• 한국융합학회논문지
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• 제10권11호
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• pp.71-77
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• 2019

본 연구에서는 다중 선택 배낭 모형의 최적해를 찾는 해법을 제시하고자 한다. 다중 선택은 동일한 집단에 소속된 구성원들이 동시에 선택되거나 동시에 배제되는 상황에서 관찰된다. 각 집단 간 관련성의 측정치인 오목 함수가 의사결정기준으로 설정되었다. 다중 선택은 비선형 제약식으로 모형화 되는데 일반 배낭 제약식으로 변환될 수 있다. 따라서 최적 해법 개발을 위해 오목함수 최소화 문제와 배낭 문제의 일반적인 해법들에서 채택하고 있는 분지 한계 접근법을 이용하였다. 단체상에서 오목함수를 가장 근접하게 하한추정하는 함수가 1차식이라는 사실이 한계 전략의 이론적 토대가 된다. 또한 하위 단계에서도 1차식 목적함수가 유일하게 결정되도록, 후보 단체를 두 개의 초평면에 투사시킴으로써 1차원 낮은 두 개의 하위 단체로 분할하는 방법이 분지 전략의 핵심이다. 앞으로 본 연구의 결과는 다양한 형태의 배낭 제약식 하에서의 오목 함수 최소화 문제의 해법을 개발하는데 응용될 수 있을 것이다.

• 한국태양에너지학회 논문집
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• 제35권1호
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• pp.9-19
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• 2015

Pyranometer have many uncertainty factors (sensitivity function, thermal offset, other spectral effect, geometric, environment, and equipment etc.) than pyrheliometer. The solution for most of the uncertainty factors have been researched, but the problem for thermal offset is being continued research so far. Under the clear sky, due to the thermal offset of pyranometer, the diffuse and global radiation have been negative value for the nighttime and lower value for the daytime, respectively. In order to understand the uncertainty of the thermal offset effect, solar radiation are observed and analyzed using Ji and Tsay method and data from modified pyranometer. As a result of performing temperature correction using the modified pyranometer, the slope (dome factor; k) and intercept ($r_0$) from a linear regression method are 0.064 and $3.457g{\cdot}m^{-2}{\cdot}k^{-1}$, respectively. And the solar radiation is decreased significantly due to the effect of thermal offset during nighttime. The solar radiation from modified pyranometer increased approximately 8% higher than its observed by general pyranometer during daytime. By the way, these results did not generalize because its result is for only single case in clear sky. Accordingly, it is to required for accurate results obtained by the various cases (clear, cloudy and rainy) with longterm observations.

• International Journal of Naval Architecture and Ocean Engineering
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• 제10권2호
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• pp.180-187
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• 2018

Corrugated bulkhead has been adopted for cargo tank bulkheads of commercial vessels such as bulk carriers, product oil carriers and chemical tankers. It is considered that corrugated bulkhead is a preferred structural solution, compared to the flat stiffened bulkhead, due to several advantages such as lower mass, easier maintenance and smaller corrosion problems. Many researches to find the optimum shape of corrugated bulkhead have been mostly carried out for bulk carriers. Compared to corrugated bulkheads of bulk carriers, ones of chemical tankers are more complicated since they are composed of transverse and longitudinal bulkheads, and they are made of higher priced materials. The purpose of this study is the development of minimum weight design method for corrugated bulkhead of chemical tankers. Evolution strategy is applied as an optimization technique. It has been verified from many researches that evolution strategy searches global optimum point prominently by using multi-individual searching technique. Multi-individual searching methods need excessive time if they connect to 3-D finite element model for repetitive structural analyses. In order to resolve this issue, 2-D beam element connected to deck and lower stool is substituted for a corrugated structure in this study. To verify the reliability of the structural responses by idealized 2-D beam model, they have been compared with ones by 3-D finite element model. In this study, optimum design for corrugated bulkhead of 30 K chemical tanker has been carried out, and the results by developed optimum design program have been compared with design data of existing ship. It is found out that optimum design is about 9% lighter than one of existing ship.

• Safety and Health at Work
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• 제1권1호
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• pp.29-36
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• 2010

This article describes a systematic roadmap master plan for advanced industrial safety and health policy in Korea, with an emphasis on. Since Korean industries had first emergence of industrial safety and health policy in 1953, enormous efforts have been made on upgrading the relevant laws in order to reflect real situation of industrial work environment in accordance with rapid changes of Korean and global business over three decades. Nevertheless, current policy has major defects; too much techniques-based articles, diverged contents in less organization, combined enforcement and punishments and finally enforcing regulations full of commands and control. These deficiencies have make it difficult to accommodate changes of social, industrial and employment environment in customized fashion. The approach to the solution must be generic at the level of paradigm-shift rather than local modifications and enhancement. The basic idea is to establish a new system integrated with a risk assessment scheme, which encourages employers to apply to their work environment under comprehensive responsibility. The risk assessment scheme is designed to enable to inspect employers' compliances afterwards. A project comprises four yearly phases based on applying zones; initially designating and operating a specified risk zone, gradually expanding the special zones during a period of 3 years (2010-2012) and the final zone expanded to entire nation. In each phase, the intermediate version of the system is updated through a process of precise and unbiased validation in terms of its operability, feasibility and sustainability with building relevant infrastructures as needed.

• 정보보호학회논문지
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• 제29권2호
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• pp.331-346
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• 2019

국내 외에서 산업제어시스템을 대상으로 한 사이버 위협이 증가하고 있다. 이에 따라 관련 연구와 협력이 활발히 진행되고 있다. 하지만 물리적인 망 분리와 경계선에 대한 보안을 강화에 치중하고 있어 내부에서 발생하는 위협에 대해서는 여전히 취약한 편이다. 왜냐하면, 가장 손쉽고 강력한 대응방법이 경계선 보안을 강화하는 것이며 내부의 보안을 강화하기 위한 솔루션들은 시스템의 가용성 문제로 인하여 적용이 쉽지 않기 때문이다. 특히, 산업제어시스템 전반에 걸쳐 레거시 시스템이 상당수 잔존하고 있어 취약점이 많이 존재하고 있다. 이러한 취약한 시스템들이 보안 프레임워크에 따라 새롭게 구축되지 않는 한 이에 대한 대응방안이 필요함에 따라 가용성을 고려한 보안 솔루션을 검증하고 활용방안을 제시하였다. Sysmon과 ELK를 이용하는 방법으로 보안 솔루션이 미구축된 산업제어시스템에서 탐지하기 어려운 사이버 위협을 탐지할 수 있다.

• 공업화학
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• 제30권4호
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• pp.389-398
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• 2019

수소에너지는 화석연료의 사용으로 인해 나타나는 기후변화의 문제를 해결할 수 있는 방안일 뿐 아니라 산업용 전력 생산, 자동차용 연료 등을 위한 대체가능한 에너지로 인식되고 있다. 수소제조 방법 중 물의 전기분해를 이용한 방법이 가장 효율적이고 실용적인 방법으로 여겨지고 있으며, 수소를 물로부터 직접 제조하는 방법은 화석연료 이용 제조 방법과 비교하여 보았을 때 지구환경 오염물질인 메탄, 이산화탄소 등의 배출이 없다. 본 총설은 수소제조 방법 중 하나인 물 전기분해의 종류인 알칼리 수전해(alkaline water electrolysis, AWE), 고분자전해질막 수전해(polymer electrolyte membrane water electrolysis, PEMWE)에 대해서 분석하고 최근 연구 중인 탄화수소 전해질막의 동향 및 전해질막의 문제점인 크로스오버현상에 대해 설명하였다.

• 한국기후변화학회지
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• 제9권1호
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• pp.1-12
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• 2018

There is an emphasis on the importance of adaptation against to climate change and related natural disasters. As a result, various climate information with different time-scale can be used for science-based climate change adaptation policy. From the aspects of Global Framework for Climate Services (GFCS), various time-scaled climate information in Korea is mainly produced by Korea Meteorological Administration (KMA) However, application of weather and climate information in different application sectors has been done individually in the fields of agriculture and water resources mostly based-on weather information. Furthermore, utilization of climate information including seasonal forecast and climate change projections are insufficient. Therefore, establishment of the Cooperation Center for Application of Weather and Climate Information is necessary as an institutional platform for the UIP (User Interface Platform) focusing on multi-model ensemble (MME) based climate service, seamless climate service, and climate service based on multidisciplinary approach. In addition, APCC Integrated Modeling Solution (AIMS) was developed as a technical platform for UIP focusing on user-centered downscaling of various time-scaled climate information, application of downscaled data into impact assessment modeling in various sectors, and finally producing information can be used in decision making procedures. AIMS is expected to be helpful for the increase of adaptation capacity against climate change in developing countries and Korea through the voluntary participation of producer and user groups within in the institutional and technical platform suggested.

• 대한토목학회논문집
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• 제38권6호
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• pp.933-940
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• 2018

본 연구에서는 전기자동차 수요에 대해 가구의 유형 및 차량 보유별로 그룹을 분류하고 개인의 특성과 가구차량보유구조 및 구매의향이 있는 경우 등에 따른 차량 구매 선택요인을 찾고자 한다. 이를 위하여 시행한 설문조사 결과를 토대로 수요예측모형을 구축하고 탄력성을 분석 하였다. 주요 결과는 다음과 같다. 첫째, 개인특성인 연령은 증가할수록 전기자동차 구매의향이 높아졌으나 성별은 구매에 있어서 유의미함을 찾아보기 어려웠다. 주택유형 또한 아파트의 경우만 유의미한 결과가 나타났다. 둘째, 차량이 있는 가구의 경우 전기자동차 구입의 중요 요인으로는 연료비와 충전시간, 주행가능거리 등과 같은 실제 사용에 있어 편의성과 관련된 요인이 탄력성이 높은 것으로 나타났다. 셋째, 차량이 없는 가구의 경우에는 차량구매가격이 탄력성이 높은 것으로 분석되었다. 본 연구에서 도출된 연구결과는 향후 전기자동차 수요예측과 보급활성화를 위한 기초적인 자료로 활용될 수 있을 것이라 판단된다.

• Healthcare Informatics Research
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• 제24권4호
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• pp.253-262
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• 2018

Objectives: We reviewed digital epidemiological studies to characterize how researchers are using digital data by topic domain, study purpose, data source, and analytic method. Methods: We reviewed research articles published within the last decade that used digital data to answer epidemiological research questions. Data were abstracted from these articles using a data collection tool that we developed. Finally, we summarized the characteristics of the digital epidemiological studies. Results: We identified six main topic domains: infectious diseases (58.7%), non-communicable diseases (29.4%), mental health and substance use (8.3%), general population behavior (4.6%), environmental, dietary, and lifestyle (4.6%), and vital status (0.9%). We identified four categories for the study purpose: description (22.9%), exploration (34.9%), explanation (27.5%), and prediction and control (14.7%). We identified eight categories for the data sources: web search query (52.3%), social media posts (31.2%), web portal posts (11.9%), webpage access logs (7.3%), images (7.3%), mobile phone network data (1.8%), global positioning system data (1.8%), and others (2.8%). Of these, 50.5% used correlation analyses, 41.3% regression analyses, 25.6% machine learning, and 19.3% descriptive analyses. Conclusions: Digital data collected for non-epidemiological purposes are being used to study health phenomena in a variety of topic domains. Digital epidemiology requires access to large datasets and advanced analytics. Ensuring open access is clearly at odds with the desire to have as little personal data as possible in these large datasets to protect privacy. Establishment of data cooperatives with restricted access may be a solution to this dilemma.

• 한국표면공학회지
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• 제51권6호
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• pp.415-420
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• 2018

The possibility of an improvement in heat dissipation performance of aluminum alloy heat sink for shipboard LED luminaries through plasma electrolytic oxidation (PEO) was investigated. Four different PEO coatings were produced on aluminum alloy 5052 in silicate based alkaline solution by varying current density ($50{\sim}200mA/cm^2$). On voltage-time response curves, three stages were clearly distinguished at all current densities, namely an initial linear increase, slowdown of increase rate, and steady state(constant voltage). It was found that the increase in current density caused the breakdown voltage to increase. Two different surface morphologies - coralline porous structure and pancake structure - were confirmed by SEM examination. The coralline porous structure was predominant in the coatings produced at lower current densities (50 and $100mA/cm^2$) while under high current densities(150 and $200mA/cm^2$) the pancake structure became dominant. The coating thickness was measured and found to be in a range between about $13{\mu}m$ and $44{\mu}m$, showing increasing thickness with increasing current density. As a result, $100mA/cm^2$ was proposed as an effective process parameter to improve the heat dissipation performance of aluminum alloy heat sink, which could lower the LED operating temperature by about 30%.