• 비파괴검사학회지
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• 제33권3호
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• pp.283-288
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• 2013

This paper describes development of a high speed Doppler OFDI system for non-invasive vascular imaging. Doppler OFDI (optical frequency domain imaging) is one of the phase-resolved second generation OCT (optical coherence tomography) techniques for high resolution imaging of moving elements in biological tissues. To achieve a phase-resolved imaging, two temporally separated measurements are required. In a conventional Doppler OCT, a pair of massively oversampled successive A-lines is used to minimize de-correlation noise at the expense of significant imaging speed reduction. To minimize a de-correlation noise between targeted two measurements without suffering from significant imaging speed reduction, several methods have been developed such as an optimized scanning pattern and polarization multiplexed dual beam scanning. This research represent novel imaging technique using frequency multiplexed dual beam illumination to measure exactly same position with aimed time interval. Developed system has been verified using a tissue phantom and mouse vessel imaging.

• 천문학회보
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• 제44권1호
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• pp.46.2-46.2
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• 2019

We propose a deep learning model that can generate a waveform of coalescing binary black holes in merging and ring-down phases in less than one second with a graphics processing unit (GPU) as an approximant of gravitational waveforms. Up to date, numerical relativity has been accepted as the most adequate tool for the accurate prediction of merger phase of waveform, but it is known that it typically requires huge amount of computational costs. We present our method can generate the waveform with ~98% matching to that of the status-of-the-art waveform approximant, effective-one-body model calibrated to numerical relativity simulation and the time for the generation of ~1500 waveforms takes O(1) seconds. The validity of our model is also tested through the recovery of signal-to-noise ratio and the recovery of waveform parameters by injecting the generated waveforms into a public open noise data produced by LIGO. Our model is readily extendable to incorporate additional physics such as higher harmonics modes of the ring-down phase and eccentric encounters, since it only requires sufficient number of training data from numerical relativity simulations.

• 한국소음진동공학회논문집
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• 제23권3호
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• pp.249-257
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• 2013

This study newly presents a synthetic phase tuning technique to suppress the unwanted torsional mode while enhancing the desired torsional mode in a pipe. Specifically, we aim at the enhancement of the first torsional mode and the suppression of the undesired, second torsional mode. Earlier efforts were to enhance the desired wave mode only in the hope that the enhancement results in the suppression of the unwanted wave mode. Unlike these efforts, the suggested technique makes the complete cancellation of the unwanted wave mode but it is shown to enhance the desired first mode for torsional wave problems. In the present study, the synthetic phase tuning is developed for the cancellation of the unwanted wave mode, meaning that the number of necessary experimental equipments is reduced. Simulation and experiment were carried out to check the effectiveness of the proposed method. As an application of the suggested technique, we investigated the reflection and mode conversion characteristics of the first torsional mode according to the step thickness variation in a stepped pipe.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제17권7호
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• pp.1807-1822
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• 2023

Innovation and rapid increased functionality in user friendly smartphones has encouraged shutterbugs to have picturesque image macros while in work environment or during travel. Formal signboards are placed with marketing objectives and are enriched with text for attracting people. Extracting and recognition of the text from natural images is an emerging research issue and needs consideration. When compared to conventional optical character recognition (OCR), the complex background, implicit noise, lighting, and orientation of these scenic text photos make this problem more difficult. Arabic language text scene extraction and recognition adds a number of complications and difficulties. The method described in this paper uses a two-phase methodology to extract Arabic text and word boundaries awareness from scenic images with varying text orientations. The first stage uses a convolution autoencoder, and the second uses Arabic Character Segmentation (ACS), which is followed by traditional two-layer neural networks for recognition. This study presents the way that how can an Arabic training and synthetic dataset be created for exemplify the superimposed text in different scene images. For this purpose a dataset of size 10K of cropped images has been created in the detection phase wherein Arabic text was found and 127k Arabic character dataset for the recognition phase. The phase-1 labels were generated from an Arabic corpus of quotes and sentences, which consists of 15kquotes and sentences. This study ensures that Arabic Word Awareness Region Detection (AWARD) approach with high flexibility in identifying complex Arabic text scene images, such as texts that are arbitrarily oriented, curved, or deformed, is used to detect these texts. Our research after experimentations shows that the system has a 91.8% word segmentation accuracy and a 94.2% character recognition accuracy. We believe in the future that the researchers will excel in the field of image processing while treating text images to improve or reduce noise by processing scene images in any language by enhancing the functionality of VGG-16 based model using Neural Networks.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.1185-1188
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• 2002

The objective of this paper is to apply experimental methods to measure the in-plane vibration intensity of a semi-infinite beam. Two experimental methods have been implemented to measure the in-plane vibration intensity of the beam. The first method is the cross spectral intensity measurement method using two accelerometers. The second method is the frequency response method using the only one acrelerometer. It has the advantages of shortening measurement time and reducing accelerometer phase error. Experimental results showed that those experimental methods can be effectively used to measure the structural In-plane vibration intensity.

• 한국멀티미디어학회논문지
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• 제7권6호
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• pp.781-790
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• 2004

This paper presents a fourth-order cumulants based iterative algorithm for blind channel equalization. It is robust with respect to the existence of heavy Gaussian noise in a channel and does not require the minimum phase characteristic of the channel. In this approach, the transmitted signals at the receiver are over-sampled to ensure the channel described by a full-column rank matrix. It changes a single-input/single-output (SISO) finite-impulse response (FIR) channel to a single-input/multi-output (SIMO) channel. Based on the properties of the fourth-order cumulants of the over-sampled channel outputs, the iterative algorithm is derived to estimate the deconvolution matrix which makes the overall transfer matrix transparent, i.e., it can be reduced to the identity matrix by simple reordering and scaling. Both a closed-form and a stochastic version of the proposed algorithm are tested with three-ray multi-path channels in simulation studies, and their performances are compared with a method based on conventional second-order cumulants. Relatively good results are achieved, even when the transmitted symbols are significantly corrupted with Gaussian noise.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.2
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• pp.15-22
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• 2006

This paper presents a novel signal tracking algorithm for GNSS receivers using a MLE technique. In order to perform a robust signal tracking in severe signal environments, e.g., high dynamics for navigation vehicles or weak signals for indoor positioning, the MLE based signal tracking approach is adopted in the paper. With assuming white Gaussian additive noise, the cost function of MLE is expanded to the cost function of NLSE. Efficient and practical approach for Doppler frequency tracking by the MLE is derived based on the assumption of code-free signals, i.e., the cost function of the MLE for carrier Doppler tracking is used to derive a discriminator function to create error signals from incoming and reference signals. The use of the MLE method for carrier tracking makes it possible to generalize the MLE equation for arbitrary codes and modulation schemes. This is ideally suited for various GNSS signals with same structure of tracking module. This paper proposes two different types of MLE based tracking method, i.e., an iterative batch processing method and a non-iterative feed-forward processing method. The first method is derived without any limitation on time consumption, while the second method is proposed for a time limited case by using a 1st derivative of cost function, which is proportional to error signal from discriminators of conventional tracking methods. The second method can be implemented by a block diagram approach for tracking carrier phase, Doppler frequency and code phase with assuming no correlation of signal parameters. Finally, a state space form of FLL/PLL/DLL is adopted to the designed MLE based tracking algorithm for reducing noise on the estimated signal parameters.

• 한국통신학회논문지
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• 제27권5C호
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• pp.530-534
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• 2002

본 논문에서는 발진기의 안정도를 높이기 위해 2차 고조파를 병렬 궤환하는 새로운 구조로 자체 위상고정의 효과를 나타낼 수 있도록 제안하였다. 이 구조는 Hair-Pin 공진 발진기를 사용한 대역통과 여파기, 방향성 결합기, 기본주파수 발진기, 체배기, 그리고 출력전력의 궤환 및 격리를 위한 Wilkinson 전력분배기로 구성되었다. 제안된 발진기는 19.5GHz에서 2.5dBm의 출력을 나타내었으며 기본 주파수 억압 -25 dBc, 위상잡음은 중심주파수 19.5 GHz의 10 kHz offset 지점에서 -76.52 dBc/Hz의 안정된 특성을 얻었다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.1694-1700
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• 2004

In this paper, we propose the AWLS/MFT (Adaptive Weighed Least Squares/ Modulation Function Technique) devised by A. E. Pearson et al. for the transfer function estimation of a modal system and investigate the performance of several algorithms, the Gram matrix method, a Luenberger Observer (LO), Least Squares (LS), and Recursive Least Squares (RLS), for the estimation of initial conditions. With the benefit of the Modulation Function Technique (MFT), we can separate the estimation problem into two phases: the transfer function parameters are estimated in the first phase, and the initial conditions are estimated in the second phase. The LO method produces excellent IC estimates in the noise free case, but the other three methods show better performance in the noisy case. Finally, we compared our result with the Prony based method. In the noisy case, the AWLS and one of the three methods - Gram matrix, LS, and RLS- show better performance in the output Signal to Error Ratio (SER) aspect than the Prony based method under the same simulation conditions.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2008년도 하계종합학술대회
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• pp.619-620
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• 2008

In this paper, we propose a new hand gesture recognition scheme using hand poses captured from a web camera. The key idea of this scheme is to extract skin color from the background-subtracted image. To extract skin color, in the first phase, we subtract background by repeatedly comparing the stored initial frame with next frames. And then we eliminate noise using dynamic table. In the second phase, we exactly recognize hand gesture by extracting skin color from ${YC_b}{C_r}$ color region.