionics Equipment to Vibration Base Shake Response (2017)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: No abstract available
    Keywords: Acoustics; Spacecraft Instrumentation and Astrionics
    Type: M17-6075 , Spacecraft and Launch Vehicle Dynamic Environments Workshop (SCLV 2017); Jun 20, 2017 - Jun 22, 2017; El Segundo, CA; United States
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  • 6
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    Dynamic Impact Tolerance of Shuttle RCC Leading Edge Panels using LS-DYNA (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: This paper describes a research program conducted to enable accurate prediction of the impact tolerance of the shuttle Orbiter leading-edge wing panels using 'physics-based- codes such as LS-DYNA, a nonlinear, explicit transient dynamic finite element code. The shuttle leading-edge panels are constructed of Reinforced-Carbon-Carbon (RCC) composite material, which issued because of its thermal properties to protect the shuttle during re-entry into the Earth's atmosphere. Accurate predictions of impact damage from insulating foam and other debris strikes that occur during launch required materials characterization of expected debris, including strain-rate effects. First, analytical models of individual foam and RCC materials were validated. Next, analytical models of individual foam cylinders impacting 6-in. x 6-in. RCC flat plates were developed and validated. LS-DYNA pre-test models of the RCC flat plate specimens established the impact velocity of the test for three damage levels: no-detectable damage, non-destructive evaluation (NDE) detectable damage, or visible damage such as a through crack or hole. Finally, the threshold of impact damage for RCC on representative Orbiter wing panels was predicted for both a small through crack and for NDE-detectable damage.
    Keywords: Space Transportation and Safety
    Format: application/pdf
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  • 7
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    Application of Probability Methods to Assess Crash Modeling Uncertainty (2007)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: Full-scale aircraft crash simulations performed with nonlinear, transient dynamic, finite element codes can incorporate structural complexities such as: geometrically accurate models; human occupant models; and advanced material models to include nonlinear stress-strain behaviors, and material failure. Validation of these crash simulations is difficult due to a lack of sufficient information to adequately determine the uncertainty in the experimental data and the appropriateness of modeling assumptions. This paper evaluates probabilistic approaches to quantify the effects of finite element modeling assumptions on the predicted responses. The vertical drop test of a Fokker F28 fuselage section will be the focus of this paper. The results of a probabilistic analysis using finite element simulations will be compared with experimental data.
    Keywords: Air Transportation and Safety
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  • 8
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    Sand Impact Tests of a Half-Scale Crew Module Boilerplate Test Article (2012)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: Although the Orion Multi-Purpose Crew Vehicle (MPCV) is being designed primarily for water landings, a further investigation of launch abort scenarios reveals the possibility of an onshore landing at Kennedy Space Center (KSC). To gather data for correlation against simulations of beach landing impacts, a series of sand impact tests were conducted at NASA Langley Research Center (LaRC). Both vertical drop tests and swing tests with combined vertical and horizontal velocity were performed onto beds of common construction-grade sand using a geometrically scaled crew module boilerplate test article. The tests were simulated using the explicit, nonlinear, transient dynamic finite element code LS-DYNA. The material models for the sand utilized in the simulations were based on tests of sand specimens. Although the LSDYNA models provided reasonable predictions for peak accelerations, they were not always able to track the response through the duration of the impact. Further improvements to the material model used for the sand were identified based on results from the sand specimen tests.
    Keywords: Spacecraft Design, Testing and Performance
    Type: NF1676L-13352 , ASCE Earth and Space 2012 Conference; Apr 15, 2012 - Apr 18, 2012; Pasadena, CA; United States
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  • 9
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    Application of Probability Methods to Assess Crash Modeling Uncertainty (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Full-scale aircraft crash simulations performed with nonlinear, transient dynamic, finite element codes can incorporate structural complexities such as: geometrically accurate models; human occupant models; and advanced material models to include nonlinear stress-strain behaviors, and material failure. Validation of these crash simulations is difficult due to a lack of sufficient information to adequately determine the uncertainty in the experimental data and the appropriateness of modeling assumptions. This paper evaluates probabilistic approaches to quantify the effects of finite element modeling assumptions on the predicted responses. The vertical drop test of a Fokker F28 fuselage section will be the focus of this paper. The results of a probabilistic analysis using finite element simulations will be compared with experimental data.
    Keywords: Air Transportation and Safety
    Type: American Helicopter Society 59th Annual Forum; May 06, 2003 - May 08, 2003; Phoenix, AZ; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 10
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    Orion Crew Module Landing System Simulation and Verification (2011)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: NASA Langley Research Center (LaRC) has developed a comprehensive test and analysis program to evaluate the ability of LS-DYNA to model the materials and the phenomena involved in soil and water landing impacts of the Orion crew module. Elemental, scale boilerplate, and full-scale prototype testing is being conducted in support of the simulation verification and validation approach. Aspects of the simulations evaluated against test data include soil constitutive properties, water equations of state, and contact algorithms. Subsystems tested include airbags, crushable energy absorbing honeycomb materials, and energy absorbing seat support struts. The procedures, instrumentation, and general observations from each test series are presented. Plans for a series of swing tests of a full-scale boilerplate into a purpose-built water basin are described. Further plans for swing tests of flight-like prototypes into the water basin are noted.
    Keywords: Spacecraft Design, Testing and Performance
    Type: IEEEAC Paper 1569 , NF1676L-11975 , 2011 IEEE Aerospace Conference; Mar 05, 2011 - Mar 12, 2011; Big Sky, MT; United States
    Format: text
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