• Korean Journal of Metals and Materials
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• v.49 no.9
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• pp.720-725
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• 2011

W-Ni-Fe heavy alloys have been used in various fields, such as kinetic energy penetrators and radiation shielding materials, due to their high density and good mechanical properties. In this study, the sintering of W-Ni-Fe alloys with various Ni/Fe ratios was demonstrated to improve the mechanical properties and penetration capabilities of heavy alloys by formation of interfacial phase. The microstructural changes and the mechanical properties of the W-Ni-Fe alloys after liquid-phase sintering were investigated. The Vickers hardness and tensile strength of the 95W1.3Ni3.7Fe sample, which had coated W grains by $Fe_7W_6$ phase (${\mu}$-phase), were 450 Hv and 1560 MPa, respectively. As a result, enhancement of the mechanical properties was considered to have uniformly generated ${\mu}$-phase around W grains.

• Journal of ILASS-Korea
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• v.26 no.1
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• pp.18-25
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• 2021

The objective of this study is to investigate the effect of cryogenic intake air temperature on the injected fuel droplet behavior in a compression ignition engine under the different start of energizing timing. To achieve this, the intake air temperatures were changed from -18℃ to 18℃ in steps of 9℃, and the result of fuel evaporation rate, Sauter mean diameter, and equivalence ratio distributions were compared. When the intake air temperature decreased in steps of 9℃, less fuel was evaporated by about 3.33% because the cylinder temperature was decreased. In addition, the evaporated fuel amount was increased with retarding the start of energizing timing because the cylinder temperature raised. However, the difference was decreased according to the retarded start of energizing timing because the cylinder pressure was also increased at the start of fuel injection. The equivalence ratio was reduced by 5.94% with decreasing the intake air temperature. In addition, the ignition delay was expected to longer because of the deteriorated evaporation performance and the reduced cylinder pressure by the low intake air temperature.

• Journal of ILASS-Korea
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• v.27 no.1
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• pp.1-10
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• 2022

In this study, an experimental investigation on the effects of the pressure ratio on the wall-impingement spray characteristics of nitrogen gas using a compressed natural gas (CNG) injector was conducted. The transient development of the impingement spray was recorded by a high speed camera with Z-type Schlieren visualization method. The spray behavior under various pressure ratio conditions were analyzed. The experimental results showed that the pressure ratio has positive effect on the development of spray wall-impingement. The effects of the above factor were evaluated in a constant volume chamber at atmospheric conditions. The data from test showed that, with the increase of the pressure ratio, the spray tip penetration (STP) quickly increases before the impingement and gradually increases after the impingement. Additionally, the spray velocity first increases and then sharply decreases on regardless of the injection pressure level. As the spray spreading angle increases, spray area and volume increases rapidly with the increase in STP at the beginning of injection, and finally entered a stable range, has a great correlation with the increase of pressure ratios.

• Nuclear Engineering and Technology
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• v.55 no.10
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• pp.3754-3767
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• 2023

Turbulent jet discharges in subcooled water pools are essential for safety systems in nuclear power plants, specifically in the pressure suppression pool of boiling water reactors and In-containment Refueling Water Storage Tank of advanced pressurized water reactors. The gas and liquid flow in these systems is investigated using multiphase flow analysis. This field has been extensively examined using a combination of experiments, theoretical models, and Computational Fluid Dynamics (CFD) simulations. ANSYS CFX offers two approaches to model multiphase flow behavior. The non-homogeneous Eulerian-Eulerian Model has been used in this work; it computes global information and is more convenient to study interpenetrated fluids. This study utilized the Large Eddy Simulation Model as the turbulence model, as it is better suited for non-stationary and buoyant flows. The CFD results of this study were validated with experimental data and theoretical results previously obtained. The figures of merit dimensionless penetration length and the dimensionless buoyancy length show good agreement with the experimental measurements. Correlations for these variables were obtained as a function of dimensionless numbers to give generality using only initial boundary conditions. CFD numerical model developed in this research has the capability to simulate the behavior of non-condensable gases discharged in water.

• Journal of ILASS-Korea
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• v.28 no.4
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• pp.176-183
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• 2023

Many countries are striving to reduce carbon emissions with the goal of net zero by 2050. Accordingly, vehicles are rapidly being electrified to reduce greenhouse gases in the transportation sector. However, many organizations predict that internal combustion engines of LDV (light-duty vehicle) will exist even in 2050, and it is difficult to electrify aircraft and large ships in a short time. Therefore, synthetic fuel (i.e., e-Fuel) that can reduce carbon emissions and replace existing fossil fuels is in the spotlight. The e-Fuel refers to a fuel synthesized by using carbon obtained through various carbon capture technologies and green hydrogen produced by eco-friendly renewable energy. The purpose of this study is to compare and analyze the injection and spray characteristics of the simulated e-Gasoline. We mixed the hydrocarbon fuel components according to the composition ratio of the synthetic fuel produced based on the FT(Fischer-Tropsch) process. As a result of injection rate measurement, simulated e-Gasoline showed no significant difference in injection delay and injection period compared to standard gasoline. However, due to the low vapor pressure of the simulated e-Gasoline, the spray tip penetration (STP) was lower, and the size of spray droplets was larger than that of traditional gasoline.

• Journal of ILASS-Korea
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• v.28 no.4
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• pp.198-206
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• 2023

In this study, visualization of in-cylinder spray behavior and spark channel stretching by air flow characteristics depending on engine operating conditions were investigated. For in-cylinder spray behavior, increase in engine rpm did not alter the counter-clockwise air flow direction and location of in-cylinder dominant air flow but increased average air flow velocity, which hindered spray propagation parallel to the piston surface. When injection timing was retarded, direction of in-cylinder dominant air flow was changed, and average air flow velocity was reduced resulting in an increase in spray penetration length and change in direction. For spark channel stretching, increase in air flow speed did not affect spark channel stretch direction but affected length due to increase in spark channel resistance and limitation of energy ignition coil can handle. Change in air flow direction affected spark channel stretch direction where the air flow was obstructed by ground electrode which caused spark channel direction to occur in the opposing direction of air flow. It also affected spark channel stretch length due to change in air flow speed around the spark plug electrode from the interaction between the air flow and ground electrode.

• Journal of Animal Science and Technology
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• v.65 no.6
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• pp.1205-1213
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• 2023

The goals of the present study were to develop a simple method for obtain highly purified pig sperm hyaluronidase (pHyase) and to assess its activity, function, and safety. In mammals, sperm-specific glycophosphatidylinositol (GPI)-anchored Hyase assists sperm penetration through the cumulus mass surrounding the egg and aids in the dispersal of the cumulus-oocyte complex. Recently, Purified bovine sperm hyaluronidase (bHyase) has been shown to enhance therapeutic drug transport by breaking down the hyaluronan barrier to the lymphatic and capillary vessels, thereby facilitating tissue absorption. Commercially available Hyase is typically isolated from bovine or ovine; which have several disadvantages, including the risk of bovine spongiform encephalopathy, low homology with human Hyase, and the requirement for relatively complex isolation procedures. This study successfully isolated highly purified pHyase in only two steps, using ammonium sulfate precipitation and fast protein liquid chromatography. The isolated Hyase had activity equal to that of commercial bHyase, facilitated in vitro fertilization, and effectively dissolved high molecule hyaluronic acid. This simple, effective isolation method could improve the availability of pHyase for research and clinical applications.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.1
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• pp.31-48
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• 2019

The artificial ground freezing (AGF) method is a groundwater cutoff and/or ground reinforcement method suitable for constructing underground structures in soft ground and urban areas. The AGF method conducts a freezing process by employing a refrigerant circulating through a set of embedded freezing pipes to form frozen walls serving as excavation supports and/or cutoff walls. However, thermal expansion of the pore water during freezing may cause excessive deformation of the ground. On the other hand, as the frozen soil is thawed after completion of the construction, mechanical characteristics of the thawed soil are changed due to the plastic deformation of the ground and the rearrangement of soil fabric. This paper performed a field experiment to evaluate the freezing rate of marine clay in the application of the AGF method. The field experiment was carried out by circulating liquid nitrogen, which is a cryogenic refrigerant, through one freezing pipe installed at a depth of 3.2 m in the ground. Also, a piezo-cone penetration test (CPTu) and a lateral load test (LLT) were performed on the marine clay before and after application of the AGF method to evaluate a change in strength and stiffness of it, which was induced by freezing-thawing. The experimental results indicate that about 11.9 tons of liquid nitrogen were consumed for 3.5 days to form a cylindrical frozen body with a volume of about $2.12m^3$. In addition, the strength and stiffness of the ground were reduced by 48.5% and 22.7%, respectively, after a freezing-thawing cycle.

• Journal of the Korea Concrete Institute
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• v.16 no.4 s.82
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• pp.477-484
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• 2004

As a part of durability improvement of concrete-structure, penetrating water repellency of liquid type is applied to concrete surface. Besides, a related standard is made recently, but the standard has been prescribe for initial settlement state of penetrating water repellency of liquid type, to the exclusion of performance variation depending time and outdoor environment factor. For measurement of performance variation, we measured the weight of outdoor exposure specimen every regular intervals and check a measured value against a measured value of different condition specimen. Moreover, after the application of penetrating water repellent, measured a adhesive strength in tension between cement-polymer modified waterproof coatings and surface of specimen. The applied penetrating water repellent is a emulsified silicon type with a deep penetration depth. In view of the results so far achieved, the more a Quantity of application and active solid content does get, the deeper penetrating water repellency of emulsion type Penetrate get longer and supplied moisture increase in quantity, a penetrating water repellency of liquid type penetrates more deep, but a quantity of water absorption increase gradually. Perhaps this result is caused by a reduction of active solid content on concrete surface, because active ingredient is moved into the concrete by dissolution.

• Korean Journal of Animal Reproduction
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• v.26 no.1
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• pp.1-7
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• 2002

The present study was carried out to investigate the effects of maturation media on penetrability of pig oocytes by liquid boar sperm coincubated with different sperm concentrations in a modified Tris­buffered medium (mTBM). Follicular oocytes collected from ovaries of prepubertal gilts were matured in a modified TCM-199 (mTCM-199) medium, modified Waymouth MB 752/1 (mWaymouth MB 752/1) medium or NCSU-23 medium. Oocytes (30~40) were transferred into each well of a Nunc 4-well multidish containing 0.5 $m\ell$ maturation medium. The sperm­ich portion of ejaculates with greater than 90% motile sperm were used in the experiment. The semen was cooled 22 to 24$^{\circ}C$ over 2 h period. The semen was diluted with Beltsville Thawing Solution (BTS) extender at room temperature to give 2$\times$10$^{8}$ sperm/$m\ell$ in 100 $m\ell$ plastic bottle. Liquid boar semen of 30 $m\ell$ in 100 $m\ell$ plastic bottle was kept at 17$^{\circ}C$ far 5 days. The sperm with greater than 70% motility after day 5 of storage were used for in-vitro fertilization (IVF). After 44 h maturation of immature oocytes in 5% $CO_2$in air at 38.5$^{\circ}C$, cumulus cells were removed and oocytes (30~40) were coincubated for 6 h in 0.5 $m\ell$ mTBM fertilization medium with five different (1$\times$10$^{6}$ , 2$\times$10$^{6}$ , 4$\times$10$^{6}$ , 6$\times$10$^{6}$, 10$\times$10$^{6}$ $m\ell$) sperm concentrations. At 6 h after IVF, oocytes were transferred into 0.5 $m\ell$ NCSU-23 culture medium fur further culture of 6 h. At 12 h after IVF, sperm penetration, polyspermy and male pronuclear formation of oocytes were evaluated. Oocytes of NCSU-23 maturation medium decreased polyspermy and increased male pronuclear formation compared to those of mTCM­199 and mWaymouth MB 752/1 maturation media. Of oocytes matured in NCSU-23 medium and inseminated in mTBM medium with 2~4$\times$10$^{6}$ $m\ell$ sperm concentrations, 50.8~50.9% showed sperm penetration, 13.3~19.5% polyspermy and 43.9~45.4% male pronuclear formation. In conclusion, we found out that oocytes matured in NCSU­23 medium and inseminated in mTBM medium showed superior in­vitro fertilization compared to those matured in mTCM­199 and mWaymouth MB 752/1 maturation media and inseminated in mTBM medium. The optimum sperm concentrations for in-vitro fertilization of oocytes matured in NCSU-23 medium by liquid boar semen stored at 17$^{\circ}C$ for 5 days were 2~4$\times$10$^{6}$ $m\ell$.