• Wind and Structures
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• v.6 no.5
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• pp.403-418
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• 2003

This paper presents an extensive analysis of the short term, unsteady wind loading on a low-rise building. The building is located in a rural environment and only the specific situation of wind flow orthogonal to the long face of the structure is considered. The data is analysed using conventional analysis and less traditional methods such as conditional sampling and wavelet analysis. The nature of the flow field over the building is found to be highly unsteady and complex. Fluctuating pressures on the windward wall are shown to a large extent to be caused by the fluctuations in the upstream flow, whereas extreme pressures on the roof are as a result of high intensity small scale flow structures. On the roof of the building a significant amount of energy is shown to exist at frequencies above 1 Hz.

• Proceedings of the KSRS Conference
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• 2007.10a
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• pp.405-409
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• 2007

Each class in remotely sensed imagery has different spectral and spatial characteristics. Natural features have relatively smaller spatial changes than spectral changes. Meanwhile, urban area in which buildings, roads, and cars are included is inclined to face more changes of spatial variation than spectral one. This study aims to propose the new urban complexity index (UCI) based on the 3D DWT computation of remotely sensed imageries considering these characteristics. And then we analyze relation between index and land cover map. The 3DWUCI values are related to class and the indices of urban area are greater than natural area. The proposed UCI could be used to express effectively the standard of urban complexity over a wide area.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.18 no.2
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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 Digital Contents Society
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• v.5 no.4
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• pp.311-315
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• 2004

In this paper, we proposed a robust watermarking algorithm based on fuzzy inference and human visual system. In the first, discrete wavelet transform(DWT) is involved to calculate additive energy strength, then we devised fuzzy inference, which was established by computing contrast and texture degree in gray-level image. Watermark is embeded into the coefficients of 3-level DWT so as to consider a spatial effects. Visual recognizable patterns such as binary image were used as a watermark Consequently, experimental results showed that proposed algorithm is robust in JPEC compression.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.10a
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• pp.542-543
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• 2018

In this paper, we propose a method of visual information of original image by encrypting only partial data of infra-red image. In this method, the infra-red image is divided into R, G, and B channels, and the outline is searched for the three channel images. Then, an average value is calculated for each contour image, and a channel to be encrypted is selected. The wavelet transform is performed on the selected channel to encrypt only the LL subband in which the highest energy is concentrated. Experimental results show that the SSIM value is less than 0.09 in the case of the proposed encryption method.

• Proceedings of the Korean Information Science Society Conference
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• 2000.10b
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• pp.467-469
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• 2000

본 논문은 웨이블릿 변환영역 하에서 칼라 히스토그램과 에너지 벡터를 이용한 컷검출 방법을 제안한다. 기존의 컷 검출 방법들은 대부분 공간영역과 변환영역 각각에 대한 특징을 이용해 컷을 검출하였다. 그러나 본 논문에서는 웨이블릿 변환영역 하에서도 공간영역 특성을 유지하는 LL밴드 상의 칼라 히스토그램과 LH와 HL밴드의 에너지 값을 변환영역 특성으로 함께 고려하였다. 최근 영상 압축 표준에 웨이블릿을 이용한 압축기법이 사용되고 있으므로, 제안한 방법은 웨이블릿 압축 영상에서 압축을 해제할 필요 없이 검출하는데 사용되어질 수 있다. 제안한 방법의 성능평가를 위하여 광고, 뉴스, 스포츠, 영화 등 5개 분야의 다양한 TV 프로그램에서 약 10,000개의 프레임으로 실험한 결과, Recall에서는 약 90%, Precision에서는 약 94%의 컷 검출 성능을 나타내었다.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.55 no.1
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• pp.31-34
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• 2006

A simple robust fundamental frequency estimator on the time-frequency domain is proposed. Combined with the appropriately designed low-pass filter, the instantaneous frequency estimator based on the Teager-Kaiser energy function can detect the fundamental frequency of speech signal. The Teager-Kaiser function can be obtained through real computation and show the change of frequency as time goes. And when a speech block with N samples is processed with a lowpass fille. with length of L, it requires $O(N{\cdot}(L+5))operations,$ compared to $O(N{\cdot}2log_2N+L))operations$ in the recently introduced wavelet and conventional instantaneous frequency method. The computer simulation confirms the usefulness of the proposed fundamental frequency estimation method.

• International Journal of Naval Architecture and Ocean Engineering
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• v.12 no.1
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• pp.258-269
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• 2020

This paper proposes Snapping Shrimp Noise (SSN) detection and corrupted Orthogonal Frequency Division Multiplexing (OFDM) reconstruction methods to increase Bit Error Rate (BER) performance when OFDM transmitted signal is corrupted by impulsive SSNs in underwater acoustic communications. The proposed detection method utilizes multilayer wavelet packet decomposition for detecting impulsive and irregularly concentrated and SSN energy in specific frequency bands of SSN, and the proposed reconstruction scheme uses iterative decision directed-subcarrier reconstruction to recover corrupted OFDM signals using multiple carrier characteristics. Computer simulations were executed to show receiver operating characteristics curve for the detection performance and BER for the reconstruction. The practical ocean experiment of SAVEX 15 demonstrated that the proposed method exhibits a better detection performance compared with conventional detection method and improves BER by 250% and 1230% for uncoded and coded data, respectively, compared with the conventional reconstruction scheme.

• Structural Engineering and Mechanics
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• v.76 no.5
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• pp.591-598
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• 2020

Ultrasonic waves provide a non-destructive and sensitive way to monitor the concrete hydration. However, limited works are reported to monitor the evolution of the mechanical parameter at early ages. In this study, modified piezoelectric aggregates are embedded inside a concrete beam to excite and receive primary waves. A hydration index, namely, the variation of ultrasonic waveform (VUW) is developed to characterize the variation of the transmitted waves during the hydration process. The recorded hydration indices are compared with the compressive strength measured by destructive test at different ages. The results show that the VUW is closer to the compressive strength than the other two traditional hydration indices, ultrasonic velocity and wave packet energy. The proposed VUW provides a simple and accurate way to monitor the concrete hydration at early ages.

• Journal of the Korean Society of Radiology
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• v.8 no.2
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• pp.65-74
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• 2014

This study extracts characteristics of signal by wavelet transform to prove that the Compton scattering, occurred by changed the energy, influenced a picture. We also analyzed the extracted data and evaluated how much the picture of scatter-rays was affected by a change of tube voltage. For this study, we wrote a program with MatLap which is engineering tool and evaluated with the program on variation of scattered-rays due to increased tube voltage. The evaluation result shows both CR and DR have frequency changes of high frequency area by tube voltage variations and it proved that Compton scattering influences the picture. In conclusion, according to this study indicates that DR is more sensitive to radiation with high energy than CR. Therefore, the research on DR detector needs to be advanced as actual condition of clinical setting is being changed to DR circumstance gradually. From the result of this study, we expect that assessment method of the image quality using MatLab Tool becomes the official assessment method and very useful method.