A force-free field (FFF) is determined solely by the normal components of magnetic field and current density on the entire boundary of the domain. Methods employing three components of magnetic field suffer from overspecification of boundary conditions and/or a nonzero divergence-B problem. A vector potential formulation eliminates the latter issue, but introduces difficulties in imposing the normal component of current density at the boundary. This paper proposes four different boundary treatment methods within the vector potential formulation. We conduct a comparative analysis of the vector potential FFF solvers that we have developed incorporating these methods against other FFF codes in different magnetic field representations. Although the vector potential solvers with the new boundary treatments do not outperform our poloidal-toroidal formulation code, they demonstrate comparable or superior performance compared to the optimization code in SolarSoftWare. The methods developed here are expected to be readily applied not only to force-free field computations but also to time-dependent data-driven simulations.

For the past 70 years, an intense rivalry has persisted on the Korean Peninsula, and North Korea's nuclear and missile threats are becoming increasingly imminent. Facing a shortage of military resources, South Korea has pursued a national defense reform, significantly reducing the number of units and troops while focusing on ground forces. However, North Korea's strategic objective of unifying South Korea through surprise attacks, prompt responses, and combined nuclear and missile assaults remains unchanged. The central issue in this context revolves around determining the appropriate size of the Korean military's standing forces. This study employs the concept of net assessment as a novel method to ascertain the optimal size of the Korean military. Threats, strategic objectives, doctrine, and unit rotations are simultaneously considered from the enemy's perspective. In anticipation of security risks on the Korean Peninsula, an acceptable troop size will be proposed using the net assessment approach to calculate the appropriate standing force size.

In the (3,3) close combat model based on the Lanchester Square Law, this study proposes a plan to optimally allocate residual combat power after the battle to other battlefields. As soon as the two camps of three units can grasp each other's information and predict the battle pattern immediately after the battle began, the Time Zero Allocation of Force (TZAF) scenario was used to initially allocate combat power to readjust the combat model. It reflects travel time, which is a "field friction" in which physical distance exists from battlefields that support combat power to battlefields that are supported. By developing existing studies that try to examine the effect of travel time on the battlefield through the combat model, this study forms a (3,3) combat model, which is a large number of minimum units. In order to achieve the combat purpose, the principle of optimal combat force operation is presented by examining the aspect that support combat power is allocated to the two battlefields and the consequent battle results. Through this, various scenarios were set in consideration of the travel time and the situation of the units, and differentiated results were obtained. Although the most traditional, it can be used as the basic logic of the training or the commander's decision-making system using the actual war game model.

In this study, the evaluation items related to the effectiveness evaluation of the LVC (Live, Virtual, Constructive) training system of the Air Force were derived and the weights of each item were analyzed. The LVC training system evaluation items for AHP (Analytic Hierarchy Process) analysis were divided into three layers, and according to the level, 3 items were derived at level 1, 11 items at level 2, and 33 items at level 3. For weight analysis of evaluation items, an AHP-based pairwise comparison questionnaire was conducted for Air Force experts related to the LVC training system. As a result of the survey, related items such as (1) Achievement of education and training goals (53.8%), (1.2) Large-scale mission and operational performance (25.5%), and (1.2.1) Teamwork among training participants (19.4%) was highly rated. Also, it was confirmed that the weights of evaluation items were not different for each expert group, that is, the priority for importance was evaluated in the same order between the policy department and the working department. Through these analysis results, it will be possible to use them as evaluation criteria for new LVC-related projects of the Air Force and selection of introduction systems.

The equivalent static load for non-structural elements has a limitation in that the sloshing effect and the interaction between the fluid and the water tank cannot be considered. In this study, the equations to evaluate the impulse and convective components in the design codes and previous research were compared with the shaking table test results of a rectangular water tank with flexible wall panels. The conclusions of this study can be summarized as follows: (1) It was observed that the natural periods of the impulsive component according to ACI 350.3 were longer than system identification results. Thus, ACI 350.3 may underestimate the earthquake load in the case of water tanks with flexible walls. (2) In the case of water tanks with flexible walls, the side walls deform due to bending of the front and back walls. When such three-dimensional fluid-structure interaction was included, the natural period of the impulsive component became similar to the experimental results. (3) When a detailed finite element (FE) model of the water tank was unavailable, the assumption   could be used, resulting in a reasonably conservative design earthquake load.

Background: Coating a culture plate with molecules that aid in cell adhesion is a technique widely used to produce animal cell cultures. Extracellular matrix (ECM) is known for its efficiency in promoting adhesion, survival, and proliferation of adherent cells. Gelatin, a cost-effective type of ECM, is widely used in animal cell cultures including feeder-free embryonic stem (ES) cells. However, the optimal concentration of gelatin is a point of debate among researchers, with no studies having established the optimal gelatin concentration. Methods: In this study, we coated plastic plates with gelatin in a concentrationdependent manner and assessed Young’s modulus using atomic force microscopy (AFM) to investigate the microstructure of the surface of each plastic plate. The adhesion, proliferation, and differentiation of the ESCs were compared and analyzed revealing differences in surface microstructure dependent on coating concentration. Results: According to AFM analysis, there was a clear difference in the microstructure of the surface according to the presence or absence of the gelatin coating, and it was confirmed that there was no difference at a concentration of 0.5% or more. ES cell also confirmed the difference in cell adhesion, proliferation, and differentiation according to the presence or absence of gelatin coating, and also it showed no difference over the concentration of 0.5%. Conclusions: The optimum gelatin-coating for the maintenance and differentiation of ES cells is 0.5%, and the gelatin concentration-mediated microenvironment and ES cell signaling are closely correlated.

Hexagonal bolt, nut, fittings, and high-pressure valves with special alloy play an important role in many industrial products, for instance, such as semiconductor facilities, hydrogen stations and fuel cell electric vehicles. The purpose of this study is to investigate the structural stability of turning wheel using the reaction force of roller in variable hexagonal rolling die. As the results, the bearing groove had the possibility of damage in turning wheel, especially, in case of Bottom condition. Furthermore, the turning wheel showed structural instability by using safety factor but structural stability using strength, respectively, as a safety criterion.

이 연구는 21세기에 들어 핵전력 강화에 전념하는 북한의 핵전략을 내 부적 법과 제도의 정비 사례를 통해 분석한다. 북한은 2012년 헌법 서문 을 개정하여 ‘핵보유국’임을 천명하였고, 2013년 “자위적 핵보유국의 지 위를 더욱 공고히 할 데 대하여(소위 핵보유국법)”와 2022년 “조선민주 주의인민공화국 핵무력정책에 대하여(소위 핵무력정책법)을 통해 핵전략 을 세부적으로 발전시키고 있다. 2013년 대비 2022년의 법률은 상당부 분 공세적, 권한위임형 핵전략을 보인다는 특징이 있다. 본 논문은 두 법 률의 내용 변화를 리케의 전략 3요소(목표, 방법, 수단)를 바탕으로 분석 하고, 비슷한 핵전략의 변화를 보였던 파키스탄의 사례와 비교하여 함의 를 도출한다. 결론적으로는 바틀렛의 모델을 바탕으로 북한 핵전략의 전 략적 균형 달성 여부를 고찰해본다.

본 논문에서는 볼트로 체결된 구조체에 대하여 초기 볼트풀림 상태에서의 볼트 체결력 예측 합성곱 신경망 훈련 방법을 제시한다. 8개의 볼트의 체결력이 변경된 상태에서 계산한 주파수응답들을 완전 체결된 상태의 초기 모델과의 크기 및 모양 유사성을 표현하는 유사성 지도로 생성한다. 주파수응답 데이터들의 생성에는 크리로프 부공간법 기반의 모델차수축소법을 적용하여 효율적인 방법으 로 수행할 수 있도록 한다. 합성곱 신경망 모델은 회귀 출력 계층을 사용하여 볼트의 체결력을 예측하도록 하였으며, 훈련 데이터의 개 수와 합성곱 신경망 계층의 개수를 다르게 준비하여 훈련시킨 네트워크들을 비교하여 그 성능을 평가하였다. 주파수응답에서 파생되 는 유사성 지도를 입력 데이터로 사용하여 초기 볼트풀림 영역에서 볼트 체결력의 진단 가능성과 유효성을 제시하였다.

초기 한국교회와 일제강점기 한국의 정치 현장 가운데서 우리나라 를 찾은 미국 선교사들의 입장은 매우 복잡했다. 그들은 정교분리와 정치적 중립 자세를 유지하기 어려웠다. 언더우드(1884년), 마펫 (1890년) 선교사의 내한 이후 한국선교를 위해 서구 선교사들의 끊임없 는 희생이 있었고, 1907년 평양 대부흥을 거쳐 빠르게 성장한 한국교회 는 스스로 세례를 받고, 성경을 번역하며 토착교회를 설립했다. 그래서 일제에 맞설 수 있는 잠재적 위협으로 인식되었다. 따라서 일제는 반일 기독교 민족주의 세력을 일거에 붕괴시키고자 하였다. 기독교 세력은 물론 그 배후에 있는 미국 선교사들을 축출하려는 의도를 지니고 있었다. 그러나 이러한 일제의 전략은 더 광범위하게 전개되는 3·1 독립운동이라는 한국 민족 최대의 항일운동으로 나타나게 되었다. 이러한 역사적 과정을 외부의 추동력과 내부의 흡인력을 모두 고려한 중도파 역사기술로 서술하고자 하는 것이 논문의 목적이다.

Laparoscopy instrument requires blood vessel ligator to prevent blood leakage. Clip ligation device is widely used to prevent blood loss and secure surgical vision by using blood vessel ligator. However, in order to properly install the clip to the vessel ligator and ligate the blood vessel by the ligation machine, the device is properly operated and the parts constituting the jaw areas should be ensuring sufficient strength and rigidity during the operating. Therefore, the clip binding forces were calculated through a dynamic model of the blood vessel ligator. As a result, the force satisfies the target value of 8.5 N or more regardless of the grip force positions. And structural analysis was carried out to find out the maximum resistance force at the tip of the inner shaft. The maximum load was about 45.6 N, which sufficiently satisfies the development target of 40.0 N or higher.

A bending experiment was conducted to verify the structural performance of the U-flange truss hybrid bean using rebars or steel pipes to reinforce the upper compression zone. As a result of evaluating the bending strength of the truss hybrid beam according to the Structural Design Standard (KDS 14 2020: 2022) by introducing the lattice member as a tensile resistance element, the following conclusions were obtained. Considering the lattice element as a tensile resistance element, the nominal bending strength was increased by 38.57 to 47.90 kN.m. As a result of reviewing the experiment as to whether the flexural member has proper ductility, it was found that it is desirable to place appropriate rebars, steel quality plans, and lateral restraints on the upper and lower parts of the hybrid beam to have sufficient ductility ratio.

As the demand for aesthetic orthodontic treatment increases, the use of self-ligating ceramic brackets is increasing. For stable treatment, there should be no fracture or deformation of the self-ligation ceramic bracket door. Therefore, considering the situation in which labial displacement of teeth occurs in the orthodontic treatment stage. For this study, a model of the mandibular anterior region of a ceramic self-ligating bracket with a passive sliding door mechanism was selected. The measured tensile force data was substituted into the simulation analysis conditions, and the tensile force, stress distribution, and deformation values were analyzed using the finite element method. Using this, it is able to use the design elements of the orthodontic bracket that should be considered as design inputs in the development stage.

Considering the non-linear behavior of structure and soil when evaluating a nuclear power plant's seismic safety under a beyond-design basis earthquake is essential. In order to obtain the nonlinear response of a nuclear power plant structure, a time-domain SSI analysis method that considers the nonlinearity of soil and structure and the nonlinear Soil-Structure Interaction (SSI) effect is necessary. The Boundary Reaction Method (BRM) is a time-domain SSI analysis method. The BRM can be applied effectively with a Perfectly Matched Layer (PML), which is an effective energy absorbing boundary condition. The BRM has a characteristic that the magnitude of the response in far-field soil increases as the boundary interface of the effective seismic load moves outward. In addition, the PML has poor absorption performance of low-frequency waves. For this reason, the accuracy of the low-frequency response may be degraded when analyzing the combination of the BRM and the PML. In this study, the accuracy of the analysis response was improved by adjusting the PML input parameters to improve this problem. The accuracy of the response was evaluated by using the analysis response using KIESSI-3D, a frequency domain SSI analysis program, as a reference solution. As a result of the analysis applying the optimal PML parameter, the average error rate of the acceleration response spectrum for 9 degrees of freedom of the structure was 3.40%, which was highly similar to the reference result. In addition, time-domain nonlinear SSI analysis was performed with the soil's nonlinearity to show this study's applicability. As a result of nonlinear SSI analysis, plastic deformation was concentrated in the soil around the foundation. The analysis results found that the analysis method combining BRM and PML can be effectively applied to the seismic response analysis of nuclear power plant structures.

The flange spreader has been used to withdraw butterfly valves during maintenance. The typical flange spreaders required an excessive working space, and the pipe and flange are damaged by the load. In the previous study, the author developed a valve easy out tool with collet, and designed collet shape to ensure structural safety. However, clamping force of the collet had not been checked. In this study, design of collet shape was performed to improve clamping force. Techniques of structural analysis were established and design parameters were selected. Through parametric study, the collet shape with clamping force of 159,748N was suggested. This will contribute to stability and efficiently of valve maintenance.

Climatologists have warned rapid climate change of the earth and it will cause a big disaster worldwide. the rapid climate change is mostly due to emission of greenhouse gases. To reduce greenhouse gases, many countries have prepared protocols, agreements, and treaties. IMO(International Maritime Organization) have established the protocol to decrease ship’s greenhouse gases emission and they consider the nuclear power source is an option to replace fossils fuels. Our study focused on elemental technologies related to a nuclear powered ship and, the passive residual heat removal system(PRHRS) is one of topics in our study. As the mandatory of the post Fukushima accident, PRHRS for a nuclear powered ship has been studied. We invented the new concepts of PRHRS which is optimized to a nuclear powered ship. The numerical analysis results indicated that the system is very reasonable. Based on the numerical analysis, an experiential loop was set and we preliminary tested the performance of the system under the reduced scale. The experimental results came with the numerical analysis results well.