• 한국수정란이식학회지
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• 제13권1호
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• pp.69-76
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• 1998

This study was carried out to establish an effective system for embryo transfer techniques by analyzing several factors affecting in-vivo embryo transfer in Korean cattle Embryos were transferred into a toral of 301 recipients. The results obtained in studies on the factors affecting pregnancy rate after embryo transfer by condition of transfer time were as follows ; 1. The pregnancy rate by the seasons of transferred fresh and frozen embryos were not different, but the pregnancy rate was slightly higher in summer(80.8%). 2. The pregnancy rate by the days of embryo transfer after estrus were not different when fresh embryos were transferred, but the pregnancy rate was highest at 8 days when frozen embryos were transferred(P<0.01, 40.0%). 3. The pregnancy rate at estrus synchronization was remarkably higher with PGF$_2$$\alpha$ treated than natural (P<0.05, 70.4%, 43.4%). 4. The pragnancy rate by the degree of estrus synchronization was best when the estrus was synchronized in both fresh and frozen embryos (83.3% and 29.7%, respectively), but the pregnancy rate was not different among $\pm$2 days. But the pregnancy rate of frozen embryos were slightly higher when the recipients exhibited estrus earlier than donors.

• 한국항공우주학회지
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• 제47권2호
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• pp.161-168
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• 2019

본 논문에서는 소형 무인기 데이터 링크 시스템에 적용이 가능한 전송률 가변 비대칭 TDD(Time Division Duplex) 방식에 대해 다루었다. 긴 복호 시간이 필요한 터보 복호기를 비대칭 TDD 방식에 적용하기 위하여 이중 버퍼 제어기 구조의 터보 복호기를 제안하였다. 제안 방법은 전송률 가변과 동일 송수신 시간에 최대의 데이터 전송이 가능하다. 제안 방식을 적용한 데이터 링크 시스템을 제작하여 성능을 확인하였다. 측정 결과, 대칭 TDD 방식에 비해 전송률은 최대 약 1.8배 증가하였다. PER(Packet Error Rate) 성능은 동일하며, 전송률 가변이 가능함을 확인하였다.

• 설비공학논문집
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• 제11권6호
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• pp.855-860
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• 1999

An experimental study of jet impingement on the surface with linear temperature gradient is conducted with the presentation of the turbulent characteristics and the heat transfer rates measured when this jet impinges normally to a flat plate. The jet Reynolds number ranges from 30,000 to 90,000, the temperature gradient of the plate is 2~$4.2^{\circ}C$/cm and the dimensionless nozzle to plate distance(H/D) is from 6 to 10. The results show that the peak of heat transfer rate occurs at the stagnation point, and the heat transfer rate decreases as the radial distance from the stagnation point increases. A remarkable feature of the heat transfer rate is the existence of the second peak. This is due to the turbulent development of the wall jet. Maximum heat transfer rate occurs when the axial distance from the nozzle to nozzle diameter(H/D) is 8. The heat transfer rate can be correlated as a power function of Prandtl number, Reynolds number and the dimensionless nozzle to plate distance(H/D). It has been found that the heat transfer rate increases with increasing turbulent intensity.

• 한국기계가공학회지
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• 제20권6호
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• pp.82-91
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• 2021

We compared the heat transfer characteristics of the parallel and the counterflow flow in the concentric double tube of the Al₂O₃/water nanofluids using numerical methods. The high- and low-temperature fluids flow through the inner circular tube and the annular tube, respectively. The heat transfer characteristics according to the flow direction were compared by changing the volume flow rate and the volume concentration of the nanoparticles. The results showed that the heat transfer rate and overall heat transfer coefficient improved compared to those of basic fluid with increasing the volume and flow rate of nanoparticles. When the inflow rate was small, the heat transfer performance of the counterflow was about 22% better than the parallel flow. As the inflow rate was increased, the parallel flow and the counterflow had similar heat transfer rates. In addition, the effectiveness of the counterflow increased from 10% to 22% rather than the parallel flow. However, we verified that the increment in the friction factor of the counterflow is not large compared to the increment in the heat transfer rate.

• Journal of Welding and Joining
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• 제15권2호
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• pp.72-80
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• 1997

The spatter generation rate of GMA welding with $CO_2$ gas shielding was measured with the change of welding conditions such as wire feeding rate and welding voltage and then the results were analized with the accompanying changes in metal transfer mode and in bead geometry. The spatter generation rate (SGR) was relatively low not only wit the short circuit transfer but with the truely globular transfer mode. However, the SGR resulted with the mixed mode were consistantly high. The resultant wave pattern of mixed mode was due to the coexistance of short-circuit and globular transfer and characterized by the frequent appearance of instantaneous short circuit. Considering the result of SGR and that of bead geometry, it could be concluded that when the wire feeding rate (or welding current) was either low or high, the optimum bead shape could be obtained along with the low spatter generation. However, in the middle range of wire feeding rate, the optimum bead shape was only obtained in the mixed mode condition resulting in the high spatter generation.

• Nuclear Engineering and Technology
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• 제49권8호
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• pp.1617-1628
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• 2017

In the passive residual heat removal system of a molten salt reactor, one of the residual heat removal methods is to use the thimble-type heat transfer elements of the drain salt tank to remove the residual heat of fuel salts. An experimental loop is designed and built with a single heat transfer element to analyze the heat transfer and flow characteristics. In this research, the influence of the size of a three-layer thimble-type heat transfer element on the heat transfer rate is analyzed. Two methods are used to obtain the heat transfer rate, and a difference of results between methods is approximately 5%. The gas gap width between the thimble and the bayonet has a large effect on the heat transfer rate. As the gas gap width increases from 1.0 mm to 11.0 mm, the heat transfer rate decreases from 5.2 kW to 1.6 kW. In addition, a natural circulation startup process is described in this paper. Finally, flashing natural circulation instability has been observed in this thimble-type heat transfer element.

• 한국수정란이식학회지
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• 제13권1호
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• pp.61-67
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• 1998

This study was carried out to establish an effective system for embryo transfer techniques by analyzing several factors affecting in-vivo embryo transfer in Korean cattle. Embryos produced in-vivo were transferred into a total of 301 recipients The results obtained in studies on the factors affacting pregnancy rate after embryo transfer by condition of recipients were as follows ; 1. The pregnancy rate by age and parity of recipients showed high in 5~8 and over 12 years old(72.7~73.9%), and 3rd~4th parity(82.1%) for fresh embryos(P<0.05). The pregnancy rate did not differ by age and parity of recipients in frozen embryos. The pregnancy rate of frozen embryos tended to be similar to that of fresh embryos(38.5% and 25.0~36.7%). 2. The number of observation for normal estrus cycles of recipients did not differ In pregnancy rate between one and 2 times in fresh embryos(64.9%, 69.8%). The pregnancy rate by transferred frozen embryos showed significantly higher after 2 times of observation(P<0.05, 16.3%, 37.5%). The pregnancy rate by days open did not differ between fresh and frozen embryos. But the pregnancy rate was slightly higher in 12 months and 6 months of days open for fresh and frozen embryos, respectively(70.1~71.1% and 24.5%, respectively). 3. The pregnancy rate of transferred fresh and frozen embryos into right and left side of uterine horn did not differ(62.1% : 65.9% 25.0% : 24.3%, respectively). The pregnancy rate by the grade of CL was not different in fresh embryos, but the pregnancy rate was significantly higher in the grade A than B for frozen embryos(P<0.01, 43.2%, 16.2%).

• Clinical and Experimental Reproductive Medicine
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• 제44권2호
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• pp.105-110
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• 2017

Objective: The purpose of this study was to evaluate the efficacy of frozen mixed double-embryo transfer (MDET; the simultaneous transfer of day 3 and day 5 embryos) in comparison with frozen blastocyst double-embryo transfer (BDET; transfer of two day 5 blastocysts) in patients with repeated implantation failure (RIF). Methods: A total of 104 women with RIF who underwent frozen MDET (n = 48) or BDET (n = 56) with excellent-quality embryos were included in this retrospective analysis. All frozen embryo transfers were performed in natural cycles. The main outcome measures were the implantation rate, clinical pregnancy rate, multiple pregnancy rate, and miscarriage rate. These measures were compared between the patients who underwent MDET or BDET using the chi-square test or the Fisher exact test, as appropriate. Results: The implantation and clinical pregnancy rates were significantly higher in patients who underwent MDET than in those who underwent BDET (60.4% vs. 39.3%, p=0.03 and 52.1% vs. 30.4%, p=0.05, respectively). A significantly lower miscarriage rate was observed in the MDET group (6.9% vs. 10.7%, p=0.05). In addition, the multiple pregnancy rate was slightly, but not significantly, higher in the MDET group (27.1% vs. 25.0%). Conclusion: MDET was found to be significantly superior to double blastocyst transfer. It could be regarded as an appropriate approach to improve in vitro fertilization success rates in RIF patients.

• 한국수정란이식학회지
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• 제23권3호
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• pp.167-175
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• 2008

This study was performed to investigate the result that in-vivo or in-vitro embryos of Hanwoo cows were transferred to Holstein cows. Seventeen Hanwoo cows were used as donors for production of in-vivo embryos and fresh hanwoo in-vivo embryos were transferred to 1,150 Holsteins. And 2 embryos were transferred to 188 Holstein recipients to produce twin calves. Diagnosis on pregnancy was performed by rectal palpation at $60\sim90$ days after transfer. The pregnancy rate of Holstein recipients was 55.8% after transfer with Hanwoo in-vivo embryos and 38.2% after transfer with Hanwoo in-vitro embryos. The delivery rate of pregnant Holstein recipients was 88.4% after transfer with Hanwoo in-vivo embryos and 75.6% after transfer with Hanwoo in-vitro embryos. The rate of delivery of Holstein recipients transferred with two Hanwoo embryos was 36.2% and the rate of twin production was 25.9%. The rate of twin production by embryo transfer with in-vivo embryos was 30.4%, whereas the fate with in-vitro embryos was 15.6%. The pregnancy rate according to the grade of corpus luteum of Holstein recipients transferred with Hanwoo in-vitro embryos was 41.5 and 36.0% for A and B grade, respectively. The pregnancy rate according to the transfer in site in the uterine lumen of recipients was 40.9 and 32.7% for anterior and middle site, respectively. The pregnancy rate according to day of embryo transfer after estrus of recipients was 45.5, 38.8 and 39.7% for day 6, day 7 and day 8, respectively. There was difference of pregnancy rate according embryo transfer technician ($30.5\sim45.8%$) individual dairy farm ($21.1\sim51.0%$). These results are supposed to indicate that the rate of pregnancy after transfer with Hanwoo embryos to Holstein recipients was similar to that within the same breed, and consequently that this method would be beneficial to enhance the productivity in Hanwoo reproduction.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2001년도 춘계학술대회 논문집
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• pp.36-43
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• 2001

Although the transferring is one of the most important factors in urban railways, there is very little analytic research in the transfer-related field. This paper analyses the transfer rate of urban railways in the Seoul Metropolitan Area and the actual passenger boardings and alightings at transfer stations using the AFC(Automatic Fare Collector) O/D data collected doling Sep. 2000. According to the results of this study the transfer rate is 0.657, which is calculated from the transfer hoardings/initial boardings. And the actual ridership of Subway Line 2 and Line 5 are different from the data which was provided by the AFC.