• 대한화학회지
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• 제56권5호
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• pp.597-602
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• 2012

본 연구는 triacetoxyvinlysilane을 첨가제로 사용하여 교차결합제인 EGDMA (ethylene glycol dimethacrylate)와 HEMA (2-hydroxyethyl methacrylate), MMA (methyl methacrylate), MA (methacrylic acid) 그리고 개시제인 AIBN (azobisisobutyronitrile)과 함께 공중합 하였다. 생성된 고분자의 물리적 특성을 측정한 결과, 함수율 35.63~32.44%, 굴절률 1.4382~1.4480, 가시광선 투과율 89.0~92.5%, 인장강도는 0.346~0.674 kgf를 나타내었다. 기본 모노머 조합에 triacetoxyvinlysilane을 첨가한 조합과 1%의 hexamethylene diisocyanate를 첨가하여 중합한 조합의 물성을 비교한 결과 hexamethylene diisocyanate 1%를 첨가하여 중합한 렌즈의 인장강도가 더 큰 값을 나타내었다. 본 실험결과로 볼 때 생성된 공중합체는 내구성 및 인장강도가 우수한 안의료용 렌즈 재료로 사용될 수 있을 것으로 판단된다.

• 한국농공학회논문집
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• 제49권4호
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• pp.51-59
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• 2007

Recently, concrete has been made porous and used for sound absorption, water permeation, vegetation and water purification according to void characteristics. Many studies are carried out on the utilization of sewage sludge, fly ash and waste concrete to reduce the environmental load. This study was performed to evaluate the void, strength, relationship between void and strength, permeability and chemical resistance properties of porous polymer concrete for pavement with different fillers. An unsaturated polyester resin was used as a binder, crushed stone and natural sand were used as an aggregate and bottom ash, fly ash and blast furnace slag were used as fillers. The mix proportions were determined to satisfy the requirement for the permeability coefficient, $1{\times}10^{-2}$ cm/s for general permeable cement concrete pavement in Korea. The void ratios of porous polymer concrete with fillers were in the range of $18{\sim}23%$. The compressive strength and flexural load of porous polymer concrete with fillers were in the range of $19{\sim}22$ MPa and $18{\sim}24$ KN, respectively. The permeability coefficients of porous polymer concrete with fillers were in the range of $5.5{\times}10^{-1}{\sim}9.7{\times}10^{-2}$ cm/s. At the sulfuric acid resistance, the weight reduction ratios of porous polymer concrete immersed during 8-week in 5% $H_{2}SO_{4}$ were in the range of $1.08{\sim}3.56%$.

• Restorative Dentistry and Endodontics
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• 제22권1호
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• pp.132-143
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• 1997

Recently composite resin luting cement have been widely used according as esthetic requirement was increased. The purpose of this study was to evaluate of shear bond strength of four resin cements to bovine dentin. The materials used in this study were All-Bond 2(dentin bonding agent), Duolink cement, Bistite resin cement, Twinlook cement, Clearfil CR inlay cement. A total 40 acrylic cylinders with bovine dentin were divided into four groups. Four experimental groups were as follows; Group l(AB) : Specimens bonded with All-Bond 2 and Duolink Cement Group 2(BT) : Specimens bonded with Bistite Resin Cement Group 3(TL) : Specimens bonded with Twinlook Cement Group 4(CR) : Specimens bonded with Clearfil CR Inlay Cement Mter 1 hour of bonding, all specimens were stored for 24 hours in water at $37^{\circ}C$ and tested with Instron universal testing machine between bovine dentin and resin cements. The data were evaluated statistically at the 95% confidence level with a one-way analysis of variance and Tukey's range statistics. The following results obtained; 1. The group l(AB) was highest shear bond strength and the group 3(TL) was 10west(p>0.05). 2. Group 2(BT), 4(CR) were similar shear bond strength and there was no significant difference(p<0.05). 3. Group 1(AB), 4(CR) with acid etching were showed resin tags on the opened dentinal tubules, but Group 2(BT), 3(TL) without acid etching were not showed resin tags. 4. Group l(AB) was showed intimate adaptation than other groups.

• The Journal of Advanced Prosthodontics
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• 제8권4호
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• pp.259-266
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• 2016

PURPOSE. The purpose of this study was to assess the effect of surface treatments on shear bond strength of resin composite bonded to thermocycled and non-thermocycled CAD/CAM resin-ceramic hybrid materials. MATERIALS AND METHODS. 120 specimens ($10{\times}10{\times}2mm$) from each material were divided into 12 groups according to different surface treatments in combination with thermal aging procedures. Surface treatment methods were airborne-particle abrasion (abraded with 50 micron alumina particles), dry grinding (grinded with $125{\mu}m$ grain size bur), and hydrofluoric acid (9%) and silane application. According to the thermocycling procedure, the groups were assigned as non-thermocycled, thermocycled after packing composites, and thermocycled before packing composites. The average surface roughness of the non-thermocycled specimens were measured after surface treatments. After packing composites and thermocycling procedures, shear bond strength (SBS) of the specimens were tested. The results of surface roughness were statistically analyzed by 2-way Analysis of Variance (ANOVA), and SBS results were statistically analyzed by 3-way ANOVA. RESULTS. Surface roughness of GC were significantly lower than that of LU and VE (P<.05). The highest surface roughness was observed for dry grinding group, followed by airborne particle abraded group (P<.05). Comparing the materials within the same surface treatment method revealed that untreated surfaces generally showed lower SBS values. The values of untreated LU specimens showed significantly different SBS values compared to those of other surface treatment groups (P<.05). CONCLUSION. SBS was affected by surface treatments. Thermocycling did not have any effect on the SBS of the materials except acid and silane applied GC specimens, which were subjected to thermocycling before packing of the composite resin.

• 청정기술
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• 제13권3호
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• pp.201-207
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• 2007

본 연구에서는 셀룰로오스계 부직포를 이용하여 상온에서 물에 녹는 카르복시메틸셀룰로오스(carboxymethylcellulose; CMC)를 합성하였다. 실험변수는 반응온도, 시간, 수산화나트륨(NaOH) 및 모노클로로아세트산(monochloroacetic acid; MCA)이다. 머서화(mercerization) 및 에테르화(etherification)할 때, 용해도와 치환도(degree of substitution ; DS)는 NaOH(또는, MCA)농도를 증가시키면서 최대 용해도와 치환도를 관찰하였다. 이때의 최대용해도와 치환도는 NaOH(또는, MCA)농도가 30%일 때 얻어졌다. 치환도를 볼 때, MCA농도의 영향은 NaOH농도에 비해 더 크게 나타났다. CMC섬유의 인장강도(Tensile strength; TS)에서는 효과적인 결과를 보였고, 반응시간, 시약농도와 반응온도에 따라 인장강도는 감소하였다. 그러나 인장강도의 큰 변화가 중성영역 부근에서 관찰되었다.

• 콘크리트학회논문집
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• 제14권4호
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• pp.589-596
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• 2002

본 연구에서는 당분류의 초지연제를 중심으로 굳지 않은 콘크리트의 유동성, 공기량, 응결특성 및 경화 콘크리트의 강도특성을 분석하였다. 실험결과 먼저, 굳지 않은 콘크리트의 슬럼프 값은 초지연제의 혼입률이 증가함에 따라 다소 증가하는 것으로 나타난 반면, 공기량은 감소하는 것으로 나타났다. 응결특성으로는 혼입률이 증가함에 따라 응결시간이 비약적으로 지연되어 혼입률 0.3%에서 글루콘산은 10일 이상, 슈크로스, 백설탕 및 황설탕은 10일 이상에서 종결이 측정되었다. 또한, 종결이후 압축강도는 초지연제 혼입시 초기강도는 플레인에 비해 낮게 측정되었지만 3일 재령 이후에서는 플레인과 동등하거나 그 이상으로 나타났다. 종합적으로 당분류의 백설탕은 가격이 저렴하면서도 응결지연 특성 및 강도특성에서 여타의 초지연제에 비해 커다란 문제점이 없는 것으로 분석되어, 향후 내구성 등 제반특성이 심도 있게 검토된다면 우수한 초지연제로서의 활용가능성을 확인 할 수 있었다.

• 폴리머
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• 제35권6호
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• pp.526-530
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• 2011

바이오매스에서 유래된 2,5-dihydroxymethylfuran(DHMF)을 $KMnO_4$ 산화반응으로 furan-2,5-dicarboxylic acid(FDCA)를 합성하였다. 합성한 FDCA와 다이올류를 에스테르화 반응과 축중합 반응을 진행시켜 폴리에스터를 중합하였다. 폴리에스터는 NMR을 통해 조성을 분석하였고 DSC와 TGA를 통해 열적특성을 분석하였다. 합성된 폴리에스터의 고유점도는 0.78~1.2 dL/g으로 상용화된 poly(ethylene terephthalate)(PET)와 비슷하였다. 다이올의 길이가 증가할수록 Young's modulus와 strength는 낮아지고 elongation-to-break는 높아지는 경향을 확인하였다. 합성한 poly(ethylene furandicarboxylate)(PEF)의 Young's modulus는 3551 MPa, strength는 103 MPa로 상용화된 PET와 비슷하였다.

• 농업과학연구
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• 제46권3호
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• pp.569-577
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• 2019

The current experiment was conducted to compare nutrient utilization in the aged laying hens with different eggshell strengths or different intensities of brown eggshell color. Two metabolic trials with 96-week-old Hy-Line Brown laying hens were conducted. Twelve hens with a strong eggshell strength (SES) and 12 hens with a weak eggshell strength (WES) were selected and used in the first experiment, whereas 12 hens with dark brown eggshells (DBE) and 12 hens with light brown eggshells (LBE) were selected and used in the second experiment. All hens were fed a common commercial layer diet. Diets included chromic oxide as an indigestible marker to determine the apparent total tract retention (ATTR) of the gross energy (GE), dry matter, acid-hydrolyzed ether extract, nitrogen, neutral detergent fiber, acid detergent fiber, ash, and minerals. The results indicate that the ATTR of Ca in the aged laying hens with SES (59.7%) was greater (p < 0.05) than in the aged laying hens with WES (48.6%). However, the ATTR of the GE and other nutrients was not different between the hens with SES or WES. There were no differences in the ATTR of GE and nutrients between the hens with DBE or LBE. In conclusion, aged laying hens with SES have a greater ability to utilize dietary Ca than those with WES, indicating that the extent of dietary Ca utilization determines the eggshell strength of aged laying hens. However, nutrient utilization in diets may have little impact on eggshell brown coloration in aged laying hens.

• 운동영양학회지
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• 제24권4호
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• pp.28-33
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• 2020

[Purpose] This study aimed to investigate the effects of branched-chain amino acid (BCAA) supplement on delayed onset muscle soreness (DOMS) by analyzing the maximum muscle strength and indicators of muscle damage. [Methods] Twelve men with majors in physical education were assigned to the BCAA group and placebo group in a double-blinded design, and repeated measurements were conducted. DOMS was induced with an isokinetic exercise. Following BCAA administration, the changes in the knee extension peak torque, flexion peak torque, aspartate aminotransferase (AST), creatine kinase (CK), and lactate dehydrogenase (LDH) concentrations were analyzed. The maximum knee muscle strength was measured at the baseline (pre-D0) following BCAA administration for 5 days before exercise (-D5, -4D, -3D, -2D, -1D). In contrast, the post-treatment measurements (D3) were recorded after BCAA administration for 3 days (post-D0, D1, D2). Blood samples were obtained before (pre-D0), immediately after (post-D0), 24 h (D1), 48 h (D2), and 72 h (D3) after the exercise to analyze the indicators of muscle strength. BCAA was administered twice daily for 8 days (5 days and 3 days before inducing DOMS and during the experimental period, respectively). [Results] There was no difference in the flexion peak torque between the groups. However, the BCAA group showed a significantly higher extension peak torque at D3 (second isokinetic exercise), compared to the placebo group (p<.05). There was no difference in AST changes between the groups. Nonetheless, the CK and LDH were significantly reduced in the BCAA group, compared to the placebo group. There was no correlation between the extension peak torque and flexion peak torque. However, the CK and LDH increased proportionately in DOMS. Moreover, their concentrations significantly increased with a decreasing peak torque (p<.01). [Conclusion] An exercise-induced DOMS results in a decrease in the peak torque and a proportional increase in the CK and LDH concentrations. Moreover, the administration of BCAA inhibits the reduction of the extension peak torque and elevation of CK and LDH concentrations. Therefore, BCAA might be administered as a supplement to maintain the muscle strength and prevent muscle damage during vigorous exercises that may induce DOMS in sports settings.

• 대한소아치과학회지
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• 제45권3호
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• pp.299-306
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• 2018

본 연구의 목적은 산부식 시간과 접착제 적용에 따른 유구치 치면열구전색제의 미세인장 결합강도를 평가하여 비교하는 것이다. 40개의 발거된 건전한 하악 유구치를 선정하여 산부식을 시행하지 않은 군과 산부식을 각각 15, 30, 60초 시행한 군으로 분류하였다. 이를 다시 접착제를 적용하지 않은 군과 적용한 군으로 나누었다. 각 군의 치아에 치면열구 전색제를 도포하여 시편을 제작한 후 미세인장 결합강도를 측정하였다. 산부식을 시행한 15, 30, 60초에 따라 미세인장 결합강도는 유의한 차이가 없었다. 전색제를 적용하기 전에 접착제를 적용한 경우가 산부식만 시행한 경우보다 더 높은 결합강도를 보였으며(p < 0.05), 산부식 시간에 따른 유의한 차이는 없었다. 결론적으로, 유구치의 교합면 법랑질에서 산부식 시간이 15초 이상이면 전색제의 미세인장 결합강도는 유의하게 증가하지 않았으며, 치면열구전색제 도포 전에 접착제를 적용하는 것은 결합강도를 증가시켰다.