• 제어로봇시스템학회논문지
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• 제4권4호
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• pp.499-505
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• 1998

In developing an automated surface inspect algorithm, we have designed a hierarchical classifier using neural network. The defects which exist on the surface of cold mill strip have a scattering or singular distribution. We have considered three major problems, that is preprocessing, feature extraction and defect classification. In preprocessing, Top-hit transform, adaptive thresholding, thinning and noise rejection are used Especially, Top-hit transform using local minimax operation diminishes the effect of bad lighting. In feature extraction, geometric, moment, co-occurrence matrix, and histogram ratio features are calculated. The histogram ratio feature is taken from the gray-level image. For defect classification, we suggest a hierarchical structure of which nodes are multilayer neural network classifiers. The proposed algorithm reduced error rate by comparing to one-stage structure.

• 한국통신학회논문지
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• 제27권4C호
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• pp.365-370
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• 2002

본 논문에서는 외부 영상에서 다중 처리된 디지털 신호를 PCI로 전송할 수 있는 시스템을 설계하였다. CPU와 주변기기들의 전송율 제한에 따른 병목 현상을 개선한 것으로 실시간으로 처리되는 영상 데이터에 대하여 효율적으로 전송 및 제어할 수 있는 구조를 제안하였다. 또한 PCI로 빠른 데이터 전송 및 DMA 기능으로 자체적인 부하 사용량을 13% 줄였다. 설계는 Max+plusII를 이용한 기능 및 타이밍에 대한 동작 검증을 하였다.

• 한국전자파학회논문지
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• 제21권10호
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• pp.1169-1176
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• 2010

본 논문에서는 L1/L2 이중-밴드 GPS(Global Positioning System) 수신기용 RF 전단부를 설계하였다. 수신기는 Low IF 구조이며, 인덕터를 사용하지 않는 광대역 저잡음 증폭기(Low Noise Amplifier: LNA)와 이미지 제거를 위하여 다상 여과기(poly-phase filter)를 포함하는 quadrature 하향 변환 주파수 혼합기(quadrature down-conversion mixer) 및 전류 모드 논리(Current Mode Logic: CML) 주파수 분배기로 구성되어 있다. 저잡음 증폭기와 이미지 제거 주파수 혼합기는 높은 이득과 헤드룸 문제를 해결하기 위하여 전류 블리딩 기술을 이용하였으며, 광대역 입력 정합을 구현하기 위하여 공통 드레인 피드백을 이용하였다. $0.18{\mu}m$ CMOS 공정을 이용해 제작된 RF 전단부는 L1 밴드에서 38 dB 그리고 L2 밴드에서 41 dB의 이득을 보이며, IIP3는 L1 밴드에서 -29 dBm, L2 밴드에서는 -33 dBm이다. 입력 정합은 50 MHz에서 3 GHz까지 -10 dB 이하를 만족하며, 잡음 지수(Noise Figure: NF)는 L1 밴드에서는 3.81dB, L2 밴드에서는 3.71 dB를 보인다. 이미지 주파수 제거율은 36.5 dB이다. 설계된 RF 전단부의 칩 사이즈는 $1.2{\times}1.35mm^2$이다.

• ETRI Journal
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• 제26권3호
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• pp.229-240
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• 2004

This paper reports on our development of a dual-mode transceiver for a CMOS high-rate Bluetooth system-onchip solution. The transceiver includes most of the radio building blocks such as an active complex filter, a Gaussian frequency shift keying (GFSK) demodulator, a variable gain amplifier (VGA), a dc offset cancellation circuit, a quadrature local oscillator (LO) generator, and an RF front-end. It is designed for both the normal-rate Bluetooth with an instantaneous bit rate of 1 Mb/s and the high-rate Bluetooth of up to 12 Mb/s. The receiver employs a dualconversion combined with a baseband dual-path architecture for resolving many problems such as flicker noise, dc offset, and power consumption of the dual-mode system. The transceiver requires none of the external image-rejection and intermediate frequency (IF) channel filters by using an LO of 1.6 GHz and the fifth order onchip filters. The chip is fabricated on a $6.5-mm^{2}$ die using a standard $0.25-{\mu}m$ CMOS technology. Experimental results show an in-band image-rejection ratio of 40 dB, an IIP3 of -5 dBm, and a sensitivity of -77 dBm for the Bluetooth mode when the losses from the external components are compensated. It consumes 42 mA in receive ${\pi}/4-diffrential$ quadrature phase-shift keying $({\pi}/4-DQPSK)$ mode of 8 Mb/s, 35 mA in receive GFSK mode of 1 Mb/s, and 32 mA in transmit mode from a 2.5-V supply. These results indicate that the architecture and circuits are adaptable to the implementation of a low-cost, multi-mode, high-speed wireless personal area network.

• Journal of Radiation Protection and Research
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• 제42권4호
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• pp.197-204
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• 2017

Background: X-ray imaging detectors for the nondestructive cargo container inspection using MeV-energy X-rays should accurately portray the internal structure of the irradiated container. Internal and external factors can cause noise, affecting image quality, and scattered radiation is the greatest source of noise. To obtain a high-performance transmission image, the influence of scattered radiation must be minimized, and this can be accomplished through several methods. The scatter rejection method using an anti-scatter grid is the preferred method to reduce the impact of scattered radiation. In this paper, we present an evaluation the characteristics of the signal and noise according to physical and material changes in the anti-scatter grid of the imaging detector used in cargo container scanners. Materials and Methods: We evaluated the characteristics of the signal and noise according to changes in the grid ratio and the material of the anti-scatter grid in an X-ray image detector using MCNP6. The grid was composed of iron, lead, or tungsten, and the grid ratio was set to 2.5, 12.5, 25, or 37.5. X-ray spectrum sources for simulation were generated by 6- and 9-MeV electron impacts on the tungsten target using MCNP6. The object in the simulation was designed using metallic material of various thicknesses inside the steel container. Using the results of the computational simulation, we calculated the change in the scatter-to-primary ratio and the signal-to-noise ratio improvement factor according to the grid ratio and the grid material, respectively. Results and Discussion: Changing the grid ratios of the anti-scatter grid and the grid material decreased the scatter linearly, affecting the signal-to-noise ratio. Conclusion: The grid ratio and material of the anti-scatter grid affected the response characteristics of a container scanner using high-energy X-rays, but to a minimal extent; thus, it may not be practically effective to incorporate anti-scatter grids into container scanners.

• 전자공학회논문지A
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• 제33A권11호
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• pp.60-69
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• 1996

In this study, when the coherent detector has been developed and manufactured in the receiver of radar system, we have suggested and realized the 'Frequecny-Feedback correction (FFC)' that extracts its errors affecting the performance of radar, such as amplitude imbalances (k), phase imbalance ($\varphi$) between channels and offset votlages and corrects them to improve radar performances. Applying the FFC proposed, we analyzed sthe properties of the coherent detector and compared its perfomances after and before correction procdure. After the correction sequence, the amplitude imbalance was improved upt o 2dB and the phase imbalance over 9$^{\circ}$. The image rejection ratio (IRR), one of the figures of merit of radar system, was made better above 9 dB after correcting the coherent detector which possessed 23 dB before.

• 한국전자파학회논문지
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• 제11권1호
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• pp.110-115
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• 2000

A K-band GaAs MMIC receiver module has been developed using 0.15 ${\mu}{\textrm}{m}$ HEMT technology process. It incorporates two front end low noise amplifiers, a double balanced diode mixer, and filters. The RF input frequency ranges 20.1 to 21 GHz and the IF output 1.1 to 2 GHz. Test results show an overall conversion gain of more than 27 dB, and less than a 2.2 dB noise figure. The image-rejection ratio greater than 21 dB has been obtained. The isolation between RF and IF ports is better than 27 dB, and between LO and IF is more than 50 dB.

• 전자공학회논문지S
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• 제35S권6호
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• pp.88-100
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• 1998

본 논문에서는 지문 영상의 개별적이고 부분적인 특성(밝기, 품질 차이 등)을 고려하여 지문의 특징량 추출을 수행함으로써 지문 입력기간의 차이에서 오는 문제점을 극복하며, 정합 과정시에는 회전 및 크기 변화, 위치 이동 등에 관계없이 균일한 성능을 보장하면서도 실시간 내에 처리가 가능한 자동 지문인식 알고리즘을 제안한다. 특히 본 방법에서는 지문의 분류 작업을 융선의 전체적인 흐름 모양과 중심점, 삼각주와 같은 특이점간의 상호 관계를 이용하여 결정하게 된다. 개발된 알고리즘을 평가하기 위해 NIST 지문 및 한국인의 연령과 직업별 인구 분포에 따라 구축된 압착 날인 지문, 그리고 회전 날인 후 수치화된 지문과 같은 다양한 영상들에 대해 제안된 방법을 적용하였으며, 전체적인 인식 성능이 타인 수락 오류율을 0%로 설정했을 때 본인 거부 오류율이 0.07%라는 결과를 얻을 수 있었다.

• 한국안전학회지
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• 제34권1호
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• pp.82-89
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• 2019

The importance of aviation safety has been emphasized recently due to the development of aviation industry. Despite the efforts of each country and the improvement of screening equipment, screening tasks are still difficult and detection failures are frequent. The purpose of this study was to examine the effect of feedback on improving signal detection performance applying a Simulated Baggage Screening Program(SBSP) for improving aviation safety. SBSP consists of three parts: image combination, option setting and experiment. The experimental images were color-coded to reflect the items' transmittance of the x-rays and could be combined as researchers' need. In the option, the researcher could set up the information, incentive, and comments needed for training to be delivered on a number of tasks and times. Experiment was conducted using SBSP and participant's performance information (hit, missed, false alarms, correct rejection, reaction time, etc.) was automatically calculated and stored. A total of 50 participants participated and each participant was randomly assigned to feedback and non-feedback group. Participants performed a total of 200 tasks and 20(10%) contained target object(gun and knife). The results showed that when the feedback was provided, the hit, correct rejection ratio and d′ were increased, however, the false alarms and miss decreased. However, there was no significant difference in response criteria(${\beta}$). In addition, implications, limitations of this study and future research were discussed.

• 전자공학회논문지SC
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• 제40권3호
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• pp.181-188
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• 2003

본 논문에서는 영구자석 자기공명영상시스템에 나쁜 영향을 기치는 외부 자기 잡음을 효율적으로 차폐하는 기술을 서술하였다. 유한요소법 전자계 해석을 통하여 영구자석의 주자계 방향과 일치하는 자기 잡음 성분이 자기공명영상에 주로 영향을 미치는 것을 밝혔고, 이의 해석 결과를 기반으로 자기잡음센서, 보상코일, 그리고 코일구동기로 구성되는 능동형 자기 잡음 차폐시스템을 개발하였다. 개발된 자기 잡음 차폐시스템은 수 Hz 미만의 저주파 대역의 자기 잡음에 대하여 30dB 이상의 차폐율을 보였으며, 0.3Tesla 전신형 자기 공명영상시스템에 자기 잡음 차폐시스템을 적용하여 자기 잡음에 의한 영상 잡음이 크게 개선됨을 실험적으로 밝혔다.