• Corrosion Science and Technology
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• 제22권1호
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• pp.1-9
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• 2023

This work studied the inhibitory effect of the combination of benzoate-intercalated hydrotalcite (HT-BZ) and Ce³⁺-loaded clay (Clay-Ce) on carbon steel (CS). HT-BZ was prepared by the co-precipitation method and Clay-Ce was fabricated by a cation exchange reaction. HT-BZ and Clay-Ce were assessed by scanning electron microscopy (SEM) and X-ray diffraction (XRD) coupled with zeta potential measurement. Electrochemical measurements coupled with scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDX) were used for studying the inhibitory action of the mixture of HT-BZ and Clay-Ce on steel electrodes immersed in 0.1 M NaCl. For comparison, the inhibitory effect of HT-BZ or Clay-Ce alone was also evaluated. The results showed that HT-BZ combined with Clay-Ce provided synergistic inhibition of the CS substrate. The mixture of 0.5 g/L HT-BZ + 0.5 g/L Clay-Ce provided 93.5% inhibition efficiency. The protective mechanism of the HT-BZ + Clay-Ce mixture consisted of the reaction of released BZ and Ce³⁺ and the deposition of HT-BZ and Clay-Ce structures on the CS substrate.

• 시스템엔지니어링학술지
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• 제19권2호
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• pp.46-58
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• 2023

Deterministic safety analysis is a crucial part of safety assessment, particularly when it comes to demonstrating the safety of nuclear power plant designs. The traditional approach to deterministic safety analysis models is to model the nuclear core using point kinetics. However, this simplified approach does not fully reflect the real core behavior with proper moderator and fuel reactivity feedbacks during the transient. The use of Multi-Physics approach allows more precise simulation reflecting the inherent three-dimensionality (3D) of the problem by representing the detailed 3D core, with instantaneous updates of feedback mechanisms due to changes of important reactivity parameters like fuel temperature coefficient (FTC) and moderator temperature coefficient (MTC). This paper addresses a CEA ejection accident at hot full power (HFP), in which the underlying strong and un-symmetric feedback between thermal-hydraulics and reactor kinetics exist. For this purpose, a multi-physics analysis tool has been selected with the nodal kinetics code, 3DKIN, implicitly coupled to the thermal-hydraulic code, RELAP5, for real-time communication and data exchange. This coupled approach enables high fidelity three-dimensional simulation and is therefore especially relevant to reactivity initiated accident (RIA) scenarios and power distribution anomalies with strong feedback mechanisms and/or un-symmetrical characteristics as in the CEA ejection accident. The Systems Engineering approach is employed to provide guidance in developing the work in a systematic and efficient fashion.

• 한국전산구조공학회논문집
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• 제27권3호
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• pp.137-145
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• 2014

본 논문에서는 브리징 스케일 분해를 기반으로 멀티스케일 문제에 대한 설계민감도 해석법을 개발하였다. 나노 기술의 급속한 발전으로 인해 나노 수준의 해석의 필요성이 지속적으로 증가하고 있다. 최근 분자동역학과 연속체역학의 연성문제에서 많은 해석 방법들이 개발되었다. 본 논문에서는 연성시스템 해석을 위해 브리징 스케일 기법을 사용한다. 전체 영역의 분자동역학 시스템의 해석은 많은 양의 계산 비용이 들기때문에 분자동역학과 연속체 시뮬레이션의 연성시스템을 선호한다. 분자동역학과 연속체 수준 사이의 정보 교환은 분자동역학과 연속체의 경계에서 일어난다. 브리징 스케일 법에서 일반화된 랑지벵 방정식은 축소된 영역의 분자동역학 시스템 해석을 위하여 요구되고, 시간이력 커널을 사용하여 구한 GLE 힘은 분자동역학 시스템에서 경계에 있는 원자들에 작용한다. 그러므로 분자동역학과 연속체 수준의 시뮬레이션을 분리해서 해석할 수 있으며 계산 과정을 가속시킬 수 있다. 연성문제의 시뮬레이션 이후에는 설계의 최적화를 위해 설계민감도 해석의 필요성이 자연스럽게 나타나며 전체 시스템의 성능은 나노 스케일의 효과를 고려해서 최적화된다. 설계구배 기반 최적화에서 설계민감도가 요구되지만 유한차분법으로 구한 민감도는 문제가 대형화될 때 계산비용의 제한때문에 비실용적이나 해석적 설계민감도는 효율적인 강점을 갖는다. 본 연구에서는 연성된 분자동역학-연속체 멀티스케일 문제에서 해석적 설계민감도를 유도하여 정확성과 향후 최적설계로의 활용 가능성을 확인하였다.

• 한국환경과학회지
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• 제26권6호
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• pp.729-739
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• 2017

The Weather Research and Forecasting (WRF) model and Vegetation Photosynthesis and Respiration Model (VPRM) were coupled to simulate atmospheric $CO_2$ concentrations. The performance of the WRF-VPRM to simulate regional scale $CO_2$ concentration was estimated over coastal basin areas. Either Hestia 2011(HST) or Vulcan 2002(VUL) anthropogenic $CO_2$ emission data were used in two numerical experiments for the study regions. Simulated meteorological variables were validated with ground and background $CO_2$ measurement data, and the results show that the model captured temporal variations of $CO_2$ concentration on a daily basis. $CO_2$ directional analysis revealed that the dominant $CO_2$ emission sources are located S and SW. The simulated Net Ecosystem Exchange (NEE) agreed relatively well with measured $CO_2$ fluxes at each vegetation class site, showing approximately 40% at max improvement at shrub areas.

• 조명전기설비학회논문지
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• 제25권8호
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• pp.39-47
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• 2011

The motion of a conductive spherical particle under uniform electric field is investigated in order to find a suitable method for removing the conducting solid impurities contained in liquid plastic. When the positive dc voltage applied to the upper electrode, the vertical up-and-down motion of a charged particle by electrostatic force is observed by a charge-coupled device (CCD) camera or a high-speed video camera. The experimental data of the static threshold voltage by which the particle starts to move toward the counter electrode in air or silicone oil are in good agreement with theoretical value. When the applied voltage is larger than the static threshold voltage, the particle motion pattern in silicone oil consists of four stages: upward motion, stopping at the upper electrode, downward motion and stopping at the lower electrode. The stopping motion on the electrode is thought to be caused by the liquid flow accompanied by the particle motion. The particle charge calculated by integrating the pulse current, which is generated by the charge exchange between the electrode and the particle, is approximately 0.1~0.25 times of the theoretical value. This study is expected to help understand the electric properties of microparticles in oil circuit breaker (OCB) and oil transformer and improve their performance and longevity.

• 한국습지학회지
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• 제14권1호
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• pp.75-87
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• 2012

지표수-지하수 혼합대는 하천 및 호소 등에서 지표수와 지하수가 교환되는 공간이다. 지표수-지하수 혼합은 하상의 토층으로 확장되어 다양한 물리적, 생지화화적, 열역학적 교환을 발생시키며 수생태계 내 고유한 생태적 전이대를 형성하는데 주요한 역할을 한다. 과거 실험 및 수치모의 연구에 의하면 혼합대에서 발생하는 물질교환은 하천의 지형적인 특징으로 발생하는 압력분포에 의해 지배된다. 특히 하천의 구간 규모에서 여울-소 구조는 혼합대의 특성을 지배하는 주요 인자로 알려져 있다. 여울-소 연속 구조는 지표수에서 재순환영역과 정체점을 형성하며 이 독특한 흐름 구조에 의해 혼합대의 흐름특성이 영향을 받는다. 본 연구에서는 3차원 동수역학 모형을 이용하여 Reynolds-averaged Navier-Stokes 방정식과 Darcy 방정식을 동시에 해석하여 연속된 여울-소 구조에서 발생하는 지표수의 흐름구조가 혼합대의 흐름에 미치는 영향을 분석하였다. 모의 결과, 여울-소 구조에서 지표수의 재순환영역 및 정체점은 상승류와 하강류 형성과 직접적 연관을 가지며, 재순환영역의 크기가 감소하면 여울 전면부 하강류 형성 구간의 길이가 감소하고 최대 하강류 발생 지점이 하부로 이동하는 특성을 파악하였다. 이와 같은 본 연구의 결과는 혼합대의 현장관측, 하천 관리 및 복원 등의 연구에 활용하여 친환경 하천 조성에 기여할 수 있을 것으로 판단된다.

• 분석과학
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• 제21권4호
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• pp.272-278
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• 2008

$AG^{(R)}$ 50W-X8 양이온교환수지를 이용하여 14종의 희토류원소와 Y를분리하고, 유도결합플라스마 원자방출분광법(ICP-AES)으로 분석하는 방법에 대해 연구하였다. 수지에 대한 희토류원소의 이온교환용량은 매우 커 pH 1~6 범위와 0.3~1.0mL/min의 흐름속도에서 희토류원소는 모두 정량적으로 이온교환 되었다. 희토류원소의 돌파점 용량 곡선은 경희토류원소(Cerium 그릅)의 이온교환능력이 중희토류원소(Yttrium 그릅) 보다 큰 것을 보여주었다. 100mg의 이온교환수지에 각각 $200{\mu}g$의 희토류원소들이 이온교환 되어있을 때 대부분의 중희토류원소는 2.0M의 질산 10 mL로, 경희토류원소는 30mL로 정량적으로 탈착시킬 수 있었다. 본 방법으로 모나자이트 중에 희토류원소를 분석하였다. 모나자이트 중에 공존하는 Ti, Mn, Mg, Ca 등의 원소는 상대적으로 희토류원소 보다 이온교환 능력이 낮아, 매트릭스 원소로 부터 희토류원소의 분리가 가능하였다. 그러나 본 방법에서 분석 결과의 상대표준편차는 1~5%로 향상되지 않았다.

• Environmental Analysis Health and Toxicology
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• 제29권
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• pp.18.1-18.9
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• 2014

Objectives The purpose of this study was to determine a separation method for each arsenic metabolite in urine by using a high performance liquid chromatography (HPLC)-inductively coupled plasma-mass spectrometer (ICP-MS). Methods Separation of the arsenic metabolites was conducted in urine by using a polymeric anion-exchange (Hamilton PRP X-100, $4.6mm{\times}150mm$, $5{\mu}m$) column on Agilent Technologies 1260 Infinity LC system coupled to Agilent Technologies 7700 series ICP/MS equipment using argon as the plasma gas. Results All five important arsenic metabolites in urine were separated within 16 minutes in the order of arsenobetaine, arsenite, dimethylarsinate, monomethylarsonate and arsenate with detection limits ranging from 0.15 to $0.27{\mu}g/L$ ($40{\mu}L$ injection). We used G-EQUAS No. 52, the German external quality assessment scheme and standard reference material 2669, National Institute of Standard and Technology, to validate our analyses. Conclusions The method for separation of arsenic metabolites in urine was established by using HPLC-ICP-MS. This method contributes to the evaluation of arsenic exposure, health effect assessment and other bio-monitoring studies for arsenic exposure in South Korea.

• 분석과학
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• 제37권2호
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• pp.123-129
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• 2024

We present a rapid method for the determination of Cs, Sr, and Ba, heat generators found in highly active liquid wastes, by gas-pressurized extraction chromatography (GPEC) using a column containing a cation-exchange resin. GPEC is a microscale column chromatographic technique that uses a constant flow rate of solvent (0.07 mL/min) with pressurized nitrogen gas supplied through a valve. In particular, because this method uses a small sample volume (a few hundred microliters), it produces less chemical waste and allows for faster separation compared to traditional column chromatography. In this study, we evaluated the separation of Cs, Sr, and Ba using GPEC. The eluate from the column (GPEC or conventional column chromatography) was quantitatively analyzed using inductively coupled plasma-mass spectrometry to measure the column recovery and precision. The column reproducibility of the proposed GPEC system (RSDs of recoveries) ranged from 2.7 to 4.1 %, and the column recoveries for the three elements ranged from 72 to 98% when aqueous HCl was used as the eluent. The GPEC results are slightly different in efficiency and separation resolution compared to those of conventional column chromatography because of the differences in the eluent flow rate as well as the internal diameter and length of the column. However, the two methods had similar recoveries for Cs and Sr, and the precision of GPEC was improved by two-fold. Remarkably, the solvent volume required for GPEC analysis was five times lower than that of the conventional method, and the total analysis time was 11 times shorter.

• 한국지열·수열에너지학회논문집
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• 제13권4호
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• pp.1-7
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• 2017

The energy slab is a ground coupled heat exchanger equipped in building slab structures, which represents a layout similar to the horizontal ground heat exchanger (GHEX). The energy slab is installed as one component of the floor slab layers in order to utilize the underground structure as a hybrid energy structure. However, as the energy slab is horizontally arranged, its thermal performance is inevitably less than the conventional vertical GHEXs. Therefore, stainless steel (STS) pipes are alternatively considered as a heat exchanger instead of high density polyethylene (HDPE) pipes in order to enhance thermal performance of GHEXs. Moreover, not only a floor slab but also a wall slab can be utilized as a heat-exchangeable energy slab in order to maximize the use of underground space effectively. In this paper, four field-scale energy slabs were constructed in a test bed, which consist of the STS and HDPE pipe, and a series of thermal response tests (TRTs) was conducted to evaluate relative heat exchange efficiency per unit pipe length according to the pipe material and the configuration of energy slabs. The energy slab equipped with the STS pipe shows higher thermal performance than the energy slab with the HDPE pipe. In addition, thermal performance of the wall-type energy slab is almost equivalent to the floor-type energy slab.