• Journal of the Korean Physical Society
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• 제73권11호
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• pp.1729-1734
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• 2018

Organic-inorganic halide perovskite single crystals undergo phase transition of being cubic, tetragonal, or orthorhombic depending on the temperature. We investigated the $CH_3NH_3PbBr_{3-x}I_x$ single crystals grown by the inverse temperature crystallization method with temperature-dependent UV-Vis absorption and photoluminescence. From the temperature-dependent absorption measurement, the optical band gap is extracted by derivation of absorption spectrum fitting and Tauc plot. In our results, $CH_3NH_3PbBr_{3-x}I_x$ single crystals show that an abrupt change in optical band gap, PL peak position and intensity appears around 120 K - 170 K regions, indicating the phase transition temperature.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제16권3호
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• pp.163-172
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• 2016

Electric load forecasting is essential for effective power system planning and operation. Complex and nonlinear relationships exist between the electric loads and their exogenous factors. In addition, time-series load data has non-stationary characteristics, such as trend, seasonality and anomalous day effects, making it difficult to predict the future loads. This paper proposes a locally-weighted polynomial neural network (LWPNN), which is a combination of a polynomial neural network (PNN) and locally-weighted regression (LWR) for daily shortterm peak load forecasting. Model over-fitting problems can be prevented effectively because PNN has an automatic structure identification mechanism for nonlinear system modeling. LWR applied to optimize the regression coefficients of LWPNN only uses the locally-weighted learning data points located in the neighborhood of the current query point instead of using all data points. LWPNN is very effective and suitable for predicting an electric load series with nonlinear and non-stationary characteristics. To confirm the effectiveness, the proposed LWPNN, standard PNN, support vector regression and artificial neural network are applied to a real world daily peak load dataset in Korea. The proposed LWPNN shows significantly good prediction accuracy compared to the other methods.

• 반도체디스플레이기술학회지
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• 제18권1호
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• pp.48-52
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• 2019

The blue emitting fluorescence of $SrAl_{12}O_{19}:Ce_{0.09}{^{3+}}$, $Eu_{0.01}{^{2+}}$ phosphor includes two kinds of independent energy transfer mechanism through electric multipole interactions between donor and acceptor ions. The first energy transfer takes place between the $Ce^{3+}$ ion and the $Eu^{2+}$ion which strongly depends on the concentration $Eu^{2+}$ions. The second energy transfer occurs between the $Ce^{3+}$ ion and the $O_{Me}-Ce^{3+}$ complexes. Both energy transfer mechanisms of blue emitting peak at 410 nm were investigated by fitting of Gaussian functions. The result shows that the peak at 410 nm is two overlapping emissions originated by $Eu^{2+}$ions and $O_{Me}-Ce^{3+}$ complexes and as time elapses $Eu^{2+}$peak remains whereas $O_{Me}-Ce^{3+}$ related peak disappears.

• Journal of Radiation Protection and Research
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• 제9권1호
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• pp.33-42
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• 1984

핵분열(核分裂) 및 방사화생성물(放射化生成)物)에서 방출(放出)하는 여러가지 감마선들은 핵연료(核燃料)를 파괴(破壞)하지 않고도 추출(抽出)할 수 있는 많은 정보(情報)를 포함(包含)한다. 그러나 반도체(半導體) 검출기(檢出器)에서 얻은 복잡한 스펙트럼에서 이러한 정보를 추출(抽出)하기가 용역(容易)하지 않기 때문에 전산(電算)코드의 사용(使用)이 필요(必要)하게 된다. 본(本) 연구(硏究)에서는 그동안 국제적(國際的)으로 널리 보급(普及)되어 사용(使用)되는 감마선 분석(分析) 프로그램들의 장점(長點)을 취하여, 감마선은 물론 X-선(線)의 스펙트럼도 피팅 (fitting)하여 피이크의 중심과 면적을 정확(正確)히 계산(計算)할 수 있는 전산코드 CAERI를 개발(開發)하였다. CAERI는 FORTRAN으로 쓰여있고, 특히 고유복사선폭(固有輻射線幅)(natural line width) 을 무시할 수 없는 X-선(線)의 피이크 표현함수(表現函數)인 Voigt 함수(函數)에 대해서는, 다른 X-선(線) 분석(分析) 프로그램들이 사용(使用)한 간단한 근사식(近似式) 대신에, 더욱 정확(正確)한 무한급수근사식(無限級數近似式)을 사용하였다. 특히 CAERI 는 U이나 Pu과 같은 중원소(重元素)의 핵종분석시(核種分析時)에 직면(直面)하는 감마선과 U이나 Pu의 X-선(線)이 임의(任意)로 간섭(干涉)하며 공존(共存)하는 복잡한 스펙트럼까지도 취급(取扱)할 수 있다. $^{177m}Lu$감마선과 $^{235}U\;U_{\alpha}$X-선(線)의 시험(試驗)스펙트럼을 피팅하여, 다른 프로그램들의 피팅결과와 비교했을 때 좋은 일치(一致)를 보았다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.1256_1257
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• 2009

We have grown, for the first time to our knowledge, N-doped ZnO thin films on sapphire substrate by employing novel dielectric barrier discharge in pulsed laser deposition (DBD-PLD). DBD guarantees an effective way for massive in-situ generation of N-plasma under the conventional PLD process condition. Low-temperature photoluminescence spectra of the N-doped ZnO film provided near band-edge emission after thermal annealing process. The emission peak was resolved by Gaussian fitting to find a dominant acceptor-bound exciton peak ($A^0X$) that indicates the successful p-type doping of ZnO with N.

• Structural Engineering and Mechanics
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• 제21권1호
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• pp.83-100
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• 2005

This paper presents results from a study to extend a performance-based shearwall selection procedure to take into account the contributions of nonstructural finish materials (such as stucco and gypsum wallboard), construction quality issues, and their effects on the displacement performance of engineered wood shearwalls subject to seismic loading. Shearwall performance is evaluated in terms of peak displacements under seismic loading (characterized by a suite of ordinary ground motion records) considering different combinations of performance levels (drift limits) and seismic hazard. Shearwalls are analyzed using nonlinear dynamic time-history analysis with global assembly hysteretic parameters determined by fitting to actual shearwall test data. Peak displacement distributions, determined from sets of analyses using each of the ground motion records taken to characterize the seismic hazard, are postprocessed into performance curves, design charts, and fragility curves which can be used for risk-based design and assessment applications.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.15-16
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• 2008

We have grown N-doped ZnO thin films on sapphire substrate by employing dielectric barrier discharge in pulsed laser deposition (DBD-PLD). DBD guarantees an effective way for massive in-situ generation of N-plasma under the conventional PLD process condition. Low-temperature photoluminescence spectra of the N-doped ZnO film provided near band-edge emission after thermal annealing process. The emission peak was resolved by Gaussian fitting and showed a dominant acceptor-bound exciton peak ($A^0X$) that indicated the successful p-type doping of ZnO with N.

• International Journal of Naval Architecture and Ocean Engineering
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• 제6권4호
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• pp.1148-1159
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• 2014

Different procedures for estimation of the extreme global wave hydroelastic responses in ships are discussed. Firstly, stochastic procedures for application in detailed numerical studies (CFD) are outlined. The use of the First Order Reliability Method (FORM) to generate critical wave episodes of short duration, less than 1 minute, with prescribed probability content is discussed for use in extreme response predictions including hydroelastic behaviour and slamming load events. The possibility of combining FORM results with Monte Carlo simulations is discussed for faster but still very accurate estimation of extreme responses. Secondly, stochastic procedures using measured time series of responses as input are considered. The Peak-over-Threshold procedure and the Weibull fitting are applied and discussed for the extreme value predictions including possible corrections for clustering effects.

• Structural Engineering and Mechanics
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• 제22권1호
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• pp.53-70
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• 2006

The paper summarizes the dynamic-based assessment of a reinforced concrete arch bridge, dating back to the 50's. The outlined approach is based on ambient vibration testing, output-only modal identification and updating of the uncertain structural parameters of a finite element model. The Peak Picking and the Enhanced Frequency Domain Decomposition techniques were used to extract the modal parameters from ambient vibration data and a very good agreement in both identified frequencies and mode shapes has been found between the two techniques. In the theoretical study, vibration modes were determined using a 3D Finite Element model of the bridge and the information obtained from the field tests combined with a classic system identification technique provided a linear elastic updated model, accurately fitting the modal parameters of the bridge in its present condition. Hence, the use of output-only modal identification techniques and updating procedures provided a model that could be used to evaluate the overall safety of the tested bridge under the service loads.

• 한국진공학회:학술대회논문집
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• 한국진공학회 1999년도 제17회 학술발표회 논문개요집
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• pp.135-135
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• 1999

It is well known that Raman spectroscopy is powerful tool in analysis of sp3/sp3 bonding fraction in diamond-like carbon(DLC) films. Raman spectra of DLC film is composed of D-peak centered at 1350cm-1 and G-peak centered at 1530cm-1. The sp3/sp3 fraction is qualitatively acquired by deconvolution method. However, in case of DLC film, it is generally observed that G-peak position shifts toward low wavenumber as th sp3 fraction increases. However, opposite results were frequently observed in ta-C films. ta-C film has much higher residual compressive stress due to its high sp3 fraction compared to the DLC films deposited by CVD method. Effect of residual stress on G-peak position is most recommendable parameter in Raman analysis of ta-C, due to its smallest fitting error among many parameters acquired by peak deconvolution of symmetric spectra. In current study, the effect of residual stress on Raman spectra was quantitatively evaluated by free-hang method. ta-C films of different residual stress were deposited on Si-wafer by modifying DC-bias voltage during deposition. The variation of the G-peak position along the etching depth were observed in the free-hangs of 20~30${\mu}{\textrm}{m}$ etching depth. Mathematical result based on Airy stress function, was compared with experimental results. The more reliable analysis excluding stress-induced shift was possible by elimination of the Raman shift due to residual compressiove stress.