• Structural Engineering and Mechanics
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• 제89권6호
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• pp.557-570
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• 2024

Due to interfacial ageing, chemical action and interfacial damage, the interface debonding may appear in the interfaces of composite laminates. Particularly, the laminates display a side-dependent effect at small scale. In this work, a three-dimensional (3D) and anisotropic thick nanoplate model is proposed to investigate the effects of imperfect interface and nonlocal parameter on the bending deformation, vibrational response and buckling stability of one-dimensional (1D) hexagonal quasicrystal (QC) layered nanoplates. By combining the linear spring model with the transferring matrix method, exact solutions of phonon and phason displacements, phonon and phason stresses of bending deformation, the natural frequencies of vibration and the critical buckling loads of 1D hexagonal QC layered nanoplates are derived with imperfect interfaces and nonlocal effects. Numerical examples are illustrated to demonstrate the effects of the imperfect interface parameter, aspect ratio, thickness, nonlocal parameter, and stacking sequence on the bending deformation, the vibrational response and the critical buckling load of 1D hexagonal QC layered nanoplate. The results indicate that both the interface debonding and nonlocal effect can reduce the stiffness and stability of layered nanoplates. Increasing thickness of QC coatings can enhance the stability of sandwich nanoplates with the perfect interfaces, while it can reduce first and then enhance the stability of sandwich nanoplates with the imperfect interfaces. The biaxial compression easily results in an instability of the QC layered nanoplates compared to uniaxial compression. QC material is suitable for surface layers in layered structures. The mechanical behavior of QC layered nanoplates can be optimized by imposing imperfect interfaces and controlling the stacking sequence artificially. The present solutions are helpful for the various numerical methods, thin nanoplate theories and the optimal design of QC nano-composites in engineering practice with interfacial debonding.

• 한국데이터정보과학회:학술대회논문집
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• 한국데이터정보과학회 2001년도 추계학술대회
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• pp.43-43
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• 2001

• 인터넷정보학회논문지
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• 제13권1호
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• pp.7-14
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• 2012

본 논문은 불완전한 채널 감지를 고려한 포화 상태에서의 IEEE 802.11 carrier-sense multiple access with collision-avoidance(CSMA/CA)의 성능을 분석한다. 불완전한 채널 감지는 missed-detection과 false alarm을 포함하는데, 이러한 불완전한 채널 감지가 IEEE 802.11의 성능에 미치는 영향을 분석하고 이를 수식적으로 표현한다. 물리 계층의 불완전한 채널 감지를 표현하기 위해, 본 논문에서는 기존의 2차원 마코프 프로세스 모델을 수정했다. 모의실험 결과와 제안된 모델의 이론적인 결과가 일치하는 것을 보였다. 이러한 실험 결과를 바탕으로, 감지 확률이 IEEE 802.11의 성능에 있어 가장 중요한 요소임을 확인하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.847-852
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• 2007

This paper investigates the characteristics of cogging torque and magnetic force of a brushless DC (BLDC) motor due to imperfect magnetization of permanent magnet (PM) numerically and experimentally which results in the magnetically induced vibration. A predicted magnetization pattern of the PM of the BLDC motor, which is derived from the measured surface magnetic flux density along the PM, is applied to the finite element analysis in order to calculate the cogging torque and the unbalanced magnetic force. This research also develops the experimental setup to measure the unbalanced magnetic force as well as the cogging torque. It shows numerically and experimentally that the imperfect magnetization of permanent magnet generates the driving frequencies of cogging torque with integer multiple of slot number in addition to the least common multiple of pole and slot. It also shows that the driving frequencies of unbalanced magnetic force are integer multiple of slot number ${\pm}1$ due to imperfect magnetization of PM even in the rotationally symmetric design.

• 한국통신학회논문지
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• 제36권9A호
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• pp.776-783
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• 2011

본 논문에서는 적응형 복호 후 전송 (decode-and-forward) 중계 프로토콜이 송신을 위해 불완전한 채널정보를 사용할 때, 목적지 노드에서만 다중 안테나를 사용하는 경우, 릴레이 노드에서만 다중안테나를 사용하는 경우, 그리고 소스 노드에서만 다중 안테나를 사용하는 경우에 대한 diversity-multiplexing tradeoff (DMT) 상계 함수들을 유도하여 그 결과를 제시한다. 또한 소스 노드와 목적지 노드, 소스 노드와 릴레이 노드, 릴레이 노드와 목적지 노드 사이의 불완전한 채널정보들이 점근적 조건하에 있을 경우, 적응형 복호 후 전송 중계 프로토콜이 얻을 수 있는 다이버시티 이득을 조사한다.

• 한국신뢰성학회:학술대회논문집
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• 한국신뢰성학회 2001년도 정기학술대회
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• pp.301-310
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• 2001

Lim et al.(1998) proposed the Bayesian Imperfect Repair Model, in which a failed system is perfectly repaired with probability P and is minimally repaired with probability 1 - P, where P is not fixed but a random variable with a prior distribution II(p). In this note, the steady state availability of the model is derived and the measure is obtained for several particular prior distribution functions.

• Journal of the Korean Statistical Society
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• 제28권3호
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• pp.389-398
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• 1999

We consider an imperfect repair model under which either a perfect repair or a minimal repair can be performed at each failure of a unit. Some stochastic properties of the number of perfect repairs and the number of minimal repairs under the imperfect repair model are investigated. We also derive the expressions for evaluating the expected numbers of perfect and minimal repairs in general and apply these formulas for certain parametric families of life distributions.

• Communications for Statistical Applications and Methods
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• 제7권2호
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• pp.525-531
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• 2000

Bayes estimators for reliability of a two-unit hot standby system with the imperfect switch based upon a complete sample of failure times observed from exponential distributions under squared error loss and some priors for failure rates are proposed, and mean squared errors of proposed several Bayes estimators for the system reliability are compared unmerically each other through the Monte Carlo simulation.

• Communications for Statistical Applications and Methods
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• 제8권3호
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• pp.711-717
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• 2001

Two imperfect repair models for system are considered, one introduced by Brown and Proschan(1983) and the other by Lee and Seoh(1999). We, in this paper, after assigning repair costs to the system, optimize both repair models, when the underlying life distributions of the system are exponential, uniform and Weibull.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2006년도 6th International Meeting on Information Display
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• pp.1660-1665
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• 2006

Drop placement accuracy and precision are the critical performance values of industrial ink jet deposition systems. Imperfect components and environments have severe impacts on drop placement. Litrex has identified over 120 error sources and developed engineering solutions to address the errors. In this paper, improved results using thermal compensation and stage mapping techniques are demonstrated. A recent progress in inkjet fabrication of multi-color electrophoretic display on flexible substrate with large distortion is also demonstrated.