• Journal of the korean academy of Pediatric Dentistry
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• v.46 no.2
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• pp.158-164
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• 2019

The purpose of this study was to compare the bond strength of resin-modified glass ionomer (RMGI) to dentin with saliva contamination at different stages and using different decontamination procedures. Extracted human permanent molars were embedded onto acrylic resin with the dentin surface exposed. Group I was a control group that was conditioned with polyacrylic acid (PAA). Groups II and III were contaminated with saliva before PAA conditioning and Groups IV, V, and VI were contaminated with saliva after PAA conditioning. After saliva contamination, Groups II and IV were dried, Groups III and V were rinsed and dried, and Group VI was additionally conditioned with PAA. After surface treatment, the dentin specimens were filled with RMGI. Group I showed significantly higher bond strength than the other groups. Group VI showed a significantly higher bond strength than the other saliva contaminated groups. However, there were no significant differences in the failure mode between the different groups. Saliva contamination impaired the bond strength of RMGI to dentin, regardless of when the saliva contamination occurred. Decontamination with washing and drying could not improve the shear bond strength of RMGIC. When saliva contamination occurred after PAA conditioning, additional PAA conditioning improved the shear bond strength.

• The korean journal of orthodontics
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• v.33 no.6 s.101
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• pp.437-451
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• 2003

The purpose of this study was to measure maximum bite force and to investigate its relationship with anteroposterior, vertical, and transverse facial skeletal measurements. From among the dental students at the College of Dentistry, forty subjects (26 male and 14 female) were selected. With two sets of strain gauge, maximum bite force at the right and left first molars and anterior teeth was measured in the morning and afternoon. After taking lateral and posteroanterior cephalograms, fifty and nineteen variables were evaluated, respectively Paired t-tests and an independent t-test were done and correlation coefficients were obtained. 1. The maximum bite force at the first molars was $68.0\pm13.9kg$. in males and $55.6\pm10.5kg$ in females (p<0.05) while the force at the anterior teeth was $8.4\pm4.9kg\;and\;1.1\pm3.4kg$ respectively (p<0.05). 2. Some tendency for a greater value of maximum bite force at the preferred side was observed but not statistically significant (p>0.05). 3. Significant difference was observed between the strong bite force group and the weak bite force group in some cephalometric and other measurements (p<0.05). N-S-Ar, S-Ar-Go, FH-Hl, IMPA and MMO showed a significant difference in posterior maximum bite force (P). N-S-Ar and FH-H1 also showed a significant difference in anterior maximum bite force (A). 4. Several cephalometric variables showed some correlation with maximum bite force (p<0.05). N-S-Ar, S-Ar-Go, UGA, FH-H6, FH-H1, body weight and MMO were significantly correlated with posterior maximum bite force (P). Go-Me, P-1 and IMPA were significantly correlated with anterior maximum bite force (A).

• The korean journal of orthodontics
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• v.29 no.4 s.75
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• pp.445-456
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• 1999

As a result of increased education and communication, the field of orthodontics has recently been expanded to include a greater number of adult treatment procedures. With this increased demand for adult orthodontic treatment, a problem that frequently arises is the placement of appliances on teeth restored with porcelain. But conventional acid-etching is ineffective in the preparation of porcelain surface for mechanical retention of orthodontic attachments. Also, it is possible to damage on porcelain. The purpose of this study was to evaluate the effect of composite bonding materials and the porcelain surface treatment methods on shear bond strength, and to observe the porcelain fracture rates. To accomplish this purpose, this study was carried out with feldsphatic porcelain, Ceram II. Porcelain surface treatment methods were divided into intact glazed porcelain which had not treatment and surface roughening. Surface roughening by etching with Hydroluoric acid(HF), sandblasting with Microetcher II and compound treatment with etching and sandblasting. Bonding materials were Ortho-two and Transbond. All porcelain specimens were applicated with porcelain primer. 1. In comparision according to porcelain surface treatment, surface roughening groups by HF etching and sandblasting had higher shear bond than intact group. No significant difference was found in Transbond group. 2. Ortho-two group had the higher shear bond strength than that of Transbond group in B:.u etching and sandblasting. 3. E(Transbond. Intact)group had the lowest shear bond strength in all experimental group. The bond strength was higher than clinically successful bond strength. 4. Non-treated group had very higher porcelain rates than treated group. 5. This study indicates that porcelain surface-roughening may not be necessary to attachment of orthodontic brackets to porcelain surfaces.

• Polymer(Korea)
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• v.26 no.6
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• pp.718-727
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• 2002

In this work, an Ar+ beam was irradiated on carbon fiber surfaces to improve the interfacial shear strength (IFSS) of the resulting composites using an ion assisted reaction (IAR) method h single fiber pull-out test was executed to investigate the basic characteristics of the single Carbon fiber/matrix interface. Based on Greszczuk's geometrical model, the debonding force for pull-out of the fiber from the resins was discussed with the applied ion beam energy as a result, it was known that an ion beam treatment produced the functional groups on fiber surface and etching lines along the fiber axis direction, resulting in increasing the adhesion forces between fibers and matrix, which caused the improvement of the IFSS in a composite system. And, it was also found that the maximum IFSS was shown at 0.8 keV ion beam energy in this system.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.05a
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• pp.141-143
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• 2006

It is well known that there are three mechanisms in the nozzle surface regression, namely ablation, mechanical erosion and chemical corrosion. There are Analogies among these three mechanisms. In order to compare the order of the magnitude of these mechanism, the analogy was adapted and the Mach number of the gas flow was expressed by the nozzle shape(location).

• Proceedings of the Membrane Society of Korea Conference
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• 1997.04b
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• pp.52-55
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• 1997

여과가 진행됨에 따라 막의 표면에서 발생하여 여과선속을 저하시키는 케이크층의 형성은 막을 이용한 고-액 분리공정에서 발생하는 가장 큰 문제점의 하나로서 이는 막 분리공정의 경제성을 좌우하는 중요한 인자가 된다. 이러한 문제점을 극복하기 위하여 유체와 막 사이의 상대속도를 증가시켜 여과속도를 향상시키는 십자흐름 여과, 즉 CFF(crossflow filtration)에 대한 연구가 활발히 진행되어 왔다. 그러나 이러한 심자흐름 여과에서도 막과 유체 사이의 상대속도의 증가에 한계가 있고 또한, 막의 기공보다 작은 입자가 막의 기공 내에 침투하여 막을 오염시키는 현상을 예측하기 어렵기 때문에 여과기의 설계에 있어서 많은 문제점이 발생하고 있다. 이에 오염된 막을 재생시키기 위하여 기계적.화학적인 여러 가지 방법들이 개발되고 여과선속을 향상시키는 방법이 꾸준히 연구되어 분리막 기술의 경제성을 향상시켜 왔다. 본 연구에서는 매우 안정된 유동의 하나로서 막 표면의 전단력을 향상시키는 데에 효과가 있다고 알려진 Taylor와류를 응용한 회전막 여과기를 사용하여 여러 가지 크기의 입자에 대한 여과실험을 수행함으로써 이러한 유동이 케이크의 형성에 미치는 영향을 살펴보았다. 또한 여과선속에 영향을 미치는 여러 매개인자를 알아보고 실험결과를 간단한 모델식에 적용해 봄으로써 막의 저항을 예측할 수 있는 모델식으로의 개선 방향을 제시하고자 한다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.4A
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• pp.291-297
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• 2009

Relaxation of high strength bolts was investigated. Block type and splice type specimens were fabricated with different types of bolts and different clamping lengths. Bolts were tightened to the specified torque. Clamping forces were measured through strain gauges installed on the shafts of bolts, while specimens were kept in a constant temperature and humidity. In all cases, ratio of clamping force reduction is less than 10%. Test results of different types of specimens and bolts and different clamping lengths were compared each other by using a simple model, which is suggested in this study for the estimation of bolt relaxation. The suggested model shows reasonably good agreements with test results for all cases. No difference is found between F13T and F10T bolts, but Dacro coated bolts shows higher relaxation than black bolts by approx. 30%. And also the comparison of test results shows that ratios of bolt relaxation become larger as clamping lengths of bolt shorter and the number of faying surfaces greater.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.12 no.6
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• pp.84-91
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• 2003

In metal cutting operation, it is very important that predict cutting force and work surface. Vibration is an unstable cutting phenomenon which is due to the interaction of the dynamics of the chip removal process and the structural dynamics of machine tool. When vibration on, it reduces tool life, results in poor surface roughness and low productivity of the machining process. In this study, the experiments were conducted in machining center without cutting fluid to investigate the phenomenon of vibration. In the experiments, accelerometers were set up at the tail stock and tool holder and signals were picked up. Surface roughness profiles are generated under the ideal condition and the occurrence of vibration based on the surface shaping simulation model.

• Proceedings of the Korean Society for Food Science of Animal Resources Conference
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• 2006.05a
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• pp.77-82
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• 2006

본 연구는 제주 재래돼지에게 감귤 부산물을 급여하고 몇 가지 특성 및 기호성을 파악하고자 하였다. 감귤 부산물을 급여한 돈육 등심과 급여하지 않은 돈육 등심 사이에 pH, VBN 및 일반 세균수의 차이는 없었다. 그러나 TBARS 값은 감귤을 급여한 돈육등심이 유의하게 낮았다(p<0.05). 감귤 부산물을 급여하지 않은 TB-0구와 급여한 TB-1의 표면색도는 $L^*$ 및 $b^*$값은 유의한 차이가 없었으나, $a^*$값은 TB-0구가 TB-1구보다 유의하게 높은 경향이었다. 보수력 및 팬 가열감량은 TB-0가 TB-1보다 유의하게 높았으며(p<0.05), 동결감량, 해동감량, 열탕가열감량은 시료들 사이에 유의한 차이가 없었다. 경도, 탄성, 응집성, 저작성 및 전단력은 감귤 부산물 급여의 영향이 없었지만 뭉침성은 TB-1이 유의하게 높았다(p<0.05). 맛, 향기, 다즙성 및 종합적인 기호도는 감귤 부산물 급여에 따른 영향이 없었으나, 연도는 감귤 부산물을 급여한 돈육 등심이 유의하게 높았다(p<0.05).

• Journal of the Society of Cosmetic Scientists of Korea
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• v.38 no.2
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• pp.139-145
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• 2012

There is a unique type of fatty acid in the hair surface. 18-methyleicosanoic acid (18-MEA) is an unusual anteiso fatty acid covalently linked to the outermost surface of hair cuticle. A layer of 18-MEA is located in the upper ${\beta}$-layer of the CMC that is responsible for the low surface energy and low friction resistance of the hair's outer surface. The high mobility of 18-MEA molecule facilitates spreading of extraneous lipid by decreasing interfacial shear strength. In this study, we introduced N-hydroxyl succinimidyl ester functional group to the one end of C10 - 40 isoalkyl acid for regenerating hair surface with covalently bound fatty acid layer. The re-hydrophobicization of hair surface has been investigated by contact angle measurement. The inner moisture content of hair at different levels of humidity (40, 55, 70 %RH) was measured by electric moisture analyzer. Treatment with Hydroxysuccinimidyl C10 - 40 Isoalkyl Acidate (HCIA) was supposed to make hair surface smoother by filling the cracks between cuticles with covalently bound fatty acid monomolecular layer like cuticle glue. This glue effect was also confirmed with line profile of AFM images. Therefore, the moisture and structural components of inner hair were not easily flown out and the optimum moisture content could be kept constantly though the outside humidity level was changed. The lateral force microscopy (LFM) by using atomic force microscope showed that the friction force of hair surface treated with HCIA was decreased. It also showed the constantly sustained friction value even after shampooing repeated 15 times.