• Proceedings of the KIPE Conference
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• 2013.07a
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• pp.368-369
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• 2013

본 논문에서는 배터리 저장 시스템을 위한 2단 인버터의 동작 특성 해석과 정확한 제어기 설계를 위한 모델링 방법을 제안한다. 한 번에 2단 인버터의 회로 해석 및 동특성 방정식을 유도하는 것은 매우 복잡하고 어렵다. 따라서 2단 인버터를 등가 전류원을 포함하는 양방향 컨버터, 단상 풀 브릿지 인버터로 각각 나누어 회로방정식을 유도한 후, 상태 공간 평균화 방법을 이용하여 소신호 모델을 얻을 수 있다. 제안된 방법의 장점은 2단 인버터의 복잡한 수학과정을 간소화하여 모델링한 점이다. 이를 바탕으로 양방향 컨버터에서는 배터리 입력 전류제어기를 설계하고, 단상 풀 브릿지 인버터에서는 DC-Link 전압 및 계통전류 제어기를 설계하였다. 시뮬레이션과 실험결과를 통해 제안된 방법의 타당성을 검증하였다.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.92.1-92.1
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• 2012

홍대용(洪大容, 1731~1783)이 저술한 "담헌서(湛軒書)" 외집 권6의 <주해수용(籌解需用)>에는 수격식 천문시계인 혼상의(渾象儀)에 대한 기록이 나온다. 우리는 홍대용 혼상의에 대한 구조와 작동 메커니즘에 대한 연구를 통해 복원 모델의 개념설계를 진행하였다. 혼상의는 세 개의 환(環)과 2개의 층(層)으로 되어 있다. 외층에 해당하는 환 구조는 자신이 제작한 혼천의인 통천의(統天儀) 구조와 유사하다. 내층에 해당되는 혼상구에는 별자리와 은하수를 그려넣고, 태양과 달의 모습을 구슬 형태로 매달아 천상의 운행 모습을 구현하였다. 통천의는 추동력으로 운행되며, 혼상의는 물에 의한 수격방식으로 운행된다. 홍대용의 수격방식은 조선에서 전통적으로 사용한 동력체계로 중국의 대표적 천문시계인 수운의상대의 동력체계를 간소화시켰다. 혼상의에 대한 기록은 조선시대 수격식 동력체계를 다룬 거의 유일한 문헌기록으로 수격식 작동 메커니즘 연구에 중요한 단서를 제공해 주고 있다.

• Korea Information Processing Society Review
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• v.22 no.5
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• pp.36-45
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• 2015

금융과 IT의 융합을 의미하는 핀테크(Fintech) 열풍이 전세계적으로 뜨겁게 불고 있다. 핀테크를 통해 신기술들이 금융 산업 전반에 융합되면서 새로운 형태의 금융서비스가 등장하고 기존의 금융 시스템들이 가져왔던 문제점들을 개선하는데 기여할 것으로 보인다. 하지만 핀테크 산업 활성화를 위한 지속적 규제 완화와 이용자 편의성을 위한 각종 절차의 간소화 그리고 채널 서비스 기술간의 융복합이 일어나는 환경에서 제공되는 핀테크 서비스의 안전성에 대해 우려가 있다. 핀테크 시대에 정보보안은 성장의 인프라이며 금융상품을 선택하는 중요한 기준이 될 것이므로 보안리스크의 정량화와 단계별 통제 방안을 수립하고 사용자 인증, 결제정보 보안, API(Application Programming Interface) 보안 등 필요한 보안요소를 사업모델에 맞게 적용함으로써 편리성과 보안성을 함께 확보할 수 있어야 한다. 본 연구에서는 정보보안 관점에서 핀테크의 서비스의 특징과 보안 취약점을 분석하고 관련 위험을 줄이기 위한 대응방안을 모색해 보았다.

• Korean Journal of Remote Sensing
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• v.18 no.2
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• pp.97-105
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• 2002

In this paper, we proposed a simplified strategy for the epipolarity of linear pushbroom imagery. The proposed strategy is verified on "Gupta and Hartly" sensor model and "Orun and Natarajan" sensor model. It is also compared with the precise epipolarity model of each sensor model on SPOT and KOMPSAT imagery. For the quantitative analysis, 20 ground control points are used as independent checking points. Based on the results, the accuracy of the proposed strategy is not different from that of the precise epipolarity model of each sensor model (below 0.1 pixels). Under the worst circumstance, the proposed strategy is robust. We can assure that the proposed strategy will show high accuracy on most of sensor models based on the co-linearity equations.

• Proceedings of the Korea Information Processing Society Conference
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• 2013.05a
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• pp.472-473
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• 2013

The growth in number and efficiency of smart devices such as GPS enabled smart phones and PDAs present an unparalleled opportunity for diverse areas of life. However extraction of GPS traces for provision of services demand a huge storage space as well as computation overhead. This is a challenging task especially for the applications which provide runtime services. In this paper we provide a simplified model to extract GPS traces of moving objects at runtime. Road segment partitioning and measure of deviation in angle of trajectory path is incorporated to identify the significant data points. The number of these data points is minimized by our proposed approach in an efficient manner to overwhelm the storage and computation overhead. Further, the competent reconstruction of complete itinerary based on gathered data, is also ensured by proposed method.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.5
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• pp.574-583
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• 2021

Predicting shipping markets is an important issue. Such predictions form the basis for decisions on investment methods, fleet formation methods, freight rates, etc., which greatly affect the profits and survival of a company. To this end, in this study, we propose a shipping freight rate prediction model for container ships using gated recurrent units (GRUs) and long short-term memory structure. The target of our freight rate prediction is the China Container Freight Index (CCFI), and CCFI data from March 2003 to May 2020 were used for training. The CCFI after June 2020 was first predicted according to each model and then compared and analyzed with the actual CCFI. For the experimental model, a total of six models were designed according to the hyperparameter settings. Additionally, the ARIMA model was included in the experiment for performance comparison with the traditional analysis method. The optimal model was selected based on two evaluation methods. The first evaluation method selects the model with the smallest average value of the root mean square error (RMSE) obtained by repeating each model 10 times. The second method selects the model with the lowest RMSE in all experiments. The experimental results revealed not only the improved accuracy of the deep learning model compared to the traditional time series prediction model, ARIMA, but also the contribution in enhancing the risk management ability of freight fluctuations through deep learning models. On the contrary, in the event of sudden changes in freight owing to the effects of external factors such as the Covid-19 pandemic, the accuracy of the forecasting model reduced. The GRU1 model recorded the lowest RMSE (69.55, 49.35) in both evaluation methods, and it was selected as the optimal model.

• Journal of KIISE:Software and Applications
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• v.35 no.11
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• pp.653-660
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• 2008

Recently, Service-oriented computing is the emerging computing paradigm. In this paradigm, we require the practical process model to support service oriented software development. The well-known development methods e.g., Unified Software Development Process, UML components have been proposed focused on component. So, these methods cannot support service-oriented computing concepts such as service definition, binding and composition concepts using Business Process Execution Language (BPEL). Also, a few proposed service-oriented approach, for example Service Oriented Unified process (SOUP), and Service Oriented Modeling and Architecture (SOMA) have appeared. However, these approaches do not explicitly represent detailed guideline, artifacts and approach. Therefore, in this paper we propose a practical and simple process model to support service oriented software development. Also, we explicitly represent process model and artifact using Software Process Engineering Metamodel (SPEM) which is proposed by OMG. By using our approach, it can enhance systematization and effectiveness for service-oriented software development.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.8
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• pp.1569-1580
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• 2016

For the 2.4 GHz active RFID to be successful in the market, one of the requirements is the increased battery life. However, currently we do not have any accurate power consumption estimation method. In this study we develop a simulation model, which can be used to estimate power consumption of tag accurately. Six different simulation models are proposed depending on collision algorithm and query command method. To improve estimation accuracy, we classify tag operating modes as the wake-up receive, UHF receive, sleep timer, tag response, and sleep modes. Power consumption and operating time are identified according to the tag operating mode. Query command for simplifying collection and ack command procedure and newly developed collision control algorithm are used in the simulation. Other performance measures such as throughput, recognition time for multi-tags, tag recognition rate including power consumption are compared with those from the current standard ISO/IEC 18000-7.

• Journal of the Korean Society of Food Culture
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• v.17 no.3
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• pp.240-251
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• 2002

This study is to describe practices of and attitude toward traditional wedding food and the attitude of housewives toward the traditional wedding food in Busan metropolitan and Kyungnam province area. Data were analyzed from the convenient sample of 525 housewives collected from September 20 to September 28, 2001. As for the necessity of traditional wedding food, the most popular food was ebagee food, pebaek food, yedan food in order. Of the various kinds of traditional wedding food, table setting for parent-in-law was chosen as the most popular one. Sociodemographic characteristics such as education level and age were statistically associated with perception of traditional wedding food being necessary as a ritual thing. The respondents preferred rice cakes as wedding food to fishes, fruits, traditional sweets and skewered slices of seasoned meats. More than half of the respondents think current practices of wedding food is prodigal and has to be done in thrifty manner. As a ritual practices of wedding food were to be readjusted to the change of social custom depending on the degree of modernization. More than half (52.1%) of the housewives expected traditional wedding food should fade away. A conclusion was that it is necessary to develop modernized wedding food reflecting traditional wedding customs with economic costs.

• Journal of Korea Water Resources Association
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• v.51 no.4
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• pp.347-354
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• 2018

In urban areas, runoff flow is drained through sewer networks as well as surface areas. Therefore, it is very important to consider sewer networks as a component of hydrological drainage processes when conducting urban inundation modelling. However, most researchers who have implemented urban inundation/flood modelling, instinctively simplified the sewer networks without the appropriate criteria. In this research, a 1D-2D fully coupled urban inundation model is applied to estimate the influence of sewer network simplification on urban inundation modelling based on the dendritic network classification. The one-dimensional (1D) sewerage system analysis model, which was introduced by Lee et al. (2017), is used to simulate inlet and overflow phenomena by interacting with surface flow. Two-dimensional (2D) unstructured meshes are also applied to simulate surface flow and are combined with the 1D sewerage analysis model. Sewer network pipes are simplified based on the dendritic network classification method, namely the second and third order, and all cases of pipes are conducted as a control group. Each classified network case, including a control group, is evaluated through their application to the 27 July 2011 extreme rainfall event, which caused severe inundation damages in the Sadang area in Seoul, South Korea. All cases are compared together regarding inundation area, inflow discharge and overflow discharge. Finally, relevant criterion for the simplification method is recommended.