• 대한치과교정학회지
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• 제27권1호
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• pp.141-155
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• 1997

교정장치의 직접접착으로 인한 프라켓 주위의 탈석회화 개선 및 산부식시 야기되는 법랑질의 목적 부위 이상으로의 산의 유출방지와 시술시 시간소요 개선을 목적으로 레이저를 조사한 치면의주사전자현미경 소견을 관찰하고 브라켓과 치면 사이의 전단접착강도 및 적합한 조사에너지량을 측정, 평가하기 위하여 실험을 시행하였다. 실험재료로 189개의 소구치를 사용하여 산부식 및 Nd:YAG 레이저로 100mj 10pps, 100mj 20pps, 150mj 20pps, 200mj 20pps를, Er:YAG 레이저로 60mj 5pps, 60mj 10pps, 100mj 10pps, 200mj 10pps, 200mj 15pps, 400mj 10pps를 조사한 각 15개 총 165개의 치 아를 교정용 접착제로 접착한후 24시간, 1주, 3주 후로 나누어 전단 접착강도를 측정하였으며, 나머지 24개의 치아에서 산부식군과 각 레이저 조사군 및 정상치아인 비처치대조군을 주사전자현미경으로 관찰하여 다음과 같은 결과를 얻었다. 1. Nd:YAG 레이저 및 Er:YAG 레이저의 각 조사에너지량에 따른 평균 및 표준편차를 얻었다. 2. 같은 에너지 밀도를 조사한 경우 Er:YAG 레이저 조사군의 전단접착강도가 Nd:YAG 레이저 조사군보다 높았다. 3. Nd:YAG 레이저 조사군에서는 150mj 20pps에서, Er:YAG 레이저 조사군에서는 200mj 15pps에서 가장 높은 전단접착강도를 보였다. 4. 전단접착강도 및 주사전자현미경 관찰 결과 브라켓 접착시 Nd:YAG 레이저 조사군에서는 150mj 20pps, Er:YAG 레이저 조사군에서는 60mj 10pps 조사가 적합하다고 인정되었다.

• 공업화학
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• 제30권6호
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• pp.698-706
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• 2019

지난 수십 년 동안, 외부 자극에 대한 응답성이 우수하면서도 인체에 적용할 수 있는 소프트 액추에이터 개발을 위한 많은 노력이 이어졌다. 본 연구에서는 동역학적 정밀 제어가 가능한 의료용 소프트 액추에이터를 개발하기 위해, 유해한 화학적 첨가제나 개시제 없이 방사선을 이용하여 전기 자극 반응성과 물리적 특성이 우수한 3차원 가교 구조의 poly(acrylic acid) (PAAc)/poly(vinyl alcohol) (PVA)/poly(ethylene glycol) (PEG) 하이드로겔을 합성하였다. 방사선 조사 후, 모든 하이드로겔은 75% 이상의 겔 분율을 나타내었고, 표면 반사 적외선 분광법을 통해 PAAc/PVA/PEG 하이드로겔이 성공적으로 합성되었음을 확인하였다. 또한 PAAc/PVA/PEG 하이드로겔의 겔 분율, 평형 수분 함량, 압축 강도를 측정하여 감마선의 총 조사 선량과 구성 성분의 함량비 조절에 따른 하이드로겔의 물리적 특성 변화를 확인하였다. 조사된 감마선의 선량이 증가하거나 poly(ethylene glycol) diacrylate (PEGDA)의 함량이 많을수록 PAAc/PVA/PEG 하이드로겔은 높은 가교 밀도와 우수한 기계적 강도를 나타내었다. 또한 PAAc/PVA/PEG 하이드로겔은 3 V의 저전압에서도 전기적인 자극에 반응하였고, 전기장 하에서 이동성 이온의 움직임에 따른 하이드로겔의 밴딩 거동은 하이드로겔의 가교 밀도, 이온기의 함량, 인가 전압 및 전해질 용액의 이온 농도 등을 조절함으로써 제어할 수 있음을 확인하였다.

• 한국임상수의학회지
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• 제24권2호
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• pp.182-191
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• 2007

Bioabsorbable devices have been utilized and experimented in many aspects of orthopaedic surgery. Depending upon their constituent polymers, these materials can be tailored to provide sufficient rigidity to allow bone healing, retain mechanical strength for certain period of time, and then eventually begin to undergo degradation. The objective of this study was to estimate extent in which Poly-L-latic acid (PLLA) implants had bioabsorbability and biocompatibility with bone and soft tissue in dogs and also to develop bioabsorbable, biocompatible materials with the appropriate strength and degradation characteristics to allow for regular clinical use for treating orthopedic problems in humans as well as animals. Eighteen dogs were used as experimental animals and were inserted two types of PLLA implants. PLLA rods were inserted into subcutaneous tissue of back or the abdomen wall. And the rods were tested for material properties including viscosity, molecular weight, melting point, melting temperature, crystallinity, flexural strength, and flexural modulus over time. PLLA screws were inserted through cortical bone into bone marrow in the femur of the dogs and stainless steel screw was inserted in the same femur. Radiographs were taken after surgery to observe locations of screw. Histological variations including cortical bone response, muscular response, bone marrow response were analyzed over the time for 62weeks. The physical properties of PLLA rods had delicate balances between mechanical, thermal and viscoelastic factors. PLLA screws did not induce any harmful effects and clinical complications on bone and soft tissue for degradation period. These results suggest that PLLA implants could be suitable for clinical use.

• 한국식품과학회지
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• 제32권2호
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• pp.356-362
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• 2000

7개의 전극을 직렬로 배열한 다중전극 고전압펄스 전기장(PEF) 처리장치를 사용하여 전기장 세기와 주파수를 달리한 square wave 펄스(너비 $1\;{\mu}s$)로 약주의 연속 살균을 시도하였다. 살균 전 약주의 총균수는 $1.88{\times}10^3{\sim}2.13{\times}10^4\;CFU/mL$, 효모는 $1.72{\times}10^3{\sim}2.39{\times}10^4\;CFU/mL$, 젖산균은 $1.55{\times}10^3{\sim}2.85{\times}10^4\;CFU/mL$이었다. 약주를 유량 1 mL/s의 속도로 PEF장치에 투입하여 처리한 결과 미생물 사멸기구는 1차반응으로 해석 될 수 있었고, 주파수 및 전기장세기가 증가함에 따라 살균율이 높아졌다. $D_{Hz}$값 및 $D_{PEF}$값은 전기장 세기가 증가함에 따라 감소하였으며, 효모는 세균에 비하여 낮은 값을 보였다. 젖산균은 30 kV/cm 이하의 전기장에서는 일반 호기성 세균에 비하여 낮은 $D_{PEF}$값을 보였으나, 40 kV/cm 이상에서는 높은 $D_{PEF}$값을 나타냈다. 미생물 종류별 $Z_{PEF}$값은 일반 호기성 세균 39.4 kV/cm 젖산균 49.3 kV/cm, 효모 47.6 kV/cm로 일반 호기성 세균의 전기장세기에 대한 의존성이 가장 큰 것으로 나타났다. PEF처리에 의한 약주의 색택 변화는 열처리에 비하여 미미하였으며, PEF살균 약주의 품질은 가열살균 약주에 비하여 월등히 우수하였다. 약주를 본 연구에서 사용한 PEF장치에 2회 통과시킬 경우 상업적 살균이 달성되었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 가을 학술발표회 논문집
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• pp.227-232
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• 2002

To evaluate the practical application of oyster shells as construction materials, an experimental study was performed. More specifically, the long-term mechanical properties and durability of concrete blended with oyster shells were investigated. Test results indicate that long-term strength of concrete blended with 10% oyster shells is almost identical to that of normal concrete. However, the long-term strength of concrete blended with 20% oyster shells Is appreciably lower than that of normal concrete. 1'hereby, concrete with higher oyster shell has the possibility giving a bad influence on the concrete long-term strength. Elastic modulus of concrete blended with crushed oyster shells decreases as the blending mixture ratio increases. Namely, the modulus is reduced by approximately 10∼15% when oyster shells are blended up to 20% replacing the fine aggregate. The drying shrinkage strain increases as the blending ratio increases. In addition, the existing model code of drying shrinkage does not coincide with the test results of this study. An adequate prediction equation needs to be developed. The utilization of oyster shells as the fine aggregate in concrete has an insignificant effect on freezing and thawing resistance, carbonation and sulfuric acid attack of concrete recycling. However, water permeability is considerably improved.

• Asian-Australasian Journal of Animal Sciences
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• 제29권6호
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• pp.845-854
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• 2016

Characteristics and properties of gelatin from goat skin pretreated with NaOH solutions (0.50 and 0.75 M) for various times (1 to 4 days) were investigated. All gelatins contained ${\alpha}$-chains as the predominant component, followed by ${\beta}$-chain. Gelling and melting temperatures of those gelatins were $23.02^{\circ}C$ to $24.16^{\circ}C$ and $33.07^{\circ}C$ to $34.51^{\circ}C$, respectively. Gel strength of gelatins increased as NaOH concentration and pretreatment time increased (p<0.05). Pretreatment for a longer time yielded gelatin with a decrease in $L^*$-value but an increase in $b^*$-value. Pretreatment of goat skin using 0.75 M NaOH for 2 days rendered the highest yield (15.95%, wet weight basis) as well as high gel strength (222.42 g), which was higher than bovine gelatin (199.15 g). Gelatin obtained had the imino acid content of 226 residues/1,000 residues and the gelatin gel had a fine and ordered structure. Therefore, goat skin gelatin could be used as a potential replacer of commercial gelatin.

• Journal of Forest and Environmental Science
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• 제34권5호
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• pp.388-394
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• 2018

An efficient and reproducible protocol for in vitro germination of seeds of Couroupita guianensis has been developed in the present study. Couroupita guianensis is a medicinally important tree and categorized as threatened plant species by the IUCN. The seeds were surface sterilized using 0.1% $HgCl_2$ and inoculated on MS (Murashige and Skoog) and Woody Plants (Llyod and McCown) medium. The seeds with partially removed seed coat responded better (100%) on half strength MS medium as compared to the full (51%), one-fourth strength MS (79%) and the WP medium. Half strength MS medium conjunct with $2.0mg{\cdot}L^{-1}$ indole-3 butyric acid (IBA) was found best among the different types of auxins and cytokinins tested for seed germination, as all the seeds germinated on this medium combination. The seedlings were successfully hardened in the greenhouse and restored in the field with 83% survival rate. The protocol can be used as conservation measure for large scale multiplication of this threatened forest tree species.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2005년도 추계학술발표대회 논문집
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• pp.23-26
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• 2005

In this work, effects of oxygen plasma on surfc1ce characteristics of carbon fibers were investigated in impact strength of carbon fibers-reinforced composites. The surface properties of the carbon fibers were determined by acid/base values, FT-IR, and X-ray photoelectron spectroscopy (XPS). Also, the mechanical properties of the composites were studied by impact strength measurements. As experimental results, the $O_{IS}/C_{IS}$ ratio of the carbon fiber surfaces treated by oxygen plasma was increased compared to that of untreated ones, possibly due to development of oxygen-containing functional groups. The mechanical properties of the composites, including impact strength had been improved by the oxygen plasma on fibers. These results could be explained that the oxygen plasma resulted in the increase of the adhesion of between fibers and matrix in a composite system.

• Fibers and Polymers
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• 제3권3호
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• pp.97-102
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• 2002

A series of waterbome poly(urethane-urea) anionomers were prepared from isophorone diisocyanate (IPDI), polycaprolactone diol (PCL), dimethylol propionic acid (DMPA), ethylene diamine (EDA), and triethylamine (TEA), NaOH, or Cu($(COOCH_3)_2$) as neutralizing agent. This study was performed to decide the effect of neutralizing agent type on the particle size viscosity, hydrogen bonding index, adhesive strength, antistaticity, antibacterial and mechanical properties. The particle size of the dispersions decreased in the following order: TEA based samples (T-sample), NaOH based samples (N-sample), and Cu($(COOCH_3)_2$) based sample (C-sample). The viscosity of the dispersions increased in the order of C-sample, N-sample, and T-sample. Metal salt based film samples Of and C-sample) had much higher antistaticity than TEA based sample. By infrared spectroscopy, it was found that the hydrogen bonding index (or fraction) of samples decreased in the order of T-sam-pie, N-sample, and C-sample. The adhesive strength and tensile modulus/strength decreased in the order of T-sample, N-sam-pie, and C-sample. The C-sample had strong antibacterial halo, however, T- and N-samples did not

• Fibers and Polymers
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• 제6권1호
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• pp.13-18
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• 2005

PLA/LPCL/HPCL blend fibers composed of poly (lactic acid) (PLA), low molecular weight poly ($\varepsilon$-caprolactone) (LPCL), and high molecular weight poly ($\varepsilon$-caprolactone) (HPCL) were prepared by melt blending and spinning for bioab­sorbable filament sutures. The effects of blending time and blend composition on the X-ray diffraction patterns and tensile properties of PLA/LPCL/HPCL blend fibers were characterized by WAXD and UTM. In addition, the effect of in vitro degra­dation on the weight loss and tensile properties of the blend fibers hydrolyzed during immersion in a phosphate buffer solu­tion at pH 7.4 and 37$^{\circ}C$ for 1-8 weeks was investigated. The peak intensities of PLA/LPCL/HPCL blend fibers in X-ray diffraction patterns decreased with an increase of blending time and LPCL contents in the blend fibers. The weight loss of PLA/LPCL/HPCL blend fibers increased with an increase of blending time, LPCL contents, and hydrolysis time while the tensile strength and modulus of the blend fibers decreased. The tensile strength and modulus of the blend fibers were also found to be increased with an increase of HPCL contents in the blend fibers. The optimum conditions to prepare PLA/LPCL/HPCL blend fibers for bioabsorbable sutures are LPCL contents of $5 wt\%, HPCL contents of $35 wt\%, and blending time of 30 min. The strength retention of the PLA/LPCL/HPCL blend fiber prepared under optimum conditions was about $93.5\% even at hydrolysis time of 2 weeks.