• Steel and Composite Structures
• /
• 제27권4호
• /
• pp.479-493
• /
• 2018

In this paper nonlocal free vibration analysis of a doubly curved piezoelectric nano shell is studied. First order shear deformation theory and nonlocal elasticity theory is employed to derive governing equations of motion based on Hamilton's principle. The doubly curved piezoelectric nano shell is resting on Pasternak's foundation. A parametric study is presented to investigate the influence of significant parameters such as nonlocal parameter, two radii of curvature, and ratio of radius to thickness on the fundamental frequency of doubly curved piezoelectric nano shell.

• 한국지진공학회논문집
• /
• 제9권2호통권42호
• /
• pp.71-80
• /
• 2005

유체자유수면의 동적거동을 합리적으로 예측하기 위해서는 비선형 특성을 보이는 자유수면의 동역학적 경계조건을 고려해야할 뿐만 아니라 시간에 따라 변화하는 자유수면의 위치변화에 따른 운동학적 경계조건을 고려하여야 한다. 이러한 문제는 대상구조물이 3차원이 될 경우 더욱 복잡해지므로 3차원 비선형 유체자유수면의 해석은 이론해의 도출이 어려우며 수치해석 방법을 이용하는 것이 효과적이다. 본 연구에서는 수치해석 안정성이 높고 3차원 문제에서도 하나의 변수로 유체거동을 모사할 수 있는 arbitrary Lagrangian-Eulerian approach 를 경계요소에 적용하여 효율적이며 안정적인 유체 대변형 해석기법을 개발하였다. 개발된 기법은 향후 자유수면의 비선형 효과를 고려한 유체-구조물 상호작용 해석에 효과적으로 적용할 수 있을 것으로 판단된다.

• Archives of Plastic Surgery
• /
• 제35권5호
• /
• pp.527-532
• /
• 2008

Purpose: Transverse type or volar oblique type of defect of thumb tip can be covered by Moberg flap or second toe pulp free flap. We compared these two methods in functional result, patients' satisfaction, and sensation, etc. to find a better way to cover the defect of the thumb tip. Methods: From 2003 to 2006, we chose the patients randomly with preoperative pictures. The patients had the defect of the thumb tip which is either transverse or volar oblique type. The 6 patients were treated with Moberg flap and other 6 patients were treated with second toe pulp free flap. We have analyzed the results by 2 point discrimination, side pinching power test, pulp to pulp pinching power test, pain scales (visual analogue scale), satisfaction scales of the patients (functional and aesthetic), the degree of the range of motion, etc. Results: All flaps survived without any complications. In the cases of Moberg flaps, the value of static 2 point discrimination test was 5.6 mm, and the value of moving 2 point discrimination test was 4.8 mm. In the cases of second toe pulp free flaps, the values were 9.6 mm and 9.3 mm. In the cases of Moberg flaps, the value of the Side pinch power test was 6.6 kg, 4.4 kg. In the case of second toe pulp free flaps, the values were 4.8 kg and 2.5 kg. The value of aesthetic satisfaction scale of the patients in Moberg flaps was 5.6, the value of functional satisfaction scale of the patients was 3.6. In cases of second toe pulp free flaps, the values were 5.6 and 3.6. The active range of motion of Interphalangeal joint in the cases of Moberg flaps was 46.6 degree, and the active range of motion of metacarpophalangeal joint was 55 degree, in the cases of second toe pulp free flaps, the values were 36.6 degree and 59 degree. Conclusion: As a result, when the defect of the thumb tip is transverse or volar oblique type, we suggest that the operators choose Moberg flap to cover the defect of the thumb tip.

• 지구물리와물리탐사
• /
• 제15권2호
• /
• pp.92-101
• /
• 2012

평탄한 자유표면을 갖는 소규모 반구형 분지에서 임의의 전단변형 점진원에 대한 3차원 유한차분 모의를 수행하였다. 자유표면 경계조건을 다루기 위한 새로운 방법을 고안하였다. 분지에서 지반운동 응답에 대한 주요한 특징들을 파악하기 위하여 분지특성 변수를 조사하였다. 분지에서 지반운동의 주파수 함량을 분석하기 위하여, 각 주파수에 대한 진폭을 분지 주변 4개의 위치에서 계산하고 서로 비교하였다. 또한 어떤 종류의 파가 이들 각 지점에서의 지반운동 응답에 우세한 역할을 하는지 보기 위하여 입자운동을 분석하였다. 계산 결과, 지진파 에너지가 진원으로부터 먼 쪽의 분지 경계부에서 집중되는 것을 알 수 있었다. 이러한 집중 효과는 주로 직접 S-파와 분지 경계에서 생성된 표면파의 보강간섭으로 인한 것이다. 또한, 분지의 가장 깊은 곳 상부에서의 지반운동 증폭은 얕은 깊이의 분지 경계 부에 비하여 상대적으로 작게 나타났다. 이러한 결과로부터, 상대적으로 단순한 기반암 경계를 갖는 소규모 분지에서의 지반운동 증폭은 분지의 깊이 보다는 진원의 방위 또는 분지 내부로 입사하는 파의 진행방향에 더 많은 관계가 있다는 것을 추정할 수 있다.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2007년도 춘계학술대회B
• /
• pp.2997-3002
• /
• 2007

A manipulator is operated for the motion of mechanical hands or arms by mechanical mechanism. When a cup including liquid inside is shifted by a manipulator, it is important to know how a free surface of the liquid moves. In this study, non-dimensional parameters have been found that affect the rise of the free surface in a cup moving with constant acceleration. The non-dimensional parameters are the dimensionless time, the ratio of inertia effect to vicous effect (Reynolds number), aspect ratio of the liquid inside the cup and acceleration ratio (Froude number). Through this study, the height of the free surface rise in a cup has been predicted. Generally the maximum rise of the free surface is dependent on the Reynolds number and Froude number strongly, but on the aspect ratio weakly. But the influence of the aspect ratio on the maximum rise of the free surface in not negligible in the range 10 < Re < 100.

• 대한기계학회논문집A
• /
• 제24권1호
• /
• pp.232-239
• /
• 2000

The paper describes the parametric instability of free-free beams subjected to a controlled pulsating follower force. The beam has a tip rigid body not a mass point, and the direction of pulsating follower force is controlled by the direction control sensor. Equations of motion are derived by Hamilton's principle and the instability regions are obtained by finite element formulation. The effects of magnitude, rotary inertia, the distance between free end of the beam and the center of gravity of the rigid body on the instability types and regions are investigated by the change of the constant and periodic part of the follower force.

• Korean Membrane Journal
• /
• 제1권1호
• /
• pp.8-24
• /
• 1999

free volume in polymers is defined as the difference of the specific volume and the volume which is not available for the particular molecular motion which is responsible or the process that is considered . Relations between free volume and viscosity free volume and diffusion coefficient are pre-sented both in the case of simple low molecular weight liquids and in the case of polymers. Molecular models and free volume models are reminded starting from the equilibrium state equation of Simha and Somcynski. The non equilibrium situations of specific volume of glass polymers below Tg are shown introducing different relaxation volume equations which involve different material's parameters and con-cept of the fictitious temperature. The diffusivity equations of Vrentas and Duda are introduced both for the glassy and rubbery states. The possibility of introducing time relaxation functions is also suggested. The importance of finding experimental evidences of the free volume is stressed. highlights of the free volume measurement methods are given in particular as to dilatometry photocromy fluorescence electron spin resonance small angle X-ray scattering positron annihilation spectroscopy.

• 한국안전학회지
• /
• 제19권3호
• /
• pp.108-117
• /
• 2004

Dynamic analysis method is Presented for analyzing rectangular liquid storage structures excited by horizontal and vertical ground motions. The irrotational motion of invicid and incompressible ideal fluid in rigid rectangular liquid storage structures subjected to horizontal and vertical ground motions and the motion of fluid induced by structural deformation are expressed by analytic solutions. Analysis methods are obtained by applying analytic solutions of the fluid motion to finite element equation of the structural motion. The fluid-structure interaction effect is reflected into the coupled equation as added fluid mass matrix. The free surface sloshing motion, hydrodynamic pressure acting on the wall and structural behavior due to horizontal and vertical ground motions are obtained by the presented method.

• International Journal of Naval Architecture and Ocean Engineering
• /
• 제8권4호
• /
• pp.320-329
• /
• 2016

An implicit method of solving the six degree-of-freedom rigid body motion equations based on the second order Adams-Bashforth-Moulten method was utilised as an improvement over the leapfrog scheme by making modifications to the rigid body motion solver libraries directly. The implementation will depend on predictor-corrector steps still residing within the hybrid Pressure Implicit with Splitting of Operators - Semi-Implicit Method for Pressure Linked Equations (PIMPLE) outer corrector loops to ensure strong coupling between fluid and motion. Aitken's under-relaxation is also introduced in this study to optimise the convergence rate and stability of the coupled solver. The resulting coupled solver ran on a free floating object tutorial test case when converged matches the original solver. It further allows a varying 70%-80% reduction in simulation times compared using a fixed under-relaxation to achieve the required stability.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제9권1호
• /
• pp.242-259
• /
• 2015

Three-dimensional video coding is one of the main challenges restricting the widespread applications of 3D video and free viewpoint video. In this paper, a novel fractal coding algorithm with motion-vector-field-based motion estimation for depth map sequence is proposed. We firstly add pre-search restriction to rule the improper domain blocks out of the matching search process so that the number of blocks involved in the search process can be restricted to a smaller size. Some improvements for motion estimation including initial search point prediction, threshold transition condition and early termination condition are made based on the feature of fractal coding. The motion-vector-field-based adaptive hexagon search algorithm on the basis of center-biased distribution characteristics of depth motion vector is proposed to accelerate the search. Experimental results show that the proposed algorithm can reach optimum levels of quality and save the coding time. The PSNR of synthesized view is increased by 0.56 dB with 36.97% bit rate decrease on average compared with H.264 Full Search. And the depth encoding time is saved by up to 66.47%. Moreover, the proposed fractal depth map sequence codec outperforms the recent alternative codecs by improving the H.264/AVC, especially in much bitrate saving and encoding time reduction.