• Journal of Radiation Protection and Research
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• 제24권3호
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• pp.161-170
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• 1999

비정질 실리콘 방사선 촬영기와 기존 X-ray filmrh과의 영상질 비교를 통하여 시스템의 성능을 평가하였다. 다양한 영상질 평가를 위하여 MTF (Modulation Transfer Function), NPS (Noise Power Spectrum), Contrast를 측정하여 계산하였다. 실험 결과 DR의 MTF는 기존 film-screen system과 유사하였다. Noise 특성은 두 시스템 모두 quantum noise가 주를 이뤘으며, 특히 DR 에서는 전기적인 noise가 발견되었다. 또한 우수한 sensitivity 특성과 영상처리를 통하여 DR 시스템이 기존의 film-screen 시스템보다 놀은 대조도를 보였다. 이와 같이 DR에서는 기존 film-screen 시스템과 유사한 해상도와 영상처리를 통해 같은 촬영조건에서도 향상된 대조도의 영상을 얻을 수 있었다. 본 연구를 통하여 의학적 활용과 관련된DR 시스템의성능에 대한 유용한 정보를 제공할 수 있으리라 기대한다.

• Smart Structures and Systems
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• 제25권5호
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• pp.569-580
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• 2020

The identification of delays and delay compensation are critical problems in real-time hybrid simulations (RTHS). Conventional delay compensation methods are mostly based on the assumption of a constant delay. However, the system delay may vary during tests owing to the nonlinearity of the loading system and/or the behavioral variations of the specimen. To address this issue, this study presents an adaptive delay compensation method based on a discrete model of the loading system. In particular, the parameters of this discrete model are identified and updated online with the least-squares method to represent a servo hydraulic loading system. Furthermore, based on this model, the system delays are compensated for by generating system commands using the desired displacements, achieved displacements, and previous displacement commands. This method is more general than the existing compensation methods because it can predict commands based on multiple displacement categories. Moreover, this method is straightforward and suitable for implementation on digital signal processing boards because it relies solely on the displacements rather than on velocity and/or acceleration data. The virtual and real RTHS results show that the studied method exhibits satisfactory estimation smoothness and compensation accuracy. Furthermore, considering the measurement noise, the low-order parameter models of this method are more favorable than that the high-order parameter models.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1992년도 한국자동제어학술회의논문집(국내학술편); KOEX, Seoul; 19-21 Oct. 1992
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• pp.537-540
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• 1992

This paper presents Samsung CNC (Computer Numerical Controller) system with an intel 80486/487 as the main CPU and a 32 bit floating point DSP(Digital Signal Processor) TMS320C30 as the motion control CPU. The Samsung CNC system diverse user-frienly characteristics such as multi-tasking, powerful menu system, internal PLC system, and 2/3 dimensional graphics in wire and solid mode. The main CPU executes central processing program, user interface program, interpreter, BMI, etc while the motion control CPU carries out some interpolations, acceleration/deceleration, and PID control algorithm with feedforward terms. Complex interpolations except linear and circular ones are performed on the main control CPU. The experimental results for the circular interpolation under linear acceleration/deceleration shows that the proposed CNC system can be widely used in controlling machining centers with good machining accuracy.

• 대한전자공학회논문지SD
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• 제38권9호
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• pp.663-670
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• 2001

본 논문은 여러 이산 신호 처리(Digital Signal Processing)에서 많이 사용되는 FIR Filter의 전력 소모를 줄이는 새로운 방법을 제안한다. FIR Filter에서 소모되는 전력 중 곱셈기가 차지하는 비중이 매우 높다라는 사실과 2D 영상에서 이웃한 픽셀 값의 공간 상관성이 높다라는 성질을 이용하였다. 곱셈기의 입력인 영상 데이터를 상대적으로 상관성이 높은 상위 비트(MSBs)와 상관성이 낮은 하위 비트(LSBs)로 구분하고, 각각에 대해서 필터링을 수행하도록 하였다. 또한, 입력의 상위 비트와 필터 계수와의 곱셈 결과는 캐쉬 (cache)에 저장하여 재사용함으로써 불필요한 상위 비트의 연산을 줄이도록 하였다. 이러한 방법을 SMT(Separated Multiplication Technique)라 부르기로 한다. FIR Filter를 사용함에 있어 제안된 SMT를 이용하였을 경우에 15%정도의 전력 이득 효과를 얻을 수 있었다.

• 대한인간공학회지
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• 제31권6호
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• pp.785-791
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• 2012

Objective: The aim of this study was to investigate the correlation between 3D visual fatigue and physiological measures by canonical correlation analysis enabling to categorical correlation. Background: Few studies have been conducted to investigate the physiological mechanism underlying the visual fatigue caused by processing 3D information which may make the cognitive mechanism overloaded. However, even the previous studies lack validation in terms of the correlation between physiological variables and the visual fatigue. Method: 9 Female and 6 male subjects with a mean age of $22.53{\pm}2.55$ voluntarily participated in this experiment. All participants were asked to report how they felt about their health sate at after viewing 3D. In addition, Low & Hybrid measurement test(Event Related Potential, Steady-state Visual Evoked Potential) and for evaluating cognitive fatigue before and after viewing 3D were performed. The physiological signal were measured with subjective fatigue evaluation before and after in watching the 3D content. For this study suggesting categorical correlation, all measures were categorized into three sets such as included Visual Fatigue set(response time, subjective evaluation), Autonomic Nervous System set(PPG frequency, PPG amplitude, HF/LF ratio), Central Nervous System set(ERP amplitude P4, O1, O2, ERP latency P4, O1, O2, SSVEP S/N ratio P4, O1, O2). Then the correlation of three variables sets, canonical correlation analysis was conducted. Results: The results showed a significant correlation between visual fatigue and physiological measures. However, different variables of visual fatigue were highly correlated to respective HF/LF ratio and to ERP latency(O2). Conclusion: Response time was highly correlated to ERP latency(O2) while the subjective evaluation was to HF/LF ratio. Application: This study may provide the most significant variables for the quantitative evaluation of visual fatigue using HF/LF ratio and ERP latency based human performance and subjective fatigue.

• 인터넷정보학회논문지
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• 제5권3호
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• pp.73-86
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• 2004

본 논문에서는 컬러 영상을 위한 하이브리드(hybrid) 디지털 워터마킹 기법을 제안한다. 즉, 두 개의 워터마크가 주파수 영역과 공간 영역 상에 각각 삽입된다. 첫 번째 워터마크는 영상 데이터를 DW(discrete wavelet transform)를 사용하여 주파수 공간으로 변환한 후, 인간의 시각이 밝기에 민감하지 않다는 사실을 이용하여 컬러 영상의 밝기(luminance) 성분에 대역확산(spread-spectrum) 방법으로 워터마크를 삽입한다. 삽입되는 워터마크는 유사난수 패턴(pseudo-random pattern)을 사용하며 워터마크 검출시에는 상관도(correlation)를 이용하여 워터마크를 추출한다. 두 번째 워터마크는 첫 번째 워터마크가 클로핑(cropping)과 같은 기하학적 공격(geometrical of attack)에 취약한 점을 보완하기 위해 삽입한다. 영상의 공간 영역에서 블루 채널 상에 두 번째 워터마크가 삽입되며, 이때 영상의 특징점의 픽셀값을 입력 값으로 하여 해쉬함수의 출력값을 구한다. 따라서 두 번째 워터마크는 영상의 위 변조를 판별할 수 있는 tamper defection의 기능을 한다.

• 센서학회지
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• 제20권3호
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• pp.172-177
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• 2011

Finger patients can't use their hands because of the paralysis their fingers. Their fingers are recovered by rehabilitating training, and the rehabilitating extent can be judged by measuring the pressing force to be contacted with two fingers(thumb and first finger, thumb and middle finger, thumb and ring finger, thumb and little finger). At present, most hospitals have used a thin plastic-plate for measuring the two-finger grasping force, and we can only judge that they can grasp the plate with their two-finger through it, because the plate can't measure the two-finger grasping force. But, recently, the force measuring system for measuring two-finger grasping force was developed using three-axis force sensor, but it is very expensive, because it has a three-axis force sensor. In this paper, two-finger force measuring system with a one-axis force sensor which can measure two-finger grasping force was developed. The one-axis force sensor was designed and fabricated, and the force measuring device was designed and manufactured using DSP(Digital Signal Processing). Also, the grasping force test of men was performed using the developed two-finger force measuring system, it was confirmed that the grasping forces of men were different according to grasping methods, and the system can be used for measuring two-finger grasping force.

• 한국멀티미디어학회논문지
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• 제21권4호
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• pp.450-463
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• 2018

Sound based machine fault diagnosis is the process consisting of detecting automatically the damages that affect the machines by analyzing the sounds they produce during their operating time. The collected sounds being inevitably corrupted by random disturbance, the most important part of the diagnosis consists of discovering the hidden elements inside the data that can reveal the faulty patterns. This paper presents a novel feature extraction methodology that combines various digital signal processing and pattern recognition methods for the analysis of the sounds produced by the drills. Using the Fourier analysis, the magnitude spectrum of the sounds are extracted, converted into two-dimensional vectors and uniformly normalized in such a way that they can be represented as 8-bit grayscale images. Histogram equalization is then performed over the obtained images in order to adjust their very poor contrast. The obtained contrast enhanced images will be used as the features of our diagnosis system. Finally, principal component analysis is performed over the image features for reducing their dimensions and a nonlinear classifier is adopted to produce the final response. Unlike the conventional features, the results demonstrate that the proposed feature extraction method manages to capture the hidden health patterns of the sound.

• 정보처리학회논문지B
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• 제13B권3호
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• pp.309-314
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• 2006

최근 다양하고 방대한 멀티미디어 데이터를 효율적으로 저장, 관리 및 검색할 수 있는 멀티미디어 데이터베이스 시스템이 정보화 사회의 중요한 핵심 기술로 대두되고 있다. 내용 기반 이미지 검색을 위해 본 논문에서는 웨이브렛 변환과 에너지 값을 사용하여 이미지 데이터로부터 특징 벡터를 완전 자동으로 추출하는 방법과 이를 이용한 효율적인 검색 기법을 제안한다. 웨이브렛 변환은 이미지 압축이나 신호 분석 등에서 많이 사용되며, 특히 웨이브렛 계수 값은 영상의 특성을 잘 반영하고 웨이브렛 영역에서 계산되는 예제영상(Query image)과 데이터베이스에 저장된 영상간의 유사성을 추정하는데 더 효율적이다. 영상 검색에 있어, 특징 벡터로 사용되는 표준편차와 평균 값을 에너지 값과 비교 분석하였다. 실험결과, 표준편차나 평균 값을 이용하는 것보다 에너지 값을 사용하는 것이 더 효과적이었다.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1998년도 추계학술대회
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• pp.191-192
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• 1998

We report on the design of a low-noise 40 channel SQUID system for biomagnetism. We used low-noise SQUID sensor with the pickup coil integrated on the same wafer as the SQUID. The SQUID electronics were simplified by increasing the voltage output of the SQUID. The SQUID insert was designed to have low thermal load, minimizing the liquid helium loss. The digital signal processing provides versatile analysis tools and the software is based on the object-oriented programming. For the effective localization of the source location, solutions of the inverse problems based on the lead-field and the simulated anneal ins were studied.