• 감성과학
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• 제16권4호
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• pp.527-534
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• 2013

본 연구에서는 코히어런스 분석을 통하여 시각집중 기간 동안 시간 변화에 대한 뇌기능과 관련된 공간-주파수간 연관관계를 해석하였다. 집중관련 시각자극 실험 데이터를 통해 ${\theta}$와 ${\alpha}$ 대역에서 서로 다른 두피 위치간 위상연관변화를 확인하였다. 좌우 전두엽, 전두엽과 두정엽 간 뇌유발전위는 P100, N200지점에서 위상동조를 보였으며, 전두엽과 후두엽 간 뇌유발전위는 시각 처리 정보가 반영되는 P300지점에서 위상동조를 보였다. 고정된 길이의 창을 이용하는 단구간 푸리에 변환에 비하여 연속 웨이블릿 변환은 모 웨이블릿의 파라미터 조정을 통한 다중해상도 분석이 가능하였다. 따라서 연속 웨이블릿 변환을 이용한 코히어런스 결과가 시간변화에 대한 뇌유발전위의 공간-주파수간 연관관계의 변화를 확인하는데 유효함을 확인하였다. 비 집중 자극수행에 대해서는 위상동조 현상이 나타나지 않았다.

• 천문학회지
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• 제41권5호
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• pp.121-137
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• 2008

We present optical and near-infrared imaging and long-slit spectroscopy for the blue compact dwarf galaxy (BCD) Mrk 49 in the Virgo Cluster. The surface brightness distribution analysis shows that Mrk 49 consists of an off-centered blue bright compact core of r = 10" and a red faint outer exponential envelope. The $H_{\alpha}$ image and color difference suggest that these two components have different stellar populations: a high surface brightness population of massive young stars and an underlying low surface brightness population of older stars. The redder near-infrared colors of the inner most region suggest that the near-infrared flux of Mrk 49 originates from evolved massive stars associated with the current star-forming activity. The total apparent magnitude is $B_T\;=\;14.32$ mag and the mean effective surface brightness is ${\mu}_{eff}(B)\;=\;21.56$ mag $arcsec^{-2}$. Long-slit spectroscopy shows that Mrk 49 rotates apparently as a solid body within r = 10" in a plane at position angle 55 degrees with an amplitude of about $20\;km\;sec^{-1}$. The measured radial velocity of Mrk 49 was derived as $1,535\;km\;sec^{-1}$; and the total mass of stars and gases is in the range of 3 to $6\;{\times}\;10^9\;M_{\odot}$. The mass-to-light ratios for the central region of Mrk 49 in I and B band are estimated 1.0 and 0.5, respectively. The upper limit of the dark matter to visible matter ratio seems to be < 5. The oxygen abundance is $12\;+\;\log(O/H)\;=\;8.21\;{\pm}\; 0.1$ which is about one quarter of the solar value while the relative helium abundance appears to be similar to that of the sun.

• 한국전자파학회논문지
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• 제23권1호
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• pp.47-55
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• 2012

본 논문에서는 고속의 단거리 탄도탄과 항공기 등의 표적을 탐지 추적할 수 있는 밀리미터파 탐색기의 종합성능 시험을 위해 개발한 HILS(Hardware-In-the-Loop Simulation)와 시험 장비를 설명한다. 이 시스템은 다양한 종류의 표적과 고속, 고기동 이동 표적의 궤적을 모사하기 위해 141개의 혼 안테나 배열, 배열 안테나 스위칭과 이득 및 위상 제어 알고리즘을 이용한다. 또한, 표적에 대한 속도, 거리뿐만 아니라, 클러터와 재밍 환경을 모사한다. 시스템 전체 구성과 표적 운동 모의기, 모의 신호 발생기, 고속 데이터 획득 장치, 통제 제어기 등과 같은 주요 구성품들의 구현과 측정 결과를 설명하였다. 이 통합 시스템은 동적 실시간 탐지/추적에 대한 밀리미터파 탐색기의 성능을 모의 비행 시나리오 기반으로 시험할 수 있다.

• 감성과학
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• 제3권2호
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• pp.17-28
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• 2000

Psychoacoustic characteristics of automobile horns play significant role in resulting subjective evaluation and psychphysiological reactions. However, comparison and differentiation of physiological responses to commercially available horns is a complicated task due to the small contrast in technical features of horns and the influence of such processes as habituation on physiological outcome with the increased number of auditory stimulation trials. In a study on 10 college students, there was performed comparative analysis of reactivity of physiological responses mediated by central and autonomic nervous systems in order to identify the role of habituation on decrement of psychophysiological responsivity and assess the ability to differentiate subjectively most and least preferred, as well as most and least appropriate horns according to physiological manifestations. The EEG and autonomic responses to 7 automobile horns were analyzed during 3 blocks of trials, with varying order of stimuli and changed acoustic parameters of horns in each block. Thus, responses were analyzed for totally 21 trials of auditory stimulation. It was shown that electrodermal and cardiovascular responses have different reactivity patterns to repeated stimulation: skin conductance measures habituated, cardiac reactivity showed no signs of habituation, and the vascular response demonstrated sensitization. The temporal EEG exhibited marked habituation of fast beta band power, while alpha-blocking effect did not habituate during the course of experiment. Differentiation of physiological responses of most and least preferred and appropriate horns was possible in our study, however, some cardiovascular reactivity measures differentiated during the entire course of the experiment, while EEG and electrodermal parameters showed significant differences only during first block of trials, and were later affected by the habituation.

• 자원환경지질
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• 제26권4호
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• pp.455-464
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• 1993

Some nodules occur in the Milyang pyrophyllite deposit which are hydrothermal alteration products by Late Cretaceous andesitic tuff. These nodules are divided into two types on the basis of mineral assemblages; diaspore and pyrophyllite nodules. The diaspore nodules consist mainly of diaspore, kaolinite, pyrophyllite and pyrite with a small amounts of wavellite and tourmaline. They are light purplish grey in color, ellipsoid in shape and range 1 cm to 15 cm in size. A small or large diffuse band exists in some nodules. The platy coarse-grained diaspore is intergrown with the fine-aggregated kaolinite in the central part of the nodule. It appears that the grain size become fine from center to margin. The pyrophyllite nodules, which have the same shape with diaspore nodules, consist dominantly of pyrophyllite accompanied by small amounts of quartz, kaolinite, svanbergite, wavellite, tourmaline and apatite. Chemical compositions of alteration zones and nodules show that the wall rock alteration involved mainly the removal of large quantities of silica and alkalies and small quantities of Ca, Mg and Fe. The sharp increase in the Al content of the nodules is the result of residual concentration of alumina by the leaching of the mobile components. The pyrophyllite nodules were formed in the fluid saturated with quartz as ${\mu}_{HK_{-1}}$ and ${\mu}_{H_{2}O}$ increase. Under this condition, the pyrophyllite-kaolinite-quartz assemblage was stable. Diaspores formed from pyrophyllites in the fluid undersaturated with quartz as ${\mu}_{H_{2}O}$ increases (decreasing temperature). Under this condition, diaspore-pyrophyllite-kaolinite assemblage become stable. The formation temperature of the nodules on the basis of mineral assemblage is estimated as $275{\sim}340^{\circ}C$.

• 천문학회보
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• 제36권2호
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• pp.121-121
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• 2011

Thanks to KMTNet's wide field of view, it is time to implement imaging survey of extensive area of clusters of galaxies in the southern sky with modern instrument. As part of potential long-term survey of nearby (D < 50 Mpc) well-known clusters of galaxies, we propose a wide-field and deep survey of Fornax cluster as a first step of the project. By imaging the 400 square deg region (100 fields) enclosed within the five times virial radius of the Fornax cluster, in three SDSSfilters(g', r', i'), we can provide an unprecedented view of structure of Fornax cluster using sample from giant to dwarf galaxies. We will secure galaxies with brightness comparable to the limiting magnitude (r'=23.1 AB mag) of SDSS. Furthermore, we also request extremely deep (limiting surface brightness of ~ 28 mag $arcsec^{-2}$forr'band) survey for the central region (16 square degree, i.e., four fields) of Fornax cluster. This will allow us to detect the diffuse intracluster light (ICL) that permeates clusters as a valuable tool for studying the hierarchical nature of cluster assembly. In order to complete whole survey, about 285 hr observing time (without overhead) is required. By combining data available at other wavelengths, it will offer unique constraints on the formation of large-scale structure and also provide important clues for theories of galaxy formation and evolution. Our proposed survey will be implemented in the close collaboration with researchers in various countries (Germany, Australia, UK, USA) and ongoing project (e.g., SkyMapper).

• 천문학회보
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• 제36권2호
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• pp.147.2-147.2
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• 2011

We have initiated a long-term identification campaign of supernova remnant candidates in X-ray regime. In the short-listed unidentified sources from the ROSAT All Sky Survey, we have chosen the brightest candidate, G308.3-1.4, as our pilot target for a dedicated investigation with Chandra X-ray Observatory. Our observation has revealed an incomplete shell-like X-ray structure which well-correlated with the radio feature. Together with the spectral properties of a shocked heated plasma, we confirm that G308.3-1.4 is indeed a supernova remnant. A bright X-ray point source which locates close to the remnant center is also uncovered in this observation. Its spectral behavior conform with those observed in a rare class of neutron stars. The properties of its optical/infrared counterpart suggests the evidence for a late-type companion star. Interestingly, possible excesses in B-band and H-alpha have been found which indicate this can be an accretion-powered system. With the further support from the putative periodicity of ~1.4 hrs, this source can possibly provide the direct evidence of a binary system survived in a supernova explosion for the first time.

• Bulletin of the Korean Chemical Society
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• 제29권2호
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• pp.438-444
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• 2008

A self-assembled monolayer of 2,2'-bipyridine (22BPY) molecules on Au(111) underwent a structural phase transition when the polarity of a bias voltage was switched in scanning tunneling microscopy (STM) experiments. The nature of two bright spots representing each 22BPY molecule on Au(111) in the high-resolution STM images was identified by calculating the partial density plots for a monolayer of 22BPY molecules adsorbed on Au(111) using tight-binding electronic structure calculations. The stacking pattern of the chains of 22BPY molecules on Au(111) was explained by examining the intermolecular interactions between the 22BPY molecules based on first principles electronic structure calculations for a 22BPY dimer, (22BPY)2. The structural instability of the 22BPY molecule arrangement caused by a change in the bias voltage switch was investigated by estimating the adsorbate-surface interaction energy using a point-charge approximation for Au(111).

• International journal of advanced smart convergence
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• 제7권3호
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• pp.23-36
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• 2018

In wireless communication, efficient spectrum usage is an issue that has been an attractive research area for many technologies. Recently new technologies innovations allow compact radios to transmit with power efficient communication over very long distances. For example, Low-Power Wide Area Networks (LPWANs) are an attractive emerging platform to connect the Internet-of-Things (IoT). Especially, LoRa is one of LPWAN technologies and considered as an infrastructure solution for IoT. End-devices use LoRa protocol across a single wireless hop to communicate to gateway(s) connected to the internet which acts as a bridge and relays message between these LoRa end-devices to a central network server. The use of the (ISM) spectrum sharing for such long-range networking motivates us to implement spectrum sensing testbed for cognitive radio network based on LoRa and GNU radio. In cognitive radio (CR), secondary users (SUs) are able to sense and use this information to opportunistically access the licensed spectrum band in absence of the primary users (PUs). In general, PUs have not been very receptive of the idea of opportunistic spectrum sharing. That is, CR will harmfully interfere with operations of PUs. Subsequently, there is a need for experimenting with different techniques in a real system. In this paper, we implemented spectrum sensing for cognitive radio networks based on LoRa and GNU Radio, and further analyzed corresponding performances of the implemented systems. The implementation is done using Microchip LoRa evolution kits, USRPs, and GNU radio.

• 한국전자파학회논문지
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• 제17권4호
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• pp.368-379
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• 2006

본 논문에서는 기존의 실험 위주의 설계 기법보다는 해석적 방법에 의하여 3단으로 구성된 평판형 리미터 설계 및 제작 기법을 제시하였다. 해석 결과 PIN 다이오드로 구성된 리미터에 고출력의 RF 입력이 인가될 경우 두 가지 형태의 누설 전력이 발생하며 이의 PIN 다이오드 파라미터와 연관성을 설명하였다. 설계된 리미터 회로는 1단과 2단은 PIN diode로 구성되며 3단은 Schottky 다이오드를 사용 구성하였다. 이를 통하여 제작된 리미터회로는 약신호시 삽입 손실 0.8 dB, 20 W RF 입력시 첨두 누설 전력(spike leakage) 12 dBm, 정상 누설 전력 12 dBm의 사양을 보여주고 있다.