• 한국환경과학회지
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• 제32권1호
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• pp.37-46
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• 2023

This study investigated the effect of May 31, 2022 Miryang wildfire on fine particle concentrations in Busan and Gimhae, which are neighboring urban areas. In addition, fine particle characteristics and air pollution concentrations were investigated in Miryang, where haze occurred. The Miryang city wildfire that occurred on May 31, 2022, at 0925 LST, was driven by strong north winds and increased fine particle concentrations in Dongsangdong and Jangyoodong, Gimhae City, which are approximately 35 km to the southeast and south, respectively, of the wildfire occurrence site. Furthermore, the fine particle concentration in Myeongjidong, which is approximately 50 km south-southeast of the wildfire site, exhibited a temporary increase at 1400 LST owing to the effects of wildfire smoke. On the morning of June 1, the day after the fire, the Miryang area had very bad visibility because of the smoke from the fire. Therefore the PM₁₀ and PM_2.5 concentrations in Naeildong, 3 km south of the wildfire site, were 276 ㎍/㎥ and 222 ㎍/㎥, respectively, at 1200 LST. In addition, the gases O₃, CO, and SO₂ showed high concentrations at the time of haze generation. This study provides insights into policy making in response to the rapid increase in fine dust when wildfire occurs near cities.

• Wind and Structures
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• 제39권3호
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• pp.163-174
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• 2024

This paper analyzes La Rumorosa I Wind Farm's wind states and their characteristics in the operation of two wind turbines over the course of one year of records. This information identifies the impact of wind states on wind power output. The study used the Gaussian Mixture Model to classify the occurrence and frequency of the dominant wind states in the generation of energy from the turbines. Results were obtained for mesoscale wind states and local scale wind states, such as cold fronts and Santa Ana winds, as well as daytime, nighttime and hot days, respectively, which were statistically analyzed to determine their relationship to power output by generating power and power coefficient curves. Between the cut-in speed and the rated speed of the wind turbines, cold fronts show higher efficiency, unlike nighttime wind states, which are the most efficient past the rated speed. In addition, cold fronts are also those that occur to the greatest extent, contributing 31.26% of the energy produced per year, compared with the Santa Ana winds, which occur to a lesser extent; however, they contribute 22.11% of the energy produced per year.

• 해양환경안전학회지
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• 제15권3호
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• pp.257-262
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• 2009

일체형 조류제어기인 UPFC는 FACTS 기기중 가장 효과적인 기기 중 하나이다. 본 논문에서는 전력시스템에서 UPFC의 최적위치를 결정하는 데 필요한 컴퓨터의 계산을 줄이는 방법에 대하여 기술한다. 이를 위해 UPFC 제어 변수들과 관련된 발전 비용의 민감도가 평가되었다. 모든 송전선로의 UPFC 민감도를 얻기 위해 단지 한 번의 최적조류제어만으로 해결하였다. 전력시스템에서 UPFC의 최적 위치를 알아내기 위해 여러 권선비와 가변 션트 어드미턴스로 구성된 이상변압기 모델을 사용하였다. 이 모델에서 UPFC 제어 변수들은 UPFC 입 출력의 전류와 전압에 대해서 종속되지 않는다. 민감도 방법은 그의 효율성을 파악하기 위해 IEEE 14 모선에서 파생된 5 모선시스템과 IEEE 14 모선시스템을 대상으로 실험하였다.

• 정보처리학회논문지D
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• 제8D권4호
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• pp.367-376
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• 2001

이동 매제를 통한 진자지도 서비스는 전송 정보의 용량이 크고 출력 장치의 자원을 많이 요구하기 때문에 기존의 지도 데이터베이스를 그대로 사용하여 서비스할 수 없는 문제점이 있다. 또한 무선 서비스 전용 지도 데이터베이스를 별도로 구축하는 것은 막대한 중복 비용이 발생하므로 받아들이기 어렵다. 본 논문에서는 기존의 지도 데이타베이스로부터 무선 서비스에 적합한 지도를 동적으로 생성하는 새로운 기법을 제시한다. 이 기법은 기존 지도의 데이타 크기를 줄이기 위한 generalization과 생성된 지도의 데이타 크기가 임계값을 넘지 않도록 제어하는 filtering을 수행한다. Generalization은 레이어를 통합하는 단계, 세부 객체를 간소화하는 단계, 그리고 사용자 인터페이스를 처리하는 단계로 나누어 처리된다. Filtering은 약도에 포함된 객체를 카운터하는 모듈과 검색 객체와 거리에 따른 중요도로 선택하는 모듈로 데이터 크기를 대역폭 임계값 이내로 처리한다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.599_600
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• 2009

In superconducting magnetic energy storage (SMES) systems, the current leads are usually divided into two parts. Normal metals like brass or copper are often used in the first part from the room temperature to the 1st stage of the cryocooler. Their dimensions were decided to minimize the conduction heat penetration and Ohm's heat generation. The second part down to the cryogenic coil is made of high temperature superconductor (HTS). HTS current leads can reduce the conductive heat penetration because they have poor thermal conductivity and generate no Ohm's heat generation. The brass current lead and the HTS current lead were designed and fabricated for application to the 10kJ class SMES system. The HTS current lead is 300A class. The HTS current lead was stacked with 2 HTS layers using the $Bi_2Sr_2Ca_2Cu_3O_x$ (BSCCO)/Ag. In this paper, we introduce the design procedure of the current leads and discuss the test results of the current leads.

• 한국수소및신에너지학회논문집
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• 제19권6호
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• pp.498-504
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• 2008

Metal-reducing bacterium, Geobacter sulfurreducens is available for mediator-less microbial fuel cell (MFC) because it has biological nanowires(pili) which transfer electrons to outside the cell. In this study, in the anode chamber of the MFC system using G. sulfurreducens, the concentrations of NaCl, sodium phosphate and sodium bicarbonate as electrolytes were mainly optimized for the generation of electricity from acetate. 0.4%(w/v) NaClO and 0.5M $H_2SO_4$ could be utilized for the sterilization of acrylic plates and proton exchange membrane (major construction materials of the MFC reactor), respectively. When NaCl concentration in anode phosphate buffer increased from 5 to 50 mM, power density increased from 6 to $20\;mW/m^2$. However, with increasing sodium phosphate buffer concentration from 5 to 50 mM, power density significantly decreased from 18 to $1\;mW/m^2$. Twenty-four mM sodium bicarbonate did not affect electricity generation as well as pH under 50 mM phosphate buffer condition. Optimized anode chamber of MFC using G. sulfurreducens generated relatively high power density ($20\;mW/m^2$) with the maximum coulombic efficiency (41.3%).

• Tribology and Lubricants
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• 제35권5호
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• pp.274-285
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• 2019

Chemical mechanical polishing (CMP), which is a material removal process involving chemical surface reactions and mechanical abrasive action, is an essential manufacturing process for obtaining high-quality semiconductor surfaces with ultrahigh precision features. Recent rapid growth in the industries of digital devices and semiconductors has accelerated the demands for processing of various substrate and film materials. In addition, to solve many issues and challenges related to high integration such as micro-defects, non-uniformity, and post-process cleaning, it has become increasingly necessary to approach and understand the processing mechanisms for various substrate materials and abrasive particle behaviors from a tribological point of view. Based on these backgrounds, we review recent CMP R&D trends in this study. We examine experimental and analytical studies with a focus on substrate materials and abrasive particles. For the reduction of micro-scratch generation, understanding the correlation between friction and the generation mechanism by abrasive particle behaviors is critical. Furthermore, the contact stiffness at the wafer-particle (slurry)-pad interface should be carefully considered. Regarding substrate materials, recent research trends and technologies have been introduced that focus on sapphire (${\alpha}$-alumina, $Al_2O_3$), silicon carbide (SiC), and gallium nitride (GaN), which are used for organic light emitting devices. High-speed processing technology that does not generate surface defects should be developed for low-cost production of various substrates. For this purpose, effective methods for reducing and removing surface residues and deformed layers should be explored through tribological approaches. Finally, we present future challenges and issues related to the CMP process from a tribological perspective.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2019년도 춘계학술대회
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• pp.79-82
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• 2019

본 논문에서는 검색엔진 최적화(SEO; Search Engine Optimization)에 인공지능 기법을 접목하여, 자동화된 SEO 도구 설계 및 구현을 목표로 한다. 기존의 SEO 온-페이지(On-page) 최적화 기법들은 웹페이지 관리자들의 경험적 지식에 의존하는 한계점을 보이고 있다. 이는 SEO 성능에 영향을 끼칠 뿐 아니라, 웹페이지 관리자들에게도 SEO 도입의 장벽으로 작용한다. 따라서, 위 문제를 해결하기 위하여 메타데이터의 효과적인 구성을 위해 다음과 같은 3단계의 접근법을 제안하고자 한다. i) 상위 랭킹 웹사이트들의 메타데이터를 추출한다. ii) 어텐션 메커니즘에 기반한 LSTM(Long Short Term Memory)을 이용하여 사용자 질의어와의 관련성 높은 메타데이터를 생성한다. iii) GAN(Generative Adversarial Network) 모델을 통하여 학습함으로써 전반적으로 성능을 높여주는 기법을 제안한다. 본 연구결과는 기업의 온라인 마케팅 프로세스를 평가하고 개선하기 위한 최적화 도구로서 유용하게 활용될 것으로 기대한다.

• 대한환경공학회지
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• 제28권4호
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• pp.438-446
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• 2006

팔당호 경안천 하류 정체수역에서 퇴적물 인 용출 저감을 위한 capping 소재를 개발하고자 실험실 규모의 batch test를 수행하였다. 조사지역 퇴적물 평균 입도는 7.7 ${\phi}$로 매우 세립하고, 유기탄소 함량은 2.4%로 매우 높게 나타났다. 최적의 capping 소재 선정을 위한 인 용출 실험을 위해 150 L 반응기 5개에 모래층, powder-gypsum($CaSO_4{\cdot}2H_2O$), granule-gypsum, 복합층(gypsum+sand)로 capping을 한 경우와 control을 45일간 비교 평가하였다. 모래로 capping할 경우, 퇴적물로부터 용출되는 인을 약 50% 차단 가능한 것으로 나타났다. 그러나 모래층 1 cm로는 $CH_4$ gas 발생으로 인한 퇴적물의 재부유와 유기물 분해에 의한 수층 용존산소 감소(3 mg/L 이하)를 초래하는 것으로 나타났다. 따라서 모래로 capping을 할 경우에는 모래층이 더 높아져야 할 것으로 판단된다. powder-Gypsum과 granule-Gypsum은 80% 이상의 인 용출 저감 효과를 보였으나 수층 ${SO_4}^{2-}$ 농도가 증가되어 상수원보호구역에 적용하기 어려운 것으로 나타났다. 따라서 ${SO_4}^{2-}$의 용해도를 감소시키기 위해 Fe-Gypsum, $SiO_2$-gypsum 소재를 개발하였다. powder-Gypsum은 물과 결합시 경화되어 퇴적물 층위에 공극이 전혀 없는 차단막을 만들기 때문에 gypsum 층에 crack이 생길 경우, $CH_4$ gas 발생으로 인한 인 용출이 한꺼번에 일어날 수 있다. 복합층(granule-Gypsum+sand(1 cm))으로 capping을 할 경우, 인 용출 차단 효과가 높을 뿐만 아니라, ${SO_4}^{2-}$ 농도 역시 powder-Gypsum, granule-Gypsum 보다 수층으로 용출이 적어 상수원보호구역에 적합한 것으로 나타났다. Gypsum으로 capping을 할 경우, 빠른 초기속성작용(early diagenesis)과 ${SO_4}^{2-}$ 농도가 퇴적물에 충분히 공급되어 SRB(sulfate reducing bacteria)의 활성이 높아져 methanogensis의 진행을 저하시킬 수 있는 것으로 나타났다.

• 한방비만학회지
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• 제23권2호
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• pp.69-77
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• 2023

Objectives: Atriplex gmelinii C. A. Meyer is a halophyte belonging to the Chenopodiaceae family, and its young leaves and stems are used as fodder for livestock. The aim of the present study was to investigate the effects of A. gmelinii extract and its solvent fractions on lipid accumulation during adipogenesis of 3T3-L1 preadipocytes. Methods: The samples of A. gmelinii were separately extracted using methylene chloride and methanol. Subsequently, they were combined to formulate the initial extract, which was then partitioned based on polarity to prepare solvent fractions. Oil Red O staining was employed to measure lipid accumulation during the differentiation of 3T3-L1 preadipocytes. To verify cytotoxicity in 3T3-L1 cells, MTT assays were conducted. The expression levels of transcription factors in 3T3-L1 preadipocytes were measured through Western blotting analysis. Results: At 50 ㎍/mL, treatment of A. gmelinii extract and its solvent fractions during the differentiation of 3T3-L1 preadipocytes significantly diminished lipid accumulation with no noteworthy cytotoxicity on cell viability. Additionally, when investigating the biochemical pathways that underlie the prevention of lipid accumulation using solvent fractions, it was found that the n-BuOH and n-hexane fractions significantly decreased the expression of key transcription factors involved in the generation of fat, such as peroxisome proliferator-activated receptor γ (PPARγ), CCAAT/enhancer binding protein α (C/EBPα), and sterol regulatory element-binding protein-1c (SREBP1c). Conclusions: These findings indicate that A. gmelinii can effectively reduce the accumulation of fat in 3T3-L1 adipocytes, making it a potentially valuable material for mitigating and preventing obesity.