• Structural Engineering and Mechanics
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• 제89권1호
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• pp.33-46
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• 2024

The present research delves into the analysis of nonlinear free and forced vibrations of porous functionally graded (FG) shallow shells reinforced with oblique stiffeners, which are embedded in a nonlinear elastic foundation (NEF) subjected to external excitation. Two distinct types of PFG shallow shells, characterized by even and uneven porosity distribution along the thickness direction, are considered in the research. In order to model the stiffeners, Lekhnitskii's smeared stiffeners technique is implemented. With the stress function and first-order shear deformation theory (FSDT), the nonlinear model of the oblique stiffened shallow shells is established. The strain-displacement relationships for the system are derived via the FSDT and utilization of the von-Kármán's geometric assumptions. To discretize the nonlinear governing equations, the Galerkin method is employed. The model such developed allows analysis of the effects of the stiffeners with various angles as desired, in addition to the quantitative investigation on the influence of the surrounding nonlinear elastic foundations. To numerically solve the problem of vibrations, the 4th-order P-T method is used, as this method, known for its enhanced accuracy and reliability, proves to be an effective choice. The validation of the present research findings includes a comprehensive comparison with outcomes documented in existing literature. Additionally, a comparative analysis of the numerical results against those obtained using the 4th Runge-Kutta method is performed. The impact of stiffeners with varying angles and material parameters on the vibration characteristics of the present system is also explored. The researchers and engineers working in this field may use the results of this study as benchmarks in their design and research for the considered shell systems.

• 한국패류학회지
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• 제30권1호
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• pp.17-23
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• 2014

여수 횡간도 지역에서 밀도별 피조개 각장 과 전중량의 성장은 밀도와 역 상관관계를 보였다. 밀도별 각장 평균성장은 10마리구가 5.21 mm로 가장 양호하였으며 밀도가 높을수록 각장 성장은 낮아졌다. 밀도별 전중량의 증가도 같은 결과를 보여 전반적으로 10-20마리구의 평균각장 및 평균 전중량의 증가가 30-40마리구에 비하여 양호하게 나타났다. 남해해역에서 밀도별 피조개 각장과 전중량의 성장도 밀도와 역 상관관계를 보였으나 여수해역보다 약한 역 상관관계를 보였다. 밀도별 각장 평균성장은 10마리구가 4.55 mm로 가장 양호한 결과를 보였으나, 20-40마리구의 밀도별 평균각장의 성장은 3.11, 3.36, 3.27 mm로 비슷하게 나타났다. 반면에 밀도별 전중량의 증가는 10-20마리구가 30-40마리구보다 많았다. 결론적으로 피조개의 수하양성시 양성밀도는 20마리/$0.12m^2$ (166마리/$1m^2$) 가 적당하다고 사료되었다. 여수해역에서 피조개의 생존율은 밀도별로 각각 68%-87%, 로 밀도의존적 결과를 보였으나, 먹이생물인 식물플랑크톤이 풍부한 남해해역의 생존율은 91%-100%로 월등히 양호한 결과를 보였는데, 이는 여수해역의 식물플랑크톤의 양이 남해해역의 55.89%에 불과하였기 때문이라 사료된다. 수하 양성 해역별의 수온범위는 $16.22-25.66^{\circ}C$였고, 염분은 30.07-33.48였으며, pH는 8.10-8.45범위였다. 그리고 용존산소 (DO) 는 4.49-9.65 mg/L 였다.

• Archives of Pharmacal Research
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• 제9권4호
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• pp.201-203
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• 1986

Forty species of marine shells were collected from Korean coasts and studied extensively for their lectin activities by using erythrocytes of human blooc A, AB, B. O group and rabbit blood. In total, 7 species contained lectines :Neptunea intersculpta, Omphalius nigerrimus and Scapharca subcrenata, blood group nonspecific; Saxidomus purpuratus, human blood A and AB group specific; Lepidozona coreana, Tegilarca granosa and Neptunea polycosta, rabbit blood specific.

• 대한토목학회논문집
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• 제11권1호
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• pp.89-98
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• 1991

본 논문에서는 본 논문의 선행논문(先行論文)( )에서 언급한 철근콘크리트 쉘구조의 재료적(材料的) 및 기하학적(幾何學的) 비선형(非線形) 해석방법(解析方法)의 타당성을 입증하기 위해서 여러가지 수식예제(數植例題)를 해석하여 실험치와 비교, 고찰하였다. 그 결과 본 논문의 해석방법이 재료적(材料的) 및 기하학적(幾何學的) 비선형성(非線形性)을 고려한 임의형상의 철근콘크리트 쉘구조의 해석에 적합한 방법임을 입증하였다.

• Structural Engineering and Mechanics
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• 제60권3호
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• pp.365-386
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• 2016

This paper describes a systematic numerical investigation into the nonlinear elastic behavior of conical shells, with various types of initial imperfections, subject to a uniformly distributed axial compression. Three different patterns of imperfections, including first axisymmetric linear bifurcation mode, first non-axisymmetric linear bifurcation mode, and weld depression are studied using geometrically nonlinear finite element analysis. Effects of each imperfection shape and tapering angle on imperfection sensitivity curves are investigated and the lower bound curve is determined. Finally, an empirical lower bound relation is proposed for hand calculation in the buckling design of conical shells.

• Steel and Composite Structures
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• 제19권1호
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• pp.1-19
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• 2015

The buckling analysis is presented for non-homogeneous (NH) orthotropic truncated conical shells subjected to combined loading of axial compression and external pressure. The governing equations have been obtained for the non-homogeneous orthotropic truncated conical shell, the material properties of which vary continuously in the thickness direction. By applying Superposition and Galerkin methods to the governing equations, the expressions for critical loads (axial, lateral, hydrostatic and combined) of non-homogeneous orthotropic truncated conical shells with simply supported boundary conditions are obtained. The results are verified by comparing the obtained values with those in the existing literature. Finally, the effects of non-homogeneity, material orthotropy, cone semi-vertex angle and other geometrical parameters on the values of the critical combined load have been studied.

• Steel and Composite Structures
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• 제27권1호
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• pp.35-48
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• 2018

In this paper, the response of a sandwich cylindrical shell over any sort of boundary conditions and under a general distributed static loading is investigated. The faces and the core are made of some isotropic materials. The faces are modeled as thin cylindrical shells obeying the Kirchhoff-Love assumptions. For the core material it is assumed to be thick and the in-plane stresses are negligible. The governing equations are derived using the principle of the stationary potential energy. Using harmonic differential quadrature method (HDQM) the equations are solved for deformation components. The obtained results primarily are compared against finite element results. Then, the effects of changing different parameters on the stress and displacement components of sandwich cylindrical shells are investigated.

• 한국결정성장학회지
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• 제10권2호
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• pp.159-165
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• 2000

본 연구에서는 남해안 일대의 굴 고막, 바지락 패각에 대한 부존환경을 조사하였으며 그리고 부존환경 개선, 환경오염 방지 등을 위한 패각의 재활용 방안을 확립하였다. 패각의 부존환경은 공유수면의 불법매립 또는 연안지역에 야적 .방치된 상태였다. 부존패각의 효율적인 재활용을 위하여 성인 메카니즘 그리고 XRD, TG-DTA분석을 행한 결과, 탄산칼슘으로의 제조가 최적임을 알았다. 본 연구에서는 부존 패각을 탄산칼슘과 과립형의 패화석비료로 재활용하였다.

• 한국공간구조학회논문집
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• 제2권4호
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• pp.45-52
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• 2002

Research about spherical shells been applying most usually is achieved by many investigators already and generalized equation has been derived. But, existent research is limited in case that spherical shell's roof rigidity is isotropy or orthotropy, and research that consider periodicity of rigidity-distribution that can happen by doing spherical shell's roof system by lattice system is not gone entirely. The purpose of this paper is applying Galerkin method to spherical shell that model periodicity of roof rigidity distribution that appear by roof lattice form of large space structure and develop structural analysis program that formularize. Rigidity-model of this research selects that of spherical shell which has 2-way grid. In this paper, buckling-strength and deformation distribution of isotopic spherical shell and 2-way grid spherical shell obtained by developed program could confirm the reliability by comparison with result of existent research.

• 한국환경보건학회지
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• 제24권3호
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• pp.124-130
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• 1998

This study was to examine the utilization of waste egg snells for removal of heavy metals in laboratory wastewater. It was estimated that pH increasing formed heavy metals into a hydroxide and then settled to remove them. Removal rate of heavy metals were increased as increased dosage, low adsorbate concentration and passed reaction time. Average adsorption volumes of Cr, Cu, Mn and Pb per g were about 1.21 mg, 1.1 mg, 0.96 mg and 1.04 mg, respectively. If we reflected the adsorption capacity(k) and adsorption intensity(1/n) of Freundlich isotherm, we couldn't consider waste egg shells as a good adsorbent. It seemed that heavy metals contained in complex wastewater was removed to be influenced by inital pH, solubilities with passed reaction rime and competitive reaction.