• Proceedings of the Acoustical Society of Korea Conference
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• 1984.12a
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• pp.63-65
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• 1984

In this paper, the implementation of the real time LPC synthesizer using NEC 77p20, the DSP (Digital Signal Processor) chip which facilitates and simplifies the digital hardware, is considered. This method shows the good quality with the low bit rate below 9.6kbps and has the advantage of the flexibility and the simplicity.

• Bulletin of the Korean Mathematical Society
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• v.44 no.1
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• pp.151-156
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• 2007

A connection between weak ${\pi}-regularity$ and the condition every prime ideal is maximal will be investigated. We prove that a certain 2-primal ring R is weakly ${\pi}-regular$ if and only if every prime ideal is maximal. This result extends several known results nontrivially. Moreover a characterization of minimal prime ideals is also considered.

• Review of KIISC
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• v.28 no.1
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• pp.43-47
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• 2018

Textual passwords are widely used for accessing online accounts. Despite the problems of current textual passwords, research has shown that there is no other strong alternatives for a textual password due to its simplicity. There has been significant research to make passwords more secure and usable through password composition policies, password managers, password meters, and multi-factor authentications. In this paper, we focus on several key research that investigates and analyzes widely used password composition policies, and summarize the latest research which aims to improve current password composition policies.

• Proceedings of the KIPE Conference
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• 2000.07a
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• pp.299-304
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• 2000

In this paper we investigate accurately the input-output characteristic of single-phase diode rectifier. The diode rectifier has some advantages of simplicity cost and high-efficiency. But it has some defects which THD of input current low PF and voltage drop of output side. In order to compensate it we analyzed using the parameter variation and introduced capacitor insertion method for reducing the distortion and increasing the PF.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1998.04a
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• pp.130-135
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• 1998

The Reciprocating compressor are widely used in the refrigeration field for its simplicity in principle and high efficiency. In this work, we developed a mathematical model of a reciprocating compressor. The suction and discharge valves are modeled by the spring-mass-damper systems. The working fluid flow is derived from unsteady Bernoulli's equation. With the design parameters, the valve motions and pressure fluctuations are studied numerically and experimentally.

• Bulletin of the Korean Mathematical Society
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• v.45 no.1
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• pp.191-205
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• 2008

In this paper, we construct the analytic solutions and numerical solutions for a two-dimensional Riemann problem for Burgers' equation. In order to construct the analytic solution, we use the characteristic analysis with the shock and rarefaction base points. We apply the composite scheme suggested by Liska and Wendroff to compute numerical solutions. The result is coincident with our analytic solution. This demonstrates that the composite scheme works pretty well for Burgers' equation despite of its simplicity.

• The Journal of the Acoustical Society of Korea
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• v.12 no.1
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• pp.37-46
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• 1993

The adaptive algorithm for the Volterra filter is considered. Owing to its simplicity, the LMS algorithm for adaptive Volterra filter(AVF) is widely used as in linear adaptive filters. However, the convergence speed is unsatisfactory. For improving the convergence speed, the frequency domain LMS second order adaptive Volterra filter(FLMS-AVF) is proposed and analyzed. We show that the time and frequency domain LMS AVF's have the same steady state performance under approprate conditons. Moreover, it can be shown that this algorithm can improve the convergence speed significantly by applying self-orthogonalizing method.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.5 no.2
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• pp.27-34
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• 2009

This paper proposes a simple numerical method to simulate ductile failure behaviors. The method is based on finite element analysis with a simple damage theory. To validate the proposed method, simulated results are compared with experimental data. Despite its simplicity, the proposed method well predicts experimental results systematic analyses are also performed to investigate the effect of the element size.

• Bulletin of the Korean Mathematical Society
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• v.41 no.3
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• pp.493-505
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• 2004

We introduce certain local Thomsen condition in a 3-web and prove that it is equivalent to the equation a－(a－b)＝b in its corresponding loop, where we denote the loop operation additively for convenience and simplicity, even though the loop is neither associative nor commutative. Also we interpret such local Thomsen condition using orthogonality of chains in a web.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.1188-1190
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• 2001

This paper presents a clustering adaptive controller to achieve robustness against parameter variations although it has simple structure and computational simplicity. The presented controller based on optimal fuzzy logic controller has an self-tuning characteristics with clustering. The controller requires no model of the system to be controlled. Simulation results show that the usefulness of the proposed controller.