• Journal of Communications and Networks
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• v.12 no.3
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• pp.240-245
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• 2010

Jacket matrices, motivated by the complex Hadamard matrix, have played important roles in signal processing, communications, image compression, cryptography, etc. In this paper, we suggest a novel approach to design a simple class of space-time block codes (STBCs) to reduce its peak-to-average power ratio. The proposed code provides coding gain due to the characteristics of the complex Hadamard matrix, which is a special case of Jacket matrices. Also, it can achieve full rate and full diversity with the simple decoding. Simulations show the good performance of the proposed codes in terms of symbol error rate. For generality, a kind of quasi-orthogonal STBC may be similarly designed with the improved performance.

• Radiation Oncology Journal
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• v.28 no.3
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• pp.155-165
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• 2010

Purpose: In order to evaluate the positional uncertainty of internal organs during radiation therapy for treatment of liver cancer, we measured differences in inter- and intra-fractional variation of the tumor position and tidal amplitude using 4-dimentional computed radiograph (DCT) images and gated orthogonal setup kilovolt (KV) images taken on every treatment using the on board imaging (OBI) and real time position management (RPM) system. Materials and Methods: Twenty consecutive patients who underwent 3-dimensional (3D) conformal radiation therapy for treatment of liver cancer participated in this study. All patients received a 4DCT simulation with an RT16 scanner and an RPM system. Lipiodol, which was updated near the target volume after transarterial chemoembolization or diaphragm was chosen as a surrogate for the evaluation of the position difference of internal organs. Two reference orthogonal (anterior and lateral) digital reconstructed radiograph (DRR) images were generated using CT image sets of 0% and 50% into the respiratory phases. The maximum tidal amplitude of the surrogate was measured from 3D conformal treatment planning. After setting the patient up with laser markings on the skin, orthogonal gated setup images at 50% into the respiratory phase were acquired at each treatment session with OBI and registered on reference DRR images by setting each beam center. Online inter-fractional variation was determined with the surrogate. After adjusting the patient setup error, orthogonal setup images at 0% and 50% into the respiratory phases were obtained and tidal amplitude of the surrogate was measured. Measured tidal amplitude was compared with data from 4DCT. For evaluation of intra-fractional variation, an orthogonal gated setup image at 50% into the respiratory phase was promptly acquired after treatment and compared with the same image taken just before treatment. In addition, a statistical analysis for the quantitative evaluation was performed. Results: Medians of inter-fractional variation for twenty patients were 0.00 cm (range, -0.50 to 0.90 cm), 0.00 cm (range, -2.40 to 1.60 cm), and 0.00 cm (range, -1.10 to 0.50 cm) in the X (transaxial), Y (superior-inferior), and Z (anterior-posterior) directions, respectively. Significant inter-fractional variations over 0.5 cm were observed in four patients. Min addition, the median tidal amplitude differences between 4DCTs and the gated orthogonal setup images were -0.05 cm (range, -0.83 to 0.60 cm), -0.15 cm (range, -2.58 to 1.18 cm), and -0.02 cm (range, -1.37 to 0.59 cm) in the X, Y, and Z directions, respectively. Large differences of over 1 cm were detected in 3 patients in the Y direction, while differences of more than 0.5 but less than 1 cm were observed in 5 patients in Y and Z directions. Median intra-fractional variation was 0.00 cm (range, -0.30 to 0.40 cm), -0.03 cm (range, -1.14 to 0.50 cm), 0.05 cm (range, -0.30 to 0.50 cm) in the X, Y, and Z directions, respectively. Significant intra-fractional variation of over 1 cm was observed in 2 patients in Y direction. Conclusion: Gated setup images provided a clear image quality for the detection of organ motion without a motion artifact. Significant intra- and inter-fractional variation and tidal amplitude differences between 4DCT and gated setup images were detected in some patients during the radiation treatment period, and therefore, should be considered when setting up the target margin. Monitoring of positional uncertainty and its adaptive feedback system can enhance the accuracy of treatments.

• Journal of Information Processing Systems
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• v.16 no.6
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• pp.1343-1358
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• 2020

In the stagewise arithmetic orthogonal matching pursuit algorithm, the weak threshold used in sparsity estimation is determined via maximum iterations. Different maximum iterations correspond to different thresholds and affect the performance of the algorithm. To solve this problem, we propose an improved variable weak threshold based on the stagewise arithmetic orthogonal matching pursuit algorithm. Our proposed algorithm uses the residual error value to control the weak threshold. When the residual value decreases, the threshold value continuously increases, so that the atoms contained in the atomic set are closer to the real sparsity value, making it possible to improve the reconstruction accuracy. In addition, we improved the generalized Jaccard coefficient in order to replace the inner product method that is used in the stagewise arithmetic orthogonal matching pursuit algorithm. Our proposed algorithm uses the covariance to replace the joint expectation for two variables based on the generalized Jaccard coefficient. The improved generalized Jaccard coefficient can be used to generate a more accurate calculation of the correlation between the measurement matrixes. In addition, the residual is more accurate, which can reduce the possibility of selecting the wrong atoms. We demonstrate using simulations that the proposed algorithm produces a better reconstruction result in the reconstruction of a one-dimensional signal and two-dimensional image signal.

• Journal of the Korean Professional Engineers Association
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• v.16 no.4
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• pp.15-19
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• 1983

Therefore the use of Hadamard transform in the image processing requires only the real number operations and results in the computational advantages. Recently, however, certain degradation aspects have been reported. In this paper we propose a WH matrixtwhich retains the main properties of Hadamard matrix. The actual improvement of the image transmission in the inner part of the picture has been demonstrated by the computer simulated image developments. The orthogonal transforms such as Hadamard transform offers a useful facility in the digital signal processing. As the size of the transmission block increases, however, the assignment of bits for each data must increase exponentially. Thus the SNR of the image tends to decline accordingly. As an attempt to increase the SNR, we propose the WH matrix whose elements are made of ${\pm}$1, ${\pm}$2, ${\pm}$3, ${\pm}$4, and the unitform is 8${\times}$8 matrix.

• Journal of Information Processing Systems
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• v.19 no.6
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• pp.756-766
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• 2023

To effectively track the illegal use of digital images and maintain the security of digital image communication on the Internet, this paper proposes a reversible multipurpose image watermarking algorithm based on a deep residual network (ResNet) and perceptual hashing (also called MWR). The algorithm first combines perceptual image hashing to generate a digital fingerprint that depends on the user's identity information and image characteristics. Then it embeds the removable visible watermark and digital fingerprint in two different regions of the orthogonal separation of the image. The embedding strength of the digital fingerprint is computed using ResNet. Because of the embedding of the removable visible watermark, the conflict between the copyright notice and the user's browsing is balanced. Moreover, image authentication and traitor tracking are realized through digital fingerprint insertion. The experiments show that the scheme has good visual transparency and watermark visibility. The use of chaotic mapping in the visible watermark insertion process enhances the security of the multipurpose watermark scheme, and unauthorized users without correct keys cannot effectively remove the visible watermark.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.10a
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• pp.69-69
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• 2003

• Transactions of the Korean Society of Machine Tool Engineers
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• v.12 no.3
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• pp.89-95
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• 2003

This research analyzes the cutting mechanism of A1100-H18 of commercially pure aluminum by image processing in SEM(Scanning Electron Microscope) for the measurement of strain rate distribution near a cutting edge in orthogonal micro-cutting. The distribution is measured using various methods in order. The methods are in-situ observations of cutting process in SEM, inputting image data, a computer image processing, calculating displacements by SSDA(Sequential Similarity Detection Algorithm) and calculating strain rates by FEM. The min results obtained are as follows: (1)It enables to measure a microscopic displacement near a cutting edge. (2) An application of this system to cutting process of various materials will help to make cutting mechanism clear.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1983.10a
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• pp.68-72
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• 1983

The Hadamard matrix is a symmetric matrix made of plus and minus ones as entries. There fore the use of Hadamard transform in the image processing requires only the real number operations and results in the computational advantages. Recently, However, certain degradation aspects have been reported. In this paper we propose a WH matrix which retains the main properties of Hadamard matrix. The actual improvement of the image transmission in the inner part of the picture has been demonstrated by the computer simulated image developments. The orthogonal transform offers a useful facility in the digital signal processing. As the size of the transmission block increases, however, the assigment of bits for each data must increase exponentially. Thus the SNR of the image tends to decline accordingly. As an attempt to increase the SNR, we propose the WH matrix whose elements are made of $\pm$1, $\pm$2, $\pm$3, and the unitform is 8$\times$8 matrix.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.6
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• pp.464-472
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• 2018

Future spaceborne satellite synthetic aperture radar(SAR) system is expected to acquire high-resolution images over wide swath areas. Conventional SAR systems suffer from ambiguity problems in both azimuth and range directions that lead to image quality degradation. Recently, multiple input multiple output(MIMO) SAR techniques having multiple orthogonal waveforms are proposed to overcome the conventional ambiguity problems in wide-swath imaging modes. In this paper, noisy orthogonal frequency division multiplex(OFDM) waveforms are developed to reduce the ambiguity problems and suppress the image quality degradation. SAR simulations are performed to evaluate the performance of the proposed technique for wide-swath SAR imaging.

• Progress in Medical Physics
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• v.3 no.1
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• pp.53-62
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• 1992

Stereotactic implantation of intracranial lesions, and the development of stereotactic convergent irradiation, radiosurgery, techniques have to obtain the accurate coordinates of the tumor locations and that of critical organ. Computed tomography(CT) provides relatively precise imformations of tumor localization and surround the normal organs for conventional radiotherapy. This CT image use to extend for stereotactic radiosurgery procedures. Since the convergent irradiation technique in linear accelerator requires the target center coincident with gantry isocenter or radosurgery frame, the target coordinates must be described in accurately. We used the BRW stereotactic system for describing the target position in CT images This algorithm provides the coordinate conversions for orthogonal or non-orthogonal CT scan image. In this experiments, the target positions have shown the small discripancy within :to.3mm uncertanty in several known target positions in the phantom through the provided programs and it compared to that of BRW stereotactic systems.