• Structural Engineering and Mechanics
• /
• 제62권3호
• /
• pp.273-279
• /
• 2017

A meso-scale model is proposed to study filament-wound composites with fiber undulations and crossovers. First, the crossover and undulation region is classified as the circumferential undulation and the helical undulation. Next, the two undulations are separately regarded as a series of sub-models to describe the meso-structure of undulations by using meso-parameters such as fiber orientation, fiber inclination angle, resin rich area, fiber volume fraction and bundle cross section. With the meso-structure model and the classic laminate theory, a method for calculating the stiffness of filament wound composites is eventually established. The effects of the fiber inclination angle, the fiber and resin volume fraction and the resin rich area on the stiffness are studied. The numerical results show that the elastic moduli for the circumferential undulation region decrease to a great extent as compared with that of the helical undulation region. Moreover, significant decrease in the elastic and shear moduli and increase in the Poisson's ratio are also found for the resin rich area. In addition, thickness and bundle section have evident effect on the equivalent stiffness of the fiber crossover and the undulation region.

• Structural Engineering and Mechanics
• /
• 제55권2호
• /
• pp.399-411
• /
• 2015

The buckling equations of filament wound composite cylindrical shell are established. The coefficients $K_{ij}$ and $L_{ij}$ of the buckling equations are determined by solving the equations. The geometric analysis and the effective stiffness calculation for the fiber crossover and undulation region are respectively accomplished. Using the effective stiffness of the undulation region, the specific formulas of the coefficients ${K^{\prime}}_{ij}$ and ${L^{\prime}}_{ij}$ of the buckling equations are determined. Numerical examples of the buckling critical loads have been performed for the different winding angles and stacking sequences cylindrical shell designs. It can be concluded that the fiber undulation results in the less effect on the buckling critical loads $P_{cr}$. $P_{cr}$ increases with the thickness-radius ratio. The effect on $P_{cr}$ due to the fiber undulation is more obvious with the thickness-radius ratio. $P_{cr}$ decreases with the length-radius ratio. The effect on $P_{cr}$ due to the fiber undulation can be neglected when the ratio is large.

• Journal of applied mathematics & informatics
• /
• 제27권5_6호
• /
• pp.1017-1031
• /
• 2009

The problem of interaction of surface water waves by small undulation at the bottom of a laterally unbounded sea is treated on the basis of linear water wave theory for both normal and oblique incidences. Perturbation analysis is employed to obtain the first order corrections to the reflection and transmission coefficients in terms of integrals involving the shape function c(x) representing the bottom undulation. Fourier transform method and residue theorem are applied to obtain these coefficients. As an example, a patch of sinusoidal ripples is considered in both the cases as the shape function. The principal conclusion is that the reflection coefficient is oscillatory in the ratio of twice the surface wave number to the wave number of the ripples. In particular, there is a Bragg resonance between the surface waves and the ripples, which is associated with high reflection of incident wave energy. The theoretical observations are validated computationally.

• 한국해양공학회지
• /
• 제16권2호
• /
• pp.27-31
• /
• 2002

The purpose of this study is to investigate the variation of resonance that is possible caused by construction of new port in a practical sea area between the existing port and the new one. The research of amplification that of the sea area was accomplished for the variation of resonance. In this study, long period wave that is observed continuously in the practical sea area was analyzed, and then secondary undulation was reproduced by numerical analysis. As a result of numerical analysis, the first mode resonant periods in the existing port is 640sec, and in the new one is 500sec. On the other hand, we know there is long period wave of 500sec from analyzation of field datas. Because that period this period is the resonant period in the new port. There is also the possibility of secondary undulation cause of resonant.

• 대한원격탐사학회:학술대회논문집
• /
• 대한원격탐사학회 2005년도 Proceedings of ISRS 2005
• /
• pp.589-592
• /
• 2005

Gravity characteristics and Moho undulations are investigated in the Korean peninsula by using satellite gravity data. According to the development of satellite geodesy, gravity potential models which have high accuracy and resolution were released. Using the EIGEN-CGOIC model based on low orbit satellite data such as CHAMP and GRACE, geoid and gravity anomaly were calculated by spherical harmonic analysis. The study area is located at $123^{\circ}\sim132^{\circ}E, 33^{\circ}\sim43^{\circ}$N including Korea. Free-air anomalies, which show the effect of terrain, have the values between $-37\sim724 mgal. After Bouguer correction, the range of simple Bouguer anomalies is $-221\sim246$ mgal. Complete Bouguer anomalies after terrain correction increase from continent to marine. This phenomenon is related rise of Moho discontinuity. The cut-frequency for extraction of Moho undulation was determined by power spectrum analysis, and then 3D inversion modeling was implemented. The mean, maximum, minimum, and standard deviation of Moho depth undulation are -26, -36, -8, and 4.9 krn, respectively.

• 한국측량학회지
• /
• 제12권2호
• /
• pp.219-226
• /
• 1994

노선의 거리와 토공량은 노선의 계획시에 경제적인 인자로써 가장 큰 비중을 차지한다. 본 논문에서는 이 두 가지 인자를 고려하여 노선을 선정하는 방법에 대하여 연구하였고 실제로 경사가 균일하고 굴곡이 존재하지 않는 지형과 경사가 없고 굴곡만이 존재하는 두 지형을 선정하여 두 인자를 고려한 최적노선의 선정을 실행하였다. 연구결과 최단거리를 갖는 노선은 지형의 경사에 관계없이 굴곡정도에 따라 결정되었으며 토공량의 산정은 지형의 굴곡정도와 보간식에 영향을 받아 차이가 발생하였음을 알게 되었다.

• 한국측량학회지
• /
• 제18권4호
• /
• pp.359-367
• /
• 2000

이 논문은 지구중력포텐셜에 대한 포텐셜계수모델이 표고이상을 계산하는데 사용될 수 있다는 것과, 지오 이드 계산에 있어서 표고이상을 고려하였을 때 보다 정밀한 지오이드고를 산출할 수 있다는 것을 보여 주고 있다. 연구를 위해 EGM96의 계수와 수정계수가 사용되었고 한반도 일원의 수치지형모델인 KODEM33이 사용되었다. 연구 결과 나타난 표고이상의 크기는 최대 0.025 m, 평균 -0.015 m의 크기를 보여주었다. 본 연구에서 계산된 중력지오이드 모델의 평가를 위하여 GPS/Leveling데이터로부터 기하학적 지오이드를 산출하였으며, 비교 결과 교차의 평균값과 표준편차는 0.0114 m와 0.2817 m를 나타내 개선된 결과를 보여 주었다.

• 한국해양공학회지
• /
• 제24권6호
• /
• pp.51-60
• /
• 2010

In this study, the performance evaluation of a conventional wave resonator at the entrance of a port or a pier against secondary undulation has been performed using 2D hydrodynamic modeling within port. A wave resonator has been designed for the attenuation of the secondary undulation induced by the long-periodic waves. The controlled performance of the wave resonator has been numerically investigated for CGWAVE MODULE of finite-element model of SMS (Surface water Modeling System) based on the elliptic mild-slope wave equation. SMS was verified though the comparisons with analytical solution performed by Ippen and Goda (1963). Also, It was confirmed that a wave resonator of a rectangular model harbor is effective enough to control the secondary undulation when it compares variation of water level with the case of no resonance system. From the above results, amplification phenomenon induced by long-period waves transferred from 1900 sec to 2100 sec when it applied a wave resonator in Busan Gamcheon Port which is a deep-sea. And it was confirmed that a wave resonator of Pohang New Port attenuates largely long-period waves which are within the range of 300 sec induced by long-period motion of the moored ship.

• 한국측량학회지
• /
• 제13권2호
• /
• pp.285-289
• /
• 1995

본 논문은 GPS로부터 측정된 타원체고와 Spirit Levelling으로부터 측정한 정표고를 이용하여 기하학적인 방법에 의하여 지오이드를 결정하였다. 기하학적인 지오이드고의 계산을 위하여 88점의 GPS측정데이타를 사용하였으며, 지오이드고는 간단하게 타원체고와 정표고의 차이를 구하고 보간법에 의하여 지오이드면을 결정하였다. 또한 보간법의 정확도를 평가하기 위하여 Minimum Curvature 방법과 Least Square Plane Fit방법을 사용하여 보간한 결과와 실측치를 비교하였으며, FFT를 적용하여 중력학적인 방법으로 결정한 지오이드고와 비교, 분석하였다.

• 한국해안·해양공학회논문집
• /
• 제24권1호
• /
• pp.58-65
• /
• 2012

본 연구에서는 장주기파에 의한 부진동 및 공진에 의한 선박의 이상동요를 저감시키기 위하여 공진장치를 실해역의 기설 항에 부착하여 그의 제어능을 수치적으로 검토하였다. 수치해석에 2차원타원형완경사방정식에 기초한 유한요소모델인 상용소프트웨어 SMS (Surface water Modeling System)의 CGWAVE MODULE을 적용하였고, 직사각형모델항만에 대한 기존의 실험 및 해석결과와의 비교 검토로부터 부진동해석에 대한 SMS의 타당성과 유효성 및 적용한 마찰계수값의 타당성을 검증하였다. 이로부터 직사각형항만에 공진장치의 부착유무에 따른 부진동의 비교검토로부터 그의 제어능을 확인하였다. 그리고, 포항신항에서 발생될 수 있는 부진동 및 계류선박의 장주기동요를 감쇠시키기 위하여 여러 크기의 공진장치를 적용하여 선박의 이상동요를 발생시키는 공진주기를 보다 장주기측으로 이동시키는 방안을 검토하였고, 이로부터 그의 유용성을 확인할 수 있었다.