• 한국초지조사료학회지
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• 제36권4호
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• pp.293-297
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• 2016

본 연구는 건초 수확 철 강우 영향을 최소화하고 국내에서 건초생산 기회를 확대하기 위하여 강우가 예상되는 전날 예취하여 반전하지 않은 상태에서 비를 맞혔을 때 사료가치 변화에 미치는 영향을 구명하기 위하여 수행되었다. 예취 후 강우에 의한 사료가치 변화를 조사하기 위하여 강우가 예상되는 전날 예취하고 반전은 하지 않은 상태로 포장에서 3일간 비를 맞추면서 매일 09:00, 13:00, 17:00에 1일 3회 시료를 500 g을 채취하여 사료가치 변화를 조사하였다. 조사료의 섬유소의 주요 구성물질인 ADF와 NDF 함량은 강우일수가 늘어남에 따라 증가하는 것으로 나타났으며 조단백질(CP) 함량은 강우일수가 증가함에 따라 소폭 감소하는 경향을 보였으나 유의적인 차이는 보이지 않았다. 조지방(CF) 함량은 강우 1일째 8.1%, 강우 2일째 15.7%, 강우 3일째에 32.8%로 감소하여 다른 영양성분에 비하여 양분 손실이 가장 큰 것으로 나타났다. 조사료의 탄수화물 중 섬유질을 제외한 나머지 부분인 비섬유성탄수화물(NFC) 함량은 강우일수가 늘어남에 따라 감소하는 것으로 나타났는데, 강우 1일째는 약간 증가(0.5%)를 보이다 강우 2일째에 7.2% 감소하였으며 강우 3일째에 8.4% 감소하였다. 총 가소화 영양분(TDN) 함량과 상대사료가치(RFV)는 강우일수가 늘어날수록 감소하는 것으로 나타났으며 강우 1일째에는 감소폭이 작은 반면 강우 3일째에는 감소폭이 더욱 커지는 것으로 나타났다. 예취 직후 강우일수에 의한 이탈리안 라이그라스의 사료가치는 전체적으로 감소하나 강우 1일째의 품질 감소폭이 작기 때문에 비가 하루나 이틀정도 예상되면 강우 전날 예취하여 비가 그친 후에 반전을 실시하면 건초생산 기간을 단축시킬 수 있을 것으로 사료된다.

• Journal of Oral Medicine and Pain
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• 제25권4호
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• pp.415-425
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• 2000

In order to obtain the basic data concerning the optimal lasing conditions in using Nd:YAG laser as an adjunctive modality of periodontal therapy of root planing without irreversible structural deterioration of cervical cementum, the author selected 36 human teeth having no cervical abrasion and caries (; 12 anteriors, 12 premolars. 12 molars) extracted due to periodontal diseases, and divided them into 4 groups as Group I, II, III and IV (; each group of 3 anteriors, 3 premolars, 3 molars), and prepared a cementum specimen with thickness of $1.0mm{\pm}0.2mm$ sectioned longitudinally at the middle of mesio-distal thickness (; Group I) or horizontally at 1mm-2mm below the cemento-enamel junction (; Group II, III, IV) from each tooth of each group by low speed diamond wheel saw, and treated them with 0.5 M ethylene diamine tetraacetic acid (; EDTA, pH=7.4) for 2 minutes for elimination of remnants during tooth-sectioning. And the author applied the laser energy from a fiberoptic delivered, free running, pulsed Nd:YAG laser (; wavelength 1064nm. pulse duration $120{\mu}sec$, fiber diameter $320{{\mu}m}$) to cementum surfaces in triplicates of one experiment under the following lasing conditions: 1. stationary mode of fiber in contact to cementum surfaces without air-spray (; Group I )/with air-spray (; Group II), 2. unidirectional moving mode of fiber in contact to cementum surfaces under speed of 3mm-4mm/sec without air-spray (; Group III)/with air-spray (; Group IV), 3. energy per pulse (mJ/pulse) [; energy density ($J/cm^{2}$)] in order of 1.0W/10Hz (100J/pulse); $124J/cm^{2}$, 0.5W/10Hz (50mJ/pulse); $62J/cm^{2}$, 0.4W/10Hz (40mJ/pulse); $50J/cm^{2}$, 0.3W/10Hz (30mJ/pulse); $37J/cm^{2}$, 4. exposure time of 1 second. And the author applied the platinum coating on surfaces of cementum specimens, and evaluated the characteristics of ultrastructural change on surfaces of cementum using the scanning electron microscopy. In general the ultrastructural loss of cervical cementum irradiated under the same lasing condition of laser energy density occurred least in specimens of Group IV. And especially, the ultrastructural loss of cervical cementum irradiated under the laser energy density of $37J/cm^{2}$ almost did not occur in specimens of Group IV. Therefore, it is considered that the pulsed Nd:YAG laser should be applied with the lasing conditions of unidirectional moving mode of fiber in contact to cementum surfaces under speed of 3mm-4mm/sec with air-spray and of laser energy density within $37J/cm^{2}$ as an adjunctive modality of periodontal therapy of root planing without irreversible structural deterioration of cervical cementum.

• Advances in nano research
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• 제16권2호
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• pp.127-140
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• 2024

Upon direct/indirect exposure to flame or heat, composite structures may burn or thermally buckle. This issue becomes more important in the natural fiber-based composite structures with higher flammability and lower mechanical properties. The main goal of the present study was to obtain an optimal eco-friendly composite system with low flammability and high thermal buckling resistance. The studied composite consisted of polypropylene (PP) and short abaca fiber (AF) with eggshell powder (ESP) and halloysite clay nanotubes (HNTs) additives. An optimal base composite, consisting of 30 wt.% AF and 70 wt.% PP, abbreviated as OAP, was initially introduced based on burning rate (BR) and the Young's modulus determined by horizontal burning test (HBT) and tensile test, respectively. The effects of adding ESP to the base composite were then investigated with the same experimental tests. The results indicated that though the BR significantly decreased with the increase of ESP content up to 6 wt.%, it had a very destructive influence on the stiffness of the composite. To compensate for the damaging effect of ESP, small amount of HNT was used. The performance of OAP composite with 6 wt.% ESP and 3 wt.% HNT (OAPEH) was explored by conducting HBT, cone calorimeter test (CCT) and tensile test. The experimental results indicated a 9~23 % reduction in almost all flammability parameters such as heat release rate (HRR), total heat released (THR), maximum average rate of heat emission (MARHE), total smoke released (TSR), total smoke production (TSP), and mass loss (ML) during combustion. Furthermore, the combination of 6 wt.% ESP and 3 wt.% HNT reduced the stiffness of OAP to an insignificant amount by maximum 3%. Moreover, the char residue analysis revealed the distinct differences in the formation of char between AF/PP and AF/PP/ESP/HNT composites. Afterward, dilatometry test was carried out to examine the coefficient of thermal expansion (CTE) of OAP and OAPEH samples. The obtained results showed that the CTE of OAPEH composite was about 18% less than that of OAP. Finally, a theoretical model was used based on first-order shear deformation theory (FSDT) to predict the critical bucking temperatures of the OAP and OAPEH composite plates. It was shown that in the absence of mechanical load, the critical buckling temperatures of OAPEH composite plates were higher than those of OAP composites, such that the difference between the buckling temperatures increased with the increase of thickness. On the contrary, the positive effect of CTE reduction on the buckling temperature decreased by raising the axial compressive mechanical load on the composite plates which can be assigned to the reduction of stiffness after the incorporation of ESP. The results of present study generally stated that a suitable combination of AF, PP, ESP, and HNT can result in a relatively optimal and environmentally friendly composite with proper flame and thermal buckling resistance with no significant decline in the stiffness.

• 대한의생명과학회지
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• 제12권1호
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• pp.9-16
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• 2006

We investigated the effects of 835-MHz electromagnetic field (EMF), one of the most popular communication frequency band in Korean code-division multiple-access (CDMA) mobile phone system, on cellular signal transduction. For this, we examined the change of intracellular calcium $([Ca^{2+}]_i)$, reactive oxygen species (ROS) and F-actin polymerization after exposure to 835-MHz EMF followed by the treatment of agonists in Rat-2 fibroblast cells. Culture cells were pretreated with serum-tree medium and concomitantly exposed to 835-MHz at specific absorption rate (SAR) of 4.0 W/kg for 24 hr in a specialized designed apparatus based on Transverse Electro Magnetics (TEM) wave theory. Intracellular $Ca^{2+}$ responses to lysophosphatidic acid (LPA) and epidermal growth factor (EGF) in Rat-2 fibroblast after exposure to 835-MHz EMF were shown to be similar pattern as observed in normal cultured cells. However, the LPA-induced calcium spiking was slightly delayed to 7 sec and sustained thereafter to a little higher ground level under 835-MHz EMF radiation compared to unexposed cells. ROS production level by LPA in the exposed cells was not different from that in control. Furthermore, LPA induced the production of stress fibers with no significant difference in the exposed and unexposed cells. These results suggest that mobile phone radiation (835-MHz, SAR 4.0 W/kg) may not be directly related to signal transduction in Rat-2 fibroblasts except the slight effect of calcium spiking in LPA-induced cells but remain to be further elucidated for possible indirect intervention.

• 한국구조물진단유지관리공학회 논문집
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• 제18권5호
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• pp.51-58
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• 2014

본 연구에서는 철근콘크리트 구조의 FRP를 이용한 보강에서 낮은 내화성능을 개선하기 위한 방안을 찾기 위하여, 보강된 FRP의 외부를 내화보강하는 방법에 대한 내화실험을 실시하였다. 특히 철근콘크리트 부재의 피복에 홈을 형성하여 FRP를 매입하는 보강 즉, NSM 보강을 대상으로 하였다. 실험에서의 주요 변수는 보강방법과 사용 내화재료로서, Perlite계 재료를 표면에 분사하여 보강하는 방법, Calcium silicate계 보드로 표면에 부착하는 방법, 그리고 추가로 홈내부에 Polymer mortar 또는 Calcium silicate조각을 삽입하여 보강하는 방법으로 보강한 뒤 가열로 내부의 온도변화에 따른 열전달을 관찰하였다. 실험결과, Perlite계 내화뿜칠로 표면을 보강하는 경우보다 Calcium Silicate계 내화보드로 표면을 보강하는 방법이 효과적인 것으로 나타났다. 홈 내부의 에폭시가 유리전이온도에 도달할 때의 외부 표면온도 $820^{\circ}C$까지 내화단열성능을 확보할 수 있는 것으로 나타났다.

• 한국구조물진단유지관리공학회 논문집
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• 제16권3호
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• pp.1-10
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• 2012

FRP 재료는 높은 부식저항성과 강도에도 불구하고 지난 20여년 동안 심각한 환경적 노출에 의한 재료의 성능저하에 대한 문제가 제기되어 왔다. 본 연구에서는 섬유와 수지로 구성된 이질재료인 FRP보강근이 온도와 화학적 노출을 복합적으로 받는 경우에 대하여 실험적으로 분석하였다. 각기 다른 형상으로 제작된 탄소, 유리 및 하이브리드 FRP 보강근 5종류에 대하여 중량변화, 계면전단강도(ILSS), SEM 및 FT-IR분석을 수행하였으며, 모든 FRP 실험편은 최대 150일까지 알칼리 용액과 증류수에 침지시킨 다음 60, 100, 150 및 300도의 온도에서 30분동안 노출하였다. 실험결과, 또한 FRP 보강근의 성능저하는 섬유의 종류뿐 아니라 수지의 종류와 제조과정에 따라 영향을 받는 것으로 관찰되었다. 침지 초기에는 ILSS 강도가 약간 증가한 후 시간경과에 따라 강도가 감소하는 것으로 나타났다. 알칼리 용액과 증류수 용액에 의해 손상을 받은 ILSS의 차이는 무시할 수 있는 수준인 것으로 관찰되었다.

• Journal of Periodontal and Implant Science
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• 제23권3호
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• pp.564-576
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• 1993

The purpose of this study was to evaluate the effects of Nd:YAG laser treatment on removal of smear layer and exposure of dentinal tubules. The experimental specimens were obtained from root planed surface of 30 human teeth which were extracted due to severe periodontal disease. The specimens were assigned randomly of three groups: root planed group, Tetracycline HCl(100mg/ml, 5min) group, and Nd:YAG laser ($Laser-35^{TM}$, U.S.A. 5 seconds )group. Nd:YAG laser group was divided into 4 subgroups according to 3.0W, 3.5W, 4.0W, 4.5W of power. The surface change of specimens were evaluated by scanning electron microscopy. The number of exposed dentinal tubules and percentage of area occupied by dentinal tubule orifices per unit area between each group was statistically analyzed by paired Student t-test. The results were as follows: 1. By root planing only, dentinal tubule was not exposed, but scale-like smear layer and parallel instrument tracks were resulted. 2. Tetracycline HCl treated surfaces exhibited the small number of partially exposed dentinal tubules with long orifices. The number($3.80{\pm}0.79$) of exposed dentinal tubules on Tetracycline HCl group was significantly less than that in laser groups above 3.5W of power(P<0.001), and the percentage ($0.68{\pm}0.19$) of area occufied by dentinal tubule orifices per unit area($192\;{\mu}m^2$) was significantly lower than that of any laser group(P<0.001). 3. The laser group irradiated with 4.5W of power showed both the most number($10.60{\pm}0.97$) of exposed dentinal tubules among the experimental groups, and the highest percentage($3.75{\pm}0.55\;%$) of area occupied by dentinal tubule orifices. 4. Energy Surge during laser pulsing and overlapping passes of the fiber resulted in melted and resolidified surface textures with lava-like appearance.

• 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.

• Biotechnology and Bioprocess Engineering:BBE
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• 제6권2호
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• pp.133-138
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• 2001

In this study, an attempt was made to increase the survival rate of bifidobacteria entrapped in alginate in the gastrointestinal tract, and to investigate the potential industrial applications, for example lyophilized capsules and yogurt. First, the protective effect of various food additives on bifidobacterial survivability was determined after exposure to simulated gastric juices and bile salts. The additives used in this study were skim milk (SM), polydextrose (PD), soy fiber (SF), yeast extract (YE), chitosan (CS), $\kappa$-carageenan ($\kappa$-C) and whey, which were added at 0.6% concentration (w/v) to 3% alginate-bifidobacterial solution. In the simulated gastric juices and bile salts, the protective effect of 0.6% skim milk-3% alginate (SM-A) beads on the survival rate of bifidobacteria proved to be higher than the other additives. Second, the hydrogen ion permeation was detected through SM-A vessel without bifidobacterial cells at different SM concentrations (0.2%, 0.4%, 0.6%, 0.8%, and 1.0%). There were no differences in terms of the pH decrease in SM-A vessels at 0.6%, 0.8%, and 1.0% (w/v) SM concentrations. The survival rate of bifidobacteria in SM-A beads would appear to be related to the SM buffering capacity against hydrogen ions and its tendency to reduce the pore size of bead. In this experiment, the survival rate of bifidobacteria entrapped in beads containing 0.6% SM showed the highest viability after exposure to simulated gastric juices for 3h, thereby indicating that 0.6% SM is the optimum concentration fir 3% alginate bead preparation. Third, the effect of SM-A beads on the freeze-drying and yogurt storage for 10 days was investigated. SM-A beads were found to be more efficient for freeze drying and yogurt storage than untrapped cells and the alginate bead. Consequently, the survival rate of bifidobacteria entrapped in SM-A beads was increased in simulated gastric juices, bile salts and probiotic products, such as lyophilized capsules and yogurt, SM-A beads can be expected to produce high value probiotic products.

• 실내환경 및 냄새 학회지
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• 제17권4호
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• pp.330-336
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• 2018

The objective of this study was to determine whether crops and fruits absorb the naturally occurring asbestos (NOA). The concentration of asbestos in various crops and fruits grown in NOA areas was analyzed and background levels of asbestos in ambient air and soil samples were assessed. Actinolite/Tremolite asbestos were detected in all soil samples. Among 21 ambient air samples, 2 samples were recorded to contain 0.0005 f/cc (fiber per cubic centimeter) but no asbestos was detected in the other samples using transmission electron microscopy (TEM). However, no evidence suggesting that the crops and fruits could be contaminated by NOA was found in this study. The excess lifetime cancer risks (ELCRs) of ABS scenarios (agricultural activities) used in this study were calculated by using the Arithmetic (AM) and Geometric mean (GM) of ELCRs. The AM and GM of ELCRs estimated from digging soil and weeding activities did not exceed $1{\times}10^{-4}$, which was defined as the general acceptable risk range for exposure. The results of this study would be informative to NOA managers and related policy makers to make plans to prevent unexpected exposure to asbestos to residents living in an NOA area.