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Decoding Saccadic Directions Using Epidural ECoG in Non-Human Primates
이제연,최호석,이세호,조백환,안경하,김인영,이경민,장동표 대한의학회 2017 Journal of Korean medical science Vol.32 No.8
A brain-computer interface (BCI) can be used to restore some communication as an alternative interface for patients suffering from locked-in syndrome. However, most BCI systems are based on SSVEP, P300, or motor imagery, and a diversity of BCI protocols would be needed for various types of patients. In this paper, we trained the choice saccade (CS) task in 2 non-human primate monkeys and recorded the brain signal using an epidural electrocorticogram (eECoG) to predict eye movement direction. We successfully predicted the direction of the upcoming eye movement using a support vector machine (SVM) with the brain signals after the directional cue onset and before the saccade execution. The mean accuracies were 80% for 2 directions and 43% for 4 directions. We also quantified the spatial-spectro-temporal contribution ratio using SVM recursive feature elimination (RFE). The channels over the frontal eye field (FEF), supplementary eye field (SEF), and superior parietal lobule (SPL) area were dominantly used for classification. The α-band in the spectral domain and the time bins just after the directional cue onset and just before the saccadic execution were mainly useful for prediction. A saccade based BCI paradigm can be projected in the 2D space, and will hopefully provide an intuitive and convenient communication platform for users.
장동수,연규석,김기성,하선효,김용성,Chang, Dong-Su,Yeon, Kyu-Seok,Kim, Ki-Sung,Ha, Seon-Hyo,Kim, Yong-Seong 한국농공학회 2011 한국농공학회논문집 Vol.53 No.3
This study aimed to investigate the engineering and environmental characteristics of phosphogypsum-cement-soil mixtures composed of phosphogypsum, soil, and a small amount of cement was analysed on the basis of the unconfined compression test, the tensile strength test, the freezing and thawing test, the wetting and drying test, SEM and EDS analysis, XRD analysis and Leaching test. The specimens were manufactured with soil, cement and phosphogypsum. The cement contents was 10 %, and the phosphogypsum contents was 10, 20, 30, and 40 % by the weight of total dry soil. Each specimen was manufactured after curing at constant temperature and humidity room for 3, 7 and 28 days, after which the engineering characteristics of phosphogypsum-cement-soil mixtures were investigated using the unconfined compression test, the tensile strength test, the freezing and thawing test, the wetting and drying test. The basic data were presented for the application of phosphogypsum-cement-soil mixtures as construction materials. To investigate the environmental characteristics, leaching test was performed and the leaching test results were far below than of regulatory requirement of Waste Management Act in Korea. Therefore the results show that phosphogypsum is environmentally safe and can be used as construction materials in environmental aspect.
Catalytic decomposition of SiO2 by Fe and the effect of Cu on the behavior of released Si species
장동수,주미연,윤한섭,김진교 한국물리학회 2016 Current Applied Physics Vol.16 No.1
Si supply mechanism in the spontaneous formation of SiO2 pattern on a Cu foil, which was previously reported to enable the selective growth of graphene in no direct contact with organic materials, was investigated. Upon annealing at 1000 C and atmospheric pressure, SiO2 in the Fe-coated SiO2/Al2O3 template covered by a Cu foil was found to be severely decomposed by Fe droplets. No signature of reaction between SiO2 and Fe droplets suggested that Si species, which contributed to the spontaneous formation of SiO2 pattern on a Cu foil, originated from SiO2 catalytically decomposed by Fe droplets. In the absence of a Cu foil covering an Fe-coated SiO2/Al2O3 template, the catalytic activity of Fe droplets was significantly suppressed because of the encapsulation of Fe droplets by a 2-nm-thin-Fe3O4 layer. Furthermore, a part of the Fe film on SiO2/Al2O3 without a Cu foil turned into nanodroplets and assisted the formation of SiO2 nanowires. These results reveal that a Cu foil made an intriguing role in preventing Fe from being encapsulated by Fe3O4, so the catalytic role of Fe droplets was not terminated until SiO2 was fully decomposed. Our experimental results provided insights into better understanding of these intriguing behaviors of Fe and Cu on SiO2 at high temperature and at atmospheric pressure.