• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.1927-1931
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• 2003

Nanometer-sized structures are being applied to many fields including micro/nano electronics, optoelectronics, quantum computing, biosensors, etc. Micro contact printing is one of the most promising methods for manufacturing the nanometer-sized structures. The crucial element for the micro contact printing is the nano-resolution printing technique using polymeric stamps. In this study, a multi-scale analysis scheme for simulating the micro contact printing process is proposed and some useful analysis results are presented. Using the slip-link model [1], the dependency of viscoelasticity on molecular weight of polymer stamp is predicted. Deformation behaviors of polymeric stamps are analyzed using finite element method based upon the predicted viscoelastic properties.

• Steel and Composite Structures
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• 제20권3호
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• pp.693-718
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• 2016

This paper presents a finite element procedure based on Bridging multi-scale method (BMM) in order to incorporate the effect of local/cross-sectional deformations (e.g., flange local buckling and web crippling) on the global behaviour of thin-walled members made of fibre-reinforced polymer composite laminates. This method allows the application of local shell elements in critical regions of an existing beam-type model. Therefore, it obviates the need for using computationally expensive shell elements in the whole domain of the structure, which is otherwise necessary to capture the effect of the localized behaviour. Consequently, highly accurate analysis results can be achieved with this method by using significantly smaller finite element model, compared to the existing methods. The proposed method can be used for composite polymer laminates with arbitrary fibre orientation directions in different layers of the material, and under various loading conditions. Comparison with full shell-type finite element analysis results are made in order to illustrate the efficiency and accuracy of the proposed technique.

• 한국군사과학기술학회지
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• 제4권2호
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• pp.189-201
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• 2001

For a design of multi-layer armor, the extensive full scale or sub-scale penetration test data are required. In generally, the collection of penetration data is in need of time-consuming and expensive processes. However, the application of numerical or analytical method is very limited due to poor understanding about penetration mechanics. In this paper, we have developed a neural network analyzer which can be used as a design tool for a new armor. Calculation results show that the developed neural network analyzer can predict relatively exact penetration depth of a new armor through the effective analysis of the pre-existing penetration database.

• 방송공학회논문지
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• 제20권4호
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• pp.521-532
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• 2015

본 논문은 효과적인 열화영상의 복원을 위해 쿼드트리 구조를 갖는 다중-스케일 블록 지역적 이진 패턴 기반의 영역검출기를 제시하고, 이를 통한 구간적 잡음 제거 기법을 제안한다. 구간적 잡음 제거 기법은 영상 내 전체 화소를 일정한 블록 단위의 영역으로 나누어 화소의 변화량에 따라 검출을 수행하는 다중-스케일 블록 영역 검출기를 쿼드트리 형태로 제시하고 검출된 영역 특성에 맞게 영상분석을 진행한다. 처리되는 영역들은 강한 변화량을 갖는 영역, 약한 변화량을 갖는 영역, 평탄한 영역의 세 가지로 분류되며 차례로 주성분분석, 양방향 필터, 구조-텍스쳐 영상 분해의 기법들이 잡음제거를 위해 적용된다. 객관적 실험결과를 통하여 기존 알고리즘들 보다 제안하는 구간적 잡음 제거 기법이 최대 신호-대-잡음비 측면에서 이득을 가지며, 주관적 화질 비교를 통해 세부정보들이 최대한 보존되어 있음과 동시에 평탄한 영역에 대해서도 왜곡이 거의 없는 향상된 복원영상이 얻어지는 것을 확인할 수 있었다.

• 전산구조공학
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• 제26권4호
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• pp.31-38
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• 2013

• Journal of Power Electronics
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• 제15권5호
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• pp.1318-1328
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• 2015

The photovoltaic (PV) power conditioning system for small-scale applications has gained significant interest in the past few decades. However, the standalone mode of operation has been rarely approached. This paper presents a two-stage multi-level micro-inverter topology that considers the different operation modes. A multi-output flyback converter provides both the DC-Link voltage balancing for the multi-level inverter side and maximum power point tracking control in grid connection mode in the PV stage. A modified H-bridge multi-level inverter topology is included for the AC output stage. The multi-level inverter lowers the total harmonic distortion and overall ratings of the power semiconductor switches. The proposed micro-inverter topology can help to decrease the size and cost of the PV system. Transient analysis and controller design of this micro-inverter have been proposed for stand-alone and grid-connected modes. Finally, the system performance was verified using a 120 W hardware prototype.

• Structural Engineering and Mechanics
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• 제30권5호
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• pp.619-645
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• 2008

This study presents the efficiency of simulating structural systems using a method that combines a simplified component model (SCM) and rigorous component model (RCM). To achieve a realistic simulation of structural systems, a numerical model must be adequately capturing the detailed behaviors of real systems at various scales. However, capturing all details represented within an entire structural system by very fine meshes is practically impossible due to technological limitations on computational engineering. Therefore, this research develops an approach to simulate large-scale structural systems that combines a simplified global model with multiple detailed component models adjusted to various scales. Each correlated multi-scale simulation model is linked to others using a multi-level hierarchical modeling simulation method. Simulations are performed using nonlinear finite element analysis. The proposed method is applied in an analysis of a simple reinforced concrete structure and the Reuipu Elementary School (an existing structure), with analysis results then compared to actual onsite observations. The proposed method obtained results very close to onsite observations, indicating the efficiency of the proposed model in simulating structural system behavior.

• 한국정보통신학회논문지
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• 제9권2호
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• pp.229-236
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• 2005

이 논문은 신호 f(t)의 실제적인 스케일 정보를 나타내는 웨이브렛 플랜을 중심으로 연속 웨이브렛 역변환의 특성에 대하여 논하였다. 웨이브렛 변환에 비해 역변환의 적용이 상대적으로 미비한 이유는 수치적인 연산의 복잡성에 기인한 것이며, 이 논문은 웨이브렛 역변환의 안정된 복원을 위한 방법에 대하여 연구하였다. 웨이브렛 역변환의 안정적인 구현은 신호 f(t)에 대한 실제적인 스케일 정보를 지니고 있는 웨이브렛 플랜이라는 새로운 "시간-스케일" 공간을 통하여 실현하였으며, 이는 완전한 멀티 필터 뱅크 시스템과 동일한 특성을 나타낸다. 즉 연속 웨이브렛 변환을 통해 신호 f(t)의 모든 스케일 성분을 독립적으로 주파수 전체 대역에 걸쳐 분산하고 다시 역변환을 통해 원래의 신호를 복원하는 과정은 필터뱅크이론의 분석과 합성과정과 일치한다 이 논문에서는 연속 웨이브렛 역변환을 이용하여 "시간-스케일" 필터를 통한 신호 f(t)의 스케일 분해와 웨이브렛 멀티 필터 뱅크이론에 대하여 논하였다.

• 제어로봇시스템학회논문지
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• 제7권8호
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• pp.689-696
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• 2001

Large-scale Multi-disciplinary Systems(LMS) such as transportation, aerospace, defense etc. are complex systems in which there are many subsystems, interfaces, functions and demanding performance requirements. Because many contractors participate in the development, it is necessary to apply methods of sharing common objectives and communicating design status effectively among all of the stakeholders. The processes and methods of systems engineering which includes system requirement analysis; functional analysis; architecting; system analysis; interface control; and system specification development provide a success-oriented disciplined approach to the project. This paper shows not only the methodology and the results of model-based systems engineering to Automated Guided Transit(AGT) system as one of LMS systems, but also propose the extension of the model-based tool to help manage a project by linking WBS (Work Breakdown Structure), work organization, and PBS (Product Breakdown Structure). In performing the model-based functional analysis, the focus was on the operation concept of an example rail system at the top-level and the propulsion/braking function, a key function of the modern automated rail system. The model-based behavior analysis approach that applies a discrete-event simulation method facilitates the system functional definition and the test and verification activities. The first application of computer-aided tool, RDD-100, in the railway industry demonstrates the capability to model product design knowledge and decisions concerning key issues such as the rationale for architecting the top-level system. The model-based product design knowledge will be essential in integrating the follow-on life-cycle phase activities. production through operation and support, over the life of the AGT system. Additionally, when a new generation train system is required, the reuse of the model-based database can increase the system design productivity and effectiveness significantly.

• Smart Structures and Systems
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• 제14권5호
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• pp.831-845
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• 2014

This paper proposed a discrete wavelet transform based method for time-varying physical parameter identification of shear type structures. The time-varying physical parameters are dispersed and expanded at multi-scale as profile and detail signal using discrete wavelet basis. To reduce the number of unknown quantity, the wavelet coefficients that reflect the detail signal are ignored by setting as zero value. Consequently, the time-varying parameter can be approximately estimated only using the scale coefficients that reflect the profile signal, and the identification task is transformed to an equivalent time-invariant scale coefficient estimation. The time-invariant scale coefficients can be simply estimated using regular least-squares methods, and then the original time-varying physical parameters can be reconstructed by using the identified time-invariant scale coefficients. To reduce the influence of the ill-posed problem of equation resolving caused by noise, the Tikhonov regularization method instead of regular least-squares method is used in the paper to estimate the scale coefficients. A two-story shear type frame structure with time-varying stiffness and damping are simulated to validate the effectiveness and accuracy of the proposed method. It is demonstrated that the identified time-varying stiffness is with a good accuracy, while the identified damping is sensitive to noise.