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Bergman Ola,Lindqvist Bjorn,Bengtsson Sven 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1
Powder grades pre-alloyed with 1.5-3 wt% chromium can be successfully sintered at the conventional temperature although well-monitored sintering atmospheres are required to avoid oxidation. Mechanical properties of the Cr-alloyed PM grades are enhanced by a higher sintering temperature in the range , due to positive effects from pore rounding, increased density and more effective oxide reduction. Astaloy CrM (Fe-3 wt% Cr-0.5 wt% Mo) with 0.6 wt% graphite added obtains an ultimate tensile strength of 1470 MPa and an impact strength of 31 J at density , after sintering at followed by cooling at and tempering.
Oxygen Removal during Sintering of Steels Prepared from Cr-Mo and Mo Prealloyed Powders
Danninger Herbert,Xu Chen,Lindqvist Bjorn 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1
The removal of oxygen during sintering by carbothermic reduction was studied for steel compacts Fe-Cr-Mo-C and Fe-Mo-C prepared from prealloyed powders. The compacts were prepared by pressing at 600 and 1000 MPa and sintering at 1100 and 1300°C in vacuum. It showed that for the Cr-Mo steel, deoxidation strongly depends on the sintering temperature, in contrast to the plain Mo steel; at 1300°C very low oxygen levels were measured with the standard density compact while at high density still significant oxygen is contained. This indicates inhibition of final deoxidation by pore closure, but apparently without adverse effect on the mechanical properties.
Location of<i>γ</i>-ray emission and magnetic field strengths in OJ 287
Hodgson, J. A.,Krichbaum, T. P.,Marscher, A. P.,Jorstad, S. G.,Rani, B.,Marti-Vidal, I.,Bach, U.,Sanchez, S.,Bremer, M.,Lindqvist, M.,Uunila, M.,Kallunki, J.,Vicente, P.,Fuhrmann, L.,Angelakis, E.,Kar Springer-Verlag 2017 Astronomy and astrophysics Vol.597 No.-
Global millimeter VLBI array survey of ultracompact extragalactic radio sources at 86 GHz
Nair, Dhanya G.,Lobanov, Andrei P.,Krichbaum, Thomas P.,Ros, Eduardo,Zensus, Johann Anton,Kovalev, Yuri Y.,Lee, Sang-Sung,Mertens, Florent,Hagiwara, Yoshiaki,Bremer, Michael,Lindqvist, Michael,de Vice Springer-Verlag 2019 Astronomy and astrophysics Vol.622 No.-
<P><I>Context</I>. Very long baseline interferometry (VLBI) observations at 86 GHz (wavelength, <I>λ</I> = 3 mm) reach a resolution of about 50 <I>μ</I>as, probing the collimation and acceleration regions of relativistic outflows in active galactic nuclei (AGN). The physical conditions in these regions can be studied by performing 86 GHz VLBI surveys of representative samples of compact extragalactic radio sources.</P><P><I>Aims</I>. To extend the statistical studies of compact extragalactic jets, a large global 86 GHz VLBI survey of 162 compact radio sources was conducted in 2010-2011 using the Global Millimeter VLBI Array (GMVA).</P><P><I>Methods</I>. The survey observations were made in a snapshot mode, with up to five scans per target spread over a range of hour angles in order to optimize the visibility coverage. The survey data attained a typical baseline sensitivity of 0.1 Jy and a typical image sensitivity of 5 mJy beam<SUP>−1</SUP>, providing successful detections and images for all of the survey targets. For 138 objects, the survey provides the first ever VLBI images made at 86 GHz. Gaussian model fitting of the visibility data was applied to represent the structure of the observed sources and to estimate the flux densities and sizes of distinct emitting regions (components) in their jets. These estimates were used for calculating the brightness temperature (<I>T</I>b) at the jet base (core) and in one or more moving regions (jet components) downstream from the core. These model-fit-based estimates of <I>T</I>b were compared to the estimates of brightness temperature limits made directly from the visibility data, demonstrating a good agreement between the two methods.</P><P><I>Results</I>. The apparent brightness temperature estimates for the jet cores in our sample range from 2.5 × 10<SUP>9</SUP> K to 1.3 × 10<SUP>12</SUP> K, with the mean value of 1.8 × 10<SUP>11</SUP> K. The apparent brightness temperature estimates for the inner jet components in our sample range from 7.0 × 10<SUP>7</SUP> K to 4.0 × 10<SUP>11</SUP> K. A simple population model with a single intrinsic value of brightness temperature, <I>T</I>0, is applied to reproduce the observed distribution. It yields <I>T</I>0 = (3.77−0.14<SUP>+0.10</SUP>) × 10<SUP>11</SUP> K for the jet cores, implying that the inverse Compton losses dominate the emission. In the nearest jet components, <I>T</I>0 = (1.42−0.19<SUP>+0.16</SUP>) × 10<SUP>11</SUP> K is found, which is slightly higher than the equipartition limit of ∼5 × 10<SUP>10</SUP> K expected for these jet regions. For objects with sufficient structural detail detected, the adiabatic energy losses are shown to dominate the observed changes of brightness temperature along the jet.</P>