• Restorative Dentistry and Endodontics
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• 제38권4호
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• pp.234-240
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• 2013

Objectives: This study evaluated the effects of intraradicular moisture on the pushout bond strength of a fibre post luted with several self-adhesive resin cements. Materials and Methods: Endodontically treated root canals were treated with one of three luting cements: (1) RelyX U100, (2) Clearfil SA, and (3) G-Cem. Roots were then divided into four subgroups according to the moisture condition tested: (I) dry: excess water removed with paper points followed by dehydration with 95% ethanol, (II) normal moisture: canals blot-dried with paper points until appearing dry, (III) moist: canals dried by low vacuum using a Luer adapter, and (IV) wet: canals remained totally flooded. Two 1-mm-thick slices were obtained from each root sample and bond strength was measured using a push-out test setup. The data were analysed using a two-way analysis of variance and the Bonferroni post hoc test with p = 0.05. Results: Statistical analysis demonstrated that moisture levels had a significant effect on the bond strength of luting cements (p < 0.05), with the exception of G-Cem. RelyX U100 displayed the highest bond strength under moist conditions (III). Clearfil SA had the highest bond strength under normal moisture conditions (II). Statistical ranking of bond strength values was as follows: RelyX U100 > Clearfil SA > G-Cem. Conclusions: The degree of residual moisture significantly affected the adhesion of luting cements to radicular dentine.

• Advanced Composite Materials
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• 제17권3호
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• pp.259-275
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• 2008

This study aims to optimize the mechanical and electrical properties of electrically conductive polymer composites (CPCs) for use as a material of bipolar plates for PEM fuel cells. The thin CPCs consisting of conductive fillers and polymer resin were fabricated by a preform molding technique. Expanded graphite (EG), flake-type graphite (FG) and carbon fiber (CF) were used as conductive fillers. This study tested two types of CPCs, EG/FG filled CPCs and EG/CF filled CPCs, to optimize the material properties. First, the characteristics of EG/FG filled CPCs were investigated according to the FG ratio for 7 and $100{\mu}m$ sized FG. CPCs using $100{\mu}m$ FG showed optimal material properties at 60 wt% FG ratio, which were an electrical conductivity of 390 S/cm and flexural strength of 51 MPa. The particle size was an important parameter to change the mechanical and electrical behaviors. The flexural strength was sensitive to the particle size due to the different levels of densification. The electrical conductivity also showed size-dependent behavior because of the different contributions to the conductive network. Meanwhile, the material properties of EG/CF filled CPCs was also optimized according to the CF ratio, and the optimized electrical conductivity and flexural strength were 290 S/cm and 58 MPa, respectively. The electrical conductivity of this case decreased similarly to the EG/FG filled case. On the other hand, the behavior of the flexural strength was more complicated than the EG/FG filled case, and the reason was attributed to the interaction between the strengthening effect of CF and the deterioration of voids.

• 대한소아치과학회지
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• 제29권1호
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• pp.125-131
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• 2002

본 증례는 경희대학교 치과대학병원 소아치과학교실에 상악 중절치의 치수노출을 동반한 외상을 주소로 내원한 아동의 치험례이다. 증례 1은 미성숙 치근을 가지는 만 8세의 남아로 치아의 치수 노출에 따른 수산화칼슘 치수절단술을 이용한 치근단 형성술을 시행한 후 치아 재부착술을 시행한 증례이며, 증례 2는 점상의 치수노출을 보이는 미성숙 영구 중절치를 직접 치수 복조 추 석회화 층을 형성하는 기간동안 레진을 이용하여 유지한 후 치아 재부착술을 시행하였고 증례 3은 치은 연하로 치경부 파절을 보이는 만 12세의 환아로 신경치료 후 골 삭제술과 골 성형술을 동반한 판막술을 시행하여 carbon fiber post를 이용한 치아 재부착술을 시행한 증례이다 이상의 증례를 통하여 치아 재부착술을 성공적으로 시행하였으며 심미적으로 양호한 결과를 얻었기에 보고하는 바이다.

• Steel and Composite Structures
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• 제23권6호
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• pp.727-736
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• 2017

The application of carbon fiber reinforced polymer (CFRP) in steel structures primarily includes two categories, i.e., the bond-critical application and the contact-critical application. Debonding failure and buckling failure are the main failure modes for these two applications. Conventional electrometric techniques may not provide precise results because of the limitations associated with single-point contact measurements. A nondestructive full-field measurement technique is a valuable alternative to conventional methods. In this study, the digital image correlation (DIC) technique was adopted to investigate the bond behavior and buckling behavior of CFRP-steel composite members. The CFRP-to-steel bonded joint and the CFRP-strengthened square hollow section (SHS) steel column were tested to verify the suitability of the DIC technique. The stereo-DIC technique was utilized to measure continuous deformation. The bond-slip relationship of the CFRP-to-steel interface was derived using the DIC data. Additionally, a multi-camera DIC system consisting of four stereo-DIC subsystems was proposed and applied to the compressive test of CFRP-strengthened SHS steel column. The precise buckling location and CFRP delamination of the CFRP-strengthened SHS steel column were identified. The experimental results confirm that the stereo-DIC technique can provide effective measurements for investigating the behaviors of CFRP-steel composite members.

• 한국자원식물학회지
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• 제25권4호
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• pp.416-432
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• 2012

흥정산에 대한 식물의 분포와 특징을 밝히기 위해 2009년 4월부터 2011년 5월까지 조사하였다. 그 결과 확인된 양치식물 이상의 관속식물은 78과 238속 343종 3아종 47변종 10품종으로 총 403분류군이었다. 조사된 종류 중에는 한국특산식물 8분류군, 희귀식물 16분류군이 포함되어 있었고, 식물구계학적 특정식물종은 V등급의 산작약, IV등급은 끈끈이장구채 등 6종류, III등급은 개고사리 등 15분류군, II등급은 낚시고사리 등 24종류, 그리고 I등급은 속새 등 25종류로 총 71분류군이었다. 귀화식물은 20분류군이었으며 귀화율은 5.0%로 산출되었다. 용도는 식용이 175 종류(43.4%)으로 가장 많았고, 약용이 126종류(31.3%), 목초용이 65종류(16.1%), 관상용이 52종류(12.9%), 목재용과 섬유용이 12종류(3.0%), 그리고 공업용이 3종류(0.7%)로 나타났다.

• 한국초지조사료학회지
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• 제12권2호
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• pp.127-131
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• 1992

남주지방에 알맞는 청예 사초용 율무의 질소시비수준을 구명코자 1989년 4월부터 1990년 8월까지 순천대학교 부속 동물사육장 내 사료작물포장에서 시험을 수행하였던 바 그 결과를 요약하면 다음과 같다. 1. 질소의 시용은 13.5kg/10a까지 직선적인 증수를 나타냈으나 18kg/a의 다비구는 시비방법에서 2구의 추비 결과로 도복과 과번무가 나타나 오히려 감수하였다. 2. 적정 시비수준은 N_$P_2O_5-K_2O$=13.5-6.6 kg/10a로 사료되었다. 즉 생초수량, 건물수량 및 조단백질함량이 가장 높고 NDF, ADF등 조섬유함량이 가장 낮으며 유의차가 인정되었다.(P<0.05).

• 한국가스학회지
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• 제23권5호
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• pp.1-7
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• 2019

호흡용 용기에 흠 등의 결함이 발생하였을 때 용기의 잔존강도를 파악하여 파열압력을 판단해야하지만, 복합재료 용기의 경우 흠에 따른 파열 강도의 예측이 어려우며 기법이 복잡하다. 따라서 본 연구에서는 Type-I 용기의 면적용량법 적용 결과를 토대로 Type-III 용기에 결함발생시 파열을 예측하기 위해 면적 용량법 모델을 개발하였으며, 그 신뢰성을 확인하기 위해 용기의 외면에 흠을 가공하여 파열시험을 실시하였다. 면적 용량법 모델의 예측 결과와 실험의 경향이 매우 일치하는 경향을 보였으며, 향후 복합재 용기의 파열압력 추정 방법에 있어 중요한 자료가 될 것으로 기대한다.

• Applied Microscopy
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• 제26권1호
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• pp.59-65
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• 1996

누에의 사료에 대한 섭식성 반응이 다른 2계통에 대한 두부의 형태적 차이를 전자현미경적 관찰을 하였다 이들 2계통의 두부와 촉각의 형태적 차이는 변이가 심하고 다양하다. 섭식성 반응이 높은 계통에 있어서는 소시지의 돌기가 매우 잘 발달되어 있는 반면 섭식성 반응이 낮은 계통에 있어서는 형태적으로 퇴화되어 있다. 또한 촉각의 셋째마디의 유병돌기가 발달되어 있지 않으며 사료에 대한 섭식 반응이 낮고 극단적으로 퇴화되어 있는 개체는 사료를 감지하지 못하여 결국에는 굶어 죽은 것으로 사료된다.

• 대한지역사회영양학회지
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• 제17권1호
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• pp.69-80
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• 2012

This study was conducted to examine the nutritional status, quality of diet and quality of life in postmenopausal women with mild climacteric symptoms based on their food group intake patterns. The data for nutritional status were obtained using 3-day records. Quality of diet was assessed by INQ, NAR, MAR, DDS, DVS, DQI-I. Climacteric symptoms were analyzed by the questionnaire of Kupperman's index and MENoL. The subjects were classified into the five groups, GMVDF, GMVdF, GMVDf, GMVdf, GmVDF according to their food group intake patterns. Analysis of nutrient intakes showed that the GMVDF group took significantly higher levels of kcal, carbohydrate, protein, fat, vitamin A, thiamin, riboflavin, folate, vitamin C, vitamin E, calcium, phosphorous, sodium, iron, zinc and fiber than GMVdf group did (p < 0.05). INQ of Ca and Fe appeared to be higher in GMVDF than in GMVdf groups (p < 0.05). Analysis of NARs showed that missing milk groups took lower riboflavin, Ca and P than other groups did as the same result with MAR (p < 0.05). Analysis of DDS and DQI showed that GMVdf group had the lowest quality of diet (p < 0.05); however, no difference was found on DVS. The GMVdf group showed the worst climacteric symptoms compared with those of the other groups (p < 0.05). However, we couldn't observe any differences in menopause-specific quality of life among the groups. In conclusion, it would be beneficial to meet all five food groups to increase the quality of diet and to reduce the climacteric symptoms in postmenopausal women.

• 한국운동역학회지
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• 제15권3호
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• pp.51-59
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• 2005

To examine the influence of aging on the mechanism of muscle fatigue, we compared the magnitude of central and peripheral fatigue in young and old women before, during and after a sustained submaximaI isometric contraction of elbow flexor muscles. Twelve women (6 young. $20.7{\pm}1.2$ years and 6 old, $68.8{\pm}29$ years) performed a contraction at 20% of maximal voluntary contraction (MVC) torque with their non-dominant arm. The old women were weaker than the young women, however their endurance time for the 20% contraction was longer compared with the young women ($1822{\pm}444$ vs. $1061{\pm}678$ sec, P <. 05). Both groups had a similar reduction in voluntary activation ratio (VA) during and after the fatiguing contraction. However, the old women showed much greater variability in VA before and after the contraction ($91.61{\pm}4.54%$ and $76.70{\pm}19.55\;%$ range of $79{\sim}99$ to $87{\sim}99%$ respectively) compared with the young women ($95.71{\pm}1.86\;%$ and $83.46{\pm}7.57\;%$ range of $39{\sim}75$ to $69{\sim}90%$, respectively). Furthermore, the EMG activity of the elbow flexor muscles and triceps brachii was greater for the old women compared with the young women throughout the fatiguing contraction, indicating different activation strategies with age. Indices of peripheral fatigue including twitch properties, showed that fatigue within the muscle was more rapid for the young women compared with the old women. These results suggest that although old women are weaker than young women, they have greater endurance due to mechanisms within muscle. Furthermore, old women showed great variability in their ability to optimally activate all muscle fiber compared with young women for an isometric contraction.