• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.6-6
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• 2016

최근 전 지구적인 기후 변화에 따라 수문 순환을 이루고 있는 다양한 수문 기상 인자들의 변동성에 영향을 미치고 있다. 특히, 증발산은 수문순환을 구성하는 중요한 인자로서 대기와 지표간의 상호 작용을 파악하기 위해서는 이에 대한 정확한 이해 및 산정이 필수적이다. 일반적으로 증발산량을 산정하기 위해서 증발 접시 및 에디 공분산 기반 플럭스 타워에서 관측된 지점 자료만을 이용하여 증발산량의 변동성을 파악하는 연구들이 수행되어왔다. 그러나 지점 자료만을 이용하여 증발산량을 산출하게 되면 공간적인 변동성을 파악하는데 있어서 한계점이 발생하게 된다. 이러한 제약 사항을 해결하기 위해서, 인공위성 기반의 수문 기상인자를 물리식 기반 증발산량 산정식의 입력 자료로 구축하여 증발산량을 산정하고 이에 대한 시 간적인 변동성을 파악하는 연구들이 활발히 이루어지고 있다. 인공위성 기반 증발산량 산정 알고리즘의 대표적인 예로 공기동역학적 항과 에너지 수지 항들을 동시에 고려할 수 있는 Penman-Monteith 방법을 근간으로 수정하여 만들어낸 Remote Sensing based Penman-Monteith (RS-PM) 알고리즘이 있다. 그러나 RS-PM 기반의 증발산량 경우 태양복사열, 풍속, 온도, 습도와 같은 많은 수문기상인자들이 입력 자료를 요구한다. 이에 따라, 본 연구에서는 기존의 방법에 비해 상대적으로 적은 입력 자료를 사용하는 Modified Satellite-Based Priestley-Taylor (MS-PT) algorithm의 적용성을 평가하기 위해 MODerate-Resolution Imaging Spectroradiometer (MODIS) 자료를 이용하여 한반도에서 순복사에너지 (Net radiation) 및 실제 증발산량 (Actual evapotranspiration)을 산정하였다. 또한, 이에 대한 검증을 위해 청미천 유역에 설치되어있는 에디 공분산 기반 플럭스 타워에서 관측된 순복사 에너지 및 실제 증발산량에 대한 통계적 검증을 실시하였다.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.119-119
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• 2023

본 연구에서는 Terra MODIS(MODerate resolution Imaging Spectroradiometer) 위성영상과 토양수분 부족지수(Soil Water Deficit Index, SWDI)를 이용하여 2012년부터 2022년까지 한반도 전국의 1km 공간 증발산량을 산정하였다. 공간 증발산량을 산정하기 위한 과정은 크게 두 가지로 구분된다. 첫 번째로 MODIS의 LST(Land Surface Temperature), NDVI(Normalized Difference Vegetation Index), 선행강우 및 무강우 누적일수를 이용해 1 km 공간 토양수분을 산정하였다. 농촌진흥청 토양수분관측망 자료 중 토지피복, 토양 속성을 고려하여 선정된 70개소 토양수분 실측데이터와 비교한 결과 지점별 평균 R² 0.63~0.90으로 유의미한 상관성을 나타내었다. 산정된 공간 토양수분은 생장저해수분점과 초기위조점의 관계를 이용한 SWDI로 변환하였다. 두 번째로 순 복사량, 기온 및 NDVI의 적은 수문인자를 통해 증발산량 산정이 가능한 MS-PT(Modified Satellite-based Priestley-Taylor) 모형을 기반으로 계절별 식생과 토양수분 상태를 고려하여 1 km 공간 증발산량을 산정하였다. MS-PT 모형에서 가정한 대기 증발 변수 Diurnal temperature (DT)와 지표 수분의 상관성 문제를 해결하기 위해 DT를 SWDI로 적용하였다. 모형 결과의 검증을 위해 국내 플럭스 타워 (설마천, 청미천, 덕유산) 증발산량 관측자료와의 결정계수(Coefficient of determination, R²), RMSE(Root Mean Square Error) 및 IOA(Index of Agreement)를 산정하였다. 본 연구의 결과로 생산되는 국내 증발산량의 시, 공간적 변동성은 증발산량을 통한 수문학적 가뭄지수 및 급성 가뭄을 파악하는데 활용될 수 있을 것으로 판단된다.

• Journal of Korea Water Resources Association
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• v.49 no.11
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• pp.903-912
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• 2016

Accurate understanding and estimating Evapotranspiration (ET) is essential for understanding the mechanism of water cycle and water budget. ET has been analyzed by many researchers in worldwide while Ground-based ET has limiation in analyzing the spatio-temporal pattrens of ET. Thus, many researches have been conducted to represent the spatio-temporal variation of ET by using hydrometeorological variables estimated from remote sensing datasets. Previous remote sensing based ET algorithms, however, have disadvantage in that various hydrometeological input datasets were required. In this study, actual ET was estimated by MODIS-based Rn and MS-PT algorithm requiring relatively less input data than previous method. The result confirmed that the observed $R_N$ and latent heat flux from the eddy-covariance based fluxtowers located at CFK and SMK showed high correlation with the estimated $R_N$ and ET. The average determination coefficients ($R^2$) of ET estimated from satellite dataset over study periods were 0.77 (0.72-0.81) in Cheongmi (CFK) and 0.70 (0.67-0.78) in Sulma (SMK), respectively. Comparing with the actual ET of two flux tower sites, however, SMK showed more overestimated patterns than CFK due to the vegetation and radiation related errors.

• Bulletin of the Korean Chemical Society
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• v.28 no.4
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• pp.581-588
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• 2007

To enhance the photodecomposition of concentrated ammonia into N2, Pt/V-TiO2 photocatalysts were prepared using solvothermal and impregnation methods. Nanometer-sized particles of 0.1, 0.5 and 1.0 mol% V-TiO2 were prepared solvothermally, and then impregnated with 1.0 wt% Pt. The X-ray diffraction (XRD) peaks assigned to V2O5 at 30.20 (010) and Pt metal at 39.80 (111) and 46.20 (200) were seen in the 1.0 wt% Pt/ 10.0 mol% V-TiO2. The particle size increased in the order: pure TiO2, V-TiO2 and Pt/V-TiO2 after thermal treatment at 500 °C, while their surface areas were in the reverse order. On X-ray photoelectron spectroscopy (XPS), the bands assigned to the Ti2p3/2 and Ti2p1/2 of Ti4+-O were seen in all the photocatalysts, and the binding energies increased in the order: TiO2 < Pt/V-TiO2 < V-TiO2. The XPS bands assigned to the V2p3/2 (517.85, 519.35, and 520.55 eV) and V2p1/2 (524.90 eV) in the V3+, V4+ and V5+ oxides appeared over V-TiO2, respectively, while the band shifted to a lower binding energy with Pt impregnation. The Pt components of Pt/ V-TiO2 were identified at 71.60, 73.80, 75.00 and 76.90 eV, which were assigned to metallic Pt 4f7/2, PtO 4f7/2, PtO2 4f7/2, and PtO 4f5/2, respectively. The UV-visible absorption band shifted closer towards the visible region of the spectrum in V-TiO2 than in pure TiO2 and; surprisingly, the Pt/V-TiO2 absorbed at all wavelengths from 200 to 800 nm. The addition of vanadium generated a new acid site in the framework of TiO2, and the medium acidic site increased with Pt impregnation. The NH3 decomposition increased with the amount of vanadium compared to pure TiO2, and was enhanced with Pt impregnation. NH3 decomposition of 100% was attained over 1.0 wt% Pt/1.0 mol% V-TiO2 after 80 min under illumination with 365 nm light, although about 10% of the ammonia was converted into undesirable NO2 and NO. Various intermediates, such as NO2, -NH2, -NH and NO, were also identified in the Fourier transform infrared (FT-IR) spectra. From the gas chromatography (GC), FT-IR and GC/mass spectroscopy (GC/MS) analyses, partially oxidized NO and NO2 were found to predominate over V-TiO2 and pure TiO2, respectively, while both molecules were reduced over Pt/V-TiO2.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.3
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• pp.143-151
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• 1995

The electrochemical impulse oscillations of the cathodic currents at the platinum group (Pt, Pd) electrode/(0.05M KHC$_{8}H_{4}O_{4}$) buffer solution interfaces have been studied using voltammetric, chronoamperometric, and electrochemical impedance methods. The periodic impulses of the cathodic currents are the activation controlled currents due to the hydrogen evolution reaction, and depend on the fractional surface coverage of the adsorbed hydrogen intermediate and potential. The oscillatory mechanism of the cathodic current impulses is connected with the unstable steady state of negative differential resistance. The widths and periods of the cathodic current impulses are 4ms or 5ms and 152.5ms or 305ms, respectively. The H$^{+}$ discharge reaction step is 38 or 61 times faster thatn the recombination reaction steps and the H$^{+}$ mass transport processes. The atom-atom recombination reaction step is twice faster thatn the atom-ion recombination reaction step. The two kinds of active sites corresponding to the atom-atom and atom-ion recombination reaction steps exist on the platinum group electrode surfaces.

• Polymer(Korea)
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• v.35 no.1
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• pp.35-39
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• 2011

In this work, mesoporous carbons (CMK-3) were prepared by a conventional templating method using mesoporous silica (SBA-15) for using catalyst supports in polymer electrolyte membrane fuel cells (PEMFCs). The CMK-3 were chemically activated to obtain high surface area and small pore diameter with different potassium hydroxide (KOH) amounts, i.e., 0, 1, 3, and 4 g as an activating agent. And then Pt-Ru was deposited onto activated CMK-3 (K-CMK-3) by a chemical reduction method. The characteristics of Pt-Ru catalysts deposited onto K-CMK-3 were determined by surface area and pore size analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and inductive coupled plasma-mass spectrometry (ICP-MS). The electrochemical properties of Pt-Ru/K-CMK-3 catalysts were also analyzed by cyclic voltammetry (CV). From the results, the K3g-CMK-3 carbon supports activated with 3 g KOH showed the highest specific surface areas. In addition, the K3g-CMK-3 led to uniform dispersion of Pt-Ru onto K-CMK-3, resulted in the enhancement of elelctro-catalystic activity of Pt-Ru catalysts.

• The Korean Journal of Ceramics
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• v.6 no.3
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• pp.315-317
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• 2000

A magnetoplumbite type of Ba ferrite(BaM) layers were deposited on Pt(111) and Pt(200) layers, and their c-axis orientation and magnetic characteristics were compared each other. The as-deposited BaM layer on Pt(111) one at the substrate temperature $T_s$ above $500^{\circ}C$ revealed remarkable c-axis orientation. The saturation magnetization 4$\piM_s$ and the perpendicular coercivity $H_{c⊥}$ of the films as-deposited at $T_s$ of $600^{\circ}C$ were 4.0kG and 2.5kOe, respectively. On the other hand, BaM ferrite layer deposited on Pt(200) layer at $T_s$ as relatively low as $500^{\circ}C$ also revealed weak c-axis orientation as well as (107) one and the films as-deposited at $T_s$ of $600^{\circ}C$ exhibited 4$\piMs_{and}$ $H_{c⊥}$ of 2.8kG and 2.5kOe, respectively. It was suggested that although chemical activity of Pt surface was effective for the formation of BaM crystallites, the lattice matching was also important for obtaining BaM layer with good c-axis orientation and large perpendicular anisotropy.sotropy.

• Bulletin of the Korean Chemical Society
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• v.31 no.2
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• pp.331-334
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• 2010

In the present study, carbon supports mixed with purified multi-walled carbon nanotubes (MWNTs) and carbon blacks (CBs) were used to improve the cell performance of direct methanol fuel cells (DMFCs). Additionally, the effect of $O_2$ plasma treatment on CBs/MWNTs supports was investigated for different plasma RF powers of 100, 200, and 300 W. The surface and structural properties of the CBs/MWNTs supports were characterized by FT-IR, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and inductive coupled plasma-mass spectrometer (ICP-MS). The electrocatalytic activity of PtRu/CBs/MWNTs catalysts was investigated by cyclic voltammetry measurement. In the experimental results, the oxygen functional groups of the supports were increased with increasing plasma RF power, while the average Pt particle size was decreased owing to the improvement of dispersibility of the catalysts. The electrochemical activity of the catalysts for methanol oxidation was gradually improved by the larger available active surface area, itself due to the introduction of oxygen functional groups. Consequently, it was found that $O_2$ plasma treatments could influence the surface properties of the carbon supports, resulting in enhanced electrocatalytic activity of the catalysts for DMFCs.

• Journal of the Korean Society of Propulsion Engineers
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• v.19 no.1
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• pp.1-8
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• 2015

Micro igniter on the glass membrane for MEMS thruster was developed. The stability of the micro igniter by using a glass membrane with a thickness of tens of microns was improved. The micro igniter was fabricated by anisotropic wet etching of photosensitive glass and deposition of Pt/Ti for electric heat coil. The solid propellant was loaded into the propellant chamber without an especial technique due to the high structural stability of the glass membrane. Ignition tests were performed successfully. The minimum ignition delay was 27.5 ms with an ignition energy of 19.3 mJ.

• YAKHAK HOEJI
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• v.55 no.2
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• pp.145-153
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• 2011

A simultaneous detection and quantification method for determining the Phenylalkylamine derivatives, such as methamphetamine (MA), amphetamine (AM), 3,4-methylenedioxymethamphetamine (MDMA), 3,4-methylenedioxyamphetamine (MDA), ketamine (KT), norketamine (NKT), phentermine (PT), fenfluramine (FFA) and phenmetrazine (PM), in oral fluid was developed and validated according to international guidelines. The validated method was applied to actual oral fluid samples collected from drug abuse suspects. The recovery of phenylalkylamines from oral fluid collection devices was also assessed. Oral fluid specimens from 20 drug abuse suspects submitted by the police were collected using Salivette$^{TM}$, Quantisal$^{TM}$ or direct expectoration. The samples were screened using a biochip array analyzer. For confirmation, the samples were analyzed by GC-MS in selected-ion monitoring (SIM) mode after extraction using automated SPE with a mixed-mode cation exchange cartridge and derivatization with trifluoroacetic anhydride (TFAA). The results from the immunoassay were consistent with those from GC-MS. All the oral fluid samples gave positive results for MA, AM, PT and/or PM. The detection of phenylalkylamines in oral fluid can provide a better indication of recent use than urine or hair. Therefore, the oral fluid specimen was useful for demonstrating phenylalkylamines abuse in the driving under the influence of drug (DUID) as an alternative specimen for urine.