1200 and 1300 K slow plastic compression properties of Ni-50Al composites

NASA Technical Reports Server (NTRS)

Whittenberger, J. D.; Kumar, K. S.; Mannan, S. K.

1991-01-01

XD synthesis, powder blending, and hot pressing techniques have been utilized to produce NiAl composites containing 4, 7.5, 15, and 25 vol pct alumina whiskers and hybrid composite materials with 15 vol pct Al2O3 + 10 or 20 vol pct, nominally 1 micron TiB2 particles. The resistance to slow plastic flow was determined at 1200 and 1300 K via compression testing in air under constant velocity conditions. The stress-strain behavior of the intermetallic composites depended on the fraction of second phases where the 4 and 7.5 percent Al2O3 materials flowed at a nominally constant stress after about 2 percent deformation, while all the other composites exhibited diffuse yielding followed by strain softening. The flow stress-strain rate properties increased with volume fraction of Al2O3 whiskers except for the 4 and 7.5 percent materials, which had similar strengths. The hybrid composite NiAl + 15Al2O3 + 10TiB2 was substantially stronger than the materials simply containing alumina. Deformation in these composites can be described by the Kelly and Street model of creep in perfectly bonded, rigid, discontinuous fiber materials.

Experimental studies on equilibrium adsorption isosteres and determination of the thermodynamic quantities of polar media on alumina Al2O3

NASA Astrophysics Data System (ADS)

Yonova, Albena

2017-03-01

The present work is a revieif of theoretical and experimental study on the adsorption performance of the adsorbent Alumina (Al2O3) used in the adsorption system. An experimental investigation on the equilibrium adsorption isosteres at low pressure (< 1 atm) of working pairs Al2O3/H2O and Al2O3/C2H6O2 is carried out. The isovolume measurement method is adopted in the test setup to directly measure the saturated vapor pressures of working pairs at vapor-liquid equilibrium (dG=0 and dμi=0). Quantity adsorbed is determined from pressure, volume and temperature using gas law. The isosteric heat of adsorption is calculated from the slope of the plot of lnP versus 1/T different amounts of adsorbate onto adsorbent as follows: 0,01 vol% Al2O3/H2O; 0,03 vol% Al2O3/H2O; 0,1 vol% Al2O3/H2O; 0,01 vol% Al2O3/C2H6O2; 0,03 vol% Al2O3/C2H6O2; 0,1 vol% Al2O3/C2H6O2. This study shows that adsorption working pair Al2O3 C2H6O2 has better adsorption performances than those of the A2O3/H2O. Surface acidity! is a most important property! far both adsorption and catalysis and therefore is examined structure of active sites of alumina surface. Thermodynamic parameters such as isosteric heat of adsorption, isosteric enthalpy and entropy of adsorption are critical design variables in estimating the performance and predicting the mechanism of an adsorption process and are also one of the basic requirements for the characterization and optimization of an adsorption process

Effect of the Different High Volume Fraction of SiC Particles on the Junction of Bismuthate Glass-SiCp/Al Composite

PubMed Central

Li, Xiaoqiang

2018-01-01

The in-house developed bismuthate glass and the SiCp/Al composites with different volume fractions of SiC particles (namely, 60 vol.%, 65 vol.%, 70 vol.%, and 75 vol.%) were jointed by vacuum hot-pressing process. The novel material can be used for the space mirror. The SiCp is an abbreviation for SiC particle. Firstly, the SiCp/Al composites with different vol.% of SiC particle were manufactured by using infiltration process. In order to obtain a stable bonding interface, the preoxide layers were fabricated on the surfaces of these composites for reacting with the bismuthate glass. The coefficient of thermal expansion (CTE) was carried out for characterizing the difference between the composites and bismuthate glass. The sealing quality of the composites and the bismuthate glass was quantified by using shear strength testing. The optical microstructures showed the particles were uniformly distributed in the Al matrix. The SEM image shows that a smooth oxidation layer was generated on the SiCp/Al composite. The CTE testing result indicated that the higher the vol.% of the particles in the composite, the lower the CTE value. The shear strength testing result disclosed that SiCp/Al composite with relatively low CTE value was favorable to obtain a bonding interface with high strength. PMID:29675118

Effect of the Different High Volume Fraction of SiC Particles on the Junction of Bismuthate Glass-SiCp/Al Composite.

PubMed

Wang, Bin; Qu, Shengguan; Li, Xiaoqiang

2018-01-01

The in-house developed bismuthate glass and the SiC p /Al composites with different volume fractions of SiC particles (namely, 60 vol.%, 65 vol.%, 70 vol.%, and 75 vol.%) were jointed by vacuum hot-pressing process. The novel material can be used for the space mirror. The SiCp is an abbreviation for SiC particle. Firstly, the SiC p /Al composites with different vol.% of SiC particle were manufactured by using infiltration process. In order to obtain a stable bonding interface, the preoxide layers were fabricated on the surfaces of these composites for reacting with the bismuthate glass. The coefficient of thermal expansion (CTE) was carried out for characterizing the difference between the composites and bismuthate glass. The sealing quality of the composites and the bismuthate glass was quantified by using shear strength testing. The optical microstructures showed the particles were uniformly distributed in the Al matrix. The SEM image shows that a smooth oxidation layer was generated on the SiC p /Al composite. The CTE testing result indicated that the higher the vol.% of the particles in the composite, the lower the CTE value. The shear strength testing result disclosed that SiC p /Al composite with relatively low CTE value was favorable to obtain a bonding interface with high strength.

Microstructure and mechanical properties of 2.5 vol. % TiBw/Ti6Al4V composites plates fabricated by hot-hydrostatic canned extrusion

NASA Astrophysics Data System (ADS)

Zhang, Wencong; Zhang, Lingjia; Feng, Yangju; Cui, Guorong; Chen, Wenzhen

2018-04-01

Plates of 2.5 vol. % TiB whisker-reinforced Ti6Al4V titanium matrix composites (TiBw/Ti64) with network structure were successfully fabricated by hot-hydrostatic extrusion with steel cup at 1100 °C. The dimensions of plates were about 150mm in length, 27mm in width and 2mm in thickness. After extrusion, the original equiaxed-network structure formed by TiB whiskers still existed, but was compressed in cross-section and stretched in longitudinal section and then the TiB whiskers were directional distribution along the extrusion direction. Furthermore, the mechanical properties results showed that the strength, hardness and ductility of the plates were significantly improved compared to as-sintered composites.

First Self-Consistent, Two-Layer Model of Near-Surface Water-Equivalent-Hydrogen on Mars

NASA Astrophysics Data System (ADS)

Feldman, W. C.; Pathare, A.; Prettyman, T. H.; Maurice, S.

2015-12-01

This study uses 9.5 years of Mars Odyssey Neutron Spectrometer (MONS) data [1]. We have used the epithermal and fast neutron count rates to determine the water-equivalent-hydrogen (WEH) content of an upper layer, Wup, having thickness D. The "crossover" technique we utilized is an improvement over previous work [2,3]. We then used Monte Carlo simulated grids of epithermal and thermal count rates spanning Wup = 1% to 15% [4] to determine the WEH content, Wdn, of a semi-infinite lower layer buried at depth, D. We also advance upon previous work by using improved deconvolution methods to reduce spatial blurring in fast and epithermal maps [5]. The resultant count-rates were digitized into a 2°x2°cylindrical grid for all WEH computations. Two sets of WEH maps will be shown. The first uses the one-layer model developed initially by Feldman et al. [6]. Comparison of the undeconvolved and deconvolved versions clearly illustrates the improvement obtained by deconvolution. We will also present the full two layer maps of Wup, Wdn, and D for the deconvolved data sets, which show: 1) contrary to our previous preliminary mapping [3], the fresh icy mid-latitude craters identified by [7] are NOT exclusively found in regions with average Wdn values that exceed the pore-filling threshold for regolith ice; 2) a maximum Wdn of about 80% by weight at the Phoenix site; 3) an isolated Wdn maximum just east of Gale crater that is centered on Aeolis Mensae; 4) a resolved Wdn maximum that overlays the Orsen Wells crater on Xanthe Terra; 5) Wdn local maxima that hug the western flanks of Olympus Mons and Elysium Mons, and 6) several Wdn maxima that cover Arabia Terra. We will present and interpret regional maps of all of these features. Refs: [1] Maurice et al. JGR, 2011; [2] Feldman et al. JGR, 2011; [3] Pathare et al. 8th Mars Conf., 2014; [4] Prettyman et al. JGR, 2004 [5] Prettyman et al. JGR, 2009; [6] Feldman et al. JGR, 2004; [7] Dundas et al. JGR, 2014.

Spaceborne Remote Sensing of Aerosol Type: Global Distribution, Model Evaluation and Translation into Chemical Speciation

NASA Astrophysics Data System (ADS)

Kacenelenbogen, M. S.; Tan, Q.; Johnson, M. S.; Burton, S. P.; Redemann, J.; Hasekamp, O. P.; Dawson, K. W.; Hair, J. W.; Ferrare, R. A.; Butler, C. F.; Holben, B. N.; Beyersdorf, A. J.; Ziemba, L. D.; Froyd, K. D.; Dibb, J. E.; Shingler, T.; Sorooshian, A.; Jimenez, J. L.; Campuzano Jost, P.; Jacob, D.; Kim, P. S.; Travis, K.; Lacagnina, C.

2016-12-01

It is essential to evaluate and refine aerosol classification methods applied to passive satellite remote sensing. We have developed an aerosol classification algorithm (called Specified Clustering and Mahalanobis Classification, SCMC) that assigns an aerosol type to multi-parameter retrievals by spaceborne, airborne or ground-based passive remote sensing instruments [1]. The aerosol types identified by our scheme are pure dust, polluted dust, urban-industrial/developed economy, urban-industrial/developing economy, dark biomass smoke, light biomass smoke and pure marine. We apply the SCMC method to inversions from the ground-based AErosol RObotic NETwork (AERONET [2]) and retrievals from the space-borne Polarization and Directionality of Earth's Reflectances instrument (POLDER, [3]). The POLDER retrievals that we use differ from the standard POLDER retrievals [4] as they make full use of multi-angle, multispectral polarimetric data [5]. We analyze agreement in the aerosol types inferred from both AERONET and POLDER and evaluate GEOS-Chem [6] simulations over the globe. Finally, we use in-situ observations from the SEAC4RS airborne field experiment to bridge the gap between remote sensing-inferred qualitative SCMC aerosol types and their corresponding quantitative chemical speciation. We apply the SCMC method to airborne in-situ observations from the NASA Langley Aerosol Research Group Experiment (LARGE, [7]) and the Differential Aerosol Sizing and Hygroscopicity Spectrometer Probe (DASH-SP, [8]) instruments; we then relate each coarsely defined SCMC type to a sum of percentage of individual aerosol species, using in-situ observations from the Particle Analysis by Laser Mass Spectrometry (PALMS, [9]), the Soluble Acidic Gases and Aerosol (SAGA, [10]), and the High - Resolution Time - of - Flight Aerosol Mass Spectrometer (HR ToF AMS, [11]). [1] Russell P. B., et al., JGR, 119.16 (2014) [2] Holben B. N., et al., RSE, 66.1 (1998) [3] Tanré D., et al., AMT, 4.7 (2011

Exploring Formation Models for Ceres Tholi and Montes

NASA Astrophysics Data System (ADS)

Ruesch, O.; Platz, T.; McFadden, L. A.; Hiesinger, H.; Schenk, P.; Sykes, M. V.; Schmidt, B. E.; Buczkowski, D.; Thangjam, G.; Raymond, C. A.; Russell, C. T.

2015-12-01

Dawn Framing Camera (FC) images of Ceres surface revealed tholi and mons, i.e., positive relief features with sub-circular to irregular basal shapes and varying height to diameter ratios and flank slopes. These domes and mounts are tentatively interpreted as volcanic constructs [1]. Alternative formation mechanisms, e.g., uplifting by diapirism or shallow intrusions [e.g., 2], could have also led to the observed features with different geological implications. FC images derived local digital elevation models reveal that the largest dome on Ceres (near Rongo crater) has a ~100 km wide base, concave downward margins with slopes of 10°-20°, a relatively flat top reaching altitudes of ~5 km relative to surrounding, and a summit pit chain of putative endogenic origin. A relevant mons on Ceres is a cone-shaped relief (10°S/316°E) with a ~30x20 km base, reaching a high of ~5 km relative to surroundings. Flank slopes approach a concave upward shape. These constructs are located in a complex geological area having resurfaced units with onlap contacts. Because of the varying morphometries of the reliefs, we explore several physical models of volcanic constructs, e.g., steep-sided dome and shield volcano. Physical models are based on radially spreading viscous gravity currents with a free upper surface [e.g., 3, 4]. Testing formation scenarios will exploit recently developed methods, such as time-variable viscosity and fixed-volume models [5], and constant flow rate models [6]. We aim to provide constraints on viable emplacement mechanisms for the different reliefs. [1] Platz et al. (2015), EPSC abstract 915, vol. 10; [2] Fagents, S.A. (2003), JGR, vol. 108, E12, 5139; [3] Huppert, H. (1982), J. Fluid Mech., vol. 121, pp. 43-58; [4] Lacey et al. (1981), EPSL, vol. 54, pp. 139-143; [5] Glaze et al. (2012), LPSC abstract 1074 ; [6] Glaze et al. (2015), LPSC abstract 1326.

Six Martian years of CO2 clouds survey by OMEGA/MEx.

NASA Astrophysics Data System (ADS)

Gondet, Brigitte; bibring, Jean-Pierre; Vincendon, Mathieu

2014-05-01

Mesospheric clouds have been detected first from Earth (Bell et al 1996 [1]), then from Mars orbit (MGS/TES and MOC, Clancy et al 1998 [2]). Their composition (CO2) was inferred from temperature. Similar detection and temperature-inferred composition was then performed by Spicam and PFS on board Mars Express (Monmessin et al [3], Formisano et al [4]., 2006). The first direct detection and characterization (altitude, composition, velocity) was performed by OMEGA/ Mars Express (then coupled to HRSC/ Mars Express, and confirmed by CRISM/MRO (Montmessin et al. [5], 2007, Maattanen et al [6]., Scholten et al. [7], 2010, Vincendon et al [8]., 2011). Omega is a very powerful tool for the study of CO2 clouds as it is able to unambiguously identify the CO2 composition of a cloud based on a near-IR spectral feature located at 4.26 μm [5],. Therefore since the beginning of the Mars Express mission (2004) OMEGA as done a systematic survey of these mesospheric clouds. Thanks to the orbit of Mars Express, we can observe this clouds from different altitudes (from apocenter to pericenter) and at different local times. We will present the result of 6 Martians years of observations and point out a correlation with the dust activity. We also observe that their time of appearance/disappearance varies slightly from year to year. We will mention also the existence of mesospheric H2O clouds. References [1] JF Bell. et al. JGR 1996; [2] RT Clancy et al., GRL 1998 [3] F. Montmessin et al. JGR 2006; [4] V. Formisano et al., Icarus 2006; [5] F. Montmessin et al JGR 2007 [6] A. Määttänen et al. Icarus 2010; [7] F. Scholten et al. PSS 2010; [8] M. Viencendon et al. JGR 2011

Mesospheric CO2 Clouds at Mars: Seven Martian Years Survey by OMEGA/MEX

NASA Astrophysics Data System (ADS)

Gondet, Brigitte; Bibring, Jean-Pierre

2016-04-01

Mesospheric clouds have been detected first from Earth (Bell et al 1996 [1]), then from Mars orbit (MGS/TES and MOC, Clancy et al 1998 [2]). Their composition (CO2) was inferred from temperature. Similar detection and temperature-inferred composition was then performed by Spicam and PFS on board Mars Express (Monmessin et al [3], Formisano et al [4]. 2006). The first direct detection and characterization (altitude, composition, velocity) was performed by OMEGA/ Mars Express (then coupled to HRSC/ Mars Express, and confirmed by CRISM/MRO (Montmessin et al. [5], 2007, Maattanen et al [6]. Scholten et al. [7], 2010, Vincendon et al [8], 2011). Omega is a very powerful tool for the study of CO2 clouds as it is able to unambiguously identify the CO2 composition of a cloud based on a near-IR spectral feature located at 4.26 μm [5] Therefore since the beginning of the Mars Express mission (2004) OMEGA as done a systematic survey of these mesospheric clouds. Thanks to the orbit of Mars Express, we can observe this clouds from different altitudes (from apocenter to pericenter) and at different local times. We will present the result of 7 Martians years of observations, point out a correlation with the dust activity and an irregular concentration of clouds from years to years. References [1] JF Bell. et al. JGR 1996; [2] RT Clancy et al., GRL 1998 [3] F. Montmessin et al. JGR 2006; [4] V. Formisano et al., Icarus 2006; [5] F. Montmessin et al JGR 2007 [6] A. Määttänen et al. Icarus 2010; [7] F. Scholten et al. PSS 2010; [8] M. Viencendon et al. JGR 2011

1200 to 1400 K slow strain rate compressive properties of NiAl/Ni2AlTi-base materials

NASA Technical Reports Server (NTRS)

Whittenberger, J. Daniel; Viswanadham, R. K.; Mannan, S. K.; Kumar, K. S.

1989-01-01

An attempt to apply the Martin Marietta Corporation's XD technology to the fabrication of NiAl-Ni2AlTi materials with improved creep properties is presented. Composite materials, containing from 0 to 30 vol pct of nominally 1-micron-diameter TiB2 particles in the intermetallic matrix have been produced by the XD process and compacted by hot pressing. Such composites demonstrated significant strength increases, approaching 3-fold for the 20 vol pct materials, in comparison to the unreinforced aluminide. This behavior was accomplished without deleterious side effects as the grain boundaries and particle-matrix interfaces were intact after compressive deformation to 10 percent or more strain. Typical true compressive stress-strain diagrams for materials tested in air between 1200 and 1400 K at approximate strain rates of 1.7 x 10 to the -6th/sec are presented.

Microstructure and Mechanical Behavior of Microwave Sintered Cu50Ti50 Amorphous Alloy Reinforced Al Metal Matrix Composites

NASA Astrophysics Data System (ADS)

Reddy, M. Penchal; Ubaid, F.; Shakoor, R. A.; Mohamed, A. M. A.

2018-06-01

In the present work, Al metal matrix composites reinforced with Cu-based (Cu50Ti50) amorphous alloy particles synthesized by ball milling followed by a microwave sintering process were studied. The amorphous powders of Cu50Ti50 produced by ball milling were used to reinforce the aluminum matrix. They were examined by x-ray diffraction (XRD), scanning electron microscopy (SEM), microhardness and compression testing. The analysis of XRD patterns of the samples containing 5 vol.%, 10 vol.% and 15 vol.% Cu50Ti50 indicates the presence of Al and Cu50Ti50 peaks. SEM images of the sintered composites show the uniform distribution of reinforced particles within the matrix. Mechanical properties of the composites were found to increase with an increasing volume fraction of Cu50Ti50 reinforcement particles. The hardness and compressive strength were enhanced to 89 Hv and 449 MPa, respectively, for the Al-15 vol.% Cu50Ti50 composites.

Estimation of radiation doses in TGFs and gamma ray glows

NASA Astrophysics Data System (ADS)

Celestin, S. J.; Pincon, J. L.; Trompier, F.

2017-12-01

Terrestrial gamma-ray flashes (TGFs) are bursts of high-energy photons originating from the Earth's atmosphere in association with thunderstorm activity [e.g., Briggs et al., JGR, 118, 3805, 2013]. TGFs are associated with initial propagation stages of intracloud lightning, which represent the most frequent type of lightning discharges [e.g., Cummer et al., GRL, 42, 7792, 2015, and references therein]. TGFs are known to be produced inside common thunderclouds [e.g., Splitt et al., JGR, 115, A00E38, 2010; Chronis et al., B. Am. Meteorol. Soc., 97, 639, 2016] typically at altitudes ranging from 10 to 14 km [e.g., Cummer et al., GRL, 41, 8586, 2014]. The global TGF occurrence rate is estimated to be 400,000 per year concerning TGFs detectable by Fermi-GBM (Gamma ray Burst Monitor) [Briggs et al., 2013], but detailed analysis of satellite measurements [Østgaard et al., JGR, 117, A03327, 2012] and theoretical studies [Celestin et al., JGR, 120, 10712, 2015] suggest that it cannot be excluded that TGFs represent a part of a regular process taking place during the propagation of lightning discharges. In addition to TGFs, another type of high-energy emissions has been observed inside thunderstorms from balloons [e.g., Eack et al., 101, 29637, 1996] and airplanes [e.g., McCarthy and Parks, 12, 393, 1985; Kelley et al., Nat. Commun., 6, 7845, 2015]. Referred to as gamma ray glows, these events correspond to significant elevations of the background radiation over long time scales that can be abruptly terminated with the occurrence of a lightning discharge. Kelley et al. [2015] estimate that a proportion larger than 8% of electrified storms produce glows. Dwyer et al. [JGR, 115, D09206, 2010] have estimated that if an aircraft were to find itself in the source electron beam giving rise to a TGF, passengers and crews might receive effective radiation doses above the regulatory limit depending on the beam diameter and Tavani et al. [Nat. Hazards Earth Syst. Sci., 13, 1127, 2013

Heavy Metal Enrichments in the Kimberley Bedrocks: Evidence of AN Ore Deposit at the Source?

NASA Astrophysics Data System (ADS)

Payre, V.; Fabre, C.; Sautter, V.; Mangold, N.; Cousin, A.; Le Deit, L.; Goetz, W.; Forni, O.; Gasnault, O.; Wiens, R. C.; Maurice, S.

2017-12-01

Three years ago, the Curiosity rover reached a sedimentary formation called Kimberley that is compositionally very different from previous and subsequent analyses. These sandstones contain elevated amounts of K2O with an average of 2.1 wt. % according to ChemCam instrument [1], explained by the occurrence of potassic minerals: a sandstone named Windjana has been analyzed by CheMin instrument, showing large amounts of sanidine [2]. Mafic minerals (augite, pigeonite, magnetite) and minor phases including F-apatites and sulfides have also been identified [2]. ChemCam analyzed several points where micas may have been sampled [1,3-4]. All these minerals are thought to be detrital having originated from igneous sources like potassic and mafic rocks in the northern rim [1-4]. High Zn and Cu contents (up to 2000ppm and 1010ppm, respectively) have been measured in these K-bedrocks [5-7]. The ChemCam instrument allows the analysis of materials with depth: a LIBS point is ablated by 30-150 laser-shots, measuring the composition of the first micrometers [8]. These depth profiles show evidences of the occurrence of a Cu-phase within K-spars. In a potassic sandstone containing up to 1010 ppm of Cu and 250 ppm of Ge according to ChemCam and APXS analysis respectively, a Cu-phase is potentially hosted in clays or micas. These high values would be related to local hydrothermalism at the igneous source region of the Kimberley detrital minerals [5,9]. These observations and the occurrence of 800 ppm of Cu in a porphyric alkali feldspar within a trachyandesite [10], suggest that these Cu enrichments may be due to a porphyry copper deposit at the source region of the potassic minerals. Another hypothesis is the presence of an ore deposit related to an impact-induced hydrothermalism. Hence, circulation of high temperature fluids would have happened at the magmatic source region of the Kimberley minerals, favoring the formation of a metallic deposit. [1] Le Deit et al, JGR 121, 784

A Novel Approach of Using Ground CNTs as the Carbon Source to Fabricate Uniformly Distributed Nano-Sized TiCx/2009Al Composites

PubMed Central

Wang, Lei; Qiu, Feng; Ouyang, Licheng; Wang, Huiyuan; Zha, Min; Shu, Shili; Zhao, Qinglong; Jiang, Qichuan

2015-01-01

Nano-sized TiCx/2009Al composites (with 5, 7, and 9 vol% TiCx) were fabricated via the combustion synthesis of the 2009Al-Ti-CNTs system combined with vacuum hot pressing followed by hot extrusion. In the present study, CNTs were used as the carbon source to synthesize nano-sized TiCx particles. An attempt was made to correlate the effect of ground CNTs by milling and the distribution of synthesized nano-sized TiCx particles in 2009Al as well as the tensile properties of nano-sized TiCx/2009Al composites. Microstructure analysis showed that when ground CNTs were used, the synthesized nano-sized TiCx particles dispersed more uniformly in the 2009Al matrix. Moreover, when 2 h-milled CNTs were used, the 5, 7, and 9 vol% nano-sized TiCx/2009Al composites had the highest tensile properties, especially, the 9 vol% nano-sized TiCx/2009Al composites. The results offered a new approach to improve the distribution of in situ nano-sized TiCx particles and tensile properties of composites. PMID:28793749

Creep and Toughness of Cryomilled NiAl Containing Cr

NASA Technical Reports Server (NTRS)

Whittenberger, J. Daniel; Aikin, Beverly; Salem, Jon

2000-01-01

NiAl-AlN + Cr composites were produced by blending cryomilled NiAl powder with approx. 10 vol % Cr flakes. In comparison to the as-consolidated matrices, hot isostatically pressed Cr-modified materials did not demonstrate any significant improvement in toughness. Hot extruded NiAl-AlN+10.5Cr, however, possessed a toughness twice that determine for the base NiAl-AlN alloy. Measurement of the 1200 to 1400 K plastic flow properties revealed that the strength of the composites was completely controlled by the properties of the NiAl-AlN matrices. This behavior could be successfully modeled by the Rule-of-Mixtures, where load is shed from the weak Cr to the strong matrix.

High-resolution records of non-dipole variations derived from volcanic edifices

NASA Astrophysics Data System (ADS)

de Groot, L. V.; Biggin, A. J.; Dekkers, M. J.

2013-12-01

necessitates a highly non-dipolar nature. Our paleointensity data obtained for Tenerife reveal high paleointensities temporally coinciding with an intensity high occurring in the Middle East around 1000 BC. If our findings are related to this ';archeomagnetic jerk', it must have extended more than 50 ° westward in longitude. Gallet et al., 2005, EPSL vol. 236, pp. 339-347 Gómez-Paccard et al., 2012, EPSL, vol. 355-356, pp. 131-143 Bowles et al, 2002, EPSL, vol. 203, pp. 967-981 Yu et al., 2012, JGR, vol. 177, p. B08101

High-resolution records of non-dipole variations derived from volcanic edifices

NASA Astrophysics Data System (ADS)

de Groot, Lennart; Biggin, Andrew; Dekkers, Mark

2014-05-01

paleointensity data obtained for Tenerife reveal high paleointensities temporally coinciding with an intensity high occurring in the Middle East around 1000 BC. If our findings are related to this 'archeomagnetic jerk', it must have extended more than 50 degrees westward in longitude. References: Gallet et al., 2005, EPSL vol. 236, pp. 339-347 Gomez-Paccard et al., 2012, EPSL, vol. 355-356, pp. 131-143 Bowles et al, 2002, EPSL, vol. 203, pp. 967-981 Yu et al., 2012, JGR, vol. 177, p. B08101

The Mechanisms of Dispersion Strengthening and Fracture in Al-based XD (TM) Alloys

NASA Technical Reports Server (NTRS)

Aiken, R. M., Jr.

1990-01-01

The influence of reinforcement size, volume fraction, and matrix deformation behavior on room and elevated temperature strength, and the fracture toughness of metal matrix composites of both pure aluminum and Al(4 percent)Cu(1.5 percent)Mg with 0 to 15 vol percent TiB2 were examined. Higher TiB2 volume fractions increased the tensile yield strength both at room and elevated temperatures, and reduced the elongation to fracture. Tensile tests also indicate that small particles provided a greater increase in strength for a given volume fraction than larger particles, whereas elongation to fracture appeared to be insensitive to reinforcement size. The fracture toughness of the Al(4 percent)Cu(1.5 percent)Mg alloys decreased rapidly with TiB2 additions of 0 to 5 vol percent and more slowly with TiB2 additions of 5 to 15 vol percent. Fracture toughness appears to be independent of TiB2 particle size. The isothermal-aging response of the precipitation strengthened Al(4 percent)Cu(1.5 percent)Mg alloys was not altered by the presence of TiB2.

Elevated temperature slow plastic deformation of NiAl/TiB2 particulate composites

NASA Technical Reports Server (NTRS)

Whittenberger, J. Daniel; Mannan, S. K.; Sprissler, B.; Viswanadham, R. K.

1988-01-01

The 'XD' process for production of discontinuously-reinforced metal-matrix composites has been used to enhance the high-temperature strength of NiAl-TiB2 composites with particulate densities of up to 30 vol pct. SEM, TEM, and optical characterizations of the resulting microstructures showed the average TiB2 particle size to be about 1 micron, while the average grain of the NiAl matrix was of the order of 10 microns. Elevated temperature compression tests conducted at 1200 and 1300 K indicated flow strengths to increase with TiB2 content, so that the 20 vol pct TiB2-reinforced composite was three times stronger than the unreinforced NiAl; this is ascribed to the very high density of microstructural tangled dislocations, loops, and subgrain boundaries connecting the particles.

The Possible Decapitation of a Megathrust Indenter: Evidence from Imaging of Time-dependent Microseismic Structures before and after the 2012 Mw 7.6 Nicoya, Costa Rica

NASA Astrophysics Data System (ADS)

Newman, A. V.; Yao, D.; Kyriakopoulos, C.; Moore-Driskell, M. M.; Hobbs, T. E.; Peng, Z.; Schwartz, S. Y.; Protti, M.; Gonzalez, V.

2016-12-01

We normally view the subduction megathrust surface as a constant structure throughout the seismic cycle, with the elastic loading, microseismicity, and slip occurring along it. However, using small events recorded from a uniquely dense seismic network directly over the active megathrust below Nicoya, Costa Rica, we find two different seismogenic structures with near exclusive time-dependent behavior immediately in the region of maximum coseismic slip. Microseismicity recorded at intervals between 1999 and 2009 showed an elevated topographic indenter beneath central Nicoya, and associated with a suture marking transition between Cocos-Nazca Spreading Center and East-Pacific Rise crusts [Kyriakopoulos et al., JGR 2015]. This indenter is located as a focus of interseismic locking and coseismic rupture [Feng et al., JGR 2012; Yue et al., JGR 2013; Protti et al., Nat. Geosc. 2014; Xue et al., JGR 2015; Kyriakopoulos & Newman, JGR 2016]. However, aftershocks recorded in the months following an MW 7.6 earthquake in 2012 define an entirely different structure about 5 km deeper and differing only in the area of maximum coseismic slip. The location of seismicity switches entirely between these faults from the shallow indenter structure beforehand to the deeper and near-linear feature after. To improve our imaging of the behavior and associated slab structure, we perform a detailed joint seismic relocation and tomographic inversion using TomoDD [Zhang and Thurber, PAGEOPH 2003]. We analyze the new locations relative to the imaged slab geometry, and compare automated formulations of the interfaces using the Maximum Seismicity Method [Kyriakopoulos et al., 2015], with data existing before and after the earthquake. Lastly, we show the sensitivity of using either surface in models for fault slip from regional GPS. We hypothesize that the bifurcated fault structure signifies either active decapitation of the indenter, possibly along the crust-mantle interface of the downgoing slab

A Novel Approach of Using Ground CNTs as the Carbon Source to Fabricate Uniformly Distributed Nano-Sized TiCx/2009Al Composites.

PubMed

Wang, Lei; Qiu, Feng; Ouyang, Licheng; Wang, Huiyuan; Zha, Min; Shu, Shili; Zhao, Qinglong; Jiang, Qichuan

2015-12-17

Nano-sized TiC x /2009Al composites (with 5, 7, and 9 vol% TiC x ) were fabricated via the combustion synthesis of the 2009Al-Ti-CNTs system combined with vacuum hot pressing followed by hot extrusion. In the present study, CNTs were used as the carbon source to synthesize nano-sized TiC x particles. An attempt was made to correlate the effect of ground CNTs by milling and the distribution of synthesized nano-sized TiC x particles in 2009Al as well as the tensile properties of nano-sized TiC x /2009Al composites. Microstructure analysis showed that when ground CNTs were used, the synthesized nano-sized TiC x particles dispersed more uniformly in the 2009Al matrix. Moreover, when 2 h-milled CNTs were used, the 5, 7, and 9 vol% nano-sized TiC x /2009Al composites had the highest tensile properties, especially, the 9 vol% nano-sized TiC x /2009Al composites. The results offered a new approach to improve the distribution of in situ nano-sized TiC x particles and tensile properties of composites.

Mechanical behaviour of AlSiC nano composites produced by ball milling and spark plasma sintering =

NASA Astrophysics Data System (ADS)

Buchheim, Claudia Sofia de Andrade Redondo Murilhas

Neste trabalho foram produzidos nanocompositos de AlSiC misturando aluminio puro com nano particulas de SiC com diâmetro de 45 - 55 nm, usando, de forma sequencial, a tecnica da metalurgia do po e a compactacao por "Spark Plasma Sintering". O composito obtido apresentava graos com 100 nm de diâmetro, encontrandose as particulas de SiC localizadas, principalmente, nas fronteiras de grao. O nanocomposito sob a forma de provetes cilindricos foi submetido a testes de compressao uniaxial e a testes de nanoindentacao para analisar a influencia das nanoparticulas de SiC, da fracao volumica de acido estearico e do tempo de moagem, nas propriedades mecânicas do material. Para efeitos de comparacao, utilizouse o comportamento mecânico do Al puro processado em condicoes similares e da liga de aluminio AA1050O. A tensao limite de elasticidade do nanocomposito com 1% Vol./Vol. de SiC e dez vezes superior a do AA1050. O refinamento de grao a escala nano constitui o principal mecanismo de aumento de resistencia mecânica. Na realidade, o Al nanocristalino sem reforco de particulas de SiC, apresenta uma tensao limite de elasticidade sete vezes superior a da liga AA1050O. A adicao de 0,5 % Vol./Vol. e de 1 % Vol./Vol. de SiC conduzem, respetivamente, ao aumento da tensao limite de elasticidade em 47 % e 50%. O aumento do tempo de moagem e a adicao de acido estearico ao po durante a moagem conduzem apenas a um pequeno aumento da tensao de escoamento. A dureza do material medida atraves de testes de nanoindentacao confirmaram os dados anteriores. A estabilidade das microestruturas do aluminio puro e do nanocomposito AlSiC, foi testada atraves de recozimento de restauracao realizado as temperaturas de 150 °C e 250 °C durante 2 horas. Aparentemente, o tratamento termico nao influenciou as propriedades mecânicas dos materiais, excepto do nanocomposito com 1 % Vol./Vol. de SiC restaurado a temperatura de 250 °C, para o qual se observou uma reducao da tensao limite de elasticidade

Numerical simulation of convective generated gravity waves in the stratosphere and MLT regions.

NASA Astrophysics Data System (ADS)

Heale, C. J.; Snively, J. B.

2017-12-01

Convection is an important source of gravity wave generation, especially in the summer tropics and midlatitudes, and coherent wave fields above convection are now routinely measured in the stratosphere and mesosphere [e.g. Hoffmann et al., JGR, 118, 2013; Gong et al., JGR, 120, 2015; Perwitasari et al., GRL, 42, 22, 2016]. Numerical studies have been performed to investigate the generation mechanisms, source spectra, and their effects on the middle and upper atmosphere [e.g. Fovell et al., AMS, 49,16, 1992; Alexander and Holton, Atmos. Chem. Phys., 4 2004; Vincent et al., JGR, 1118, 2013], however there is still considerable work needed to fully describe these parameters. GCMs currently lack the resolution to explicitly simulate convection generation and rely on simplified parameterizations while full cloud resolving models are computationally expensive and often only extend into the stratosphere. More recent studies have improved the realism of these simulations by using radar derived precipitation rates to drive latent heating in models that simulate convection [Grimsdell et al., AMS, 67, 2010; Stephan and Alexander., J. Adv. Model. Earth. Syst, 7, 2015], however they too only consider wave propagation in the troposphere and stratosphere. We use a 2D nonlinear, fully compressible model [Snively and Pasko., JGR, 113, 2008] to excite convectively generated waves, based on NEXRAD radar data, using the Stephan and Alexander [2015] algorithms. We study the propagation, and spectral evolution of the generated waves up into the MLT region. Ambient atmosphere parameters are derived from observations and MERRA-2 reanalysis data, and stratospheric (AIRS) and mesospheric (Lidar, OH airglow) observations enable comparisons with simulation results.

Microstructure and tribological properties of in situ synthesized TiC, TiN, and SiC reinforced Ti 3Al intermetallic matrix composite coatings on pure Ti by laser cladding

NASA Astrophysics Data System (ADS)

Pu, Yuping; Guo, Baogang; Zhou, Jiansong; Zhang, Shitang; Zhou, Huidi; Chen, Jianmin

2008-12-01

TiC, TiN, and SiC reinforced Ti 3Al intermetallic matrix composite (IMC) coatings were in situ synthesized on a pure Ti substrate by laser cladding. It was found that the surface hardness and the wear resistance of the Ti 3Al coating were improved by the formation of these Ti 3Al IMC coatings. The surface hardness and the wear resistance of the TiC/Ti 3Al IMC coatings increased with the increasing volume fraction of TiC powder. Under the same dry sliding test conditions, the wear resistance of TiC, TiN, and SiC reinforced Ti 3Al IMC coatings with 40 vol.% reinforced powder was in the following order: TiN/Ti 3Al IMC coating > TiC/Ti 3Al IMC coating > SiC/Ti 3Al IMC coating. It should be noted that both the TiC/Ti 3Al IMC coating with 40 vol.% TiC powder and the TiN/Ti 3Al coating with 40 vol.% TiN powder showed excellent wear resistance under 5 N normal load.

Al2O3/ZrO2/Y3Al5O12 Composites: A High-Temperature Mechanical Characterization

PubMed Central

Palmero, Paola; Pulci, Giovanni; Marra, Francesco; Valente, Teodoro; Montanaro, Laura

2015-01-01

An Al2O3/5 vol%·ZrO2/5 vol%·Y3Al5O12 (YAG) tri-phase composite was manufactured by surface modification of an alumina powder with inorganic precursors of the second phases. The bulk materials were produced by die-pressing and pressureless sintering at 1500 °C, obtaining fully dense, homogenous samples, with ultra-fine ZrO2 and YAG grains dispersed in a sub-micronic alumina matrix. The high temperature mechanical properties were investigated by four-point bending tests up to 1500 °C, and the grain size stability was assessed by observing the microstructural evolution of the samples heat treated up to 1700 °C. Dynamic indentation measures were performed on as-sintered and heat-treated Al2O3/ZrO2/YAG samples in order to evaluate the micro-hardness and elastic modulus as a function of re-heating temperature. The high temperature bending tests highlighted a transition from brittle to plastic behavior comprised between 1350 and 1400 °C and a considerable flexural strength reduction at temperatures higher than 1400 °C; moreover, the microstructural investigations carried out on the re-heated samples showed a very limited grain growth up to 1650 °C. PMID:28787961

Production of Ionospheric Perturbations by Cloud-to-Ground Lightning and the Recovery of the Lower Ionosphere

NASA Astrophysics Data System (ADS)

Liu, Ningyu; Dwyer, Joseph; Rassoul, Hamid

2013-04-01

The fact that lightning/thunderstorm activities can directly modify the lower ionosphere has long been established by observations of the perturbations of very low frequency (VLF) signals propagating in the earth-ionosphere waveguide. These perturbations are known as early VLF events [Inan et al., 2010, JGR, 115, A00E36, 2010]. More recently discovered transient luminous events caused by the lightning/thunderstorm activities only last ~1-100 ms, but studies of the early VLF events show that the lightning ionospheric effects can persist much longer, >10s min [Cotts and Inan, GRL, 34, L14809, 2007; Haldoupis et al., JGR, 39, L16801, 2012; Salut et al., JGR, 117, A08311, 2012]. It has been suggested that the long recovery is caused by long-lasting conductivity perturbations in the lower ionosphere, which can be created by sprites/sprite halos which in turn are triggered by cloud-to-ground (CG) lightning [Moore et al., JGR, 108, 1363, 2003; Haldoupis et al., 2012]. We recently developed a two-dimensional fluid model with simplified ionospheric chemistry for studying the quasi-electrostatic effects of lightning in the lower ionosphere [Liu, JGR, 117, A03308, 2012]. The model chemistry captures major ion species and reactions in the lower ionosphere. Additional important features of the model include self-consistent background ion density profiles and full description of electron and ion transport. In this talk, we present the simulation results on the dynamics of sprite halos caused by negative CG lightning. The modeling results indicate that electron density around 60 km altitude can be enhanced in a region as wide as 80 km. The enhancement reaches its full extent in ~1 s and recovers in 1-10 s, which are on the same orders as the durations of slow onset and post-onset peaks of some VLF events, respectively. In addition, long-lasting electron and ion density perturbations can occur around 80 km altitude due to negative halos as well as positive halos, which can explain

Mechanical Properties and Wear Characteristics Al-ZrO2-SiCp and Graphite Hybrid Metal Matrix Composites

NASA Astrophysics Data System (ADS)

Nayak, S. K.; Mahanta, T.; Sahoo, J. K.; Mishra, A.

2018-03-01

Development of Aluminum Metal Matrix Co mposites (AMMCs) has been one of the major requirements in engineering applicat ions due to their excellent mechanical properties, light weight and high strength. In the present investigation, Stir casting technique has been used for fabrication of co mposites, taking Alu miniu m as parent metal, Silicon Carbide (SiCp) of 7 vol. % of 220 mesh size and 1.75 vol. % of graphite as reinforcements. The Zirconia content was varied as 2.75, 4.5 and 6 vol. % to fabricate three d ifferent types of hybrid composites. The tensile strength and hardness were measured in UTM and Vickers hardness tester respectively and the wear characteristics were studied in a pin on disc friction monitor under dry sliding condition against steel counter face. The tensile strength was found to be 90 MPa, 120 MPa, 130 MPa and hardness 80.25 VHN, 103.22 VHN, 103.77 VHN for 2.75, 4.5 and 6vol. % of Zirconia respectively. Fro m the above investigation, it is recommended that composition with Al, 7 %-SiCp, 1.75 % -Gr and 6 vol %-ZrO2 showed better mechanical p roperties i.e . h igh tensile strength (130MPa) and reasonably good hardness (103.77 VHN) . The co mposite with Al, 7 % - SiCp, 1.75 % -Gr and 6 %-ZrO2 is good for short run frictional applicat ion and the composite with Al, 7 %- SiCp, 1.75 % -Gr and 4.5 %- ZrO2 may be used for long run frictional applicat ions after testing.

Measuring attachment to life in old age: the Portuguese version of the Positive Valuation of Life Scale (Positive VOL).

PubMed

Araújo, Lia; Ribeiro, Oscar; Teixeira, Laetitia; Azevedo, Maria João; Jopp, Daniela S; Rott, Christoph; Paúl, Constança

2015-10-01

This study aims to present the psychometric properties of the Portuguese version of the Positive Valuation of Life Scale (Lawton et al. in J Aging Ment Healt 13:3-31, 2001). Sample included 207 community-dwelling elders (129 women; M Age = 77.2 years, SD = 7.5). The data collection included the translated and adapted Portuguese version of Positive Valuation of Life Scale, Life Satisfaction Index Z, Meaning in Life Questionnaire and Geriatric Depression Scale. From exploratory factor analysis, two factors emerged, existential beliefs and perceived control, explaining 49 % of the total variance. Both factors were positively related with meaning in life and life satisfaction and negatively related with depression (p < 0.05). The values obtained for internal consistency for the total scale and for each subscale were good (α > 0.75). The Portuguese version of Positive VOL Scale represents a reliable and valid measure to capture the subjective experience of attachment to one's life. The two-factor structure is an update to Lawton's previous work and in line with findings obtained in the USA (Dennis et al. in What is valuation of life for frail community-dwelling older adults: factor structure and criterion validity of the VOL, Thomas Jefferson University, Center for Applied Research on Aging and Health Research, 2005) and Japan (Nakagawa et al. in Shinrigaku Kenkyu 84:37-46, 2013). Future research is required to investigate VOL predictors and the potential changes toward the end of the life span.

Modeling of Pulses in Terrestrial Gamma-ray Flashes

NASA Astrophysics Data System (ADS)

Xu, Wei; Celestin, Sebastien; Pasko, Victor

2015-04-01

Terrestrial Gamma-ray Flashes (TGFs) are high-energy photon bursts originating from the Earth's atmosphere that are associated with lightning activities. After their discovery in 1994 by the Burst and Transient Source Experiment (BATSE) detector aboard the Compton Gamma-Ray Observatory [Fishman et al., Science, 264, 1313, 1994], this phenomenon has been further observed by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) [Smith et al., Science, 307, 1085, 2005], the Fermi Gamma-ray Space Telescope [Briggs et al., JGR, 115, A07323, 2010] and the Astrorivelatore Gamma a Immagini Leggero (AGILE) satellite [Marisaldi et al., JGR, 115, A00E13, 2010]. Photon spectra corresponding to the mechanism of relativistic runaway electron avalanches (RREAs) usually provide a very good agreement with satellite observations [Dwyer and Smith, GRL, 32, L22804, 2005]. On the other hand, Celestin and Pasko [JGR, 116, A03315, 2011] have shown theoretically that the large flux of thermal runaway electrons generated by streamers during the negative corona flash stage of stepping lightning leaders in intracloud lightning flashes could be responsible for TGFs. Recently, based on analysis of the temporal profiles of 278 TGF events observed by the Fermi Gamma-Ray Burst Monitor, Foley et al. [JGR, 119, 5931, 2014] have suggested that 67% of TGF pulses detected are asymmetric and these asymmetric pulses are consistent with the production mechanism of TGFs by relativistic feedback discharges. In the present work, we employ a Monte Carlo model to study the temporal distribution of photons at low-orbit satellite altitudes during TGF events. Using the pulse fitting method described in [Foley et al., 2014], we further investigate the characteristics of TGF pulses. We mainly focus on the effects of Compton scattering on the symmetry properties and the rise and fall times of TGF pulses.

Improvement of thermal stability of nano-granular TMR films by using a Mg-Al-O insulator matrix

NASA Astrophysics Data System (ADS)

Kanie, S.; Koyama, S.

2018-05-01

A new metal-insulator nano-granular tunneling magnetoresistance (TMR) film made of (Fe-Co)-(Mg-Al-O) has been investigated. It is confirmed that the film has granular structure in which crystal Fe-Co granules are surrounded by an amorphous Mg-Al-O matrix. A large MR ratio of 11.8 % at room temperature is observed for a 42 vol.%(Fe0.6Co0.4)-(Mg-Al-O) film annealed at 395 °C. The electrical resistivity increases rapidly by annealing at above the changing point (500 °C). The changing point is about 300 °C higher than that of conventional (Fe-Co)-(Mg-F) nano-granular TMR films. The 42 vol.%(Fe0.6Co0.4)-(Mg-Al-O) film also exhibits less degradation in the MR ratio at high annealing temperatures such as 600 °C. These results suggest the (Fe-Co)-(Mg-Al-O) film is superior to the (Fe-Co)-(Mg-F) film in thermal stability.

Nonlinear Acoustic Waves Generated by Surface Disturbances and Their Effects on Lower Thermospheric Composition

NASA Astrophysics Data System (ADS)

Pineyro, B.; Snively, J. B.

2017-12-01

Recent 1D and 2D nonlinear atmospheric models have provided important insight into acoustic waves generated by seismic events, which may steepen into shocks or saw-tooth trains while also dissipating strongly in the thermosphere [e.g., Chum et al., JGR, 121, 2016; Zettergren et al., JGR, 122, 2017]. Although they have yield results that agree with with observations of ionospheric perturbations, dynamical models for the diffusive and stratified lower thermosphere [e.g., Snively and Pasko, JGR, 113, 2008] often use single gas approximations with height-dependent physical properties (e.g. mean molecular weight, specific heats) that do not vary with time (fixed composition). This approximation is simpler and less computationally expensive than a true multi-fluid model, yet captures the important physical transition between molecular and atomic gases in the lower thermosphere. Models with time-dependent composition and properties have been shown to outperform commonly used models with fixed properties; these time-dependent effects have been included in a one-gas model by adding an advection equation for the molecular weight, finding closer agreement to a true binary-gas model [Walterscheid and Hickey, JGR, 106, 2001 and JGR, 117, 2012]. Here, a one-dimensional nonlinear mass fraction approach to multi-constituent gas modeling, motivated by the results of Walterscheid and Hickey [2001, 2012], is presented. The finite volume method of Bale et al. [SIAM JSC, 24, 2002] is implemented in Clawpack [http://www.clawpack.org; LeVeque, 2002] with a Riemann Solver to solve the Euler Equations including multiple species, defined by their mass fractions, as they undergo advection. Viscous dissipation and thermal conduction are applied via a fractional step method. The model is validated with shock tube problems for two species, and then applied to investigate propagating nonlinear acoustic waves from ground to thermosphere, such as following the 2011 Tohoku Earthquake [e

Effects of In Situ Intermetallics on the Microstructural Array and Saline Corrosion Performance of Cast Al/WCp Composites

NASA Astrophysics Data System (ADS)

Lekatou, A. G.; Gkikas, N.; Gousia, V.; Lentzaris, K.; Karantzalis, A. E.

2018-06-01

Al-matrix composites, ex situ reinforced with WC nanoparticles and in situ reinforced with Al3(Ti,W), Al12W, Al5W and Al4W, have been fabricated by casting assisted by K2TiF6 wetting agent addition and mechanical stirring. A satisfactory particle incorporation and distribution accompanied by a high reactivity have been attained. The presence, topography, chemical composition of all included phases and their occurrence as clusters or single particles are clarified and justified. Al12W is the predominant aluminide phase at WC ≤ 1.5 vol.%. Al4W (primarily) and Al5W (secondarily) are the predominant aluminide phases at WC ≥ 2.0 vol.%. WC nanoparticles have acted as heterogeneous nucleation sites to Al3Ti particles. Reverse polarization tests in 3.5 wt.% NaCl show that the governing form of corrosion is intergranular corrosion of Al around Al3FeSi2 eutectic, fine plates. The corrosion steps/mechanisms are identified. Clusters of aluminides and carbide nanoparticles, as well as intergranular WC nano-dispersoids and their Al-matrix have remained corrosion-free. The role of the aluminides combined with WC remaining nano-cores as inhibitors of the eutectic Al3FeSi2 cathodic activity is highlighted.

Improvements in SiC{sub w}/Al{sub 2}O{sub 3} composites through colloidally stabilized suspensions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Crimp, M.J.; Oppermann, D.A.; Zhang, M.

1994-12-31

Through manipulation of colloidal parameters, suspensions of SiC(whisker)/Al{sub 2}O{sub 3} were prepared, at 5, 10 and 20 vol% SiC whisker, using processing conditions established in Stable Suspension{copyright}. Utilizing Hogg, Healy and Furstenau`s modifications to DLVO theory, this program predicts stability conditions for composite suspensions. Variations in the suspension pH induce changes in the attractive/repulsive interactions between components. This type of interaction in turn influences the packing and green density. Composite suspensions were prepared, freeze dried, then cold consolidated. The distribution of the SiC whiskers within the Al{sub 2}O{sub 3} matrix was determined from SEM micrographs and the composite green densitymore » correlated to the extent of homo- versus heterostability within the composite suspension. The green density of the pure Al{sub 2}O{sub 3} and the 5 vol% SiC whisker additions was the highest at the pH of maximum stability for each interaction. In contrast, at whisker additions of 10 and 20 vol%, the green density is the highest at a pH of low heterostability.« less

What can we learn about Mars from satellite magnetic field measurements?

NASA Astrophysics Data System (ADS)

Morschhauser, A.; Mittelholz, A.; Thomas, P.; Vervelidou, F.; Grott, M.; Johnson, C.; Lesur, V.; Lillis, R. J.

2017-12-01

The Mars orbiters MGS and MAVEN provide vector magnetic field data for Mars at a variety of altitudes, locations, and local times. In spite of the abundance of data, there are many open questions concerning the crustal magnetic field of Mars. In this contribution, we present our efforts to estimate the shutdown time of the Martian core dynamo and to estimate Martian paleopole locations, using magnetic field satellite data and models derived from these data [1]. Models are primarily based on MGS data, and we shortly present our recent advances to include MAVEN data. There exists some controversy concerning the timing of the Martian core dynamo shutdown [e.g., 2-5]. We address this question by studying the so-called visible magnetization [6-7] of impact craters larger than 400 km in diameter, and conclude that the dynamo ceased to operate in the Noachian period [8]. Further, paleopole locations have been used to constrain the dynamics of the Martian core dynamo [e.g. 4-5, 9]. However, such estimates are limited by the inherent non-uniqueness of inferring magnetization from magnetic field measurements. Here, we discuss how estimated paleopoles are influenced by this non-uniqueness and the limited signal-to-noise ratio of satellite measurements [6]. Furthermore, we discuss how paleopole locations may still be obtained from satellite magnetic field measurements. In this context, we present some new paleopole estimates for Mars including estimates of uncertainties. References: [1] A. Morschhauser et al. (2014), JGR, doi: 10.1002/2013JE004555 [2] R.J. Lillis et al. (2015), JGR, doi: 10.1002/2014je004774 [3] L.L. Hood et al. (2010), Icarus, doi: 10.1016/j.icarus.2010.01.009 [4] C. Milbury et al. (2012), JGR, doi: 10.1029/2012JE004099 [5] B. Langlais and M. Purucker (2007), PSS, 10.1016/j.pss.2006.03.008 [6] F. Vervelidou et al., On the accuracy of paleopole estimations from magnetic field measurements, GJI, under revision 2017 [7] D. Gubbins et al. (2011), GJI, doi: 10

Assessment of Atmospheric Water Vapor Abundance Above RSL Locations on Mars

NASA Astrophysics Data System (ADS)

Berdis, Jodi R.; Murphy, Jim; Wilson, Robert John

2016-10-01

The possible signatures of atmospheric water vapor arising from Martian Recurring Slope Lineae (RSLs)1 are investigated. These RSLs appear during local spring and summer on downward slopes, and have been linked to liquid water which leaves behind streaks of briny material. Viking Orbiter Mars Atmospheric Water Detector (MAWD)2 and Mars Global Surveyor (MGS) Thermal Emission Spectrometer (TES)3-5 derived water vapor abundance values are interrogated to determine whether four RSL locations at southern mid-latitudes (Palikir Crater, Hale Crater, Horowitz Crater, and Coprates Chasma) exhibit episodic enhanced local water vapor abundance during southern summer solstice (Ls = 270°) and autumnal equinox (Ls = 360°) when RSLs are observed to develop6,7. Any detected atmospheric water vapor signal would expand upon current knowledge of RSLs, while non-detection would provide upper limits on RSL water content. Viking Orbiter Infrared Thermal Mapper (IRTM) and MGS TES derived temperature values are also investigated due to the appearance of active RSLs after the surface temperature of the slopes exceeds 250 K1.A high spatial resolution Martian atmospheric numerical model will be employed to assess the magnitude and temporal duration of water vapor content that might be anticipated in response to inferred RSL surface water release. The ability of past and future orbiter-based instruments to detect such water vapor quantities will be assessed.References1. McEwen, A. et al. 2011, Sci., 333, 7402. Jakosky, B. & Farmer, C. 1982, JGR, 87, 29993. Christensen, P. et al. 1992, JGR, 97, 77194. Christensen, P. et al. 2001, JGR, 106, 238235. Smith, M. 2002, JGR, 107, 51156. Ojha, L. et al. 2015, Nature Geosci., 8, 8297. Stillman, D. et al. 2014, Icarus, 233, 328

Vertical Coupling and Observable Effects of Evanescent Acoustic-Gravity Waves in the Mesosphere and Thermosphere

NASA Astrophysics Data System (ADS)

Snively, J. B.

2017-12-01

Our understanding of acoustic-gravity wave (AGW) dynamics at short periods ( minutes to hour) and small scales ( 10s to 100s km) in the mesosphere, thermosphere, and ionosphere (MTI) has benefited considerably from horizontally- and vertically-resolved measurements of layered species. These include, for example, imagery of the mesopause ( 80-100 km) airglow layers and vertical profiles of the sodium layer via lidar [e.g., Taylor and Hapgood, PSS, 36(10), 1988; Miller et al., PNAS, 112(49), 2015; Cao et al., JGR, 121, 2016]. In the thermosphere-ionosphere, AGW perturbations are also revealed in electron density profiles [Livneh et al., JGR, 112, 2007] and maps of total electron content (TEC) from global positioning system (GPS) receivers [Nishioka et al., GRL, 40(21), 2013]. To the extent that AGW signatures in layered species can be quantified, and the ambient atmospheric state measured or estimated, numerical models enable investigations of dynamics at intermediate altitudes that cannot readily be measured (e.g., above and below the 80-100 km mesopause region). Here, new 2D and 3D versions of the Model for Acoustic-Gravity Wave Interactions and Coupling (MAGIC) [e.g., Snively and Pasko, JGR, 113(A6), 2008, and references therein] are introduced and applied to investigate spectra of short-period AGW that can pass through the mesopause region to reach and impact the thermosphere. Simulation case studies are constructed to investigate both their signatures through the hydroxyl airglow layer [e.g., Snively et al., JGR 115(A11), 2010] and their effects above. These waves, with large vertical wavelengths and fast horizontal phase speeds, also include those that may be subject to evanescence at mesopause or in the middle-thermosphere, with potential for ducting or dissipation between where static stability is higher. Despite complicating interpretations of momentum fluxes, evanescence plays an under-appreciated role in vertical coupling by AGW [Walterscheid and Hecht

Formation Timescales of the Martian Valley Networks

NASA Astrophysics Data System (ADS)

Hoke, M. T.; Hynek, B. M.

2010-12-01

Late Noachian and Early Hesperian [15, 16], approximately 3.6 to 3.8 billion years ago. The preferred model scenario includes bankfull flows of 4-5 m depths corresponding to precipitation rates of 5 to 36 mm/day, depending on the valley network, and occurring intermittently 5% of the time. Results of the preferred model include formation timescales of 104 years (3°S, 5°E) to 108 years (east branch of Naktong Valles and 6°S, 45°E). References: [1] Hynek et al. (2010) JGR, doi:10.1029/2009JE003548; [2] Di Achille and Hynek (2010) Nature Geoscience, 3, 459-463; [3] Irwin et al. (2005) JGR, 110, E12S15; [4] Fassett and Head (2008) Icarus, 198, 37-56; [5] Craddock and Howard (2002) JGR, 107, 5111; [6] Howard et al. (2005) JGR, 110, E12S14; [7] Barnhart et al. (2009) JGR, 114, E01003; [8] Komar (1979) Icarus, 37, 156-181; [9] Goldspiel and Squyres (1991) Icarus, 89, 392-410; [10] Wilson et al. (2004) JGR, 109, E09003; [11] Leopold et al. (1964) Fluvial Processes in Geomorphology, 522pp; [12] Bathurst (1993) in Channel Network Hydrology, eds. Beven and Kirkby, p69-98; [13] Komar (1980) Icarus, 42, 317-329; [14] Kleinhans (2005) JGR, 110, E12003; [15] Fassett and Head (2008) Icarus, 195, 61-89; [16] Hoke and Hynek (2009) JGR, 114, E08002.

Testing Orbital Parameters as a Hypothesis for the Presence of CO2 Deposits on Mars's South Pole

NASA Astrophysics Data System (ADS)

Bain, Z. M.; Bierson, C. J.

2017-12-01

] Kieffer (2013) JGR, Vol.118 Is.3 pp.451-470 [4] Laskar et al. (2004) Icarus, Vol.170 Is.2 pp.343-364

Regional Heat Flow Map and the Continental Thermal Isostasy Understanding of México

NASA Astrophysics Data System (ADS)

Espinoza-Ojeda, O. M.; Harris, R. N.

2014-12-01

The first heat flow values made in Mexico were reported by Von Herzen [Science, 1963] for the marine environment and Smith [EPSL, 1974] for the continent. Since that time the number of measurements has increased greatly but are mostly from oil and gas exploration and in and around geothermal areas. We have compiled published values of conductive heat flow for Mexico and the Gulf of California to generate a new regional heat flow map consisting of 261 values. In addition to those original values, published heat flow sources include, Lee and Henyey [JGR, 1975], Lawver and Williams [JGR, 1979] Smith et al. [JGR, 1979], Lachenbruch et al. [JGR, 1985], and Ziagos et al. [JGR, 1985]. Although the geographic distribution is uneven, heat flow data are present in each of the eight main tectonic provinces. Our new compilation indicates relatively high regional heat flow averages in the Gulf Extensional Province (n=114, 92±22 mW/m2) and Mexican Basin and Range (n=21, 82±20 mW/m2) and are consistent with geologic estimates of extension. Lower regional averages are found in the Baja California Microplate (n=91, 75±19 mW/m2), the Sierra Madre Occidental (n=9, 75±12 mW/m2), the Sierra Madre Oriental (n=4, 68±15 mW/m2) and Mesa Central (n=X 77±23 mW/m2). In contrast low and variable heat flow value characterize the forearc region of the Middle America Trench (n=6, 35±16 mW/m2). A higher mean heat flow is associated with the Trans-Mexican Volcanic Belt (n=6, 78±26 mW/m2). Continental elevation results from a combination of buoyancy (i.e. compositional and thermal) and geodynamic forces. We combine these regional heat flow values with estimates of crustal thickness and density for each tectonic province and compute the thermal and compositional buoyancy following the approach of Hasterok and Chapman [JGR, 2007a,b]. We find that within uncertainties most provinces lie near the theoretical isostatic relationship with the exception of the Mesa Central and Sierra Madre del Sur

Multiple ion species fluid modeling of sprite halos and the role of electron detachment from O- in their dynamics

NASA Astrophysics Data System (ADS)

Liu, N.

2011-12-01

Sprite halos are brief descending glows appearing at the lower ionosphere boundary, which follow impulsive cloud-to-ground lightning discharges [e.g., Barrington-Leigh et al., JGR, 106, 1741, 2001, Wescott et al., JGR, 106, 10467, 2001; Pasko, JGR, 115, A00E35, 2010]. They last for a few milliseconds, with horizontal extension of tens of kilometers and vertical thickness of several kilometers. According to global survey of the occurrence of transient luminous events by the ISUAL instruments on the FORMOSAT-2 satellite, on average sprite halos occur once every minute on Earth [Chen et al., JGR, 113, A08306, 2008]. It has been established that sprite halos are caused by electron heating, and molecule excitation and ionization in the lower ionosphere due to lightning quasi-electrostatic field [e.g., Pasko et al., JGR, 102, 4529, 1997; Barrington-Leigh et al., 2001; Pasko, 2010]. Past modeling work on sprite halos was conducted using either a two dimensional (2D) model of at most three charged species or a zero dimensional model of multiple ion species. In this talk, we report a modeling study of sprite halos using a recently developed 2D fluid model of multiple charged species. The model charged species include the ion species set used in [Lehtinen and Inan, GRL, 34, L08804, 2007] to study the dynamics of ionization perturbations produced by gigantic jets in the middle and upper atmosphere. In addition, another charged species, O-, is added to this set, because electron detachment of O- can proceed very fast under moderate electric field [Rayment and Moruzzi, Int. J. Mass Spectrom., 26, 321, 1978], requiring a separate treatment from the other light negative ions. The modeling results of a sprite halo driven by positive cloud-to-ground lightning indicate that the halo can descend to lower altitude with much higher electron density behind its front when the O- detachment process is included. Electron density ahead of the halo front is not significantly reduced from the

Flight Experience, Risk Taking, and Hazardous Attitudes in Glider Instructors (Experience de vol, Prise de Risque et Attitudes Dangereuses des Instructeurs de vol sur Planeur)

DTIC Science & Technology

2010-11-01

sur planeur . On a également examiné le rôle que jouent l’expérience de vol et la propension à prendre des risques dans le but d’anticiper les...données transversales, obtenues par l’observation de 144 instructeurs de vol sur planeur , en activité ou non, œuvrant dans cinq centres de vol à...137 Sommaire ..... Expérience de vol, prise de risque et attitudes dangereuses des instructeurs de vol sur planeur Ann-Renee Blais

What Can Spectral Properties of Martian Surface and Snc Can Tell Us about the Martian Crust Composition and Evolution

NASA Astrophysics Data System (ADS)

Ody, A.; Poulet, F.; Baratoux, D.; Quantin, C.; Bibring, J. P.

2014-12-01

While the study of Martian meteorites can provide detailed information about the crust and mantle composition and evolution, remote-sensing observations, through the merging of compositional and geological data, allow highlighting planetary-scale trends of the Martian crustal evolution [1,2]. Recently, the analysis of the global distribution of mafic minerals [3] has put new constraints on the Martian crust formation and evolution. One of the major results is a past global event of olivine-bearing fissural volcanism that has filled craters and low depressions in the southern highlands and a large part of the Northern plains during the late Noachian/early Hesperian. Petrologic models show that this sudden increase of the olivine content at the Noachian-Hesperian boundary could be the result of a rapid thickening of the lithosphere at the end of the Noachian era [4]. A recent study based on the OMEGA/MEx data has shown that the spectral properties of the shergottites are similar to those of some Noachian and Hesperian terrains [5]. To contrary, the Nakhla spectral properties are very different from those of the observable surface and could be representative of Amazonian terrains buried under dust. These results are best explained with an old age of the shergottites [6] and with the present understanding of the evolution of magma composition at a planetary scale [7]. On the other hand, if shergottites are young [8], the similarities between the shergottites and ancient terrains implies that exceptional conditions of melting with respect to the ambient mantle (e.g., hot spots or water-rich mantle source) were responsible for the formation of these samples [9]. References: [1] McSween et al., 2009, Science, 324. [2] Ehlmann & Edwards 2014, AREPS, vol. 42. [3] Ody et al., 2013, JGR,117,E00J14. [4] Ody et al., 2014, 8th Inter. Conf. on Mars,#1190. [5] Ody et al., 2013, 44th LPSC, #1719. [6] Bouvier et al., 2009, EPSL, 280. [7] Baratoux et al., 2013, JGR, 118. [8] Nyquist

Doping of Czochralski-grown bulk β-Ga2O3 single crystals with Cr, Ce and Al

NASA Astrophysics Data System (ADS)

Galazka, Zbigniew; Ganschow, Steffen; Fiedler, Andreas; Bertram, Rainer; Klimm, Detlef; Irmscher, Klaus; Schewski, Robert; Pietsch, Mike; Albrecht, Martin; Bickermann, Matthias

2018-03-01

We experimentally evaluated segregation of Cr, Ce and Al in bulk β-Ga2O3 single crystals grown by the Czochralski method, as well as the impact of these dopants on optical properties. The segregation of Cr and Ce and their incorporation into the β-Ga2O3 crystal structure strongly depends on O2 concentration in the growth atmosphere which has a noticeable impact on decomposition of Ga2O3 and Cr2O3, as well as on the charge state of Cr and Ce. Effective segregation coefficients for Cr are in the range of 3.1-1.5 at 7-24 vol% O2, while for Ce they are roughly below 0.01 at 1.5-34 vol% O2. The effective segregation coefficient for Al is 1.1 at 1.5-21 vol% O2. Both dopants Ce and Al have a thermodynamically stabilizing effect on β-Ga2O3 crystal growth by supressing decomposition. While Ce has no impact on the optical transmittance in the ultraviolet and visible regions, in Cr doped crystals we observe three absorption bands due to Cr3+ on octahedral Ga sites, one in the ultraviolet merging with the band edge absorption of β-Ga2O3 and two in the visible spectrum, for which we estimate the absorption cross sections. Al doping also does not induce dopant related absorption bands but clearly shifts the absorption edge as one expects for a solid-solution crystal Ga2(1-x)Al2xO3 still in the monoclinic phase. For the highest doping concentration (Ga1.9Al0.1O3) we estimate an increase of the energy gap by 0.11 eV.

Excavation of Stratified Phyllosilicate-Bearing Rocks in the Northern Plains of Mars

NASA Astrophysics Data System (ADS)

Gross, C.; Carter, J.; Tornabene, L. L.; Sowe, M.; Bishop, J. L.

2014-12-01

The Noachian southern highlands of Mars bear old crustal material which appears mostly unaltered (Bandfield, 2002; Bibring et al., 2005; Christensen et al., 2005) and contains phyllosilicate-rich material. Phyllosilicates are of particular interest, as they require the presence of liquid water over long terms and may represent habitable environments. Most phyllosilicates formed early in Mars' history during the Noachian period (Bibring et al., 2006). However, a set of Hesperian-aged impact craters, Toro (Marzo et al., 2010) and Majuro (Mangold et al., 2012) bear evidence for impact-induced hydrothermal activity in the southern highlands. Phyllosilicate outcrops in the northern plains are exclusively found in and around impact craters. This could lead to the conclusion that they might form excavation products of preexisting, buried deposits, exposed by impacting and erosion (Carter et al. 2010; Bibring et al. 2006; Murchie et al. 2009). Nevertheless, when investigating alteration associated with impact craters, pre-, syn- and post-impact scenarios have to be considered (Osinski et al., 2013; Tornabene et al., 2013). We revisited a set of impact sites described by Carter et al. (2010) for further investigation and to test the theory of impact excavation of old preexisting strata versus impact-induced hydrothermal activity. This can be achieved as coverage of high resolution data has drastically increased during the time of that study. We here report the presence of uplifted, stratified, phyllosilicate-rich material in an impact crater, located in the northern plains of Mars, close to the dichotomy boundary. References: Bandfield (2002) JGR, 107, E6, 5042. Bibring et al. (2005) Science, 307, 1576-1581. Christensen et al. (2005) Nature, 436, 504-509. Bibring et al. (2006) Science, 312, 400-404. Marzo et al. (2010) Icarus, 208, 667-683. Mangold et al. (2012) PSS, 72, 18-30. Carter et al. (2010) Science, 328, 1682-1686. Murchie et al. (2009) JGR, 114, E00D06. Osinski et

Three-Dimensional FIB/EBSD Characterization of Irradiated HfAl3-Al Composite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hua, Zilong; Guillen, Donna Post; Harris, William

2016-09-01

A thermal neutron absorbing material, comprised of 28.4 vol% HfAl3 in an Al matrix, was developed to serve as a conductively cooled thermal neutron filter to enable fast flux materials and fuels testing in a pressurized water reactor. In order to observe the microstructural change of the HfAl3-Al composite due to neutron irradiation, an EBSD-FIB characterization approach is developed and presented in this paper. Using the focused ion beam (FIB), the sample was fabricated to 25µm × 25µm × 20 µm and mounted on the grid. A series of operations were carried out repetitively on the sample top surface tomore » prepare it for scanning electron microscopy (SEM). First, a ~100-nm layer was removed by high voltage FIB milling. Then, several cleaning passes were performed on the newly exposed surface using low voltage FIB milling to improve the SEM image quality. Last, the surface was scanned by Electron Backscattering Diffraction (EBSD) to obtain the two-dimensional image. After 50 to 100 two-dimensional images were collected, the images were stacked to reconstruct a three-dimensional model using DREAM.3D software. Two such reconstructed three-dimensional models were obtained from samples of the original and post-irradiation HfAl3-Al composite respectively, from which the most significant microstructural change caused by neutron irradiation apparently is the size reduction of both HfAl3 and Al grains. The possible reason is the thermal expansion and related thermal strain from the thermal neutron absorption. This technique can be applied to three-dimensional microstructure characterization of irradiated materials.« less

SEM and TEM characterization of the microstructure of post-compressed TiB2/2024Al composite.

PubMed

Guo, Q; Jiang, L T; Chen, G Q; Feng, D; Sun, D L; Wu, G H

2012-02-01

In the present work, 55 vol.% TiB(2)/2024Al composites were obtained by pressure infiltration method. Compressive properties of 55 vol.% TiB(2)/2024Al composite under the strain rates of 10(-3) and 1S(-1) at different temperature were measured and microstructure of post-compressed TiB(2)/2024Al composite was characterized by scanning electron microscope (SEM) and transmission electron microscope (TEM). No trace of Al(3)Ti compound flake was found. TiB(2)-Al interface was smooth without significant reaction products, and orientation relationships ( [Formula: see text] and [Formula: see text] ) were revealed by HRTEM. Compressive strength of TiB(2)/2024Al composites decreased with temperature regardless of strain rates. The strain-rate-sensitivity of TiB(2)/2024Al composites increased with the increasing temperature. Fracture surface of specimens compressed at 25 and 250°C under 10(-3)S(-1) were characterized by furrow. Under 10(-3)S(-1), high density dislocations were formed in Al matrix when compressed at 25°C and dynamic recrystallization occurred at 250°C. Segregation of Mg and Cu on the subgrain boundary was also revealed at 550°C. Dislocations, whose density increased with temperature, were formed in TiB(2) particles under 1S(-1). Deformation of composites is affected by matrix, reinforcement and strain rate. Copyright © 2011 Elsevier Ltd. All rights reserved.

Hydrogeological and Seismic Responses to Incoming Materials at the Non-Accreting Margin, Offshore the Osa Peninsula, Costa Rica

NASA Astrophysics Data System (ADS)

Harris, R. N.; Kameda, J.; Shimizu, M.; Ujiie, K.; Tsutsumi, A.; Ikehara, M.; Uno, M.; Yamaguchi, A.; Hamada, Y.; Namiki, Y.; Kimura, G.

2015-12-01

The relationship between temperature and the updip limit of seismicity has been demonstrated for accretionary margins where the incoming sediment is thick relative to basement relief (e.g., Oleskevich et al., JGR 1999). Here we show an example offshore the Osa Peninsula where this relationship does not appear to hold. At this non-accreting margin, the incoming sediment thickness is thin and the basement relief is substantial. The MW 6.4, 16 June 2002, Osa, Costa Rica earthquake occurred along the plate interface, 25 km landward of the trench at a depth of approximately 5-10 km (Arroyo et al., G3, 2014). Two-dimensional thermal models indicate that the temperature at this position is approximately 70-90° C (Harris et al., G3, 2010), and is cooler than the reported correlation between temperature and the updip limit of seismicity. We estimate the incoming fluid budget based on the 100 m section from the Costa Rica Seismogenesis Project reference site (IODP Exp. 334 Site U1381) using porosity and bulk mineral assemblage based on X-ray diffraction analysis of core samples. The porosity (76%) combined with the water content in smectite (~40 vol.%) and biogenic silica (~24 vol.%), leads to a total sedimentary water influx estimate of 6.9 m3/yr per m of trench length. The dehydration source term is calculated with respect to silica diagenesis and clay diagenesis using the thermal model. Peak mineral dehydration occurs at temperatures of approximately ~100 °C, 40-30 km landward of the trench and 5-10 km landward of the shallowest seismicity (Arroyo et al., G3, 2014). These results suggest that in this region the presence of subducting bathymetric relief may be more important in influencing the updip extent of seismicity than the thermal regime. This interpretation is consistent with the observed patchy seismicity (Bilek et al. Geology, 2003) and emphasizes the importance of frictional heterogeneities along the subduction thrust (Bilek and Lay, GRL, 2002).

Water vapor effect on high-temperature oxidation behavior of Fe3Al intermetallics

PubMed Central

Chevalier, Sebastian; Juzon, Pitor; Przybylski, Kazimierz; Larpin, Jean-Pierre

2009-01-01

Fe3Al intermetallics (Fe3Al, Fe3Al-Zr, Fe3Al-Zr,Mo and Fe3Al-Zr, Mo, Nb) were oxidized at 950 °C in dry and humid (11 vol% water) synthetic air. Thermogravimetric measurements showed that the oxidation rates of the tested intermetallics were lower in humid air than in dry air (especially for Fe3Al-Zr, Mo and Fe3Al-Zr, Mo, Nb). The addition of small amounts of Zr, Mo or Nb improved the kinetics compared with that of the undoped Fe3Al. Fe3Al showed massive spallation, whereas Fe3Al-Zr, Fe3Al-Zr, Mo and Fe3Al-Zr, Mo, Nb produced a flat, adherent oxide layer. The rapid transformation of transient alumina into alpha alumina may explain the decrease in the oxidation rate in humid air. PMID:27877306

Termination Shock Transition in Multi-ion Multi-fluid MHD Models of the Heliosphere

NASA Astrophysics Data System (ADS)

Zieger, B.; Opher, M.; Toth, G.

2013-12-01

As evidenced by Voyager 2 observations, pickup ions (PUIs) play a significant role in the termination shock (TS) transition of the solar wind [Richardson et al., Nature, 2008]. Recent kinetic simulations [Ariad and Gedalin, JGR, 2013] came to the conclusion that the contribution of the high energy tail of PUIs is negligible at the shock transition. The Rankine-Hugoniot (R-H) relations are determined by the low energy body of PUIs. Particle-in-cell simulations by Wu et al. [JGR, 2010] have shown that the sum of the thermal solar wind and non-thermal PUI distributions downstream of the TS can be approximated with a 2-Maxwellian distribution. It is important to note that this 2-Maxwellian distribution neglects the suprathermal tail population that has a characteristic power-law distribution. These results justify the fluid description of PUIs in our large-scale multi-ion multi-fluid MHD simulations of the heliospheric interface [Prested et al., JGR, 2013; Zieger et al., GRL, 2013]. The closure of the multi-ion MHD equations could be implemented with separate momentum and energy equations for the different ion species (thermal solar wind and PUIs) where the transfer rate of momentum and energy between the two ion species are considered as source terms, like in Glocer et al. [JGR, 2009]. Another option is to solve for the total energy equation with an additional equation for the PUI pressure, as suggested by Fahr and Chalov [A&A, 2008]. In this paper, we validate the energy conservation and the R-H relations across the TS in different numerical implementations of our latest multi-ion multi-fluid MHD model. We assume an instantaneous pickup process, where the convection velocity of the two ion fluids are the same, and the so-called strong scattering approximation, where newly born PUIs attain their spherical shell distribution within a short distance on fluid scales (spatial scales much larger than the respective ion gyroradius).

Constraining the 0-20 km Vertical Profile of Water Vapor in the Martian Atmosphere with MGS-TES Limb Sounding

NASA Astrophysics Data System (ADS)

McConnochie, T. H.; Smith, M. D.; McDonald, G. D.

2016-12-01

The vertical profile of water vapor in the lower atmosphere of Mars is a crucial but poorly-measured detail of the water cycle. Most of our existing water vapor data sets (e.g. Smith, 2002, JGR 107; Smith et al., 2009, JGR 114; Maltagliati et al., 2011, Icarus 213) rely on the traditional assumption of uniform mass mixing from the surface up to a saturation level, but GCM models (Richardson et al., 2002, JGR 107; Navarro et al., 2014, JGR 119) imply that this is not the case in at least some important seasons and locations. For example at the equator during northern summer the water vapor mixing ratio in aforementioned GCMs increases upwards by a factor of two to three in the bottom scale height. This might influence the accuracy of existing precipitable water column (PWC) data sets. Even if not, the correct vertical distribution is critical for determining the extent to which high-altitude cold trapping interferes with inter-hemispheric transport, and its details in the lowest scale heights will be a critical test of the accuracy of modeled water vapor transport. Meanwhile attempts to understand apparent interactions of water vapor with surface soils (e.g. Ojha et al. 2015, Nature Geoscience 8; Savijärvi et al., 2016, Icarus 265) need an estimate for the amount of water vapor in the boundary layer, and existing PWC data sets can't provide this unless the lower atmospheric vertical distribution is known or constrained. Maltagliati et al. (2013, Icarus 223) have obtained vertical profiles of water vapor at higher altitudes with SPICAM on Mars Express, but these are commonly limited to altitudes greater 20 km and they never extend below 10 km. We have previously used Mars Global Surveyor (MGS) Thermal Emission Spectrometer (TES) limb-sounding to measure the vertical profile of water vapor (e.g. McConnochie and Smith, 2009, Fall AGU #P54B-06), but these preliminary results were clearly not quantitatively accurate in the lower atmosphere. We will present improved TES

Response of Al-Based Micro- and Nanocomposites to Rapid Fluctuations in Thermal Environments

NASA Astrophysics Data System (ADS)

Dash, K.; Ray, B. C.

2018-05-01

The focus of this work is to highlight the relative response of Al-based micro- and nanocomposites in the form of enhancement in flexural strength via induced thermal stresses at high and cryogenic temperatures in ex situ and in situ atmospheres. In this investigation, we have tried to explore the reliability, matrix-reinforcement interaction and microstructural integrity of these materials in their service period by designing appropriate heat treatment regimes. Al-Al2O3 micro- and nanocomposites had been fabricated by powder processing method. The micro- and nanocomposites were subjected to down-thermal shock (from positive to negative temperature) and up-thermal shock (from negative to positive temperature) with varying thermal gradients. For isothermal conditioning, the composites were exposed to + 80 and - 80 °C for 1 h separately. High-temperature three-point flexural tests were performed at 100 and 250 °C on the composites. All the composites subjected to thermal shock and isothermal conditioning was tested in three-point flexural mode post-treatments. Al-1 vol.% Al2O3 nanocomposite's flexural strength improved to 118 MPa post-thermal shock treatment of gradient of 160 °C. The Al-5 and 10 vol.% Al2O3 microcomposites possessed flexural strength of 200 and 99.8 MPa after thermal shock treatment of gradient of 160 and 80 °C, respectively. The observed improvement in flexural strength of micro- and nanocomposites post-thermal excursions were compared and have been discussed with the support of fractography. The microcomposites showed a higher positive scale of response to the thermal excursions as compared to that of the nanocomposites.

Slow Slip Predictions Based on Gabbro Dehydration and Friction Data Compared to GPS Measurements in Northern Cascadia

NASA Astrophysics Data System (ADS)

Rice, J. R.; Liu, Y.

2008-12-01

For episodic slow slip transients in subduction zones, a large uncertainty in comparing surface deformations predicted by rate and state friction modeling [Liu and Rice, JGR, 2007] to GPS measurements lies in our limited knowledge of the frictional properties and fluid pore pressure along the fault. In this study, we apply petrological data [Peacock et al., USGS, 2002; Hacker et al., JGR 2003; Wada et al., JGR, 2008] and recently reported friction data [He et al., Tectonophys, 2006, 2007] for gabbro, as a reasonable representation of the seafloor, to a Cascadia-like 2D model in order to produce simulations which show spontaneous aseismic transients. We compare the resulting inter-transient and transient surface deformations to GPS observations along the northern Cascadia margin. An inferred region along dip of elevated fluid pressure is constrained by seismological observations where available, and by thermal and petrological models for the Cascadia and SW Japan subduction zones. For the assumed a and a-b profiles, we search the model parameter space, by varying the level of effective normal stress σ, characteristic slip distance L in the source areas of transients, and the fault width under that low σ, to identify simulation cases which produce transient aseismic slip and recurrence interval similar to the observed 20-30 mm and 14 months, respectively, in northern Cascadia. Using a simple planar fault geometry and extrapolating the 2D fault slip to a 3D distribution, we find that the gabbro gouge friction data allows a much better fit to GPS observations than is possible with the granite data [Blanpied et al., JGR, 1995, 1998] which, for lack of a suitable alternative, has been used as the basis for most previous subduction earthquake modeling, including ours. Nevertheless, the values of L required to reasonably fit the geodetic data during a transient event are somewhat larger than 100 microns, rather than in the range of 10 to a few 10s of microns as might be

Mechanism of Lightning Associated Infrasonic Pulses from Thunderclouds

NASA Astrophysics Data System (ADS)

Pasko, V. P.

2008-12-01

The infrasonic waves correspond to the region of frequencies of acoustic sound waves 0.02-10 Hz, higher than the acoustic cut-off frequency but lower than the audible frequencies [e.g., Blanc, Ann. Geophys., 3, 673, 1985]. There is a strong experimental evidence that thunderstorms represent significant sources of infrasonic wave activity spanning a broad altitude range from the troposphere and up to the thermosphere [e.g., Blanc, 1985; Few, in Handbook of Atmospheric Electrodynamics, Vol. 2, edited by H. Volland, pp. 1-31, CRC Press, 1995; Drob et al., JGR, 108, 4680, 2003]. This evidence includes electrostatic production of 0.1- 1 Hz infrasonic waves from thunderclouds [Few, 1995] and recent discovery of infrasound from lightning induced transient luminous events in the mesosphere called sprites [Liszka, J. Low Freq. Noise Vibr. Active Control, 23, 85, 2004; Farges et al., GRL, 32, L13824, 2005; Liszka and Hobara, JASTP, 68, 1179, 2006]. The understanding and classification of different infrasonic waves and their sources is of great current interest from a Comprehensive Nuclear-Test-Ban Treaty (CTBT) verification perspective [e.g., Assink et al., GRL, 35, L15802, 2008]. It has been pointed many decades ago by C. T. R. Wilson [Phil. Trans. R. Soc. London A, 221, 73, 1920] that sudden reduction of the electric field inside a thundercloud immediately following a lightning discharge should produce an infrasound signature. Wilson [1920] noted that the pressure within a charged cloud must be less than the pressure outside, similarly to that within a charged soap bubble. In contrast to the sudden expansion of the air along the track of a lightning flash, the sudden contraction of a large volume of air must furnish a measurable rarefaction pulse [Wilson, 1920]. Many experimental and theoretical contributions followed these predictions by C. T. R. Wilson (see [Few, JGR, 90, 6175, 1985] and extensive list of references therein). Modeling investigation of related scenarios

The formation of ultrafine iodine particles from coastal macroalgae

NASA Astrophysics Data System (ADS)

McFiggans, G.; Coe, H.; Allan, J. D.; Plane, J. M. C.; Saunders, R.

2003-04-01

detection threshold of an aerosol mass spectrometer (AMS). It was found that the dominant m/z fragments above 100 Daltons at all sizes of particle were derived from iodine-containing species, but the mass spectrum exhibited significant differences from that reported for particles generated in the laboratory from iodocarbon photolysis(5,6). Subsequent experiments at UMIST have found a similar response from the related and more widespread macroalga Laminaria hyperborea. In addition, further results from the laboratory program investigating ufp formation from both inorganic and organic precursor molecules will be presented and discussed to aid mechanistic interpretation of the release of ufps from macroalgae. 1. O’Dowd et al., GRL, 1707-1710, 1999, 2. Coe et al., JGR, 26891-26905, 2000, 3. Kolb, Nature, 597-598, 2002, 4. Hoffmann et al., GRL, 1949-1952, 2001, 5. O’Dowd et al., Nature, 632-636, 2002, 6. Jimenez et al., JGR in press, 2003, 7. McFiggans et al., EGS presentation, 2002, 8. McFiggans, CERC3 presentation, 2002, 9. McFiggans et al., 2003, in prep, 10. Alicke et al., Nature, 572-573, 1999, 11. Allan et al., JGR, 14363-14369, 2000, 12. Carpenter et al., JGR, 1679-1689, 1999, 13. McFiggans et al., JGR, 14371-14385, 2000, 14. Carpenter et al., GBC, 1191-1204, 2000, 15. Carpenter et al., ACP, 9-18, 2001.

Feasibility study of short-term earthquake prediction using ionospheric anomalies immediately before large earthquakes

NASA Astrophysics Data System (ADS)

Heki, K.; He, L.

2017-12-01

We showed that positive and negative electron density anomalies emerge above the fault immediately before they rupture, 40/20/10 minutes before Mw9/8/7 earthquakes (Heki, 2011 GRL; Heki and Enomoto, 2013 JGR; He and Heki 2017 JGR). These signals are stronger for earthquake with larger Mw and under higher background vertical TEC (total electron conetent) (Heki and Enomoto, 2015 JGR). The epicenter, the positive and the negative anomalies align along the local geomagnetic field (He and Heki, 2016 GRL), suggesting electric fields within ionosphere are responsible for making the anomalies (Kuo et al., 2014 JGR; Kelley et al., 2017 JGR). Here we suppose the next Nankai Trough earthquake that may occur within a few tens of years in Southwest Japan, and will discuss if we can recognize its preseismic signatures in TEC by real-time observations with GNSS.During high geomagnetic activities, large-scale traveling ionospheric disturbances (LSTID) often propagate from auroral ovals toward mid-latitude regions, and leave similar signatures to preseismic anomalies. This is a main obstacle to use preseismic TEC changes for practical short-term earthquake prediction. In this presentation, we show that the same anomalies appeared 40 minutes before the mainshock above northern Australia, the geomagnetically conjugate point of the 2011 Tohoku-oki earthquake epicenter. This not only demonstrates that electric fields play a role in making the preseismic TEC anomalies, but also offers a possibility to discriminate preseismic anomalies from those caused by LSTID. By monitoring TEC in the conjugate areas in the two hemisphere, we can recognize anomalies with simultaneous onset as those caused by within-ionosphere electric fields (e.g. preseismic anomalies, night-time MSTID) and anomalies without simultaneous onset as gravity-wave origin disturbances (e.g. LSTID, daytime MSTID).

Community Radiative Transfer Model for Inter-Satellites Calibration and Verification

NASA Astrophysics Data System (ADS)

Liu, Q.; Nalli, N. R.; Ignatov, A.; Garrett, K.; Chen, Y.; Weng, F.; Boukabara, S. A.; van Delst, P. F.; Groff, D. N.; Collard, A.; Joseph, E.; Morris, V. R.; Minnett, P. J.

2014-12-01

., and S. Boukabara, 2013: RSE [3] Boukabara et al., 2011: TGARS [4] Wang, LK, Zou C-Z. 2013: JGR [5] Weng et al, 2012: JGR [6] Han, Y., et al., 2013: JGR [7] Caoet al, 2013: GR [8] Liang, X, A. Ignatov, 2013: JGR [9] Nalliet al 2011: BAMS [10] Minnett et al, 2001: JAOT

Analysis of the Phoenix Mission's Thermal and Electrical Conductivity Probe (TECP) Relative Humidity Data

NASA Astrophysics Data System (ADS)

Fischer, E.; Martinez, G.; Renno, N. O.; Tamppari, L.; Zent, A.

2015-12-01

With funding from NASA's Mars Data Analysis Program, we plan to enhance the scientific return of the Phoenix mission by producing and archiving high-level relative humidity (RH) data from the measurements made by the Thermal and Electrical Conductivity Probe (TECP). Values of temperature and RH covered in the pre-flight calibration [1] overlap only partially with the environmental conditions found at the Phoenix landing site [2,3]. In particular, there is no overlap at dawn, when temperatures are the lowest and the expected RH is the highest [4] and in the middle of the day, when temperatures are relatively high and the expected RH is very low [5]. Here we plan to produce high-level RH data by calibrating an Engineering Model of the TECP in the Michigan Mars Environmental Chamber (MMEC). The MMEC is capable of simulating the entire range of environmental conditions found at the Phoenix landing site. The MMEC is a cylindrical chamber with internal diameter of 64 cm and length of 160 cm. It is capable of simulating temperatures ranging from 145 to 500 K, CO2 pressures ranging from 10 to 105 Pa, and relative humidity ranging from nearly 0 to 100% [6]. The analysis of high-level RH data has the potential to shed light on the formation of liquid brines at Mars' polar latitudes, where it is most likely to occur [7]. In addition, the RH sensor aboard Curiosity is similar to that on the TECP [8], allowing a direct comparison of the near-surface RH measurements at these two different locations on the surface of Mars. REFERENCES: [1] Zent, A. P., et al, 2009, JGR (1991-2012) 114.E3. [2] Tamppari, L. K., et al. 2010, JGR, 115, E00E17. [3] Davy, R., et al., 2010, JGR, 115, E00E13. [4] Whiteway, J., et al., 2009, Science, 325, 68-70. [5] Savijärvi, H., and A. Määttänen, 2010, Q. J. R. Meteorol. Soc., 136, 1497-1505. [6] Fischer, E., et al., 2014, GRL, 41, 4456-4462. [7] Martínez, G., and Rennó, N., 2013, Space Sci. Rev., 175, 29-51. [8] Harri, A-M., et al., 2014, JGR 119

Synthesis of Ti-6Al-4V alloy with nano-TiN microstructure via spark plasma sintering technique

NASA Astrophysics Data System (ADS)

E Falodun, O.; Obadele, B. A.; Oke, S. R.; E Maja, M.; Olubambi, P. A.

2017-12-01

The effect of nano-TiN dispersion strengthened Ti-6Al-4V via spark plasma sintering method has been investigated. Ti-6Al-4V with 4 vol. percent of nano-TiN were mixed in a Turbula shaker mixer for 8 h at a speed of 49 rpm and the admixed powders were sintered at sintering temperature range of 1000 - 1100 °C, holding time of 10-30 mins, heating rate of 100 °C/min under an applied pressure of 50 MPa. The morphology of the as-received and sintered compacts was examined by scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS) and phase analysis was done by X-ray diffractometry (XRD). The sintered compacts without nano-TiN reveal lamellar structure while reinforced Ti-6Al-4V with nano-TiN shows a bimodal structure and titanium nitride has a great influence on a grain growth at high temperature. Furthermore, the microstructural formation mechanism was investigated. With the addition of the content of Ti-6Al-4V with 4 vol.% of nano-TiN, the micro-hardness also improved and this was due to homogenous distribution of TiN in Ti-6Al-4V matrix.

Airborne dust and soil particles at the Phoenix landing site, Mars

NASA Astrophysics Data System (ADS)

Madsen, M. B.; Drube, L.; Goetz, W.; Leer, K.; Falkenberg, T. V.; Gunnlaugsson, H. P.; Haspang, M. P.; Hviid, S. F.; Ellehøj, M. D.; Lemmon, M. T.

2009-04-01

The three iSweep targets on the Phoenix lander instrument deck utilize permanent magnets and 6 different background colors for studies of airborne dust [1]. The name iSweep is short for Improved Sweep Magnet experiments and derives from MER heritage [2, 3] as the rovers carried a sweep magnet, which is a very strong ring magnet built into an aluminum structure. Airborne dust is attracted and held by the magnet and the pattern formed depends on magnetic properties of the dust. The visible/near-infrared spectra acquired of the iSweep are rather similar to typical Martian dust and soil spectra. Because of the multiple background colors of the iSweeps the effect of the translucence of thin dust layers can be studied. This is used to estimate the rate of dust accumulation and will be used to evaluate light scattering properties of the particles. Some particles raised by the retro-rockets during the final descent came to rest on the lander deck and spectra of these particles are studied and compared with those of airborne dust and with spectra obtained from other missions. High resolution images acquired by the Optical Microscope (OM) [4] showed subtle differences between different Phoenix soil samples in terms of particle size and color. Most samples contain orange dust (particles smaller than 10 micrometer) as their major component and silt-sized (50-80 micrometer large) subrounded particles. Both particle types are substantially magnetic. Based on results from the Mars Exploration Rovers, the magnetization of the silt-sized particles is believed to be caused by magnetite. Morphology, texture and color of these particles (ranging from colorless, red-brown to almost black) suggest a multiple origin: The darkest particles probably represent lithic fragments, while the brighter ones could be impact or volcanic glasses. [1] Leer K. et al. (2008) JGR, 113, E00A16. [2] Madsen M.B. et al. (2003) JGR, 108, 8069. [3] Madsen M.B. et al. (2008) JGR (in print). [4] Hecht M.H. et

Wear properties of 10 vol.% silicon carbide particulate-reinforced aluminum composite fabricated by powder injection molding

NASA Astrophysics Data System (ADS)

Patcharawit, T.; Ngeekoh, A.; Chuankrekkul, N.

2017-09-01

Wear properties of aluminum matrix composites reinforced with silicon carbide particulate of 10 vol.% addition was investigated in as-sintered and heat-treated conditions under varying loads at -5, -25, -45 and -65N using a ball on flat type of wear test. The composite was fabricated by powder injection molding and sintering at 650 °C for 3 hours. Solution treatment was carried out at 550 °C for 2 hours followed by age-hardening at 160 °C for 6 hours. SEM and XRD results indicated Al and SiCp are present as matrix and reinforcement, while AlN, Al2Cu and Mg2Si were also detected. Further precipitation of Al2Cu and Mg2Si in heat-treated samples promoted maximum macro and micro Vickers hardness values, which were achieved at 161 and 157 Hv respectively. Wear weight loss increased with increasing minus load level. The coefficient of friction was found in the range of 0.042-0.048. Wear mechanisms were determined as the combination of abrasive, adhesion and oxidation.

Mars Organic Matter Revealed by the Detection of Organo-chlorinated Molecules from Pyro-GCMS Analyses of Yellowknife Bay Mudstone

NASA Astrophysics Data System (ADS)

Szopa, C.; Freissinet, C.; Glavin, D. P.; Buch, A.; Coll, P. J.; Cabane, M.; Millan, M.; Belmahadi, I.; Navarro-Gonzalez, R.; Steele, A.; Summons, R. E.; Eigenbrode, J. L.; Mahaffy, P. R.

2015-12-01

Mudstones collected on the Yellowknife Bay site in Gale crater by the Curiosity rover, were analyzed with the Sample Analysis at Mars (SAM) chemical laboratory with the aim (among others) to detect and identify organic molecules in the Martian reglith [1]. The pyrolysis (to 900°C)-gas chromatography-mass spectrometry (Pyro-GCMS) analytical mode was systematically used to reach that goal. It revealed the existence of complex interactions between compounds present in the soil sample (e.g. oxychlorines [2]) and internal components of the SAM experiment (e.g. derivatization reactant) resulting in signals complex to interpret [3]. By comparing these results with those obtained for the other Mars samples analysed with SAM, and by carefully identifying, from laboratory work, the possible SAM internal contributions to the organic molecules detected [4], chlorobenzene has already been identified as mainly originating from organics present in the mudstone [5]. Since this discovery, we did additional studies of the chromatograms that reveal the presence of dichlorobenzene originating from an organic source endogenous to the sample. Even if the exact original source of these organic molecules cannot be strictly identified, the detection of several chlorinated aromatic molecules suggests the presence of a significant amount of aromatized materials which are in an oxidized state involving oxygen in the mudstone. We present here the corresponding results and the implication it can have on the origin of these organic materials References: [1] Mahaffy, P. et al. (2012) Space Sci Rev, 170, 401-478. [2] Glavin, D. et al. (2013), JGR. [3] Ming D. et al. (2013), Science 32, 64, [4] Miller K. et al. (In press), JGR, [5] Freissinet et al., (2015), JGR Pla. 120, 495.

Petrogenesis of the Northwest Africa 4898 high-Al mare basalt

NASA Astrophysics Data System (ADS)

Li, Shaolin; Hsu, Weibiao; Guan, Yunbin; Wang, Linyan; Wang, Ying

2016-07-01

Northwest Africa (NWA) 4898 is the only low-Ti, high-Al basaltic lunar meteorite yet recognized. It predominantly consists of pyroxene (53.8 vol%) and plagioclase (38.6 vol%). Pyroxene has a wide range of compositions (En12-62Fs25-62Wo11-36), which display a continuous trend from Mg-rich cores toward Ca-rich mantles and then to Fe-rich rims. Plagioclase has relatively restricted compositions (An87-96Or0-1Ab4-13), and was transformed to maskelynite. The REE zoning of all silicate minerals was not significantly modified by shock metamorphism and weathering. Relatively large (up to 1 mm) olivine phenocrysts have homogenous inner parts with Fo ~74 and sharply decrease to 64 within the thin out rims (~30 μm in width). Four types of inclusions with a variety of textures and modal mineralogy were identified in olivine phenocrysts. The contrasting morphologies of these inclusions and the chemical zoning of olivine phenocrysts suggest NWA 4898 underwent at least two stages of crystallization. The aluminous chromite in NWA 4898 reveals that its high alumina character was inherited from the parental magma, rather than by fractional crystallization. The mineral chemistry and major element compositions of NWA 4898 are different from those of 12038 and Luna 16 basalts, but resemble those of Apollo 14 high-Al basalts. However, the trace element compositions demonstrate that NWA 4898 and Apollo 14 high-Al basalts could not have been derived from the same mantle source. REE compositions of its parental magma indicate that NWA 4898 probably originated from a unique depleted mantle source that has not been sampled yet. Unlike Apollo 14 high-Al basalts, which assimilated KREEPy materials during their formation, NWA 4898 could have formed by closed-system fractional crystallization.

Improvement in dielectric and mechanical performance of CaCu3.1Ti4O12.1 by addition of Al2O3 nanoparticles

PubMed Central

2012-01-01

The properties of CaCu3.1Ti4O12.1 [CC3.1TO] ceramics with the addition of Al2O3 nanoparticles, prepared via a solid-state reaction technique, were investigated. The nanoparticle additive was found to inhibit grain growth with the average grain size decreasing from approximately 7.5 μm for CC3.1TO to approximately 2.0 μm for the unmodified samples, while the Knoop hardness value was found to improve with a maximum value of 9.8 GPa for the 1 vol.% Al2O3 sample. A very high dielectric constant > 60,000 with a low loss tangent (approximately 0.09) was observed for the 0.5 vol.% Al2O3 sample at 1 kHz and at room temperature. These data suggest that nanocomposites have a great potential for dielectric applications. PMID:22221316

Effects of metal binder on the microstructure and mechanical properties of Al2O3-based micro-nanocomposite ceramic tool material

NASA Astrophysics Data System (ADS)

Ni, Xiu-ying; Zhao, Jun; Sun, Jia-lin; Gong, Feng; Li, Zuo-li

2017-07-01

The Al2O3-(W,Ti)C composites with Ni and Mo additions varying from 0vol% to 12vol% were prepared via hot pressing sintering under 30 MPa. The microstructure was investigated via X-ray diffraction (XRD) and scanning electron microscopy (SEM) equipped with energy dispersive spectrometry (EDS). Mechanical properties such as flexural strength, fracture toughness, and Vickers hardness were also measured. Results show that the main phases A12O3 and (W,Ti)C were detected by XRD. Compound MoNi also existed in sintered nanocomposites. The fracture modes of the nanocomposites were both intergranular and transgranular fractures. The plastic deformation of metal particles and crack bridging were the main toughening mechanisms. The maximum flexural strength and fracture toughness were obtained for 9vol% and 12vol% additions of Ni and Mo, respectively. The hardness of the composites reduced gradually with increasing content of metals Ni and Mo.

Fabrication of TiCx-TiB₂/Al Composites for Application as a Heat Sink.

PubMed

Shu, Shili; Yang, Hongyu; Tong, Cunzhu; Qiu, Feng

2016-07-29

Metal matrix composites reinforced with ceramic particles have become the most attractive material in the research and development of new materials for thermal management applications. In this work, 40-60 vol. % TiC x -TiB₂/Al composites were successfully fabricated by the method of combustion synthesis and hot press consolidation in an Al-Ti-B₄C system. The effect of the TiC x -TiB₂ content on the microstructure and compression properties of the composites was investigated. Moreover, the abrasive wear behavior and thermo-physics properties of the TiC x -TiB₂/Al composite were studied and compared with the TiC x /Al composite. The compression properties, abrasive wear behavior and thermo-physics properties of the TiC x -TiB₂/Al composite are all better than those of the TiC x /Al composite, which confirms that the TiC x -TiB₂/Al composite is more appropriate for application as a heat sink.

Study of Mare Moscoviense based on orbital NIR hyperspectral data

NASA Astrophysics Data System (ADS)

Bhatt, Megha; Wöhler, Christian; Bhardwaj, Anil; Mall, Urs; Grumpe, Arne; Rommel, Daniela

2016-07-01

The Moscoviense basin is an important lunar farside impact basin. Previous studies of this region suggest compositional variations across the mare basalts, and significant positive gravity anomaly within the basin [1, 2]. In the highlands immediately west of the mare regions inside the Moscoviense basin, unusual spectral signatures indicating small deposits of orthopyroxene, olivine and spinel have been detected [3]. A detailed study of the Moscoviense basin thus allows for an examination of lunar farside highland materials and mare basalts of varying composition and age, providing insights into the lunar mantle composition and magmatic history. We present a geological study of Mare Moscoviense based on near-infrared high-resolution hyperspectral data obtained by the Moon Mineralogy Mapper (M3) [4] and the near-infrared spectrometer, SIR-2 [5]. An M3 reflectance mosaic of the region has been prepared after applying corrections for thermal emission and topography. Two SIR-2 orbits recorded from 100 km spacecraft altitude have also been used for mineralogical study of the region. Elemental abundance maps of Ti, Ca and Mg as well as a petrologic map have been prepared based on the method described in [6]. Furthermore, we utilized the three different algorithms described in [6, 7, 8] for estimating Fe abundances using the 1-µm and/or 2-µm absorption band parameters. This comparative study aims to identify and map the major morphological and compositional units within the Mare Moscoviense region. References: [1] Gillis et al. (1998) Ph.D. thesis, 248 pp., Rice Univ., Houston, Texas; [2] Kramer et al. (2008) JGR 113, E01002, doi:10.1029/2006JE002860; [3] Pieters et al. (2011) JGR 116, E00G08, doi:10.1029/2010JE003727; [4] Pieters C. M. et al. (2009) Current Science 96, 500-505; [5] Mall, U. et al. (2009) Current Science 96, 506-511; [6] Wöhler C. et al. (2014) Icarus 235, 86-122; [7] Lucey P. G. et al. (2000) JGR 105, 20297-20306; [8] Bhatt M. et al. (2015) Icarus 248

Modeling the clouds on Venus: model development and improvement of a nucleation parameterization

NASA Astrophysics Data System (ADS)

Määttänen, Anni; Bekki, Slimane; Vehkamäki, Hanna; Julin, Jan; Montmessin, Franck; Ortega, Ismael K.; Lebonnois, Sébastien

2014-05-01

steady state. Preliminary results are evaluated against observations. [1] Jumelet et al., JGR, 2009. [2] Kliore et al., 1986. [3] Kurtén et al., BER, 2007 [4] Larsen et al., JGR, 2000. [5] Lebonnois et al. JGR, 2010. [6] McGouldrick and Toon, Icarus 191, 2007. [7] Vehkamäki et al. JGR, 2002 [9] Wilemski and Wyslouzil, J.Chem.Phys. 1995.

Dynamic Rupture Benchmarking of the ADER-DG Method

NASA Astrophysics Data System (ADS)

Gabriel, Alice; Pelties, Christian

2013-04-01

We will verify the arbitrary high-order derivative Discontinuous Galerkin (ADER-DG) method in various test cases of the 'SCEC/USGS Dynamic Earthquake Rupture Code Verification Exercise' benchmark suite (Harris et al. 2009). The ADER-DG scheme is able to solve the spontaneous rupture problem with high-order accuracy in space and time on three-dimensional unstructured tetrahedral meshes. Strong mesh coarsening or refinement at areas of interest can be applied to keep the computational costs feasible. Moreover, the method does not generate spurious high-frequency contributions in the slip rate spectra and therefore does not require any artificial damping as demonstrated in previous presentations and publications (Pelties et al. 2010 and 2012). We will show that the mentioned features hold also for more advanced setups as e.g. a branching fault system, heterogeneous background stresses and bimaterial faults. The advanced geometrical flexibility combined with an enhanced accuracy will make the ADER-DG method a useful tool to study earthquake dynamics on complex fault systems in realistic rheologies. References: Harris, R.A., M. Barall, R. Archuleta, B. Aagaard, J.-P. Ampuero, H. Bhat, V. Cruz-Atienza, L. Dalguer, P. Dawson, S. Day, B. Duan, E. Dunham, G. Ely, Y. Kaneko, Y. Kase, N. Lapusta, Y. Liu, S. Ma, D. Oglesby, K. Olsen, A. Pitarka, S. Song, and E. Templeton, The SCEC/USGS Dynamic Earthquake Rupture Code Verification Exercise, Seismological Research Letters, vol. 80, no. 1, pages 119-126, 2009 Pelties, C., J. de la Puente, and M. Kaeser, Dynamic Rupture Modeling in Three Dimensions on Unstructured Meshes Using a Discontinuous Galerkin Method, AGU 2010 Fall Meeting, abstract #S21C-2068 Pelties, C., J. de la Puente, J.-P. Ampuero, G. Brietzke, and M. Kaeser, Three-Dimensional Dynamic Rupture Simulation with a High-order Discontinuous Galerkin Method on Unstructured Tetrahedral Meshes, JGR. - Solid Earth, VOL. 117, B02309, 2012

Dynamic Rupture Benchmarking of the ADER-DG Method

NASA Astrophysics Data System (ADS)

Pelties, C.; Gabriel, A.

2012-12-01

We will verify the arbitrary high-order derivative Discontinuous Galerkin (ADER-DG) method in various test cases of the 'SCEC/USGS Dynamic Earthquake Rupture Code Verification Exercise' benchmark suite (Harris et al. 2009). The ADER-DG scheme is able to solve the spontaneous rupture problem with high-order accuracy in space and time on three-dimensional unstructured tetrahedral meshes. Strong mesh coarsening or refinement at areas of interest can be applied to keep the computational costs feasible. Moreover, the method does not generate spurious high-frequency contributions in the slip rate spectra and therefore does not require any artificial damping as demonstrated in previous presentations and publications (Pelties et al. 2010 and 2012). We will show that the mentioned features hold also for more advanced setups as e.g. a branching fault system, heterogeneous background stresses and bimaterial faults. The advanced geometrical flexibility combined with an enhanced accuracy will make the ADER-DG method a useful tool to study earthquake dynamics on complex fault systems in realistic rheologies. References: Harris, R.A., M. Barall, R. Archuleta, B. Aagaard, J.-P. Ampuero, H. Bhat, V. Cruz-Atienza, L. Dalguer, P. Dawson, S. Day, B. Duan, E. Dunham, G. Ely, Y. Kaneko, Y. Kase, N. Lapusta, Y. Liu, S. Ma, D. Oglesby, K. Olsen, A. Pitarka, S. Song, and E. Templeton, The SCEC/USGS Dynamic Earthquake Rupture Code Verification Exercise, Seismological Research Letters, vol. 80, no. 1, pages 119-126, 2009 Pelties, C., J. de la Puente, and M. Kaeser, Dynamic Rupture Modeling in Three Dimensions on Unstructured Meshes Using a Discontinuous Galerkin Method, AGU 2010 Fall Meeting, abstract #S21C-2068 Pelties, C., J. de la Puente, J.-P. Ampuero, G. Brietzke, and M. Kaeser, Three-Dimensional Dynamic Rupture Simulation with a High-order Discontinuous Galerkin Method on Unstructured Tetrahedral Meshes, JGR. - Solid Earth, VOL. 117, B02309, 2012

A Self-consistent Thermal Emission Model for Io

NASA Astrophysics Data System (ADS)

Veeder, G. J.; Matson, D. L.; Johnson, T. V.; Davies, A. G.; Blaney, D. L.

2002-05-01

Io's unusual infrared properties first became evident in the 1960's when eclipse measurements and infrared radiometry yielded results that could not be easily explained by lunar-like models. When Voyager observations in 1979 discovered active volcanism and a geologically youthful surface some of the reasons for this bizarre behavior became evident. The first determination of Io's heat flow resulted from examining the signature of volcanic heat in telescopic observations (Matson et al., JGR, 86, 1664, 1981). Since then, numerous telescopic observations and Galileo observations have greatly expanded our understanding of Io's volcanism. However, significant problems remain. Any successful model must reconcile the various observations and constraints on Io's thermal output: 1. small volcanic hot spots; 2. multi-wavelength radiometry at all longitude; 3. multi-wavelength eclipse observations; and 4. temperature distributions observed by NIMS and PPR on Galileo. Two particularly difficult observational constraints have proved to be the daytime long-wavelength flux (20 microns) from Io, which is actually lower than expected for most passive models despite the obvious presence of volcanic contributions (Veeder et al., JGR, 99, 17095, 1994), and the surprising observation of ubiquitous warm regions at high latitudes in both the day and night (Spencer et al., Sci., 288, 1198, 2000; Rathbun et al., LPSC XXXIII, abs 1371, 2002). This paper presents preliminary results of a self-consistent thermal model that involves small volcanic hot spots, both high and low thermal inertia components on Io's surface, and significant thermal output from cooling lava flows preferentially at high latitudes. The resulting heat flow is ~ 3 W/m2, somewhat higher than previous estimates and well below the upper limit of 13.5 W/m2 derived earlier (Matson et al., JGR, 106, 33021, 2001).

AmeriFlux US-SRM Santa Rita Mesquite

DOE Data Explorer

Scott, Russell [United States Department of Agriculture

2016-01-01

This is the AmeriFlux version of the carbon flux data for the site US-SRM Santa Rita Mesquite. Site Description - Semidesert grassland encroached by mesquite (Prosopis velutina) trees. Please see Scott et al. 2009 JGR-Biogeo, 114, G04004

Fabrication of TiCx-TiB2/Al Composites for Application as a Heat Sink

PubMed Central

Shu, Shili; Yang, Hongyu; Tong, Cunzhu; Qiu, Feng

2016-01-01

Metal matrix composites reinforced with ceramic particles have become the most attractive material in the research and development of new materials for thermal management applications. In this work, 40–60 vol. % TiCx-TiB2/Al composites were successfully fabricated by the method of combustion synthesis and hot press consolidation in an Al-Ti-B4C system. The effect of the TiCx-TiB2 content on the microstructure and compression properties of the composites was investigated. Moreover, the abrasive wear behavior and thermo-physics properties of the TiCx-TiB2/Al composite were studied and compared with the TiCx/Al composite. The compression properties, abrasive wear behavior and thermo-physics properties of the TiCx-TiB2/Al composite are all better than those of the TiCx/Al composite, which confirms that the TiCx-TiB2/Al composite is more appropriate for application as a heat sink. PMID:28773765

Coupled Photochemical and Condensation Model for the Venus Atmosphere

NASA Astrophysics Data System (ADS)

Bierson, Carver; Zhang, Xi; Mendonca, Joao; Liang, Mao-Chang

2017-10-01

Ground based and Venus Express observations have provided a wealth of information on the vertical and latitudinal distribution of many chemical species in the Venus atmosphere [1,2]. Previous 1D models have focused on the chemistry of either the lower [3] or middle atmosphere [4,5]. Photochemical models focusing on the sulfur gas chemistry have also been independent from models of the sulfuric acid haze and cloud formation [6,7]. In recent years sulfur-bearing particles have become important candidates for the observed SO2 inversion above 80 km [5]. To test this hypothesis it is import to create a self-consistent model that includes photochemistry, transport, and cloud condensation.In this work we extend the domain of the 1D chemistry model of Zhang et al. (2012) [5] to encompass the region between the surface to 110 km. This model includes a simple sulfuric acid condensation scheme with gravitational settling. It simultaneously solves for the chemistry and condensation allowing for self-consistent cloud formation. We compare the resulting chemical distributions to observations at all altitudes. We have also validated our model cloud mass against pioneer Venus observations [8]. This updated full atmosphere chemistry model is also being applied in our 2D solver (altitude and altitude). With this 2D model we can model how the latitudinal distribution of chemical species depends on the meridional circulation. This allows us to use the existing chemical observations to place constraints on Venus GCMs [9-11].References: [1] Arney et al., JGR:Planets, 2014 [2] Vandaele et al., Icarus 2017 (pt. 1 & 2) [3] Krasnopolsky, Icarus, 2007 [4] Krasnopolsky, Icarus, 2012 [5] Zhang et al., Icarus 2012 [6] Gao et al., Icarus, 2014 [7] Krasnopolsky, Icarus, 2015 [8] Knollenberg and Hunten, JGR:Space Physics, 1980 [9] Lee et al., JGR:Planets, 2007 [10] Lebonnois et al., Towards Understanding the Climate of Venus, 2013 [11] Mendoncca and Read, Planetary and Space Science, 2016

Effect of hot plastic deformation on the structural state of a Al-10%SiC composite

NASA Astrophysics Data System (ADS)

Pugacheva, N. B.; Vichuzhanin, D. I.; Michurov, N. S.; Smirnov, A. S.

2017-12-01

The paper studies the microstructure of honeycomb aluminum matrix composites with a granulated Al-Zn-Cu-Mg alloy matrix filled SiC particles amounting to 10 vol % after hot plastic deformation at near-solidus temperatures. It demonstrates the possibility of the collapse of the SiC filler network and the formation of filler clusters separated from each other.

Connecting Informal and Formal Learning Experiences in the Age of Participatory Media: Commentary on Bull et al. (2008)

ERIC Educational Resources Information Center

Greenhow, Christine

2008-01-01

The recent editorial in this journal by Bull et al. ("Connecting Informal and Formal Learning Experiences in the Age of Participatory Media" Vol 8, Iss 2) discussed the challenges of bridging formal learning practices and informal learning opportunities within the context of today's Web-enhanced world. In this commentary, Christine…

CTC Sentinel. Volume 1, Issue 6, May 2008. Abu Yahya al-Libi’s Human Shields in Modern Jihad

DTIC Science & Technology

2008-05-01

own include The Healing of the Believers’ Chests and The Exoneration. 7 Although the essay is dated January 6, 2006, it was not published and widely...Yahya’s small essay on al-Tatarrus is nothing short of a religious revolution. Early Islamic thinkers typically used three general forms of shielding...traditional Islamic discussions in that it simplifies mat- ters considerably. MAY 2008 . VoL 1 . IssUE 6 “Abu Yahya’s small essay on al-Tatarrus is nothing

Effect of SiC addition to the characteristics of Al-11Zn-6.7Mg composite produced by squeeze casting for ballistic application

NASA Astrophysics Data System (ADS)

Adiputra, R. F.; Wijanarko, R.; Angela, I.; Sofyan, B. T.

2018-01-01

Aluminium composite material as an alternative to steel used in body of tactical vehicles has been studied. Addition of SiC was expected to have strengthening effect on the composite matrix therefore improving its ballistic performance. Composites of Al-11Zn-6.7Mg matrix and SiC strengthening particles with the fraction of 0, 10, and 15 vol. % were fabricated through squeeze casting process. Composite samples were then precipitation strengthened at 130 °C for 102 h to further improve their toughness. Final products were characterized by using chemical composition testing, optical microscopy, Scanning Electron Microscope - Energy Dispersive Spectroscopy (SEM-EDS) and quantitative metallography to calculate porosity, hardness test, impact test, and type III ballistic test in accordance with NIJ 0108.04 standard. The results showed that increase in SiC volume fraction from 0 to 10 and 15 vol. % managed to improve the hardness from 73 to 85 and 87 HRB, respectively, while on the other hand reduced the impact values from 12,278.69 to 11,290.35 and 9,924.54 J/m2. SEM-EDS observation confirmed the presence of Mg3Zn3Al2 intermetallic compound which formed during solidification and indicated the precipitation of MgZn2 precipitates during ageing. The ballistic testing demonstrated a promising result of the potential of Al-11Zn-6.7Mg composite strengthened by 15 vol. % SiC to withstand penetration of type III bullet (7.62 mm).

Identification of a Spectrally and Thermophysically Unique Region in Northern Amazonis Planitia, Mars: Surface Analysis using TES and THEMIS Data

NASA Astrophysics Data System (ADS)

Rogers, D.; Christensen, P. R.

2002-12-01

et al. 1977, JGR, 82, 4249-4291; [2] Moersch and Christensen, 1995, JGR, 100, 7465-7477; [3] Bandfield et al. 2000, Science, 287, 1626-1630; [4] Christensen et al. 2000, JGR, 105, 9609-9621; [5] Christensen et al. 2000, JGR, 105, 9623-9642; [6] Hamilton et al. 2001, LPSC XXXII Abstracts, abstract 2184

Ultrasonication effect on thermophysical properties of Al2O3 nanofluids

NASA Astrophysics Data System (ADS)

Shah, Janki; Ranjan, Mukesh; Gupta, Sanjeev K.; Sonvane, Yogesh

2018-04-01

In this work, we studied the thermal conductivity and viscosity of alumina nanofluids for their excellent thermophysical properties. Here we considered the bath sonication time effects on thermal conductivity, viscosity and zeta potential of alumina nanofluid with different concentration (0.2, 0.3, 0.4, 0.5 Vol.%). We observed that the thermal conductivity of the nanofluids increased nonlinearly with an increased sonication time/energy as well as viscosity decreased. An enhancement of the thermal conductivity and viscosity at higher particle concentration is also observed. The results indicate that thermal properties of Al2O3 nanofluid enhances as the sonication time increases and prove Al2O3 nanofluid is one of the best thermostable heat transfer fluids compared to conventional cooling fluids.

Infrared Detection of Evidence for Microscopic Organisms on Europa

NASA Astrophysics Data System (ADS)

Dalton, J. B.; Mogul, R.

2002-12-01

bound water of hydration, as well as narrow features on the order of 10 to 20 nm. Cryogenic reflectance spectra of D. radiodurans are similarly dominated by asymmetric, water-related absorption features but also have two sharp (5-10 nm) features arising from amide bonds within the cells. These amide bonds are two orders of magnitude stronger than the hydration bonds in the salts [16]. Thus, the features arising from the amides could be exploited for remote-sensing investigations. In comparison, the Europa spectra from Galileo NIMS also contain the broad, asymmetric absorption features attributed to water and several other weaker absorptions. Together, the narrow features are suggestive of a mixture of materials. The NIMS data are consistent with the presence of water ice, with up to 50% sulfuric acid octahydrate, 20-45% hydrated salts, and possibly as much as 0.2 mg /cm3 carbonaceous material which may be of biological origin. However, inherent noise in the observations and limitations of spectral resolution must be taken into account when discussing these findings. References:[1]Greenberg et al.,Icarus 141,1999. [2]Pappalardo et al., JGR 104, 1999. [3]McCord et al., Science 280, 1998. [4]McCord et al., LPSC XXX,1508,1999a.[5]McCord et al., LPSC XXX,1510,1999b.[6]McCord et al., JGR 104,1999c. [7]McCord et al., DPS 31,1171,1999d.[8]McCordet al., JGR 104,1999e.[9]McCord et al., JGR 106,2001.[10]McCord et al.,JGR 107,E1-4,2002.[11]Dalton et al., NAI AstroBiol. Sci. Con. 2,2002.[12]Ventkataswaran et al., Appl Environ Microbiol. 66, 2000.[13]Mogul et al., PNAS, subm., 2002.[14]Cooper et al., Icarus 149, 2000.[15]Dalton, PhD Diss., U. Colorado,Boulder,2000.[16]Darwent, Nat. Bur. Stand., NSRDS-NBS 31,1970.

High-Temperature Active Soldering of SiC Particle-Reinforced Al-MMC Using a Novel ZnAlGaMgTi Filler Metal

NASA Astrophysics Data System (ADS)

Chen, Biqiang; Zhang, Guifeng; Zhang, Linjie; Xu, Tingting

2017-10-01

In order to broaden the application of SiC particle-reinforced aluminum matrix composite in electronics packaging, newly developed ZnAlGaMgTi filler with a low melting point of 418-441 °C was utilized as filler metal for active soldering of aluminum matrix composites (70 vol.%, SiCp/Al-MMCs) for the first time. The effect of loading pressure on joint properties of ZnAlGaMgTi active filler was investigated. The experimental results indicated that novel filler could successfully solder Al-MMCs, and the presence of Mg in the filler enhanced the penetration of Zn, while the forming of Zn-rich barrier layer influenced the active element MPD (melting point depressant) diffusion into parent composite, and the bulk-like (Mg-Si)-rich phase and Ti-containing phase were readily observed at the interface and bond seam. With the increase in loading pressure, the runout phenomenon appeared more significant, and the filler foil thickness and the Zn penetration depth varied pronouncedly. Sound joints with maximum shear strength of 29.6 MPa were produced at 480 °C at 1 MPa, and the crack occurred adjacent to the boundary of SiC particle and then propagated along the interface. A novel model describing the significant mutual diffusion of Al and Zn atoms between the parent material and solder was proposed.

A New Type of Transient Luminous Events Produced by Terrestrial Gamma-ray Flashes

NASA Astrophysics Data System (ADS)

Xu, W.; Celestin, S. J.; Pasko, V. P.; Marshall, R. A.

2016-12-01

Discovered in 1994 by the Burst and Transient Source Experiment (BATSE) detector aboard the Compton Gamma-Ray Observatory [Fishman et al., Science, 264, 1313, 1994], Terrestrial Gamma-ray Flashes (TGFs) are high-energy photon bursts originating from the Earth's atmosphere characterized by their close association with thunderstorm activities. Since the discovery, TGFs have also been observed by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) [Smith et al., Science, 307, 1085, 2005], the Fermi Gamma-ray Space Telescope [Briggs et al., JGR, 115, A07323, 2010], and the Astrorivelatore Gamma a Immagini Leggero (AGILE) satellite [Marisaldi et al., JGR, 115, A00E13, 2010]. Space-borne measurements have revealed the temporal and spectral features of TGFs: typically lasting from fractions of to a few milliseconds, having a fluence of fractions of photons/cm2, and exhibiting a hard energy spectra extending up to a few tens of MeVs [Dwyer et al., Space Sci. Rev., 173, 133, 2012]. Moreover, detailed analyses of radio emissions have pointed out the close correlation between TGFs and the initial development stages of normal polarity intra-cloud lightning that transports negative charge upward (+IC) [e.g., Lu et al., GRL, 37, L11806, 2010; JGR, 116, A03316, 2011]. In this work, we show that, while TGFs pass through the atmosphere, the large quantities of energetic electrons knocked out during collisions of gamma-rays with air molecules can generate significant amount of excited species of neutral and ionized nitrogen molecules, thereby leading to production of a new type of transient luminous events (TLEs). The spectroscopic and morphological features of this predicted luminous phenomenon have been theoretically quantified in the framework of Monte Carlo simulations. Considering the measurability of this type of events and its close relation with TGFs, corresponding measurements would provide a novel perspective to investigate TGFs, as well as the initial

Deformation processed Al/Ca nano-filamentary composite conductors for HVDC applications

NASA Astrophysics Data System (ADS)

Czahor, C. F.; Anderson, I. E.; Riedemann, T. M.; Russell, A. M.

2017-07-01

Efficient long-distance power transmission is necessary as the world continues to implement renewable energy sources, often sited in remote areas. Light, strong, high-conductivity materials are desirable for this application to reduce both construction and operational costs. In this study an Al/Ca (11.5% vol.) composite with nano-filamentary reinforcement was produced by powder metallurgy then extruded, swaged, and wire drawn to a maximum true strain of 12.7. The tensile strength increased exponentially as the filament size was reduced to the sub-micron level. In an effort to improve the conductor’s ability to operate at elevated temperatures, the deformation-processed wires were heat-treated at 260°C to transform the Ca-reinforcing filaments to Al2Ca. Such a transformation raised the tensile strength by as much as 28%, and caused little change in ductility, while the electrical conductivity was reduced by only 1% to 3%. Al/Al2Ca composites are compared to existing conductor materials to show how implementation could affect installation and performance.

Effect of the temperature, strain rate and microstructure on flow and fracture characteristics of Ti-45Al-2Nb-2Mn+0.8vol.% TiB2 XD alloy

NASA Astrophysics Data System (ADS)

Erice, B.; Pérez-Martín, M. J.; Cendón, D. A.; Gálvez, F.

2012-05-01

A series of quasi-static and dynamic tensile tests at varying temperatures were carried out to determine the mechanical behaviour of Ti-45Al-2Nb-2Mn+0.8vol.% TiB2 XD as-HIPed alloy. The temperature for the tests ranged from room temperature to 850 ∘C. The effect of the temperature on the ultimate tensile strength, as expected, was almost negligible within the selected temperature range. Nevertheless, the plastic flow suffered some softening because of the temperature. This alloy presents a relatively low ductility; thus, a low tensile strain to failure. The dynamic tests were performed in a Split Hopkinson Tension Bar, showing an increase of the ultimate tensile strength due to the strain rate hardening effect. Johnson-Cook constitutive relation was used to model the plastic flow. A post-testing microstructural of the specimens revealed an inhomogeneous structure, consisting of lamellar α2 + γ structure and γ phase equiaxed grains in the centre, and a fully lamellar structure on the rest. The assessment of the duplex-fully lamellar area ratio showed a clear relationship between the microstructure and the fracture behaviour.

Evolution of Tides and Tidal Dissipation Over the Past 26,000 Years Using a Multi-Scale Model of Global Barotropic Tides

NASA Astrophysics Data System (ADS)

Salehipour, H.; Peltier, W. R.

2014-12-01

In this paper we will describe the results obtained through integration of a further refined version of the truly global barotropic tidal model of Salehipour et al. (Ocean Modell., 69, 2013) using the most recent reconstruction of ice-age bathymetric conditions as embodied in the recently constructed ICE-6G_C (VM5a) model of Peltier et al. (JGR-Solid Earth, in press, 2014). Our interest is in the spatial and temporal evolution of tidal amplitude, phase and dissipation from the Last Glacial Maximum (LGM) 26,000 years ago until the present. The state-of-the-art higher order nonlinear tidal model of Salehipour et al. (2013) includes a highly parallelized multi-scale framework in which an unstructured tessellation of the global ocean enables extensive local refinement around regions of interest such as the Hawaiian Ridge, the Brazil Basin and the Southern Ocean. At LGM, features such as the Patagonian Shelf were fully exposed land which during the deglaciation process would have been flooded leading to significant changes of tidal range along the evolving coastline. In the further development of this model we have included the fully iterated treatment of the influence of gravitational self-attraction and loading as in, e.g. Egbert et al. (JGR-Oceans, 109, 2004). The treatment of the dissipation of the barotropic tide through dissipation of the internal tide has also been significantly improved. Our paleobathymetry and coastline data sets extend from LGM to present at 500 year intervals and constitute a significant refinement of the widely employed ICE-5G (VM2) model of Peltier (Annu. Rev. Earth Planet. Sci., 32, 2004). Our results will be compared with those recently published by Green & Nycander (JPO, 43, 2013) and Wilmes & Green (JGR-Oceans, 119, 2014) as well as with the earlier results of Griffiths & Peltier (GRL, 35, 2008; J. Clim., 22, 2009).

The Preservation and Detection of Organic Matter within Jarosite

NASA Astrophysics Data System (ADS)

Lewis, J. M. T.; Eigenbrode, J. L.; McAdam, A.; Andrejkovicova, S. C.; Knudson, C. A.; Wong, G. M.; Millan, M.; Freissinet, C.; Szopa, C.; Li, X.; Bower, D. M.

2017-12-01

Since its arrival at Mt. Sharp in 2014 the Mars Science Laboratory Curiosity rover has been examining the mountain's lower stratigraphy, which shows a progression from clay-bearing to sulfate-bearing strata. Clay minerals are known to be effective long-term preservers of organic matter [1], but it is important to also consider the potential for Martian sulfate minerals to host organic molecules. The Sample Analysis at Mars (SAM) instrument suite on board the rover uses pyrolysis to liberate organic fragments from sampled materials [2]. However, the surface of Mars hosts widespread oxychlorine phases, which thermally decompose to release oxygen and chlorine that can degrade and destroy organic signals [3]. Francois et al. (2016) demonstrated that synthetic magnesium sulfate can incorporate phthalic acid and protect it from oxychlorine phases during pyrolysis [4]. Magnesium sulfate as well as calcium sulfate and jarosite have all been observed by instruments on the rover. The addition of organic standards to the starting materials in jarosite synthesis reactions has conclusively demonstrated that jarosite can incorporate organic molecules. The samples were analyzed by SAM-like evolved gas analysis (EGA) and gas chromatography-mass spectrometry (GC-MS) and the influence of perchlorates assessed. Jarosite has been observed by multiple missions to the Martian surface and from orbit, thus the probability of future organic detection missions encountering the mineral is high. Samples from this study were examined by laser desorption/ionization mass spectrometry and Raman spectroscopy, which will be utilized by the ExoMars rover and Mars 2020 rover respectively. The data inform the sampling and analysis strategies for sulfate-rich regions of Mars for present and future organic-detection missions. [1] Farmer & Des Marais (1999) JGR: Planets 104, [2] Mahaffy et al., (2012) Space Science Reviews 170 [3] Glavin et al., (2013) JGR: Planets 118 [4] Francois et al., (2016) JGR

Observations of a solar storm from the stratosphere: The BARREL Mission

NASA Astrophysics Data System (ADS)

Halford, Alexa

2016-07-01

During the Balloon Array for Radiation belt Relativistic Electron Losses (BARREL) second campaign, BARREL observed with a single primary instrument, a 3"x3" NaI spectrometer measuring 20 keV - 10 MeV X-rays [Woodger et al 2015 JGR], portions of an entire solar storm. This very small event, in terms of geomagnetic activity, or one of the largest of the current solar cycle, in terms of solar energetic particle events, has given us a very clear set of observations of the response of the day side magnetosphere to the arrival of an interplanetary coronal mass ejection shock. The BARREL mission of opportunity working in tandem with the Van Allen Probes was designed to study the loss of radiation belt electrons to the ionosphere and upper atmosphere. However BARREL is able to see X-rays from a multitude of sources. During the second campaign, the Sun produced, and BARREL observed, an X-class flare [McGregor et al in prep.]. This was followed by BARREL observations of X-rays, gamma-rays, and directly injected protons from the solar energetic particle (SEP) event associated with the eruption from the Sun while simultaneously the Van Allen Probes observed the SEP protons in the inner magnetosphere [Halford et al 2016 submitted JGR]. Two days later the shock generated by the interplanetary coronal mass ejection (ICME-shock) hit the Earth while BARREL was in conjunction with the Van Allen Probes and GOES [Halford et al 2015 JGR]. Although this was a Mars directed CME and the Earth only received a glancing blow [Möstl et al 2015 Nat. Commun., Mays et al 2015 ApJ], the modest compression led to the formation of ultra low frequency (ULF) waves, electromagnetic ion cyclotron (EMIC) waves, and very low frequency (VLF) whistler mode waves [Halford and Mann 2016 submitted to JGR]. The combination of these waves and the enhancement of the local particle population led to precipitation of electrons remotely observed by BARREL. This was not a Halloween, Bastille Day, or one of the now

Microstructure and Mechanical Behavior of Amorphous Al-Cu-Ti Metal Foams Synthesized by Spark Plasma Sintering

NASA Astrophysics Data System (ADS)

Li, Maoyuan; Lu, Lin; Dai, Zhen; Hong, Yiqiang; Chen, Weiwei; Zhang, Yuping; Qiao, Yingjie

Amorphous Al-Cu-Ti metal foams were prepared by spark plasma sintering (SPS) process with the diameter of 10mm. The SPS process was conducted at the pressure of 200 and 300MPa with the temperature of 653-723K, respectively. NaCl was used as the space-holder, forming almost separated pores with the porosity of 65 vol%. The microstructure and mechanical behavior of the amorphous Al-Cu-Ti metal foams were systematically investigated. The results show that the crystallinity increased at elevated temperatures. The effect of pressure and holding time on the crystallization was almost negligible. The intermetallic compounds, i.e. Al-Ti, Al-Cu and Al-Cu-Ti were identified from X-ray diffraction (XRD) patterns. It was found that weak adhesion and brittle intermetallic compounds reduced the mechanical properties, while lower volume fraction and smaller size of NaCl powders improved the mechanical properties.

Index to Nuclear Safety. A technical progress review by chronology, permuted title, and author. Vol. 11, No. 1--Vol. 17, No. 6

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cottrell, W.B.; Klein, A.

1977-02-23

This index to Nuclear Safety covers articles in Nuclear Safety Vol. 11, No. 1 (Jan.-Feb. 1970), through Vol. 17, No. 6 (Nov.-Dec. 1976). The index includes a chronological list of articles (including abstract) followed by KWIC and Author Indexes. Nuclear Safety, a bimonthly technical progress review prepared by the Nuclear Safety Information Center, covers all safety aspects of nuclear power reactors and associated facilities. The index lists over 350 technical articles in the last six years of publication.

Slow plastic deformation of extruded NiAl-10TiB2 particulate composites at 1200 and 1300 K

NASA Technical Reports Server (NTRS)

Whittenberger, J. D.; Kumar, S.; Mannan, S. K.; Viswanadham, R. K.

1990-01-01

A dispersion of 1-micron TiB2 particles in the B2 crystal structure NiAl intermetallic can effectively increase its elevated temperature strength, in association with increasing deformation resistance with TiB2 volume fraction. Attention is presently given to alternative densification methods, which may increase the initial as-fabricated dislocation density and lead to enhanced elevated-temperature strength. The 'XD' extrusion method was used to produce NiAl with 10 vol pct TiB2. Although apparent extrusion defects were occasionally found, neither grain-boundary cracking nor particle-matrix separation occurred.

Measuring carbon and oxygen isotope signals of photosynthesis and respiration: first field results from a chamber system coupled to tunable diode laser spectrometers

NASA Astrophysics Data System (ADS)

Wingate, L.; Burlett, R.; Bosc, A.; Cross, A.; Devaux, M.; Grace, J.; Loustau, D.; Seibt, U.; Ogée, J.

2007-12-01

Studying the carbon and oxygen stable isotope signals from plants and soils can help us gain insight to mechanistic processes responsible for the net exchange of CO2 and water cycled between terrestrial ecosystems and the atmosphere. Chamber field measurements of component fluxes and their isotopic composition have been reported for a few ecosystems. These observations have revealed that isotopic signals for carbon and oxygen are dynamic over relatively short time scales (hrs and days) for both branches and soils (Seibt et al., 2006a; 2006b; Wingate et al., 2007), and not fully explained by currently available models (Seibt et al., 2006b; Wingate et al., 2007). Ecosystem isotope studies have been limited by flask sampling requirements in the past. To evaluate and refine our models of isotopic fractionation by plants and soil, we need high resolution continuous isotopic measurements over the growing season for different ecosystems. In this study, we coupled chambers with tunable diode laser spectroscopy techniques in the field to continuously capture the isotopic signals from the most important component fluxes contributing to the net ecosystem exchange of CO2 in a Pinus pinaster forest in south-west France. We obtained profiles of the carbon and oxygen isotope content of CO2 within and above the forest canopy. In addition, we measured branch photosynthetic 13C and 18O discrimination alongside the 13C and 18O isotopic composition of the branch, stem and soil respiration during a 6-month period in 2007. In this talk, we will present the first results from this field campaign. References Seibt, U., Wingate, L., Berry, J.A. and Lloyd, J. (2006a) Non steady state effects in diurnal 18O discrimination by Picea sitchensis branches in the field. Plant, Cell and Environment Vol 29, 928-939. Seibt, U., Wingate, L., Lloyd, J. and Berry, J.A. (2006b) Diurnally variable δ18O signatures of soil CO2 fluxes indicate carbonic anhydrase activity in a forest soil. JGR

Biosignatures Preservation Potential and Habitability in Phyllosilicates vs. Iron-rich Environments

NASA Astrophysics Data System (ADS)

Bonaccorsi, R.; Stoker, C. R.; McKay, C. P.; Science Team

2008-12-01

:400-404; [2] Wang et al., 2006 JGR E02S16 Vol. 111; [3] Sumner, 2004, JGR, 109; [4] Bonaccorsi and Stoker, Astrobiology 2008; in press.

New ZrO2/Al2O3 Nanocomposite Fabricated from Hybrid Nanoparticles Prepared by CO2 Laser Co-Vaporization

PubMed Central

Bartolomé, José F.; Smirnov, Anton; Kurland, Heinz-Dieter; Grabow, Janet; Müller, Frank A.

2016-01-01

Alumina toughened zirconia (ATZ) and zirconia toughened alumina (ZTA) are currently the materials of choice to meet the need for tough, strong, and bioinert ceramics for medical devices. However, the mechanical properties of ZrO2/Al2O3 dispersion ceramics could be considerably increased by reducing the corresponding grain sizes and by improving the homogeneity of the phase dispersion. Here, we prepare nanoparticles with an intraparticular phase distribution of Zr(1−x)AlxO(2−x/2) and (γ-, δ-)Al2O3 by the simultaneous gas phase condensation of laser co-vaporized zirconia and alumina raw powders. During subsequent spark plasma sintering the zirconia defect structures and transition alumina phases transform to a homogeneously distributed dispersion of tetragonal ZrO2 (52.4 vol%) and α-Al2O3 (47.6 vol%). Ceramics sintered by spark plasma sintering are completely dense with average grain sizes in the range around 250 nm. Outstanding mechanical properties (flexural strength σf = 1500 MPa, fracture toughness KIc = 6.8 MPa m1/2) together with a high resistance against low temperature degradation make these materials promising candidates for next generation bioceramics in total hip replacements and for dental implants. PMID:26846310

New ZrO2/Al2O3 Nanocomposite Fabricated from Hybrid Nanoparticles Prepared by CO2 Laser Co-Vaporization

NASA Astrophysics Data System (ADS)

Bartolomé, José F.; Smirnov, Anton; Kurland, Heinz-Dieter; Grabow, Janet; Müller, Frank A.

2016-02-01

Alumina toughened zirconia (ATZ) and zirconia toughened alumina (ZTA) are currently the materials of choice to meet the need for tough, strong, and bioinert ceramics for medical devices. However, the mechanical properties of ZrO2/Al2O3 dispersion ceramics could be considerably increased by reducing the corresponding grain sizes and by improving the homogeneity of the phase dispersion. Here, we prepare nanoparticles with an intraparticular phase distribution of Zr(1-x)AlxO(2-x/2) and (γ-, δ-)Al2O3 by the simultaneous gas phase condensation of laser co-vaporized zirconia and alumina raw powders. During subsequent spark plasma sintering the zirconia defect structures and transition alumina phases transform to a homogeneously distributed dispersion of tetragonal ZrO2 (52.4 vol%) and α-Al2O3 (47.6 vol%). Ceramics sintered by spark plasma sintering are completely dense with average grain sizes in the range around 250 nm. Outstanding mechanical properties (flexural strength σf = 1500 MPa, fracture toughness KIc = 6.8 MPa m1/2) together with a high resistance against low temperature degradation make these materials promising candidates for next generation bioceramics in total hip replacements and for dental implants.

Formation of crystalline phase in the glass matrix of Zr-Co-Al glass-matrix composites and its effect on their mechanical properties

NASA Astrophysics Data System (ADS)

Kim, Woo Chul; Kim, Kang Chul; Na, Min Young; Jeong, Seok Hoan; Kim, Won Tae; Kim, Do Hyang

2017-11-01

The microstructural evolution and mechanical properties of Zr-Co-Al alloys, with compositions of (Zr50Co50)x (Zr56Co26Al18)1-x (x = 1/6, 2/6, 3/6, 4/6, 5/6, 1) and Zr54Co35Al11, (referred to as Z1, Z2, Z3, Z4, Z5, Z6, and Z4.5), were investigated. Alloys Z1-Z3 consisted of crystalline phases, while alloys Z4 and Z4.5 consisted of crystalline phase particles ( 3 vol% and 35 vol%, respectively) embedded within the glassy matrix. Alloys Z5 and Z6 consisted of a monolithic glass phase. The crystalline phase of alloys Z1-Z4.5 consisted of primary B2-ZrCo dendrite and an interdendritic B2-ZrCo/Zr6CoAl2 eutectic phase. The B2-ZrCo dendritic phase exhibited a high work-hardening rate, which originated from the deformation-induced B2-to-B33 martensitic transformation. However, when the brittle interdendritic B2-ZrCo/Zr6CoAl2 eutectic phase fraction increased, the work-hardening rate significantly decreased. The ductility of the glass-matrix composites was significantly impaired by the presence of the interdendritic eutectic phase in the crystalline phase. The results indicate that the design of the crystalline particle microstructure is important with regard to enhancing the plasticity of glass-matrix composites.

Impact of convective activity on precipitation δ18O in isotope-enabled models

NASA Astrophysics Data System (ADS)

Hu, J.; Emile-Geay, J.; Dee, S.

2017-12-01

The ^18O signal preserved in paleo-archives (e.g. speleothem, tree ring cellulose, ice cores) is widely used to reconstruct precipitation or temperature. In the tropics, the inverse relationship between precipitation ^18O and rainfall amount, namely "amount effect" [Dansgaard, Tellus, 1964], is often used to interpret precipitation ^18O. However, recent studies have shown that precipitation ^18O is also influenced by precipitation type [Kurita et al, JGR, 2009; Moerman et al, EPSL, 2013], and recent observations indicate that it is negatively correlated with the fraction of precipitation associated with stratiform clouds [Aggarwal et al, Nature Geosci, 2016]. It is thus important to determine to what extent isotope-enabled climate models can reproduce these relationships. Here we do so using output from LMDZ, CAM2, and isoGSM from the Stable Water Isotope Intercomparison Group, Phase 2 (SWING2) project and results of SPEEDY-IER [Dee et al, JGR, 2015] from an AMIP-style experiment. The results show that these models simulate the "amount effect" well in the tropics, and the relationship between precipitation ^18O and precipitation is reversed in many places in mid-latitudes, in accordance with observations [Bowen, JGR, 2008]. Also, these models can all reproduce the negative correlation between monthly precipitation ^18O and stratiform precipitation proportion in mid-latitude (30°N-50°N; 50°S-30°S), but in the tropics (30°S-30°N), models show a positive correlation instead. The reason for this bias will be investigated within idealized experiments with SPEEDY-IER. The correct simulations of the impact of convective activity on precipitation ^18O in isotope-enabled models will improve our interpretation of paleoclimate proxies with respect to hydroclimate variability. P. K. Aggarwal et al. (2016), Nature Geosci., 9, 624-629, doi:10.1038/ngeo2739. G. J. Bowen. (2008), J. Geophys. Res., 113, D05113, doi:10.1029/2007JD009295. W. Dansgaard (1964), Tellus, 16(4), 436

Precipitation Sequence of a SiC Particle Reinforced Al-Mg-Si Alloy Composite

NASA Astrophysics Data System (ADS)

Shen, Rujuan; Wang, Yihan; Guo, Baisong; Song, Min

2016-11-01

In this study, the precipitation sequence of a 5 vol.% SiC particles reinforced Al-1.12 wt.%Mg-0.77 wt.%Si alloy composite fabricated by traditional powder metallurgy method was investigated by transmission electron microscopy and hardness measurements. The results indicated that the addition of SiC reinforcements not only suppresses the initial aging stage but also influences the subsequent precipitates. The precipitation sequence of the composite aged at 175 °C can be described as: Guinier-Preston (G.P.) zone → β″ → β' → B', which was confirmed by high-resolution transmission electron microscopy. This work might provide the guidance for the design and fabrication of hardenable automobile body sheet by Al-based composites with enhanced mechanical properties.

Understanding feedbacks between ocean acidification and coral reef metabolism

NASA Astrophysics Data System (ADS)

Takeshita, Yuichiro

2017-03-01

Biogeochemical feedbacks from benthic metabolism have been hypothesized as a potential mechanism to buffer some effects of ocean acidification on coral reefs. The article in JGR-Oceans by DeCarlo et al. demonstrates the importance of benthic community health on this feedback from Dongsha Atoll in the South China Sea.

Mass Spectrometry in Jupiter's Atmosphere: Vertical Variation of Volatile Vapors

NASA Astrophysics Data System (ADS)

Wong, Michael H.; Atreya, Sushil K.; Mahaffy, Paul R.

2014-05-01

bulk abundances and spatial variation of these species will be further constrained by the Juno mission, scheduled to arrive at Jupiter in 2016. References: [1] Niemann, H.B. et al. 1992, SSRv 60, 111-142 [2] Niemann, H.B. et al. 1996, Science 272, 846-849 [3] Niemann, H.B. et al. 1998, JGR 103, 22831-22845 [4] Mahaffy, P.R. et al. 2000, JGR 105, 15061-15071 [5] Wong, M.H. et al. 2004, Icarus 171, 153-170 [6] Atreya, S.K. et al., 1999, Planet. Space Sci. 47, 1243-1262 [7] Atreya, S.K. et al., 2003, Planet. Space Sci. 451, 105-112 [8] Wong, M.H. et al., 2008, in Reviews in Mineralogy and Geochemistry, vol. 68. Mineralogical Society of America, Chantilly, VA, pp. 219-246 [9] Wong, M.H., 2009, Icarus 199, 231-235

Effects of particle reinforcement and ECAP on the precipitation kinetics of an Al-Cu alloy

NASA Astrophysics Data System (ADS)

Härtel, M.; Wagner, S.; Frint, P.; F-X Wagner, M.

2014-08-01

The precipitation kinetics of Al-Cu alloys have recently been revisited in various studies, considering either the effect of severe plastic deformation (e.g., by equal-channel angular pressing - ECAP), or the effect of particle reinforcements. However, it is not clear how these effects interact when ECAP is performed on particle-reinforced alloys. In this study, we analyze how a combination of particle reinforcement and ECAP affects precipitation kinetics. After solution annealing, an AA2017 alloy (initial state: base material without particle reinforcement); AA2017 + 10 vol.-% Al2O3; and AA2017 + 10 vol.-% SiC were deformed in one pass in a 120° ECAP tool at a temperature of 140°C. Systematic differential scanning calorimetry (DSC) measurements of each condition were carried out. TEM specimens were prepared out of samples from additional DSC measurements, where the samples were immediately quenched in liquid nitrogen after reaching carefully selected temperatures. TEM analysis was performed to characterize the morphology of the different types of precipitates, and to directly relate microstructural information to the endo- and exothermic peaks in our DSC data. Our results show that both ECAP and particle reinforcement are associated with a shift of exothermic precipitation peaks towards lower temperatures. This effect is even more pronounced when ECAP and particle reinforcement are combined. The DSC data agrees well with our TEM observations of nucleation and morphology of different precipitates, indicating that DSC measurements are an appropriate tool for the analysis of how severe plastic deformation and particle reinforcement affect precipitation kinetics in Al-Cu alloys.

The effect of TiB2 reinforcement on the mechanical properties of an Al-Cu-Li alloy-based metal-matrix composite

NASA Technical Reports Server (NTRS)

Langan, T. J.; Pickens, J. R.

1991-01-01

Weldalite 049, an Al-base Cu-Li-Mg-Ag-Zr alloy, achieves 700 MPa tensile strengths in the near-peak-aged temper in virtue of the nucleation of a T(1)-type platelike strengthening precipitate. Attention is presently given to the possibility that the alloy's modulus could be further increased through the addition of high-modulus TiB2 particles, using the 'XD' process, due to TiB2's good wettability with liquid Al. An 8-percent modulus increase is obtained with 4 vol pct TiB2.

On improving the fracture toughness of a NiAl-based alloy by mechanical alloying

NASA Technical Reports Server (NTRS)

Kostrubanic, J.; Koss, D. A.; Locci, I. E.; Nathal, M.

1991-01-01

Mechanical alloying (MA) has been used to process the NiAl-based alloy Ni-35Al-20Fe, such that a fine-grain (about 2 microns) microstructure is obtained through the addition of 2 vol pct Y2O3 particles. When compared to a conventionally processed, coarse-grained (about 28 microns) Ni-35-20 alloy without the Y2O3 particles, the MA alloy exhibits two to three times higher fracture toughness values, despite a 50-percent increase in yield strength. Room-temperature K(O) values as high as 34 MPa sq rt m are observed, accompanied by a yield strength in excess of 1100 MPa. Fractography confirms a change in fracture characteristics of the fine-grained MA alloy.

Micro-nano filler metal foil on vacuum brazing of SiCp/Al composites

NASA Astrophysics Data System (ADS)

Wang, Peng; Gao, Zeng; Niu, Jitai

2016-06-01

Using micro-nano (Al-5.25Si-26.7Cu)- xTi (wt%, x = 1.0, 1.5, 2.0, 2.5 and 3.0) foils as filler metal, the research obtained high-performance joints of aluminum matrix composites with high SiC particle content (60 vol%, SiCp/Al-MMCs). The effect of brazing process and Ti content on joint properties was investigated, respectively. The experimental results indicate that void free dense interface between SiC particle and metallic brazed seam with C-Al-Si-Ti product was readily obtained, and the joint shear strength enhanced with increasing brazing temperature from 560 to 580 °C or prolonging soaking time from 10 to 90 min. Sound joints with maximum shear strength of 112.5 MPa was achieved at 580 °C for soaking time of 90 min with (Al-5.25Si-26.7Cu)-2Ti filler, where Ti(AlSi)3 intermetallic is in situ strengthening phase dispersed in the joint and fracture occured in the filler metal layer. In this research, the beneficial effect of Ti addition into filler metal on improving wettability between SiC particle and metallic brazed seam was demonstrated, and capable welding parameters were broadened for SiCp/Al-MMCs with high SiC particle content.

Stationary table CT dosimetry and anomalous scanner-reported values of CTDI{sub vol}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dixon, Robert L., E-mail: rdixon@wfubmc.edu; Boone, John M.

2014-01-15

Purpose: Anomalous, scanner-reported values of CTDI{sub vol} for stationary phantom/table protocols (having elevated values of CTDI{sub vol} over 300% higher than the actual dose to the phantom) have been observed; which are well-beyond the typical accuracy expected of CTDI{sub vol} as a phantom dose. Recognition of these outliers as “bad data” is important to users of CT dose index tracking systems (e.g., ACR DIR), and a method for recognition and correction is provided. Methods: Rigorous methods and equations are presented which describe the dose distributions for stationary-table CT. A comparison with formulae for scanner-reported values of CTDI{sub vol} clearly identifiesmore » the source of these anomalies. Results: For the stationary table, use of the CTDI{sub 100} formula (applicable to a moving phantom only) overestimates the dose due to extra scatter and also includes an overbeaming correction, both of which are nonexistent when the phantom (or patient) is held stationary. The reported DLP remains robust for the stationary phantom. Conclusions: The CTDI-paradigm does not apply in the case of a stationary phantom and simpler nonintegral equations suffice. A method of correction of the currently reported CTDI{sub vol} using the approach-to-equilibrium formula H(a) and an overbeaming correction factor serves to scale the reported CTDI{sub vol} values to more accurate levels for stationary-table CT, as well as serving as an indicator in the detection of “bad data.”.« less

Determining the Magnitude of Neutron and Galactic Cosmic Ray (GCR) Fluxes at the Moon using the Lunar Exploration Neutron Detector during the Historic Space-Age Era of High GCR Flux

NASA Astrophysics Data System (ADS)

Chin, G.; Sagdeev, R.; Boynton, W. V.; Mitrofanov, I. G.; Milikh, G. M.; Su, J. J.; Livengood, T. A.; McClanahan, T. P.; Evans, L.; Starr, R. D.; litvak, M. L.; Sanin, A.

2013-12-01

that determines the absolute flux of neutrons at the Moon and then subsequently to deduce the proper scale of the GCR flux. References: [1] H. S. Ahluwakia and R. C. Ygbuhay (2010) Twelfth International Solar Wind Conference, 699-702. [2] F. B. McDonald et al. (2010) JRL, 37, L18101. [3] H. Moraal and P. H. Stoker (2010) JGR, 115, 12109-12118. [4] R. Kataoka et al. (2012) Space Weather, 10, 11001-11007. [4] C-L. Huang et al. (2009), JRL, 37, L09109-L09104. [5] R. A. Mewaldt et al. (2010) Ap. J Lett., 723, L1-L6. [6] I. G. Mitrofanov et al. (2010) Space Science Rev., 150, 283-207. [7] C. R. Tooley et al. (2010) Space Science Rev., 150, 23-62. [8] G. W. McKinney et al. (2006) JGR, 111, 6004-6018. [9] P. M. O'Neil (2010) IEEE Trans. Nucl. Sci., 57(6), 3148-3153. [10] American National Standards Institute Tech. Rep. ISO 15390 (2004). [11] I. G. Usokin et al. (2008) JGR, 110, A12108. [12] M. D. Looper et al. (2013) Space Weather, 11, 142-152. [13] A. I. Mrigakshi et al. (2012) JGR, 117, A08109-A08121.

Isothermal reduction kinetics of Panzhihua ilmenite concentrate under 30vol% CO-70vol% N2 atmosphere

NASA Astrophysics Data System (ADS)

Zhang, Ying-yi; Lü, Wei; Lü, Xue-wei; Li, Sheng-ping; Bai, Chen-guang; Song, Bing; Han, Ke-xi

2017-03-01

The reduction of ilmenite concentrate in 30vol% CO-70vol% N2 atmosphere was characterized by thermogravimetric and differential thermogravimetric (TG-DTG) analysis methods at temperatures from 1073 to 1223 K. The isothermal reduction results show that the reduction process comprised two stages; the corresponding apparent activation energy was obtained by the iso-conversional and model-fitting methods. For the first stage, the effect of temperature on the conversion degree was not obvious, the phase boundary chemical reaction was the controlling step, with an apparent activation energy of 15.55-40.71 kJ·mol-1. For the second stage, when the temperatures was greater than 1123 K, the reaction rate and the conversion degree increased sharply with increasing temperature, and random nucleation and subsequent growth were the controlling steps, with an apparent activation energy ranging from 182.33 to 195.95 kJ·mol-1. For the whole reduction process, the average activation energy and pre-exponential factor were 98.94-118.33 kJ·mol-1 and 1.820-1.816 min-1, respectively.

Elevated temperature slow plastic deformation of NiAl-TiB2 particulate composites at 1200 and 1300 K

NASA Technical Reports Server (NTRS)

Whittenberger, J. Daniel; Viswanadham, R. K.; Mannan, S. K.; Sprissler, B.

1990-01-01

Elevated temperature compression testing has been conducted in air at 1200 and 1300 K with strain rates varying from about 10 to the -4th to about 10 to the -7th/sec on NiAl-TiB2 particulate composites. These materials, which consisted of a B2 crystal structure intermetallic Ni-50 at. pct Al matrix and from 0 to 30 vol pct of approximately 1- micron diameter TiB2 particles, were fabricated by XD synthesis and hot pressed to full density. Flow strength of the composites increased with volume fraction of the strengthening phase with NiAl-30TiB2 being approximately three times stronger than NiAl. Comparison of the light optical and TEM microstructures of as-received and tested samples revealed that reactions did not occur between the two phases, and NiAl-TiB2 interfaces were not cracked during deformation. Additional TEM indicated that the particles stabilize a vastly different microstructure in the NiAl matrix of the composites than that formed in unreinforced NiAl.

Wear Resistance of Aluminum Matrix Composites Reinforced with Al2O3 Particles After Multiple Remelting

NASA Astrophysics Data System (ADS)

Klasik, Adam; Pietrzak, Krystyna; Makowska, Katarzyna; Sobczak, Jerzy; Rudnik, Dariusz; Wojciechowski, Andrzej

2016-08-01

Based on previous results, the commercial composites of A359 (AlSi9Mg) alloy reinforced with 22 vol.% Al2O3 particles were submitted to multiple remelting by means of gravity casting and squeeze-casting procedures. The studies were focused on tribological tests, x-ray phase analyses, and microstructural examinations. More promising results were obtained for squeeze-casting method mainly because of the reduction of the negative microstructural effects such as shrinkage porosity or other microstructural defects and discontinuities. The results showed that direct remelting may be treated as economically well-founded and alternative way compared to other recycling processes. It was underlined that the multiple remelting method must be analyzed for any material separately.

Dust-Driven Halos on the Martian South Polar Residual CAP

NASA Astrophysics Data System (ADS)

Becerra, P.; Byrne, S.; Brown, A. J.

2013-12-01

-consistent set of CO2 ice grain sizes and dust contents can explain the appearance of the halos. As the halos have larger ice grains, small dust deficiencies in the halos explain their brighter appearance. Our observations constrain the composition of the ice to a small range of parameter space (10 - 20 μm dust grains at ~ 400 (halos) - 700 (surroundings) ppm, in ~8 mm CO2 ice grains). One plausible halo-formation mechanism is that an outward flow of gas caused by the higher sublimation rate from the pit walls, acts to deflect settling dust particles, effectively keeping these areas clean and causing them to appear brighter than their surroundings. This suggests that the cap darkened this year rather than the halos having brightened. Small changes in SPRC albedo can have large effects on the cap's stability, and the cap was likely in negative mass balance this year. The study of these halos' episodic existence could help characterize the mass balance of the SPRC during other anomalous years such as MY9 and MY25, which also contained global dust storms. References: [1] McEwen et al. JGR 112, (2007). [2] Malin et al., JGR 112, (2007). [3] Thomas et al., Icarus 203 (2009). [4] Clancy et al., JGR 105, (2000). [5] Murchie et al., JGR 112 (2007). [6] Brown et al., JGR 115, (2010). [7] Hapke, B., Cambridge Univ. Press, (2012).

CIRF Publications, Vol. 12, No. 5.

ERIC Educational Resources Information Center

International Labour Office, Geneva (Switzerland).

CIRF Publications, Vol. 12, No. 5 is a collection of 80 abstracts giving particular attention to education, training, and economic growth in developing countries, Iran, Japan, Kenya, the Solomon Islands, and Sri Lanka; vocational rehabilitation in Italy, Spain, the United Kingdom, and the U. S. A.; agriculture in Chad, developing countries, and…

Experimental Investigation of Adsorption Kinetics: Implications for Diurnals Variations of Martian Atmospheric Water.

NASA Astrophysics Data System (ADS)

Slank, R.; Farris, H. N.; Chevrier, V.

2017-12-01

Introduction: Ice at Mars' equatorial regions is unstable at geologically short timescales, due to factors like thermal properties of the regolith and depth [1]. The distribution of ice is governed by thermodynamics and kinetics, which largely depends on diffusive and adsorptive properties of the regolith [2] and are studied through simulation experiments on regolith analogs. Numerical models of water ice stability [3] often require kinetic parameters that are lacking for Mars relevant materials. Previous measurements were limited to clays [4] or did not account for temperature dependence [5]. Method: Measurements of input parameters are performed for different regoliths relevant to observations of the Martian surface: smectite, basalt, JSC-Mars 1, and nanophase ferric oxides [6]. While diffusive properties of some of these materials are well understood [7; 1; 8; 9], we seek to determine adsorption parameters, specifically the temperature dependencies for kinetics. Adsorption kinetic constants are derived from the change in mass of water adsorbed as a function of time on a thin layer ( 1mm thick) of regolith, resulting in minimum diffusion and maximum surface in contact with the atmosphere. The samples are baked for 24 hours at 100°C and then sealed in a desiccators placed in a freezer to cool the sample. All experiments are run in the Aries Mars Simulation Chamber. The chamber is evacuated to less that 1 mbar, filled with dry CO2 gas to atmospheric pressure, and chilled to the determined temperature. Once conditions are stable, the sample is measured and placed in the chamber. The sample is then exposed to a 6 mbar CO2 atmosphere at various temperatures (-12 to 3°C) and humidities (5 to 80%). Experiments are run for 4 to 8 hours, to allow the sample to reach steady state. During this time, mass, pressure, temperature, relative humidity, and water vapor pressure are recorded. References: [1] Beck, P. et al. (2010) JGR 115. [2] Chevrier, V.F. et al. (2008) Icarus

Unraveling the effect of primary versus secondary processes on the volatile content of MORB glasses: an example from the equatorial Mid-Atlantic Ridge

NASA Astrophysics Data System (ADS)

Le Voyer, M.; Hauri, E. H.; Kelley, K. A.; Cottrell, E.

2012-12-01

, CO2 and S do not show any clear tendencies. The trend (R2=0.7) between the CO2 contents and their calculated H2O-CO2 saturation pressures (Psat, 315-526 bar [5]) indicates that some of the CO2 variation is due to equilibrium degassing of a CO2-rich fluid phase (77-98 mol% CO2). By comparing the Psat with the collection pressure (3440-4530 mbsl, i.e. 337-444 bar), we found that half of the samples are affected by variable degrees of supersaturation (up to 82 bars in the deepest sample with the smallest vesicularity). This non-equilibrium state could be caused by a delay in bubble formation due to rapid ascent rates [6]. Finally, unlike CO2, S is poorly correlated with Psat, but displays a very good correlation with FeO*, indicating S saturation and partitioning of S into a sulfide phase rather than into a fluid phase. [1] Javoy and Pineau, 1991, EPSL 105, 598-611. [2] Schilling et al., 1994, JGR 99,12005-12028. [3] Schilling et al., 1995, JGR 100,10057-10076. [4] Hannigan et al., 2001, Chem. Geol. 175, 397-428. [5]: Dixon and Stolper, 1995, JPet 36, 1633-1646. [6] Dixon et al., 1988, EPSL 90, 87-104.

Global Geological Map of Venus

NASA Astrophysics Data System (ADS)

Ivanov, M. A.

2008-09-01

units is ~81.7% of the map area, whereas the younger units cover ~14.1% of the surface. Depending upon the estimates of T (750 Ma [36], 500 Ma [37], 300 Ma [38]), duration of Fortunian Period can be from 300 m.y (T=750 Ma) to 120 m.y (T=300 Ma). The minimum integrated resurfacing rate (both volcanic and tectonic) at this time was from ~1.2 to ~3.1 km2/y. Duration of Atlian Period is estimated to be from 750 to 300 m.y and the integrated resurfacing rate during this period could be from ~0.2 to ~0.4 km2/y. Such a significant drop of the resurfacing rates suggests that Fortunian and Atlian periods correspond to two different geodynamic regimes that probably were related to different regimes of mantle convection and lithospheric properties. References: 1) Basilevsky, A. T. and J.W. Head, PSS, 43, 1523, 1995; 2) Basilevsky, A.T. and J.W. Head, PSS, 48, 75, 2000 3) DeShon, H.R. et al., JGR, 105, 6983, 2000; 4) Head, J.W. et al., JGR, 97, 13153, 1992; 5) Solomon, S.C. et al., JGR, 97, 13199, 1992; 6) Squyres, S.W. et al., JGR, 97, 13579, 1992; 7) Stofan, E. R. et al., JGR, 97, 13347, 1992; 8) Guest, J.E., and E.R., Icarus139, 56, 1999; 9) Basilevsky, A.T.,et al., in: Venus II, S.W. Bougher et al. eds., Univ. Arizona Press 1047, 1997; 10) Head, J.W. and A.T. Basilevsky, Geology, 26, 35, 1998; 11) Ivanov, M.A. and J.W. Head, JGR, 106, 17515, 2001; 12) Price, M. and J., Nature, 372, 756, 1994; 13) Price, M. et al., JGR, 101, 4657, 1996 14) Namiki, N. and S.C. Solomon, Science, 265, 929, 1994 15) Parmentier, E.M. and P.C. Hess, GRL, 19, 2015, 1992; 16) Head, J.W. et al., PSS, 42, 803, 1994; 17) Turcotte, D.L., JGR, 98, 127061, 1993; 18) Arkani-Hamed, J. and M.N. Toksoz, PEPI, 34, 232, 1984; 19) Solomon, S.C, LPSC (Abstr.), XXIV, 1331, 1993; 20) Phillips R.J. and V.L. Hansen, Science, 279, 1492, 1998; 21) Solomatov, S.V. and L.-N. Moresi, JGR, 101, 4737, 1996; 22) Bender, K.C., et al., USGS Map I-2620, 2000; 23) Rosenberg, E. and G. E. McGill, USGS Map I-2721, 2001; 24) Ivanov, M

The Cryospheres of Mars and Ceres - What thermal observations tell us about near surface ice.

NASA Astrophysics Data System (ADS)

Titus, T. N.; Li, J. Y.; Moullet, A.

2017-12-01

Mars and Ceres both have near surface water ice that forms a cryosphere at polar latitudes. Gamma ray and neutron observations have provided important constraints on the location and depths of the cryosphere for both planetary bodies, but these observations have very low spatial resolution [e.g. 1, 2]. Thermal observations, which are also sensitive to the presence of a near-surface cryosphere as demonstrated by several studies of Mars [e.g. 3, 4], provide additional constraints. Thermal observations can identify depth to the cryosphere (as long as it is within a few thermal skin depths) and water-ice stability. This presentation will compare both the similarities and the differences of these two planetary cryospheres, as well as the thermal observations from Mars Global Surveyor (MGS) Thermal Emission Spectrometer (TES) [5], the Atacama Large Millimeter/submillimeter Array (ALMA) [6], and publically available Dawn Visible Infrared spectrometer (VIR) [7]. The KRC thermal model [8] will use these observed surface temperatures to constrain depths to near surface ice (i.e. the cyropshere). References: [1] Feldman et al., 2002, Science, 297(5578), 75-78. [2] Prettyman et al., 2017, Science, 355(6320), 55-59. [3] Titus et al., 2003, Science, 299(5609), 1048-1051 [4] Mellon et al., 2008, JGR, 113(E12), CiteID E00A25. [5] Christensen et al., 1998, Science, 279(5357), 1692. [6] Wootten A. et al. (2015) IAU General Assembly, Meeting #29, #2237199 [7] de Santis et al., 2011, Space Science Reviews, 163(1-4), 329-369. [8] Kieffer, 2013, JGR, 118, Issue 3, pp. 451-470.

Thunderstorm Charge Structures Producing Negative Gigantic Jets

NASA Astrophysics Data System (ADS)

Boggs, L.; Liu, N.; Riousset, J. A.; Shi, F.; Rassoul, H.

2016-12-01

Here we present observational and modeling results that provide insight into thunderstorm charge structures that produce gigantic jet discharges. The observational results include data from four different thunderstorms producing 9 negative gigantic jets from 2010 to 2014. We used radar, very high frequency (VHF) and low frequency (LF) lightning data to analyze the storm characteristics, charge structures, and lightning activity when the gigantic jets emerged from the parent thunderstorms. A detailed investigation of the evolution of one of the charge structures by analyzing the VHF data is also presented. The newly found charge structure obtained from the observations was analyzed with fractal modeling and compared with previous fractal modeling studies [Krehbiel et al., Nat. Geosci., 1, 233-237, 2008; Riousset et al., JGR, 115, A00E10, 2010] of gigantic jet discharges. Our work finds that for normal polarity thunderstorms, gigantic jet charge structures feature a narrow upper positive charge region over a wide middle negative charge region. There also likely exists a `ring' of negative screening charge located around the perimeter of the upper positive charge. This is different from previously thought charge structures of the storms producing gigantic jets, which had a very wide upper positive charge region over a wide middle negative charge region, with a very small negative screening layer covering the cloud top. The newly found charge structure results in leader discharge trees in the fractal simulations that closely match the parent flashes of gigantic jets inside and outside the thundercloud. The previously used charge structures, while vital to the understanding of gigantic jet initiation and the role of charge imbalances inside the cloud, do not produce leader discharge trees that agree with observed gigantic jet discharges.Finally, the newly discovered gigantic jet charge structures are formed near the end of a convective pulse [Meyer et al., JGR, 118

Electron hybrid simulations of whistler-mode chorus generation with real parameters in the Earth's inner magnetosphere

NASA Astrophysics Data System (ADS)

Katoh, Y.; Omura, Y.

2016-12-01

Whistler-mode chorus emissions play curial roles in the evolution of radiation belt electrons. Chorus emissions are narrow band emissions observed in the typical frequency range of 0.2 to 0.8 fce0 with a gap at half the fce0, where fce0 represents the electron gyrofrequency at the magnetic equator. The generation process of chorus has been explained by the nonlinear wave growth theory [see review by Omura et al., in AGU Monograph "Dynamics of the Earth's Radiation Belts and Inner Magnetosphere, 2012] and has been reproduced by self-consistent numerical experiments [e.g., Katoh and Omura, GRL 2007, JGR 2011, 2013]. In the present study, we show the result of electron hybrid simulation of the generation process of whistler-mode chorus emissions under realistic initial conditions. We refer in-situ observations by Cluster [Santolik et al., 2003] for the initial parameters of energetic electrons and the spatial inhomogeneity of the background magnetic field. In the simulation results we observe chorus emissions with rising tones whose the spectral characteristics are consistent with the observation. We also find that the simulation results are consistently explained by the theoretically estimated threshold and optimum wave amplitudes of chorus elements based on the nonlinear wave growth theory. A series of simulations reveal properties of the chorus generation depending on the velocity distribution of energetic electrons [Katoh and Omura, JGR 2011] and the background magnetic field inhomogeneity [Katoh and Omura, JGR 2013]. These properties should be evaluated by comparison with in-situ and ground-based observations.

The Effect of Neutral Winds on Simulated Inner Magnetospheric Electric Fields During the 17 March 2013 Storm

NASA Astrophysics Data System (ADS)

Chen, M.; Lemon, C.; Walterscheid, R. L.; Hecht, J. H.; Sazykin, S. Y.; Wolf, R.

2017-12-01

We investigate how neutral winds and particle precipitation affect the simulated development of electric fields including Sub-Auroral Polarization Streams (SAPS) during the 17 March 2013 storm. Our approach is to use the magnetically and electrically self-consistent Rice Convection Model - Equilibrium (RCM-E) to simulate the inner magnetospheric electric field. We use parameterized rates of whistler-generated electron pitch-angle scattering from Orlova and Shprits [JGR, 2014] that depend on equatorial radial distance, magnetic activity (Kp), and magnetic local time (MLT) outside the simulated plasmasphere. Inside the plasmasphere, parameterized scattering rates due to hiss [Orlova et al., GRL, 2014] are used. Ions are scattered at a fraction of strong pitch-angle scattering where the fraction is scaled by epsilon, the ratio of the gyroradius to the field-line radius of curvature, when epsilon is greater than 0.1. The electron and proton contributions to the auroral conductance in the RCM-E are calculated using the empirical Robinson et al. [JGR, 1987] and Galand and Richmond [JGR, 2001] equations, respectively. The "background" ionospheric conductance is based on parameters from the International Reference Ionosphere [Bilitza and Reinisch, JASR, 2008] but modified to include the effect of specified ionospheric troughs. Neutral winds are modeled by the empirical Horizontal Wind Model (HWM07) in the RCM-E. We compare simulated precipitating particle energy flux, E x B velocities with DMSP observations during the 17 March 2013 storm with and without the inclusion of neutral winds. Discrepancies between the simulations and observations will aid us in assessing needed improvements in the model.

Earthquake-Ionosphere Coupling Processes

NASA Astrophysics Data System (ADS)

Kamogawa, Masashi

After a giant earthquake (EQ), acoustic and gravity waves are excited by the displacement of land and sea surface, propagate through atmosphere, and then reach thermosphere, which causes ionospheric disturbances. This phenomenon was detected first by ionosonde and by HF Doppler sounderin the 1964 M9.2 Great Alaskan EQ. Developing Global Positioning System (GPS), seismogenic ionospheric disturbance detected by total electron content (TEC) measurement has been reported. A value of TEC is estimated by the phase difference between two different carrier frequencies through the propagation in the dispersive ionospheric plasma. The variation of TEC is mostly similar to that of F-region plasma. Acoustic-gravity waves triggered by an earthquake [Heki and Ping, EPSL, 2005; Liu et al., JGR, 2010] and a tsunami [Artu et al., GJI, 2005; Liu et al., JGR, 2006; Rolland, GRL, 2010] disturb the ionosphere and travel in the ionosphere. Besides the traveling ionospheric disturbances, ionospheric disturbances excited by Rayleigh waves [Ducic et al, GRL, 2003; Liu et al., GRL, 2006] as well as post-seismic 4-minute monoperiodic atmospheric resonances [Choosakul et al., JGR, 2009] have been observed after the large earthquakes. Since GPS Earth Observation Network System (GEONET) with more than 1200 GPS receiving points in Japan is a dense GPS network, seismogenic ionospheric disturbance is spatially observed. In particular, the seismogenic ionospheric disturbance caused by the M9.0 off the Pacific coast of Tohoku EQ (henceforth the Tohoku EQ) on 11 March 2011 was clearly observed. Approximately 9 minutes after the mainshock, acoustic waves which propagated radially emitted from the tsunami source area were observed through the TEC measurement (e. g., Liu et al. [JGR, 2011]). Moreover, there was a depression of TEC lasting for several tens of minutes after a huge earthquake, which was a large-scale phenomenon extending to a radius of a few hundred kilometers. This TEC depression may be

Radiation Resistance of the U(Al, Si)3 Alloy: Ion-Induced Disordering

PubMed Central

Yaniv, Gili; Horak, Pavel; Vacik, Jiri; Mykytenko, Natalia; Rafailov, Gennady; Dahan, Itzchak; Fuks, David; Kiv, Arik

2018-01-01

During the exploitation of nuclear reactors, various U-Al based ternary intermetallides are formed in the fuel-cladding interaction layer. Structure and physical properties of these intermetallides determine the radiation resistance of cladding and, ultimately, the reliability and lifetime of the nuclear reactor. In current research, U(Al, Si)3 composition was studied as a potential constituent of an interaction layer. Phase content of the alloy of an interest was ordered U(Al, Si)3, structure of which was reported earlier, and pure Al (constituting less than 20 vol % of the alloy). This alloy was investigated prior and after the irradiation performed by Ar ions at 30 keV. The irradiation was performed on the transmission electron microscopy (TEM, JEOL, Japan) samples, characterized before and after the irradiation process. Irradiation induced disorder accompanied by stress relief. Furthermore, it was found that there is a dose threshold for disordering of the crystalline matter in the irradiated region. Irradiation at doses equal or higher than this threshold resulted in almost solely disordered phase. Using the program “Stopping and Range of Ions in Matter” (SRIM), the parameters of penetration of Ar ions into the irradiated samples were estimated. Based on these estimations, the dose threshold for ion-induced disordering of the studied material was assessed. PMID:29393870

Radiation Resistance of the U(Al, Si)₃ Alloy: Ion-Induced Disordering.

PubMed

Meshi, Louisa; Yaniv, Gili; Horak, Pavel; Vacik, Jiri; Mykytenko, Natalia; Rafailov, Gennady; Dahan, Itzchak; Fuks, David; Kiv, Arik

2018-02-02

During the exploitation of nuclear reactors, various U-Al based ternary intermetallides are formed in the fuel-cladding interaction layer. Structure and physical properties of these intermetallides determine the radiation resistance of cladding and, ultimately, the reliability and lifetime of the nuclear reactor. In current research, U(Al, Si)₃ composition was studied as a potential constituent of an interaction layer. Phase content of the alloy of an interest was ordered U(Al, Si)₃, structure of which was reported earlier, and pure Al (constituting less than 20 vol % of the alloy). This alloy was investigated prior and after the irradiation performed by Ar ions at 30 keV. The irradiation was performed on the transmission electron microscopy (TEM, JEOL, Japan) samples, characterized before and after the irradiation process. Irradiation induced disorder accompanied by stress relief. Furthermore, it was found that there is a dose threshold for disordering of the crystalline matter in the irradiated region. Irradiation at doses equal or higher than this threshold resulted in almost solely disordered phase. Using the program "Stopping and Range of Ions in Matter" (SRIM), the parameters of penetration of Ar ions into the irradiated samples were estimated. Based on these estimations, the dose threshold for ion-induced disordering of the studied material was assessed.

Service Vessel Analysis. Vol. II : Detailed District Plots.

DOT National Transportation Integrated Search

1987-09-01

This is a supplement to Service Vessel Analysis, Vol. I: Seagoing and Coastal Vessel Requirements for Servicing Aids to Navigation. The material included is not intended to stand alone but is prepared for use in conjunction with the original study. T...

[Reliability of % vol. declarations on labels of wine bottles].

PubMed

Schütz, Harald; Erdmann, Freidoon; Verhoff, Marcel A; Weiler, Günter

2005-01-01

The Council Regulation (EC) no. 1493/1999 of 17 May 1999 on the common organisation of the market in wine (Abl. L 179 dated 14/7/1999) and the GMO Wine 2000 (Annex VII A) stipulates that the labels of wine bottles have to indicate, among others, information on the sales designation of the product, the nominal volume and the alcoholic strength. The latter must not differ by more than 0.5% vol. from the alcoholic strength as established by analysis. Only when quality wines are stored in bottles for more than three years, the accepted tolerance limits are +/- 0.8% vol. The presented investigation results show that deviations have to be taken into account which may be highly relevant for forensic practice.

Characterization of the dimensional stability of advanced metallic materials using an optical test bench structure

NASA Technical Reports Server (NTRS)

Hsieh, Cheng; O'Donnell, Timothy P.

1991-01-01

The dimensional stability of low-density high specific-strength metal-matrix composites (including 30 vol pct SiC(p)/SXA 24-T6 Al, 25 vol pct SiC(p)/6061-T6 Al, 40 vol pct graphite P100 fiber/6061 Al, 50 vol pct graphite P100 fiber/6061 Al, and 40 vol pct P100 graphite fiber/AZ91D Mg composites) and an Al-Li-Mg metal alloy was evaluated using a specially designed five-strut optical test bench structure. The structure had 30 thermocouple locations, one retroreflector, one linear interferometer multilayer insulation, and various strip heaters. It was placed in a 10 exp -7 torr capability vacuum chamber with a laser head positioned at a window port, and a laser interferometer system for collecting dimensional change data. It was found that composite materials have greater 40-C temporal dimensional stability than the AL-Li-Mg alloy. Aluminum-based composites demonstrated better 40-C temporal stability than Mg-based composites.

Success! Detailed Pre-event Analysis Identified the Slip Area and Magnitude of the Sept. 2012 MW 7.6 Nicoya Earthquake

NASA Astrophysics Data System (ADS)

Newman, A. V.; Protti, M.; Gonzalez, V. M.; Dixon, T. H.; Schwartz, S. Y.; Feng, L.; Peng, Z.; Marshall, J.; Malservisi, R.; Owen, S. E.

2013-05-01

On September 5th, 2012 a moment magnitude (MW) 7.6 earthquake struck the seismogenic megathrust of Nicoya Costa Rica. Though, we knew not precisely when, this event was not unexpected, and occurred after the development of substantial pre-event scientific discovery and earthquake infrastructural development. Beginning in the late- 1990's Nicoya Costa Rica was recognized by the U.S. National Science Foundation -MARGINS program as a focus area for seismogenic zone studies in part because of the unique proximity of land to the active subduction megathrust. The region also has very fast convergence (~9 cm/a) and has suffered from regular M7+ earthquakes in 1853, 1900 and 1950. Another similar event was expected by many. Pre-event analysis identified the structure of the subduction interface [Newman et al., GRL, 2002; DeShon et al., GJI, 2006], the location and rate changes of ongoing microseismicity [Newman et al., GRL, 2002, Ghosh et al.,GRL, 2008], the location and degree of locking that developed during the late interseismic [Norabuena et al., JGR, 2006; Feng et al., JGR, 2012], and its relation to ongoing low-frequency earthquakes, subduction tremor, and episodic slip events [Walter et al., GRL, 2011; Outerbridge et al., JGR, 2010, Jiang et al., G3, 2012]. Feng et al., [2012] using campaign and continuous GPS data through 2012, identified complex locked 50x50 km patch along the central coast of Nicoya, the locale that failed in Sept 2012, and concluded that the region had the potential to fail in an MW 7.8 event should the most recent locking be representative of behavior since the last major event in 1950. In operation at the time of the event was a substantial NSF-funded continuous GPS (17 station) and seismic (18 station) network maintained by USF, UCSC, and GIT, in cooperation with OVSICORI. The seismic network captured the initial motions of the mainshock before clipping, as well as pre-shock and aftershock activity [Walter et al., (this meeting), 2013]. The

Initiation of Positive Streamer Corona From Two Hydrometeors With Different Radii in Low Thundercloud Fields

NASA Astrophysics Data System (ADS)

Cai, Q.; Jansky, J.; Pasko, V. P.

2017-12-01

In order to initiate streamers and leaders under thunderstorm conditions the electric field should reach values on the order of critical breakdown field ( 30 kV cm-1 atm-1). The related conditions can be achievable in relatively small volumes around precipitation particles and recent studies [e.g., Sadighi et al., JGR, 120, 3660, 2015; Dubinova et al., Phys. Rev. Lett., 115, 015002, 2015; Babich et al., JGR, 121, 6393, 2016; Cai et al., GRL, 44, 5758, 2017] discuss different configurations of charged and uncharged hydrometeors as physical means for creating such conditions. In the present work formation of streamers by two spherical hydrometeors with different radii in uniform ambient field is investigated. Based on work [Cai et al., 2017], we note that two particles with same radius 2.5 mm can initiate streamer in the minimum field required for propagation of positive streamers in air (i.e., 4.4 kV/cm at ground level). We focus on 4.4 kV/cm since streamers will propagate and grow in electric field higher than this value and can form a leader. An image charge model of two spherical hydrometeors with different radius in uniform ambient field and avalanche-to streamer transition criterion from [Qin et al., JGR, 116, A06305, 2011] are used for investigating avalanche-to-streamer transition. Solution accuracy of electric field is confirmed by comparing our results with analytical results based on [Davis, Quart. J. Mech. Appl. Math., 27, 499-511, 1964] and [Lekner, J. Electrost. 69, 559-563, 2011]. We note that if we increase the radius of one of these two spheres, the radius of the other one should be decreased to keep streamer initiation at 4.4 kV/cm at ground level. Quantitative results on collision frequency of scenarios when avalanche to streamer transition is possible between two spherical hydrometeor particles with different radius at field 4.4 kV/cm are presented. The results are discussed by using different particle distribution from [Atlas and Ludlam, Quart. J

Dose equations for tube current modulation in CT scanning and the interpretation of the associated CTDI{sub vol}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dixon, Robert L.; Boone, John M.

2013-11-15

Purpose: The scanner-reported CTDI{sub vol} for automatic tube current modulation (TCM) has a different physical meaning from the traditional CTDI{sub vol} at constant mA, resulting in the dichotomy “CTDI{sub vol} of the first and second kinds” for which a physical interpretation is sought in hopes of establishing some commonality between the two.Methods: Rigorous equations are derived to describe the accumulated dose distributions for TCM. A comparison with formulae for scanner-reported CTDI{sub vol} clearly identifies the source of their differences. Graphical dose simulations are also provided for a variety of TCM tube current distributions (including constant mA), all having the samemore » scanner-reported CTDI{sub vol}.Results: These convolution equations and simulations show that the local dose at z depends only weakly on the local tube current i(z) due to the strong influence of scatter from all other locations along z, and that the “local CTDI{sub vol}(z)” does not represent a local dose but rather only a relative i(z) ≡ mA(z). TCM is a shift-variant technique to which the CTDI-paradigm does not apply and its application to TCM leads to a CTDI{sub vol} of the second kind which lacks relevance.Conclusions: While the traditional CTDI{sub vol} at constant mA conveys useful information (the peak dose at the center of the scan length), CTDI{sub vol} of the second kind conveys no useful information about the associated TCM dose distribution it purportedly represents and its physical interpretation remains elusive. On the other hand, the total energy absorbed E (“integral dose”) as well as its surrogate DLP remain robust between variable i(z) TCM and constant current i{sub 0} techniques, both depending only on the total mAs = t{sub 0}=i{sub 0} t{sub 0} during the beam-on time t{sub 0}.« less

Effect of the presence of chlorates and perchlorates on the pyrolysis of organic compounds: implications for measurements done with the SAM experiment onboard the Curiosity rover

NASA Astrophysics Data System (ADS)

Millan, Maeva; Szopa, Cyril; Buch, Arnaud; Belmahdi, Imène; Coll, Patrice; Glavin, Daniel P.; Freissinet, Caroline; Archer, Doug; Sutter, Brad; Summons, Roger E.; Navarro-Gonzalez, Rafael; Cabane, Michel; Mahaffy, Paul

2016-04-01

/or quantitative effects. The experiments are performed on a laboratory GC-QMS with a Restek Rxi-5 column (30m x 0.25mm x 0.25μm) and an Intersciences pyrolyser. The mixture is pyrolyzed at different temperatures up to 900°C to cover the SAM temperature range. Different experiments are done to discriminate the pyrolysis products directly coming from the organics, and those produced from the reaction with oxychlorine. These experiments are under progress and should bring key information on the potential to identify Martian organics when pyrolyzing solid samples. Depending on the organic families studied, we may find recurring molecules, which are potentially present in Mars' surface samples. This work could thus highlight some organic precursors of the chlorinated compounds found on Mars, and support the interpretation of SAM measurements. References: [1] Mahaffy, P. et al. (2012) Space Sci Rev, 170, 401-478. [2] Biemann, K. et al (1977) JGR, 82, 4641-4658. [3] Glavin, D. et al. (2013), JGR 118, 1955-1973. [4] Freissinet, C. et al. (2015) JGR. [5] Leshin L. et al. (2013), Science. [6] Hecht, (2009), Science, 325 64-67. [7] Navarro-Gonzalez et al. (2010) JGR 115, EI12010. [8] Steninger, H. et al (2012) Planet. Space Sci. 71, 9-17. Acknowledgments: French Space Agency (CNES) support for SAM-GC development and exploitation.

The feasibility of a regional CTDI{sub vol} to estimate organ dose from tube current modulated CT exams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khatonabadi, Maryam; Kim, Hyun J.; Lu, Peiyun

Purpose: In AAPM Task Group 204, the size-specific dose estimate (SSDE) was developed by providing size adjustment factors which are applied to the Computed Tomography (CT) standardized dose metric, CTDI{sub vol}. However, that work focused on fixed tube current scans and did not specifically address tube current modulation (TCM) scans, which are currently the majority of clinical scans performed. The purpose of this study was to extend the SSDE concept to account for TCM by investigating the feasibility of using anatomic and organ specific regions of scanner output to improve accuracy of dose estimates. Methods: Thirty-nine adult abdomen/pelvis and 32more » chest scans from clinically indicated CT exams acquired on a multidetector CT using TCM were obtained with Institutional Review Board approval for generating voxelized models. Along with image data, raw projection data were obtained to extract TCM functions for use in Monte Carlo simulations. Patient size was calculated using the effective diameter described in TG 204. In addition, the scanner-reported CTDI{sub vol} (CTDI{sub vol,global}) was obtained for each patient, which is based on the average tube current across the entire scan. For the abdomen/pelvis scans, liver, spleen, and kidneys were manually segmented from the patient datasets; for the chest scans, lungs and for female models only, glandular breast tissue were segmented. For each patient organ doses were estimated using Monte Carlo Methods. To investigate the utility of regional measures of scanner output, regional and organ anatomic boundaries were identified from image data and used to calculate regional and organ-specific average tube current values. From these regional and organ-specific averages, CTDI{sub vol} values, referred to as regional and organ-specific CTDI{sub vol}, were calculated for each patient. Using an approach similar to TG 204, all CTDI{sub vol} values were used to normalize simulated organ doses; and the ability of each

Letter to the Editor: On the definition and measurement of human scent: Comments on Curran et al.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Preti, George; Willse, Alan R.; Labows, John N.

A recent article by Curran et al (J. Chem. Ecol. vol. 31 (7); 1607-1619, 2005) describes the collection and chemical analysis of ''human scent''. Contrary to the authors? claims, a great deal is known about the chemical constituents of human scent, and its measurement. Here we clarify what is known about human scent, and highlight several shortcomings concerning the authors analysis related to (1) the definition of human scent, (2) chemical analysis of human scent, and (3) conclusions about individual differences. More than 15 years of research has presented both organoleptic and analytical evidence that a mixture of C6-C11 normal,more » branched, hydroxy-and unsaturated acids present in axillary sweat constitute the characteristic axillary odor. (Zeng et al., 1991; 1992; 1996; 1996a; Natsch et al., 2003). In addition to this mixture of major odor constituents are trace amounts of thio-alcohols (Natsch et al., 2004; Troccaz et al., 2004; Hasegawa et al., 2004) with high odor impact (low olfactory threshold). The details of the chemical identification, exact structures and synthesis (of non-commercially available compounds) as well as biogenesis of many of these compounds have been described in the above cited manuscripts.« less

Mathematical modeling and numerical simulation of unilateral dynamic rupture propagation along very-long reverse faults

NASA Astrophysics Data System (ADS)

Hirano, S.

2017-12-01

For some great earthquakes, dynamic rupture propagates unilaterally along a horizontal direction of very-long reverse faults (e.g., the Mw9.1 Sumatra earthquake in 2004, the Mw8.0 Wenchuan earthquake in 2008, and the Mw8.8 Maule earthquake in 2010, etc.). It seems that barriers or creeping sections may not lay along the opposite region of the co-seismically ruptured direction. In fact, in the case of Sumatra, the Mw8.6 earthquake occurred in the opposite region only three months after the mainshock. Mechanism of unilateral mode-II rupture along a material interface has been investigated theoretically and numerically. For mode-II rupture propagating along a material interface, an analytical solution implies that co-seismic stress perturbation depends on the rupture direction (Weertman, 1980 JGR; Hirano & Yamashita, 2016 BSSA), and numerical modeling of plastic yielding contributes to simulating the unilateral rupture (DeDonteny et al., 2011 JGR). However, mode-III rupture may dominate for the very-long reverse faults, and it can be shown that stress perturbation due to mode-III rupture does not depend on the rupture direction. Hence, an effect of the material interface is insufficient to understand the mechanism of unilateral rupture along the very-long reverse faults. In this study, I consider a two-dimensional bimaterial system with interfacial dynamic mode-III rupture under an obliquely pre-stressed configuration (i.e., the maximum shear direction of the background stress is inclined from the interfacial fault). First, I derived an analytical solution of regularized elastic stress field around a steady-state interfacial slip pulse using the method of Rice et al. (2005 BSSA). Then I found that the total stress, which is the sum of the background stress and co-seismic stress perturbation, depends on the rupture direction even in the mode-III case. Second, I executed a finite difference numerical simulation with a plastic yielding model of Andrews (1978 JGR; 2005

Solar wind control of stratospheric temperatures in Jupiter's auroral regions?

NASA Astrophysics Data System (ADS)

Sinclair, James Andrew; Orton, Glenn; Kasaba, Yasumasa; Sato, Takao M.; Tao, Chihiro; Waite, J. Hunter; Cravens, Thomas; Houston, Stephen; Fletcher, Leigh; Irwin, Patrick; Greathouse, Thomas K.

2017-10-01

Auroral emissions are the process through which the interaction of a planet’s atmosphere and its external magnetosphere can be studied. Jupiter exhibits auroral emission at a multitude of wavelengths including the X-ray, ultraviolet and near-infrared. Enhanced emission of CH4 and other stratospheric hydrocarbons is also observed coincident with Jupiter’s shorter-wavelength auroral emission (e.g. Caldwell et al., 1980, Icarus 44, 667-675, Kostiuk et al., 1993, JGR 98, 18823). This indicates that auroral processes modify the thermal structure and composition of the auroral stratosphere. The exact mechanism responsible for this auroral-related heating of the stratosphere has however remained elusive (Sinclair et al., 2017a, Icarus 292, 182-207, Sinclair et al., 2017b, GRL, 44, 5345-5354). We will present an analysis of 7.8-μm images of Jupiter measured by COMICS (Cooled Mid-Infrared Camera and Spectrograph, Kataza et al., 2000, Proc. SPIE(4008), 1144-1152) on the Subaru telescope. These images were acquired on January 11th, 12th, 13th, 14th, February 4, 5th and May 17th, 18th, 19th and 20th in 2017, allowing the daily variability of Jupiter’s auroral-related stratospheric heating to be tracked. Preliminary results suggest lower stratospheric temperatures are directly forced by the solar wind dynamical pressure. The southern auroral hotspot exhibited a significant increase in brightness temperature over a 24-hour period. Over the same time period, a solar wind propagation model (Tao et al. 2005, JGR 110, A11208) predicts a strong increase in the solar wind dynamical pressure at Jupiter.

Directional Emissivity Effects on Martian Surface Brightness Temperatures

NASA Astrophysics Data System (ADS)

Pitman, K. M.; Wolff, M. J.; Bandfield, J. L.; Clancy, R. T.; Clayton, G. C.

2001-11-01

The angular dependence of thermal emission from the surface of Mars has not been well characterized. Although nadir sequences constitute most of the MGS/TES Martian surface observations [1,2], a significant number scans of Martian surfaces at multiple emission angles (emission phase function (EPF) sequences) also exist. Such data can provide insight into surface structures, thermal inertias, and non-isotropic corrections to thermal emission measurements [3]. The availability of abundant EPF data as well as the added utility of such observations for atmospheric characterization provide the impetus for examining the phenomenon of directional emissivity. We present examples of directional emissivity effects on brightness temperature spectra for a variety of typical Martian surfaces. We examine the theoretical development by Hapke (1993, 1996) [4,5] and compare his algorithm to that of Mishchenko et al. (1999) [6]. These results are then compared to relevant TES EPF data. This work is supported through NASA grant NAGS-9820 (MJW) and JPL contract no. 961471 (RTC). [1] Smith et al. (1998), AAS-DPS meeting # 30, # 11.P07. [2] Kieffer, Mullins, & Titus (1998), EOS, 79, 533. [3] Jakosky, Finiol, & Henderson (1990), JGR, 17, 985--988. [4] Hapke, B. (1993), Theory of Reflectance & Emittance Spectroscopy, Cambridge Univ. Press, NY. [5] Hapke, B. (1996), JGR, 101, E7, 16817--16831. [6] Mishchenko et al. (1999), JQSRT, 63, 409--432.

A 1-D Cryothermal Model of Ceres’ Megaregolith: Predictions for Surface Vapor Flux, Subsurface Temperatures and Pore Ice Distribution

NASA Astrophysics Data System (ADS)

Reynolds, Dylan; Wood, Stephen E.; Bapst, Jonathan; Mehlhaff, Joshua; Griffiths, Stephen G.

2014-11-01

We have applied a self-consistent 1-D model for heat diffusion, vapor diffusion, and ice condensation/sublimation, and surface energy balance to investigate our hypothesis for the source of the recently observed water vapor around Ceres [1]. As described in a companion presentation [2], we find that the estimated global flux of 6 kg/s can be produced by steady-state sublimation of subsurface ice driven by the “geothermal” temperature gradient for a heat flux of 1 mW/m2 - the value estimated for a chondritic abundance of heat-producing elements [3,4]. We will present a detailed description of our Ceres cryothermal diffusion model and comparisons with previous models. One key difference is the use of a new physics-based analytic model (‘MaxRTCM’) for calculating the thermal conductivity (Kth) of planetary regolith [5] that has been validated by comparisons to a wide range of laboratory data [6]. MaxRTCM predicts much lower Kth values in the upper regolith than those in previous work [3]. It also accounts for a process first modeled in a study of unstable equatorial ground ice on Mars [7,8], where vapor diffusing up from a receding ice table toward the surface can recondense at shallower depths - eventually forming a steady-state profile of pore ice volume fraction that increases with depth and maintains a constant flux of vapor at all depths [7]. Using MaxRTCM we calculate the corresponding Kth(z) profiles and will present predictions and implications of the resulting temperature profile in the upper few kilometers of Ceres’ megaregolith.References: [1] Küppers et al. (2014), Nature, 505(7484), 525-527. [2] Wood et al., 2014, this meeting. [3] Fanale & Salvail (1989) Icarus 82, 97-110. [4] McCord and Sotin (2005) JGR 110, E05009. [5] Wood (2013) LPSC Abs. 44, 3077. [6] Wood (2014), Icarus, in revision. [7] Mellon et al. (1997), JGR, 102, 19357-69. [8] Clifford (1993), JGR, 98, 10973-11016.

Thermal Reactivity Of Organic Molecules With Perchlorates And The Detection Of Organics In Mars Samples With SAM Onboard Curiosity Rover

NASA Astrophysics Data System (ADS)

Szopa, C.; Millan, M.; Buch, A.; Freissinet, C.; Guzman, M.; Glavin, D. P.; Mahaffy, P. R.; Navarro-Gonzalez, R.

2017-12-01

. [1] Kounaves et al. (2010), JGR 115; [2] Glavin et al. (2013), JGR 181; [3] Sutter et al., JGR (in press);

A Clementine Derived Control Network and Topographic Model - The Unified Lunar Control Network 2005

NASA Astrophysics Data System (ADS)

Archinal, B. A.; Rosiek, M. R.; Kirk, R. L.; Redding, B. L.

2006-08-01

generated [9] will be registered to the ULCN 2005. We will also further improve this network through the addition of Mariner 10, Galileo, and LO image measurements, and Clementine stereo [10], and by adding ties to the current absolute LLR and ALSEP network [11]. Although unfunded, the Clementine mosaics could also be regenerated in this system. It will be absolutely essential to further update and improve this network with data from future missions. This is necessary so that these new datasets can be compared to the prior data, particularly the LO and Clementine multispectral products. References: [1] Davies, M. E. et al. (1994) JGR, 99, E11, 23,211-23,214. [2] Edwards, et al. (1996), LPS XXVII, 335-336. [3] Smith, D. E. et al. (1997), JGR, 102, E1, 1591-1611. [4] Cook, A. C. et al. (2000), JGR, 105, E5, 12,023-12,033. [5] Rosiek, M. R. et al. (1998), LPS XXX, Abstract #1853. Rosiek, M. R., and Aeschliman, R. A. (2001) LPS XXXII, Abstract #1943. [6] Margot, J-L. C. (1999), PhD Thesis, Cornell University. [7] Wu, S. S. C. and Doyle, F. J. (1990), in Planetary Mapping, R. Greeley and R.M. Batson, eds., CUP, 169-207. [8] Nozette, S., et al. (1994), Science, 266, 1835-1839. [9] Weller, L., et al. (2006), LPS XXXVII, Abstract #2143. [10] Cook, A. C. et al. (2002), AGU Fall Meeting, Abstract #P22D-09. [11] Davies, M. E. and Colvin, T. R. (2000), JGR, 105, E8, 20,277-20,280.

Synthesis of Al₂Ca Dispersoids by Powder Metallurgy Using a Mg-Al Alloy and CaO Particles.

PubMed

Fujita, Junji; Umeda, Junko; Kondoh, Katsuyoshi

2017-06-28

The elemental mixture of Mg-6 wt %Al-1 wt %Zn-0.3 wt %Mn (AZ61B) alloy powder and CaO particles was consolidated by an equal-channel angular bulk mechanical alloying (ECABMA) process to form a composite precursor. Subsequently, the precursor was subjected to a heat treatment to synthesize fine Al₂Ca particles via a solid-state reaction between the Mg-Al matrix and CaO additives. Scanning electron microscopy-energy-dispersive spectroscopy (SEM-EDS) and electron probe micro-analysis on the precursor indicated that 4.7-at % Al atoms formed a supersaturated solid solution in the α-Mg matrix. Transmission electron microscopy-EDS and X-ray diffraction analyses on the AZ61B composite precursor with 10-vol % CaO particles obtained by heat treatment confirmed that CaO additives were thermally decomposed in the Mg-Al alloy, and the solid-soluted Ca atoms diffused along the α-Mg grain boundaries. Al atoms also diffused to the grain boundaries because of attraction to the Ca atoms resulting from a strong reactivity between Al and Ca. As a result, needle-like (Mg,Al)₂Ca intermetallics were formed as intermediate precipitates in the initial reaction stage during the heat treatment. Finally, the precipitates were transformed into spherical Al₂Ca particles by the substitution of Al atoms for Mg atoms in (Mg,Al)₂Ca after a long heat treatment.

Radial diffusion with outer boundary determined by geosynchronous measurements: Storm and post-storm intervals

NASA Astrophysics Data System (ADS)

Chu, F.; Haines, P.; Hudson, M.; Kress, B.; Freidel, R.; Kanekal, S.

2007-12-01

Work is underway by several groups to quantify diffusive radial transport of radiation belt electrons, including a model for pitch angle scattering losses to the atmosphere. The radial diffusion model conserves the first and second adiabatic invariants and breaks the third invariant. We have developed a radial diffusion code which uses the Crank Nicholson method with a variable outer boundary condition. For the radial diffusion coefficient, DLL, we have several choices, including the Brautigam and Albert (JGR, 2000) diffusion coefficient parameterized by Kp, which provides an ad hoc measure of the power level at ULF wave frequencies in the range of electron drift (mHz), breaking the third invariant. Other diffusion coefficient models are Kp-independent, fixed in time but explicitly dependent on the first invariant, or energy at a fixed L, such as calculated by Elkington et al. (JGR, 2003) and Perry et al. (JGR, 2006) based on ULF wave model fields. We analyzed three periods of electron flux and phase space density (PSD) enhancements inside of geosynchronous orbit: March 31 - May 31, 1991, and July 2004 and Nov 2004 storm intervals. The radial diffusion calculation is initialized with a computed phase space density profile for the 1991 interval using differential flux values from the CRRES High Energy Electron Fluxmeter instrument, covering 0.65 - 7.5 MeV. To calculate the initial phase space density, we convert Roederer L* to McIlwain's L- parameter using the ONERA-DESP program. A time averaged model developed by Vampola1 from the entire 14 month CRRES data set is applied to the July 2004 and Nov 2004 storms. The online CRESS data for specific orbits and the Vampola-model flux are both expressed in McIlwain L-shell, while conversion to L* conserves phase space density in a distorted non-dipolar magnetic field model. A Tsyganenko (T04) magnetic field model is used for conversion between L* and L. The outer boundary PSD is updated using LANL GEO satellite fluxes

Magnetic Sorting of the Regolith on the Moon: Lunar Swirls

NASA Astrophysics Data System (ADS)

Pieters, C. M.; Garrick-Bethell, I.; Hemingway, D.

2014-12-01

(their magnitude, size, orientation, and depth) remains to be resolved. Refs: 1. Blewett, DT et al. 2011, JGR , 116. 2. Wieser, M et al. 2010, GRL 37. 3. Taylor, LA et al., 2001 & 2010 JGR; Pieters, CM et al., 2000, MaPS. 4. Pieters et al., 2014, LPSC45 1408. 5. Hemingway, D., and I. Garrick-Bethell 2012, JGR, 117. 6. Adams, JB and TB McCord 1973, 4th LPSC. Cosmochim. Acta, 1, 163-177.

Modelling Thermal Emission to Constrain Io's Largest Eruptions

NASA Astrophysics Data System (ADS)

Davies, A. G.; De Pater, I.; de Kleer, K.; Head, J. W., III; Wilson, L.

2016-12-01

] Davies, A. (2007) Volcanism on Io, Cambridge. [3] Davies, A. et al. (2010) JGR, 194, 75.99. [4] Davies, A. (1996) Icarus, 124, 45-61. [5] Keszthelyi, L. et al., (2001) JGR, 106, 33025-33052. [6] Williams, D. et al. (2001) JGR, 106, 33105-33120. [7] dePater, I. et al. (2014) Icarus, 242, 365-378. [8] de Kleer, K. et al. (2014) Icarus, 242, 352-364.

On fracture energy of flash heating

NASA Astrophysics Data System (ADS)

Garagash, D.

2011-12-01

Statically-strong faults that operate at low stress level require existence of strong dynamic weakening processes, of which the flash heating (FH) on asperities and the thermal pressurization (TP) are likely the most universal ones [e.g. Rice, JGR 2006]. The classical rate- and state-dependence of the fault friction inferred from laboratory observations at below-seismic rates can account for only a small fraction (<10% of the Byerlee's friction fp ˜0.7-0.8) of the required fault weakening, and its effect is likely to be dwarfed by the FH and TP processes during a mature rupture. This assertion is supported by dynamic rupture calculations [Noda et al., JGR 2009], which also show that the FH weakening is localized in a very small region near the rupture tip, as the most of the corresponding friction drop from the static fp to the dynamic fw ˜0.1-0.2 value takes place over small slip distance δ FH ˜0.01-1 mm associated with the evolution of the state of the frictional contact. The low-end value of the δ FH-range (0.01 mm) is comparable to the asperity size. The high-end value (1 mm) was reported by [Kohli et al., JGR 2011] based on the velocity-stepping experiments at coseismic slip rates in serpentinite, and was interpreted by these authors as the slip distance over which the severe localization of the sheared gouge layer takes place, as required for the onset of the FH at asperities contacts. The FH part of the fracture energy can, therefore, be estimated as GFH} ˜(f{p}-f_{w})/line{σ }_{0}δ {FH ˜10-3-0.1 {MJ}/{m}2 (using the effective, fault-normal stress /line{σ }0 ˜100 MPa) [see also Beeler et al., JGR 2008], which is a fraction of the seismologically-inferred values of the fracture energy of moderate to large earthquakes, G ˜0.1-10 {MJ}/{m}2. Using the FH constitutive formulation of Noda et al. [2009], based on Rice [2006], we develop the universal (boundary layer type) solution near the tip of the propagating rupture, which embodies the FH weakening

Vacuum brazing of electroless Ni-P alloy-coated SiCp/Al composites using aluminum-based filler metal foil

NASA Astrophysics Data System (ADS)

Wang, Peng; Xu, Dongxia; Niu, Jitai

2016-12-01

Using rapidly cooled (Al-10Si-20Cu-0.05Ce)-1Ti (wt%) foil as filler metal, the research obtained high-performance joints of electroless Ni-P alloy-coated aluminum matrix composites with high SiC particle content (60 vol%, SiCp/Al-MMCs). The effect of brazing process on joint properties and the formation of Al-Ni and Al-Cu-Ni intermetallic compounds were investigated, respectively. Due to the presence of Ni-P alloy coating, the wettability of liquid filler metal on the composites was improved obviously and its contact angle was only 21°. The formation of Al3Ni2 and Al3(CuNi)2 intermetallic compounds indicated that well metallurgical bonding occurred along the 6063Al matrix alloy/Ni-P alloy layer/filler metal foil interfaces by mutual diffusion and dissolution. And the joint shear strength increased with increasing the brazing temperature from 838 to 843 K or prolonging the soaking time from 15 to 35 min, while it decreased a lot because of corrosion occurring in the 6063Al matrix at high brazing temperature of 848 K. Sound joints with maximum shear strength of 112.5 MPa were obtained at 843 K for soaking time of 35 min. In this research, the beneficial effect of surface metallization by Ni-P alloy deposits on improving wettability on SiCp/Al-MMCs was demonstrated, and capable welding parameters were broadened as well.

Continental growth by successive accretion of oceanic lithosphere: Evidence from tilted seismic anisotropy

NASA Astrophysics Data System (ADS)

Babuska, V.; Plomerova, J.; Karato, S. I.

2012-04-01

Although many studies indicate that subduction-related accretion, subduction-driven magmatism and tectonic stacking are major crustal-growth mechanisms, how the mantle lithosphere forms remains enigmatic. Cook (AGU Geod. Series 1986) published a model of continental 'shingling' based on seismic reflection data indicating dipping structures in the deep crust of accreted terranes. Helmstaedt and Gurney (J. Geoch. Explor. 1995) and Hart et al. (Geology 1997) suggest that the Archean continental lithosphere consists of alternating layers of basalt and peridotite derived from subducted and obducted Archean oceanic lithosphere. Peridotite xenoliths from the Mojavian mantle lithosphere (Luffi et al., JGR 2009), as well as xenoliths of eclogites underlying the Sierra Nevada batholith in California (Horodynskij et al., EPSL 2007), are representative for oceanic slab fragments successively attached to the continent. Recent seismological findings also seem to support a model of continental lithosphere built from systems of paleosubductions of plates of ancient oceanic lithosphere (Babuska and Plomerova, AGU Geoph. Monograph 1989), or by stacking of the plates (Helmstaedt and Schulze, Geol. Soc. Aust. Spec. Publ. 1989). Seismic anisotropy in the oceanic mantle lithosphere, explained mainly by the olivine A- (or D-) type fabric (Karato et al., Annu. Rev. Earth Planet. Sci. 2008), was discovered almost a half century ago (Hess, Nature 1964). Though it is difficult to determine seismic anisotropy within an active subducting slab (e.g., Healy et al., EPSL 2009; Eberhart-Phillips and Reyners, JGR 2009), field observations and laboratory experiments indicate the oceanic olivine fabric might be preserved there to a depth of at least 200-300 km. Dipping anisotropic fabrics in domains of the European mantle lithosphere were interpreted as systems of 'frozen' paleosubductions (Babuska and Plomerova, PEPI 2006), and the lithosphere base as a boundary between a fossil anisotropy in the

Comparisons of Simulated and Observed Sub-Auroral Polarization Stream (SAPS) during the 17 March 2013 Storm

NASA Astrophysics Data System (ADS)

Chen, M.; Lemon, C.; Sazykin, S. Y.; Wolf, R.; Anderson, P. C.

2016-12-01

Sub-Auroral Polarization Streams (SAPS), characterized by large subauroral E x B velocities that span from dusk to the early morning sector for high magnetic activity, result from strong magnetosphere-ionosphere coupling. We investigate how electron and ion precipitation and the ionospheric conductance affect the simulated development of the SAPS electric field for the 17 March 2013 storm. Our approach is to use the magnetically and electrically self-consistent Rice Convection Model - Equilibrium (RCM-E) of the inner magnetosphere to simulate the SAPS. We use parameterized rates of whistler-generated electron pitch-angle scattering from Orlova and Shprits [JGR, 2014] that depend on equatorial radial distance, magnetic activity (Kp), and magnetic local time (MLT) outside the simulated plasmasphere. Inside the plasmasphere, parameterized scattering rates due to hiss [Orlova et al., GRL, 2014] are used. Ions are scattered at a fraction of strong pitch-angle scattering where the fraction is scaled by epsilon, the ratio of the gyroradius to the field-line radius of curvature, when epsilon is greater than 0.1. The electron and proton contributions to the auroral conductance in the RCM-E are calculated using the empirical Robinson et al. [JGR, 1987] and Galand and Richmond [JGR, 2001] equations, respectively. The "background" ionospheric conductance is based on parameters from the International Reference Ionosphere [Bilitza and Reinisch, JASR, 2008] but modified to include the effect of specified ionospheric troughs. Parameterized simulations will aid in understanding the underlying physical process. We compare simulated precipitating particle energy flux and E x B velocities with DMSP observations where SAPS are observed during the 17 March 2013 storm. Analysis of discerpancies between the simulation results and data will aid us in assessing needed improvements in the model.

Determination of sulfuric acid concentration for anti-cavitation characteristics of Al alloy by two step anodizing process to forming nano porous.

PubMed

Lee, Seung-Jun; Kim, Seong-Kweon; Jeong, Jae-Yong; Kim, Seong-Jong

2014-12-01

Al alloy is a highly active metal but forms a protective oxide film having high corrosion resistance in atmosphere environment. However, the oxide film is not suitable for practical use, since the thickness of the film is not uniform and it is severly altered with formation conditions. This study focused on developing an aluminum anodizing layer having hardness, corrosion resistance and abrasion resistance equivalent to a commercial grade protective layer. Aluminum anodizing layer was produced by two-step aluminum anodizing oxide (AAO) process with different sulfuric acid concentrations, and the cavitation characteristics of the anodized coating layer was investigated. In hardness measurement, the anodized coating layer produced with 15 vol.% of sulfuric acid condition had the highest value of hardness but exhibited poor cavitation resistance due to being more brittle than those with other conditions. The 10 vol.% of sulfuric acid condition was thus considered to be the optimum condition as it had the lowest weight loss and damage depth.

MSL/SAM Measurements of Non Condensable Volatiles, Comparison with Viking Lander, and Implications for Seasonal Cycle

NASA Astrophysics Data System (ADS)

Atreya, Sushil; Squyres, Steve; Mahaffy, Paul; Leshin, Laurie; Franz, Heather; Trainer, Melissa; Wong, Michael; McKay, Christopher; Navarro-Gonzalez, Rafael; ScienceTeam, MarsScienceLab

2013-04-01

increase of a factor of 2-3 over south polar region in the winter. No data exist on the seasonal behavior of N2. For the first time, SAM will monitor the seasonal behavior of N2 over the two-year prime mission of Curiosity, together with other NCV's, Ar and CO, which will reveal whether they track one another, as expected, and whether the present SAM ratio of N2/Ar =1 holds up over the seasons at roughly one-half the value obtained by Viking. These data will in turn provide crucial constraints to climate evolution and general circulation models of Mars. (www.umich.edu/~atreya). References: [1] Mahaffy P.R. et al., EGU 2013. [2] Owen T. et al., JGR 82, 4635-4639, 1977. [3] Aoudjehane, H.C. et al., Science 338, 785-788, 2012. [4] Sprague A.L. et al., JGR 117, E04005, 2012. [5] Economou T.E. and Pierrehumbert R.T., Abstract 2179.pdf, LPI Conference, 2010. [6] Wong A.S., Atreya S.K., Encrenaz T., JGR.108 (E4), 5026, doi:10.1029/2002JE002003. [7] Encrenaz T. et al., A&A 459, 265-270, 2006. [8] Smith M.D. et al., JGR.114, E00D03, doi:10.1029/2008JE003288, 2009.

JPRS Report, Science & Technology China

DTIC Science & Technology

1989-02-23

Protoplast Culture of Rice (Oryza sativa L.), Plant Regeneration From Protoplast-Derived Calli 40091011a Beijing YICHUAN XUEBAO [ACTA GENETICA ...YICHUAN XUEBAO [ACTA GENETICA SINICA] in Chinese Vol 15 No 5, Oct 88 pp 329-334 [English abstract of article by Tao Zirong [7118 5261 2837], et al...Chang, et al., ACTA GENETICA SINICA, Vol 7 No 3, 1980 pp 283-288. 7. Zhu Zhongchun, et al., ACTA GENETICA SINICA, Vol 8 No 1, 1981 pp 63-65, 8. Mix, G

Cassini Imaging of Io's Visible Aurora

NASA Astrophysics Data System (ADS)

Geissler, P.; McEwen, A.; Porco, C.; Strobel, D.; Saur, J.; Ajello, J.

2003-04-01

Io is the only moon in the solar system known to display visible atmospheric emissions that would be bright enough to be seen with the naked eye by a hypothetical human visitor to the jovian system. Earlier imaging of Io's colorful aurorae [1,2,3], obtained by the Galileo spacecraft while the satellite was in eclipse, left a number of questions unanswered. The temporal behavior of the emissions was difficult to discern from the occasional glimpses afforded by Galileo. The identities of the emitting species were poorly known. Unlike the far-ultraviolet emissions from Io's atmosphere that closely tracked the tangent points of Jupiter's magnetic field lines [5,6], the brightest visible glows were clearly linked to actively erupting volcanic plumes. Cassini, with its fully functioning high-gain antenna, near-ultraviolet sensitivity and better spectral resolution, was able to fill many of the gaps in our knowledge of these mysterious phenomena [6]. Cassini monitored Io's appearance over entire eclipses, documenting temporal changes on time scales of minutes. These data help constrain the degree of atmospheric collapse during eclipse and establish the relationship of the emissions to the changing orientation of the jovian magnetic field. Cassini detected glows at previously unknown wavelengths, providing new evidence of molecular SO2 emission and other atmospheric constituents. The spatial distribution of the glows indicates the presence of a giant volcanic plume near Io's north pole at the time of the observations and also reveals stratification of the satellite's tenuous atmosphere. [1] McEwen et al., Icarus 135, 181, 1998. [2] Geissler et al., Science 285, 870, 1999. [3] Geissler et al., JGR 106, 26137, 2001. [4] Roesler et al., Science 283, 353, 1999. [5] Retherford et al., JGR 105, 27157, 2000. [6] Porco et al., Science, in prep. 2003.

Mars surface hydration seen by MEx/OMEGA

NASA Astrophysics Data System (ADS)

Jouglet, D.; Poulet, F.; Bibring, J. P.; Langevin, Y.; Gondet, B.

2007-08-01

permafrost [3]. - Finally seasonal variations are also detected with the decrease of the surface hydration between spring and summer for mid latitudes regions. This phenomenon is associated to an increase of hydration with latitude in spring. This temporal variation is not instrumental or atmospheric and can be explained by the presence of frost in winter which makes water fix on minerals. During spring, when ice has disappeared, the amount of adsorbed water returns to equilibrium with the atmosphere. These variations seem to confirm the important role of regolith on water cycle, which was predicted from numerical simulations (e.g. [18] or [2]). [1] Farmer C. B. et al. (1976), Science, 194, 1339-1341. [2] Titov D. V. (2002), Adv. Space Res,29, 183-191. [3] Feldman W. C. et al. (2004), JGR, 109, E09006. [4] Cooper C. D. and Mustard J. F. (1999), Icarus 142, 557-570. [5] Jouglet D. et al. (2007), JGR, in press. [6] Rivkina E. M. et al. (2000), Appl. Environ. Microb. 66 (8), 3230-3233. [7] Möhlmann D. T. (2004), Icarus, 168, 318-323. [8] Yen A. S. et al. (1998) JGR E5, 103, 11,125-11,133. [9] Langevin Y. et al. (2005), Science, 307, 1581-1584. [10] Jouglet D. et al. (2006), LPS XXXVII, Abstract #1741. [11] Zent A. P. and Quinn R. C. (1997) JGR E4, 102, 9085-9095.[12] Yen A. S. et al. (2005), Nature 436, 49-54 [13] Hurowitz J. A. et al. (2006) JGR, 111, E02S19. [14] Poulet F. et al. (2005) Nature 438, 623-627. [15] Gendrin A. et al. (2005) Science, 307, 1587-1591. [16] Poulet F. et al. (2005), LPSC XXXVI, Abstract #1828. [17] Milliken R. E. et al. (2007), JGR, in press. [18] Böttger H. M. et al. (2005) Icarus 177, 174-189.

Bonding of TRIP-Steel/Al2O3-(3Y)-TZP Composites and (3Y)-TZP Ceramic by a Spark Plasma Sintering (SPS) Apparatus

PubMed Central

Miriyev, Aslan; Grützner, Steffen; Krüger, Lutz; Kalabukhov, Sergey; Frage, Nachum

2016-01-01

A combination of the high damage tolerance of TRIP-steel and the extremely low thermal conductivity of partially stabilized zirconia (PSZ) can provide controlled thermal-mechanical properties to sandwich-shaped composite specimens comprising these materials. Sintering the (TRIP-steel-PSZ)/PSZ sandwich in a single step is very difficult due to differences in the sintering temperature and densification kinetics of the composite and the ceramic powders. In the present study, we successfully applied a two-step approach involving separate SPS consolidation of pure (3Y)-TZP and composites containing 20 vol % TRIP-steel, 40 vol % Al2O3 and 40 vol % (3Y)-TZP ceramic phase, and subsequent diffusion joining of both sintered components in an SPS apparatus. The microstructure and properties of the sintered and bonded specimens were characterized. No defects at the interface between the TZP and the composite after joining in the 1050–1150 °C temperature range were observed. Only limited grain growth occurred during joining, while crystallite size, hardness, shear strength and the fraction of the monoclinic phase in the TZP ceramic virtually did not change. The slight increase of the TZP layer’s fracture toughness with the joining temperature was attributed to the effect of grain size on transformation toughening. PMID:28773680

Energization of Radiation Belt Electrons by High and Low Azimuthal Mode Number Poloidal Mode ULF Waves

NASA Astrophysics Data System (ADS)

Hudson, M. K.; Brito, T.; Elkington, S. R.; Kress, B. T.; Liang, Y.

2011-12-01

and MINIS balloon observations for the January 21, 2005 CME-driven storm. Thus Pc 5 poloidal mode ULF waves cause competing increase and decrease in relativistic electron flux. The relative efficiencies of both coherent and diffusive processes will be examined. 1Zong et al., JGR, doi:10.1029/2009JA014393, 2009. 2Tan et al., JGR, doi:10.1029/2010JA016226, 2011. 3Ozeke and Mann, JGR, doi:10.1029/2007JA012468, 2008. 4Elkington et al., doi:10.1029/2001JA009202, 2003, 2003. 5Perry et al., doi:10.1029/2004JA010760, 2005.

Stratigraphy in the Samarkand Sulci Region of Enceladus

NASA Astrophysics Data System (ADS)

Roatsch, T.; Wagner, R. J.; Schmedemann, N.; Helfenstein, P.; Stephan, K.; Voigt, J.; Jaumann, R.; Giese, B.; Porco, C.

2016-12-01

Saturn's cryovolcanically active moon Enceladus is a primary target for NASA's Cassini Saturn orbiter. In a flyby on Dec. 19, 2015 (orbit 228EN), images with 65 m spatial resolution were taken from the Samarkand Sulci and Anbar Fossae [1] region with the Cassini ISS NAC camera. This study area was geologically mapped, based on the geological context by [2]. Crater counts for age dating were carried out and compared to our previous counts done in a global mosaic at lower resolution [3]. A stereo-derived digital elevation model reveals intense tectonic faulting causing a remarkable height range of up to 1750 meters with respect to the surrounding cratered plains [4]. Relative ages of geologic units can be inferred from mutual crosscutting and/or superposition, but ages from craters counts are comparably uncertain due to low crater frequencies and small areas of measurement. Tectonic features of the study area cut through older densely cratered plains with model ages ranging from 3.9 Gyr to only 500 Ma, depending of impact chronology model [5, and ref's therein] applied to crater frequency measurements. In the units characterized by intense tectonism, larger craters like those found in the cratered plains in parts have survived but smaller much less frequent craters reflect the age of tectonic resurfacing, with model ages ranging from 1.5 Gyr to 15 Myr. Geologic units which show putative small craters (number < 3) at the given resolution have considerably low estimated (maximum) ages on the order of << 10 Myr suggesting intense tectonism has been taking place in the recent past. References: [1] Roatsch, T., et al. (2013), Planet. Space Sci. 77, 118-125. [2] Crow-Willard, E. N., and Pappalardo, R. T. (2015), JGR 120, doi:10.1002/2015JE004818. [3] Jaumann R., et al. (2011), EPSC Abstracts Vol. 6, abstr. No. EPSC-DPS2011-435-1. [4] Giese B., et al. (2016), paper in preparation. [5] Dones, L., et al. (2009), In: Saturn from Cassini-Huygens, Springer Publ., pp. 613-635.

Effect of microstructural features on the laser efficiency of Nd{sup 3+}:Y{sub 3}Al{sub 5}O{sub 12} ceramics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vorona, I O; Yavetskiy, R P; Tolmachev, A V

2015-09-30

The optical properties and microstructure of transparent Nd{sup 3+}:Y{sub 3}Al{sub 5}O{sub 12} ceramics synthesised by different reactive sintering routes are studied. It is found that the residual porosity of optical ceramics is directly related to the homogeneity of the microstructure of initial compacts, which can be estimated by the existence of particle agglomerates larger than 1 mm in initial nanopowders. A qualitative correlation is established between the residual porosity, the optical losses and the lasing slope efficiency of Nd{sup 3+}:Y{sub 3}Al{sub 5}O{sub 12} ceramics. The maximum laser efficiency (η = 49%) was observed in the samples with the lowest porositymore » (2.3 × 10{sup -3} vol %). (lasers)« less

Ceres’ Evolution and Potential Habitability

NASA Astrophysics Data System (ADS)

Raymond, Carol Anne; Ammannito, Eleonora; Bland, Michael T.; Castillo-Rogez, Julie; De Sanctis, Maria Cristina; Ermakov, Anton; Fu, Roger; McCord, Thomas; Park, Ryan; Prettyman, Thomas H.; Ruesch, Ottaviano; Russell, Christopher T.; Dawn Team

2017-10-01

Dawn’s observations at Ceres confirm it is a volatile-rich body that has undergone ice-rock differentiation and global alteration [1-4], indicating that, as predicted by pre-Dawn thermochemical models, Ceres harbored an ancient subsurface ocean [5,6]. Density and shape data indicate that at present, Ceres has a crust composed of silicate, salts, clathrates and ≤ 35% water ice, overlying a denser core of hydrated silicates [7,8,9,10], whereas the original ice-dominated outer shell was likely lost to impact-induced sublimation early in Ceres’ history [11]. The interior structure constrains the maximum internal temperature to have been only a few hundred degrees [9]; however, rather than indicating a late formation for Ceres, it may indicate that circulation of fluids within Ceres modulated the temperature [12].The extent and longevity of the ocean are debatable; however, the modern surface of Ceres shows evidence of brine extrusion [e.g., 13], indicating at least pockets of subsurface liquid remain. Carbonates are found to dominate the composition of the brightest deposits on the surface, attesting to transport of crystallized brine material to the surface [14]. These multiple lines of evidence point to a warm aqueous subsurface environment with complex chemistry early in Ceres’ history and processes that exchanged material between the muddy ocean layer and the surface. Such history and the presence of organic material in localized deposits [15, 16] make Ceres an enticing target for future exploration. [1] Russell et al., Science, 2016 [2] Prettyman et al., Science, 2017 [3] De Sanctis et al., 2015 10.1038/nature18290 [4] Ammannito et al., Science, 2016 [5] McCord and Sotin, JGR, 2005 [6] Castillo-Rogez and McCord, Icarus, 2010 [7] Park et al., Nature, 2016 [8] Ermakov et al., JGR, 2017 [9] Fu et al., EPSL, 2017 [10] Bland et al., Nat. GeoSci., 2016 [11] Castillo-Rogez et al., LPSC, 2016 [12] Travis et al., Icarus, subm. [13] Ruesch et al., Science, 2106 [14

Widespread Surface Weathering on Early Mars: possible implication on the Past Climate

NASA Astrophysics Data System (ADS)

Loizeau, Damien; Carter, John; Mangold, Nicolas; Poulet, François; Rossi, Angelo P.; Allemand, Pascal; Lozac'h, Loïc; Quantin, Cathy; Bibring, Jean-Pierre

2015-04-01

by the more intense erosion of that time. Also, it is difficult to date older terrains by crater counting on small surfaces. These observations make a strong constrain concerning the past habitability of Mars: liquid water has been widely available at the surface of the planet, in contact with different rocks, until the early Hesperian time. Acknowledgment: Some of the authors have received funding from the ERC (FP7/2007-2013)/ERC Grant agreement n° 280168. References: [1] Ehlmann B., et al. Nature, 479, 53-60 (2011). [2] Carter J., et al. JGR, 118, 831-858 (2013) [3] Gaudin A., et al. Icarus, 216(1), 257-268 (2011). [4] Loizeau D., et al. Icarus, 205, 396-418 (2010). [5] Noe Dobrea E., et al. JGR, 115, E00D19 (2010). [6] Le Deit L., et al. JGR, 117, E00J05 (2012). [7] Velde B., et al. Ed. Springer, Berlin, (1995). [8] Wilson M. Clay Minerals, 39, 233-266 (2004). [9] Carter J., et al. Icarus, 248, 373-382.

Photocopy from Evan Leigh's Modern Cotton Spinning (Vol 1), Manchester, ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Photocopy from Evan Leigh's Modern Cotton Spinning (Vol 1), Manchester, 1873 (PL XX); illustration used by eminent British textile engineer to exemplify the ultimate development in American cotton mill technology. - Harmony Manufacturing Company, Mill Number 3, 100 North Mohawk Street, Cohoes, Albany County, NY

MARIUS HILLS REGION, MOON: Stratigraphy of low shields and mare basalts

NASA Astrophysics Data System (ADS)

Gebhart, Jennifer; Hiesinger, Harry; van der Bogert, Carolyn; Hendrik Pasckert, Jan; Weinauer, Julia; Lawrence, Samuel; Stopar, Julie; Robinson, Mark

2016-04-01

dated basalts. We find that in several cases the low shields are younger than their adjacent mare basalts. However, the stratigraphic relationships might be more complicated because [2,5] observed that basalts embay the low shields. Thus, further studies are required to unambiguously constrain the stratigraphic relationships and to characterize possible effects of small count areas and topography on the determination of AMAs with CSFD measurements. Provided the AMAs were not affected by the relatively small size of the count areas and topographic slopes, these results imply that the volcanic activity in the Marius Hills region lasted > 1 Ga longer than previously thought [e.g., 4]. [1] McCauley (1967b) Mantles of the Earth an terrestrial planets, 431-460; [2] Lawrence et al. (2013) JGR 118; [3] Wilhelms (1987) USGS Spec. Pub. 1348; [4] Heather et al. (2003) JGR 108; [5] Weitz and Head (1999) JGR 104; [6] Hiesinger et al. (2003) JGR 108; [7] Kneissl et al. (2012) PSS 59; [8] Michael and Neukum, (2010) EPSL 294; [9] Neukum et al. (2001) SSR 96.

A deformation-processed Al-matrix/Ca-nanofilamentary composite with low density, high strength, and high conductivity

DOE PAGES

Tian, Liang

2017-03-06

Light, strong materials with high conductivity are desired for many applications such as power transmission conductors, fly-by-wire systems, and downhole power feeds. However, it is difficult to obtain both high strength and high conductivity simultaneously in a material. In this study, an Al/Ca (20 vol%) nanofilamentary metal-metal composite was produced by powder metallurgy and severe plastic deformation. Fine Ca metal powders (~200 µm) were produced by centrifugal atomization, mixed with pure Al powder, and deformed by warm extrusion, swaging, and wire drawing to a true strain of 12.9. The Ca powder particles became fine Ca nanofilaments that reinforce the compositemore » substantially by interface strengthening. The conductivity of the composite is slightly lower than the rule-of-mixtures prediction due to minor quantities of impurity inclusions. As a result, the elevated temperature performance of this composite was also evaluated by differential scanning calorimetry and resistivity measurements.« less

A deformation-processed Al-matrix/Ca-nanofilamentary composite with low density, high strength, and high conductivity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tian, Liang

Light, strong materials with high conductivity are desired for many applications such as power transmission conductors, fly-by-wire systems, and downhole power feeds. However, it is difficult to obtain both high strength and high conductivity simultaneously in a material. In this study, an Al/Ca (20 vol%) nanofilamentary metal-metal composite was produced by powder metallurgy and severe plastic deformation. Fine Ca metal powders (~200 µm) were produced by centrifugal atomization, mixed with pure Al powder, and deformed by warm extrusion, swaging, and wire drawing to a true strain of 12.9. The Ca powder particles became fine Ca nanofilaments that reinforce the compositemore » substantially by interface strengthening. The conductivity of the composite is slightly lower than the rule-of-mixtures prediction due to minor quantities of impurity inclusions. As a result, the elevated temperature performance of this composite was also evaluated by differential scanning calorimetry and resistivity measurements.« less

Spectroscopic Detection of Minerals in Martian Meteorites using Reflectance and Emittance Spectroscopy and Applications to Surface Mineralogy on Mars

NASA Astrophysics Data System (ADS)

Bishop, J. L.; Hamilton, V. E.

2001-12-01

al., MAPS 33, 693, 1998b. Christensen P., et al., JGR 105, 9609, 2000. Hamilton V. et al., JGR 102, 25593, 1997. Hamilton V. et al., LPSC XXXII, #2184, 2001. Hoefen T. et al., Bull. Am. Astron. Soc. 32, 1118, 2000.

Effect of Pre-Oxidation Treatment of Nano-SiC Particulates on Microstructure and Mechanical Properties of SiC/Mg-8Al-1Sn Composites Fabricated by Powder Metallurgy Combined with Hot Extrusion

PubMed Central

Li, Chuan-Peng; Wang, Zhi-Guo; Zha, Min; Wang, Cheng; Yu, Hong-Chen; Wang, Hui-Yuan; Jiang, Qi-Chuan

2016-01-01

Nano-SiC particulates (n-SiCp) reinforced Mg-8Al-1Sn (AT81) composites with different pre-oxidation parameters were fabricated by powder metallurgy (P/M) process combined with hot extrusion. The effects of pre-oxidization treatment of n-SiCp on the microstructure and tensile properties of 0.5 vol % n-SiCp/AT81 composites were investigated accordingly. The distribution of n-SiCp with different pre-oxidation parameters was homogeneous in the composites. Moreover, it was found that a thin MgAl2O4 layer formed at the interface when the n-SiCp were pre-oxidized at 1073 K for 2 h, while the MgAl2O4 layer became much thicker with pre-oxidization temperature increasing to 1273 K for 2 h. After an appropriate pre-oxidization treatment of n-SiCp at 1073 K for 2 h, the as-extruded 0.5 vol % n-SiCp/AT81 composites exhibited an enhanced strength. It was found that the yield strength (YS) and ultimate tensile strength (UTS) increased from 168 MPa and 311 MPa to 255 MPa and 393 MPa compared with the as-extruded AT81 alloy, reflecting 51.8% and 26.4% increments, respectively. The improvement of mechanical properties should be mainly attributed to the grain refinement and homogeneous distribution of n-SiCp in the composites. Moreover, a well-bonded interface and the formation of an appropriate amount of interfacial product (MgAl2O4) benefited the material’s mechanical properties. PMID:28774083

Constraints on Lunar Heat Flow Rates from Diviner Lunar Radiometer Polar Observations

NASA Astrophysics Data System (ADS)

Paige, D. A.; Siegler, M. A.; Vasavada, A. R.

2010-12-01

The heat flow rate from the lunar interior is a fundamental property of the moon that is related to its composition, interior structure and history. Lunar heat flow rates have been measured at the Apollo 15 and 17 landing sites [1], but it is widely believed that the measured values of 0.021 Wm-2 and 0.016 Wm-2 respectively may not be representative of the moon as a whole due to the presence of enhanced radiogenic elements at these landing sites [2]. The Diviner Lunar Radiometer Experiment on the Lunar Reconnaissance Orbiter [3] has acquired an extensive set of thermal emission from the lunar surface at infrared wavelengths, including the first radiometric measurements of surface temperatures at the lunar poles [4]. Due to its low obliquity and rough topography, the moon has extensive cryogenic regions at high latitudes that never receive direct sunlight. The temperatures of the coldest of these regions can be used to place upper limits on the heat flow rate from the lunar interior because if other heat sources are neglected, then surface thermal emission is balanced by heat flow from warmer lunar interior [5]. Diviner has mapped the north and south polar regions over a complete annual cycle and we have identified a 4 km2 area within Hermite Crater in the north polar region that has a winter season nighttime Channel 9 (100-400 micron) brightness temperatures in of less than 20K. These low temperatures would imply a lunar heat flow rate of less than 0.010 Wm-2, which may be consistent with expectations for regions of the moon that do not contain enhanced concentrations of radiogenic elements [2,6], as is the case for the north polar region of the moon [7]. [1] Langseth, M. G. et al, Proc. Lunar Sci. Conf, 7th, 3143-3171, 1976. [2] Warren, P. H. and K. K. L. Rasmussen, JGR 92, 3453-3465, 1987. [3] Paige, D. A. et al, Space Sci. Rev, 150:125-160, 2010. [4] Paige, D. A. et al., Science, in press, 2010. [5] Watson, K. JGR 72, 3301-3302, 1967. [6] Wieczorek, M. A. and R

Simulating spontaneous aseismic and seismic slip events on evolving faults

NASA Astrophysics Data System (ADS)

Herrendörfer, Robert; van Dinther, Ylona; Pranger, Casper; Gerya, Taras

2017-04-01

Plate motion along tectonic boundaries is accommodated by different slip modes: steady creep, seismic slip and slow slip transients. Due to mainly indirect observations and difficulties to scale results from laboratory experiments to nature, it remains enigmatic which fault conditions favour certain slip modes. Therefore, we are developing a numerical modelling approach that is capable of simulating different slip modes together with the long-term fault evolution in a large-scale tectonic setting. We extend the 2D, continuum mechanics-based, visco-elasto-plastic thermo-mechanical model that was designed to simulate slip transients in large-scale geodynamic simulations (van Dinther et al., JGR, 2013). We improve the numerical approach to accurately treat the non-linear problem of plasticity (see also EGU 2017 abstract by Pranger et al.). To resolve a wide slip rate spectrum on evolving faults, we develop an invariant reformulation of the conventional rate-and-state dependent friction (RSF) and adapt the time step (Lapusta et al., JGR, 2000). A crucial part of this development is a conceptual ductile fault zone model that relates slip rates along discrete planes to the effective macroscopic plastic strain rates in the continuum. We test our implementation first in a simple 2D setup with a single fault zone that has a predefined initial thickness. Results show that deformation localizes in case of steady creep and for very slow slip transients to a bell-shaped strain rate profile across the fault zone, which suggests that a length scale across the fault zone may exist. This continuum length scale would overcome the common mesh-dependency in plasticity simulations and question the conventional treatment of aseismic slip on infinitely thin fault zones. We test the introduction of a diffusion term (similar to the damage description in Lyakhovsky et al., JMPS, 2011) into the state evolution equation and its effect on (de-)localization during faster slip events. We compare

Investigations of charged particle motion on the surfaces of dusty, airless solar system bodies (Invited)

NASA Astrophysics Data System (ADS)

Dove, A.; Colwell, J. E.

2013-12-01

Dynamic charging conditions exist on the dusty surfaces of planetary bodies such as the Moon, asteroids, and the moons of Mars. On these so-called 'airless bodies', the motions of dust particles above the surface become complex due to grain-grain and grain-plasma interactions. For example, tribocharging and other charge transfer processes can occur due to relative dust grain movements, and charged dust grains immersed in plasma interact with local electromagnetic forces. This is thought to lead to effects such as the lunar 'horizon glow,' (Rennilson and Criswell, 1974, The Moon, 10) and potential dusty 'fountains' above the lunar surface (Stubbs et al., 2006, Adv. Sp. Res., 37). Regolith grains can be mobilized by impacts or other mechanical disturbances, or simply by the Coulomb force acting on grains. Previous work has increased our theoretical understanding of the behavior of charged particles in these low-gravity environments (i.e. Poppe and Horanyi, 2010, JGR, A115; Colwell et al., 2007, Rev. Geophys., 45 (and references therein)). Experimental work has also analyzed grain surface charging due to plasma or tribocharging (Sickafoose et al., 2001, JGR, 106) and the motion of grains on surfaces in the presence of an electric field (Wang et al., 2009, JGR, 114). Occasionally, there is disagreement between theoretical predictions and observations. We present the results of new laboratory experiments aimed at understanding particle charging and the dynamics of charged particles on the surfaces of airless bodies. In the initial experiments, we analyze the motion of particles in the presence of an electric field in vacuum, either in a bell-jar or in a 0.75-second microgravity drop tower experiment box. Prior to motion, particles may be charged due to triboelectric effects, plasma interactions, or a combination of the two. Motion is induced by shaking or by low-velocity impacts in order to simulate the natural motion of slow-moving objects on regolith surfaces, or

Frictional weakening of Landslides in the Solar System

NASA Astrophysics Data System (ADS)

Lucas, Antoine; Mangeney, Anne; Ampuero, Jean-Paul

2014-05-01

] Lucas, Nat. Geosc. News & Views, 2012. [3] Lucas & Mangeney, GRL, 2007. [4] Pudasaini & Hutter, Springer, 2007. [5] Campbell et al., JGR, 1995. [6] Smart et al., AGU Fall Meeting, 2010. [7] Lucas et al., JGR, 2011. [8] Rice, JGR, 2006. N.B. This work is subject to press embargo.

Shallow repeating slow-slip-events along the convergent block boundary in northern Hokkaido, Japan

NASA Astrophysics Data System (ADS)

Ikeda, S.; Heki, K.; Kimura, T.

2015-12-01

The Japanese Islands are divided into several crustal blocks [e.g. Loveless and Meade, 2010 JGR]. In the Northern Hokkaido, the boundary between the Amurian and the North American Plates run north-south between 44.0N and 45.4N. The east-west block convergence is considered to be as fast as ~1 cm/year there, but few large earthquakes are known to have occurred along this boundary. Recently, a slow slip event (SSE) is reported to have occurred in a segment at ~45.0N over a 4 months period from 2012 summer to the early 2013 [Ohzono et al., 2014 GJI]. The maximum surface movements was about 15 mm, and the moment magnitude of the SSE would not exceed 6.0 (fault slip is estimated as 10 cm). This suggests that plate convergence takes place as episodic SSEs in this block boundary. In this research, we looked for signatures of repeating SSEs along this block boundary using continuous GNSS data of the dense array GEONET in Japan. In order to detect faint signatures of SSEs in the coordinate time series, we adopted the method using AIC (Akaike's Information Criterion) similar to Nishimura et al. [2013 JGR] and Nishimura [2014 PEPS]. As a result, we were able to find numbers of SSE signals in various segments along the boundary. The detected SSEs are all fairly small, and surface movements did not exceed a few millimeters (except the 2012-2013 SSE reported in Ohzono et al. [2014]). We also searched earthquakes that may have triggered these SSEs. Although the 2012 SSE seems to have been triggered by a deep earthquake beneath Sakhalin on Aug. 14, 2012, no clear triggering earthquakes were identified for other SSEs. SSEs in subduction zones are known to recur fairly regularly, e.g. biannually repeating SSE in the SW part of the Ryukyu Arc [Heki and Kataoka, 2008 JGR]. However, shallow SSEs along the block boundary in the northern Hokkaido did not show such regular occurrences. We plan to confirm these SSE occurrences by comparing GNSS data with the Hi-Net tiltmeter records.

High-speed and supersonic upward plasma drifts: multi-instrumental study

NASA Astrophysics Data System (ADS)

Astafyeva, E.; Zakharenkova, I.; Hairston, M. R.; Huba, J.; Coley, W. R.

2017-12-01

Since the pioneering observations by Aggson et al. (1992, JGR, doi: 10.1002/92JA00644), there have been several reports of the occurrence of high-speed (Vz>800 m/s) and supersonic plasma flows in the post-sunset (e.g., Hysell et al., 1994, JGR, doi: 10.1029/94JA00476; Hanson et al., 1997, JGR, doi: 10.1029/96JA03376) and the pre-dawn sector (Astafyeva and Zakharenkova, 2015, GRL, doi:10.1002/2015GL066369). However, despite this observational evidence, these events remain rare and are not well understood. The main issue is to determine the background conditions leading to the occurrence of these high-speed plasma drifts. In this work, we perform a multi-instrumental study of high-speed and supersonic upward plasma drift events/structures. For this purpose, we analyze data from several ground-based and space-borne instruments, including data from the DMSP, Swarm and C/NOFS (IVM instrument) satellites. In addition to the space-borne instruments, we use data from ground-based GPS-receivers and ionosondes to further investigate the background ionosphere conditions, as well as the effects produced by the plasma bubbles and ionospheric irregularities. Besides the observations, we add the SAMI3/ESF modeling results on plasma bubble simulations and high-speed drifts inside plasma bubbles. TIE-GCM runs (from the CCMC, https://ccmc.gsfc.nasa.gov) are used to define the background atmospheric/ionospheric and electrodynamical conditions leading to the occurrence of the high-speed and supersonic plasma drift events. Our search of events with upward plasma drift exceeding 800 m/s in the data of DMSP for the years 2002-2016 shows that such high-speed events are extremely rare. During this period of time, only 6 events were found, two of them occurred during the recovery phase of a geomagnetic storm, while the other four were detected during geomagnetically quiet conditions. Concerning the generation of such events, our preliminary results show that enhanced electric fields are

Effects of Small Electrostatic Fields on the Ionospheric Density Profile

NASA Astrophysics Data System (ADS)

Salem, M. A.; Liu, N.; Rassoul, H.

2014-12-01

It is well known that short-lived strong electric fields produced by natural lightning activities in tropospheric altitudes can significantly affect the upper atmosphere. This effect is directly evidenced by the production of transient luminous events (TLEs), such as sprites, jets, and elves. It has also been demonstrated that thunderstorms can modify ionospheric densities on a longer time scale, during which TLEs may or may not occur [e.g., Cheng and Cummer, GRL, 32, L08804, 2005; Han and Cummer, JGR, 115, A09323, 2010; Shao et al., Nat. Geosci., doi: 10.1038/NGEO1668, 2012]. In particular, according to Shao et al. [2012], the electron density at 75-80 km altitudes may be reduced by about 2-3 orders of magnitude. In this talk, we study the modification of the ionospheric density profile by small electrostatic fields that may exist in the upper atmosphere during a thunderstorm. A simplified ion chemistry model described by Liu [JGR, 117, A03308, 2012] has been used to conduct this study. The model is based on the one developed by Lehtinen and Inan [GRL, 34, L08804, 2007], which is in turn an improved version of the GPI model discussed in Glukhov et al. [JGR, 97, 16971, 1992]. According to this model, the charged particles can be grouped into five species: electrons, light negative ions, cluster negative ions, light positive ions, and cluster positive ions. In this chemistry model, the three-body electron attachment is the only process whose rate constant depends on the electric field, when it is below about one third of the conventional breakdown threshold field. We have compared various sources of the three-body attachment rate constant. The result shows that the rate constant increases linearly with the reduced electric field in the range of 0 to 0.1 Td, while decreases exponentially from 0.1 Td to about one third of the conventional breakdown threshold field. With this dependence, our modeling results indicate that under the steady-state condition, the nighttime

Experimental and multiphase analysis of nanofluids on the conjugate performance of micro-channel at low Reynolds numbers

NASA Astrophysics Data System (ADS)

Nimmagadda, Rajesh; Venkatasubbaiah, K.

2017-06-01

The present study investigates the laminar forced convection flow of single walled carbon nanotube (SWCNT), gold (Au), aluminum oxide (Al2O3), silver (Ag) and hybrid (Al2O3 + Ag) nanofluids (HyNF) in a wide rectangular micro-channel at low Reynolds numbers. The heat transfer characteristics of de-ionized (DI) water and SWCNT nanofluid with different nanoparticle volume concentrations have been experimental studied. Furthermore, numerical study has also been carried out to investigate the flow and heat transfer characteristics of DI water, SWCNT, Au, Al2O3, Ag and HyNF at different Reynolds numbers with different nanoparticle volume concentrations and particle diameters. The numerical study consider the effects of both inertial and viscous forces by solving the full Navier-Stokes equations at low Reynolds numbers. A two dimensional conjugate heat transfer multiphase mixture model has been developed and used for numerical study. A significant enhancement in the average Nusselt number is observed both experimentally and numerically for nanofluids. The study presents four optimized combinations of nanofluids (1 vol% SWCNT and 1 vol% Au with d_p = 50 nm), (2 vol% SWCNT and 3 vol% Au with d_p = 70 nm), (3 vol% Al2O3 and 2 vol% Au with d_p = 70 nm) as well as (3 vol% HyNF (2.4% Al2O3 + 0.6% Ag) and 3 vol% Au with d_p = 50 nm) that provides a better switching option in choosing efficient working fluid with minimum cost based on cooling requirement. The conduction phenomenon of the solid region at bottom of the micro-channel is considered in the present investigation. This phenomenon shows that the interface temperature between solid and fluid region increases along the length of the channel. The present results has been validated with the experimental and numerical results available in the literature.

'tomo_display' and 'vol_tools': IDL VM Packages for Tomography Data Reconstruction, Processing, and Visualization

NASA Astrophysics Data System (ADS)

Rivers, M. L.; Gualda, G. A.

2009-05-01

One of the challenges in tomography is the availability of suitable software for image processing and analysis in 3D. We present here 'tomo_display' and 'vol_tools', two packages created in IDL that enable reconstruction, processing, and visualization of tomographic data. They complement in many ways the capabilities offered by Blob3D (Ketcham 2005 - Geosphere, 1: 32-41, DOI: 10.1130/GES00001.1) and, in combination, allow users without programming knowledge to perform all steps necessary to obtain qualitative and quantitative information using tomographic data. The package 'tomo_display' was created and is maintained by Mark Rivers. It allows the user to: (1) preprocess and reconstruct parallel beam tomographic data, including removal of anomalous pixels, ring artifact reduction, and automated determination of the rotation center, (2) visualization of both raw and reconstructed data, either as individual frames, or as a series of sequential frames. The package 'vol_tools' consists of a series of small programs created and maintained by Guilherme Gualda to perform specific tasks not included in other packages. Existing modules include simple tools for cropping volumes, generating histograms of intensity, sample volume measurement (useful for porous samples like pumice), and computation of volume differences (for differential absorption tomography). The module 'vol_animate' can be used to generate 3D animations using rendered isosurfaces around objects. Both packages use the same NetCDF format '.volume' files created using code written by Mark Rivers. Currently, only 16-bit integer volumes are created and read by the packages, but floating point and 8-bit data can easily be stored in the NetCDF format as well. A simple GUI to convert sequences of tiffs into '.volume' files is available within 'vol_tools'. Both 'tomo_display' and 'vol_tools' include options to (1) generate onscreen output that allows for dynamic visualization in 3D, (2) save sequences of tiffs to disk

The Influence of Al2O3 Powder Morphology on the Properties of Cu-Al2O3 Composites Designed for Functionally Graded Materials (FGM)

NASA Astrophysics Data System (ADS)

Strojny-Nędza, Agata; Pietrzak, Katarzyna; Węglewski, Witold

2016-08-01

In order to meet the requirements of an increased efficiency applying to modern devices and in more general terms science and technology, it is necessary to develop new materials. Combining various types of materials (such as metals and ceramics) and developing composite materials seem to be suitable solutions. One of the most interesting materials includes Cu-Al2O3 composite and gradient materials (FGMs). Due to their potential properties, copper-alumina composites could be used in aerospace industry as rocket thrusters and components in aircraft engines. The main challenge posed by copper matrix composites reinforced by aluminum oxide particles is obtaining the uniform structure with no residual porosity (existing within the area of the ceramic phase). In the present paper, Cu-Al2O3 composites (also in a gradient form) with 1, 3, and 5 vol.% of aluminum oxide were fabricated by the hot pressing and spark plasma sintering methods. Two forms of aluminum oxide (αAl2O3 powder and electrocorundum) were used as a reinforcement. Microstructural investigations revealed that near fully dense materials with low porosity and a clear interface between the metal matrix and ceramics were obtained in the case of the SPS method. In this paper, the properties (mechanical, thermal, and tribological) of composite materials were also collected and compared. Technological tests were preceded by finite element method analyses of thermal stresses generated in the gradient structure, and additionally, the role of porosity in the formation process of composite properties was modeled. Based on the said modeling, technological conditions for obtaining FGMs were proposed.

Properties investigation and microstructures characterization of SiCp/6061Al composites produced by PM route

NASA Astrophysics Data System (ADS)

Wang, A. Q.; Tian, H. W.; Xie, J. P.

2018-01-01

In this study, 35 vol.% SiC particles with different sizes reinforced 6061 aluminium alloy matrix composites were prepared by a powder metallurgy method. The Scanning Electron Microscope (SEM) images of composites were observed, the Coefficient of Thermal Expansion (CTE) and tensile strength of composites were examined, and the influences of SiC particle size on microstructures and properties of the composites were analyzed. Furthermore, the SiCp/6061Al composites with SiC particle size of 7.5 µm were selected to investigate the SiCp/Al interface microstructure and precipitated phases by the means of SEM, TEM and HRTEM. The study indicated that, with the increase of SiC particle size, the SiC particles distributed more uniformly in the matrix, the CTE of composites increased, but the tensile strength of composites decreased. The SiCp/Al interface in this experiment is clean and smooth, and the combination mechanism of SiC and Al is the formation of a half coherent interface by closely matching of atoms. Some micron-sized coarse intermetallic particles existed in the hot-pressed composites, such as random-shaped Mg2Si, long stick shaped Al15(Mn, Fe, Cu)3Si2. When the composites were solution treated at 510 °C for 2 h and then aging treated at 190 °C for 9 h, except long stick shaped Al15(Mn, Fe, Cu)3Si2, numerous nano-sized precipitated phases (Mg2Si) with diameters of 50-200 nm dispersively distributed in the matrix. After heat treatment, the tensile strength of composite with SiC particle size of 7.5 µm enhance from 298 MPa to 341 MPa.

Preseismic Lithosphere-Atmosphere-Ionosphere Coupling

NASA Astrophysics Data System (ADS)

Kamogawa, Masashi

Preseismic atmospheric and ionospheric disturbances besides preseismic geo-electric potential anomalies and ultra-low-frequency (ULF) geomagnetic variations observed on the ground have been reported. Both the phenomena have been found since the 1980s and a number of papers have been published. Since most of the reported phenomena transiently appear with accompanying quiescence before the mainshock, this prevents us to intuitively recognize a correlation between the anomaly appearance and the earthquake occurrence. Some of them, however, showed that anomalies monotonically grew into the mainshock, of which a variation supports the concept of seismic nucleation process under the pre-earthquake state. For example, Heki [GRL, 2011] reported that ionospheric electron density monotonically enhanced tens of minutes prior to the subduction mega-earthquake. However, this preseismic enhancement is apparent variation attributed to tsunamigenic ionospheric hole [Kakinami and Kamogawa et al, GRL, 2012], namely wide and long-duration depression of ionospheric electron after tsunami-excited acoustic waves reach the ionosphere. Since the tsunamigenic ionospheric hole could be simulated [Shinagawa et al., GRL, 2013], the reported variations are high-possibly pseudo phenomena [Kamogawa and Kakinami, JGR, 2013]. Thus, there are barely a few reports which show the preseismic monotonic variation supported by the concept of the seismic nucleation process. As far as we discuss the preseismic geoelectromagnetical and atmospheric-ionospheric anomalies, preseismic transient events from a few weeks to a few hours prior to the mainshock are paid attention to for the precursor study. In order to identify precursors from a number of anomalies, one has to show a statistical significance of correlation between the earthquake and the anomalies, to elucidate the physical mechanism, or to conduct both statistical and physical approach. Since many speculation of the physical mechanism have been

Atmospheric Production of Perchlorate on Earth and Mars

NASA Astrophysics Data System (ADS)

Claire, M.; Catling, D. C.; Zahnle, K. J.

2009-12-01

Natural production and preservation of perchlorate on Earth occurs only in arid environments. Isotopic evidence suggests a strong role for atmospheric oxidation of chlorine species via pathways including ozone or its photochemical derivatives. As the Martian atmosphere is both oxidizing and drier than the driest places on Earth, we propose an atmospheric origin for the Martian perchlorates measured by NASA's Phoenix Lander. A variety of hypothetical formation pathways can be proposed including atmospheric photochemical reactions, electrostatic discharge, and gas-solid reactions. Here, we investigate gas phase formation pathways using a 1-D photochemical model (Catling et al. 2009, accepted by JGR). Because perchlorate-rich deposits in the Atacama desert are closest in abundance to perchlorate measured at NASA's Phoenix Lander site, we start with a study of the means to produce Atacama perchlorate. We found that perchlorate can be produced in sufficient quantities to explain the abundance of perchlorate in the Atacama from a proposed gas phase oxidation of chlorine volatiles to perchloric acid. These results are sensitive to estimated reaction rates for ClO3 species. The feasibility of gas phase production for the Atacama provides justification for further investigations of gas phase photochemistry as a possible source for Martian perchlorate. In addition to the Atacama results, we will present a preliminary study incorporating chlorine chemistry into an existing Martian photochemical model (Zahnle et al. JGR 2008).

On the Spectral Variance of MGS TES Spectra in the 300-500 cm-1 Range

NASA Astrophysics Data System (ADS)

Altieri, F.; Bellucci, G.

2001-11-01

The Thermal Emission Spectrometer (TES) aboard NASA mission Mars Global Surveyor (MGS) is collecting 200 - 1600 cm-1 thermal emission spectra since September 1997. The principal purpose of TES is to determine and map the Mars surface composition. Spectral features directly ascribable to surface minerals have been identified in the 300 - 500 cm-1 spectral range. Outcrops of hematite have been localized in Sinus Meridiani, Aram Chaos and Valles Marineris [1, 2] and areas with olivine have been individuated in Nili Fossae and in other limited regions [3]. On the other hand, TES spectra show, in general, significant variance between 300 and 500 cm-1; this variance is not directly attributable to surface mineralogical components. In this study we report some examples of spectra with typical hematite and olivine bands and spectra with a different spectral contrast. The spectral masking effect of a dust layer is suggested to explain this behaviour. Spectra characterized by hematite features have been localized also inside a crater near Baldet Crater. The MOC narrow-angle image M02-0039 acquired on the same area shows dark layers at the crater bottom. References: [1] Christensen P. R., et al., JGR, 105, 9623-9642, 2000. [2] Christensen P. R., et al., JGR, in press., 2001. [3] Hoefen T. M. and Clark R. N., LPS XXXII, 2049, 2001.

High-Resolution Topography and its Implications for the Formation of Europa's Ridged Plains

NASA Astrophysics Data System (ADS)

Leonard, E. J.; Pappalardo, R. T.; Yin, A.; Patthoff, D. A.; Schenk, P.

2015-12-01

The Galileo Solid State Imager (SSI) recorded nine very high-resolution frames—eight at 12 m/pixel and one at 6 m/pixel—during the E12 flyby of Europa in Dec. 1997. To understand the implications for the small-scale structure and evolution of Europa, we mosaicked these frames (observations 12ESMOTTLE01 and 02, incidence ≈18°, emission ≈77°) into their regional context (part of observation 11ESREGMAP01, 220 m/pixel, incidence ≈74°, emission ≈23°). The topography data, which was created from the image mosaic overlaps, is sparse and segmented over the high-resolution images but connected by the underlying regional resolution topography. The high-resolution topography (24 m/pixel) is among the best for the current Europan dataset. From this dataset we ascertain the root mean square, or RMS, slope for some of the most common Europan surface features in a new region. We also employ a Fourier Transform method previously used on Ganymede and on other areas of Europa (Patel et al., 1999 JGR), to derive common wavelengths for the subunits of the ubiquitous ridged plains terrain. These results have important implications for differentiating between possible formation mechanisms—extensional tilt blocks (Pappalardo et al., 1995 JGR) or folds (Leonard et al., 2015 LPSC Abstract)—and for potential future missions. We continue this method for another high-resolution region taken in the E12 orbit, WEDGES01 and 02, with the specific goal of investigating how the variations in ridged plains morphologies relate across the surface of Europa.

Strong enhancement in thermal conductivity of ethylene glycol-based nanofluids by amorphous and crystalline Al{sub 2}O{sub 3} nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gangwar, J.; Department of Physics, Panjab University, Chandigarh 160014; Srivastava, A. K., E-mail: aks@nplindia.org, E-mail: avanish.aks555@gmail.com

2014-08-11

In the present work, the temperature and concentration dependence of thermal conductivity (TC) enhancement in ethylene glycol (EG)-based amorphous and crystalline Al{sub 2}O{sub 3} nanofluids have been investigated at temperatures ranging from 0 to 100 °C. In our prior study, nanometer-sized particles of amorphous-, γ-, and α-Al{sub 2}O{sub 3} were prepared via a simple sol-gel process with annealing at different temperatures and characterized by various techniques. Building upon the earlier study, we probe here the crystallinity, microstructure, and morphology of the obtained α-Al{sub 2}O{sub 3} nanoparticles (NPs) by using X-ray powder diffraction with Rietveld full-profile refinement, scanning electron microscopy, and high-resolutionmore » transmission electron microscopy, respectively. In this study, we achieved a 74% enhancement in TC at higher temperature (100 °C) of base fluid EG by incorporating 1.0 vol. % of amorphous-Al{sub 2}O{sub 3}, whereas 52% and 37% enhancement is accomplished by adding γ- and α-Al{sub 2}O{sub 3} NPs, respectively. The amorphous phase of NPs appears to have good TC enhancement in nanofluids as compared to crystalline Al{sub 2}O{sub 3}. In a nutshell, these results are demonstrating the potential consequences of Al{sub 2}O{sub 3} NPs for applications of next-generation efficient energy transfer in nanofluids.« less

Microstructure, strengthening mechanisms and hot deformation behavior of an oxide-dispersion strengthened UFG Al6063 alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Asgharzadeh, H.; Kim, H.S.; Simchi, A., E-mail: simchi@sharif.edu

2013-01-15

An ultrafine-grained Al6063/Al{sub 2}O{sub 3} (0.8 vol.%, 25 nm) nanocomposite was prepared via powder metallurgy route through reactive mechanical alloying and hot powder extrusion. Scanning electron microcopy, transmission electron microscopy, and back scattered electron diffraction analysis showed that the grain structure of the nanocomposite is trimodal and composed of nano-size grains (< 0.1 {mu}m), ultrafine grains (0.1-1 {mu}m), and micron-size grains (> 1 {mu}m) with random orientations. Evaluation of the mechanical properties of the nanocomposite based on the strengthening-mechanism models revealed that the yield strength of the ultrafine-grained nanocomposite is mainly controlled by the high-angle grain boundaries rather than nanometricmore » alumina particles. Hot deformation behavior of the material at different temperatures and strain rates was studied by compression test and compared to coarse-grained Al6063 alloy. The activation energy of the hot deformation process for the nanocomposite was determined to be 291 kJ mol{sup -1}, which is about 64% higher than that of the coarse-grained alloy. Detailed microstructural analysis revealed that dynamic recrystallization is responsible for the observed deformation softening in the ultrafine-grained nanocomposite. - Highlights: Black-Right-Pointing-Pointer The strengthening mechanisms of Al6063/Al{sub 2}O{sub 3} nanocomposite were evaluated. Black-Right-Pointing-Pointer Hot deformation behavior of the nanocomposite was studied. Black-Right-Pointing-Pointer The hot deformation activation energy was determined using consecutive models. Black-Right-Pointing-Pointer The restoration mechanisms and microstructural changes are presented.« less

Microstructural stability of fine-grained fully lamellar XD TiAl alloys by step aging

NASA Astrophysics Data System (ADS)

Zhu, Hanliang; Maruyama, K.; Seo, D. Y.; Au, P.

2005-05-01

XD TiAl alloys (Ti-45 and 47Al-2Nb-2Mn+0.8 vol pct TiB2) (at. pct) were oil quenched to produce fine-grained fully lamellar (FGFL) structures, and aging treatments at different temperatures for different durations were carried out to stabilize the FGFL structures. Microstructural examinations show that the aging treatments cause phase transformation of α 2 to γ, resulting in stabilization of the lamellar structure, as indicated by a significant decrease in α 2 volume fraction. However, several degradation processes are also introduced. After aging, within lamellar colonies, the α 2 lamellae become finer due to dissolution, whereas most of the γ lamellae coarsen. The dissolution of α 2 involves longitudinal dissolution and lateral dissolution. In addition, at lamellar colony boundaries, lamellar termination migration, nucleation and growth of γ grains, and discontinuous coarsening occur. With the exception of longitudinal dissolution, all the other transformation modes are considered as degradation processes as they result in a reduction in α 2/ γ interfaces. Different phase transformation modes are present to varying degrees in the aged FGFL structures, depending on aging conditions and Al content. A multiple step aging reduces the drive force for phase transformation at high temperature by promoting phase transformation via longitudinal dissolution at low temperatures. As a result, this aging procedure effectively stabilizes the lamellar structure and suppresses other degradation processes. Therefore, the multiple step aging is suggested to be an optimal aging condition for stabilizing FGFL XD TiAl alloys.

Gram-negative Biomass in Clay Minerals Analogs: Testing Habitability Potential for the 2011 Mars Science Laboratory Mission

NASA Astrophysics Data System (ADS)

Bonaccorsi, R.; McKay, C. P.

2009-12-01

al., 2006 JGR E02S16 Vol.111; [3] Bishop et al., 2008. Science, 321,830-833.

Niobium Carbide-Reinforced Al Matrix Composites Produced by High-Energy Ball Milling

NASA Astrophysics Data System (ADS)

Travessa, Dilermando Nagle; Silva, Marina Judice; Cardoso, Kátia Regina

2017-06-01

Aluminum and its alloys are key materials for the transportation industry as they contribute to the development of lightweight structures. The dispersion of hard ceramic particles in the Al soft matrix can lead to a substantial strengthening effect, resulting in composite materials exhibiting interesting mechanical properties and inspiring their technological use in sectors like the automotive and aerospace industries. Powder metallurgy techniques are attractive to design metal matrix composites, achieving a homogeneous distribution of the reinforcement into the metal matrix. In this work, pure aluminum has been reinforced with particles of niobium carbide (NbC), an extremely hard and stable refractory ceramic. Its use as a reinforcing phase in metal matrix composites has not been deeply explored. Composite powders produced after different milling times, with 10 and 20 vol pct of NbC were produced by high-energy ball milling and characterized by scanning electron microscopy and by X-ray diffraction to establish a relationship between the milling time and size, morphology, and distribution of the particles in the composite powder. Subsequently, an Al/10 pct NbC composite powder was hot extruded into cylindrical bars. The strength of the obtained composite bars is comparable to the commercial high-strength, aeronautical-grade aluminum alloys.

Experimental Constraints On Transparency of The 1052;1040;rtian Atmosphere Out of Dust Storm

NASA Astrophysics Data System (ADS)

Korablev, O.; Moroz, V. I.; Rodin, A. V.

In the absence of a dust storm so-called permanent dust haze with = 0.2 in the atmo- sphere of Mars determines its thermal structure, as it has been shown by Gierasch and Goody [1972 JAS 29, 400] and is confirmed by modern Mars GCMs that include dust cycle. Dust loading varies substantially with the season and geographic location, and only the data of mapping instruments are adequate to characterize it. Presently, these are the data of thermal IR instruments, benefiting from being insensitive to condensa- tional clouds: TES/MGS and IRTM/Viking. In calm atmospheric conditions (aphelion season) a typical value of 9-µm optical depth 9 of 0.05-0.15 is observed by these instruments [Smith et al. 2000, 2001 JGR 105, 9539; JGR 106, 23929; Martin and Richardson 1993 JGR 98, 10941]. In order to quantify the typical optical depth of the permanent dust haze, we will discuss, among others, the following two questions: 1) How to agree the above values and reliable measurements from the surface (VL, Pathfinder) which give the typical optical depth (out of dust storms) of = 0.5 from one side, and some ground-based observations (in UV-visible range) that frequently reveal < 0.02 on the other side. 2) What is the relationship between 9 and the visi- ble optical depth? Comparison of IRTM and VL measurements (the only simultaneous observations available so far) suggest vis/9 = 2.5, that contradict to vis/9 = 0.9 that follow from IRIS/Mariner 9 mineralogy model, which is confirmed by recent re- analysis of IRIS data.

Young Lunar Volcanic Features: Thermophysical Properties and Formation

NASA Astrophysics Data System (ADS)

Elder, C. M.; Hayne, P. O.; Donaldson Hanna, K. L.; Bandfield, J.; Ghent, R. R.; Williams, J. P.; Paige, D. A.

2016-12-01

Irregular Mare Patches (IMPs) are small features (100 - 5000 m) on the lunar nearside characterized by uneven terrain interspersed with topographically higher smooth terrain. Crater counting suggests that they are less than 100 Myr old [1, 2]. Several formation hypotheses have been proposed for IMPs, including: caldera collapse [3], explosive outgassing [2], lava flow inflation [4], pyroclastic eruption [5], and regolith drainage [6]. In this study, we use thermal infrared data from the Lunar Reconnaissance Orbiter (LRO) Diviner radiometer to investigate the thermophysical properties of the IMPs. We find that their average rock abundance is approximately a factor of two higher than the surrounding terrain. Comparison of Diviner data with thermal models rules out extensive competent rocks within 5-10 cm of the surface at the IMPs. We also derive the regolith thermal inertia [7] of the four largest IMPs. Sosigenes, Maskelyne, and Cauchy-5 have thermal inertias slightly higher than their surrounding terrain, likely due to the presence of small rocks surrounding nearby craters. Ina has an average thermal inertia lower than the surrounding terrain, and the only resolved smooth mound in Ina has an even lower thermal inertia which implies material that is less consolidated than typical regolith and/or contains fewer small rocks. Formation by lava flows or regolith drainage is not expected to result in material with a lower thermal inertia than pre-existing regolith, so in the case of at least Ina, some other process such as explosive outgassing or pyroclastic eruptions must have occurred. [1] Braden, S. et al. (2014) Nature Geo 7, 787-791. [2] Schultz, P. H. et al. (2006) Nature 444, 184-186. [3] El-Baz, F. (1973) Apollo 17: Preliminary Science Report 330, 30-13. [4] Garry, W. B. et al. (2012) JGR 117, E00H31. [5] Carter, L. B. et al. (2013) LPSC 44, 2146. [6] Qiao, L. et al. (2002) LPSC 47, 2002. [7] Vasavada, A. R. et al. (2012) JGR 117, E00H18.

The Maturely, Immature Orientale Impact Basin

NASA Astrophysics Data System (ADS)

Cahill, J. T.; Lawrence, D. J.; Stickle, A. M.; Delen, O.; Patterson, G.; Greenhagen, B. T.

2015-12-01

Lunar surface maturity is consistently examined using the NIR optical maturity parameter (OMAT) [1]. However, the NIR only provides a perspective of the upper microns of the lunar surface. Recent studies of Lunar Prospector (LP) and Lunar Reconnaissance Orbiter data sets are now demonstrating additional measures of maturity with sensitivities to greater depths (~2 m) in the regolith. These include thermal infrared, S-band radar, and epithermal neutron data sets [2-4]. Interestingly, each of these parameters is directly comparable to OMAT despite each measuring slightly different aspects of the regolith. This is demonstrated by Lawrence et al. [3] where LP-measured non-polar highlands epithermal neutrons trend well with albedo, OMAT, and the Christensen Feature (CF). Lawrence et al. [3] used these data to derive and map highlands hydrogen (H) which is dominantly a function of H-implantation. With this in mind, areas of enriched-H are mature, while areas of depleted H are immature. Surface roughness as measured by S-band radar [4], also provides a measure of maturity. In this case, the circular polarization ratio (CPR) is high when rough and immature, and low when smooth and mature. Knowing this, one can recognize areas in the non-polar lunar highlands that show contradictory measures of maturity. For example, while many lunar localities show consistently immature albedo, OMAT, CF, CPR, and H concentrations (e.g., Tycho), others do not. Orientale basin is the most prominent example, shown to have immature CPR, CF, and H concentrations despite a relatively mature albedo and OMAT values as well as an old age determination (~3.8 Ga). To better understand how the lunar regolith is weathering in the upper 1-2 m of regolith with time we examine the Orientale basin relative to other highlands regions. [1] Lucey et al. (2000) JGR, 105, 20377; [2] Lucey et al. (2013) LPSC, 44, 2890; [3] Lawrence et al. (2015) Icarus, j.icarus.2015.01.005; [4] Neish et al. (2013) JGR, 118

Microstructure and mechanical properties of aluminium matrix composites reinforced by Al{sub 62}Cu{sub 25.5}Fe{sub 12.5} melt spun ribbon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lityńska-Dobrzyńska, Lidia, E-mail: l.litynska@imim.pl; Mitka, Mikołaj; Góral, Anna

Aluminium matrix composites containing 15, 30 and 50 vol.% of pulverized Al{sub 62}Cu{sub 25.5}Fe{sub 12.5} (in at.%) melt spun ribbons have been prepared by a vacuum hot pressing (T = 673 K, P = 600 MPa). The microstructure of the initial ribbon and the composites was investigated using X-ray, scanning and transmission electron microscopy. In the as-spun ribbon the quasicrystalline icosahedral phase (i-phase) coexisted with the cubic copper rich β-Al(Cu, Fe) intermetallic compound. The phase composition of Al-Cu-Fe particles changed after consolidation process and the i-phase transformed partially to the ω-Al{sub 70}Cu{sub 20}Fe{sub 10} phase. Additionally, the Θ-Al{sub 2}Cu phasemore » formed at the α(Al)/Al-Cu-Fe particle interfaces. With an increase in volume fraction of the reinforcement the hardness of the composites increased up to HV = 180 for the highest amount of added particles. The ultimate compression strength of the same sample reached the value of 545 MPa. - Highlights: • Al and 15, 30, 50% of pulverized Al{sub 62}Cu{sub 25.5}Fe{sub 12.5} melt spun ribbon were consolidated. • The initial ribbon consisted of the icosahedral i-phase and copper rich β-Al(Cu, Fe). • The i-phase partially transforms to ω-Al{sub 7}Cu{sub 2}Fe phase in all composites. • Increase of microhardness and compressive strength with content of reinforcement • Ultimate compression strength 545 MPa for 50% of added particles.« less

Linking petrology and seismology of the southwest Greenland lithosphere

NASA Astrophysics Data System (ADS)

Lesher, C. E.; Vestergaard, C.; Brown, E.; Schutt, D.

2015-12-01

Mantle xenoliths from late-Proterozoic diamond-bearing kimberlitic dikes in the Kangerlussuaq, Sarfartoq and Maniitsoq areas of southwestern Greenland provide constraints on the composition and thermal state of lithospheric mantle beneath Greenland to depths of ~200 km [1]. Similarly, surface wave tomography studies carried out as part of the GLATIS project use a range of Rayleigh wave periods sensitive to structures at a similar depth interval within southwestern Greenland lithospheric mantle [2]. Here we link petrologic and seismologic constraints on the mantle lithosphere beneath Greenland utilizing methods of [3] that show that inferred chemical and mineralogical stratification inferred from petrology, showing mantle peridotite transitioning from garnet-free harzburgite to garnet lherzolite between ~70 and 180 km, cannot readily be resolved with fundamental mode Rayleigh waves. On the other hand, comparing phase velocities predicted from xenolith compositions, mineralogy and last equilibration temperatures and pressures, defining the continental geotherm during late-Proterozoic time, with those for the present-day mantle lithosphere suggest significant cooling of the cratonic mantle to a modern geotherm characterized by a heat flux of 30 mW/m2 and average crustal heat production of 0.3 mW/m3 [4]. These preliminary findings point to the weak dependence of shear wave velocities on mantle peridotite composition and mineralogy, and further illustrate its strong temperature dependence. Comparison of ancient and modern continental geotherms made possible by combining petrologic and seismological data, as shown here for southwest Greenland, provide additional constraints on secular cooling of cratonic regions linked to large-scale tectonic processes. [1] Bizzarro et al., 2003, CMP, 146; Sand et al., Lithos, 112. [2] Darbyshire et al., 2004, GJI, 158. [3] Schutt and Lesher, 2006, JGR, 111. [4] Meirerbachtol et al., 2015, JGR/ES, 120.

AGARD Flight Test Techniques Series. Volume 12. The Principles of Flight Test Assessment of Flight-Safety-Critical Systems in Helicopters (Les Principes de l’Evaluation, dans le Cadre des Essais en Vol, des Systemes Indispensables a la Securite de Vol des Helicopteres)

DTIC Science & Technology

1994-08-01

AGARD-AG-300 Vol. 12 04 ADVISORY GROUP FOR AEROSPACE RESEARCH & DEVELOPMENT 7 RUE ANCELLE, 92200 NEUILLY-SUR-SEINE, FRANCE AUG 0195 AGARDograph 300...AGARD Flight Test Techniques Series Volume 12 on The Principles of Flight Test Assessment of Flight-Safety-Critical Systems in Helicopters (Les...and Availability on Back Cover AGARD-AG-300 Vol. 12 ADVISORY GROUP FOR AEROSPACE RESEARCH & DEVELOPMENT 7 RUE ANCELLE, 92200 NEUILLY-SUR-SEINE, FRANCE

Elevated temperature creep properties of NiAl cryomilled with and without Y2O3

NASA Technical Reports Server (NTRS)

Whittenberger, J. Daniel; Luton, Michael J.

1995-01-01

The creep properties of lots of NiAl cryomilled with and without Y2O3 have been determined in compression and tension. Although identical cryomilling procedures were used, differences in composition were found between the lot ground with 0.5 vol% yttria and the lot ground without Y2O3. Compression testing between 1000 and 1300 K yielded similar creep strengths for both materials, while tensile creep rupture testing indicated that the yttria-containing alloy was slightly stronger than the Y2O3-free version. Both compression and tensile testing showed two deformation regimes; whereas the stress state did not affect the high stress exponent (n approximately equals 10) mechanism, the low stress exponent regime n was approximately 6 in tension and approximately 2 in compression. The strengths in tension were somewhat less than those measured in compression, but the estimated activation energies (Q) of approximately 600 kJ/mol for tensile testing were closer to the previously measured values (approximately 700 kJ/mol) for NiAl-AlN and very different from the Q's of 400 and 200 kJ/mol for compression tests in the high and low stress exponent regimes, respectively. A Larson-Miller comparison indicated that cryomilling can produce an alloy with long-term, high-temperature strength at least equal to conventional superalloys.

Intercomparison of Carbonate Deposits on Mars: VNIR Spectral Character and Geologic Context

NASA Astrophysics Data System (ADS)

Wiseman, S.; Mustard, J. F.; Ehlmann, B. L.

2012-12-01

[1,10], and possibly talc [11].These carbonates are hypothesized to have formed via alteration of olivine and/or serpentine under surface or low temperature hydrothermal conditions [1,11,12] Laboratory spectra of Mg carbonates (magnesite/hydromagnesite) are the closest matches to the Nili Fossae carbonates [1]. CRISM spectra of carbonates in and around Huygens basin are interpreted to be Fe and/or Ca carbonates [3], similar to carbonate spectra described by [2]. However, the CRISM carbonate-bearing spectra are mixed with Fe/Mg phyllosilicates [1,2,3], making a one to one comparison among Martian and laboratory carbonate spectra challenging. [1] Ehlmann et al. (2008), Sci., 322, 1828-1831, [2] Michalski and. Niles (2010), Nat. Geo., 3, 751-55, [3] Wray et al. (2011), LPSC, #2635, [4] Bishop et al. (2012), LPSC, #2330, [5] Carter and Poulet (2012), Icarus, [6] Gaffey (1987), JGR, 92, 1429-1440, [7] Stamnes et al. (1999), Appl. Opt., 27, 2502-2509, [8] Wolff et al. (2009), JGR, 11, [9] Wiseman et al., 2010, LPSC , #2461, [10] Ehlmann et al. (2010), GRL, 37, [11] Brown et al. (2010), EPSL, 297, 174-182. [12] Ehlmann et al. (2009), JGR, 114.

Optimization of In-Situ Shot-Peening-Assisted Cold Spraying Parameters for Full Corrosion Protection of Mg Alloy by Fully Dense Al-Based Alloy Coating

NASA Astrophysics Data System (ADS)

Wei, Ying-Kang; Luo, Xiao-Tao; Li, Cheng-Xin; Li, Chang-Jiu

2017-01-01

Magnesium-based alloys have excellent physical and mechanical properties for a lot of applications. However, due to high chemical reactivity, magnesium and its alloys are highly susceptible to corrosion. In this study, Al6061 coating was deposited on AZ31B magnesium by cold spray with a commercial Al6061 powder blended with large-sized stainless steel particles (in-situ shot-peening particles) using nitrogen gas. Microstructure and corrosion behavior of the sprayed coating was investigated as a function of shot-peening particle content in the feedstock. It is found that by introducing the in-situ tamping effect using shot-peening (SP) particles, the plastic deformation of deposited particles is significantly enhanced, thereby resulting in a fully dense Al6061 coating. SEM observations reveal that no SP particle is deposited into Al6061 coating at the optimization spraying parameters. Porosity of the coating significantly decreases from 10.7 to 0.4% as the SP particle content increases from 20 to 60 vol.%. The electrochemical corrosion experiments reveal that this novel in-situ SP-assisted cold spraying is effective to deposit fully dense Al6061 coating through which aqueous solution is not permeable and thus can provide exceptional protection of the magnesium-based materials from corrosion.

Tailoring nanostructured, graded, and particle-reinforced Al laminates by accumulative roll bonding.

PubMed

Göken, Mathias; Höppel, Heinz Werner

2011-06-17

Accumulative roll bonding (ARB) is a very attractive process for processing large sheets to achieve ultrafine-grained microstructure and high strength. Commercial purity Al and many Al alloys from the 5xxx and the precipitation strengthened 6xxx alloy series have been successfully processed by the ARB process into an ultrafine-grained state and superior ductility have been achieved for some materials like technical purity Al. It has also been shown that the ARB process can be successfully used to produce multi-component materials with tailored properties by reinforcement or grading, respectively. This allows optimizing the properties based on two or more materials/alloys. For example, to achieve high corrosion resistance and good visual surface properties it is interesting to produce a composite of two different Al alloys, where for example a high strength alloy of the 5xxx series is used as the core material and a 6xxx series alloy as the clad material. It has been shown that such a composite achieves more or less the same strength as the core material although 50% of the composite consists of the significant softer clad alloy. Furthermore, it has been found, that the serrated yielding which typically appears in 5xxx series alloys and limits applications as outer skin materials completely disappears. Moreover, the ARB process allows many other attractive ways to design new composites and graded material structures with unique properties by the introduction of particles, fibres and sheets. Strengthening with nanoparticles for example is a very attractive way to improve the properties and accelerate the grain refining used in the severe plastic deformation process. With an addition of only 0.1 vol.-% Al2O3 nanoparticles a significantly accelerated grain refinement has been found which reduces the number of ARB passes necessary to achieve the maximum in strength. The paper provides a short review on recent developments in the field of ARB processing for producing

The dissimilar brazing of Kovar alloy to SiCp/Al composites using silver-based filler metal foil

NASA Astrophysics Data System (ADS)

Wang, Peng; Xu, Dongxia; Zhai, Yahong; Niu, Jitai

2017-09-01

Aluminum metal matrix composites with high SiC content (60 vol.% SiCp/Al MMCs) were surface metallized with a Ni-P alloy coating, and vacuum brazing between the composites and Kovar alloy were performed using rapidly cooled Ag-22.0Cu-15.9In-10.86Sn-1.84Ti (wt%) foil. The effects of Ni-P alloy coating and brazing parameters on the joint microstructures and properties were researched by SEM, EDS, and single lap shear test, respectively. Results show that Ag-Al intermetallic strips were formed in the 6063Al matrix and filler metal layer because of diffusion, and they were arranged regularly and accumulated gradually as the brazing temperature was increased ( T/°C = 550-600) or the soaking time was prolonged ( t/min = 10-50). However, excessive strips would destroy the uniformity of seams and lead to a reduced bonding strength (at most 70 MPa). Using a Ni-P alloy coating, void free joints without those strips were obtained at 560 °C after 20 min soaking time, and a higher shear strength of 90 MPa was achieved. The appropriate interface reaction ( 2 μm transition layer) that occurred along the Ni-P alloy coating/filler metal/Kovar alloy interfaces resulted in better metallurgical bonding. In this research, the developed Ag-based filler metal was suitable for brazing the dissimilar materials of Ni-P alloy-coated SiCp/Al MMCs and Kovar alloy, and capable welding parameters were also broadened.

Thermal Treatment, Sliding Wear and Saline Corrosion of Al In Situ Reinforced with Mg2Si and Ex Situ Reinforced with TiC Particles

NASA Astrophysics Data System (ADS)

Lekatou, A. G.; Poulia, A.; Mavros, H.; Karantzalis, A. E.

2018-02-01

The main objective of this work is to produce a composite consisting of (a) a cast heat-treatable Al-Mg-Si alloy with high contents of Mg for corrosion resistance and Si to offset the Mg-due poor castability (in situ hypoeutectic Mg2Si/Al composite) and (b) TiC particles at high enough volume fractions (≤ 15%), in order to achieve a satisfactory combination of wear and corrosion performance. TiCp/Al-7Mg-5Si (wt.%) composites were produced by flux-assisted casting followed by solution and aging heat treatment. Solution treatment led to a relatively uniform dispersion and shape rounding of Mg2Si precipitates and Si particles. TiC particle addition resulted in refinement of primary Al, modification of the Mg2Si Chinese script morphology and refinement/spheroidization of primary Mg2Si. Heat treatment combined with TiC addition notably improved the sliding wear resistance of Al-7Mg-5Si. A wear mechanism has been proposed. The TiC/Al interfaces remained intact of corrosion during potentiodynamic polarization of the heat-treated materials in 3.5 wt.% NaCl. Different main forms of localized corrosion in 3.5 wt.% NaCl were identified for each TiC content (0, 5, 15 vol.%), depending on specific degradation favoring microstructural features (topology/size/interface wetting) at each composition.

10. Fifth floor plan,published in 'Architectural Record',Vol 31,No. 4, April ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

10. Fifth floor plan,published in 'Architectural Record',Vol 31,No. 4, April 1912,p. 356 (?),courtesy of Art Institute of Chicago, permission to duplicate courtesy of 'Architectural Record' - Chicago City Hall, 121 North LaSalle Street, Chicago, Cook County, IL

Pedestal Craters in Utopia Planitia and Malea Planum: Evidence for a Past Ice-Rich Substrate from Marginal Sublimation Pits.

NASA Astrophysics Data System (ADS)

Kadish, S. J.; Head, J. W.; Barlow, N. G.; Marchant, D. R.

2008-09-01

water-ice accumulations during periods of high obliquity [26,27]. Discussion: The morphologic similarity between the marginal pits associated with Pd and ice sublimation pits leads us to favor an origin of preferential sublimation of ice/snow from the Pd scarp. In this interpretation, an impact crater forms in a thick (~10s to ~100s m) regional highlatitude deposit of ice and snow, mixed with dust. The area around the crater (the future pedestal surface) is armored by proximal ejecta and distal sintering effects of impact melt and atmospheric blast/thermal effects accompanying crater formation [5-6]. Following crater formation, obliquitydriven climate change leads to removal of the intervening snow and ice, leaving the Pd perched. Over time, the volatile-rich scarp margins, where the armoring tapers off, undergo continued sublimation to produce the pits, while the heavily armored Pd surface inhibits/prevents sublimation of underlying volatiles (Fig. 3). Ice-rich layered substrates are thus interpreted to be preserved under Pd. On the basis of our analysis, Pd represent the remnants of a past extensive, layered, climate-related deposit, similar to, but thicker than the latitude-dependent mantle emplaced in a recent ice age [11,18]. Due to the large number and widespread distribution of Pd (Fig. 1) [8,9,16], we believe that this climate-related deposit persisted for a considerable part of the recent past, implying that obliquity was relatively higher than at present during a significant portion of the Amazonian period of the history of Mars. References: [1] Barlow, N. et al. (2000) JGR, 105, 26733. [2] McCauley, J. (1973) JGR, 78, 4123. [3] Arvidson, R. (1976) Icarus, 27, 503. [4] Osinski, G. (2006) MAPS, 41, 1571. [5] Schultz, P. and Mustard, J. (2004) JGR, 109, E01001. [6] Wrobel, K. et al. (2006) MAPS, 41, 1539. [7] Mouginis-Mark, P. (1979) JGR, 84, 8011. [8] Kadish, S. and Barlow, N. (2006) LPSC 37, #1254. [9] Kadish, S. et al. (2008) LPSC 39, #1766. [10] Jakosky, B

Dose equations for shift-variant CT acquisition modes using variable pitch, tube current, and aperture, and the meaning of their associated CTDI{sub vol}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dixon, Robert L., E-mail: rdixon@wfubmc.edu; Boone, John M.; Kraft, Robert A.

2014-11-01

Purpose: With the increasing clinical use of shift-variant CT protocols involving tube current modulation (TCM), variable pitch or pitch modulation (PM), and variable aperture a(t), the interpretation of the scanner-reported CTDI{sub vol} is called into question. This was addressed for TCM in their previous paper published by Dixon and Boone [Med. Phys. 40, 111920 (14pp.) (2013)] and is extended to PM and concurrent TCM/PM as well as variable aperture in this work. Methods: Rigorous convolution equations are derived to describe the accumulated dose distributions for TCM, PM, and concurrent TCM/PM. A comparison with scanner-reported CTDI{sub vol} formulae clearly identifies themore » source of their differences with the traditional CTDI{sub vol}. Dose distribution simulations using the convolution are provided for a variety of TCM and PM scenarios including a helical shuttle used for perfusion studies (as well as constant mA)—all having the same scanner-reported CTDI{sub vol}. These new convolution simulations for TCM are validated by comparison with their previous discrete summations. Results: These equations show that PM is equivalent to TCM if the pitch variation p(z) is proportional to 1/i(z), where i(z) is the local tube current. The simulations show that the local dose at z depends only weakly on the local tube current i(z) or local pitch p(z) due to scatter from all other locations along z, and that the “local CTDI{sub vol}(z)” or “CTDI{sub vol} per slice” do not represent a local dose but rather only a relative i(z) or p(z). The CTDI-paradigm does not apply to shift-variant techniques and the scanner-reported CTDI{sub vol} for the same lacks physical significance and relevance. Conclusions: While the traditional CTDI{sub vol} at constant tube current and pitch conveys useful information (the peak dose at the center of the scan length), CTDI{sub vol} for shift-variant techniques (TCM or PM) conveys no useful information about the associated dose

Summary of types of radiation belt electron precipitation observed by BARREL

NASA Astrophysics Data System (ADS)

Halford, Alexa

2016-07-01

The Balloon Array for Relativistic Radiation belt Electron Loss (BARREL) was able to infer precipitation of radiation belt electrons on multiple time scales and due to multiple loss mechanisms. One storm will be specifically highlighted which occurred on 26 January 2013 when a solar wind shock hit the Earth. Although MeV electrons were observed to be lost due to an EMIC wave event [Zhang et al in prep], and multiple periods of electron loss during substorms were observed [Rae et al submitted JGR, Mann et al in prep], we will consider an event period where loss associated with multiple time scales, and thus possibly different loss mechanisms was observed from 1000 - 1200 UT on 26 January 2013. At about 1005 UT on 26 January 2013 an injection of radiation belt electrons followed by drift echoes for energies of ˜80 - 400 keV. BARREL observed X-rays with energies less than 180 keV associated with multiple temporal structures during the drift echo event period. The Van Allen Probes were at similar L-values but upwards of 2 hours away in MLT. Upper band chorus and ULF waves were observed during the event period. Throughout the beginning of the event period, microbursts were clearly observed. During this time lower band chorus waves as well as time domain structures were observed at Van Allen Probe A located upwards of 2 hours away in MLT. This large difference in MLT meant that neither potential loss mechanism was able to be clearly associated with the microbursts. As the lower band chorus and time domain structures were observed to recede, the microbursts were also observed to subside. ULF time scale modulation of the X-rays was also observed throughout most of the event period. We will examine if the ULF waves are the cause of the precipitation themselves, or are modulating the loss of particles from a secondary loss mechanism [Brito et al 2015 JGR, Rae et al Submitted JGR]. Although the 100s ms and ULF time scales are clearly observed, there is an ˜20 minute

Spin and Magnetism: Two Transfer Matrix Formulations of a Classical Heisenberg Ring in a Magnetic Field.

DTIC Science & Technology

1998-06-01

determination of the partition function could be attempted. According to Gatteschi et al, however, [Ref. 15] when commenting on the quantum mechanical...1995 15. Gatteschi , D. et al, "Large Clusters of Metal Ions: The Transition from Molecular to Bulk Magnets" Science vol. 265, pp. 1054-1058, August... Gatteschi , D. et al, "Spin Dynamics in Mesoscopic Size Magnetic Systems... ", Phys. Rev. B, vol. 55, no. 21, 01 June, 1997 18. Tejeda, J. etal, "Quantum

Reduction of the field-aligned potential drop in the polar cap during large geomagnetic storms

NASA Astrophysics Data System (ADS)

Kitamura, N.; Seki, K.; Nishimura, Y.; Hori, T.; Terada, N.; Ono, T.; Strangeway, R. J.

2013-12-01

We have studied photoelectron flows and the inferred field-aligned potential drop in the polar cap during 5 large geomagnetic storms that occurred in the periods when the photoelectron observations in the polar cap were available near the apogee of the FAST satellite (~4000 km) at solar maximum, and the footprint of the satellite paths in the polar cap was under sunlit conditions most of the time. In contrast to the ~20 V potential drop during geomagnetically quiet periods at solar maximum identified by Kitamura et al. [JGR, 2012], the field-aligned potential drop frequently became smaller than ~5 V during the main and early recovery phases of the large geomagnetic storms. Because the potential acts to inhibit photoelectron escape, this result indicates that the corresponding acceleration of ions by the field-aligned potential drop in the polar cap and the lobe region is smaller during the main and early recovery phases of large geomagnetic storms compared to during geomagnetically quiet periods. Under small field-aligned current conditions, the number flux of outflowing ions should be nearly equal to the net escaping electron number flux. Since ions with large flux originating from the cusp/cleft ionosphere convect into the polar cap during geomagnetic storms [e.g., Kitamura et al., JGR, 2010], the net escaping electron number flux should increase to balance the enhanced ion outflows. The magnitude of the field-aligned potential drop would be reduced to let a larger fraction of photoelectrons escape.

9. First floor plan,published in 'Architectural Record',Vol 31,No. 4, April ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

9. First floor plan,published in 'Architectural Record',Vol 31,No. 4, April 1912,p 356,courtesy of the Art Institute of Chicago,permission to duplicate courtesy of'Architectural Record' - Chicago City Hall, 121 North LaSalle Street, Chicago, Cook County, IL

Chemistry Comes Alive! Vol. 3: Abstract of Special Issue 23 on CD-ROM

NASA Astrophysics Data System (ADS)

Jacobsen, Jerrold J.; Moore, John W.

1999-09-01

Literature Cited

1. Jacobsen, J. J.; Moore, J. W. Chemistry Comes Alive! Vol. 1 [CD-ROM]; J. Chem. Educ. Software 1998, SP 18.

2. Jacobsen, J. J.; Moore, J. W. Chemistry Comes Alive! Vol. 2 [CD-ROM]; J. Chem. Educ. Software 1998, SP 21.

3. Moore, J. W.; Jacobsen, J. J.; Hunsberger, L. R.; Gammon, S. D.; Jetzer, K. H.; Zimmerman, J. ChemDemos Videodisc; J. Chem. Educ. Software 1994, SP 8.

4. Moore, J. W.; Jacobsen, J. J.; Jetzer, K. H.; Gilbert, G.; Mattes, F.; Phillips, D.; Lisensky, G.; Zweerink, G. ChemDemos II; J. Chem. Educ. Software 1996, SP 14.

5. Jacobsen, J. J.; Jetzer, K. H.; Patani, N.; Zimmerman, J. Titration Techniques Videodisc; J. Chem. Educ. Software 1995, SP9.

The Electrical Impact of Lightning Quasi-Electrostatic Fields on the Nighttime Lower Ionosphere: The Case of Negative Sprite Halos

NASA Astrophysics Data System (ADS)

Salem, M. A.; Liu, N.; Rassoul, H.

2016-12-01

It is well known that electrostatic (ES) and quasi-electrostatic (QE) fields can be established in the lower ionosphere by underlying thunderstorms. We recently found that although the thunderstorm ES field is not strong enough to produce transient luminous events (TLEs) such as halos and sprites, it generates significant effects on the electrical properties of the nighttime lower ionosphere [Salem et al., GRL., 42(6), doi: 10.1002/2015GL063268, 2015; Salem et al., GRL., 43(1), doi: 10.1002/2015GL066933, 2016]. In particular, according to Salem et al. [2016], the nighttime lower ionospheric height measured using the VLF wave reflection technique can be increased due to the effects of the ES field. In this work, we continue to study the nighttime lower ionospheric response to QE fields of cloud-to-ground (CG) lightning flashes. In contrast to thunderstorm ES fields, QE fields can be much stronger and trigger halos. Halos are relatively homogeneous glows centered on 75-85 km altitude, with a horizontal extent of tens of kilometers and a vertical thickness of several kilometers. They typically appear within a few milliseconds of their parent CGs. In particular, negative halos are caused by unusually impulsive negative CGs [Boggs et al., JGR. Atmos., doi: 10.1002/2015JD024188, 121(2), 2016; Liu et al., GRL., 43(6), doi: 10.1002/2016GL068256, 2016]. This study uses a one-dimensional plasma discharge fluid model combined with a simplified ionospheric ion chemistry model described by Liu [JGR., 117, doi: 10.1029/2011JA017062, 2012]. The response of the nighttime lower ionosphere to impulsive negative CGs is investigated for different ambient ionospheric density profiles and different CG properties (e.g., charge moment changes and charge transfer times). Finally, the modeling results of the lower ionosphere recovery time are analyzed to investigate the role of negative halos in producing different types of early VLF events.

Semi-automatic measures of activity in selected south polar regions of Mars using morphological image analysis

NASA Astrophysics Data System (ADS)

Aye, Klaus-Michael; Portyankina, Ganna; Pommerol, Antoine; Thomas, Nicolas

results of these semi-automatically determined seasonal fan count evolutions for Inca City, Ithaca and Manhattan ROIs, compare these evolutionary patterns with each other and with surface reflectance evolutions of both HiRISE and CRISM for the same locations. References: Aye, K.-M. et. al. (2010), LPSC 2010, 2707 Hansen, C. et. al (2010) Icarus, 205, Issue 1, p. 283-295 Kieffer, H.H. (2007), JGR 112 Portyankina, G. et. al. (2010), Icarus, 205, Issue 1, p. 311-320 Thomas, N. et. Al. (2009), Vol. 4, EPSC2009-478

Reliability-Limiting Defects in GaN/AlGaN High Electron Mobility Transistors

DTIC Science & Technology

2011-12-01

GaN grown by plasma-assisted molecular beam epitaxy”, Appl. Phys. Lett., vol. 77, no. 18, pp. 2885- 2887, 2000. [24] A. Hierro , A. R. Arehart, B...defects and impurities: Applications to III-nitrides”, J. Appl. Phys., vol. 95, pp.3851-3879, 2004. [43] A. Hierro , S. A. Ringel, M. Hansen, J. S

1. Photocopied December 1977, from original in 'Report of J.B.J.,'Vol. ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

1. Photocopied December 1977, from original in 'Report of J.B.J.,'Vol. I, Jervis Library. ELEVATION OF SING SING KILL BRIDGE, SHOWING ORIGINAL PLAN FOR AN 80-FOOT ARCH. - Old Croton Aqueduct, Sing Sing Kill Bridge, Spanning Aqueduct Street & Broadway, Ossining, Westchester County, NY

Spectrometric Studies of Selected Nitrocompounds Using Laser-Induced Photofragmentation/Photoionization at 193 nm.

DTIC Science & Technology

1994-11-01

Hohmann, and Wehry (1987); Lee et al. (1992); Sausa, Alfano , and Miziolek (1987); Clark et al. (1992); Marshall et al. (1992); Oldenborg and Baughcum...enhanced excitation process of the metastable carbon atom via its well-known (Sausa, Alfano , and Miziolek 1987; D6bele and RUckle 1982, 1992) (2p3s 1P...Davis. Applied Optics, vol. 19, p. 3597, 1980. Sausa, R. C., A. J. Alfano , and A. W. Miziolek. Applied Optics, vol. 26, p. 3588, 1987. 15 Schendel, J

Overview of Lockheed Martin cryocoolers

NASA Astrophysics Data System (ADS)

Nast, T.; Olson, J.; Champagne, P.; Evtimov, B.; Frank, D.; Roth, E.; Renna, T.

2006-02-01

Lockheed Martin's Advanced Technology Center (LM-ATC) in Palo Alto, California, has been active in space cryogenic developments for over 30 years. In prior years, work focused on stored cryogen systems for temperatures up to 125 K. As the mechanical cryocoolers matured and demonstrated reliable operation these stored cryogen systems gradually became replaced. LM-ATC is currently developing solid hydrogen systems for temperatures below 7 K [Naes L, Wu S, Cannon J. WISE solid hydrogen cryostat design overview. In: Proceedings of SPIE, cryogenic optical systems and instruments XI, vol. 5904, August, 2005], but these coolers will soon be replaced by mechanical cryocoolers. This paper will present a summary of cryocooler developments at LM-ATC and will describe the recent performance of multiple stage systems. A four-stage pulse tube cryocooler developed under contract to the Jet Propulsion Laboratory (JPL) has been recently developed and operated at 3.8 K [Olson JR, Moore M, Champagne P, Roth E, Evtimov B, Jensen J, et al. Development of a space-type-4-stage pulse tube cryocooler for very low temperatures, Adv Cryogen Engr, vol. 50, Amer Inst of Physics, New York, in press]. Coolers with one, two and three stages have also been widely developed [Nast TC et al. Miniature pulse tube cryocooler for space applications. Cryocoolers, vol. 11. New York: Plenum Press; 2000. p. 145-54; Olson J et al. Development of a 10 K pulse tube cryocooler for space applications. In: Ross R, editor. Cryocoolers, vol. 12. New York: Kluwer Academic/Plenum Publishers; 2003. p. 241-6; Nast TC et al. Lockheed Martin two-stage pulse tube cryocooler for GIFTS. Cryocoolers, vol. 13. New York: Kluwer Academic/Plenum Publishers; 2005; Frank D et al. Lockheed Martin RAMOS engineering model cryocooler. Cryocoolers, vol. 13. New York: Kluwer Academic/Plenum Publishers; 2005]. A staging approach is required to achieve very low temperatures, and also provides cooling at warmer temperatures, which is

Study the effect of mechanical alloying parameters on synthesis of Cr{sub 2}Nb–Al{sub 2}O{sub 3} nanocomposite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shayesteh, Payam, E-mail: shayesteh.payam@gmail.com; Mirdamadi, Shamseddin; Razavi, Hossein

2014-01-01

Graphical abstract: - Highlights: • Cr{sub 2}Nb–Al{sub 2}O{sub 3} nanocomposite synthesized through MA. • Effect of BPR, rotating speed, milling time and PCA concentration investigated. • After annealing at 1100 °C crystalline phase were appeared. • Williamson–Hall analysis was used in order to study the grain size of nano composite. - Abstract: In this study, Cr{sub 2}Nb–20 vol.% Al{sub 2}O{sub 3} nanocomposite was prepared successfully by mechanochemical reaction between Al, Nb and Cr{sub 2}O{sub 3} powders. Amorphization of powder occurred during mechanical alloying because of high energy collisions between powders and steel balls in milling container which transfer high degreemore » of energy to powders. Therefore, annealing was needed to form crystalline phases. The influence of different mechanical alloying parameters such as BPR, rotating speed, milling time and PCA concentration on synthesis of composite material were investigated. After mechanical alloying, the powder was encapsulated in quartz and then annealed at 1100 °C for 3 h. After annealing, 3 different phases were appeared (Cr{sub 2}Nb (cubic), Cr{sub 2}Nb (hexagonal) and α-Al{sub 2}O{sub 3}). The structural changes of powder particles during mechanical alloying were studied by X-ray diffractometry (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM)« less

Synthesizing (ZrAl3 + AlN)/Mg-Al composites by a 'matrix exchange' method

NASA Astrophysics Data System (ADS)

Gao, Tong; Li, Zengqiang; Hu, Kaiqi; Han, Mengxia; Liu, Xiangfa

2018-06-01

A method named 'matrix exchange' to synthesize ZrAl3 and AlN reinforced Mg-Al composite was developed in this paper. By inserting Al-10ZrN master alloy into Mg matrix and reheating the cooled ingot to 550 °C, Al and Mg atoms diffuse to the opposite side. As a result, liquid melt occurs once the interface areas reach to proper compositions. Then dissolved Al atoms react with ZrN, leading to the in-situ formation of ZrAl3 and AlN particles, while the Al matrix is finally replaced by Mg. This study provides a new insight for preparing Mg composites.

Experimental investigation of convective heat transfer agumentation using Al2O3/water nanofluid in circular pipe

NASA Astrophysics Data System (ADS)

Chavan, Durgeshkumar; Pise, Ashok T.

2015-09-01

In the present paper, experimental study is performed to investigate convective heat transfer and flow characteristics of nanofluids through a circular tube. The heat transfer coefficient and friction factor of the γ-Al2O3-water nanofluid flowing through a pipe of 10 mm inner ID and 1 m in length, with constant wall temperature under turbulent flow conditions are investigated. Experiments are conducted with 30 nm size γ-Al2O3 nanoparticle with a volume fraction between 0.1 and to 1.0 and Reynolds number between 8,000 and 14,000. Experimental results emphasize the heat transfer enhancement with the increase in a Reynolds number or nanoparticle volume fraction. The maximum enhancement of 36 % in the heat transfer coefficient for a Reynolds number of 8,550, by using nanofluid with 1.0 vol% was observed compared with base fluid. Experimental measurement also shows the considerable increase in the pressure drop with small addition of nanoparticles in base fluid. Experimental results of nanofluids were compared with existing convective heat transfer correlations in the turbulent regime. Comparison shows that Maiga's correlation has close agreement with experimental results in comparison with Dittus Boelter correlation.

AGARD Flight Test Techniques Series. Volume 18. Flight Testing of Radio Navigation Systems. (Les Essais en Vol des Systemes de Radionavigation)

DTIC Science & Technology

2000-04-01

18 Flight Testing of Radio Navigation Systems (les Essais en vol des systemes de radionavigation) This AGARDograph has been sponsored by the Systems...Techniques Series - Volume 18 Flight Testing of Radio Navigation Systems (les Essais en vol des syst~mes de radionavigation) Edited by H. Bothe H.J...Landing Test and Other Short-Range 19853 Applications by P. de Benquoe D’Agut, H. Rieheek and A. Pool 17. Analogue Signal Conditioning for Flight Test

The feasibility of a scanner-independent technique to estimate organ dose from MDCT scans: Using CTDI{sub vol} to account for differences between scanners

DOE Office of Scientific and Technical Information (OSTI.GOV)

Turner, Adam C.; Zankl, Maria; DeMarco, John J.

2010-04-15

Purpose: Monte Carlo radiation transport techniques have made it possible to accurately estimate the radiation dose to radiosensitive organs in patient models from scans performed with modern multidetector row computed tomography (MDCT) scanners. However, there is considerable variation in organ doses across scanners, even when similar acquisition conditions are used. The purpose of this study was to investigate the feasibility of a technique to estimate organ doses that would be scanner independent. This was accomplished by assessing the ability of CTDI{sub vol} measurements to account for differences in MDCT scanners that lead to organ dose differences. Methods: Monte Carlo simulationsmore » of 64-slice MDCT scanners from each of the four major manufacturers were performed. An adult female patient model from the GSF family of voxelized phantoms was used in which all ICRP Publication 103 radiosensitive organs were identified. A 120 kVp, full-body helical scan with a pitch of 1 was simulated for each scanner using similar scan protocols across scanners. From each simulated scan, the radiation dose to each organ was obtained on a per mA s basis (mGy/mA s). In addition, CTDI{sub vol} values were obtained from each scanner for the selected scan parameters. Then, to demonstrate the feasibility of generating organ dose estimates from scanner-independent coefficients, the simulated organ dose values resulting from each scanner were normalized by the CTDI{sub vol} value for those acquisition conditions. Results: CTDI{sub vol} values across scanners showed considerable variation as the coefficient of variation (CoV) across scanners was 34.1%. The simulated patient scans also demonstrated considerable differences in organ dose values, which varied by up to a factor of approximately 2 between some of the scanners. The CoV across scanners for the simulated organ doses ranged from 26.7% (for the adrenals) to 37.7% (for the thyroid), with a mean CoV of 31.5% across all organs

Exploring Subsurface Geology Using Radar Techniques: Experiments in Sahara and Consequences for Mars Exploration

NASA Astrophysics Data System (ADS)

Paillou, P.; Grandjean, G.; Heggy, E.; Farr, T.

2004-05-01

For several years, we have conducted a quantitative study of radar penetration performances in various desert arid environments. This study combines both SAR (Synthetic Aperture Radar) imaging from orbital and airborne platforms and in situ GPR (Ground Penetrating Radar) measurements. Laboratory characterization of various minerals and rocks are used as input to electromagnetic models such as IEM (Integral Equation Model) and FDTD (Finite Difference Time Domain) that describe the subsurface scattering process for inversion purposes. Several test sites were explored, mainly the Sahara. Our first experiment was realized in Republic of Djibouti, an arid volcanic area which is a good analog to Mars. We observed a very little radar penetration there because of the presence of iron oxides and salts in the subsurface that make the soil conductive [Paillou et al., GRL, 2001]. A more favorable site for radar penetration was then explored in southern Egypt: the Bir Safsaf area where buried river channels were discovered using orbital SAR images. We showed how to combine SAR and GPR in order to obtain a complete description of subsurface geology down to several meters [Paillou et al., IEEE TGRS, 2003]. Such field experiments were the basis for more systematic laboratory measurements of the electromagnetic properties of various rocks and minerals which were used in numerical models in order to simulate the performances of future Martian radars, e.g. MARSIS and NETLANDER low frequency radars [Heggy et al., Icarus, 2001; Berthelier et al., JGR, 2003; Heggy et al., JGR, 2003]. More recently, new explorations were conducted in Mauritania in order to demonstrate radar capacities for geologic mapping [Grandjean et al., Coll. Afr. Geol., 2004] and in Libya where radar discovered a double impact crater in the southern desert [Paillou et al., C.R. Geoscience, 2003]. More local radar experiments were also conducted on a test site located in France, the Pyla sand dune, where we observed

A method for measuring enthalpy of volatilization of a compound, Delta(vol)H, from dilute aqueous solution.

PubMed

Wang, Tianshu

2006-01-01

This study has developed a method for measuring the enthalpy of volatilization (Delta(vol)H) of a compound in a dilute solution via ion-molecule reactions and gas-phase analysis using selected ion flow tube mass spectrometry (SIFT-MS). The Delta(vol)H/R value was obtained using an equation with three variant forms either from the headspace concentration of the solution or from individual product ion(s). Under certain experimental conditions, the equation has the simplest form [formula: see text], where R is the gas constant (8.314 J . mol(-1) . K(-1)), i(n) and I are the respective product and precursor ion count rates, and T is the temperature of the solution. As an example, a series of 27.0 micromol/L aqueous solutions of acetone was analyzed over a temperature range of 25-50 degrees C at 5 degrees C intervals using H3O+, NO+ and O2+* precursor ions, producing a mean Delta(vol)H/R value of 4700 +/- 200 K. This corresponds with current literature values and supports the consistency of the new method. Notably, using this method, as long as the concentration of the solution falls into the range of Henry's law, the exact concentration does not have to be known and it can require only one sample at each temperature. Compared with previous methods which involve the measurement of Henry's law constant at each temperature, this method significantly reduces the number of samples required and avoids the labour and difficulties in preparing standard solutions at very low concentrations. Further to this, if the contents of a solution were unknown the measured Delta(vol)H/R from individual product ion(s) can help to identify the origin of the ion(s). Copyright 2006 John Wiley & Sons, Ltd.

Spectral heterogeneity on Phobos and Deimos: HiRISE observations and comparisons to Mars Pathfinder results

USGS Publications Warehouse

Thomas, N.; Stelter, R.; Ivanov, A.; Bridges, N.T.; Herkenhoff, K. E.; McEwen, A.S.

2011-01-01

The High-Resolution Imaging Science Experiment (HiRISE) onboard Mars Reconnaissance Orbiter (MRO) has been used to observe Phobos and Deimos at spatial scales of around 6 and 20 m/px, respectively. HiRISE (McEwen et al.; JGR, 112, CiteID E05S02, DOI: 10.1029/2005JE002605, 2007) has provided, for the first time, high-resolution colour images of the surfaces of the Martian moons. When processed, by the production of colour ratio images for example, the data show considerable small-scale heterogeneity, which might be attributable to fresh impacts exposing different materials otherwise largely hidden by a homogenous regolith. The bluer material that is draped over the south-eastern rim of the largest crater on Phobos, Stickney, has been perforated by an impact to reveal redder material and must therefore be relatively thin. A fresh impact with dark crater rays has been identified. Previously identified mass-wasting features in Stickney and Limtoc craters stand out strongly in colour. The interior deposits in Stickney appear more inhomogeneous than previously suspected. Several other local colour variations are also evident. Deimos is more uniform in colour but does show some small-scale inhomogeneity. The bright streamers (Thomas et al.; Icarus, 123, 536556,1996) are relatively blue. One crater to the south-west of Voltaire and its surroundings appear quite strongly reddened with respect to the rest of the surface. The reddening of the surroundings may be the result of ejecta from this impact. The spectral gradients at optical wavelengths observed for both Phobos and Deimos are quantitatively in good agreement with those found by unresolved photometric observations made by the Imager for Mars Pathfinder (IMP; Thomas et al.; JGR, 104, 90559068, 1999). The spectral gradients of the blue and red units on Phobos bracket the results from IMP. ?? 2010 Elsevier Ltd. All rights reserved.

Origin and Constraints on Ilmenite-rich Partial Melt in the Lunar Lower Mantle

NASA Astrophysics Data System (ADS)

Mallik, A.; Fuqua, H.; Bremner, P. M.; Panovska, S.; Diamond, M. R.; Lock, S. J.; Nishikawa, Y.; Jiménez-Pérez, H.; Shahar, A.; Panero, W. R.; Lognonne, P. H.; Faul, U.

2015-12-01

Existence of a partially molten layer at the lunar core-mantle boundary has been proposed to explain the lack of observed far-side deep moonquakes, the observation of reflected seismic phases from deep moonquakes, and the dissipation of tidal energy within the lunar interior [1,2]. However, subsequent models explored the possibility that dissipation due to elevated temperatures alone can explain the observed dissipation factor (Q) and tidal love numbers [3]. Using thermo-chemical and dynamic modeling (including models of the early lunar mantle convection), we explore the hypothesis that an ilmenite-rich layer forms below crustal anorthosite during lunar magma ocean crystallization and may sink to the base of the mantle to create a partial melt layer at the lunar core-mantle boundary. Self-consistent physical parameters (including gravity, pressure, density, VP and Vs) are forward calculated for a well-mixed mantle with uniform bulk composition versus a mantle with preserved mineralogical stratigraphy from lunar magma ocean crystallization. These parameters are compared against observed mass, moment of inertia, real and imaginary parts of the Love numbers, and seismic travel times to further limit the acceptable models for the Moon. We have performed a multi-step grid search with over twenty thousand forward calculations varying thicknesses of chemically/mineralogically distinct layers within the Moon to evaluate if a partially molten layer at the base of the lunar mantle is well-constrained by the observed data. Furthermore, dynamic mantle modeling was employed on the best-fit model versions to determine the survivability of a partially molten layer at the core-mantle boundary. This work was originally initiated at the CIDER 2014 program. [1] Weber et al. (2011). Science 331(6015), 309-12. [2] Khan et al. (2014). JGR 119. [3] Nimmo et al. (2012). JGR 117, 1-11.

Young Lunar Volcanic Features: How Did They Form?

NASA Astrophysics Data System (ADS)

Elder, Catherine; Hayne, Paul O.; Donaldson Hanna, Kerri; Bandfield, Joshua; Ghent, Rebecca; Williams, Jean-Pierre; Paige, David A.

2016-10-01

Irregular mare patches (IMPs) on the Moon are younger than 100 Myr [1, 2], but their formation mechanism is unknown. Previous work has suggested caldera collapse [3], explosive outgassing [2], pyroclastic eruptions [4], basaltic lava flows [1, 5], and regolith drainage into graben [6]. Here we present observations from the Lunar Reconnaissance Orbiter (LRO) Diviner thermal radiometer of the four largest IMPs. These observations suggest that the surfaces of the IMPs are on average only slightly rockier than the surrounding regolith. The nighttime cooling curves of the IMPs and the surrounding regolith do not intersect, which suggests that there is no layering in the top 5-10 cm of the IMPs. We also measure the thermal inertia (parameterized through the "H-parameter" [7]) of the IMPs. We find that the thermal inertia of Sosigenes is higher than that of the surrounding regolith (probably due to mass wasting), the thermal inertia of Cauchy-5 and Maskelyne is not significantly different from the surrounding regolith, and the thermal inertia of the largest smooth mound in Ina is significantly lower than the surrounding regolith. Only some IMPs are in topographic depressions or associated with graben, so neither caldera collapse nor drainage into graben can explain the formation of all IMPs. It is unlikely that basaltic lava flows would lead to a thermal inertia lower than that of lunar regolith. Therefore, of the formation mechanisms proposed to date, pyroclastic eruptions or another type of explosive outgassing [e.g. 2] possibly accompanied by basaltic lava flows or drainage into graben best explain the available observations of IMPs.[1] Braden, S. et al. (2014) Nature Geo 7, 787-791. [2] Schultz, P. H. et al. (2006) Nature 444, 184-186. [3] El-Baz, F. (1973) Apollo 17: Preliminary Science Report 330, 30-13. [4] Carter, L. B. et al. (2013) LPSC 44, 2146. [5] Garry, W. B. et al. (2012) JGR 117, E00H31. [6] Qiao, L. et al. (2002) LPSC 47, 2002. [7] Vasavada, A. R. et al

On the usefulness of optical maturity for relative age classification of fresh craters

NASA Astrophysics Data System (ADS)

Ravi, S.; Meyer, H. M.; Mahanti, P.; Robinson, M. S.

2016-12-01

Copernican and Eratosthenian craters represent the two most recent geologic periods in the lunar timescale, and their characterization is essential for understanding impact crater flux over the last 3 Gy. Craters from both periods exhibit crisp morphologies, but Copernican craters are 'rayed craters' per Wilhelms (1) classification scheme. Distinguishing compositional from maturity rays is possible using compositional estimates and the optical maturity parameter (OMAT; 2). From OMAT estimates, Grier et al. (3) classified 50 fresh craters (diameter (D) > 20 km) into young (OMAT > 0.22), intermediate, and old (OMAT < 0.16) classes. In this work we analyze morphology and optical maturity for a population of 12,000 craters (D> 10 km; 60 to investigate the applicability of OMAT for relative age classification among Copernican craters. Craters obtained from (4,5) were initially classified based on crispness of morphology (LROC WAC observations (6)) and then were then analyzed based on OMAT values averaged from rim out to one crater radius (n=2000). We found that typically craters larger than Copernicus (D = 95 km) were had lower OMAT values than Copernicus (OMAT = 0.17) except for Vavilov, Pythagorus, Fizeau and Moretus which had OMAT > 0.17. These large craters are clearly affected by rays from small, nearby craters. We estimate that at least 250 craters (D > 10 km; OMAT > 0.22) on the Moon are Copernican (> 2% of all craters analyzed) and of these at least 100 are as optically immature (or more so) than Tycho crater (OMAT >= 0.24). A calibration curve (OMAT vs Absolute Model Age) obtained for craters with known ages showed that OMAT <=0.15 displays little change with AMA and are thus unsuitable for estimating relative ages. Normalization by crater size was found to reduce the uncertainty associated with the relation between AMA and OMAT. 1) Wilhelms (1987), The Geologic History of the Moon, USGS, pp. 1348. 2) Lucey et al (2000), JGR, 105, 20377-20386. 3) Grier et al

Implications for Titan's potentially active regions: A study on Cassini/VIMS data.

NASA Astrophysics Data System (ADS)

Solomonidou, Anezina; Coustenis, Athena; Rodriguez, Sebastien; Bratsolis, Emmanuel; Le Mouelic, Stephane; Sotin, Christophe; Bampasidis, Georgios; Kyriakopoulos, Konstantinos; Moussas, Xenophon

Continuing investigations of Titan's surface have shown that this Earth-like Saturnian satellite presents an extremely complex geology [1, 2, 3]. The Cassini Mission Visual and Infrared Mapping Spectrometer (VIMS) acquires data operating as a multi-spectral camera that allow for a complete analysis of the composition, geology and morphology of Titan's surface [4]. Two of the most geologically interesting areas on Titan are Xanadu's Tui Regio (20S, 130W) and Hotei Regio (26S, 78W) as they present higher 5m reflectivities than the surrounding areas [5] and have been interpreted as cryovolcanic in origin [6]. We present our study on both possibly active regions with the aim to identify the composition as well as the alterations of the components that compose the possible calderas and lava flows [7], by using radiative transfer modeling [8] and a classical staitistical method, the Principal Component Analysis [9]. [1] Jaumann, R. et al., (2009) Springer Netherlands pp. 75-140. [2] Nelson, R. M. et al., (2009) Icarus 199, 429-441. [3] Solomonidou, A. et al., (2009) European Planetary Science Congress Vol. 4, EPSC2009-710. [4] Jaumann, R. et al., (2006) Planet Space Science 54:1146-1155. [5] Barnes, J. W. et al., (2006) Geophysical Research Letters Vol. 33, L16204. [6] Lopes, R. M. C. et al., (2010) Icarus Vol. 205 pp:540-558. [7] Sotin, C. (2005) Nature, Vol 435. [8] Rodriguez, S. et al., (2009) Workshop on Hyperspectral Image and Signal Processing: Evolution on Remore Sensing pp. 1-4. [9] Bellucci, G. et al., (2004) Advances in Space Research 34 pp. 1640-1646.

The Bulletin of Military Operations Research, PHALANX, Vol. 31, No. 2.

DTIC Science & Technology

1998-06-01

introduction of the Pentium II processor, the writeable CD, and the Digital Video Disc (DVD). Just around the corner, around the turn of the century...broader audi- ence. Presentations that use special visual aids ( videos , computers, etc.), short presen- tations best depicted with color charts...Throughout the treatment of data, anoth- er weapon we should take is Tukey’s Tor- pedo (John W. Tukey, "Sunset Salvo," The American Statistician, vol

Problems of Construction of Black Holes and Traversed Wormholes in Various Theories of Gravity

NASA Astrophysics Data System (ADS)

Karbanovski, Valeri; Kairov, Taimuraz.; Melehina, Olga

In the framework of general relativity found new vacuum solutions [1,2] for the spherically symmetric non-static metrics as a constant source ("dynamic analog" gravitational radius), and a source in the form of time-dependent functions. In the latter case, the conditions for a smooth cross-linking with the original static metric. Within Post-Einstein theory of gravitation (PETG, [3]), is consider the variant with zero scalar curvature of space-time is considered. Found external solutions for spherically symmetric objects that allow a smooth stitching at distances slightly exceeding the gravitational radius of the source. We also show that in the studied approach the traversable vacuum wormholes can not be realized. In the theory of gravity with vacuum polarization (TGVP, [4]) built vacuum static spherically symmetric nonsingular solutions. At this the "polarization effects" appear only under the gravitational radius of the source. Also obtained metric describing the vacuum traversable wormhole. References begin{enumerate} Karbanovski V.V. et. al. - JETP, 2012, Vol. 115, No. 2, pp. 208-211. Karbanovski V.V. et. al. - JETP, 2012, Vol. 115, No. 4, pp. 733. Karbanovski V.V. et. al. - Class. Quantum Grav., 2012, Vol. 29, No. 6, 065007. Karbanovski V.V. et. al. - Acta Phys. Pol. B, 2011, Vol. 42, No.1, p. 171.

The Model Intercomparison Project on the Climatic Response to Volcanic Forcing (VolMIP): Experimental Design and Forcing Input Data for CMIP6

NASA Technical Reports Server (NTRS)

Zanchettin, Davide; Khodri, Myriam; Timmreck, Claudia; Toohey, Matthew; Schmidt, Anja; Gerber, Edwin P.; Hegerl, Gabriele; Robock, Alan; Pausata, Francesco; Ball, William T.;

Multi-scale Characterization and Modeling of Surface Slope Probability Distribution for ~20-km Diameter Lunar Craters

NASA Astrophysics Data System (ADS)

Mahanti, P.; Robinson, M. S.; Boyd, A. K.

2013-12-01

computed over multiple scales. This slope analysis showed that local slope distributions are non-Gaussian for both crater walls and floors. Over larger baselines (~100 meters), crater wall slope probability distributions do approximate Gaussian distributions better, but have long distribution tails. Crater floor probability distributions however, were always asymmetric (for the baseline scales analyzed) and less affected by baseline scale variations. Accordingly, our results suggest that use of long tailed probability distributions (like Cauchy) and a baseline-dependant multi-scale model can be more effective in describing the slope statistics for lunar topography. Refrences: [1]Moore, H.(1971), JGR,75(11) [2]Marcus, A. H.(1969),JGR,74 (22).[3]R.J. Pike (1970),U.S. Geological Survey Working Paper [4]N. C. Costes, J. E. Farmer and E. B. George (1972),NASA Technical Report TR R-401 [5]M. N. Parker and G. L. Tyler(1973), Radio Science, 8(3),177-184 [6]Alekseev, V. A.et al (1968), Soviet Astronomy, Vol. 11, p.860 [7]Burns et al. (2012) Int. Arch. Photogramm. Remote Sens. Spatial Inf. Sci., XXXIX-B4, 483-488.[8]Smith et al. (2010) GRL 37, L18204, DOI: 10.1029/2010GL043751. [9]Wagner R., Robinson, M., Speyerer E., Mahanti, P., LPSC 2013, #2924.

Magnetism of Al-substituted magnetite reduced from Al-hematite

NASA Astrophysics Data System (ADS)

Jiang, Zhaoxia; Liu, Qingsong; Zhao, Xiang; Roberts, Andrew P.; Heslop, David; Barrón, Vidal; Torrent, José

2016-06-01

Aluminum-substituted magnetite (Al-magnetite) reduced from Al-substituted hematite or goethite (Al-hematite or Al-goethite) is an environmentally important constituent of magnetically enhanced soils. In order to characterize the magnetic properties of Al-magnetite, two series of Al-magnetite samples were synthesized through reduction of Al-hematite by a mixed gas (80% CO2 and 20% CO) at 395°C for 72 h in a quartz tube furnace. Al-magnetite samples inherited the morphology of their parent Al-hematite samples, but only those transformed from Al-hematite synthesized at low temperature possessed surficial micropores, which originated from the release of structural water during heating. Surface micropores could thus serve as a practical fingerprint of fire or other high-temperature mineralogical alteration processes in natural environments, e.g., shear friction in seismic zones. In addition, Al substitution greatly affects the magnetic properties of Al-magnetite. For example, coercivity (Bc) increases with increasing Al content and then decreases slightly, while the saturation magnetization (Ms), Curie temperature (Tc), and Verwey transition temperature (Tv) all decrease with increasing Al content due to crystal defect formation and dilution of magnetic ions caused by Al incorporation. Moreover, different trends in the correlation between Tc and Bc can be used to discriminate titanomagnetite from Al-magnetite, which is likely to be important in environmental and paleomagnetic studies, particularly in soil.

Harnessing Post-Conflict Transitions: A Conceptual Primer

DTIC Science & Technology

2010-09-01

aid community uses transition as a key indi- cator of success for development and aid programs (Cliffe et al., 2003; Crane et al., 2009; Crichton ...3, pp. 345-365. Barnett, M ., (2006), “Building a republican peace: Stabilizing states after war,” International Security, Vol. 30, No. 4, pp. 87-112...Security, Vol. 29, No. 4, pp. 157-195. Berdal, M . R., (2009), Building Peace After War, Abingdon, UK; New York; London, UK: Routledge: International

Water content in the SW USA mantle lithosphere: FTIR analysis of Dish Hill and Kilbourne Hole pyroxenites

NASA Astrophysics Data System (ADS)

Gibler, R.; Peslier, A. H.; Schaffer, L. A.; Brandon, A. D.

2014-12-01

Kilbourne Hole (NM, USA) and Dish Hill (CA, USA) mantle xenoliths sample continental mantle in two different tectonic settings. Kilbourne Hole (KH) is located in the Rio Grande rift. Dish Hill (DH) is located in the southern Mojave province, an area potentially affected by subduction of the Farallon plate beneath North America [1]. FTIR analyses were obtained on well characterized pyroxenite, dunite and wehrlite xenoliths, thought to represent crystallized melts at mantle depths. PUM normalized REE patterns of the KH bulk-rocks are slightly LREE enriched and consistent with those of liquids generated by < 5% melting of a spinel peridotite source [2]. Clinopyroxenes contain from 272 to 313 ppm weight H2O similar to the lower limit of KH peridotite clinopyroxenes (250-530 ppm H2O, [3]). This is unexpected as crystallized melts like pyroxenites should concentrate water more than residual mantle-like peridotites, given that H is incompatible. PUM normalized bulk REE of the DH pyroxenites are characterized by flat to LREE depleted REE profiles consistent with > 6% melting of a spinel peridotite source. Pyroxenite pyroxenes have no detectable water but one DH wehrlite, which bulk-rock is LREE enriched, has 4 ppm H2O in orthopyroxene and <1ppm in clinopyroxene. The DH pyroxenites may thus come from a dry mantle source, potentially unaffected by the subduction of the Farallon plate. These water-poor melts either originated from shallow oceanic lithosphere overlaying the Farallon slab [4] or from continental mantle formed > 2 Ga [5]. The Farallon subduction appears to have enriched in water the southwestern United States lithospheric mantle further east than DH, beneath the Colorado plateau [6]. [1] Atwater, 1970 Tectonophysics 31, 145-165. [2] Shaw, 2000 CM 38, 1041-1064. [3] Schaffer et al, 2013 AGU Fall Meeting. [4] Luffi et al, 2009 JGR 114, 1-36. [5] Armytage et al, 2013 GCA 137, 113-133. [6] Li et al, 2008 JGR 113, 1-22.

Influence of Porosity on Mechanical Properties and In vivo Response of Ti6Al4V Implants

PubMed Central

Bandyopadhyay, Amit; Espana, Felix; Balla, Vamsi Krishna; Bose, Susmita; Ohgami, Yusuke; Davies, Neal M

2009-01-01

Metallic biomaterials are widely used to restore the lost structure and functions of human bone. Due to the large number of joint replacements, there is a growing demand for new and improved orthopedic implants. More specifically, there is a need for novel load bearing metallic implants with low effective modulus matching to that of bone in order to reduce stress shielding and consequent increase in the in vivo life-span of the implant. In this study, we have fabricated porous Ti6Al4V alloy structures, using Laser Engineered Net Shaping (LENS™) to demonstrate that advanced manufacturing techniques such as LENS™ can be used to fabricate low-modulus, tailored porosity implants with a wide variety of metals/alloys, where the porosity can be designed in areas based on the patient's need to enhance biological fixation and achieve long-term in vivo stability. The effective modulus of Ti6Al4V alloy structures has been tailored between 7 and 60 GPa and porous Ti alloy structures containing 23 to 32 vol. % porosity showed modulus equivalent to human cortical bone. In vivo behavior of porous Ti6Al4V alloy samples in male Sprague-Dawley rats for 16 weeks demonstrated significant increase in calcium within the implants indicating excellent biological tissue ingrowth through interconnected porosity. In vivo results also showed that total amount of porosity plays an important role in tissue ingrowth. PMID:19913643

Familial ALS

PubMed Central

Boylan, Kevin

2015-01-01

Synopsis Genes linked to ALS susceptibility are being identified at an increasing rate owing to advances in molecular genetic technology. Genetic mechanisms in ALS pathogenesis appear to exert major effects in ~10% of patients, but genetic factors at some level may be important components of disease risk in most ALS patients. Identification of gene variants associated with ALS has informed concepts of the pathogenesis of ALS, aided the identification of therapeutic targets, facilitated research to develop new ALS biomarkers, and supported the establishment of clinical diagnostic tests for ALS-linked genes. Translation of this knowledge to ALS therapy development is ongoing. PMID:26515623

Ab initio modeling of zincblende AlN layer in Al-AlN-TiN multilayers

DOE PAGES

Yadav, S. K.; Wang, J.; Liu, X. -Y.

2016-06-13

An unusual growth mechanism of metastable zincblende AlN thin film by diffusion of nitrogen atoms into Al lattice is established. Using first-principles density functional theory, we studied the possibility of thermodynamic stability of AlN as a zincblende phase due to epitaxial strains and interface effect, which fails to explain the formation of zincblende AlN. We then compared the formation energetics of rocksalt and zincblende AlN in fcc Al through direct diffusion of nitrogen atoms to Al octahedral and tetrahedral interstitials. Furthermore, the formation of a zincblende AlN thin film is determined to be a kinetically driven process, not a thermodynamicallymore » driven process.« less

Interfacial characterization of Al-Al thermocompression bonds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Malik, N., E-mail: nishantmalik1987@gmail.com; SINTEF ICT, Department of Microsystems and Nanotechnology, P.O. Box 124 Blindern, N-0314 Oslo; Carvalho, P. A.

2016-05-28

Interfaces formed by Al-Al thermocompression bonding were studied by the transmission electron microscopy. Si wafer pairs having patterned bonding frames were bonded using Al films deposited on Si or SiO{sub 2} as intermediate bonding media. A bond force of 36 or 60 kN at bonding temperatures ranging from 400–550 °C was applied for a duration of 60 min. Differences in the bonded interfaces of 200 μm wide sealing frames were investigated. It was observed that the interface had voids for bonding with 36 kN at 400 °C for Al deposited both on Si and on SiO{sub 2}. However, the dicing yield was 33% for Al onmore » Si and 98% for Al on SiO{sub 2}, attesting for the higher quality of the latter bonds. Both a bond force of 60 kN applied at 400 °C and a bond force of 36 kN applied at 550 °C resulted in completely bonded frames with dicing yields of, respectively, 100% and 96%. A high density of long dislocations in the Al grains was observed for the 60 kN case, while the higher temperature resulted in grain boundary rotation away from the original Al-Al interface towards more stable configurations. Possible bonding mechanisms and reasons for the large difference in bonding quality of the Al films deposited on Si or SiO{sub 2} are discussed.« less

Identification des parametres du moteur de l'avion Cessna Citation X pour la phase de croisiere a partir des tests en vol et a base des reseaux de neurones =

NASA Astrophysics Data System (ADS)

Zaag, Mahdi

La disponibilite des modeles precis des avions est parmi les elements cles permettant d'assurer leurs ameliorations. Ces modeles servent a ameliorer les commandes de vol et de concevoir de nouveaux systemes aerodynamiques pour la conception des ailes deformables des avions. Ce projet consiste a concevoir un systeme d'identification de certains parametres du modele du moteur de l'avion d'affaires americain Cessna Citation X pour la phase de croisiere a partir des essais en vol. Ces essais ont ete effectues sur le simulateur de vol concu et fabrique par CAE Inc. qui possede le niveau D de la dynamique de vol. En effet, le niveau D est le plus haut niveau de precision donne par l'autorite federale de reglementation FAA de l'aviation civile aux Etats-Unis. Une methodologie basee sur les reseaux de neurones optimises a l'aide d'un algorithme intitule le "grand deluge etendu" est utilisee dans la conception de ce systeme d'identification. Plusieurs tests de vol pour differentes altitudes et differents nombres de Mach ont ete realises afin de s'en servir comme bases de donnees pour l'apprentissage des reseaux de neurones. La validation de ce modele a ete realisee a l'aide des donnees du simulateur. Malgre la nonlinearite et la complexite du systeme, les parametres du moteur ont ete tres bien predits pour une enveloppe de vol determinee. Ce modele estime pourrait etre utilise pour des analyses de fonctionnement du moteur et pourrait assurer le controle de l'avion pendant cette phase de croisiere. L'identification des parametres du moteur pourrait etre realisee aussi pour les autres phases de montee et de descente afin d'obtenir son modele complet pour toute l'enveloppe du vol de l'avion Cessna Citation X (montee, croisiere, descente). Cette methode employee dans ce travail pourrait aussi etre efficace pour realiser un modele pour l'identification des coefficients aerodynamiques du meme avion a partir toujours des essais en vol. None None None

A review of porosity-generating mechanisms in crustal shear zones

NASA Astrophysics Data System (ADS)

Fusseis, F.; Regenauer-Lieb, K.; Revets, S.

2009-04-01

seems reasonable to assume that the total porosity in shear zones is the sum of porosities generated by all of these mechanisms, and that the individual porosities have different effects on permeability. We propose that a fundamental understanding of the porosity evolution in a shear zone can be derived from an assessment of the stress-temperature-fluid/rock chemistry-time path during the tectonometamorphic history of a rock. In this contribution we present a first evaluation of typical porosity-permeability evolutions. We furthermore present a new generation of numerical experiments that allows the quantitative assessment of the roles of the thermal, chemical and mechanical generation of porosity and their feedbacks on the evolution of shear zones. References: Baumgartner et al., 1997, in Jamtveit & Yardley, eds. Fluid flow and transport in rocks, 83-98, Berner & Holdren, 1979, Geochim Cosmochim Acta 43, 1173-1186, Cox & Etheridge, 1989, JSG 11/1-2, 147-162, Etheridge et al., 1984, JGR 89/B6, 4344-4358, Fei, 1995, in Ahrens, ed. Mineral Physics and Crystallography, AGU, 29-44, Fusseis et al., in review, Nature, Gleeson et al., 2003, Geofluids 3, 33-48, Hacker, 1997, JGR 102/B11, 24459-24467, Higgs et al., 2007, J Sed Res 77, 1003-1025, Holdren & Berner, 1979, Geochim Cosmochim Acta 43, 1161-1171, Jamtveit et al., 1997, in Jamtveit & Yardley, eds. Fluid flow and transport in rocks, 57-82, Jamtveit et al., 2007, EPSL 267, 620-627, Dyson et al., 1976, Proc Roy Soc London A, 349/1657, 245-259, Kassner & Hayes, 2003, Int J Plasticity 19, 1715-1748, Kerrich et al., 1984, JGR 89/B6, 4331-4343, Kranz, 1983, Tectonophysics 100, 449-480, McCaig 1988, Geology 16, 867-870, Oliver, 1996, JMG 14, 477-492, Oliver et al., 1990, JMG 8, 311-331, Putnis, 2002, Min Magaz 66/5, 689-708, Putnis et al., 2007, Lithos 2007, 10-18, Rumble et al., 1982, Amer J Sci 282, 886-919, Rumble, 1994, JGR 99/B8, 15499-15502, Rybacki et al., 2008, GRL 35, L04304, Sprunt & Brace, 1974, Int J Rock Mech Min

Water vapor in the Martian atmosphere by SPICAM IR/Mars-Express

NASA Astrophysics Data System (ADS)

Trokhimovskiy, Alexander; Fedorova, Anna; Korablev, Oleg; Bertaux, Jean-Loup; Villard, Eric; Rodin, Alexander V.

resources and uncertainty about Martian atmosphere octal depths. Right now we are using data from SPICAM UV channel and PFS instrument onboard Mars Express. Calculations of Martian atmospheric dust optical for different particle models properties are done as well to shift data from one wavelength to another For today SPICAM data from January 2004 to January 2010, i.e. three Martian years, is fully processed in aspect of water vapor retrievment in the assumption of clear atmosphere. The seasonal trend of water vapor obtained by SPICAM IR is consistent with TES results and disagrees with MAWD South pole maximum measurements. The maximum abundance is 50-55 pr. m at the North pole (during MY28 data are missing) and 13-16 pr.m at the South pole. The northern tropical maximum amounts to 11-14 pr m. The seasonal trend of water vapor obtained by SPICAM IR is consistent for MY27 with TES results [11]. The South Pole maximum for MY28 agrees well with the MAWD South Pole measurements in 1977 [12]. It assumes the same dust conditions and global dust storm happened at MY28 Ls 270 like during the MAWD observations. The maximum near 30-60S at Ls 260 relates to Hellas observations. Recent observations of water vapour distribution during the same period by CRISM spectrometer onboard Mars Reconnaissance Orbiter support these results [6] References [1] Fouchet, T., (2007), Icarus 190, 32-49. [2] Melchiorri, R. (2007), PSS 55, 333-342. [3] Encrenaz, Th. (2005), AA 441, L9-L12. [4] Fedorova, A. et al. (2006), JGR 111, DOI:10.1029/2006JE002695. [5] R. Melchiorri. et al. (2009), Icarus, Volume 201, Issue 1, May 2009, Pages 102-112. [6] Smith, M. et al. (2009), JGR 114, , DOI:10.1029/2008JE003288, 2009 [7] Bertaux, J.-L. et al. (2006), JGR 111, DOI:10.1029/2006JE002690. [8] Korablev, O. et al. (2006), JGR 111, DOI:10.1029/2006JE002696. [9] Rothman, L.S. et al. (2005), JQSRT, 96, 139-204. [10] Forget, F. et al. (2007), LPICo1353.3098F. [11] Smith, M., (2004), Icarus 167, 148-165. [12] Jakosky, B. M

Intercontinental Transport of Tropical Ozone from Biomass Burning: Views from Satellite and SHADOZ (Southern Hemisphere Additional Ozonesondes)

NASA Technical Reports Server (NTRS)

Thompson, A. M.; Witte, J. C.; Chatfield, R. B.; Guam, H.

2003-01-01

There has been interest in the connection between tropical fires and ozone since about 1980. Photochemically reactive gases released by fires (e.g. NO, CO, volatile organic carbon) interact as they do in an urban environment to form ozone. Interacting with chemical sources, tropical meteorology plays a part in tropospheric ozone distributions in the tropics, through large-scale circulation, deep convection, and regional phenomena like the West African and Asian monsoons. An overview of observations, taken from satellite and from ozone soundings, illustrates regional influences and intercontinental- range ozone transport in the tropics. One of the most striking findings is evidence for impacts of Indian Ocean pollution on the south Atlantic ozone maximum referred to as the "ozone paradox" [Thompson et al., GRL, 2000; JGR, 2003; Chatfield et al., GRL, 20031.

Thermal Modeling of Al-Al and Al-Steel Friction Stir Spot Welding

NASA Astrophysics Data System (ADS)

Jedrasiak, P.; Shercliff, H. R.; Reilly, A.; McShane, G. J.; Chen, Y. C.; Wang, L.; Robson, J.; Prangnell, P.

2016-09-01

This paper presents a finite element thermal model for similar and dissimilar alloy friction stir spot welding (FSSW). The model is calibrated and validated using instrumented lap joints in Al-Al and Al-Fe automotive sheet alloys. The model successfully predicts the thermal histories for a range of process conditions. The resulting temperature histories are used to predict the growth of intermetallic phases at the interface in Al-Fe welds. Temperature predictions were used to study the evolution of hardness of a precipitation-hardened aluminum alloy during post-weld aging after FSSW.

Correction to Hilton et al. (2004)

ERIC Educational Resources Information Center

Hilton, N. Zoe; Harris, Grant T.; Rice, Marnie E.; Lang, Carol; Cormier, Catherine A.; Lines, Kathryn J.

2005-01-01

This paper reports errors in the article "A Brief Actuarial Assessment for the Prediction of Wife Assault Recidivism: The Ontario Domestic Assault Risk Assessment," by N. Zoe Hilton, Grant T. Harris, Marnie E. Rice, Carol Lang, Catherine A. Cormier, and Kathryn J. Lines (Psychological Assessment, 2004, Vol. 16, No. 3, pp. 267-275). On page 272,…

Correction to Cantor et al. (2005)

ERIC Educational Resources Information Center

Cantor, James M.; Blanchard, Ray; Robichaud, Lori K.; Christensen, Bruce K.

2005-01-01

This paper reports an error in the original article by James M. Cantor, Ray Blanchard, Lori K. Robichaud, and Bruce K. Christensen ("Psychological Bulletin," 2005, Vol. 131, No. 4, pp. 555-568). As a result of an editorial error the article listed the link to online supplemental data incorrectly. The correct URL is provided here. (The following…

Why do magmas stall? Insights from petrologic and geodetic data

NASA Astrophysics Data System (ADS)

Zimmer, M. M.; Plank, T.; Freymueller, J.; Hauri, E. H.; Larsen, J. F.; Nye, C. J.

2007-12-01

Magmas stall at various depths in the crust due to their internal properties (magma viscosity, buoyancy) and external crustal controls (local stress regime, wallrock strength). Annen et al. (JPet 2006) propose a petrological model in which buoyant magma ascends through the crust until the depth of water saturation, after which it crystallizes catastrophically and stalls due to the large increase in magma viscosity. Magmas may erupt from this storage region, or viscous death may result in pluton formation. In order to test this model, and constrain magma storage depths, we combine petrological and geodetic data for several active volcanoes along the Aleutian-Alaska arc. We analyzed glassy, primarily olivine-hosted melt inclusions by SIMS in tephra samples for their pre-eruptive volatile contents, which can be related to the depth of entrapment via pressure-dependent H2O-CO2 solubility models (e.g., VolatileCalc). Melt inclusions are not in equilibrium with pure water vapor (all will contain S and C species), but >50% of the inclusion population are in equilibrium with a vapor containing >85% H2O. Geodetic data (InSAR, GPS) record surface deformation related to volcano inflation/deflation, and can be inverted to solve for the depths of volume change (magma storage) in the crust. In the Aleutians, we find that the maximum melt inclusion trapping depths and geodetic depths correlate, suggesting both techniques record crustal magma storage and crystallization. Melt inclusions from the 1997 Okmok eruption are trapped at ≤3 km; deformation during the eruption and subsequent inflation occurred at 3±0.5 km (Miyagi et al., EPSL 2004; Lu & Masterlark, JGR 2005). At Akutan, melt inclusions and GPS data indicate magma storage at ~5-7 km. Inclusions from flank cones of Makushin yield depths of 7 km, similar to inflation observed beneath the main edifice (6.8 km, Lu et al., JGR 2002). Pleistocene inclusions from Augustine volcano indicate magma storage at 10-18 km, in accord

The Location and most Viable Magnetic Mineral of the Magnetic Layer of Mars Crust

NASA Astrophysics Data System (ADS)

Boutin, D.; Arkani-Hamed, J.

2010-12-01

directly beneath, suggesting that impacts have effectively disturbed the crust. Many of the craters have well-defined magnetic signatures. Modeling a magnetic anomaly under the assumption that a) the mantle plug beneath a crater is non magnetic, b) the anomaly is due to impact demagnetization of the crust, and c) the impact heating has elevated the temperature and further enhanced viscous decay of magnetization in the lower part of the crust, provides a means to identify magnetite as the most viable magnetic carrier in the Martian crust. [1] Acuña, M.H. et al., Science 284, 790-793, 1999. [2] Voorhies, C.V. JGR, 821, 113, E04004, 2008. [3] Arkani-Hamed, J., JGR,110, 585, E08005, 2005. [4] Shahnas, H. and J. Arkani-Hamed, JGR, 112, E02009, 2007. [5] Bezaeva, N.S. et al., PEPI, 197, 7-20, 2010. [6] Mohit, P.S. and J. Arkani-Hamed, Icarus 168, 305-317, 2004. [7] Lillis, R.J.,et al., LPSC, XL, Abs. No. 1444, 2009. [8] Louzada, K.L., et al., EPSL, submitted, 2010. [9] Pierazzo, E. et al., Icarus 127, 408-423, 1997.

Proton irradiation studies on Al and Al5083 alloy

NASA Astrophysics Data System (ADS)

Bhattacharyya, P.; Gayathri, N.; Bhattacharya, M.; Gupta, A. Dutta; Sarkar, Apu; Dhar, S.; Mitra, M. K.; Mukherjee, P.

2017-10-01

The change in the microstructural parameters and microhardness values in 6.5 MeV proton irradiated pure Al and Al5083 alloy samples have been evaluated using different model based techniques of X-ray diffraction Line Profile Analysis (XRD) and microindendation techniques. The detailed line profile analysis of the XRD data showed that the domain size increases and saturates with irradiation dose both in the case of Al and Al5083 alloy. The corresponding microstrain values did not show any change with irradiation dose in the case of the pure Al but showed an increase at higher irradiation doses in the case of Al5083 alloy. The microindendation results showed that unirradiated Al5083 alloy has higher hardness value compared to that of unirradiated pure Al. The hardness increased marginally with irradiation dose in the case of Al5083, whereas for pure Al, there was no significant change with dose.

Development of CASI (Computer Aided Speckle Interferometry) and LSS (Laser Speckle Sensor) with Application to Material Response under High Strain Rate, High Temperature, Vibration and Fatigue

DTIC Science & Technology

1991-02-10

25. 1"S. revised mcp recerved Apnil 10, 19W, thnnsmte into a VAX- 11� computer. Fringf_ spacing * acceped for puablI Al 126. 1990 This paPetis a...W.Il.Peters, W.F.llanson mtid S.WI.-MN1il, "Detcrintation of dis. placements using an improved (digit al rorrela Ii’’i ii’’ h. . 111 aad Vision Y*omput ing...experiimental mcchaniics", Experiment al Mechianics, Vol.25, No.3, pp 232-.1-1 (1985). 5.~ A.Rosenfeld and A.C.Kak, Digital Pict nre processing, Vol 1

Combustion synthesis of AlB2-Al2O3 composite powders with AlB2 nanowire structures

NASA Astrophysics Data System (ADS)

Yang, Pan; Xiao, Guoqing; Ding, Donghai; Ren, Yun; Yang, Shoulei; Lv, Lihua; Hou, Xing

2018-05-01

Using of Al and B2O3 powders as starting materials, and Mg-Al alloy as additives, AlB2-Al2O3 composite powders with AlB2 nanowire structures were successfully fabricated via combustion synthesis method in Ar atmosphere at a pressure of 1.5 MPa. The effect of different amount of Mg-Al alloy on the phase compositions and morphology of the combustion products was investigated. The results revealed that AlB2 and Al2O3 increased, whereas Al decreased with the content of Mg-Al alloy increasing. The impurities MgAl2O4 and AlB12 would exist in the sample with adding of 18 wt% Mg-Al alloy. Interestingly, FESEM/TEM/EDS results showed that AlB2 nanowires were observed in the products when the content of Mg-Al alloy is 6 wt% and 12 wt%. The more AlB2 nanowires can be found as the content of Mg-Al alloy increased. And the yield of AlB2 nanowires with the diameter of about 200 nanometers (nm) and the length up to several tens of micrometers (μm) in the combustion product is highest when the content of Mg-Al alloy is 12 wt%. The vapor, such as Mg-Al (g), B2O2 (g), AlO (g) and Al2O (g), produced during the process of combustion synthesis, reacted with each other to yield AlB2 nanowires by vapor-solid (VS) mechanism and the corresponding model was also proposed.

Revolutions in Science and Technology: Future Threats to US National Security

DTIC Science & Technology

2011-04-01

34Ultrafast ytterbium-doped bulk lasers and laser amplifiers, " Applied Physics B. Vol. 69, 1999. pp. 3-17. 47 See Martin Richardson et al. page 15...breakout and surprise 53 Martin Richardson, Timothy McComb, and Vikas Sudesh, "High Power Fiber Lasers and Applications to Manufacturing," Conference...Journal of Applied Physics, Vol. 49, 2010. ss1n 2008, Martin Richardson, et al. stated that the "high power fiber laser market, currently estimated to

Picosecond Optical Electronics

DTIC Science & Technology

1988-08-01

Optoelecironics, New York: Springer-Verlag, 1987 65. J. Archer, "Millimeter Wavelength Frequency Multipliers", IEEE MTr, Vol. 29, No. 6, June * 1981. 66. R. Majidi ...337-339. I 74. R. Majidi -Ahy et al., "Electrooptic Sampling Measurement of Coplanar Waveguide (Coupled Slot Line) Modes", Elect. Lett., Vol. 23, No...24, Nov. 1987, pp. 1262-1263. 1 75. R. Majidi -Ahy et al., "Electrooptic Sampling Measurement of Dispersion Characteristics of Slot line and Coplanar

Sensitive Detection of Gas-Phase Nitro-Containing Energetic Materials Employing 226-nm Radiation

DTIC Science & Technology

1993-07-01

Miziolek, and Long 1986; Sausa, Alfano , and Miziolek 1987; Wehry et al. 1987; Schendel, Hohmann, and Wehry 1987; McQuaid et al. 1991; Moss, Trentelman, and...K. Asai, and D. D. Davis. Applied Optics, vol. 19, no. 21, p. 3597, 1980. Sausa, R. C., A. J. Alfano , and A. W. Miziolek. Applied Optics, vol. 26...Hopkins University Chemical Propulsion Information Agency ATTN: T.W. Christian 10630 Little Patuxent Parkway. Suite 202 Columbia, MD 21044-3200 23 No. of

Background Measurements Made Above Five Kilometers: A Survey of the Literature

DTIC Science & Technology

1969-06-01

Corporation of America’s Astro - Electronics Division, Greenbelt, Md., 1961. NASA Facts, Vol. II, No. 7, 1965. Nimbus I High Resolution Radiation Data...cept for data in which noise degradation occurred. This applies chiefly to the 2.7- fx data. REFERENCES Unclassified J. Hoyem et al., NOTS - Michigan...et al., "A Revised Analysis of the Solar Spectrum From 2990 to 2635 A," Astro - phys. J., Vol. 119, No. 3, May 1954. UNCLASSIFIED 153

Interfacial Phenomena in Al/Al, Al/Cu, and Cu/Cu Joints Soldered Using an Al-Zn Alloy with Ag or Cu Additions

NASA Astrophysics Data System (ADS)

Pstruś, Janusz; Gancarz, Tomasz

2014-05-01

The studies of soldered joints were carried out in systems: Al/solder/Al, Al/solder/Cu, Cu/solder/Cu, where the solder was (Al-Zn)EUT, (Al-Zn)EUT with 0.5, 1.0, and 1.5 at.% of Ag and (Al-Zn)EUT with 0.5, 1.0, and 1.5 at.% of Cu addition. Brazing was performed at 500 °C for 3 min. The EDS analysis indicated that the composition of the layers starting from the Cu pad was CuZn, Cu5Zn8, and CuZn4, respectively. Wetting tests were performed at 500 °C for 3, 8, 15, and 30 min, respectively. Thickness of the layers and their kinetics of growth were measured based on the SEM micrographs. The formation of interlayers was not observed from the side of Al pads. On the contrary, dissolution of the Al substrate and migration of Al-rich particles into the bulk of the solder were observed.

Orientation relationship of eutectoid FeAl and FeAl2.

PubMed

Scherf, A; Kauffmann, A; Kauffmann-Weiss, S; Scherer, T; Li, X; Stein, F; Heilmaier, M

2016-04-01

Fe-Al alloys in the aluminium range of 55-65 at.% exhibit a lamellar microstructure of B2-ordered FeAl and triclinic FeAl 2 , which is caused by a eutectoid decomposition of the high-temperature Fe 5 Al 8 phase, the so-called ∊ phase. The orientation relationship of FeAl and FeAl 2 has previously been studied by Bastin et al. [ J. Cryst. Growth (1978 ▸), 43 , 745] and Hirata et al. [ Philos. Mag. Lett. (2008 ▸), 88 , 491]. Since both results are based on different crystallographic data regarding FeAl 2 , the data are re-evaluated with respect to a recent re-determination of the FeAl 2 phase provided by Chumak et al. [ Acta Cryst. (2010 ▸), C 66 , i87]. It is found that both orientation relationships match subsequent to a rotation operation of 180° about a 〈112〉 crystallographic axis of FeAl or by applying the inversion symmetry of the FeAl 2 crystal structure as suggested by the Chumak data set. Experimental evidence for the validity of the previously determined orientation relationships was found in as-cast fully lamellar material (random texture) as well as directionally solidified material (∼〈110〉 FeAl || solidification direction) by means of orientation imaging microscopy and global texture measurements. In addition, a preferential interface between FeAl and FeAl 2 was identified by means of trace analyses using cross sectioning with a focused ion beam. On the basis of these habit planes the orientation relationship between the two phases can be described by ([Formula: see text]01) FeAl || (114)[Formula: see text] and [111] FeAl || [1[Formula: see text]0][Formula: see text]. There is no evidence for twinning within FeAl lamellae or alternating orientations of FeAl lamellae. Based on the determined orientation and interface data, an atomistic model of the structure relationship of Fe 5 Al 8 , FeAl and FeAl 2 in the vicinity of the eutectoid decomposition is derived. This model is analysed with respect to the strain which has to be

Automated Texture Classification of the Mawrth Vallis Landing Site Region

NASA Astrophysics Data System (ADS)

Parente, M.; Bayley, L.; Hunkins, L.; McKeown, N. K.; Bishop, J. L.

2009-12-01

. (2008) Science, 321, 830-833. [4] Wray, J. J., et al. (2008) GRL, 35, L12202. [5] Loizeau, D., et al. (2009) Icarus, (in press). [6] McKeown, N. K., et al. (2009) JGR- Planets, (in press). [7] Noe Dobrea, E. Z., et al. (2009) JGR- Planets, (in revision). [8] McKeown, N. K. et al. (2009) LPSC abs. #2433. [9] Galloway, M. M., (1975),Computer Graphics and Image Processing 4, 172-179. [10] Haralick, R. M., (1973) IEEE Trans. on Systems, Man and Cybernetics 3, 610-621. [11] Curran, P. J., Remote Sensing of Environment 24, 493-507, 1988. [12] Hastie T., et al. (2005), The elements of statistical learning. Springer. [13] McKeown, N. K., et al. (2009) AGU

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ohmi, Tatsuya; Matsuura, Kiyotaka; Iguchi, Manabu

A centrifugal combustion synthesis (CCS) process has been investigated to join a Ni-Al intermetallic compound and a Ni-TiC cermet. The cermet, a tubular graphite mold, and a green compact of reactants consisting of Al, Ni and NiO were set in a centrifugal caster. When the combustion synthesis reaction was induced in the centrifugal force field, a synthesized molten Ni-Al alloy flowed into the graphite mold and joined to the cermet. The soundness of the joint interface depended on the volume percentage of TiC phase in the cermet. A lot of defects were formed near the interface between the Ni-TiC cermetmore » and the cast Ni-Al alloy when the volume percentage of TiC was 50% or higher. For this kind of cermet system, using a functionally graded cermet such as Ni-10 vol.%TiC/Ni-25 vol.%TiC/Ni-50 vol.%TiC overcame this difficulty. The four-point bending strength of the joined specimen consisting of the three-layered FGM cermet and cast Ni-29 mol%Al alloy was 1010 MPa which is close to the result for a Ni-29 mol%Al alloy specimen.« less

Modeling of Mastcam Visible/Near-Infrared Spectrophotometric Observations at Yellowknife Bay

NASA Astrophysics Data System (ADS)

Johnson, J. R.; Bell, J. F., III; Hayes, A.; Liang, W.; Lemmon, M. T.; Grundy, W. M.; Deen, R. G.

2017-12-01

Mastcam data sets. [1] Johnson, J., et al., LPSC, 44, abstract #1374, 2013;[2] Johnson, J., et al. 8th Int. Conf. Mars, #1073, 2014; [3] Johnson, J., et al., LPSC, #1424, 2015; [4] Johnson, J., et al., AGU, #P43B-2125 2015; [5] Johnson, J., et al., JGR, 111, E02S14, 2006; [6] Johnson, J., et al. JGR, 111, E12S16, 2006; [7] Johnson, J. et al., Icarus, 248, 25-71, 2015.

A Parallel Icosahedral, Higher Order Discontinuous Galerkin, Global Shallow Water Model: Global Ocean Tides and Aquaplanet Benchmarks

NASA Astrophysics Data System (ADS)

Salehipour, H.; Stuhne, G.; Peltier, W. R.

2012-12-01

The development of models of the ocean tides with higher resolution near the coastlines and courser mesh offshore, has been required due to the significant impacts of coastline configuration and bathymetry (associated with sea level rise) on the amplitude and phase of tidal constituents, not only under present conditions but also in the deep past [Griffiths and Peltier GRL 2008, Griffiths and Peltier AMS 2009, Hill et al. JGR 2011]. A global tidal model with enhanced resolution at the poles has been developed by Griffiths and Peltier [2008, 2009], which, although capable of highly resolving polar ocean tides , is based upon a standard structured Arakawa C grid and hence is not capable of resolving coastlines locally. Furthermore the use of a nested modelling approach, although it may enable local spatial refinement [Hill et al. 2011], nevertheless suffers from its inherent dependence on the availability of a global tidal model with necessarily low spatial resolution to provide the open boundary conditions required for the local high resolution model. On the other hand, an unstructured triangulation of the global domain provides a standalone framework that may be employed to study highly resolved regions without relying on secondary models. The first step in the development of the structure we are employing was described in Stuhne and Peltier [Ocean Modeling, 2009]. In further extending this modelling structure we are employing a new discontinuous Galerkin (DG) discretization of the governing equations in order to provide very high order of accuracy while also ensuring that momentum transport is locally conserved [Giraldo et al. JCP 2002]. After validating the 2D shallow water model with several test suites appropriate to aquaplanets [Williamson et al. JCP 1992, Galewsky et al. Tellus 2004, Nair and Lauritzen JCP 2010], the governing equations are extended to include the influence of internal tide drag in the deep ocean as well as the drag in shallow marginal seas

Ohmic contacts to Al-rich AlGaN heterostructures

DOE PAGES

Douglas, E. A.; Reza, S.; Sanchez, C.; ...

2017-06-06

Due to the ultra-wide bandgap of Al-rich AlGaN, up to 5.8 eV for the structures in this study, obtaining low resistance ohmic contacts is inherently difficult to achieve. A comparative study of three different fabrication schemes is presented for obtaining ohmic contacts to an Al-rich AlGaN channel. Schottky-like behavior was observed for several different planar metallization stacks (and anneal temperatures), in addition to a dry-etch recess metallization contact scheme on Al 0.85Ga 0.15N/Al 0.66Ga 0.34N. However, a dry etch recess followed by n +-GaN regrowth fabrication process is reported as a means to obtain lower contact resistivity ohmic contacts onmore » a Al 0.85Ga 0.15N/Al 0.66Ga 0.34N heterostructure. In conclusion, specific contact resistivity of 5×10 -3 Ω cm 2 was achieved after annealing Ti/Al/Ni/Au metallization.« less

Growth and stress-induced transformation of zinc blende AlN layers in Al-AlN-TiN multilayers

DOE PAGES

Li, Nan; Yadav, Satyesh K.; Wang, Jian; ...

2015-12-18

We report that AlN nanolayers in sputter deposited {111}Al/AlN/TiN multilayers exhibit the metastable zinc-blende-structure (z-AlN). Based on density function theory calculations, the growth of the z-AlN is ascribed to the kinetically and energetically favored nitridation of the deposited aluminium layer. In situ nanoindentation of the as-deposited {111}Al/AlN/TiN multilayers in a high-resolution transmission electron microscope revealed the z-AlN to wurzite AlN phase transformation through collective glide of Shockley partial dislocations on every two {111} planes of the z-AlN.

numerical broadband modelling of ocean waves, from 1 to 300 s: implications for seismic wave sources and wave climate studies

NASA Astrophysics Data System (ADS)

Ardhuin, F.; Stutzmann, E.; Gualtieri, L.

2014-12-01

Ocean waves provide most of the energy that feeds the continuous vertical oscillations of the solid Earth. Three period bands are usually identified. The hum contains periods longer than 30 s, and the primary and secondary peaks are usually centered around 15 and 5 s, respectively. Motions in all three bands are recorded everywhere on our planet and can provide information on both the solid Earth structure and the ocean wave climate over the past century. Here we describe recent efforts to extend the range of validity of ocean wave models to cover periods from 1 to 300 s (Ardhuin et al., Ocean Modelling 2014), and the resulting public database of ocean wave spectra (http://tinyurl.com/iowagaftp/HINDCAST/ ). We particularly discuss the sources of uncertainty for building a numerical model of acoustic and seismic noise on this knowledge of ocean wave spectra. For acoustic periods shorter than 3 seconds, the main uncertainties are the directional distributions of wave energy (Ardhuin et al., J. Acoust. Soc. Amer. 2013). For intermediate periods (3 to 25 s), the propagation properties of seismic waves are probably the main source of error when producing synthetic spectra of Rayleigh waves (Ardhuin et al. JGR 2011, Stutzmann et al. GJI 2012). For the longer periods (25 to 300 s), the poor knowledge of the bottom topography details may be the limiting factor for estimating hum spectra or inverting hum measurements in properties of the infragravity wave field. All in all, the space and time variability of recorded seismic and acoustic spectra is generally well reproduced in the band 3 to 300 s, and work on shorter periods is under way. This direct model can be used to search for missing noise sources, such as wave scattering in the marginal ice zone, find events relevant for solid earth studies (e.g. Obrebski et al. JGR 2013) or invert wave climate properties from microseismic records. The figure shows measured spectra of the vertical ground acceleration, and modeled

The Venus Emissivity Mapper - gaining a global perspective on the surface composition of Venus

NASA Astrophysics Data System (ADS)

Helbert, Joern; Dyar, Melinda; Widemann, Thomas; Marcq, Emmanuel; Maturilli, Alessandro; Mueller, Nils; Kappel, David; Ferrari, Sabrina; D'Amore, Mario; Tsang, Constantine; Arnold, Gabriele; Smrekar, Suzanne; VEM Team

2017-10-01

.E., et al., Science, 2010. 328(5978): p. 605-8.2. Helbert, J., et al., GRL, 2008. 35(11).3. Mueller, N., et al., JGR, 2008. 113.4. Helbert, J., et al. 2016. San Diego, CA: SPIE.5. Mueller, N.T., et al., JGR, 2017.

Estimated Rock Abundance and Thermophysical Parameters in Oppenheimer Crater on the Moon

NASA Astrophysics Data System (ADS)

Bauch, Karin E.; Hiesinger, Harald; Ivanov, Mikhail; van der Bogert, Carolyn H.; Pasckert, Jan-Hendrik; Weinauer, Julia

2016-04-01

anisothermal surfaces and, thus, the abundance of rocks within a field of view [e.g., 6, 9, 10]. The thermal maps show low temperatures, thus low thermal inertia and low rock abundances on the flat floor of Oppenheimer. Dark mantle deposits have similar thermal signatures as the floor. Higher rock abundances and thermal inertias are associated with the graben structures close to the rim of Oppenheimer and the floors of Oppenheimer-U and -H. We found that the highest values correlate with fresh craters in the northern part of Oppenheimer. High-resolution NAC images confirm the presence of boulders on the surface. References: [1] Petro, N.E., Pieters, C. M. (2004), JGR 109, E6. [2] Hiesinger, H. et al. (2012), LPSC XLIII, #2863. [3] Ivanov, M. et al. (2015), LPSC IIIX, #1070. [4] Paige, D. et al. (2010), Spac. Sci. Rev. 150, Num 1-4, p125-160. [5] Bauch, K.E. et al. (2014), PSS 101, 27-36. [6] Bauch, K.E. at al. (2013), EGU2013-8053. [7] Urquhart, M.L. and Jakosky, B.M. (1997), JGR 102, 10,959-10,969. [8] Mellon, M.T. et al. (2000), Icarus 148, 437-455. [9] Christensen, P.R. (1986), Icarus 68, 217-238. [10] Bandfield, J.L. et al. (2011), JGR 108, E12, 8086.

Thermal conductivity enhancement and sedimentation reduction of magnetorheological fluids with nano-sized Cu and Al additives

NASA Astrophysics Data System (ADS)

Rahim, M. S. A.; Ismail, I.; Choi, S. B.; Azmi, W. H.; Aqida, S. N.

2017-11-01

This work presents enhanced material characteristics of smart magnetorheological (MR) fluids by utilizing nano-sized metal particles. Especially, enhancement of thermal conductivity and reduction of sedimentation rate of MR fluids those are crucial properties for applications of MR fluids are focussed. In order to achieve this goal, a series of MR fluid samples are prepared using carbonyl iron particles (CIP) and hydraulic oil, and adding nano-sized particles of copper (Cu), aluminium (Al), and fumed silica (SiO2). Subsequently, the thermal conductivity is measured by the thermal property analyser and the sedimentation of MR fluids is measured using glass tubes without any excitation for a long time. The measured thermal conductivity is then compared with theoretical models such as Maxwell model at various CIP concentrations. In addition, in order to show the effectiveness of MR fluids synthesized in this work, the thermal conductivity of MRF-132DG which is commercially available is measured and compared with those of the prepared samples. It is observed that the thermal conductivity of the samples is much better than MRF-132DG showing the 148% increment with 40 vol% of the magnetic particles. It is also observed that the sedimentation rate of the prepared MR fluid samples is less than that of MRF-132DG showing 9% reduction with 40 vol% of the magnetic particles. The mixture optimized sample with high conductivity and low sedimentation was also obtained. The magnetization of the sample recorded an enhancement of 70.5% when compared to MRF-132DG. Furthermore, the shear yield stress of the sample were also increased with and without the influence of magnetic field.

A Study to Determine the Reasons Retirees Use CHAMPUS Rather Than the Fort Carson Army Community Hospital

DTIC Science & Technology

1986-08-01

al (1968), p. 868. 7Korsch, et al (1968), p. 869. 8William A. Flexner and Eric N. Berkowitz, " Marketing Research in Health Services Planning : A Model...34 Marketing Research in Health Services Planning: A Model." Public Health Reports, Vol. 94, No. 6 (November-December, 1979), pp. 503-513. Fuchs...34Patients’ Priorities for Medical Care", Medical Care, Vol. 21, No. 2 (February 1983), pp. 234-242. 13William A. Flexner and Eric N. Berkowitz, " Marketing

Comparing the Thermodynamic Behaviour of Al(1)+ZrO2(s) to Al(1)+Al2O3(s)

NASA Technical Reports Server (NTRS)

Copland, Evan

2004-01-01

In an effort to better determine the thermodynamic properties of Al(g) and Al2O(g). the vapor in equilibrium with Al(l)+ZrO2(s) was compared to the vapor in equilibrium with Al(l)+Al2O3(s) over temperature range 1197-to-1509K. The comparison was made directly by Knudsen effusion-cell mass spectrometry with an instrument configured for a multiple effusion-cell vapor source (multi-cell KEMS). Second law enthalpies of vaporization of Al(g) and Al2O(g) together with activity measurements show that Al(l)+ZrO2(s) is thermodynamically equivalent to Al(l)+Al2O3(s), indicating Al(l) remained pure and Al2O3(s) was present in the ZrO2-cell. Subsequent observation of the Al(l)/ZrO2 and vapor/ZrO2 interfaces revealed a thin Al2O3-layer had formed, separating the ZrO2-cell from Al(l) and Al(g)+Al2O(g), effectively transforming it into an Al2O3 effusion-cell. This behavior agrees with recent observations made for Beta-NiAl(Pt) alloys measured in ZrO2 effusion-cell.

Properties of boride-added powder metallurgy magnesium alloys

NASA Astrophysics Data System (ADS)

Tanaka, Atsushi; Yoshimura, Syota; Fujima, Takuya; Takagi, Ken-ichi

2009-06-01

Magnesium alloys with metallic borides, magnesium diboride (MgB2) or aluminum diboride (AlB2), were investigated regarding their mechanical properties, transverse rupture strength (TRS) and micro Vickers hardness (HV). The alloys were made from pure Mg, Al and B powders by mechanical alloying and hot pressing to have boride content of between 2.0 and 20 vol%. The alloy with AlB2 exhibited an obvious improvement of HV around a boride content of 6 vol% though the other alloy, with MgB2, did not. TRS showed moderate maxima around the same boride content region for the both alloys. X-ray diffraction measurements indicated an intermetallic compound, Mg17Al12, formed in the alloy with AlB2, which was consistent with its higher hardness.

Nanoporous Al sandwich foils using size effect of Al layer thickness during Cu/Al/Cu laminate rolling

NASA Astrophysics Data System (ADS)

Yu, Hailiang; Lu, Cheng; Tieu, A. Kiet; Li, Huijun; Godbole, Ajit; Kong, Charlie

2018-06-01

The roll bonding technique is one of the most widely used methods to produce metal laminate sheets. Such sheets offer interesting research opportunities for both scientists and engineers. In this paper, we report on an experimental investigation of the 'thickness effect' during laminate rolling for the first time. Using a four-high multifunction rolling mill, Cu/Al/Cu laminate sheets were fabricated with a range of thicknesses (16, 40, 70 and 130 μm) of the Al layer. The thickness of the Cu sheets was a constant 300 μm. After rolling, TEM images show good bonding quality between the Cu and Al layers. However, there are many nanoscale pores in the Al layer. The fraction of nanoscale pores in the Al layer increases with a reduction in the Al layer thickness. The finite element method was used to simulate the Cu/Al/Cu rolling process. The simulation results reveal the effect of the Al layer thickness on the deformation characteristics of the Cu/Al/Cu laminate. Finally, we propose that the size effect of the Al layer thickness during Cu/Al/Cu laminate rolling may offer a method to fabricate 'nanoporous' Al sandwich laminate foils. Such foils can be used in electromagnetic shielding of electrical devices and noisy shielding of building.

Multi-Sensor Mapping of Diffuse Degassing of C-O-H Compounds in Terrestrial Hydrothermal Systems

NASA Astrophysics Data System (ADS)

Schwandner, F. M.; Shock, E. L.

2004-12-01

and partially map a previously-inferred active lineament in the Obsidian Pool area. In addition, reduced gas data are yielding areal ratio distributions of CO/CO2, H2/CH4, and CO/CH4, that may be indicative of reactions such as the catalytic hydrogenation of CO2 (Sabatier-Process) and of CO (Fischer-Tropsch-Process) within the shallow hydrothermal system. Barberi & Carapezza (1994). Bull. Volcanol. 56(5): 335-342. Brombach, et al. (2001). Geophys. Res. Lett. 28(1): 69-72. Crenshaw et al. (1982). Nature 300: 345-346. Chiodini et al. (1996). Bull. Volcanol. 58(1): 41-50. Schwandner et al. (2004). JGR D 109: D04301, doi:10.1029/2003JD003890. Werner & Brantley (2004) JGR B 105: 10,831-10,846. Werner et al. (2003). Earth Planet. Sci. Lett. 210: 561-577. Williams (1985). Science 229(4713): 551-553. Williams-Jones et al. (2000). Bull. Volcanol. 62: 130-142.

Friction and wear of oxide-ceramic sliding against IN-718 nickel base alloy at 25 to 800 C in atmospheric air

NASA Technical Reports Server (NTRS)

Sliney, Harold E.; Deadmore, Daniel L.

1989-01-01

The friction and wear of oxide-ceramics sliding against the nickel base alloy IN-718 at 25 to 800 C were measured. The oxide materials tested were mullite (3Al2O3.2SiO2); lithium aluminum silicate (LiAlSi(x)O(y)); polycrystalline monolithic alpha alumina (alpha-Al2O3); single crystal alpha-Al2O3 (sapphire); zirconia (ZrO2); and silicon carbide (SiC) whisker-reinforced Al2O3 composites. At 25 C the mullite and zirconia had the lowest friction and the polycrystalline monolithic alumina had the lowest wear. At 800 C the Al2O3-8 vol/percent SiC whisker composite had the lowest friction and the Al2O3-25 vol/percent SiC composite had the lowest wear. The friction of the Al2O3-SiC whisker composites increased with increased whisker content while the wear decreased. In general, the wear-resistance of the ceramics improve with their hardness.

Observations of H2O in Titan's atmosphere with Herschel

NASA Astrophysics Data System (ADS)

Moreno, R.; Lellouch, E.; Lara, L. M.; Courtin, R.; Hartogh, P.; Rengel, M.

2012-04-01

by ISO) and the shallower profiles from the Hörst et al (2008) photochemical model fail to explain the observations. Additional profiles, described in Lara et. al., (this workshop) are tested against the data. References: Anderson, C.M. and Samuelson, R.E.: “Titan's aerosol and stratospheric ice opacities between 18 and 500 μm: Vertical and spectral characteristics from Cassini CIRS”. Icarus, Vol. 212, pp. 762-778, 2011 Borysow, A. and Frommhold, L.: “Collision-induced rototranslational absorption spectra of N2-N2 pairs for temperatures from 50 to 300 K”. Astrophysical Journal, vol. 311, pp. 1043-1057, 1986 Borysow, A. and Frommhold, L.: “Collision-induced rototranslational absorption spectra of CH4-CH4 pairs at temperatures from 50 to 300 K”. Astrophysical Journal, vol. 318, pp. 940-943, 1987. Borysow, A. and Tang, C., “Far Infrared CIA Spectra of N2-CH4 Pairs for Modeling of Titan's Atmosphere”. Icarus, Vol. 105, pp. 175-183, 1993. Coustenis et al.: “Evidence for water vapor in Titan's atmosphere from ISO/SWS data”. Astronomy and Astrophysics, vol. 336, L85-L89, 1998. Hartogh, P., et al.: “Water and related chemistry in the solar system. A guaranteed time key programme for Herschel”. Planetary and Space Science, Vol. 57, pp. 1596-1606, 2011. Hörst, S.M., et al.: “Origin of oxygen species in Titan's atmosphere”. J. of Geophys. Res., Vol. 113, Issue E10, CiteID E10006, 2008 Lara, L.M., et al.: “Vertical distribution of Titan's atmospheric neutral constituents”. J. of Geophys. Res., Vol. 101, Issue E10, pp. 23261-23283, 1996 Moreno, R., et al.: “First detection of hydrogen isocyanide (HNC) in Titan's atmosphere”. Astronomy & Astrophysics, Volume 536, L12, 2011 Pickett et al.: “Submillimeter, millimeter and microwave spectral line catalog.”. JQSRT, vol. 60, pp. 883-890, 1998.

Refrigeration and Food Safety

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Bovine Spongiform Encephalopathy: Production and Inspection

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Food Safety Tips for College Students

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Frozen, Fully-Cooked Products and Botulism--Food Safety Advisory

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Fires and Food Safety

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Safe Minimum Internal Temperature Chart

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Kitchen Thermometers

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Parasites and Foodborne Illness

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Natural Flavorings on Meat and Poultry Labels

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Freezing and Food Safety

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Formation of Ganymede's Grooved Terrain by Convection-Driven Resurfacing

NASA Astrophysics Data System (ADS)

Hammond, N. P.; Barr, A. C.

2013-12-01

with heat flow estimates for dark terrain [14] and conditions which favor the formation of long-wavelength, low-amplitude compressional folds [15], similar to those observed on Europa [16]. Such folds may be detectable by the upcoming Jupiter-Icy-Moon-Explorer Mission. Acknowledgements: This work is supported by NASA PG&G #NNX12AI76G References: [1] Collins G. et al., (1998) GRL 25, 3, 233-236 [2] Lucchitta B. (1980) Icarus 44, 481-501 [3] Squyres S. & Croft S. (1986) Satellites 293-341 [4] Showman A. P. et al., (1997) Icarus 129, 367-383 [5] Nimmo F. et al. (2002) GRL 29, 62-65 [6] Bland M. & Showman A. (2007), Icarus 189, 439-456. [7] Barr A. C. (2008) JGR 113, E07009 14 [8] Solomatov V. (2004) JGR 109, B01412 [9] O'Neill C. & Nimmo F. (2010) Nat. Geo. 3 v2 88-91 [10] Moresi L. & Solomatov V. (1995) Phys. Fluids 7, 2154-2162 [11] Goldsby D. & Kohlstedt D. (2001) JGR 106, B6 11017-11030 [12] Solomatov V. (2004) JGR 109, B01412 [13] Nimmo F. & Schenk P. (2006) J. Struc. Geol. 28, 2194-2203 [14] Nimmo F. & Pappalardo R. (2004) GRL 31, L19701 [15] Bland M. & McKinnon W. (2012) Icarus 221, 2, 694-709 [16] Prockter L. & Pappalardo R. (2000) Science 289, 5481, 941-944

Localized Deformation Beginning more than 15 km Beneath the Mid-Atlantic Ridge, 14 to 16 N

NASA Astrophysics Data System (ADS)

Kelemen, P.

2003-12-01

ODP Leg 209 drilled 19 holes at 8 sites along the Mid-Atlantic Ridge from 14° 43 to 15° N. All sites were surveyed by submersible, and chosen to be < 200 m from peridotite or dunite exposed on the seafloor; outcrops of gabbroic rock were also close to some sites. One of our primary goals was to constrain the mechanism of mantle upwelling, corner flow and exhumation of shallow mantle rocks. Drilling at Sites 1268, 1270-72, 1274 and 1275 penetrated 1075 meters, and recovered 354 m of core. At Sites 1268 and 1270-72 we recovered 25% gabbroic rocks and 75% residual mantle peridotite. Core from Site 1274 was mainly residual peridotite, while core from Site 1275 was mainly gabbroic. Most of the residual peridotites have nearly undeformed, protogranular textures. Orthopyroxenes are interstitial to olivine or even poikilitic. Rare, isolated clinopyroxene grains are also interstitial. Skeletal spinel grains have mm-scale extensions in three dimensions, with no discernable shape fabric. These textures are clearly different from porphyroclastic textures typical in ophiolites and fracture zone dredges. As described elsewhere at this meeting, impregnated peridotites contain olivine, 2 pyroxenes, plagioclase and spinel, and equilibrated at 0.54 GPa (+/-0.14 GPa, 2σ ) and 1220° C (+/-16° C, 2σ ) [Kinzler & Grove, JGR 92]. Melts entered the thermal boundary layer beneath the Mid-Atlantic Ridge at about 20 km [e.g., Sleep, JGR 75; Reid & Jackson, MGR 82; Grove et al JGR 92; Cannat JGR 96; Michael & Chase CMP 97; Braun et al., EPSL 00], and began to crystallize within impregnated peridotites and as discrete plutons intruding peridotite. Gabbroic rocks and peridotites from most sites underwent large tectonic rotations since aquiring remanent magnetization. At some sites, rotations may have exceeded 60° around near-horizontal axes parallel to the Mid-Atlantic Ridge. Such large rotations are unlikely to have been accomodated along a single fault, and instead blocks were

Structure-processing correlations and mechanical properties in freeze-cast Ti-6Al-4V with highly aligned porosity and a lightweight Ti-6Al-4V-PMMA composite with excellent energy absorption capability

DOE PAGES

Weaver, Jordan S.; Kalidindi, Surya R.; Wegst, Ulrike G. K.

2017-02-12

In contrast to freeze-cast ceramics and polymers, few freeze-cast metals have been described, to date. This systematic study on structure-processing correlations in freeze-cast Ti-6Al-4V scaffolds reports how processing parameters determine the architecture formed during the directional solidification of water-based metal slurries and after sintering. Additionally, sedimentation in the slurry during freezing and volume shrinkage during burnout and sintering were found to significantly affect both structure and properties of the scaffolds. In using two freezing rates, 1 and 10 °C min -1, two water-based polymer solutions as binders (chitosan and carboxymethyl cellulose) and two different metal volume fractions in the slurry,more » 20 and 30 vol%, Ti-6Al-4V scaffolds could be prepared with pore length, width, and porosity ranging from 41 to 523 μm, 14.5–76.5 μm, and 65 to 34%, respectively. Their compressive strength, stiffness, and toughness (work to 20% strain) fall in the range of 83–412 MPa, 7–29 GPa, and 14–122 MJ m -3, respectively. In order to improve the properties a select composition was infiltrated with poly(methyl methacrylate). This increased the average yield strength by a factor of 2.3 from 83 to 193 MPa and the average toughness (work to 50% strain) by a factor of 2.7 from 28.1 to 76.8 MJ m -3.« less

Structure-processing correlations and mechanical properties in freeze-cast Ti-6Al-4V with highly aligned porosity and a lightweight Ti-6Al-4V-PMMA composite with excellent energy absorption capability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weaver, Jordan S.; Kalidindi, Surya R.; Wegst, Ulrike G. K.

In contrast to freeze-cast ceramics and polymers, few freeze-cast metals have been described, to date. This systematic study on structure-processing correlations in freeze-cast Ti-6Al-4V scaffolds reports how processing parameters determine the architecture formed during the directional solidification of water-based metal slurries and after sintering. Additionally, sedimentation in the slurry during freezing and volume shrinkage during burnout and sintering were found to significantly affect both structure and properties of the scaffolds. In using two freezing rates, 1 and 10 °C min -1, two water-based polymer solutions as binders (chitosan and carboxymethyl cellulose) and two different metal volume fractions in the slurry,more » 20 and 30 vol%, Ti-6Al-4V scaffolds could be prepared with pore length, width, and porosity ranging from 41 to 523 μm, 14.5–76.5 μm, and 65 to 34%, respectively. Their compressive strength, stiffness, and toughness (work to 20% strain) fall in the range of 83–412 MPa, 7–29 GPa, and 14–122 MJ m -3, respectively. In order to improve the properties a select composition was infiltrated with poly(methyl methacrylate). This increased the average yield strength by a factor of 2.3 from 83 to 193 MPa and the average toughness (work to 50% strain) by a factor of 2.7 from 28.1 to 76.8 MJ m -3.« less

Ti{sub 2}AlN thin films synthesized by annealing of (Ti+Al)/AlN multilayers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cabioch, Thierry, E-mail: Thierry.cabioch@univ-poitiers.fr; Alkazaz, Malaz; Beaufort, Marie-France

2016-08-15

Highlights: • Epitaxial thin films of the MAX phase Ti{sub 2}AlN are obtained by thermal annealing. • A new metastable (Ti,Al,N) solid solution with the structure of α-T is evidenced. • The formation of the MAX phase occurs at low temperature (600 °C). - Abstract: Single-phase Ti{sub 2}AlN thin films were obtained by annealing in vacuum of (Ti + Al)/AlN multilayers deposited at room temperature by magnetron sputtering onto single-crystalline (0001) 4H-SiC and (0001) Al{sub 2}O{sub 3} substrates. In-situ X-ray diffraction experiments combined with ex-situ cross-sectional transmission electron microscopy observations reveal that interdiffusion processes occur in the multilayer at amore » temperature of ∼400 °C leading to the formation of a (Ti, Al, N) solid solution, having the hexagonal structure of α-Ti, whereas the formation of Ti{sub 2}AlN occurs at 550–600 °C. Highly oriented (0002) Ti{sub 2}AlN thin films can be obtained after an annealing at 750 °C.« less

Heat transfer and pressure drop characteristics of a plate heat exchanger using water based Al2O3 nanofluid for 30° and 60° chevron angles

NASA Astrophysics Data System (ADS)

Elias, M. M.; Saidur, R.; Ben-Mansour, R.; Hepbasli, A.; Rahim, N. A.; Jesbains, K.

2018-04-01

Nanofluid is a new class of engineering fluid that has good heat transfer characteristics which is essential to increase the heat transfer performance in various engineering applications such as heat exchangers and cooling of electronics. In this study, experiments were conducted to compare the heat transfer performance and pressure drop characteristics in a plate heat exchanger (PHE) for 30° and 60° chevron angles using water based Al2O3 nanofluid at the concentrations from 0 to 0.5 vol.% for different Reynolds numbers. The thermo-physical properties has been determined and presented in this paper. At 0.5 vol% concentration, the maximum heat transfer coefficient, the overall heat transfer coefficient and the heat transfer rate for 60° chevron angle have attained a higher percentage of 15.14%, 7.8% and 15.4%, respectively in comparison with the base fluid. Consequently, when the volume concentration or Reynolds number increases, the heat transfer coefficient and the overall heat transfer coefficient as well as the heat transfer rate of the PHE (Plate Heat Exchangers) increases respectively. Similarly, the pressure drop increases with the volume concentration. 60° chevron angle showed better performance in comparison with 30° chevron angle.

Solar Cycle Changes in the Position of the Intermediate Transition in the Venus Ionosheath.

NASA Astrophysics Data System (ADS)

Perez De Tejada, H. A.; Lundin, R. N. A.; Durand-Manterola, H. J.; Reyes-Ruiz, M.; Barabash, S.; Zhang, T.; Sauvaud, J. A.

2014-12-01

Measurements conducted with the ASPERA plasma probe and the magnetometer of the Venus Express (VEX) spacecraft in orbits that probed by the midnight plane within the Venus wake show the presence of a sharp plasma transition outside the region where enhanced fluxes of planetary ions are observed. That transition agrees with a feature reported earlier [1] from the VEX electron measurements and that is now also characterized by a sharp change in the speed and density of the solar wind H+ ions [2]. From the analysis of the plasma data of 10 VEX orbits in two different time periods (August 2006 and September 2009) it is possible to derive the position of the VEX spacecraft at the time when the plasma transition is observed in all 10 orbits. The data show a collection of different distances downstream from Venus where the plasma transition is detected and that are grouped for each time period. As a whole the X-distance on the sun-Venus line downstream from the planet for each of the 5 orbits corresponding to the August 2006 time period is smaller than that corresponding to the 5 orbits of the September 2009 time period. The average distance difference between both sets of data points is nearly one half planetary radius thus leading to two different groups in their distribution. The position of the plasma transition downstream from Venus will vary along the solar cycle being displaced to regions that extend farther away from the inner wake under solar maximum conditions. [1] Pérez-de-Tejada, H.et al., JGR, 116, JA015216, 2011. [2] Pérez-de-Tejada, H.et al., JGR, 118, JA019029, 2013.

Lagrangian clustering detection of internal wave boluses

NASA Astrophysics Data System (ADS)

Allshouse, M.; Salvador Vieira, G.; Swinney, H. L.

2016-02-01

The shoaling of internal waves on a continental slope or shelf produces boluses that travel up the slope with the wave. The boluses are regions of trapped fluid that are transported along with the wave, unlike fluid in the bulk that is temporarily pertubed by a passing wave. Boluses have been observed to transport oxygen-depleted water and induce rapid changes in temperature (Walter et al, JGR, 2012), both of which have potential ramifications for marine biology. Several previous studies have investigated boluses in systems with two layers of different density (e.g., Helfrich, JFM, 1992, and Sutherland et al., JGR, 2013). We conduct laboratory and computational studies of bolus generation and material transport in continuously stratified fluids with a pycnocline, as in the oceans. Our laboratory experiments in a 4 m long tank are complemented by 2-dimensional direct numerical simulations of the Navier-Stokes equations. Efforts have been made to identify boluses with Eularian measures in the past, but a Lagrangian perspective is necessary to objectively identify the bolus over its lifespan. Here we use a Lagrangian based coherent structure method relying on trajectory clustering using the fuzzy c-means approach (Froyland and Padberg-Gehle, Chaos, 2015). The objective detection of a bolus enables examination of the volume, distance traveled, and increased available potential energy of a bolus, as a function of the stratification, wave properties, and the angle of the sloping topography. The decay of a bolus through turbulent mixing is investigated by locating where the Richardson number drops below ¼, where velocity shear overcomes the tendency of a stratified fluid to remain stratified. (supported by ONR MURI grant N000141110701)

EDM machinability of SiCw/Al composites

NASA Technical Reports Server (NTRS)

Ramulu, M.; Taya, M.

1989-01-01

Machinability of high temperature composites was investigated. Target materials, 15 and 25 vol pct SiC whisker-2124 aluminum composites, were machined by electrodischarge sinker machining and diamond saw. The machined surfaces of these metal matrix composites were examined by SEM and profilometry to determine the surface finish. Microhardness measurements were also performed on the as-machined composites.

Upper Hybrid Effects in Artificial Ionization

NASA Astrophysics Data System (ADS)

Papadopoulos, K.; Eliasson, B. E.

2014-12-01

A most fascinating result of recent ionospheric experiments has been the discovery of artificial ionization by Pedersen et al. (GRL, 37, L02106, 2010). The Artificial Ionospheric Layers (AIL) were the result of F-region O-mode HF irradiation using the HAARP ionospheric heater operating at 3.6 MW power. As demonstrated by Eliasson et al. (JGR, 117, A10321, 2012) the physics controlling the observed phenomenon and its threshold can be summarized as: " Collisional ionization due to high energy (~ 20 eV) electron tails generated by the interaction of strong Langmuir turbulence with plasma heated at the upper hybrid resonance and transported at the reflection height". The objective of the current presentation is to explore the role of the upper hybrid heating in the formation of AIL and its implications to future experiments involving HF heaters operating in middle and equatorial latitudes.

Trends in Southern Ocean Eddy Kinetic Energy

NASA Astrophysics Data System (ADS)

Chambers, Don

2016-04-01

A recent study by Hogg et al. (JGR, 2015) has demonstrated a 20-year trend in eddy kinetic energy (EKE) computed from satellite altimetry data. However, this estimate is based on an averaging over large spatial areas. In this study, we use the same methods to examine regional EKE trends throughout the Southern Ocean, from 1993-2015. We do find significant positive trends in several areas of the Southern Ocean, mainly in regions with high mean EKE associated with interactions between jets and bathymetry. At the same time, however, there are also regions with significant negative trends. Overall, EKE in the majority of the Southern Ocean has not changed. These results suggest that the estimates of Hogg et al. may have been biased by these regional extremes, and that more work is needed to quantify climatic changes in EKE.

Trends in Southern Ocean Eddy Kinetic Energy

NASA Astrophysics Data System (ADS)

Chambers, D. P.

2016-02-01

A recent study by Hogg et al. (JGR, 2015) has demonstrated a 20-year trend in eddy kinetic energy (EKE) computed from satellite altimetry data. However, this estimate is based on an averaging over large spatial areas. In this study, we use the same methods to examine regional EKE trends throughout the Southern Ocean, from 1993-2015. We do find significant positive trends in several areas of the Southern Ocean, mainly in regions with high mean EKE associated with interactions between jets and bathymetry. At the same time, however, there are also regions with significant negative trends. Overall, EKE in the majority of the Southern Ocean has not changed. These results suggest that the estimates of Hogg et al. may have been biased by these regional extremes, and that more work is needed to quantify climatic changes in EKE.

United States Air Force Summer Research Program -- 1993. Volume 9. Rome Laboratory

DTIC Science & Technology

1993-12-01

Walter Field: Electrical Engineering MS Laboratory: RL/IR Electrical Engineering University of Maine Vol-Page No: 9- 9 Orono, ME 4469-0000 Swindal, J...0000 Tipton, Kevin Field: Zoology MS Laboratory: AL/CF Nutrition and Food Scienc Auburn University Vol-Page No: 7-11 Auburn, AL 36849-5605 Tornow ...deterministic analysis assumed only 1-17 one handling. w ~vA-A-, PPIMAJý PATH Legen(3ND P"ysCaI LinK (forwarid VPC P’ýs Cal L-,* (reverse VPC) Figure 8. OPNET

ALS Association

MedlinePlus

... toward a world without ALS! Walk to Defeat ALS® Walk to Defeat ALS® draws people of all ... We need your help. I Will Advocate National ALS Registry The National ALS Registry is a congressionally ...

Plasticizing aqueous suspensions of concentrated alumina with maltodextrin sugar

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schilling, C.H.; Bellman, R.A.; Smith, R.M.

1999-01-01

Aqueous suspensions of submicrometer, 20 vol% Al{sub 2}O{sub 3} powder exhibited a transition from strongly flocculated, thixotropic behavior to a low-viscosity, Newtonian-like state upon adding small amounts of maltodextrin (0.03 g of maltodextrin/(g of Al{sub 2}O{sub 3})). These suspensions could be filter pressed to highly dense (57%) and extrudable pastes only when prepared with maltodextrin. The authors analyzed the interaction of maltodextrin with Al{sub 2}O{sub 3} powder surfaces and quantitatively measured the resulting claylike consolidation, rheological, and extrusion behaviors. Benbow extrusion parameters were comparable to, but higher than, those of kaolin at approximately the same packing density of 57 vol%.more » In contrast, Al{sub 2}O{sub 3} filter cakes without maltodextrin at 57 vol% density were too stiff to be extruded. Measurements of rheological properties, acoustophoresis, electrophoresis, sorption isotherms, and diffuse reflectance Fourier infrared spectroscopy supported the hypothesis that sorbate-mediated steric hindrance, rather than electrostatic, interparticle repulsion, is important to enhancing the consolidation and fluidity of maltodextrin-Al{sub 2}O{sub 3} suspensions. Viscosity measurements on aqueous maltodextrin solutions indicated that free maltodextrin in solution does not improve suspension fluidity by decreasing the viscosity of the interparticle solution.« less

The Effects of Perchlorate and its Precursors on Organic Molecules under Simulated Mars Conditions

NASA Astrophysics Data System (ADS)

Carrier, B. L.; Beegle, L. W.; Bhartia, R.; Abbey, W. J.

2016-12-01

. References: [1] Hecht et al., Science, Vol. 325, 2009 [2] Glavin et al., J. Geophys. Res. Planets, Vol. 118, 2013 [3] Kounaves et al., Icarus, Vol. 229, 2014 [4] Navarro-Gonzalez et al., J. Geophys. Res., 115, 2010 [5] Carrier & Kounaves, Geophys. Res. Lett., Vol. 42, 2015 [6] Quinn et al, Astrobiology, Vol. 13, 2013 [7] Peters et al., Icarus, Vol. 197, 2008.

Processing, microstructure and mechanics of functionally graded Al A359/SiC(p) composite

NASA Astrophysics Data System (ADS)

Rodriguez-Castro, Ramon

2000-11-01

testing were machined from the cast blocks. No published work has reported specimens of similar characteristics (size of the specimens and continuous reinforcement gradation). Fracture mechanics of the composite specimens with the crack parallel to the gradation in elastic properties was studied to investigate the effect of the nonhomogeneous microstructure on fracture toughness. Fatigue pre-cracking was used and a limited amount of fatigue crack propagation data was gathered. Low values of DeltaKth and increased crack growth resistance in the Paris region were observed for the functionally graded composite compared to a homogeneous 20 vol% composite. R-curve (KR) behavior of fracture was investigated in the functionally graded composite. At elevated SiC concentrations (low values of crack length), limited dissipation of energy by restrained plastic deformation of the matrix at the crack tip produced low fracture toughness values. On the contrary, at longer crack lengths SiC content decreased and there was more absorption of energy, resulting in higher fracture toughness values. In addition, the crack growth resistance behavior of the FGM composite was compared to the corresponding behavior of an Al A359/SiCp 20 vol% homogeneous composite. The latter exhibited a declining KR-curve behavior whereas the FGM composite displayed an increasing KR-curve behavior. Consequently, this increasing crack growth resistance behavior displayed by the functionally graded Al A359/SiCp composite shows that tailored changes in the microstructure could circumvent the low toughness inherent in MMCs.

Shear-wave Velocity Structure and Inter-Seismic Strain Accumulation in the Up-Dip Region of the Cascadia Subduction Zone: Similarities to Tohoku?

NASA Astrophysics Data System (ADS)

Collins, J. A.; McGuire, J. J.; Wei, M.

2013-12-01

The up-dip region of subduction zone thrusts is difficult to study using land-based seismic and geodetic networks, yet documenting its ability to store and release elastic strain is critical for understanding the mechanics of great subduction earthquakes and tsunami generation. The 2011 Tohoku earthquake produced extremely large slip in the shallowest portion of the subduction zone beneath a region of the fore-arc that is comprised of extremely low-velocity, unconsolidated sediments [Tsuru et al. JGR 2012]. The influence of the sediment material properties on the co-seismic slip distribution and tsunami generation can be considerable through both the effects on the dynamic wavefield during the rupture [Kozdon and Dunham, BSSA 2012] and potentially the build up of strain during the inter-seismic period. As part of the 2010-2011 SeaJade experiment [Scherwath et al, EOS 2011], we deployed 10 ocean bottom seismographs (OBS) on the continental slope offshore of Vancouver Island in the region of the NEPTUNE Canada observatory. One goal of the experiment is to measure the shear modulus of the sediments lying above the subducting plate using the seafloor compliance technique. Using seafloor acceleration measured by broadband seismometer and seafloor pressure measured by Differential Pressure Gauge (DPG), we estimate the compliance spectrum in the infra-gravity wave band (~0.002-0.04 Hz) at 9 sites following the methodology of Crawford et al. [JGR, 1991]. We calibrated DPG sensitivities using laboratory measurements and by comparing teleseismic Rayleigh arrivals recorded on the seismometer and DPG channels [Webb, pers. comm]. We correct the vertical-component seismometer data for tilt using the procedure of Crawford and Webb [BSSA, 2000], Corrections for the gravitational attraction of the surface gravity waves [Crawford et al., JGR, 1998] are important at frequencies of 0.003-0.006 Hz only. Typically, the coherences are high (>0.7) in the 0.006 to 0.03 Hz range. We invert

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tan, Xiao-Dong; Xu, Yun-Bo, E-mail: yunbo_xu@126.com; Yang, Xiao-Long

Microstructures composed of lath martensite and retained austenite with volume fraction between 8.0 vol.% and 12.0 vol.% were obtained in a low-C low-Si Al-free steel through hot-rolling direct quenching and dynamical partitioning (HDQ&DP) processes. The austenite stabilization mechanism in the low-C low-Si Al-free steel under the special dynamical partitioning processes is investigated by analyzing the carbon partition behavior from martensite to austenite and the carbide precipitation-coarsening behavior in martensite laths combining with the possible hot rolling deformation inheritance. Results show that the satisfying retained austenite amount in currently studied low-Si Al-free HDQ&DP steel is caused by the high-efficiency carbon enrichmentmore » in the 30–80 nm thick regions of austenite near the interfaces in the hot-rolled ultra-fast cooled structure and the avoidance of serious carbides coarsening during the continuous cooling procedures. The excellent strength-elongation product reaching up to 26,000 MPa% shows that the involved HDQ&DP process is a promising method to develop a new generation of advanced high strength steel. - Highlights: • HDQ&DP processes were applied to a low-C low-Si Al-free steel. • Effective partitioning time during the continuous cooling processes is 1–220 s. • Retained austenite with volume fraction between 8.0 vol. % and 12.0 vol. % has been obtained. • The special austenite stabilization mechanism has been expounded.« less

Piezo-tunnel effect in Al/Al2O3/Al junctions elaborated by atomic layer deposition

NASA Astrophysics Data System (ADS)

Rafael, R.; Puyoo, E.; Malhaire, C.

2017-11-01

In this work, the electrical transport in Al/Al2O3/Al junctions under mechanical stress is investigated in the perspective to use them as strain sensors. The metal/insulator/metal junctions are elaborated with a low temperature process (≤200 °C) fully compatible with CMOS back-end-of-line. The conduction mechanism in the structure is found to be Fowler-Nordheim tunneling, and efforts are made to extract the relevant physical parameters. Gauge factors up to -32.5 were found in the fabricated devices under tensile stress. Finally, theoretical mechanical considerations give strong evidence that strain sensitivity in Al/Al2O3/Al structures originates not only from geometrical deformations but also from the variation of interface barrier height and/or effective electronic mass in the tunneling oxide layer.

Influence of AlN(0001) Surface Reconstructions on the Wettability of an Al/AlN System: A First-Principle Study.

PubMed

Cao, Junhua; Liu, Yang; Ning, Xiao-Shan

2018-05-11

A successful application of a hot dip coating process that coats aluminum (Al) on aluminum nitride (AlN) ceramics, revealed that Al had a perfect wettability to the ceramics under specific circumstances, which was different from previous reports. In order to elucidate the mechanism that controlled the supernormal wetting phenomenon during the dip coating, a first-principle calculation of an Al(111)/AlN(0001) interface, based on the density functional theory (DFT), was employed. The wettability of the Al melt on the AlN(0001) surface, as well as the effect that the surface reconstruction of AlN and the oxygen adsorption had on Al for the adhesion and the wettability of the Al/AlN system, were studied. The results revealed that a LCM (laterally contracted monolayer) reconstruction could improve the adhesion and wettability of the system. Oxygen adsorption on the free surface of Al decreased the contact angle, because the adsorption reduced of the surface tension of Al. A prefect wetting was obtained only after some of the oxygen atoms adsorbed on the free surface of Al. The supernormal wetting phenomenon came from the surface reconstruction of the AlN and the adsorption of oxygen atoms on the Al melt surface.

Japanese version of the ALS-FTD-Questionnaire (ALS-FTD-Q-J).

PubMed

Watanabe, Yasuhiro; Beeldman, Emma; Raaphorst, Joost; Izumi, Yuishin; Yoshino, Hiide; Masuda, Michihito; Atsuta, Naoki; Ito, Satoru; Adachi, Tadashi; Adachi, Yoshiki; Yokota, Osamu; Oda, Masaya; Hanashima, Ritsuko; Ogino, Mieko; Ichikawa, Hiroo; Hasegawa, Kazuko; Kimura, Hideki; Shimizu, Toshio; Aiba, Ikuko; Yabe, Hayato; Kanba, Makoto; Kusumi, Kimiyoshi; Aoki, Tetsuya; Hiroe, Yu; Watanabe, Hirohisa; Nishiyama, Kazutoshi; Nomoto, Masahiro; Sobue, Gen; Nakashima, Kenji

2016-08-15

Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) share common clinical, genetic and neuropathological features. Some ALS patients have behavioral/personality changes, which could result in significant obstacles in the care provided by family members and caregivers. An easy screening tool would contribute greatly to the evaluation of these symptoms. We translated the ALS-FTD-Questionnaire, developed in the Netherlands, into Japanese (ALS-FTD-Q-J) and examined the clinimetric properties (internal consistency, construct and clinical validity). Patients with ALS and/or behavioral variant FTD (bvFTD) were evaluated alongside healthy controls in this multicenter study. All ALS patients, regardless of bvFTD status, were further evaluated by the frontal behavioral inventory (FBI) and for frontal/executive function, cognition, anxiety/depression, and motor functions. Data from 146 subjects were analyzed: ALS (92), ALS-bvFTD (6), bvFTD (16), and healthy controls (32). The internal consistency of the ALS-FTD-Q-J was good (Cronbach α=0.92). The ALS-FTD-Q-J showed construct validity as it exhibited a high correlation with the FBI (r=0.79). However, correlations were moderate with anxiety/depression and low with cognitive scales, in contrast to the original report, i.e. a moderate correlation with cognition and a low correlation with anxiety/depression. The ALS-FTD-Q-J discriminated ALS patients from (ALS-)bvFTD patients and controls. Thus, the ALS-FTD-Q-J is useful for evaluating Japanese ALS/FTD patients. Copyright © 2016 Elsevier B.V. All rights reserved.

3-Dimensional Microstructure of Al-Al3Ti Alloy Severely Deformed by ECAP

NASA Astrophysics Data System (ADS)

Sato, Hisashi; Hishikawa, Takahisa; Makino, Yuuki; Kunimine, Takahiro; Watanabe, Yoshimi

Microstructure of Al-Al3Ti alloy deformed by Equal-Channel-Angular Pressing (ECAP) is 3-dimensionally investigated. Especially, distribution of Al3Ti particles is focused in this study. The Al-Al3Ti alloy has coarse Al3Ti platelet particles in α-Al matrix. When the Al-Al3Ti alloy is deformed by ECAP under route A, fine Al3Ti platelet particles are observed. These Al3Ti platelet particles are aligned along to deformation axis, and its plane normal is perpendicular to the deformation axis. On the other hand, Al-Al3Ti alloy ECAPed under route Bc forms several groups consisted of fine Al3Ti platelet particles. Moreover, longitudinal size of the Al3Ti particle groups is close to that of initial Al3Ti particles with 4-pass ECAP specimen. These distribution behaviors of the Al3Ti particle can be explained by plastic flow of α-Al matrix. Finally, it is concluded that distribution of Al3Ti particle in Al-Al3Ti alloy by ECAP is controlled by plastic deformation of α-Al matrix.

Experimental and Analytical Study of Two-Phase Flow in Zero Gravity.

DTIC Science & Technology

1988-03-01

in Imitated Reduced Gravity Fields," 4th International Heat Transfer Conference, Versailles, France, Vol. 6, 1970. 11. S. S. Papell and 0. C. Faber...K. D. Timmerhaus, ed.) Vol. 9, p 45, Plenum, New York, 1963. 63. S. S. Papell et al., "Buoyancy Effects on Critical Heat Flux of Forced Convective

Abu al-Layth al-Libi

DTIC Science & Technology

2015-02-01

in the region and apparently “showed brilliance in this regard through his perfect memorization , clever understanding, persistence, and patience...Taliban’s officials quietly left the capital without informing 73 Vernie Liebl, “Al-Qaida on the US Invasion of Afghanistan in Their Own Words ,” Small Wars... memorization . A talented and charismatic orator, he also used to deliver eulogies and `Id sermons. As to `Abdallah Sa`id al-Libi, his profile is similar

Defect structures in ordered intermetallics; grain boundaries and surfaces in FeAl, NiAl, CoAl and TiAl

NASA Astrophysics Data System (ADS)

Mutasa, Batsirai Manyara

Ordered intermetallics based on transition metal aluminides have been proposed as structural materials for advanced aerospace applications. The development of these materials, which have the advantages of low density and high operating temperatures, have been focused on the aluminides of titanium, nickel and iron. Though these materials exhibit attractive properties at elevated temperatures, their utilization is limited due to their propensity for low temperature fracture and susceptibility to decreased ductility due to environmental effects. A major embrittlement mechanism at ambient temperatures in these aluminides has been by the loss of cohesive strength at the interfaces (intergranular failure). This study focuses on this mechanism of failure, by undertaking a systematic study of the energies and structures of specific grain boundaries in some of these compounds. The relaxed atomistic grain boundary structures in B2 aluminides, FeAl, NiAl and CoAl and L10 gamma-TiAl were investigated using molecular statics and embedded atom potentials in order to explore general trends for a series of B2 compounds as well as TiAl. The potentials used correctly predict the proper mechanism of compositional disorder of these compounds. Using these potentials, point defects, free surface energies and various grain boundary structures of similar energies in three B2 compounds, FeAl, NiAl and CoAl were studied. These B2 alloys exhibited increasing anti-phase boundary energies respectively. The misorientations chosen for detailed study correspond to the Sigma5(310) and Sigma5(210) boundaries. These boundaries were investigated with consideration given to possible variations in the local chemical composition. The effects of both boundary stoichiometry and bulk stoichiometry on grain boundary energetics were also considered. Defect energies were calculated for boundaries contained in both stoichiometric and off-stoichiometric bulk. The surface energies for these aluminides were also

Analysis of Mars surface hydration through the MEx/OMEGA observation of the 3 μm absorption band.

NASA Astrophysics Data System (ADS)

Jouglet, D.; Poulet, F.; Bibring, J. P.; Langevin, Y.; Gondet, B.; Milliken, R. E.; Mustard, J. F.

may be explained by a decrease of pressure with altitude so that less water can adsorb on minerals. Study of global maps reveals a strong increase of hydration with high latitudes (over 60°N), maybe due to a change in composition [9]. Careful analysis also shows seasonal variations of the hydration of soils with the decrease of hydration between spring and summer for mid latitudes regions (from 40°N to 60°N). This hydration enrichment is not due to instrumental effect or to the presence of aerosols or water ice. It is associated to an increase of hydration with latitude in spring, increase that has disappeared in summer. This temporal variation may be explained by the presence of frost in winter. Frost is in contact with minerals and imposes a high water vapor pressure, which makes water to fix on minerals during winter. Then the hydration of the surface returns to equilibrium with the atmosphere by releasing water. These variations seem to confirm the important role of regolith on water cycle, which was predicted from numerical simulations (e.g. [10]). [1] Cooper C.D. and Mustard J.F. (1999) Icarus 142, 557-570. [2] Jouglet D.et al., article in preparation. [3] Yen A.S. et al (1998) JGR E5, 103, 11,125-11,133. [4] Zent A.P. and Quinn R.C.(1997) JGR E4, 102, 9085-9095. [5] Yen A.S. et al (2005), Nature 436, 49-54. [6] Hurowitz J.A. et al (2006) JGR, 111, E02S19, doi:10.1029/2005JE002515. [7] Poulet F. et al (2005) Nature 438, 623-627. [8] Gendrin A. et al. (2005) Science 307, 1587-1591. [9] Milliken et al, article in preparation. [10] Böttger H.M.et al. (2005) Icarus 177, 174-189. 2

A Rechargeable Al/S Battery with an Ionic-Liquid Electrolyte.

PubMed

Gao, Tao; Li, Xiaogang; Wang, Xiwen; Hu, Junkai; Han, Fudong; Fan, Xiulin; Suo, Liumin; Pearse, Alex J; Lee, Sang Bok; Rubloff, Gary W; Gaskell, Karen J; Noked, Malachi; Wang, Chunsheng

2016-08-16

Aluminum metal is a promising anode material for next generation rechargeable batteries owing to its abundance, potentially dendrite-free deposition, and high capacity. The rechargeable aluminum/sulfur (Al/S) battery is of great interest owing to its high energy density (1340 Wh kg(-1) ) and low cost. However, Al/S chemistry suffers poor reversibility owing to the difficulty of oxidizing AlSx . Herein, we demonstrate the first reversible Al/S battery in ionic-liquid electrolyte with an activated carbon cloth/sulfur composite cathode. Electrochemical, spectroscopic, and microscopic results suggest that sulfur undergoes a solid-state conversion reaction in the electrolyte. Kinetics analysis identifies that the slow solid-state sulfur conversion reaction causes large voltage hysteresis and limits the energy efficiency of the system. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

"Defining 'peerness' in peer-delivered health and wellness interventions for serious mental illness": Correction to Muralidharan et al. (2017).

PubMed

2017-06-01

Reports an error in "Defining "peerness" in peer-delivered health and wellness interventions for serious mental illness": Response to letter to the editor" by Jody Silver and Patricia B. Nemec ( Psychiatric Rehabilitation Journal , 2017[Mar], Vol 40[1], 116). The article was mislabeled as Editorial and should be a Comment. The Response to Letter to the Editor section should be a Reply and now has its own http://dx.doi.org/10.1037/ h0101580. (The following abstract of the original article appeared in record 2017-13876-001.) Replies to comments by Muralidharan et al (see record 2017-13255-009) on the original article by Silver and Nemec (see record 2016-43088-001). The original authors thank the commentators for raising additional questions regarding "peerness." They were honored that their paper prompted this thought and effort to submit comments. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

Development of tearing instability in a current sheet forming by sheared incompressible flow

NASA Astrophysics Data System (ADS)

Tolman, Elizabeth A.; Loureiro, Nuno F.; Uzdensky, Dmitri A.

2018-02-01

Sweet-Parker current sheets in high Lundquist number plasmas are unstable to tearing, suggesting they will not form in physical systems. Understanding magnetic reconnection thus requires study of the stability of a current sheet as it forms. Formation can occur due to sheared, sub-Alfvénic incompressible flows which narrow the sheet. Standard tearing theory (Furth et al. Phys. Fluids, vol. 6 (4), 1963, pp. 459-484, Rutherford, Phys. Fluids, vol. 16 (11), 1973, pp. 1903-1908, Coppi et al. Fizika Plazmy, vol. 2, 1976, pp. 961-966) is not immediately applicable to such forming sheets for two reasons: first, because the flow introduces terms not present in the standard calculation; second, because the changing equilibrium introduces time dependence to terms which are constant in the standard calculation, complicating the formulation of an eigenvalue problem. This paper adapts standard tearing mode analysis to confront these challenges. In an initial phase when any perturbations are primarily governed by ideal magnetohydrodynamics, a coordinate transformation reveals that the flow compresses and stretches perturbations. A multiple scale formulation describes how linear tearing mode theory (Furth et al. Phys. Fluids, vol. 6 (4), 1963, pp. 459-484, Coppi et al. Fizika Plazmy, vol. 2, 1976, pp. 961-966) can be applied to an equilibrium changing under flow, showing that the flow affects the separable exponential growth only implicitly, by making the standard scalings time dependent. In the nonlinear Rutherford stage, the coordinate transformation shows that standard theory can be adapted by adding to the stationary rates time dependence and an additional term due to the strengthening equilibrium magnetic field. Overall, this understanding supports the use of flow-free scalings with slight modifications to study tearing in a forming sheet.

Growth of Ni-Al alloys on Ni(1 1 1), from Al deposits of various thicknesses: (II) Formation of NiAl over a Ni 3Al interfacial layer

NASA Astrophysics Data System (ADS)

Le Pévédic, S.; Schmaus, D.; Cohen, C.

2007-01-01

This paper describes the second part of a study devoted to the growth of thin Ni-Al alloys after deposition of Al on Ni(1 1 1). In the previous paper [S. Le Pévédic, D. Schmaus, C. Cohen, Surf. Sci. 600 (2006) 565] we have described the results obtained for ultra-thin Al deposits, leading, after annealing at 750 K, to an epitaxial layer of Ni 3Al(1 1 1). In the present paper we show that this regime is only observed for Al deposits smaller than 8 × 10 15 Al/cm 2 and we describe the results obtained for Al deposits exceeding this critical thickness, up to 200 × 10 15 Al/cm 2. Al deposition was performed at low temperature (around 130 K) and the alloying process was followed in situ during subsequent annealing, by Auger electron spectroscopy, low energy electron diffraction and ion beam analysis-channeling measurements, in an ultra-high vacuum chamber connected to a Van de Graaff accelerator. We evidence the formation, after annealing at 750 K, of a crystallographically and chemically well-ordered NiAl(1 1 0) layer (whose thickness depends on the deposited Al amount), over a Ni 3Al "interfacial" layer (whose thickness—about 18 (1 1 1) planes—is independent of the deposited Al amount). The NiAl overlayer is composed of three variants, at 120° from each other in the surface plane, in relation with the respective symmetries of NiAl(1 1 0) and Ni 3Al(1 1 1). The NiAl layer is relaxed (the lattice parameters of cc-B2 NiAl and fcc-L1 2 Ni 3Al differ markedly), and we have determined its epitaxial relationship. In the case of the thickest alloyed layer formed the results concerning the structure of the NiAl layer have been confirmed and refined by ex situ X-ray diffraction and information on its grain size has been obtained by ex situ Atomic Force Microscopy. The kinetics of the alloying process is complex. It corresponds to an heterogeneous growth leading, above the thin Ni 3Al interfacial layer, to a mixture of Al and NiAl over the whole Al film, up to the

Why publish with AGU?

NASA Astrophysics Data System (ADS)

Graedel, T. E.

The most visible activity of the American Geophysical Union is its publication of scientific journals. There are eight of these: Journal of Geophysical Research—Space Physics (JGR I), Journal of Geophysical Research—Solid Earth (JGR II), Journal of Geophysical Research—Oceans and Atmospheres (JGR III), Radio Science (RS), Water Resources Research (WRR), Geophysical Research Letters (GRL), Reviews of Geophysics and Space Physics (RGSP), and the newest, Tectonics.AGU's journals have established solid reputations for scientific excellence over the years. Reputation is not sufficient to sustain a high quality journal, however, since other factors enter into an author's decision on where to publish his or her work. In this article the characteristics of AGU's journals are compared with those of its competitors, with the aim of furnishing guidance to prospective authors and a better understanding of the value of the products to purchasers.

Multidisciplinary ALS care improves quality of life in patients with ALS.

PubMed

Van den Berg, J P; Kalmijn, S; Lindeman, E; Veldink, J H; de Visser, M; Van der Graaff, M M; Wokke, J H J; Van den Berg, L H

2005-10-25

To examine the effect of multidisciplinary ALS care on the quality-of-life (QoL) in patients with ALS and their caregivers. In a cross-sectional study, 208 patients with ALS and their caregivers were interviewed. QoL was assessed using the 36-item Short Form Health Survey (SF-36) and two visual analogue scales (VAS). Criteria for multidisciplinary ALS care were: an ALS team headed by a consultant in rehabilitation medicine and consisting of at least a physical therapist, occupational therapist, speech pathologist, dietician and a social worker; use of the Dutch ALS consensus guidelines for ALS care; and at least six incident ALS patients per year. Clinical characteristics and functional loss of the 133 patients receiving multidisciplinary ALS care and the 75 patients receiving general ALS care were similar. The percentage of patients with adequate aids and appliances was higher in those with multidisciplinary ALS care (93.1 vs 81.3%, p = 0.008), whereas the number of visits to professional caregivers was similar in both groups. Patients in the multidisciplinary ALS care group had a better mental QoL on the SF-36 Mental Summary Score than those in the general care group (p = 0.01). The difference in QoL was most pronounced in the domains of Social Functioning and Mental Health, and was independent of the presence of aids and appliances. No significant differences were found in the SF-36 Physical Summary Score, VAS, or in QoL of caregivers of patients with ALS. High standard of care improves mental quality-of-life in patients with ALS.

Theoretical Investigations of Dielectric Breakdown in CO2: Implications for Atmospheric Discharges on Mars (and Venus)

NASA Astrophysics Data System (ADS)

Riousset, J. A.

2017-12-01

The detection of an atmospheric discharge in the Martian atmosphere by Ruf et al. [GRL, 36, L13202, 2009] supports the idea of a Martian atmospheric electric circuit [Farrell and Desch, JGR, 106, E4, 2001]. However, the lack of subsequent detection of similar events raises the question of the conditions of their initiation, and the existence of Martian lightning remains a controversial question. On Earth, atmospheric electricity manifests itself in the form of glow, corona, streamer, and leader discharges observed as Saint Elmo's fire, sprites, lightning and jets discharges, and other Transient Luminous Events (TLEs). All of these are dielectric breakdown governed by different physics. Their initiation is associated with the crossing of specific electric field thresholds: relativistic runaway, streamer propagation, conventional breakdown, or thermal runaway thresholds, some better understood than others. For example, the initiation of a lightning discharge is known to occur when the local electric field exceeds a value similar to relativistic runaway field, but the exact threshold, as well as the physical mechanisms at work, remain unclear to date. Scaling laws for electric fields (and other quantities) have been established by Pasko et al. [GRL, 25(12), 2123-2126, 1998] and Pasko [NATO Sci. Series, Springer, 253-311, 2006]. In this work, we develop profiles for initiation criteria in air and in other atmospheric environments. We further calculate their associated scaling laws to determine the ability to trigger lightning flashes and TLEs on Mars. This lets us predict the likelihood of electrical discharges and calculate the expected electric field conditions, under which discharges could be observed. We develop the analogy between Earth sand storm [Nicoll et al., Env. Res. Lett., 6, 014001, 2001] and Martian dust storms [Melnik and Parrot, JGR, 103(A12), 1998] to investigate the charge structure and resulting electric fields necessary to initiate dielectric

Structure-property relationships in an Al matrix Ca nanofilamentary composite conductor with potential application in high-voltage power transmission

NASA Astrophysics Data System (ADS)

Tian, Liang

This study investigated the processing-structure-properties relationships in an Al/Ca composites using both experiments and modeling/simulation. A particular focus of the project was understanding how the strength and electrical conductivity of the composite are related to its microstructure in the hope that a conducting material with light weight, high strength, and high electrical conductivity can be developed to produce overhead high-voltage power transmission cables. The current power transmission cables (e.g., Aluminum Conductor Steel Reinforced (ACSR)) have acceptable performance for high-voltage AC transmission, but are less well suited for high-voltage DC transmission due to the poorly conducting core materials that support the cable weight. This Al/Ca composite was produced by powder metallurgy and severe plastic deformation by extrusion and swaging. The fine Ca metal powders have been produced by centrifugal atomization with rotating liquid oil quench bath, and a detailed study about the atomization process and powder characteristics has been conducted. The microstructure of Al/Ca composite was characterized by electron microscopy. Microstructure changes at elevated temperature were characterized by thermal analysis and indirect resistivity tests. The strength and electrical conductivity were measured by tensile tests and four-point probe resistivity tests. Predicting the strength and electrical conductivity of the composite was done by micro-mechanics-based analytical modeling. Microstructure evolution was studied by mesoscale-thermodynamics-based phase field modeling and a preliminary atomistic molecular dynamics simulation. The application prospects of this composite was studied by an economic analysis. This study suggests that the Al/Ca (20 vol. %) composite shows promise for use as overhead power transmission cables. Further studies are needed to measure the corrosion resistance, fatigue properties and energized field performance of this composite.

AlGaN-based ultraviolet light-emitting diodes on sputter-deposited AlN templates with epitaxial AlN/AlGaN superlattices

NASA Astrophysics Data System (ADS)

Zhao, Lu; Zhang, Shuo; Zhang, Yun; Yan, Jianchang; Zhang, Lian; Ai, Yujie; Guo, Yanan; Ni, Ruxue; Wang, Junxi; Li, Jinmin

2018-01-01

We demonstrate AlGaN-based ultraviolet light-emitting diodes (UV-LEDs) grown by metalorganic chemical vapor deposition (MOCVD) on sputter-deposited AlN templates upon sapphire substrates. An AlN/AlGaN superlattices structure is inserted as a dislocation filter between the LED structure and the AlN template. The full width at half maximum values for (0002) and (10 1 bar 2) X-ray rocking curves of the n-type Al0.56Ga0.44N layer are 513 and 1205 arcsec, respectively, with the surface roughness of 0.52 nm. The electron concentration and mobility measured by Hall measurement are 9.3 × 1017cm-3 and 54 cm2/V·s at room temperature, respectively. The light output power of a 282-nm LED reaches 0.28 mW at 20 mA with an external quantum efficiency of 0.32%. And the values of leakage current and forward voltage of the LEDs are ∼3 nA at -10 V and 6.9 V at 20 mA, respectively, showing good electrical performance. It is expected that the cost of the UV-LED can be reduced by using sputter-deposited AlN template.

volBrain: An Online MRI Brain Volumetry System

PubMed Central

Manjón, José V.; Coupé, Pierrick

2016-01-01

The amount of medical image data produced in clinical and research settings is rapidly growing resulting in vast amount of data to analyze. Automatic and reliable quantitative analysis tools, including segmentation, allow to analyze brain development and to understand specific patterns of many neurological diseases. This field has recently experienced many advances with successful techniques based on non-linear warping and label fusion. In this work we present a novel and fully automatic pipeline for volumetric brain analysis based on multi-atlas label fusion technology that is able to provide accurate volumetric information at different levels of detail in a short time. This method is available through the volBrain online web interface (http://volbrain.upv.es), which is publically and freely accessible to the scientific community. Our new framework has been compared with current state-of-the-art methods showing very competitive results. PMID:27512372

volBrain: An Online MRI Brain Volumetry System.

PubMed

Manjón, José V; Coupé, Pierrick

2016-01-01

The amount of medical image data produced in clinical and research settings is rapidly growing resulting in vast amount of data to analyze. Automatic and reliable quantitative analysis tools, including segmentation, allow to analyze brain development and to understand specific patterns of many neurological diseases. This field has recently experienced many advances with successful techniques based on non-linear warping and label fusion. In this work we present a novel and fully automatic pipeline for volumetric brain analysis based on multi-atlas label fusion technology that is able to provide accurate volumetric information at different levels of detail in a short time. This method is available through the volBrain online web interface (http://volbrain.upv.es), which is publically and freely accessible to the scientific community. Our new framework has been compared with current state-of-the-art methods showing very competitive results.

LROC Observations of Geologic Features in the Marius Hills

NASA Astrophysics Data System (ADS)

Lawrence, S.; Stopar, J. D.; Hawke, R. B.; Denevi, B. W.; Robinson, M. S.; Giguere, T.; Jolliff, B. L.

2009-12-01

, to enable measurements of color variations within and amongst deposits and provide possible compositional insights, including the location of possibly related pyroclastic deposits. References: [1] J. D. Stopar et al. (2009), LRO Science Targeting Meeting, Abs. 6039 [2] Greeley R (1971) Moon, 3, 289-314 [3] Guest J. E. (1971) Geol. and Phys. of the Moon, p. 41-53. [4] McCauley J. F. (1967) USGS Geologic Atlas of the Moon, Sheet I-491 [5] Weitz C. M. and Head J. W. (1999) JGR, 104, 18933-18956 [6] Heather D. J. et al. (2003) JGR, doi:10.1029/2002JE001938 [7] Whitford-Stark, J. L., and J. W. Head (1977) Proc. LSC 8th, 2705-2724 [8] Gruener J. and Joosten B. K. (2009) LRO Science Targeting Meeting, Abs. 6036 [9] Campbell B. A. et al. (2009) JGR, doi:10.1029/2008JE003253.

Prevalence of Bowel Incontinence

MedlinePlus

... Urinary Incontinence in Adults. December 12, 2007. Drossman DA, Li Z, Andruzzi E, et al. U.S. Householder ... Rectum Vol. 41, No. 10 October 1998. Drossman DA, Sandler RS, Broom CM, et al. Urgency and ...

Cyclic oxidation resistance of a reaction milled NiAl-AlN composite

NASA Technical Reports Server (NTRS)

Lowell, Carl E.; Barrett, Charles A.; Whittenberger, J. D.

1990-01-01

Based upon recent mechanical property tests a NiAl-AlN composite produced by cryomilling has very attractive high temperature strength. This paper focuses on the oxidation resistance of the NiAl-AlN composite at 1473 and 1573 K as compared to that of Ni-47Al-0.15Zr, one of the most oxidation resistant intermetallics. The results of cyclic oxidation tests show that the NiAl-AlN composite has excellent properties although not quite as good as those of Ni-47Al-0.15Zr. The onset of failure of the NiAl-AlN was unique in that it was not accompanied by a change in scale composition from alumina to less protective oxides. Failure in the composite appears to be related to the entrapment of AlN particles within the alumina scale.

ALS-Plus Syndrome: Non-Pyramidal Features in a Large ALS Cohort

PubMed Central

McCluskey, Leo; Vandriel, Shannon; Elman, Lauren; Van Deerlin, Vivianna M.; Powers, John; Boller, Ashley; Wood, Elisabeth McCarty; Woo, John; McMillan, Corey T.; Rascovsky, Katya; Grossman, Murray

2014-01-01

Objective Autopsy studies show widespread pathology in amyotrophic lateral sclerosis (ALS), but clinical surveys of multisystem disease in ALS are rare. We investigated ALS-Plus syndrome, an understudied group of patients with clinical features extending beyond pyramidal and neuromuscular systems with or without cognitive/behavioral deficits. Methods In a large, consecutively-ascertained cohort of 550 patients with ALS, we documented atypical clinical manifestations. Genetic screening for C9orf72 hexanucleotide expansions was performed in 343 patients, and SOD1, TARDBP, and VCP were tested in the subgroup of patients with a family history of ALS. Gray matter and white matter imaging was available in a subgroup of 30 patients. Results Seventy-five (13.6%) patients were identified with ALS-Plus syndrome. We found disorders of ocular motility, cerebellar, extrapyramidal and autonomic functioning. Relative to those without ALS-Plus, cognitive impairment (8.0% vs 2.9%, p=0.029), bulbar-onset (49.3% vs 23.2%, p<0.001), and pathogenic mutations (20.0% vs 8.4%, p=0.015) were more than twice as common in ALS-Plus. Survival was significantly shorter in ALS-Plus (29.66 months vs 42.50 months, p=0.02), regardless of bulbar-onset or mutation status. Imaging revealed significantly greater cerebellar and cerebral disease in ALS-Plus compared to those without ALS-Plus. Conclusions ALS-Plus syndrome is not uncommon, and the presence of these atypical features is consistent with neuropathological observations that ALS is a multisystem disorder. ALS-Plus syndrome is associated with increased risk for poor survival and the presence of a pathogenic mutation. PMID:25086858

SOA Measurements vs. Models: A Status Report

NASA Astrophysics Data System (ADS)

Jimenez, Jose-Luis; de Gouw, Joost; Hodzic, Alma

2010-05-01

The advent of fast and chemically-resolved organic aerosol (OA) and VOC measurements in the last decade has allowed more detailed model-measurement comparisons for OA and secondary OA (SOA). Large model underpredictions have been reported for SOA at many locations, but this is not always the case. Here we summarize the patterns emerging from studies to date, focusing on studies that use highly time and/or chemically resolved OA measurements. The model-measurement comparisons exhibit clear patterns depending on the region of the atmosphere. • At least 8 studies have reported a large (x5-10) underestimation of SOA for polluted regions when using traditional models (those developed until ~2006) (Heald GRL05, Volkamer GRL06, Johnson ACP06, Kleinman ACP08, Matsui JGR09, Dzepina ACP09, Hodzic ACP09, Tsimpidi ACP09). This is especially obvious when models are evaluated with the ΔOA/ΔCO ratio. • Close to pollution sources, discrepancies of an order-of-magnitude in SOA lead to smaller discrepancies (often x2-3) for total OA due to the presence of primary OA (de Gouw EST09). Such OA discrepancies have been repeatedly observed (e.g. Vutukuru JGR06, McKeen JGR07&09, Heald JGR07, Fast ACP09, Hodzic ACP09). • The discrepancy is reduced when recently-updated yields for aromatics (Ng ACP07) and SOA from glyoxal (Volkamer GRL07) are used, and is eliminated when using SOA formation from S/IVOC (Robinson Sci07) although with an overprediction of SOA at long aging times (Dzepina ACP09; Hodzic ACP10), especially with the Grieshop (ACP09) update of the Robison mechanism (Hodzic10). It is not clear whether the urban discrepancy is removed for the right reasons. • 4 evaluations of biogenic SOA formed in unpolluted regions find reasonable agreement between SOA from traditional models and field measurements (Tunved Sci06; Hodzic ACP09; Chen GRL09; Slowik ACPD09). One evaluation reports a significant underprediction (Capes ACP09), although the amount of precursor reacted was

Self-Consistent Generation of Continental Crust in Global Mantle Convection Models

NASA Astrophysics Data System (ADS)

Jain, C.; Rozel, A. B.; Tackley, P.

2016-12-01

Numerical modelling commonly shows that mantle convection and continents have strong feedbacks on each other (Philips and Coltice, JGR 2010; Heron and Lowman, JGR 2014), but the continents are always inserted a priori while basaltic (oceanic) crust is generated self-consistently in such models (Rolf et al., EPSL 2012). We aim to implement self-consistent generation of continental crust in global models of mantle convection using StagYY (Tackley, PEPI 2008). The silica-rich continental crust appears to have been formed by fractional melting and crystallization in episodes of relatively rapid growth from late Archaean to late Proterozoic eras (3-1 Ga) (Hawkesworth & Kemp, Nature 2006). It takes several stages of differentiation to generate continental crust. First, the basaltic magma is extracted from the pyrolitic mantle. Second, it goes through eclogitic transformation and then partially melts to form Na-rich Tonalite-Trondhjemite-Granodiorite (TTG) which rise to form proto-continents (Rudnick, Nature 1995; Herzberg & Rudnick, Lithos 2012). TTGs dominate the grey gneiss complexes which make up most of the continental crust. Based on the melting conditions proposed by Moyen (Lithos, 2011), we parameterize TTG formation and henceforth, the continental crust. Continental crust can also be destroyed by subduction or delamination. We will investigate continental growth and destruction history in the models spanning the age of the Earth.

Self-consistent generation of continental crust in global mantle convection models

NASA Astrophysics Data System (ADS)

Jain, Charitra; Rozel, Antoine; Tackley, Paul

2017-04-01

Numerical modeling commonly shows that mantle convection and continents have strong feedbacks on each other (Philips and Coltice, JGR 2010; Heron and Lowman, JGR 2014), but the continents are always inserted a priori while basaltic (oceanic) crust is generated self-consistently in such models (Rolf et al., EPSL 2012). We aim to implement self-consistent generation of continental crust in global models of mantle convection using StagYY (Tackley, PEPI 2008). The silica-rich continental crust appears to have been formed by fractional melting and crystallization in episodes of relatively rapid growth from late Archean to late Proterozoic eras (3-1 Ga) (Hawkesworth & Kemp, Nature 2006). It takes several stages of differentiation to generate continental crust. First, the basaltic magma is extracted from the pyrolitic mantle. Second, it goes through eclogitic transformation and then partially melts to form Na-rich Tonalite-Trondhjemite-Granodiorite (TTG) which rise to form proto-continents (Rudnick, Nature 1995; Herzberg & Rudnick, Lithos 2012). TTGs dominate the grey gneiss complexes which make up most of the continental crust. Based on the melting conditions proposed by Moyen (Lithos, 2011), we parameterize TTG formation and henceforth, the continental crust. Continental crust can also be destroyed by subduction or delamination. We will investigate continental growth and destruction history in the models spanning the age of the Earth.

The Effect of Wavelength-Dependent Emissivity on the Melting Temperatures of Iron From Shock Wave Measurements

NASA Astrophysics Data System (ADS)

Heinz, D. L.; Mark, H.

2012-12-01

The high-pressure melting curve of iron at the conditions of the outer core is anchored by the shock wave measurements of Bass et. al. 1987. They used spectral radiometric techniques, looking at shocked iron films or foils through a transparent anvil. They assumed that the emissivity of the iron was independent of wavelength. The wavelength dependence of the emissivity of fcc and bcc iron was measured by Taylor, 1952. Both structures have a change in emissivity of 20% over 200nm in the visible, although the absolute magnitude of the emissivity is different. In the measurement of temperature using spectral radiometry, the absolute value of the emissivity does not effect the temperature measurement. In iron the 3d-bands straddle the Fermi Energy in any close packed structure (Boness and Brown, 1990). The electrons at the Fermi Energy can easily be promoted into the empty states of the conduction band, and thus are the basis of the electronic contribution to the heat capacity. It is these same electrons in the 3d-bands that also control the emissivity. With increasing wavelength, more electrons are promoted into the conduction band, which means the emissivity is higher at shorter wavelengths than at longer wavelengths. We reanalyzed the shock wave data of Bass et. al. using the wavelength dependent emissivity. The corrected melting temperature of iron at 243 GPa is 5900 +/-500 K compared to Bass et. al.'s determination of 6700 +/- 400 K. This is just slightly higher then the estimate (based upon the assumption of the heat capacity being equal to 5R) of Brown and McQueen, 1986 of 5000-5700 K, and in good agreement with theoretical calculations of Alfe, 2010. Alfe, D., 2010, Rev. Min. and Geochem., 71, 337-354. Bass, J. D., B. Svendsen, and T. J. Ahrens, 1987, M. H. Manghnani and Y. Syono, Terra Scientific Publishing Co. / American Geophysical Union, Washington, D. C., 393-402. Boness, D. A., and J. M. Brown, 1990, JGR, 95, 21,721-30. Brown, J. M. and R. G. Mc

Developing a Hygrometer for Water-Undersaturated Lherzolite Melts

NASA Astrophysics Data System (ADS)

Guild, M. R.; Till, C. B.

2017-12-01

The effect of water on the composition of primitive mantle melts at arc volcanoes is a topic of wide interest and has been addressed in a number of previous experimental studies including Hirose & Kawamoto (1995), Gaetani & Grove (1998), Till et al. (2012) and Mitchell & Grove (2015). The current study builds upon the work by previous authors in an effort to develop a more robust hygrometer for primitive lherzolite melts at water-undersaturated conditions. The starting composition for this experimental study is a mixture of 75% primitive upper mantle and 25% primitive basalt (Baker et al., 1991) with a bulk H2O content of 2 wt. %. Experiments were performed at Arizona State University in the Experimental Petrology and Igneous processes Center (EPIC) from 1.2-1.6 GPa at 1150-1300 ºC for 2 days in a piston cylinder apparatus to reflect conditions relevant for arc melt equilibration (Till 2017). A double capsule design was used to prevent Fe and H2O loss with an inner Fe-presaturated Au80Pd20 capsule and an outer Au80Pd20 capsule. Run products were analyzed by electron microprobe and determined to be successful when they demonstrated 0-5% Fe-loss, olivine-melt KDs of 0.27-0.30, and minimal H2O loss. The water-undersaturated melt composition are in equilibrium with ol+opx+sp±cpx. Run products at 1.6 GPa do not contain cpx in the mineral assemblage over the studied temperature range. Observed melt compositions have SiO2 contents of 48-49 wt. % at 1.2 GPa and 46-49 wt.% at 1.6 GPa. Our experimental results suggest an enhanced effect of water on increasing the SiO2 content of the melt compared to previous studies on systems with similar water contents and anhydrous systems. Baker, et al., JGR 96, 21819-21842 (1991). Gaetani & Grove, CMP 131, 323-346 (1998). Hirose & Kawamoto, EPSL 133, 463-473 (1995). Mitchell & Grove, CMP 170, 13 (2015). Till, Am. Mineral, 102, 931-947 (2017). Till, et al., JGR 117 (2012).

Modeling of Small Martian Volcanoes: A Changing View of Volcanic Shield and Cone Fields

NASA Astrophysics Data System (ADS)

Sakimoto, S. E.; Bradley, B. A.; Garvin, J. B.

2001-05-01

The small volcanic features on Mars (channels, flows, shields, and cratered cones) are key to understanding eruption styles, rates, and volumes because they are ubiquitous and simple enough to attempt modeling. Several of these small features have been suggested to be geologically recent [1,2,3]. This study measures and models small (3-50 km) volcanic edifices. Recent Mars Global Surveyor data reveal that these small features are more common that we had previously thought from the lower resolution Viking mission data (e.g., [3,4]). Furthermore, there are clear geometric differences in the Mars Orbiter Laser Altimeter (MOLA) data between regions suggesting local and regional eruption styles may vary with latitude. While a few of the pre-MGS construction models predict the martian mid-latitude volcanic shield shapes fairly well, the small explosive volcanic edifice shapes were not well predicted by existing models (see[5]), and there are a host of types-mostly polar-that are not well described by prior modeling. We compare small edifice construction model results for a percolation style model of effusive and mixed effusive and explosive edifices to prior model results for several martian volcanic regions. While mid-latitude edifices match well to predicted cross-section shapes, steeper flank slopes (See [6]; Glaze and Sakimoto, this volume) for the polar edifices suggest that the magma supply rate or the edifice permeability may be higher in the polar regions for some edifices types. However, polar edifice flank slopes do not commonly reach the greater than 10 degree flanks expected from prior explosive edifice models. Additionally, we do not observe shallow flank slope shields in the polar regions. This suggests that simple shield building may be significantly influenced or modified by volatile involvement near the martian poles, while a range of poorly understood explosive activity may be active in both regions. [1] Keszthelyi et al. JGR 105, 15027-15049, 2000. [2

SOA Measurements vs. Models: a Status Report

NASA Astrophysics Data System (ADS)

Jimenez, J. L.; de Gouw, J. A.

2009-12-01

The advent of fast and more detailed organic aerosol (OA) and VOC measurements in the last decade has allowed clearer model-measurement comparisons for OA and secondary OA (SOA). Here we summarize the patterns emerging from studies to date.

Valence subband coupling effect on polarization of spontaneous emissions from Al-rich AlGaN/AlN quantum wells.

PubMed

Lu, Huimin; Yu, Tongjun; Yuan, Gangcheng; Jia, Chuanyu; Chen, Genxiang; Zhang, Guoyi

2012-12-03

The optical polarization properties of Al-rich AlGaN/AlN quantum wells (QWs) were investigated using the theoretical model based on the k·p method. Numerical results show that there is valence subband coupling which can influence the peak emission wavelength and emission intensity for TE and TM polarization components from Al-rich AlGaN/AlN QWs. Especially the valence subband coupling could be strong enough when CH1 is close to HH1 and LH1 subbands to modulate the critical Al content switching dominant emissions from TE to TM polarization. It is believed that the valence subband coupling may give important influence on polarization properties of spontaneous emissions and should be considered in designing high efficiency AlGaN-based ultraviolet (UV) LEDs.

Modulating optical polarization properties of Al-rich AlGaN/AlN quantum well by controlling wavefunction overlap

NASA Astrophysics Data System (ADS)

Chen, X. J.; Yu, T. J.; Lu, H. M.; Yuan, G. C.; Shen, B.; Zhang, G. Y.

2013-10-01

Using modified k.p perturbation method, the optical polarization properties of Al-rich AlGaN/AlN quantum wells (QWs) are studied. It is found that change of wavefunction overlaps between conduction band and valance subbands of heavy hole, light hole, and crystal-field split off hole is different. Such difference leads to the overturn of polarization degree and modulates optical polarization properties as well width and strain vary. This prompts that changing wavefunction overlaps of electron and hole can lead to a way to modulate optical polarization properties of Al-rich AlGaN/AlN QWs, on no condition that valence band order changes.

Effect of AlB2 on the P-threshold in Al-Si alloy

NASA Astrophysics Data System (ADS)

Wu, Yuying; Liu, Xiangfa

2018-06-01

The nucleation of primary Si in Al-Si alloys has been investigated in this work. It was found that there was a threshold concentration of P, below which AlP can not heterogeneous nucleate primary Si in Al-12 wt%Si alloy. AlB2 can not nucleate primary Si directly, but the presence of AlB2 may assist the nucleation of AlP leading to the nucleation of primary Si particles. In addition, with addition of AlB2, the nucleation efficiency of AlP can be improved in Al-18 wt%Si alloy. The orientation relationship between AlB2 and AlP has been calculated, and the adsorption model for AlB2 and AlP was proposed in this work.

Spontaneous Aseismic and Seismic Slip Transients on Evolving Faults Simulated in a Continuum-Mechanics Framework

NASA Astrophysics Data System (ADS)

Herrendoerfer, R.; Gerya, T.; van Dinther, Y.

2016-12-01

The convergent plate motion in subduction zones is accommodated by different slip modes: potentially dangerous seismic slip and imperceptible, but instrumentally detectable slow slip transients or steady slip. Despite an increasing number of observations and insights from laboratory experiments, it remains enigmatic which local on- and off-fault conditions favour slip modes of different source characteristics (i.e., slip velocity, duration, seismic moment). Therefore, we are working towards a numerical model that is able to simulate different slip modes in a consistent way with the long-term evolution of the fault system. We extended our 2D, continuum mechanics-based, visco-elasto-plastic seismo-thermo-mechanical (STM) model, which simulated cycles of earthquake-like ruptures, albeit only at plate tectonic slip rates (van Dinther et al, JGR, 2013). To model a wider slip spectrum including seismic slip rates, we, besides improving the general numerical approach, implemented an invariant reformulation of the conventional rate-and state dependent friction (RSF) and an adaptive time-stepping scheme (Lapusta and Rice, JGR, 2001). In a simple setup with predominantly elastic plates that are juxtaposed along a predefined fault of certain width, we vary the characteristic slip distance, the mean normal stress and the size of the rate-weakening zone. We show that the resulting stability transitions from decaying oscillations, periodic slow slip, complex periodic to seismic slip agree with those of conventional RSF seismic cycle simulations (e.g. Liu and Rice, JGR, 2007). Additionally, we will present results of the investigation concerning the effect of the fault width and geometry on the generation of different slip modes. Ultimately, instead of predefining a fault, we simulate the spatio-temporal evolution of a complex fault system that is consistent with the plate motions and rheology. For simplicity, we parametrize the fault development through linear slip-weakening of

High temperature deformation of NiAl and CoAl

NASA Technical Reports Server (NTRS)

Nix, W. D.

1982-01-01

The high temperature mechanical properties of the aluminides are reviewed with respect to their potential as high temperature structural materials. It is shown that NiAl and CoAl are substantially stronger than the pure metals Ni and Co at high temperatures and approach the strength of some superalloys, particularly when those superalloys are tested in "weak" directions. The factors that limit and control the high temperature strengths of NiAl and CoAl are examined to provide a basis for the development of intermetallic alloys of this type.

Atomistic Modeling of RuAl and (RuNi) Al Alloys

NASA Technical Reports Server (NTRS)

Gargano, Pablo; Mosca, Hugo; Bozzolo, Guillermo; Noebe, Ronald D.; Gray, Hugh R. (Technical Monitor)

2002-01-01

Atomistic modeling of RuAl and RuAlNi alloys, using the BFS (Bozzolo-Ferrante-Smith) method for alloys is performed. The lattice parameter and energy of formation of B2 RuAl as a function of stoichiometry and the lattice parameter of (Ru(sub 50-x)Ni(sub x)Al(sub 50)) alloys as a function of Ni concentration are computed. BFS based Monte Carlo simulations indicate that compositions close to Ru25Ni25Al50 are single phase with no obvious evidence of a miscibility gap and separation of the individual B2 phases.

America’s Holy War

DTIC Science & Technology

2006-04-14

Journal. 24 April 2002. http://www.mepc.org/public_asp/journal/ vol10 /0306_alqaeda.asp accessed on 21 Sept 05. 21 “Translation of April 24, 2002 al...Qaeda document”. Middle East Policy Council Journal. 24 April 2002. http://www.mepc.org/public_asp/journal/ vol10 /0306_alqaeda.asp accessed on 21 Sept... vol10 /0306_alqaeda.asp accessed on 21 Sept 05. 23 “Osama bin Laden’s Speech on the Eve of the 2004 US Elections”. The Middle East Media Research

Mechanical Properties of Structural Polymers. Computer Simulations and Key Experiments

DTIC Science & Technology

1992-09-30

Technology", edited by R.W. Cahn, P. Haasen, and E.J. Kramer, (VCH: Weinheim, Germany) (vol. editor H. Mughrabi ) Vol. 6, in the press (1992). 14. A.S. Argon...34, Acta Metall. et Mater., submitted for publication. 5 32. A. Galeski, Z. Bartczak, A.S. Argon and R.E. Cohen, "Morphological Al - terations during

Monitoring of Microseismicity with ArrayTechniques in the Peach Tree Valley Region

NASA Astrophysics Data System (ADS)

Garcia-Reyes, J. L.; Clayton, R. W.

2016-12-01

This study is focused on the analysis of microseismicity along the San Andreas Fault in the PeachTree Valley region. This zone is part of the transition zone between the locked portion to the south (Parkfield, CA) and the creeping section to the north (Jovilet, et al., JGR, 2014). The data for the study comes from a 2-week deployment of 116 Zland nodes in a cross-shaped configuration along (8.2 km) and across (9 km) the Fault. We analyze the distribution of microseismicity using a 3D backprojection technique, and we explore the use of Hidden Markov Models to identify different patterns of microseismicity (Hammer et al., GJI, 2013). The goal of the study is to relate the style of seismicity to the mechanical state of the Fault. The results show the evolution of seismic activity as well as at least two different patterns of seismic signals.

Ejecta emplacement: from distal to proximal

NASA Astrophysics Data System (ADS)

Artemieva, N.

2008-09-01

ballistically and included rheologic models for Newtonian or Bingham materials based on observations (runout distance, height of the distal ridge). Our model establishes better initial conditions for ejecta flow formation and provide estimates for the properties of fluidized ejecta directly on the basis of the particles/gas ratio, particle size, and temperaturedensity conditions in the ejecta. Venus. Ejecta deposition on Venus is substantially non-ballistic due to thick Venusian atmosphere. Some of impact craters are surrounded by "dark halos" [26- 28], others have unique dark parabolas, representing surficial deposits of loose material lifted during crater formation [29-30]. Methods of two-phase hydrodynamics may be useful to describe mechanism of their formation. References [1] Dobrovolskis A. (1981) Icarus 47, 203-219. [2] Cintala M.J., et al. (1999) M&PS. 34, 605-623. [3] Oberbeck V.R. (1975) Rev. Geophys. Space Phys. 13, 337-362. [4] Dressler et al. (2004) M&PS 39, 857- 878. [5] Hörz F. et al. (1983) Rev Geophys.Space Phys. 21, 1667-1725. [6] Valentine G.A. and Wohletz K.H. (1989) JGR 94, 1867-1887. [7] Dobran F. and Neri A. (1993) JGR 98, 4231-4259. [8] Neri A. et al. (2003) JGR 108, doi:10.1029/ 2001JB000508. [9] Boothroyd R.G. (1971) Flowing gas-solids suspension, Chapman and Hall Ltd, London. [10] Shuvalov V.V. (1999) Shock waves 9, 381-390. [11] Nakamura A. and Fujiwara A. (1991) Icarus 92, 132- 146. [12] Grady D.E. and Kipp M.E. (1980) Int. J. Rock Mech. Min. Sci. Geomech. Abstr. 17, 147-157. [13] Melosh H.J. et al. (1992) JGR 97, 14735-14759. [14] Gault, D.E. et al. (1963) NASA TND-1767. [15] Vickery A.M. (1986) Icarus 67, 224-236. [16] Melosh H.J. (1984) Icarus 59, 234-260. [17] Shuvalov V.V. (2002) LPSC-33, abstr.#1259. [18] Stöffler et al. (2002) M&PS 37, 1893-1908. [19] Melosh H.J. and Artemieva N.A. (2004) LPSC-35, abstr. #1723. [20] Osinski et al. (2004) Meteoritics Planet. Sci. 39, 1655-1683. [21] Ivanov B.A. et al. (1997) LPSC 28, 637-638. [22] Garvin J

Al6H18: A baby crystal of γ-AlH3

NASA Astrophysics Data System (ADS)

Kiran, B.; Kandalam, Anil K.; Xu, Jing; Ding, Y. H.; Sierka, M.; Bowen, K. H.; Schnöckel, H.

2012-10-01

Using global-minima search methods based on the density functional theory calculations of (AlH3)n (n = 1-8) clusters, we show that the growth pattern of alanes for n ≥ 4 is dominated by structures containing hexa-coordinated Al atoms. This is in contrast to the earlier studies where either linear or ring structures of AlH3 were predicted to be the preferred structures in which the Al atoms can have a maximum of five-fold coordination. Our calculations also reveal that the Al6H18 cluster, with its hexa-coordination of the Al atoms, resembles the unit-cell of γ-AlH3, thus Al6H18 is designated as the "baby crystal." The fragmentation energies of the (AlH3)n (n = 2-8) along with the dimerization energies for even n clusters indicate an enhanced stability of the Al6H18 cluster. Both covalent (hybridization) and ionic (charge) contribution to the bonding are the driving factors in stabilizing the isomers containing hexa-coordinated Al atoms.

Simulated Microstructure-Sensitive Extreme Value Probabilities for High Cycle Fatigue of Duplex Ti-6Al-4V

DTIC Science & Technology

2010-04-01

of texture on  mechanical   properties  in an advanced  titanium  alloy,"  Materials Science and Engineering A, vol. 319‐321, pp. 409‐414, 2001.  Simulated... mechanisms  of fatigue facet nucleation in  titanium  alloys," Fatigue  and Fracture of Engineering Materials and  Structures , vol. 31, pp. 949‐958, 2008...crack initiation in Ti‐6Al‐4V  titanium   alloy," Fatigue and Fracture of Engineering Materials and  Structures , vol. 25, pp. 527‐545, 2002.  [20]  I

The Enigma of Io's Warm Polar Regions

NASA Astrophysics Data System (ADS)

Matson, D. L.; Veeder, G. J.; Davies, A. G.; Johnson, T. V.; Blaney, D. L.

[3,4,6]. References: [1] Spencer J. R. et al. (2000) Science, 288, 1198-1201. [2] Rathbun J. A. et al. (2001) EOS Trans. AGU, 82, P11A-11. [3] Matson D. L. et al. (2001) LPSC XXXII, 1938. [4] Matson D. L. et al. (2001) JGR, in press [5] Veeder G. J. et al. (1994) JGR, 99, 17095- 17162. [6] Matson D. L. et al. (2000) EOS, 81, F788. [7] Lopes-Gautier R. et al. (2000) Science, 288, 1201-1204. This work was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract to NASA.

Extremes and bursts in complex multi-scale plasmas

NASA Astrophysics Data System (ADS)

Watkins, N. W.; Chapman, S. C.; Hnat, B.

2012-04-01

Quantifying the spectrum of sizes and durations of large and/or long-lived fluctuations in complex, multi-scale, space plasmas is a topic of both theoretical and practical importance. The predictions of inherently multi-scale physical theories such as MHD turbulence have given one direct stimulus for its investigation. There are also space weather implications to an improved ability to assess the likelihood of an extreme fluctuation of a given size. Our intuition as scientists tends to be formed on the familiar Gaussian "normal" distribution, which has a very low likelihood of extreme fluctuations. Perhaps surprisingly, there is both theoretical and observational evidence that favours non-Gaussian, heavier-tailed, probability distributions for some space physics datasets. Additionally there is evidence for the existence of long-ranged memory between the values of fluctuations. In this talk I will show how such properties can be captured in a preliminary way by a self-similar, fractal model. I will show how such a fractal model can be used to make predictions for experimental accessible quantities like the size and duration of a buurst (a sequence of values that exceed a given threshold), or the survival probability of a burst [c.f. preliminary results in Watkins et al, PRE, 2009]. In real-world time series scaling behaviour need not be "mild" enough to be captured by a single self-similarity exponent H, but might instead require a "wild" multifractal spectrum of scaling exponents [e.g. Rypdal and Rypdal, JGR, 2011; Moloney and Davidsen, JGR, 2011] to give a complete description. I will discuss preliminary work on extending the burst approach into the multifractal domain [see also Watkins et al, chapter in press for AGU Chapman Conference on Complexity and Extreme Events in the Geosciences, Hyderabad].

Interrelationships of Prenatal and Postnatal Growth, Hormones, Diet, and Breast Cancer

DTIC Science & Technology

2006-03-01

Breslow NE, Day NE. Statistical methods in cancer research, vol. 1. The analysis of case-control studies, IARC Sci. Publ. 32, Lyon, IARC, 1980 . 9...weight (Ekbom et al, 1992; Innes et al, 2000; Michels et al, 1996; Sander- son et al, 1996). Conversely, high adolescent (Coates et al, 1999; Hislop et...Brinton and Swanson, 1992; Choi et al, 1978; Coates et al, 1999; Franceschi et al, 1996; Hislop et al, 1986; Le Marchand et al, 1988a; Pryor et al, 1989

27Al MQMAS of the δ-Al 13-Keggin

DOE PAGES

Pilgrim, C. D.; Callahan, J. R.; Colla, C. A.; ...

2017-01-20

Here, one-dimensional 27Al, 23Na Magic-Angle-Spinning (MAS) NMR and 27Al Multiple-Quantum Magic-Angle-Spinning NMR (MQMAS) measurements are reported for the δ-isomer of the Al 13 Keggin structure at high spinning speed and 14.1 T field. Values for the CQ and η parameters are on the same scale as those seen in other isomers of the Al 13 structure. Density functional theory (DFT) calculations are performed for comparison to the experimental fits using the B3PW91/6-31+G* and PBE0/6-31+G* levels of theory, with the Polarizable Continuum Model (PCM).

Pressure induced coordination change of Al in silicate melts from Al K edge XANES of high pressure NaAlSi2O6-NaAlSi3O8 glasses

NASA Astrophysics Data System (ADS)

Li, Dien; Secco, R. A.; Bancroft, G. M.; Fleet, M. E.

Aluminum K-edge XANES spectra of high pressure and high temperature (4.4 GPa and 1575°C) glasses along the NaAlSi2O6 (Jd)-NaAlSi3O8 (Ab) join are reported using synchrotron radiation, and shown to provide direct experimental evidence for the pressure-induced coordination change of Al. Five- and six-fold coordinated Al (5Al and 6Al), characterized by Al K-edge positions at 1567.8 and 1568.7 eV, respectively, first appear in glass of composition Jd60Ab40 and increase in proportion progressively with increasing Jd content. The end-member jadeite glass contains about 6% of each of 5Al and 6Al. The present direct measurements confirm literature suggestions for the important role of Al in controlling viscosity and diffusion in mantle melts.

Assessing behavioural changes in ALS: cross-validation of ALS-specific measures.

PubMed

Pinto-Grau, Marta; Costello, Emmet; O'Connor, Sarah; Elamin, Marwa; Burke, Tom; Heverin, Mark; Pender, Niall; Hardiman, Orla

2017-07-01

The Beaumont Behavioural Inventory (BBI) is a behavioural proxy report for the assessment of behavioural changes in ALS. This tool has been validated against the FrSBe, a non-ALS-specific behavioural assessment, and further comparison of the BBI against a disease-specific tool was considered. This study cross-validates the BBI against the ALS-FTD-Q. Sixty ALS patients, 8% also meeting criteria for FTD, were recruited. All patients were evaluated using the BBI and the ALS-FTD-Q, completed by a carer. Correlational analysis was performed to assess construct validity. Precision, sensitivity, specificity, and overall accuracy of the BBI when compared to the ALS-FTD-Q, were obtained. The mean score of the whole sample on the BBI was 11.45 ± 13.06. ALS-FTD patients scored significantly higher than non-demented ALS patients (31.6 ± 14.64, 9.62 ± 11.38; p < 0.0001). A significant large positive correlation between the BBI and the ALS-FTD-Q was observed (r = 0.807, p < 0.0001), and no significant correlations between the BBI and other clinical/demographic characteristics indicate good convergent and discriminant validity, respectively. 72% of overall concordance was observed. Precision, sensitivity, and specificity for the classification of severely impaired patients were adequate. However, lower concordance in the classification of mild behavioural changes was observed, with higher sensitivity using the BBI, most likely secondary to BBI items which endorsed behavioural aspects not measured by the ALS-FTD-Q. Good construct validity has been further confirmed when the BBI is compared to an ALS-specific tool. Furthermore, the BBI is a more comprehensive behavioural assessment for ALS, as it measures the whole behavioural spectrum in this condition.

Spectrophotometric Modeling of MAHLI Goniometer Observations

NASA Astrophysics Data System (ADS)

Liang, W.; Johnson, J. R.; Hayes, A.; Lemmon, M. T.; Bell, J. F., III; Grundy, W. M.; Deen, R. G.

2017-12-01

include all images in the DTM and incorporate sky models to correct for diffuse skylight. [1] Johnson, J., et al. 8th Int. Conf. Mars, #1073, 2014; [2] Johnson, J., et al., LPSC, #1424, 2015; [3] Johnson, J., et al., AGU, #P43B-2125 2015; [4] Johnson, J., et al., JGR, 111, E02S14, 2006; [5] Johnson, J., JGR, 111, E12S16, 2006; [6] Johnson,J. et al., Icarus, 248, 25-71, 2015.

Thermal Profile of the Lunar Interior Constrained by Revised Estimates of Concentrations of Heat Producing Elements

NASA Astrophysics Data System (ADS)

Fuqua-Haviland, H.; Panovska, S.; Mallik, A.; Bremner, P. M.; McDonough, W. F.

2017-12-01

present-day lunar interior thermal state. We also present plausible internal structures that best match the mass, moment of inertia and bulk silicate Moon composition along this conductive selenotherm. [1] Wanke et al (1973) LPSC; [2] Warren et al (1979) Rev Geophy; [3] Wieczorek et al (2000) JGR; [4] Grimm (2013) JGRP; [5] Hagerty et al (2006) GCA; [6] Peplowski et al (2016) JGR.

Doping and compensation in Al-rich AlGaN grown on single crystal AlN and sapphire by MOCVD

NASA Astrophysics Data System (ADS)

Bryan, Isaac; Bryan, Zachary; Washiyama, Shun; Reddy, Pramod; Gaddy, Benjamin; Sarkar, Biplab; Breckenridge, M. Hayden; Guo, Qiang; Bobea, Milena; Tweedie, James; Mita, Seiji; Irving, Douglas; Collazo, Ramon; Sitar, Zlatko

2018-02-01

In order to understand the influence of dislocations on doping and compensation in Al-rich AlGaN, thin films were grown by metal organic chemical vapor deposition (MOCVD) on different templates on sapphire and low dislocation density single crystalline AlN. AlGaN grown on AlN exhibited the highest conductivity, carrier concentration, and mobility for any doping concentration due to low threading dislocation related compensation and reduced self-compensation. The onset of self-compensation, i.e., the "knee behavior" in conductivity, was found to depend only on the chemical potential of silicon, strongly indicating the cation vacancy complex with Si as the source of self-compensation. However, the magnitude of self-compensation was found to increase with an increase in dislocation density, and consequently, AlGaN grown on AlN substrates demonstrated higher conductivity over the entire doping range.

The Existence of a Designer Al=Al Double Bond in the LiAl2 H4- Cluster Formed by Electronic Transmutation.

PubMed

Lundell, Katie A; Zhang, Xinxing; Boldyrev, Alexander I; Bowen, Kit H

2017-12-22

The Al=Al double bond is elusive in chemistry. Herein we report the results obtained via combined photoelectron spectroscopy and ab initio studies of the LiAl 2 H 4 - cluster that confirm the formation of a conventional Al=Al double bond. Comprehensive searches for the most stable structures of the LiAl 2 H 4 - cluster have shown that the global minimum isomer I possesses a geometric structure which resembles that of Si 2 H 4 , demonstrating a successful example of the transmutation of Al atoms into Si atoms by electron donation. Theoretical simulations of the photoelectron spectrum discovered the coexistence of two isomers in the ion beam, including the one with the Al=Al double bond. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Lou Gehrig's Disease (ALS)

MedlinePlus

... for Educators Search English Español Lou Gehrig's Disease (ALS) KidsHealth / For Kids / Lou Gehrig's Disease (ALS) What's ... with ALS in the 1930s. What Happens in ALS? ALS damages motor neurons in the brain and ...

Space Operations for the 21st Century: A Functional Approach

DTIC Science & Technology

1997-03-01

Air Force, vol. II, March 1992, Essay H , 66. 9Ibid., 66-7. 10AFM 1-1, Vol. I, 1,7,8 and Vol. II, Essay J, 79-83. 11Air Force Doctrine Document (AFDD) 4...The Spacecast 2020 Process (Maxwell AFB, AL: Air University, 22 June 1994), 4. 2Ernest Y. Robinson, Henry Helvajian , and Siegfried W. Janson, “Small and... Helvajian , Henry and Janson, Siegfried W. “Small and Smaller: The World of MNT,” Aerospace America, 34, no 9 (September 1996), 26-32. U.S. Air Force

Characterization of N-polar AlN in GaN/AlN/(Al,Ga)N heterostructures grown by metal-organic chemical vapor deposition

NASA Astrophysics Data System (ADS)

Li, Haoran; Mazumder, Baishakhi; Bonef, Bastien; Keller, Stacia; Wienecke, Steven; Speck, James S.; Denbaars, Steven P.; Mishra, Umesh K.

2017-11-01

In GaN/(Al,Ga)N high-electron-mobility transistors (HEMT), AlN interlayer between GaN channel and AlGaN barrier suppresses alloy scattering and significantly improves the electron mobility of the two-dimensional electron gas. While high concentrations of gallium were previously observed in Al-polar AlN interlayers grown by metal-organic chemical vapor deposition, the N-polar AlN (Al x Ga1-x N) films examined by atom probe tomography in this study exhibited aluminum compositions (x) equal to or higher than 95% over a wide range of growth conditions. The also investigated AlN interlayer in a N-polar GaN/AlN/AlGaN/ S.I. GaN HEMT structure possessed a similarly high x content.

Pure AlN layers in metal-polar AlGaN/AlN/GaN and AlN/GaN heterostructures grown by low-temperature ammonia-based molecular beam epitaxy

NASA Astrophysics Data System (ADS)

Kaun, Stephen W.; Mazumder, Baishakhi; Fireman, Micha N.; Kyle, Erin C. H.; Mishra, Umesh K.; Speck, James S.

2015-05-01

When grown at a high temperature (820 °C) by ammonia-based molecular beam epitaxy (NH3-MBE), the AlN layers of metal-polar AlGaN/AlN/GaN heterostructures had a high GaN mole fraction (∼0.15), as identified by atom probe tomography in a previous study (Mazumder et al 2013 Appl. Phys. Lett. 102 111603). In the study presented here, growth at low temperature (<740 °C) by NH3-MBE yielded metal-polar AlN layers that were essentially pure at the alloy level. The improved purity of the AlN layers grown at low temperature was correlated to a dramatic increase in the sheet density of the two-dimensional electron gas (2DEG) at the AlN/GaN heterointerface. Through application of an In surfactant, metal-polar AlN(3.5 nm)/GaN and AlGaN/AlN(2.5 nm)/GaN heterostructures grown at low temperature yielded low 2DEG sheet resistances of 177 and 285 Ω/□, respectively.

Interdiffusion in U 3Si-Al, U 3Si 2-Al, and USi-Al dispersion fuels during irradiation

NASA Astrophysics Data System (ADS)

Kim, Yeon Soo; Hofman, Gerard L.

2011-03-01

Uranium-silicide compound fuel dispersion in an Al matrix is used in research and test reactors worldwide. Interaction layer (IL) growth between fuel particles and the matrix is one of performance issues. The interaction layer growth data for U 3Si, U 3Si 2 and USi dispersions in Al were obtained from both out-of-pile and in-pile tests. The IL is dominantly U(AlSi) 3 from out-of-pile tests, but its (Al + Si)/U ratio from in-pile tests is higher than the out-of-pile data, because of amorphous behavior of the ILs. IL growth correlations were developed for U 3Si-Al and U 3Si 2-Al. The IL growth rates were dependent on the U/Si ratio of the fuel compounds. During irradiation, however, the IL growth rates did not decrease with the decreasing U/Si ratio by fission. It is reasoned that transition metal fission products in the IL compensate the loss of U atoms by providing chemical potential for Al diffusion and volume expansion by solid swelling and gas bubble swelling. The addition of Mo in U 3Si 2 reduces the IL growth rate, which is similar to that of UMo alloy dispersion in a silicon-added Al matrix.

Al-Manakh. Language Centre Journal, Vol. 3, No. 2.

ERIC Educational Resources Information Center

Language Centre Journal, 1979

1979-01-01

The following articles appear in this issue of a journal devoted to teaching English for science and technology in Kuwait: (1) "An Approach to the Implementation of Dr. J.L. Munby's 'Communicative Syllabus Design'" by Bill Robinson, (2) "Une experience d'elaboration de materiel pedagogique" (An Experiment in Developing Teaching…

ALS - resources

MedlinePlus

Resources - ALS ... The following organizations are good resources for information on amyotrophic lateral sclerosis : Muscular Dystrophy Association -- www.mda.org/disease/amyotrophic-lateral-sclerosis National Amyotrophic Lateral Sclerosis (ALS) ...

Study of the Al m 26 ( d , p ) Al 27 Reaction and the Influence of the Al 26 0 + Isomer on the Destruction of Al 26 in the Galaxy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Almaraz-Calderon, S.; Rehm, K. E.; Gerken, N.

The existence of 26Al (t 1/2 = 7.17 × 10 5 yr) in the interstellar medium provides a direct confirmation of ongoing nucleosynthesis in the Galaxy. The presence of a low-lying 0 + isomer ( 26Al m), however, severely complicates the astrophysical calculations. Here we present for the first time a study of the 26Al m (d, p) 27 Al reaction using an isomeric 26Al beam. The selectivity of this reaction allowed the study of ℓ = 0 transfers to T = 1/2, and T = 3/2 states in 27Al . Mirror symmetry arguments were then used to constrain themore » 26Al m (p,γ) 27Si reaction rate and provide an experimentally determined upper limit of the rate for the destruction of isomeric 26Al via radiative proton capture reactions, which is expected to dominate the destruction path of 26Al m in asymptotic giant branch stars, classical novae, and core collapse supernovae.« less

Study of the Al m 26 ( d , p ) Al 27 Reaction and the Influence of the Al 26 0 + Isomer on the Destruction of Al 26 in the Galaxy

DOE PAGES

Almaraz-Calderon, S.; Rehm, K. E.; Gerken, N.; ...

2017-08-17

The existence of 26Al (t 1/2 = 7.17 × 10 5 yr) in the interstellar medium provides a direct confirmation of ongoing nucleosynthesis in the Galaxy. The presence of a low-lying 0 + isomer ( 26Al m), however, severely complicates the astrophysical calculations. Here we present for the first time a study of the 26Al m (d, p) 27 Al reaction using an isomeric 26Al beam. The selectivity of this reaction allowed the study of ℓ = 0 transfers to T = 1/2, and T = 3/2 states in 27Al . Mirror symmetry arguments were then used to constrain themore » 26Al m (p,γ) 27Si reaction rate and provide an experimentally determined upper limit of the rate for the destruction of isomeric 26Al via radiative proton capture reactions, which is expected to dominate the destruction path of 26Al m in asymptotic giant branch stars, classical novae, and core collapse supernovae.« less

Study of the ^{26}Al^{m}(d,p)^{27}Al Reaction and the Influence of the ^{26}Al 0^{+} Isomer on the Destruction of ^{26}Al in the Galaxy.

PubMed

Almaraz-Calderon, S; Rehm, K E; Gerken, N; Avila, M L; Kay, B P; Talwar, R; Ayangeakaa, A D; Bottoni, S; Chen, A A; Deibel, C M; Dickerson, C; Hanselman, K; Hoffman, C R; Jiang, C L; Kuvin, S A; Nusair, O; Pardo, R C; Santiago-Gonzalez, D; Sethi, J; Ugalde, C

2017-08-18

The existence of ^{26}Al (t_{1/2}=7.17×10^{5}  yr) in the interstellar medium provides a direct confirmation of ongoing nucleosynthesis in the Galaxy. The presence of a low-lying 0^{+} isomer (^{26}Al^{m}), however, severely complicates the astrophysical calculations. We present for the first time a study of the ^{26}Al^{m}(d,p)^{27}Al reaction using an isomeric ^{26}Al beam. The selectivity of this reaction allowed the study of ℓ=0 transfers to T=1/2, and T=3/2 states in ^{27}Al. Mirror symmetry arguments were then used to constrain the ^{26}Al^{m}(p,γ)^{27}Si reaction rate and provide an experimentally determined upper limit of the rate for the destruction of isomeric ^{26}Al via radiative proton capture reactions, which is expected to dominate the destruction path of ^{26}Al^{m} in asymptotic giant branch stars, classical novae, and core collapse supernovae.

Reduced electron back-injection in Al2O3/AlOx/Al2O3/graphene charge-trap memory devices

NASA Astrophysics Data System (ADS)

Lee, Sejoon; Song, Emil B.; Min Kim, Sung; Lee, Youngmin; Seo, David H.; Seo, Sunae; Wang, Kang L.

2012-12-01

A graphene charge-trap memory is devised using a single-layer graphene channel with an Al2O3/AlOx/Al2O3 oxide stack, where the ion-bombarded AlOx layer is intentionally added to create an abundance of charge-trap sites. The low dielectric constant of AlOx compared to Al2O3 reduces the potential drop in the control oxide Al2O3 and suppresses the electron back-injection from the gate to the charge-storage layer, allowing the memory window of the device to be further extended. This shows that the usage of a lower dielectric constant in the charge-storage layer compared to that of the control oxide layer improves the memory performance for graphene charge-trap memories.

JPRS Report, Science & Technology China

DTIC Science & Technology

1989-02-02

40091007b Beijing WEISHENGWU XUEBAO [ACTA MICROBIOLOGICA SINICA] in Chinese Vol 28 No 3, Sep 88 pp 257- 264 [English abstract of article by Gong Jianhua...G.H., KAPL-M-SMS-31, 1956, pp 4-6. 4. Caldwell, C.S., WAPD -CP-1030, 1956, pp 1-5. 5. Himmelblau, D.M., et al., J. CHEM. ENG. DATA, Vol 5 No 1, 1

Extreme Sensitivity of Botulinum Neurotoxin Domains Toward Mild Agitation

DTIC Science & Technology

2009-09-01

Department Molecular Biology, Integrated Toxicology Division, United States Army Medical Research Institute of Infectious Diseases, Fort Detrick...hydroxyethylpiperazine-N0-2-ethanesulfo- cular dichroism. AL OF PHARMACEUTICAL SCIENCES, VOL. 98, NO. 9, SEPTapplications. Botulinum neurotoxins (BoNTs) are...Dr. S. Ashraf Ahmed (Telephone: 301- 619-6299; Fax: 301-619-2348; E-mail: syed.ahmed@amedd.army.mil) Journal of Pharmaceutical Sciences, Vol. 98

Field-Induced Phenomena in Electrical Insulation.

DTIC Science & Technology

1984-09-29

Dis- charges," Jour. of App. Phys., Vol. 55, No. 1, 1984, pp. 9-14. 112 • ’ -. ; . - -. A " . i . . .- L ."L 35. A. Tomago and T. Suzuki, "A New...Impregnated with Supercritical Helium," IEE PROC., Vol. 129, pt. A, No. 3, 1982, pp. 176-182. 31. A. Tomago , et. al., "Development of Oil-Impregnated, All

77 FR 73732 - In the Matter of Amendment of the Designation of al-Qa'ida in Iraq, aka Jam'at al Tawhid wa'al...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-12-11

...'ida in Iraq, aka Jam'at al Tawhid wa'al-Jihad, aka The Monotheism and Jihad Group, aka The al-Zarqawi Network, aka al-Tawhid, aka Tanzim Qa`idat al-Jihad fi Bilad al-Rafidayn, aka The Organization of al-Jihad... Rivers, aka al-Qaida of Jihad Organization in the Land of the Two Rivers, aka al- Qaida Group of Jihad in...

Phenotypic and genotypic studies of ALS cases in ALS-SMA families.

PubMed

Corcia, Philippe; Vourc'h, Patrick; Blasco, Helene; Couratier, Philippe; Dangoumau, Audrey; Bellance, Remi; Desnuelle, Claude; Viader, Fausto; Pautot, Vivien; Millecamps, Stephanie; Bakkouche, Salah; Salachas, FranÇois; Andres, Christian R; Meininger, Vincent; Camu, William

2018-08-01

Amyotrophic lateral sclerosis (ALS) and spinal muscular atrophy (SMA) are the most frequent motor neuron disorders in adulthood and infancy, respectively. There is a growing literature supporting common pathophysiological patterns between those disorders. One important clinical issue for that is the co-occurrence of both diseases within a family. To collect families in which ALS and SMA patients co-exist and describe the phenotype and the genotype of ALS patients. Nine families with co-occurrence of SMA and ALS have been gathered over the last 15 years. Epidemiological, phenotype and genetic status were collected. Out of the nine families, six corresponded to the criteria of familial ALS (FALS). Clinical data were available for 11 patients out of the 15 ALS cases. Mean age of onset was 58.5 years, site of onset was lower limbs in nine cases (81.8%), median duration was 22 months. Four ALS patients carried a mutation: three mutations in SOD1 gene (G147N in two cases and one with E121G) and one repeat expansion in the C9ORF72 gene. Three patients had abnormal SMN1 copy numbers. While the high proportion of familial history of ALS cases in these ALS-SMA pedigrees could have suggested that these familial clusters of the two most frequent MND rely on a genetic background, we failed to exclude that this occurred by chance.

Distribution and size of lava shields on the Al Haruj al Aswad and the Al Haruj al Abyad Volcanic Systems, Central Libya

NASA Astrophysics Data System (ADS)

Elshaafi, Abdelsalam; Gudmundsson, Agust

2017-05-01

The Al Haruj Volcanic Province (AHVP) consists of two distinct volcanic systems. In the north is the system of Al Haruj al Aswad, covering an area of 34,200 km2, while in the south the system of Al Haruj al Abyad, covering an area of 7,850 km2. The systems have produced some 432 monogenetic volcanoes, primarily scoria (cinder) cones, lava shields, and maars. The density distribution of the volcanoes in each system, plotted as eruption points or sites, has a roughly elliptical surface expression, suggesting similar plan-view geometry of the magma sources, here suggested as deep-seated reservoirs. More specifically, the Al Haruj al Aswad magma reservoir has major and minor axes of 210 km and 119 km, respectively, and an area of 19,176 km2, the corresponding figures for the Haruj al Abyad reservoir being 108 km and 74 km, for the axes, and 6209 km2 for the area. We measured 55 lava shields on the AHVP. They are mostly restricted to the northern and southern parts of AHVP and date from late Miocene to (at least) the end of Pleistocene, while some may have been active into Holocene. In fact, although primarily monogenetic, some of the lava shields show evidence of (possibly Holocene) fissure eruptions in the summit parts. The early lava shields tend to be located at the edges of volcanic systems and with greater volumes than later (more central) shields. The average lava shield basal diameter is 4.5 km and height 63 m. There is strong linear correlation between lava shield volume and basal area, the coefficient of determination (R2) being about 0.75. When 22 Holocene Icelandic lava shields are added to the dataset, for comparison, the correlation between volume and basal area becomes R2 = 0.95. Numerical models suggest that the local stress fields favoured rupture and dyke injection at the margins of the source reservoirs during late Miocene - early Pliocene, in agreement with the distribution of the early, large-volume shields.

Formation of gamma'-Ni3Al via the Peritectoid Reaction: gamma plus beta (+Al2O3) equals gamma'(+Al2O3)

NASA Technical Reports Server (NTRS)

Copland, Evan

2008-01-01

The activities of Al and Ni were measured using multi-cell Knudsen effusion-cell mass spectrometry (multi-cell KEMS), over the composition range 8 - 32 at.%Al and temperature range T = 1400 - 1750 K in the Ni-Al-O system. These measurements establish that equilibrium solidification of gamma'-Ni3Al-containing alloys occurs by the eutectic reaction, L (+ Al2O3) = gamma + beta (+ Al2O3), at 1640 plus or minus 1 K and a liquid composition of 24.8 plus or minus 0.2 at.%Al (at an unknown oxygen content). The {gamma + beta + Al2O3} phase field is stable over the temperature range 1633 - 1640 K, and gamma'-Ni3Al forms via the peritectiod, gamma + beta (+ Al2O3) = gamma'(+ Al2O3), at 1633 plus or minus 1 K. This behavior is inconsistent with the current Ni-Al phase diagram and a new diagram is proposed. This new Ni-Al phase diagram explains a number of unusual steady state solidification structures reported previously and provides a much simpler reaction scheme in the vicinity of the gamma'-Ni3Al phase field.

Molecular Dynamics Studies of CaAl2Si2O8 Liquid to 800 GPa: An Equation of State (EOS), Hugoniot Analysis, and Thermodynamic Model Over the Temperature-Range 2500-5000 K (Invited)

NASA Astrophysics Data System (ADS)

Ghiorso, M. S.; Cutler, I.; Nevins, D.; Spera, F. J.

2009-12-01

Equilibrium Molecular Dynamics (MD) simulations are applied to molten CaAl2Si2O8 using a Coulomb-Born-Mayer-van der Waals pair potential form and parameters from Matsui (1996, GRL 23:395). Experiments were performed in the microcanonical ensemble (NEV) using 8000 atoms, a 1 fs time step, and simulation durations of 50 ps. Computations were carried out every 500 K over a temperature range of 2500 - 5000 K along 21 isochores to yield a grid of 141 state points spanning the pressure range 0-800 GPa. Atomic coordination statistics are determined by counting nearest neighbor configurations up to a cutoff distance defined by the first minima of the pair correlation function. A thermodynamic model (and EOS) for this liquid is developed from the MD simulation results by combining the Rosenfeld-Tarazona (1998, Mol Phys 95:141) potential energy-temperature scaling law with the Universal EOS (1986, J Phys C, 19:L467). The resulting model is used to estimate thermodynamic properties and the sound speed of the liquid near zero pressure and these compare favorably to physical experiments. By contrast to our previous work (DOI: 10.1016/j.gca.2009.08.012), which utilized an alternate pair potential, no structural phase transition is required to thermodynamically model these results — a single parameterization describes the properties of the system over the entire range of ~4-fold compression. Our analysis indicates the existence of polyamorphism with a critical point at ~0.6 GPa and ~3000 K. A modeled Hugoniot is consistent with the low-pressure shock experiments of Rigden et al. (JGR 94:9508) but inconsistent with the more recent measurements of Asimow and Ahrens (EOS 89,MR32B-04). The latter experiments are matched with a model isentrope emanating from just above the zero pressure melting point of anorthite, which also coincides with the initial conditions of the shock. The MD simulations reveal that near zero-pressure, CaAl2Si2O8 liquid is dominated by Si in tetrahedral

Directional Solidification and Mechanical Properties of NiAl-NiAlTa Alloys

NASA Technical Reports Server (NTRS)

Johnson, D. R.; Chen, X. F.; Oliver, B. F.; Noebe, R. D.; Whittenberger, J. D.

1995-01-01

Directional solidification of eutectic alloys is a promising technique for producing in-situ composite materials exhibiting a balance of properties. Consequently, the microstructure, creep strength and fracture toughness of directionally solidified NiAl-NiAlTa alloys were investigated. Directional solidification was performed by containerless processing techniques to minimize alloy contamination. The eutectic composition was found to be NiAl-15.5 at% Ta and well-aligned microstructures were produced at this composition. A near-eutectic alloy of NiAl-14.5Ta was also investigated. Directional solidification of the near-eutectic composition resulted in microstructures consisting of NiAl dendrites surrounded by aligned eutectic regions. The off-eutectic alloy exhibited promising compressive creep strengths compared to other NiAl-based intermetallics, while preliminary testing indicated that the eutectic alloy was competitive with Ni-base single crystal superalloys. The room temperature toughness of these two-phase alloys was similar to that of polycrystalline NiAl even with the presence of the brittle Laves phase NiAlTa.

Theory and X-ray Absorption Spectroscopy for Aluminum Coordination Complexes – Al K-Edge Studies of Charge and Bonding in (BDI)Al, (BDI)AlR2, and (BDI)AlX2 Complexes.

PubMed

Altman, Alison B; Pemmaraju, C D; Camp, Clément; Arnold, John; Minasian, Stefan G; Prendergast, David; Shuh, David K; Tyliszczak, Tolek

2015-08-19

Polarized aluminum K-edge X-ray absorption near edge structure (XANES) spectroscopy and first-principles calculations were used to probe electronic structure in a series of (BDI)Al, (BDI)AlX2, and (BDI)AlR2 coordination compounds (X = F, Cl, I; R = H, Me; BDI = 2,6-diisopropylphenyl-β-diketiminate). Spectral interpretations were guided by examination of the calculated transition energies and polarization-dependent oscillator strengths, which agreed well with the XANES spectroscopy measurements. Pre-edge features were assigned to transitions associated with the Al 3p orbitals involved in metal-ligand bonding. Qualitative trends in Al 1s core energy and valence orbital occupation were established through a systematic comparison of excited states derived from Al 3p orbitals with similar symmetries in a molecular orbital framework. These trends suggested that the higher transition energies observed for (BDI)AlX2 systems with more electronegative X(1-) ligands could be ascribed to a decrease in electron density around the aluminum atom, which causes an increase in the attractive potential of the Al nucleus and concomitant increase in the binding energy of the Al 1s core orbitals. For (BDI)Al and (BDI)AlH2 the experimental Al K-edge XANES spectra and spectra calculated using the eXcited electron and Core-Hole (XCH) approach had nearly identical energies for transitions to final state orbitals of similar composition and symmetry. These results implied that the charge distributions about the aluminum atoms in (BDI)Al and (BDI)AlH2 are similar relative to the (BDI)AlX2 and (BDI)AlMe2 compounds, despite having different formal oxidation states of +1 and +3, respectively. However, (BDI)Al was unique in that it exhibited a low-energy feature that was attributed to transitions into a low-lying p-orbital of b1 symmetry that is localized on Al and orthogonal to the (BDI)Al plane. The presence of this low-energy unoccupied molecular orbital on electron-rich (BDI)Al distinguishes

Development of Al2O3 fiber-reinforced Al2O3-based ceramics.

PubMed

Tanimoto, Yasuhiro; Nemoto, Kimiya

2004-09-01

The purpose of this study was to use a tape casting technique to develop an Al2O3 fiber-reinforced Al2O3-based ceramic material (Al2O3-fiber/Al2O3 composite) into a new type of dental ceramic. The Al2O3-based ceramic used a matrix consisting of 60 wt% Al2O3 powder and 40 wt% SiO2-B2O3 powder. The prepreg sheets of Al2O3-fiber/Al2O3 composite (in which uniaxially aligned Al2O3 fibers were infiltrated with the Al2O3-based matrix) were fabricated continuously using tape casting technique with a doctor blade system. Multilayer preforms of Al2O3-fiber/Al2O3 composite sheets were then sintered at a maximum temperature of 1000 degrees C under an atmospheric pressure in a furnace. The results showed that the shrinkage and bending properties of Al2O3-fiber/Al2O3 composite exceeded those of unreinforced Al2O3--hence demonstrating the positive effects of fiber reinforcement. In conclusion, the tape casting technique has been utilized to successfully develop a new type of dental ceramic material.

Properties of the Medussae Fossae Formation and its relation to the volcanic history of Mars

NASA Astrophysics Data System (ADS)

Ivanov, Anton B.; Cantini, Federico

2016-10-01

Medussae Fossae (MFF) is a well known formation, stretching west of Tharsis volanoes. It is characterized as a relatively young Amazonian units (Amm, Amu), due to widespread signs of erosion. Earth based imaging radar observations at 3.5 cm [1] and 12 cm [2] have discovered a dark radar feature (Stealth), which roughly correlates with the MFF outline.Recent investigations [3], suggested that the unit emplacement is in fact during Hesperian period, but it is composed of material that can be easily eroded. It is not clear when the erosion happened and if it is a continuing process. Hypotheses on MFF formation range from volcanic material emplacement (ash flow tuffs or pyroclastic materials) to an ice-rich dusty mantle, deposited during high obliquity.In this work, we will present the latest observations of the East Medussae Fossae formation by the long wavelength MARSIS radar, continuing the work reported in [4], as well as complementing data surveyed by SHARAD data in [5]. The MARSIS radar has detected strong subsurface interfaces in the areas of Gordi and Eumenides Dorsae at depths up to 1.5km. We will present our analysis of the data, inferring the dielectric properties of the material to constrain properties of the material constituting the Medusae Fossae formation. We will also demonstrate an efficient user interface to work with MARSIS data inside a Geographical Information System (GIS).The research leading to these results has received funding from the European Unions Seventh Framework Programme (FP7/2007-2013) under iMars grant agreement 607379.[1] D. Muhleman, et al., "Radar images of mars," Science, vol. 253, no. 5027, 1991.[2] J. K. Harmon, et al., "Arecibo radar imagery of Mars: The major volcanic provinces," Icarus, vol. 220, aug 2012.[3] L. Kerber, et al., "The dispersal of pyroclasts from Apollinaris Patera, Mars: Implications for the origin of the Medusae Fossae Formation," Icarus, vol. 216, nov 2011.[4] T. R. Watters, et al., "Radar Sounding of the

NiAl-base composite containing high volume fraction of AlN for advanced engines

NASA Technical Reports Server (NTRS)

Hebsur, Mohan (Inventor); Whittenbeger, John D. (Inventor); Lowell, Carl F. (Inventor)

1994-01-01

A particulate reinforced NiAl-AlN composite alloy has a NiAl matrix and greater than about 13 volume percent fine particles of AlN within the matrix. The particles preferably have a diameter from about 15 nanometers to about 50 nanometers. The particulate reinforced NiAl-AlN composite alloy may be prepared by cryomilling prealloyed NiAl in liquid nitrogen using grinding media having a diameter of from about 2 to 6 mm at an impeller speed of from about 450 RPM to about 800 RPM. The cryomilling may be done for a duration of from about 4 hours to about 20 hours to obtain a cryomilled powder. The cryomilled powder may be consolidated to form the particulate reinforced NiAl-AlN composite alloy. The particulate reinforced alloy can further include a toughening alloy. The toughening alloy may include NiCrAlY, FeCrAlY, and FeAl.

Lakshmi Planum, Venus: Assessment of models using observations from geological mapping

NASA Astrophysics Data System (ADS)

Ivanov, M. A.; Head, J. W.

2008-09-01

of western Ishtar; a layered suite of low-lying plains surrounded a tessera craton. (2) Compression from the N led to deformation of plains against the craton foreland and formation of higher mountain ranges; displacement of the craton may have caused formation of Danu Montes. (3) Continued underthrusting finally caused limited uplift of N mountain ranges and the N portion of Lakshmi, creating the plateau asymmetry; two different events may have followed, with or without delamination [33]. (4a) In the beginning of delamination, fertile mantle flowed toward the base of the massif, melted, and led to emplacement of rp1 in the Lakshmi interior. (5a) During mature stages of delamination, the deepest portion of the slab would start to melt to form the youngest lava plains at Colette and Sacajawea Paterae. (4b) If no delamination occurs then formation of unit rp1 could be due to broad melting of the underthrust slab as it crosses the melting isotherm. (5b) As underthrusting proceeded, the relatively colder slab deflected the isotherm downward and new deeper portions of the slab melted, producing the younger lavas near Lakshmi center. When either delamination or continued underthrusting waned, the thicker crust of the northern mountain ranges rose epeirogenically, which led to additional elevation of the ranges and the northern portion of Lakshmi. References: 1) Masursky, H., et al., 1980, JGR, 85, 8232; 2) Pettengill, G.H., et al., 1980, JGR, 85, 8261; 3) Campbell, D.B., et al., 1983, Science, 221 644; 4) Barsukov, V.L., et al., 1986, JGR, 91, D399; 5) Pronin, A.A., et al, 1986, AV, 20, 83 (in Russian); 6) Stofan, E. R., et al, 1987, EMP, 38, 183; 7) Solomon, S.C. and J.W. Head, 1984, JGR, 89, 6885; 8) Solomon, S.C. and J.W. Head, 1990, GRL, 17, 1393; 9) Sjogren W. L., et al., 1997, In: Venus II, 1125; 10) Pronin, A.A., 1986, Geotectonika, 20, 271 (in Russian); 11) Head, J.W. 1990, Geology, 18, 99; 12) Kaula, W.M., et al., 1992, JGR, 97, 16085; 13) Solomon, S.C., et al

Molecular dynamics study of Al and Ni 3Al sputtering by Al clusters bombardment

NASA Astrophysics Data System (ADS)

Zhurkin, Eugeni E.; Kolesnikov, Anton S.

2002-06-01

The sputtering of Al and Ni 3Al (1 0 0) surfaces induced by impact of Al ions and Al N clusters ( N=2,4,6,9,13,55) with energies of 100 and 500 eV/atom is studied at atomic scale by means of classical molecular dynamics (MD). The MD code we used implements many-body tight binding potential splined to ZBL at short distances. Special attention has been paid to model dense cascades: we used quite big computation cells with lateral periodic and damped boundary conditions. In addition, long simulation times (10-25 ps) and representative statistics (up to 1000 runs per each case) were considered. The total sputtering yields, energy and time spectrums of sputtered particles, as well as preferential sputtering of compound target were analyzed, both in the linear and non-linear regimes. The significant "cluster enhancement" of sputtering yield was found for cluster sizes N⩾13. In parallel, we estimated collision cascade features depending on cluster size in order to interpret the nature of observed non-linear effects.

Al/CuxO/Cu Memristive Devices: Fabrication, Characterization, and Modeling

DTIC Science & Technology

2012-01-01

where Js is the current density, q is the electron charge, ε0 is the permittivity of free space, εr is the dielectric constant of the material, k is...and N. Nagaosa, “Interfaces of Correlated Electron Systems: Proposed Mechanism for Colossal Electroresistance,” Phys. Rev. Lett., Vol. 95, p. 266403

A Geochemical and Mineralogical Model for Formation of Layered Sulfate Deposits at Meridiani Planum by Hydrothermal Acid-sulfate Alteration of Pyroclastic Basalt

NASA Astrophysics Data System (ADS)

McCollom, T. M.; Hynek, B. M.

2012-12-01

of acid-sulfate alteration of martian pyroclastic basalt predict that the early stages of alteration will produce amorphous silica, anhydrite (or gypsum at lower temperature), Fe-bearing natroalunite, and kieserite as predominant secondary phases, along with relict glass and silicates protected within the glass. Hematite may form with continued heating through partial decomposition of Fe-bearing natroalunite [9], and some of the glass phase may partially devitrify to form minor phyllosilicates such as nontronite and nanophase Fe oxides. The resulting rock would have a chemical and mineralogical composition closely resembling that observed at Meridiani Planum. We conclude that hydrothermal acid-sulfate alteration of pyroclastic basalt provides the most parsimonious explanation for the composition of the sulfate deposits. References: [1] Glotch et al., JGR (2006). [2] Klingelhöfer et al. Science (2004). [3] McLennan et al., EPSL (2005). [4] McCollom & Hynek, Nature (2005). [5] Squyres et al. Science (2006). [6] Knauth et al. Nature (2005). [7] Niles & Michalski, Nat. Geosci. (2009). [8] Berger et al. Am. Mineral. (2009). [9] McCollom et al. JGR-Planets (submitted ms.)

How does the association of iron oxides and perchlorate salts influence organic matter evolution when using Sample Analysis at Mars pyrolysis onboard Curiosity?

NASA Astrophysics Data System (ADS)

François, Pascaline; Coll, Patrice; Szopa, Cyril; Buch, Arnaud; Cabane, Michel; McAdam, Amy; Freissinet, Caroline; Eigenbrode, Jennifer L.; Glavin, Daniel P.; Navarro-Gonzalez, Rafael; Mahaffy, Paul R.

2014-05-01

al. (2013), JGR. [3] Ming, D. et al. (2013), Science, DOI: 10.1126/science.1245267 [4] Navarro-Gonzalez, R. et al. (2010), JGR. [5] Vaniman, D. T. et al (2013), Science, DOI: 10.1126/science.1243480. 71, 9-17. [6] Iniguez, E. et al. (2009), Geophysical Research Letters, 36. Acknowledgments: SAM-GC team acknowledges support from the French Space Agency (CNES), French National Programme of Planetology (PNP), National French Council (CNRS), Pierre Simon Laplace Institute, Institut Universitaire de France (IUF) and ESEP Labex. J. Eigenbrode and D. Glavin were supported by the NASA MSL participating scientist program.

Recent Flood Volcanism on Mars: Implications for Climate Change, Layered Deposits, and Lava-Water Interactions

NASA Astrophysics Data System (ADS)

Keszthelyi, L.; McEwen, A.

2001-05-01

. There is evidence from MOC and MOLA that recent floods of both water and lava originated from Cerberus Rupes, a fracture system which has been active very recently (it cuts the young lavas). This may be the very best place on Mars to search for current geothermal activity. Keszthelyi et al. (2000) JGR 105, 15027-15049. Hartmann and Berman (2000) JGR, 105, 15011-15025. Thordarson and Self (1996) JVGR 74, 49-73. Keszthelyi and Thordarson, (2000) GSA Ann. Meet. Abst. #5293. McSween, et al. (2001), Nature 409, 487-490. Lanagan et al., (submitted) GRL.

A Comparative Study of Shock Structures for the Halloween 2003 and the 23 July 2012 CME Events

NASA Astrophysics Data System (ADS)

Wu, C. C.; Liou, K.

2015-12-01

Interplanetary (IP) shocks driven by coronal mass ejections (CMEs) play an important role in space weather. For example, solar energetic particles are accelerated at the shock and storm sudden commencements are produced by the impingement of the Earth by the shocks. Here, we study shocks associated with two major CME events - the Halloween 2003 and the 23 July 2012 CME events, using a three-dimensional (3D) magnetohydrodynamics model (H3DMHD). The H3DMHD (Wu et al. 2007, JGR) combines the kinematic solar wind model (HAF) for regions near the solar surface (2.5-18 Rs) and a 3D magnetohydrodynamics model (Han et al. 1988), which takes output from HAF at 18 Rs and propagates outward up to 1.7 AU. The H3DMHD code has been fully tested and is capable of simulating disturbances propagating in the solar wind. We will focus on the temporal and spatial structure of the CME-driven shocks, including the shock type and strength.

Measurements of ClONO2 by Improved Limb Atmospheric Spectrometer (ILAS) in the high latitude stratosphere

NASA Astrophysics Data System (ADS)

Nakajima, H.; Irie, H.; Sugita, T.; Yokota, T.; Sasano, Y.

2003-12-01

Improved Limb Atmospheric Spectrometer (ILAS) was a solar-occultation sensor onboard the ADEOS satellite. ILAS measured vertical profiles of O3, HNO3, NO2, N2O, CH4, H2O, and aerosol extinction coefficients at high latitude stratosphere from November 1996 to June 1997 [JGR, ILAS Special Section, Vol. 107, No. D24, 2002]. The latest retrieval algorithm of ILAS (Version 6.0) enabled us to retrieve vertical profiles of ClONO2 and N2O5 with typical vertical resolution of 1.6-2.0 km in addition to these species. The advantage of ILAS ClONO2 measurements is that it continuously measured this gas species at high latitude stratosphere with high vertical resolution. ILAS ClONO2 profiles were compared with correlative balloon-borne measurements by MIPAS-B2 [Fischer and Oelhaf, 1996], FIRS-2 [Johnson et al., 1995], and MkIV [Toon, 1991]. In all comparisons, it was found that ILAS ClONO2 values were systematically lower by around 30% between 15 and 32 km altitudes. Also, the precision and accuracy of ILAS ClONO2 for altitude of 15-35 km were estimated to be around 20-40% and 30%, respectively. The Arctic winter/spring in 1996/1997 was characterized its relatively low temperature and its long lasting polar vortex. Many PSC activities were observed by ILAS in January-March 1997 [Hayashida et al., 2000]. ILAS succeeded to measure vertical profiles of ClONO2 for whole period of this Arctic winter/spring. After the PSC activity in February, enhancement of ClONO2 reaching 1.5 ppbv at around 20 km was observed for the data inside the polar vortex in March. In April 1997, enhanced ClONO2 amount decreased towards 1.0 ppbv at more than 10 days prior to the polar vortex breakup. This suggest the change of partitioning of chlorine species from ClONO2 into HCl at this period. Initial measurements of ClONO2 resumed by ILAS-II onboard the ADEOS-II satellite from April 2003 will also be presented at the meeting.

Nb/Al-AlOx/Nb Edge Junctions for Distributed Mixers

NASA Astrophysics Data System (ADS)

Amos, R. S.; Lichtenberger, A. W.; Tong, C. E.; Blundell, R.; Pan, S.-K.; Kerr, A. R.

We have fabricated high quality Nb/Al-oxide/Al/Nb edge junctions using a Nb/SiO/sub 2/ bi-layer film as the base electrode, suitable for use as traveling wave mixers. An edge is cut in the bi-layer with an ion gun at a 45 degree angle using a photoresist mask. The wafer is then cleaned in-situ with a physical ion gun clean followed by the deposition of a thin Al (a1) film, which is then thermally oxidized, an optional second Al (a2) layer, and a Nb counter electrode. It was found that devices with an a2 layer resulted in superior electrical characteristics, though proximity effects increased strongly with a2 thickness. The counter electrode is defined with an SF/sub 6/+N/sub 2/ reactive ion etch, using the Al barrier layer as an etch stop. The Al barrier layer is then either removed with an Al wet etch to isolate the individual devices, or the devices are separated with an anodization process. Various ion gun cleaning conditions have been examined; in addition, both wet and plasma etch bi-layer edge surface pre-treatments were investigated. It was found that edge junctions with large widths (i.e., those more suitable for traveling wave mixers) typically benefited more from such treatments. Initial receiver results at 260 GHz have yielded a DSB noise temperature of 60 K.

Photoelectrical, photophysical and photocatalytic properties of Al based MOFs: MIL-53(Al) and MIL-53-NH{sub 2}(Al)

DOE Office of Scientific and Technical Information (OSTI.GOV)

An, Yang; Li, Huiliang; Liu, Yuanyuan, E-mail: yyliu@sdu.edu.cn

Two Al based MOFs (MIL-53(Al) and MIL-53-NH{sub 2} (Al)) were synthesized, and their photoelectrical, photophysical and photocatalytic properties towards oxygen evolution from water were investigated. Different from the ligand to metal charge transfer process previously reported, we proposes a new photocatalytic mechanism based on electron tunneling according to the results of theoretical calculation, steady state and time resolved fluorescence spectra. The organic linkers absorb photons, giving rise to electrons and holes. Then, the photogenerated electrons tunnel through the AlO{sub 6}-octahedra, which not only inhibit the recombination of photogenerated charge carriers, but also is a key factor to the photocatalytic activitymore » of Al based MOFs. - Graphical abstract: The photoelectrical, photophysical and photocatalytic properties towards oxygen evolution from water of two Al based MOFs were investigated. A new photocatalytic mechanism was proposed based on electron tunneling according to the results of both theoretical calculation and steady state, time resolved fluorescence spectra. The electron tunneling process not only inhibit the recombination of photogenerated charge carriers, but also is a key factor to the photocatalytic activity of Al based MOFs.« less

Would-Be Warriors: Incidents of Jihadist Terrorist Radicalization in the United States Since September 11, 2001

DTIC Science & Technology

2010-01-01

NEFA Foundation (2009). 8 Would-Be Warriors: Incidents of Jihadist Terrorist Radicalization in the United States be strong, but the means are not at...Radicalization: Pathways Toward Terrorism,” Terrorism and Political Violence, Vol. 20, 2008. The NEFA Foundation, Anwar al Awlaki: Pro Al-Qaida

Global Counterinsurgency: A Way Out of the Global War on Terrorism Quagmire?

DTIC Science & Technology

2008-05-22

disseminating al Qaeda news and information regarding political and military operations, publishing the Arabic daily, Nashrat al- akhbar , and developing...Forces for Counterinsurgency,” Parameters Vol. XXXVI (Summer 2006) 47-62. Cohen, Eliot, LTC Conrad Crane US Army (Retired), LTC Jan Horvath US Army

Oxidation of Al2O3 continuous fiber-reinforced/NiAl composites

NASA Technical Reports Server (NTRS)

Doychak, J.; Nesbitt, J. A.; Noebe, R. D.; Bowman, R. R.

1992-01-01

The 1200 C and 1300 C isothermal and cyclic oxidation behavior of Al2O3 continuous fiber-reinforced/NiAl composites were studied. Oxidation resulted in formation of Al2O3 external scales in a similar manner as scales formed on monolithic NiAl. The isothermal oxidation of an Al2O3/NiAl composite resulted in oxidation of the matrix along the fiber/matrix interface near the fiber ends. This oxide acted as a wedge between the fiber and the matrix, and, under cyclic oxidation conditions, led to further oxidation along the fiber lengths and eventual cracking of the composite. The oxidation behavior of composites in which the Al2O3 fibers were sputter coated with nickel prior to processing was much more severe. This was attributed to open channels around the fibers which formed during processing, most likely as a result of the diffusion of the nickel coating into the matrix.

Structure of oxides prepared by decomposition of layered double Mg–Al and Ni–Al hydroxides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cherepanova, Svetlana V.; Novosibirsk State University, Novosibirsk; Leont’eva, Natalya N., E-mail: n_n_leonteva@list.ru

2015-05-15

Abstracts: Thermal decomposition of Mg–Al and Ni–Al layered double hydroxides LDH at temperatures lower than 800 °C leads to the formation of oxides with different structures. Mg–Al oxide has a very defective structure and consists of octahedral layers as in periclase MgO and mixed octahedral–tetrahedral layers as in spinel MgAl{sub 2}O{sub 4}. Mixed Ni–Al oxide has a sandwich-like structure, consisting of a core with Al-doped NiO-like structure and some surface layers with spinel NiAl{sub 2}O{sub 4} structure epitaxial connected with the core. Suggested models were verified by simulation of X-ray diffraction patterns using DIFFaX code, as well as HRTEM, IR-,more » UV-spectroscopies, and XPS. - Graphical abstract: In the Mg–Al layered double hydroxide Al{sup 3+} ions migrate into interlayers during decomposition. The Mg–Al oxide represents sequence of octahedral and octahedral–tetrahedral spinel layers with vacancies. The Ni–Al oxide has a sandwich-like structure with NiO-like core and surface spinel layers as a result of migration of Al{sup 3+} ions on the surface. The models explain the presence and absence of “memory effect” for the Mg–Al and Ni–Al oxides, respectively. - Highlights: • We study products of Mg(Ni)–Al LDH decomposition by calcination at 500(400)–800 °C. • In Mg–Al/Ni–Al LDH Al ions migrate into interlayers/on the surface during decomposition. • Mg–Al oxide represents sequence of periclase- and spinel-like layers with vacancies. • Ni–Al oxide has a sandwich-like structure with NiO-like core and surface spinel layers. • The models explain the presence/absence of “memory effect” for Mg–Al/Ni–Al oxides.« less

Sequential Data Assimilation for Seismicity: a Proof of Concept

NASA Astrophysics Data System (ADS)

van Dinther, Y.; Fichtner, A.; Kuensch, H. R.

2015-12-01

Our physical understanding and probabilistic forecasting ability of earthquakes is significantly hampered by limited indications of the state of stress and strength on faults and their governing parameters. Using the sequential data assimilation framework developed in meteorology and oceanography (e.g., Evensen, JGR, 1994) and a seismic cycle forward model based on Navier-Stokes Partial Differential Equations (van Dinther et al., JGR, 2013), we show that such information with its uncertainties is within reach, at least for laboratory setups. We aim to provide the first, thorough proof of concept for seismicity related PDE applications via a perfect model test of seismic cycles in a simplified wedge-like subduction setup. By evaluating the performance with respect to known numerical input and output, we aim to answer wether there is any probabilistic forecast value for this laboratory-like setup, which and how many parameters can be constrained, and how much data in both space and time would be needed to do so. Thus far our implementation of an Ensemble Kalman Filter demonstrated that probabilistic estimates of both the state of stress and strength on a megathrust fault can be obtained and utilized even when assimilating surface velocity data at a single point in time and space. An ensemble-based error covariance matrix containing velocities, stresses and pressure links surface velocity observations to fault stresses and strengths well enough to update fault coupling accordingly. Depending on what synthetic data show, coseismic events can then be triggered or inhibited.

Molecular structure of Mg-Al, Mn-Al and Zn-Al halotrichites-type double sulfates--an infrared spectroscopic study.

PubMed

Palmer, Sara J; Frost, Ray L

2011-05-01

Near infrared (NIR), X-ray diffraction (XRD) and infrared (IR) spectroscopy have been applied to halotrichites of the formula MgAl(2)(SO(4))(4)·22H(2)O, MnAl(2)(SO(4))(4)·22H(2)O and ZnAl(2)(SO(4))(4)·22H(2)O. Comparison of the halotrichites in different spectral regions has shown that the incorporation of a divalent transition metal into the halotrichite structure causes a shift in OH stretching band positions to lower wavenumbers. Therefore, an increase of the hydrogen bond strength of the bonded water is observed for divalent cations with a larger molecular mass. XRD has confirmed the formation of halotrichite for all three samples and characteristic peaks of halotrichite have been identified for each halotrichite-type compound. It has been observed that Mg-Al and Mn-Al halotrichite are very similar in structure, while Zn-Al showed several differences particularly in the NIR spectra. This work has shown that compounds with halotrichite structures can be synthesised and characterised by infrared and NIR spectroscopy. Copyright © 2011 Elsevier B.V. All rights reserved.

Mechanisms of elevated-temperature deformation in the B2 aluminides NiAl and CoAl

NASA Technical Reports Server (NTRS)

Yaney, D. L.; Nix, W. D.

1988-01-01

A strain rate change technique, developed previously for distinguishing between pure-metal and alloy-type creep behavior, was used to study the elevated-temperature deformation behavior of the intermetallic compounds NiAl and CoAl. Tests on NiAl were conducted at temperatures between 1100 and 1300 K while tests on CoAl were performed at temperatures ranging from 1200 to 1400 K. NiAl exhibits pure-metal type behavior over the entire temperature range studied. CoAl, however, undergoes a transition from pure-metal to alloy-type deformation behavior as the temperature is decreased from 1400 to 1200 K. Slip appears to be inherently more difficult in CoAl than in NiAl, with lattice friction effects limiting the mobility of dislocations at a much higher tmeperature in CoAl than in NiAl. The superior strength of CoAl at elevated temperatures may, therefore, be related to a greater lattice friction strengthening effect in CoAl than in NiAl.

CVD Fiber Coatings for Al2O3/NiAl Composites

NASA Technical Reports Server (NTRS)

Boss, Daniel E.

1995-01-01

While sapphire-fiber-reinforced nickel aluminide (Al2O3/NiAl) composites are an attractive candidate for high-temperature structures, the significant difference in the coefficient of thermal expansion between the NiAl matrix and the sapphire fiber creates substantial residual stresses in the composite. This study seeks to produce two fiber-coating systems with the potential to reduce the residual stresses in the sapphire/NiAl composite system. Chemical vapor deposition (CVD) was used to produce both the compensating and compliant-fiber coatings for use in sapphire/NiAl composites. A special reactor was designed and built to produce the FGM and to handle the toxic nickel precursors. This process was successfully used to produce 500-foot lengths of fiber with coating thicknesses of approximately 3 microns, 5 microns, and 10 microns.

Optical Emissions of Sprite Streamers in Weak Electric Fields

NASA Astrophysics Data System (ADS)

Liu, N.; Pasko, V. P.

2004-12-01

Sprites commonly consist of large numbers of needle-shaped filaments of ionization [e.g., Gerken and Inan, JASTP, 65, 567, 2003] and typically initiate at altitudes 70-75 km in a form of upward and downward propagating streamers [Stanley et al., GRL, 26, 3201, 1999; Stenbaek-Nielsen et al., GRL, 27, 3829, 2000; McHarg et al., JGR, 107, 1364, 2002; Moudry et al., JASTP, 65, 509, 2003]. The strong electric fields E exceeding the conventional breakdown threshold field Ek are needed for initiation of sprite streamers from single electron avalanches and recent modeling studies indicate that streamers propagating in fields E>Ek experience strong acceleration and expansion in good agreement with the above cited observations [Liu and Pasko, JGR, 109, A04301, 2004]. The initiated streamers are capable of propagating in fields substantially lower than Ek [Allen and Ghaffar, J. Phys. D: Appl. Phys., 28, 331, 1995] and it is expected that a significant part of sprite optical output comes from regions with Eal., GRL, 27, 653, 2000; Takahashi et al., Adv. Space Res., 26, 1205, 2000; Morrill et al., GRL, 29, 100, 2002; Pasko and George, 107, 1458, 2002; Chern et al., JASTP, 65, 647, 2003; Miyasato et al., JASTP, 65, 573, 2003] and understanding of optical emissions produced by streamers propagating in weak electric fields represents an important component of related studies needed for correct interpretation of the existing experimental data. In this talk we will report results on application of time dependent optical emission model developed in [Liu and Pasko, 2004] to studies of sprite streamers in weak electric fields (E

Twenty five years of planetary science: Discoveries and new questions

NASA Astrophysics Data System (ADS)

Hauck, Steven A.; Baratoux, David; Stanley, Sabine

2016-10-01

This year marks the 25th anniversary of the first issue of JGR-Planets. We are marking this occasion with a collection of review papers focused on enduring and fundamental themes in planetary science that have framed the past quarter century and will strongly influence research and exploration in the next quarter century. With topics covering bodies small and large, processes on and in solid planets and giant planets, in atmospheres, and around other stars, this collection samples the broad scope of planetary science and of JGR-Planets.

Multi-Nozzle Spray Cooling in a Closed Loop (POSTPRINT)

DTIC Science & Technology

2011-03-01

characteristics and critical heat flux (CHF) at cooling surfaces (Sehmbey et al., 1992, Mudawar and Estes, 1996, Rini et al., 2002, Lin and Ponnappan, 2003...surface characteristics in evaporative spray cooling, Journal of Thermophysics and heat Transfer, 1992, Vol. 6, pp. 505-512. 3. Mudawar , I., and

Study on Mg/Al Weld Seam Based on Zn–Mg–Al Ternary Alloy

PubMed Central

Liu, Liming; Liu, Fei; Zhu, Meili

2014-01-01

Based on the idea of alloying welding seams, a series of Zn–xAl filler metals was calculated and designed for joining Mg/Al dissimilar metals by gas tungsten arc (GTA) welding. An infrared thermography system was used to measure the temperature of the welding pool during the welding process to investigate the solidification process. It was found that the mechanical properties of the welded joints were improved with the increasing of the Al content in the Zn–xAl filler metals, and when Zn–30Al was used as the filler metal, the ultimate tensile strength could reach a maximum of 120 MPa. The reason for the average tensile strength of the joint increasing was that the weak zone of the joint using Zn–30Al filler metal was generated primarily by α-Al instead of MgZn2. When Zn–40Al was used as the filler metal, a new transition zone, about 20 μm-wide, appeared in the edge of the fusion zone near the Mg base metal. Due to the transition zones consisting of MgZn2- and Al-based solid solution, the mechanical property of the joints was deteriorated. PMID:28788508

Chemical failure modes of AlQ3-based OLEDs: AlQ3 hydrolysis.

PubMed

Knox, John E; Halls, Mathew D; Hratchian, Hrant P; Schlegel, H Bernhard

2006-03-28

Tris(8-hydroxyquinoline)aluminum(III), AlQ3, is used in organic light-emitting diodes (OLEDs) as an electron-transport material and emitting layer. The reaction of AlQ3 with trace H2O has been implicated as a major failure pathway for AlQ3-based OLEDs. Hybrid density functional calculations have been carried out to characterize the hydrolysis of AlQ3. The thermochemical and atomistic details for this important reaction are reported for both the neutral and oxidized AlQ3/AlQ3+ systems. In support of experimental conclusions, the neutral hydrolysis reaction pathway is found to be a thermally activated process, having a classical barrier height of 24.2 kcal mol(-1). First-principles infrared and electronic absorption spectra are compared to further characterize AlQ3 and the hydrolysis pathway product, AlQ2OH. The activation energy for the cationic AlQ3 hydrolysis pathway is found to be 8.5 kcal mol(-1) lower than for the neutral reaction, which is significant since it suggests a role for charge imbalance in promoting chemical failure modes in OLED devices.

Optical, structural, and nuclear scientific studies of AlGaN with high Al composition

NASA Astrophysics Data System (ADS)

Lin, Tse Yang; Chung, Yee Ling; Li, Lin; Yao, Shude; Lee, Y. C.; Feng, Zhe Chuan; Ferguson, Ian T.; Lu, Weijie

2010-08-01

AlGaN epilayers with higher Al-compositions were grown by Metalorganic Chemical Vapor Deposition (MOCVD) on (0001) sapphire. Trimethylgallium (TMGa), trimethylaluminium (TMAl) and NH3 were used as the source precursors for Ga, Al, and N, respectively. A 25 nm AlN nucleation layer was first grown at low-temperature of 590 °C at 300 Torr. Followed, AlxGa1-xN layers were grown at 1080 °C on low-temperature AlN nucleation layers. The heterostructures were characterized by a series of techniques, including x-ray diffraction (XRD), Rutherford backscattering (RBS), photoluminescence (PL), scanning electron microscopy (SEM) and Raman scattering. Precise Al compositions were determined through XRD, RBS, and SEM combined measurements. Room Temperature Raman Scattering spectra shows three major bands from AlGaN alloys, which are AlN-like, A1 longitudinal optical (LO) phonon modes, and E2 transverse optical (TO) band, respectively, plus several peak comes from the substrate. Raman spectral line shape analysis lead to an optical determination of the electrical property free carrier concentration of AlGaN. The optical properties of AlGaN with high Al composition were presented here.

Epitaxial growth of Al9Ir2 intermetallic compound on Al(100): Mechanism and interface structure

NASA Astrophysics Data System (ADS)

Kadok, J.; Pussi, K.; Šturm, S.; Ambrožič, B.; Gaudry, É.; de Weerd, M.-C.; Fournée, V.; Ledieu, J.

2018-04-01

The adsorption of Ir adatoms on Al(100) has been investigated under various exposures and temperature conditions. The experimental and theoretical results reveal a diffusion of Ir adatoms within the Al(100) surface selvedge already at 300 K. Above 593 K, two domains of a (√{5 }×√{5 }) R 26 .6∘ phase are identified by low energy electron diffraction (LEED) and scanning tunneling microscopy measurements. This phase corresponds to the initial growth of an Al9Ir2 compound at the Al(100) surface. The Al9Ir2 intermetallic domains are terminated by bulklike pure Al layers. The structural stability of Al9Ir2 (001) grown on Al(100) has been analyzed by density functional theory based calculations. Dynamical LEED analysis is consistent with an Ir adsorption leading to the growth of an Al9Ir2 intermetallic compound. We propose that the epitaxial relationship Al9Ir2(001 ) ∥Al (100) and Al9Ir2[100 ] ∥Al [031 ]/[013 ] originates from a matching of Al atomic arrangements present both on Al(100) and on pure Al(001) layers present in the Al9Ir2 compound. Finally, the interface between Al9Ir2 precipitates and the Al matrix has been characterized by transmission electron microscopy measurements. The cross-sectional observations are consistent with the formation of Al9Ir2 (001) compounds. These measurements indicate an important Ir diffusion within Al(100) near the surface region. The coherent interface between Al9Ir2 and the Al matrix is sharp.

Formation of gamma(sup prime)-Ni3Al via the Peritectoid Reaction: gamma + beta (+ Al2O3)=gamma(sup prime)(+ Al2O3)

NASA Technical Reports Server (NTRS)

Copeland, Evan

2008-01-01

The activities of Al and Ni were measured using multi-cell Knudsen effusion-cell mass spectrometry (multi-cell KEMS), over the composition range 8-32 at.%Al and temperature range T=1400-1750 K in the Ni-Al-O system. These measurements establish that equilibrium solidification of gamma(sup prime)-Ni3Al-containing alloys occurs by the eutectic reaction, L (+ Al2O3)=gamma + Beta(+ Al2O3), at 1640 +/- 1 K and a liquid composition of 24.8 +/- 0.2 at.%al (at an unknown oxygen content). The {gamma + Beta (+Al2O3} phase field is stable over the temperature range 1633-1640 K, and gamma(sup prime)-Ni3Al forms via the peritectoid, gamma + Beta (+ Al2O3)=gamma(sup prime) (+ Al2O3), at 1633 +/- 1 K. This behavior is consistent with the current Ni-Al phase diagram and a new diagram is proposed. This new Ni-Al phase diagram explains a number of unusual steady-state solidification structures reported previously and provides a much simpler reaction scheme in the vicinity of the gamma(sup prime)-Ni2Al phase field.

Chemical trend of superconducting transition temperature in hole-doped delafossite of CuAlO2, AgAlO2 and AuAlO2

NASA Astrophysics Data System (ADS)

Nakanishi, Akitaka; Katayama-Yoshida, Hiroshi

2012-12-01

We have performed the first-principles calculations about the superconducting transition temperature Tc of hole-doped delafossite CuAlO2, AgAlO2 and AuAlO2. Calculated Tc are about 50 K (CuAlO2), 40 K (AgAlO2) and 3 K(AuAlO2) at maximum in the optimum hole-doping concentration. The low Tc of AuAlO2 is attributed to the weak electron-phonon interaction caused by the low covalency and heavy atomic mass.

Petrology and geochemistry of feldspathic impact-melt breccia Abar al' Uj 012, the first lunar meteorite from Saudi Arabia

NASA Astrophysics Data System (ADS)

Mészáros, Marianna; Hofmann, Beda A.; Lanari, Pierre; Korotev, Randy L.; Gnos, Edwin; Greber, Nicolas D.; Leya, Ingo; Greenwood, Richard C.; Jull, A. J. Timothy; Al-Wagdani, Khalid; Mahjoub, Ayman; Al-Solami, Abdulaziz A.; Habibullah, Siddiq N.

2016-10-01

Abar al' Uj (AaU) 012 is a clast-rich, vesicular impact-melt (IM) breccia, composed of lithic and mineral clasts set in a very fine-grained and well-crystallized matrix. It is a typical feldspathic lunar meteorite, most likely originating from the lunar farside. Bulk composition (31.0 wt% Al2O3, 3.85 wt% FeO) is close to the mean of feldspathic lunar meteorites and Apollo FAN-suite rocks. The low concentration of incompatible trace elements (0.39 ppm Th, 0.13 ppm U) reflects the absence of a significant KREEP component. Plagioclase is highly anorthitic with a mean of An96.9Ab3.0Or0.1. Bulk rock Mg# is 63 and molar FeO/MnO is 76. The terrestrial age of the meteorite is 33.4 ± 5.2 kyr. AaU 012 contains a 1.4 × 1.5 mm2 exotic clast different from the lithic clast population which is dominated by clasts of anorthosite breccias. Bulk composition and presence of relatively large vesicles indicate that the clast was most probably formed by an impact into a precursor having nonmare igneous origin most likely related to the rare alkali-suite rocks. The IM clast is mainly composed of clinopyroxenes, contains a significant amount of cristobalite (9.0 vol%), and has a microcrystalline mesostasis. Although the clast shows similarities in texture and modal mineral abundances with some Apollo pigeonite basalts, it has lower FeO and higher SiO2 than any mare basalt. It also has higher FeO and lower Al2O3 than rocks from the FAN- or Mg-suite. Its lower Mg# (59) compared to Mg-suite rocks also excludes a relationship with these types of lunar material.

Identification and Expression Profile of Multiple Genes in Response to Magnesium Exposure in Culex quinquefasciatus Larvae

DTIC Science & Technology

2010-11-01

Vol. 47, no. 6 Potter and Wadkins 2006; Cui et al. 2007a, 2007b; Cummins et al. 2007; Holmes et al. 2009). One study showed that the activities of...carboxylesterases in re- sponse to three insecticides (i.e.,malathion, propoxur, and permethrin) differed by mosquito species: high activities of...al. 2004). Chitotrio- sidase secreted by activated human macrophages is involved in the defense against chitin-containing pathogens such as fungi

Atomistic simulation of Al-graphene thin film growth on polycrystalline Al substrate

NASA Astrophysics Data System (ADS)

Zhang, Lan; Zhu, Yongchao; Li, Na; Rong, Yan; Xia, Huimin; Ma, Huizhong

2018-03-01

The growth of Al-Graphene composite coatings on polycrystalline Al substrate was investigated by using classical molecular dynamics (MD) simulations. Unlike the diffusion behaviors on single crystal surface, most of adatoms were easily bound by the steps on polycrystalline Al surface, owing to the local accelerated energy. Both Ehrlich-Schwoebel (ES) barriers and the steering effect backed up the volmer-weber growth mode, which was consistent with the dynamic growth process observed in the deposit. The morphology of composite coatings was significantly affected by graphene flakes. Enrichment of graphene flakes gave rise to an increase of the local thickness, and graphene flakes only existed in Al grain boundaries. The size of Al grains in the composite coating visibly decreased when compared with that in the pure Al coating. This grain refinement and the mechanical property can be reinforced by the increase of graphene flakes.

Insulator-semiconductor interface fixed charges in AlGaN/GaN metal-insulator-semiconductor devices with Al2O3 or AlTiO gate dielectrics

NASA Astrophysics Data System (ADS)

Le, Son Phuong; Nguyen, Duong Dai; Suzuki, Toshi-kazu

2018-01-01

We have investigated insulator-semiconductor interface fixed charges in AlGaN/GaN metal-insulator-semiconductor (MIS) devices with Al2O3 or AlTiO (an alloy of Al2O3 and TiO2) gate dielectrics obtained by atomic layer deposition on AlGaN. Analyzing insulator-thickness dependences of threshold voltages for the MIS devices, we evaluated positive interface fixed charges, whose density at the AlTiO/AlGaN interface is significantly lower than that at the Al2O3/AlGaN interface. This and a higher dielectric constant of AlTiO lead to rather shallower threshold voltages for the AlTiO gate dielectric than for Al2O3. The lower interface fixed charge density also leads to the fact that the two-dimensional electron concentration is a decreasing function of the insulator thickness for AlTiO, whereas being an increasing function for Al2O3. Moreover, we discuss the relationship between the interface fixed charges and interface states. From the conductance method, it is shown that the interface state densities are very similar at the Al2O3/AlGaN and AlTiO/AlGaN interfaces. Therefore, we consider that the lower AlTiO/AlGaN interface fixed charge density is not owing to electrons trapped at deep interface states compensating the positive fixed charges and can be attributed to a lower density of oxygen-related interface donors.

26Al- 26Mg and 207Pb- 206Pb systematics of Allende CAIs: Canonical solar initial 26Al/ 27Al ratio reinstated

NASA Astrophysics Data System (ADS)

Jacobsen, Benjamin; Yin, Qing-zhu; Moynier, Frederic; Amelin, Yuri; Krot, Alexander N.; Nagashima, Kazuhide; Hutcheon, Ian D.; Palme, Herbert

2008-07-01

The precise knowledge of the initial 26Al/ 27Al ratio [( 26Al/ 27Al) 0] is crucial if we are to use the very first solid objects formed in our Solar System, calcium-aluminum-rich inclusions (CAIs) as the "time zero" age-anchor and guide future work with other short-lived radio-chronometers in the early Solar System, as well as determining the inventory of heat budgets from radioactivities for early planetary differentiation. New high-precision multi-collector inductively-coupled plasma mass spectrometry (MC-ICP-MS) measurements of 27Al/ 24Mg ratios and Mg-isotopic compositions of nine whole-rock CAIs (six mineralogically characterized fragments and three micro-drilled inclusions) from the CV carbonaceous chondrite, Allende yield a well-defined 26Al- 26Mg fossil isochron with an ( 26Al/ 27Al) 0 of (5.23 ± 0.13) × 10 - 5 . Internal mineral isochrons obtained for three of these CAIs ( A44A, AJEF, and A43) are consistent with the whole-rock CAI isochron. The mineral isochron of AJEF with ( 26Al/ 27Al) 0 = (4.96 ± 0.25) × 10 - 5 , anchored to our precisely determined absolute 207Pb- 206Pb age of 4567.60 ± 0.36 Ma for the same mineral separates, reinstate the "canonical" ( 26Al/ 27Al) 0 of 5 × 10 - 5 for the early Solar System. The uncertainty in ( 26Al/ 27Al) 0 corresponds to a maximum time span of ± 20 Ka (thousand years), suggesting that the Allende CAI formation events were culminated within this time span. Although all Allende CAIs studied experienced multistage formation history, including melting and evaporation in the solar nebula and post-crystallization alteration likely on the asteroidal parent body, the 26Al- 26Mg and U-Pb-isotopic systematics of the mineral separates and bulk CAIs behaved largely as closed-system since their formation. Our data do not support the "supra-canonical" 26Al/ 27Al ratio of individual minerals or their mixtures in CV CAIs, suggesting that the supra-canonical 26Al/ 27Al ratio in the CV CAIs may have resulted from post

Effects of Al(III) and Nano-Al13 Species on Malate Dehydrogenase Activity

PubMed Central

Yang, Xiaodi; Cai, Ling; Peng, Yu; Li, Huihui; Chen, Rong Fu; Shen, Ren Fang

2011-01-01

The effects of different aluminum species on malate dehydrogenase (MDH) activity were investigated by monitoring amperometric i-t curves for the oxidation of NADH at low overpotential using a functionalized multi-wall nanotube (MWNT) modified glass carbon electrode (GCE). The results showed that Al(III) and Al13 can activate the enzymatic activity of MDH, and the activation reaches maximum levels as the Al(III) and Al13 concentration increase. Our study also found that the effects of Al(III) and Al13 on the activity of MDH depended on the pH value and aluminum speciation. Electrochemical and circular dichroism spectra methods were applied to study the effects of nano-sized aluminum compounds on biomolecules. PMID:22163924