• Journal of the Korean Institute of Landscape Architecture
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• v.27 no.4
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• pp.50-58
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• 1999

This study was carried out to investigate the growth characteristics and propagation methods of L. obtusiloba as a woody landscape plant. The results are obtained as follows: L. obtusiloba was dioecious shrub and shaped with bush type. Leaves were ovate, obtuse, cordate, 7.05 cm long, 7.20 cm wide, and petiole 2.0 cm long. Flowers of L. obtusiloba were diclinous. Soil acidity ranged from pH 4.06 to 5.53 with the lowest at the Mt. Soo-Ri. Mt. Soo-Ri located near factory district, which was considered to damaged by environmental deteoration. While soil organic matter was highest at Mt. Soo-Ri, inorganic nutrients were low. L. obtusiloba grows in the area with low soil acidity and low content of inorganic. Therefore it seemed to be tolerant to air pollution. L. Obtusiloba was high seed germination rate in the plug box and its shoots were longer than seeding box and softwood cutting of L. obtusiloba showed the rooting rate of 50% at 5,000ppm on June 23. To develop a mass propagation method of Korean native L. obtusiloba through an axillary bud culture as a woody landscape plant, about 2∼3 cm shoots induced from explant were subcultured to new media contained different growth regulators. Shoots multiplied most effectively on a WPM containing 1.0 mg/l BA, producing 5.5 shoots with a shoot length of 2.5 cm per shoot explant.

• Journal of the Korean Society of Combustion
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• v.5 no.1
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• pp.91-98
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• 2000

We investigated a uniform temperature zone, produced by double flame structure of a co flow CH4/air partially premixed flame, to be used as a temperature calibration source for laser diagnostics. A broadband N2 CARS(coherent anti-Stokes Raman spectroscopy) system with a modeless laser was used for temperature measurement. When the stoichiometric ratio was 1.5, we found the uniform temperature zone in radial direction of the flame of which the averaged temperature was 2110 K with standard deviation 24 K. In the stoichiometric ratio range between 2.0 and 2.5, we found very stable temperature-varying zones in vertical direction at the center of the flame. The size of the zone was approximately 15 mm and it covered a temperature range from 300 K to 1900 K. We also suggest that this zone can be used as a calibration source for 2-D PLIF(planar laser induced flurescence) temperature measurement.

• Tribology and Lubricants
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• v.24 no.6
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• pp.362-367
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• 2008

Tubes in nuclear steam generators are held up by supports because the tubes are long and slender. Fluid flows of high-pressure and high-temperature in the tubes cause oscillating motions between tubes and supports. This is called as FIV (flow induced vibration), which causes fretting wear in contact parts of tube-support. The fretting wear of tube-support can threaten the safety of nuclear power plant. The tube and support materials were Inconel 690 and STS 409. The wear tests were conducted in various environments, which are in water without flow, in flowing water and in flowing water with air. The results showed that the flow of water influenced on the wear-life of tube. The wear-life of tube decreased in water flow as compared with wear-life in stationary water.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.2
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• pp.83-91
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• 2003

Pantograph design Process must be considered in terms of stability of aerodynamics and reduction of aeroacoustics. Furthermore pantograph needs to be insensible to severe circumstance condition like typhoon, tunnel, a change of season. In this paper, robust design of panhead sections is conducted based on the Taguchi's design of experiment method. In the aeroacoustic noise analysis, an acoustic analogy using the Ffowcs Williams and Hawkings(FW-H) equation is used to calculate the flow induced sound pressure level in aeroacoustics. From the near-field CFD analysis data, the far-field noise is predicted at the positions of 25 m away from Pantograph. Based on aerodynamic(CFD) and aeroacoustic(FW-H) analysis data, the optimal sizing and Positioning of panhead elements are determined using robust design optimization method. Design parameters such as thickness, length and radius are controllable factors, while outdoor air temperature and atmospheric pressure are considered as uncontrollable factors in the context of Taguchi's approach. A number of CFD simulation and aeroacoustic analysis are performed based on orthogonal arrays. In this paper, two-step optimization method is used as a parameter design procedure. It is executed using signal to noise(S/N) ratio and analysis of means(ANOM) method. So Thus, an optimal level of design parameters Is extracted to minimize the disconnection ration between contact strips and catenary system, and reduce the far-field aeroacoustic noise.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.149-150
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• 2006

We describe a novel method of scanning probe nanofabrication using a AFM(atomic force microscopy) tip with assistance of Femtosecond laser pulses to enhance fabrication capability. Illumination of the AFM tip with ultra-short light pulses induces a strong electric field between the tip and the metal surface, which allows removing metal atoms from the surface by means of field evaporation. Quantum simulation reveals that the field evaporation is triggered even en air when the induced electric field reaches the level of a few volts per angstrom, which is low enough to avoid unwanted thermal damages on most metal surfaces. For experimental validation, a Ti: sapphire Femtosecond pulse laser with 10 fs pulse duration at 800 nm center wavelength was used with a tip coated with gold to fabricate nanostructures on a thin film gold surface. Experimental results demonstrate that fine structures with critical dimensions less than ${\sim}10nm$ can be successfully made with precise control of the repetition rate of Femtosecond laser pulses.

• Korean Journal of Veterinary Research
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• v.56 no.3
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• pp.155-160
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• 2016

This study was conducted to evaluate three different mixed formulations of sodium hyaluronate (SH) and carboxymethyl cellulose (CMC) using a low-humidity air flow-induced rat dry eye model and determine the most suitable mixture. The total thickness of the cornea, corneal epithelial thickness, corneal stroma thickness, damaged corneal epithelium percentage region, thickness of the bulbar conjunctiva epithelium, number of goblet cells, goblet cell occupation percentage region, and damaged bulbar conjunctiva epithelium percentage region were measured by histomorphological evaluation. After 5 h exposure to drying airflow, the thickness of the cornea and conjunctiva was decreased with desquamation of the corneal and conjunctiva epithelium. However, these dry eye symptoms were markedly inhibited by treatment with the reference and test formulations. More favorable effects on decreased thickness were detected in response to the CMC than the SH. However, SH had a greater protective effect against corneal and conjunctiva epithelial damage. The application of a mixture of 0.1% SH and 0.2% CMC showed more favorable effects on the corneal and conjunctival damage and the stabilization of the ocular surface than SH or CMC alone.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.4
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• pp.1-11
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• 2004

Combustion and fuel distribution characteristics of heavy duty engine with the liquid phase LPG injection(LPLI) were studied in a single cylinder engine, Swirl ratio were varied between 1.2, 2.3, and 3.4 following Ricardo swirl number(Rs) definition, Rs=2.3 showed the best results with lower cycle-by-cycle variation and shorter burning duration in the lean region while strong swirl(Rs=3.4) made these worse for combustion enhancement. Excessive swirl resulted in reverse effects due to high heat transfer and initial flame kernel quenching. Fuel injection timings were categorized with open valve injection(OVI) and closed valve injection(CVI). Open valve injection showed shorter combustion duration and extended lean limit. The formation of rich mixture in the spark plug vicinity was achieved by open valve injection. With higher swirl strength(Rs=3.4) and open valve injection, the cloud of fuel followed the flow direction and the radial air/fuel mixing was limited by strong swirl flow. It was expected that axial stratification was maintained with open-valve injection if the radial component of the swirling motion was stronger than the axial components. The axial fuel stratification and concentration were sensitive to fuel injection timing in case of Rs=3.4 while those were relatively independent of the injection timing in case of Rs=2.3.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.11a
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• pp.245-251
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• 2001

A fretting wear tester is developed for experimental study on the fuel fretting problem of light water reactor. The feature of the developed tester is it can simulate the existence of gap between spring and fuel rod as well as different contacting force including the just-contact condition (0 N on the contact). Used are a servo-motor, an eccentric cylinder and lever mechanism for driving system. A spacer grid cell is constituted with four strap segments (each segment has a spring). This fretting wear tester can also be used as a fatigue tester of a spacer grid spring with the frequency of more than 10 Hz. It is required to simulate the frequency of the vibrating fuel rod due to flow-induced vibration in a reactor. In fretting wear test, up to two span-length of a fuel cladding tube can be accommodated. A specimen of cladding tube of one span-length is specially designed, which can be extended for two-span test. For .fatigue test, a device for clamping the spring fixture is installed additionally, Presently, the tester is designed for the condition of air environment and room temperature. The variation of the reciprocal distance is measured to check the stability of input force, which will be exerted to the cladding (for fretting wear. test) and the spring (for fatigue test) specimen.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.48-53
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• 2014

Rocket, held using the CCA for the mission, a plurality of recording devices, and navigation equipment. In case of a projectile which is entered the water after fired into the air, after performing stages and fairing separated in flight to enter the underwater. It is caused by the explosion of gunpowder mainly, vibration phenomenon of a large transition is induced structurally very, also on entering the water, have a significant shock structurally separated. If shock is transmitted directly to the CCA through the body, it can be caused malfunction of payloads, resulting in failure of the mission of the projectile. In order to ensure the stability against shock, in this paper, Calculating a target resonacne frequency of the CCA, and verified through modal test and analysis. Maximum acceleration position of CCA is checked by SRS analysis. In addition, effectiveness of shock isolation system through shock analysis.

• Journal of the Korean Society of Visualization
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• v.8 no.1
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• pp.31-38
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• 2010

An experimental study to evaluate dynamic structures of flow and turbulence characteristics in bubble-driven liquid flow in a rectangular tank with a varying flow rate of compressed air is conducted. Liquid flow fields are measured by time-resolved particle image velocimetry (PIV) with fluorescent tracer particles to eliminate diffused reflections, and by an image intensifier to acquire enhanced clean particle images. Instantaneous vector fields are investigated by using the two frame cross-correlation function and bad vectors are eliminated by magnitude difference technique. By proper orthogonal decomposition (POD) analysis, the energy distributions of spatial and temporal modes are acquired. When Reynolds number increases, bubble-induced turbulent motion becomes dominant rather than the recirculating flow near the side wall. The total kinetic energy transferred to the liquid from the rising bubbles shows a nonlinear relation regarding the energy input because of the interaction between bubbles and free surface.