• The Transactions of the Korean Institute of Power Electronics
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• v.13 no.3
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• pp.206-212
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• 2008

This paper proposes the PLL(Phase-Locked Loop) algorithm by a new FFT(Fast Fourier Transform) in a grid-connected PV PCS(Photovoltaics Power Conditionning System). The grid-connected inverter that is applied in a new renewable energy field needs the grid phase information for synchronism. Unlike the PLL which is normally used by three phase D-Q conversion, the preposed PLL algorithm using FFT has non-gain tuning and the powerful noise elimination by the characteristics of FFT. Both simulation and experimental result show that proposed algorithm has the good capacity.

• Journal of the Korean Society of Radiology
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• v.17 no.6
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• pp.911-917
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• 2023

The method of observing nodular changes on the liver surface using clinical ultrasonography is useful for diagnosing cirrhosis. However, the speckle noise that inevitably occurs in ultrasound images makes it difficult to identify changes in the liver surface and echo patterns, which has a negative impact on the diagnosis of cirrhosis. The purpose of this study is to model the median modified Wiener filter (MMWF), which can efficiently reduce noise in cirrhotic ultrasound images, and confirm its applicability. Ultrasound images were acquired using an ACR phantom and an actual cirrhotic patient, and the proposed MMWF algorithm and conventional noise reduction algorithm were applied to each image. Coefficient of variation (COV) and edge rise distance (ERD) were used as quantitative image quality evaluation factors for the acquired ultrasound images. We confirmed that the MMWF algorithm improved both COV and ERD values compared to the conventional noise reduction algorithm in both ACR phantom and real ultrasound images of cirrhotic patients. In conclusion, the proposed MMWF algorithm is expected to contribute to improving the diagnosis rate of cirrhosis patients by reducing the noise level and improving spatial resolution at the same time.

• The Transactions of the Korean Institute of Power Electronics
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• v.7 no.5
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• pp.499-508
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• 2002

In this paper, a novel wireless parallel operation algorithm of N+l redundant UPS system with no control interconnections for load-sharing is presented. The proposed control system eliminates the sensing noise and interconnections interference of conventional parallel operation system. To reduce a reactive power deviation in wireless control method, this technique automatically compensates for inverter parameter variation and line impedance imbalances with wireless auto-tuning method. In addition, to increase reliability on transient characteristics of parallel operation, a virtual injected impedance is adopted to eliminate a circulation current among inverter modules. Simulation results are provided in this paper to prove the proposed novel wireless algorithm.

• Proceedings of the KIEE Conference
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• 2002.07d
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• pp.2777-2779
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• 2002

본 논문에서는 영상안에서의 노이즈를 제거하기 위한 방법과 영상을 압축하기 위한 방법을 제안하였다. 영상을 필터링하기 위한 방법으로 해상도의 손상 없이 영상의 신호대잡음비(SNR)를 개선시킬 수 있는 국부 형태 적응 필터링을 제안하였다. 제안한 알고리즘에서는 템플릿 형태가 고정되어 있는 기존의 필터링 방법 대신에 다중 템플릿들을 정의하였다. 적응 템플릿 필터링을 자기공명영상에 적용할 때 기존의 필터링 방법들에 비하여 향상된 결과를 얻을 수 있으나. $T_1$ 영상과 같이 비교적 작은 동적 범위를 가진 영상에서는 에지에서 계단모양의 artifact가 발견되곤 한다. 본 논문에서는 다중 성분을 갖는 복셀들을 선별하여 이들에 대해서는 가장 큰 크기의 템플릿을 할당함으로써 artifact를 제거하는 방법을 제안하였다. 영상 압축에 있어서는 두 가지 모델이 제안되었다. 첫 번째로, 향상된 정수 기반 웨이블렛 변환을 사용한 무손실에 가까운 압축을 제안하였으며, 두 번째로, 완전 복원이 가능한 정수 기반 웨이블렛 변환을 사용한 통합된 유/무손실 압축을 제안하였다. 모의 실험에서, 제안된 알고리즘에 의해 재구성된 영상들은 부동 소수점 기반 웨이블렛 변환과 JPEG에 의해 재구성된 영상들에 비해 높은 신호대잡음비를 보였다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.16 no.4
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• pp.80-91
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• 2002

An on-line ultrasonic detector was developed to continuously monitor the ultrasonic signal due to partial discharge in transformer in service. The on-line ultrasonic detector has a band-pass filter designed to measure only the frequencies from 50 to 300[㎑] of ultrasonic signal, to remove electrical and mechanical noises from outside of the transformer, and tlle ultrasonic sensor contains a pre-amplifier with 60[dB] gain. The ultrasonic signal discrimination algorithm which discriminates the ultrasonic signal duration was developed to remove the ultrasonic signal due to OLTC operation having similar characteristics to those due to partial discharge. The reliability of the on-line ultrasonic detector developed in this study was convinced of measurement the ultrasonic signals from the model. transformer in laboratory and transformer in service.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.8
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• pp.1655-1666
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• 2015

In this paper, user-position estimation method is proposed by using a single camera for both indoor and outdoor environments. Conventionally, the GPS of RF-based estimation methods have been widely studied in the literature for outdoor and indoor environments, respectively. Each method is useful only for indoor or outdoor environment. In this context, this study adopts a vision-based approach which can be commonly applicable to both environments. Since the distance or position cannot be extracted from a single still image, the reference images pro-stored in image database are used to identify the current position from the single still image captured by a single camera. The reference image is tagged with its captured position. To find the reference image which is the most similar to the current image, the SURF algorithm is used for feature extraction. The outliers in extracted features are discarded by using RANSAC algorithm. The performance of the proposed method is evaluated for two buildings and their outsides for both indoor and outdoor environments, respectively.

• Journal of KIISE:Software and Applications
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• v.37 no.8
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• pp.599-610
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• 2010

Color laser printers are nowadays abused to print or forge official documents and bills. Identifying color laser printers will be a step for media forensics. This paper presents a new method to identify color laser printers with printed color images. Since different printer companies use their own printing process, each of printed papers from different printers has a little different invisible noise. After the wiener-filter is used to analyze the invisible noises from each printer, we extract some features from these noises by calculating a gray level co-occurrence matrix. Then, these features are applied to train and classify the support vector machine for identifying the color laser printer. In the experiment, we use total 2,597 images from 7 color laser printers. The results prove that the presented identification method performs well using the noise features of color printed images.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.05a
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• pp.184-187
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• 2018

The most important factor in the prevention and treatment of cerebral infarction is to increase cerebral blood flow. Methods for increasing cerebral blood flow include drug-based methods, the surgery, invasive procedures directly inserting medical devices into the artery(NeuroFloTM) and so on. The noninvasive cerebral blood flow increasing device proposed in this paper can reduce the burden on the patient because the probability of complication is low and the treatment level can be determined according to the blood pressure state of the patient. In implementing such a noninvasive cerebral blood flow increasing device, it is important to measure the accurate mean arterial pressure for provision the appropriate level of treatment for the patient. Therefore, to remove a noise, analog and digital filters were used and algorithm for peak value detection, pump control algorithms and so on were.

• Journal of the Institute of Convergence Signal Processing
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• v.11 no.2
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• pp.151-156
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• 2010

This paper is a study on image noise reduction of modified sigma filter by image decomposition using directivity. Conventional sigma filter has been shown to be a good solution both in terms of filtering accuracy and computational complexity. However, the sigma filter does not preserve well small edges especially for high level of additive noise. In this paper, we propose here a new method using a modified sigma filter. In our proposed method the input image is first decomposed in two components that have features of horizontal, vertical and diagonal direction. Then, two components are applied HPF and LPF. By applying a conventional sigma filter separately on each of them, the output image is reconstructed from the filtered components. Added noise is removed and our proposed method preserves the edges from the image. Comparative results from experiments show that the proposed algorithm achieves higher gains, on average, 2.6 dB PSNR than the sigma filter and 0.5 dB PSNR than the modified sigma filter. When relatively high levels of noise added, the proposed algorithm shows better performance than two conventional filters.

• Journal of radiological science and technology
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• v.40 no.4
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• pp.589-594
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• 2017

The objective of this study was to evaluate the enhancement effects of the quantum denoising system (QDS) on brain CT images. This retrospective study was conducted with 45 adults who visited G Radiology located in Gyungbuk for having brain CT tests between Jul 2017 and Oct 2017 after receiving consents. Subjects were divided into a control group (A group; no QDS(-) application during the brain CT test) and a treatment group (B Group; QDS(+) application during the brain CT test). The following conclusions were obtained from the study. The noise values at the Pons part and the Vermis part were significantly (p<0.05) lower in B Group ($Pons=5.41{\pm}1.05HU$; $Vermis=5.28{\pm}0.73HU$) than A Group ($Pons=6.92{\pm}0.98HU$; Vermis=6.72). The SNR values at the Pons part and the Vermis part were significantly (p<0.05) higher in B Group ($Pons=7.28{\pm}2.56$; $Vermis=8.63{\pm}3.04$) than A Group ($Pons=5.21{\pm}1.28$; $Vermis=6.23{\pm}1.49$). In conclusion, the results of this study suggested that the application of QDS to the brain CT test would enhance the signal to noise ratio (SNR) and the contrast to noise ratio (CNR) to provide an image more appropriate for diagnosis.