• Journal of the Korean Society of Industry Convergence
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• v.20 no.2
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• pp.115-124
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• 2017

This paper aims to develop an SMPS topology for handling a high range of input voltages based on a DC-DC flyback converter circuit. For this purpose, 2 capacitors of the same specifications were serially connected on the input terminal side, with a flyback converter of the same circuit configuration serially connected to each of them, so as to achieve high input voltage and an effect of dividing input voltage. The serially connected flyback converters have the transformer turn ratio of 1:1, so that each coil is used for the winding of a single transformer, which is a characteristic of doubly-fed configuration and enables the correction of input capacitor voltage imbalance. In addition, a pulse transformer was designed and fabricated in a way that can achieve the isolation and noise robustness of the PWM output signal of the PWM controller that applies gate voltage to individual flyback converter switches. PSIM simulation was carried out to verify such a structure and confirm its feasibility, and a 100W class stack was fabricated and used to verify the feasibility of the proposed high voltage SMPS topology.

• Journal of Korean language education
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• v.23 no.1
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• pp.257-282
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• 2012

Sakhalin, Russia is a very specific area for Korean language education. The imposed separation and isolation in this region means the language in Sakhalin is mixed with South Korean, North Korean, Gyeongsang Province dialect, Japanese, and Russian. Scrutiny of the use of the actual language of Sakhalin Koreans is needed, and it is required in supporting Korean language education. In this study, I will cover: 1. Approach should differ depending on the situation of Korean, foreigners, Korean Language School(Hangeul Hakgyo) and Korean classes in local Schools. 2. Tailor-made textbooks for Sakhalin are required. 3. Korean textbooks to match local circumstances are needed. There should be a basic writing text written by a local Korean department professor and supervision or modification, supplements from Korean language education researchers in Korea. 4. Enlarged Korean training programs are needed. Furthermore, if Korean and Russian university students are to study in Korea, there should be programs offering a dual degree among other things. 5. Methodical, overall examination of overseas Korean regions like Sakhalin is necessary. Also in the case of far east Russia, connectivity between Vladivostok, Khabarovsk and Sakhalin needs to be strengthened.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.7
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• pp.774-783
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• 2007

This paper presents an integrated packaging antenna-diplexer module for wireless communication systems in the Cellular and SDMB band. The design and the realization of the proposed one are experimentally analyzed and discussed. It consists of a dual-resonance antenna and a diplexer with a multi-layer LTCC(${\varepsilon}_r=7.8,\;tan\;{\delta}=0.0043$) technology with integration capability and low loss. The dual-resonance antenna of the proposed module has the meander line structure for size reduction and has the shorting structure of an inverted F antenna to achieve good impedance matching. The diplexer of the proposed module was designed with the combination of low pass filter(LPF) and high pass filter(HPF). Decreasing the mutual interference between them provides a high isolation characteristic. The proposed antenna-diplexer module with dimensions of $27.5{\times}12.0{\times}2.2mm$ operates within a range from 813 MHz to 902 MHz for the cellular band and from 2,586 MHz to 2,655 MHz for the SDMB band. And the measured gain of the fabricated module is -1.96 dBi for Cellular band and -5.43 dBi for SDMB band. The parameters for the antenna-diplexer module are investigated and the several performances are discussed.

• Journal of Advanced Navigation Technology
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• v.20 no.4
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• pp.344-351
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• 2016

In the present study, a dual-band multiple-input-multiple-output (MIMO) antenna covering WLAN frequency bands of 2.4 GHz (2.4 ~ 2.484 GHz) and 5 GHz (5.15 ~ 5.825 GHz) is newly presented to avoid use of decoupling structure for increasing isolation. The antenna consists of two L-shaped slots with n-shaped slots etched on the floating ground plane surrounded by open ended L-shaped slots which are placed in the left and right corner of PCB respectively. The proposed antenna is designed and fabricated on one side of FR4 substrate with dielectric constant of 4.3, thickness of 1.6 mm, and size of $50{\times}50mm2$. It has been observed that the measured impedance bandwidths ($S_{11}{\leq}-10dB$) are 0.3 GHz (2.28 ~ 2.58 GHz) in 2.4 GHz frequency band and 0.89 GHz (5.11 ~ 6 GHz) in 5 GHz frequency band respectively. In addition, It has been observed that the whole efficiency are more than 80 % in the whole operating frequency band and envelope correlation coefficient of the antenna is less than 0.05 as a very small value in spite of nothing of the decoupling structure.

• Journal of IKEEE
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• v.2 no.1 s.2
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• pp.1-14
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• 1998

In this paper, Antenna, LNA, Mixer, VCO, and Modulation/Demodulation in Baseband processor which are the RF main components in Wireless LAN system for ultra high-speed communications network are studied. Antenna bandwidth and selective fading due to multipath can be major obstacles in high speed digital communications. To solve this problem, wide band MSA which has loop-structure magnetic antenna characteristics is designed. Distributed mixer using dual-gate GaAs MESFET can achieve over 10dB LO/RF isolation without hybrid, and minimize circuit size. As linear mixing signal is produced, distortions can be decreased at baseband signals. Conversion gain is achieved by mixing and amplification simultaneously. Mixer is designed to have wide band characteristics using distributed amplifier. In VCO design, Oscillator design method by large signal analysis is used to produce stable signal. Modulation/Demodulation system in baseband processor, DS/SS technique which is robust against noise and interference is used to eliminate the effect of multipath propagation. DQPSK modulation technique with M-sequences for wideband PN spreading signals is adopted because of BER characteristic and high speed digital signal transmission.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.4B
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• pp.388-396
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• 2002

In this paper, An aperture-coupled microstrip patch antenna operating at WLL frequency range(Rx : 2.3∼2.33Ghz, Tx : 2.37 ∼2.4Ghz) for WLL repeater is designed and fabricated. FR-4 epoxy substrate with 4.7 relative permittivity is inserted between feed-line and patch plane. Aperture-coupled structure is employed for consideration of bandwidth improvement and gain\`s characteristics. Air gap is arranged at each layer for bandwidth extension and radome is used as a protector in the upper patch. In this paper, both 1 port and 2 port are designed as 1$\times$2 array antenna which uses T-junction and λ$\_$g//4 transformer. Here, 1 port is used as transmitting/receiving antenna and 2 port is used as receiving antenna. Functionally independent two antennas using space diversity arrange slots between two antennas in order to be placed at the same place. As a result, we obtained a excellent isolation below -40dB and return loss is reduced by means of slots arrangement between patch and antenna.

• The Plant Pathology Journal
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• v.35 no.6
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• pp.674-683
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• 2019

Some species of the Trichoderma genus are reported as the major problem in oak wood mushroom production in Korea. In spite of economic loss by the fungi, scientific information on airborne Trichoderma species is not much available. To generate information for disease management development we analyzed airborne Trichoderma. A total of 1,063 fungal isolates were purely obtained from indoor air sampling of cultivation houses used for oak wood mushroom using sawdust media. Among the obtained isolates, 248 isolates were identified as Trichoderma fungi including T. harzianum, T. atroviride, T. citrinoviride, and T. pseudokoningii, by morphological and molecular analysis. T. harzianum was dominant among the four identified species. All the four Trichoderma species grew fast on solid nutrient media tested (potato dextrose agar [PDA], malt extract agar [MEA], Czapek's Dox + yeast extract agar [CYA] and cornmeal dextrose agar). Compact mycelia growth and mass spore production were better on PDA and CYA. In addition, T. harzianum and T. citrinoviride formed greenish and yellowish mycelium and spores on PDA and CYA. Greenish and yellowish pigment was saturated into PDA only by T. pseudokoningii. These four Trichoderma species could produce extracellular enzymes of sawdust substrate degradation such as β-glucosidase, avicelase, CM-cellulase, amylase, pectinase, xylanase, and protease. Their mycelia inhibited the growth of oak wood mushroom mycelia of two tested cultivars on dual culture assay. Among of eleven antifungal agents tested, benomyl was the best to inhibit the growth of the four Trichoderma species. Our results demonstrate that the airborne Trichoderma fungi need to be properly managed in the cultivation houses for safe mushroom production.

• Natural Product Sciences
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• v.17 no.2
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• pp.90-94
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• 2011

An in vitro bioassay-guide revealed that the methanol (MeOH) extract of the whole plant of Patrinia saniculaefolia (Valerianaceae) showed cyclooxygenase-2 (COX-2) and 5-lipoxygenase (5-LOX) dual inhibitory activity by assessing their effects on the production of prostaglandin $D_2$ ($PGD_2$) and leukotriene $C_4$ ($LTC_4$) in mouse bone marrow-derived mast cells (BMMCs). Phytochemical study of the MeOH extract of this plant led to the isolation of twelve compounds; ${\beta}$-farnesene (1), squalene (2), nardostachin (3), patridoid I (4), patridoid II (5), patridoid II-A (6), oleanolic acid (7), oleanonic acid (8), 23-hydroxyursolic acid (9), oleanolic acid 3-O-${\alpha}$-L-arabinopyranoside (10), oleanolic acid 3-O-${\beta}$-D-glucopyranoside (11), oleanolic acid 3-O-[${\beta}$-D-xylopyranosyl-(1${\rightarrow}$3)-${\beta}$-D-(6-O-butyl)glucuronopyranoside] (12). Among the compounds, 4 and 5 strongly inhibited both the COX-2-dependent $PGD_2$ generation with $IC_{50}$ values of 8.7 and 13.6 ${\mu}M$, respectively, and the generation of $LTC_4$ in the 5-LOX dependent phase with $IC_{50}$ values of 41.7 and 46.9 ${\mu}M$, respectively, which suggest that the anti-inflammatory activity of P. saniculaefolia might occur in part via the inhibition of both $PGD_2$ and $LTC_4$ generation by 4 and 5.

• Journal of Life Science
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• v.13 no.4
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• pp.535-540
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• 2003

The antagonistic microorganisms against Streptococcus sanguis, S. salivarius and S. mutans causing the dental caries of oral diseases were isolated from Korean traditional soy sauce. Twenty five strains were isolated by pairing culture, paper disc culture and dual culture methods. The isolate NG 06 strain was observed with various cultural and physiological test, and $Biolog^{(R)}$ Bacterial Identification System. The strain was identified as Bacillus racemilacticus. The isolate NG 16 strain was confirmed to Gram-positive, rods, endospore production, utilization of melibiose, casein hydrolysis and starch hydrolysis. Also the second strain NG 16 was identified as $\beta$. amyloliquefaciens.

• The Korean Journal of Pesticide Science
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• v.14 no.4
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• pp.421-426
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• 2010

Many bacterial strains inhabit strong saline condition, such as tidal mudflat and salted seafoods, were identified and reported for the proposed protease activities and salt resistance; however antifungal activities against plant fungal pathogen have not well been studied until now. In this study, primary screening was performed for the isolation of promising strains against major plant pathogens like Sclerotinia sclerotiorum, Fusarium oxysporum, Phytophthora capsici, Botrytis cineria, Collectotrichum acutatum and Pythium ultimum. Totally 423 bacterial strain were isolated from laboratory media which was based on different morphological characteristics and all the strains were dual cultured against major fungal pathogens on PDA, finally 40 strains were selected as antifungal bacterial strain and identified by fatty acid phylogenic difference analysis from MIDI shorlock gas chromatography system. As a result, antifungal strains from tidal mudflat were 10 species of 6 genus. Paenibacillus macerans was dominant species; 5 strains among the 17 isolates from tidal mudflat. Antifungal strains from salted seafoods were 7 species of 3 genus and Bacillus atrophaeus was dominant species; 12 strains among the 23 isolates from salted fishes.