• 한국전산유체공학회:학술대회논문집
• /
• 1999.11a
• /
• pp.23-28
• /
• 1999

In this paper we study numerically the shock-vortex interaction in the shear layer generated by moving shock waves above and below a flat plate. The faster normal shock is diffracted at the tip of the flat plate, producing a starting vortex. The slower normal shock below the flat plate arrives soon later to run across the vortex and make interaction. The two shocks are merged together and reflected back at the closed end of the shock tube to impinge on the shear layer developing multiple vortexlets. The computational simulation based on Euler and Navier-Stokes equations shows good prediction.

• 한국전산유체공학회:학술대회논문집
• /
• 2008.03b
• /
• pp.300-303
• /
• 2008

In the present study, the simple form of the heat transfer equation were suggested to estimate the temperature variation inside the oil pipe in order to determine the thickness of the insulating materials to retain the working oils below the critical temperature. The conservation of the thermal energy at arbitrary time were modeled to one dimensional unsteady equation with the empirical formula or data. The calculating results for non-insulation case showed that the temperature were very sensitive to the thermal convection by the velocity of the external wind. For insulation case, the insulation material which has higher density and specific heat, lower thermal conductivity should be chosen with more brighter coloring outside the pipe in order to retain the working oils below the critical temperature.

• Proceedings of the Korean Society of Marine Engineers Conference
• /
• 2011.10a
• /
• pp.59-59
• /
• 2011

H-mode or X-mode predominates in marine engines according to the number of cylinder. Generally, H-mode noticeably happen in the engine below 7-cylinder and X-mode remarkably happen above 8-cylinder in the engine operating range. Until now, FEA (Finite Element Analysis) of 3D engine model has been mainly used to estimate the engine vibration but it is very time consuming for simulation and difficult to model simplification. Furthermore, the accuracy of simulation shows a marked difference according to modeling method. Therefore it is very difficult to have contentable result from FEA for beginners and laymen. In this paper, the estimation method based on a test has been suggested to solve the difficulty.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 2000.04a
• /
• pp.585-590
• /
• 2000

Recently, It is gradually raised necessity that thickness of thin film is measured accuracy and managed in industrial circles and medical world. Ultrasonic Signal processing method is likely to become a very powerful method for NDE method of detection of microdefects and thickness measurement of thin film below the limit of Ultrasonic distance resolution in the opaque materials, provides useful information that cannot be obtained by a conventional measuring system. In the present research, considering a thin film below the limit of ultrasonic distance resolution sandwiched between three substances as acoustical analysis model, demonstrated the usefulness of ultrasonic Signal processing technique using information of ultrasonic frequency for NDE of measurements of thin film thickness, sound velocity, and step height, regardless of interference phenomenon. Numeral information was deduced and quantified effective information from the image. Also, pattern recognition of a defected input image was performed by neural network algorithm. Input pattern of various numeral was composed combinationally, and then, it was studied by neural network. Furthermore, possibility of pattern recognition was confirmed on artifical defected input data formed by simulation. Finally, application on unknown input pattern was also examined.

• Fisheries and Aquatic Sciences
• /
• v.10 no.2
• /
• pp.68-73
• /
• 2007

Based on four juvenile specimens of Lutjanus collected from the southern coast of Jeju Island, three species, L. argentimaculatus, L. fulviflamma, and L. quinquelineatus, are described as the first record from Korea. The first species is easily differentiated from other lutjanid juveniles by distinct coloring of the dorsal, pelvic, and anal fins as well as two blue lines below the eye; the second species is characterized by having six yellowish brown stripes below the lateral line and a black spot on the side; the third species is identified by five longitudinal blue stripes and a black spot on the side when fresh. The new Korean names "Bul-geun-tung-dom," "Yuk-seon-jeomtung-dom," and "O-seon-tung-dom" are proposed for L. argentimaculatus, L. fulviflamma, and L. quinquelineatus, respectively.

• Journal of Korean Ophthalmic Optics Society
• /
• v.1 no.2
• /
• pp.77-84
• /
• 1996

As the results of phoria measurement of Korean adults for 106 males and 55 females, the elevens (6.8%) are orthophoria, the nineties (55.9%) are esophoria and the fifty fives (34.2%) are exophoria respectively. Also the thirty threes (20.4%) are right hyperphoria against the left eye and the thirty eights (23.6%) are left hyperphoria against the right eye. Horizontal phoria is below $10{\Delta}$ mostly and vertical phoria is below $5{\Delta}$.

• Korean Journal of Materials Research
• /
• v.25 no.12
• /
• pp.678-682
• /
• 2015

The electrical property of polymer matrix composites with added carbon powder is studied based on the temperature dependency of the conduction mechanism. The temperature coefficient of the resistance of the polymer matrix composites below the percolation threshold (x) changed from negative to positive at 0.20 < x < 0.21; this trend decreased with increasing of the percolation threshold. The temperature dependence of the electrical property(resistivity) of the polymer matrix composites below the percolation threshold can be explained by using a tunneling conduction model that incorporates the effect of the thermal expansion of the polymer matrix composites into the tunneling gap. The temperature coefficient of the resistance of the polymer matrix composites above the percolation threshold has a positive value; its absolute value increased with increasing volume fraction of carbon powder. By assuming that the electrical conduction through the percolating paths is a thermally activated process and by incorporating the effect of thermal expansion into the volume fraction of the carbon power, the temperature dependency of the resistivity above the percolation threshold can be well explained without violating the universal law of conductivity.

• Journal of the Korean institute of surface engineering
• /
• v.28 no.6
• /
• pp.361-367
• /
• 1995

When steels are heated at $1000^{\circ}C$ in a fused borax bath containing $V_2O_5$ and $B_4C$powders, vanadium carbide layers are formed on the steel surfaces. Since a decrease in carbon concentration and in microhardness in the substrate just below the carbide layer has been observed, gas nitrocarburizing and vanadium carbide forming processes were combined to form a V(C,N) type layer which prevented the decrease in carbon concentration in the substrate. EPMA analysis was done for this V(C,N) type layer. Hardness just below the layer and wear resistance properties of such treated specimens were investigated.

• Journal of the Korean institute of surface engineering
• /
• v.29 no.6
• /
• pp.660-665
• /
• 1996

Thin films of indium oxide and indium tin oxide have been prepared by d.c. magnetron sputtering onto the fused silica substrates kept at 90, 200 and $300^{\circ}C$. In order to elucidate the optical absorption process in low energy region below 3 eV, we have analyzed the absorption coefficients obtained from reflectance and transmittance measurements for these films based on the Lucovsky model. It has been found for the first time that a defect center in the band gap is located at 0.8~1.4 eV below the Fermi level in all films and arises from oxygen vacancies in their films. The optical absorption in low energy region is explained to be dominated by the transition of electrons trapped at the positively charged (+2e) oxygen vacancies with s-like nature to the conduction band formed from the 5s-orbit in indium atoms.

• Journal of Korean Ophthalmic Optics Society
• /
• v.6 no.1
• /
• pp.59-63
• /
• 2001

Once refractive error of the eye was fully corrected. Polarization Test was used to investigate binocular vision function. As the results of phoria measurement of Korean adults for 53males and 59 females, orthophoria in 27.68%, esophoria in 12.50%, exophoria in 48.21%, verical phoria in 3.75%, esophoria(+verical phoria) in 2.68%, and exophoria(+vertical phoria) in 5.36%, respectively. Horizontal phoria is below $3{\Delta}$ mostly and verical phoria is below $1{\Delta}$.