• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.12
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• pp.1239-1247
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• 2003

OFDM(orthogonal frequency division multiplexing) communications system is very attractive for the high data rate transmission in the frequency selective lading channel. Since OFDM has high PAPR(peak-to-average power ratio), OFDM signal may be distorted by the nonlinear HPA(high power amplifier). In this paper, we propose the DSI(dummy sequence insertion) method for OFDM communication system. Some sub-carriers are inserted for PAPR reduction. They carry the specified dummy data sequence which are used for only PAPR reduction and do not work as side information like the conventional PTS(partial transmit sequence) or SLM(selected mapping) method. We use the complementary sequence and the combination of the correlation sequence as the dummy sequence. Flipping technique is used for the DSI method to get the effective PAPR reduction. It is important that BER of the proposed method is independent of the damage of the dummy data sequence. And DSI method has better spectral efficiency than the conventional block coding. On the other hand, threshold PAPR method is applied to cut down the processing time. However, this DSI method is not better than the conventional PTS method in the respect of the PAPR reduction performance. The DSI method includes the threshold PAPR lower than the PAPR of the OFDM signal, reduces the processing time and improves the BER performance.

• Food Science and Preservation
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• v.13 no.1
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• pp.88-94
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• 2006

This study was carried out to produce antimicrobial peptides from casein using various proteases. To examine whether the hydrolysis of casein would produce antimicrobial substance and the application as natural antimicrobial material, casein was hydrolyzed by five different proteases. The casein hydrolysate was fractionated with regenerated membrane filter (molecular weight cut-off 30,000 10,000 and 3,000) and antimicrobial activity was measured for each fraction. Antimicrobial activity appeared great in the fraction below 3,000 molecular weight The fraction was re-fractionated by high performance liquid chromatography and substance of main peak (retention time: 13.2 min) collected was used as a sample to measure antimicrobial activity. Among the casein hydrolysates produced by protease, antimicrobial activity was observed the greatest in hydrolysate treated with Aspergillus oryzae protease. The minimum inhibition concentrations of the Asp. oryzae protease hydrolysate were 1.0-1.5 mg/mL. This hydrolysate was a heat stable peptide since antimicrobial activity was maintained after treating with heat for 20 min at $121^{\circ}C$.

• Journal of Photoscience
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• v.9 no.2
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• pp.457-459
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• 2002

Sunlight causes various types of adverse skin changes on the sun-exposed areas of the skin, in which the most hazardous one is the induction of malignant skin tumours. FT -IR spectra were obtained from specimens excised from normal skin, BCCs, SCCs, MMs, nevi, lesions of solar keratosis and Bowen's disease. Tissue samples from freshly frozen specimens were cut into 2 sections in strictly sequential order to be stained with H & E for histopathological analysis, and then to be air-dried on CaF$_2$ slide glasses for further spectral data acquisition from defined area of interest. Intra- and inter-sample variations were estimated within grouped lesion categories according to each skin component. Mean spectra for each type of tissue pathology in the 800-1800 $cm^{-1}$ / region was interpreted using the classical group frequency approach that showed the most visible differences in spectra of benign, premalignant and malignant changes directly related to protein conformation and nucleic acid bases. The relative intensity of the nucleic acid peak was increased with progression to malignancy. In addition, PCA was able to evaluate and maximise the differences in the spectra by reducing the number of variables characterizing each patient and pathology category. This type of approach to non-destructively estimate the complexity of IR-spectra of inhomogeneous samples such as skin demonstrates the advantage of FT -IR microspectroscopy to be able to observe diseased states (benign, premalignant, malignant) and distinguish them from normal against a huge background of inter- and intra-subject variability.

• The Transactions of the Korean Institute of Power Electronics
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• v.7 no.2
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• pp.171-177
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• 2002

The Photovoltaic systems with solar cell way Provide electrical energy to the utility/consumers, which are becoming one of the promising energy substitutes. The photovoltaic system can be classified into two types : One is the stand-alone type, and the other utility interactive one. The latter can return the generated power to the utility, but the former can't. The utility interactive systems are so valuable for peak power cut in summer season. In the photovoltaic systems the maximum power point tracking (MPPT) has been studied for the increase of the generating energy of the photovoltaic system. There are many control methods of MPPT, but a new MPPT algorithm is proposed to overcome the disadvantages of the conventional ones, and as a result the proposed method enables to improve both tracking ability and generating efficiency of photo voltaic system without DC chopper.

• Journal of Environmental Science International
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• v.24 no.5
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• pp.679-687
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• 2015

Atmospheric aerosol particles were investigated at GNTECH university in Jinju city. Samples were collected using the Nanosampler period from January to December 2014. The Nanosampler is a 6 stage cascade impactor(1 stage : > $10{\mu}m$, 2 stage : $2.5{\sim}10{\mu}m$, 3 stage : $1.0{\sim}2.5{\mu}m$, 4 stage : $0.5{\sim}10{\mu}m$, 5 stage : $0.1{\sim}0.5{\mu}m$, back-up : < $0.1{\mu}m$) with the stages having 50% cut-off ranging from 0.1 to $10{\mu}m$ in aerodynamic diameter. The mass size distribution of Atmospheric aerosol particles was unimodal with peak at $1.0{\sim}2.5{\mu}m$ or $0.5{\sim}1.0{\mu}m$. The annual average concentrations of TSP, $PM_{10}$, $PM_{2.5}$, $PM_1$, $PM_{0.5}$ and $PM_{0.1}$ were $44.0{\mu}g/m^3$, $40.3{\mu}g/m^3$, $31.4{\mu}g/m^3$, $18.0{\mu}g/m^3$, $8.0{\mu}g/m^3$, $3.0{\mu}g/m^3$, respectively. On average $PM_{10}$, $PM_{2.5}$, $PM_1$, $PM_{0.5}$ and $PM_{0.1}$ make up 0.91, 0.70, 0.41, 0.19 and 0.07 of TSP, respectively. The annual average of $PM_{2.5}/PM_{10}$ ratio was 0.77.

• KIEAE Journal
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• v.12 no.4
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• pp.89-95
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• 2012

At present, many countries are trying to reduce green gas emissions to mitigate the effects of these gases on climate change. Year after year, there have been efforts to cut energy use for heating and cooling. Heating and cooling systems, common in all forms of housing, are increasing due to the constant supply of new housing resulting from improvements in economic growth and the quality of life. Thus, studies related to the design of cooling and heating systems to improve energy efficiency are expanding. Among the new designs, radiant floor cooling and heating systems which use capillary tubes are becoming viable means of reducing energy use. Radiant floor cooling and heating systems which use capillary tubes are creative and sustainable systems in which cool and hot water is circulated into capillary tube which has small diameter. In this study, the cooling and heating performance of this type of capillary tube system is investigated in an experimental study and a simulation using TRNSYS. The results of the experimental study show that under a peak load, a capillary tube radiant floor cooling system using geothermal energy can achieve desired indoor temperature without an additional heat source. The set room air temperature is maintained while the floor surface temperature, PMV and PPD remain within the comfort range. Also, this system is more economic than a packaged air conditioner system due to its higher COP. The results of the simulation show that the capillary tube radiant floor heating system maintains set temperature more stable than a PB pipe radiant floor heating system due to its lower supply temperature of hot water. In terms of energy consumption, the capillary tube radiant floor heating system is more efficient than the PB pipe radiant floor heating system.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.599-602
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• 2005

In this paper, we have performed a study that modifies the CPW Pad configurations to improve an $f_{max}$ characteristic of metamorphic HEMT. To analyze the CPW Pad structures of MHEMT, we use the ADS momentum simulator developed by $Agilent^{TM}$. Comparing the employed structure (G/W = 40/100 m), the optimized structure (G/W = 20/25 m) of CPW MHEMT shows the increased $S_{21}$ by 2.5 dB, which is one of the dominant parameters influencing the $f_{max}$ of MHEMT. To compare the performances of optimized MHEMT with the employed MHEMT, DC and RF characteristics of the fabricated MHEMT were measured. In the case of optimized CPW MHEMT, the measured saturated drain current density and transconductance $(g_m)$ were 693 mA/mm and 647 mS/mm, respectively. RF measurements were performed in a frequency range of $0.1{\sim}110$ GHz. A high $S_{21}$ gain of 5.5 dB is shown at a millimeter-wave frequency of 110 GHz. Two kinds of RF gains, $h_{21}$ and maximum available gain (MAG), versus the frequency, and a cut-off frequency ($f_t$) of ${\sim}154$ GHz and a maximum frequency of oscillation ($f_{max}$) of ${\sim}358$ GHz are obtained, respectively, from the extrapolation of the RF gains for a device biased at a peak transconductance. An optimized CPW MHEMT structure is one of the first reports among fabricated 0.1 m gate length MHEMTs.

• Korean Journal of Food Science and Technology
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• v.20 no.1
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• pp.45-51
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• 1988

To improve the individual packaging method and extend the shelf life of hair tail(Trichiurus japonicus), salted an unsalted hair tail chunk (cut in 8-10cm) were packaged in laminated plastic film bag(Nylon/PE: $20{\mu}m,\;12{\times}15cm$) filled with with free-$O_2$ absorber, in vacuum, and stored at 0 and/or $5^{\circ}C$. The other samples were packaged in plastic foam trays, overwraped with oxygen permeable film(control), and stored at same temperature. Volatile basic nitrogen (VBN), trimethylamine (TMA) and viable cell counts (VCC) were progressed with increase of storage time, but thiobarbituric acid (TBA) values decreased gradually after reaching at a maximum peak in 5-15 days. Judging from 4 chemical components, VBN was the most available component in quality judgement of hair tail chunk and its upper limiting content was 29 mg%. Regression equation for shelf life prediction of hair tail chunk with sensory evalution and VBN component was determined.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2000.11a
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• pp.73.2-77
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• 2000

A possibility of the implementation of a quartz crystal sensor to the detennination of chemical oxygen demand is examined by checking the electrochemical behavior of the sensor in a glucose solution. Since the surface of a quartz crystal has to be oxidized, a relatively active metal is coated on the surface of a usual 9 MHz AT-cut crystal. The electrochemical behavior is investigated by measuring the changes of current, resonant frequency and resonant resistance while a constant potential is applied. The crystal is installed in a specially designed container, and a QUartz crystal analyzer is utilized to measure the frequency and resistance simultaneously. The variations of the measurements are examined at different concentrations of glucose solution and the effect of the concentration is analyzed to find a proper relation between the concentration and the measurements. It is fOlmd that a linear relation between the concentration of less than 900 Dpm and the peak current when a constant potential of -180 m V vs. Ag/ AgCI reference is applied.

• Tunnel and Underground Space
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• v.9 no.4
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• pp.350-363
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• 1999

The precision cyclic shear test system was established to investigate the mechanical characteristics of rough rock joints under cyclic loading conditions. Laboratory cyclic shear tests were conducted for saw-cut joints and artificial rough rock joints using Hwangdeung granite and Yeosan marble. Surface roughness and aperture characteristics of specimens were examined by measuring surface topography using the laser profilometer. Peak shear strength, phase difference during loading and unloading, and anisotropic shear behavior were investigated throughout the cyclic shear test results. These features and their subsequent variations in each loading cycle are significantly dependent upon the second order asperities and the strength of intact rock. It was observed that degradation of asperities for rough rock joints under cyclic shear loading followed the exponential degradation laws of asperity angle and that the mechanism for asperity degradation would be different depending upon the normal stress level, roughness of joint surface and the loading stage.