• 천문학회보
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• 제43권1호
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• pp.36.2-36.2
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• 2018

Radiative transfer models were developed to understand the optical polarizations in edge-on galaxies, which are observed to occur even outside the geometrically thin dust disk, with a scale height of ~0.2 kpc. In order to reproduce the vertically extended polarization structure, we find it is essential to include a geometrically thick dust layer in the radiative transfer model, in addition to the commonly-known thin dust layer. The models include polarizations due to both dust scattering and dichroic extinction which is responsible for the observed interstellar polarization in the Milky Way. It is found that the magnetic fields in edge-on galaxies are in general vertical (or poloidal) except the central part, where the magnetic fields are mainly toroidal. We also find that the polarization level is enhanced if the clumpiness of the interstellar medium, and the dichroic extinction by vertical magnetic fields in the outer regions of the dust lane are included in the radiative transfer model. The predicted degree of polarization outside the dust lane was found to be consistent with that (ranging from 1% to 4%) observed in NGC 891.

• 천문학회보
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• 제24권2호
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• pp.88-88
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• 1999

• 기술사
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• 제20권4호
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• pp.27-37
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• 1987

• 천문학회보
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• 제10권
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• pp.4.1-4.1
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• 1985

• 한국대기환경학회지
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• 제28권1호
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• pp.86-93
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• 2012

We present a retrieval method to obtain dust backscatter coefficient from the mixed Asian dust and pollutant layer. In the present study, vertically resolved quartz (silicon dioxide, silica) concentration was calculated using Raman scattering signals from quartz at 546 nm. Dust concentration was obtained based on typical mass percentage of quartz in Asian dust. The highest value of dust concentration at 3.7 km in March 21, 2010 was 22.3 and 10.9 ${\mu}gm^{-3}$ according to the quartz percentage in Asian dust as 65 and 30% based on literature survey, respectively. OPAC (Optical Properties of Aerosol and Clouds) simulations were conducted to calculate dust backscatter coefficient. The retrieved dust concentration was used as an input parameter for the OPAC calculations. Utilization of quartz Raman channel in Lidar measurements is considered useful for distinguishing optical properties of dust and nondust aerosol in the mixing state of Asian dust.

• Journal of Information Processing Systems
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• 제16권3호
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• pp.733-741
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• 2020

A smart dust monitoring system is useful for obtaining information on rough terrain that is difficult for humans to access. One of ways to deploy sensors to gather information in smart dust environment is to use an aircraft in the Amazon rainforest to scatter an enormous amount of small and cheap sensors (or smart dust devices), or to use an unmanned spacecraft to throw the sensors on the moon's surface. However, scattering an enormous amount of smart dust devices creates the difficulty of managing such devices as they can be scattered into inaccessible areas, and also causes problems such as bottlenecks, device failure, and high/low density of devices. Of the various problems that may occur in the smart dust environment, this paper is focused on solving the bottleneck problem. To address this, we propose and construct a three-layered hierarchical smart dust monitoring system that includes relay dust devices (RDDs). An RDD is a smart dust device with relatively higher computing/communicating power than a normal smart dust device. RDDs play a crucial role in reducing traffic load for the system. To validate the proposed system, we use climate data obtained from authorized portals to compare the system with other systems (i.e., non-hierarchical system and simple hierarchical system). Through this comparison, we determined that the transmission processing time is reduced by 49%-50% compared to other systems, and the maximum number of connectable devices can be increased by 16-32 times without compromising the system's operations.

• 천문학회보
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• 제46권2호
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• pp.81.2-81.2
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• 2021

Emission features formed through Raman scattering with atomic hydrogen provide unique and crucial information to probe the distribution and kinematics of a thick neutral region illuminated by a strong far-ultraviolet radiation source. We introduce a new 3-dimensional Monte-Carlo code to describe the radiative transfer of line photons subject to Raman and Rayleigh scattering with atomic hydrogen. In our Sejong Radiative Transfer through Raman and Rayleigh Scattering (STaRS) code, the position, direction, wavelength, and polarization of each photon is traced until escape. The thick neutral scattering region is divided into multiple cells. Each cell is characterized by its velocity and density, which ensures flexibility of the code in analyzing Raman-scattered features formed in a neutral region with complicated kinematics and density distribution. We are continuously developing STaRS to adopt the absorption and scattering effect by dust. This presentation introduces STaRS and its current state and study.

• 한국전자파학회논문지
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• 제15권7호
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• pp.722-729
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• 2004

2004년 3월과 4월중 우리나라에 발생한 황사가 위성통신신호에 미치는 영향을 분석하기 위하여 중앙전파관리소 위성전파감시센터를 통하여 황사 발생기간 중 L, S, C, Ku 및 Ka대역의 위성신호에 대한 실효등방성방사전력(EIRP)을 측정하였다. 이 측정값을 동 황사 발생기간중 기상청에서 측정한 미세먼지농도(PM10)와 미세먼지를 수치화 한 광학입자계수기(OPC)의 측정값을 기준으로 위성통신신호세기에 미치는 황사의 농도와 대기중의 입자의 수치들의 변화량에 대하여 분석하였다.

• 천문학논총
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• 제23권2호
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• pp.25-29
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• 2008

Scattering of incident light by the interstellar dust is usually approximated by Henyey-Greenstein scattering phase function. Recently, Draine (2003) proposed a new analytic phase function with two parameters. We describe an algorithm to generate random numbers distributed according to the Draine’s function, and compare two phase functions. It is also derived exact solutions of two parameters for given values ${\langle}cos{\theta}{\rangle}$ and ${\langle}cos^2{\theta}{\rangle}$. It is found that Henyey-Greenstein function with g = ${\langle}cos{\theta}{\rangle}$ provides a good approximation for ${\lambda}\;>\;2000{\AA}$. At shorter wavelengths, more realistic phase function may be needed for radiative transfer models.

• 한국화재소방학회논문지
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• 제32권3호
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• pp.134-139
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• 2018

최근 초미세먼지는 사회적 재난으로 간주될만큼 국민건강에 심각하게 영향을 미쳐 사회문제가 되고 있다. 기존의 미세먼지 측정 방식은 베타선 흡수방식을 사용하여 실시간 측정 및 소형화가 어려운 단점이 존재한다. 본 논문에서는 광산란 방식을 사용하여 소형화 및 저비용의 센싱 장치를 개발하였다. 광산란 방식을 적용한 센서는 내부에 반도체 레이저 다이오드를 사용하여 구성하였으며, 전압레벨의 신호를 주파수레벨로 변환하여 기존 방식의 한계를 극복하고 미세먼지 입자 크기별 분리가 가능하도록 구현하였다. 또한 개발 시스템은 블루투스 통신으로 스마트폰과 연결하여 미세먼를 모니터링하고, 장치를 제어할 수 있다.