• 한국항공우주학회지
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• 제36권8호
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• pp.734-739
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• 2008

본 논문에서는 미시 및 중시 역학의 2-단계 해석 전략을 채택하여 유연직물 복합재료의 기계적 거동을 예측하였다. 미시역학에서는 섬유다발의 유효물성치를 계산하였고 그 결과를 이용해 중시역학에서 유연직물복합재료의 인장탄성계수를 예측하였다. 중시역학 해석 과정에서는 섬유다발의 회전 및 전단 대변형에 의한 기하학적 비선형성을 고려하기 위하여 사용자 정의 부프로그램을 개발하여 ABAQUS 내에 삽입하였다. 해석결과, 인장하중을 받는 유연직물복합재료의 응력-변형률은 비선형 거동을 보였고, 계산된 유효탄성계수는 시험값과 잘 일치하는 것으로 나타났다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.2
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• pp.888-891
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• 2003

This paper describes on the fabrication and characteristics of micro ceramic thin-film type pressure sensors based on Ta-N strain-gauges for high-temperature applications. The Ta-N thin-film strain-gauges are deposited onto thermally oxidized Si diaphragms by RF sputtering in an argon-nitrogen atmosphere($N_2$ gas ratio: 8 %, annealing condition: $900^{\circ}C$, 1 hr.), Patterned on a wheatstone bridge configuration, and use as pressure sensing elements with a high stability and a high gauge factor. The sensitivity is $1.097{\sim}1.21mV/V.kgf/cm^2$ in the temperature range of $25{\sim}200^{\circ}C$ and the maximum non-linearity is 0.43 %FS. The fabricated pressure sensor presents a lower TCR, non-linearity than existing Si piezoresistive pressure sensors. The fabricated micro ceramic thin-film type pressure sensor is expected to be usefully applied as pressure and load sensors that is operable under high-temperature environments.

• 제어로봇시스템학회논문지
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• 제22권6호
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• pp.389-396
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• 2016

The sealing robot must be able to calculate the slope of a contact surface for complete adherence of the sealing on different concrete shapes. After the slope is obtained, the robot will track on the surface of the concrete, but this process contains an error in the actual purpose of the force command. The reason this a phenomenon occurs, the non-linearity of the contact surface and the end-effector, is due to parasitic coupling. Errors like make it difficult to measure accurately the respective factors. Therefore, it is regarded as a disturbance that occurs when it follows the work surface it. In this paper, we selected the friction coefficient of the surface as a control factor and designed a compensator to reduce effects of disturbance. Finally, in view of the non-linearity of the end-effector of a robot to contact surfaces directly, we propose a robust force tracking controller in the finite range for managing disturbances that occur during the sealing.

• 한국해양공학회지
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• 제15권2호
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• pp.72-78
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• 2001

The bead is used to provide properly restraining force in the sheet metal forming process. This bead process includes bending and geometrical non-linearity, and affects the state of binderwrap. Therefore, the analysis of bead process is very important to obtain the desired formability. In this paper, the research about the influence of the punch stroke of bead on the draw-bead process was conducted. Results from the analysis will give useful information to the effective tool design of blank forming process. To analyze the bead process, and elasto-plastic finite element formulation is constructed from the equilibrium equation and the considered boundary conditions involved a proper contact condition. The static-explicit finite element method as a numerical method for the analysis was applied to the analysis program code. It was found that this method could solve too much computation time and convergence problem owing to high non-linearity of bead forming process.

• 한국통신학회논문지
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• 제27권10C호
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• pp.993-998
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• 2002

전력증폭기에서는 특유의 비선형 특성에 의해 출력에 왜곡이 발생하므로 이를 보상할 수 있는 방안을 강구하여야 한다. 본 논문에서는 쇼트키 다이오드를 직렬로 삽입한 전력증폭기용 프리디스토터의 특성에 관하여 연구하였다. 이를 통해 쇼트키 다이오드의 비선형 특성을 이용한 프리디스토터를 전력증폭기 전단에 삽입하면 전력증폭기를 선형화 시킬 수 있음을 확인하였다. 즉, 입력 신호 레벨이 낮으면 입력된 신호는 전력증폭기로 그대로 들어가지만 입력 신호레벨이 높으면 프리디스토터에서 감쇄되어 전달된다. 그러므로 전력증폭기는 항상 saturation 영역에서만 동작하게 된다. Serenade 8.0을 이용하여 모의 실험을 통해 약 3% 가량의 효율이 개선됨을 확인할 수 있었다. 또한 500MHz에서 2.2㎓까지의 대역 중 1.8㎓ 대역에서 가장 확실한 비선형특성을 얻을 수 있음을 확인하였다.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2016년도 추계학술대회
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• pp.913-914
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• 2016

본 논문에서는 성형망 기반 위성통신시스템에서 주파수 효율 향상을 위한 동일 위성채널 전송기술 개발을 위한 위성 TWTA(Traveling Wave Tube Amplifier) 비선형 특성 영향을 분석하고자 한다. 성형망에서 동일 위성채널 전송을 위해서는 중심국에서 단말로 송신한 DVB-S2 포워드 링크 신호를 위성을 거쳐 다시 되돌아오는 자기 간섭 신호를 제거하여야 하며, 수신하고자 하는 단말국 신호만을 추출하는 자기 간섭 제거기가 필요하다. 자기 간섭제거를 위해 위성 TWTA의 비선형 HPA (High Power Amplifier) 모델의 유무에 따라 간섭제거된 신호의 수신 성능을 분석하였다.

• Structural Engineering and Mechanics
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• 제88권5호
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• pp.439-449
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• 2023

Non-linear vibration characteristics of functionally graded CNT-reinforced composite (FG-CNTRC) cylindrical shell panel on elastic foundation have not been sufficiently examined. In this situation, this study aims at the profound numerical investigation of the non-linear vibration response of FG-CNTRC cylindrical panels on Winkler-Pasternak foundation by introducing an accurate and effective 2-D meshfree-based non-linear numerical method. The large-amplitude free vibration problem is formulated according to the first-order shear deformation theory (FSDT) with the von Karman non-linearity, and it is approximated by Laplace interpolation functions in 2-D natural element method (NEM) and a non-linear partial derivative operator H_NL. The complex and painstaking numerical derivation on the curved surface and the crucial shear locking are overcome by adopting the geometry transformation and the MITC3+ shell elements. The derived nonlinear modal equations are iteratively solved by introducing a three-step iterative solving technique which is combined with Lanczos transformation and Jacobi iteration. The developed non-linear numerical method is estimated through the benchmark test, and the effects of foundation stiffness, CNT volume fraction and functionally graded pattern, panel dimensions and boundary condition on the non-linear vibration of FG-CNTRC cylindrical panels on elastic foundation are parametrically investigated.

• 한국항공우주학회지
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• 제32권3호
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• pp.37-44
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• 2004

본 논문에서는 압전재의 재료 비선형성을 고려한 경량 압전 복합재 작동기(LIPCA)의 성능 해석을 수행하였다. 성능 해석을 위해 9절점 쉘 요소 정식화에 바탕을 둔 압전 쉘 요소를 이용하였다. LIPCA의 작동 변위를 보다 정확히 예측하기 위하여, 실험을 통해 얻은 압전 변형률 함수와 증분 정식화를 추가하여 기존 선형 유한요소 프로그램을 수정하였다. 이렇게 개발된 재료 비선형 압전 옐 프로그램을 이용하여 LIPCA의 작동변위를 재 계산하였고, 재료 비선형 해석으로 얻은 작동 변위가 선형 해석으로 계산된 작동 변위 보다 측정 변위에 훨씬 근접함을 확인하였다.

• 전기화학회지
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• 제17권2호
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• pp.119-123
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• 2014

Here I report on how Fourier Transform Electrochemical Impedance Spectroscopy (FTEIS) overcomes the potential-current linearity problem encountered in the impedance calculation process. FTEIS was first invented to solve the time-related drawback of the conventional impedance technique. The dramatic time reduction of FTEIS enabled the real-time impedance measurement but brought about the linearity problem at the same time. While the conventional method circumvents the problem using the steady-state made by a sufficiently long measurement time, FTEIS cannot because of its real-time function. However, according to the mathematical development reported in this article, the potential step used in FTEIS is proved to avoid the linearity problem. During the step period, the potential and the current are linearized by the electrochemical impedance. Also, Fourier transform of the differentiated potential and current is proved to give the same result of the original ones.

• 한국농공학회지
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• 제45권5호
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• pp.140-150
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• 2003

Observational methods such as the Asaoka's method and the hyperbolic method are widely applied on the settlement analysis using observed settlement. The most unreliable aspects in those methods is arose from the subjective discretion of initial non-linearity on linear regression. The initial non-linearity is inevitable due to the settlement behaviour itself. Therefore an objective method is essential to achieve more reliable results on settlement analysis. It was found that the initial non-linear data are statistical outliers. New automation algorithms of the hyperbolic and the Asaoka's method were developed based on outlier detection method. The methods are a successive detection of outliers and a searching method of suitable hyperbolic range for the Asaoka's and the hyperbolic method respectively. Applicability of the algorithms was verified through case studies.