• Structural Engineering and Mechanics
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• 제78권5호
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• pp.557-572
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• 2021

The current study considers free vibration of the spherical panel with magnetorheological (MR) fluids core and magneto-electro-elastic face sheets. The panel is subjected to electro-magnetic loads and also is located on an orthotropic visco-Pasternak elastic foundation. To describe the displacement components of the structure, the first-order shear deformation theory (FSDT) is used and the motion equations are extracted by employing Hamilton's principle. To solve the motion differential equations, Navier's method is selected as an exact analytical solution for simply supported boundary conditions. Effect of the most important parameters such as magnetic field intensity, loss factor, multi-physical loads, types of an elastic medium, geometrical properties of the panel, and also different material types for the face sheets on the results is considered and discussed in details. The outcomes of the present work may be used to design more efficient smart structures such as sensors and actuators.

• 산업노동연구
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• 제23권2호
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• pp.169-193
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• 2017

본 연구는 우리나라에서 동학적 고용안정성을 진단하기 위해서 고용유지율에 영향을 미치는 결정요인을 분석하였다. 고용유지 결정요인 분석을 위해서 사업체 패널자료와 고용보험 이력자료를 연계하고, 다층적 위계적 자료 분석에 적절한 다층 분석모형을 활용하여 결정요인을 분석하였다. 분석결과, 우리나라에서 고용안정성이 매우 낮은 것은 임금수준이 낮고 비정규직 활용수준이 높은 주변부 부문이 광범위하게 존재하기 때문으로 추정된다. 또한 우리나라의 고용구조는 고용과 실업이 반복되는 단기간 고용이 상당한 영역을 차지하면서 전반적으로 고용안정성이 약한 것으로 평가된다. 이러한 사실은 기업이나 개인적 차원에서 숙련향상 및 숙련형성기회가 제한되면서 지속적인 성장 제약요인으로 작용할 가능성이 높으며, 이에 대한 적극적 대응책으로 고용구조의 질적 개선노력이 요구된다.

• Journal of Information Display
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• 제1권1호
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• pp.3-8
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• 2000

We have developed a high performance vertical alignment TFT-LCD (Thin Film Transistor Liquid Crystal Display), that shows a high light transmittance, and wide viewing angle characteristics with an unusually high contrast ratio. In order to optimize the electro-optical properties we have studied the effect of cell parameters, multi-domain structure and retardation film compensation. With the optimized cell parameters and process conditions, we have achieved a 24" wide UXGA TFTLCD monitor (16:10 aspect ratio 1920X1200) showing a contrast ratio of over 500:1, panel transmittance near 4.5%, response time near 25 ms, and viewing angle higher than 80 degree in all directions.

• 한국정밀공학회지
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• 제18권9호
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• pp.71-81
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• 2001

This paper analyzes the effectiveness of minimizing vibration and sound transmission on/through a thin rectangular plate by both feedback control and hybrid control which combines adaptive feedforward control with a feedback loop. An experimental system identification technique using the matrix-fractional curve-fitting of the frequency response data is introduced for complex shaped structures. This identification technique reduces the model order o the MIMO(Multi-Input Multi-Output) system which simplifies the practical implementation. The adaptive feedforward control uses a Multiple filtered-x LMS(Least Mean Square) algorithm and the feedback control uses a multivariable digital LQG(Linear Quadratic Gaussian) algorithm. Experimental results show that an effective reduction of sound transmission is achieved by the hybrid control scheme when both vibration and noise measurement signals are incorporated in the controller.

• 한국지진공학회논문집
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• 제15권1호
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• pp.39-48
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• 2011

본 연구에서는 복강판-모듈러 시스템과 같이 구조 기준에 명시되지 않은 새로운 시스템의 반응수정계수를 산정하는 절차를 제안하였다. 기본 개념은 구조성능 실험결과를 바탕으로 모델링 된 시스템의 비선형 정적 해석 곡선으로부터 세부 구성요소인 초과강도계수와 연성계수의 도출하고, 단자유도 시스템으로 간주하고 평가된 반응수정계수를 다자유도 동적 거동을 고려한 다자유도 밑면전단 수정계수로 수정하여 시스템의 최종적인 반응수정계수를 결정하는 것이다. 제안한 절차에 따라 이중골조시스템으로 설계된 2층부터 5층까지의 복강판-모듈러 시스템에 대해 평가한 결과, 최종적인 반응수정계수는 5층(층고 4m기준)을 복강판-모듈러 시스템의 적용 가능한 층수의 상한으로 하여 4로 결정하는 것이 타당할 것으로 판단하였다.

• 대한교통학회지
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• 제20권7호
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• pp.79-85
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• 2002

각 개인이 발생하는 통행 행태와 이들 가구 구성원간의 연관관계 및 영향에 대한 이해는 활동기반모형의 궁극적 목표라 할 수 있는 미래의 활동패턴 예측의 가장 기본이 되는 연구사항이라 할 수 있다. 일반적인 회귀 모형의 경우 개인의 활동/통행 패턴을 알아내기 위하여 모집단으로부터 수집되는 개인자료는 가구라는 부분모집단으로 세분화되어 계층적 구조(Hierarchical structure)의 성향을 고려하지 못하고 있어, 그 결과는 편이된 추정치를 낳는다. 따라서, 본 연구에서는 계층적 구조를 갖고 있는 자료를 이용하여 다수준 모형(Multi-Level Model)을 사용하여 개인의 활동/통행 패턴 영향을 규명해내고 활동/통행 패턴의 변화를 가구수준의 변동과 개인수준의 변동으로 나누어 분석하였다. 사용된 자료는 미국 Puget Sound 지역의 Transportation Panel 자료(PSTP)를 이용하였다. 분석 결과 개인의 통행사슬 발생모형에서 가구수준의 변동이 전체변동의 1/4를 차지하고 생계활동 지속시간 모형에서는 전체 변동의 1/8을 차지하는 등의 매우 큰 값을 나타내어 개인의 활동/통행 패턴 분석시 다수준 모형을 통한 분석의 필요성이 대두되었다.

• 한국전기전자재료학회논문지
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• 제25권1호
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• pp.44-47
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• 2012

The $TiO_2/Si_3N_4/Ag/Si_3N_4/TiO_2$ multi layered structure was designed for the possible application of transparent electrodes in PDP (Plasma Display Panel). Multi layered film was deposited on a glass substrate at room temperature by DC/RF magnetron sputtering system and EMP (Essential Macleod Program) was adopted to optimize the optical characteristics of film. During the deposition process, the Ag layer in $TiO_2/Ag/TiO_2$ became heavily oxidized and the filter characteristic was degraded easily. In thus study, Si3N4 layer was used as a diffusion buffer layer between $TiO_2$ and Ag. in order to prevent the oxidation of Ag layer in $TiO_2/Si_3N_4/Ag/Si_3N_4/TiO_2$ structure. It was confirmed that $Si_3N_4$ layer is one of candidate materials acting as diffusin barrier between $TiO_2/Ag/TiO_2$.

• 한국안전학회지
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• 제30권3호
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• pp.107-113
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• 2015

The goal of this paper is to investigate structural integrity factors of RMI(reflective metal insulation) to confirm the design requirements in nuclear power plant. Currently, a glass wool insulation is using now, but it will gradually be replaced with the reflective metal insulation maded by stainless steel plates. The main function of an insulation is to minimize a heat loss of vessel and pipes in RCS(reactor coolant system). It has to maintain structural a integrity in nuclear power plant life duration. In this study, the structural integrity analysis was carried out both multi-plate and outer shell plate by using a static analysis and experimental test. First, inner multi-plate has a self support structure for being air space. Because the effect of total static weight in multi-layer plate is low, a plate collapse possibility is not high. Considering optimum thin plate pressing process, it has to pre-check the basic physical properties. Second, the outer segment thickness and stiffener shape are verified by the numerical static analysis, and sample test for both type of panel and cylindrical pipe model.

• 한국군사과학기술학회지
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• 제13권5호
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• pp.933-940
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• 2010

A numerical analysis for the space frame structure under ballistic and blast loads was performed using LS-DYNA, a commercial code. The space frame structure was developed to be adapted to the ground vehicle in the future and it was designed to build with Al7039 frames and lightweight multi-layered panels for the purpose of weight reduction and shock mitigation. The analyses have done for side impacts by a cylindrical projectile and Comp. C-4 explosive representing major threats to the vehicle. The deformed shape of the panel section and stresses as well as accelerations of the frames calculated from LS-DYNA were compared to the test results to validate the analysis model. The internal energies for panels and frames from LS-DYNA were also compared to each other to discern their role in absorbing the ballistic and blast impact.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2000년도 제18회 학술발표회 논문개요집
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• pp.212-212
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• 2000

Since the first obserbvation of carbon nanotubes, extensive researches have been done for the synthesis using arc discharge, laser vaporization, and plasma-enhanced chemical vapor deposition. Carbon nanotubes have unique physical and chemical properties and can allow nanoscale devices. Vertically aligned carbon nanotubes with high quality on a large area is particularly important to enable both fundamental studies and applications, such as flat panel displays and vacuum microelectronics. we have grown vertically aligned carbon nanotubes on a large area of Si substrates by thermal chemical vapor deposition using C2H2 gas at 750-950$^{\circ}C$. we deposited catalytic metal on Si susbstrate using thermal evaporation. The nanotubes reveal highly purified surface. The carbon nanotubes have multi-wall structure with a hollow inside and it reveals bamboo structure agreed with base growth model. Figure 1 shows SEM micrograph showing vertically aligned carbon nanotubes whih were grown at 950$^{\circ}C$ on a large area (20mm${\times}$30mm) of Si substrates. Figure 2 shows TEM analysis was performed on the carbon nanotubes grown at 950$^{\circ}C$ for 10 min. The carbon nanotubes are multi-wall structure with bamboo shape and the lack of fringes inside the nanotube indicates that the core of the structure is hollow. In our experiment, carbon nanotubes grown by the thermal CVD indicate base growth model.