• Archives of Plastic Surgery
• /
• 제38권6호
• /
• pp.733-739
• /
• 2011

Purpose: Cellulose is a natural substance from plants or bacteria. It is known that bacterial synthesized cellulose has an effect of wound healing. The aim of this study is to show the effect of bacterial synthesized cellulose from citrus on wound healing. Methods: Three full-thickness skin defects were made on the back of Sprague-Dawley rats. Three wounds were treated by vaseline gauze (Group V), Algisite $M^{(R)}$ (Group A) and bacterial synthesized cellulose from citrus (Group C) was used for dressing on skin defect on rats. We analyzed the gross, histological and biochemistry finding. Results: Group C showed more decrease of wound size compared to Group V (33% versus 7.2%) after 14 days. The histologic findings revealed Group C and Group A preceed the process of wound healing rather than Group V (More rapid collagen deposition and neovascularization and reduced inflammation). Also, the expressions of vascular endothelial growth factor (VEGF) and transforming growth factor (TGF)-${\beta}1$ were increased in the Group C and Group A compared with the Group V in 7 days. VEGF and TGF-${\beta}1$ expression were decreased in the Group C and Group A in 14 days, however Group V was not decreased at 14 day because of delayed wound healing process. Conclusion: Bacterial synthesized cellulose from citrus affects wound healing by reducing the inflammatory stage. And stimulates wound contracture by the deposition of extracellular matrix, thus preventing the formation of chronic wounds.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 1996년도 추계학술대회논문집
• /
• pp.105-112
• /
• 1996

Aluminium alloy have been used extensively as forging materials for aircraft components due to their high specific strength and corrosion resistance. A large portions of these materials are used as airframe components consisted of various combination of such Rib-Web structure. But the problem of high forging pressure and defect which were caused by narrow Rib thickness prevented from the favorable developments and laboratory scaled trials. In this study, optimization of forging variables such as corner radius and temperature in Rib-Wed structure were established. The 2 mm of corner radius minimized the forging pressure to get the fixed Rib height, which well coincided with theoretical result according to Upper-Bound analysis. And optimum workpiece temperature was below 450$^{\circ}C$ in consideration of grain growth and forging defects by local melting.

• E2M - 전기 전자와 첨단 소재
• /
• 제10권10호
• /
• pp.1034-1040
• /
• 1997

A solar cell conversion effiency was degraded by grain boundary effect in polycrystalline silicon. Grain boundaries acted as potential barriers as well as recombination centers for the photo-generated carriers. To reduce these effects of the grain boundaries we investigated various influencing factors such as emitter thickness thermal treatment preferential chemical etching of grain boundaries grid design contact metal and top metallization along boundaries. Pretreatment in $N_2$atmosphere and gettering by POCl$_3$and Al were performed to obtain multicrystalline silicon of the reduced defect density. Structural electrical and optical properties of slar cells were characterized before and after each fabrication process. Improved conversion efficiencies of solar cell were obtained by a combination of pretreatment above 90$0^{\circ}C$ emitter layer of 0.43${\mu}{\textrm}{m}$ Al diffusion in to grain boundaries on rear side fine grid finger top Yb metal and buried contact metallization along grain boundaries.

• 대한기계학회논문집
• /
• 제19권6호
• /
• pp.1490-1500
• /
• 1995

Compression molding of SMC (Sheet Molding Compound) in a thin plaque with substructures like a rib is involved with the formation of surface defect along the centerline over the rib area called by sink mark depending on process parameters. The surface quality of the external panels in automotive manufacturing is so critical that this kind of defect should be eliminated during manufacturing stages. The effect of process parameters on sink mark formation and the distribution of chopped fiberglasses in the compression molded thin plaque with a rib was experimentally investigated in the present study. In order to estimate the effect of the molding parameters such as molding temperature, mold closing speed, depth of the rib, corner radius of the rib, and final molded part thickness of flat portion on the depth of sink mark and the distribution of fiberglasses in the molded SMC part with the rib under the present experimental conditions, the molding parameters used in experiments were non-dimensionalized equation for predicting the depth of sink mark was determined through dimensional analysis based on the experimental data. The orientation and distribution of fiberglasses and fillers which directly affect the formation and depth of sink mark were investigated by taking the photographs of the cross-sectional area of the molded specimen using scanning electron microscope. The experimental results proposed from this investigation are useful in understanding the formation of sink mark and predicting the depth of sink mark in compression molding of SMC with substructures.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 1997년도 추계학술대회 논문집
• /
• pp.907-910
• /
• 1997

With increasing the needs for micro and precision parts, micro machining technology has been studied to fabricate a small part with high density such as electronics, optics, communications, and medicine industry more than before. But there are many problems to be solved requiring a high-level technology. So this research presents the new method to fabricate a small part through applying chemical mechanical micro machining (C3M) for the Al wafer. Al(thickness I ,u m) was sputtered on the Si substrate. Al is widely used as a lightweight material. However form defect such as burr has a bad effect on products. To improve machinability of ductile material, oxide layer was formed on the surface of AI wafcr before grooving by chemical reaction with HN03(10wt%). And then workpieces were machined to compare conventional micro-machining process with newly suggested method at different machining condition such as load and feed rate. To evaluate whether or not the machinability was improved by the effect of chemical condition, such as the size, the width of grooves 'and burr generation were measured. Finally, it is confirmed that C3M is one of the feasible tools for micro machining with the aid of effect of the chemical reaction.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
• /
• pp.815-820
• /
• 2011

The railway bridge of the domestic still has been used steel base such as sperical bearing and pot bearing widely. However, the bearing of steel series is occured corrosion frequently, reduced durability and raised maintenance cost excessively due to the nature of the material. If the elastomeric bearing which is widely used in highway bridge is applied to the railway bridge, it will be able to compensate this defect a lot. In order to apply to the railway bridge used for highway bridge, is needed the control of the bridge ends deflection, lateral displacement and negative reaction. Therefore, the elastomeric bearing can be applied to the railway bridge enough, if installed negative reaction key for control of the bridge ends deflection, improved shear wedge performance for control of the lateral force, adjust the thickness of the elastomeric pad for the minimize deflection, in addition, can be economic design of sub-structures due to damping effect.

• 한국전기전자재료학회논문지
• /
• 제16권3호
• /
• pp.214-218
• /
• 2003

We studied the nematic liquid crystal (NLC) aligning capabilities by the UV alignment method on a diamond like carbon (DLC) thin film surface A good LC alignment by UV exposure on the DLC thin film surface at 200${\AA}$ of layer thickness was achieved. Also, a good LC alignment by the UV alignment method on the DLC thin film surface was observed at annealing temperature of 180$^{\circ}C$. However, the alignment defect of the NLC was observed above annealing temperature of 200$^{\circ}C$. Consequently, the good thermal stability of LC alignment by the UV alignment method o the DLC thin film surface can be achieved.

• Archives of Plastic Surgery
• /
• 제32권5호
• /
• pp.607-612
• /
• 2005

A traditional tie-over dressing may be applied to support the take of a skin graft. Although there are many advantage of this method, it has significant disadvantages, including time-consuming application. Furthermore, when the dressing is changed, the gauze becomes hard and can be stuck to the graft, causing damage and pain upon removal. The purpose of our study is to evaluate the effect of semi-occlusive dressing using polyurethane foam and film dressing($Allevyn^{(R)}$, $Opsite^{(R)}$) after full thickness skin graft. The authors treated 45 cases including burn scar contracture(n=38), syndactyly (n=1), absence of nipple-areolar complex(n=4), traumatic skin defect(n=1) and contact burn(n=1) with authors' method and 39 patients including burn scar contracture (n=39) with the tie-over dressing between 2000 and 2004. The patients in polyurethane foam and film dressing group ranged from 1 to 62 years of age (mean age, 15.1 years) and the patients in tie-over dressing group ranged from 2 to 60 years of age(mean age, 21.3 years). The postoperative results were analyzed according to the following measures: (1) the duration of graft-taking, (2) the admission period, (3) complications. Compared with the traditional tie-over dressing, polyurethane foam and film dressing was shown to be more successful in a reduced duration of graft-taking, in which was similar to the former in the rate of graft-taking, a reduced admission period and patient's discomfort. We concluded that semi-occlusive dressing using $Allevyn^{(R)}$ and $Opsite^{(R)}$ was an effective method after full thickness skin graft, which was easy to shape to difficult body locations, such as web spaces, fingers and maintains a moist environment for wound healing and does not stick to the wound.

• Structural Monitoring and Maintenance
• /
• 제10권3호
• /
• pp.221-242
• /
• 2023

Internal and external corrosion are common in pressure pipes used in a variety of industries, often resulting in defects that compromise their integrity. This economically and industrially significant problem calls for both preventive and curative technical solutions to guarantee the reliability of these structures. With this in mind, our study focuses on the influence of composite and metallic patch repairs on the limit loads of pipes, particularly elbows, the critical component of piping systems. To this end, we used the nonlinear extended finite element method (X-FEM) to study elbows, a priori corroded on the internal surface of the extrados section, then repaired with composite and metallic patches. In addition, the effect of the geometry of composite materials and metal patches was examined, in particular the effect of their thickness and material on the increase in limit loads of repaired structures. The results obtained provide information on the effectiveness and optimization of patch repair of corroded elbows, with the aim of increasing their service life.

• 치위생과학회지
• /
• 제15권2호
• /
• pp.98-105
• /
• 2015

본 연구는 외과적으로 형성된 흰쥐 하악골 결손부에 S.mutan에서 분리 정제된 mutan을 주사하고, ${\mu}CT$로 촬영하여 골결손부의 치유에 미치는 영향을 3차원 골 미세구조 지표로 평가하기 위하여 실시하였다. 흰쥐 치조골에 임계 크기 결손부인 1.5 mm 지름의 원형 결손부를 형성하여 대조군에는 동일량의 saline을 투여하고, 실험군으로 LPS와, mutan을 주사하여 골치유에 미치는 영향을 관찰하였다. 수술 후 4주에 희생하고 치유 결과를 3차원 미세구조의 형태 계측학적 지표값을 비교 분석하여 다음과 같은 결론을 얻었다. 실험동물의 체중변화는 총 12회 투여 기간 동안 일정한 증가를 나타냈다. 8회차부터 mutan 처리군은 대조군과 비교하여 유의한 차이를 보였으며(p<0.05), 9회차에는 mutan 처리군이 대조군과 LPS 처리군과 비교하여(p<0.05), 10~12회차에는 LPS 처리군과 비교하여 유의한 체중증가를 나타냈다(p<0.01). Mutan이 생체 내에서 하악의 골치유 효과를 알아보기 위해 ${\mu}CT$를 통해 형태계측학적 지표 분석 결과, 대조군에 비해 LPS 처리군에서 뚜렷한 골결손부 치유 지연 및 골흡수 양상을 보였으며, mutan 처리군 은 LPS의 작용보다 미약하지만 골치유를 지연시키는 것으로 확인되었다. ${\mu}CT$를 통해 골밀도 분석 결과, 대조군과 비교하여 LPS와 muatn 처리군에서 낮은 골밀도치를 나타냈고, mutan은 LPS 처리군보다 유의하게 높은 골밀도치를 보였다(p<0.01).