Cu-Xwt%Sn 합금 위에 선택적 산화막 SnO2 형성 유·무에 따른 내변색 및 내부식특성 평가

최지웅 ( Ji Woong Choi ),김혜성 ( Hye Sung Kim ) 한국열처리공학회 2021 熱處理工學會誌 Vol.34 No.6

In this study, anti-tarnishing and corrosion characteristics of a single β1’ and Bangjja Yugi alloy in the Cl¯ ion environment before and after potentiostatic electrolysis treatment were compared. Stable and uniform SnO₂ oxide film with several nanometer thickness is formed after potentiostatic electrolysis treatment. In the case of Bangjja Yugi prior to potentiostatic electrolysis (PE) treatment for exposure in Cl¯ environment, tarnishing occurs rapidly within 0.5hr, whereas PE treated Bangjja Yugi indicates stable surface without tarnishing up to 3hr. Especially, it is noticeable that anti-tarnishing and corrosion characteristic of PE treated single β1’, which were significantly improved by 3 times and 15 times, respectively, compared to conventional Bangja Yugi. (Received Septemer 16, 2021; Revised Septemer 27, 2021; Accepted October 7, 2021)

OWL DL을 사용한 GPM 핵심 모델의 구현

최지웅(Ji-Woong Choi),박호병(Ho-Byung Park),김형진(Hyung-Jean Kim),김명호(Myung-Ho Kim) 한국컴퓨터정보학회 2010 韓國컴퓨터情報學會論文誌 Vol.15 No.1

GPM(Generic Product Model)은 원자력 플랜트의 라이프 사이클 데이터를 통합, 공유하기 위하여 일본의 Hitachi에서 개발한 공통 데이터 모델이다. GPM은 추상 모델 성격의 GPM 핵심 모델과 핵심 모델의 기술을 위한 구현 언어 그리고 구현 언어로 작성된 참조 라이브러리로 구성되어 있다. GPM 핵심 모델은 객체들 사이의 의미가 부여된 관계 정의를 통하여 객체 의미 관계 네트워크 모델을 구성할 수 있는 특성이 있다. 초기의 GPM은 GPM 핵심 모델의 특성을 반영한 신택스의 GPML이라는 구현 언어를 개발하여 제공하였으나 원자력 플랜트 라이프 사이클동안 다양한 목적으로 GPM 데이터 모델에 접근하는 이기종 애플리케이션들과의 상호운용성을 위하여 XML을 기반으로 하는 GPM-XML로 교체되었다. 그러나 현재 GPM-XML을 사용하여 구축한 GPM 데이터 모델이 객체 의미 관계 네트워크 모델로서 활용되기 위한 GPM-XML 기반의 연구가 미비한 상태이다. 따라서 본 논문에서는 객체 의미 관계 네트워크와 유사한 성격의 온톨로지를 기술할 수 있으며 이를 지원하는 기술 표준 및 도구들이 이미 활용 가능한 수준에 있는 OWL을 GPM 핵심 모델을 위한 구현 언어로서 제안한다. OWL은 XML 기반의 RDF/XML 형식으로 기술될 수 있으므로 상호운용성 또한 보장받을 수 있다. 본 논문은 OWL의 세 가지 하위 언어 사양 중 추론기능을 완벽히 제공받을 수 있는 가운데 문법적 제약이 가장 덜 엄격한 OWL DL을 사용한다. 본 논문은 OWL DL을 GPM 핵심 모델의 구현 언어로서 사용하기 위하여 GPM과 OWL 두 모델 사이의 차이점을 도출한 후 이를 해소할 수 있는 방법을 제안하며 이 방법을 적용하여 GPML로 작성된 참조 라이브러리를 OWL DL 기반의 온톨로지로 변환하여 구축하는 방법을 기술한다. GPM(Generic Product Model) developed by Hitachi in Japan is a common data model to integrate and share life cycle data of nuclear power plants. GPM consists of GPM core model, an abstract model, implementation language for the model and reference library written in the language. GPM core model has a feature that it can construct a semantic network model consisting of relationships among objects. Initial GPM developed and provided GPML as an implementation language to support the feature of the core model, but afterwards the GPML was replaced by GPM-XML based on XML to achieve data interoperability with heterogeneous applications accessing a GPM data model. However, data models written in GPM-XML are insufficient to be used as a semantic network model for lack of studies which support GPM-XML and enable the models to be used as a semantic network model. This paper proposes OWL as the implementation language for GPM core model because OWL can describe ontologies similar to semantic network models and has an abundant supply of technical standards and supporting tools. Also, OWL which can be expressed in terms of RDF/XML based on XML guarantees data interoperability. This paper uses OWL DL, one of three sublanguages of OWL, because it can guarantee complete reasoning and the maximum expressiveness at the same time. The contents of this paper introduce the way how to overcome the difference between GPM and OWL DL, and, base on this way, describe how to convert the reference library written in GPML into ontologies based on OWL DL written in RDF/XML.

복층터널 비상대피구간 유지관리에 따른 중간슬래브 응력 분석

최지웅 ( Choi Ji Woong ),박범근 ( Park Beom Keun ),김성민 ( Kim Seong-min ) 한국구조물진단유지관리공학회 2019 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.23 No.1

The stresses occurred in the middle slab at the areas of the emergency passageway in a double-deck tunnel are analyzed when the slab is lifted to replace bearing pads placed between the middle slab and supporting bracket as a maintenance process. The middle slab can be lifted at several different points near the emergency passageway areas and the stresses of the middle slab depend on the lifting points. This study presents the effect of the lifting location of the middle slab on the stress occurrence for the maintenance work of replacing bearing pads under the middle slab near the emergency passageway areas.

한강수계의 시공간적 수질변화 특성 및 연속적 인공호의 경험적 모델

최지웅 ( Ji Woong Choi ),안광국 ( Kwang Guk An ) 한국환경생태학회 2015 한국환경생태학회 학술대회지 Vol.2015 No.2

The objective of this study was to determine temporal patterns and longitudinal gradients of water chemistry at eight artificial reservoirs and ten streams within the Han-River watershed along the main axis of the headwaters to the downstreams during 2009-2010. Also, we evaluated chemical relations and their variations among major trophic variables such as total nitrogen (TN), total phosphorus (TP), and chlorophyll-a (CHL-a) and determined intense summer monsoon and annual precipitation effects on algal growth using empirical regression model. Stream water quality of TN, TP, and other parameters degradated toward the downstreams, and especially was largely impacted by point-sources of wastewater disposal plants near Jungrang Stream. In contrast, summer river runoff and rainwater improved the stream water quality of TP, TN, and ionic contents, measured as conductivity (EC) in the downstream reach. Empirical linear regression models of log-transformed CHL-a against log-transformed TN, TP, and TN:TP mass ratios in five reservoirs indicated that the variation of TP accounted 33.8% (R2=0.338, p<0.001, slope=0.710) in the variation of CHL-a and the variation of TN accounted only 21.4% (R2=0.214, p<0.001) in the CHL-a. Overall, our study suggests that, primary productions, estimated as CHL-a, were more determined by ambient phosphorus loading rather than nitrogen in the lentic systems of artificial reservoirs, and the stream water quality as lotic ecosystems were more influenced by a point-source locations of tributary streams and intense seasonal rainfall rather than a presence of artificial dam reservoirs along the main axis of the watershed.

계절성 강우패턴 및 토지 이용도에 따른 남한강의 수질변화 양상

최지웅 ( Ji-woong Choi ),김선영 ( Seon-young Kim ),안광국 ( Kwang-guk An ) 한국환경생태학회 2016 한국환경생태학회 학술대회지 Vol.2016 No.2

본 연구는 남한강 수계의 토지이용도에 따른 계절별, 연별 수질 특성 분석을 위해 2001년부터 2010년 기간 동안72개 하천을 대상으로 수온 (WT), 전기전도도 (EC), 용존산소 (DO), 유기물 오염도 (BOD, COD), 총부유물 (SS)농도 및 영양염류 (TN, TP) 항목들에 대한 분석을 실시하였다. 토지 이용도에 대한 계절적 수질경향을 분석한 결과에 따르면, 유기물의 오염지표인 BOD와 COD는 농지형 하천과 주거형 하천에서 갈수기에 높은 값을 보였으며, 총부유물 및 전기전도도는 강우량과 높은 연관성을 보였다. 총질소 (TN)와 총인 (TP)은 토지이용도 별 농도 차가 큰 것으로 분석되었는데, TN과 TP 모두 주거형 하천에서 산림형 및 농지형 하천들 보다 뚜렷하게 높은 농도를 보였고, 전기전도도 또한 주거형 하천에서 가장 높은 수치를 보였다. 토지이용도 비율에 따른 수질특성으로는 산림형 하천의 비율이 높을수록 BOD, COD, TN, TP, SS, EC의 최대치는 각각 낮은값을 보였다. 전기전도도의 경우 산림형 토지이용 비율이 증가함에 따라 감소하는 경향을 보인 반면, 농지의 토지이용 비율이 증가할수록 증가하는 경향을 보이는 것으로 나타났다. 농지형 토지이용 비율에 따른 수질 특성을 비교해 보면, DO는 농지 비율과는 관계가 미미한 것으로 나타났고, BOD, COD는 농지 비율이 높은 지점에서 최대치가 증가하는 것으로 나타났다. 하천 차수 (Stream order)에 따른 수질 특성을 분석한 결과, 4차 하천에서 유기물 오염(BOD, COD) 및 인 (P). 질소 (N)에 의한 오염부하가 가장높게 나타났으며, 4차 이후의 하천들에서는 유량증가에 의한 희석과 물리·화학적 자정작용 등에 의해 수질이 향상되는 것으로 나타났다. 본 연구를 종합해보면, 남한강 수계에서 인과 질소의 오염부하 및 유기물 오염은 주거형 하천과농지형 하천에서 가장 큰 것으로 나타났고, 이를 관리하기 위해서는 각 하천에 대한 BOD와 COD의 농도 저감 및 4차하천에 대한 수질관리를 통하여 수질을 개선할 수 있을 것으로 판단된다.

모니터링 기법 적용에 따른 어종별 생존율 평가 및 어도에서 어류이동성 평가

최지웅 ( Ji Woong Choi ),안광국 ( Kwang Guk An ) 한국환경과학회 2014 한국환경과학회지 Vol.23 No.8

The objective of this study was to evaluate survival rate and fish movement (migration) using a tagging approach of passive integrated transponder (PIT) in Juksan Weir, which was constructed as a four major river restoration projects. For this study, survival rates of each fish species and the mobility of fish individuals were analyzed during 2 weeks by the insertion of PIT tags to various fish species in the laboratory. According to tagging tests in the laboratory, the survival rate 37.5% (30 survivals of 80 individuals) after the insertion of PIT tags. The survival rate of Carassius auratus and Hemibarbus labeo was 100% and 80% after the insertion of the tags, respectively, whereas it was only 13.3% for Zacco platypus. In the field experiments of Juksan Weir, 6 species and 157 individuals from 8 species (563 individuals) were detected in the fixed automatic data-logging system, indicating a detection rate of 27.9% in the fishway of Juksan Weir. In the meantime, some species with no or low detection rates in the fixed automatic data-logging system were turn out to be stagnant-type species, which prefer stagnant or standing water to live.

GA를 이용한 전력 계통의 FACTS 최적 할당 연구

최지웅(Ji-Woong Choi),이호준(Ho-Jun Lee),프라스티안토노(Adji Prastiantono),윤민한(Minhan Yoon) 대한전기학회 2023 대한전기학회 학술대회 논문집 Vol.2023 No.10-2

강섬유 보강 고강도 철근콘크리트 기둥의 전단강도 기여분 평가

최지웅(Choi, Ji Woong),최창식(Choi, Chang Sik) 한국콘크리트학회 2017 한국콘크리트학회 학술대회 논문집 Vol.29 No.1

인공보 건설에 따른 어류의 이동성 변화 및 어도효율성 평가를 위한 다양한 기법 적용

최지웅 ( Ji-woong Choi ),이상재 ( Sang-jae Lee ),안광국 ( Kwang-guk An ) 한국환경생태학회 2016 한국환경생태학회 학술대회지 Vol.2016 No.2

Major objective of the research was to analyze impacts of fish movements and migrations after the constructions of weirs and fishways using various fish monitoring methodologies during 2011 - 2014. In the presentation, we introduce some physical, chemical, and biological impacts based on the serial discontinuity concept and demonstrate the results of fish monitoring from our field surveys. The specific targets of our research are summarized as follows. First, fish species distribution and compositions were evaluated in the tributaries and mainstem sites of Yeongsan-River watershed after the completion of the fishway and weir constructions in 2011. Second, we analyzed the impacts of fish migrations and fish passage in fishways and weirs. Third, we traced the passage of migratory and non-migratory fishes using various fish tracking methodologies including Passive Integrated Transpondents (PITs) tags, ultrasonic telemetry, video recording, trap-setting, and ultra eco-sounder monitoring approaches, and evaluated some impacts of the weir/fishway constructions. Lastly, we are trying to establish a "national protocol of fish monitoring methodology" for the surveys of the weirs and fishways in Korea. Currently, this study is just finished in December 2014. Our outcomes are preliminary results now, but will contribute to ecological conservation of rivers and streams with weirs or fishways after the completion of our research.

강섬유 혼입률에 따른 고강도 철근콘크리트 기둥의 전단강도에 대한 실험적 연구

최지웅(Choi, Ji-Woong),배백일(Bae, Baek-Il),최창식(Choi, Chang-Sik) 대한건축학회 2017 大韓建築學會論文集 : 構造系 Vol.33 No.4

The purpose of this study is to evaluate the shear strength of steel fiber reinforced concrete columns quantitatively through the experimental program. For this purpose, the volume fraction of steel fiber is determined to main parameter (0%, 1%, 2%), and the cyclic lateral loading tests of columns were performed with constant axial loads. According to the test results, the shear strength of the column with 1% of steel fiber increased 1.61 times and shear strength of the column with 2% of steel fiber increased 1.67 times compared to RC column. Also, it was investigated that the cracks are distributed and angle of cracks is reduced in specimens with steel fiber. This resulted in an increase of the number of transverse reinforcement located on the crack face. Therefore, the shear strength of columns was evaluated by dividing the shear strength contribution by the concrete, transverse reinforcement, and the shear strength increase by the steel fiber. As a result, the shear strength contributions of concrete increased about 29% with 1% of steel fiber and increased about 36% with 2%. Also, the shear strength contributions of transverse reinforcement increased when steel fiber is mixed.