• Journal of Korea Multimedia Society
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• v.15 no.1
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• pp.9-17
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• 2012

Recently, a new image appearance model, named iCAM06, was developed for High-Dynamic-Range (HDR) image rendering. The dynamic range of a HDR image needs to be mapped on the range of output devices, which is called the tone reproduction or tone mapping. The iCAM06, the representative HDR rendering algorithm also uses the tone compression using a S-curve mapping function for image reproduction on the dynamic range of output devices. However the iCAM06 occurs white point shift during its tone compression process. Therefore, we propose a compensation method for white point shift problem using the corrected channel gain function. Experiment results show that the proposed method has better performance than the iCAM06.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.2
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• pp.22-28
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• 2007

High PAPR (peak-to-average power ratio) is a major drawback of OFDM (orthogonal frequency division multiplexing) signals. In this paper, a modified SLM (selective mapping) technique that uses erasure decoding of RS (Reed-Solomon) codes is presented. At the transmitter a set of phase sequences are multiplied such that some portions of check symbols in RS-coded OFDM data blocks are phase-rotated. At the receiver, RS decoding is performed with the phase-rotated check symbols being treated as erasures. Hence, there is no need to send side information about the phase sequence selected to transmit for the lowest PAPR. In addition, the estimation process for the selected phase sequence is no longer needed at the receiver, leading to improvement in terms of complexity and performance. To evaluate the performance of this technique, the CCDF (complementary cumulative distribution function) of PAPR, the BER (bit error rate) and the decoding failure probability are compared with those of the previous SLM techniques.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.5
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• pp.1316-1332
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• 2012

Formation flying is an important technology that enables high cost-effective organization of outer space aircrafts. The ad-hoc wireless network based on direct-sequence ultra-wideband (DS-UWB) techniques is seen as an effective means of establishing wireless communication links between aircrafts. In this paper, based on the theory of matched filter and error bits correction, a hybrid detection algorithm is proposed for realizing multiuser detection (MUD) when the DS-UWB technique is used in the ad-hoc wireless network. The matched filter is used to generate a candidate code set which may contain several error bits. The error bits are then recognized and corrected by an novel error-bit corrector, which consists of two steps: code mapping and clustering. In the former step, based on the modified optimum MUD decision function, a novel mapping function is presented that maps the output candidate codes into a feature space for differentiating the right and wrong codes. In the latter step, the codes are clustered into the right and wrong sets by using the K-means clustering approach. Additionally, in order to prevent some right codes being wrongly classified, a sign judgment method is proposed that reduces the bit error rate (BER) of the system. Compared with the traditional detection approaches, e.g., matched filter, minimum mean square error (MMSE) and decorrelation receiver (DEC), the proposed algorithm can considerably improve the BER performance of the system because of its high probability of recognizing wrong codes. Simulation results show that the proposed algorithm can almost achieve the BER performance of the optimum MUD (OMD). Furthermore, compared with OMD, the proposed algorithm has lower computational complexity, and its BER performance is less sensitive to the number of users.

• Journal of IKEEE
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• v.28 no.3
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• pp.271-278
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• 2024

An encryption and decryption method using phase mapping of a gray scale image based on a phase-shifting interferometry principle is proposed in which an encrypted image is formed into complex digital hologram function by symmetric security key in the proposed encryption system.. The gray scale image to be encrypted is converted to phase mapped function that is mixed with a randomly generated binary security encryption key and is used as an input. Decryption of phase information is performed by complex digital hologram and security encryption key, which reconstructs the original gray scale image by phase unmapping. The proposed method confirms that correlation coefficient of the decrypted image is 0.995 when quantization level of CCD is 8-bits(2⁸=256 levels).

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.11
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• pp.2702-2719
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• 2013

A new optimal scheme based on curvelet transform is proposed for retinal image enhancement (RIE) using real-coded quantum genetic algorithm. Curvelet transform has better performance in representing edges than classical wavelet transform for its anisotropy and directional decomposition capabilities. For more precise reconstruction and better visualization, curvelet coefficients in corresponding subbands are modified by using a nonlinear enhancement mapping function. An automatic method is presented for selecting optimal parameter settings of the nonlinear mapping function via quantum genetic search strategy. The performance measures used in this paper provide some quantitative comparison among different RIE methods. The proposed method is tested on the DRIVE and STARE retinal databases and compared with some popular image enhancement methods. The experimental results demonstrate that proposed method can provide superior enhanced retinal image in terms of several image quantitative evaluation indexes.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.4
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• pp.1648-1672
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• 2020

There are several types of image registration in the sense of stitching separated images that overlap each other. One of these is feature-based registration by a common feature descriptor. In this study, we generate a mosaic of images using feature-based registration for drone aerial images. As a feature descriptor, we apply the scale-invariant feature transform descriptor. In order to investigate the authenticity of the feature points and to have the mapping function, we employ the sample consensus method; we consider the sensed image's inherent characteristic such as the geometric congruence between the feature points of the images to propose a novel hypothesis estimation of the mapping function of the stitching via some optimally chosen initial candidate inliers in the sample consensus method. Based on the experimental results, we show the efficiency of the proposed method compared with benchmark methodologies of random sampling consensus method (RANSAC); the well-ordering property defined in the context and the extensive stitching examples have supported the utility. Moreover, the sample consensus scheme proposed in this study is uncomplicated and robust, and some fatal miss stitching by RANSAC is remarkably reduced in the measure of the pixel difference.

• Geomechanics and Engineering
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• v.11 no.3
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• pp.325-343
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• 2016

A total stress-based bounding surface model is developed to predict the undrained behaviour of saturated soft clays under cyclic loads based on the anisotropic hardening modulus field and bounding-surface theories. A new hardening rule is developed based on a new interpolation function of the hardening modulus that has simple mathematic expression and fewer model parameters. The evolution of hardening modulus field is described in the deviatoric stress space. It is assumed that the stress reverse points are the mapping centre points and the mapping centre moves with the variation of loading and unloading paths to describe the cyclic stress-strain hysteresis curve. In addition, by introducing a model parameter that reflects the accumulation rate and level of shear strain to the interpolation function, the cyclic shakedown and failure behaviour of soil elements with different combinations of initial and cyclic stresses can be captured. The methods to determine the model parameters using cyclic triaxial compression tests are also studied. Finally, the cyclic triaxial extension and torsional shear tests are performed. By comparing the predictions with the test results, the model can be used to describe undrained cyclic stress-strain responses of elements with different stress states for the tested clays.

• Journal of the Korean Operations Research and Management Science Society
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• v.12 no.2
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• pp.21-35
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• 1987

This paper presents a method for propagating fuzzy concepts through fuzzy IF-THEN-ELSE rules. A fuzzy IF-THEN-ELSE rule consists of a set of fuzzy condition and conclusion pairs. These pairs assumed to contain informations about a fuzzy mapping from fuzzy concepts of condition parts to the fuzzy concepts of conclusion parts. Conventionally, vectors are used to define fuzzy concepts and matrices are used to define a fuzzy mapping between fuzzy conditions and conclusions. This approach, however, does not satisfy the existing condition property, i.e., when a fuzzy input data exactly matches to a fuzzy condition, fuzzy output data should be mapped to a corresponding fuzzy conclusion. Alternatively, we propose a parameterized approach in which every fuzzy concept is described by a parameterized standard function, including fuzzy conditions and fuzzy conclusions. A fuzzy IF-THEN-ELSE rule takes the parameterized fuzzy concept as an input, and produces a standard function with new parameters as an output. New parameters are determined by a parameterwise interpolation. That is, each output parameters are determined by interpolating parameters of the same class contained in fuzzy conclusions. Obviously, the proposed scheme always satisfies the existing condition property.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.29B no.7
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• pp.87-97
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• 1992

Fuzzy controllers have been successfully applied to many cases to which conventional control algorithms are difficult to be applied. Even though the representations and the processings of data and information in the fuzzy controller are quite different from those in other control algorithms, the information processing operation that it caries out is basically a function ∫: $A{\subset}R^n{\to}R^m$, from a bounded subset A of an n-dimensional Euclidean space to a bounded subset f[A] of an m-dimensional Euclidean space, where n and m are the number of measured states and the number of control inputs of the controlled system, respectively. Under the assumptions of Mamdani's direct reasoning method and C.O.G.(center of gravity) defuzzification method, the fuzzy controllers are proven to perform the mapping of any given functions f with appropriately defined fuzzy sets. The mapping capabilities of fuzzy controllers are analyzed in detail for two cases, ∫: $R^{1}{\to}R^{1}$ and g: $R^{2}{\to}R^{1}$. Also, it will be shown that the results can be extended to multiple dimensional cases.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.1
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• pp.143-158
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• 1994

X.435 is the EDI communication protocol published by CCITT and ISO/IEC in 1990. The message types and abstract services of EDI-MS are specified in X.435 recommendation. In this paper, the design methodology on implementation of MSIB in the case that MHS-MS is required to be extended into EDI-MS has been studied. The design methodology presented in this paper is the one using the mapping function of the object relation. This methodology considers the EDI message types and characterictics. The proposed design methodology han an advantage that is able to design the component tables of MSIB satisfying the third normal form and it does not require the normalization processing. The MSIB constructed by the proposed method can store and retrieve multi-values efficiently.