• JSTS:Journal of Semiconductor Technology and Science
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• 제16권1호
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• pp.80-90
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• 2016

Thanks to superior leakage energy efficiency compared to SRAM cells, STTRAM cells are considered as a promising alternative for a memory element in on-chip caches. However, the main disadvantage of STTRAM cells is high write energy and latency. In this paper, we propose a low-cost write filter (WF) cache which resides between the load/store queue and STTRAM-based L1 data cache. To maximize efficiency of the WF cache, the line allocation and access policies are optimized for reducing energy consumption of STTRAM-based L1 data cache. By efficiently filtering the write operations in the STTRAM-based L1 data cache, our proposed WF cache reduces energy consumption of the STTRAM-based L1 data cache by up to 43.0% compared to the case without the WF cache. In addition, thanks to the fast hit latency of the WF cache, it slightly improves performance by 0.2%.

• Journal of Radiation Protection and Research
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• 제46권4호
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• pp.160-169
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• 2021

Background: Dual-energy X-ray images (DEI) can distinguish or improve materials of interest in a two-dimensional radiographic image, by combining two images obtained from separate low and high energies. The concepts of DEI performance describing the performance of double-exposure DEI systems in the Fourier domain been previously introduced, however, the performance of double-exposure DEI itself in terms of various parameters, has not been reported. Materials and Methods: To investigate the DEI performance, signal-difference-to-noise ratio, modulation transfer function, noise power spectrum, and noise equivalent quanta were used. Low- and high-energy were 60 and 130 kVp with 0.01-0.09 mGy, respectively. The energy-separation filter material and its thicknesses were tin (Sn) and 0.0-1.0 mm, respectively. Noise-reduction (NR) filtering used the Gaussian-filter NR, median-filter NR, and anti-correlated NR. Results and Discussion: DEI performance was affected by Sn-filter thickness, weighting factor, and dose allocation. All NR filtering successfully reduced noise, when compared with the dual-energy (DE) images without any NR filtering. Conclusion: The results indicated the significance of investigating, and evaluating suitable DEI performance, for DE images in chest radiography applications. Additionally, all the NR filtering methods were effective at reducing noise in the resultant DE images.

• 방사성폐기물학회지
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• 제5권3호
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• pp.257-265
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• 2007

한국원자력연구원 방사성폐기물 저장시설에는 2006년 기준으로 약 1,000 여개(200L 환산)의 폐필터가 저장중이며, 그 발생량은 계속 증가하는 추세에 있다. 현재 저장시설의 저장 공간 확보뿐만 아니라 폐필터의 효율적인 관리를 위하여 비닐 백에 넣어 저장 및 관리되고 있는 폐필터들을 적절한 압축 처리 과정을 거쳐 최종적으로 규격화된 드럼에 포장하려는 계획을 가지고 있다. 이를 위해, 먼저 과거 발생이력을 조사함으로서 저장중인 폐필터들의 분류를 통한 그룹화를 수행하였다. 또한 드럼포장을 위해서는 사전에 핵종평가가 수행되어야 하며, 그 방법으로는 폐필터의 해체 없이 표면선량률을 측정하여 대표시료를 채취하며, 이 시료에 대하여 방사성폐기물 인도규정에서 요구하는 수준의 핵종분석을 수행할 것이다. 그리고 드럼포장을 위해, 방사성폐기물 처리시설에서 개발된 폐필터 처리장치를 이용하여 직육면체 형의 폐필터를 원주형 성형을 함으로서 드럼에 넣은 후, 최종적으로 수직 압축함으로써 폐필터를 처리하고자 한다.

• 한국방사선학회논문지
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• 제15권1호
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• pp.71-78
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• 2021

엑스선 영상을 획득하는 경우에 연속 엑스선을 사용할 경우, 다양한 엑스선 에너지로 인해 같은 물질이라도 두께에 따라 영상에서 정확하게 표현되지 않을 수 있다. 이를 해결하기 위해 엑스선 에너지스펙트럼을 변경하여 영상의 질을 향상 시킬 수 있도록 하였다. SPEKTR v3.0을 사용하여 부가 필터를 추가한 엑스선 에너지스펙트럼과 고유 필터만을 사용한 일반 엑스선 에너지스펙트럼을 획득하였다. 획득한 엑스선 에너지스펙트럼을 Geant4 Application for Tomographic Emission(GATE)의 방사선원으로 사용하여 시뮬레이션을 수행하였다. GATE 데이터를 사용하여 부가 필터가 사용된 엑스선 영상과 부가 필터를 사용하지 않은 엑스선 영상을 재구성한 영상을 74 keV의 단일 에너지 영상을 통해서 비교 분석하였다. 부가 필터를 사용하지 않은 엑스선 에너지스펙트럼을 사용한 경우 같은 물질이라도 두께에 따라 투과한 엑스선의 양이 물질 두께에 따라 감소되는 양과는 상이한 양상을 보인 반면, 부가 필터를 사용한 경우 두께에 따라 투과된 엑스선의 양이 물질 두께에 따라 감소되는 양과 유사한 결과가 나왔다. 즉, 감소되는 선량이 단일 에너지를 사용했을 때와 비슷한 결과가 나왔다. 부가 필터를 사용하여 엑스선 에너지스펙트럼을 변경하여 엑스선 영상을 획득할 경우 엑스선의 투과에 대한 보다 정확한 결과의 값을 획득할 수 있다. 영상의학검사에서 부가 필터의 적절한 사용이 영상의 질을 높이는데 크게 작용한다는 것을 확인하였다.

• 한국음향학회지
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• 제22권8호
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• pp.687-693
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• 2003

본 논문에서는 적응적인 방식으로 필터의 성능을 향상시킴으로써 잡음에 의해 열화된 오디오 신호의 음질을 개선하는 알고리즘을 제안한다. 주파수 영역으로 변환된 잡음에 의해 열화된 신호를 바크 대역으로 분할하여 청각 자극 에너지를 계산하고, 필터를 적응적으로 적용하여 잡음 에너지를 제거함으로써 본래의 신호를 획득하는 방식을 사용하였다. 기존의 방식에서는 묵음 구간에서 획득한 잡음 에너지를 사용하여 필터를 구성하여 사용하며, 이때 잡음의 에너지가 급격하게 변화한다면 음질의 개선률이 급격하게 감소함을 알 수 있다. 그러나 제안하는 방식에서는 잡음 에너지가 급격하게 변화하여도 음질 개선률에는 변화가 적음을 알 수 있었다. 기존 방식과의 비교를 위하여 신호대 잡음비와 잡음대 마스킹비를 비교하였고 청각 테스트를 수행하여 그 결과로부터 향상된 음질 개선을 확인할 수 있었다.

• 상하수도학회지
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• 제19권2호
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• pp.144-148
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• 2005

The industrial development of large scale deep bed filters has been a very important step in the process of drinking water production and more recently in the tertiary treatment of wastewater. The target of deep bed filtration is the retention is the retention of small particles generally smaller than 30 microns at relatively small concentration, generally less than 30 mg/l from natural water (surface water or aquifers) or secondary treated wastewater. The relation between the retention efficiency and the characteristics of the particles has been extensively studied experimentally and through different models of retention. During the last years the development of new technologies (fiber filter, membrane modules) lead to more intensive processes compared to conventional sand filtration. Fiber filters can combine intensification with a decrease in specific energy needed however they cannot be operated under gravity like sand filters. Membrane filters (UF or MF) are much more intensive and efficient than sand filters. The specific energy needed is not so high (about $0.1Kwh/M^3$) but is higher than sand or fiber filter. A Life Cycle Analysis (LCA) has to be made for a complete comparison between these technologies taking in account that the efficiency of particle retention obtained by membrane filters is unique.

• 대한방사선기술학회지:방사선기술과학
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• 제44권1호
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• pp.39-46
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• 2021

This study confirmed the usefulness of the copper filter according to the mode change by comparing and analyzing the energy change according to the application of the copper filter and the change in effective dose and image quality according to the distance to the subject in the DR(Digital Radiography) system. The average energy increased when the copper filter was applied and the reduction rate by 50% of mAs was increased as the thickness of the copper filter increased according to the application of the 10 kVp rule in AEC mode. The effective dose decreased as the thickness increased when the copper filter was applied in AEC(Automatic Exposure Control) mode and manual mode according to the application of the 10 kVp rule, and the decrease rate decreased with increasing 10 kVp increments. As a result of analyzing the dicom images for AEC mode and manual mode with Image J. the PSNR(Peak Signal to Noise Ratio) values were approximate values of less than 30 dB for each mode and for each copper filter thickness. When the copper filter was applied, the average energy increased, so when the 10 kVp rule was applied, the mAs for each mode could be reduced, and the effective dose could also be reduced. However, as the distance and tube voltage increased, the reduction rate of mAs decreased, and the quality of the image was found to decrease when the copper filter was applied, but there was no difference in quality of the image when the copper filter thickness increased.

• 대한원격탐사학회지
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• 제27권6호
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• pp.693-701
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• 2011

Image registration is an essential process to analyze the time series of satellite images for the purpose of image fusion and change detection. The Mutual Information (MI) is commonly used as similarity measure for image registration because of its robustness to noise. Due to the radiometric differences, it is not easy to apply MI to multi-temporal satellite images using directly the pixel intensity. Image features for MI are more abundantly obtained by employing a Gabor filter which varies adaptively with the filter characteristics such as filter size, frequency and orientation for each pixel. In this paper we employed Bidirectional Gabor Filter Energy (BGFE) defined by Gabor filter features and applied the BGFE to similarity measure calculation as an image feature for MI. The experiment results show that the proposed method is more robust than the conventional MI method combined with intensity or gradient magnitude.

• Journal of Information Processing Systems
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• 제15권3호
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• pp.550-569
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• 2019

We propose approaches for improving Bloom filter in terms of false positive probability and membership query speed. To reduce the false positive probability, we propose special type of additional Bloom filters that are used to handle false positives caused by the original Bloom filter. Implementing the proposed approach for a routing table lookup, we show that our approach reduces the routing table lookup time by up to 28% compared to the original Bloom filter by handling most false positives within the fast memory. We also introduce an approach for improving the membership query speed. Taking the hash table-like approach while storing only values, the proposed approach shows much faster membership query speed than the original Bloom filter (e.g., 34 times faster with 10 subsets). Even compared to a hash table, our approach reduces the routing table lookup time by up to 58%.

• 한국멀티미디어학회논문지
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• 제7권12호
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• pp.1657-1664
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• 2004

We propose a method that classifies images into two object types man-made and natural objects. A central object is extracted from each image by using central object extraction method[1] before classification. A central object in an images defined as a set of regions that lies around center of the image and has significant color distribution against its surrounding. We define three measures to classify the object images. The first measure is energy of edge direction histogram. The energy is calculated based on the direction of only non-circular edges. The second measure is an energy difference along directions in Gabor filter dictionary. Maximum and minimum energy along directions in Gabor filter dictionary are selected and the energy difference is computed as the ratio of the maximum to the minimum value. The last one is a shape of an object, which is also represented by Gabor filter dictionary. Gabor filter dictionary for the shape of an object differs from the one for the texture in an object in which the former is computed from a binarized object image. Each measure is combined by using majority rule tin which decisions are made by the majority. A test with 600 images shows a classification accuracy of 86%.