• Smart Structures and Systems
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• 제21권6호
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• pp.777-791
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• 2018

This paper discusses the shape control of deformable mirrors for Adaptive Optics in the dynamic range. The phenomenon of control-structure interaction appears when the mirror becomes large, lowering the natural frequencies $f_i$, and the control bandwidth $f_c$ increases to improve the performance, so that the condition $f_c{\ll}f_i$ is no longer satisfied. In this case, the control system tends to amplify the response of the flexible modes and the system may become unstable. The main parameters controlling the phenomenon are the frequency ratio $f_c/f_i$ and the structural damping ${\zeta}$. Robustness tests are developed which allow to evaluate a lower bound of the stability margin. Various passive and active strategies for damping augmentation are proposed and tested in simulation.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권6호
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• pp.3121-3142
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• 2017

We present a method for 3D shape reconstruction of inextensible deformable surfaces from a single image. The key of our approach is to represent the surface as a 3D triangulated mesh and formulate the reconstruction problem as a sequence of Linear Programming (LP) problems. The LP problem consists of data constraints which are 3D-to-2D keypoint correspondences and shape constraints which are designed to retain original lengths of mesh edges. We use a closed-form method to generate an initial structure, then refine this structure by solving the LP problem iteratively. Compared with previous methods, ours neither involves smoothness constraints nor temporal consistency, which enables us to recover shapes of surfaces with various deformations from a single image. The robustness and accuracy of our approach are evaluated quantitatively on synthetic data and qualitatively on real data.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 봄 학술발표회 논문집
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• pp.265-272
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• 2000

This study introduces the current theory of the SWCC and tries to verify the theory by performing laboratory tests for the local soils of Korea. First, the SWCCs of Poi-dong soil and Shinnae-dong soil, the most typical weathered residual soils in Korea, were experimentally obtained and the results were compared among others. Second, a SWCC model for deformable soils was proposed. For deformable soils, which show huge volume change during desaturation, the volume change behavior should be considered, and the SWCC should be expressed as a function of void ratio as well as suction.

• 한국HCI학회:학술대회논문집
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• 한국HCI학회 2008년도 학술대회 1부
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• pp.78-84
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• 2008

이 논문에서는 부채꼴 모양을 가진 요소의 집합으로 3 차원 도자기 모델을 구성하고 사용자가 촉감을 느끼면서 가상공간의 도자기를 제작할 수 있도록 하는 새로운 모델을 제안한다. 변형체를 다루기 위해 기존에 사용하던 유한 요소법(finite element method)과 같은 방법은 모델이 복잡하고 연산량이 많아 실시간 햅틱 렌더링(haptic rendering)에 사용하기에는 많은 제약이 있다. 제안한 모델에서는 도자기 모양의 특징에 착안하여 부채꼴 모양을 가진 요소들이 원통 형태로 모여 쌓여있는 구조를 이용하였다. 이를 통해 요소의 개수를 줄이고 복잡한 연산을 최대한 단순화면서 효율적인 모델링이 가능하도록 하였다.

• Journal of Pharmaceutical Investigation
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• 제38권5호
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• pp.319-323
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• 2008

For transdermal delivery of ceramides, various liposomes formulations were studied and evaluated. Sodium deoxycholate (SDC), Tween 20 and Span 85 were used as edge activators. The skin permeation of ceramides was performed using a Franz cell apparatus with hairless mouse skin. Among edge activators, SDC showed the higher values of deformability index and skin permeation than did others. For optimization of formulations, we varied the ratios of lipids to edge activators and the compositions between phosphatidylcholine (PC) and ceramides. The optimal ratio of lipid to SDC was observed to be 6:1 (w:w) and that of PC and ceramide was 1:1. Our results suggest that the skin permeation of ceramides could be enhanced by optimized deformable formulations of liposomes containing SDC as a major edge activator.

• Structural Engineering and Mechanics
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• 제19권1호
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• pp.73-96
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• 2005

For the spatially coupled free vibration analysis of shear deformable thin-walled non-symmetric curved beam subjected to initial axial force, an exact dynamic element stiffness matrix of curved beam is evaluated. Firstly equations of motion and force-deformation relations are rigorously derived from the total potential energy for a curved beam element. Next a system of linear algebraic equations are constructed by introducing 14 displacement parameters and transforming the second order simultaneous differential equations into the first order simultaneous differential equations. And then explicit expressions for displacement parameters are numerically evaluated via eigensolutions and the exact $14{\times}14$ dynamic element stiffness matrix is determined using force-deformation relations. To demonstrate the accuracy and the reliability of this study, the spatially coupled natural frequencies of shear deformable thin-walled non-symmetric curved beams subjected to initial axial forces are evaluated and compared with analytical and FE solutions using isoparametric and Hermitian curved beam elements and results by ABAQUS's shell elements.

• Radiation Oncology Journal
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• 제35권2호
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• pp.101-111
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• 2017

The number of imaging data sets has significantly increased during radiation treatment after introducing a diverse range of advanced techniques into the field of radiation oncology. As a consequence, there have been many studies proposing meaningful applications of imaging data set use. These applications commonly require a method to align the data sets at a reference. Deformable image registration (DIR) is a process which satisfies this requirement by locally registering image data sets into a reference image set. DIR identifies the spatial correspondence in order to minimize the differences between two or among multiple sets of images. This article describes clinical applications, validation, and algorithms of DIR techniques. Applications of DIR in radiation treatment include dose accumulation, mathematical modeling, automatic segmentation, and functional imaging. Validation methods discussed are based on anatomical landmarks, physical phantoms, digital phantoms, and per application purpose. DIR algorithms are also briefly reviewed with respect to two algorithmic components: similarity index and deformation models.

• ETRI Journal
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• 제29권6호
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• pp.817-819
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• 2007

A low-stress organic polymer membrane is proposed as a deformable mirror that can be incorporated into a cellular phone camera to achieve auto focusing without motor-type moving parts. It is demonstrated that our fabricated device has an optical power of 20 diopters and can switch focus in 14 ms. The surface roughness of the organic membrane is measured around 15 nm, less than ${\lambda}$/20 of the visible light. With curve fitting, we found that the actuated membrane is almost parabolic in shape, which leads to less aberration than spherical surfaces. It is suitable for reflective-optics systems.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.221-224
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• 1996

Since impact phenomenon is highly nonlinear, the analysis and control of the contact motion has been a challenging subject. Various researches have been carried out mostly for the contact of a rigid robotic manipulator with a stiff and elastic environment. This paper is motivated by a new contact task: the in-circuit test of a printed circuit board. In this process, high speed contact occurs between a rigid probing manipulator and a plastically deformable work environment. A new dynamic model of the impact controlled probing task has been proposed, considering contact with the plastically deformable object. Approaching velocity conditions to avoid an excess of the allowable penetration depth and control the generated impact force properly are derived from the proposed model. The results of the simulation studies are made for various probing conditions and show the validity of the proposed model.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.125-129
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• 1996

This paper presents the haptic rendering algorithm which gives the feel information to the operator by manipulating a virtual tool with a haptic device in the simulated environment. The movement of a virtual tool grasped by the operator, which is modeled as a square is displayed in the graphic screen of a computer and the virtual environment is modeled as deformable thin film. When the tool contacts with the virtual environment, the operator is forced to feel the contact and the feature of the deformed virtual environment through the torque control of th haptic device. Contact situations are modeled as close as to the reality considering friction, elasticity and multiple contacts. Several experiments are conducted and the effectiveness of the proposed algorithm is confirmed.