• Environmental Engineering Research
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• v.17 no.3
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• pp.125-132
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• 2012

The removal of Cd(II) and Cu(II) from aqueous solution by an agricultural solid waste biomass prepared from Moringa oleifera bark (MOB) was investigated. The biosorbent was characterized by Fourier transform infrared spectroscopy and elemental analysis. Furthermore, the effect of initial pH, contact time, biosorbent dosage, initial metal ion concentration and temperature on the biosorption of Cd(II) and Cu(II) were studied using the batch sorption technique. Kinetic studies indicated that the biosorption process of the metal ions followed the pseudo-second order model. The biosorption data was analyzed by the Langmuir, Freundlich, Dubinin-Radushkevich, and Temkin isotherm models. Based on the Langmuir isotherm, the maximum biosorption capacities for Cd(II) and Cu(II) onto MOB were 39.41 and 36.59 mg/g at 323 K, respectively. The thermodynamic parameters, Gibbs free energy (${\Delta}G^o$), enthalpy (${\Delta}H^o$), and entropy (${\Delta}S^o$) changes, were also calculated, and the values indicated that the biosorption process was endothermic, spontaneous and feasible in the temperature range of 303-323 K. It was concluded that MOB powder can be used as an effective, low cost, and environmentally friendly biosorbent for the removal of Cd(II) and Cu(II) ions from aqueous solution.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.14 no.3
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• pp.97-106
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• 2000

This paper proposes on-line based a deterioration diagnosis device for diagnosis pole transformers using tan$\delta$ and FFT(fast Fourier transform). We measured tan$\delta$ and temperature to diagnose pole transformer insulating oil, diagnostic results are processed by FFT. For measuring convenience, we use R/F(radio frequency) wireless data communication module operating by secondary voltage of pole transformer. We have voltage variation test and oil temperature variation test to prove usability of proposed diagnosis device. The result of this paper shows that the proposed device can be used as deterioration diagnosis device of pole transformers.

• Proceedings of the KIEE Conference
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• 1998.07g
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• pp.2411-2413
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• 1998

In this paper, using tile concept of block digital filtering, and the design procedure of time-interleaved oversampling converter are presented. it is shown that arbitrary sigma-delta A/D converter can be converted into corresponding time-interleaved structure. The TIM structure of this paper is designed by the bilinear transform. To verify the simulation results, a second-order TIM structure A/D converter has been implemented and the design process as well as experimented results are presented.

• Korean Chemical Engineering Research
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• v.57 no.5
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• pp.652-665
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• 2019

Analytical solutions of the reactant concentration inside porous spherical catalytic particles were obtained from unsteady reaction-diffusion equation by applying eigenfunction expansion method. Various surface concentrations as exponentially decaying or oscillating function were considered as boundary conditions to solve the unsteady partial differential equation as a function of radial distance and time. Dirac delta function was also used for the instantaneous injection of the reactant as the surface boundary condition to calculate average reactant concentration inside the particles as a function of time by Laplace transform. Besides spherical morphology, other geometries of particles, such as cylinder or slab, were considered to obtain the solution of the reaction-diffusion equation, and the results were compared with the solution in spherical coordinate. The concentration inside the particles based on calculation was compared with the bulk concentration of the reactant molecules measured by photocatalytic decomposition as a function of time.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2020.07a
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• pp.546-549
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• 2020

본 논문에서는 최신 비디오 코딩 기술에서 잔차(Residual)신호 변환을 효율적으로 수행하기 위한 부동기저(Basis)를 사용하는 방법을 제안한다. 기존의 DCT-II 나 DST-VII 과 같은 고정 기저를 사용하는 방법은 대부분의 잔차신호들에 대해 효과적으로 비상관화(decorrelation)를 수행하지만 복잡한 잔차 신호일수록 성능이 떨어지는 문제가 있었다. 이러한 압축 성능하락 문제를 줄이기 위하여 PCA(Principle Component Analysis) 방법 중 하나인 KLT(Karhunen-Loeve Transform)를 이용하여 부동(floating) 변환 기저를 유도하는 방법을 제안한다. 기존의 KLT 를 이용한 변환 커널 유도 방법들의 문제점인 부호화기 및 복호화기 계산 복잡도를 줄이기 위하여 KL 커널을 분해가능한(Separable) 2 개의 1 차원 커널로 유도하는 방법을 제안하고, 원본 잔차신호와 유사한 텍스처를 찾아 커널을 예측하는 과정을 간소화하는 방법을 제안한다. 제안하는 방법은 HEVC 에서 실험되었으며 정지영상 코딩 Main-Profile 에서 평균 1.4%가량의 BD-PSNR(Bjontegaard Delta-Peak Signal to Noise Ratio) 성능 향상을 보였으며 특히 스크린 컨텐츠 영상에서 최대 4.5%의 성능 향상을 보인다.

• Journal of Environmental Science International
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• v.25 no.12
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• pp.1613-1622
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• 2016

Zeolite (FZ), prepared from fly ash, was immobilized with polyacrylonitrile (PAN) to fabricate PAN/FZ beads. The prepared PAN/FZ beads were characterized by scanning electron microscopy, thermogravimetric analysis, and Fourier transform infrared spectroscopy. The optimum ratio to prepare PAN/FZ beads was 0.3 g of PAN to 0.3 g of FZ. The diameter of the prepared PAN/FZ beads was about 3 mm. Sr and Cu ion adsorption experiments were conducted with PAN/FZ beads. A pseudo-second-order model fit the kinetic data for Sr and Cu ion adsorption by PAN/FZ beads well. The equilibrium data fitted well with the Langmuir isotherm model, and the maximum adsorption capacities were 96.5 mg/g and 74.6 mg/g for the Sr and Cu ions, respectively. Additionally, the values of thermodynamic parameters such as Gibbs free energy (${\Delta}G^o$), enthalpy (${\Delta}H^o$) and entropy (${\Delta}S^o$) were determined. The positive values of ${\Delta}H^o$ revealed the endothermic nature of the adsorption process and the negative values of ${\Delta}G^o$ were indicative of the spontaneity of the adsorption process.

• Publications of The Korean Astronomical Society
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• v.27 no.5
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• pp.399-409
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• 2012

As a part of the short-period variability survey (SPVS) at Bohyunsan Optical Astronomy Observatory, we obtained time-series BV CCD images in the region of Cyg OB3 association centered on the open cluster NGC 6871. The observations were performed for 18 nights from September 5, 2008 to September 1, 2009. We found 15 short-period variable stars in the region. They are ${\delta}$ Scuti type stars belonging to the local spiral arm, Orion spur. Among them, only two stars were previously known, and the rest are newly discovered ones. In this paper, we have performed a multiple-frequency analysis to determine frequencies of the 15 ${\delta}$ Scuti type stars, using the discrete Fourier transform and linear least-square fitting methods. One of the newly discovered variable stars is a double-mode ${\delta}$ Scuti type star with the fundamental and the first overtone modes, and two are high amplitude ${\delta}$ Scuti stars.

• Proceedings of the KIEE Conference
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• 2008.04a
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• pp.137-138
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• 2008

수많은 방식의 ECG 압축 코딩 알고리즘이 개발되어왔고 현재도 개발 중이지만 각자의 알고리즘의 성능에 유리한 특정 데이터만을 분석하고 압축율이 다름으로 인해 다른 알고리즘과의 성능 비교를 객관화하고 있지 못하였다. 본 연구에서는 기존의 MIT-BIH에서 제공하는 ECG 신호와 달리 시뮬레이션된 ECG 신호를 기반으로 각각의 알고리즘에 대한 성능비교를 하여 ECG신호의 특성에 따른 코딩 알고리즘의 압축율 및 평균 오차 에러의 정도를 분석비교하였다. 비교 대상 알고리즘으로는 상용화되어 널리 사용되는 Delta 코팅 방식의 문턱치를 갖는 Discrete Pulse Code Modulation과 Discrete Cosine Transform, Lifting Wavelet Transform과 Wavelet 기반 Linear Prediction 4가지 알고리즘을 대상으로 분석하였다. Compression Ratio (CR)을 2,4로 고정하고 Percentage of Root-mean-square difference (PDR)를 분석 한 결과, EMG 잡음의 진폭변 화에는 0.1mV이하의 경우 OCT, Wavelet Lifiting Transform이 낮은 PDR을 보였고, 01.mV이상의 경우 Wavelet based Linear Prediction (WLP)이 낮은 PDR을 보였다. Heart Rate의 간격에 변화를 주어 불규칙성이 있는 경우 WLP가 가장 안좋은 PDR 결과를 보였으며, DCT가 가장 낮고 안정된 PDR 결과를 보였다. DPCM은 노이즈와 진폭간격의 변화에 상관없이 압축율에 의해 크게 PDR 성능 결과가 변화함을 나타내었다.

• Interaction and multiscale mechanics
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• v.6 no.3
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• pp.287-300
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• 2013

In this paper, the effect of impulsive line on the propagation of shear waves in non-homogeneous elastic layer is investigated. The rigidity and density in the intermediate layer is assumed to vary quadratic as functions of depth. The dispersion equation is obtained by using the Fourier transform and Green's function technique. The study ends with the mathematical calculations for transmitted wave in the layer. These equations are in complete agreement with the classical results when the non-homogeneity parameters are neglected. Various curves are plotted to show the effects of non-homogeneities on shear waves in the intermediate layer.

• The Pure and Applied Mathematics
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• v.19 no.2
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• pp.87-102
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• 2012

In this paper, we consider the Fourier-type functionals introduced in [16]. We then establish the analytic Feynman integral for the Fourier-type functionals. Further, we get a series expansion of the analytic Feynman integral for the Fourier-type functional $[{\Delta}^kF]^{\^}$. We conclude by applying our series expansion to several interesting functionals.