• Restorative Dentistry and Endodontics
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• 제12권2호
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• pp.101-108
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• 1987

The purpose of this study was to investigate the pulpal responses of dental adhesive resins. A total of 40 cavities of the permanent healthy teeth from 4 dogs were prepared. In the experimental group, the cavities were etched for 1 minute with citric acid and filled with experimental resins (ie. Super-Bond C & B$^{(R)}$). In the control group, the cavities were filled with calcium hydroxide base materials (ie. Dycal$^{(R)}$) without etching. The dogs were sacrificed at one, two, three and four weeks after the time of filling and the specimens were routinely prepared and stained with Hematoxylin-Eosin. The microscopic findings were as follows: Infiltration of inflammatory cells was not observed in both experimental and control groups. Change in the odontoblastic layer was not observed in all control groups but severe swelling was observed in deep dental pulp tissue of the control two and three week cases. Pulp tissue was recovered with plenty of fibrous component in the control four week case and reparative dentin formation was not occurred in all cases. Slight changes of the odontoblastic layer beneath the cavity were observed in the experimental one week case. In experimental two and three week cases, swelling of deep pulp tissue was increased and localized reparative dentin formation was observed. In the experimental four week case, odontoblastic layer was recovered with regular appearance and fibrous component of the pulp was increased, but reparative dentin formation was not evident.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제26권2호
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• pp.146-153
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• 2000

The purpose of present study is comparing the effect of Teflon Membrane and Nylon Membrane on bone regeneration in rabbit tibia. The 6 defects of $8{\times}8{\times}5mm$ size were drilled with dental handpiece in rabbit tibia, which on left side as an order of Control group(no coverage), Group 1(Nylon $5{\mu}m$ size), Group 3(Nylon $10{\mu}m$ size), and on right side Control group, Group 2($5{\mu}m$ Teflon), Group 4($10{\mu}m$ Teflon). Animals were killed at 7, 10, 14, 42 days to make specimens and observed the difference of healing potentials with light microscopy. The results were as follows ; 1. New bone formation has taken place at 14 days in Guided Bone Regeneration (GBR) group comparing to the Control group of massive inflammatory status. 2. Larger pore membrane allows more favorable healing potentials. Bone formation started earlier in larger membrane pore groups than smaller groups, until 14 days. 3. Bone forming potentials of Teflon membrane group was higher than Nylon membrane groups, Control group has the lowest bone forming potentials. 4. New bone formation was almost ended in 42 days, and there was no difference of bone formation between Nylon and Teflon membrane group of different size. There was no difference of bone formation at final stage(42 days) between Nylon membrane and Teflon membrane of same pore size. So nylon membrane may be clinically usable in guided bone regeneration case with further studies.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제31권3호
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• pp.228-238
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• 2005

Purpose: Several cryoprotectants are in use to help the survival of cells during cryopreservation of bone in maxillofacial region. Among them, $Me_2SO$(dimethyl sulfoxide), EG(ethylene glycol), sucrose were used for experimentally created defects with accompanying cryopreserved bone graft in the rabbit model. The aim of this study is to analyze the effect of above mentioned agents on bone formation using histologic and histomorphometrical methods, thus to provide experimental support for clinical application of these agents. Materials and methods: Nine rabbits were used as experimental animals. Surgical defects were created on the distal femoral heads and mesial tibial heads of each animal using trephine drill(5mm diameter and 5mm length). The harvested bones were cryopreserved in $-80^{\circ}C$ refrigerator for one week. The defects were filled with cryopreserved bone with cryoprotectants as experimental groups and cryopreserved bone without cryoprotectant as control. Then, the animals were sacrificed at 1, 2, and 3 weeks after surgery. With Goldner's modified Masson trichrome staining and semiautomatic image analysis system, we observed the change of the cells and bone formation. Results: After bone graft, bone formation and active remodeling process were examined in all experimental groups and the control. But the intensity of such activities of the control were somewhat weaker than that of the experiments. Especially $Me_2SO$+sucrose group was the best in bone formation and bone remodeling. $Me_2SO$ group was more than that of EG group in bone fomation. Sucrose seems to be helpful in survival of the bone cell. Histologic findings showed superior bony quantity and quality in experimental groups than that in control. Conclusions: The data from this study provides the basis for future studies for evaluating the effect of cryoprotectants in the cryopreservation of bone and clinical study for predictable use of these agents.

• Journal of Astronomy and Space Sciences
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• 제35권3호
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• pp.163-173
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• 2018

This paper presents relative navigation using intermittent laser-based measurement data for spacecraft flying formation that consist of two spacecrafts; namely, chief and deputy spacecrafts. The measurement data consists of the relative distance measured by a femtosecond laser, and the relative angles between the two spacecrafts. The filtering algorithms used for the relative navigation are the extended Kalman filter (EKF), unscented Kalman filter (UKF), and least squares recursive filter (LSRF). Numerical simulations reveal that the relative navigation performances of the EKF- and UKF-based relative navigation algorithms decrease in accuracy as the measurement outage period increases. However, the relative navigation performance of the UKF-based algorithm is 95 % more accurate than that of the EKF-based algorithm when the measurement outage period is 80 sec. Although the relative navigation performance of the LSRF-based relative navigation algorithm is 94 % and 370 % less accurate than those of the EKF- and UKF-based navigation algorithms, respectively, when the measurement outage period is 5 sec; the navigation error varies within a range of 4 %, even though the measurement outage period is increased. The results of this study can be applied to the design of a relative navigation strategy using the developed algorithms with laser-based measurements for spacecraft formation flying.

• 한국항공우주학회지
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• 제39권11호
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• pp.1042-1051
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• 2011

본 논문에서는 복수 무인기의 편대 비행을 위한 탑재 무선 통신 및 임무통제 네트워크 (지상관제시스템)를 포함하는 통합 운영 시스템의 구성 방안을 제시한다. 이를 위해 편대비행을 위한 무인기에 탑재되는 시스템들의 구성 형태에 따라 다양한 운영 시스템들을 분류하였다. 또한 각각의 운영 시스템에 대한 장단점 및 고장에 대한 신뢰성을 파악하였다. 이 결과를 바탕으로 편대기의 임무비행을 수행하는데 있어 적절한 운영 시스템의 형태를 결정하고 구성 요소들을 개발하였다. 제안된 운영 시스템을 이용하면, 이종의 비행체로 편대를 구성할 수 있으며, 복잡한 임무를 여러 무인기에 나누어 수행 가능하고, 단일 임무의 협업 또는 다양한 임무의 동시 수행이 가능하다.

• Journal of Astronomy and Space Sciences
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• 제26권1호
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• pp.59-74
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• 2009

Relative navigation system is presented using GPS measurements from a single-channel global positioning system (GPS) simulator. The objective of this study is to provide the real-time inter-satellite relative positions as well as absolute positions for two formation flying satellites in low earth orbit. To improve the navigation performance, the absolute states are estimated using ion-free GRAPHIC (group and phase ionospheric correction) pseudo-ranges and the relative states are determined using double differential carrier-phase data and singled-differential C/A code data based on the extended Kalman filter and the unscented Kalman filter. Furthermore, pseudo-relative dynamic model and modified relative measurement model are developed. This modified EKF method prevents non-linearity of the measurement model from degrading precision by applying linearization about absolute navigation solutions not about the priori estimates. The LAMBDA method also has been used to improve the relative navigation performance by fixing ambiguities to integers for precise relative navigation. The software-based simulation has been performed and the steady state accuracies of 1 m and 6 mm ($1{\sigma}$ of 3-dimensional difference errors) are achieved for the absolute and relative navigation using EKF for a short baseline leader/follower formation. In addition, the navigation performances are compared for the EKF and the UKF for 10 hours simulation, and relative position errors are mm-level for the two filters showing the similar trends.

• Journal of Periodontal and Implant Science
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• 제30권1호
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• pp.27-39
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• 2000

To evaluate the effects of Dexamethasone(Dex), Platelet derived growth factor-BB(PDGF) and combination of Dex and PDGF(DP) on the growth and differentiation of MC3T3-E1 cells, Dex($10^{-7}\;M$) and PDGF(10 ng/ml) in experimental group were added to the cells at the days 5, 10, 15, 20, 25 and examined for cell proliferation activities, DNA synthesis activities, ALP activities and bone nodule formation. The results were as follows : 1. In Dex group, cell proliferation, DNA synthesis and ALP activities were lower until 15 days when compared to the control group. Bone nodules formation were shown at 10 days. 2. In PDGF group, cell proliferation and DNA synthesis activities were higher until 15 days and ALP activities were lower when compared to the control and Dex groups. Bone nodules formation were shown at 20 days. 3. In DP group, cell proliferation and DNA synthesis activities of PDGF were suppressed by Dex and synergistic effects of combination of Dex and PDGF on ALP activities were shown at days 5 when compared to control and Dex groups. Bone nodules formation activities of Dex were suppressed by PDGF.

• Journal of Animal Science and Technology
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• 제59권2호
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• pp.4.1-4.5
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• 2017

Background: Biofilms were the third-dimensional structure in the solid surface of bacteria. Bacterial biofilms were difficult to control by host defenses and antibiotic therapies. Escherichia coli (E. coli) and Salmonella were popular pathogenic bacteria that live in human and animal intestines. Essential oils are aromatic oily liquids from plant materials and well known for their antibacterial activities. Method: This study was conducted to determine effect of essential oil on anti-biological biofilm formation of E. coli and Salmonella strains in in vitro experiment. Two kinds of bacterial strains were separated from 0.2 g pig feces. Bacterial strains were distributed in 24 plates per treatment and each plates as a replication. The sample was coated with a Bacterial biofilm formation was. Result: Photographic result, Escherichia coli (E. coli) and Salmonella bacteria colony surface were thick smooth surface in control. However, colony surface in blended and single essential oil treatment has shown crack surface layer compared with colony surfaces in control. Conclusion: In conclusion, this study could confirm that essential oils have some interesting effect on anti-biofilm formation of E. coli and Salmonella strains from pig feces.

• 한국항공우주학회지
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• 제36권6호
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• pp.565-573
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• 2008

본 연구에서는 다수 무인기의 군집비행을 위한 행위기반 분산형 제어기법을 제안한다. 각 무인기는 특정한 영역으로 비행해야하는 고유의 임무와 동시에 무인기 간의 거리를 유지해야하는 요구조건도 가지고 있다. 이러한 두 가지 요구조건은 서로 상충된다. 제어기를 설계하기 위하여 각 무인기가 통신채널을 통하여 상태변수를 교환할 수 있다는 가정 하에 결합형 동역학을 적용하였다. 군집비행의 성능을 개선하기 위하여 제어이득 행렬의 최적화를 수행하였다. 제어기의 성능을 평가하기 위하여 다수 무인기의 경로점 통과 임무를 위한 수치 시뮬레이션을 수행하였다.

• International Journal of Oral Biology
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• 제45권4호
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• pp.143-151
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• 2020

Streptococcus mutans and Streptococcus sobrinus play important roles in dental caries. Coptis chinensis is a natural product with antimicrobial activity against enterobacteria; however, its effects on oral streptococci are still unknown. Therefore, the effects of C. chinensis on the growth and biofilm formation of the representative cariogenic bacteria S. mutans and S. sobrinus were investigated for the possible use of C. chinensis as an anticaries agent. The C. chinensis extract was diluted with sterile distilled water, and 0.1-2.5% of the extract was used in the experiment. The effects of the C. chinensis extract on the growth and glucan formation of S. mutans and S. sobrinus were measured by viable cell counting and spectrophotometry at 650 nm absorbance, respectively. Crystal violet staining was also carried out to confirm the C. chinensis extract's inhibitory effect on biofilm formation. The C. chinensis extract significantly inhibited the growth of S. mutans and S. sobrinus at concentrations of ≥ 0.3% as compared with the control group. The viable cell count of colonies decreased by 1.7-fold and 1.2-fold at 2.5% and 1.25%, respectively, compared with the control group. The biofilm formation of S. mutans and S. sobrinus was inhibited by > 20-fold at C. chinensis extract concentrations of ≥ 1.25% as compared with the control group. In summary, the C. chinensis extract inhibited the growth and biofilm and glucan formation of S. mutans and S. sobrinus. Therefore, C. chinensis might be a potential candidate for controlling dental caries.