• International Journal of Oral Biology
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• 제41권2호
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• pp.63-68
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• 2016

The aim of this study was to investigate the effect of n-3 polyunsaturated fatty acids (PUFAs) on eruptive movement during tooth development. Sprague-Dawley (SD) rat pups were randomly divided into two groups; control group and experimental group. The experimental group was administered daily with n-3 PUFA by intraperitoneal (IP) injection. After 10 days postpartum, rat pups were sacrificed to evaluate the effect of n-3 PUFA on eruptive tooth movement. Histological analyses were by hematoxylin-eosin (H&E) staining. Tartrate-resistant acid phosphatase (TRAP) assay was performed to compare the osteoclast distribution in the bone matrix above the developing molar teeth. Incisor teeth eruptions were noticeably observed in IP group, as compared to control group. Rat pups in IP group showed faster tooth eruption on day 8 after birth. Through histological analyses, IP group showed thinner bone matrix and more osteoclasts above the $1^{st}$ molar teeth, as compared to control group. TRAP assay showed significantly stronger stained pattern that the osteoclast above the $1^{st}$ molar teeth in IP group, as compared to control group. The results suggested that n-3 PUFA could affect osteoclastic activity involved in bony remodeling during eruptive tooth movement.

• 한국분무공학회지
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• 제9권1호
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• pp.21-29
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• 2004

The flow characteristics of a swirl injector were investigated with the variation of the flow condition and geometric dimensions, such as orifice length for considering the viscous effect and tangential entry port area for considering the swirl intensity. The liquid film thickness strongly influencing on the formed drop size of the spray was measured using a new technique. The film thickness measurement technique proposed here, used the attenuation of fluorescence signal near the injector exit. The breakup length that is important for the flame location as well as the spray cone angle which influences on the ignition performance was measured using a backlit stroboscopic photography technique. From the experimental results, it is found that an increase in injection pressure decreased the film thickness and breakup length, and also enlarged the spray cone angle. A decrease in orifice length and tangential entry port area has a similar tendency of thinner film thickness, shorter breakup length and larger spray cone angle. In the present study, we proposed empirical models of the flow characteristics of the swirl injectors.

• 열처리공학회지
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• 제35권5호
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• pp.262-269
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• 2022

In order to process materials such as engineering plastics, which are difficult to mold due to their high strength compared to conventional polymer materials, it is necessary to improve the hardness and strength of parts such as screws and barrels of injection equipment in extrusion system. High-velocity oxygen fuel (HVOF) process is well known for its contribution on enhancement of surface properties. Thus in this study, using the HVOF process, WC coating layers of different thicknesses were bonded to the surface of S30C substrate by controlling the movement speed of the spray nozzle and each property was evaluated to decide the optimization condition. Through the results, the thickness of WC coating layer increased from 0 to 200 ㎛ maximum, along with the decrement of nozzle movement speed and the surface hardness get increased. Especially, the coated layer with the thickness over 180 ㎛ under the nozzle speed 500 mm/s had high hardness than thinner layer. In addition, the amount of wear consumed per unit time was also significantly reduced due to the formation of the coating layer.

• 한국가스학회지
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• 제22권5호
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• pp.53-61
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• 2018

저염수 기반 폴리머공법은 기존의 폴리머공법과 저염수주입공법의 시너지 효과를 통해 오일회수율을 더욱 증진시킬 수 있는 기술로서, 공법의 효율성을 극대화하기 위해서는 폴리머의 특성을 고려한 저염수 설계가 필수적이다. 이에 본 연구에서는 탄산염암 오일 저류층에 저염수 기반 폴리머공법 적용 시, 주입수의 pH와 주입수 내 PDI(Potential Determining Ion) 이온 중 $SO_4{^{2-}}$ 이온이 오일 생산량에 미치는 영향을 규명하고자 하였다. 우선, 주입수의 pH와 주입수 내 $SO_4{^{2-}}$의 농도에 따른 폴리머 분자의 안정성 및 흡착 현상을 분석하였다. 그 결과, 주입수의 pH와 주입수 내 $SO_4{^{2-}}$의 농도에 상관없이, 주입수 내 $SO_4{^{2-}}$가 함유되어 있는 경우 폴리머 용액의 안정성이 확보되었다. 그러나, 폴리머 용액의 정체 현상 분석 결과, 주입수의 pH가 중성인 7일 때에는 $SO_4{^{2-}}$ 이온이 폴리머의 흡착을 방해하여 $SO_4{^{2-}}$의 농도가 높을수록 폴리머 흡착층의 두께가 더 얇은 것으로 나타난 반면에, 주입수가 pH 4로 산성인 경우에는 폴리머 용액을 주입함에 따라 폴리머의 흡착량이 증가하여 폴리머 용액의 유동성이 크게 낮아졌다. 다음으로, 저염수 효과에 의한 습윤도 변환을 살펴본 결과, 주입수가 중성일 때에는 $SO_4{^{2-}}$의 농도가 높을수록 탄산염암 표면에 흡착되어 있던 오일의 탈착이 증가하여 암석의 습윤도가 친유성에서 친수성으로 크게 변환되었다. 반면에, 주입수가 산성일 때에는 용해와 폴리머 흡착의 복합적 작용으로 인해 전체 코어 시스템의 습윤도는 중성일 때에 비해 비교적 덜 변환되는 것으로 나타났다. 이에 따라 $SO_4{^{2-}}$ 농도가 높은 중성의 저염수 기반 폴리머 용액을 주입할 경우 오일 생산량은 저염수주입공법에 비해 최대 12.3% 증진되어 보다 양호한 EOR(Enhanced Oil Recovery) 효과를 얻을 수 있는 것으로 평가되었다.

• Journal of Periodontal and Implant Science
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• 제31권2호
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• pp.389-400
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• 2001

Previous studies have demonstrated an increase in bone mass and density with the use of bisphosphonate in osteoporosis. This agent acts as an inhibitor of osteoclastic activity, and results in increase of net osteoblastic activity. Currently, it has been reported that bisphosphonate has direct effect on osteoblast. This study was designed to evaluate the effect of alendronate on bone regeneration in defect of rat calvaria. The animals used for these experiments were 48 male rats, over 6-8 weeks old. They were divided into three groups according to the dose of alendronate($MK-217^{(R)}$, Merck, USA) administered. After the calvarial defects were surgically created, the rats received a peritoneal alendronate(0.25mg/kg) in group I, a peritoneal alendronate(1.25mg/kg) in group II, and a peritoneal normal saline injection in the control group. Three and six weeks later, blood was sampled and evaluated for alkaline phosphatase activity. The animals were sacrificed for histological observation and histometric analysis of the level of bone formation. The alkaline phosphatase activity was similar in three groups at 3 weeks of experiment. The activity at 6 weeks increased more than twice, compared to 3 weeks, and was slightly higher in group I than the other two groups. In histological observation, all the groups at 3 weeks, osteoblast rimming and new bone formation were observed along the defect margin. At 6 weeks, the defect was almost closed with new and more mature bone, but new bone is thinner than original bone in the central portion of defect. In histometric analysis, group I and II at 3 weeks showed significantly greater new bone formation than the control, and all the groups at 6 weeks showed similar amount of bone formation. These result suggest that alendronate administration in the dose of 0.25mg/kg and 1.25mg/kg promote osseous regeneration.

• 한국표면공학회지
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• 제49권3호
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• pp.316-321
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• 2016

To study emission characteristics for dual-emission tandem organic light emitting display (OLED), we fabricated blue fluorescent OLED according to thickness variation of $MoO_x$ as charge generation layer and Al as cathode. The bottom emission characteristics of OLED with $MoO_x$ 2, 3, 5 nm thickness showed threshold voltage of 9, 7, 9 V, maximum current emission efficiency of 19.32, 23.18, 15.44 cd/A and luminance of $1,000cd/m^2$ at applied voltage of 17.6, 13.2, 16.5 V, respectively. The top emission characteristics of OLED with $MoO_x$ 2, 3, 5 nm thickness indicated threshold voltage of 13, 10, 13 V, maximum current emission efficiency of 0.17, 0.23, 0.16 cd/A and luminance of $50cd/m^2$ at applied voltage of 22.6, 16.5, 20.1 V, respectively. In case of thicker or thinner than $MoO_x$ of 3 nm, the emission characteristics were decreased because of mismatching of electron and hole in emission layer. The bottom emission characteristics of OLED with Al 15, 20, 25 nm thickness showed threshold voltage of 8, 8, 7 V, maximum current emission efficiency of 18.42, 22.98, 23.18 cd/A and luminance of $1000cd/m^2$ at applied voltage of 16.2, 13.9, 13.2 V, respectively. The reduction of threshold voltage and increase of maximum current emission efficiency are caused by the increase of current injection according to increase of Al cathode thickness. The top emission characteristics of OLED with Al 15, 20, 25 nm thickness indicated threshold voltage of 7, 7, 8 V, maximum emission luminance of 371, 211, $170cd/m^2$, respectively. The top emission OLED of Al cathode with 15 nm thickness showed maximum luminance and it decreased at thickness of 20 nm. These phenomena are caused by the decrease of intensity of emitted light by reduction of optical transmittance according to increase of Al cathode thickness.

• 생명과학회지
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• 제14권6호
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• pp.975-985
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• 2004

발생기 횐쥐 대뇌피질 발생의 형태적 변화와 이에 미치는 ECEE 영향을 구명하기 위해, 태생 14일, 태생 18일, 생후 수유기 및 이유기와 성체 대뇌를 각 부위로 나누어 H-E 염색으로 관찰하였다. EGEE 투여시 태생 14일에 대뇌피질의 두께는 두정엽피질이 제일 두꺼웠으나$(95{\pm}12.7\;{\mu}m)$, 대조군$(102{\pm}14.0\;{\mu}m)$에 비해 얇았고, 다른 피질에 비해 후두엽피질$(57{\pm}10.5\;{\mu}m)$이 제일 얇았다. 각 엽의 두께는 수유기 때에 급성장하는 경향을 나타내었으나, 이유기 이후 성장이 둔화되어 성체기 때와 유사했으며, 성체기 때는 두정엽피질$(93.4{\pm}21.6\;{\mu}m)$에서 가장 많이 성장하였다. EGEE 투여시 대뇌피질내 신경모세포의 수는 태생 14일 두정엽피질의 외투층에서 제일 많았으나$(207.7{\pm}11.4/10^{-2}\;mm$, 대조군에 비해 감소되었고$(224.2{\pm}13.8/10^{-2}\;mm$, 크기는 출생후 3일 후두엽피질의 뇌실막세포층에서 제일 크게 나타났으나$(7.5{\pm}1.3\;{\mu}m)$), 대조군$(9.0{\pm}1.2\;{\mu}m)$에 비해 감소되었다. 대조군과 같이 과립세포와 추체세포의 수는 두정엽피질의 II층과 III층에서 가장 많았으나, 대조군에 비해 감소되었고, 크기는 후두엽피질의 IV층과 V층에서 가장 컸으나, 대조군에 비해 감소되었다. EGEE 투여시 대조군과 같이 태생기와 출생후 3일까지의 대뇌피질은 뇌실막세포층, 외투층, 연변층의 3층으로 분화되나, 조직내 빈 강소와 공포가 나타나고, 신경모세포가 합착된 양상이 나타났다. 출생후 5일이후 수유기 때 대뇌피질층은 대조군과 동일하게 4층으로 나눌 수 있으나, 과립세포와 추체세포 내에 빈 강소나 공포가 나타났고, 신경세포의 수는 감소하였다. 이유기와 성체기 때는 대뇌피질의 세포층 구분이 뚜렷하지 않고, 외과립세포, 외추체세포들이 섞여 조직내 빈 강소나 공포가 형성되며, 신경세포 주위 혈관의 내강이 확대되거나 합착되어 나타났다.