• Journal of the Computational Structural Engineering Institute of Korea
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• v.13 no.2
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• pp.221-230
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• 2000

Sweep geometric models are based on the notion of moving a curve, surface or solid along some path. Sweeping allows definition of prismatic shell surfaces in a simple way, This paper describes an application of sweep geometric models for the optimization of prismatic shells. This geometric model is integrated with finite element formulations. A nine-node degenerated shell element is adopted to calculate the response of prismatic shells. Several examples we presented to demonstrate the process of optimization. From numerical examples, it is observed that sweep geometric models provide an efficient and reliable way of obtaining optimal solutions for a large class of prismatic shell structures.

• The Korean Journal of Malacology
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• v.27 no.3
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• pp.223-228
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• 2011

To understand the role of hemocytes in the shell repair process, a hole was drilled in the right valves of the Pacific oyster, Crassostrea gigas, and the repair process was observed. Histological observations suggested that the exterior surface of the shell was repaired by aggregated hemocytes. The nuclei of the hemocytes were cleary stained in the regenerated shell while appearing fragmented after calcification at the $7^{th}$ day. Globular calcium granules were genegenerated from the hemocytic monolyer after 6 days of incubation which were morphologically and chemically identical with those from prismatic shell. Our finding suggested that the repaired prismatic shell was composed by aggregated hemocytes and that their endogenous calcium component might support the nucleation of calcium biomineralization during shell repair.

• The Korean Journal of Malacology
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• v.11 no.1
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• pp.70-77
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• 1995

The purpose of this study is to determine the differences of the conchiolin layer, prismatic layer and nacreous layer deposited within the shell of the freshwater family Unionidae. shether they possess species-specific characteristics and differences of the microstructure of these layers, A Scanning electron microscopic obwervations were conducted on seven species. The results indicate that all species possess thin and homogeneous layers within the periostracum. The prismatic layers of these species were composed of ednsely packed prisms. The prismatic layers of the shell in six species were typical shape of prisms. especially Inio douglasiae and Lamprotual gottschei. But, in Unio douglasiae sinuolatus, it was irregular and oblique prism shape.The nacreous layer of weven unionids characterized by possession of three types by lamillae shape: thin and homogeneous on genus Anodonta(0.4 pm size of lamella), Unio(1.3pm) and Lamprotual (1.7pm), homogeneous in shape and irregular in size of lamillae in Lanceolaria(1.0 pm)and irregulat in shape and size in Solenaia(0.2-0.4 pm). The microstructure of the naceous layer may be useful as a taxonomic character at the generic level.

• Structural Engineering and Mechanics
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• v.37 no.2
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• pp.253-256
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• 2011

• Steel and Composite Structures
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• v.4 no.4
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• pp.281-301
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• 2004

The paper begins by presenting a unified variational approach to the lateral-torsional buckling (LTB) analysis of doubly symmetric prismatic and tapered thin-walled beams with open cross-sections, which accounts for the influence of the pre-buckling deflections. This approach (i) extends the kinematical assumptions usually adopted for prismatic beams, (ii) consistently uses shell membrane theory in general coordinates and (iii) adopts Trefftz's criterion to perform the bifurcation analysis. The proposed formulation is then applied to investigate the influence of the pre-buckling deflections on the LTB behaviour of prismatic and web-tapered I-section simply supported beams and cantilevers. After establishing an interesting analytical result, valid for prismatic members with shear centre loading, several elastic critical moments/loads are presented, discussed and, when possible, also compared with values reported in the literature. These numerical results, which are obtained by means of the Rayleigh-Ritz method, (i) highlight the qualitative differences existing between the LTB behaviours of simply supported beams and cantilevers and (ii) illustrate how the influence of the pre-buckling deflections on LTB is affected by a number of factors, namely ($ii_1$) the minor-to-major inertia ratio, ($ii_2$) the beam length, ($ii_3$) the location of the load point of application and ($ii_4$) the bending moment diagram shape.

• Wind and Structures
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• v.5 no.2_3_4
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• pp.89-100
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• 2002

Accidental gaseous losses from industrial processes can pose considerable health and environmental risks but assessing their health, safety and environmental impact is problematic. Improved understanding and simulation of the dispersion of emissions in the vicinity of storage tanks is required. The present study aims to assess the capability of the turbulence closures and meshing alternatives in a commercially available CFD code for predicting dispersion in the vicinity of cubes and circular cylindrical storage tanks. The performance of the $k-{\varepsilon}$ and Reynolds Stress turbulence models and meshing alternatives for these cases are compared to experimental data. The CFD simulations are very good qualitatively and, in many cases, quantitatively. A mesh with prismatic elements is more accurate than a tetrahedral mesh. Overall the Reynolds stress model performs slightly better than the $k-{\varepsilon}$ model.

• Journal of the Mineralogical Society of Korea
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• v.30 no.4
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• pp.149-159
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• 2017

We investigated the mineralogical and chemical characteristics of oyster shell as the possible substitute for the limestone used as an absorbent of $SO_2$ gas. The oyster shells from Taean and Tongyeong were used for the comparison with limestone and those from Boyreong and Yeosu were additionally investigated. XRD results show that all shells are composed of calcite with the exception of the myostracum layer attached to adductor muscle and ligament, which is composed of aragonite. The marine sediments as impurities exist on the surface of shells or as inclusions in the shells. Calcite is the main mineral composition of the shell of barnacle which is also one of the impurities. The oyster shell is composed of three main layers; prismatic, foliated, and chalk. The oyster shell from Tongyeong with the largest shell size, has the smallest thickness of prismatic and foliated layers which contain protein called conchiolin, whereas that from Taean with the smallest shell size has the largest prismatic and foliated layers. The sizes of those two layers of the shells from Boryeong and Yeosu are larger than that from Tongyeong but smaller than Taean. Those differences are supposed to be due to the different growth environments because the oysters from Tongyeong are cultured under the sea while those from Taean are in the tidal zone. The oyster shells generally show higher amount of sulfur and phosphorus than limestone, mainly due to the composition of protein. Some elements such as Mg show significant variations in different layers. As for trace elements, Li shows much higher amount in oyster shells than limestone, suggesting the influence of the composition of the sea water on the formation of the oyster shells.

• Korean Journal of Mineralogy and Petrology
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• v.33 no.3
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• pp.185-193
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• 2020

There have been many studies on the calcination of oyster shells in the perspective of recycling of resources. The quicklime made by the calcination of oyster shells is used either as it is or after reacting with water to transform to liquid lime before being used. However, the liquid lime made from calcined oyster shells show slightly different properties from that of limestone. In this study, to compare these properties of oyster shell with those of limestone, the samples were calcined and reacted with water at various temperatures to transform to a liquid lime and filtered using 150 ㎛ sieves to calculate the transform rate to liquid lime. The calcined limestone was transformed to liquid lime at all temperatures, but calcined oyster shell did not show any transformation at 30℃ and 50℃ under the experimental conditions of this study, and rather increased the weight for the remaining after filtration due to the presence of Ca(OH)₂ produced by the reaction with water, Even at 90℃, the transformation rate of calcined oyster shell to liquid lime was lower than that of limestone. This difference in oyster shell can be explained partly by the preventing calcined one from reacting with water by conchiolin which is protein found in the prismatic and pearl layers of oyster shell. Conchiolin is also known to be stable and does not decompose even at high temperature. However, even the calcined chalk layer without conchiolin shows lower transformation rate than that of calcined limestone, probably due to the small amount of Na in oyster shell, which may cause additional reaction including eutectic melt during calcination process.

• Composites Research
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• v.14 no.6
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• pp.9-15
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• 2001

In the present work, a linear static analysis is presented for thin-walled prismatic box-beams made of generally anisotropic materials. A mixed beam theory has been used to model and carry out the analysis. Several different constitutive assumptions for the shell-wall of the beam section are assessed into the beam formulation. Simple layup cases of box-beams representing bending-torsion or extension-torsion coupled configuration have been considered and tested to clearly show the effects of elastic couplings of the beam. A detailed finite element structural analysis using the MSC/NASTRAN has been carried out to validate the current analytical results. Numerical results show that appropriate assumptions for the constitutive relations are important and crucial for the accurate prediction of beam stiffness constants and also thor the beam behavior.