• 한국자동차공학회논문집
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• 제20권4호
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• pp.125-132
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• 2012

Urea-SCR system, which converts nitrogen oxides to nitrogen and water in the presence of a reducing agent, usually AdBlue urea solution, is known as one of the powerful NOx reduction systems for mobile as well as stationary applications. For its consistent and reliable operation in mobile applications, such various problems as transient injection, ammonia slip, and freezing in cold weather have to be resolved. In this work, therefore, numerical study on three-dimensional unsteady heating problems were analyzed to understand the melting and heat transfer characteristics such as urea liquid volume fraction, temperature profiles and generated natural convection behavior in urea solution by using the commercial software Fluent 6.3. After validating by comparing numerical and experimental data with pure gallium melting phenomena, numerical experiment for urea melting is conducted with three different coolant heating models named CH1, 2, and 3, respectively. Finally, it can be found that the CH3 model, in which more coolant is concentrated on the lower part of the urea tank, has relatively better melting capability than others in terms of urea quantity of $1{\ell}$ for start-up schedule.

• 한국주조공학회지
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• 제27권6호
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• pp.243-249
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• 2007

The effect of Re addition and solidification rate on the directional solidification behavior of Ni-Al model alloy has been investigated. Directional solidification (DS) were carried out using the modified Bridgman furnace with various solidification rates. The solid/liquid interface during directional solidification was preserved by quenching the specimen after the desired volume fraction of original liquid was solidified. The equilibrium partition coefficients of Al and Re Were estimated by measuring the compositions at the quenched solid/liquid interface. Then, the effect of Re addition on the elemental segregation behavior was carefully analyzed. The differential scanning calorimetry results showed that the Re addition results in increased ${\gamma}'$ solvus and freezing range of the alloy. It was also shown that the primary dendrite arm spacing gradually decreases with increasing the Re content, while the secondary dendrite arm spacing appears to be independent on the Re content. The compositional analyses clearly revealed that the segregation of Al increased with increasing the Re content and solidification rate, while that of Re was found to be independent on the solidification rate in the range of $10{\sim}100{\mu}m/s$ due to its sluggish diffusion rate in the Ni solid solution.

• Nuclear Engineering and Technology
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• 제32권4호
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• pp.395-409
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• 2000

Parametric studies were performed to assess the sensitivity in determining the maximum in-vessel heat removal capability from the core material relocated into the lower plenum of the reactor pressure vessel (RPV）during a core melt accident. A fraction of the sensible heat can be removed during the molten jet delivery from the core to the lower plenum, while the remaining sensible heat and the decay heat can be transported by rather complex mechanisms of the counter-current flow limitation (CCFL) and the critical heat flux (CHF）through the irregular, hemispherical gap that may be formed between the freezing oxidic debris and the overheated metallic RPV wall. It is shown that under the pressurized condition of 10MPa with the sensible heat loss being 50% for the reactors considered in this study, i.e. TMI-2, KORI-2 like, YGN-3&4 like and KNGR like reactors, the heat removal through the gap cooling mechanism was capable of ensuring the RPV integrity as much as 30% to 40% of the total core mass was relocated to the lower plenum. The sensitivity analysis indicated that the cooling rate of debris coupled with the sensible heat loss was a significant factor The newly proposed heat removal capability map (HRCM) clearly displays the critical factors in estimating the maximum heat removal from the debris in the lower plenum. This map can be used as a first-principle engineering tool to assess the RPV thermal integrity during a core melt accident. The predictive model also provided ith a reasonable explanation for the non-failure of the test vessel in the LAVA experiments performed at the Korea Atomic Energy Research Institute (KAERI), which apparently indicated a cooling effect of water ingression through the debris-to-vessel gap and the intra-debris pores and crevices.

• 한국항공우주학회지
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• 제40권2호
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• pp.146-156
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• 2012

비행 중 결빙은 항공기 운용에 위험한 상황을 초래하게 되며, 개발 및 감항 인증 과정중 성능과 안전에 미치는 영향이 평가되어야 한다. 평가를 위한 결빙 풍동시험에서 스케일링 기법은 실제와 동등한 수집율과 결빙량이 모사되는 대체시험 조건을 결정하는 기법이다. 본 논문에서는 Olsen 및 Ruff-IV 기법과 무차원 Weber 수를 일치시켜 속도를 계산하는 방법을 적용하여 연구자들이 쉽게 이용할 수 있도록 스케일링 프로그램을 개발하였다. 동일조건에서 수행된 NASA 스케일링 결과와 비교하여 프로그램을 검증하였다. 또한 FAR Part 25 Appendix C를 적용한 스케일링 사례를 제시하고 결빙코드 FENSAP-ICE를 이용하여 스케일링 기법을 검증하였다.

• 한국항공우주학회지
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• 제38권8호
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• pp.747-757
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• 2010

날개위에 쌓인 얼음은 날개의 공기역학적 성능을 저하시키고 항공기 사고를 야기하는 주요한 원인이 된다. 결빙된 날개의 형상 예측 연구는 얼음으로 변형된 날개의 공기역학적 성능 파악과 제빙 방빙 장치 설계에 선행 되어야 한다. 이를 위해 본 연구에서는 2차원 익형에 발생하는 유리얼음 형상을 예측할 수 있는 코드를 개발하였다. 계산의 효율성을 위해 익형 주위의 유동장 계산은 정상 용출 및 중첩 패널기법을 사용하였고 날개표면과 날개에 유입된 물의 열전달은 Messinger 모델을 통해 고려하였다. 본 코드의 해석 결과는 실험 및 LEWICE 등 기존 해석 프로그램과 상호 검증되었다. 결빙형상의 주요한 요소인 얼음 뿔의 진행 방향 및 얼음 두께는 실험 및 타 프로그램과 유사한 결과를 나타내었다. 또한 대기온도, 수증기 함량, 입자 반지름, 자유류 등이 착빙 형상에 미치는 영향을 체계적으로 분석하였다.

• 한국동물번식학회:학술대회논문집
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• 한국동물번식학회 2001년도 발생공학 국제심포지움 및 학술대회 발표자료집
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• pp.57-57
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• 2001

This study was carried out to investigate the general characteristics such as volume, sperm concentration, sperm motility, sperm abnormality on whole semen, RSP-S and RSP-T semen and fractional semen of small size dogs, and the effect of temperature and preservation time and cryoproservation on motility of whole and RSP-S and RSP- T semen. Multiple ejaculates were collected from small dogs by the digital manipulation of penis. 1. The volume per ejaculate semen, sperm of concentration and motility and abnormal sperm rate of 1st fractional semen were 0.65±0.09㎖, 4.52±0.35×10/sup 6/ cells/㎖, 15.64±3.85% and 5.50±0.62%. Also, 2nd fractional semen were 1.25±0.20㎖, 3.35±0.48×10/sup 6/cells/㎖, 96.25±4.65% and 4.24±0.46%. And 3rd fractional semen were 1.45±0.21㎖, 3.85±0.52×10/sup 6/cell/㎖, 92.82±4.24% and 4.66±0.58%, respectively. 2. The sperm of concentration and motility and abnormal sperm rates of whole, RSP-S and RSP-T semen were 5.45±0.82×10/sup 6/ cells/㎖, 95.55±4.65%, 4.58±0.45% and 4.82±0.36×10/sup 6/cells/㎖, 90.10±3.42%, 6.48±0.68% and 4.55±0.45× 10/sup 6/cells/㎖, 93.25±3.85%, 4.82±0.58%, respectively. 3. The motility of whole, RSP-S and RSP-T semen were higher at 4℃ than at 38℃. When preservation temperature was at 4℃, survival rates of RSP-S and RSP-T sperm were 97.54%-6.25% at 1-72 hrs, 97.40%-5.62% at 1-100 hrs, respectively. 4. The survival rates of slow and rapid frozen 2nd fraction, RSP-S and RSP-T semen were 67.3±4.45%, 88.8±4.46% and 46.4±3.84%, 74.4±4.20%, respectively. Survival rates was significantly higher in frozen RSP-S and RSP-T semen than that in control group(8.5±2.12%).

• Asian-Australasian Journal of Animal Sciences
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• 제16권2호
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• pp.180-184
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• 2003

The intrauterine inseminator (IUI) was developed to provide the method of depositing dog semen into the uterine body instead of the vagina. The IUI consists of a vaginal endoscope, a balloon sheath, and injection catheter. When the endoscope is inserted into the vagina and the balloon expanded with air, the cervical os becomes visible so a injection catheter can be inserted through the cervix for deposition of the frozen-thawed semen. The efficacy of the IUI device was compared to intra-vaginal artificial insemination using semen that had been collected and frozen from pooled sperm-rich fraction of ejaculates collected from two Jindo dog donors. Aliquots of semen were extended with a Tris-egg yolk diluent, centrifuged, the seminal plasma removed, the pellet resuspended with the same diluent, and cooled to $5^{\circ}C$ over a 2 h period. A Tris-egg yolk-glycerol extender was added at $5^{\circ}C$; after 1 h, semen was loaded into 0.5 ml straws, and straws were frozen in LN vapor for 5 min, and immersed in LN for storage. The final sperm concentration for freezing was approximately $100{\times}10^{6}cells/ml$. The straws were thawed at $70^{\circ}C$ for precisely 6 sec, 1.5 ml Tris-egg yolk buffer at $38^{\circ}C$ added, and the 2 ml of thawed semen was used for a single insemination using the IUI device. Each bitch was inseminated at optimal insemination point, which was estimated by vaginal epithelial cells staining and progesterone concentration analysis. Use of the IUI device resulted in 21 of 26 females giving birth to 89 pups ($4.2{\pm}1.6$ pups per litter), while intra-vaginal AI resulted in 6 of 15 females whelping a total of 17 pups ($2.8{\pm}1.2$ pups per litter). We believe the IUI device is easier to use than previously described devices used for intrauterine insemination. In our experience the expansion of the balloon has a calming effect on the bitch that aids the inseminator. These results indicate that the IUI device was able to provide high fertility with 50 million frozen sperm per insemination and two inseminations.

• 한국가축번식학회지
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• 제23권2호
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• pp.127-132
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• 1999

본 연구는 소형견 정액의 원정액과 정장제거 정액의 일반성상, 채취분획별 및 단기보존시 정자의 생존성과 아울러 동결보존시의 정자의 생존성에 대해 조사하고자 수행하였다. 1. 원정액과 정장제거 정액에 saline 및 Tris-buffer를 희석 후 각각 일반성상 검사를 실시했을 때 원정액의 경우 정자농도는 5.07$\pm$2.32$\times$$10^{6}$cells/$m\ell$, 정자의 운동성은 95.42$\pm$2.65%, 기행정자수는 4.42$\pm$0.15%로 나타났으며, RSP(saline 및 Tris-buffer)군의 경우 정자농도는 4.69$\pm$3.27~4.25$\pm$3.65$\times$$10^{6}$cells/$m\ell$, 정자의 운동성은 91.17$\pm$3.85~88.52$\pm$3.85%, 기형정자수는 6.57$\pm$0.43~5.54$\pm$0.52%로 나타났다. 2. 분획별 채취 전정액중 제 1 분획에서는 정액량이 0.92$\pm$0.7$m\ell$, 정자농도는 4.57$\pm$0.78$\times$$10^{6}$cells/$m\ell$, 정자활력은 10.72$\pm$3,21%, 기형정자수는 5.50$\pm$0.70%로 나타났으며, 제 2분획에서는 정액량이 2.14$\pm$0.19$m\ell$, 정자농도는 2.01$\pm$0.12$\times$$10^{6}$cells/$m\ell$, 정자활력은 95.44$\pm$4.21%, 기형정자수는 4.31$\pm$0.53%로 나타났다. 또한, 제3 분획에서는 정액량이 2.66$\pm$0.23$m\ell$, 정자농도는 2.35$\pm$0.21$\times$$10^{6}$cells/$m\ell$, 정자활력은 90.71$\pm$2.63%, 기형정자수는 6.33$\pm$0.91%로 나타났다. 3. 원정액과 정장제거 정액을 4$^{\circ}C$ 와 2$0^{\circ}C$ 및 37$^{\circ}C$ 에서 각각 보존했을 때 보존시간별 정자의 활력은 2$0^{\circ}C$ 의 경우 1, 6, 13, 24, 30 및 40 시간에서 각각 98.51%와 98.32%, 86.32%와 92.15%, 83.71% 와 89.20%, 74.29% 와 82.08%, 52.98% 와 72.07%, 15.45% 와 60.02%, 2.41% 와 37.19% 의 정자활력을 나타내어 4$^{\circ}C$와 37$^{\circ}C$에 비해 높은 정자운동성을 나타냈다. 4. 제 2 분획 정액과 정장제거 정액을 각각 제 1차 및 제 2차 희석액으로 희석 평형 시킨 후 동결 융해했을 때 정자의 생존율은 각각 33.3$\pm$8.7, 54.7$\pm$9.5%로서 대조군의 15.4$\pm$5.2% 에 비해 높게 나타났다.

• 한국가축번식학회지
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• 제25권3호
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• pp.269-275
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• 2001

본 연구는 소형 개의 동결정액을 개발하여 인공수정에 이용하고자 제 2차 분획정액을 생리적 식염수와 Iris-buffer액으로 희석하고 원심분리에 의해 정장성분을 제거한 RSP-5 및 RSP-T 정액의 일반성상과 단기보존 및 동결보존시의 생존성에 대해 조사하였다. 1, 제 1분획의 정액량은 0.65$\pm$0.09 $m\ell$, 정자농도는 4.52$\pm$0.35$\times$$10^{6}$cells/$m\ell$, 활력은 15,64$\pm$3.85%, 기형정자수는 84.36$\pm$0.62%였으며, 제 2분획의 정액량은 1.25$\pm$0.20 $m\ell$, 정자농도는 3.35$\pm$0.48$\times$$10^{6}$cells/$m\ell$, 활력은 96.25$\pm$4.65%, 기형정자수는 3.75$\pm$0.46%였으며, 제 3분획의 정액량은 1.45$\pm$0.21 $m\ell$, 정자농도는 3.85$\pm$0.52$\times$$10^{6}$cells/$m\ell$, 활력은 92.82$\pm$4.24%, 기형정자수는 4.66$\pm$0.58%였다. 2. 제 2분획 정액의 RSP-5군의 정자농도는 4.82$\pm$0.36$\times$$10^{6}$cells/$m\ell$, 활력은 90.10$\pm$3.42%, 기형정자수는 9.90$\pm$0.68%였으며, RSP-T군의 정자농도는 4.55$\pm$0.45$\times$$10^{6}$cells/$m\ell$, 활력은 93.25$\pm$3.85%, 기형정자수는 6.75$\pm$0.58%였다. 이는 대조군의 정자농도 5.45$\pm$0.82$\times$$10^{6}$cells/$m\ell$, 활력 95.55$\pm$4.65%, 기형정자수 4.45$\pm$0.45%에 비해 높게 나타났다. 3. 제 2분획 정액을 RSP-5와 RSP-T로 처리한 정액을 4$^{\circ}C$에서 보존했을 때 각각 1~72시간(97.54~6.25%)과 1~100시간(97.40~5.62%)에서 생존성이 유지되었고, 38$^{\circ}C$에서 보존했을 때 1~40시간(96.45~7.45%)과 1~50시간(95.60~B.65%)에서 생존성이 유지되었다. 이는 무처리 대조군의 1~50시간(97.24~4.82%)과 1~30시간(95.52~5.55%)에 비해 생존성이 높게 나타났다. 4. 제 2분획 정액을 처리한 RSP-5군의 정액을 완만 및 초급속 동결후 융해했을 때 생존율은 각각 67.3$\pm$4.45%와 46.4$\pm$3.84%였으며, RSP-T군 정액은 58.8$\pm$4.46%와 74.4$\pm$4.20%로서 대조군의 8.5$\pm$2.12%에 비해 높게 나타났다.