• Journal of Ocean Engineering and Technology
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• v.13 no.3B
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• pp.65-72
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• 1999

A deep-ocean mining riser pipe is subjected to floating vessel motion as well as environmental forces arising from currents and waves. The dynamic analysis is carried out for a deep-ocean mining riser pipe by using a finite element method. The vortex shedding which excites risers in a direction perpendicular to the flow and induces transverse response is considered. It is demonstrated that transverse displacements due to vortex shedding is greatly increased in lock-in regions. The result of this study is compared with other results having good agreements.

• Journal of the Korean Academy of Esthetic Dentistry
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• v.21 no.1
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• pp.4-22
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• 2012

치경부에 발생된 병소 부위(cervical lesion)는 "우식성 병소(caries lesion)"와 "비우식성 병소(non-caries lesion)"로 분류할 수 있다. 우식성 병소는 구강 내 세균들의 활동에 기인하여 발생된 병소로서 경조직 손상 부위의 수복과 함께 우식이 재발하지 않도록 체계적으로 대응하는 것이 필요하다. 비우식성 병소는 산성 물질, 저작력 및 이물질에 의한 마모 작용과 같은 다양한 원인에 의해 발생될 수 있으며, 수복 치료에 앞서 병소에 발생 원인을 규명하는 것이 중요하다. 먼저 병소 유발 원인에 대한 분석과 이에 대한 적절한 조치를 취한 후에 수복 치료를 시행하는 것이 바람직하다. 심미적인 요구가 높은 치경부 병소의 수복을 위하여 사용될 수 있는 재료는 "불소를 방출하는 재료"와 "불소를 방출하지 않는 재료"로 나뉘어지는데, 세균의 활동에 의해 형성된 우식성 병소의 수복에는 불소를 방출하는 재료를 사용하는 것이 추천된다. 우수한 심미성과 보다 강력한 유지력이 요구되는 경우에는 복합 레진계 수복 재료들을 사용하여 수복하게 되는데, 이 경우에는 "접착 술식(bonding procedure)"이 중요한 역할을 수행하게 된다. "접착 술식"은 수복물의 일차적인 유지 뿐 아니라 지각과민을 해소하고 2차 우식을 방지하며, 궁극적으로 수복물의 수명을 좌우하는 결정적인 역할을 수행한다. 자연 치아를 최대한 보존하고자 하는 "최소침습(minimum intervention)" 개념에 바탕을 두고 세심하게 형성된 와동에 각각의 증례에 최적화된 수복 재료를 선택하여 수복치료를 시행한다면 보다 심미적이고 환자가 편안한 치경부 수복물을 완성할 수 있을 것이다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.2
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• pp.169-174
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• 2011

Acoustic emission (AE) signals were detected and analyzed in real time during the polymerization shrinkage of composite resin restoration in an artificial dental ring with a class I cavity. Most AE hit events were observed in the initial curing period of the 1st region with high contraction rate. The range of the $2^{nd}$ region for the stainless steel specimen was shorter than that for the PMMA specimen but longer than that for the human dentin specimen. AE hit events showed a blast-type signal having an amplitude in the range of 25.45 dB and a frequency band of 100.200 kHz or 240.300 kHz. These values of amplitude and frequency indicated the fracture of resin or of the adhesive layer.

• Composites Research
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• v.22 no.6
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• pp.45-51
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• 2009

The marginal integrity at the composite resin-tooth interface has been analyzed in real time through acoustic emission (AE) monitoring during the polymerization shrinkage of composite resin subjected to the light exposure. It was found that AE signals were generated by the polymerization shrinkage. Most AE hit events showed a blast type signal having the principal frequency band of 100-200kHz. Bad bonding states were indicated by many hit events in the initial curing period of 1 minute with high contraction rate. The quantity of hit events for the human molar dentin specimen was much less than that for the steel ring specimen but more than that for the PMMA ring specimen. The better the bonding state, the less the AE hit events. The AE characteristics were related with the tensile crack propagation occurring in the adhesive region between the composite resin and the ring substrate as well as the compressive behavior of the ring substrate, which could be used for a nondestructive characterization of the marginal disintegrative fracture of the dental restoration.

• Composites Research
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• v.23 no.6
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• pp.39-46
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• 2010

Acoustic emission (AE) signals are detected during the polymerization shrinkage of composite resin restoration in artificial dental ring according to various interfacial treatment conditions. AE amplitudes and the number of AE hit events were compared through the non-parametric statistics of Mann-Whitney method and Kruskal-Wallis method. The AE amplitudes detected from the PMMA and human tooth ring specimens were not significantly different according to adhesive conditions. The stainless steel ring specimen, meanwhile, had a difference in AE amplitude (p<0.05). The quantity of hit events for the human molar dentin specimens of the good bonding state was much less than that for the steel ring specimen but more than that for the PMMA ring specimen. For the same substrate, the better the bonding state, the less the AE hit events (p<0.05). The degree of marginal disintegration measured by SEM was proportional to the amount of AE hit events detected.

• 한국해양학회지
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• v.29 no.1
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• pp.50-63
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• 1994

A three-dimensional time-dependent coastal ocean model experiment of two different turbulence parameterizations is conducted. One of the turbulence parameterization is the constant eddy-mixing formulation, C1, and the other a stratification dependent eddy-mixing formulation, C2. The flow in C2 in strongly baroclinic, and limits vertical mixing of fresh and saline waters. The outflow discharged from an estuary is highly inertial and form a strong front of plume in C2 than that in C1. Because of the stronger outflow in C2, supercritical flow state, for which the near surface outflow velocity exceeds the baroclinic phase speed, can exist off the mouth of the estuary. The adjustment process of flow in the less saline waters are quite different for C1 and C2, which is dictated by the strongly baroclinic nature of the flow in C2.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.8 no.1
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• pp.81-86
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• 1996

Subsea pipelines have an important role in the overall tasks of offshore oil and gas production but arc exposed to various hazards with high potential risks of damage resulting in serious economic loss and impact on ocean environment. In this paper, the dynamic free span is analysed, which is one of main risk factors against the safety of subsea pipelines and the allowable length of dynamic free span which is important for the design of subsea pipelines is determined. The allowable free span length is examined by considering the relationship between vortex shedding frequency and natural frequency of pipeline free span, and the variation of the allowable length is analysed for different boundary conditions of pipe ends. The free span is regarded as a beam on elastic foundations and the boundary condition of the beam is generalized by modelling as restrained by linear and rotational spring at each end. A non-dimensionalized curve is obtained to facilitate the determination of exact allowable length of dynamic free span for subsea pipelines and is applied to the pipelines which is to be installed in the gas fields of the south of East Sea of Korea.

• Journal of the korean academy of Pediatric Dentistry
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• v.28 no.4
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• pp.683-693
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• 2001

The purpose of this study was to evaluate the effects of Er:YAG laser on cutting efficacy and its histologic findings. Dentin specimens of human premolars and molars were used and irradiated by Er:YAG laser with noncontact handpiece type delivery system under different treatment condition of irradiation time. Cavity pattern and volume were evaluated to determine the cutting efficacy and following results were obtained. 1. Cutting volume of sound dentin was getting larger with time immersed in water increase 2. With the condition of irradiation (150mJ, 10Hz, 30sec), surface irregularity was more increased in sound dentin comparing to carious dentin. For the light microscopic examination, dentinal tubules were opened and ash flecks and cracks were noted with inconsistence of dentinal tubules. 3. In case of 30 sec. irradiation in carious dentin, dark zone was limited to small focus whereas 1 min. irradiation, more wider, and cracks were noted in the perpendicular to direction of dentinal tubules. For the 2 min. irradiation, cavity was the widest and more cracks were found.

• Journal of the korean academy of Pediatric Dentistry
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• v.34 no.1
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• pp.73-80
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• 2007

Compomer that release fluoride could be used on proximal caries of child effectively. But oral cavity is always wet, so saliva inhibits bonding of tooth and compomer. When the saliva exist on bonding, it can be occured microleakages. The purpose of this study was to evaluate the influence of salivary contamination on compomer restoration and degree of microleakage according to restoration methods. Dyract $AP^{(R)}$ and prime and $bond^{(R)}$ NT was applied by the manufacture s instructions. Elipar Trilight was applied for light curing. Saliva pool was made for reconstruction of oral cavity. Two premolar was embedded in acrylic resin. After class II cavity preperation, Dyract $AP^{(R)}$ was restored under several condition, the specimen was thermocycled 500 times with 30 second dwell time. 0.5% methylene blue was used for microleakage test. Micoleakage was measured by the ratio of the infiltration length to occlusal and gingival side interface. Data were analyzed statistically using Kruskal Wallis Test, Mann-Whitney Test. The Result were as follows ; 1. In occlusal side, there were no statistical differences. 2. In gingival side, there were no statistical differences in Group III ($ContactMatrix^{TM}$, Rubber dam, $Oraseal^{(R)}$), Group IV (No saliva contamination). 3. In gingival side, there were no statistical differences in Group I$(ContactMatrix^{TM})$, II($ContactMatrix^{TM}$, Rubber dam). 4. In gingival side, there were statistical differences in Group I$(ContactMatrix^{TM})$, II($ContactMatrix^{TM}$, Rubber dam).