전기화학적 기법에 의한 미생물연료전지 내부저항 특성 파악 및 전력관리시스템 연계 전압 변화와 유기물 저감에 미치는 영향

장재경,박혜민,김태영,양윤석,여정진,강석원,백이,권진경,Jang, Jae Kyung,Park, Hyemin,Kim, Taeyoung,Yang, Yoonseok,Yeo, Jeongjin,Kang, Sukwon,Paek, Yee,Kwon, Jin Kyung 대한의용생체공학회 2018 의공학회지 Vol.39 No.5

The internal resistance of microbial fuel cell (MFC) using stainless steel skein for oxidizing electrode was investigated and the factors affecting the voltage generation were identified. We also investigated the effect of power management system (PMS) on the usability for MFC and the removal efficiency of organic pollutants. The performance of a stack microbial fuel cell connected with (PMS) or PMS+LED was analyzed by the voltage generation and organic matter reduction. The maximum power density of the unit cells was found to be $5.82W/m^3$ at $200{\Omega}$. The maximum current density was $47.53A/m^3$ without power overshoot even under $1{\Omega}$. The ohmic resistance ($R_s$) and the charge transfer resistance ($R_{ct}$) of the oxidation electrode using stainless steel skein electrode, were $0.56{\Omega}$ and $0.02{\Omega}$, respectively. However, the sum of internal resistance for reduction electrode using graphite felts loaded Pt/C catalyst was $6.64{\Omega}$. Also, in order to understand the internal resistance, the current interruption method was used by changing the external resistance as $50{\Omega}$, $300{\Omega}$, $5k{\Omega}$. It has been shown that the ohm resistance ($R_s$) decreased with the external resistance. In the case of a series-connected microbial fuel cell, the reversal phenomenon occurred even though two cells having the similar performance. However, the output of the PMS constantly remained for 20 hours even when voltage reversal occurred. Also the removal ability of organic pollutants (SCOD) was not reduced. As a result of this study, it was found that buffering effect for a certain period of time when the voltage reversal occurred during the operation of the microbial fuel cell did not have a serious effect on the energy loss or the operation of the microbial fuel cell.

Magnetic States of Iron-based Superconducting Compounds: A Comparative Study with Fe3Al Alloy

장재경,이주열 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.66 No.4

The magnetic moments per Fe atom in the high-Tc iron-based superconducting compoundsBaFe2As2 and LaFeAsO obtained from first-principles calculations with the local-spin-density approximationare much larger than those obtained from experiments. To resolve the contradictoryresults between theory and experiment we employed the so-called +U technique with negative Uin the first-principles calculation. The calculated values with negative U, −0.09 Ry and −0.10 Ryfor BaFe2As2 and LaFeAsO, respectively, are in excellent agreement with the experimental ones. By comparing the differences in the d-orbital occupation numbers and spin densities calculated byusing a simple Generalized-Gradient approximation (GGA) and the GGA+U with negative U, wefound the magnetic moments of the two compounds to be similar to the case of the low-spin stateof the metamagnetic Fe3Al alloy.

가축분뇨를 이용한 미생물연료전지내 미생물군집의 탄소 기질 이용도에 관한 연구

장재경,홍선화,이미향,유영선,장인섭,김종구,강연구,이은영 한국폐기물자원순환학회 2012 한국폐기물자원순환학회지 Vol.29 No.8

This study was attempted to evaluate the change of microbial community in inoculums, lag, and stationary phase using the community level physiological profiles (CLPP) base on C-substrate utilization. It was to ascertain the characterizing microbial community over time in the enrichment step of microbial fuel cells. Microbial fuel cell is a device that converts chemical energy to electricity with aid of the catalytic reaction of microorganisms using C-substrate included wastewater. Microbial fuel cells enriched by a mixture of anaerobic digestive sludge of the sewage treatment plant and livestock wastewater were used. The current after enrichment was generated about 0.84 ± 0.06 mA. Microbial community in inoculums, lag and stationary phase used amine group, phosphorylated chemical group, and carboxylic acid group (some exclusion). However, phenolic compound did not use by microorganisms in lag and stationary phase. It means that there are not the microorganisms capable of decompose the phenol in microbial fuel cell enriched by livestock wastewater. In case of substrates of amino acid and carbohydrates group, these C-substrates were only used by microorganisms in the stationary phase. It may be that electrochemically active microorganisms (EAM) which we want to know should utilize the better these C-substrates than that of lag phase. This study showed that the electrochemically active bacteria that can be distinguished by electron changes of C-substrate utilization over time could be separated.

산소 유속 변화에 따른 마이크로버블에 의한 가축분뇨 제거능

장재경,진유정,김태영,강석원,성제훈,백이,김영화 대한환경공학회 2017 대한환경공학회 학술발표논문집 Vol.2017 No.11

유기성폐기물 처리 및 재활용 : 미생물연료전지를 이용한 에너지회수 및 슬러지 감량화

장재경,조경숙,김병홍 한국폐기물자원순환학회(구 한국폐기물학회) 2007 한국폐기물자원순환학회 추계학술발표논문집 Vol.2007 No.-

서처와 정보검색

장재경,Jang, Jae-Gyeong 한국데이터베이스진흥원 1995 디지털콘텐츠 Vol.8 No.-

우리말 문헌정보검색을 위한 지식베이스 설계에 관한 연구

장재경,Chang, Jae-Gyong 한국정보관리학회 1986 정보관리학회지 Vol.3 No.1

본 연구는 인공지능의 한 응용분야인 전문가 시스팀중, 그의 핵심 영역인 지식베이스와 추론기제를 문헌정보검색을 위하여 개발하였다. 이는 어느 특정주제를 검색하고자 하는 이용자는 일반적으로 그 주제분야에 대한 선행지식이 부족할 것이다는 가정하에 선행지식이 부족한 이용자의 질의어를 시스팀에서 지적으로 처리하도록 지식베이스를 설계하어 결과적으로 정보검색의 효율을 향상시킴을 목적으로 한다. 또한 우리말 문헌정보의 주제어에서 주가 되는 복합명사의 특성을 구조적으로 분석하여 지식베이스에 포함시켰다. This study is an attempt to develop a knowledge base with Inference mechanism for document retrieval, which is the core element of expert system. The purpose of this study is to design the knowledge base in order to intellectually process user queries eventually improving the effectiveness of information retrieval, under the assumption that the user who wants to search a certain subject generally lack the prior knowledge about that subject. In this paper, some characteristics of Korean complex nouns are structurally analyzed and are represented in the knowledge base.

레이저 유도 충격파의 실험적인 제어를 기반으로 한 점형 파이로 충격파 응답 스팩트럼 예측 알고리즘 개발

장재경,이정률 한국항공우주학회 2014 한국항공우주학회 학술발표회 논문집 Vol.2014 No.4

충격파 응답 스팩트럼의 예측은 안전한 점화 장치의 작동을 위해 중요하다. 본 연구는 비파괴적으로 레이저 유도 충격파를 이용하여 파이로 충격파 SRS 예측 방법을 제안한다. 폭약과 레이저 자극을 이용한 서로 다른 두 가지 실험이 수행된다. 최적의 레이저 유도 충격파 측정을 위한 실험적인 조건은 파이로 충격파의 예측을 위해 조사된다. 이를 위해 빔의 사이즈, 에너지, 그리고 플루언스와 같은 변수가 고려된다. 측정된 두 충격파의 유사성은 MAD 를 기반으로 비교된다. 실험적으로 획득된 최적의 실험 조건은 파이로 충격파의 전파 경로에 위치한 네 개의 지점에 적용된다. 각 지점에서 SRS 을 일치시키기 위해 레이저 유도 충격파는 증폭되고 이때, 세 가지 gain 컨셉이 제안된다. 제안 된 기술은 pyro 충격파와 높은 유사성을 보이는 SRS 를 얻기 위해 비 파괴 파이로 SRS 예측을 가능하게 한다. The prediction of shock response spectrum (SRS) is important for safe operation of pyrotechnical devices. This paper proposed a nondestructive pyro SRS prediction method using laser-induced shock. Two different experiments are performed using explosive and laser excitation. The optimum laser-induced shock experimental conditions to predict pyroshock are investigated, where the considered parameters are the size, energy and fluence of the laser beam. The similarity of both shock waves is evaluated based on MAD. The experimentally found optimal conditions are also applied to four points on the path of the pyroshock propagation. To match the SRS at each point, the laser-induced shock is amplified, where three different gain concepts are proposed. The proposed technology enables nondestructive pyro SRS prediction to obtain an SRS with high similarity to the pyroshock.

단지 접근성 및 대형 부품의 신뢰성 향상에 따른 해상풍력단지 O&M 성능 비교

장재경,박미호,박종포 한국풍력에너지학회 2020 풍력에너지저널 Vol.11 No.3

In the renewable energy field, wind energy has grown the most over the past decade. Many wind farms are being developed offshore to overcome the limitations of onshore wind farms and to utilize strong and steady wind resources. However, the initial investment costs for offshore farms are larger than for onshore ones, and the costs of operation and maintenance may be substantially higher imited maintenance and accessibility to the wind turbines due to weather. Maintenance strategy and planning optimization can significantly reduce operating costs. This process is important for offshore wind farms to reduce the high economic risks associated with uncertainties about the accessibility and reliability of wind turbine systems. In this study, O&M performance was compared with a case study in which different maintenance strategies were reflected. We investigated the advantages of reducing the distance between the O&M port and the wind farm and applying a condition-based maintenance strategy for the large components of wind turbines. As a result, it is possible to improve the availability of wind turbines and reduce maintenance costs by improving accessibility to the farm and the reliability of large parts.

광역주파수 음향반사자료의 K-L 변환을 이용한 해저면 분류: 지질음향 모델링을 위한 유용한 방법

장재경,김한준,주형태,석봉출,박건태,유해수,양승진,Chang, Jae-Kyeong,Kim, Han-Joon,Jou, Hyeong-Tae,Suk, Bong-Chool,Park, Gun-Tae,Yoo, Hai-Soo,Yang, Sung-Jin 한국해양학회 1998 바다 Vol.3 No.3

광대역 주파수변조(wide-band FM) 선호를 음원으로 사용하는 Chirp sonar 시스템을 이용하여 획득한 음향반사 자료의 통계학적 처리를 통하여 해저면을 분류하였다. 음향학적 분류변수로서 Chirp 자료의 K-L(Karhunen-Lo$\grave{e}$ve) 변환을 이용하여 계산된 유사도 지수(similarity index)를 고안하였다. 유사도 지수는 근접한 트레이스 자료들에 포함된 공통된 반사신호성분의 양을 지시하므로 해저면 퇴적물의 성분에 따른 음향학적 거침도를 반영한다고 할 수 있다. 유사도 지수는 0에서 1사이의 값을 가지며, 각기 다른 퇴적상을 나타내는 지점에서 획득된 Chirp 자료를 처리한 결과, 퇴적물의 성분이 균질할수록, 입자의 크기가 작을수록, 그리고 연한 퇴적층일수록 증가하는 것을 관측할 수 있었다. 실제의 응용 예로서 제주도 성산포 해역을 이 방법으로 분류하였으며, 그 결과를 검증하기 위해 동일해역에서 획득된 side-scan sonar 자료 및 퇴적물로부터 해석된 해저면의 퇴적상과 비교하였다. 그 결과 음향자료의 유사도 지수에 의해 분류된 해저면은 실제의 퇴적상을 매우 잘 반영할 뿐만 아니라 퇴적물 성분의 특성에 따른 음향반응을 더욱 세밀히 나타내었다. 그러므로 이러한 방법은 음향자료로부터 직접 해저면을 분류하는 지질음향 모델링으로서 매우 효과적이다. We introduce a statistical scheme to classify seabed from acoustic profiling data acquired using Chirp sonar system. The classification is based on grouping of signal traces by similarity index, which is computed using the K-L (Karhunen-Lo$\grave{e}$ve) transform of the Chirp profiling data. The similarity index represents the degree of coherence of bottom-reflected signals in consecutive traces, hence indicating the acoustic roughness of the seabed. The results of this study show that similarity index is a function of homogeneity, grain size of sediments and bottom hardness. The similarity index ranges from 0 to 1 for various types of seabed material. It increases in accordance with the homogeneity and softness of bottom sediments, whereas it is inversely proportional to the grain size of sediments. As a real data example, we classified the seabed off Cheju Island, Korea based on the similarity index and compared the result with side-scan sonar data and sediment samples. The comparison shows that the classification of seabed by the similarity index is in good agreement with the real sedimentary facies and can delineate acoustic response of the seabed in more detail. Therefore, this study presents an effective method for geoacoustic modeling to classify the seafloor directly from acoustic data.