• Journal of Aerospace System Engineering
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• v.16 no.3
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• pp.99-104
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• 2022

Aircraft pylon connects the engine or external stores to the main wing, and transfers the load acting on the pylon to the main structure of the aircraft. In particular, it should perform the function of separating the external store mounted on the pylon in case of emergency or mission performance. At this time, if the separation of the external store is not performed properly due to peripheral air flow or functional problems during the separation process of the external store, it may seriously impact the survivability of the aircraft. For this reason, to apply an external attachment to an aircraft, it is necessary to prove the stability of the external attachment in the separation situation in advance. In this paper, we present the result of the ground separation test performed to confirm that the external fuel tank, which is an external attachment, can be safely separated from the pylon. As a result of the test, the separation movement of the external fuel tank was measured with a high-speed camera, and the stability of the separation of the external fuel tank from the pylon were confirmed through the ground separation test. Additionally, the test result provides basic data for the stability evaluation of the separation of external attachments in actual aircraft.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.36 no.4
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• pp.213-220
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• 2023

This paper presents a model simulating the folding process and collision dynamics of "ddakji", a traditional Korean game played using paper tiles (which are also referred to as ddakji). The model uses two A4 sheets as the base materials for ddakji. The folding process involves a series of boundary conditions that transform the wing part of the paper structure into a twisted configuration. A rigid plate boundary condition is also adopted for squeezing, establishing the shape and stress state of the game-ready ddakji through dynamic relaxation analysis. The gaming process analysis involves a forced displacement of the striking ddakji to a predetermined collision position. Collision analysis then follows at a given speed, with the objective of overturning the struck ddakji--a winning condition. A genetic algorithm-based optimization analysis identifies the optimal collision conditions that result in the overturning of the struck ddakji. For efficiency, the collision analysis is divided into two stages, with the second stage carried out only if the first stage predicts a possible overturn. The fitness function for the genetic algorithm during the first stage is the direction cosine of the struck ddakji, whereas in the second stage, it is the inverse of the speed, thus targeting the lowest overall collision speed. Consequently, this analysis provides optimal collision conditions for various compression thicknesses.

• Journal of Aerospace System Engineering
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• v.17 no.6
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• pp.54-62
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• 2023

Flapping-wing air vehicles, well known for their free vertical take-off and excellent flight capability, are currently under intensive development and research. While most of the studies have explored the effect of various parameters of synchronized motions on the unsteady aerodynamics of flapping wings, limited attention has been given to the effect of nonsynchronous motions on the unsteady aerodynamic characteristics of flapping wings. In the present study, we conducted a numerical analysis to investigate the unsteady aerodynamic characteristics of an airfoil flapping with different frequency ratios between pitch and heave oscillations. We identified the motions and angle of attacks due to nonsynchronous motions. It was found that the synchronous motion produced thrust with zero lift, but the nonsynchronous motion generated a large lift with little drag. The aerodynamic characteristics of the airfoil undergoing the non-synchronous motion were also analyzed using the vorticity distributions and the pressure coefficient around and on the airfoil. When r was equal to 0.5, larger leading and trailing edge vortices were observed compared to the case when r was equal to 1.0, and these vortices significantly affected the aerodynamic characteristics of the airfoil undergoing the nonsynchronous motion. In future, the effect of pitch amplitude on the unsteady aerodynamic characteristics of the airfoil will be studied.

• Journal of the Daesoon Academy of Sciences
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• v.21
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• pp.323-367
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• 2013

한국의 대순진리회는 증산 성사의 가르침을 숭신하는 종교단체로서, 한국 사회에 상당한 영향력을 가지고 있다. 1969년 창설된 대순진리회는 포덕·교화·수도를 삼대 기본사업으로, '음양합덕·신인조화·해원상생·도통진경'을 종지로, '안심·안신·경천·수도'를 사강령으로, '성·경·신'을 수도의 삼요체로 삼고 있다. 또한 인간개조와 포덕천하·구제창생·보국안민을 통하여 지상천국을 건설하는 것을 목표로 한다. 대순진리회는 사상적 측면에서 무(巫)와 유(儒)·불(佛)·도(道)를 포용하고 있다. 이러한 대순사상을 바탕으로 대순진리회의 도인들은 근엄하고 세밀한 실천수도를 수행하는데, 그 내용을 살펴보면 중국 유·불·도의 양생문화와 많은 공통점이 있는 동시에, 또한 뚜렷한 한국 문화의 특색을 띠는 부분도 있다. 이런 면들은 모두 개인적 수도와 사회적 안정을 실현하는 데 큰 도움이 되고 있다. '안심·안신·경천·수도'의 사강령은 대순진리회의 도인들이 지켜야 할 가장 기본적인 행위규범이다. '성·경·신'의 삼요체는 사강령을 실천하기 위한 내면적 수양으로서 모든 수도활동의 근본이 되는 것이다. 삼요체 중에서 '성'을 가장 근본적인 것으로 생각하는데, 그 이유는 오직 '성'을 갖춘 사람만이 '경'과 '신'을 논할 수 있기 때문이다. 반대로 마음속에 망념이 있거나 경거망동을 하는 사람들은 상제에 대한 '경'과 '신'을 잃게 된다. '성실함'이라는 내면적 도덕 품성은 인간으로 하여금 더욱 정직하고 안정되며 오래 지속되게 한다. 뿐만 아니라 '성'은 수도자들로 하여금 더욱 순수해지고, 어리석음을 버리게 한다. 크나큰 도를 성취하려면 먼저 이렇게 얼핏 보기에는 어리석지만 끈기 있는 마음이 필요하다. '성'하면 기운이 솟구쳐 내면이 더욱 안정되고 번뇌는 사라진다. 성심을 수련하면 마음이 안정되고, 마음이 안정되면 정신이 안정되는데, 정신이 안정되면 걱정이 사라지기에 몸도 건강해진다. 삼요체중 '경'과 '신'에 있는 큰 의미 가운데 하나는 상제님에 대한 경배와 믿음을 끝까지 가지라는 것이다. '해원상생·보은상생'은 대순사상의 가장 중요한 대도(大道) 윤리로서 도인들의 수도를 인도하는 기본적인 법칙이다. 대순진리회에서 말하는 해원은 단지 개인 한 사람의 해원이 아니라 우주의 질서를 바로잡는 해원이라는 점에서 중요하다. 그렇기 때문에 대순진리회 도인들은 개개인으로 시작하여 자신의 원한을 해결할 뿐만 아니라, 땅의 원한, 천민의 원한, 여인의 원한 등 모든 원을 해결해 주고자 한다. 즉 삼계의 모든 불평등을 해소하고 불합리한 부분을 바로잡는 것이다. 해원의 다른 측면은 보은이라 할 수 있다. 해원과 보은은 상보상조의 관계에 있는데, 이는 곧 도인들이 행하는 수도의 양 날개라 생각된다. 해원을 통하여 과거의 장애를 제거하고, 보은을 통하여 현재의 덕을 쌓는 것이다. 보은을 하려면 항상 감사의 마음을 간직해야 한다. 그 의미는 인간관계에 있어서 다른 사람이 베푼 은혜를 항상 고맙게 생각해야 한다는 것이며, 더 나아가 천지가 우리에게 베푼 은혜도 감사하게 생각해야 한다는 것이다. 모든 원한이 풀어지고, 모든 은혜를 다 갚았을 때 삼계가 조화롭고 통하게 될 것이다. 대순진리회에서는 도인들의 실천수도 면에서 두 가지 측면을 강조하는데, 즉 포덕교화와 근언신행이다. 근언신행은 자아발전을 위한 도인들의 내적 수련이며, 포덕교화는 도인들이 외부 세상에 대순사상을 알리고 가르치는 것을 말한다. 양자는 동전의 양면과 같이 떨어질 수 없는 관계에 있다. 다른 사람을 포덕·교화 하려면 도인들 스스로가 먼저 말과 행동에 조심해야 한다. 왜냐하면 말과 행동을 조심하는 것 자체가 곧 포덕교화에서 다른 사람의 모범이 되기 때문이다. 인생을 살면서 추구해야 할 가장 높은 목표는 덕(德)을 세우는 것이고, 그 다음은 공(功)을 세우는 것이며, 그 다음은 언(言)을 세우는 것이다. 덕·공·언은 세월이 지나도 그 가치가 빛을 바래지 않는다. 이 세 가지 중 한 가지를 이룬 사람이면 불후하다고 할 수 있다. 성인들이 성인으로 칭송 받았던 이유는 모두 육체를 초월한 덕·공·언으로 세상을 풍요롭게 했기 때문이다. 그렇기 때문에 비록 그들이 세상을 떠났다 하더라도 마치 살아있는 것처럼 영원히 추앙되니, 이것을 통하여 영생을 얻는 것이다. '영생(永生)' 만큼 높은 경지에 도달하는 '양생'이 또 어디에 있겠는가? 대순진리회 실천수도의 최고목표는 바로 인간 내면의 수양을 최고의 경지로 끌어올리는 것으로서 이는 곧 음양합덕·도통진경이다. 다시 말해서 영원히 불후한 경지에 이르고 만세(萬歲)토록 영생하는 것이며 신(神) 그리고 성인이 되는 것이다.

• Korean Chemical Engineering Research
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• v.46 no.2
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• pp.423-429
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• 2008

Currently, Ash-free clean coal producing process by solvent extraction is under development. The produced ash-free clean coal can be directly combusted in a gas turbine which results in substantial improvement of power generation efficiency. However, the clean coal produced by the solvent extraction still contain trace amount of alkali metal which may cause corrosion on turbine blades during the direct combustion. In present work ${\alpha},{\beta}$-metal (Zr and Ti) phosphates and H-Y zeolite were synthesized and their ion exchange characterizations were investigated for the application on alkali metal removal for clean coal production. $Na^+$ ion removal capacities of the metal phosphates and H-Y zeolite were measured and compared in both aqueous solution (100 ppmw, $Na^+$) and coal dissolved N-methyl-2-pyrrolidone (NMP, 12 ppmw $Na^+$) at elevated temperature. In aqueous solution, the ${\beta}$ form metal phosphates showed very high ion exchange capacities compared to ${\alpha}$ form. ${\beta}$ form metal phosphates also showed higher $Na^+$ removal capacities than H-Y zeolite. In ion exchange medium of NMP, all the ${\alpha}$ form metal phosphates showed over 90% of $Na^+$ ion removal efficiency in the temperature range of 200 to 400 while that of H-Y zeolite decreased as a half when the temperature was over 350. In addition, the regenerated metal phosphates by acid treatment showed no sign of degradation in $Na^+$ removal efficiency. Among the metal phosphates used, $Zr_{0.75}Ti_{0.25}(HPO_4)_2$ showed the best performance in $Na^+$ removal and is expected to be the most suitable inorganic ion exchanger for the alkali metal removal process.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.8
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• pp.759-769
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• 2013

Electronic equipment has been applied to virtually every area associated with commercial, industrial, and military applications. Specifically, electronics have been incorporated into avionics components installed in aircraft. This equipment is exposed to dynamic loads such as vibration, shock, and acceleration. Especially, avionics components installed in a helicopter are subjected to simultaneous sine and random base excitations. These are denoted as sine on random vibrations according to MIL-STD-810F, Method 514.5. In the past, isolators have been applied to avionics components to reduce vibration and shock. However, an isolator applied to an avionics component installed in a helicopter can amplify the vibration magnitude, and damage the chassis, circuit card assembly, and the isolator itself via resonance at low-frequency sinusoidal vibrations. The objective of this study is to investigate the dynamic characteristics of an avionics component installed in a helicopter and the structural dynamic modification of its tray plate without an isolator using both a finite element analysis and experiments. The structure is optimized by dynamic loads that are selected by comparing the vibration, shock, and acceleration loads using vibration and shock response spectra. A finite element model(FEM) was constructed using a simplified geometry and valid element types that reflect the dynamic characteristics. The FEM was verified by an experimental modal analysis. Design parameters were extracted and selected to modify the structural dynamics using topology optimization, and design of experiments(DOE). A prototype of a modified model was constructed and its feasibility was evaluated using an FEM and a performance test.

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.41 no.4
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• pp.8-20
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• 2023

Although the landscape architectural facilities need to be repaired according to historical and authentic techniques, the repair criteria of the standard specification for repairing cultural heritages still remain at a theoretical level, and there are little research analyzing detailed techniques from specific cases. This study discussed the repair techniques based on historical facts, around terraced flower beds, ponds, waterways and pavement in the government-managed spaces in the Joseon Dynasty. It analyzed the materials and finish of stone wall elements, the structural reinforcement and backfill materials, and topsoil surface protection measures, and drew out stones for foundation reinforcement, plastering material for agglutination, and stone processing techniques for the terraced flower beds. It examined the materials and structures of the rock revetment, foundation reinforcement and waterproofing techniques and drew out the outstanding characteristics of the foundation work, the recycle of used elements and the management of water quality, for the ponds. It primarily investigated the materials, foundation reinforcement and waterproofing techniques and discovered the repair techniques such as cover stone finishing methods, foundation and backfill materials, and flow reduction methods, for the waterways. Finally, it provided actual cases of the foundation composition, auxiliary materials and tools, and the use of cyperaceae and highlighted the existence of professional craftsmen called Bangjeonjang(方磚匠), for the pavement. This study is expected to be a staring point for discovering the repair techniques for landscape architectural facilities and used as basic data for revising specifications in the future.