• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.5
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• pp.481-486
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• 2011

It is important to predict the behavior of a liquid film around a rotating cylinder in the film coating process of the steel industry. When the cylinder rotates, the behavior of the liquid film on the rotating cylinder surface is influenced by the cylinder diameter, the rotation speed, the gravitational force, and the fluid properties. These parameters determine the liquid film thickness and the rise of the film on the cylinder surface. In the present study, the two-phase interfacial flow of the liquid film on the rotating cylinder were numerically investigated by using a VOF method. For various rotation speeds, cylinder diameters and fluid viscosities, the behavior of liquid film on the rotating cylinder were predicted. Thicker film around the rotating cylinder was observed with an increase in the rotation speed, cylinder diameter, and fluid viscosity. The present results for the film thickness agreed well with available experimental and analytical results.

• Solar Energy
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• v.4 no.2
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• pp.13-28
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• 1984

Direct Absorption Receiver and Thermal Storage System is a complex problem. This paper describes only characteristic of fluid flow on the receiver. The fluid thicknesses of Molten Salts (Melting Point : $397^{\circ}C$) flowing on the receiver of modified protopype ($10m{\times}10m$) were calculated theorectically, changing the receiver slope from 60 degree to 85 degree (5 steps). The receiver temperatures were $430^{\circ}C$ at the top part and $950^{\circ}C$ at the low part. The flow thickness of the Molten Salts at the top part of the receiver are around 1.9mm in the case of maximum insolution ($50{\times}10^6$juoule/sec; 58.898kg/sec of flow rate) and 2.0mm at the low part. In the case of 3/10 of maximum insolation (flow rate = 17.669kg/sec) the flow thickness at the top part are around 0.9mm and 0.4mm at the low part, and in the case of 1/10 of maximum insolation (flow rate = 5.889 kg/see) the flow thickness at the top part are around 0.6mm and 0.3mm at the low part. From experimental measurements of a normal fresh water thickness flowing on the model plate ($12.7cm{\times}111.76cm$), around 0.8mm at the top part of the plate and around 0.7mm at the low part were obtained in the case of maximum insolation (flow rate = 0.12496 kg/see). In the case of 3/10 (flow rate = 0.03748 kg/see) and 1/10 (flow rate = 0.012496 kg/see) of maximum insolation, around 0.5mm and 0.4mm at the top part, and around 0.3mm and 0.2mm at the low part were obtained respectively. The reason why the thickness of the Molten Salts increase at the low part of the receiver only in case of maximum insolation is that decreasing rate of the viscosity of the Molten Salts is larger than decreasing rate of the density of the Molten Salts during temperature increase from the top to the low receiver plate and decrease of the fluid velocity in accordance with continuity principle. In all cases without the above maximum insolation, the thickness of the Molten Salts and the fresh water decreased at the low part of the plate because of gravity force effects rather than friction effects and of continuity principle. All simillar flow patterns were obtained through all cases of the insolation making an exception of only maximum insolation.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.880-894
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• 2010

The Grout injected precast pile is widely used in rapid-transit railway bridge recently. The existing portland cement of well used filling at injected precast method that with low strength and environmental pollution, unstable in which ground water contamination by cement flow out, ground relaxation by water down, decrease of horizontality resistance and durability and load transfer divide etc. In particular, as in rapid-transit railway bridge need to secure safety from different angle with vibration of high speed train, horizontal force when train stop and earthquake. Works of foundation construction consider to requirements of the times to coal yard green growth. Together, new green foundation method for possible economics and securing of reduce the term of works are material to developments. Therefore, we carried out study that it is using and development new concept environment - friendly filling include durability and earthquake resistance, for secure safety and minimize environment pollution. To achieve this, we carried out difference tests that new green fillings of underwater concrete, high liquidity, high viscosity, early stiffness as compared to existing portland cement fillings. As results, new green filling have outstanding application at precast pile method and micropile construction method with vertical bearing capacity, horizontal bearing capacity and many case. From now on we will be looking forward to development of new environment-friendly foundation method from various further studies.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.26 no.2
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• pp.77-83
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• 2020

A series of foamed plastic sheets containing biomass (as HMR container) were developed via different foaming process temperatures, and their density, porosity, WVTR, and pore morphology were evaluated. Thermal stability of samples during re-heating the food in oven, change in morphology, density, porosity, and WVTR were investigated using a simulated thermal shock process according to MIL-STD-883E assay. As such, the pore size of samples was generally increased with increasing temperature of the foaming process. It can be explained that as foaming temperature increased, the viscosity of molten resins and the repulsive force against pore expansion decreased. In addition, an increase in the thermal shock cycle reduced the pore size and WVTR, while density increased because high temperature treatment that softened the sheet matrix was followed by a low temperature incubation, which contracted the matrix, thereby changing the physical and morphological properties of samples. However, an insignificant change in density was observed and WVTR tended to be decreased, indicating that as-prepared foamed plastic sheets could be used as a high thermal stable container for HMR application. Therefore, it found that the properties of newly developed HMR containers containing biomass were dependent on the foaming process temperature. Moreover, to better understanding of these newly developed containers, further investigations dealing with foaming process temperature based on various food items and cooking conditions are needed.

• Applied Chemistry for Engineering
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• v.30 no.5
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• pp.597-605
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• 2019

In order to improve the adhesion of water-based adhesive, gemini type nonionic reactive surfactants were synthesized and applied to water-based adhesives. The surfactants were synthesized by using maleic acid and polyoxyethylene cetyl ether having different length of ethylene oxide and confirmed by FT-IR and $^1H-NMR$. Their appearance was light yellow wax. The cloud point of the compound was more than $78^{\circ}C$. The measured critical micelle concentration (c.m.c) was $1.0{\times}10^{-4}{\sim}7.0{\times}10^{-4}mol/L$ and surface tension at c.m.c was 25.9~32.0 mN/m. As the number of ethylene oxide increased, the emulsifying power was improved. The foaming height of each compound by Ross-Miles method was 1.4~4.5 cm. The synthesized surfactants was then used as an emulsifier in emulsion polymerization of water-based adhesives and its physical properties were evaluated. The solid contents of prepared adhesives was 59%. The average particle size and initial tackiness of the prepared adhesives were 164~297 nm and ball no. of 20~32, respectively. The peel strength was $1.8{\sim}2.1kg_f/mm$. The retention rate of adhesives viscosity was evaluated to 99% during 30 days. Therefore, synthesized gemini type nonionic reactive surfactants are expected to be applied as an emulsifier for the high adhesive force.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.44 no.3
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• pp.10-21
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• 2021

Recently, the demand for atypical structures with functions and sculptural beauty is increasing in the construction industry. Existing mold-based structure production methods have many advantages, but building complex atypical structures represents limitations due to the cost and technical characteristics. Production methods using molding are suitable for mass production systems, but production cost, construction period, construction cost, and environmental pollution can occur in small quantity batch production. The recent trend in the construction industry calls for new construction methods of customized small quantity batch production methods that can produce various types of sophisticated structures. In addition to the economic effects of developing related technologies of 3D Concrete Printers (3DCP), it can enhance national image through the image of future technology, the international status of the construction civil engineering industry, self-reliance, and technology export. Until now, 3DCP technology has been carried out in producing and utilizing residential houses, structures, etc., on land or manufacturing on land and installing them underwater. The final purpose of this research project is to produce marine structures by directly printing various marine structures underwater with 3DCP equipment. Compared to current underwater structure construction techniques, constructing structures directly underwater using 3DCP equipment has the following advantages: 1) cost reduction effects: 2) reduction of construct time, 3) ease of manufacturing amorphous underwater structures, 4) disaster prevention effects. The core element technology of the 3DCP equipment is to extrude the transferred composite materials at a constant quantitative speed and control the printing flow of the materials smoothly while printing the output. In this study, the extruding module of the 3DCP equipment operates underwater while developing an extruding module that can control the printing flow of the material while extruding it at a constant quantitative speed and minimizing the external force that can occur during underwater printing. The research on the development of 3DCP equipment for printing concrete structures underwater and the preliminary experiment of printing concrete structures using high viscosity low-flow concrete composite materials is explained.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.4
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• pp.73-80
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• 2022

This study evaluated changes in fluidity and rheological properties over time for 3D printed composite materials, and evaluated compressive strength and splitting tensile strength properties for laminated and molded specimens. The composite material for 3D printing starts to change rapidly after 30 minutes of extrusion, and the viscosity of the material tends to be maintained up to 90 minutes, but it was confirmed that construction within 60 minutes after mixing is effective. The compressive strength of the laminated test specimen showed equivalent or better performance at all ages compared to the molded test specimen. In the stress-strain curve of the laminated specimen, the initial slope was similar to that of the molded specimen, but the descending slope was on average 1.9 times higher than that of the molded specimen, indicating relatively brittle behavior. The splitting tensile strength of the P-V laminated specimen was about 6% lower than that of the molded specimen. It is judged that this is because the interfacial adhesion force against the vertical load is affected by the pattern direction of the laminated test specimen.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.12
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• pp.496-503
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• 2016

To analyze an infinite slope that is reinforced with stabilizing piles, the forces on the stabilizing pile were estimated by the theory of plastic deformation and the theory of plastic flow and the effects of diverse factors on the factor of safety of an infinite slope were investigated. According to the results of the analyses, the factor of the safety of the slope reinforced with stabilized piles were increased tremendously and the factor of safety decreased as the center to center distance of the stabilizing pile increased. The effect of the existence of seepage of the infinite slope with stabilizing piles on the factor of safety appears to be insignificant. Considering the formulated factor of safety of an infinite slope with stabilizing piles, the width and length of the element of the infinite slope and force on the stabilizing pile influence the factor of safety of the infinite slope with a stabilizing pile including the soil strength parameter, inclination of the slope and depth of the slope, which are important for calculating the factor of safety of a non-reinforced infinite slope. The factor of safety of an infinite slope with stabilizing piles derived from the theory of plastic deformation were increased significantly with the internal friction angle of the soil, and the minimum and the maximum factor of safety under the conditions considered in this study were 13.7 and 65.6, respectively. As the diameter of the stabilizing pile increased, the forces on the stabilizing pile also increased but the factor of safety of the infinite slope with stabilizing piles decreased due to the effects of the width and the length of the element of the infinite slope. The factor of safety of the infinite slope with stabilizing piles derived from plastic flow were much larger than that of the non-reinforced infinite slope and the factor safety of the infinite slope with a stabilizing pile increased with increasing product of the flow velocity and plastic viscosity ( ) and the factor of safety of the infinite slope with stabilizing piles decreased with increasing center to center distance of the pile.

• Journal of Gifted/Talented Education
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• v.11 no.3
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• pp.131-153
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• 2001

The importance of identifying gifted children during early childhood is becoming recognized. Nonetheless, most researchers preferred to study the primary and secondary levels where children are already and more clearly demonstrating what talents they have, and where more reliable predictions of gifted may be made. Comparatively lisle work has been done in this area. When we identify giftedness during early childhood, we have to consider the potential of the young children rather than on actual achievement. Giftedness during early childhood is still developing and less stable than that of older children and this prevents us from making firm and accurate predictions based on children's actual achievement. Dynamic assessment, based on Vygotsky's concept of the zone of proximal development(ZPD), suggests a new idea in the way the gifted young children are identified. In light of dynamic assessment, for identifying the potential giftedness of young children. we need to involve measuring both unassisted and assisted performance. Dynamic assessment usually consists of a test-intervene-retest format that focuses attention on the improvement in child performance when an adult provides mediated assistance on how to master the testing task. The advantages of the dynamic assessment are as follows: First, the dynamic assessment approach can provide a useful means for assessing young gifted child who have not demonstrated high ability on traditional identification method. Second, the dynamic assessment approach can assess the learning process of young children. Third, the dynamic assessment can lead an individualized education by the early identification of young gifted children. Fourth, the dynamic assessment can be a more accurate predictor of potential by linking diagnosis and instruction. Thus, it can make us provide an educational treatment effectively for young gifted children.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.34 no.6
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• pp.643-651
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• 2001

Paddlewheel-driven circulation in a culture pond has been simulated based on the depth integrated 2 dimensional hydrodynamic model. Acceleration by paddlewheel is expressed as shaft force divided by water mass discharged by paddlewheel blades. The model has been calibrated and applied to culture ponds as following steps:- i) The model predicted velocities at every 10 m along longitudinal direction from the paddlewheel. The model was calibrated comparing the results with the measured values at mass correction factor $\alpha$ and dimensionless eddy viscosity constant $\gamma$, respectively, in a range $15\~20$ and 6. ii) Wind shear stress was simulated under conditions of direction $0^{\circ}C,\;90^{\circ}C\;and\;180^{\circ}C$ and speed 0.0, 2.5, 5.0 and 7.5 m/s. Change rate of current speed was <$1\%$ at wind in parallel or opposite direction to the paddlewheel-driven jet flow, while $4\%$ at orthogonal angle. iii) The model was then applied to 2 culture ponds located at the Western coast of Korea. The measured and predicted currents for the ponds were compared using the regression analysis. Analysis of flow direction and speed showed correlation coefficients 0.8928 and 0.6782 in pond A, 0.8539 and 0.7071 in pond B, respectively. Hence, the model is concluded to accurately predict circulation driven by paddlewheel such that it can be a useful tool to provide pond management strategy relating to paddlewheel operation and water quality.