• Restorative Dentistry and Endodontics
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• v.27 no.6
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• pp.561-568
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• 2002

Purpose of this research is estimating polymerization depth of different source of light. XL 3000 for halo-gen light, Apollo 95E for plasma arc light and Easy cure for LED light source were used in this study. Different shade (B1 & A3) resin composites (Esthet-X, Dentsply, U.S.A.) were used to measure depth of cure. 1, 2, and 3 mm thick samples were light cured for three seconds, six seconds or 10 seconds with Apollo 95E and they were light cured with XL-3000 and Easy cure for 10 seconds, 20 seconds, or 40 seconds. Vicker's hardness test carried out after store samples for 24 hours in distilled water. Results were as following. 1. Curing time increases from al1 source of lights, oui$.$ing depth increased(p<0.05). 2. Depth (that except 1mm group and 2mm group which lighten to halogen source of light) deepens in all groups, Vickers hardness decreased(p<0.05). 3. Vicker's hardness of A3 shade composite was lower in all depths more than B1 shade composites in group that do polymerization for 10 seconds and 20 seconds using halogen source of light(p<0.05), but group that do polymerization lot 40 seconds did not show difference(p>0.05). 4. Groups that do polymerization using Plasma arc and LED source of light did not show Vicker's hardness difference according to color at surface and 1mm depth(p>0.05), but showed difference according to color at 2mm and 3mm depth(p<0.05). The results showed that Apollo 95E need more polymerization times than manufacturer's recommendation (3 seconds), and Easy cure need polymerization time of XL-3000 at least.

• Polymer(Korea)
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• v.30 no.6
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• pp.538-544
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• 2006

Two kinds of novel bifunctional methacrylated prepolymers (170-2MA and 631-2MA) which have similar structure with 2,2-bis[4- (2'-hynroxy-3'-methacryloyloxypropoxy)phenyl] propane (Bis-GMA) was synthesized for dental applications as an alternative to Bis-GMA containing bisphenol A that is doubtful as an endocrine disrupter. The organic matrices were prepared by mixing a diluent and/or a monomer with the synthesized methacrylated prepolymers. The yield, viscosity, and chemical structures of the prepolymers and the physical and methanical properties of the organic matrices were evaluated. The yields of the prepolymers synthesized through a ring-opening reaction of epoxy compound and methacrylic acid were above 90% and the viscosities of the prepolymers were much lower than that of the Bis-GMA control. From the results of $^1H-NMR$ and FTIR analyses, the chemical structures of the prepolymers were similar to that of Bis-GMA. In addition, the curing time, poly-merization shrinkage, photoconversion, polymerization depth, and compressive strength of the organic matrices formulated with 170-2MA and 631-2MA prepolymers exhibited comparable to or better than those of the existing Bis-GMA-based one. These results suggest that the novel methacrylated prepolymers which have no endocrine disrupter can be an alternative to Bis-GMA and be applicable to dental polymer materials.

• Journal of Periodontal and Implant Science
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• v.34 no.3
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• pp.623-637
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• 2004

중증 만성 치주염과 1L-1B+3954 및 1L-1A+4845 유전자의 대립유전자 2 보유 유전자 다변성이 관련된다고 보고되었다. 그러나 이러한 1L-1 복합유전자 다변성과 만성 치주염 및 급진성 치주염과의 관련성에 대해서는 상반되게 보고되고 있는데 이는 인종적 배경과 질환특성의 차이에 기인한 것으로 보인다. 이 연구는 한국인에서 경도, 중등도와 중증의 만성 치주염 그리고 급진성 치주염 환자를 대상으로 하여 1L-1A+4845, 1L-1B+3954, 1L1B-511, 1L-1 RN intron 2 (VNTR) 유전자 다변성의 분포를 평가하고, 치주질환의 심도와 유형에 관련되는지 알아보고자 시행되었다. 전남대학교 병원 치주과에서 검진과 치료를 받은 100명의 치주질환자를 대상으로 하였고 질환군은 치주낭 깊이, 부착 소실, 골 소실을 기준으로 하여 경도, 중등도, 중증의 만성 치주염, 급진성 치주염군으로 분류하였다. 대조군으로는 전남대학교 병원 소아치과에 내원한 전신적으로 건강한 92명의 아동을 포함하였다. 각 대상 환자에서 채취된 협점막상피에서 genomic DNA를 얻어 1L-1A+4845, 1L-1B+3954, 1L-1B-511 genotype은 중합효소 연쇄반응을 시행한 후 제한 효소분해과정을 거쳐 전기영동 후 분리한 결과를 해석하였으며 1L-1 RN(VNTR) 유전형은 중합효소연쇄반응 후 분리한 결과를 해석하여 다음의 결과를 얻었다. 대립유전자 2 보유자 비율은 치주질환자에서 1L-1A+4845, 1L-1B+3954, 1L-1B-511, 1L-1 RN이 각각 61%, 13%, 76.6%, 34%였으며 대조군에서는 76.9%, 7.7%, 62.2%, 19.1%였다. 1L-1B+3954과 1L-1A+4845 대립유전자 2 보유자인 양성유전자형 비율은 경도, 중등도, 중증의 만성치주염, 급진성 치주염환자에서 각각 10%, 7.9%, 22.2%, 12% 였으며 치주질환자의 13%, 대조군의 7.7%에서 양성 복합유전자형(positive genotype)을 보였다. IL-1B-511 유전자 다변성은 치주질환자에서 대조군에 비하여 높았으며 급진성 치주염환자에서 대립유전자 2 보유자율이 유의하게 높았다(p<0.01). IL-1 RN intron 2 유전자 다변성은 중등도 및 중증 만성 치주염환자에서 대립유전자 2 보유자율이 유의하게 증가하였다. 이러한 결과는 IL-1 gene cluster의 유전형이 한국인에서도 치주염의 유형과 질환 심도에 관련될 수 있음을 시사하였다.

• Geophysics and Geophysical Exploration
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• v.15 no.1
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• pp.8-15
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• 2012

To estimate the S-wave velocity structure beneath the KS31 broad-band station in Wonju, Korea, we used $H-{\kappa}$ stacking and joint inversion of receiver functions and surface-wave dispersion curves derived from 297 teleseismic events (Mw > 5.5) recorded during the period between 2002 and 2009. We thereby determined that the average depth to a nearly flat Moho is $32.4{\pm}0.5\;km$ within tens of kilometer radius of the seismic station. For the crust at this location, we estimate an average shear-wave velocity of 3.69 km/s and a ratio of P- to S-wave velocities, $V_p/V_s$, of $1.72{\pm}0.04$, as is typical for continental crust. A negative phase in the receiver functions at 1 s indicates the presence of a shearwave low velocity layer in a depth interval of 10 to 18 km in the upper crust beneath the KS31 station.

• Journal of Wetlands Research
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• v.11 no.3
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• pp.1-8
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• 2009

The groundwater dependent ecosystem associated with a natural stream is the area where mixing and exchange of surface water and groundwater occurs due to large chemical and hydraulic gradients. Surface-groundwater interactions play an important role in biogeochemical processes in groundwater dependent ecosystems and make this area a hydro-ecological hot spot. The objective of this study is to characterize the groundwater dependent ecosystem in a natural stream where nitrate contamination of stream water is observed by means of hydrogeological, chemical, and biological methods. In this study, vertical flow exchange(hyporheic flow) rates between stream and groundwater were estimated based on vertical hydraulic gradients measured at mini-piezometers of various depths. To investigate the biological natural attenuation potential, biological analyses using polymerase chain reaction(PCR)-cloning methods were performed in this study. Results show that the veritical hyporheic water fluxes affect nitrate concentrations and bacterial densities in groundwater dependent ecosystems to some degree. Also, denitrifying bacteria were identified in hyporheic soils, which may support the biodegradation potential of the groundwater dependent ecosystems under certain conditions.

• Journal of Sensor Science and Technology
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• v.10 no.5
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• pp.314-319
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• 2001

In this study, the highly sensitive $CaSO_4$:Tm-PTFE TLDs has been fabricated for the purpose of measurement of high energy electron. $CaSO_4$:Tm phosphor powder was mixed with polytetrafluoroethylene(PTFE) powder and moulded in a disk type(diameter 8.5mm, thickness $90mg/cm^2$) by cold pressing. The batch uniformities were average deviation 3.1%. The TLDs were applied to measurement of absorbed dose distribution for high energy electron, the ranges were determined to be $R_{100}=14.5mm$, $R_{50}=24.1mm$ and $R_p=31.8mm$, respectively. The beam flatness were 4.5% as the variation of dose relative to the central axis over the central 80% of the field size at a maximum dose depth in a plane perpendicular to the central axis.

• Geophysics and Geophysical Exploration
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• v.5 no.1
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• pp.18-22
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• 2002

As a single arrival traveltime, maximum energy arrival traveltime has been known as the most proper operator for Kirchhoff migration. In case of the model having the simple structure, both the first arrival traveltime and the maximum energy arrival traveltime can be used as the correct operators for Kirchhoff migration. However for some model having the complex and high velocity contrast structure, the migration using the first arrival traveltime can't give the correct depth section. That is, traveltime to be required in Kirchhoff migration is the maximum energy traveltime, but, needs considerably more calculation time than that of first arrival. In this paper, we propose the method for calculating the traveltime approximated to the maximum energy arrival using one-way wave equation. After defining the WAS(Wrap Around Suppression) factor to be used for calculating the first arrival traveltime using one-way wave equation as the function of lateral grid interval and depth and considering the delay time of source wavelet. we calculate the traveltime approximated to the maximum energy arrival. to verify the validity of this traveltime, we applied this to the migraion for simple structure and complex structure and compared the depth section with that obtained by using the first arrival traveltime.

• Journal of the korean academy of Pediatric Dentistry
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• v.28 no.3
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• pp.403-411
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• 2001

The aim of this study was to evaluate the resistance to degradation of four commercial composite resins in an alkaline solution. The brands studied were Unifil(GC, Japan), Palfique(Tokuyama Japan). Definite$Degussa-H\ddot{u}ls$ AG, Germany). Revolution(Kerr, U.S.A.). Preweighed discs of each brand were exposed 0.1N NaOH solution at $60^{\circ}C$. After 14 days they were removed, neutralized with HCl, washed with water and dried. Resistance to degradation was evaluated on the basis of following parameters: (a) mass loss(%) - determined from pre-and post-exposed specimen weights; (b) Si loss(ppm) - obtained from ICP-AE analysis of solution exposed to specimens; and (c) degradation depth$({\mu}m)$ - measured microscopically (SEM) from polished circular sections of exposed specimens. The results were follows: 1. The mass loss of Unifil was 3.21%, it was the highest of materials. But, there was no significant difference among the materials. 2. The degree of degradation layer depth was $107.69\sim47.40{\mu}m$, the sequence of the degree pf degradation layer depth was in descending order by Unifil, Palfique, Revolution, Definite. There was significant difference among the materials except Palfique and Definite. 3. The Si loss of Paltique was 8940.0ppm, it was the highest. There was significant difference among the materials, except Revolution and Definite(p<0.05). 4. The correlation coefficient between mass loss and degradation depth was relatively high(r = 0.06, p<0.05). 5. There was no significant coefficient correlation between Si loss and mass loss, and/or the degree of degradation layer depth and Si loss. 6. When observed with SEM, destruction of bonding is observed between resin matrix and filler. Above results suggested that the hydrolytic degradation is considered as evaluation factor of composite resins.

• Journal of the Korean Institute of Gas
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• v.8 no.2 s.23
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• pp.15-27
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• 2004

The purpose of this paper is to improve the performance of Polymer electrolyte fuel cell(PEMFC) by studying the channel dimension of bipolar plates using commercial CFD program 'Fluent'. Simulations are done ranging from 0.5 to 3.0mm for different size in order to find the channel size which shoves the highst hydrogen consumption. The results showed that the smaller channel width, land width, channel depth, the higher hydrogen consumption in anode. When channel width is increased, the pressure drop in channel is decreased because total channel length Is decreased, and when land width is increased, the net hydrogen consumption is decreased because hydrogen is diffused under the land width. It is also found that the influence of hydrogen consumption is larger at different channel width than it at different land width. The change of hydrogen consumption with different channel depth isn't as large as it with different channel width, but channel depth has to be small as can as it does because it has influence on the volume of bipolar plates. however the hydrogen utilization among the channel sizes more than 1.0mm which can be machined in reality is the most at channel width 1.0, land width 1.0, channel depth 0.5mm and considered as optimum channel size. The fuel cell combined with 2cm${\times}$2cm diagonal or serpentine type flow field and MEA(Membrane Electrode Assembly) is tested using 100W PEMFC test station to confirm that the channel size studied in simulation. The results showed that diagonal and serpentine flow field have similarly high OCV and current density of diagonal (low field is higher($2-40mA/m^2$) than that of serpentine flow field under 0.6 voltage, but the current density of serpentine type has higher performance($5-10mA/m^2$) than that of diagonal flow field under 0.7-0.8 voltage.

• Journal of Periodontal and Implant Science
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• v.28 no.4
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• pp.659-678
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• 1998

In the present study, oligonucleotide probes based on 16S rRNA were taken to investigate the diversity of oral spirochetes without culture method. This is the first study that revealed oral spirochetes of both presently cultivable and uncultured oral spirochetes in Korean adult periodontitis patients. Subgingival plaque samples were taken from diseased sites(probing depth ${\geq}6\;mm$, experimental group, n=116) and healthy sites(probing depth${\leq}3mm$, control 1 group, n=28) in 29 patients with adult periodontitis, and from 20 periodontally healthy subjects(probing depth${\leq}3mm$, control 2 group, n=100). Following being examined under phase-contrast microscope, all samples were submitted to dot-blot hybridization after polymerase chain reacton with eubacterial primers. 5 species-specific probes(TVIN, TDEN, TMAL, TSOC, and TPEC) and 7 group-specific probes(TRE I, TRE II, TRE III, TRE IV, TRE V, TRE VI, and TRE VII) were used one by one for the identification of both cultivable and so far uncultivable oral spirochetes. All probes were labeled with digoxigenin(DIG)-ddUTP and detected by chemilumininescence. The following results were obtained. 1. Under phase-contrast microscope, 91.37% and 14.28% of oral spirochetes were observed in the experimental and control 1 groups, respectively. None of oral spirochetes were observed in control 2 group. 2. With universal probe, 98.27%, 46.42%, and 22.0% of oral spirochetes were observed in experimental, control 1, and control 2 groups, respectively. 3. With specific probe, 95.68%, 35.71%, and 19.0% of oral spirochetes were observed in experimental, control 1, and control 2 groups, respectively. 4. With species-specific probes, T. socranskii were recovered in a high percentage of sites(81.89%) examined, followed by T. maltophilum(50.0%), T. vincentii(36.20%), T. denticola(13.79%), respectively. With group- specific probes, TRE IV was recovered in a high percentage of sites(85.34%) examined, followed by TRE II(77.58%), TRE I(56.89%), TRE III(25.86%), TRE VI(5.17%), and TRE V(2.58%), respectively. 5. T. vincentii were only observed in the diseased sites, not in the healthy sites. 6. Neither T. pectinovorum nor group VII oral spirochetes were observed in any sites. The findings warrant further investgations of the recovered spirochetes to elucidate the possible associations of oral spirochetal prevalence in race and types of periodontitis, pathogenesis of T. vincentii and the possible distributional change of oral spirochetes before and after treatments.