• Tribology and Lubricants
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• 제32권2호
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• pp.44-49
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• 2016

Diamond mechanical polishing (DMP) is a crucial process in a sapphire wafering process to improve flatness and achieve the target thickness by using free abrasives. In a DMP process, material removal rate (MRR) is a key factor to reduce process time and cost. Controlling mechanical parameters, such as velocity and pressure, can increase the MRR in a DMP process. However, there are limitations of using high velocities and pressures for achieving a high MRR owing to their side effects. In this paper, we present the lapping characteristics and improvement of MRR by using a fixed abrasive plate through an experimental study. The change in MRR as a function of velocity and pressure follows Preston's equation. The surface roughness of a wafer decreases as the plate velocity and pressure increases. We observe a sharp decrease in MRR over the lapping time at a high velocity and pressure in the velocity and pressure test. An analysis of surface roughness (Rq and Rpk) indicates that wear of abrasives decreases the MRR sharply. In order to investigate the effect of abrasive wear on the MRR, we utilize a cutting fluid and a rough wafer. The cutting fluid delays the wear of abrasives resulting in improvement of MRR drop. The rough wafer maintains the MRR at a stable rate by self-dressing.

• Journal of Periodontal and Implant Science
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• 제42권6호
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• pp.217-223
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• 2012

Purpose: Several parameters have been described for determining the success or failure of dental implants. The surface properties of transgingival implant components have had a great impact on the long-term success of dental implants. The purpose of this study was to compare the tendency of two periodontal pathogens to adhere to and colonize zirconia abutments and titanium alloys both in hard surfaces and soft tissues. Methods: Twelve patients participated in this study. Three months after implant placement, the abutments were connected. Five weeks following the abutment connections, the abutments were removed, probing depth measurements were recorded, and gingival biopsies were performed. The abutments and gingival biopsies taken from the buccal gingiva were analyzed using real-time polymerase chain reaction to compare the DNA copy numbers of Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, and total bacteria. The surface free energy of the abutments was calculated using the sessile water drop method before replacement. Data analyses used the Mann Whitney U-test, and P-values below 0.05 find statistical significance. Results: The present study showed no statistically significant differences between the DNA copy numbers of A. actinomycetemcomitans, P. gingivalis, and total bacteria for both the titanium and zirconia abutments and the biopsies taken from their buccal gingiva. The differences between the free surface energy of the abutments had no influence on the microbiological findings. Conclusions: Zirconia surfaces have comparable properties to titanium alloy surfaces and may be suitable and safe materials for the long-term success of dental implants.

• 대한치과보철학회지
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• 제34권1호
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• pp.151-167
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• 1996

Temporary soft liners can be used to prevent chronic soreness from dentures or to aid in its treatment are as adjuncts in tissue conditioning, for temporary obturators, and to stabilize baseplate or surgical stent. The purpose of this study was to evaluate the shock absorption properties of several temporary soft denture liners using a free drop test with an accelerometer. The materials tested inclued Coe-comfort, Softone, Tissue conditioner and Viscogel. The specimens were fabricated with the thickness of 1, 2, 3mm and were stored in distilled water at $37^{\circ}C$ for a day, 1, 2, and 3 weeks. Six samples were made with each material for each test condition and the shock-absorbing behavior was evaluated according to material, thickness and duration. The results were as following : 1. Softone of 3mm thickness stored for a day showed the most excellent shock absorbability. 2. The shock absorbing behavior of duration according to materials and thickness showed a day to be the highest and decreased in 1 week, 2 weeks and 3 weeks in that order(p<0.05). And there was no significant difference between durations in Tissue conditioner. 3. The shock absorbability of thickness according to materials and duration showed 3mm to be highest and decreased in the order of 2mm, 1mm(p<0.05). 4. In comparison of the shock absorbability of temporary soft denture liners according to thickness, there was statistically significant difference between Softone and Visocgel, Tissue conditioner, Coe-comfort / Viscogel and Tissue conditioner, Coe-comfort in 1,2mm thickness, and between Softone, Viscogel and Tissue conditioner, Coe-comfort in 3mm thickness (p<0.05).

• 해양환경안전학회지
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• 제28권7호
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• pp.1201-1208
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• 2022

일반적으로 부유식 해상풍력발전 에너지의 수급성과 효율을 극대화하기 위해서는 하부구조물의 파랑 감쇠로 인한 운동을 저감시키는 것이 중요하다. 선행 연구들에 따르면 파도 중 하부구조물에 설치된 감쇠판에 의해서 발생한 와류점성으로 인해 운동 응답이 감소되는 것으로 나타났다. 본 연구에서는 5MW급 반잠수식 OC5 플랫폼과 감쇠판이 부착된 두가지 플랫폼을 설계하고, 와류점성으로 인한 운동저감효과를 확인하기 위해 자유감쇠실험과 수치계산을 수행하였다. 모형시험 결과로 낙하 높이를 30 mm, 40 mm, 50 mm에서의 상하 자유감쇠실험을 수행하였을 때 OC5 플랫폼 대비 두 가지의 형태의 감쇠판이 부착된 플랫폼이 상대적으로 운동감쇠성능이 향상되었다. 모형시험과 수치계산 결과에서 형상화한 감쇠판 모델(KSNU Plate 1, KSNU Plate 2)들이 각각 OC5 대비 상하운동 진폭이 1.1배, 1.3배 각각 감소했으며, KSNU Plate 2 플랫폼은 KSNU Plate 1 플랫폼보다 OC5 대비 약 2배 감쇠성능이 좋아진 것으로 나타났다. 본 연구에서는 감쇠판의 면적과 와류점성이 상하동요의 감쇠율과 밀접한 관련을 보여준다.

• Clinical and Experimental Reproductive Medicine
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• 제26권1호
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• pp.75-81
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• 1999

The beneficial effect of glucose and phosphate ions in culture medium on the development of human embryos in vitro has not been fully elucidated. The purpose of this study was to evaluate the influence of fertilization and culture of embryos in glucose/phosphate-free m-TALP medium on pregnancy rates in IVF-ET program. The patients in 244 IVF-ET cycles received GnRH agonist + HMG regimens. A does of 10,000 IU HCG was administered when two or more dominent follicles reached 18mm in diameter. Thirty-six hours after HCG, oocytes were recovered transvaginally using ultrasound guidance. Aspirated oocytes were matured for 4 to 6 h in TCM-199 supplemented with 10% follicular fluid (FF). Insemination was carried out with 50,000 motile spermatozoa in TCM-199 + 10% FF or m-TALP + 5% FF + 5% fetal cord serum (FCS) according to experimental design. After 6 h, oocytes were washed 3 to 4 times and cultured in each fresh medium. After 20 h, oocytes were freed from cumulus/corona cells and examined for the presence of pronuclei. Fertilized oocytes were transferred into each co-culture drops and cultured for further incubation. On day 3, embryo transfer was performed with grade 1 and 2 embryos. Monolayers for co-culture of embryos were prepared by plating $1{\times}10^5$ cumulus cells/ml in 10ul drop of TCM-199 + 10% FF or m-TALP + 5% FF + 5% FCS media 24 h prior to the onset of co-culture. Development to 4 to 16 cell stage was observed at 70x magnification following two days of incubation. Pregnancy was confirmed by detecting increasing serum ${\beta}$-hCG concentrations for 11 days following embryo transfer. Data were analyzed by ${\chi}^2$-test. Oocytes from 244 IVF-ET cycles were randomized. The number of cycles and mean age of patients were 97 and 147, 31.3 yrs and 31.2 yrs for TCM-199 (control) and m-TALP groups, respectively. The mean number of retrieved oocytes/cycle, fertilization rates, number of embryos transferred/ET and pregnancy rates were 11.1 and 10.3, 65.1% and 67.3%, 4.1 and 4.7, 28.9% and 43.8% for TCM-199 and m-TALP groups, respectively. Differences in the pregnancy rates were found between control and m-TALP groups (p<0.05). The pregnancy rate of patients divided according to maternal age groups of ${\leq}30$, 31-35, $36{\leq}$ were 44.4% and 49.0%, 26.1% and 41.3%, 29.2% and 41.2% for control and m-TALP groups, respectively. These data indicate that culture of human embryos in glucose/phosphate-free m-TALP medium improves pregnancy rates.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2006년 추계학술발표대회 개요집
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• pp.136-138
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• 2006

Recently a lots of problems have observed in high densified and high integrated electronic components. One of them is ion migration phenomena, which induce the electrical short of electrical circuit. Ion migration phenomena has been observed in the field of exposing the specific environment and using for a long time. Also as the RoHS restriction was started in July 1st, 2006, Pb-free solder was utilized in electronics assemblies. In this case, it is very important to compatible between components and printed circuit board(PCB), thus surface treatment materials of PCB was changed to Sn, Sn-3.0Ag-0.5Cu, Cu. Therefore these new application become to need to reevaluate the sensitivity about electrochemical ion migration. This study was evaluated the occurrence time of electrochemical ion migration using by water drop test. We utilized PCB(printed circuit board) having a comb pattern as follows 0.1, 0.318, 0.5, 1.0 mm pattern distance. Sn-3.0Ag-0.5Cu and Sn-37Pb were electroplated on the comb pattern. 6.5V and 15.0V were applied in the comb pattern and then we measured the electrical short time causing by occurring the ion migration. In these results, we evaluate the sensitivity and derived the prediction models of ion migration occurrence time depending on the pattern materials, applied voltage and pattern spacing of PCB conductor.

• 한국정보통신학회논문지
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• 제8권2호
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• pp.509-515
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• 2004

폐 기능 검사는 임상에서 환자의 진단 및 치료 판단에 널리 이용되고 있을 뿐 아니라 폐의 연구, 특히 폐의 생리학 및 폐질환의 역학 연구에 일찍부터 사용되어 왔다. 여러 가지 폐 기능 검사 중 가장 쉽고 경제적으로 시행할 수 있는 기본적인 검사법으로 폐활량 검사법(Spirometer)이 있다. 폐활량 검사기는 호흡 기체의 용적 유량의 순간적인 변화량을 측정하는 의학 기기이다. 과거에는 기계식 폐활량기가 주로 사용되었으며, 현재까지도 많이 사용되는 방법은 유체 흐름의 "양" 변화를 유체의 압력 변화로 전환시키는 차압식 방식이다. 그러나 이러한 형태는 압력 손실과 유지 보수가 힘들고, 특성 검사 주기가 짧은 단점을 가지고 있다. 본 논문에서 구현하고자 하는 것은 관성의 오차 및 압력의 오차에 영향을 거의 받지 않는, 그리고 반영구적으로 사용이 가능한 초음파 센싱 방식을 이용한 임베디드 환경의 호흡 량 측정기의 개발을 최종 목표로 하여, 호흡 기체 특성에 적합한 센서, 신호 측정 구현 회로를 포함한 유량 측정 단말부 개발과 측정신호를 이용한 호흡 측정 알고리즘과 진단 알고리즘 구현에 중점을 두었다.

• 한국재료학회지
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• 제21권12호
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• pp.685-689
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• 2011

The goal of this investigation was to produce a zirconia-family black ceramics that has enhanced functionality and reliability. Color zirconia ceramics have been produced by adding pigments. Pigments cause structural defects within zirconia and result in a drop in physical properties. Using environmentally friendly rice husk, we produced a black zirconia that is free of structural defects. In optimal firing conditions for black zirconia the calcining temperatures of the molding product are changed from $400^{\circ}C$ to $1200^{\circ}C$, and the firing temperatures are changed from $1400^{\circ}C$ to $1600^{\circ}C$. Color of testing the specimens was analyzed using Ultraviolet (UV) spectroscopy. Scanning Electron Microscope (SEM), EDAX (EDX), and Fourier transform infrared spectroscopy (FT-IR) analyses were carried out in order to examine impregnation properties and crystal phases. Universial Test Machine (UTM) was used to measure the flexual strength as well as the compressive strength. From experimental results, it was found that in optimal firing conditions the sample was calcined from $1000^{\circ}C$ to $1500^{\circ}C$. Commission internationalde I'Edairage (CIE) values of manufactured black zirconia color were $L^*$ = 29.73, $a^*$ = 0.23, $b^*$ = -2.68. The bending strength was 918 MPa and the compressive strength was 2676 MPa. These strength values are similar to typical strength values of zirconia, which confirms that carbon impregnation did not influence physical properties.

• 대한조선학회논문집
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• 제56권4호
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• pp.308-315
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• 2019

In this study, numerical simulations of slamming impact pressure acting on the flat plate and wedge type models using the cartesian-grid system and Modified Marker-Density Method (MMD method) were performed and the results were examined. The flat plate and wedge type models were selected as target objects, the turbulence characteristics were considered by applying the Sub-Grid Scale (SGS) turbulence model. Through this study, how the pressure acting on the target objects according to the incident angle influences the slamming impact pressure was examined and the results were compared with the flow characteristics of other experimental results. Also, the degree of slamming impact pressure is evaluated with respect to the cartesian-grid system and MMD method, which is easy to use and has a high degree of calculation for free surface.

• Archives of Plastic Surgery
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• 제48권4호
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• pp.457-461
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• 2021

Background Pedicled perforator flaps can present postoperative complications similar to those encountered in free flap surgery. Beyond a clinical evaluation, there is still no reliable technical aid for the early prediction of vascular issues. The aim of this study was to assess the support of near-infrared spectroscopy technology as an intraoperative tool to anticipate postsurgical flap ischemia. Methods We prospectively enrolled 13 consecutive patients who were referred to our hospital from March 2017 to July 2018 and required a reconstructive procedure with a pedicled fasciocutaneous perforator flap. We measured flap peripheral capillary oxygen saturation (SpO₂) in each patient with a Somanetics INVOS 5100C Cerebral/Somatic Oximeter (Medtronic), both before and after transposition. Patient demographics, operative data, and complications were then recorded during the following 6 months. We analyzed the data using the Wilcoxon signed-rank test and linear regression. Results The mean flap SpO₂ before and after transposition was 92%±3% and 78%±19%, respectively. The mean change in SpO₂ was 14%±17%, with a range of 0% to 55%. The change in saturation and mean saturation ratio were significantly different between patients with and without postoperative flap necrosis. Conclusions An immediate quantitative analysis of flap peripheral capillary SpO₂ after transposition has never before been described. In our experience, an intraoperative drop in SpO₂ equal to or greater than 15%-20% predicted vascular complications in pedicled perforator flaps. Conversely, flap size and rotation angle were not correlated with the risk of flap necrosis.