• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.6A
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• pp.611-616
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• 2006

In this paper, we propose a practical implementation method of a soft bit decision expression for an R-QAM (Gray coded Rectangular Quadrature Amplitude Modulation) signal based on the Max-Log-MAP algorithm. The parameters of the soft decision expression for the practical implementation can be obtained with simple arithmetic functions associated with some deterministic parameters such as a received value, distances between symbols, and the order of modulation on a signal space. Also, we analyze the performance of an iterative decoding scheme for the QAM signal with I/Q phase unbalance. The unbalance results from the non-ideal characteristic of components such as a phase shifter between in-phase and quadrature paths for quadrature modulator/demondulator.

• Journal of the Society of Naval Architects of Korea
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• v.31 no.4
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• pp.41-50
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• 1994

An iterative time marching procedure for solving incompressible viscous flows has been applied to the flow around a propeller. This procedure solves three-dimensional Navier-Stokes equations on a moving, body-fitted, non-orthogonal grid using first-order accurate scheme for the time deivatives and second-and third-order accurate schemes for the spatial derivatives. To accelerate iterative process, a multigrid technique has been applied. This procedure is suitable for efficient execution on the current generation of vector or massively parallel computer architectures. Generally good agreement with published experimental and numerical data has been obtained. It was also found that the multigrid technique was efficient in reducing the CPU time needed for the simulation and improved the solution quality.

• Nonlinear Functional Analysis and Applications
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• v.29 no.1
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• pp.131-164
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• 2024

In this research, we study a modified relaxed Tseng method with a single projection approach for solving common solution to a fixed point problem involving finite family of τ-demimetric operators and a quasi-monotone variational inequalities in real Hilbert spaces with alternating inertial extrapolation steps and adaptive non-monotonic step sizes. Under some appropriate conditions that are imposed on the parameters, the weak and linear convergence results of the proposed iterative scheme are established. Furthermore, we present some numerical examples and application of our proposed methods in comparison with other existing iterative methods. In order to show the practical applicability of our method to real word problems, we show that our algorithm has better restoration efficiency than many well known methods in image restoration problem. Our proposed iterative method generalizes and extends many existing methods in the literature.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.7 s.337
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• pp.27-34
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• 2005

Iterative detection (ID) has proven to be a near-optimal solution for concatenated Finite State Machines (FSMs) with interleavers over an additive white Gaussian noise (AWGN) channel. When perfect channel state information (CSI) is not available at the receiver, an adaptive ID (AID) scheme is required to deal with the unknown, and possibly time-varying parameters. The basic building block for ID or AID is the soft-input soft-output (SISO) or adaptive SISO (A-SISO) module. In this paper, Reduced State SISO (RS-SISO) algorithms have been applied for complexity reduction of the A-SISO module. We show that serially concatenated CPM (SCCPM) with AID has turbo-like performance over fading ISI channels and also RS-A-SISO systems have large iteration gains. Various design options for RS-A-SISO algorithms are evaluated. Recently developed density evolution technique is used to analyze RS-A-SISO algorithms. We show that density evolution technique that is usually used for AWGN systems is also a good analysis tool for RS-A-SISO systems over frequency-selective fading channels.

• Communications of the Korean Mathematical Society
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• v.30 no.3
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• pp.209-219
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• 2015

In this article, we first give metric version of an iteration scheme of Agarwal et al. [1] and approximate fixed points of two finite families of nonexpansive mappings in hyperbolic spaces through this iteration scheme which is independent of but faster than Mann and Ishikawa scheme. Also we consider case of three finite families of nonexpansive mappings. But, we need an extra condition to get convergence. Our convergence theorems generalize and refine many know results in the current literature.

• Journal of the Korea Society for Simulation
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• v.3 no.1
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• pp.55-63
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• 1994

FMS is two or more computer controlled units interconnected with automated workhandling equipment and supervised by an executive computer having random scheduling capabilities. The complex nature of a FMS, coupled with the need to maximize its performance, means that such a system can be effectly designed only by iterative computer simulation methods. At the operational level, simulation had a reduced role to evaluate the performance of planned FMS under a variety of operating strategies. This is probably due to the fact that few simulation models are able to access the current status data of the system. This study reviews the role of simulation for design/operation of FMS and suggests an interface scheme for incorporating a simulation package with a FMS operational database. This scheme can be used for reducing the performance gap between design and real operation of a FMS.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1996.10a
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• pp.176-183
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• 1996

A new iterative scheme is proposed for finite element analysis of wrinkling or tension structures. This enables us to update the stress state and the internal forces correctly taking into account the existence of wrinkling. The finite element implementation of the scheme is straightforward and simple, and only minor modifications of the existing total Lagrangian finite element codes for membranes are needed. The validity of the scheme is demonstrated via numerical examples for the torsion of a membrane and the quasi-static inflation of an automotive airbag, both made of isotropic or anisotropic elastic membranes

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.11
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• pp.2776-2788
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• 1996

A new feature-based motion parameter estimation for arbitrary-shaped regions is proposed. Existing motion parameter estimation algorithms such as gradient-based algorithm require iterations that are very sensitive to initial values and which often converge to a local minimum. In this paper, the motion parameters of an object are obtained by solving a set of linear equations derived by the motion of salient feature points of the object. In order to estimate the displacement of the feature points, a new process called the "bi-directional correspondence scheme" is proposed to ensure the robjstness of correspondence. The proposed correspondence scheme iteratively selects the feature points and their corresponding points until unique one-to-one correspondence is established. Furthermore, initially obtained motion paramerters are refined using an iterative method to give a better performance. The proposed algorithm can be used for motion estimationin object-based image coder, and the experimental resuls show that the proposed method outperforms existing schemes schemes in estimating motion parameters of objects in image sequences.sequences.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1395-1400
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• 2003

This paper introduces a novel scheme for determining the thermal diffusivity of solids using the photothermal mirage technique. The suggested scheme extends the thermal-wave coupling method, employing the solution to the heat conduction equation in close proximity to the pump beam. Therefore, determination of thermal diffusivity is possible by detecting the mirage signal with small separation between the probe and pump beams, with enhanced intensity of the mirage signal. Though the method requires information about the probe-beam height, the absolute transverse position of the probe beam need not be known as it is automatically evaluated by the iterative-computation procedure. The thermal diffusivity of Ni is measured by the proposed scheme and the result demonstrates good agreement with the literature value to within 5 %.

• Journal of electromagnetic engineering and science
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• v.6 no.4
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• pp.203-208
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• 2006

Channel estimation and data detection for OFDM systems over time- and frequency-selective channels are investigated. Relying on the complex exponential basis expansion channel model, a pilot-embedded channel estimation scheme with low computational complexity and spectral efficiency is proposed. A periodic pilot sequence is superimposed at a low power on information bearing sequence at the transmitter before modulation and transmission. The channel state information(CSI) can be estimated using the first-order statistics of the received data. In order to enhance the performance of channel estimation, we recover the transmitted data which can be exploited to estimate CSI iteratively. Simulation results show that the proposed method is suitable for doubly-selective channel estimation for the OFDM systems and the performance of the proposed method can be better than that of the Wiener filter method under some conditions. Through simulations, we also analyze the factors which can affect the system performances.