• 한국소음진동공학회논문집
• /
• 제11권6호
• /
• pp.181-192
• /
• 2001

The power flow analysis (PFA) has been performed to analyze the vibration of coupled plates excited by a point force in an arbitrary direction. The point force generates the out-of-plane vibration associated wish flexural waves and the in-plane vibration associated with longitudinal and shear waves. The energy governing equation for each type of waves was introduced and solved to Predict the vibrational energy density and intensity generated by the out-of-plane and in-plane components of the point force in an arbitrary direction. The wave transmission approach was used to consider the mode conversion at the joint of the coupled plates. Numerical results for vibrational energy density and intensity on the coupled plates were presented. Comparison of the results by PFA with exact results showed that PFA can be an effective tool to predict the spatial variation of the vibrational energy and intensity on the coupled plates at high frequencies.

• Structural Engineering and Mechanics
• /
• 제70권5호
• /
• pp.551-562
• /
• 2019

In the present study, a suitable mathematical model considering parabolic transverse shear strains for dynamic analysis of laminated composite skew plates under different types of impulse and spatial loads was presented for the first time. The proposed mathematical model satisfies zero transverse shear strain at the top and bottom of the plate. On the basis of the cubic variation of thickness coordinate in in-plane displacement fields of the present mathematical model, a 2D finite element (FE) model was developed including skew transformations in the mathematical model. No shear correction factor is required in the present formulation and damping effect was also incorporated. This is the first FE implementation considering a cubic variation of thickness coordinate in in-plane displacement fields including skew transformations to solve the forced vibration problem of composite skew plates. The effect of transverse shear and rotary inertia was incorporated in the present model. The Newmark-${\beta}$ scheme was adapted to perform time integration from step to step. The $C^0$ FE formulation was implemented to overcome the problem of $C^1$ continuity associated with the cubic variation of thickness coordinate in in-plane displacement fields. The numerical studies showed that the present 2D FE model predicts the result close to the analytical results. Many new results varying different parameter such as skew angles, boundary conditions, etc. were presented.

• 한국수자원학회:학술대회논문집
• /
• 한국수자원학회 2016년도 학술발표회
• /
• pp.326-326
• /
• 2016

단층은 지질학적 관점에서 국부적인 지구구조응력(tectonic stress)이 암반 내에 존재하는 어떤 면을 따라 파괴 분기값을 초과하는 경우에 발생하는 매우 큰 공간적 변이에 의한 파괴 면으로 정의된다. 이러한 단층의 수문지질학적 특성은 단층의 공간적인 분포와 간극의 연결성에 따라 변화된다. 단층의 형성이 단층 내의 간극의 생성과 파괴를 이끄는 과정이 포함될 때 단층을 따라 발생되는 변이와 간극의 변화 사이에 복잡한 관계가 존재한다. 본 연구에서는 단층의 기하학적 특성에 따라 변화되는 흐름 변화를 3차원 이산 균열망 모형을 통해 모의 및 분석을 수행하였다. 단층의 기하학적 특성에 대해 3가지 경우를 고려하였다. 첫 번째는 영역 중심에 위치한 폭이 매우 좁고 상대적으로 주위 암반보다 매우 높은 투수성을 가진 단층, 두 번째는 단층 주변에 손상지역(damaged zone)이 존재하는 경우 그리고 세 번째는 relay 구조를 가진 단층이다.

• Imaging Science in Dentistry
• /
• 제36권1호
• /
• pp.55-62
• /
• 2006

Purpose : To find the cause of root curvature by use of panoramic and lateral cephalometric radiograph. Materials and Methods : Twenty six 1st graders whose mandibular 1st molars .just emerged into the mouth were selected. Panoramic and lateral cephalometric radiograph were taken at grade 1 and 6, longitudinally. In cephalometric radio graph, mandibular plane angle, ramus-occlusal plane angle, gonial angle, and gonion-gnathion distance (Go-Gn distance) were measured. In panoramic radio graph, elongated root length and root angle were measured by means of digital subtraction radiography. Occlusal plane-tooth axis angle was measured, too. Pearson correlations were used to evaluate the relationships between root curvature and elongated length and longitudinal variations of all variables. Multiple regression equation using related variables was computed. Results : The Pearson correlation coefficient between curved angle and longitudinal variations of occlusal plane-tooth axis angle and ramus-occlusal plane angle was 0.350 and 0.401, respectively (p<0.05). There was no significant correlation between elongated root length and longitudinal variations of all variables. The resulting regression equation was $Y=10.209+0.208X_1+0.745X_2$ (Y: root angle, $X_1$: variation of occlusal plane-tooth axis angle, $X_2$: variation of ramus-occlusal plane angle). Conclusion : It was suspected that the reasons of root curvature were change of tooth axis caused by contact with 2nd deciduous tooth and amount of mesial and superior movement related to change of occlusal plane.

• Composites Research
• /
• 제23권6호
• /
• pp.61-66
• /
• 2010

본 논문에서는 필라멘트 와인딩 시 장력에 의해 압밀을 유발하는 압력을 선행연구자들의 연구를 참조하여 결정한 후 T800 탄소섬유/에폭시 복합재료의 기본적인 물성과 성형압력 변화에 따른 면 내 외의 물성 변화를 측정하였다. 실험 시편은 오토클레이브 진공백 성형을 통해 압력(절대압력 0.1MPa, 0.3MPa, 0.7MPa)을 조절하여 제조되었다. 모든 시편은 적층판 형태로 정화된 후 워터젯을 이용하여 시편 모양으로 절단되었으며, 층간 전단시편의 V-노치는 밀링가공을 통하여 제작되었다. 평면 내 물성을 위해 다양한 인장실험이 실시되었으며, 평면 외 물성을 측정하기 위해 층간 전단 실험이 수행되었다 성형압력과 물성 변화를 관련시키기 위해 시편의 섬유 부피분율을 측정하였다. 본 연구에서 측정된 물성은 동일한 탄소섬유 (T800 탄소섬유)를 사용하여 필라멘트 와인딩 공정으로 제작되는 차량용 Type III 수소저장용기의 설계에 유용하게 활용될 수 있을 것으로 기대된다.

• 한국해양공학회:학술대회논문집
• /
• 한국해양공학회 2006년 창립20주년기념 정기학술대회 및 국제워크샵
• /
• pp.457-460
• /
• 2006

This study is to investigate the variation characteristics of run-up height over sandy beach due to the plane distribution of submerged breakwaters. In this study, Three-Dimensional numerical model with Large Eddy Simulation, which is able to simulate directly WAve Structure Seabed interaction (hereafter, LES-WASS-3D) has been newly developed. A comparison between the numerical model and existing experimental results was made to verify accuracy of newly proposed LES-WASS-3D model, and showed fairly nice agreement. In addition, based on the LES-WASS-3D model, the variation characteristics of run-up height over sandy beach are discussed with relation to the offshore distance and opening width of submerged breakwaters.

• Structural Engineering and Mechanics
• /
• 제6권2호
• /
• pp.143-159
• /
• 1998

The objective of this present work is to estimate the failure loads, associated maximum transverse displacements, locations and the modes of failure, including the onset of delamination, of thin, square symmetric laminates under the action in-plane positive (+ve) shear load. Two progressive failure analyses, one using the Hashin criterion and the other using a Tensor polynomial criterion, are used in conjunction with finite element method. First order shear deformation theory along with geometric non-linearity in the von Karman sense have been employed. Variation of failure loads and failure characteristics with five type of lay-ups and three types of boundary conditions has been investigated in detail. It is observed that the maximum difference between failure loads predieted by various criteria depends strongly on the laminate lay-up and the flexural boundary restraint. Laminates with clamped edges are found to be more susceptible to failure due to transverse shear (ensuing from the out of plane bending) and delamination, while those with simply supported edges undergo total collapse at a load slightly higher than the fiber failure load. The investigation on negative (-ve) in-plane shear load is in progress and will be communicated as part-II of the present work.

• 한국정보통신학회논문지
• /
• 제4권2호
• /
• pp.365-370
• /
• 2000

본 논문에서는 접지면의 크기가 안테나의 성능에 미치는 영향을 분석하기 위하여 기존의 프린트형 안테나의 특성 개선 요구에 부응한 안테나를 설계ㆍ제작하여 프린트형 안테나의 접지면의 크기에 따른 특성을 측정, 분석하여 최적의 접지면 크기를 산출하였다. 폴디드 안테나의 특성에 미치는 접지면 효과를 알아보기 위해 동박판을 잘라 기존의 폴디드 슬롯 안테나의 접지면을 확장시켰을 때 임피던스 및 방사 특성의 변화를 조사한 결과 임피던스 특성에는 별로 영향을 주지 않았으나, 방사 특성에는 많은 영향을 미치고 있음을 확인 할 수 있었다. 접지면의 크기를 고려한 엄격한 설계를 위해서는 복잡한 과정을 거쳐야 하지만, 접지면의 효과를 무시할 수 있는 적당한 크기를 산정하여 제작한다면 좀더 간단하게 안테나를 제작할 수 있을 것이다.

• 수산해양기술연구
• /
• 제32권4호
• /
• pp.395-401
• /
• 1996

In this paper, the propagation characteristics due to the horizontal water temperature variations in the sea such as thermal fronts is analyzed by the ray theory. Two models for the temperature anomaly layer are chosen. One is a plane type and the other is a cylindrical type. In the plane type, the temperature increases linearly from a isothermal region to 5km with the gradient of about $2^{\circ}C.$/km, and decreases with the same gradient in next 5km. In the cylindrical type, water temperature increases only with the same gradient from a half cylindrical thermal boundary surface. The result showed that the gradient of acoustic rays decreases in the temperature increasing region and vice versa in temperature decreasing region. And, the transmission loss due to the temperature variation was less than O.2dB in the plane type model as well as in the cylindrical one.

• 한국안광학회지
• /
• 제8권2호
• /
• pp.77-83
• /
• 2003

본 연구에서는 안경렌즈 전면의 conic 계수 변화에 따른 상측정점초점면에서의 착락원 직경 변화를 조사하기 위해 Code V와 LOSA 2.9 프로그램을 사용하였다. 이때 상측정점굴절력은 -4.00D이고 직경은 70mm인 근시교정용 안경렌즈를 고려하였으며, 전면 굴절력은 2.00D, 4.00D, 6.00D, 그리고 8.00D인 경우를, 굴절률은 $n_d$=1.498, 1.523, 1.586, 그리고 1.660인 경우를 각각 고려하였다. 최적 conic 계수를 사용한 비구면 렌즈의 경우에 상측정점초점면에서의 착락원 크기가 구면렌즈의 경우 보다 작아졌으며, 가장자리의 두께는 감소하였다. 또한 전면굴절력이 작을수록 상측정점초점면에서의 착락원의 크기가 감소하였다. 이러한 결과들로부터 상측점검초점면에서의 착락원 직격을 최소화하여 광학적 결상능력을 향상시킬 수 있는 최적 conic 계수를 결정하였다.