• Proceedings of the Korean Vacuum Society Conference
• /
• 2014.02a
• /
• pp.180.1-180.1
• /
• 2014

이중층 그래핀(graphene)의 한쪽 표면에 전하를 주입하면 반전 대칭(inversion symmetry)이 깨지며 라만-비활성 진동모드가 활성화되면서 라만 G-봉우리 부근에 새로운 봉우리가 나타난다고 알려져 있다. 삼중층 그래핀은 그래핀이 적층되는 방식에 따라 ABA (Bernal), ABC (rhombohedral) 그래핀으로 나뉘며, ABC 그래핀은 ABA와는 달리 반전 대칭성을 가지고 있다. 본 연구에서는 화학적인 방법을 이용하여 ABC 그래핀의 반전 대칭을 제어하고 그에 따른 라만 스펙트럼의 변화를 탐구하였다. ABA 그래핀과는 달리 이중층 그래핀과 ABC 그래핀에서는 저진공 열처리 또는 요오드 흡착반응을 한 후에 G-봉우리 부근에서 새로운 봉우리가 나타나는 것을 관찰하였고, 전하밀도 정도가 증가 할수록 G-봉우리와 새로운 봉우리의 위치 차이는 증가하는 것을 관찰하였다. 물과 메탄올에 의한 세척 반응으로부터 열처리는 복층 그래핀과 기판 계면에 그리고 요오드 흡착은 그래핀의 상단표면에 잉여 전하를 유발하여 반전 대칭을 깨트린다는 사실을 확인하였다. 또한 G-봉우리와 새로운 봉우리의 진동수 차이가 반전 대칭을 유발한 전하밀도의 그래디언트에 대한 척도가 될 가능성을 제시하였다.

• Analytical Science and Technology
• /
• v.16 no.4
• /
• pp.269-276
• /
• 2003

A new type of stripping voltammetry, inverted catalytic stripping voltammetry $IC_tSV$, is introduced. The rhodium-formaldehyde complex in hydrochloric acid gives an inverted catalytic hydrogen peak (reduction current peak during positive-going scan). The characteristics of the inverted peak were studied. By using the peak as analytical peak the detection limit of $1.2{\times}10^{-10}M$ Rh (50s preconcentration) can be reached at the optimal conditions: 0.015% (W/V) HCHO-0.42 M HCl; accumulation potential, -1.1 V; scan rate, 100 mV/s.

• Analytical Science and Technology
• /
• v.15 no.4
• /
• pp.388-391
• /
• 2002

Rancidity of a soybean oil is investigated by an electrochmical method. The redox process of the soybean oil is totally irreversible and diffusion-controlled reaction. As scan rates are faster, the anodic peak potential of the soybean oil is shifted to the positive potential and the anodic current is increased. The anodic peak potentials of the soybean oil is not rarely changed up to open-42 days in the both atmosphere and room temperature. After the open times, the anodic peak potential is largely shifted to a negative direction. This indicates the oxidation of the soybean oil becomes easier. The anodic peak current of the soybean oil is decreased gradually up to open-42 days. But after the open times, the anodic peak current increases suddenly. It must be due to the formation of a carbonyl group owing to rancidity of the soybean oil.

• Analytical Science and Technology
• /
• v.10 no.3
• /
• pp.216-224
• /
• 1997

In the study of cyclic voltammogram of rubeanic acid, rubeanic acid has two reduction peaks; first peak is similar with that of $S^{2-}$ and thiourea, which is conceded to by HgS, second peak is very weak and unidentified. The study also describes the differential pulse cathodic stripping voltammetric method for the determination of rubeanic acid. The followings were optimal conditions of rubeanic acid for the study : 0.05M borate buffer solution(pH 10.0) ; an accumulation potential of -0.30V(vs. Ag/AgCl); accumulation time of 120sec. : scan rate of 10mV/sec. The detection limit of trace analysis shows $2.7{\times}10^{-8}M$ of rubeanic and at optimal conditions.

• The Bulletin of The Korean Astronomical Society
• /
• v.36 no.1
• /
• pp.45.2-45.2
• /
• 2011

WMAP이 7년 동안 관측해 얻은 우주배경복사의 온도비등방성 지도로부터 파워스펙트럼을 측정하는 프로그램을 개발하였다. WMAP의 가상관측 자료를 분석하여 파워스펙트럼이 제대로 측정되는지를 시험하였으며, 실제 WMAP 자료에서 측정한 파워스펙트럼이 WMAP팀의 결과와 통계적으로 일치함을 확인하였다. 본 연구에서는 천구를 다양한 영역으로 나누어 파워스펙트럼을 측정해 보았다. 특히, 남, 북반구의 은위 30도 이상 영역에서 측정한 파워스펙트럼을 비교한 결과, 셋째 봉우리가 남(북)반구에서 상대적으로 높(낮)게 나타났으며 봉우리 높이의 남북 차이는 표준 ${\Lambda}CDM$ 우주모형으로 분석하여 보면 $3{\sigma}$ 정도의 통계적인 유의성을 보였다. 이러한 남북 이상(anomaly)의 원인으로서 WMAP의 기기 잡음, 우리은하의 방출선, 은하 외부적인 점광원에 의한 오염 가능성을 조사하고 토의하였다. 파워스펙트럼의 셋째 봉우리는 WMAP 해상도의 한계 지점이며 기기 잡음이 우세한 지역이므로, WMAP의 자료만으로 검출된 남북 이상의 원인을 찾기에는 한계가 있다. 앞으로 Planck 위성의 관측 자료가 공개되면 그 원인이 규명이 될 수 있을 것으로 예상된다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2011.10a
• /
• pp.593-596
• /
• 2011

본 논문에서는 안테나 주변 지형 및 장애물들이 전계강도에 미치는 영향을 알아보기 위하여 두가지 주변 지형을 고려한 전계강도 변화를 살펴보았다. 먼저 안테나 주변 지형의 봉우리 유무에 따른 전계강도 변화는 봉우리가 안테나로부터 200m 떨어진 지점에 높이가 40m, 너비가 30m, $60^{\circ}$의 경사를 갖는 지형이고, 다음으로 봉우리 높이에 따른 전계강도 변화는 경사가 $85^{\circ}$이고, 높이가 h 인 봉우리 지형을 갖는 형태로 구현방법으로는 MWS 시뮬레이터를 이용하여 구현하였다.

• Journal of Sensor Science and Technology
• /
• v.9 no.4
• /
• pp.316-326
• /
• 2000

A new signal processing algorithm for white light interferometry has been proposed and investigated theoretically. The goal of the algorithm is to determine the absolute optical path length of an interferometer with very high precision (<< one optical wavelength). The algorithm features cross-correlation of interferometer fringe scans and hypothesis testing. The hypothesis test looks for a zero order fringe peak candidate about which the cross-correlation is symmetric minimizing the uncertainty of misidentification. The shot noise limited performance of the proposed signal processing algorithm has been analyzed using computer simulations. Simulation results were extrapolated to predict the misidentification rate at Signal to-Shot noise ratio (SNR) higher than 31 dB. Root-mean-square phase error between the computer-generated zero order fringe peak and the estimated zero order fringe peak has been calculated for the changes of three different parameters (SNR, fringe scan sampling rate, coherence length of light source). Results of computer simulations showed the ability of the proposed signal processing algorithm to identify the zero order fringe peak correctly. The proposed signal processing algorithm uses a software approach, which is potentially inexpensive, simple and fast.

• Analytical Science and Technology
• /
• v.18 no.5
• /
• pp.369-375
• /
• 2005

The differential pulse anode stripping voltammograms of some rare earth elements and their complexes with catechol have been investigated in various pH and electrolytes. In a 0.1 M LiCl and pH 5.3 solution, $Euv^{3+}$ and $Pr^{3+}$ showed a single oxidation peak at -0.2 V and the oxidation currents were linearly increased with the concentration of those ions. $Tm^{3+}$, $Tb^{3+}$, $Yb^{3+}$ and $Sm^{3+}$ showed two oxidation peaks at -0.5 V and -0.2 V and the oxidation currents at -0.5 V were increased with the concentration increase of those ions. The linear range of those calibration curves was in 1 ppm-10 ppm. In the case of voltammograms of catechol complexes of rare earth elements, $Tb^{3+}$-catechol and $Eu^{3+}$-catechol complex showed a single oxidation peak at -0.95 V and -0.65V, respectively and $Sm^{3+}$-catechol, $Pr^{3+}$-catechol, $Tm^{3+}$-catechol and $Yb^{3+}$-catechol complexes showed two oxidation peaks. The linear range of the calibration curves of those complex was 0.1 ppm~1.0 ppm.

• Analytical Science and Technology
• /
• v.15 no.3
• /
• pp.214-220
• /
• 2002

The interfacial accumulation of the chromium-cupferron complex and the catalytic wave of its redox process is characterized by cyclic voltammetry. One cathodic peak is observed in the forward scan at -1.45 V. Scanning in the reverse direction produces a inverted peak at -1.39 V, which is indicative of a catalytic process. The optimal conditions of inverted peak were found to be 1 mM borate buffer solution(pH 9.48) containing $1{\times}10^{-4}M$ cupferron, holding potential of -1.8 V and scan rate of 20 mV/s. Using main peak, a preconcentration time of 1 min results in a detection limit of $3.2{\times}10^{-10}M$.

• Korean Journal of Optics and Photonics
• /
• v.11 no.6
• /
• pp.395-399
• /
• 2000

In white light interferometry, fast and accurate localization of the fringe visibility is the most essential part in application of the principle. So much attention has been concentrated on speeding up the process, we in this study decided to investigate the results of the various peak-finding algorithms. Of the many approaches, two most simplistic algorithms were selected for their straightforwardness and robustness. Both were equally accurate in measuring the step height of a sample, but the method based on the weighted average technique proved to be truer to the surface topography. A model explaining the shortcomings of the correlation technique is presented. ented.