• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.3
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• pp.58-64
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• 2003

Pogo is the instability resulting from the interaction between rocket structure and propulsion system of liquid propellant rocket. The coupling of structure and propulsion system can lead to severe problem in rocket. For the analysis of pogo, a time-invariant linearized mathematical model is developed for a selected flight time. Propulsion system is modeled using element representations for each components. Rocket structure is modeled using FEM. Form the results of modal analysis of structure, the behavior of structure can be represented. System equations for coupling structure and propulsion system are composed. The stability in obtained by the eigen solution of system matrix. The optimization of the design variables such as size, place of accumulator for suppressing pogo instability in carried out. This article of study can be used to determine the degree of stability, and guide the design of pogo suppression system.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.39-39
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• 2011

반도체 생산의 주요 공정 중 하나인 세정 공정은 공정 중 발생하는 여러 가지 부산물에 의한오염을 효과적으로 제거하여 수율 향상에 큰 영향을 미친다. 현재 주로 쓰이는 세정 공정은 습식 세정 공정으로 화학 약품을 이용하지만 패턴 손상 및 웨이퍼 대구경화에 따른 문제 등이 대두되어 이를 대체할 세정 공정의 도입이 요구되고 있다. 이에 따라 건식 세정에 대한 관심이 증가하고 있으며 에어로졸 세정이 대표적 공정으로 개발 되었으나 마이크로 단위의 발생 에어로졸 입경으로 인해 패턴 손상 문제를 해결하지 못하였다. 이러한 문제점을 극복하기 위하여 응축에 의해 형성되는 입자 크기를 줄이는 것에 관한 연구가 진행되어 왔고, 대응 방안으로 개발된 것이 가스 클러스터 세정이다. 가스 클러스터란 작동 기체의 분자가 수십, 수백 개 뭉쳐있는 형태 (cluster)를 뜻하며 이 때 형성된 클러스터는 수 nm 크기를 가진다. 그리고 짧은 시간의 응축에 의해 수십 nm 크기까지 성장하게 된다. 즉, 입자로 성장할 수 있는 시간과 환경을 형성하지 않음으로써 작은 크기의 클러스터에 의해 패턴 사이의 오염물질을 물리적으로 제거하고 다시 기체상 물질로 환원되어 부산물을 남기지 않는 공정이다. 이러한 작동 환경을 조성하기 위해서는 진공도와 노즐 출구 속도에 대한 설계 단계부터의 이론적 연구를 통한 입자 크기 예측과 세정 조건에 따라서 발생하는 클러스터의 크기 분포 특성을 측정하는 것이 필수적이다. 따라서 본 연구에서는 실시간 저압 환경에서의 측정이 가능하며, 다양한 크기의 입자를 실시간으로 측정할 수 있는 particle beam mass spectrometer (PBMS)를 이용하여 세정 공정 중 발생하는 클러스터의 크기 분포를 측정하는 연구를 수행하였다. 클러스터의 측정은 노즐에 유입되는 유량과 냉매 온도를 변수로 하여 수행하였다. 각각의 조건에 따라서 최빈값은 오차범위 내에서 일정한 것을 확인하였으며, 50 nm 이하의 값으로 가스 클러스터 공정이 패턴 손상 없이 오염입자를 제거할 수 있음을 실험적으로 확인할 수 있었다. 또한 유량의 증가에 따라 세정에 사용되는 클러스터의 입경이 증가하며, 냉매 온도가 낮아질수록 클러스터 입경이 증가하는 경향을 확인할 수 있었다. 클러스터 크기는 오염 입자와의 충돌에 의해 작용하는 힘으로 오염입자를 제거하는 메커니즘을 사용하는 가스 클러스터 세정 장치에 있어 중요성이 크다 할 수 있으며 추후 지속적 연구에 의한 세정 기술의 최적화가 기대된다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.2
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• pp.1-8
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• 2014

The present study proposes a simple equation to straightforwardly determine the potential plastic hinge length in boundary element of reinforced concrete shear walls. From the idealized curvature distribution along the shear wall length, a basic formula was derived as a function of yielding moment, maximum moment, and additional moment owing to diagonal tensile crack. Yielding moment and maximum moment capacities of shear wall were calculated on the basis of compatability of strain and equilibrium equation of internal forces. The development of a diagonal tensile crack at web was examined from the shear transfer capacity of concrete specified in ACI 318-11 provision and then the additional moment was calculated using the truss mechanism along the crack proposed by Park and Paulay. The moment capacities were simplified from an extensive parametric study; as a result, the equivalent plastic hinge length of shear walls could be formulated using indices of longitudinal tensile reinforcement at the boundary element, vertical reinforcement at web, and applied axial load. The proposed equation predicted accurately the measured plastic hinge length, providing that the mean and standard deviation of ratios between predictions and experiments are 1.019 and 0.102, respectively.

• Journal of Korean Association for Spatial Structures
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• v.8 no.1
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• pp.41-48
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• 2008

Spatial structure is an appropriate shape that resists external force only with in-plane forte by reducing the influence of bending moment, and it maximizes the effectiveness of structure system. the spatial structure should be analyzed by nonlinear analysis regardless static and dynamic analysis because it accompanys large deflection for member. To analyze the spatial structure geometrical and material nonlinearity should be considered in the analysis. In this paper, a geometrically nonlinear finite element model for plane truss structures is developed, and material nonlinearity is also included in the analysis. Arc-length method is used to solve the nonlinear finite element model. It is found that the present analysis predicts accurate nonlinear behavior of plane truss.

• Elastomers and Composites
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• v.48 no.2
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• pp.156-160
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• 2013

A study on compressive creep behavior of ACM rubber for automotive engine gasket was performed using TMA thermal analysis. From the results of isothermal measurements with constant load of 1 N at several different temperatures of 160, 180, 200, and $220^{\circ}C$, compressive creep data at the given temperatures were obtained, and therefrom, shift factor ($a_T$) and master curve at reference temperature of $160^{\circ}C$ were obtained using time-temperature superposition principle (TTSP). $C_1$ and $C_2$ of WLF (Williams-Landel-Ferry) equation were calculated through the WLF plot as -1.107 and 11.571, respectively. From this, life time of ACM rubber at $120^{\circ}C$ was predicted as about 24,000 hrs.

• Journal of the Korean Society for Railway
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• v.12 no.4
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• pp.472-480
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• 2009

The stability analysis for CWR is difficult in the theory itself because both geometric and material nonlinearity should be considered. Also the analysis results are varied according to the loading history. In contrast to the complexity in the theory, the analysis results for CWR on the railway bridges are quite simple and can be predicted because of a small buckling effect and its negligible nonlinearity. In this study, refined nonlinear analysis methods for the stability analysis of CWR on the railway bridges were developed which consider only material nonlinearity beeause the effects of geometric nonlinearity are nominal. In this study, the analysis results can be found within limited number of iterations with idealized linear force-displacement relationship. From the analysis result comparisons, it was found that the stability analysis for CWR on the railway bridges can be performed effectively by this method.

• Journal of the Korean Institute of Intelligent Systems
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• v.22 no.5
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• pp.533-539
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• 2012

The purpose of this study is to estimate a validity of control signal through a design of Exoskeleton Robot Arm's capable of intelligent recognition as a human arm's motion by using realtime processed data of generated EMG signals. By an intelligent algorithm, the EMG output value of human biceps and triceps muscles contraction can be recognized and used for the control over exoskeleton arm corresponding to human's recognition and judgement. The EMG sensing data of muscles contraction and relaxation are used as the input signal from human's body to operate the Exoskeleton Robot Arm thus copying human arm motion. An intelligent control of Exoskeleton Robot Arm is to design the analog control circuit which processes the input data, and then to manufacture an integrated control board. And then abstracted signal is passed by DSP signal processing, Fuzzy logic algorithm is designed for a accurate prediction of weight or load through the intelligent algorithm, and design an Exoskeleton Robot Arm to express a human's intention.

• Archives of design research
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• v.15 no.3
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• pp.201-212
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• 2002

This thesis is to study about The Issue of Treating Information, according to the circumstance of Digital Media in Contemporary Design. The Digital Design is being able to be organized by developed Science and Technology. Ultra fashionable mode of digital design is leading human life more comfortable and serviceable: and proceeded by technology aheaded by science Developed Computer will help the Space science and virtual reality. and They will lead more developed industrial culture. The design is influencing international society and economic circumstance, and it's making the changedness of product and commercial route. virtual reality and simulation made by developed science is resulting in new design revolution in our society. Especially, it is able to make more bigger result in image breaking and reassimilation. The technology of developed information treating infra is able to transmit & receive a message, which are beyond our sensual boundary and is the meaning of the human-being's progressive development of science culture. Developed information treating methodology made by technology and science of restoration will be Neo-reality for artists and are the cause of great changedness in 21st century's art & design.

• 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.27 no.4
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• pp.339-344
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• 2007

Safety of large scale cable in bridge is very important because it may cause the unwanted catastrophic failure. Although the proof load were considered at the design stage, its soundness must be monitored continuously because the cable may be broken out without warning by the variable external load. The cable tension of in-use structures has been mainly measured by the resonance method and its use has been limited because of relatively large measurement uncertainty. Recently a new magnetic method was developed and its reliability is known to be good for evaluating the cable tension. In this study a system which can deliver the calibrated load to the cable was developed and the measurement reliability of developed magnetic sensor according to the change of external load was analyzed quantitatively. The effect of magnetization frequency, bias magnetic field, and temperature on the sensor output was also evaluated.