• Journal of computational fluids engineering
• /
• v.14 no.1
• /
• pp.9-17
• /
• 2009

In this study we investigated the characteristics of fluid flow and heat transfer within a coolant passage in the cylinder head assembly of an internal combustion engine by using a commercial CFD code, CFX The complex coolant passage of the cylinder head assembly was modelled by suitable choice of a grid system and careful attention was paid in the construction of meshes near the walls where significant cooling occurs. To treat the simultaneous heating and cooling of the combustion walls we invented a methodology allowing a heat source within the solid wall and the convective cooling at the interface between the solid and the fluid. We managed to reproduce the experimental results by adjusting parameters appropriately. We have found that high temperature was concentrated at the surface of the cylinder jacket. It turned out that the effect of oil cooling from the piston head was unexpectedly significant. On the other hand the effect of cooling from the ambient air is almost negligible. The CFD method proposed in this study is believed to be useful in the early stage of the design of the engine-cooling system.

• Journal of the Korean Society for Aviation and Aeronautics
• /
• v.19 no.3
• /
• pp.43-53
• /
• 2011

It is well known some Foreign aircraft used to fly INCHEON FIR(Flight Information Region), especially the island of IEODO without a flight plan, even though foreign aircraft is subject to submitting a flight plan to Flight Information Center(FIC) before its flight. IEODO is a sunken rock 4.6m beneath the sea level, 149km away from Marado. Facing the Yangtze river's sea entrance horizontally and military zones of Korea and China vertically, IEODO is a very important place for national security of North East Asia because it is located at the boundary between China East Sea and Yellow Sea of South Korea. Moreover, JDZ(the 7th mine lot) is just 77NM from IEODO, which possesses natural gas eight times bigger than the gulf region and oil 4.5 times bigger than that of the U.S. In addition, INCHEON FIR, managed by MLTM(Air Traffic Control Center) and Japanese Self-Defense Force's JADIZ(Japanese Air Defense Identification Zone) are overlapping on IEODO whose air space is very complex. This paper focuses on air space, FIR, ADIZ(Air Defense Identification Zone) and related airspace system and suggests strategic implications of how to prevent foreign aircraft from invading INCHEON FIR without permission and of how to utilize the airspace efficiently.

• Biomolecules & Therapeutics
• /
• v.8 no.4
• /
• pp.293-298
• /
• 2000

Bergenin is a C-glucoside of 4-O-methyl gallic acid that has been isolated from the cortex of Mallotus japonicus (Euphorbiaceae). Acetylbergenin was synthesized by acetylation from bergenin to increase lipophilic and physiological activities. The therapeutic effects of bergenin and acetylbergenin were evaluated against carbon tetrachloride ($CCl_4$)-induced hepatotoxicity in rats. Bergenin and acetylbergenin were administered orally once daily for successive 5 days, after the intraperitoneal injection of a mixture 0.5 m1/kg of $CCl_4$ in olive oil (1:1). The substantially elevated serum enzymatic activities of alanine/aspartate aminotransferase, sorbitol dehydrogenase and ${\gamma}$-glutamyltransferase induced by $CCl_4$ were restored towards normalization by posttreatment with bergenin and acetylbergenin. Bergenin and acetylbergenin also significantly prevented the elevation of hepatic malondialdehyde formation and depletion of glutathione content induced by $CCl_4$ in a dose dependent fashion. In addition, the decreased activities of glutathione S-transferase and glutathione reductase were restored towards normalization. These results suggest that therapeutic effects of bergenin and acetylbergenin may be related complex mechanisms that involve prevention of lipid peroxidation and preservation of hepatic GSH. The results of this study clearly indicate that bergenin and acetylbergenin have potent hepatothrapeutic action against $CCl_4$-induced hepatotoxicity in rats. In addition, acetylbergenin 50 mgHg showed almost the same levels of hepatoprotective activity as those of bergenin 100 mgAg, indicating the fact that lipophilic acetylbergenin is more effective in the hepatoprotective action against $CCl_4$ than bergenin.

• Progress in Superconductivity and Cryogenics
• /
• v.14 no.3
• /
• pp.38-42
• /
• 2012

Fixtures such as bushings in terminations of high temperature superconducting(HTS) power cable systems are subjected to high voltages, which have to transition from ambient to cryogenic temperatures. As such it is imperative to ensure the integrity of the dielectrics under all operating conditions, including thermal aspects brought about by the passage of current. Gaseous helium(GHe) at high pressure is regarded as a potential coolant for superconducting cables. The dielectric aspects of cryogenic helium gas are both complex and demanding. In this experimental study we looked at the interface between a smooth epoxy surface and high pressure helium gas in a homogeneous electric field. The alternating current(AC) flashover voltages of epoxy samples are presented. The results have been analyzed by using Weibull statistics. In addition to the behavior of the epoxy in gaseous helium as a function of pressure and temperature we also present data of the characteristics of the epoxy in mineral oil and in liquid nitrogen($LN_2$). The breakdown characteristics of a uniform field gap in gaseous helium as a function of pressure and temperature under AC, direct current(DC) and lightning impulse voltages are also given. Electric field calculations have been made for one of the experimental geometries in an attempt to explain some of the anomalies in the experimental results.

• Proceedings of the KIEE Conference
• /
• 2000.11c
• /
• pp.413-415
• /
• 2000

Piezoelectric ceramics of PZT have been developed to apply for transformers in notebook. Use of piezoelectric ceramics in applications like piezoelectric transformers was made possible by the development of new materials with high electromechanical coupling coefficients and high mechanical quality factor. "Hard" ferroelectiric ceramics of complex composition based on lead zirconate titanate with Mn additive have been prepared. The perovskitic phase reaction of the oxides. The crucial role played by the intermediate mixing and grinding procedures in the assessment of the final properties of the material was investigated. Densification up to approximately the theoretical density value was achieved. The polarization was obtained by subjecting the samples at $30kVcm^{-1}$ poling electric field, in a silicon oil bath heated at $110^{\circ}C$. Their microstructural and morphological properties were checked by X-ray diffraction analysis and scanning electron microscopy. The optimized samples presented very high qualify and electromechanical coupling factors, together with small dielectric loss.

• Transactions on Electrical and Electronic Materials
• /
• v.8 no.6
• /
• pp.278-282
• /
• 2007

In the complex insulation system that is used in extra high voltage(EHV) devices, according to the trend for electric power equipment of high capacity and reduction of its size, macro interfaces between two different bulk materials which affect the stability of insulation system exist inevitably. In this paper, the dielectric strength decrease of the macro interfaces between epoxy and ethylene propylene diene terpolymer(EPDM) was estimated by using the applied voltage to breakdown time characteristics. Firstly, the AC short time dielectric strength of specimens was measured at room temperature. Then, the breakdown time was measured under the applied constant voltage which is 70% of short time breakdown voltage. With these processes, the life exponent n was determined by inverse power law, and the long time breakdown voltage can be evaluated. The best condition of the interface was LOS(low viscosity(350 cSt) silicone oil spread specimen). When 30 years last on the specimens, the breakdown voltage was estimated 44% of the short time breakdown voltage.

• Advances in Traditional Medicine
• /
• v.4 no.1
• /
• pp.1-8
• /
• 2004

Ginseng root has been used as a tonic remedy in Traditional Chinese Medicine for centuries. Modern studies have demonstrated that ginseng root has complex components and multiple pharmacological properties. The effects of ginseng leaf, however, are not well known. Recent studies show that compared to ginseng root, ginseng leaf and stem exhibit a higher content of active compositions such as ginsenosides, polysaccharides, triterpene flavonoids, volatile oil, polyacetylenic alcohols, peptides, amino acids and fatty acids. Ginseng leaf possesses multiple pharmacological effects in the central nervous, cardiovascular, growth and metabolism systems. Additionally, the leaf has anti-fatigue, anti-hyperglycemic, anti-oxidant, and anti-aged effects. In general, ginseng leaf is quite safe, but adverse effects may occur if it is abused or is of poor quality. Thus, attention must be paid to dosages, quality, and standardization of ginseng leaf products.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.23 no.7
• /
• pp.918-927
• /
• 1999

In the fully developed internal flow fields, there are complex transition flows caused by interaction of the cross flow and jet when jet is Injected Into the flow. These interactions are studied by means of the flow visualization methods. An instantaneous laser tomographic method is used to reveal the physical mechanism and the structure of vortices formation in the branch pipe flow. The velocity range of cross flow of the pipe is 0.7m/s and the corresponding Reynolds number $R_{cf}$, based on the duct height is $5.6{\times}10^3$, diameter/height ratios(d/H) 0.14 and velocity ratios 3.0. Oil mist with the size of $10{\mu}m$ diameter is used for the scattering particle. The instantaneous topological features of the vortex ring roll-up of the jet shear layer and characteristics of this flow are studied in detail by performing flow visualization in rectangular duct flow. It is found that the formation and roll-up of ring vortices is a periodic phenomenon. The detailed topology of the vortices in the near field of a cross -flow jet and the mechanism associated with them give enforced hints of vortex breakdown within the vortex system due to the interaction of the jet and the cross-flow.

• Journal of the Korean Society of Safety
• /
• v.8 no.1
• /
• pp.29-34
• /
• 1993

Two major hazardous gases. SOx and NOx. are emissioned from fossile fuels. SOx has been removed when oil is refined but NOx hasn't. So NOx is very serious problem in air pollution now There are several technologies to remove NOx. e.g. cooling method. scrubbers method. combustion method, polymer membrane method and adsorbent methods. Polymer membrane and adsorbent methods have good economic merit in removal systems of low content hazard gases. Traditional absorbents are porous silicas, aluminas. active carbon and zeolites. But these absorbents act only physisorption which has less removal performance than chemisorption. In this study. polymeric absorbent which has chemisorption as well as physisorption was analyzed about chemical structure and experimented about optimum operation conditions. The results showed that the chemical structure of the polymeric absorbent was expected as polystyrene having -N-CH$_2$COOH absorbent was revealed about 310$m^2$/g. The molar ratio of absored NO to charged NO in absorption experiments was shown 60% of the polymeric absorbent and 45% of zeolite absorbent at 3$0^{\circ}C$.

• Biotechnology and Bioprocess Engineering:BBE
• /
• v.6 no.6
• /
• pp.419-425
• /
• 2001

A dense pellicular solid matrix has been fabricated by coating 4% agarose gel on to dense zironia-silica(ZS) spheres by watr-in-oil emulsification . The agarose evenly laminated the ZS bead to a depth of 30㎛, and the resultin gpellicular assembly was characterised by densities up to 2.39g/mL and a mean particle dimeter of 136 ㎛. In comparative fluidisation tests, the pellicular solid phase exhibited a two-fold greater flow velocity than commercial benchmark ad-sorbents necessary to achieve common values of bed expansion. Furthermore, the perlicular parti-cles were characterised by improved qualities of chromatographic behaviour, particularly with re-spect to a three-fold increase in the apparent effective diffusivity of lysozyme within a pellicular assembly modified with Cibacron Blue 3GA. The properties of rapid protein adsorption/desorp-tion were attributed to the physical design and pellicular deployment of the reactive surface in the solid phase. When combined with enhanced feedstock throughput, such practical advantages recommend the pellicular assembly as a base matrix for the selective recovery of protein products from complex, particulate feedstocks(whole fermentation broths, cell disruptates and biological extracts).