• Steel and Composite Structures
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• 제44권3호
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• pp.371-388
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• 2022

The present study tackles the problem of forced vibration of imperfect axially functionally graded shell structure with truncated conical geometry. The linear and nonlinear large-deflection of the structure are considered in the mathematical formulation using von-Kármán models. Modified coupled stress method and principle of minimum virtual work are employed in the modeling to obtain the final governing equations. In addition, formulations of classical elasticity theory are also presented. Different functions, including the linear, convex, and exponential cross-section shapes, are considered in the grading material modeling along the thickness direction. The grading properties of the material are a direct result of the porosity change in the thickness direction. Vibration responses of the structure are calculated using the semi-analytical method of a couple of homotopy perturbation methods (HPM) and the generalized differential quadrature method (GDQM). Contradicting effects of small-scale, porosity, and volume fraction parameters on the nonlinear amplitude, frequency ratio, dynamic deflection, resonance frequency, and natural frequency are observed for shell structure under various boundary conditions.

• Geomechanics and Engineering
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• 재33권6호
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• pp.529-542
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• 2023

Wave propagation with high transverse deflection could affect the stability of the ball in its trajectory. For low stiffness balls similar to soccer and volleyball balls, the waves are more noticeable in comparison to other balls like ping-pong ball. On the other hand, the soccer balls are under heavy impact loads from shoots and contacting different objects in the field. The maximum recorded speed of a soccer ball after kicking is the 211 km/hr and the average maximum speed is around 112 km/hr. Therefore, in such speeds the aerodynamic forces become important which are directly related to geometrical shape of the ball. In this regard, the wave propagation in soccer ball is examined in the current study using large deformation shear deformable formulations. Classical relations of stress-strain components are taken into consideration along with minimum total energy principle. The final derived relations were solved by using harmonic differential quadrature method. The results are generally presented ion term of phase velocity as function of different influencing parameters of the materials, geometry and mass of the ball.

• 한국콘텐츠학회논문지
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• 제20권7호
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• pp.212-222
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• 2020

본 연구의 목적은 전 세계 산업수학의 흐름을 주도하는 미국산업응용수학 학회에서 출판하는 논문들의 연구현황 및 동향을 거시적으로 파악하는 데 있다. 이를 위해 2016년부터 2019년까지 6,255편의 논문 제목 및 초록을 수집하였으며, LDA 기법을 활용한 토픽모델링과 시계열회귀모형 분석을 수행하였다. 분석 결과 첫째, 산업수학 분야는 해석학을 중심으로 기하학, 대수학, 위상수학, 이산수학, 확률 및 통계 등 다양한 분야에서 연구가 진행되었다. 둘째, 시간이 흐름에 따라 상승하는 연구 주제는 수리유체역학, 그래프이론, 확률미분방정식이었으며, 하강하는 연구 주제는 계산이론과 고전기하로 나타났다. 연구 결과는 산업수학 분야의 지적 구조에 대한 전체적인 흐름 및 변화에 대한 이해를 바탕으로 연구자들에게는 향후 연구 방향에 대해서, 그리고 교육 현장에는 시대 변화를 반영한 산업수학 교육과정을 수립하는데 시사점을 제공할 것이다.