756 research outputs found
Lyman alpha line formation in starbursting galaxies II. Extremely Thick, Dustless, and Static HI Media
The Lya line transfer in an extremely thick medium of neutral hydrogen is
investigated by adopting an accelerating scheme in our Monte Carlo code to skip
a large number of core or resonant scatterings. This scheme reduces computing
time significantly with no sacrifice in the accuracy of the results. We applied
this numerical method to the Lya transfer in a static, uniform, dustless, and
plane-parallel medium. Two types of photon sources have been considered, the
midplane source and the uniformly distributed sources. The emergent profiles
show double peaks and absorption trough at the line-center. We compared our
results with the analytic solutions derived by previous researchers, and
confirmed that both solutions are in good agreement with each other. We
investigated the directionality of the emergent Lya photons and found that limb
brightening is observed in slightly thick media while limb darkening appears in
extremely thick media. The behavior of the directionality is noted to follow
that of the Thomson scattered radiation in electron clouds, because both Lya
wing scattering and Thomson scattering share the same Rayleigh scattering phase
function. The mean number of wing scatterings just before escape is in exact
agreement with the prediction of the diffusion approximation. The Lya photons
constituting the inner part of the emergent profiles follow the relationship
derived from the diffusion approximation. We present a brief discussion on the
application of our results to the formation of Lya broad absorption troughs and
P-Cygni type Lya profiles seen in the UV spectra of starburst galaxies.Comment: 24 papges, 12 figures, The revised version submitted to Ap
A Spectral Line Survey from 138.3 to 150.7 GHZ toward Orion-KL
We present the results of a spectral line survey from 138.3 to 150.7 GHz
toward Orion-KL. The observations were made using the 14 m radio telescope of
Taeduk Radio Astronomy Observatory. Typical system temperatures were between
500 and 700 K, with the sensitivity between K in units of .
A total of 149 line spectra are detected in this survey. Fifty lines have
been previously reported, however we find 99 new detections. Among these new
lines, 32 are `unidentified', while 67 are from molecular transitions with
known identifications. There is no detection of H or He recombination lines.
The identified spectra are from a total of 16 molecular species and their
isotopic variants. In the range from 138.3 to 150.7 GHz, the strongest spectral
line is the J=3-2 transition of CS molecule, followed by transitions of the
, , , and . Spectral lines from
the large organic molecules such as , , , and are prominent; with 80 % of the
identified lines arising from transitions of these molecules. The rotational
temperatures and column densities are derived using the standard rotation
diagram analysis for (), , and with and . These estimates are fairly comparable to the values for the
same molecule in other frequency regions by other studies.Comment: 10 figures, 2 tex files for a manuscript and tables, accepted to Ap
A Scaling-up Synthesis From Laboratory Scale to Pilot Scale and to Near Commercial Scale for Paste-Glue Production
This paper concerns on developing a synthesis method of paste-glue production for gummed tape using a corn-based starch as an alternative feedstock from laboratory-scale to pilot-scale and to near commercial scale. Basically, two methods of synthesis were developed to produce paste-glue in laboratory scale. Based on the two methods, we then scale-up the earlier laboratory scale data to pilot-scale and near commercial-scale for developing a large scale process production of paste-glue. Scaling up production from 1,000 ml reactor to 500 L pilot-scale reactor and 1,500 L near commercial scale reactor, we monitored pathway of temperature increase during reaction as well as adjustment of operating condition conducted for laboratory experimental data in order to produce a good quality of paste-glue. Some scaling up parameters have been found as well as critical parameters for a good product quality such as viscosity and ceiling temperature of the reaction which are very crucial in order to give optimum operating condition. We have selected synthesis method of paste-glue production and found the range of the parameters in order to produce a very good quality of paste-glue in pilot scale and near commercial scale
Diffusive Capture Process on Complex Networks
We study the dynamical properties of a diffusing lamb captured by a diffusing
lion on the complex networks with various sizes of . We find that the life
time and the survival probability becomes finite on scale-free networks with degree exponent
. However, for has a long-living tail on
tree-structured scale-free networks and decays exponentially on looped
scale-free networks. It suggests that the second moment of degree distribution
kn(k)n(k)\sim k^{-\sigma}\gamma<3n(k)k\approx k_{max}n(k)n(k)\sim k^2P(k)N_{tot}, which
causes the dependent behavior of and $.Comment: 9 pages, 6 figure
Molecular Weight and Structural Properties of Biodegradable PLA Synthesized with Different Catalysts by Direct Melt Polycondensation
Production of biodegradable polylactic acid (PLA) from biomassbased lactic acid is widely studied for substituting petro-based plastics or polymers. This study investigated PLA production from commercial lactic acid in a batch reactor by applying a direct melt polycondensation method with two kinds of catalyst, Îł-aluminium(III) oxide (Îł-Al2O3) or zinc oxide (ZnO), in reduced pressure. The molecular weight of the synthesized PLA was determined by capillary viscometry and its structural properties were analyzed by functional group analysis using FT-IR. The yields of polymer production with respect to the theoretical conversion were 47% for Îł-Al2O3 and 35% for ZnO. However, the PLA from ZnO had a higher molecular weight (150,600 g/mol) than that from Îł-Al2O3 (81,400 g/mol). The IR spectra of the synthesized PLA from both catalysts using polycondensation show the same behavior of absorption peaks at wave numbers from 4,500 cm-1 to 500 cm-1, whereas the PLA produced by two other polymerization methods â polycondensation and ring opening polymerization âshowed a significant difference in % transmittance intensity pattern as well as peak area absorption at a wave number of 3,500 cm-1 as âOH vibration peak and at 1,750 cm-1 as âC=O carbonyl vibrational peak
Perturbative Expansion around the Gaussian Effective Action: The Background Field Method
We develop a systematic method of the perturbative expansion around the
Gaussian effective action based on the background field method. We show, by
applying the method to the quantum mechanical anharmonic oscillator problem,
that even the first non-trivial correction terms greatly improve the Gaussian
approximation.Comment: 16 pages, 3 eps figures, uses RevTeX and epsf. Errors in Table 1 are
corrected and new references are adde
Observation of Scarred Modes in Asymmetrically Deformed Microcylinder Lasers
We report observation of lasing in the scarred modes in an asymmetrically
deformed microcavity made of liquid jet. The observed scarred modes correspond
to morphology-dependent resonance of radial mode order 3 with their Q values in
the range of 10^6. Emission directionality is also observed, corresponding to a
hexagonal unstable periodic orbit.Comment: 4 pages, 6 figure
Lyman alpha line formation in starbursting galaxies I. Moderately thick, dustless, and static HI media
We investigate the Lyman alpha line transfer in nearby and high redshift
starbursting galaxies, where the effect of high optical depths and the role of
dust in the scattering medium are expected to be conspicuous and should be
treated in a very careful manner. We present our first results in dustless,
static, and uniform HI media with moderate Lyman alpha line center optical
depths \tau_0=10^{3-6}. We assume that the temperatures of media to be
T=10^{1-4}K, and use a Monte Carlo technique. We investigate the basic
processes of the line transfer and confirm the criterion of a\tau_0>10^3 for
the validity of diffusion approximation suggested by Neufeld in 1990, where
is the Voigt parameter. Adopting the model suggested by Tenorio-Tagle et al.,
we performed calculations on the Lyman alpha line formation for each
evolutionary stage of an expanding supershell. The emergent Lyman alpha
profiles are characterized by the double peaks and the absorption trough at the
line center. We found that the absorption troughs expected in most of the
evolutionary stages are not wide enough to be observed with current
instruments. However, the absorption trough in the Lyman alpha emission profile
from an expanding recombining supershell can be marginally detected.Comment: 38 pages, 12 figures, Accepted for publication in the Ap
An Optical Source Catalog of the North Ecliptic Pole Region
We present a five (u*,g',r',i',z') band optical photometry catalog of the
sources in the North Ecliptic Pole (NEP) region based on deep observations made
with MegaCam at CFHT. The source catalog covers about 2 square degree area
centered at the NEP and reaches depths of about 26 mag for u*, g', r' bands,
about 25 mag for i' band, and about 24 mag for z' band (4 sigma detection over
an 1 arcsec aperture). The total number of cataloged sources brighter than r'=
23 mag is about 56,000 including both point sources and extended sources. From
the investigation of photometric properties using the color-magnitude diagrams
and color-color diagrams, we have found that the colors of extended sources are
mostly (u*-r') 0.5. This can be used to separate the
extended sources from the point sources reliably, even for the faint source
domain where typical morphological classification schemes hardly work
efficiently. We have derived an empirical color-redshift relation of the red
sequence galaxies using the Sloan Digital Sky Survey data. By applying this
relation to our photometry catalog and searching for any spatial overdensities,
we have found two galaxy clusters and one nearby galaxy group.Comment: 34 pages, 15 figures, 2 tables. Accepted for publication in ApJS. The
pdf file with high resolution figures can be downloaded from
http://astro.snu.ac.kr/~nhwang/index.files/nep.htm
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