• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 춘계학술대회 논문집 유기절연재료 방전 플라즈마연구회
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• pp.61-64
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• 2003

In the response to an increasing demand for electrical energy, much effort aimed to develop and commercialise HTS power equipments is going on around the world. For the development, it is necessary to establish the dielectric technology in $LN_2$. Hence many types of dielectric tests should be carried out to understand the dielectric phenomena at cryogenic temperature and to gather various dielectric data. Among the many types dielectric tests, the barrier effect were conducted with the simulated electrode after analysing the insulating configuration of the pancake coil type HTS transformer. The influence of a barrier on the dielectric strength was measured according to the size and the position of the barrier. It was shown that the effectiveness, the ratio of the breakdown voltage in presence of barrier to the voltage without barrier, is highest when the barrier is placed at the needle electrode side. And the barrier effect was not depend on the electrode array. The life time to breakdown with decreasing the applied voltage was increased remarkably having wide error band but the shape parameter in Weibull distribution was almost constant.

• Journal of Advanced Marine Engineering and Technology
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• 제37권1호
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• pp.22-28
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• 2013

본 논문은 액화 천연 가스(LNG)를 주 연료로 사용하는 선박용의 LNG기화기의 특성을 조사하기 위하여 기화기 내부에서의 열전달 특성을 연구하였다. LNG를 기화하기 위한 가열열원으로서는 주 엔진에서 발생하는 워터 쟈켓의 가온수를 직접 이용하지 않고 열교환기를 통하여 간접 가열된 글리콜 워터(Glycol Water)를 사용하는 시스템을 채택하였다. LNG의 기화 과정은 상변화를 동반하기 때문에 이를 검증하기 위하여 액화질소(LN2)의 기화과정을 통하여 신뢰성을 확보하였고, LNG 기화기 내부의 최적 열적특성을 도출하기 위하여 LNG의 유입량과 가열열원인 글리콜 워터 유량변화에 대한 LNG 기화특성을 연구하였다. 해석 결과 LNG 질량유량이 0.111 kg/s과 가열원수인 부동액 질량유량이 1.805 kg/s일 경우 가스 출구 온도는 약 $6^{\circ}C$로서 LNG 선박의 최적 운전 조건임을 알 수 있었다.

• Nuclear Engineering and Technology
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• 제40권6호
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• pp.467-476
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• 2008

To keep the superconducting (SC) magnet coils of KSTAR at proper operating conditions, not only the coils but also other cold components, such as thermal shields (TS), magnet structures, SC bus-lines (BL), and current leads (CL) must be maintained at their respective cryogenic temperatures. A helium refrigeration system (RRS) with an exergetic equivalent cooling power of 9 kW at 4.5 K without liquid nitrogen ($LN_2$) pre-cooling has been manufactured and installed. The main components of the KST AR helium refrigeration system (HRS) can be classified into the warm compression system (WCS) and the cryogenic devices according to the operating temperature levels. The process helium is compressed from 1 bar to 22 bar passing through the WCS and is supplied to cryogenic devices. The main components of cryogenic devices are consist of cold box (C/B) and distribution box (D/B). The C/B cool-down and make the various cryogenic helium for the KSTAR Tokamak and the various cryogenic helium is distributed by the D/B as per the KSTAR requirement. In this proceeding, we will present the commissioning results of the KSTAR HRS. Circuits which can simulate the thermal loads and pressure drops corresponding to the cooling channels of each cold component of KSTAR have been integrated into the helium distribution system of the HRS. Using those circuits, the performance and the capability of the HRS, to fulfill the mission of establishing the appropriate operating condition for the KSTAR SC magnet coils, have been successfully demonstrated.

• 한국가금학회지
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• 제41권4호
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• pp.261-270
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• 2014

동결 닭 PGCs의 생식계열 키메라를 이용한 생체에의 복원을 실용화 하기 위해서는, 닭 PGCs의 동결 보존 기술의 향상에 의해 동결 및 융해 후의 많은 생존 세포를 확보하는 것과, 생식계열 키메라의 제작 효율을 높이는 것이 반드시 필요하다. 닭 PGCs는 배양 5.5~6일령의 닭 원시 생식선으로부터 채취하고, MACS 방법에 의해서 순수 닭 PGCs를 분리했다. 15% 각각의 EG와 DMSO를 동결 보호제로 사용한 처리군이 각 군의 농도에 상관없이 유의적(p<0.05)으로 PG 처리군보다 동결 및 융해 후의 세포의 생존율이 높음을 확인하였다. 특히, 10% EG+FBS 조합의 처리군에서 상업용 닭인 한협육종협회3호종(B : 88.7%)이 오계종(A : 85.1%), 아사 브라운종(C : 84.6%) 그리고 화이트 레그혼종(D : 85.9%)의 세 품종보다 동결 및 융해 후의 닭 PGCs의 생존율이 유의적(p<0.05)으로 높음을 확인하였다. 간이 동결에 있어서 가장 높은 생존율을 보인 10% EG이 10% DMSO와 함께 최적의 동결 보호제로서 사용 가능성을 확인하였다.

• 한국동물생명공학회지
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• 제34권4호
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• pp.272-279
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• 2019

The study was conducted to evaluate the seminal attributes and cryobanking of Achhami (Bos indicus) bull semen. Of two Achhami bulls, 8 ejaculates from each bull were evaluated for seminal attributes. For semen freezing and cryo-banking, 4 ejaculates (having ≥2 mL semen volume, ≥75% of sperm motility and ≥1,000 × 10⁶ cells/mL of sperm concentration) from each bull were used. Semen samples were diluted in egg-yolk-tris-citrate extender using a two-step dilution protocol, and were frozen in liquid nitrogen (LN₂) vapour in a styrofoam box. The mean semen volume, colour, sperm mass activity, motility, viability, concentration, abnormal acrosome, midpiece and tail and, abnormal head of two Achhami bulls were 4.4 ± 0.5 mL vs. 2.5 ± 0.2 mL, 2.5 ± 0.1 vs. 2.4 ± 0.1, 3.5 ± 0.1 vs. 3.5 ± 0.1, 77.0 ± 1.1% vs. 78.3 ± 1.3%, 94.4 ± 0.5% vs. 91.0 ± 0.6%, 1137.7 ± 73.7 × 10⁶ cells/mL vs. 1060.0 ± 44.3 × 10⁶ cells/mL, 10.2 ± 0.5% vs. 10.3 ± 0.5% and 6.7 ± 0.5% vs. 8.2 ± 0.3%, respectively. The post-thawed sperm motility and viability were 53.0 ± 2.0% vs. 50.0 ± 0.0% and 80.2 ± 0.4% vs. 73.2 ± 0.7%, while evaluating by computer-assisted sperm analysis (CASA) system, the percentage of the progressive motility, fast motility, slow motility, local motility and immotile sperm were 75%, 68%, 7.4%, 16.6% and 8.6%, respectively. A total number of 620 doses semen straw were cryo-banked. Due to the acceptable post-thawed sperm motility and viability recorded, cryopreservation of Achhami semen is hereby recommended so as to preserve the Achhami breed. For further validation, the fertility will be observed from the produced frozen semen.

• 한국발생생물학회지:발생과생식
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• 제20권3호
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• pp.219-225
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• 2016

Most of the commercial devices for vitrification are directly immersed into the warming solution (WS) for increasing of warming rate. However, the previous modified cut standard straw (MCS) which has reported is difficult to immerse into the WS. The aim of this study was to investigate whether the long cut straw (LCS) could be useful as a stable tool for vitrified-warmed human blastocysts. A total of 138 vitrified-warmed cycles were performed between November 2013 and November 2014 (exclusion criteria: women ${\geq}38$ years old, poor responder, surgical retrieval sperm, and severe male factor). The artificial shrinkage was conducted using 29-gauge needles. Ethylene glycol and dimethyl sulfoxide (7.5% and 15% (v/v)) were used as cryoprotectants. Freezing and warming were conducted using the LCS tool. The cap of LCS was removed using the forceps in the liquid nitrogen ($LN_2$) and then directly immersed into the first WS for 1 min at $37^{\circ}C$ (1 M sucrose). Only re-expanded blastocysts were transferred after it was cultured in sequential media for 18-20 h. A total of 294 blastocysts were warmed, and all were recovered (100%). Two hundred eighty-five embryos were survived (96.9%). The vitrified-warmed blastocysts of all patients were transferred without any cancellation. We were able to achieve a reasonable implantation (24.2%), following by clinical pregnancy (36.2%), which then continued to ongoing pregnancy (36.2%), and live birth (31.2%). Using LCS is achieved the acceptable rates of survival, pregnancy and live birth. Therefore, the LCS could be considered as a stable and simple tool for human embryo vitrificaton.

• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2002년도 Proceedings
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• pp.161-163
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• 2002

The BNCT(Boron Neutron Capture Therapy) facility has been developed in Hanaro(High-flux Advanced Neutron Application Reactor), a research reactor of Korea Atomic Energy Research Institute. A typical tangenial beam port is utilized with this BNCT facility. Thermal neutrons can be penetrated within the limits of the possible maximum instead of being filtered fast neutrons and gamma rays as much as possible using the silicon and bismuth single crystals. In addition to, the liquid nitrogen (LN$_2$) is used to cool down the silicon and bismuth single crystals for the increase of the penetrated thermal neutron flux. Neutron beams for BNCT are shielded using the water shutter. The water shutter was designed and manufactured not to interfere with any other subsystem of Hanaro when the BNCT facility is operated. Also, it is replaced with conventional beam port plug in order to cut off helium gas leakage in the beam port. A circular collimator, composed of $\^$6/Li$_2$CO$_3$ and polyethylene compounds, is installed at the irradiation position. The measured neutron flux with 24 MW reactor power using the Au-198 activation analysis method is 8.3${\times}$10$\^$8/ n/cm$^2$ s at the collimator, exit point of neutron beams. Flatness of neutron beams is proven to ${\pm}$ 6.8% at 97 mm collimator. According to the result of acceptance tests of the water shutter, the filling time of water is about 190 seconds and drainage time of it is about 270 seconds. The radiation leakages in the irradiation room are analyzed to near the background level for neutron and 12 mSv/hr in the maximum for gamma by using BF$_3$ proportional counter and GM counter respectively. Therefore, it is verified that the neutron beams from BNCT facility in Hanaro will be enough to utilize for the purpose of clinical and pre-clinical experiment.

• 한국수정란이식학회지
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• 제32권4호
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• pp.311-317
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• 2017

Cryopreservation of oocytes by vitrification technique may contribute a lot in the field of reproductive biotechnology. The objectives of the present study were to evaluate the effectiveness of two cryo-devices for vitrification of immature oocytes of indigenous zebu cows. Slaughter house derived immature cumulus-oocyte-complexes (COCs) of cows were vitrified using 15% dimethyl sulphoxide (DMSO) as cryoprotective agent (CPA) with 0.5 mol sucrose in TCM 199 supplemented with 20% FBS. Vitrification of COCs was completed after immediate plunging of COCs loaded cryotop or French mini straw into the liquid nitrogen ($LN_2$). Then the COCs containing cryotop or French mini straws were warmed in 0.25 mol sucrose and 20% FBS supplemented TCM 199 followed by in vitro culture in $50{\mu}l$ droplets of bicarbonate buffered TCM 199 supplemented with 10% FBS, pyruvate, FSH and oestradiol for 24 hrs at $39^{\circ}C$ with 5% CO2 in humidified air. After maturation culture, oocytes were denuded and examined under inverted microscope for presence of polar body as the indication of maturation. Denuded oocytes were also stained by whole mount technique using 1% orcein to examine the maturation by presence of MII chromosomes. The in vitro maturation rate was significantly (p<0.05) higher in oocytes vitrified and warmed using crytop ($47.1{\pm}6.9%$) than that of French mini straw ($15.9{\pm}12.5%$). Moreover, in vitro maturation rate was significantly (p<0.05) highe r in control oocytes (not vitrified) ($84.5{\pm}14.2%$) than that of vitrified oocytes. In conclusion, cryotop is better than French mini straw as cryo-device for vitrification of bovine immature oocytes.

• 한국수정란이식학회:학술대회논문집
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• 한국수정란이식학회 2002년도 국제심포지엄
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• pp.92-92
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• 2002

Considerable attention has been focused on the cryopreservation of semen and estrus induction in dog, as consequence of poor productivity caused by long anestrus period, in order to enhance the productivity of youngs and to preserve the breeds. The objectives of this study were to evaluate semen quality after cryopreservation and to evaluate the Pregnancy rate after insemination (AI). Fifty infertilie dogs (age 2∼3 years) were selected for the study and divided into three different estrus induction treatment groups. Group 1: dogs (n=15) were given clomifene (0.1 mg/kg) orally for five days at 12 hr intervals. Group 2: dogs (n=15) were given bromocriptine (50 $\mu\textrm{g}$/kg) orally for five days at 12 hr intervals, followed by single injection intravenously of 500 IU GnRH (Group 3, n=20) when pro-estrus occurred. The rates of pregnancy in estrus inducted dogs mated naturally compared to those inseminated artificially with ejaculated fresh semen and frozen-thawed semen. Estrus detection was performed using the method of vaginal smear and confirmed by the plasma progesterone assay. The ejaculated semen to freeze was exposed to a mixture of Tris extender with cryoprotectant (Trisma, 81 mM: TES, 209 mM: citric acid, 6 mM; glucose, 5 mM; glycerol, 8%) and cryopreserved gradually by slow-cooling at 17 cm above the surface of liquid nitrogen (LN$_2$) for 23 min. The motility of frozen-thawed spermatozoa was assessed by phase-contrast microscopy. To assess their viability and acrosome content, spermatozoa were stained with a vital stain and Fluorescence conjugated lectin Pisum Savitum Agglutinin (FITC/PAS), respectively. Pregnancy was confirmed by ultrasonograpy on day 25, 35 and 55 post insemination. The use of fresh semen, the pregnancy rates were observed 66.6, 66.6, 75.0 and 83.3% in natural estrus, clomifene induced, bromocriptine induced and a combination of GnRH and bromocriptine, respectively. The use of frozen-thawed semen, the pregnancy rates were observed 66.6, 33.3, 50.0 and 60.0% in natural estrus, clomifene induced, bromocriptine induced and a combination of GnRH and bromocriptine, respectively. No difference was observed in the number of offspring produced among natural estrus and treated groups inseminated with fresh or frozen-thawed semen. In conclusion, the pregnancy rate of dogs treated with a combination of GnRH and bromocriptine was more effective than use of clomifene or bromocriptine only. In addition, frozen-thawed semen can be used successfully far artificial insemination in dog.

• 한국수정란이식학회지
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• 제21권3호
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• pp.263-271
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• 2006

본 연구는 미니 돼지와 일반 돼지(Duroc)의 동결융해 후 정자의 수정 능력을 비교하여 동결 보존체계의 기틀을 확립하고자 하였다. 정액 제조는 수압법으로 정액 채취하여 1차 희석하였다. 동결은 LEY (1차: 11% ${\alpha}$-lactose+egg yolk, 2차: 1차 동결액+glycerol+OEP) 동결액을 이용하여 동결을 실시하여 동결 보존하였다. 동결 정액의 융해는 0.5 ml straw를 각각 20, 37 및 $50^{\circ}C$ water bath에서 1분, 40 초 및 10초간 융해하여 세척 과정 후 BTS 5 ml를 첨가하여 $37^{\circ}C$에서 배양하였다. 정자 성상 검사로는 기형율(Rose Bengal staining), 첨체율(Chlortetra-cycline staining) 및 생존율(SYBR-14/PI staining)등을 배양 후 0, 3, 6, 9 및 12시간에서 검토하여 다음과 같은 결과를 얻었다. 정자의 보존 시간에 따른 기형율은 동결 융해 직후 miniature pig가 $19.5{\pm}1.7%$ 로 Duroc의 $13.9{\pm}0.3%$에 비해 유의적으로 높았다. (p<0.05). 첨체 검사에서 수정능 획득이 일어나지 않은 F pattern은 동결 융해 후 miniature pig와 Duroc 종 정액이 $24.1{\pm}2.8%$와 $37.9{\pm}1.1%$로 Duroc 종에서 유의적(p<0.05)으로 높게 나타났으며, 동결 융해후 miniature pig와 Duroc 종의 AR pattern은 $21.1{\pm}1.6%$ 및 $15.5{\pm}2.2%$로 miniature pig가 유의적(p<0.05)으로 높게 나타났다. 융해 온도별 생존율에서는 20과 $37^{\circ}C$에서는 두 종간에서 유의적 차이는 없었으나, $50^{\circ}C$에서는 miniature pig가 $63.8{\pm}3.6%$로 $47.4{\pm}3.2%$인 Duroc 종에 비해 유의적(p<0.05)으로 높게 나타났다. 본 연구의 결과로부터 첨체율과 기형율에 대한 연구를 보완함으로써 miniature pig정액의 안정적인 동결 체계를 확립할 수 있을 것으로 판단된다.