• Fibers and Polymers
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• 제6권2호
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• pp.127-130
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• 2005

Intrinsic UV reflection and fluorescence behaviors of polycarbonate, polyurethane and poly(ethylene terephthalate) films were investigated in order to characterize the interaction of water in these films. During water sorption process, UV reflection spectra of polycarbonate and polyurethane films showed little peak position changes. Fluorescence emission spectra of polycarbonate films showed red spectral shifts from 332 nm with water immersion time. This red-shifted peak could be due to phenyl-2-phenoxybenzoate, which is one of the major thermal degradation products in polycarbonate. Fluorescence peaks of polyurethane films appeared at two different positions and the ratio of these peak intensities increased with increasing immersion time. In the case of PET films, the UV reflection spectrum showed the peak intensity around 340 nm to change in response to water sorption. The fluorescence near 388 nm probably due to ground state dimer exhibited sensitivity with water sorption, when excited at 340 nm.

• 한국소음진동공학회논문집
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• 제13권6호
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• pp.438-444
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• 2003

A method using beamforming algorithm has been developed to measure oblique incidence reflection coefficients of sound absorption materials. MUSIC(multiple signal classification) method detects the angles of incidence and reflection. By separating the incident and reflected waves using beamforming method, the reflection coefficient is calculated. Spatial smoothing technique Is also used to reduce the coherence between the incident and reflected waves. Numerical and experiment results are performed to verify the accuracy of proposed method.

• 공학교육연구
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• 제19권5호
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• pp.65-71
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• 2016

The purpose of this paper is to research the effect of a reflection journal on self motivated-learners' study. The learners were divided into experimental and control groups, we carried out the pre- and post- surveys, and compared the groups' academic achievements. As a result, their persistent learning, self-efficacy, learning attitude somewhat improved and their academic achievement as well.

• 대한수학교육학회지:학교수학
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• 제10권2호
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• pp.199-222
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• 2008

본 연구는 수학교사의 전문성 관점에서 최근 활발히 대두되고 있는 수업 반성의 의미와 방법 등을 살펴보고, 수학과 수업 반성의 효율적 실현을 위한 분석의 준거를 고찰하고 제안해 보고자 시도되었다. 선행연구 분석 결과, 기존의 자기 평가적 체크 리스트의 결과와는 차별화 된 세부 항목들을 통합한 총체적이고 체계적인 반성적 분석 준거 개발이 요구되는 것으로 나타났다. 이에 선행연구의 고찰 결과를 토대로 수학과 수업 반성을 위한 분석 절차를 수업 전 중 후로 분류하고 이에 따르는 세부 영역에 적합한 반성적 질문들을 도출하여 수학과 수업 반성을 위한 준거를 제안하였다.

• 한국의학물리학회지:의학물리
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• 제32권4호
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• pp.179-184
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• 2021

This study aimed to determine the optimal thickness of the active layer and scan mode for a flexible radiochromic film (F-RCF) based on the active lithium salt of pentacosa-10,12-diynoic acid (LiPCDA). F-RCFs of 90, 120, 140, and 170-㎛ thickness were fabricated using LiPCDA. Several pieces of the F-RCFs were exposed to doses ranging from 0 to 3 Gy. Transmission and reflection modes were used to scan the irradiated F-RCFs. Their dose-response curves were obtained using a second-order polynomial equation. Their sensitivity was evaluated for both scanning modes, and the uniformity of the batch was also examined. For both the transmission and reflection modes, the sensitivity increased as the film thickness increased. For the reflection mode, the dose response increased dramatically under 1 Gy. The value of the net optical density varied rapidly as the thickness of the film increased. However, the dose-response curves showed a supralinear-curve relationship at doses greater than 2 Gy. The sensitivity of the reflection scan at doses greater than 2 Gy was higher than that of the reflection scan within 0-2 Gy. The sensitivity steadily decreased with increasing doses, and the sensitivity of the two modes was within 0.1 to 0.2 at 2 Gy and was saturated beyond that. For the transmission scan, the sensitivity was approximately 0.2 at 3 Gy. For the intra-batch test result, the maximum net optical density difference of the intra-batch was 5.5% at 2 Gy and 7.4% at 0.2 Gy in the transmission and reflection scans, respectively. In the low-dose range, film thickness of more than 120-㎛ was proper in the transmission mode. In contrast, the transmission mode showed a better result compared to the reflection mode. Therefore, the proper scan mode should be selected according to the dose range.

• Transactions on Electrical and Electronic Materials
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• 제10권4호
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• pp.111-115
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• 2009

We present a study on the reflection of optically controlled microwave pulses from non uniform plasma layers in semiconductors. The transient response of the microwave pulses in different plasma layers has been evaluated by means of the reflection function of dielectric microstrip lines. The lines were used with an open-ended termination containing an optically induced plasma region, which was illuminated by a light source. The reflection characteristics impedance resulting from the presence of plasma is evaluated by means of the equivalent transmission line model. We have analyzed the variation of the transient response in a 0.01 cm layer with a surface frequency in the region of 128 GHz. In the reflection the variation of the diffusion length $L_D$ is large compared with the absorption depth $1/{\alpha}_l$. The variation of the characteristic response of the plasma layer with differentially localized pulses has been evaluated analytically. The change of the reflection amplitude has been observed at depths of 0.1 cm, 0.01 cm and $0.1{\times}10^{-5}$ cm respectively.

• Progress in Superconductivity
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• 제2권1호
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• pp.43-46
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• 2000

We report on the tunneling spectroscopy of tunnel junctions using d-wave superconductor in relation to Andreev reflection. The zero bias conductance peak (ZBCP) which has maximum on [110] direction of ab-plane is observed on metal $Au/YBa_2Cu_3O_y$ tunnel junctions while it is suppressed on the ferromagnetic $Co/Au/YBa_2Cu_3O_y$ tunnel junctions. The effects of Andreev reflection on the differential conductance of each junction are dependent on the tunnel direction. For the $Co/Au/YBa_2Cu_3O_y$ junction, the suppression of Andreev reflection takes place by spin-polarized quasiparticles tunneling from a ferromagnetic material to a d-wave superconductor. By comparing these experimental results with recent theoretical works on Andreev reflection, the existence of Andreev bound state due to the d-wave symmetry of the pair potential is verified in high-$T_c$ superconductor.

• Geomechanics and Engineering
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• 제18권6호
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• pp.605-614
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• 2019

The present paper seeks to investigate propagation and reflection of waves at free surfaces of homogeneous, anisotropic and rotating micropolar fibre-reinforced medium with voids. It has been observed that, in particular when P-wave is incident on the free surface, there exist four coupled reflected plane waves traveling in the medium; quasi-longitudinal displacement (qLD) wave, quasi-transverse displacement (qTD) wave, quasi-transverse microrotational wave and a wave due to voids. Normal mode Analysis usually called harmonic solution method is adopted in concomitant with Snell's laws and appropriate boundary conditions in determination of solution to the micropolar fibre reinforced modelled problem. Amplitude ratios which correspond to reflected waves in vertical and horizontal components are presented analytically. Also, the Reflection Coefficients are presented using numerical simulated results in graphical form for a particular chosen material by the help of Mathematica software. We observed that the micropolar fibre-reinforced, voids and rotational parameters have various degrees of effects to the modulation, propagation and reflection of waves in the medium. The study would have impact to micropolar fibre-reinforecd rotational-acoustic machination fields and future works about behavior of seismic waves.

• 한국진공학회지
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• 제19권5호
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• pp.341-346
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• 2010

본 논문에서는 반응성 스퍼터링(Reactive Sputtering) 공정으로 $Si_xO_y$ 박막과 $Si_xN_y$ 박막을 4층 구조로 적층하고 400~700 [nm]의 가시광 영역에서 빛의 반사를 줄이기 위한 반사방지 코팅(Anti-Reflection Coating)으로의 응용 가능성을 조사하였다. 스퍼터링 타겟으로 6 [inch] 직경의 Si 단결정을 사용하였고, 반응성 스퍼터링 가스는 $Si_xO_y$ 박막 증착에서 Ar과 $O_2$를, $Si_xN_y$ 박막 증착에서는 Ar과 $N_2$를 사용하였으며, 스퍼터링 파워로는 DC pulse를 사용하였다. 1,900 [W] DC pulse power에서 Ar:$O_2$=70:13 [sccm]의 반응성 스퍼터링으로 2.3 [nm/sec]의 증착률과 1.50의 굴절률을 보이는 $Si_xO_y$ 박막을 제작하였고, Ar:$N_2$=70:15 [sccm]의 반응성 스퍼터링으로 1.8 [nm/sec]의 증착률과 1.94의 굴절률을 보이는 $Si_xN_y$ 박막을 제작하였다. 이 두 종류의 박막을 이용해서 시뮬레이션을 통해 4층 구조의 반사방지 코팅 구조를 설계한 후, 설계결과에 따라 각 박막의 두께를 순차적으로 변화시켜 증착하였다. 4층 구조 $Si_xO_y-Si_xN_y$의 반사도 측정 결과 550 [nm] 대역에서 1.7 [%]의 반사와 400 [nm]와 650 [nm] 영역에서 1 [%]의 반사를 보였으며, 가시광 영역에서 성공적인 "W" 형태의 반사방지 코팅 특성을 보였다.

• 한국과학교육학회지
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• 제37권4호
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• pp.553-564
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• 2017

이 연구에서는 초등 예비교사 8명을 대상으로 과학 수업 비디오에 기초한 개인적, 협동적 반성 활동이 예비교사의 전문적 시각을 어떻게 변화시키는지 그 과정을 탐색하였다. 본 연구의 데이터로는 예비교사와의 개별 면담 녹음 자료, 예비교사의 과학 수업 지도안, 과학수업 비디오, 연구자가 수업 참관 시 작성한 현장 노트, 연구 일지, 예비교사가 작성한 이벤트 맵 등이 활용되었다. 예비교사의 전문적 시각은 '선택적 주목'과 '교육적 추론'의 두 가지 범주로 분석하였다. 선택적 주목은 1) 수업 운영과 통제, 2) 교사의 지도, 3) 학생의 사고와 학습 4) 내용 지식 5) 평가의 다섯 측면으로 구분하였고 교육적 추론수준은 증거의 수, 증거의 영역, 유형에 따라 6 수준으로 구분하였다. 연구 결과 수업 비디오에 기초한 개인적 반성은 '수업 운영과 통제'에 대한 주목을 줄이고 '교사의 지도'에 대해 좀 더 주목하도록 하는 효과가 있었다. '학생의 사고나 학습'에 대한 주목을 증진시키기 위해서는 수업 비디오에 대한 개인적 반성 활동만으로는 그 효과가 충분하지 않고 협동적 반성 활동이 필요한 것으로 나타났다. 교육적 추론수준은 개인적 반성과 협동적 반성을 거치며 점진적으로 증가하였다. 학생의 사고나 학습에 대한 주장에서 하나의 증거보다는 여러 증거를 사용하게 되었고 증거의 영역과 유형도 좀 더 다양해졌다. 그러나 증거 형태는 직접적인 관찰에 의한 것이 대부분이었고, 교육이론에 기초한 증거는 거의 나타나지 않았다. 교사교육 과정에서 수업 비디오의 활용에 대한 시사점을 논의하였다.