• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.5
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• pp.97-106
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• 2018

This paper summarizes the technical difficulties pertaining the double-compression ramp scramjet inlet model testing in a shock tunnel and their corresponding solutions. Four technical difficulties are identified: 1) test facility unstart, 2) flow disturbance and model damage due to the impact of diaphragm debris, 3) lack of fuel jet development due to multiple injection, and 4) short test time. After overcoming the identified technical difficulties, the improved results were confirmed through the results of shadowgraph images and shock tube end wall pressure.

• Nuclear Engineering and Technology
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• v.54 no.7
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• pp.2702-2713
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• 2022

A steam generator tube rupture accompanying a core damage may cause the fission product to be released to environment bypassing the containment. In such an accident, the steam generator is the major path of the radioactive aerosol release. AEOLUS facility, the scaled-down model of Korean type steam generator, was built to examine the aerosol removal in the steam generator during the steam generator tube rupture accident. Integral and separate effect tests were performed with the facility for the dry and flooded conditions, and the decontamination factors were presented for different tube configurations and submergences. The dry test results were compared with the existing test results and with the analyses to investigate the aerosol retention physics by the tube bundle, with respect to the particle size and the bundle geometry. In the flooded tests, the effect of submergence were shown and the retention in the jet injection region were presented with respect to the Stokes number. The test results are planned to be used to constitute the aerosol retention model, specifically applicable for the analysis of the steam generator tube rupture accident in Korean nuclear power plants to evaluate realistic fission product behavior.

• Journal of Embryo Transfer
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• v.28 no.3
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• pp.169-175
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• 2013

Recently, the transgenic animal production technique is very important for the production of bio-parmaceutical as animal bio-reactor system. However, the absence of survival evaluation in vitro produced transgenic embryos has been a problem of the low productivity of transgenic animal because of absent of pre-estimate of pregnancy after transgenic embryos transferred into recipient. Therefore, this study is conducted to improve efficiency of transgenic cattle production by improving the non-surgical embryo transfer (ET) method. Transgenic bovine embryos were produced by injection of feline immunodeficiency virus enhanced green fluorescent protein (FIV-EGFP) lentiviral vector into perivitelline space of in vitro matured MII stage oocytes, and then in vitro fertilization (IVF) was occured. Normal IVF and EGFP expressing blastocysts were transferred into recipients. Results indicated that 2 expanded blastocysts (34.7%) transferred group showed significantly (P<0.05) higher pregnancy rate than 1 expanded blastocyst (26.8%) transferred group. In case of parity of recipient, ET to heifer (34.9%) showed significantly (P<0.05) higher pregnancy rate than ET to multiparous recipient (21.2%). However, there are no significant differences of pregnancy rate between natural induced estrus and artificial induced estrus groups. Significantly (P<0.05) higher pregnancy rate was obtained from recipient group which have normal corpus luteum with crown group (34.8%) than normal corpus luteum without crown (13.6%). Additionally, treatment of $100{\mu}g$ Gn-RH injection to recipient group (38.6%) 1 day before ET significantly (P<0.05) increase pregnancy rate than non- Gn-RH injection to recipient group (38.6%). We also transferred 2 EGFP expressing expanded blastocysts to each 19 recipients, 7 recipients were pregnant and finally 5 EGFP transgenic cattle were produced under described ET condition. Therefore, our result suggested that transfer of 2 good-quality expanded blastocysts to $100{\mu}g$ of Gn-RH injected recipient which have normal corpus luteum with crown is feasible to produce transgenic cattle.

• Journal of Korean Tunnelling and Underground Space Association
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• v.17 no.2
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• pp.141-151
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• 2015

A new rock excavation method using an abrasive injection waterjet system has been developed to enhance the efficiency and reduce the vibration of tunnel excavation. The abrasive feed rate is an important factor for the cutting performance and the economical efficiency of waterjet-based excavation. In this study, various experiments were performed to explore the effects of major process parameters for both the abrasive feed rate and the suction pressure occurring inside the mixing chamber when the abrasives are inhaled. Experimental results reveal that the abrasive feed rate is affected by geometry parameters (abrasive pipe height, length, and tortuosity), abrasive parameters (abrasive particle size), and jet energy parameters (water pressure and water flow rate). In addition, the relation between the cutting performance and the abrasive feed rate was discussed on the basis of the results of an experimental study. The cutting performance can be maximized when the abrasive feed rate is controlled appropriately via careful management of major process parameters.

• Journal of Embryo Transfer
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• v.27 no.4
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• pp.223-228
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• 2012

This study was designed to adopt two estrus synchronization protocols in zebu and crossbred heifers and their effects on pregnancy rate after timed artificial insemination (TAI). A number of 120 cyclic heifers were allotted for two different treatment groups and one control group. Heifers under protocol A were injected with GnRH at first day followed by a single dose of $PGF_{2{\alpha}}$ at Day 11 and injection of GnRH at the day of AI; and heifers belonged to protocol B were treated with GnRH, two $PGF_{2{\alpha}}$ injections at 11 days apart and injection of GnRH at AI. AI was done at fixed time (within 72~96 hours after $PGF_{2{\alpha}}$ injection) in both protocols and pregnancy was confirmed by rectal palpation on 80~120 days of post AI. In control group; local heifers were conceived higher (30%) proportion than that of crossbred heifers (25%; p<0.05). In protocol A, the local breed were conceived higher (38.9%) proportion compared with crossbred (25%; p<0.05). In protocol B, local breed heifers were conceived higher (38.9%) proportion compared with crossbred heifers (33.3%; p<0.05). The overall pregnancy rate in protocol A and protocol B was 33.3% and 36.6%, respectively. The proportion of pregnancy rate of local heifers (38.9%; Protocol A) was significant (p<0.05) in comparison with local heifers (30%) in control group (p<0.05). The overall pregnancy rate between pooled control group (28.3%) and treatment group (35%) was significantly (p<0.05) differ from each other's. Results of present study concluded that estrus synchronization followed by fixed time AI could be applied for higher pregnancy rate in zebu and crossbred heifers.

• Journal of Embryo Transfer
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• v.29 no.4
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• pp.339-344
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• 2014

The clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR associated protein (Cas9) system can be applied to produce transgenic pigs. Therefore, we applied CRISPR/Cas9 system to generate FoxN1-targeted pig parthenogenetic embryos. Using single guided RNA targeted to pig FoxN1 genes was injected into cytoplasm of in vitro matured oocyte before electrical activation. In results, regardless of the concentrations of vector, the cleavage rate were significantly (p<0.05) decreased ($4ng/{\mu}l$, 51.24%; $8ng/{\mu}l$, 40.88%; and $16ng/{\mu}l$; 45.22%) compared to no injection group (70.44%). The blastocyst formation rates were also decreased in vector injected 3 groups ($4ng/{\mu}l$, 7.96%; $8ng/{\mu}l$, 6.4%; and $16ng/{\mu}l$; 9.04%) compared to no injection group (29.07%). In addition, the blastocyst formation rates between sham injected group (13.51%) and no injection group (29.07%) also showed significant difference (p<0.05). The mutation rates were comparable between groups ($4ng/{\mu}l$, 18.4%; $8ng/{\mu}l$, 12.5%; and $16ng/{\mu}l$; 20.0%). The sequencing analysis showed that blastocysts derived from each group were successfully mutated in FoxN1 loci regardless of the vector concentrations. However, the deletion patterns were higher than the patterns of point mutation and insertion regardless of the vector concentrations. In conclusion, we described that cytoplasmic microinjection of FoxN1-targeted CRISPR/Cas9 vector could efficiently generate transgenic pig parthenogenetic embryos in one-step.

• Composites Research
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• v.35 no.2
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• pp.115-119
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• 2022

The performance of carbon fiber is important for the production of these high-quality polymer composite materials such as CFRP (Carbon Fiber Reinforced Plastic). For this purpose, it is essential to use an optimized spinning process for improving the mechanical, physical, and structural properties of the precursor fiber, which greatly affects the properties of the carbon fiber, and the use of a suitable precursor polymer. In this study, the content of MAA (Methacrylic Acid), MAA injection time, and concentration of AIBN (2,2'-Azobis(2-methylpropionitrile)) were set as parameters for the polymer synthesis process, and Poly(AN-co-MAA) (poly(acrylonitrile-co-methacrylic acid)) was polymerized by solution polymerization. Poly(AN-co-MAA) with a molecular weight of 305,138 g/mol and an MAA ratio of 4.2% was dissolved in DMF (N,N-dimethylformamide) at a concentration of 16.0 wt%, and then a precursor fiber was prepared through dry-jet-wet spinning. The precursor fiber had a tensile strength of ~1.06 GPa and a tensile modulus of ~22.01 GPa, and no voids and structural defects were observed on the fiber.

• Journal of Embryo Transfer
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• v.29 no.1
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• pp.51-57
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• 2014

The objectives of this study were to investigate the effects of trehalose as a cryoprotectant for porcine freeze-dried spermatozoa, to find the optimal freeze-drying time and storage periods of freeze-dried spermatozoa, and to find out pronuclear formation rates, cleaved rates, and embryo development through intracytoplasmic injection of freeze-dried spermatozoa on porcine oocytes. The survival rates of spermatozoa after freeze-drying with trehalose treatment were significantly higher than those of them without trehalose treatment (p<0.05). The highest survival rates were found at 75 mM trehalose treatment. The longer storage periods after freeze-drying seemed to have a lower survival rates. Development in culture of pig by ICSI with trehalose treatment were significantly higher than those of them without trehalose treatment (p<0.05). Shorter freeze-drying time of spermatozoa was resulted in the highest cleaved rates and embryo development.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.137-145
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• 2004

Limestone zone in korea have been distributed to diagonal line so that it is wide from the Gangwondo to the Jeonlanamdo. The limestone cavity and fractured zone were formed by chemical weathering. Limestone cavity and fractured zone was reinforced with cemented milk(w/c=60%)by high pressure jet grouting by tripple -pipe to establish bridge foundation on the ground condition like limestone cavity. To analyze property of limestone and solid of cement milk(w/c=65%), mixed solid of cement, core NX size in the limestone cavity and fractured zone and compressive strength. Seismic tomograpy exploration was pcrforn1cd to analyze deformation modulus of limestone. The analysis suggests that deformation modulus of limestone has effect on uniaxial compressive strength, seismic velocity, seismic elasticity modulus. Average static elasticity modulus of limestone is $5.08{\times}10^5kgf/cm^2$, cement and coal mixed solid is $0.25{\times}10^5kgf/cm^2$, $0.095{\times}10^5kgf/cm^2$. Average seismic velocity of limestone is 5.240m/sec, cement and coal mixed solid is 2,211.3m/sec, 1,447.5m/sec. Average uniaxial compressive strength of limestone was $1,221.3kgf/cm^2$ and limestone specimen mixed with cement milk and solid of cement milk mixed with coal were $125.22kgf/cm^2$, $35kgf/cm^2$ each other. Average friction angle of limestone was $49.14^{\circ}$ and limestone specimen mixed with cement milk and solid of cement milk mixed with coal were $38.39^{\circ}, 25.83^{\circ}$ each other. Average cohesion of limestone was $137.7kgf/cm^2$ and limestone specimen mixed with cement milk and solid of cement milk mixed with coal were $23.5kgf/cm^2$, $15.5kgf/cm^2$ each other. Average deformation modulus of limestone was $2.84{\times}10^5kgf/cm^2$ and limestone specimen mixed with cement milk and solid of cement milk mixed with coal were $0.4{\times}10^5kgf/cm^2, 0.12{\times}10^5kgf/cm^2$ each other. It was analyzed that the elasticity and uniaxial compressive strength, seismic velocity of solid of cement milk mixed limestone pieces and coal had an highly interrelation regardless of existence of limestones pieces and coal but it had shown that limestones had an lower interrelation. In case of field seismic velocity and deformation of limestone, SIC solid of cement milk mixed with coal and limestone pieces had an highly interrelation.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.48-54
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• 2004

The effects of injector spacing s and injector diameter d on mixing are numerically investigated in supersonic combustor with perpendicular injection behind a backward-facing step. Simulations are reported for airstream Mach number of 2.4. Parameters are changed on following 4 cases to investigate the effects of injector configuration on mixing efficiency $\eta_m$. In the case of varying d or s, dynamic pressure ratio $Rq(=(pu^2)_j/(pu^2)_a)$ is also varied to keep bulk equivalence ratio $\Phi({\oe})Rq.d^2/s)$ constant. (l) Injector spacing s is varied at constant $\Phi$=0.5, 1, 2 for injector diameter d=6mm. In the case of $\Phi$=1, $\eta_m$ has its maximum value at s=24mm. The reason is that increase of $\eta_m$. , by widening spacing at Rq=constant competes with decrease of $\eta_m$ by increasing Rq at s=constant. When spacing is narrow, the flow field of vicinity of injector becomes two-dimensional because adjacent jets interferes each other. By widening spacing, air is easily entrained by three-dimensional effect. This mechanism also appears in the case of $\Phi$=0.5, 2 for d=6mm, and $\eta_m$. reaches its maximum value at s=24mm for $\Phi$=0.5 and at s=42mm for $\Phi$=2. (2) In the case of injector diameter d varied at $\Phi$=1 for s=30mm, $\eta_m$. has its maximum value at d=3mm. The reason is that decrease of $\eta_m$ by increasing injector diameter competes with increase of $\eta_m$ by decreasing Rq at d=constant.(3) In the case of s varied at $\Phi$=0.5, 1,2 for d=3mm, the injector spacing at which mixing efficiency has its maximum value is s= 18mm for $\Phi$=0.5, s=24mm for $\Phi$=1, s=24mm for $\Phi$=2. Therefore it is found that d=3mm and s=24mm can be optimum configuration over a range of $\Phi$=0.5~2.(4) The effect of h on the optimum spacing is investigated. s is varied for d=6mm at step height h=4, 6, 8mm. The simulation results do not show significant change on the step height.