• Korean Journal of Animal Reproduction
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• v.19 no.1
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• pp.49-54
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• 1995

This experiments were carried out to investigate the viabilities and the pregnancy rate of frozen-thawed IVF bovine embryos in various media, cryoprotectants and age of embryos produced. Hanwoo oocyte were collected in size of 2~7mm follicles, matured for 20~22hrs at 38.5$^{\circ}C$ in 5% CO2 incubator and then in vitro fertilized with Hanwoo semen. Blastocysts or more developed embryos at Day 7, 8 and 9 were frozen in 1.5 or 1.8M ethylene glycol. Viability of frozen thawed IVF embryos were identified the reformation of blastocoele after thawing and culture for 24~48 hours at 38.5$^{\circ}C$ in 5% CO2 incubator. Production rate of Hanwoo IVF embryos in TCM 199 and CR1aa ws 21.3%(39/183) and 28.1%(41/146), respectively. The viability of frozen thawed IVF embryos was higher rate in 1.8M ethylene glycol and Day 7 embryos than that in 1.5M and Day 8.53 cows out of 100 Hanwoo receipients transfered IVF embryos were pregnant and twin production rate was 26.3%.

• Solar Energy
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• v.12 no.1
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• pp.48-58
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• 1992

In the present investigation, experimental analysis was performed to research heat transfer phenomena generated by means of conduction and natural convection at a succession of tube-inclimations relative to the vertical tube during inward melting process of a phase change material. The phase change material used in the experiments is 99 percent pure n-docosane paraffin($C_{22}H_{46}$). When the tube is vertical, the dominant mode of energy transfer between the tube wall and the melting interface is natural convection. On the other hand, when the tube is inclined to the vertical, the melting solid is brought into direct contact with the tube wall by the action of gravity. In the experimental results, direct contact gave rise to substantial enhancements in the amount of melted mass, relative to those for natural-convection-dominated melting.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.7
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• pp.615-619
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• 2008

A molecular memory device which has a structure of Al/$Al_2O_3$/ASA-15 LB monolayer/Ti/Al device, was fabricated. To study a charge transfer mechanism of molecular memory devices, current density-voltage (J-V) characteristics were measured at an increasing temperature range from 10 K to 300 K with an interval of 30 K. Strong temperature-dependent electrical property and tunneling through organic monolayer at low bias (below 0.5 V) were appeared. These experimental data were fitted by using a theoretical formula such as the Simmons model. In comparison between the theoretical and the experimental results, it was verified that the fitting results using the Simmons model about direct tunneling was fairly fitted below 0.5 V at both 300 K and 10 K. Hopping conduction was also dominant at all voltage range above 200 K due to charges trapped by defects located within the dielectric stack, including the $Al_2O_3$, organic monolayer and Ti interfaces.

• Journal of Mechanical Science and Technology
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• v.16 no.10
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• pp.1346-1354
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• 2002

The purpose of this work is to study the effects of specularly reflecting wall under the combined radiative and laminar free convective heat transfer in an infinite square duct. An absorbing and emitting gray medium is enclosed by the opaque and diffusely emitting walls. The walls may reflect diffusely or specularly. Boussinesq approximation is used for the buoyancy term. The radiative heat transfer is evaluated using the direct discrete ordinates method. The parameters under considerations are Rayleigh number, conduction to radiation parameter, optical thickness, wall emissivity and reflection mode. The differences caused by the reflection mode on the stream line, and temperature distribution and wall heat fluxes are studied. Some differences are observed for the categories mentioned above if the order of the conduction to radiation parameter is less than order of 10$\^$-3/ fer the range of Rayleigh number studied. The differences at the side wall heat flux distributions are observed as long as the medium is optically thin. As the top wall emissivity decreases, the differences between these two modes are increased. As the optical thickness decreases at the fixed wall emissivity, the differences also increase. The difference of the streamlines or the temperature contours is not as distinct as the side wall heat flux distributions. The specular reflection may alter the fluid motion.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.5
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• pp.543-552
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• 2003

The effects of a directionally emitting and reflecting dielectric surface on the wall heat flux and medium temperature distribution are studied. The system is an infinite square duct enclosing an absorbing and emitting medium. The emissivity and reflectivity of opaque and gray wall vary with direction. Combined effect of conductive and radiative heat transfer is analyzed using finite difference and the direct discrete-ordinates method. The parameters under study are conduction to radiation parameter, optical depth, refractive index ratio. The results with directional and diffuse properties deviate each other when the conduction to radiation parameter is less than around 0.01. The wall heat flux differs fur optical thickness less than around 0.1. However, the medium temperature profiles differ for optical thickness greater than around 1. Deviations from diffuse property calculations are larger for hot wall with directional property than cold wall with directional property. As n increases from 1.5, the trend changes are observed fur refractive index ratio about n=6.10

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.10
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• pp.1451-1458
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• 2001

The effects of a specularly reflecting surface on the wall heat flux and medium temperature distribution are studied. The system is an infinite square duct enclosing an absorbing and emitting medium. The walls are opaque, and black or gray. The walls emit diffusely but reflect diffusely or speculary. Heat is transferred by the combined effect of conduction and radiation. The radiative heat transfer is analyzed using direct discrete-ordinates method. The parameters under study are conduction, to radiation parameter, optical depth, wall emissivity, and reflection characteristics. The specular reflection and diffuse reflection show sizeable differences when the conduction to radiation parameter is less than around 0.01. The differences appear only either on the side wall heat flux or on the medium temperature profiles for the range of this study. The differences on the side wall heat flux are observed for optical thickness less than around 0.1 However the differences on the medium temperate profiles are found for optical thickness greater than around 1. The difference increase with increasing reflectance. The specular reflection increases the well heat flux gradient along the side wall.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.1
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• pp.189-205
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• 1996

The twin-roll type strip continuous casting process(or direct rolling process) of steel materials is characterized by two rotating water cooled rolls receiving a steady supply of molten metal which solidifies onto the rolls. A solidification analysis of molten metal considering phase transformation and thermofluid is performed using finite diffefence method with curvilinear coordinate to reduce computing time and molten region analysis with arbitrary shape. An enthalpy-specific heat method is used to determine the temperatures inthe roll and the steel. The temperature distribution of cooling roll is calculated using two dimensional finite element method, because of complex roll shape due to cooling hole in rolls and improvemnt accuracy of calculation result. The energy equaiton of cooling roll is solved simultanuously with the conservation equaiton of molten metal in order to consider heat transfer through the cooling roll. The calculated roll temperature is compared to experimental results and the heat transfer coefficient between cooling roll surface and rolling material(steel) is also determined from comparison of measured roll temperature and calculated temperature.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.473-473
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• 2011

In recent years, organic thin film transistors OTFTs based on conductive-conjugated molecules have received significant attention. We report a fabrication of organic single crystal nanowires that made on Si substrates by liquid bridge-mediated nanotransfer molding (LB-nTM) with polyurethane acrylate (PUA) mold. LB-nTM is based on the direct transfer of various materials from a stamp to a substrate via a liquid bridge between them. In liquid bridge-transfer process, the liquid layer serves as an adhesion layer to provide good conformal contact and form covalent bonding between the organic single crystal nanowire and the Si substrate. Pentacene is the most promising organic semiconductors. However pentacene has insolubility in organic solvents so pentacene OTFTs can be achieved with vacuum evaporation system. However 6, 13-bis (triisopropylsilylethynyl) (TIPS) pentacene has high solubility in organic solvent that reported by Anthony et al. Furthermore, the substituted rings in TIPS-pentacene interrupt the herringbone packing, which leads to cofacial ${\pi}-{\pi}$ stacking. The patterned TIPS-Pentacene single crystal nanowires have been investigated by Atomic force microscopy (AFM), Transmission Electron Microscopy (TEM), X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and electrical properties.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.11
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• pp.1289-1301
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• 2004

Direct numerical simulation (DNS) of strongly-heated air flows moving upward in a vertical tube has been conducted to investigate the effect of gas property variations on turbulence modification. Three heating conditions(q$_1$$^{+}$=0.0045, 0.0035 and 0.0018) are selected to reflect the experiment of Shehata and McEligot (1998) at the inlet bulk Reynolds numbers of 4300 and 6000. At these conditions, the flow inside the heated tube remains turbululent or undergoes a transition to subturbulent or laminarizing flow. Consequently, a significant impairment of heat transfer occurs due to the reduction of flow turbulence. The predictions of integral parameters and mean profiles such as velocity and temperature distributions are in excellent agreement with the experiment. The computed turbulence data indicate that a reduction of flow turbulence occurs mainly due to strong flow acceleration effects for strongly-heated internal gas flows. Thus, buoyancy influences are secondary but not negligible especially for turbulent flow at low heating condition. Digital flow visualization also shows that vortical structures rapidly decay as the heating increases.s.

• Bulletin of the Korean Chemical Society
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• v.20 no.10
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• pp.1177-1180
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• 1999

The ab initio SCF MO and density functional theory (DFT) studies are carried out on the electrophilic (1a) and electron transfer (1b) addition reactions to the vinyl double bond of aryl vinyl sulfides and ethers. In the electrophilic addition processes, a double bond shift from C3 = C4 to X = C3 occurs with occupation number (1.97) close to the normal two. Due to this shift direct conjugation between the cationic center, X = S or O, and the para electron-donor substituent becomes impossible so that the reaction energies (or log K) are correlated with σ rather than σ+. By contrast, radical cation formation leads to delocalization of the SOMO, a lone-pair πorbital on X, with four major resonance structures in which cationic charge as well as spin density is delocalized over C4 , X and C7 atoms. As a result, partial πbonds are formed over C1 -X and C3 - C4 with occupation numbers (0.82) lower than one. In two of the cannonical structures, III(Ⅹ) and III(X+), direct conjugation between the cationic center, X, and the para substituent is achieved so that a better correlation with σ+ rather than σis obtained. The SCF MO energies at the HF/3-21G* and HF/6-31G* levels lead to very much inferior Hammett correlations in the σ/ σ+ diagnostic criterion. In contrast, the ρvalues evaluated with the DFT energies can give reliable diagnostic distinction between the two addition mechanisms.