• Restorative Dentistry and Endodontics
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• 제35권6호
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• pp.479-485
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• 2010

연구목적: 이 연구의 목적은 레진 시멘트의 포스트 공간 내 적용 방법에 따른 포스트의 push-out접착 강도를 비교하는 것이었다. 연구 재료 및 방법: 30개의 발거된 하악소구치를 사용하여 시멘트의 적용 방법에 따라 세 그룹으로 나누었는데 lentulo-spiral을 이용하여 포스트 공간 내에 레진 시멘트를 적용하는 그룹 (group Lentulo), 직접 포스트 표면에 레진 시멘트를 도포하는 그룹 (group Direct), elongation tip을 이용하여 포스트 공간 내에 레진 시멘트를 적용하는 그룹 (group Elongation tip)으로 나누었다. 근관을 성형, 충전한 뒤 Rely-X post drill을 사용하여 포스트 공간을 형성하였고, Rely-X fiber post를 Rely-X Unicem 적용하여 광중합 하였다. 시편을 아크릴릭 레진에 포매 하고 저속 절단기로 치아 장축에 수직으로 절단하여, 하나의 치아에서 치관부, 중앙, 근단부의 세 개의 시편을 얻었다. 절단한 시편을 Universal Testing Machine으로 push-out 접착 강도를 측정하였다. 접착 실패가 일어난 시편을 수술용 현미경 하에서 관찰하여 그 실패 양상을 결정하였다. 결과: 치근의 위치에 따른 push-out 접착 강도는 유의한 차이를 보였으며, 전용의 elongation tip을 사용한 그룹이 가장 높은 push-out 접착 강도를 나타냈다. 결론: 레진 시멘트를 포스트에 직접 적용하거나 lentulo-spiral을 사용하는 기존의 방법에 비해 elongation tip을 사용하는 것이 self-adhesive 계면의 결함을 줄이고 근관치료한 치아의 수복 성공율을 높일 수 있을 것으로 생각된다.

• International Journal of Industrial Entomology and Biomaterials
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• 제33권2호
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• pp.132-137
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• 2016

Although silk textile shows excellent performance when used in clothing over a long period, its limited elongation and elasticity have restricted its extension to other textile and non-textile applications. In the present study, silk textile was produced using silk/polyurethane core-spun yarn and degummed to enhance its elongation and elasticity. The effects of degumming on the structure and mechanical properties of the silk textile were examined. Scanning electron microscopy observation revealed that the silk filaments became finer and more flexible with degumming, resulting in increased tangling of weft yarns and a highly shrunk textile structure in the weft direction. Although the strength of the degummed silk textile was decreased, its elongation greatly increased by 383% (a 16-fold increase) because of the degumming treatment. In particular, the elasticity of the silk textile was greatly improved. The silk textile exhibited ~30% reduction in the elongation after the second extension; however, the elongation almost did not change after 18 additional extension-recovery tests.

• 한국작물학회지
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• 제43권4호
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• pp.273-278
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• 1998

Carbohydrate metabolism and partitioning are dependent on relationships between sources and sinks which can be affected by rates of photosynthesis and respiration. Fructan, the major form of stored carbohydrate in tall fescue (festuca arundineacea Schreb.), changes in concentration during growth and in response to the environment. Objectives of this study were i) to examine the content and the composition of carbohydrates in five tissues (mature leaf blade, immature leaf blade, leaf elongation zone, terminal meristem, and root tips) of two tall fescue genotypes, one with high yield per tiller (HYT) and one with low yield per tiller (LYT), and ii) to compare the reserved and utilized carbohydrates among above five different tissues, particularly between the leaf elongation zone and root tips. The established vegetative tillers of the HYT and LYT genotypes were grown in a controlled-environment growth chamber. Water-soluble carbohydrate (WSC) in the leaf elongation zone was about 22% of dry weight in the HYT and about 19% in the LYT genotype. The root tip also had high WSC, about 12% of dry weight in the HYT and 6% in the LYT genotype. Hexoses and sucrose were the major components of total WSC in all tissues except the leaf elongation zone. The growing tissues (sinks), i.e., the leaf elongation zone and root tip, had a high proportion of low degree of polymerization fructan, i.e., 3 to 8 hexose units.

• 한국전기전자재료학회논문지
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• 제17권8호
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• pp.893-897
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• 2004

In this paper, we studied the mechanical and thermal properties on slice XLPE sheet from 22 kV and 154 kV power cables. Interface structures are XLPE/semiconductor and XLPE/water/semiconductor. We evaluated mechanical property, thermal analysis, moisture analysis. Based on mechanical and thermal properties of the 22 kV XLPE sheet, elongation, mechanical strength, and melting point were evaluated to be 485.48 %, 1.74 kgf/$\textrm{mm}^2$ and $102.48^{\circ}C$, respectively. It was also evaluated from the mechanical and thermal properties of 154 kV XLPE sheet that elongation, mechanical strength, and melting point are 507.81 %, 1.8 kgf/$\textrm{mm}^2$, $106.9^{\circ}C$, respectively. A region shows a rapid increase in tension strength, and B region only shows increase in elongation under 1.0 kgf/$\textrm{mm}^2$, C region shows increase in both elongation and tension strength. Difference of melting point came from the chain of XLPE polymer and the difference of crystallization. Moisture density of semiconductor showed 800 ∼ 1200 ppm before extrude, 14000 ∼24000 ppm after extrude. These values were higher than the moisture density of XLPE (300∼560) ppm.

• 수산해양교육연구
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• 제25권4호
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• pp.766-774
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• 2013

Biodegradable polybutylene succinate(PBS) is a kind of environmentally friendly plastics for fisheries, because it can mitigate the ghost fishing problem caused by gill-net and trap fisheries. To evaluate durability of PBS monofilament, each of different diameter 3 types of monofilaments were spun and exposed to 56 month outdoor and then their gravity, modification of surface, breaking strength, and elongation were analysed. The gravity of PBS monofilament was estimated to be approximately 1.24 when spinning ratio from 4.8 to 6.1. PBS monofilaments did not show any crack after 56 month exposed to outdoor and load-elastic elongation curve was showed sigmoid type. Decreasing ratio of elongation was appeared in the thinnest monofilament 0.2mm diameter and breaking strength was in the thickest monofilament 0.4mm diameter. Breaking strength and elongation at break were decreased rapidly after 48 month exposed to outdoor. Breaking strength reduced linearly after 48 month exposure, while no such linear relationship was found in the case of elongation at break. In results, it was investigated that the durability of PBS monofilament nets for gillnet and trap were 24, 50 month when keep to land, respectively.

• 한국의류학회지
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• 제25권2호
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• pp.350-357
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• 2001

In this study, seam strength, seam elongation and seam efficiency of polyurethane coated fabrics were examined under various sewing conditions using three kinds of fabrics, four kinds of sewing threads and three kinds of stitch lengths. And the sewability of polyurethane coated fabrics were evaluated by FAST system. The results were as follows: 1. Seam strength decreased with the increase of stitch length. The loop strength of sewing thread and the type of base fabric than the type of coated surface had an effect on seam strength. 2. Seam elongation also decreased with the increase of stitch length and was affected by the type of base fabric. The tensile elongation of polyurethans coated fabric had an effect on seam elongation. 3. Sean efficiency also was related to stitch length, the type of base fabric, and seam strength. The suitable seam efficiency was within 50%∼65% in which polyurethane coated fabric and sewing thread broke at the same time. Therefore PS thin and PPC thin sewing threads and 3mm stitch length were suitable to polyurethane coated fabrics. 4. The relaxation shrinkage(RS) of polyurethane coated fabric was smaller than the smallest value of control chart in FAST system. And the extensibility(E) and the shear rigidity(G) were larger than the largest value.

• 한국의류학회지
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• 제29권11호
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• pp.1454-1464
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• 2005

The study was based on a three-stage, non-repetitive factorial experiment in which chemical-rotted kenaf fibers were treated separately with hydrogen peroxide concentrations of $0.5\%,\;1\%\;and\;2\%$, with pH solutions of 7, 9 and 11, and treatment times of 30, 60 and 90 minutes. Under optimal conditions, the study was conducted to determine the strength and elongation of kenaf fibers by the addition of chelators, penetrants and surfactants. The hydrogen peroxide concentration, solution pH and treatment time directly affected the strength of kenaf fibers. The hydrogen peroxide concentration, solution pH affected the elongation of kenaf fibers. It was found, however, that the interaction between pH and treatment time, concentration and treatment time, concentration and treatment time and pH affected the strength of kenaf fibers. Also, It was found that the interaction between pH and concentration, concentration and treatment time, concentration and treatment time and pH affected the elongation of kenaf fibers. Under the hydrogen peroxide conditions of $2\%$ concentration, pH 11 and a treatment time of 60 minutes, there were no effects on the strength and elongation of kenaf fibers with the addition of chelator SP, CA.

• Journal of Welding and Joining
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• 제22권1호
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• pp.77-82
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• 2004

The effect of bonding condition on tensile properties of joints diffusion bonded spheroidal graphite cast iron, FCD60 to Cr-Mo steel, SCM 440 was investigated. Diffusion bonding was performed with various temperatures, holding times, pressures and atmospheres. All tensile specimens were fractured at the bonding interface. The tensile strength and elongation was increased with increasing bonding temperature. Especially, tensile strength of joints bonded at 1123K was higher than that of a raw material, FCD60, and tensile strength of joints bonded at 1173K was equal to that of a raw material, SCM440, but elongation of all joints was lower than those of raw materials. There was little the effect of holding time on the tensile properties. In comparison with bonding atmosphere, the difference of tensile strength was not observed, but elongation of joint bonded at vacuum(6.7mPa and 67mPa) was higher than that of Ar gas. Higher the degee of vacuum, elongation increased. Tensile properties of diffusion bonds depended on microstructures of cast iron at the interface and void ratio. Microstructures of cast iron at interface changed with temperature, because decarburizing and interdiffusion at the interface occurs and transformation of austenite-1 ferrite + graphite occurs on the cooling process. The void ratio decreased with increasing temperature, especially, effected on the elongation.

• 열처리공학회지
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• 제35권4호
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• pp.211-219
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• 2022

It is known that superplastic materials with ultrafine grains have high elongation mainly due to grain boundary sliding. Therefore, in the present study we examined the influence of grain refinement, caused by a repetitive cold rolling and annealing process, on both superplastic elongation and superplastic deformation mechanism. The cold rolling and annealing process was repetitively applied up to 4 times using Fe-10Mn-3.5Si alloy. High-temperature tensile tests were conducted at 763 K with an initial strain rate of 1 × 10^-3 s^-1 using the specimens. The superplastic elongation increased with the number of the repetitive cold rolling and annealing process; in particular, the 4 cycled specimen exhibited the highest elongation of 372%. The primary deformation mechanism of all specimens was grain boundary sliding between recrystallized α-ferrite and reverted γ-austenite grains. The main reason for the increase in elongation with the number of the repetitive cold rolling and annealing process was the increase in fractions of fine recrystallized α-ferrite and reverted γ-austenite grains, which undergo grain boundary sliding.

• 대한안과학회지
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• 제59권11호
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• pp.1009-1016
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• 2018

목적: 중등도 이하 소아 근시에서 안경과 각막굴절교정렌즈(orthokeratology lens, OK) 착용이 안축장 성장에 미치는 영향 및 관련인자를 알아보고자 하였다. 대상과 방법: 2013년부터 2015년까지 내원한 6세에서 13세 사이 -4.50디옵터 이하의 구면렌즈대응치를 가진 소아 100명을 대상으로 후향적으로 OK군(75안)과 안경군(64안) 간에 안축장 변화와 안축장과 관계된 인자들을 분석하였다. 결과: 안축장 변화는 1년째에 OK군이 $0.24{\pm}0.29mm$의 증가를, 안경군이 $0.42{\pm}0.20mm$의 증가를 보였으며, OK군에서 안경군에 비해 유의하게 안축장 성장이 억제되는 양상을 보였다(Mann-Whitney U test, p<0.05). OK군에서 처음 착용한 나이만이 안축장 변화와 음의 상관관계가 있는 것으로 나타났다(Pearson's correlation, r=-0.481, p<0.05). 안경군에서는 처음 착용한 나이가 안축장 변화와 음의 상관관계(Pearson's correlation, r=-0.462, p<0.05)를, 그 외에 현성굴절검사의 초기 구면렌즈대응치 및 초기 구면렌즈값, 난시값은 안축장 변화와 양의 상관관계를 보였다. 안축장 변화를 비교해 보았을 때 OK를 착용한 경우 6세 이상 9세 미만군(28안)에 비해 9세 이상 13세 이하군(47안)에서 유의하게 안축장 성장이 더 억제되는 양상을 보였다(Mann-Whitney U test, p<0.05). 결론: OK 착용은 안경 착용에 비해 효과적으로 안축장의 성장을 억제할 수 있으며, 9세 이상 13세 이하의 소아에서도 효과적인 안축장 성장 억제가 가능하다.