• Journal of the Korean Institute of Telematics and Electronics A
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• v.30A no.8
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• pp.63-71
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• 1993

To verify validity of the steady-state Nyquist theorem and the steady-state Nyquist theorem with hot carrier effects in semiconductor devices, we calculate thermal noise in n-i-n structures using both the steady-state Nyquist theorem and the Monte-Carlo method, and compare the results from these two-methods. When the carrier temperature is not far from the lattice temperature, the results from both methods agree with each other very well, but in the hot carrier regime there are some discrepancies. Our results support the argument that for MOSFETs and MESFETs operating in the linear region, the channel thermal noise should be explained by the steady-state Nyquist theorem rather than by the existing theories.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.10
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• pp.114-118
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• 1994

To resolve thd discrepancy between the existing channel thermal noise theory of MOSFETs and a new theory called the stady-state Nyquist theorem, we have measured the channel thermal noise of specially designed MOSFETs with both uniform and nonuniform channels. the experimental results clearly show that the correct theory of the channel thermal nois in MOSFETs should be the steady-state Nyquist theorem.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.34S no.4
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• pp.42-49
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• 1997

A conventional adaptive noise canceller (ANC) using LMS algorithm suffers from the misadjustment of adaptive filter weights due to the gradient-estimate noise by input speech signal at steady state. In this paper, an ANC is proposed which uses the combination of VSLMS (variable step size LMS) and SA (sign algorithm) to improve steady state performance and convergence rate. SA algorithm is applied in speech region to prevent the weights from perturbing by output speech of ANC and VSLMS algorithm is applied to improve convergence rate and channel tracking ability in silence region and adaptive transient region. In compute rsimulation, the performance of the proposed VSLMS-SA combination algorithm is much better than LMS algorithm and the algorithm, recently proposed by greenberg, with adaptation step-size parameter determine dby sum method in convergence rate, channel tracking and steady state performance.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.3
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• pp.110-117
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• 1995

New formulas for the minimum noise figure and the optimum source impedance of microwave FETs are derived using the noise equivalent circuits obtained from the steady-state Nyquist theorem for multi-terminal semiconductor devices. The derived formulas manifest the relationships between the noise sources and the physical parameters of a noise equivalent circuit. Furthermore the formulas can explain the effect of gate leakage current on the minimum noise figure and the optimum source impedance. comparisons with the published experimental data confirm the validity and usability of our formula.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.9
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• pp.861-869
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• 2012

This paper presents a high performance position controller in a driving system using a time optimal control which is widely used to control driving systems to a desired reference position or velocity in minimum response time. The main purpose of this study is an improvement of transient response performance rather than steady-state response comparing with another various control strategies. In order to improve the performance of time optimal control, we tried to find the cause of the steady-state error in the driving system we have already made up and also suggest the newly modified type of time optimal control method in this paper.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.04a
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• pp.827-830
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• 2011

The equation of motion for the piping system conveying harmonically pulsating fluid is presented. When pulsating fluid flows, the properties of this system like mass, stiffness and damp is changing according to fluid fluctuation. To solve the steady-state time response of this system, numerical integration method of differential equation was usually used. But this method has some problem such time consuming method and difficulty of converging. Therefore this research suggests reliable and efficient numerical method to solve steady-state time response of piping system by using displacement assumption method.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.790-795
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• 2004

The characteristics of refrigerator noise recorded in anechoic chamber was investigated in condition of a the real living room and a kitchen. To predict the noise propagation in an apartment unit, room acoustic simulation software was used. It was found that the noise level in the real living room was $4\sim8dB$ higher than in the anechoic chamber. When a noise barrier and absorption materials were used on the rear wall and floor, the noise level reduced up to $3\sim4dB$. In addition, when the subjective evaluation of auralized refrigerator noise was undertaken using headphone, it was revealed that 21dB (A) is the allowable sound pressure level of 95% satisfaction.

• Journal of the Korean Institute of Telematics and Electronics
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• v.19 no.3
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• pp.37-45
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• 1982

This paper is a sequel of the Part I paper[1] on the modified digital Costas loop. In this Part II we analyze the performance of the system in the presence of noise. It is shown that, when the input signal is corrupted by additive white Gaussian noise, the noise process in the loop becomes Rician as a result of the tan-1 (.) function of the phase error detector. Steady state probability density functions of phase errors of the first-and second-order loops have been obtained by solving the Chapman-Kolmogorov equation numerically. Also, the mean and variance of phase error in the steady state have been obtained analytically, and are compared with the results obtained by computer simulation.

• Proceedings of the KIPE Conference
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• 2001.07a
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• pp.276-279
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• 2001

Direct torque control(DTC) is known to produce quick response in ac drives. Some drawbacks of the classical DTC are the relatively large torque ripple in a low speed range and notable current pulsation during steady state. They are reflected speed response and increased acoustical noise. In this paper, The DTC quick response are preserved at transient state, while better qualify steady state performance is produced by Space Vector Modulation(SVM). It is able to reduce the acoustical noise, torque ripple and current pulsation during steady state. The system presented are closed loop stator flux and torque observer for wide speed range that inputs are currents and voltages sensing of motor terminal. Simulation results for the 2.2kw general purposed induction motor are presented and discussed.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.1
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• pp.42-49
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• 2008

Most of vessels are not evaluated for their vibration and noise effects to human body. The vibration and noise generated by engine and auxiliary machine in vessel is a negative element for seamen. Therefore, in this paper, the diagnosis and evaluation of vibration and noise from vessel is accomplished by a shipbuilding corporation. The vibration and noise transferred from engine room and auxiliary machine was measured during the steady-state operation, and the vibration and noise map of vessel was made. Also, in order to evaluate the ship environment for human, the diagnosis is carried out on the base of measurement results.