• 한국전산유체공학회지
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• 제21권4호
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• pp.28-32
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• 2016

In the previous study, it is proved by numerical simulation that the baffle shaped as the porous plate installed in the inlet chambers improves the redistribution of the flow injecting to the tube bundles. In the present study, numerical simulation has been performed to investigate the effects of the flow distributors on the thermal characteristics of the shell and tube heat exchangers. The flow fields have been analysed by the three-dimensional Navier-Stokes solvers including the thermal conditions on the shell sides. The numerical results showed that the presence of the baffles improves the redistribution of the heat transfer to the tube bundles though the overall performance drop slightly on the present flow conditions.

• 보존과학회지
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• 제34권4호
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• pp.295-303
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• 2018

The application of reinforcing agents with hydraulic property and strength development characteristics was studied under conditions similar to those of mural-painting mortar made with oyster shell powder. Reinforcement mortar made with oyster shell powder showed hydraulic properties and strength to supplement the weaknesses of natural hydraulic lime(NHL); this confirmed its possibility as a wall-reinforcing material with enough strength for preserving mural paintings. Reinforcement mortar 1 showed hydraulic property and general characteristics of lime mortar, such as consistency and viscosity, as well as lower strength and higher whiteness compared to an NHL product. For Reinforcement mortar 2, the original wall sample characteristics were reflected by mixing more shell produced through calcination; and it showed similar strength to that of Reinforcement mortar 1 as well as high whiteness. In measuring the contraction ratio of reinforcement mortar samples, Reinforcement mortar 1 and 2 showed more stability in property change compared to the NHL Group.

• 한국정밀공학회지
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• 제16권10호
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• pp.118-125
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• 1999

In the grinding process, generally, the exciting forces with high frequency can be generated due to the wheel wear and the grinding process. As the grinding speed increases, the precise investigation about the wheel dynamic characteristics is required. Conventionally the wheel-spindle has been considered with lumped model in dynamic modeling. With this lumped model, the significant mode resulted from the shell mode of wheel can be readily ignored. This paper suggests the new analysis model which includes the shell mode of wheel in modeling the wheel-spindle assembly. Furthermore, based on the suggested model, the effects of the bolt tightening force and the taper tightening force on the dynamic properties are investigated by the finite element modal analysis and the experimental method. As a result of investigation, the shell mode vibration of wheel affects the dynamic characteristics of the spindle assembly. Also, the vibration modes of the spindle assembly are significantly affected by the joint tightening forces.

• 한국정밀공학회지
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• 제16권6호
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• pp.108-113
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• 1999

For cylindrical shells, the closed-form solutions are confined to the specific boundary and/or loading conditions. Though the finite element method is certainly a powerful solution approach for the structural dynamics problems, it has been well known to provide the solution reliable only in the low frequency region due to the inherent high sensitivities of structual and numerical modeling errors. Instead, the spectral element method has been proved to provide accurate dynamic characteristics of a structure even at the ultrasonic frequency region. Since the wave characteristic of a cylindrical shell becomes identical to that fo a flat plate as the frequency increases, an equivalent plate model (EPM) representing the high-frequency dynamic characteristics of the cylindrical shell is introduced herein. The EPM-based spectral element analysis solutions are compared with the known analytical solutions for the cylindrical shells to confirm the validity of the present modeling approach.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.284-284
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• 2003

The free vibration characteristics of the cylindrical shell submerged in water is investigated using by FEM and experiment. In the FE analysis, the fluid-structure interaction effect is concerned. The restraint condition is clamped-free. In the results, the natural frequency and mode shape characteristics are evaluated with various water height. This results are compared with those of experiment to verify the validation of the FE analysis. The change of damping ratio is also presented by experiment.

• 한국식생활문화학회지
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• 제34권1호
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• pp.61-67
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• 2019

This study examined the quality characteristics of dumpling shells prepared with 0, 2, 4, 6, and 8% mulberry leaf powder. According to the amylograph data, the composite of mulberry leaf powder-wheat flour samples reduced the gelatinization temperatures, viscosities at $95^{\circ}C$, and maximum viscosity with increasing mulberry leaf powder content. The lightness (L) and redness (a) values decreased with increasing mulberry leaf powder content, whereas the yellowness (b) value increased. In addition, the weight, volume, and turbidity increased after cooking. In terms of the textural characteristics, addition of mulberry leaf powder increased the hardness, springiness, cohesiveness, chewiness, and adhesiveness. The DPPH free radical scavenging activity of the dumpling shells increased significantly (p<0.05) with increasing levels of mulberry leaf powder. The taste, chewiness and texture of the dumpling shells prepared with added 4% mulberry leaf powder were preferred. The sensory evaluation showed that the overall preference of the dumpling shell with the addition of 4% mulberry leaf powder was more effective than the control.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문집
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• pp.810-815
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• 2002

Vibration analysis of rotating blade is the main purpose of this study. In the present work, general formulation is proposed to analyze the rotating shell-type structures including the effect of centrifugal force, Coriolis acceleration and initial twist. Furthermore, simplified equations are derived for the case of an open circular cylindrical shell. Based on the concept of degenerated shell element with the Reissner-Mindlin's assumptions, the finite element method is adopted for solving the governing equations. In addition, it is investigated the effect of thermal load on the vibration characteristics of pretwisted blade. Numerical results are summarized for the various parameters such as rotating speed, angle of pretwist and stacking sequence of a composite blade. Also, present results are compared with the previous works and experimental data.

• International Journal of Industrial Entomology and Biomaterials
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• 제25권2호
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• pp.205-208
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• 2012

Antheraea pernyi silkworm is a well known wild silkworm to produce a valuable silk fiber. A. pernyi silkworm was reared in Korean oak field and examined the cocoon characteristics, such as cocoon weight, cocoon shell weight, and percentage of cocoon shell weight. Degumming loss was also measured after alkali degumming process. A. pernyi silkworm spins tawny color cocoon in oval shape. Cocoon shell weight of A. pernyi silkworm, 0.78 g, was heavier than that of B. mori silkworm, 0.51 to 0.63 g. Cocoon shell percentage of A. pernyi silkworm, 32.8%, was higher than that of B. mori silkworm, 23.4 to 25.2%. Degumming loss percentage of A. pernyi silkworm, 17.1%, was lower than that of B. mori silkworm, 25.0%. SEM showed that the surface of the cocoon filament was coarse and oriented with longitudinal direction.

• 한국자동차공학회논문집
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• 제5권4호
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• pp.48-69
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• 1997

The use of advanced composite materials in many engineering structures has steadily increased during the last decade. Advanced composite materials allow the design engineer to tailor the directional stiffness and the strength of materials as required for the structures. Design variables to the design engineer include multiple material systems. ply orientation, ply thickness, stacking sequence and boundary conditions, in addition to overall structural design parameters. Since the vibration and impact strength of composite cylindrical shell is an important consideration for composite structures design, the reliable prediction method and design methodology should be required. In this study, the optimum design of composite cylindrical shell for maximum natural frequency, buckling strength and impact strength are developed by analytic and numerical method. The effect of parameters such as the various composite material orthotropic properties (CFRP, GFRP, KFRP, Al-CFRP hybrid), the stacking sequences, the shell thickness, and the boundary conditions on structural characteristics are studied extensively.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2002년도 가을 학술발표회 논문집
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• pp.120-128
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• 2002

In order to analyze shell structures more accurately and effectively, a hybrid 4-node quadrilateral shell element is formulated. The element includes the frilling degrees of freedom and the independent parameter terms of the stress resultants are appropriately selected to overcome some of the shortcomings of the standard 4-node quadrilateral elements. In order to show the accuracy and convergent characteristics of the proposed shell element, three numerical examples are analyzed and the results are compared with the existed. As a result of this study, following conclusions are obtained. (1)Analysis results by the proposed element are less sensitive to the element geometric distortion. (2)The proposed element does not produce any spurious zero-energy modes