해양공간 정책시뮬레이션 기술 개발 - 현황 및 도전과제

조성진(Sung-Jin Cho),강전영(Jeon-Young Kang),박재영(Jaeyoung Park),최희정(Hee-Jung Choi),남정호(Jungho Nam) 한국해양환경·에너지학회 2021 한국해양환경·에너지학회 학술대회논문집 Vol.2021 No.5

“실제로 존재하지 않는 대상을 존재하는 것처럼 만들어 놓은 인공물"을 뜻하는 라틴어 '시뮬라크르(simulacre)'에서 파생된 시뮬레이션(simulation)은, 복잡한 문제를 해석하기 위해서 실제와 비슷한 상태(시스템)를 모델로서 구현하고, 반복 연산을 통해 최적해를 찾는 과정을 뜻한다(Baudrillard, 1994). 전통적인 분석적 방법론(analytical method)은 계수 추정을 통해서 특정 시점의 두 변수, 즉 독립변수와 종속변수의 상관성을 규명하는데 반해, 시뮬레이션 방법론(simulation method)은 현상의 재현을 통해서 과정을 파악하는데 목적을 둔다. 이러한 특징으로 말미암아 시뮬레이션 기법은 문제의 최적해보다 현상의 규명에 더 적합한 방법론이다. 자연계 (nature system)의 문제(가령, 산사태의 발생원인)는 요인들 간 단순하고 명확한 관계에 의해서 정의되지만, 인간계(human system)의 문제(가령, 부동산 가격상승의 원인)는 비교적 복잡하고 불명확한 관계에 의해서 규정된다. 따라서 주로 인간관계에서 비롯되는 사회 문제를 해결하기 위한 수단으로써 정책은 시뮬레이션 기술을 적용하기에 적합한 대상이다. 일반적으로 정책은 결과 못지않게 과정도 중요하며(당위성), 현재·미래 문제를 포괄하고, 긍정적·부정적 효과(양면성)를 함께 고려하므로, 시뮬레이션은 이러한 요건에 잘 부합하는 기술이다. 최근 노인복지(백의현, 2019), 미세먼지(심창섭, 2019), 주택시장(최명섭&변세일, 2016), 인구센서스(배장현 외, 2016) 등 다양한 정책분야에서 시뮬레이션 기술이 활용되고 있다. 2019년에 재정된 “해양공간계획 및 관리에 관한 법률”에 근거한 해양공간기본·관리계획, 해양용도구역, 해양공간적합성협의 등은 해양자원의 효율적 이용과 해양공간의 갈등 및 상충을 해소하기 위한 해양수산 분야의 新정책수단이다. 최근 해양관광, 골재채취, 해상풍력, 해상경계분쟁 등 사회적 이용 및 갈등이 심화되면서 실효성 있는 해양공간정책의 요구가 높아지고 있는 실정으로, 해양정책을 정확하게 평가하고 지원할 수 있는 과학적 도구가 절실하다. 해양공간은 환경·생태계, 지역사회, 수산업, 관광업, 에너지개발 등 복잡한 이해관계가 얽혀 있으며, 정책평가 시 이러한 관계를 명확하게 정의하고 고려해야 한다. 본 연구는 해양공간정책 지원도구로써 해양정책시뮬레이터(Ocean Policy Simulator, OPSim)를 제안하며, 대표적인 복잡계 연구방법론으로서 거시적 현상을 미시적 행위자의 상호작용으로 설명하기 위해 제안된 행위자기반모형(Agent-Based Model, ABM)을 적용하고자 한다. ABM은 정책 대상 및 환경의 동적 변화와 더불어, 자연·인문 환경과의 상호작용(상충 또는 시너지)이 활발한 해양 분야에 적합한 방법이지만, 동시에 시뮬레이션 결과에 대한 검증의 어려움과 모델 인자의 초기값에 대한 의존성 등 한계점을 내포하고 있다. 따라서 ABM을 적용한 OPSim 개발 과정에서 빅 데이터를 활용한 AI기술, 자가진화 시뮬레이션 기법(self-evolving simulation), 시스템다이나믹스(system dynamics) 등을 활용하여 한계점을 보완할 수 있다(Scheutz et al., 2016; Kang et al., 2016; Bae et al., 2018; Kavak et al., 2018). Simulation derived from the Latin word "simulacre" for "artificial objects that actually do not exist" means the process of modeling a realistic state (system) to interpret complex problems and finding an optimal solution through repeated operations (Baudrillard, 1994). While a traditional analytical method defines the correlation of two variables (i.e., independent variables and dependent variables) through coefficient estimation, a simulation method aims to identify the process through the reproduction of phenomena. Therefore, a simulation technique is a more suitable methodology for identifying phenomena rather than finding an optimal solution. The problem of the natural system (e.g. landslides) is defined by simple and clear relationships between factors, but that of the human system (e.g. real estate prices) is defined by relatively complex and unclear relationships. Therefore, a policy as a means of solving social problems, primarily derived from human relationships, is suitable for applying a simulation technique. Simulation is a technology that meets these requirements well, as a policy addresses the procedure as important as the result, solving current and future problems, and considering both positive and negative effects. Recently, simulation technology has been used in various policy areas such as welfare for senior citizens (Baek, 2019), fine dust (Shim, 2019), housing market (Choi&Byun, 2016), and population census (Bae et al, 2016). Marine space policies based on the Marine Space Planning and Management Act, which was enacted in 2019, such as marine spatial basic and management plans, marine use zones, and marine space suitability consultations are new political tools for efficient use of marine resources and management of conflicts. As social use and conflicts such as maritime tourism, aggregate collection, off-shore wind power, and maritime border disputes have intensified recently, calls for effective marine spatial policies are increasing, and scientific tools are urgently needed to accurately evaluate marine policies. Since marine space is intertwined with complex interests such as the environment, ecosystem, community, fisheries, tourism, and energy development, a marine spatial policy support tool should define and consider these relationships for policy evaluation. This paper proposes Ocean Policy Simulator (OPSim) as a support tool for marine spatial policy. Specifically, we aim to highlight the usefulness of an agent-based model (ABM) to explore human-nature interactions (i.e., conflict or synergy) and to provide policy implications. Using an ABM for such purposes often meet the issues in regard to verification and validation of the model’s structures and outcomes. However, AI technology using spatiotemporal bigdata, self-evolution simulation techniques, and system dynamics can help to tackle validation and verification procedures in the development process of OPSim using ABM (Scheutz et al., 2016; Kang et al., 2016; Bae et al., 2018; Kavak et al., 2018).

Risk-Seeking Behavior of Financial Institutions due to Deposit Insurance: Evidence from Korea

Jungho Choi,Duckhyun Cho 한국유통과학회 2019 The Journal of Asian Finance, Economics and Busine Vol.6 No.1

The purpose of this paper is to examine how the social system of deposit insurance affected the financial market in Korea. Specifically, we want to know how much the risk-seeking behavior of financial institutions has increased or decreased. The most important feature of the deposit insurance system is to prevent the insolvency of financial institutions and to properly protect depositors. In recent studies, it has been argued that characteristics of deposit insurance bring moral hazard of financial institutions and that financial institutions make unreasonably risky investments. Therefore, in this study, we will first examine whether such previous research can be applied to the Korean financial market. Next, we will examine the appropriateness of the differential premium rate that is currently used for each financial institution in the Korean financial market. In order to test the first hypothesis, we used the Capital Asset Pricing Model (CAPM) to calculate the total risk for each financial institution. As a result, significant changes were found in all regions before and after the introduction of the deposit insurance system. As for testing the second hypothesis, we conducted a variance analysis of financial institutions' indexes before and after the introduction of the deposit insurance and we discovered significance of the total risk difference.

Development of partial liquefaction system for liquefied natural gas carrier application using exergy analysis

Choi, Jungho The Society of Naval Architects of Korea 2018 International Journal of Naval Architecture and Oc Vol.10 No.5

The cargo handling system, which is composed of a fuel gas supply unit and cargo tank pressure control unit, is the second largest power consumer in a Liquefied Natural Gas (LNG) carrier. Because of recent enhancements in ship efficiency, the surplus boil-off gas that remains after supplying fuel gas for ship propulsion must be reliquefied or burned to regulate the cargo tank pressure. A full or partial liquefaction process can be applied to return the surplus gas to the cargo tank. The purpose of this study is to review the current partial liquefaction process for LNG carriers and develop new processes for reducing power consumption using exergy analysis. The developed partial liquefaction process was also compared with the full liquefaction process applicable to a LNG carrier with a varying boil-off gas composition and varying liquefaction amounts. An exergy analysis showed that the Joule-Thomson valve is the key component needed for improvements to the system, and that the proposed system showed an 8% enhancement relative to the current prevailing system. A comparison of the study results with a partial/full liquefaction process showed that power consumption is strongly affected by the returned liquefied amount.

Development of partial liquefaction system for liquefied natural gas carrier application using exergy analysis

Jungho Choi 대한조선학회 2018 International Journal of Naval Architecture and Oc Vol.10 No.5

The cargo handling system, which is composed of a fuel gas supply unit and cargo tank pressure control unit, is the second largest power consumer in a Liquefied Natural Gas (LNG) carrier. Because of recent enhancements in ship efficiency, the surplus boil-off gas that remains after supplying fuel gas for ship propulsion must be reliquefied or burned to regulate the cargo tank pressure. A full or partial liquefaction process can be applied to return the surplus gas to the cargo tank. The purpose of this study is to review the current partial liquefaction process for LNG carriers and develop new processes for reducing power consumption using exergy analysis. The developed partial liquefaction process was also compared with the full liquefaction process applicable to a LNG carrier with a varying boil-off gas composition and varying liquefaction amounts. An exergy analysis showed that the JouleeThomson valve is the key component needed for improvements to the system, and that the proposed system showed an 8% enhancement relative to the current prevailing system. A comparison of the study results with a partial/ full liquefaction process showed that power consumption is strongly affected by the returned liquefied amount.

Assessment of Strain-Generated Oxygen Vacancies Using SrTiO₃ Bicrystals

Choi, Si-Young,Kim, Sung-Dae,Choi, Minseok,Lee, Hak-Sung,Ryu, Jungho,Shibata, Naoya,Mizoguchi, Teruyasu,Tochigi, Eita,Yamamoto, Takahisa,Kang, Suk-Joong L.,Ikuhara, Yuichi American Chemical Society 2015 NANO LETTERS Vol.15 No.6

<P>Atomic-scale defects strongly influence the electrical and optical properties of materials, and their impact can be more pronounced in localized dimensions. Here, we directly demonstrate that strain triggers the formation of oxygen vacancies in complex oxides by examining the tilt boundary of SrTiO<SUB>3</SUB> bicrystals. Through transmission electron microscopy and electron energy loss spectroscopy, we identify strains along the tilt boundary and oxygen vacancies in the strain-imposed regions between dislocation cores. First-principles calculations support that strains, irrespective of their type or sign, lower the formation energy of oxygen vacancies, thereby enhancing vacancy formation. Finally, current–voltage measurements confirm that such oxygen vacancies at the strained boundary result in a decrease of the nonlinearity of the <I>I</I>–<I>V</I> curve as well as the resistivity. Our results strongly indicate that oxygen vacancies are preferentially formed and are segregated at the regions where strains accumulate, such as heterogeneous interfaces and grain boundaries.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2015/nalefd.2015.15.issue-6/acs.nanolett.5b01245/production/images/medium/nl-2015-01245s_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl5b01245'>ACS Electronic Supporting Info</A></P>

범주형 데이터에 대한 스카이라인 검색 알고리즘

최중호(JungHo Choi),이우기(Wookey Lee),송종수(JongSu Song) 한국정보과학회 2009 한국정보과학회 학술발표논문집 Vol.36 No.2A

Upshift of Phase Transition Temperature in Nanostructured PbTiO₃ Thick Film for High Temperature Applications

Ryu, Jungho,Han, Guifang,Song, Tae Kwon,Welsh, Aaron,Trolier-McKinstry, Susan,Choi, Hongsoo,Lee, Jong-Pil,Kim, Jong-Woo,Yoon, Woon-Ha,Choi, Jong-Jin,Park, Dong-Soo,Ahn, Cheol-Woo,Priya, Shashank,Choi, American Chemical Society 2014 ACS APPLIED MATERIALS & INTERFACES Vol.6 No.15

<P>Thick polycrystalline pure PbTiO<SUB>3</SUB> films with nano size grains were synthesized for the first time by aerosol deposition. Annealed 7 μm thick films exhibit well-saturated ferroelectric hysteresis loops with a remanent polarization and coercive field of 35 μC/cm<SUP>2</SUP> and 94 kV/cm, respectively. A large-signal effective <I>d</I><SUB>33,eff</SUB> value of >60 pm/V is achieved at room temperature. The measured ferroelectric transition temperature (<I>T</I><SUB>c</SUB>) of the films ∼550 °C is >50 °C higher than the reported values (∼490 °C) for PbTiO<SUB>3</SUB> ceramics. First-principles calculations combined with electron energy loss spectroscopy (EELS) and structural analysis indicate that the film is composed of nano size grains with slightly decreased tetragonality. There is no severe off-stoichiometry, but a high compressive in-plane residual stress was observed in the film along with a high transition temperature and piezoelectric response. The ferroelectric characteristics were sustained until 200 °C, providing significant advancement toward realizing high temperature piezoelectric materials.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2014/aamick.2014.6.issue-15/am5000307/production/images/medium/am-2014-000307_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am5000307'>ACS Electronic Supporting Info</A></P>

Ubiquitous magneto-mechano-electric generator

Ryu, Jungho,Kang, Ju-Eun,Zhou, Yuan,Choi, Si-Young,Yoon, Woon-Ha,Park, Dong-Soo,Choi, Jong-Jin,Hahn, Byung-Dong,Ahn, Cheol-Woo,Kim, Jong-Woo,Kim, Yang-Do,Priya, Shashank,Lee, Seung Yong,Jeong, Seongsu The Royal Society of Chemistry 2015 Energy & environmental science Vol.8 No.8

<P>Stray magnetic field considered as harmful noise for the human body can be a ubiquitous energy source. We are surrounded with 50/60 Hz parasitic magnetic noise arising from power delivery infrastructure, but it cannot be readily utilized by traditional electromagnetic harvesters. Here, we introduce a novel magneto-mechano-electric (MME) generator with a colossal power density that can turn on 35 LEDs and drive a wireless sensor network under a weak magnetic field of 5–7 × 10<SUP>−4</SUP> T at a low frequency of 60 Hz. The MME generator is a cantilever structured magnetoelectric (ME) laminate composite in which the ⟨011⟩ oriented anisotropic single crystal fiber composite (SFC) is bonded to Ni plate and Nd permanent magnet proof mass. The ME laminate composite has a strong ME coupling (<I>α</I><SUB>ME</SUB>∼ 160 V cm<SUP>−1</SUP> Oe<SUP>−1</SUP>) even without magnetic bias due to the intrinsic property of Ni. The MME generator is also found to exhibit a colossal output power density of 46 mW cm<SUP>−3</SUP> Oe<SUP>−2</SUP> under a weak magnetic field of 1.6 × 10<SUP>−4</SUP> T at 60 Hz. This MME generator can be a ubiquitous power source for wireless sensor networks, low power electric devices, and wireless charging systems by harvesting tiny amounts of parasitic magnetic energy from our living environment.</P> <P>Graphic Abstract</P><P>A novel energy capturing technique for wasted parasitic magnetic noise based upon a magneto-mechano-electric (MME) generator, consisting of piezoelectric single crystal fibers and Ni metal plate in the form of cantilever structure. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c5ee00414d'> </P>

분산형 용수공급시스템 기반 스마트 정수장 수운영시스템 구축

최현석(Choi HyunSeok),이상희(SangHee Lee),유민호(MinHo Yoo),최정호(JungHo Choi),장용해(YongHae Jang),손경락(Kyung-Rak Sohn) 한국통신학회 2023 한국통신학회 학술대회논문집 Vol.2023 No.11

SURF와 Optical Flow의 병렬 처리 기술을 이용한 이동 물체 인식 및 추적 알고리즘

최정호(Jungho Choi),조영완(Youngwan Cho) 한국지능시스템학회 2011 한국지능시스템학회 학술발표 논문집 Vol.21 No.2

본 논문에서는 물체 인식을 위한 SURF와 물체 추적을 위한 Optical Flow(Lucas-Kanade) 두 가지 알고리즘에 병렬 처리 기술을 이용하여 이동 물체를 인식하고 추적하는 방법을 제안한다. 물체 인식 및 추적은 컴퓨터 비전에서 중요한 작업 중 하나지만 특징점 추출 및 정합 부분은 연상량이 많아 처리 속도가 느리다는 단점이 있다. 제안된 방법에서는 이러한 단점을 줄이고 움직이는 물체를 실시간으로 인식 및 추적하기 위해 대표적인 특징 추출 방법인 SURF와 움직임을 추적하는 방법인 Optical Flow를 이용하였고, 속도 개선을 위해 병렬 처리 기법을 이용하였다. 먼저 DB에 있는 물체와 카메라를 통해 획득한 영상을 분석하여 똑같은 물체가 있는지 SURF를 통해 인식한 후 관심영역을 설정하고 관심영역 내에 있는 특징점들의 움직임을 Optical Flow로 추적하는데 이 두 알고리즘을 Multi-Thread를 이용하여 병행으로 처리함으로써 처리 속도와 인식률을 향상시켰다. 본 논문에서 제안하는 알고리즘은 실험을 통하여 성능을 평가하였고 그 알고리즘의 효율성을 검증하였다.