• 한국해안·해양공학회논문집
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• 제31권3호
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• pp.158-169
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• 2019

추계학적 확률과정의 하나인 감마 확률과정을 이용하여 구조물의 잔류유효수명을 확률론적으로 예측할 수 있는 수학적 모형을 수립하였다. 수립된 모형은 과거부터 현재 시점까지 관측된 피해자료와 관련된 표본의 불확실성과 장래 시간 진행에 따른 누적피해의 불확실성을 올바로 고려할 수 있다. 또한 최소자승법과 모멘트법을 함께 사용하여 경사제의 재령, 운용환경 그리고 피해이력을 고려할 수 있는 모수 추정법을 제시하였다. 먼저 현재 재령의 단일 피해 자료를 갖는 임의의 조건에서 모수에 대한 민감도 분석을 수행하여, 잔류유효수명과 관련된 여러가지 거동 특성들을 분석하였다. 또한 잔류유효수명 예측모형을 경사제에 적용하였다. 경사제 피복재의 피해 이력에 대한 실험자료를 이용하여 감마 확률과정의 모수를 추정하였는데 실험자료와 매우 잘 일치하였다. 해석 결과에 의하면 현재 시점으로부터 상당히 오랜 시간이 경과하면 파괴한계를 초과할 확률이 일정한 값으로 수렴해야 하는 제약 조건을 잘 만족하였다. 한편 기대 잔류유효수명은 피해 이력의 거동 특성에 따라 각기 다르게 산정되었다. 특히 피해의 변동계수가 크면 추계학적으로 산정된 기대 잔류유효수명은 결정론적 회기모형의 해석 결과와 큰 차이를 보인다. 이는 해석과정에 포함된 불확실성의 영향으로 판단된다. 변동계수가 크면 파괴한계에 도달하는 시간의 분포가 넓게 퍼지기 때문이다. 따라서 본 연구에서 수립된 추계학적 잔류유효수명 예측모형은 현재 재령에서 경사제의 피해에 대한 확률적 평가를 수행할 수 있을 뿐만 아니라 장래 시간의 진행에 따른 누적피해의 불확실성을 올바로 고려할 수 있다.

• 전자공학회논문지CI
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• 제48권4호
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• pp.43-50
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• 2011

센서 네트워크는 향후 유비쿼터스 환경 서비스 구현을 위한 기본 인프라와 서비스 영역 정보수집 및 기기제어 등에 중요한 역할을 담당할 것으로 예상되며, 최근 센서 네트워크 기반 시스템에서의 에너지의 효율적 공급 방안에 대한 관심이 높아지고 있다. 본 논문에서는 계층적 구조 클러스터 기반 센서 네트워크에서 네트워크 생명주기를 최대로 유지하면서 클러스터 헤드에 공급되는 에너지를 최소화하는 센서 네트워크 에너지 공급 문제를 구성한다. 이 문제에 대한 해를 수학적으로 구하고 이를 기반으로 각 클러스터 헤드에 공급하는 에너지양을 결정하는 기법을 제안한다. 또한 모의실험을 통해 제안된 방식이 단순히 클러스터 헤드마다 최대 공급가능 에너지를 제공하는 것에 비해 주어진 실험 조건에서 최소 33% 이상의 에너지 절감 효과가 있음을 보였다.

• Journal of Microbiology and Biotechnology
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• 제27권3호
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• pp.552-560
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• 2017

Quorum quenching (QQ) bacteria entrapped in a polymeric composite hydrogel (QQ medium) have been successfully applied in membrane bioreactors (MBRs) for effective biofouling control. However, in order to bring QQ technology closer to practice, the physical strength and lifetime of QQ media should be improved. In this study, enforcement of physical strength, as well as an extension of the lifetime of a previously reported QQ bacteria entrapping hollow cylinder (QQ-HC), was sought by adding a dehydration procedure following the cross-linking of the polymeric hydrogel by inorganic compounds like $Ca^{2+}$ and boric acid. Such prepared medium demonstrated enhanced physical strength possibly through an increased degree of physical cross-linking. As a result, a longer lifetime of QQ-HCs was confirmed, which led to improved biofouling mitigation performance of QQ-HC in an MBR. Furthermore, QQ-HCs stored under dehydrated condition showed higher QQ activity when the storage time lasted more than 90 days owing to enhanced cell viability. In addition, the dormant QQ activity after the dehydration step could be easily restored through reactivation with real wastewater, and the reduced weight of the dehydrated media is expected to make handling and transportation of QQ media highly convenient and economical in practice.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권8호
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• pp.3621-3640
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• 2016

In the process of k-coverage of the target node, there will be a lot of data redundancy forcing the phenomenon of congestion which reduces network communication capability and coverage, and accelerates network energy consumption. Therefore, this paper proposes a novel energy balanced k-coverage control algorithm based on probability model (EBKCCA). The algorithm constructs the coverage network model by using the positional relationship between the nodes. By analyzing the network model, the coverage expected value of nodes and the minimum number of nodes in the monitoring area are given. In terms of energy consumption, this paper gives the proportion of energy conversion functions between working nodes and neighboring nodes. By using the function proportional to schedule low energy nodes, we achieve the energy balance of the whole network and optimizing network resources. The last simulation experiments indicate that this algorithm can not only improve the quality of network coverage, but also completely inhibit the rapid energy consumption of node, and extend the network lifetime.

• 전기학회논문지P
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• 제66권4호
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• pp.236-241
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• 2017

This paper presents a single-phase grid connected voltage-ed inverter with a power decoupling circuit. In the single-phase grid connected voltage-ed inverter, it is well known that a power pulsation with twice the grid frequency is contained in the input power. In a conventional voltage type inverter, electrolytic capacitors with large capacitance have been used in order to smooth the DC voltage. However, lifetime of those capacitors is shortened by the power pulsation with twice grid frequency. The authors have been studied a active power decoupling(APD) method that reduce the pulsating power on the input DC bus line, this enables to transfer the ripple energy appeared on the input DC capacitors into the energy in a small film capacitor on the additional circuit. Hence, extension of the lifetime of the inverter can be expected because the small film capacitor substitutes for the large electrolytic capacitors. Finally, simulation and experimental results are discussed.

• 한국경영과학회:학술대회논문집
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• 한국경영과학회 2003년도 추계학술대회 및 정기총회
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• pp.187-190
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• 2003

Since the early 1980s, the concept of relationship management in marketing area has gained its importance. Acquiring and retaining the most profitable customers are serious concerns of a company to perform more targeted marketing campaigns. For effective CRM (Customer Relationship Management), it is important to gather information on customer value. Many researches have been performed to calculate customer value based on CLV (Customer Lifetime Value). It, however, has some limitations. It is difficult to consider the churn of customers, because the previous prediction models have focused mainly on expected future cash flow derived from customers'past profit contribution. In this paper we suggest a CLV model considering past profit contribution, potential benefit, and churn probability of a customer. We also cover a framework for analyzing customer value and segmenting customers based on their value. Customer value is classified into three categories: current value, potential value and customer loyalty. Customers are segmented according to the three categories of customer value. A case study on calculating customer value of a wireless communication company will be illustrated.

• 경영과학
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• 제31권4호
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• pp.151-163
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• 2014

The sports industry is expected to develop into a huge business through convergence with existing industries such as the broadcasting/information communications, health/medicine, and entertainment/leisure. This paper aims to extract and analyse the candidated promising sports industries at the national level in order to promote them in the long term, and adopts a policy-based approach to such efforts. To extract promising sports industries at the national level, a methodology that considers economic effects such as global competitiveness, technological characteristics, and the creation of jobs, as well as technical development projects, should be adopted. In this study, It was extracted 59 candidated promising sports industries using literature review and expert opinions. As a result of in-depth survey, we found some critical implications each area as follows; health club operation in the lifetime and participation sports area, female sports dance in the welfare sports area, new material sports shoes in the lifetime and welfare sports area, and dynamic training system in the professional sports area.

• Journal of Information Display
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• 제11권4호
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• pp.154-159
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• 2010

Single-sustainer driving is an AC PDP driving scheme to reduce the circuitry by maintaining the sustain electrode at ground level. To date, however, the research on the discharge characteristics in such driving scheme is insufficient. In this study, the panel performance and discharge characteristics of the single-sustainer driving scheme were observed while varying the address electrode condition. In single-sustainer driving, the address electrode is strongly involved in the sustain discharge when the former is maintained at ground level, and the dependence of the luminous efficacy on the sustain voltage is different from that in the conventional driving scheme. The dependence of the luminous efficacy on the sustain voltage appeared similar, however, to that in the conventional driving scheme when the address electrode was floated in single-sustainer driving. In the investigation of the temporal evolution of the sustain discharge using an IICCD camera, it was found that the sustain discharge in single-sustainer driving with a floating address electrode is similar to that in the conventional driving scheme, and the strong plasma formation region was located in the vicinity of the MgO surface, which seems to be related to the lifetime of a PDP with single-sustainer driving. In the investigation of the operation characteristics, the PDP that was operated with a floated address electrode showed a narrower dynamic operation margin, but a longer lifetime was expected.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권10호
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• pp.5014-5034
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• 2016

This paper discusses how to effectively guarantee the coverage and connectivity quality of wireless sensor networks when joint perception model is used for the nodes whose communication ranges are multi-level adjustable in the absence of position information. A Connect Coverage Algorithm Based on Joint Sensing model (CCAJS) is proposed, with which least working nodes are chosen based on probability model ensuring the coverage quality of the network. The algorithm can balance the position distribution of selected working nodes as far as possible, as well as reduce the overall energy consumption of the whole network. The simulation results show that, less working nodes are needed to ensure the coverage quality of networks using joint perception model than using the binary perception model. CCAJS can not only satisfy expected coverage quality and connectivity, but also decrease the energy consumption, thereby prolonging the network lifetime.

• 전기전자학회논문지
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• 제23권2호
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• pp.407-412
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• 2019

LED 조명은 많은 장점으로 인하여 다양한 분야에서 사용이 점점 증가되고 있다. 특히 플라이백 컨버터는 전력밀도와 구조적 단순성 그리고 소형화가 가능하여 많은 컨버터 설계자들에게 LED 조명용 드라이버로 선택되어지고 있다. 또한 컨버터의 직류출력전압을 안정화하기 위하여 저렴한 가격의 정전용량이 큰 전해커패시터를 사용한다. 전해 커패시터를 갖는 전력변환기를 LED 조명시스템에 적용할 경우에 일반적으로 LED의 수명이 짧아지는 결과를 가져온다. 제안하는 논문은 LED 수명연장과 컨버터 출력리플을 감소시키기 위하여 소용량의 필름 커패시터 LC 필터를 컨버터에 적용하였다.