• Journal of Communications and Networks
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• v.12 no.4
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• pp.317-329
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• 2010

In recent years, many sparse estimation methods, also known as compressed sensing, have been developed. However, most of these methods presume that the measurement matrix is completely known. We develop a new blind maximum likelihood method-the expectation-sparse-maximization (ESpaM) algorithm-for models where the measurement matrix is the product of one unknown and one known matrix. This method is a variant of the expectation-maximization algorithm to deal with the resulting problem that the maximization step is no longer unique. The ESpaM algorithm is justified theoretically. We present as well numerical results for two concrete examples of blind channel identification in digital communications, a doubly-selective channel model and linear time invariant sparse channel model.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.12
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• pp.1007-1010
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• 2017

In this paper, a frequency selective surface(FSS) with bandstop operation for radio-frequency spectrum management is presented. The proposed FSS is composed of patterns of fractal-based miniaturized unit cells for stable performance for angles of incidence and polarizations. For practical applications requiring high productivity and environmental compatibility, we fabricated a film-type FSS by screen-printing using Ag ink, rather than a conventional manufacturing method using a printed circuit board. To validate this study, we measured the transmission characteristics of the proposed FSS using the free-space measurement method, and observed the received strength of signal penetrating the FSS film applied to a wall.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.267-267
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• 2013

Band engineering of a nanowire is related to the question what is the minimum size of a nanowire-based device. At the subnanometer scale, there has been a long standing problem whether it is possible to both control an energy band of an isolated nanowire by a dopant and measure it using angle-resolved photoemission spectroscopy (ARPES). This is because an extra atom in the subnanometer wire plays as a defect rather than a dopant and it is challenging to assemble isolated subnanometer wires into an array for an ARPES measurement. We demonstrate that only one of multiple metallic subnanometer wires canbe controlled electronically by a dopant maintaining the whole metallic bands of other wires, which was observed directly by ARPES. Here,the multiple metallic subnanometer wires were produced on a stepped Si(111) surface by a self-assembly method. The selective band engineering proves that the selectively-controlled metallic wire is nearly isolated electronically from other metallic wires and an electronic structure controlcan be realized down to subnanometer scale.

• Journal of Electrical Engineering and Technology
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• v.9 no.4
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• pp.1360-1364
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• 2014

In this paper, RCS characteristics on defect pattern of crossed dipole slot FSS having a finite size have been analyzed. To analyze RCS, we applied the electric field integral equation analysis which applies BiCGSTab algorithm with iterative method and uses RWG basis function. To verify the validity of this paper, RCS of PEC sphere has been compared to the theoretical results and FSSs with defect patterns are fabricated and measured. As defect patterns in FSS, missing one column, missing some elements, and discontinuity in surfaces are simulated and compared with the measurement results. Resonant frequency shifts in pass band and changes in bandwidth are observed. From the results, precisely predicting and designing frequency characteristics over defect patterns are essential when applying FSS structures such as FSS radomes.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.4
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• pp.565-571
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• 2021

In this paper, a compensation scheme of frequency selective IQ mismatch for high-performance radar systems based on commercial RFIC's is proposed. Besides, an optimization model and its solution based on the dimension reduction scheme using singular value decomposition are also proposed to design the optimal IQ mismatch compensation digital filter with complex coefficients. The performance of the proposed method had been analyzed through experiments using the IQ mismatch measurement and compensation system implemented on an FPGA board with a target RFIC and compared with the previous method. The experiment result showed a performance improvement of the proposed method over the existing one without noticeable increments in complexities. These performance analysis results showed that the limitation of using commercial RFIC's in high-performance radar systems due to the undesirable maximum SNR cap caused by their IQ mismatches could be overcome by employing the proposed method.

• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.12.1-12.1
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• 2010

We have developed a facile method to position different dyes (N719 and N749) sequentially in a mesoporous TiO2 layer through selective desorption and adsorption processes. Only upper part of the first adsorbed N719 dye was selectively removed by the desorption solution formulated with polypropylene glycol and tetrabutylammonium hydroxide without any damages of the dye. The desorption depth was controlled by the number of desorption process. Multi-dyed dye-sensitized solar cells (MDSSC) were fabricated by utilizing the method and their photovoltaic properties were investigated. From the incident photon-to-current conversion efficiency (IPCE) measurement, it was found that the MDSSC exhibited the extended spectral response for the solar spectrum while without decrease of maximum IPCE value compare to the DSSCs using one kind of dye (N719 or N749). The highest photocurrent density of 19.3 mA/cm2 was obtained from the MDSSC utilizing $15\;{\mu}m$ N719 / $14\;{\mu}m$ N749 bi-layered mesoporous TiO2 film. The photocurrent density was 25% and 8% higher than that of the DSSC using only N719 and N749 dye as a sensitizer, respectively. The power conversion efficiency of 9.8% was achieved from the MDSSC under the AM 1.5G one sun illumination.

• Bulletin of the Korean Chemical Society
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• v.32 no.3
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• pp.977-980
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• 2011

A new analytical method for measurement of 3,4-dihydroxyphenylalanine (DOPA) in human urine was developed. DOPA from an aqueous solution was converted into an ethoxycarbonyl (EOC) derivative. A tertbutyldimethylsilyl (TBDMS) reaction under anhydrous conditions was then attempted for analysis by gas chromatography-mass spectrometry in selected ion monitoring mode. A new mass spectral data on DOPA as a tri-EOC/mono-TBDMS derivative was built. This method showed good linearity (r ${\geq}$ 0.999), precision (% relative standard deviation = 3.1-9.2), and accuracy (% relative error = -7.2-8.8), with a detection limit of 0.05 ng/mL. This selective and accurate method of DOPA analysis will be useful for biochemical monitoring of various neurological disorders including Parkinson's disease in biological fluids.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.54 no.6
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• pp.974-981
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• 2021

The aim of this study was to evaluate genetic parameters of growth traits for improving selective breeding in olive flounder Paralichthys olivaceus produced in April 2019. The total length and body weight at 11-, 18-, and 22-months-old were measured for 7,479, 2,831 and 1,904 individuals, respectively. Since 2004, we have been conducting a selective breeding program to improve growth traits in the olive flounder. Data were analyzed using the restricted maximum likelihood method using the multiple traits animal model. The effect of sex and production period showed significant differences in all traits (P<0.05). The heritability of all traits was 0.428-0.520, which is relatively high by measurement month. Therefore, it is considered that individual selection will be more advantageous than family selection. However, to maintain an appropriate degree of inbreeding and genetic diversity for future generations, it is necessary to consider family selection adequately. Results of the correlation analysis between the same traits according to the measurement period indicated that considering production costs such as feed cost, selection at 18-months-old will be advantageous. Olive flounder is a major aquaculture species in Korea, and continuous selective breeding research is essential to improve productivity.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.2
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• pp.127-136
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• 2008

This paper proposes the efficient system for automatic design of FSS(Frequency Selective Surface) with periodic pattern and frequency characteristics specified by operator. The proposed system derives optimal design parameters through tool for analysis of FSS with arbitrary pattern, DB(Data Base) implemented from limited simulation and measurement data of FSS, and GA(Genetic Algorithm) for optimizing design parameters. FSS analysis tool consists of two analysis tools. One is the simulator for analysis of monolayer FSS that using moment method, another is the tool with approximated analysis method of FSS with dielectric layer. Given pattern configuration and characteristics specified by operators, the DB system searches the best matching FSS, and provides initial genes to GA from the searched parameters, which drastically reduces running time of GA for finding the FSS design parameters. In this paper, the proposed design system is verified through simulation and measurement about FSS with various patterns.

• Proceedings of the ESK Conference
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• 1997.04a
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• pp.50-55
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• 1997

본 연구에서는 일반적으로 생산 현장에서의 로봇 작업이 "getting"과 "putting"의 동작으로 구서 되는 것에 기초하여 이들 동작을 분류. 표준화하여 2단계의 단위동작 (GET, PUT) 별로 여러 가지의 모듈을 설정하고, 동작거리별로 표준시간을 산출하는 기법을 다룬다. 즉 기존의 로봇 작업측정법이 작업을 기존동작으로 분석하는 것과는 다르게 시간의 변동요인인 모듈의 Type과 동작거리의 Case를 선택함으로써 표준시간을 설정한다.를 선택함으로써 표준시간을 설정한다.