• The Journal of the Acoustical Society of Korea
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• v.38 no.5
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• pp.543-548
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• 2019

The tonal signal caused by the machinery component of a vessel such as an engine, gearbox, and support elements, can be modeled as a sparse signal in the frequency domain. Recently, compressive sensing based techniques that recover an original signal using a small number of measurements in a short period of time, have been applied for the tonal frequency detection. These techniques, however, cannot avoid a basis mismatch error caused by the discretization of the frequency domain. In this paper, we propose a method to detect the tonal frequency with a small number of measurements in the continuous domain by using the atomic norm minimization technique. From the simulation results, we demonstrate that the proposed technique outperforms conventional methods in terms of the exact recovery ratio and mean square error.

• The KIPS Transactions:PartB
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• v.18B no.3
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• pp.147-156
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• 2011

This paper proposes a 3-stage (preprocessing, feature extraction, and classification) fault detection and classification algorithm for induction motors. In the first stage, a low-pass filter is used to remove noise components in the fault signal. In the second stage, a discrete cosine transform (DCT) and a statistical method are used to extract features of the fault signal. Finally, a back propagation neural network (BPNN) method is applied to classify the fault signal. To evaluate the performance of the proposed algorithm, we used one second long normal/abnormal vibration signals of an induction motor sampled at 8kHz. Experimental results showed that the proposed algorithm achieves about 100% accuracy in fault classification, and it provides 50% improved accuracy when compared to the existing fault detection algorithm using a cross-covariance method. In a real-world data acquisition environment, unnecessary noise components are usually included to the real signal. Thus, we conducted an additional simulation to evaluate how well the proposed algorithm classifies the fault signals in a circumstance where a white Gaussian noise is inserted into the fault signals. The simulation results showed that the proposed algorithm achieves over 98% accuracy in fault classification. Moreover, we developed a testbed system including a TI's DSP (digital signal processor) to implement and verify the functionality of the proposed algorithm.

• Journal of Korean Society of Transportation
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• v.10 no.2
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• pp.43-54
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• 1992

전통적인 신호제어모형은 다음의 두가지 결점을 내포하고 있다. 신호현시의 방법을 적정화하는 점이다. Rouphail(1990)은 전통적으로 행해온 신호주기와 녹색시간분할의 적정화에서 더 나아가 현시방법(signal timing)과 좌회전의 문제를 동시적으로 적정화 시킬 수 있는 모형을 제시한 바 있다. 그러나 Rouphail의 모형은 4개 현시에 국한되었고 현시방법(또는 현시의 선택)도 대단히 제약적이었다. 본연구는 이러한 Rouphail의 모형을 실제상황 에 보다 일반성있게 적용할 수 있도록 확장하는 연구이다. 여기서는 현시방법(또는 선택하는 현시으 형태와 수)을 확대시키고 또 연속변수와 이산변수를 동시에 적정화시키는 혼합정수선형계획법을 적용한 컴퓨터 모형을 구성하고 이를 사례 지역에 적용하엿다. 분석결과는 본 모형이 Rouphail 모형과 비교할 때 현시방법의 선택문제에 있어서 뿐만 아니라 좌회전(비보호, 보호 또는 혼합적)현시의 처리에 있어서 훨씬 더 효율적임을 확인하였다.

• Aerospace Engineering and Technology
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• v.9 no.1
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• pp.98-105
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• 2010

Fast Fourier Transform is the fast implementation of Discrete Fourier Transform, which deletes periodic operation of DFT. According to the definition, radix-2 FFT can be implemented byre cursive call which divides the input signal points into 2 signal points. Because of its time-consuming stack-copy operation, this recursive method is very slow. To overcome this drawback, butterfly operation with signal rearrangement was devised. Based on the ideas of signal rearrangement and butterfly operation, this paper applies the signal rearrangement method to the Radix-3 FFT and checks the validity of this method.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.43 no.12 s.354
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• pp.8-14
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• 2006

This paper proposed noise insensitive 4*4 mid frequency-OCT (MF-DCT) focus measure operator. Proposed operator enhanced low power 8*8 MDCT operator to have 4*4 rotationally same form for Gaussian noise. MF-DCT operator acting like band-pass filter suppresses both low-frequency signal useless for focus measure and high-frequency signal affected by impulsive noise. Also it is proved to be linear because it uses the energy of band-pass filtered signal as focus measure. Experimental result shows its superiority by comparing AUM with traditional operators.

• The Journal of the Korea institute of electronic communication sciences
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• v.3 no.4
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• pp.260-265
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• 2008

The arc-fault occurring in the customer system becomes the direct cause of electric fire. However, it is very difficult to identify the arc-fault using the existing fault detection mechanism because the magnitude of the fault current is very small. Accordingly, this paper analyzes the causes of arc fault and designs the basic detection mechanism of arc fault. And then, it proposes an signal processing-based arc-fault determination methodology which can enhance the of accuracy of the arc-fault determination by applying DFT/DWT to the voltage and current waveform. Finally, this paper showed the application methodology of the proposed signal processing based fault determination method by applying and analyzing DFT/DWT to an high voltage in-rush current waveform.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.9
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• pp.702-708
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• 2002

The spectrum of impulse response signal from an impulse hammer testing is widely used to obtain frequency response function(FRF). However the FRFs obtained from impact hammer testing have not only leakage errors but also finite record length errors when the record length for the signal processing is not sufficiently long. The errors cannot be removed with the conventional signal analyzer which treats the signals as if they are always steady and periodic. Since the response signals generated by the impact hammer are transient and have damping, they are undoubtedly non-periodic. It is inevitable that the signals be acquired for limited recording time, which causes the errors. This paper makes clear the relation between the errors of FRF and the length of recording time. A new method is suggested to reduce the errors of FRF in this paper. Several numerical examples for 1-dof model are carried out to show the property of the errors and the validity of the proposed method.

• The Journal of the Acoustical Society of Korea
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• v.22 no.5
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• pp.345-350
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• 2003

Acoustic intensity is usually estimated by the cross-spectrum of acoustic pressure at two adjacent microphones. The cross-spectrum calculated by digital Fourier transform technique will unavoidably have leakage error since the period of signal will not be usually coincident with record length. Therefore, the acoustic intensity estimated by the conventional FFT analyzer will show distorted value. In this paper, the expression of the Fourier transformed data of a harmonic signal with a single frequency is formulated when there is leakage error. The method to eliminate the effect of leakage error from the contaminated data is also proposed. Some numerical examples show the validation of the proposed method.

• Journal of Korea Society of Industrial Information Systems
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• v.22 no.2
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• pp.43-52
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• 2017

Pattern Analysis is One of the Most Important Techniques in the Signal and Image Processing and Text Mining Fields. Discrete Fourier Transform (DFT) is Generally Used to Analyzing the Pattern of Signals and Images. We thought DFT could also be used on the Analysis of Text Patterns. In this Paper, DFT is Firstly Adapted in the World to the Sentence Plagiarism Detection Which Detects if Text Patterns of a Document Exist in Other Documents. We Signalize the Texts Converting Texts to ASCII Codes and Apply the Cross-Correlation Method to Detect the Simple Text Plagiarisms such as Cut-and-paste, term Relocations and etc. WordNet is using to find Similarities to Detect the Plagiarism that uses Synonyms, Translations, Summarizations and etc. The Data set, 2013 Corpus, Provided by PAN Which is the One of Well-known Workshops for Text Plagiarism is used in our Experiments. Our Method are Fourth Ranked Among the Eleven most Outstanding Plagiarism Detection Methods.

• Journal of Korea Multimedia Society
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• v.9 no.5
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• pp.624-634
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• 2006

This paper presents a new watermarking scheme that is robust against geometrical attacks such as translation and rotation. The proposed method is based on the conventional PSADT(Polar Coordinates Shape Adaptive Discrete Transform) method which is an robust watermarking scheme for an arbitrarily-shaped image such as character images. The PSADT method shows perfect robustness against geometrical attack if there is no change in the shape of the image object. However, it cannot be utilized to watermark general rectangular images because of the missing alignment between the watermarked signals in the embedding and extracting side. To overcome this problem we propose a new watermarking scheme that aligns the watermark signal using the image inherent feature, especially corner. Namely the proposed method decides a consistent target region whose shape and position isn't changed by any malicious attack and then embeds the watermark in it using the PSADT method. Experimental results show the robustness of the proposed method against geometrical attacks as well as image compression.