• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2004.04b
• /
• pp.125-128
• /
• 2004

In this paper, a novel processing technique for fabrication of high-temperature MEMS based on polymer-derived SiCN microstructures is described. PDMS molds are fabricated on SU-8 photoresist using standard UV-photolithographic processes. Liquid precursors are injected into the PDMS mold. And then, the resulting solid polymer structures are crosslinked under isostatic pressure, and pyrolyzed to form a ceramic capable of withstanding over $1500^{\circ}C$. These fabricated SiCN structures would be applied for high-temperature applications, such as heat exchanger and combustion chamber.

• 연구논문집
• /
• s.25
• /
• pp.55-65
• /
• 1995

Three-dimensional incompressible turbulent flow fields within the passage of the steam turbine nozzle with/without tip clearance have been simulated by solving the Navier-Stokes equations with SIMPLE scheme. The extended k-e model is applied to modeling the Reynolds stresses. Grids in the computational domain are generated by solving the Poisson's equations to improve the smoothness and orthogonality. Flow losses, secondary flow, velocity profiles, and deviation angles are obtained. The computated results without tip clearance show good agreement with the experimental data.

• 연구논문집
• /
• s.26
• /
• pp.43-50
• /
• 1996

Present paper describes on/off design performance analysis of an 74KW industrial turboshaft gasturbine engine. Procedures to match between the compressor, combustor and turbine have been incorporated into the developed program satisfying compatibility requirement of flow and work and ratational speed. The validity of the performance results from the developed program are yet to be proved through performance experiments of the resultant engine, but comparison of the present results with those from "GASCAN(Thermoflow:America) under similar mass inlet flow, pressure ratio, and speed condition show good agreement despite present results underpredict 6-10% for power and up to 3% in efficiency, respectively.

• Korean Journal of Veterinary Research
• /
• v.17 no.1
• /
• pp.1-4
• /
• 1977

Two hundred and twenty-seven strains of Escherichia coli isolated from 25 hens (12 hens received tetracycline neomycin and sulfadimethoxine, and 13 hens not received antibiotics) were studied for the drug resistance and distribution of R factors. About 74 per cent of E. coli strains isolated from hens of a herd received antibiotics were resistance to tetracycline (TC) streptomycin (SM), chloramphenicol (CM), kanamycin (KM), ampicillin (AP) and sulfisomidine (Su), alone or in combination thereof, but only a hen among a herd not received antibiotics excreted E. coli resistant to TC and SM. Among resistant strains, about 7% were found to be resistant to TC and SM, whereas 93% were resistant to three or more antibiotics. The most common pattern was the quadruple resistant to SM, TC, KM and Su (28.7%), and followed by triple ones to SM, TC and Su (25.3%), and SM, TC and KM (24.7%). About 84% of resistant strains carried R factors which were transferable to the recipient by conjugation.

• Korean Journal of Veterinary Research
• /
• v.17 no.1
• /
• pp.5-8
• /
• 1977

One hundred and fifty seven Escherichia coli strains isolated from 18 cattle (9 dairy cattle received penicillin, streptomycin (SM) or sulfadimethoxine for treatment of diseases and 9 Korean native cattle not received antibiotics) were studied for the drug resistance and distribution of R factors. Of 88 E. coli strains isolated from cattle not received antibiotics, only 1 strain was resistant to SM, but about 46 per cent of 69 E. coli strains isolated from cattle received antibiotics were resistant to SM, tetracycline (TC), ampicillin (AP), kanamycin (KM), chloramphenicol (CM), and sulfisomidine (Su), alone or in combination thereof. Of resistant strains, about 72% were resistant to three or more antibiotics, but 28% were found to singly resistant. The most frequent resistant pattern was triple resistance to AP, KM and Su (37.6%), and quadruple one to SM, TC, CM and Su (12.5%). About 28% of resistant strains carried R factors which were transferable to E. coli ML 1410 $NA^r$ by conjugation.

• 대한예방의학회:학술대회논문집
• /
• 2000.10a
• /
• pp.209-210
• /
• 2000

• Textile Coloration and Finishing
• /
• v.2 no.2
• /
• pp.7-13
• /
• 1990

The polyacrylonitrile (PAN)/polypyrrole (PPy) composite films have been prepaxed by exposing the PAN films containing oxidizing agent such as ferric chloride or cupric chloride to pyrrole vapor. The formation of PPy in PAN was confirmed by means of IR spectroscopy and scanning electron microscopy and the X-ray differaction study showed the amorphous structure of PPy. The breaking strength of PAN/PPy composite films was 3-5 times lower but the breaking elongation of them was 4-5 times higher than that of PAN film.

• Journal of the Korean Mathematical Society
• /
• v.53 no.5
• /
• pp.1149-1165
• /
• 2016

In this paper, we show that there exists no left invariant Riemannian metric h on the Heisenberg group H such that (H, h) is a symmetric Riemannian manifold, and there does not exist any H-invariant metric $\bar{h}$ on the Heisenberg manifold $H/{\Gamma}$ such that the Riemannian connection on ($H/{\Gamma},\bar{h}$) is a Yang-Mills connection. Moreover, we get necessary and sufficient conditions for a group homomorphism of (SU(2), g) with an arbitrarily given left invariant metric g into (H, h) with an arbitrarily given left invariant metric h to be a harmonic and an affine map, and get the totality of harmonic maps of (SU(2), g) into H with a left invariant metric, and then show the fact that any affine map of (SU(2), g) into H, equipped with a properly given left invariant metric on H, does not exist.

• Korean Architects
• /
• no.3 s.251
• /
• pp.66-86
• /
• 1990

• Radioisotope journal
• /
• v.18 no.1
• /
• pp.30-33
• /
• 2003