• 한국인터넷방송통신학회논문지
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• 제19권3호
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• pp.173-178
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• 2019

Blazed 격자구조에 의한 광 신호의 회절 특성을 분석하기 위하여 처음으로 격자구조의 Toeplitz 유전율 tensor를 2D spatial Fourier 급수로 정의하고 공식화하였다. 그때 각 층에서의 필드들은 고유치 문제에 기초하여 표현하였으며, 완전한 해는 적절한 경계 값 문제에 의존하는 모드 전송선로 이론 (MTLT)을 사용하여 정확하게 유도하였다. 비대칭형 blazed 격자구조의 Toeplitz 유전율 tensor에 기초하여 대칭형과 톱니형 격자구조의 Toeplitz 행렬을 정의하고 각 격자구조에 대한 회절특성을 수치해석 하였다. 수치해석 결과, 비대칭형과 대칭형 구조는 무반사 (anti-reflection) GMR 필터 특성을 나타내었으며, 대칭형 구조가 비대칭형 구조보다 광대역 필터특성을 보였다. 이에 반하여 톱니형 격자 구조는 무반사보다 무투과 (anti-transmission) 필터의 특성이 더욱 강하게 나타났다.

• 한국콘텐츠학회논문지
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• 제19권6호
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• pp.236-248
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• 2019

수도권의 그린벨트는 도시 경계선을 설치하여 생태 보호체계를 구축하고 도시의 탄성을 강화하는 데 목적이 있다. 베이징시에서 현재 진행되고 있는 도시종합계획이 실시되는 기한 동안 두 그린벨트가 포함하는 지역의 녹색 공간은 변화에 따라 그 비율에 큰 차이가 존재한다. 본 연구는 이를 출발점으로 삼아 '도시 구조체계요소' 및 '정책과 계획요소'가 녹색 공간 규모의 변화와 갖는 상관성을 연구하여, 베이징시 녹색 공간의 계획 시행에 영향을 미치는 요소들을 탐구하고자 한다. 본 연구는 다변량 선형 회귀 모형을 이용하여 베이징의 두 그린벨트를 대상으로 삼아 도시체계요소 및 계획정책요소(독립 변수)와 그린벨트 내의 건설용 토지의 증가(종속 변수)간의 상관관계를 검증하였다. 인구밀집과 건설용 토지가 확장될 수 있는 동력의 영향을 받아 산지, 물가, 단위 면적당 임대료, 대중교통의 접근성, 신설된 국가 소유의 건설용 토지 등 도시체계요소는 녹색 밸트 내의 건설용 토지의 규모 변화와 상관관계를 보인다는 것을 알 수 있었다.

• 한국정보통신학회논문지
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• 제24권1호
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• pp.28-36
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• 2020

조선소에서 이루어지는 선박 건조는 용접에 의해 수행되고 있으며, 친환경선박에 대한 국제적인 요구에 따라 용접물량은 증가하고 있다. 용접부는 비파괴검사를 통하여 품질을 보증하고 있으며, 검사 정보를 나타내는 리포트는 인력이 설계된 도면을 확인하여 수작업으로 용접검사 리포트가 작성된다. 이 과정에서 소요되는 많은 공수와 인적오류로 인하여 손실이 발생하고 있다. 이러한 문제 해결을 위해 본 논문에서는 조선 전용 CAD 소프트웨어를 기반으로 설계된 데이터를 입력하여 용접검사에 관한 리포트가 자동으로 생성되는 시스템에 대하여 다룬다. 개발하는 시스템은 모델링의 도면으로부터 형상 데이터를 분석하여 부재 면의 확장을 통해 용접부를 판단 및 태그 넘버를 생성하고, 용접길이, 두께, 재질 등 검사에 필요한 정보를 자동으로 추출하는 기능을 제공한다. 시스템의 유용성을 검증하기 위해 시스템을 통해 추출된 검사 정보와 모델링 도면을 비교하여 일치하는 것을 확인하였다.

• 대기
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• 제32권4호
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• pp.277-295
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• 2022

The global weather prediction model, Korean Integrated Model (KIM), has been in operation since April 2020 by the Korea Meteorological Administration. This study assessed the performance of heat waves (HWs) in Korea in 2020. Case experiments during 2018-2020 were conducted to support the reliability of assessment, and the factors which affect predictability of the HWs were analyzed. Simulated expansion and retreat of the Tibetan High and North Pacific High during the 2020 HW had a good agreement with the analysis. However, the model showed significant cold biases in the maximum surface temperature. It was found that the temperature bias was highly related to underestimation of downward shortwave radiation at surface, which was linked to cloudiness. KIM tended to overestimate nighttime clouds that delayed the dissipation of cloud in the morning, which affected the shortage of downward solar radiation. The vertical profiles of temperature and moisture showed that cold bias and trapped moisture in the lower atmosphere produce favorable conditions for cloud formation over the Yellow Sea, which affected overestimation of cloud in downwind land. Sensitivity test was performed to reduce model bias, which was done by modulating moisture mixing parameter in the boundary layer scheme. Results indicated that the daytime temperature errors were reduced by increase in surface solar irradiance with enhanced cloud dissipation. This study suggested that not only the synoptic features but also the accuracy of low-level temperature and moisture condition played an important role in predicting the maximum temperature during the HWs in medium-range forecasts.

• 한국환경복원기술학회지
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• 제24권3호
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• pp.1-18
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• 2021

England's green belt policy as it delivered its framework to designating the development restriction zones(DRZ) in Korea is the key to address issues which try to change green belt boundary or/and housing development. Therefore it should necessarily be reviewed on the understanding of how England has been formulating a national policy to deal with the issues focusing on opportunities for housing development and recreation. This study explored the discourse and framework of England's green belt policy as well as driver changes of housing development and recreation. Results show several characteristics of England's green belt policy which are civil society consensus on conservation and management, limited small-scale housing development through management of release rates, a systematic procedure for application and approval, open-recreation space expansion and utilisation under the premise of conservation of natural green areas, and management structure by the involvement of NGO organisations. Therefore, five suggestions can be delivered to developing Korea's DRZ frameworks: first, preceding social consensus on the preservation value of development-restricted zones, second, addressing housing shortages in different alternatives e.g.) environmental-friendly small-scale housing, third, institutionalising the total proportion of release, fourth, establishing an open-recreation space, fifth, introducing expanded public-private partnerships. Ultimately securing the legitimacy of the nation's development-restricted zone system can contribute positively to the environment preservation and human health by promoting public leisure activities in terms of the recent increase in external activities caused by the Covid-19 crisis. Concluding remarks are here that the understanding of England's green belt policy can be delivered to and help formulate domestic policy addressing current issues.

• 대한간호학회지
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• 제52권2호
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• pp.187-201
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• 2022

Purpose: This study discovered a substantive theory of the experience and process of peer support work among people with mental illness. Methods: The participants were members of community-based mental health facilities and had been working as peer supporters for more than six months. The data were collected through in-depth interviews with twelve participants and analyzed using Corbin and Strauss's grounded theory approach. Results: The core category was "becoming a healer going with patients in the journey of recovery," and the core phenomenon was "identity confusion as a peer supporter." The causal conditions were "starting peer support work without certainty" and "standing at the boundary between the therapist and patient." The intervening conditions were "willingness to become a successful peer supporter," "feeling a sense of homogeneity with the patient," "accepting the mental illness," and "support from people around." The action and interaction strategies were "letting go of greed," "being open about oneself," "developing professional skills," "maintaining wellness in the body and mind," and "being with the patient." The consequences were "becoming a useful person," "changing attitude toward life," "expansion of the sense of self-existence," "recovering from mental illness," and "discovering a role as peer supporter." Finally, the substantive theory of "becoming a healer going with patients in the journey of recovery" was derived. Conclusion: This study provides a holistic understanding of peer support work and the implications of interventions to help people with mental illness in a person-centered recovery process.

• Journal of Electrochemical Science and Technology
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• 제13권1호
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• pp.112-119
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• 2022

Molten carbonate fuel cells (MCFCs) are environmentally friendly, large-capacity power generation devices operated at approximately 650℃. If MCFCs are to be commercialized by improving their competitiveness, their cell life should be increased by operating them at lower temperatures. However, a decrease in the operating temperature causes a reduction in the cell performance because of the reduction in the electrochemical reaction rate. The cell performance can be improved by introducing a coating on the cathode of the cell. A coating with a high surface area expands the triple phase boundaries (TPBs) where the gas and electrolyte meet on the electrode surface. And the expansion of TPBs enhances the oxygen reduction reaction of the cathode. Therefore, the cell performance can be improved by increasing the reaction area, which can be achieved by coating nanosized LiCoO₂ particles on the cathode. However, although a coating improves the cell performance, a thick coating makes gas difficult to diffuse into the pore of the coating and thus reduces the cell performance. In addition, LiCoO₂-coated cathode cell exhibits stable cell performance because the coating layer maintains a uniform thickness under MCFC operating conditions. Therefore, the performance and stability of MCFCs can be improved by applying a LiCoO₂ coating with an appropriate thickness on the cathode.

• Steel and Composite Structures
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• 제47권2호
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• pp.269-287
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• 2023

The WGJ420 fire-resistant weathering (FRW) steel is developed and manufactured with standard yield strength of 420 MPa at room temperature, which is expected to significantly enhance the performance of steel structures with excellent fire and corrosion resistances, strong seismic capacity, high strength and ductility, good resilience and robustness. In this paper, the mechanical properties of FRW steel plates and buckling behavior of columns are investigated through tests at elevated temperatures. The stress-strain curves, mechanical properties of FRW steel such as modulus of elasticity, proof strength, tensile strength, as well as corresponding reduction factors are obtained and discussed. The recommended constitutive model based on the Ramberg-Osgood relationship, as well as the relevant formulas for mechanical properties are proposed, which provide fundamental mechanical parameters and references. A total of 12 FRW steel welded I-section columns with different slenderness ratios and buckling load ratios are tested under standard fire to understand the global buckling behavior in-depth. The influences of boundary conditions on the buckling failure modes as well as the critical temperatures are also investigated. In addition, the temperature distributions at different sections/locations of the columns are obtained. It is found that the buckling deformation curve can be divided into four stages: initial expansion stage, stable stage, compression stage and failure stage. The fire test results concluded that the residual buckling capacities of FRW steel columns are substantially higher than the conventional steel columns at elevated temperatures. Furthermore, the numerical results show good agreement with the fire test results in terms of the critical temperature and maximum axial elongation. Finally, the critical temperatures between the numerical results and various code/standard curves (GB 51249, Eurocode 3, AS 4100, BS 5950 and AISC) are compared and verified both in the buckling resistance domain and in the temperature domain. It is demonstrated that the FRW steel columns have sufficient safety redundancy for fire resistance when they are designed according to current codes or standards.

• 한국수소및신에너지학회논문집
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• 제33권6호
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• pp.761-768
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• 2022

In the hope of realizing carbon neutrality, Korea has established the goal of expanding the supply of hydrogen electric vehicles through a roadmap to revitalize the hydrogen economy. A prerequisite for successful supply expansion is securing the safety of hydrogen electric vehicles. Certain parts, such as the hydrogen transport pipe and tank, in hydrogen electric vehicles are exposed to high-pressure hydrogen gas over long periods of time, so the hydrogen enters the grain boundary of material, resulting in a degradation of the parts referred to as hydrogen embrittlement. In addition, since the safety of parts utilizing hydrogen varies depending on the type of material used and its environmental characteristics, the necessity for the enactment of a hydrogen embrittlement regulation has emerged and is still being discussed as a Global Technical Regulation (GTR). In this paper, we analyze a hydrogen compatibility material evaluation method discussed in GTR and present a direction for the development of Korean-type hydrogen compatibility material evaluation methods.

• Advances in nano research
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• 제16권2호
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• pp.111-125
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• 2024

Recently, a lot of research has been done on the analysis of axial vibrations of homogeneous and FG nanotubes (nanorods) with various aspects of vibrations that have been fully mentioned in history. However, there is a lack of investigation of the dynamic internal resonances of FG nanotubes (nanorods) between them. This is one of the essential or substantial characteristics of nonlinear vibration systems that have many applications in various fields of engineering (making actuators, sensors, etc.) and medicine (improving the course of diseases such as cancers, etc.). For this reason, in this study, for the first time, the dynamic internal resonances of FG nanorods in the simultaneous presence of large-amplitude size dependent behaviour, inertial and shear effects are investigated for general state in detail. Such theoretical patterns permit as to carry out various numerical experiments, which is the key point in the expansion of advanced nano-devices in different sciences. This research presents an AFG novel nano resonator model based on the axial vibration of the elastic nanorod system in terms of derivation from large-amplitude size dependent internal modals interactions. The Hamilton's Principle is applied to achieve the basic equations in movement and boundary conditions, and a harmonic deferential quadrature method, and a multiple scale solution technique are employed to determine a semi-analytical solution. The interest of the current solution is seen in its specific procedure that useful for deriving general relationships of internal resonances of FG nanorods. The numerical results predicted by the presented formulation are compared with results already published in the literature to indicate the precision and efficiency of the used theory and method. The influences of gradient index, aspect ratio of FG nanorod, mode number, nonlinear effects, and nonlocal effects variations on the mechanical behavior of FG nanorods are examined and discussed in detail. Also, the inertial and shear traces on the formations of internal resonances of FG nanorods are studied, simultaneously. The obtained valid results of this research can be useful and practical as input data of experimental works and construction of devices related to axial vibrations of FG nanorods.