• 산업경영시스템학회지
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• 제42권4호
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• pp.49-60
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• 2019

Recently the concentration of fine dust and ultra fine dust becomes so bad, which seriously threatens the health and even the life of people. So, government started to investigate several ways to reduce the amount of fine dust and ultra fine dust. From a few years ago it has been known that ships anchored at port emit a lot of pollution and seriously affect air quality of neighboring cities. To reduce the pollution emitted by ship AMP (Alternative Maritime Power Supply) has been proposed, which uses the electricity instead of bunker C oil or diesel. Many developed countries already installed AMP to improve air quality in port area. Korea is in the stage of planning to install AMP at port. However, there are many complicated problems to be handled before AMP installation. Due to huge initial cost and long period of construction ship owner and habour operating company are reluctant to AMP installation. And there are serious technological difficulties in constructing AMP in existing harbour. Lack of AMP core technology and operational difficulties of AMP are also big challenges to be conquered. In this study SWOT/AHP method is used to find strategic and efficient ways to handle above complicated challenges and then to vitalize the AMP installation.

• 천문학회보
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• 제37권1호
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• pp.55.2-55.2
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• 2012

Silicate-carbon stars are characterized by oxygen-rich (O-rich) dust features despite their carbon-rich (C-rich) photospheres. While the origin of silicate-carbon stars has been a mystery ever since their discovery, the most widely accepted hypothesis is that the silicate-carbon stars have a low-luminosity companion and the O-rich material is stored in a circumbinary disk or a circumstellar disk even after the primary star becomes a carbon star. In order to study the properties of circumstellar dust envelopes of silicate-carbon stars, we perform radiative transfer model calculations using RADMC-3D with an axi-symmetric dust density distribution (a disk) as well as a spherically symmetric dust distribution. For various dust envelope models with different shapes and chemistry, we calculate the model spectral energy distributions (SEDs) and compare the model results with the observed SEDs of selected 5 silicate-carbon stars. The Circumstellar disk models are fairly well fitted with the observational data of 5 silicate-carbon stars. We find some evidences that the circumbinary disk model could be a better explanation for the origin of silicate carbon stars than the simple detached silicate dust shell model of the transition phase of the stellar chemistry.

• Journal of the Optical Society of Korea
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• 제14권3호
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• pp.178-184
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• 2010

We present linear particle depolarization ratios (LPDRs) retrieved from measurements with an AERONET Sun photometer at the Gwangju Institute of Science and Technology (GIST), Korea ($35.10^{/circ}N$, $126.53^{\circ}E$) between 19 October and 3 November 2009. The Sun photometer data were classified into three categories according to ${\AA}$ngstr$\ddot{o}$ exponent and size distribution: 1) pure Asian dust (19 October 2009), 2) Asian dust mixed with urban pollution observed in the period from 20-26 October 2009, and 3) clean conditions (3 November). We show that the LPDRs can be used to distinguish among Asian dust, mixed aerosol, and non-Asian dust in the atmosphere. The mean LPDR of the pure Asian dust case is 23 %. Mean LPDRs are 13 % for the mixed case. The lowest mean LPDR is 6 % in the clean case. We compare our results to vertically resolved LPDRs (at 532 nm) measured by a Raman LIDAR system at the same site. In most cases, we find good agreement between LPDRs derived with Sun photometer and measured by LIDAR.

• 천문학회지
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• 제47권4호
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• pp.123-135
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• 2014

A silicate carbon star is a carbon star which shows circumstellar silicate dust features. We collect a sample of 44 silicate carbon stars from the literature and investigate the validity of the classification. For some objects, it is uncertain whether the central star is a carbon star. We confirm that 29 objects are verified silicate carbon stars. We classify the confirmed objects into three subclasses based on the evolution phase of the central star. To investigate the effect of the chemical transition phase from O to C, we use the radiative transfer models for the detached silicate dust shells. The spectral energy distributions and the infrared two-color diagrams of the silicate carbon stars are compared with the theoretical model results. For the chemical transition model without considering the effect of a disk, we find that the life time of the silicate feature is about 50 to 400 years depending on the initial dust optical depth.

• 천문학회보
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• 제39권1호
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• pp.59.2-59.2
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• 2014

Radiative transfer models in a spherical, turbulent interstellar medium (ISM), in which the photon source is situated at the center, are calculated to investigate the correlation between the scattered light and the dust column density. The medium is modeled using fractional Brownian motion structures that are appropriate for turbulent ISM. The correlation plot between the scattered light and optical depth shows substantial scatter and deviation from simple proportionality. It was also found that the overall density contrast is smoothed out in scattered light. In other words, there is an enhancement of the dust-scattered flux in low-density regions, while the scattered flux is suppressed in high-density regions. The correlation becomes less significant as the scattering becomes closer to being isotropic and the medium becomes more turbulent. Therefore, the scattered light observed in near-infrared wavelengths would show much weaker correlation than the observations in optical and ultraviolet wavelengths. We also find that the correlation plot between scattered lights at two different wavelengths shows a tighter correlation than that of the scattered light versus the optical depth.

• 영어어문교육
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• 제9권1호
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• pp.189-203
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• 2003

This paper attempts to prove Dickens's hopeful view of the future in his last completed novel Our Mutual Friend. This novel has been usually regarded as one of the "dark" novels, "dark" in the sense of viewing social reality and the future negatively. However, although it has the dark descriptive color of society typical in Dickens's later novels, it still contains some elements that point to a better future. To prove this positive view of future, this paper will disentangle the intricate narrative structure of Our Mutual Friend and find out the true meaning of the dust--money. In addition, it will investigate how people react to dust(-like money). From a close study of several characters' lives, it will testify that the dark world of Our Mutual Friend, in the end, could be a world of regeneration, a world that will lead to a better future.

• 천문학논총
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• 제27권4호
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• pp.253-256
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• 2012

We present the IRC images of M51, a pair of interacting galaxies. Given the high angular resolution (7.4") and the wide field of view (~ 10') covering almost the entire M51 system, we investigate dust properties and their connection to the spiral arm structure. We have applied image-filtering processes including the wavelet analysis to the N3 image, which traces the total stellar mass best among the IRC bands. From this filtered image, the center, arm, and interarm regions are defined. A color, or flux ratio among the MIR bands, has been measured at each pixel (3.7" in size). We find a wide variety of S7/S11 with a difference between arm and interarm regions. We also find that at some positions S11 seems to be higher than predicted by MW dust models. Estimated contributions from the stellar continuum and gas emission lines to the band are not enough to explain this discrepancy. From these results, we deduce that the PAH ionization condition and its fraction to the total dust mass in M51 are different from those in MW.

• 한국대기환경학회지
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• 제17권1호
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• pp.85-96
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• 2001

The objective of this study is to develop the water spraying which can effectively by applied to the control or suppression of the fugitive dust generated from the scrap metal handling area at the Port of Inchon. As a first step toward this goal, we carried out some preliminary analyses on the chemical composition, physical shape, and particle size distribution of the sample dust. Next, to quantitatively investigate the effect of adding surfactants to the spraying water on the wettability of the sample dust, the Standard Sink Test was carried out for four different surfactants and at six different concentrations using the surfactants considered in this study. Results of from the preliminary analysis indicated that the main chemical component consisting of the sample dust is Goethite(FeO(OH)) and that the particles smaller than 10 ${\mu}{\textrm}{m}$ in geometric diameter occupy about 36% of the sample dust in mass. This result implies that the fugitive dust generated from the scrap metal handling area at the Port of Inchon should affect the environment nearby more than we have expected. This is because of relatively large mass percentage of the small metal particles less than 10${\mu}{\textrm}{m}$ in geometric diameter, what we may call respirable particles. As for the results of the Standard Sink Test, higher surfactant concentration tends to result in the higher wettability of the sample dust for the surfactants considered in this study, which in turn ensures the high particle collection efficiency of the droplets generated from the water spraying system. Based upon this preliminary results, studies to develop more sophisticated scaled model for dynamic test in underway and the effort to find the best surfactants as well as the optimum operating conditions are being made at the same time.

• 한국화재소방학회논문지
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• 제13권2호
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• pp.26-32
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• 1999

쌀겨분진의 연소 및 전기적 점화에너지에 의한 폭발 위험성을 조사하기 위하여 시차주사열량계(DSC, Differential Scanning Calorimeter) 및 열중량 분석기(TGA, Thermogravimetric Analysis)와 순간승압조정기를 이용하여 온도 및 전기 스파크에 따른 발열개시온도, 발열량 등을 조사하였으며, 또한 Hartman 식 측정장치를 이용하여 쌀겨분진의 폭발 위험성을 측정하고자 하였다. DSC 분석 결과 대기 분위기에서 발열량이 증가하였으며 또한 승온속도가 증가하고 입도가 미세해질수록 발열량이 증가하였고, TGA 분석 결과 입도가 미세해질수록 분해량이 증가하였다. 한편 쌀겨분진의 폭발 위험성은 입도가 감소하고 농도가 증가할수록 또한 전기적 점화에너지가 클수록 폭발압력이 증가하였으며, 전기 점화원에 인가된 전압변화에 따른 폭발압력의 변화를 조사하였고, 50/60 mesh, 1.5mg/㎤에서 약 13.5kgf/$\textrm{cm}^2$의 최대 폭발압력을 나타내었다.

• 천문학회보
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• 제40권2호
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• pp.41.3-41.3
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• 2015

As part of the Herschel key program "Water in Star-forming Regions with Herschel (WISH)", PACS imaging spectroscopy data have been taken toward ten massive young stellar objects (YSOs): four high mass protostellar objects (HMPOs), two hot molecular cores (HMCs), and four ultracompact HII regions (UCHIIs). The spectra cover a broad range of wavelengths (55 to 210 micron) presenting various atomic and molecular lines as well as excellent dust thermal continua. By fitting the continua utilizing a modified black-body formula we estimate mass-weighted temperature and column density distributions of warm dust and find that UCHII regions are warmer and HMCs are more deeply embedded than the other types. We also estimate rotational temperature and column density distributions of warm CO gas using the rotational diagram analysis. In addition, based on the comparison of high J CO line fluxes to the RATRAN estimates of central heating envelope models, we find that majority of warm CO is originated from bipolar outflow shocks.