• 천문학회보
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• 제43권1호
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• pp.44.1-44.1
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• 2018

We present a spectroscopic study of the Galactic supernova remnant (SNR) Cygnus Loop using the fifth Data Release (DR5) of LAMOST. The LAMOST (Large Sky Area Multi-Object Fiber Spectroscopic Telescope) features both a large field-of-view (about 20 deg2) and a large aperture (~4 m in diameter), which allow us to obtain 4000 spectra simultaneously. Its wavelength coverage ranges from ${\sim}3700{\AA}$ to $9000{\AA}$ with a spectral resolution of $R{\approx}1800$. The Cygnus Loop is a prototype of middle-aged SNRs, which has advantages of being bright, large in angular size (${\sim}3.8^{\circ}{\times}3^{\circ}$), and relatively unobscured by dust. Along the line of sight of the Cygnus Loop, 2747 LAMOST DR5 spectra are found in total, which are spatially distributed over the entire remnant. Among them, 778 spectra are selected based on the presence of emission lines (i.e., [O III]${\lambda}5007$, Ha, and [S II]${\lambda}{\lambda}$ 6717, 6731) for further visual inspection. About half of them (336 spectra) show clear spectral features to confirm their association with the remnant, 370 spectra show stellar features only, and 72 spectra are ambiguous and need further investigation. For those associated with the remnant, we identify emission lines and measure their intensities. Spectral properties considerably vary within the remnant, and we compare them with theoretical models to derive physical properties of the SNR such as electron density and temperature, and shock velocity. While some line ratios are in good agreement with model prediction, others cannot be explained by simple shock models with a range of shock velocities. We discuss these discrepancies between model predictions and the observations and finally highlight the powerfulness of the LAMOST data to investigate spatial variations of physical properties of the Cygnus Loop.

• 한국항공우주학회지
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• 제42권6호
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• pp.515-521
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• 2014

본 논문에서는 Ray-tracing 기법을 이용하여 그레고리안 안테나의 부반사판을 축변환 후 회전하여 급전혼으로 회귀되는 전파를 없애 이득 및 정재파비를 개선 시키고 부반사판의 크기와 전체적인 부피를 줄여 효율적인 구조를 갖는 축변위그레고리안 안테나를 설계하였다. 설계된 급전혼의 방사패턴을 이용하여 급전혼-부반사판-주반사판으로 전달되는 전파의 경로를 추적하여 주반사판 개구면에서의 전계분포를 구하고 이로부터 원거리 복사패턴을 계산하는 프로그램을 작성하여 안테나 성능을 최적화 하였다. 설계된 안테나는 CST와 제작 측정을 통해 계산결과와 비교하여 이득, 빔폭, 방사패턴, 부엽준위, 반사손실이 계산 결과와 매우 유사함을 확인함으로써 Ray-tracing기법에 대한 타당성을 검증하였다.

• 한국수자원학회논문집
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• 제34권5호
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• pp.439-448
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• 2001

본 연구에서는 단일절리에서 2상유체 동시거동을 해석하기 위해서 2차원 유한차분 수치모형을 개발하였다. 개발된 모형은 압력에 따른 점성의 변화가 포화도에 따른 상대투과계수의 변화를 절리간극의 크기별로 고려할 수 있다. 수치기법으로는 IMPES해법을 적용하여 물과 가스의 압력변화량과 포화도를 차례로 구하였다. 개발된 수치 모형에 이용할 상대투과계수의 특성식 도출을 위해서 일곱가지 경우의 평판모형실험을 실시하였다. 실험으로부터 도출된 상대투과계수 특성곡선은 기존의 경험식으로는 표현되기 어려웠으며, 따라서 새로운 경험식으로 로지스틱 방정식을 제시하였다. 이 방정식은 간극의 크기가 포함된 매개변수를 사용하였기 때문에 임의의 절리 간극크기의 적용이 가능한 형태이다.

• Journal of Species Research
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• 제4권2호
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• pp.159-168
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• 2015

Although airborne pollen is invisible to the eye, it has been known as a major source to respiratory allergic reactions. For this reason, airborne pollen is monitoring in many countries to predict pollen concentration based on locality and season. However, the morphological characteristics of airborne pollen and their potential tendency as an allergen are still obscure. In the present study, we selected 52 airborne pollen samples based on previously reported data and investigated their detail pollen characteristics using LM and SEM. Major airborne pollen in Korea has sorted in 19 families (most angiosperms except four gymnosperm families), and all pollen grains are small to medium in size ($P=17.34-49.86{\mu}m$) apart from the bisaccate pollen grains of Pinaceae ($P=46.49-106.20{\mu}m$). The aperture number and shape vary from sulcate to polyporate. While the inaperture pollen has found only in gymnosperm (Cupressaceae and Taxaceae), triporate or polyporate is common pollen type in angiosperm. The sexine ornamentations could divide into several types, but the most sculpturing types are inconspicuous like psilate, rugulate and granulate. Reticulate pollen grains as a semitectum have occurred the species of genera Platanus and Fraxinus only. To estimate the possible relationships between pollen features and allergen, the results are discussed in botanical context.

• Korean Chemical Engineering Research
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• 제47권3호
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• pp.355-361
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• 2009

선택적 고체순환을 위한 2탑 유동층 공정에서 고체분리기에 의한 고체분리속도에 미치는 조업변수들의 영향을 측정 및 고찰하였다. 본 연구에서 개발한 고체분리기를 이용하여 굵은입자(212~300 또는 $425{\sim}600{\mu}m$)와 고운입자($63{\sim}106{\mu}m$)의 분리가 가능하였으며 고체분리속도는 66~987 g/min의 범위를 나타내었다. 고체분리속도는 고체분사노즐의 유속, 고체층 높이, 고체분사노즐의 직경, 고운입자와 굵은입자의 입자크기 차이, 고체분리기 금속망 간극크기 및 혼합입자 중 고운입자의 무게분율이 증가함에 따라 증가하였으며 유동화 속도의 영향은 크지 않았다.

• 지질공학
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• 제17권4호
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• pp.623-631
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• 2007

경기도 하남시 풍산동 소재 시험시추공에서 획득된 SPS 속도검층자료를 이용하여 이 지역에 분포하는 호상편마암의 동적물성치를 추정하였다. 연구방법은 전처리과정과 속도분석, 감쇄지수와 관련된 Q factor를 도출하였고 단열정보와 탄성파 속도관계식을 산출하였다. 신선한 암반의 Vp는 5,559m/s, Vs는 3,063m/s로 나타났으며 포아슨비는 0.28로 해석되었다. 이를 이용하여 동적물성치를 구하였고 초음파 텔레뷰어로 산출한 단열정보를 이용하여 단열에 따른 초동지연, 진폭변화비, 속도와의 상관성을 파악하였다. 측정된 검층공은 미세단열이 대부분이며 이러한 경암내 미세단열 지역에서는 단열틈 크기와 단열빈도가 탄성파 속도의 변수로 작용하는 것으로 나타난다.

• 정보저장시스템학회논문집
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• 제1권2호
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• pp.115-120
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• 2005

As a popularity of a portable digital device such as a cellular phone, a digital camera and a MP3 player is spreading, the demand of the mobile storage device increases rapidly. A bluray technology using 405nm laser diode and objective lens having high NA(Numerical Aperture), 0.85, satisfies a miniaturization and a high capacity which are the requirements of the portable device. To develop SFFOP(small form factor optical pickup), it is prerequisite to minimize the number of optical components and establish evaluation and assembly method of micro optical pickup system as well as mass production method of micro optical component. To minimize optical elements of optical pickup, there have been many researches to use P-HOE(Polarized Holographic Optical Element) due to its extremely small size and versatile function. However, P-HOE is handled and assembled very accurately in SFFOP. In this paper, static error signal detection method is developed for an alignment of P-HOE in SFFOP. Using developed static error signal detection method, P-HOE can be aligned very accurately with real time result of static error signals of pickup such as FES(focusing error signal) and TES(Tracking Error Signal). The developed static error signal detection method is verified by the evaluation of commercialized DVD Pickup. And finally. developed static error signal detection method is applied for the assembly of P-HOE in SFFOP system satisfies specification of BD(Blu-ray Disk).

• Journal of the Optical Society of Korea
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• 제9권1호
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• pp.16-21
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• 2005

Using a cantilever type nanoprobe having a 100㎚m aperture at the apex of the pyramidal tip of a near-field scanning optical microscope (NSOM), nanopatterning of polymer films are conducted. Two different types of polymer, namely a positive photoresist (DPR-i5500) and an azopolymer (Poly disperse orange-3), spincoated on a silicon wafer are used as the substrate. A He-Cd laser with a wavelength of 442㎚ is employed as the illumination source. The optical near-field produced at the tip of the nanoprobe induces a photochemical reaction on the irradiated region, leading to the fabrication of nanostructures below the diffraction limit of the laser light. By controlling the process parameters properly, nanopatterns as small as 100㎚ are produced on both the photoresist and azopolymer samples. The shape and size variations of the nanopatterns are examined with respect to the key process parameters such as laser beam power, irradiation time or scanning speed of the probe, operation modes of the NSOM (DC and AC modes), etc. The characteristic features during the fabrication of ordered structures such as dot or line arrays using NSOM lithography are investigated. Not only the direct writing of nano array structures on the polymer films but also the fabrication of NSOM-written patterns on the silicon substrate were investigated by introducing a passivation layer over the silicon surface. Possible application of thereby developed NSOM lithography technology to the fabrication of data storage is discussed.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2019년도 학술발표회
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• pp.152-152
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• 2019

This study demonstrates a novel approach of remotely sensed estimates of stream flow at fifteen hydrological station in the Han River Basin, Korea. Multi-temporal data of the European Space Agency's Sentinel-1 SAR satellite from 19 January, 2015 to 25 August, 2018 is used to develop and validate the flow estimation model for each station. The flow estimation model is based on a power law relationship established between the remotely sensed surface area of water at a selected reach of the stream and the observed discharge. The satellite images were pre-processed for thermal noise, radiometric, speckle and terrain correction. The difference in SAR image brightness caused by the differences in SAR satellite look angle and atmospheric condition are corrected using the histogram matching technique. Selective area filtering is applied to identify the extent of the selected stream reach where the change in water surface area is highly sensitive to the change in stream discharge. Following this, an iterative procedure called the Optimum Threshold Classification Algorithm (OTC) is applied to the multi-temporal selective areas to extract a series of water surface areas. It is observed that the extracted water surface area and the stream discharge are related by the power law equation. A strong correlation coefficient ranging from 0.68 to 0.98 (mean=0.89) was observed for thirteen hydrological stations, while at two stations the relationship was highly affected by the hydraulic structures such as dam. It is further identified that the availability of remotely sensed data for a range of discharge conditions and the geometric properties of the selected stream reach such as the stream width and side slope influence the accuracy of the flow estimation model.

• 한국광학회지
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• 제32권4호
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• pp.153-162
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• 2021

본 논문에서는 적외선 탐색 및 추적 기능을 수행하는 광각 주사 광학계와 표적의 전자광학 추적 기능을 수행하는 협/중시계 광학계의 기능이 통합된 가변 F/수 삼중 배율 적외선 광학계를 설계하였다. 기존 광각 주사 광학계를 기반으로 무한 초점 광학계를 전단부에 설계하여 협/중시계 기능을 수행할 수 있는 광학계를 구현하였다. 시스템 성능 분석을 통해 성능 목표를 설정하고, 이를 바탕으로 광학계 설계를 위한 설계 사양을 도출하였으며, F/수가 다른 광학계를 추가하기 위해 조리개 크기를 줄여주는 웜 스톱을 적용하였고, 설계된 광학계에 적합하도록 세부 형상을 설계하였다. 설계 완료된 협/중시계 광학계 설계 결과를 분석하여 MTF (modulation transfer function)와 같은 목표 성능을 만족하는 것을 확인하였으며 운용성을 고려하여 비열화와 표적 거리에 따른 초점 렌즈군의 이동량을 분석하였고, 이를 통해 광역 탐색 및 추적 기능과 정밀 추적 및 3차원 정보 획득 기능이 통합된 단일 광학 시스템의 구현이 가능함을 확인하였다.