• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.231-231
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• 2008

최근 인터넷의 보급과 함께 고화질 및 양방향 TV, VOD 방송, 화상 전화 등의 멀티미디어 시대가 열리면서 초고속 통신 시스템에 대한 관심이 증가되고 있다. 특히 화상이나 동영상 같은 대량의 정보가 졸은 품질 및 빠른 속도로 전달될 수 있는 통신 시스템의 필요성이 대두됨에 따라 가장 효율적인 고속 전송 수단으로 광통신이 이용되고 있으며 그에 따른 광통신 능 수동 소자 개발에 관한 연구도 활발히 이루어지고 있다. 이러한 광통신 소자 중 원하는 빛을 선택적으로 투과하고 반사할 수 있는 flat-band pass(FP) filter의 역할이 중요한 부분을 차지하고 있다. 본 논문에서는 IR 영역에서 투과성이 우수한 칼코게나이드 물질을 이용해 l 차원 광자결정구조의 FP-filter를 설계, 제작하고 그에 대한 특성을 평가하였다. 시료는 5N의 순도를 갖는 As, Se, Te 물질을 준비하고 $As_xSe_yTe_z$를 조성비에 맞추어서 석영관에 진공 봉입한 후 용융 혼합하여 $As_{33}Se_{67}$과 $As_{40}Se_{25}Te_{35}$ 조성의 두 가지 비정질 벌크를 제작하였다. 제작된 시료의 굴절률은 ellipsometer을 사용하여 측정하였고, 본 연구진이 자체 개발한 계산툴에 따라 다중층막 구조를 설계하였다. 열 증착법을 이용하여 설계된 구조에 맞게 기판에 올리는 방법으로 1차원 광자결정 구조의 다중층막 샘플을 제작하였고 UV-Vis-IR Spectroscopy를 사용하여 반사도와 투과도를 측정하였다. 광통신용 L/C 밴드 주파수 범위에서 투과성이 우수한 칼코게나이드 박막의 1차원 광자결정 구조는 FP-filter등의 소자로써 유용하게 사용될 수 있다.

• Korean Journal of Optics and Photonics
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• v.20 no.5
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• pp.266-271
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• 2009

We designed a thermo-optic switch based on a directional coupler with not only a high extinction ratio but also significantly low power consumption. The switch operates by using the thermo-optic effect of the polymer which the refractive index changes by heating the electrode. If the electrode is not powered (OFF), the input light will be coupled completely to the other waveguide. When the electrode is powered at a certain level (ON), input light launched into the input waveguide will remain in that waveguide due to the lower index adjusted in the other waveguide. The switch based on the directional coupler was designed using the generalized extinction ratio curve and the lateral shift of the input waveguide. The coupling length is 1,610 ${\mu}m$ and the extinction ratios are -28 and -30 dB for ON and OFF states, respectively. The electrode structures were optimized by thermal analysis. The transported heat into the waveguide is increased, as the electrode width (w) is increased and the center distance between the electrode and the waveguide (d) is decreased. Also, because the heat generated in the electrode affects the other waveguide, the temperature difference between two waveguides is varied as the given w and d. There are specific conditions which have the maximum of the temperature difference. That of the temperature difference is increased as the width and the temperature of the electrode are increased. Especially, when the switch is designed using the condition with the maximum of the temperature difference for switching, the temperature of the electrode can be decreased. We expect this condition will be the novel method for the reduction of the power consumption in a thermo-optic switch.

• Geophysics and Geophysical Exploration
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• v.13 no.1
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• pp.24-30
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• 2010

This study utilises repeated numerical tests to understand the effects of variable near-surface conditions on time-lapse seismic surveys. The numerical tests were aimed at reproducing the significant scattering observed in field experiments conducted at the Naylor site in the Otway Basin for the purpose of $CO_2$ sequestration. In particular, the variation of elastic properties of both the top soil and the deeper rugose clay/limestone interface as a function of varying water saturation were investigated. Such tests simulate the measurements conducted in dry and wet seasons and to evaluate the contribution of these seasonal variations to seismic measurements in terms of non-repeatability. Full elastic pre-stack modelling experiments were carried out to quantify these effects and evaluate their individual contributions. The results show that the relatively simple scattering effects of the corrugated near-surface clay/limestone interface can have a profound effect on time-lapse surveys. The experiments also show that the changes in top soil saturation could potentially affect seismic signature even more than the corrugated deeper surface. Overall agreement between numerically predicted and in situ measured normalised root-mean-square (NRMS) differences between repeated (time-lapse) 2D seismic surveys warrant further investigation. Future field studies will include in situ measurements of the elastic properties of the weathered zone through the use of 'micro Vertical Seismic Profiling (VSP)' arrays and very dense refraction surveys. The results of this work may impact on other areas not associated with $CO_2$ sequestration, such as imaging oil production over areas where producing fields suffer from a karstic topography, such as in the Middle East and Australia.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.1
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• pp.888-894
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• 2015

Inorganic composite particles have excellent physical and chemical characteristics and have been applied in various industries. Recently, many studies have examined the optical properties, such as light scattering, refraction, transmission characteristics, by coating organic-inorganic materials on a substrate, such as mica. Mica is widely applied as a pigment, plastics, painted products, and ceramics because of its high chemical stability, durability and non-toxicity. Magnesium oxide has a range of properties, such as high light transmittance, corrosion resistance and non-toxicity, and it is used as an optical material and polymer additives. To use the optical properties of mica and magnesium oxide, mica was coated with magnesium hydroxide by a dissolution and recrystallization process. In this study, the optimal conditions for the haze value of the particles were found by adjusting the amount of precursors and pH. Magnesium hydroxide layers were formed on the surfaces of mica and converted to MgO after calcination at $400^{\circ}C$ for 4 h. The results showed that the value of MgO-coated mica haze can be controlled easily by the amount of the magnesium hydroxide and pH. The optical properties of the inorganic composite powder were analyzed using a hazemeter and the highest haze value was 85.92 % at pH 9. The physicochemical properties of the synthesized composite was analyzed by SEM, XRD, EDS, and PSA.

• Proceedings of the Korean Society of Postharvest Science and Technology of Agricultural Products Conference
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• 2003.04a
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• pp.120-121
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• 2003

과수원에서 재배되는 배는 과수원 내의 위치, 시비, 토양 등의 요인에 따라 다양한 품질을 나타내며, 당도와 숙도의 편차가 크기 때문에 과수농가에서는 경험에 의존하여 적정 숙기로 판단되는 배를 수확하고 있다. 그러나 과학적이지 못한 사실에 기초한 수확 관행은 시장유통되는 배에 대하여 소비자들의 신뢰성 저하를 초래하게 되고 소비 감소와 더불어 농가 소득 감소로 이어지게 된다. 최근, 전국의 청과물 산지유통센터에는 근적외선을 이용하여 과일 내부의 당도, 산도, 결함 등을 실시간으로 판정할 수 있는 비파괴 선별기가 보급되고 있으나 이는 수확이후의 선별.규격화 유통을 위한 것이다. 본 연구에서는 이와는 달리, 수확 이전, 즉 재배 단계에서 배의 당도와 숙도를 판정하여 수확적기를 판단할 수 있도록 나무에 매달린 배에 대하여 가시광선과 근적외선 반사스펙트럼을 측정할 수 있고 이를 이용하여 당도와 숙도가 판정가능한 휴대형 센서를 개발하였으며, 개발된 시작기를 이용하여 당도판정의 가능성을 시험하였다. 휴대형 당도판정센서는 광원과 광섬유프로브, 광검출부, 당도판정부, 전원공급부로 구성된다. 광원은 할로겐램프(6V)를 이용하였고, 광섬유프로브는 동심원 형태로서 외부의 광섬유를 통하여 광원에서 시료로 빛이 조사되게 하고, 내부의 광섬유를 통하여 광검출기로 확산반사되는 광이 전달될 수 있도록 하였다. 전원공급부는 휴대와 충전이 가능한 배터리(12V, 2AH)와 이 배터리에서 정전류가 광원으로 보내어 질 수 있도록 제작된 회로로 구성하였다. 당도 판정을 위하여 518nm에서 1046nm의 파장대역에서의 반사스펙트럼을 이용하였고, 레퍼런스로써 백색 테플론 구를 제작하여 사용하였다. 수원 농산물 도매시장에서 판매중인 2002년산 신고 배를 구매하고, 시작기를 이용하여 총 113개의 배에 대한 반사스펙트럼을 측정하였다. 다음으로 굴절당도계로 당도값을 측정하고 반사스펙트림을 이용하여 당도값을 예측하기 위한 부분최소제곱회귀(PLSR)모델을 개발하였다. 여기서 모델의 정밀도는 교차검정법을 이용하여 검증하였다. 시료 표면과 광섬유프로브와의 접촉상태 불균일, 광원의 시간에 따른 경시 변화, 과일 형상의 차이 등에 의하여 측정된 반사스펙트럼은 상당한 변이를 나타내었으므로 이를 보정하기 위하여 반사 스펙트럼은 다분산보정처리하여 이용하였다. 당도 예측용 PLSR모델 개발의 결과, 모델의 결정계수($R^2$)는 0.67, SEC는 $\pm$0.4brix.로 나타났으며, 교차검정에 의한 미지 시료의 예측에서 총 113개의 미지 시료에 대한 결정계수는 0.57, SEP는 $\pm$ 0.46brix.로 나타났으며, 이는 현장에서 충분히 활용가능할 것으로 판단되었다. 금후, 전체 시스템의 부피와 중량을 줄이고 각 부분품들의 전력소모의 최소화할 수 있도록 개선할 계획이다.

• Journal of The Korean Association For Science Education
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• v.24 no.6
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• pp.1189-1205
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• 2004

The purpose of this study is to understand the types of teacher and student's concept on ray-tracing and spectrum in middle school. This study suggest key-concepts that is most important to "Light" unit in the seven grades: the ray-tracing and the spectrum. We examined the types of teacher and student's concept. We selected 10 teacher and 328 students who had learned by 10 teachers in Seoul and Gyeonggi. The problems were composed with the question item regarding all ray-tracing or the spectrum. From the analysis, it was found that the types of teacher and student's concept on ray-tracing and spectrum is different. The most of teacher and student didn't understand the basic principle of image formation. In case of context about formation of image by reflection and refraction, because they don't know ray-tracing, they do not try to find the position of the image by drawing two rays. Most of them used one ray comes from the one position of the object and indicated the position of image by memorized position. Also almost there was not a case which uses a ray tracing accurately. In the case of understanding color, they didn't understand the concept of color(or spectrum) and teachers represented to students the color phenomena without explanation of principles. In the result teachers and students would learn color science by rote.

• Journal of the Korean Vacuum Society
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• v.19 no.2
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• pp.81-90
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• 2010

We introduce a novel and versatile approach for preparing self-assembled nanoporous multilayered films with antireflective properties. Protonated polystyrene-block-poly (4-vinylpyrine) (PS-b-P4VP) and anionic polystyrene-block-poly (acrylic acid) (PS-b-PAA) block copolymer micelles (BCM) were used as building blocks for the layer-by-layer assembly of BCM multilayer films. BCM film growth is governed by electrostatic and hydrogen-bonding interactions between the oppositely BCMs. Both film porosity and film thickness are dependent upon the charge density of the micelles, with the porosity of the film controlled by the solution pH and the molecular weight (Mw) of the constituents. PS7K-b-P4VP28K/PS2K-b-PAA8K films prepared at pH 4 (for PS7K-b-P4VP28K) and pH 6 (for PS2K-b-PAA8K) are highly nanoporous and antireflective. In contrast, PS7K-b-P4VP28K/PS2K-b-PAA8K films assembled at pH 4/4 show a relatively dense surface morphology due to the decreased charge density of PS2K-b-PAA8K. Films formed from BCMs with increased PS block and decreased hydrophilic block (P4VP or PAA) size (e.g., PS36K-b-P4VP12K/PS16K-b-PAA4K at pH 4/4) were also nanoporous. Furthermore, we demonstrate that the nanostructured electrochemical sensors based on patterning methods show the electrochemical activities. Anionic poly(styrene sulfonate) (PSS) layers were selectively and uniformly deposited onto the catalase (CAT)-coated surface using the micro-contact printing method. The pH-induced charge reversal of catalase can provide the selective deposition of consecutive PE multilayers onto patterned PSS layers by causing the electrostatic repulsion between next PE layer and catalase. Based on this patterning method, the hybrid patterned multilayers composed of platinum nanoparticles (PtNP) and catalase were prepared and then their electrochemical properties were investigated from sensing $H_2O_2$ and NO gas. This study was based on the papers reported by our group. (J. Am. Chem. Soc. 128, 9935 (2006); Adv. Mater. 19, 4364 (2007); Electro. Mater. Lett. 3, 163 (2007)).

• Journal of the Korean Society of Radiology
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• v.13 no.6
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• pp.825-830
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• 2019

A detector module measuring a depth of interaction was developed using silicon photomultiplier (SiPM) and two layers of scintillation crystal array treated with multiple reflectors. When reconstructing an image based on a signal obtained by using different types of reflector of each layer, the interaction positions of scintillation pixels and gamma rays could be tracked by utilizing the feature that all scintillation pixels were recorded at different positions. The bottom layer uses a specular reflector, and the top layer uses a diffuse reflector to differently process the size of the signal obtained from the SiPM. The optical grease was used to recude the sharp refractive index change between the layers of scintillator and the SiPM. The signals obtained from the 16 SiPMs were reduced to four signals using the Anger equations, and the images were reconstructed using them. All the scintillation pixels composed of the two layers appeared in the reconstructed image, which distinguished the layer where the scintillation pixels and gamma rays interacted. If the detectors, which measure the interaction depth of two layers using different reflectors, will be applied to preclinical positron emission tomography, the degradation of spatial resolution appearing outside the field of interest could be solved.

• Journal of The Korean Ophthalmological Society
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• v.58 no.8
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• pp.960-967
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• 2017

Purpose: To compare the macular choroidal thickness in patients with thyroid-associated ophthalmopathy (TAO) with those with normal tension glaucoma (NTG). Methods: A total of 70 normal eyes, 74 eyes with TAO and 60 eyes with NTG were enrolled in this study. All patients underwent spectral-domain optical coherence tomography (SD-OCT) (Cirrus HD-OCT, Carl Zeiss Meditec Inc., Dublin, CA, USA). Macular choroidal thickness was assessed using enhanced depth imaging. The average macular choroidal thickness was defined as the average value of three measurements: at the fovea and at the points located 1.5 mm in the nasal and temporal directions from the fovea. Generalized estimating equations were used to uncover factors affecting the average macular choroidal thickness. Results: The average, superior and inferior quadrant retinal nerve fiber layer thicknesses were significantly thinner in the NTG group compared with the TAO and control groups (p < 0.001). The average macular choroidal thickness of the TAO group, NTG group and controls was $281.01{\pm}60.06{\mu}m$, $241.66{\pm}55.00{\mu}m$ and $252.07{\pm}55.05{\mu}m$, respectively, which were significantly different (p = 0.013). The subfoveal, nasal and temporal side choroidal thicknesses were significantly thinner in the NTG group compared with the TAO group (p = 0.014, 0.012 and 0.034, respectively). Subjects with TAO were associated with a thicker average macular choroidal thickness compared with the NTG group after adjusting for age, sex, spherical equivalent and intraocular pressure (${\beta}=32.61$, p = 0.017). Conclusions: Macular choroidal thickness was significantly thicker in patients with TAO compared with those with NTG. Further evaluation is required to determine if a thick choroid in subjects with TAO has any role in glaucomatous optic neuropathy.

• Journal of the Mineralogical Society of Korea
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• v.16 no.4
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• pp.333-339
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• 2003

A new mineral, Zn analogue of rancieite (Chimooite), has been discovered at the Dongnam mine, Korea. It occurs as compact subparallel fine­grained flaky or acicular aggregates in the massive manganese oxide ores which were formed by supergene oxidation of rhodochrosite­sulfide ores in the hydrothermal veins trending NS­N25E and cutting the Pungchon limestone of the Cambrian age. The flakes of chimooite are 0.2 mm for the largest one, but usually less than 0.05 mm. The acicular crystals are elongated parallel to and flattened on (001). This mineral shows gradation to rancieite constituting its marginal part, thus both minerals are found in one and the same flake. Color is bluish black, with dull luster and brown streak in globular or massive aggregates. Cleavage is perfect in one direction. The hardness ranges from 2.5 to 4. Under reflected light it is anisotropic and bireflectant. It shows reddish brown internal reflection. Chemical analyses of different parts of both minerals suggest that rancieite and chimooite constitute a continuous solid solution series by cationic substitution. The empirical chemical formula for chimooite has been calculated following the general formula, $R_2_{x}$ M $n^{4+}$$_{9­x}$ $O_{18}$ $.$n$H_2O$ for the 7 $\AA$ phyllomanganate minerals, where x varies from 0.81 to 1.28 in so far studied samples, thus averaging to 1.0. Therefore, the formula of Zn­rancieite is close to the well­known strochiometric formula $_Mn_4^{4+}$ $O_{9}$ $.$4$H_2O$. The mineral has the formula (Z $n_{0.78}$N $a_{0.15}$C $a_{0.08}$M $g_{0.01}$ $K_{0.01}$)(M $n^{4+}$$_{3.98}$F $e^{3+}$$_{0.02}$)$_{4.00}$ $O_{9}$ $.$3.85$H_2O$, thus the ideal formula is (Zn,Ca)M $n^{4+}$$_4$ $O_{9}$ $.$3.85$H_2O$. The mineral has a hexagonal unit ceil with a=2.840 $\AA$ c=7.486 $\AA$ and a : c = 1 : 2.636. The DTA curve shows endothermic peaks at 65, 180, 690 and 102$0^{\circ}C$. The IR absorption spectrum shows absorption bands at 445, 500, 1630 and 3400 c $m^{1}$. The mineral name Chimooite has been named in honour of late Prof, Chi Moo Son of Seoul National University.ity.versity.ity.y.