• Journal of Periodontal and Implant Science
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• 제36권1호
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• pp.211-221
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• 2006

The aim of present study was to evaluate the influence of periodontal status of adjacent tooth and loading time to the prevalence of red complex of implant sulcus. In 97 patients, partially edentulous subjects with endosseous root-form implants were selected. All subjects were medically healthy and had not taken systemic antibiotics and professional plaque control 3 months before sampling. The number was as follows: clinically healthy implants:161, clinically unhealthy implants:22, clinically healthy adjacent teeth:73, clinically unhealthy adjacent teeth:38. All teeth and implants of each patient were examined probing depth(PD), modified sulcus bleeding index(mSBI), and modified plaque index(mPI), and samples of subgingival plaque were obtained at each site with sterile curet or fine paper points, then the plaque transferred to PBS. Obtained samples were examined for the presence of P. gingivalis, T. forsythensis, and T. denticola by the polymerase chain reaction (PCR). The relationship among clinical parameters and the colonizations by the 3 bacterial species from adjacent teeth and implants region were analyzed by student t-test (p<0.05). The results of this study were as follows: 1. mPI and mSBI of implant increased with increasing of same indices of adjacent tooth(p=0.03,0.001), but not in the PD . 2. The mPI, mBI, PD of implants was higher when red complex exist. 3. The prevalence of red complex was higher when the periodontal condition is unhealthy. 4. The prevalence of red complex of implants has no significant relation to the probing depth of adjacent tooth. 5. Prevalence of P. gingivalis, T. forsythensis of implants increased with loading time. (p=0.02,0.018) These results shows the importance of oral hygiene and supportive periodontal therapy.

• 한국환경과학회지
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• 제8권5호
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• pp.617-623
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• 1999

This study was carried out to obtain the optimal operating parameter on organic matters and nutrient removal of mixed wastewater which was composed of sewage and stable wastewater using SBR. A laboratory scale SBR was operated with An/Ae(Anaerobic/Aerobic) ratio of 3/3, 2/4 and 4/2(3.5/2.5) at organic loading rate of 0.14 to 0.27 kgBOD/$m^3$/d. TCOD/SCOD ratio of mixed wastewater was 3, so the important operating factor depended upon the resolving the particulate parts of wastewater. Conclusions of this study were as follows: 1) For mixed wastewater, BOD and COD removal efficiencies were 93-96% and 85-89%, respectively. It was not related to each organic loading rate, whereas depended on An/Ae ratio. During Anarobic period, the amount of SCOD consumption was very little, because ICOD in influent was converted to SCOD by hydrolysis of insoluble matter. 2) T-N removal efficiencies of mixed wastewater were 55-62% for Exp. 1, 66-76% for Exp. 2, and 67-81% for Exp. 3, respectively. It was found that nitrification rate was increased according to organic concentration in influent increased. Therefore, the nitrification rate seemed to be achieved by heterotrophs. During anoxic period, denitrification rate depended on SCOD concentration in aerobic period and thus, was not resulted by endogenous denitrification. However, the amount of denitrification during anaerobic period were 3.5-14.1 mg/cycle, and that of BOD consumed were 10-40 mg/cycle. 3) For P removal of mixed wastewater, EBPR appeared only Mode 3($3^＊$). It was found that the time in which ICOD was converted to VFA should be sufficient. For mode 3 in each Exp., P removal efficiencies were 74, 87, and 81%, respectively. But for 45-48 of COD/TP ratio in influent, P concentration in effluent was over 1 mg/L. It was caused to a large amount of ICOD in influent. However, as P concnetration in influent was increased, the amounts of P release and uptake were increased linearly.

• 대한금속재료학회지
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• 제47권11호
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• pp.707-715
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• 2009

This paper deals with cyclic stress and strain responses during isothermal low cycle fatigue (LCF) and thermo-mechanical fatigue (TMF) loadings on Nb and Mo containing 15Cr stainless steel, which is used for exhaust manifolds in automobiles. The test temperatures ($T_{i}$) of the isothermal LCF were 600 and $800^{\circ}C$. The minimum temperature of the TMF test was $100^{\circ}C$ and the maximum temperaures ($T_{p}$) were varied between 500 and $800^{\circ}C$. In both loading conditions, weak cyclic softening is observed at $T_{i}=T_{p}=800^{\circ}C$, but the transition to strong cyclic hardening is completed with the temperature decrease below $T_i=600{\sim}700^{\circ}C$ for LCF and $T_{p}=500{\sim}600^{\circ}C$ for TMF. The stress-strain hysteresis loops in the TMF loading show a significant stress relaxation during compressive (heating) half cycle at $T_{p}>500^{\circ}C$, which develops tensile mean stress during cycling. Due to the stress relaxation, the TMF test sample reveals much lower dislocation density than the isothermally fatigued sample at the same temperature with $T_{p}$. A detailed correlation between fatigue microstructure and cycling deformation behavior is discussed.

• 지질공학
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• 제16권3호
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• pp.235-244
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• 2006

한국원자력연구소 내에서 시추된 화강암 코어시료를 대상으로 1550회의 반복하중을 가할 때 미세균열의 발달 정도를 미소파괴음(AE)을 이용하여 연구하였다. 반복하중 조건에서 미소파괴음은 반복횟수에 따라 두 가지 type의 발생 특성을 보였다. 첫 번째 type은 반복횟수가 적었을 때 나타나는 특성으로 낮은 에너지와 분산된 주파수가 특징이며, 두 번째 type은 반복횟수가 많았을 때 나타나는 특성으로 높은 에너지와 일정한 주파수가 특징적이다. Type 1은 시료내의 공극이나 미세균열이 닫히거나 성장하는 과정에서 발생하는 미소파괴음의 특성을 나타내는 반면에, type 2는 하중을 가할 때에는 미세균열이 전단되거나 닫혔다가 하중이 제거될 때에는 전단으로부터 회복하거나 미세균열이 열리면서 발생하는 미소파괴음의 특성으로 판단된다. 또한 반복횟수 50, 150, 350, 750, 1550회 때 탄성파(P파) 속도와 Felicity 비를 측정하였다. 측정결과 탄성파속도는 반복횟수가 증가하여도 변화가 없었으나 Felicity 비의 경우 반복횟수가 증가함에 따라 점점 감소하여 시료가 반복하중에 의해 손상을 받고 있음을 지시하였다. 따라서 암석의 손상정도를 판단하는데 있어서 미소파괴음 측정을 통한 Felicity 비가 탄성파속도보다 더 효과적으로 판단된다.

• 대한치과보존학회:학술대회논문집
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• 대한치과보존학회 2008년도 Spring Scientific Meeting(the 129th) of Korean Academy if Conservative Dentistry
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• pp.198-203
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• 2008

본 연구의 목적은 동적하중 하에서 네 종류의 근관치료용 임시충전재의 밀폐효과를 비교하는 것이다. 44개의 건전한 인간 대구치에 표준화된 근관와동을 형성한 후 Caviton, MD-Temp, IRM 및 ZOE를 이용하여 충전하였다. 이 후, 1% 메틸렌블루 용액에 담근 상태에서 반복하중기를 이용하여 1 Hz의 속도로 98 N의 하중을 기능교두에 1,000번 가한 다음 시편을 양분해 미세누출을 평가하고 one-way ANOVA (p = 0.05)와 사후 검정으로 Duncan's multiple range tests로 통계분석 하였다. Caviton 군과 MD-Temp군이 IRM군과 ZOE군보다 통계적으로 적은 미세누출을 보였으며 (p < 0.05), 본 실험결과로 볼 때 Caviton과 MD-Temp가 IRM과 ZOE보다 동적하중 하에서 근관와동 밀폐효과가 우수하다고 사료된다.

• Restorative Dentistry and Endodontics
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• 제33권3호
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• pp.198-203
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• 2008

본 연구의 목적은 동적하중 하에서 네 종류의 근관치료용 임시충전재의 밀폐효과를 비교하는 것이다. 44개의 건전한 인간 대구치에 표준화된 근관와동을 형성한 후 Caviton, MD-Temp, IRM 및 ZOE를 이용하여 충전하였다. 이 후, 1% 메틸렌블루 용액에 담근 상태에서 반복하중기를 이용하여 1 Hz의 속도로 98 N의 하중을 기능교두에 1,000번 가한 다음 시편을 양분해 미세누출을 평가하고 one-way ANOVA (p = 0.05)와 사후 검정으로 Duncan's multiple range tests로 통계분석 하였다. Caviton 군과 MD-Temp군이 IRM군과 ZOE군보다 통계적으로 적은 미세누출을 보였으며 (p < 0.05), 본 실험결과로 볼 때 Caviton과 MD-Temp가 IRM과 ZOE보다 동적하중 하에서 근관와동 밀폐효과가 우수하다고 사료된다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.1161-1166
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• 2001

Fatigue behavior of reinforced concrete(RC) elements has been experimentally and analytical investigated. Fatigue behavior influenced by longitudinal reinforcement ratio, strength of concrete and load ratio $P_{u}$/ $P_{o}$. The purpose of these studies is to propose an empirical formula for fatigue behavior on basis of experimental results. Also an analytical method to predict the crack propagation of RC beams has been developed based on the relationships between bond stress and slip.

• 한국분말재료학회지
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• 제9권5호
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• pp.303-306
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• 2002

P/M high speed steels with various Co contents were fabricated by gas atomization and Canning/HIP process. As Co content in P/M high speed steel increased, hardness, transverse rupture strength and yield strength in compressive testing increased due to solid solution hardening of Co in matrix. Especially, PM high speed steels with Co have high deformation resistance to repeated compressive loading.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2001년도 춘계학술대회 논문집
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• pp.443-452
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• 2001

Fatigue behavior of reinforced concrete(RC) and steel fiber reinforced concrete(SFRC) beams has been experimentally investigated. Fatigue behavior influenced by longitudinal reinforcement ratio, volume and type of steel fiber, strength of concrete and load ratio $P_{u}/P_{o}$. It can be observed from experimental results that addition of steel fiber to reinforced concrete beam reduces crack widths and increases stiffness, and thus enhances the behavior in serviceability limit states also for high cyclic fatigue loading.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2001년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Fall 2001
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• pp.431-438
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• 2001

Fatigue behavior of reinforced concrete(RC) and steel fiber reinforced concrete(SFRC) elements has been experimentally investigated. Fatigue behavior influenced by longitudinal reinforcement ratio, volume and type of steel fiber, strength of concrete and load ratio $P_{u}$ $P_{o}$. It can be observed from experimental results that addition of steel fiber to reinforced concrete beam reduces crack widths and increases stiffness, and thus enhances the behavior in serviceability limit states also for high cyclic fatigue loadingngng