• Proceedings of the KACD Conference
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• 2003.05a
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• pp.288-288
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• 2003

1960년대 중반부터 도입된 구치부 복합레진 수복은 복합레진과 접착시스템의 향상된 물성 때문에 구치부 사용에 대한 주목할 만한 결과를 보고하고 있다. 현재는 다수의 1급, 2급 수복물에 복합레진이 적응증으로 기술되며, 사실상 미국치과의사 협회(ADA)도 초기와 중등과 크기의 병소를 보존적 I, II급 와동으로 형성된 뒤 복합레진으로 수복하는 시술의 적절성을 인정하고 있다. ADA는 "복합레진을 유치나 영구치의 I급, II급, V급 수복에 올바르게 적용하면 아발감의 수명에 뒤지지 않는다."라고 기술하고 있다. 이에 본 강연에서는 I급과 II급 복진레진 수복을 위한 관련된 재료들의 특성과 단점들을 극복하기 위한 노력들을 설명하고자 한다. 특히 중합수축과 관련된 문제점들을 해결하기 위해 제시되고 있는 방법들의 임상적 적용 가능성의 한계와 술후 과민증을 줄이기 위한 방법, 그리고 구치부에 적용된 레진들의 마모를 줄일 수 있는 방법들을 모색하고 한다. 더불어 구치부 복합레진 수복을 위한 임상 시술 시 가장 흔하게 발생되는 단조로운 인접면 외형 형성 및 접촉점 개방의 문제점을 인식하고 이를 막기 위한 노력 및 기구들의 사용 조작에 대해 토의해 보고자 한다.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.25 no.6
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• pp.374-385
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• 2013

Sediment particle motions have been numerically simulated over a sinusoidal ripple. Turbulent boundary layer flows are generated by Large Eddy Simulation, and the sediment particle motions are simulated using Lagrangian particle tracking method. Two unsteady flow conditions are used in the experiment by employing two different wave amplitudes while keeping other conditions such as wave period same. As expected, the amount of suspended sediment particles is clearly dependent on the wave amplitude as it is increasing with increasing flow intensity. However, it is also observed that the pattern of suspension may be different as well due to the only different condition caused by wave amplitude. Specially, the time of maximum sediment suspension within the wave period is not coincident between the two cases because sediment suspension is strongly affected by the existence of turbulent eddies that are formed at different times over the ripple between the two cases as well. The role of these turbulent eddies on sediment suspension is important as it is also confirmed in previous researches. However, it is also found the time of these eddies' formation may also dependent on the wave amplitude over rippled beds. Therefore, it has been proved that various flow as well as geometric conditions under waves has to be considered in order to have better understanding on the sediment suspension process over ripples. In addition, it is found that high turbulent energy and strong upward flow velocities occur during the time of eddy formation, which also supports high suspension rate at these time steps. The results indicate that the relationship between the structure of flows and bedforms has to be carefully examined in studying sediment suspension at coastal regions.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.11
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• pp.2126-2135
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• 1992

In order to prevent the decay heat removal system from failure due to air entrainment or free surface vortex in the piping system, a set of simulating experiments for the midloop operation of nuclear power plant was performed. Through these experiments, a relation between the dimensionless numbers, such as submergence H/d, froude number, reynolds number, was found. However, the effect of reynolds number was negligible for the operation conditions of Nuclear power plant. It was also found that the perturbation of the system by the disturbance such as pump start, valve operation, etc., has a strong effect on the free surface vortex. Furthermore, from a view point of reactor safery, a modified inlet device of reducer type is strongly recommendable for the prevention of air entrainment.

• 한국해양학회지
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• v.30 no.3
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• pp.170-183
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• 1995

Eddies and surface current field in the southwestern part of the East Sea were investigated using satellite-tracked drifters, CTD, and ADCP from November 1992 to September 1993. Trajectories of surface drifters provided information for the first time on the meandering motion of the East Korean Warm Current in the Ullung Basin (referred as UB) and clearly indicated the existence of cyclonic and anticyclonic eddies of various scales. Anticyclonic eddies persisting for a relatively long period were observed in UB and the southwestern corner of the Northern (Japan) Basin (SNB), while a cyclonic eddy was found in the coastal area between Sokcho and Donghae during the summer. Analysis shows that the eddy in UB behaved as a stationary eddy at least during the observation period and the cyclonic eddy was closely related to the existence of a cold water mass. The anticyclonic eddy in SNB was larger than that in UB, but much elongated in shape. The eddy in UB is characteristic of major and minor axes of about 120 and 70 km, revolution period of 13.6 days, mean swirl velocity of about 24 cm/s, and mean eddy kinetic energy of 392 cm$\^$2//s$\^$2/. The eddy in SNB is described as follows; major and minor axes of 168 and 86 km, period of 14.9 days, mean swirl velocity of 29 cm/s and mean eddy kinetic energy of 629 cm$\^$2//s$\^$2/. The mean translational speed is about 3 cm/s for both eddies. The agreement of the surface current pattern in UB observed by ADCP with the geostrophic flow pattern may suggest that the eddy in UB was nearly in geostrophic balance. The eddy was found to be strongly bottom-controlled.

• Journal of the korean academy of Pediatric Dentistry
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• v.26 no.3
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• pp.479-485
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• 1999

Materials for posterior teeth includes amalgam, gold inlay and composite resin inlay. Amalgam and gold inlay have unsatisfyine esthetics. And because they simply obturate the cavity preparation, they do not strengthen the remaining tooth structure. Posterior composite resin has become established in recent years. However, its polymerization shrinkage and insufficient wear resistance were the most undesirable characteristic. The physical and mechanical properties of the composite resin inlay are further improved through heat treatment in an oven. The major part of polymerization contraction of the resin inlay takes place be fore cementation, and possible gap formation is only due to shrinkage of the thin layer of resin cement. With the semidirect technique, the inlay material is placed directly in the prepared tooth, and the primary polymerization is made by light activation with a handhold curing unit. Additional curing may take place extraorally with use of different curing ovens. It provides the patient with the benefits of luted restorations without the procedure of indirect lab-made inlay. I report three successfully treated cases by semidirect resin inlay technique. Entire clinical steps are described in detail with some discussions on the outcome.

• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.3
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• pp.325-330
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• 2016

Sea level is upward trend since the end of 19th century, it is accelerating after 20th century. Because sea level height has regional differences, we concerned sea level change in Korean Peninsula. We used Topex/Poseidon, Jason-1 and Jason-2 satellite altimetry data which has $1/4^{\circ}$ resolution. From 1993 to 2013, for 21 years, monthly mean sea level anomaly was negative between January and April, positive between March and October. Bohai Bay in China, affected the continental climate, showed big sea level changes. Mean sea level data showed remarkably affecting the continental climate in Bohai Bay in China, the Kuroshio Current and eddy affects the sea level change.

• Fire Science and Engineering
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• v.23 no.1
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• pp.55-62
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• 2009

A general combustion characteristics of forcing nonpremixed jet in laminar flow rates have been conducted experimentally to investigate the effect of forcing amplitude with the resonant frequency of fuel tube. There are two patterns of the flame lift-off feature according to the velocity increasing; one has the decreasing values of forcing amplitude on the lift-off occurrence when a fuel exit velocity is increasing, while the other has the increasing values. These mean that there are the different mechanisms in the lift-off stability of forced jet diffusion flame. Especially, the characteristics of attached jet flame regime are concentrically observed with flame lengths, shapes, flow response and velocity profiles at the nozzle exit as the central figure. The notable observations are that the flame enlogation, in-homing flame and the occurrence of a vortical motion turnabout have happened according to the increase of forcing amplitude. It is understood by the velocity measurements and visualization methods that these phenomena have been relevance to an entrainment of surrounding oxygen into the fuel nozzle as the negative part of the fluctuating velocity has begun at the inner part of the fuel nozzle.

• Journal of the korean academy of Pediatric Dentistry
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• v.27 no.3
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• pp.419-430
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• 2000

The purpose of this study was to compare the microleakage pattern of preventive resin restoration using conventional composite resin and flowable composite resin that recently developed. 60 sound premolar teeth were allocated to three groups. Flowable composite resin was used for the experimental groups(Group I and II) and conventional resin for the control group(Group III). After composite filling and sealant application, all teeth were thermocycled and evaluated for microleakage under light microscope. Additionally, a variety of voids formed inside restorations were also evaluated. Data were analyzed statistically using Kruskal-Wallis test and/or Mann-Whitney U-test. The results of the present study were as follows. 1. Microleakage found in all samples was only limited to the interface of restoration margin and enamel. 2. The flowable composite resin groups (Group I, II) generally showed less microleakage than control groups (conventional preventive resin restoration) (p<0.05) 3. Various types of voids were observed in most specimens. Especially, there was a tendency for more and larger voids to be found in group I, II than group III (p<0.05).

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.12 no.2
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• pp.70-80
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• 2000

Princeton Ocean Model (POM) is modified to construct a three-dimensional, semi-implicit hydro¬dynamic model with a wetting-and-drying scheme. The model employs semi-implicit treatment of the barotropic pressure gradient terms and the vertical mixing terms in the momentum equations, and the velocity divergence term in the vertically-integrated continuity equation. Such treatment removes the external mode and thus the mode splitting scheme in POM, allowing the semi-implicit model to use a larger time step. Applied to hypothetical systems, both the semi-implicit model and POM give nearly the same results. The semi-implicit model, however, runs approximately 4.4 times faster than POM showing its improved computational efficiency. Applied to a hypothetical system with intertidal flats, POM employing the mode splitting scheme produces noises at the intertidal flats, that propagate into the main channel resulting in unstable current velocities. Despite its larger time step, the semi-implicit model gives stable current velocities both at the intertidal flats and main channel. The semi-implicit model when applied to Kyeonggi Bay gives a good reproduction of the observed tides and tidal currents throughout the modeling domain, demonstrating its prototype applicability.

• Restorative Dentistry and Endodontics
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• v.30 no.6
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• pp.461-469
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• 2005

The aim of this study was to compare the root canal systems of maxillary and mandibular premolars that had a single root using radiographs and clearing samples. 142 single rooted premolars were selected and mesio-distal and bucco-lingual views were radiographed using intra-oral dental standard films. Four equally trained examiners classify the root canal types from the developed radiographs. After opening the tooth for access, it was stored in $5\%$ NaOCl to dissolve the pulp tissue. Indian ink was then injected into the pulp cavity to stain the pulp tissue. It was cleared in methyl salicylate after being decalcified with $5\%$ nitric acid for 48 hours, and the root canal type was evaluated at a magnification of $\times$ 20 using a stereomicroscope. The results are as follows ; There were statistically significant differences between the radiographs and clearing samples of the root canal types among examiners (p < 0.05). There might be differences in the root canal types among examiners when the same radiograph is used. Therefore, considering the difficulty in estimating the root canal types, clinicians need to be careful when interpreting radiographs before root canal therapy.