• Transactions of the Korean Society of Machine Tool Engineers
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• v.15 no.6
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• pp.88-96
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• 2006

The objective of this research works is to develop back panel dies of PDP TV with a large size. In order to design the geometry of the dies and an initial size of blank optimally, the finite element analysis has been carried out using AUTOFORM V4.2. The conner radius of the upper trimming area and the distance from the outer line of the blank holder to the outer line of the blank have been selected as design parameters to remove the wrinkling of the trimming area. The results of the analyses have been shown that a feasible product without wrinkles and skid lines can be obtained when the conner radius ranges from 6mm to 8mm and the distance lines in the range of 40-60mm. From the proposed design of the dies and an initial blank size, the final die set of the back panel has been successfully manufactured.

• Transactions of Materials Processing
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• v.23 no.6
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• pp.363-368
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• 2014

Electromagnetic forming(EMF) is one of the high-speed forming methods, and has been used to deform metal sheets. The advantages of electromagnetic forming are reduced wrinkling due to non-contact characteristic and fine formability because of the high speed impact. In the current study, we suggest the application of electromagnetic forming to emboss pattern shapes using electromagnetic forces with only one forming coil and one punch. The high impact of the sheet at speeds of 100~300m/s produces significant coining pressure. In the current paper, electromagnetic forming was applied to Al 1100-O sheets; with thickness of 1.27mm and an area of $40mm{\times}40mm$. Using a single spiral coil, totally different types of patterns were created. Four different patterns were successfully produced on the aluminum sheet. The length and depth of the patterns were measured by three-dimensional scanning. Comparisons to the die shape showed good agreement. The test results confirm that emboss pattern forming by EMF using a single die can be used to replace the costly conventional method.

• 한국연소학회:학술대회논문집
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• 1998.10a
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• pp.139-154
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• 1998

Under certain circumstance, premixed turbulent flame can be treated as wrinkled thin laminar flame and its motion in a hydrodynamic flow field has been investigated by employing G-equation. Past studies on G-equation successfully described certain aspects of laminar flame propagation such as effects of stretch on flame speed. In those studies, flames were regarded as a passive interface that does not influence the flow field. The experimental evidences, however, indicate that flow field can be significantly modified by the propagation of flames through the volume expansion of burned gas. In the present study, a new method to be used with G -equation is described to include the effect of volume expansion in the flame dynamics. The effect of volume expansion on the flow field is approximated by Biot-Savart law. The newly developed model is validated by comparison with existing analytical solutions of G -equation to predict flames propagating in hydrodynamic flow field without volume expansion. To further investigate the influence of volume expansion, present method was applied to initially wrinkled or planar flame propagating in an imposed velocity field and the average flame speed was evaluated from the ratio of flame surface area and projected area of unburned stream channel. It was observed that the initial wrinkling of flame cannot sustain itself without velocity disturbance and wrinkled structure decays into planar flame as the flame propagates. The rate of decay of the structure increased with volume expansion. The asymptotic change in the average burning speed occurs only with disturbed velocity field. Because volume expansion acts directly on the velocity field, the average burning speed is affected at all time when its effect is included. With relatively small temperature ratio of 3, the average flame speed increased 10%. The combined effect of volume expansion and flame stretch is also considered and the result implied that the effect of stretch is independent of volume release.

• Polymer(Korea)
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• v.37 no.1
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• pp.1-4
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• 2013

We proposed a new process to fabricate a high-aspect-ratio microhair having surface wrinkles using the contact-and-tension of a microstamp. Through this work, we observed that regular surface wrinkles were generated on the hair with a diameter of around $20{\mu}m$ due to the uni-directional compressive stress during the photocuring process by ultraviolet light. To do this, we conducted an experimental system setup for contact-and-tension process. From the preliminary test results, we believed that the proposed method can be applied to make a long polymer hair having surface wrinkles for special applications to biomimetics, and some research fields related on surface area such as heat transfer and catalyst enhancement.

• Composites Research
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• v.37 no.1
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• pp.7-14
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• 2024

Due to the structural characteristic of a double roller, the double roller can have various deformation behaviors depending on a gap block design, even if dimensions and loading conditions for the double roller are the same. Based on this feature, we propose a strategy for designing the gap block of the carbon-fiber reinforced plastic (CFRP) double roller to minimize defects (e.g., sagging and wrinkling), which can be raised during the product conveying process, with the pursue of the lightweight design. In the suggested strategy, analysis cases are first selected by considering main design parameters and engineering tolerances of the gap block, and then deformation behaviors of these selected cases are extracted using the finite element method (FEM). Here, to obtain the optimal gap block parameters that satisfy the purpose of this study, deformation deviations in the contact area are calculated and compared using the extracted deformation behaviors. Note that the contact area in this work is located between the product and the roller. As a result, through the design method of the gap block proposed in this work, it is possible to construct the CFRP double roller that can significantly decrease the defects without changing the overall sizes of the roller. A detailed method is suggested herein, and the results are evaluated in a numerical way.

• Journal of Radiation Protection and Research
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• v.20 no.3
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• pp.181-186
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• 1995

UV irradiation causes a variety of biologic effects on the skin. These effects can be devided to acute reactuons and chronic reacxtions by duration of UV irradiation. Acute reactions are erythema reaction, pigment reactions and changes in epidermal thickness. Among them erythema reaction is most common and conspicuous acute effects of the skin. Upon exposure to sun or artificial UV soures, a faint redness response of skin may begin. Larger exposure causes sunburn reaction which is exaggerated erythema reactionassociated with pain, swelling, vesicle and dulla. Extent and time course of erythema reaction depend upon several factors including wavelength and dose of UVR, skin conditions likeas skin type, site, color, temperature, humidity and environmental factors. Evaluation of erythema erythema induced by UV irradiation is difficult to quantify. Degree of redness of skin are usually estimated by subjective visual evaluation. The lowest exposure dose required to protuce erythema is called minimal erythema dose (mod). Repeated exposures of UVR result in photaging skin. In this condition we can see wrinkling, skin atrophy, dilated blood vessels and keratoses. In sensitive persons photocarcinogenesis is can Be developed on exposed area of skin. Recently skin canser is increasing now in our country. An effective public education and photopreventive method must be developed.

• Archives of Plastic Surgery
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• v.32 no.1
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• pp.85-92
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• 2005

Botulinum toxin type A is widely used for anti-wrinkling therapy, and correction of the square face. The toxin ultimately prevent the release of membrane-bound acetylcholine at the neuromuscular junction of striated muscles and thus produce chemical denervation and paralysis of the muscles. Our purpose of study is to know if application of botulinum toxin type A on calf reduction is effective, how much dosage is effective, and what are the possible complications. We reviewed data of 30 consecutive patients subjected to calf reduction in Dong-A University Hospital from February 2003 to April 2003. We injected normal saline 2cc on both calves region in 15 control group patients, and the other patients was divided 3 group. Group 1, Group 2, Group 3 was injected 50U, 100U, 150U botulinum toxin A on each calf region and followed up for 6 month. Maximal circumference of calf was not changed in the control group but an average of 0.7 cm reduction was noted in group 1, average 1.34 cm(right calf) and 1.26cm(left calf) in group 2, average 1.44cm(right calf) and 1.58cm(left calf) in group 3. Maximal area of calf was not changed in the control group but average reduction of 12.5%(right calf) and 12.7%(left calf) was obtained in group 1, average 19.4% (right calf) and 19.9%(left calf) in group 2, average 24.8%(right calf) and 21.07%(left calf) in group 3, as measured on CAT scan. Total fat amount and fat amount in the lower extremity was no change in all the groups, but lean body mass was decreased average 1.27%(right calf) and 1.15%(left calf) in group 1, average 3.47%(right calf) and 2.98%(left calf) in group 2, average 3.58%(right calf) and 3.95%(left calf) in group 3. Photography of the preoperative and postoperative 6 month state revealed higher satisfaction in Group 2, 3 compared to Group 1. Use of botulinum toxin type A in calf reduction is a very simple, safe, non-invasive method and effective in terms of calf contouring rather than reduction of calf circumference.