• Journal of the Korean Society for Precision Engineering
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• v.19 no.11
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• pp.200-210
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• 2002

In twin roll strip casting process, coupled analyses of heat transfer and deformation for the cast roll are carried out by using the finite element program MARC to examine the thermal crown. Shrink fit effect and plastic deformation are considered. The results shows that the thermal crown is greatly influenced by shrink ft and that the thermal crown for POSCO Pilot Caster 2 Copper Roll has “M” shape. The effects of several factors on thermal crown are also investigated. The amount of thermal crown increases as heat flux, casting speed, steeve thickness and casting roll width increase and decreases as the casting roll diameter increases.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.8
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• pp.1451-1457
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• 1992

In hot strip rolling, the thickness of strip cannot be retained uniform by several irregular parameters. It has been shown that the load distribution can affect only a small fraction of the excess strip crown, whereas the thermal effects of working roll are the major reason on large changes in the strip center crown during hot rolling. In this study, the temperature distribution of working roll is represented by fourier series expansion. The analytical solution of the resulting thermo-elasticity problem is obtained by love's strain function. The results which are compared with those of the finite element method show good agreements.

• Journal of the Korean Society for Precision Engineering
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• v.7 no.3
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• pp.14-25
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• 1990

A model predicting thermal and wear crown in order to control strip crown and shape has been investigated at the hot roll mill. A basic equation of predicting wear crown was obtained experimentally whereas thermal crown was approximately analyzed by the integral method. The calculated result based on the accumulative model of basic eauation coincides with that measured under the real rolling conditions. The effect of wear corwn is also analyzed by the longitudinal feeding method of the work roll. The high frequency feeding method is recommended in removing local wear effectively.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2002.05a
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• pp.39-43
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• 2002

A new model for heat transfer and thermal deformation analysis according to strip mm in coiling process has been proposed. Finite difference analyses for heat transfer of cold rolled coil have been carried out under various coiling tensions and strip crown using the equivalent thermal conductivity for the radial direction of cold rolled coil which is a function of strip thickness, surface characteristics and compressive pressure. The compressive pressure is calculated from a equation expressed as a function of hoop stress and coil tension considering strip mm obtained by experiment. Finite element method for thermal deformation of cold rolled coil has been performed to investigate the effects of the strip crown, the coil tension and temperature. From these analyses, it is found that the axial inhomogeneity of thermal deformation is increased as the strip crown, compressive pressure, and temperature drop in cold coiled strip increase.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.2
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• pp.92-98
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• 2001

We determined the transfer coefficient through the analysis of three dimensional temperature distribution in comparison with the measured temperature on the piston in the turbocharged diesel engine. And we analyzed the thermal stress and the thermal deformation with that heat transfer coefficient by using finite element method. According to this results, we found that maximum tempetature range of the piston appeared at the upper part of the piston crown and that the heat transfer coefficient of the upper part of the piston is smaller than that of the lower one. It showed that the maximum thermal deformation is shown at the edge of the upper part of piston and that the maximum thermal stress was shown on the lower part of the piston crown. Finally, we defined the method of determination of a piston heat transfer analysis by using measured temperature on the piston and analyzed temperature with finite element method.

• Polymer(Korea)
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• v.37 no.2
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• pp.211-217
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• 2013

Potassium tert-butoxide (t-BuOK) with $CO_2$ or benzoyl chloride (BzC) as a polymerization initiator system was used with crown ether or TMAC as catalyst to synthesize very high molecular weight nylon 4 homo- and copolymers by anionic ring opening polymerization. Effect of different amounts of catalyst, crown ether and TMAC on the polymerization was studied in terms of intrinsic viscosity, yield and thermal properties. By adding crown ether or TMAC, polymers with very higher intrinsic viscosity values were obtained in a high yield. It was possible to synthesize nylon 4 homopolymer with such a high intrinsic viscosity value of 6.36 dL/g. Crown ether was found to be more efficient in terms of intrinsic viscosity and polymer yields than TMAC. Thermal analysis confirmed that molecular weight effect on the thermal properties of both nylon 4 and nylon 4 copolymer was marginal.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.184-187
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• 2003

The simulation program is developed to get the target strip crown of high strength steel in the continuous hot strip rolling. The developed program consists of several sub-program, which contains work roll shifting pattern, roll wear profile, roll thermal expanded profile and strip profile. Also, the variation of strip profile is investigated according to roll deflection and flattening. The results are compared with the values observed from the actual hot rolling of high strength steel. And effect of bender force on the strip profile is studied. The strip crown is shown to decrease with increasing bender force.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.8
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• pp.847-854
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• 2007

The battery electrode of a mobile phone is made of layered polymer coated on aluminum foils and the hot rolling process is applied to increase the density per volume of an electrode for a high capacity battery. The flatness of batteries surfaces should be less than $2{\mu}m$. To satisfy the required flatness, the deformation of roll surface due to bending and heating of the roll should be minimized. Complicated hot oil paths of $100^{\circ}C$ inside the roll are required for heating the polymer layers. FEA was used to calculate thermal deformations and temperatures distributions of the roller. Based on FEA, a modified surface curvature called a crown roll was suggested and this gave the area of 30% improved flatness compared with a flat roll. The flat roll satisfied the flatness of $2{\mu}m$ in the length of 340 mm and the crown roll resulted in the longer length of 460 mm. Experiments to measure the temperature distribution and thermal strain were performed and compared with FEA. There were only 6% difference between two results.

• Macromolecular Research
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• v.13 no.2
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• pp.141-146
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• 2005

Calix[4]crown-6-2,4-bis(4-aminobutyl ether), which has a crown-6 moiety at the 1,3-position and amino function at the 2,4-position, was prepared as an intermediate for the subsequent synthesis of calix[4]crown-6-containing polyamide and polyimide using adipoyl chloride and 1,2,4,5-benzenetetracarboxylic dianhydride. The chemical structures were characterized by IR, $^{1}H NMR$ spectroscopy and elemental analysis, and some of their physical properties, including their thermal behavior, were examined. The ion binding characteristics of the monomer and polymers for alkali metal and alkali earth metal ions were measured by liquid-liquid extraction from the aqueous phase into the organic phase. It has been observed that polyamide has a high binding ability towards various metal cations as compared to polyimide, which showed cesium ion selectivity.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.24 no.4
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• pp.15-29
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• 2021

Urban green spaces offer a variety of benefits to living things and humans. However, existing green spaces have been reduced and fragmented due to urbanization, and there is a limit to creating new large green spaces in densely developed cities. Street trees have fewer restrictions on land use, which can be a measure to secure green areas in cities. In Korea, excessive pruning is being done on some street trees for reasons such as blocking of building signboards, contact with electric wires, and restrictions on sidewalk widths. Therefore, it is necessary to quantitatively understand the relationship between the benefits provided by street trees and their structures to come up with an efficient and systematic planning and management plan for urban street trees. In this study, we quantitatively analyzed the relationship between the thermal comfort improvement by the shades of street trees and the vertical structure, planting environment, and types of street trees. To calculate the thermal comfort felt by human body, we calculated UTCI (Universal Thermal Climate Index) of each street tree. For the vertical structure of street trees, we used Terrestrial LiDAR and the point clouds of street tree's crown was sliced vertically at 1m intervals. We conducted a multiple regression analysis on the thermal comfort improvement using the variables we obtained from fields. As a result, in the case of a street tree's vertical structure, the lager the volume of tree's crown located 3-4m (β=0.298, p<.05) and 6-7m (β=0.568, p<.001) above clear length, the better the cooling effect. In addition, the thermal comfort improvement was assessed to decrease as the DBH increased (β=-0.435, p<.001). In general, the crown diameter and DBH are positively correlated, with a cooling effect occurring as crown diameter increases. In this study, the opposite result was obtained due to the small number of trees measured, so additional research is needed by increasing the number of tree samples. In the case of the planting environment, the effect of improving thermal comfort was higher in the shaded area of trees planted to the south (β=-0.541, p<.001). Since unsystematic management of street trees can deteriorate the function of them, quantitative evaluations of the vertical structure of street trees are required, which can provide specific measures for planning and management of urban street trees with thermal comfort effect.