• The Journal of the Acoustical Society of Korea
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• v.37 no.1
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• pp.12-20
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• 2018

Efforts have been made to reconstruct low-resolution underwater images to high-resolution ones by using the image SR (Super-Resolution) method, all to improve efficiency when acquiring side-scan sonar images. As side-scan sonar images are similar with the optical images with respect to exploiting 2-dimensional signals, conventional image restoration methods for optical images can be considered as a solution. One of the most typical super-resolution methods for optical image is a sparse coding and there are studies for verifying applicability of sparse coding method for underwater images by analyzing sparsity of underwater images. Sparse coding is a method that obtains recovered signal from input signal by linear combination of dictionary and sparse coefficients. However, it requires huge computational load to accurately estimate sparse coefficients. In this study, a sparse coding based underwater image super-resolution method is applied while a selective reconstruction method for object region is suggested to reduce the processing time. For this method, this paper proposes an edge detection and object and non object region classification method for underwater images and combine it with sparse coding based image super-resolution method. Effectiveness of the proposed method is verified by reducing the processing time for image reconstruction over 32 % while preserving same level of PSNR (Peak Signal-to-Noise Ratio) compared with conventional method.

• Journal of the Korean Society of Radiology
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• v.15 no.2
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• pp.173-179
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• 2021

Scattered x-ray generated by digital radiography systems also have the advantage of increasing signals, but ultimately detectability is reduced by decreasing resolution and increasing noise of x-ray images transmitted objects. An indirect method of measuring scattered x-ray in a modulation-transfer function (MTF) for evaluating resolution in a spatial-frequency domain can be considered as a drop in the MTF value corresponding to zero-frequency. In this study, polymethyl methacrylate (PMMA) was used as a patient tissue equivalent, and MTFs were obtained for various thicknesses to quantify the effect of scattered x-ray on resolution. X-ray image signals were observed to decrease by 35 ~ 83% with PMMA thickness increasing, which is determined by the absorption or scattering of x-rays in PMMA, resulting in reduced MTF and increased scatter fraction. The method to compensate for MTF degradation by PMMA resulted in the MTF inflation without considering the optical spreading generated by the indirect-conversion type detector. Data fitting or zero-padding are needed to compensate for MTF more reasonably on edge-spread function or line-spread function.

• Journal of the KSME
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• v.16 no.4
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• pp.41-48
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• 1976

재료의 피로문제에 대해서는 꽤 오래 전부터 많은 연구가 이루어져왔고, 피로의 현상파악에서부 터 피로이론의 구명, 나아가서는 실제문제로서의 피로설계, 피로수명예측 등에 기여한 업적은 아 주 크다 하겠다. 그러나 종래의 피로문제연구의 방향이, S-N 곡선에서 얻어지는 피로한계강도 (더 정확한 표현으론 피로파괴한계강동)에 바탕을 두고, 정력확적인 설계관례인 안전계수의 도입 을 빌려, 피로강도를 실용화할려는 선에서 이루어져 왔다고 보겠다. 재료의 피로한계강도란, 그 정의로 미루어, 다분히 정적으로는 극한강도 또는 피로강도의 개념에 견주어 질 수 있는 공칭응 력으로써 탄성학적으로 해석될 수도 없고, 다만 탄역성이론의 개념을 바탕으로 근사해석례만이 허용되고 있을 뿐이다. 재료에는 소위 평활재이건 절결재이건 간에 또 검출여부에 관계없이, 내외 부에 대소각종의 결함이나 역학적 불연속부가 잠재해있음은 이미 공지의 사실이며, 이들 결합, 불 연속부등이 외하중하에서 응분의 응력집중원이 되어 재료를 전반적인 파괴로 몰고 갈 수 있다 함 도, 또한 이러한 역학적거동이 피로파괴에 까지 확장해석될 수 있을 것이란 것도 이미 잘 알려져 있는 터이라 하겠다. 재료내외부의 제결합을 응력집중이 극대인 crack로 대체해서 외하중하에서 의 응력장거동을 해석한 선형탄성파괴역학(LEFM)은, 바로 이러한 실제재료의 강도설계에 보다 큰 정확성을 부여한 방법론적 학문이라 하겠고, 나아가서는 재료의 파괴기구를 파헤치는데 진일 보적인 역학적인 수법이라 하겠다. 취성파괴, 연성파괴에 바탕을 둔 파괴역학(LEFM)을 피로파괴 에 적용시키는 데는 상당한 문제점들을 수반할 것임은 충분히 인지되나, 제한된 경계조건하에서 의 적용 예는 종래의 어떤 방법에 의한 것 보다도 피로강도설계, 안전사용 피로수명예측 등에 획기적인 진전을 보여주고 있다. 파괴역학은 crack 재의 강도학이고, 더 구체적으로 음력학대계수 (stress intensity factor) K 또는 이와 연연되는 parameter 인 strain energy release rate(G), crack-tip plactic zone size r$_{p}$,.rho., crack-tip opening displacement .phi., strain intensity 등을 쓰는 재료강도학이기 때문에, 이 수법을 피로파괴에 적용시킴은, 종래의 공칭응력으로 피로 문제를 다루던 방법과는 판이하다 하겠다. 본고에선 파괴역학의 관점에서 피로구열의 안정성장을 논하고, 과거 10여년간의 피로 crack문제에 대한 연구방법, 실험방법 등을 소개하는 방향으로 고 를 진행시켜 나가겠다.

• Journal of the Korean Association of Geographic Information Studies
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• v.9 no.4
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• pp.224-232
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• 2006

This study investigates to detect Sea Surface Temperature (SST) and land cover change after tide embankment construction using Landsat Thematic Mapper (TM) Thermal Infrared (TIR) band data at Shihwa Lake and surrounding area. SST measurement is important for studies of both the structure of the ocean and as the thermal boundary between the ocean and the atmosphere. Since 1970s, the derivation of SST by satellite remote sensing (RS) has been applied to earth surface using Advanced Very High Resolution Radiometer (AVHRR) and Landsat TM. However, AVHRR has restriction in deriving SST in the area whose shoreline is complicated like western coast in South Korea because of coarse spatial resolution. The TIR band of TM images can be used to detect SST change whose shoreline is complicated and narrow like the study site. Thus, multi-temporal TM images were used for SST change detection in this study.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.8
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• pp.903-910
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• 2016

This paper investigates an advanced receiver for interference mitigation of downlink control channel in the 3GPP Rel-13 standard. There are several features for downlink throughput performance improvement with inter-cell interference management such as network coordination and advanced receivers during Rel-10~Rel-12. These features can be operated always under the assumption that UE perfectly decodes control channels (PCFICH and PDCCH) of serving cell. However, the performance of control channels could be deteriorated in the cell edge region due to inter-cell interference. In this paper, we introduce the advanced receivers and analyze performance for control channel interference mitigation (CCIM) based on 3GPP Rel-13 standard. Additionally, we propose UE behavior depending on network condition.

• The KIPS Transactions:PartB
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• v.16B no.4
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• pp.281-288
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• 2009

This paper proposes a novel algorithm for the efficient classification and annotation of medical images, especially X-ray images. Since X-ray images have a bright foreground against a dark background, we need to extract the different visual descriptors compare with general nature images. In this paper, a Color Structure Descriptor (CSD) based on Harris Corner Detector is only extracted from salient points, and an Edge Histogram Descriptor (EHD) used for a textual feature of image. These two feature vectors are then applied to a multi-class Support Vector Machine (SVM), respectively, to classify images into one of 20 categories. Finally, an image has the Annotation Code Array based on the pre-defined hierarchical relations of categories and priority code order, which is given the several optimal keywords by the Annotation Code Array. Our experiments show that our annotation results have better annotation performance when compared to other method.

• Journal of Biomedical Engineering Research
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• v.16 no.3
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• pp.289-300
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• 1995

The conventionally used method requires centerline of vessels to estimate the vessel diameter. Two methods of estimating the centerline of vessels are reported : One is manually observer-defined method. This potentially contributes to inter-and intra-observer variability. And the other is to auto- matically detect the centerline of vessels. But this is very complicated method. In this paper, we propose a new method of estimating vessel diameter using direction codes and position informs:ion without detecting centerline. Since this method detects the vessel boundary and direction code at d same time, it simplifies the procedure and reduces execution time in estimating the vessel diameter. Compared to a method that automatically estimates the vessel diAmeter uslng centerline, our method provides improved accuracy in image with poor contrast, branching or obstructed vessels. Also, this provides a good compression of boundary description, because each direction code element can be coded with 3 bits only, instead of the 4 bytes required for the storage of the coordinates of each border pixel. Our experiments demonstrate the usefulness of the technique using direction code for quantitative analysis of coronary angiography Experimental results Justify the validity of the proposed method.

• Journal of Broadcast Engineering
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• v.9 no.1
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• pp.43-53
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• 2004

In this paper, we propose a robust deinterlacing algorithm which combines edge dependent interpolation (EDI) and global motion compensation (GMC). Generally, EDI algorithm shows a visually better performance than any other deinterlacing algorithm using one field. However, due to the restriction of information in one field, a high duality progressive image from Interlaced sources cannot be acquired by intrafield methods. On the contrary, since algorithms based on motion compensation make use of not only spatial information but also temporal information, they yield better results than those of using one field. However, performance of algorithms based on motion compensation depends on the performance of motion estimation. Hence, the proposed algorithm makes use of mixing process of EDI and GMC. In order to obtain the best result, an adaptive thresholding algorithm for detecting the failure of GMC is proposed. Experimental results indicate that the proposed algorithm outperforms the conventional approaches with respect to both objective and subjective criteria.

• Journal of Broadcast Engineering
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• v.18 no.3
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• pp.372-379
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• 2013

In this paper, we proposed a content-based image retrieval algorithm using local binary patterns and HSV color histogram. Images are retrieved using image input in image retrieval system. Many researches are based on global feature distribution such as color, texture and shape. These techniques decrease the retrieval performance in images which contained background the large amount of image. To overcome this drawback, the proposed method extract background fast and emphasize the feature of object by shrinking the background. The proposed method uses HSV color histogram and Local Binary Patterns. We also extract the Local Binary Patterns in quantized Hue domain. Experimental results show that the proposed method 82% precision using Corel 1000 database.

• Journal of Satellite, Information and Communications
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• v.6 no.1
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• pp.57-62
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• 2011

The VLC (visible light communication) system is communication technology using visible rays (RGB) that come out in LED device. It is energy curtailment effect and possible in ubiquitous network service applications. Also, VLC system has the above advantage about that the communication throughout the whole room is enabled by high power lighting and lighting equipment with white colored LED which are easy to install and have good outward appearance. However, the signal detection performance for the receiver near the network of transmitter boundary is severely degraded and the transmission efficiency decreased due to the influence of the interference signal from the adjacent networks. In this paper, we propose an interference mitigation method with optical beamforming in VLC systems, and evaluate the reception performance. For the system BER, the proposed optical beamforming transmission demonstrates the performance enhancement compared to the not using the optical beamforming scheme, and up to about 5~6dB SNR performance gain is achieved.