• Journal of Korea Multimedia Society
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• v.8 no.7
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• pp.961-973
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• 2005

In this paper, we proposed an adaptive steganography of color image using bit-planes and multichannel characteristics. Applying fixing threshold, if we insert information into all bit-planes of RGB channel, each channels showed different image quality. Therefore, we first defined the channel weight and the bit-plane weight to solve the fixing threshold problem of BPCS (bit-plane complexity steganography) method. We then proposed a new adaptive threshold method using the bit-plane weight of channels and the bit-plane complexity of cover image to increase insertion capacity adaptively In the experiment, we inserted information into the color images with the same image quality and same insertion capacity, and we analyzed the Insertion capacity and image quality. As a result, the proposed method increased the insertion capacity and improved the image quality than BPCS method.

• Journal of KIISE:Software and Applications
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• v.30 no.7_8
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• pp.719-726
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• 2003

This paper proposes a multimodal registration method for segmentation of the Visible Human color images, in which color characteristics of bones are very similar to those of its surrounding fat areas. Bones are initially segmented in CT images, and then registered into color images to lineate their boundaries in the color images. For the segmentation of bones in CT images, a thresholding method is developed. The registration method registers boundaries of bodies in CT and color images using a cross-correlation approach, in which the boundaries of bodies are extracted by thresholding segmentation methods. The proposed method has been applied to segmentation of bones in a head and legs whose boundary is ambiguous due to surrounding fat areas with similar color characteristics, and produced promising results.

• Proceedings of the Korea Multimedia Society Conference
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• 1998.04a
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• pp.143-147
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• 1998

카메라 영상에 의한 자동차 번호판 인식시스템은 영상 획득, 번호판 추출, 전처리, 문자 분리, 문자 인식 등 크게 5자기의 핵심 부분으로 구성된다. 따라서 자동차 번호판 인식시스템의 성능을 향상시키기 위해서는 이들 부분들 각각의 성능의 최적화가 필요하다. 본 연구는 자동차 번호판 인식시스템의 여러 단계 중 전처리에 해당하는 번호판 영역의 이진화에 관한 연구로서, 기존의 단일 임계치 방법과 다중 임계치 방법이 해결하지 못했던 부분을 보완하는 새로운 다중 임계치 방법을 제안한다. 본 논문에서 제안하는 다중 임계치 알고리즘(Adaptive Multi-threshold Algorithm)을 사용함으로써 gray-level 번호판 영상에 대해서 보다 깨끗한 이진 영상을 얻을 수 있었으며, 또한 이 알고리즘은 번호판 영역의 밝기값이 고르지 않은 영상에 대해서도 효율적인 알고리즘 임을 알 수 있었다.

• Korean Journal of Remote Sensing
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• v.24 no.4
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• pp.341-349
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• 2008

This study proposes new automatic thresholding method, which is important step for detecting binary change/non-change information using satellite images. Result value through pixel-based similarity measurement is calculated cumulatively with regular interval, and thresholding is pointed at the steep slope position. The proposed method is assessed in comparison with expectation-maximization algorithm and coner method using synthetic images, ALI images, and Hyperion images. Throughout the results, we validated that our method can guarantee the similar accuracy with previous algorithms. It is simpler than EM algorithm, and can be applied to the binormal histogram unlike the coner method.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.11A
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• pp.1087-1094
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• 2008

In this paper, we propose the acquisition method of the Cyclic-Prefix CDMA using Good-Autocorrelation-Sequence (GAS-CP-CDMA) system. The sequences for GAS-CP-CDMA are m-sequence and constant amplitude zero autocorrelation code (CAZAC) with good autocorrelation property. The GAS-CP-CDMA system is proposed for interference cancellation in multi-user and -path environment in co-cell. However, the reliable initial acquisition in multi-path fading channel and multi-user system environment is crucial. In this paper, non-coherent power detector and threshold value are used for discriminating signal acquisition. The sequence used for computer simulation is CAZAC. The simulation results show proper threshold value depends on the number of users. Through the computer simulation, we draw setting up method of the optimum threshold value for the GAS-CP-CDMA system.

• The KIPS Transactions:PartB
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• v.12B no.7 s.103
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• pp.729-736
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• 2005

In this paper. the proposed method for the digital watermarking is based on the multiresolution wavelet transform. The 1-level Discrete Wavelet Transform(DWT) coefficients of a $2N_{wx}{\times}2N_{wy}$ binary logo image used as a watermarks. The LL band and middle frequency band of the host image that the 3-level DWT has been performed are divided into $N_{wx}{\times}N_{wy}$ size and we use large coefficients at the divided blocks to make threshold. we set the thresholds that completely insert the watermark in each frequency of the host image. The thresholds in each frequency of the host image differ each other. The watermarks where is the same positions are added to the larger coefficients than threshold in the blocks at LL band and middle frequency band in order to prevent the quality deterioration of the host image. The watermarks are inserted in LL band and middle frequency band of the host image. In order to be invisibility of the watermark, the Human Visual System(HVS) is applied to the watermark. We prove the proper embedding method by experiment. We rapidly detect the watermark using this watermarking method. And because the small size watermarks are inserted by HVS, the results confirm the superiority of the proposed method on invisibility and robustness.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.11
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• pp.2636-2644
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• 2013

This paper is proposed a wavelet-based the order statistics MAD(Median Absolute Deviation) method of image fusion of Multi-image contaminated with visible image and infrared image. also The method of compared and defined the threshold the wavelet coefficients using MAD of the wavelet coefficients of the detail subbands was proposed to effectively fusion which of selected the high quality image of the two images. The existed fusion rule may be possible to get the distorted fusion image especially by the distortion in the relation between the pixel and indicator of two images in the existed fusion rules. In order to complement the disadvantage, the threshold of the proposed method sets up the image statistic and excludes the distortion. The hardware design is used FPGA of Xilinx and DSP system for the image fusion and compressed encoding of the proposed algorithm. Therefore the proposed method is totally verified by comparing with the several other multi-image and the proposed image fusion.

• Progress in Medical Physics
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• v.22 no.1
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• pp.42-51
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• 2011

Nuclear medicine images (SPECT, PET) were widely used tool for assessment of myocardial viability and perfusion. However it had difficult to define accurate myocardial infarct region. The purpose of this study was to investigate methodological approach for automatic measurement of rat myocardial infarct size using polar map with adaptive threshold. Rat myocardial infarction model was induced by ligation of the left circumflex artery. PET images were obtained after intravenous injection of 37 MBq $^{18}F$-FDG. After 60 min uptake, each animal was scanned for 20 min with ECG gating. PET data were reconstructed using ordered subset expectation maximization (OSEM) 2D. To automatically make the myocardial contour and generate polar map, we used QGS software (Cedars-Sinai Medical Center). The reference infarct size was defined by infarction area percentage of the total left myocardium using TTC staining. We used three threshold methods (predefined threshold, Otsu and Multi Gaussian mixture model; MGMM). Predefined threshold method was commonly used in other studies. We applied threshold value form 10% to 90% in step of 10%. Otsu algorithm calculated threshold with the maximum between class variance. MGMM method estimated the distribution of image intensity using multiple Gaussian mixture models (MGMM2, ${\cdots}$ MGMM5) and calculated adaptive threshold. The infarct size in polar map was calculated as the percentage of lower threshold area in polar map from the total polar map area. The measured infarct size using different threshold methods was evaluated by comparison with reference infarct size. The mean difference between with polar map defect size by predefined thresholds (20%, 30%, and 40%) and reference infarct size were $7.04{\pm}3.44%$, $3.87{\pm}2.09%$ and $2.15{\pm}2.07%$, respectively. Otsu verse reference infarct size was $3.56{\pm}4.16%$. MGMM methods verse reference infarct size was $2.29{\pm}1.94%$. The predefined threshold (30%) showed the smallest mean difference with reference infarct size. However, MGMM was more accurate than predefined threshold in under 10% reference infarct size case (MGMM: 0.006%, predefined threshold: 0.59%). In this study, we was to evaluate myocardial infarct size in polar map using multiple Gaussian mixture model. MGMM method was provide adaptive threshold in each subject and will be a useful for automatic measurement of infarct size.

• Journal of Satellite, Information and Communications
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• v.9 no.1
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• pp.22-27
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• 2014

In this paper, we analyzed performance of FFT based on pilot sensing scheme for DTV signal in fading environments. In order to detect the present and absent for advanced television system committee digital television (ATSC DTV), a pilot detection scheme based on FFT is employed. Also, these signals are applied to each fading environment. For evaluating the spectrum sensing performance, detection probability is derived. When threshold is decided, we refer to constant false alarm rate (CFAR) scheme. From simulation results, it is confirmed that the spectrum sensing performance is improved as increase of the false alarm rate. The result of this paper can be applied to implement the spectrum sensing part of cognitive radio (CR) systems.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.11A
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• pp.1113-1119
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• 2006

For a multi-user OFDM system in mobile channels which requires low-complexity in adaptive resource allocations, resource allocation algorithm using multi-threshold is proposed. The allocation scheme, which is performed by the multi-threshold values in descending order, considers only subcarriers over each threshold level. Moreover, some subcarriers with the lowest channel gain can be· removed in the present threshold level within the constraint of satisfaction of the required data rate, in order to allocate them to the other users when the allocation process of next threshold is executed. As a result, the proposed bandwidth and subcarrier algorithm has better system performances than the conventional allocation schemes in terms of required power and processing time, which is expected as a technique that improves the spectral efficiency of OFDM systems in a mobile environment.