• The Journal of Advanced Prosthodontics
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• 제15권2호
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• pp.55-62
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• 2023

PURPOSE. The aim of this study is to evaluate the accuracy of removable partial denture (RPD) frameworks produced using different digital protocols. MATERIALS AND METHODS. 80 frameworks for RPDs were produced using CAD-CAM technology and divided into four groups of twenty (n = 20): Group 1, Titanium frameworks manufactured by digital metal laser sintering (DMLS); Group 2, Co-Cr frameworks manufactured by DMLS; Group 3, Polyamide PA12 castable resin manufactured by multi-jet fusion (MJF); and Group 4, Metal (Co-Cr) casting by using lost-wax technique. After the digital acquisition, eight specific areas were selected in order to measure the Δ-error value at the intaglio surface of RPD. The minimum value required for point sampling density (0.4 mm) was derived from the sensitivity analysis. The obtained Δ-error mean value was used for comparisons: 1. between different manufacturing processes; 2. between different manufacturing techniques in the same area of interest (AOI); and 3. between different AOI of the same group. RESULTS. The Δ-error mean value of each group ranged between -0.002 (Ti) and 0.041 (Co-Cr) mm. The Pearson's Chi-squared test revealed significant differences considering all groups paired two by two, except for group 3 and 4. The multiple comparison test documented a significant difference for each AOI among group 1, 3, and 4. The multiple comparison test showed significant differences among almost all different AOIs of each group. CONCLUSION. All Δ-mean error values of all digital protocols for manufacturing RPD frameworks optimally fit within the clinical tolerance limit of trueness and precision.

• 한국자동차공학회논문집
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• 제20권1호
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• pp.39-45
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• 2012

In the standard CFD code, Lagrangian-Eulerian method is very popular to simulate the liquid spray penetrating into gaseous phase. Though this method can give a simple solution and low computational cost, it have been reported that the Lagrangian spray models have numerical grid dependency, resulting in serious numerical errors. Many researches have shown the grid dependency arise from two sources. The first is due to unaccurate prediction of the droplet-gas relative velocity, and the second is that the probability of binary droplet collision is dependent on the grid resolution. In order to solve the grid dependency problem, the improved spray models are implemented in the KIVA-3V code in this study. For reducing the errors in predicting the relative velocity, the momentum gain from the gaseous phase to liquid particles were resolved according to the gas-jet theory. In addition, the advanced algorithm of the droplet collision modeling which surmounts the grid dependency problem was applied. Then, in order to validate the improved spray model, the computation is compared to the experimental results. By simultaneously regarding the momentum coupling and the droplet collision modeling, successful reduction of the numerical grid dependency could be accomplished in the simulation of the high-pressure injection diesel spray.

• 한국항공우주학회지
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• 제45권4호
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• pp.342-348
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• 2017

본 연구에서는 초음속 주유동 환경에서의 막냉각 특성에 대해 적외선 열상법을 적용한 시험을 수행하였다. 막냉각 시험은 수축형 막냉각 노즐을 갖는 쐐기형 막냉각 시편을 이용해 마하수 3.0, 단위 길이 당 레이놀즈수 $42.53{\times}10^6$ 와 $69.35{\times}10^6$ 인 조건을 구현한 자유-제트 시험 설비에서 수행하였다. 모사 탐색창에 해당하는 PEEK의 표면 온도를 계측하여 막냉각 효율을 산출하였고 받음각 및 분사율이 막냉각 효율에 미치는 영향을 분석하였다. 막냉각을 적용하지 않는 경우와 비교할 때, 막냉각을 적용할 경우 측정된 PEEK의 표면 온도가 크게 감소하였다. 막냉각의 유용성은 시간에 따른 PEEK의 표면 온도로부터 산출한 열유속 특성으로도 확인할 수 있다. 분사율이 증가할수록 보호되는 PEEK의 영역이 주유동과 막냉각 유동의 흐름 방향으로 확장되었다.

• 한국산학기술학회논문지
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• 제13권9호
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• pp.4334-4340
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• 2012

본 연구에서는 미세 액적을 발생시키는 액적 발생 장치를 개발 제작하고 이에 대한 성능 평가를 실시하였다. 액적 발생 장치는 spray-evaporation method를 기초로 제작하였으며, 0.3mm, 0.5mm의 오리피스를 사용하였다. 압축 공기 공급 압력을 1bar에서 4bar로 증가시키면서 공급 압력에 따른 발생되는 액적 크기의 미세 정도를 비교하였다. 또한 SMPS(Scanning Mobility Particle Sizer)와 OPC(Optical Particle Counter)를 이용하여 서로 다른 오리피스를 장착한 액적 발생 장치에서 발생되는 액적의 크기 분포를 측정하였다. 연구 결과, 0.3mm 오리피스를 장착한 장치에서 발생되는 액적은 $0.3{\mu}m$ 인근의 크기가 가장 많았으며, 미립화되는 입자는 매우 안정적이었다. 또한 0.5mm 오리피스를 장착한 장치가 0.3mm 오리피스를 장착한 장치에 비해 발생되는 액적의 크기가 큰 것으로 나타났다. 이러한 액적 발생 장치는 입자의 미세한 응집 현상이 나타나는데, 이것은 내부 액체가 미세한 액적으로 미립화되어 분사되기 때문인 것으로 사료된다. 본 연구에서 제작한 액적 발생 장치는 미세 입자를 미립화하기 위한 에어로졸 발생 장치로 사용 가능한 것으로 판단된다.

• 한국수정란이식학회지
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• 제29권2호
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• pp.171-175
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• 2014

This study was conducted to determine the efficacy of anthelmintics against gastrointestinal parasitic infestation in periparturient dairy cows and its effect on milk yield and quality. Sixty pregnant cows of 1st & 2nd parity were divided into four groups. The efficacy of anthelmintic treatment was evaluated by counting faecal egg per gram (EPG) compared with pre-treatment values. The milk yield of each cow was recorded in pre and post treatment lactations. Cows of group A were treated with Nitroxynil 10 mg/kg body weight subcutaneously 30 days before parturition, group B were treated with combination of triclabendazole and levamisole 19.5 mg/kg body weight orally at calving and group C treated with $Endex^{(R)}$ at calving and 42 days after. The mean change in EPG 14 days after treatment was significantly higher (p<0.05) in treated (79.1%) cows than control. Average milk yield of group C ($2.8{\pm}0.8$) was significantly higher (p<0.01) than group A ($2.6{\pm}0.7$). Similarly, the average milk yield in all the treated cows was significantly (p<0.01) higher in treated lactation ($2.5{\pm}0.7$) than in the previous lactation ($2.2{\pm}0.7$). The average milk yield in all treated cows was significantly (p<0.01) higher than the control cows. Although, milk yields were higher in second parity than the first, there was no significant difference (p>0.05). The milk protein percentage was significantly higher (p<0.05) in treated group than the control group. Therefore, it may be concluded that periparturient anthelmintic treatment effectively reduced the gastrointestinal parasitic load and improved milk yield.

• 한국수정란이식학회지
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• 제32권2호
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• pp.53-58
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• 2017

It is very difficult to get the information about semen quality analysis in transgenic pigs because of limited numbers and research facilities. Therefore, in the present study, we analyzed the semen quality of transgenic boars generated for xenotransplantation research. Briefly, the semen samples were collected from 5 homozygous ${\alpha}1,3$-Galactosyltransferase knock-out ($GalT^{-/-}$) transgenic boars and immediately transported to the laboratory. These semen samples were decupled with DPBS and conducted to analyze semen parameters by a computer-assisted semen analysis (CASA) system. The boar semen were examined all 12 parameters such as total motility (TM), curvilinear velocity (VCL), straight line velocity (VSL), average path velocity (VAP), and hyperactivated (HYP), etc. In results, among the 5 $GalT^{-/-}$ boars, three boars (#134, 144, and 170) showed normal range of semen parameters, but #199 and 171 boars showed abnormal ranges of semen parameters according to standard ranges of semen parameters. Unfortunately, #171 boar showed azoospermia symptom with rare sperm counts in the original semen. Conclusively, assessment of semen parameters by CASA system is useful to pre-screening of reproductively healthy boar prior to natural mating and artificial insemination for multiplication and breeding.

• 한국항공우주학회지
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• 제32권4호
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• pp.12-17
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• 2004

고속 유동 속에 놓인 모델 표변의 압력분포를 정량적으로 측정하기 위해 PSP 기술이 사용되고 있다. 본 연구에서는 아음속 유동에 적용 가능한 PSP 기술을 개발하였다. 2가지의 백금계열 (PtOEP와 PtTFPP)의 발광분자와 2 가지의 폴리머 (Poly(TMSP)와 RTV-118)를 사 용하여 4가지의 PSP 조합을 만들어 그 성능을 확인하였다. 압력변화에 따른 PSP의 발광강 도를 측정하기 위해 $0{\sim}11kPa$까지 0.5, 1, 2kPa썩 압력을 증가시키면서 정적보정실험을 수행하였다. 4가지의 PSP 조성 중에 PtOEP 와 RTV-118의 조합이 가장 좋은 성능을 보였다. 충돌평판에 작용하는 압력장 분포를 측정하기 위하여 경사충돌분류에 본 연구에서 개발된 PSP 기술을 응용하였다.

• 한국태양에너지학회 논문집
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• 제31권3호
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• pp.23-28
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• 2011

In this study, the ejector design was modeled using Fluent 6.3 of FVM(Finite Volume Method) CFD(Computational Fluid Dynamics) techniques to resolve the flow dynamics in the ejector. A vacuum system with the ejector has been widely used because of its simple construction and easy maintenance. Ejector is the main part of the desalination system, of which designs determine the efficiency of system. The effects of the ejector was investigated geometry and the operating conditions in the hydraulic characteristics. The ejector consists mainly of a nozzle, suction chamber, mixing tube (throat), diffuser and draft tube. Liquid is supplied to the ejector nozzle, the fast liquid jet produced by the nozzle entrains and the non condensable gas was sucked into the mixing tube. The multiphase CFD modeling was carried out to determine the hydrodynamic characteristics of seawater-air ejector. Condition of the simulation was varied in entrance mass flow rate (1kg/s, 1.5kg/s, 2kg/s, 2.5kg/s, 3kg/s), and position of driving nozzle was located from the central axis of the suction at -10mm, 0mm, 10mm, 20mm, 30mm.. Asaresult, suction flow velocity has the highest value in central axis of the suction.

• 대한기계학회논문집
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• 제13권1호
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• pp.140-152
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• 1989

본 논문에서는 소형 고속 디젤 분무의 반경 방향의 연류 농도 분포를 고려한 비균질 분무의 분무 선단 도달 거리에 대한 관계식을 유도하고, 비정상 분무인 디젤 분무의 분사 차압-시간 곡선을 입력시킴으로써, 분사 초기 뿐 아니라 전 분사 기간의 분무 선단 도달 거리를 예측할 수 있는 새로운 모델을 제안하여 실험치와 비교 분석하였다. 그리고 분사각과 분열장의 무차원 실험식을 도출하여 계산에 사용하였고 분무 선단 도달 거리의 천이점과 분열장에 대하여 고찰하였다.

• 한국수정란이식학회지
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• 제28권1호
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• pp.73-78
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• 2013

The present study examined the histological characteristics of adult testis in the long-beaked common dolphin (Delphinus capensis) from Korean waters and the localization of DEAD-box polypeptide 4 (DDX4; a germ cell marker) and vimentin (a Sertoli cell marker) expression in the dolphin testis compared with that in terrestrial mammals, including dogs and rats. The seminiferous tubules of dolphin testis have very small or completely closed lumens, and spermatogenic cells and Sertoli cells within the tubules cannot be differentiated. Immunohistochemical analysis showed that, in the dolphin testis, DDX4- and vimentin-positive cells were scattered extensively within the tubule, whereas in the dog and rat testis, DDX4 immunoreactivity was localized in spermatogenic cells of the adluminal compartment, and vimentin immunoreactivity was localized in Sertoli cells of the basal compartment in the seminiferous epithelium. These results suggest that the histological characteristics of the seminiferous tubules in the dolphin testis differ from those of terrestrial species.