In 2017, the permanent shutdown of Kori Unit 1 was decided, marking the initiation of preparations for the decontamination and decommissioning of Kori Unit 1. The dismantling of radiologically contaminated equipment and concrete structures such as the Reactor Vessel (RV), Reactor Vessel Internals (RVI), and the Bio shield is crucial in the nuclear decommissioning process. These components became radiologically contaminated due to nuclear fission reactions occurring in the reactor during its operational period. The RVI dismantling at Spain’s Jose Cabrera Nuclear Power Plant involved the use of mechanical saws and disk cutters to divide it into approximately 430 pieces, taking 16 months to complete. Germany’s Stade Nuclear Power Plant employed mechanical circular saws to segment their RVI into about 170 pieces, which took 30 months to accomplish. Meanwhile, the RVI at Germany’s Wurgassen Nuclear Power Plant was subdivided into approximately 1,200 pieces using a combination of mechanical saws and abrasive water jets, requiring 61 months for completion. Due to the radioactivity in Kori Unit 1’s Reactor Vessel (RV) and Reactor Vessel Internals (RVI), remote-controlled systems were developed for cutting within the cavity to reduce radiation exposure. Specialized equipment was developed for underwater cutting operations. This paper focuses on modeling related to RVI operations using the MAVRIC code. The upper and lower parts of the RVI are classified as low-level radioactive waste, while the sides of the RVI that come into contact with fuel are classified as intermediate-level radioactive waste. Therefore, the modeling presented in this paper only considers the RVI sides since the upper and lower parts have a minimal impact on radiation exposure. Accurate calculations were performed through geometric modeling and radiation dose modeling. These research findings are anticipated to contribute to enhancing the efficiency and safety of nuclear reactor decommissioning operations

With the advancement of optical design and manufacturing technology, optical components have found diverse applications, spanning from semiconductors to the aerospace industry. A reflective mirror is a basic component in optics and plays a crucial role as the medium to reflect light. In this paper, a large mirror with a 700mm diameter was designed as a primary mirror using fused silica. The rear side of the mirror was subdivided into several equal angles, and neighboring vertices on the circumference were connected to establish a polygon. Accordingly, the geometric shapes of triangle, square, pentagon, and hexagon were formed. Furthermore, the mirror structure was strengthened by employing straight lines passing the vertices and the center of the circle. Based on the finite element analysis, deformations of the mirrors caused by the gravitational force were evaluated. Weight and deformation of the mirror structures were compared and analyzed to find a proper structure to reduce weight and deformation. This paper, therefore, presents a structural solution aimed at reducing the weight and deformation of a large aperture mirror induced by gravitational forces, thereby suggesting a geometric shape based structure to reduce surface deformation of a mirror.

DWI 검사 시 인체 조직 및 병변에 근접한 공기는 영상왜곡을 가중해 병변 감별에 어려움을 준다. 이에 본 연구는 팬텀을 제작하 여 기하학적 왜곡을 줄여주는 SMS RESOLVE DWI를 통해 공기 자화율에 의한 왜곡 변화를 정량화하였다. 팬텀은 원통형으로 내부에 공기가 존재하도록 설계하였다. 제한된 환경 속에서 다양한 자화율에 의해 왜곡이 영상에 구현되도록 팬텀 내부에는 증류수, 젤라틴 외 혼합 물질과 공기를 구분되게 채웠다. 팬텀의 정렬을 다르게 하여 공기 있는 상태 실험을 진행 후, 공기 대신 혼합액 넣은 상태 실험을 같은 방식으로 진행하였고 혼합액 대신 증류수 넣은 상태 실험을 진행하였다. 3T MRI 장비로 T2WI, C DWI, SMS-RESOLVE DWI를 촬영하였고 파이썬 OpenCV로 이미지 유사도를 측정 후 비교 분석하였다. 실험 결과 공기 있는 상태 SMS-RESOLVE DWI b0에서 SSIM 평균 0.898, MSE 평균 0.068로 영상왜곡이 가장 적었다. SMS-RESOLVE DWI의 공기 자화율 왜곡 변화는 b0 기준 SSIM, MSE 모두 –0.033~0.003 이미지 유사도 차이를 보였다. SMS-RESOLVE DWI b1000은 수치상 이미지 유사도 차이가 크지 않거나 감쇄되는 때도 있어서 향후 SNR 보완에 초점을 둔다면 보다 개선된 영상진단 성능을 제공할 것으로 기대되고 오픈 소스 라이브러리를 통해 오차를 최소화한 이미지 처리와 유사도를 분석하는 새로운 시도는 앞으로의 연구 방향에 새 모델을 제시한다.

Discontinuities exert great influence on the thermal, hydraulic, and mechanical behavior of rock mass. Rock joint is one of the most frequently encountered discontinuities in many engineering applications, such as tunnel, rock slope and repository for high level radioactive waste. Therefore, the effects of rock joint should be thoroughly investigated in various aspects. Rock joint has gone through many geological processes and its behavior can be characterized by many properties. Among them, geometric properties, such as joint roughness, aperture, and contact area can affect mechanical and hydraulic properties and vice versa. Therefore, accurate understanding and characterization of the geometric properties are of importance. Generally, the geometric properties of a joint are obtained or estimated using the surface height or elevation, which could be measured by various contact or noncontact methods. Then, the coordinates of the surfaces are used to calculate several parameters, for instance roughness indexes and mechanical aperture, in a quantitative manner. This paper is a part of SKB task force project that aims to evaluate the geometric properties of rock joints and to analyze the hydromechanical behavior within a rough joint considering the properties. Four pairs of joint surfaces were laser-scanned in order to obtain coordinates of the surfaces and then the coordinates were used to calculate the roughness, directional roughness, aperture, and spatial correlations. At the same time, fluid flow within a rough joint were simulated by a commercial FEM code, considering the variation of aperture space due to normal load. Flowrate, flow path, and channelization were investigated in an aperture scale. Since rock mass consists of several joints and/or joint sets, characterization of a single rock joint can be utilized for analyzing the behavior of rock mass as a reference.

본 논문은 코시 모멘텀(Cauchy’s Momentum) 방정식을 이산화하기 위해 GC-LSM(Geometric Conservative Least Squares Method) 을 사용한 새로운 Meshless 방법을 제시한다. FEM(Finite Element Method) 방법이 구조해석에 널리 사용되고 있지만 무격자 기법은 격자를 이동해야 할 때 장점이 많기 때문에 개발되었다. 본 작업은 무격자 기반의 FSI(Fluid-Structure Interaction) 프로그램을 개발하 기 위한 기틀을 다지는 단계이다. 본 논문에서는 Cauchy’s Momentum 방정식을 GC-LSM을 사용하여 강형식 형태로 이산화하였고, 시간 적분을 위해 New Mark Beta 방법을 사용하였다. 개발된 기법은 1D, 2D 및 3D 벤치마킹 문제에서 검증했으며, 정적 해석 및 동적 해석 결과가 해석해와 비교시 매우 정확한 결과를 보여준다.

자율운항선박이 상용화되어 연안을 항해하기 위해서는 해상의 장애물을 탐지할 수 있어야 한다. 연안에서 가장 많이 볼 수 있 는 장애물 중의 하나는 양식장의 부표이다. 이에 본 연구에서는 YOLO 알고리즘을 이용하여 해상의 부표를 탐지하고, 카메라 영상의 기하 학적 해석을 통해 선박으로부터 떨어진 부표의 거리와 방위를 계산하여 장애물을 시각화하는 해상물체탐지시스템을 개발하였다. 1,224장 의 양식장 부표 사진으로 해양물체탐지모델을 훈련시킨 결과, 모델의 Precision은 89.0 %, Recall은 95.0 % 그리고 F1-score는 92.0 %이었다. 얻 어진 영상좌표를 이용하여 카메라로부터 떨어진 물체의 거리와 방위를 계산하기 위해 카메라 캘리브레이션을 실시하고 해상물체탐지시 스템의 성능을 검증하기 위해 Experiment A, B를 설계하였다. 해상물체탐지시스템의 성능을 검증한 결과 해상물체탐지시스템이 레이더보 다 근거리 탐지 능력이 뛰어나서 레이더와 더불어 항행보조장비로 사용이 가능할 것으로 판단된다.

This paper reports critical heat flux(CHF) performance on wire heater according to material, thickness, length, cross sectional shape. Water was employed as the working fluid, which was saturated at 1 atm. By comparison of CHF values with difference conditions of wire length, contact resistance inherent in the experimental apparatus could be analyzed, which had made the bias error in many research groups. So, exact value of CHF could be measured, which was consistent with the literatures. The CHF value showed decrease tendency, as the cross sectional area increased and reach to the capillary length of the working fluid. Meanwhile, the effect of thermal properties on CHF was not observed in the experimental cases. This data would be used as a reference data in research field of CHF using wire heater, i.e. reactivity initiative accident(RIA).

We derive the geometric albedo of a near-Earth asteroid, (4179) Toutatis, to investigate its surface physical conditions. The asteroid has been studied rigorously not only via ground-based photometric, spectrometric, polarimetric, and radar observations but also via in situ observation by the Chinese Chang'e-2 space probe; however, its geometric albedo is not well understood. We conducted V-band photometric observations when the asteroid was at opposition in April 2018 using the three telescopes in the southern hemisphere that compose the Korea Microlensing Telescope Network (KMTNet). The observed time-variable cross section was corrected using the radar shape model. We nd that Toutatis has a geometric albedo pV = 0:185+0:045 -0:039, which is typical of S-type asteroids. We compare the geometric albedo with archival polarimetric data and further nd that the polarimetric slope{albedo law provides a reliable estimate for the albedo of this S-type asteroid. The thermal infrared observation also produced similar results if the size of the asteroid is updated to match the results from Chang'e-2. We conjecture that the surface of Toutatis is covered with grains smaller than that of the near-Sun asteroids including (1566) Icarus and (3200) Phaethon.

A numerical method is proposed to calculate the response of detectors measuring particle energies from incident isotropic fluxes of electrons and positive ions. The isotropic flux is generated by injecting particles moving radially inward on a hypothetical, spherical surface encompassing the detectors. A geometric projection of the field-of-view from the detectors onto the spherical surface allows for the identification of initial positions and momenta corresponding to the clear field-of-view of the detectors. The contamination of detector responses by particles penetrating through, or scattering off, the structure is also similarly identified by tracing the initial positions and momenta of the detected particles. The relative contribution from the contaminating particles is calculated using GEANT4 to obtain the geometric factor of the instrument as a function of the energy. This calculation clearly shows that the geometric factor is a strong function of incident particle energies. The current investigation provides a simple and decisive method to analyze the instrument geometric factor, which is a complicated function of contributions from the anticipated field-of-view particles, together with penetrating or scattered particles.

Comprehensive calculations of the Rh decoration effect on zigzag CNTs with n ranging from 7 to 12 were conducted in this work to understand the effect of Rh doping on geometric structures and electronic behaviors upon metallic and semiconducting CNTs. The obtained results indicated that Rh dopant not only contributes to the deformation of C-C bonds on the sidewall of CNTs, but also transforms the electron distribution of related complexes, thereby leading to a remarkable increase of the conductivity of pure CNTs given the emerged novel state within the energy gap for metallic CNTs and the narrowed energy gap for semiconducting CNTs. Our calculations will be meaningful for exploiting novel CNT-based materials with better sensitivity to electrons and higher electrical conductivity compared with pure CNTs.

본 논문은 류동식의 신학사상의 중심을 “포월(包越)”사상으로 파악하고, 기하학적인 해석을 통해 선교신학적으로 조명한다. 류동식의 신학은 토착화된 풍류신학이라기 보다는 오히려 예술신학으로 보아 야 더 깊이 있게 이해할 수 있다. 류동식의 신학적 사유구조가 기하학적이고 도형적이기 때문이다. 포월 사상이 가장 강력하게 작용하는 상황은 대립과 차이가 발생하는 지점이다. 기하학적으로 디아드(Dyad), 즉 양극이 이질적으로 충돌하는 지점이다. 밀어내는 동시에 끌어당기는 속성과 ‘하나’에 대한 기억은 파르마콘, 즉 약이면서 동시에 독인 상황에서 혼돈을 초래한다. 그러나 이 역설과 모순이 포월에서 극복된다. 무엇보다도 포월사상이 완성되는 곳은 트리아드(Triad), 즉 삼태극이 다. 절대적인 타자였던 하나님이 자기 부정의 인격적 매개인 그리스도의 심허속천(心虛屬天)으로 인해 인간과 하나가 된다. 이것이 삼태극에서 역동하는 부활이다. 풍류신학의 삼태극의 관점에서 그리스도는 하늘과 사람 사이의 중심을 이어주고, 사람과 사람 사이의 중심을 이어주는 것은 지상에서 존재하는 가장 아름다운 사건을 만드는 선교적 예술가인 것이다.