• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2013년도 추계 학술논문 발표대회
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• pp.146-147
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• 2013

The oyster shells of about 240,000 tons have been annually produced in south coast of South Korea. However, about 25% of the oyster shells (60,000tons) was recycled as oyster seeding and fertilizer due to the limited amount of consumption for such purposes. The stored amount of oyster shell in the fertilizer manufacturing company is overfilled, and thus cannot accept any more of the waste oyster shells. As a result, landfill and illegal dumping of waste oyster shells have become an increasingly serious issue since 2011. In this research, the problems generated by the oyster shells were investigated through surveying activities. One of the possible alternative solutions that can process large amount of waste economically was found to be the application of oyster shells as a construction materials.

• 한국산학기술학회논문지
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• 제6권6호
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• pp.525-530
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• 2005

본 연구에서는 비등방성 두꺼운 셀 및 얇은 쉘의 휨문제에 대한 해석결과를 제시하였다. 복잡한 편미분방정식을 포함하는 쉘의 역학적 문제에 대한 수치해석을 위해 유한요소법을 사용하였으며, 비등방성 셀의 휨문제에 대한 지배방정식은 키르호프 가정에 의한 얇은 쉘이론과 민들린 가정에 의한 두꺼운 쉘이론을 이용하여 유도하였으며, 쉘의 폭 - 두께비에 따른 해석결과를 비교 검토하였으며, 본 연구의 수치해석방법은 비등방성 쉘의 휨거동 분석 및 설계에 사용될 수 있을 것으로 본다.

• 복합신소재구조학회 논문집
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• 제1권3호
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• pp.17-23
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• 2010

본 연구는 비등방성 원통형 쉘의 휨문제에 대한 해석 기법을 제시하였다. 비등방성 원통형 쉘의 지배방정식을 해석하기 위해 유한요소법을 사용하였다. 두꺼운 쉘이론과 얇은 쉘이론을 사용하여 쉘의 폭-두께비 및 여러 가지 경계조건을 갖는 비등방성 원통형 쉘에 대한 해석결과를 비교 분석하였다. 본 연구의 수치해석 결과는 비등방성 원통형 쉘의 휨 거동 분석에 기여할 것으로 보인다.

• 한국염색가공학회지
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• 제29권2호
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• pp.62-68
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• 2017

Coffee sludge and onion shells are known typically as waste resources as well as simultaneously being the raw material for dye having a golden brown color. This research studies the dyeability, functionality, and colors of woolen fabric after being dyed by different dyeing method using coffee sludge and onion shells extract. The woolen fabric was refined and pre-mordanted with tannin. The dyeing process conducted was single-dye, using coffee sludge and onion shells extract, sequential multi-dye, consecutively dyeing with coffee sludge and onion shells, and mixed-dye, blending coffee sludge extract and onion shells extract to dye. The dyeing was measured on the surface color, color fastness, and UV-protection ability. As a result, the expression of various hues of tan using coffee sludge and onion shells extract were shown to be possible. Additionally, single-dye, sequential multi-dye, mixed-dye had generally superiority in color fastness to light, all rating 3 and color fastness to washing, rating 3 or 4, showing relatively stable color fastness to washing. The UV protection ability was shown to be better, especially appearing satisfactory in the UV-B protection, all measured to be over 90%.

• Steel and Composite Structures
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• 제48권3호
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• pp.335-351
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• 2023

This research studies the primary resonance and nonlinear vibratory responses of multilayer functionally graded shallow (MFGS) shells under external excitations. The shells considered with functionally graded porous (FGP) core and resting on two types of nonlinear viscoelastic foundations (NVEF) governed by either a linear model with two parameters of Winkler and Pasternak foundations or a nonlinear model of hardening/softening cubic stiffness augmented by a Kelvin-Voigt viscoelastic model. The shells considered have three layers, sandwiched by functionally graded (FG), FGP, and FG materials. To investigate the influence of various porosity distributions, two types of FGP middle layer cores are considered. With the first-order shear deformation theory (FSDT), Hooke's law, and von-Kármán equation, the stress-strain relations for the MFGS shells with FGP core are developed. The governing equations of the shells are consequently derived. For the sake of higher accuracy and reliability, the P-T method is implemented in numerically analyzing the vibration, and the method of multiple scales (MMS) as one of the perturbation methods is used to investigate the primary resonance. The results of the present research are verified with the results available in the literature. The analytical results are compared with the P-T method. The influences of material, geometry, and nonlinear viscoelastic foundation parameters on the responses of the shells are illustrated.

• Steel and Composite Structures
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• 제21권1호
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• pp.217-247
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• 2016

Five extended cylindrical reticulated shells are proposed by changing distribution rule of diagonal rods based on three fundamental types. Modeling programs for fundamental types and extended types of cylindrical reticulated shell are compiled by using the ANSYS Parametric Design Language (APDL). On this basis, conditional formulas are derived when the grid shape of cylindrical reticulated shells is equilateral triangle. Internal force analysis of cylindrical reticulated shells is carried out. The variation and distribution regularities of maximum displacement and stress are studied. A shape optimization program is proposed by adopting the sequence two-stage algorithm (RDQA) in FORTRAN environment based on the characteristics of cylindrical reticulated shells and the ideas of discrete variable optimization design. Shape optimization is achieved by considering the objective function of the minimum total steel consumption, global and locality constraints. The shape optimization for three fundamental types and five extended types is calculated with the span of 30 m~80 m and rise-span ratio of 1/7~1/3. The variations of the total steel consumption along with the span and rise-span ratio are analyzed with contrast to the results of shape optimization. The optimal combination of main design parameters for five extended cylindrical reticulated shells is investigated. The total steel consumption affected by distribution rule of diagonal rods is discussed. The results show that: (1) Parametric modeling method is simple, efficient and practical, which can quickly generate different types of cylindrical reticulated shells. (2) The mechanical properties of five extended cylindrical reticulated shells are better than their fundamental types. (3) The total steel consumption of cylindrical reticulated shells is optimized to be the least when rise-span ratio is 1/6. (4) The extended type of three-way grid cylindrical reticulated shell should be preferentially adopted in practical engineering. (5) The grid shape of reticulated shells should be designed to equilateral triangle as much as possible because of its reasonable stress and the lowest total steel consumption.

• Structural Engineering and Mechanics
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• 제55권3호
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• pp.555-581
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• 2015

Triangular pyramid and Quadrangular pyramid elements for partial double-layer spherical reticulated shells of pyramidal system are investigated in the present study. Macro programs for six typical partial double-layer spherical reticulated shells of pyramidal system are compiled by using the ANSYS Parametric Design Language (APDL). Internal force analysis of six spherical reticulated shells is carried out. Distribution regularity of the stress and displacement are studied. A shape optimization program is proposed by adopting the sequence two-stage algorithm (RDQA) in FORTRAN environment based on the characteristics of partial double-layer spherical reticulated shells of pyramidal system and the ideas of discrete variable optimization design. Shape optimization is achieved by considering the objective function of the minimum total steel consumption, global and locality constraints. The shape optimization of six spherical reticulated shells is calculated with the span of 30m~120m and rise to span ratio of 1/7~1/3. The variations of the total steel consumption along with the span and rise to span ratio are discussed with contrast to the results of shape optimization. The optimal combination of main design parameters for six spherical reticulated shells is investigated, i.e., the number of the optimal grids. The results show that: (1) The Kiewitt and Geodesic partial double-layer spherical reticulated shells of triangular pyramidal system should be preferentially adopted in large and medium-span structures. The range of rise to span ratio is from 1/6 to 1/5. (2) The Ribbed and Schwedler partial double-layer spherical reticulated shells of quadrangular pyramidal system should be preferentially adopted in small-span structures. The rise to span ratio should be 1/4. (3) Grids of the six spherical reticulated shells can be optimized after shape optimization and the total steel consumption is optimized to be the least.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
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• pp.507-512
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• 2001

An investigation into using Oyster Shells partially or wholly as aggregate in concrete is reported. The proportion of shells was varied with ratios of 10, 30, 50 and 100% by volume of fine and coarse aggregate. Two water/cement ratios of 0.45, 0.55 were considered and air-entraining superplasticizer was used to improve concrete workability Two strength properties (compressive and flexural) were considered. Strength tests were carried out at the ages of 1, 3, 7, 14 and 28 days. The variations of workability, weight and density of the specimens with different proportions of Oyster Shells were also studied. Results showed that compressive and flexural strengths decreased with increase in proportion of Oyster Shells to aggregate in the reference mixes. The workability of concrete batches decreased with increase in the proportion of Oyster Shells in the mixes. The same trend was observed with density and weight of the specimens

• 한국패류학회지
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• 제31권3호
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• pp.221-232
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• 2015

Observations in beach, intertidal and upper subtidal environments in Peter the Great Bay (north-western East Sea) have shown that attached algae were found on empty shells of 13 species of epifaunal and infaunal bivalve mollusks. Thirteen algae species were identified on empty dislodged shells but more than 50 species are known to be epibiotic on living bivalves. The dislodgement of shells with attached algae takes place in semi-enclosed, low-energy areas, as well as those which are open and affected by strong wave action, indicating the large scale of this phenomenon. The significance of seaweed transportation of living mollusks and their empty shells in the coastal zone, involving both taphonomic and ecological processes, is stressed. Algae appear to be a taphonomic agent and play a similar role as compared to birds or hermit crabs, but they act passively and contribute to environmental mixing in death assemblages in coastal environments.

• Steel and Composite Structures
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• 제20권5호
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• pp.1043-1066
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• 2016

A new analytical solution based on a third order shear deformation theory for the problem of static analysis of cross-ply doubly-curved shells is presented. The boundary-discontinuous generalized double Fourier series method is used to solve highly coupled linear partial differential equations with the mixed type simply supported boundary conditions prescribed on the edges. The complementary boundary constraints are introduced through boundary discontinuities generated by the selected boundary conditions for the derivation of the complementary solution. The numerical accuracy of the solution is compared by studying the comparisons of deflections, stresses and moments of symmetric and anti-symmetric laminated shells with finite element results using commercially available software under uniformly distributed load. Results are in good agreement with finite element counterparts. Additional results of the symmetric and anti-symmetric laminated and sandwich shells under single point load at the center and pressure load, are presented to provide data for the unsolved boundary conditions, benchmark comparisons and verifications.