• The Transactions of the Korean Institute of Electrical Engineers P
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• v.53 no.3
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• pp.129-133
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• 2004

As In DS/CDMA(direct sequence code division multiple access) system, the system capacity is limited by multiple access interference(MAI), and self-interference(SI) resulting from the multi-path propagation of the desired user signal. This paper, which the approximated analytic chip waveforms are nearly the same as the computer generated chip waveforms are shown. And then, the BER(Bit Error Rate) performances in CDMA system using the approximated analytic chip waveforms are shown.

• Journal of the Korean Institute of Telematics and Electronics
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• v.24 no.1
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• pp.1-9
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• 1987

In this paper, the acquisition performance of a receiver that utilizes a non-coherent digital correlator is analyzed. In order to analyze the acquisition performance, the probability density function of a receiver output random variable has been derived approximately. Using this function, the acquisition performance of the coarse acquisition code receiver in a global positioning system is analyzed.

• Journal of Power Electronics
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• v.9 no.5
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• pp.691-699
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• 2009

This paper presents the analysis of series active power filter for reactive power compensation, load balancing, harmonic elimination, and neutral current eradication in three-phase four-wire power systems. Generally, the three-phase four-wire system is widely employed in distributing electric energy to several office building and manufacturing plants. In such systems, the third harmonic and its 3rd harmonics are termed as triple and zero sequence components that do not cancel each other in the system neutral. Consequently, the triple harmonics add together creating a primary source of excessive neutral current. Regarding this concern, this paper presents a new control algorithm for a series hybrid active system, whereas the control approach it adopts directly influence its compensation characteristics. Hence, the advantage of this control algorithm is the direct extraction of compensation voltage reference without phase transformations and multiplying harmonic current value by gain and the required rating of the series active filter is much smaller than that of a conventional shunt active power filter. In order to show the effectiveness of the proposed control algorithm, experiments have been carried out.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.4 s.334
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• pp.1-6
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• 2005

For the low power and low cost transceivers, direct sequence spread spec01m frequency-shift keying (DSSS-FSK) is proposed. A transmitter of the DSSS-FSK signal can be implemented by a simple direct modulation using the phase locked loop. Since the DSSS-FSK signal has negligible power around the carrier frequency, low cost direct conversion receiver can be used. Optimum coherent and semi-coherent correlation detection methods for the DSSS-FSK signal are proposed and analyzed. Segmented semi-coherent correlation detection method is proposed to improve the bit error rate performance in the large carrier frequency offset.

• Biotechnology and Bioprocess Engineering:BBE
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• v.10 no.6
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• pp.505-509
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• 2005

For the purpose of developing a direct label-free electrochemical detection system, we have systematically investigated the electrochemical signatures of each step in the preparation procedure, from a bare gold electrode to the hybridization of label-free complementary DNA, for the streptavidin-modified electrode. For the purpose of this investigation, we obtained the following pertinent data; cyclic voltammogram measurements, electrochemical impedance spectra and square wave voltammogram measurements, in $Fe(CN)_6^{3-}/Fe(CN)_6^{4-}$ solution (which was utilized as the electron transfer redox mediator). The oligonucleotide molecules on the streptavidin-modified electrodes exhibited intrinsic redox activity in the ferrocyanide-mediated electrochemical measurements. Furthermore, the investigation of electrochemical electron transfer, according to the sequence of oligonucleotide molecules, was also undertaken. This work demonstrates that direct label-free oligonucleotide electrical recognition, based on biofunctional streptavidin-modified gold electrodes, could lead to the development of a new biosensor protocol for the expansion of rapid, cost-effective detection systems.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.157.2-157.2
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• 2012

Direct-conversion receivers often suffer from a DC-offset that is a by-product of the direct conversion process to baseband. In general, a basic approach to reduce the DC-offset is to do simple average of the baseband signal and remove the DC by subtracting the average. However, this gives rise to a residual DC offset which degrades the performance when the receiver adopts the coding schemes with high coding rates such as 8-PSK. Therefore, more advanced methods should be additionally required for better performance. While the training sequences are basically designed to have good auto-correlation properties to facilitate the channel estimation, they may be not good for the simultaneous estimation of the channel response and the DC-offset. Also the DC offset compensation under a bad condition does not give good results due to the estimation error. Correspondingly, the proposed scheme employs the two important points. First, the training sequence codes are divided into two groups by MSE(Mean Squared Errors) for estimating the channel taps and then SNR calculated from each group is compared to predefined threshold to do fine DC-offset estimation. Next, ON/OFF module is applied for preventing performance degradation by large estimation error under severe channel conditions. The simulation results of the proposed scheme shows good performances compared to the existing algorithm. As a result, this scheme is surely applicable to the receiver design in many communications systems.

• Journal of Power Electronics
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• v.12 no.6
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• pp.895-903
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• 2012

This paper presents a fast switching direct torque control (FS-DTC) using only a single DC-link current sensor. In FS-DTC, six new active voltage complex space vectors (CSVs) are synthesized by the conventional active voltage space vectors (SVs). The corresponding sectors are rotated in the anticlockwise direction by 30 degrees. A selection table is defined to select the CSVs. Based on the "Different Phase Mode", the output sequence of the selected CSV is optimized. Accordingly, a reconstruction method is proposed to acquire the phase currents. The core of the FS-DTC is that all of the three phase currents can be reliably reconstructed during every two sampling periods, which is the result of the fast switching between different phases. The errors between the reconstructed and actual currents are strictly limited in one sampling period. The FS-DTC has the advantages of the standard DTC scheme such as simple structure, quick torque response and robustness. As can be seen in the analysis, the FS-DTC can be thought of as an equivalent standard DTC scheme with 86.6% of the maximum speed, 173.2% of the torque ripple, and 115% of the response time of the torque. Based on a dSPACE DS1103 controller, the FS-DTC is implemented in an induction machine drive system. The results verify the effectiveness of the FS-DTC.

• The Korean Journal of Mycology
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• v.28 no.1
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• pp.22-25
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• 2000

This study was carried out to compare DNA sequence of mating type locus concerning with direct formation of fruiting body in Schizophyllum commune which is growing in North America with that of same species growing in South America. The nucleotide sequence appeared to have about 96% homology to 1-71 $A{\alpha}3$ allele from South America strain, showing a conservative feature. The polypeptide sequence showed about 82% homology when compared partially with mating activity region of 1-71 $A{\alpha}3$ allele. In addition, this polypeptide sequence indicated 74% and 82% identity in homeodomain and acidic-rich regions known as a transcription factor respectively.

• Animal cells and systems
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• v.3 no.1
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• pp.89-96
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• 1999

Nucleotide sequences of a 501 base-pair (bp) fragment in the mitochondrial cytochrome b (cyt b) gene were analyzed for 12 populations of Rana rugosa from Korea and Japan using a polymerase chain reaction (PCR) and direct silver sequencing. Two genetically distinct groups (type-A and type-B) were found in Korea. Type-A was found throughout most of South Korea and type-B was restricted to the mid-southeastern regions (Samchok, Yongdok, Chongsong and Pohang). But in the Tonghae population, both types were found. The level of mitochondrial DNA (mtDNA) sequence differences ranged from 0% to .0.8% among six populations of type-A, and 0 to 1.0% among 4 populations of type-B. However, sequence differences between type-A and type-B ranged from 5.4% to 6.6%, Using Kimura's two-parameter distance, the level of genetic sequence divergence between type-A and type-B was 6.7%. The Japanese R. rugosa was clustered very far from the Korean R. rugosa with 14.7%. In the neighbor-joining and UPGMA tree, all Korean samples were grouped, but subdivided into two types in 99% of the bootstrap iteration.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.12
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• pp.1013-1020
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• 2013

In this paper the super-resolution time delay estimation algorithms based on eigen-analysis are developed for spread spectrum signals along with their comparative performance analysis. First, we shall develop super-resolution time delay estimation algorithms using the representative eigen-analysis based AOA (angle-of-arrival) estimation algorithms such as MUSIC, Minimum-Norm, and ESPRIT, and apply them to the ISO/IEC 24730-2.1 real-time locating system (RTLS) employing a direct sequence spread spectrum (DS-SS) technique to compare their performances in RTLS environments. Simulation results illustrate that all the three algorithms can resolve multipath signals whose delay differences are even smaller than the Rayleigh resolution limit. Simulation results also show that MUSIC and Minimum-Norm provide a similar performance while ESPRIT is inferior to both algorithms in RTLS environments.