• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제18권2호
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• pp.143-156
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• 2014

This paper aims to give a quick view on denoising without comprehensive details. Denoising can be understood as removing unwanted parts in signals and images. Noise incorporates intrinsic random fluctuations in the data. Since noise is ubiquitous, denoising methods and models are diverse. Starting from what noise means, we briefly discuss a denoising model as maximum a posteriori estimation and relate it with a variational form or energy model. After that we present a few major branches in image and signal processing; filtering, shrinkage or thresholding, regularization and data adapted methods, although it may not be a general way of classifying denoising methods.

• Journal of Information Processing Systems
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• 제8권3호
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• pp.445-458
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• 2012

Image feature extraction is one of the basic works for biometric analysis. This paper presents the novel concept of application of ridgelets for iris recognition systems. Ridgelet transforms are the combination of Radon transforms and Wavelet transforms. They are suitable for extracting the abundantly present textural data that is in an iris. The technique proposed here uses the ridgelets to form an iris signature and to represent the iris. This paper contributes towards creating an improved iris recognition system. There is a reduction in the feature vector size, which is 1X4 in size. The False Acceptance Rate (FAR) and False Rejection Rate (FRR) were also reduced and the accuracy increased. The proposed method also avoids the iris normalization process that is traditionally used in iris recognition systems. Experimental results indicate that the proposed method achieves an accuracy of 99.82%, 0.1309% FAR, and 0.0434% FRR.

• 방송공학회논문지
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• 제4권2호
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• pp.134-143
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• 1999

본 논문에서는, IDWT(inverse discrete wavelet transform)를 효율적으로 구현하는 한 방법으로 홀수 탭(tap)의 선형위상 필터의 VLSI 구조를 제안한다. 제안한 필터 구조는 선형 위상 필터의 대칭 특성을 이용하여 대칭적인 위치에 있는 입력을 먼저 합한 다음 필터링을 수행한다. 이때 발생하는 전역 연결을 해결하기 위하여 입력의 흐름을 U자형으로 만듦으로써 국부적인 연결로 필터를 구현한다. 제안한 필터는 지연 소자부, 연산부, 덧셈부, 그리고 후처리부 등으로 이루어진다. 그리고, 각 부분들을 규칙적으로 배열하고, 국부적으로 연결함으로써 제안한 구조를 설계하기 때문에, 단순히 해당 부분들을 추가/삭제함으로써 임의의 선형 위상 IDWT 필터를 구현할 수 있다는 장점이 있다. 그리고, 제안한 필터를 직렬 연결 혹은 반순환적(semi-recursive) 구조로 배열함으로써 M 레벨 IDWT를 구현할 수 있음을 보인다. 본 논문에서 제안한 IDWT 구조는 기존의 구조들에 비해 간단하기 때문에 MPET-4 등 관련 분야에 효과적으로 적용될 것으로 기대된다.

• 지구물리와물리탐사
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• 제10권2호
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• pp.131-137
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• 2007

초동발췌 방법과 이와 관련된 오차문제를 고찰하고 자료처리 전산화 측면에서 초동발췌 및 오차계산의 실용적 알고리즘을 제안하였다. 제안한 초동발췌 방법은 2단계로 구성된다. 1) 초동신호 중 트레이스 간 연속성이 양호한 최초의 피크(peak) 또는 트라프(trough)를 발췌한다. 2) 발췌시점 전방 일정구간의 기록을 직선으로 근사화 하고 이 직선의 시간 절편을 초동주시로 한다. 근사화 구간의 길이는 대략 초동 웨이브렛 폭의 1/4보다 다소 작게 설정한다. 초동발췌에 내재된 오차의 정량적인 척도는 기록의 특정시점에 초동의 도착 여부를 판단하는 데 필요한 기록의 길이로 정의한다. 기록의 길이를 나타내는 공식은 신호의 주파수대역과 신호대잡음비의 함수로 표시된다. 3개의 공대공 탄성파기록의 초동을 수동 및 제안한 방법으로 발췌하였고 각 트레이스의 오차한계를 계산하였다. 실험결과 제안한 근사직선 시간절편법의 우수한 성능과 발췌된 초동평가에 있어서 발췌오차의 유용성을 확인하였다.

• 비파괴검사학회지
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• 제23권3호
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• pp.246-253
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• 2003

항공기 구조를 모사하여 일련의 리벳 구멍을 갖는 AA2024-T3 박판 구조를 대상으로 피로하중에 의한 단균열(short crack)의 발생시점과 성장거동을 음향방출(AE)을 위주로 한 측정으로 평가하였다. AE 위치표정에 의해 단균열의 좌표를 정확하게 결정하였으며, 이동식 현미경으로 균열의 크기를 측정하였다. 누적 AE 발생수 곡선은 단균열의 발생과 성장에 따라 일정한 간격을 두고 급격히 증가하는 양상을 보임으로써 여러 차례의 계단식 곡선을 형성하였다. AE 위치표정에서는 리벳 구멍을 중심으로 파괴역학에 근거한 관심영역(ROI)을 설정하였으며, 웨이블릿변환 잡음제거 방법을 사용하여 위치표정의 정확도를 향상할 수 있었다. 실제로 탐지된 신호의 대부분이 단 균열의 발생 및 성장과 관계없는 외부 잡음신호로 나타났으며, ROI 내에서 발생한 AE 발생원의 위치도 구조의 기하학적 특징이나 신호대잡음비의 영향에 의해 왜곡될 수 있음을 알 수 있었다.

• 한국멀티미디어학회논문지
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• 제6권2호
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• pp.247-258
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• 2003

얼굴인식 기술 분야에 있어서 Principal component analysis (PCA)기반 알고리즘은 많은 관련 알고리즘의 기초가 되고 있다. PCA는 매우 통계적인 접근이며 얼굴인식 분야에 응용하기 위해서는 많은 설계 결정요인 (design derision)을 필요로 한다. 본 논문에서는 일반적인 modular PCA알고리즘을 소개하면서 design decision을 얻는다. 얼굴인식 알고리즘 평가에 대한 표준 접근 방법인 September 1996 FERET evaluation protocol을 활용하여 각 모듈에 대한 서로 다른 구현방법을 실험하고 평가한다. 실험조건으로는 (1) 조도의 정규화 과정 을 변화 (2) JPEG과 wavelet compression 알고리즘 사용에 대한 성능효과를 분석 (3) 표현방법에서 eigenvectors의 수를 조절 (4) 분류과정에서 유사도 측정방법을 변경하는 등이다. 본 논문에서는 standard September 1996 FERET의 대용량 gallery image set에 대해 적용해 본 결과에 대해 정리하며, 100개의 무작위로 발생된 image set에 대해서도 알고리즘의 성능 변화를 평가한다.

• 대한원격탐사학회지
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• 제22권1호
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• pp.49-61
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• 2006

The lifting scheme has been found to be a flexible method for constructing scalar wavelets with desirable properties. In this paper, it is extended to the UDAR data compression. A newly developed data compression approach to approximate the UDAR surface with a series of non-overlapping triangles has been presented. Generally a Triangulated Irregular Networks (TIN) are the most common form of digital surface model that consists of elevation values with x, y coordinates that make up triangles. But over the years the TIN data representation has become an important research topic for many researchers due its large data size. Compression of TIN is needed for efficient management of large data and good surface visualization. This approach covers following steps: First, by using a Delaunay triangulation, an efficient algorithm is developed to generate TIN, which forms the terrain from an arbitrary set of data. A new interpolation wavelet filter for TIN has been applied in two steps, namely splitting and elevation. In the splitting step, a triangle has been divided into several sub-triangles and the elevation step has been used to 'modify' the point values (point coordinates for geometry) after the splitting. Then, this data set is compressed at the desired locations by using second generation wavelets. The quality of geographical surface representation after using proposed technique is compared with the original UDAR data. The results show that this method can be used for significant reduction of data set.

• Nuclear Engineering and Technology
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• 제53권1호
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• pp.148-163
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• 2021

Timely fault identification is important for safe and reliable operation of the electric valve system. Many research works have utilized different data-driven approach for fault diagnosis in complex systems. However, they do not consider specific characteristics of critical control components such as electric valves. This work presents an integrated shallow-deep fault diagnostic model, developed based on signals extracted from DN50 electric valve. First, the local optimal issue of particle swarm optimization algorithm is solved by optimizing the weight search capability, the particle speed, and position update strategy. Then, to develop a shallow diagnostic model, the modified particle swarm algorithm is combined with support vector machine to form a hybrid improved particle swarm-support vector machine (IPs-SVM). To decouple the influence of the background noise, the wavelet packet transform method is used to reconstruct the vibration signal. Thereafter, the IPs-SVM is used to classify phase imbalance and damaged valve faults, and the performance was evaluated against other models developed using the conventional SVM and particle swarm optimized SVM. Secondly, three different deep belief network (DBN) models are developed, using different acoustic signal structures: raw signal, wavelet transformed signal and time-series (sequential) signal. The models are developed to estimate internal leakage sizes in the electric valve. The predictive performance of the DBN and the evaluation results of the proposed IPs-SVM are also presented in this paper.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2003년도 추계학술발표회
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• pp.574-578
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• 2003

There are so many methods to estimate the groundwater recharge. These methods can be categorized into four groups. First groupis related to the water balance analysis, second group is concerned with baseflow/springflow recession, and third group is interested in some types of tracers; environmental tracers and/or temperature profile. The limitation of these types of methods is that the estimated results of recharge are presented in the form of an average over some time period. Forth group has a little different approach. They use the time series data of hydraulic head and specific yield evaluated from field test, and the results of estimation are described in the sequential form. But their approach has a serious problem. The estimated results in forth typeof methods are generally underestimated because they cannot consider the discharge phase of water table fluctuation coupled with the recharge phase. Ketchum el. at. (2000) proposed calibrated method, considering recharge- and discharge-coupled water table fluctuation. But the dischargeis considered just as the areal average with discharge rate. On the other hand, there are many methods to estimate the source wavelet with observed data set in geophysics/signal processing and geophysical methods are rarely applied to the estimation of groundwater recharge. The purpose this study is the evaluation of the applicability of one of the geophysical method in the estimation of sequential recharge rate. The applied geophysical method is called minimum entropy deconvolution (MED). For this purpose, numerical modeling with linearized Boussinesq equation was applied. Using the synthesized hydraulic head through the numerical modeling, the relative sequenceof recharge is calculated inversely. Estimated results are very concordant with the applied recharge sequence. Cross-correlations between applied recharge sequence and the estimated results are above 0.985 in all study cases. Through the numerical test, the availability of MED in the estimation of the recharge sequence to groundwater was investigated

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2004년도 학술대회지
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• pp.772-775
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• 2004

Generally, arterial pulse waves are measured at the radial arterial of wrist or carotid arterial of neck using a sensor such as pressure sensor, piezoelectric sensor or optic sensor. But in this paper, arterial pulse wave is measured at the temple using PZT piezo sensor which is attached on the temple in form of a hair-band. Arterial Pulse waves are generally measured when a reagent is in a static state. But in this paper, we implemented the arterial pulse wave measurement system, as a previous stage of the arterial pulse wave measurement system for running at outdoors or on a running machine, that measures arterial pulse waves at the temple, which is the least moving part when running. Thorough the continuous study, if the motion artifact when running is possible to be removed, the system will be able to perform monitoring of running men's states and especially emergency signals such as serious pulse waves of an/old and feeble persons and handicapped persons.