• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.437-438
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• 2006

Generally, the vertical roll process is used to achieve extensive width reduction in hot strip mill. However, it is difficult to avoid the defects such as dog-bone and seam-defect. The sizing press has been developed in response to the defects mentioned above. Especially, this study is carried out to investigate the deformation of slab by two-step sizing press. The deformation behavior in the width sizing process is more favorable than that in conventional vertical rolling edger. The objective of this study is to determine the optimal anvil shape parameters in the sizing press with two-step die from the viewpoint of edge-seam length. In general, the edge-seam defect occurs parallel to the rolling direction at both edges in horizontal rolling process after sizing press. The optimal combination of the parameters is determined by FE-simulation and Artificial Neural Network (ANN). The slab deformation in sizing press with convex anvil is analyzed by FE-simulation. The most suitable profile of the anvil is also discussed fur the improvement of trimming loss because of the side seam defect by FE-simulation and ANN.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.44 no.1
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• pp.3-11
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• 2018

Objectives: The unilateral cleft lip (UCL) repair technique has evolved extensively over the past century into its modern form and has been identified as an important determinant of treatment outcome. The aim of this study was to evaluate and compare treatment outcomes following repair of UCL using either the Tennison-Randall (triangular) technique or the Millard rotation-advancement technique. Materials and Methods: This was a prospective randomized controlled study conducted at the Lagos University Teaching Hospital between January 2013 and July 2014. A total of 48 subjects with UCL presenting for primary surgery and who satisfied the inclusion criteria were recruited for the study. The subjects were randomly allocated into two surgical groups through balloting. Group A underwent cleft repair with the Tennison-Randall technique, while group B underwent cleft repair with the Millard rotation-advancement technique. Surgical outcome was assessed quantitatively according to anthropometric measurements, using a method described by Cutting and Dayan (2003). Results: Our 48 enrolled subjects were evenly divided into the two surgery groups (n=24 for both group A and group B). Twenty-seven subjects were male (56.3%) and 21 were female (43.8%), making a sex ratio of 1.3:1. The Millard group showed a greater increase in postoperative horizontal length and vertical lip height and a greater reduction in nasal width and total nasal width. Meanwhile, the Tennison-Randall group showed better reduction of Cupid's-bow width and better philtral height. Conclusion: We did not find any significant differences in the surgical outcomes from the two techniques. The expertise of the surgeon and individual patient preferences are the main factors to consider when selecting the technique for unilateral cleft repair.

• Journal of Korean Society for Atmospheric Environment
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• v.26 no.3
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• pp.245-252
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• 2010

For the purpose of evaluating to remove elemental mercury using SCR (Selective Catalytic Reduction) catalysts, the result of the concentration variation of elemental mercury in lab experiment and field measurement was compared. The effect of the elemental mercury oxidation on commercial catalysts was studied in simulated gas. Three species of SCR catalyst, $V_2O_5-TiO_2$ type, were selected. The elemental mercury reduced 30% without HCl gas in SCR operating condition. But the width of reduction increased 60% at 20 ppm HCl gas. According to the result of field measurement, reduction rate of elemental mercury at SCR outlet showed 60%. The total mercury concentration decreased about 20%. The results were similar to the lab test. The results of chemical analysis of test sample showed increase of mercury concentration but surface change was not observed.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1574_1575
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• 2009

This paper investigates the reduction of RE(Radiated Emission) noise in a high power LED module circuit using PWM(Pulse Width Module) switching controller circuit. Poorly designed LED lighting module can experience the RE and CE(Conducted Emission) noise problem. This paper propose the reduction of noise source and improvement of EMI filter design in a high power LED lighting module. The experimental and simulation results showed that reduce the RE noise level effectively.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.5
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• pp.228-234
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• 2002

The CO$_2$ laser beam irradiation strengthening of 35kgf/mm$_2$ grade steel sheet is investigated to reduce the weight of bumper beam. The increase of tensile strength is dominated by the number of fully penetrated melting lines. The optimal laser irradiation pattern is obtained by 3-point bending test of hat-type specimens. Laser should be irradiated not only on the center specimen densely in the width direction, but also on the edge densely in the longitudinal direction. Local laser strengthening may be effective for the weight reduction of automobile bumper beam.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.3
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• pp.389-395
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• 2006

The fluid force reduction of a square prism having fences on the corner was studied by the measuring the drag and lift acting on the prism and by the visualization experiment of the flow around the prism. The height of the fence was 10% of the square width and the range of Reynolds number considered was from $Re=0.9{\times}104$ to $Re=2.1{\times}104$. The drag of the prism was reduced about 6.8% and the amplitude of the lift was reduced by attaching two normal fences on the rear corners of the prism. In this case, the separated flow at the front corners was reattached on the upper and lower sides of the prism and the vortex streets at the wake region were appeared more slowly than that of the prototype prism.

• Journal of Power Electronics
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• v.17 no.6
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• pp.1490-1499
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• 2017

The modular multilevel converter (MMC) is generally considered to be a promising topology for medium-voltage and high-voltage applications. However, in order to apply it to high-power applications, a huge number of switching devices is essential. The numerous switching devices lead to considerable switching losses, high cost and a larger heat sink for each of the switching device. In order to reduce the switching losses of a MMC, this paper analyzes the performance of the conventional discontinuous pulse-width modulation (DPWM) method and its efficiency. In addition, it proposes a modified novel DPWM method for advanced switching losses reduction. The novel DPWM scheme includes an additional rotation method for voltage-balancing and power distribution among sub modules (SMs). Simulation and experimental results verify the effectiveness and performance of the proposed modulation method in terms of its switching losses reduction capability.

• The Transactions of the Korean Institute of Power Electronics
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• v.24 no.1
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• pp.56-61
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• 2019

In this study, a reduction method of leakage current in a three-level photovoltaic power-conditioning system (PCS) is proposed and verified by simulation and experiment. Leakage current generation is analyzed through an equivalent model of the common mode voltage considering a significant parasitic capacitance existing between the photovoltaic array and ground. A leakage current reduction method using pulse-width modulation (PWM) method is also proposed, and a 10-kW three-level photovoltaic PCS simulation and experiment is performed with a $1{\mu}F$ parasitic capacitor based on 100 nF/kW. The proposed method using the PWM method is verified to reduce the leakage current by 73% compared with the conventional PWM method.

• Transactions of Materials Processing
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• v.33 no.4
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• pp.291-300
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• 2024

To compare the lubrication performance improvement of different laser texturing surface treatment patterns, ring-shaped specimens were prepared by processing line and dot patterns using a fiber laser device. Ring compression tests were conducted to compare the reduction rates of the inner diameter corresponding to the same height reduction of the specimens. Laser processing conditions were set to create patterns with a depth of 9㎛ and a width of 45㎛. Ring specimens were processed with varying spacings between dots and lines. The forging lubricant TECTYL FORM CF 351S was uniformly applied to the upper and lower compression tools, and the rings were compressed by 40% using a hydraulic press, after which the inner diameter was measured. The comparison of inner diameter reduction rates indicated that pattern processing improves lubrication performance, with line patterns being more effective than dot patterns in enhancing lubrication performance.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.38 no.1
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• pp.50-54
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• 2012

According to Luhr's classification, a fracture in the mandible with a width of less than 15-20 mm is considered to be an atrophic mandibular fracture and its incidence is very rare. Because of the reduced cross-sectional area and smaller contact area of the fractured ends as well as the poorly vascularized bony structure and delayed bone healing, an atrophic mandibular fracture is a great challenge for oral and maxillofacial surgeons. Surgeons tend to perform closed reduction, because open reduction is considered a non-life-saving surgery among elderly patients. Thus, most of them have limited experience in surgical management. According to recent reports, open reduction yields a good result, and the Association for Osteosynthesis (AO) group has recommended open reduction. This is a case report of our two experiences of open reduction and rigid fixation of atrophic mandibular fractures by the AO principle. Articles were also reviewed here.