• Journal of Yeungnam Medical Science
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• v.9 no.1
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• pp.167-174
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• 1992

Microvascular tissue transfers have facilitated primary closure of various complex defects after radical ablation of head and neck cancers. From Oct 1991 to Feb 1992, we used forearm free flap in two patients and delto-pectoral flap in one patient who had preoperative irradiation for pharyngoesophageal reconstruction. The stricture and fistular formation were most troublesome complication in forearm free flap, so we designed as lazy S shape in distal flap margin to prevent circular contraction and longitudinal margin was deepithelized(5mm) and sutured double layer to withstand fistular formation and this can be considered useful in place of a free jejunal transfer.

• 한국연소학회:학술대회논문집
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• 2005.10a
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• pp.328-336
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• 2005

Effects of surface defect distribution on flame instability during flame-surface interaction are experimentally investigated. To examine the chemical quenching phenomenon, we prepared thermally grown silicon oxide plates with well-defined defect density. Ion implantation was used to control the number of defects, i.e. oxygen vacancies. In an attempt to preferentially remove the oxygen atoms from silicon dioxide surface, argon ions with low energy level from 3keV to 5keV were irradiated at the incident angle of $60^{\circ}C$. Compositional and structural modification of $SiO_2$ induced by low-energy $Ar^+$ ion irradiation has been characterized by Atomic Force Microscopy (AFM) and X-ray Photoelectron Spectroscopy (XPS). The analysis shows that as the ion energy increases, the number of structural defect also increases and non-stoichiometric condition of $SiO_x(x{\le}2)$ plates is enhanced. From the quenching distance measurements, we found out that when the surface temperature is under $300^{\circ}C$, the quenching distance decreases on account of reduced heat loss; as the surface temperature increases over $300^{\circ}C$, however, quenching distance increases despite reduced heat loss effect. Such aberrant behavior is caused by heterogeneous chemical reaction between active radicals and surface defect sites. The higher defect density, the larger quenching distance. This results means that chemical quenching is governed by radical adsorption and can be parameterized by the oxygen vacancy density on the surface.

• Nuclear Engineering and Technology
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• v.52 no.2
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• pp.337-343
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• 2020

Oxide dispersed strengthened (ODS) steel is an important candidate for Gen-IV reactors. Oxide embedded in Fe can help to trap irradiation defects and enhances the strength of steel. It was observed in this study that the size of oxide has a profound impact on the depinning mechanism. For smaller sizes, the oxide acts as a void; thus, letting the dislocation bypass without any shear. On the other hand, oxides larger than 2 nm generate new dislocation segments around themselves. The depinning is similar to that of Orowan mechanism and the strengthening effect is likely to be greater for larger oxides. It was found that higher shear deformation rates produce more fine-tuned stress-strain curve. Both molecular dynamics (MD) simulations and BKS (Bacon-Knocks-Scattergood) model display similar characteristics whereby establishing an inverse relation between the depinning stress and the obstacle distance. It was found that (110)_oxide || (111)_Fe (oriented oxide) also had similar characteristics as that of (100)_oxide || (111)_Fe but resulted in an increased depinning stress thereby providing greater resistance to dislocation bypass. Our simulation results concluded that critical depinning stress depends significantly on the size and orientation of the oxide.

• Archives of Plastic Surgery
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• v.36 no.4
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• pp.397-405
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• 2009

Purpose: Soft tissue defect of anterior chest wall is caused by trauma, infection, tumors and irradiation. To reconstruct damaged anterior chest wall does require to consider the patient's body condition, the cause, the location, the depth and the size of deletion, the circulation of surrounding tissue and minimization of functional and cosmetic disability. In this report, we suggest the algorithm of configuration for reconstruction methods. Methods: A retrospective study of 20 patients who underwent anterior chest wall reconstruction with pedicled musculocutaneous flap and fasciocutaneous flap was conducted. We collected the information of the patient's body condition, the cause, the size, the depth and the location of deletion, implemented flap and complication. We observed and evaluated flap compatibility, functional and cosmetic results. Patients completed survey about the extent to their satisfaction. Result: Follow up period after surgery was from 6 to 26 months, survival of flap were confirmed in all of patients' case. Two cases of local necrosis, one case of wound disruption were reported, but all these were cured by the debridement and primary closure. One hematoma and one seroma formation were observed in donor site. Longer surgery time, more bleeding amount and more transfusion volume were reported in the group of musculocutenous flap. Conclusion: Long term follow up result showed the successful reconstruction in all patients without recurrence and with minimal donor site morbidity. In addition, the patients' satisfaction for cosmetic and functional results were scaled relatively higher. This confirmed the importance of reconstruction algorithm for the chest wall reconstruction.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.29 no.1
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• pp.151-167
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• 2003

Melanin biosynthesis is a human defense mechanism to protect skin from UV irradiation and also determines colors of hair and skin. However, as a interest on skin-whitening increases, researches to prevent pigmentation and hypersynthesis of melanin in skin are being actively in progress. Active components used as a whitening agent in cosmeceuticals are kojic acid, arbutin, vitamin C and hydroquinone. However, until now, because comparison researches among them in the aspect of both melanin formation and cellular toxicity have not been performed, we can't exactly estimate merits and defects of them as a whitening agent. To this end, we performed experiments to compare their effects on cell viability and melanin formation. As a first step, in vitro tyrosinase inhibition assay was done. While kojic acid and hydroquinone showed strong inhibition activities(their IC$\_$50/s are all < 100uM), arbutin and vitamin C showed weak activities. IC$\_$50/s of arbutin and vitamin C are 100uM and 400∼500uM, respectively. In B16BL6 melanoma cells, like in vitro tyrosinase inhibition assay, arbutin and kojic acid showed more strong inhibition effect on melanin synthesis than vitamin C. And unlike arbutin, vitamin C and kojic acid induced cell death at high concentration. Although arbutin showed no cytotoxicity, it has side effect to induce morphological change at high concentration.. In this paper, we suggest both kojic acid and arbutin have stronger ability to inhibit melanogenesis than vitamin C. And they also have side effect, that is, kojic acid induces cell death like vitamin C and arbutin changes cell morphology respectively.

• Korean Journal of Materials Research
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• v.19 no.4
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• pp.192-197
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• 2009

Carbon nanotubes (CNT) were used as a catalyst support where catalytically active Pd and Pt metal particles decorated the outside of the external CNT walls. In this study, Pd and Pt nanoparticles supported on $HNO_3$-treated CNT were prepared by microwave-assisted heating of the polyol process using $PdCl_2$ and $H_2PtCl_6{\codt}6H_2O$ precursors, respectively, and were then characterized by SEM, TEM, and Raman. Raman spectroscopy showed that the acid treated CNT had a higher intensity ratio of $I_D/I_G$ compared to that of non-treated CNT, indicating the formation of defects or functional groups on CNT after chemical oxidation. Microwave irradiation for total two minutes resulted in the formation of Pd and Pt nanoparticles on the acid treated CNT. The sizes of Pd and Pt nanoparticles were found to be less than 10 nm and 3 nm, respectively. Furthermore, the $SnO_2$ films doped with CNT decorated by Pd and Pt nanoparticles were prepared, and then the $NO_2$ gas response of these sensor films was evaluated under $1{\sim}5\;ppm$ $NO_2$ concentration at $200^{\circ}C$. It was found that the sensing property of the $SnO_2$ film sensor on $NO_2$ gas was greatly improved by the addition of CNT-supported Pd and Pt nanoparticles.

• Korean Journal of Optics and Photonics
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• v.16 no.2
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• pp.113-120
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• 2005

Luminous efficiency and uniformity in a LCD-BLU are mainly determined by fine scattering patterns formed on the light guide panel. We propose a novel fabrication method of 3-dimensional scattered patterns based on anisotropic etching of silicon wafers. Micro-pyramid patterns with 70.5 degree apex-angle and micro-prism patterns with 109.4 degree apex-angle can be self-constructed by the wet, anisotropic etching of (100) and (110) silicon wafers, respectively, and those patterns are easily duplicated by the PDMS replica process. Experimental results on spatial and angular distributions of irradiation from the light guide panel with the micro-pyramid patterns were very consistent with the calculation results. Surface roughness of the silicon-based micro-patterns is free from any artificial defects since the micro-patterns are inherently formed with silicon crystal surfaces. Therefore, we expect that the silicon based micro-patterning process makes it possible to fabricate perfect 3-dimensional micro-structures with crystal surface and apex angles, which may guarantee mass-reproduction of the light guide panels in LCD-BLU.

• Journal of the Mineralogical Society of Korea
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• v.22 no.4
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• pp.407-415
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• 2009

The change of the nitrogen-related centers and the color change of electron beam irradiated type Ia natural diamonds were studied. The irradiation of diamond with high-energy electron beam creates lattice defects which are neutral single vacancy $V^0$. It increased with increasing electron dose density. The B aggregation seems to produce vacancies more easily than the A aggregation, because diamonds with more B aggregation have more platelets, which are sufficient breakable size by electron beam. Greenish blue color of irradiated diamond is changed to darker with increasing electron dose density. GR1 centers with a zero-phonon line at 741 nm and phonon sidebands make transmit visible light at 530 nm and it moves to 500 nm with higher intensity of GR1 centers.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.52 no.12
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• pp.545-552
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• 2003

When a Si PIN diode is exposed to fast neutrons, it results in displacement damage to the Si lattice structure of the diode. Defects induced from structural dislocation become effective recombination centers for carriers which pass through the base of a PIN diode. Hence, increasing the resistivity of the diode decreases the current for the applied forward voltage. This paper involves the development of a neutron sensor based on the phenomena of the displacement effect damaged by neutron exposure. The neutron effect on the semiconductor was analyzed. Several PIN diode arrays with various thickness and cross-section area of the intrinsic layer(I layer) were fabricated. Under irradiation tests with a neutron beam, the manufactured diodes have a good linearity to neutron dose and show that the increase of thickness of I layer and the decrease of cross-section of PIN diodes improve the sensitivity. Newly developed PIN diodes with thicker I layer and various cross section, were retested and then showed the best neutron sensitivity at the condition that the I layer thickness was similar to a side length. On the basis of two test results, final discrete PIN diodes with a rectangular shape were manufactured and the characteristics as neutron detectors were analyzed through the neutron beam test using on-line electronic dosimetry system. Developed PIN diode shows a good linearity as dosimetry in the range of 0 to 1,000cGy(Tissue) and its neutron sensitivity is 13mV/cGy at constant current of 5mA, that is three times higher than that of commercially available neutron detectors. And the device shows little dependency on the orientation of the neutron beam and a considerable stability in annealing test for a long period.

• Archives of Craniofacial Surgery
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• v.22 no.4
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• pp.204-208
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• 2021

Sebaceous carcinoma is a malignant neoplasm that usually arises in the sebaceous glands of the eyelids. Its pathogenesis is unknown; however, irradiation history, immunosuppression, and use of diuretics are known risk factors. The mainstay of treatment for sebaceous carcinoma of the eyelid is wide surgical resection with a safety margin of 5 to 6 mm, which often results in full-thickness defects. The reconstruction of a full-thickness defect of the eyelid should be approached using a three-lamella method: a mucosal component replacing the conjunctiva, a cartilage component for the tarsal plate, and a flap or skin graft for the skin of the eyelid. In this case, a full-thickness defect of the upper eyelid was reconstructed after tumor removal using a combination of a nasal septum chondromucosal composite graft and a forehead transposition flap, also known as a "Fricke flap." The flap was designed to include a line of the eyebrow on the lower margin of the flap to replace the eyelash removed during tumor excision. The wound healed completely, without any early or late complications, and the outcome was satisfactory.