• Journal of Advanced Navigation Technology
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• v.15 no.2
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• pp.197-203
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• 2011

A triple-band antenna which can be used at GSM900, PCS1900 and Bluetooth(or Wi-Fi) frequency band is proposed. The proposed antenna is designed based upon switching between IFA(Inverted F Antenna) that has a resonant length of ${\lambda}/4$ and loop antenna that has a resonant length of ${\lambda}/2$. It can be applied to triple-band only by use of single printed pattern due to the switching characteristic. It is designed by use of the IFA for the application to the GSM900, while it is designed by use of the loop antenna for the application to the PCS1900 and by use of additional pattern of IFA for the application to the Bluetooth(or Wi-Fi) respectively. As a result, it has been observed that the proposed antenna satisfies the required return loss(${\leq}10dB$) and also has efficiency(${\geq}80%$) over the whole band. Moreover the proposed antenna has omni-directional radiation pattern which is suitable to apply to the mobile phone.

• Journal of Advanced Navigation Technology
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• v.16 no.1
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• pp.27-34
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• 2012

In this paper, Coplanar waveguide(CPW)-fed slot loop antenna, which is applicable to the dual band(2.4GHz~2.4835GHz, 5.15GHz~5.825GHz) for the wireless LAN, is proposed. In order to miniaturize the proposed antenna, slot loop is bent by meandering. The resonant frequencies in the required dual band are adjusted by variation of the resonant length of slot loop as well as slot width. In particular, use of capacitive coupling CPW feed provides impedance matching without a seperate matching circuit, because the amount of electromagnetic coupling can be controlled by the offset between feed and radiator. As a result, it has been observed that the proposed antenna satisfies not only the required return loss(${\leq}10dB$) but also has high efficiency(${\geq}80%$) over the whole frequency band. In order to check the validity of the proposed antenna, some simulated results for return loss and radiation pattern are presented in comparison with the measured results.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.11
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• pp.1575-1581
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• 2014

In this paper, eddy current loss, iron loss and heat transfer of PMSG with 2,000kW capacities were analyzed for wind turbine. The PMSG with 3 split magnet was analyzed using ansoft maxwell commercial program and, generator was tested by Back to Back converter with no load condition at laboratory. Rotor surface temperature was measured by Pt100 sensors for investigating heat transfer from rotor to atmosphere. The simulation results shows 27.4kW eddy current loss in no load condition and 50.2kW eddy current loss in rated load condition with 3 split magnet, and also shows 4.3kW iron loss in no load condition and 7.3kW iron loss rated load condition. The heat transfer coefficient of convection between rotor surface and atmosphere was investigated by $9.6W/m^2{\cdot}K$. Therefore the heat transfer from rotor to atmosphere was about 17kW(54%) and from rotor to air-gap was about 14.6kW(46%) in no load condition. It is identified that the cooling system for stator have to include the 46% of iron loss, and heat dissipation structure of rotor surface have to be suggested and designed for efficiency improvement of generator.

• Journal of Microbiology and Biotechnology
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• v.16 no.2
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• pp.226-231
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• 2006

Several white-rot fungi are able to produce extracellular lignin-degrading enzymes such as manganese peroxidase (MnP), lignin peroxidase (LiP), and laccase. In order to enhance the production of laccase and MnP using Trametes versicolor KCTC 16781 in suspension culture, the effects of major medium ingredients, such as carbon and nitrogen sources, on the production of the enzymes were investigated. The decolorization mechanism in terms of biodegradation and biosorption was also investigated. Among the carbon sources used, glucose showed the highest potential for the production of laccase and MnP. Ammonium tartrate was a good nitrogen source for the enzyme production. No significant difference in the laccase production was observed, when glucose concentration was varied between 5 g/l and 30 g/l. As the concentration of nitrogen source increased, a lower MnP activity was observed. The optimal C/N ratio was 25 for the production of laccase and MnP. When the concentrations of glucose and ammonium tartrate were simultaneously increased, the laccase and MnP activities increased dramatically. The maximum laccase and MnP activities were 33.7 U/ml at 72 h and 475 U/ml at 96 h, respectively, in the optimal condition. In this condition, over 90% decolorization efficiency was observed.

• Journal of The Korean Society of Agricultural Engineers
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• v.59 no.5
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• pp.93-99
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• 2017

A model was developed using Artificial Neural Networks (ANNs) based on Principal Component Analysis (PCA), to accurately predict the air humidity inside an experimental greenhouse located in Daegu (latitude $35.53^{\circ}N$, longitude $128.36^{\circ}E$, and altitude 48 m), South Korea. The weather parameters, air temperature, relative humidity, solar radiation, and carbon dioxide inside and outside the greenhouse were monitored and measured by mounted sensors. Through the PCA of the data samples, three main components were used as the input data, and the measured inside humidity was used as the output data for the ALYUDA forecaster software of the ANN model. The Nash-Sutcliff Model Efficiency Coefficient (NSE) was used to analyze the difference between the experimental and the simulated results, in order to determine the predictive power of the ANN software. The results obtained revealed the variables that affect the inside air humidity through a sensitivity analysis graph. The measured humidity agreed well with the predicted humidity, which signifies that the model has a very high accuracy and can be used for predictions based on the computed $R^2$ and NSE values for the training and validation samples.

• Journal of the Mineralogical Society of Korea
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• v.26 no.3
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• pp.139-150
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• 2013

In order to effectively leach Fe from pyrite, the application of microwave energy and ammonia solution has been conducted. Pyrite transforms into hematite and pyrrhotite when treated with microwave radiation for 60 minutes, and in this time the highest amount of Fe was leached by the ammonia solution. Up to 99% of the Fe was leached when the experimental conditions were: 325-400 mesh particle size for the pyrite and 60 min. was the microwave exposure time. The ammonia leaching conditions were 0.3 M sulfuric acid, 2.0 M ammonium sulfate and 0.1 M hydrogen peroxide concentration. The pyrite, hematite, and pyrrhotite were not detected using XRD analysis from the solid-residues treated by the ammonia solution except for quartz.

• Current Photovoltaic Research
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• v.5 no.3
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• pp.69-74
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• 2017

Here we report the influence of thermal treatment on the performance of high efficiency polymer solar cells with the bulk heterojunction films of poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b'] dithiophene-alt-3-fluorothieno[3,4-b]thiophene-2-carboxylate] (PTB7-Th) and [6,6]-phenyl $C_{71}$ butyric acid methyl ester ($PC_{71}BM$). The crystalline nanostructure of PTB7-Th:$PC_{71}BM$ layers, which were annealed at three different temperatures, was investigated by employing synchrotron radiation grazing incidence X-ray diffraction (GIXD) technique. Results showed that the device performance was slightly reduced by thermal annealing at $50^{\circ}C$ but became significantly poor by thermal annealing at $100^{\circ}C$. The poor device performance by thermal annealing was attributed to the collapse in the crystalline nanostructure of PTB7-Th in the PTB7-Th:$PC_{71}BM$ layers as evidenced by the GIXD measurements that exhibited huge reduction in the intensity of PTB7-Th (100) peak even at $50^{\circ}C$.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.27 no.1
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• pp.66-71
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• 1982

Field experiments of nitrogen application (0, 100, 200, 400, 800kg N/ha year) were carried out to study the nitrogen response of Sudangrass at College Farm, Seoul National Univ., in 1979 and 1980. Dry matter yield and leaf area index increased up to 400kg N/ha in 1979 and 800kg N/ha in 1980. The forage yield of 1980 was less than that of 1979, due to the extraordinarily low temperature and the decreased solar radiation during summer. Total nitrogen contents in forage increased with nitrogen application, but maximum contents were found either 400 or 800kg N levels depend on each cutting stages. Nitrate nitrogen content in forage exceded over 2000 ppm at 800kg N application. Overall percentages of N recovery were below 50% with average 34%. Net assimilation rate and nitrogen use efficiency of Sudangrass were improved in higher temperature and more sunlight condition during regrowth period.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.3 s.118
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• pp.288-297
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• 2007

The novel internal monopole chip antenna of penta-band operation for GSM850/GSM900/DCS/USPCS/WCDMA bands for mobile phones is proposed. This antenna occupies a small volume $8\times3.2\times20mm^3$ and is suitable to be embedded in a mobile phone as an internal antenna. The minimization of the proposed antenna was realized by using spiral line structure and meander line structure on FR-4 of dielectric$(\varepsilon_r=4.4)$. The designed antenna has the wide-band operation in the upper band by overlapping high order resonances. The measured bandwidth of this antenna (VSWR>3) is 150MHz$(1,030\sim1,180\;MHz)$ in the lower band operation and 650 MHz$(1,760\sim2,410\;MHz)$ in higher band operation. The measured radiation efficiency within bandwidth(VSWR 3:1) is over 50 %. The antenna has been designed by a commercial software HFSS.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.1
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• pp.14-19
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• 2016

In this paper, a wideband slot antenna with corrugated structure antenna is proposed. The proposed antenna consists of a ground plane with corrugated slot and microstrip feed-line. Even with a limited dimension of $70{\times}70{\times}1.6mm$, the proposed antenna has wide bandwidth due to the longer current path formed by the corrugated slot structure. Measured bandwidth(10 dB return loss) and fractional bandwidth of the proposed antenna are 2,180 MHz(2.5~4.68 GHz) and 60.7 % at the center frequency of 3.59 GHz. The proposed antenna has an omni-directional radiation pattern and measured gains and average efficiency were 3.48~5.83 and dBi, 81.55 %, respectively.