• Proceedings of the KIEE Conference
• /
• 2001.04a
• /
• pp.467-469
• /
• 2001

An investigation into power conditioners that interface with photovoltaic array and utilities has been completed. The rating for this investigation is residential system(3-5kW) that interface with a 220V single phase utility connection. As the result of this investigation, a 3kW high frequency PWM IGBT inverter feeding a high frequency isolation transformer with a sinusoidal current wave was selected. The output of the transformer rectified with a diode bridge rectifier, four IGBT, used as 60Hz switched, reverse the polarity of the rectified current on every other half cycle of the utility voltage. Even though the high frequency link system used more power semiconductors, a net size, weight, and parts cost saving result compared to the other systems due to elimination of 60Hz transformer.

• Proceedings of the KIEE Conference
• /
• 1998.07g
• /
• pp.2458-2460
• /
• 1998

To drive motor or heating machine, it needs the electric power system like the apparatus of inverter. This electric power system obviously comprises power switching devices and drivers to run them. And this system has the topology comprised one/many arm(s), - each arm has high side switching device and low side switching device. Transformer, photocoupler, and HVIC having functions of isolation and level shift which are important thing to drive high side switching device are used as component of drivers in conventional apparatus. Piezoelectric transformers are proposed in this paper, and applied to drive high side swiching device. Through experiments, the possiblities of driving high side switching device are presented and the problems are mooted concurrently. But, we also consider a counterplan for solving the mooted trouble issues.

• Proceedings of the KIEE Conference
• /
• 2000.07b
• /
• pp.1050-1052
• /
• 2000

An investigation into power conditioners that interface with photovoltaic array and utilities has been completed. The rating for this investigation is residential system (3-5kW) that interface with a 220V single phase utility connection. As the result of this investigation. a 3kW high frequency PWM IGBT inverter feeding a high frequency isolation transformer with a sinusoidal current wave was selected. The output of the transformer rectified with a diode bridge rectifier four IGBT, used as 60Hz switched, reverse the polarity of the rectified current on every other half cycle of the utility voltage. Even though the high frequency link system used more power semiconductors, a net size, weight, and parts cost saving result compared to the other systems due to elimination of 60Hz transformer.

• Proceedings of the KIPE Conference
• /
• 2001.07a
• /
• pp.46-49
• /
• 2001

An investigation into power conditioners that interface with photovoltaic array and utilities has been completed. The rating for this investigation is residential system(3-5kVA) that interface with a 220V single phase utility connection. As the result of this investigation, a 3kVA high frequency PWM IGBT inverter feeding a high frequency isolation transformer with a sinusoidal current wave was selected. The output of the transformer rectified with a diode bridge rectifier. four IGBT, used as 60Hz switched, reverse the polarity of the rectified current on every other half cycle of the utility voltage. Even though the high frequency link system used more power semiconductors, a net size, weight, and parts cost saving result compared to the other systems due to elimination of 60Hz transformer.

• KSBB Journal
• /
• v.9 no.4
• /
• pp.378-384
• /
• 1994

An improved method for the selective isolation of high-yielding mutant strains for the production of antifungal antibiotic KRF-001 was investigated. The mutant strain U. V 4, which produces high titer of KRF-001, was selected on the high potency agar plate after ultraviolet light irradiation. The U. V 4 strain produced 2-fold more KRF-001 than the mother strain in production media. Large scale fermentation was performed using the U. V 4 strain in 100$\ell$ fermenter. The antifungal antibiotic KRF-001 secreted into culture broth was detected by HPLC in 24hrs of fermentation.

• Proceedings of the KIEE Conference
• /
• 1995.07a
• /
• pp.371-375
• /
• 1995

This paper presents equipment for charging and discharging with high power factor and high efficiency. This equipment is consisted of $3{\phi}$ SPWM AC/DC converter for improving input current waveform and input power factor, and bidirectional DC/DC converter for electric isolation in the DC link Part. Therefore, Input power factor and the total efficiency in the proposed system can be increased more than in the conventional phase-controlled thyristor charging-discharging System.

• KIEE International Transactions on Electrophysics and Applications
• /
• v.11C no.4
• /
• pp.150-154
• /
• 2001

In this paper, we presented a novel structure of microstrip directional coupler for realizing the high directivity characteristic and tight coupling. The achievement of the high directivity with microstrip configuration was carried out by matching the even and odd mode effective phase velocities. By using 2-dimensional finite element (FE) calculations, the phase velocity for each mode and design parameters were extracted for given dimensions. Based on the extracted design parameter with phase-matched condition, we designed and fabricated 3dB and 4.7dB directional coupler at 2.0GHz. Experimental results of microstrip coupler show good performance with excellent isolation characteristics.

• Korean Journal of Microbiology
• /
• v.51 no.4
• /
• pp.427-434
• /
• 2015

Most of halophilic archaea are found in the various hypersaline environments including solar saltern, salt lake with very high salt concentration. The present study is about isolation and characterization of halphilic archaea from Gomso solar saltern known as a representative high salt environment in Korea. In order to isolate the halophilic archaea, we prepared and used high salt medium. Finally, total 7 strains obtained were tentatively identified based on comparative similarity analysis for 16S rRNA gene sequence and physiological traits. All halophilic archaea belonged to Haloruburm, Halogeometriucm, Halobacterium, and Haloarcula genera. These isolates were all Gram-staining negative, and growth was not observed using nitrate as an alternative electron acceptor under anaerobic conditions. In addition, all isolates required about 12-30% (w/v, NaCl) salt. This case study might provide basic information on microbial isolation technologies and related research in halophilic microorganisms from domestic halophilic environments, and contribute to obtaining useful indigenous halophilic archaea in a variety of extreme environmental conditions.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.43 no.4 s.346
• /
• pp.8-15
• /
• 2006

In this paper, the 94 GHz, low conversion loss, and high isolation single balanced mixer is designed and fabricated using GaAs-based metamorphic high electron mobility transistors (MHEMTs) with 70 nm gate length and the hybrid ring coupler with the micromachined transmission lines, dielectric-supported air-gapped microstrip lines (DAMLs). The 70 nm MHEMT devices exhibit DC characteristics with a drain current density of 607 mA/mm an extrinsic transconductance of 1015 mS/mm. The current gain cutoff frequency ($f_T$) and maximum oscillation frequency ($f_{max}$) are 320 GHz and 430 GHz, respectively. The fabricated hybrid ring coupler shows wideband characteristics of the coupling loss of $3.57{\pm}0.22dB$ and the transmission loss of $3.80{\pm}0.08dB$ in the measured frequency range of 85 GHz to 105 GHz. This mixer shows that the conversion loss and isolation characteristics are $2.5dB{\sim}>2.8dB$ and under -30 dB, respectively, in the range of $93.65GHz{\sim}94.25GHz$. At the center frequency of 94 GHz, this mixer shows the minimum conversion loss of 2.5 dB at a LO power of 6 dBm To our knowledge, these results are the best performances demonstrated from 94 GHz single balanced mixer utilizing GaAs-based HEMTs in terms of conversion loss as well as isolation characteristics.

• The Journal of the Korean Society for Microbiology
• /
• v.20 no.1
• /
• pp.35-44
• /
• 1985

Isolation and identification of anaerobic bacteria from blood cultures are still technically demanding procedures. Recently, with the use of gas liquid chromatography, the accuracy of identification is much improved. However, there has never been a satisfactory data analysis on anaerobic bacteremia in Korea. The authors evaluated both the clinical and the bacteriological data of 129 anaerobic bacteremias found at the Yonsei Medical Center during the period of 1973 to 1984. The most frequently isolated anaerobic bacteria were Bacteroides (52.7%), among which the major species was B. fragilis (38.7%). Incidence of anaerobic bacteremia by sex was 57% in male and 43% in female. Mortality was higg in groups below 1-year old and above 50-year old. The cause of death seemed closely correlated with the patient's age, general condition and the severity of the underlying disease. Various neoplasms were the most common (20%) underlying diseases predisposing the anaerobic bacteremia. Biliary tract was considered the most frequent route of infection in anaerobic bacteremia. The frequent clinical signs in anaerobic bacteremia were fever (65%), followed by liver function abnormality (29%), jaundice (20%) and hypotention(18%). When analysis of positive rate of blood culture was made on the patients from whom 4 cultures were done within 24 hours, it was found that 33% of the samples were positive. Isolation rate of anaerobic bacteria in thioglycollate medium was 83.8%, while it was 44% in Tryptic soy broth. Among the anaerobic bacteremia, 25.4% were polymicrobial infections with aerobic bacteria (92.5%), such as E. coli(33.3%). From these studies, it is concluded that B. fragilis is the most important causative organism in anaerobic bacteremia, with high fatality, particularly in those who have underlying diseases. The ports of entry are mainly biliary, gastrointestinal and female genital tract. Fever is the most frequent clinical sign. Single blood culture is not sufficient to detect all anaerobic bacteremia, therefore more cultures with optimal time interval are needed. The incidence of polymicrobial infection in anaerobic bacteremia is higher than that in overall bacteremia.