• Proceedings of the Korean Vacuum Society Conference
• /
• 2000.02a
• /
• pp.167-167
• /
• 2000

전지 재료의 충방전 과정 연구에는 X-선 분말회절(x-ray powder diffraction techniques)과 중성자회절을 많이 사용하였다. 하지만 이러한 분석기술은 long-range order의 구조에 관한 정보를 제공하는데 유용하지만 atomic scale의 구조에 관한 정보를 얻기에는 한계가 있다. Li 전지에서의 전기화학적 반응에서는 cathode 물질에 포함된 전이금속의 산화, 환원 반응에 의한 Li 이온의 intercalation (charge process)과 deintercalation (discharge process) 현상이 일어난다. 이러한 충방전 과정은 알려지지 않은 다양한 형태의 위상 변화를 동반하게 되는데 x-선 이나 중성자를 이용한 powder diffraction techniques 로는 단지 정성적인 결정학적 정보를 얻을 수 있다. 따라서 최근에 원자 단위의 local structure에 관한 정보와 electrochemical state에 관한 정보를 동시에 얻을 수 있는 X-ray Absorption Fine Structure (XAFS) 분석기술을 Li 전지분석에 활용하기 시작하였다. XAFS는 하나의 x-ray 흡수원자에 대해서 주변원자들의 원자구조에 관한 정보와 구성 원소의 electrochemical state에 관한 정보를 얻을 수 있는 분석방법이다. X-ray Induced Electron Emission Spectroscopy (XIEES)는 x-ray에 의해서 방출된 전자를 검출하여 스펙트럼을 얻는 기능을 함축적으로 나타낸 것으로, x-ray를 물질 표면에 조사하여 발생하는 광전자, Auger 전자, 이차전자 등을 전자검출기(Channel Electron Multiplier: CEM)로 검출하는 기능과, 시료를 투과한 x-ray와 시료에서 발생하는 형광 x-ray를 비례계수기로 검출하는 기능을 가지고 있다. 이러한 검출 능력을 바탕으로 EXAFS, XANES, Standing Wave Technique, Elemental Composition Analysis, DXRD, Total Reflection Technique 등을 이용하여 물질을 구성하고 있는 원소의 성분, 미세원자구조, 전자구조에 관한 정보를 얻을 수 있는 새로운 spectrometer이다. 본 연구에서는 자체 개발한 XIEES의 XAFS 기능을 이용하여 여러 가지 방법으로 제조한 LiMn2-xO4와 LiMnO2, MnO2에서 Mn K-absorption edge에 대한 chemical state 변화를 측정하였다. Absorption edge에서 chemical shift를 측정하기 위해서는 방사광 가속기 수준의 에너지 분해능(~0.3eV)이 필요하다. 이번 연구에서는 SiO2(3140) monochromator를 사용하고 여기에 맞는 적절한 parameter를 적용하여 x-ray 에너지 분해능을 포항방사광가속기 수준으로 개선하였다. XIEES에서 얻은 스펙트럼과 포항방사광가속기에서 얻은 스펙트럼을 비교하였다. Chemical shift가 일어나는 경향은 두 실험 결과가 잘 일치하였다.

• Proceedings of the KSME Conference
• /
• 2007.05a
• /
• pp.1282-1287
• /
• 2007

The nature of the signal collected by an SEM(Scanning Electron Microscope) in order to form images are all dependent on the detector used to collect them, and the quality of an acquired images is strongly influenced by detector performance. Therefore, the development of detector with high performance is very important for improving on the resolution of SEM. This paper presents the manufacture of secondary electron detector and the optimal position of electron detector through numerical analysis in SEM.

• Journal of the Institute of Electronics Engineers of Korea SP
• /
• v.38 no.4
• /
• pp.325-334
• /
• 2001

It is shown that the multiscale prewhitening matched filter for detecting Gaussian objects in Markov noise can be implemented by the undecimated wavelet transform with a biorthogonal spline wavelet. If the object to be detected is Gaussian shaped and its scale coincides with one of those computed by the wavelet transform, and if the background noise is truly Markov, then optimum detection is realized by thresholding the appropriate details image. Our detection algorithm is applied to the digitized mammograms for detecting microcalcifications. However, microcalcifications are not exactly Gaussian shaped and its background noise may not be Markov. In order to campensate for these discrepancy, Hotelling observer is employed, which is applied to feature vectors comprised of 3-octave wavelet coefficients.

• Journal of the Institute of Electronics Engineers of Korea SC
• /
• v.40 no.1
• /
• pp.19-29
• /
• 2003

This paper proposes a CMOS readout circuit for uncooled micro-bolometer arrays adopting a four-point step calibration technique. The proposed readout circuit employing an 11b analog-to-digital converter (ADC), a 7b digital-to-analog converter (DAC), and an automatic gain control circuit (AGC) extracts minute infrared (IR) signals from the large output signals of uncooled micro-bolometer arrays including DC bias currents, inter-pixel process variations, and self-heating effects. Die area and Power consumption of the ADC are minimized with merged-capacitor switching (MCS) technique adopted. The current mirror with high linearity is proposed at the output stage of the DAC to calibrate inter-pixel process variations and self-heating effects. The prototype is fabricated on a double-poly double-metal 1.2 um CMOS process and the measured power consumption is 110 ㎽ from a 4.5 V supply. The measured differential nonlinearity (DNL) and integrat nonlinearity (INL) of the 11b ADC show $\pm$0.9 LSB and $\pm$1.8 LSB, while the DNL and INL of the 7b DAC show $\pm$0.1 LSB and $\pm$0.1 LSB.

• Journal of the Institute of Electronics Engineers of Korea TE
• /
• v.42 no.3
• /
• pp.19-24
• /
• 2005

Arc Fault Current is an electric discharge which is occurred in two opposite electrode. In this paper, arc current control algorithm is designed for the interruption of arc fault current which is occurred in the local electric network. This arc is one of the main causes of electric fire. Arc fault in electrical network has the characteristics of low current, high impedance and high frequency. Conventional arc current controller does not have the arc current interrupt function. Hence, Controller of arc current is designed for the interruption of arc fault current which has the modified arc characteristics.

• Journal of Software Engineering Society
• /
• v.28 no.1
• /
• pp.13-22
• /
• 2019

To enhance effective and efficient applications of automated security vulnerability checkers in highly competitive and fast-evolving IT industry, this paper studies a comprehensive set of security bug checkers in open-source static analysis frameworks and how they can be utilized for source code inspections according to the security vulnerability inspection guidelines by MOIS. This paper clarifies the relationship be tween all 42 inspection criteria in the MOIS guideline and total 323 security bug checkers in 4 popular open-source static analysis frameworks for Java web applications. Based on the result, this paper also discuss the current challenges and issues in the MOIS guideline, the comparison among the four security bug checker frameworks, and also the ideas to improve the security inspection methodologies using the MOIS guideline and open-source static security bug checkers.

• Proceedings of the KIPE Conference
• /
• 2006.06a
• /
• pp.331-332
• /
• 2006

교류 전동기는 전류의 측정오차와 데드타임 등의 영향으로 전기각 주파수에 동기된 주기적인 토크 리플이 발생한다. 본 논문에서는 주기적인 토크리플 보상 알고리즘을 제안한다. 보상기는 속도리플 관측기와 토크리플 보상기로 나누어진다. 본 논문에서는 토크리플 보상기의 해석을 통해 정상상태에서 속도 리플이 제거됨을 증명하였고 속도리플 관측기는 속도의 리플을 검출하여 토크리플 보상기를 통해 토크리플 성분이 보상됨을 시뮬레이션과 실험을 통해 검증하였다.

• The Journal of the Acoustical Society of Korea
• /
• v.40 no.2
• /
• pp.155-160
• /
• 2021

This paper proposes an automatic method for detecting snore sound, one of the important symptoms of sleep apnea patients. In the proposed method, sound signals generated during sleep are input to detect a sound generation section, and a spectrogram transformed from the detected sound section is applied to a classifier based on a Convolutional Bidirectional Gated Recurrent Unit (CBGRU) with attention mechanism. The applied attention mechanism improved the snoring sound detection performance by extending the CBGRU model to learn discriminative feature representation for the snoring detection. The experimental results show that the proposed snoring detection method improves the accuracy by approximately 3.1 % ~ 5.5 % than existing method.

• Journal of IKEEE
• /
• v.19 no.3
• /
• pp.282-287
• /
• 2015

In this study, an optical fiber detector was constructed by using a Ce:GAGG scintillator, optical fiber, and photomultiplier. The single crystal size of the scintillator was set to $3{\times}3{\times}20mm^3$ after simulating the counting efficiency of gamma rays in the scintillator by using the MCNPX code. The constructed detector used the standard gamma ray sources $^{137}Cs$ and $^{133}Ba$ to measure radiation and analyze the spectral characteristics of gamma rays. The resulting trend curve showed excellent linearity with an R-squared value of 0.99741, and the detector characteristics were found to vary 2% or less with distance based on comparison with the MCNPX value. Furthermore, the spectroscopic analysis of the gamma ray energy from the single-ray and mixed-ray sources showed that $^{137}Cs$ had its peak energy at 662 keV, and $^{133}Ba$ had at 356 keV. It seems that if the fiber-optics detector is used, working hours and exposure of worker can be reduced.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.51 no.11
• /
• pp.101-106
• /
• 2014

This paper presents a wide dynamic range radio-frequency (RF) root-mean-square (RMS) power detector using an automatic gain control (AGC) loop. The AGC loop consists of a variable gain amplifier (VGA), RMS conversion block and gain control block. The VGA exploits dB-linear gain characteristic of the cascade VGA. The proposed circuit utilizes full-wave squaring and generates a DC voltage proportional to the RMS of an input RF signal. The proposed RMS power detector operates from 500MHz to 5GHz. The detecting input signal range is from 0 dBm to -70 dBm or more with a conversion gain of -4.53 mV/dBm. The proposed RMS power detector is designed in a 65-nm 1.2-V CMOS process, and dissipates a power of 5 mW. The total active area is $0.0097mm^2$.