• Steel and Composite Structures
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• 제51권1호
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• pp.73-91
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• 2024

This paper has focused on presenting vibration analysis of trapezoidal sandwich plates with a damaged core and FG wavy CNT-reinforced face sheets. A damage model is introduced to provide an analytical description of an irreversible rheological process that causes the decay of the mechanical properties, in terms of engineering constants. An isotropic damage is considered for the core of the sandwich structure. The classical theory concerning the mechanical efficiency of a matrix embedding finite length fibers has been modified by introducing the tube-to-tube random contact, which explicitly accounts for the progressive reduction of the tubes' effective aspect ratio as the filler content increases. The First-order shear deformation theory of plate is utilized to establish governing partial differential equations and boundary conditions for the trapezoidal plate. The governing equations together with related boundary conditions are discretized using a mapping-generalized differential quadrature (GDQ) method in spatial domain. Then natural frequencies of the trapezoidal sandwich plates are obtained using GDQ method. Validity of the current study is evaluated by comparing its numerical results with those available in the literature. After demonstrating the convergence and accuracy of the method, different parametric studies for laminated trapezoidal structure including carbon nanotubes waviness (0≤w≤1), CNT aspect ratio (0≤AR≤4000), face sheet to core thickness ratio (0.1 ≤ ${\frac{h_f}{h_c}}$ ≤ 0.5), trapezoidal side angles (30° ≤ α, β ≤ 90°) and damaged parameter (0 ≤ D < 1) are carried out. It is explicated that the damaged core and weight fraction, carbon nanotubes (CNTs) waviness and CNT aspect ratio can significantly affect the vibrational behavior of the sandwich structure. Results show that by increasing the values of waviness index (w), normalized natural frequency of the structure decreases, and the straight CNT (w=0) gives the highest frequency. For an overall comprehension on vibration of laminated trapezoidal plates, some selected vibration mode shapes were graphically represented in this study.

• 재활치료과학
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• 제12권2호
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• pp.55-68
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• 2023

목적 : 본 연구는 뇌성마비 아동에게 시지각 중재를 적용한 연구들에 대해 체계적으로 고찰하여, 시지각중재의 효과에 대해 분석하고자 한다. 연구방법 : 데이터 베이스는 PubMed, EMbase, Science Direct, ProQuest, Koreanstudies Information Service System (KISS), Research Information Sharing Service (RISS), 국회도서관을 사용하였다. 키워드는 뇌성마비, 시지각, cerebral palsy, CP, visual perception을 사용하였다. PRISMA Flowchart에 따라 2012년 1월 1일부터 2022년 3월 30일까지 게재된 연구 중에서 10편을 선정하였다. 선정된 연구들의 질적 수준, 연구 대상자의 인구학적 특성, 중재의 효과, 중재의 영역과 전략, 중재의 효과를 측정하기 위한 평가도구, 비뚤림 위험에 대해 분석하였다. 결과 : 선정된 모든 연구에서 시지각 중재가 시지각 기능 증진에 효과적임을 확인하였다. 또한 시지각중재는 시지각 기능뿐만 아니라 상지기능, 일상생활활동, 자세조절, 목표달성, 심리사회 영역에서도 긍정적인 결과를 나타냈다. 눈-손 협응 영역은 모든 연구에서 중재되었다. 결론 : 시지각 중재 시 시지각 기능을 영역별로 평가하고, 개인별 체계적으로 단계화된 맞춤 중재를 적용해야 한다.