• Journal of the Korean Institute of Intelligent Systems
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• v.23 no.2
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• pp.172-177
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• 2013

With Brain Computer Interface (BCI) system, a person with disabled limb could use this direct brain signal like electroencephalography (EEG) to control a device such as the artifact arm. The precise force control for the artifact arm is necessary for this artificial limb system. To understand the relationship between control EEG signal and the gripping force of hands, We proposed a study by measuring EEG changes of three grades (25%, 50%, 75%) of hand grip MVC (Maximal Voluntary Contract). The acquired EEG signal was filtered to obtain power of three wave bands (alpha, beta, gamma) by using fast fourier transformation (FFT) and computed power spectrum. Then the power spectrum of three bands (alpha, beta and gamma) of three classes (MVC 25%, 50%, 75%) was classified by using PCA (Principal Component Analysis) and LDA (Linear Discriminant Analysis). The result showed that the power spectrum of EEG is increased at MVC 75% more than MVC 25%, and the correct classification rate was 52.03% for left hand and 77.7% for right hand.

• Composites Research
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• v.13 no.4
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• pp.54-66
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• 2000

Interfacial and microfailure properties of carbon fiber/epoxy matrix composites were evaluated using both tensile fragmentation and compressive Broutman tests with an aid of acoustic emission (AE) monitoring. A polymeric maleic anhydride coupling agent and a monomeric amino-silane coupling agent were used via the electrodeposition (ED) and the dipping applications, respectively. Both coupling agents exhibited significant improvements in interfacial shear strength (IFSS) compared to the untreated case under tensile and compressive tests. The typical microfailure modes including fiber break of cone-shape, matrix cracking, and partial interlayer failure were observed during tensile test, whereas the diagonal slippage in fiber ends was observed under compressive test. For both loading types, fiber breaks occurred around just before and after yielding point. In both the untreated and treated cases AE amplitudes were separately distributed for the tensile testing, whereas they were closely distributed for the compressive tests. It is because of the difference in failure energies of carbon fiber between tensile and compressive loading. The maximum AE voltage for the waveform of carbon or basalt fiber breakages under tensile tests exhibited much larger than those under compressive tests, which can provide the difference in the failure energy of the individual failure processes.

• Aerospace Engineering and Technology
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• v.1 no.1
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• pp.8-27
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• 2002

In this study, the load analysis of a composite canard aircraft is performed numerically. Excel visual basic program for PC is used to calculate aerodynamic coefficients, loads and moments etc.. The basic data required for the load analysis such as aircraft configuration and dimension, parts and its weight and coordinate etc. are obtained from Catia modeling, measurement or material density. Aircraft weight, center of gravity, inertia moment, structural design speeds, wing load distribution, forces and moments are evaluated by using these data. V-n diagram is also represented for selecting critical loads applied to the wing and fuselage. The V-n diagram is investigated to decide the flight envelope of canard aircraft for design speed VA, VC, VD and load factor +3.8G, -1.52G at maximum weight of 2,573 lbs and sea level. In the future, the results of the wing and fuselage load analysis is to represented by using selected critical loads.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.1
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• pp.55-60
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• 2013

Compound bows use levering systems consisting of cables and cam pulleys to bend limbs that are much stiffer than those of recurve bows, thus storing more energy while requiring less force for the archer to hold the bow at a fully drawn position. Many patents have thus far been proposed to improve the efficiency and performance of compound bows through empirical methods, whereas only a few analytical methods have been proposed. In this light, this paper presents a method for the kinematic analysis of levering systems in compound bows so that a designer can easily predict the effects of changes in the cam profiles and limb materials.

• Journal of the Korean Society for Nondestructive Testing
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• v.24 no.1
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• pp.38-44
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• 2004

An experimental study for a crane hook was performed to investigate the stress distribution along a certain line where the maximum and minimum stresses to be developed. On this line, the isoclinic fringe and/or principal stress direction is constant. The crane hook was modeled into a 2-dimensional plate made of urethane rubber called 'Photoflex' The Photoflex is very sensitive to a load and has low photoelastic fringe constant. The Tardy compensation method with the fringe sharpening process and the 4-step phase shifting method, was used for the photoelastic technique. Experimental results by photoelasticity were compared with the calculated stresses from the simple curved beam theory and tile finite element analysis. Ail the results were close to each other.

• Journal of the Earthquake Engineering Society of Korea
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• v.6 no.4
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• pp.7-13
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• 2002

The behaviors of the reinforced concrete membrane elements are expected by Navier's three principles of the mechanics of materials. The adopted cyclic stress-strain curves of concrete consist of seven different unloading and loading stages in the compressive zone and six other stages in the tensile zone. The curves took into account the softening of concrete that was influenced by the tensile strain in the perpendicular direction of cracks. The stress-strain relationships for steel bar embedded in concrete subjected to reversed cyclic forces considered the tension stiffening effect and Baushinger effect. The predicted results of the analysis based on Navier's principles were in good agreement with the observed shear stress-strain relationships as well as transverse and longitudinal strains.

• Journal of the Korea Society for Simulation
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• v.29 no.3
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• pp.49-55
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• 2020

A goal of improving projectile is to increasing achievable range. The shape of a projectile is generally selected on the basis of combined aerodynamics and structural considerations. The choice of body, nose and boattail shape has a large effect on aerodynamic design. One of the main design factors that affect projectile configuration is aerodynamic drag. The aerodynamic drag refers to the aerodynamic force that acts opposite to the relative motion of a projectile. An investigation was made to predict the effects of nose, boattail and body shapes on the aerodynamic characteristics of projectiles using a semi-empirical technique. A parametric study is conducted which includes different projectile geometry. Performance predictions of achievable range are conducted using a trajectory simulation model. The potential of extending the range of a projectile using optimization of projectile configuration is evaluated. The maximum range increase is achieved due to the combination of optimal body shapes.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.32 no.4
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• pp.223-231
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• 2019

A continuum-based design sensitivity analysis(DSA) method is developed for electrostatic problems. To consider high order objective functions, we use 9-node finite element basis functions for analysis and DSA methods. As the design variables are parameterized with B-spline functions, smooth boundary variations are naturally obtained. To solve mesh entanglement problems during the optimization process, a mesh regularization scheme is employed. By minimizing the Dirichlet energy functional, mesh uniformity can be automatically achieved. In numerical examples for maximizing dielectrophoresis forces, the numerical results are compared with well-known electrode geometries and the obtained characteristics are discussed.

• Korean Architects
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• s.600
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• pp.34-41
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• 2019

대통령 소속 국가건축정책위원회, 건축정책기본계획, 건축도시공간연구소, 공공건축가. 지금 우리 건축계를 정의하는 중요한 개념들이다. 이 모두 2007년 제정된 건축기본법에 근거한 내용으로서 당시 건설기술 건축문화선진화위원회, 건설교통부, 문화관광부의 '건축문화 선진화전략' 핵심과제였다. 그러나 '건축기본법'이 있어야 한다고 처음 주장한 사람은 김광현 서울대학교 건축학과 명예교수였다. 그가 연구책임자로서 건축기본법의 바탕을 만들었으며, 오늘의 건축계를 정의하는 건축기본법의 틀과 개념 그리고 용어의 설정도 거의 그의 구상에서 나왔다. 대한건축사협회(한명수 명예회장)와 건설기술 건축문화선진화위원회(김진애 위원장)가 이 법 제정을 위해 큰 힘을 기울였다면, 그는 이론적 기틀을 확립한 인물이다. 그는 학계에 있었지만 설계대가 제값 받기에 유독 관심이 많았다. 이유는 학생들이 사회에 나가 전문가로서 좋은 일을 할 수 있는 최대의 근거는 제대로 된 설계대가에 있다는 그의 지론 때문이었다. "학생들을 가르치는 최고의 목표는 그들이 사회에 나가 좋은 대접을 받게 하는 겁니다. 건축계에서 해야 할 가장 중요한 게 뭐냐고 지금 또 묻는다면 단언컨대 나는 제대로 된 '설계대가'라고 말할 겁니다." 김광현 명예교수는 과거 '공공발주사업에 대한 건축사의 업무범위와 대가기준'에서 '친환경건축물, 에너지효율등급' 등 추가업무에 대한 대가를 제대로 받을 수 있게 하자고 주장하고 이를 연구한 책임자이기도 했다. 그는 지금 젊은 건축사 건축교육 저변확대를 위한 '공동건축학교'를 설립해 활발히 운영 중이다. 월간 "건축사"가 국내 건축계 발전을 위해 힘써오다가 작년 2월 정년퇴임한 김광현 서울대학교 건축학과 명예교수를 3월 18일 그의 대학로 연구실에서 만났다. 그는 지난날을 회고하며 건축에 얽힌 이야기와 현재 하고 있는 일, 그리고 구상 중인 향후계획까지 다양한 이야기를 전했다.

• Journal of Advanced Navigation Technology
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• v.25 no.3
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• pp.211-216
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• 2021

Multiple UAV System has been used for various purposes such as reconnaissance, networking and aerial photography. In such systems, it is essential to form and maintain the formation of multiple UAVs. This paper proposes the algorithm that produces an autonomous distributed control for each vehicle for a flexible formation. This command is a repulsive force in the form of the second-order system by the nearest UAV or mission area. The algorithm uses the relative position/speed through sensing and communication for calculating the command without external intervention. The command allows each UAV to follow the reference distance and fill the mission area as densely as possible without overlapping. We determine the reference distance via optimization technique solving the packing problem. The mission area comprises the desired formation outline and can be set flexibly depending on the mission. Numerical simulation is carried out to verify the performance of the proposed algorithm under a complex and flexible environment. The formation is formed in 26.94 seconds and has a packing density of 71.91%.