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  • Weitere Quellen  (9)
  • Lunar and Planetary Science and Exploration  (6)
  • Inorganic, Organic and Physical Chemistry  (1)
  • Life Sciences (General)  (1)
  • METALLIC MATERIALS  (1)
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  • Weitere Quellen  (9)
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  • 1
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    Identification of a cast iron alloy containing nonstrategic elements (1989)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: A program was performed to address the mechanical and environmental needs of Stirling engine heater head and regenerator housing components, while reducing the dependence on strategic materials. An alloy was developed which contained no strategic elemental additions per se. The base is iron with additions of manganese, molybdenum, carbon, silicon, niobium, and ferro-chromium. Such an alloy should be producible on a large scale at very low cost. The resulting alloy, designated as NASAUT 4G-Al, contained 15 Mn, 15 Cr, 2 Mo, 1.5 C, 1.0 Si, 1.0 Nb (in weight percent) with a balance of Fe. This alloy was optimized for chemistry, based upon tensile strength, creep-rupture strength, fracture behavior, and fatigue resistance up to 800 C. Alloys were also tested for environmental compatibility. The microstructure and mechanic properties (including hardness) were assessed in the as-cast condition and following several heat treatments, including one designed to simulate a required braze cycle. The alloy was fabricated and characterized in the form of both equiaxed and columnar-grained castings. The columnar grains were produced by directional solidification, and the properties were characterized in both the longitudinal and transverse orientations. The NASAUT 4G-Al alloy was found to be good in cyclic-oxidation resistance and excellent in both hydrogen and hot-corrosion resistance, especially in comparison to the baseline XF-818 alloy. The mechanical properties of yield strength, stress-rupture life, high-cycle-fatigue resistance, and low-cycle-fatigue resistance were good to excellent in comparison to the current alloy for this application, HS-31 (X-40), with precise results depending in a complex manner on grain orientation and temperature. If required, the ductility could be improved by lowering the carbon content.
    Schlagwort(e): METALLIC MATERIALS
    Materialart: NASA-CR-185174 , DOE/NASA/0282-1 , NAS 1.26:185174 , R89-917447-32
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  • 2
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    An EAP response to JPL's losses of the 1999 Mars missions (2001)
    In:  Other Sources
    Details
    Publikationsdatum: 2018-06-08
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: Looking at EAP Intervention Techniques; Vancouver, British Columbia; Canada
    Format: text
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  • 3
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    An EAP response to the 1999 Mars missions (2001)
    In:  Other Sources
    Details
    Publikationsdatum: 2018-06-08
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: Looking at EAP Intervention Techniques; Vancouver, British Columbia; Canada
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  • 4
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    Deployment of an Advanced Electrocardiographic Analysis (A-ECG) to Detect Cardiovascular Risk in Career Firefighters (2011)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: INTRODUCTION: Sudden cardiac death is the leading cause of line of duty death among firefighters, accounting for approximately 45% of fatalities annually. Firefighters perform strenuous muscular work while wearing heavy, encapsulating personal protective equipment in high ambient temperatures, under chaotic and emotionally stressful conditions. These factors can precipitate sudden cardiac events like myocardial infarction, serious dysrhythmias, or cerebrovascular accidents in firefighters with underlying cardiovascular disease. PURPOSE: The purpose of this study was to deploy and then evaluate the contribution of resting advanced ECG (A-ECG) in addition to other screening tools (family history, lipid profiles, and cardiopulmonary exercise tests, XT) in assessment of an individual fs cardiac risk profile. METHODS: Forty-four career firefighters were recruited to perform comprehensive baseline assessments including tests of aerobic performance, fasting lipids and glucose. Five-min resting 12-lead A-ECGs were obtained in a subset of firefighters (n=21) and transmitted over a secure networked system to a NASA physician collaborator. Using myocardial perfusion and other imaging as the gold standard, A-ECG scoring has been proven useful in accurately identifying a number of cardiac pathologies including coronary artery disease (CAD), left ventricular hypertrophy, hypertrophic cardiomyopathy, and non-ischemic and ischemic cardiomyopathy. RESULTS: Subjects f mean (SD) age was 43 (8) years, weight 91 (13) kg, and BMI 28 (3) kg/m2. Fifty-one percent of subjects had .3 cardiovascular risk factors. One subject had ST depression on XT ECG, at least one positive A-ECG score for CAD, and documented CAD based on cardiology referral. While all other subjects, including those with fewer risk factors, higher aerobic fitness, and normal exercise ECGs, were classified as healthy by A-ECG, there was no trend for association between risk factors and any of 20 A-ECG parameters in the grouped data.
    Schlagwort(e): Life Sciences (General)
    Materialart: JSC-CN-25097 , 59th American College of Sports Medicine Annual meeting; May 29, 2012 - Jun 02, 2012; San Francisco, CA; United States
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  • 5
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    Development of Large Bandgap Materials Using Reactive Growth in Al-SI Eutectic for Optical and RF Applications (2018)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-19
    Beschreibung: Carbon was utilized as reactive element to modify the microstructure using forced mixing during crystallization of the Al-Si alloy by rotation and stirring. We nucleated the material on SiC substrates while the Al-Si melt was rotated with a speed of 30rpm in a graphite crucible. Several experiments were performed and parameters such as time of mixing, soaking temperature, rotation rate of the substrate and rate of cooling during the solidification was changed. We observed dendrite and cell morphologies during the solidification of rotating melt. The microstructure was characterized by optical microscopy and SEM-EDX and compositional spectroscopy. The effect of carbon impurities was studied on the solidifying microstructure. When we used the longer soak time of the melt in presence of carbon impurities we observed the destruction of dendritic morphology and the formation of cellular and colony structures. Similar approach has been used for Ga2O3, a novel large bandgap material also.
    Schlagwort(e): Inorganic, Organic and Physical Chemistry
    Materialart: M18-6926 , Materials Science & Technology (MS&T) 2018; Oct 14, 2018 - Oct 18, 2018; Columbus, OH; United States
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  • 6
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    Compositional Characteristics and Trends Within the Vera Rubin Ridge, Gale Crater, Mars as Determined by APXS: Sedimentary, Diagenetic and Alteration History (2019)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-20
    Beschreibung: The Mars Science Laboratory (MSL) Curiosity rover has spent the last two years investigating a prominent resistant ridge, informally named the Vera Rubin Ridge (VRR), at the base of Mount Sharp (Aeolis Mons). The ridge has been a high priority science target for the MSL mission since landing in Gale crater more than 6 years ago because of the detection of a strong hematite spectral signature, and its distinct topography. Examining the chemistry of the ridge can aid in determining the relationship to other rocks analyzed during the rover traverse, specifically the Murray formation (fm) encountered below the ridge. We can also determine compositional trends with elevation and/or laterally within the ridge, and whether spectral properties observed on the ridge, both from orbit and in situ, correspond with changes in chemistry. The composition of the ridge, combined with mineralogy of drilled samples, can help to elucidate bigger picture questions regarding depositional environment, possible changing lake water chemistry and diagenetic/alteration history.
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: JSC-E-DAA-TN66081 , Lunar and Planetary Science Conference (LPSC); Mar 18, 2019 - Mar 22, 2019; Woodlands, TX; United States
    Format: application/pdf
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  • 7
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    Understanding Martian Alteration Processes by Comparing In-Situ Chemical Measurements from Multiple Landing Sites (2019)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-30
    Beschreibung: Characterizing the history of aqueous activity at the martian surface has been an objective of the Mars Exploration Rovers (MER) and the Mars Science Laboratory (MSL). Although the geologic context of the three landing sites are different, comparisons across the datasets can provide greater insight than using data from one mission alone. The Alpha Particle X-ray Spectrometer (APXS) is common to all three rovers (Spirit at Gusev crater, Opportunity at Meridiani Planum, and Curiosity at Gale crater) and provides a consistent basis for these comparisons. Soil and Dust: Fine grained basaltic soils and dust are remarkably uniform in chemical composition across multiple landing sites. These similarities in the concentrations of major, minor, and a few trace elements (Fig. 1) are indicative of planet-wide consistency in the composition of source materials for the soils. S and Cl vary by a factor of two in the soil and dust, but there is no clear association with any bulk cation (e.g., no correlation between S and total Ca, Mg, or Fe in soils). These volatile elements, however, are clearly associated with the nanophase-ferric iron component in the soil established by Mssbauer spectroscopy [1,2]. S and Cl likely originated as acidic species from volcanic out-gassing and subsequently coalesced on dust and sand grain surfaces, possibly with an affinity towards Fe3+ sites. Importantly, given the mobility of S and Cl in aqueous exposures, soil samples maintaining the typical molar S/Cl ratio of ~3.7:1 indicate minimal interactions with liquid water after the addition of S and Cl. In contrast to this well-established baseline, soil samples have been discovered at all three landing sites with atypical S/Cl ratios (e.g., subsurface soils), indicative of a more complex aqueous history.
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: JSC-E-DAA-TN70395 , International Conference on Mars; Jul 22, 2019 - Jul 25, 2019; Pasadena, CA; United States
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  • 8
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    Sulfur on Mars (2019)
    In:  CASI
    Details
    Publikationsdatum: 2019-08-06
    Beschreibung: The S contents of rocks and soils are indicative of various alteration processes on Mars, e.g.[1]. It has been quantified along traverses at 4 landing sites Pathfinder, both MERs and MSL by the APXS [2,3]. At the MSL and MER sites, sulfur abundances, correlations with likely bound cations and other elements, and complementary mineralogical and textural data have provided important insights into alteration processes and periods of more habitable environments in the distant past.
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: JSC-E-DAA-TN70393 , International Conference on Mars; Jul 22, 2019 - Jul 25, 2019; Pasadena, CA; United States
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  • 9
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    Global Distribution of Dissected Duricrust on Mars (2000)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-07-10
    Beschreibung: Evidence for dissected duricrust was identified in high resolution MOC images. Analysis of all available images was used to map the global distribution of this terrain. It is apparently restricted to two latitude bands: 30-60 deg. N and 30-60 deg. S.
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: Lunar and Planetary Science XXXI; LPI-Contrib-1000
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