• ETRI Journal
• /
• v.31 no.6
• /
• pp.755-764
• /
• 2009

This paper presents a switched self-biasing and a tail current-shaping technique to suppress the 1/f noise from a tail current source in differential cross-coupled inductance-capacitance (LC) voltage-controlled oscillators (VCOs). The proposed LC VCO has an amplitude control characteristic due to the creation of negative feedback for the oscillation waveform amplitude. It is fabricated using a 0.13 ${\mu}m$ CMOS process. The measured phase noise is -117 dBc/Hz at a 1 MHz offset from a 4.85 GHz carrier frequency, while it draws 6.5 mA from a 0.6 V supply voltage. For frequency tuning, process variation, and temperature change, the amplitude change rate of the oscillation waveform in the proposed VCO is 2.1 to 3.2 times smaller than that of an existing VCO with a fixed bias. The measured amplitude change rate of the oscillation waveform for frequency tuning from 4.55 GHz to 5.04 GHz is 131 pV/Hz.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.30 no.2B
• /
• pp.21-26
• /
• 2005

A routing algorithm using the Hopfield Neural Netork (HNN) is proposed in this paper. The proposed algorithm modifies the energy function for achieving the optimality of the solution and higher convergence rate. Experimental results show that the proposed algorithm outperforms convensional methods both in optimality and convergence.

• Journal of the Korean Society of Industry Convergence
• /
• v.8 no.3
• /
• pp.155-160
• /
• 2005

Kinetic studies were carried out for aquation of carbonatobis(ethylenediamine)cobalt(III) complexes in [H+] aqueous solution by UV/VIS-spectrophotometry. The rate law that in deduced from rate data is $rate=k_H{^+}[H^+]^{1.4}$ {$[Co(en)_2(CO_3)]^+$}1.0 where $k_H{^+}$ is the rate constant considering acidic catalyst, $H^+$ ion whose value is $0.241l{\cdot}mol^{-1}{\cdot}sec^{-1}$. The values of activation parameters Ea, ${\Delta}H^{\ast}$ and ${\Delta}S^{\ast}$ were $15.33Kcal{\cdot}mol^{-1}$, $14.52Kcal{\cdot}mol^{-1}$ and -57.49 e.u. respectively. On the basis of kinetic data and the observed activation parameters, we have proposed the mechanism that proceeds with two step protonations. The rate equation derived from the proposed mechanism has been in agreement with the observed rate equation. It has been seen that our modified mechanism for Harris's proton freequilibrium one prefer to the his concerted mechanism, and more the last product substitute $H_2O$ for $OH^-$ the Harris's mechanism in the acidity range 2 < pH < 5.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.20 no.11
• /
• pp.17-23
• /
• 2021

A cyclone is a dust-separating mechanism that works on the principle of centrifugal force. The performance of a cyclone is evaluated using pressure loss and collection efficiency. A multi-cyclone arrangement is used to improve the collection efficiency within a limited area. In this study, experiments and numerical analyses were conducted on a dual arrangement of mini-hydrocyclone separators, which was fabricated using 3D printing. The experiment was performed at an inlet flow rate of 0.7 m/s, and alumina powder with a particle size of 0.5, 15, and 50 ㎛. ANSYS FLUENT, was used for the numerical analysis. The reliability of the numerical analysis was verified through a comparison with the experimental results. The errors in the experiment and numerical analysis were confirmed to be 2% at the outlet flow rate.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.23 no.3
• /
• pp.213-217
• /
• 2014

A hybrid search method based on the artificial bee colony algorithm (ABCA) with harmony search (HS) is suggested for finding a global solution in the field of optimization. Three cases of the suggested algorithm were examined for improving the accuracy and convergence rate. The results showed that the case in which the harmony search was implemented with the onlooker phase in ABCA was the best among the three cases. Although the total computation time of the best case is a little bit longer than the original ABCA under the prescribed conditions, the global solution improved and the convergence rate was slightly faster than those of the ABCA. It is concluded that the suggested algorithm improves the accuracy and convergence rate, and it is expected that it can effectively be applied to optimization problems with many design variables and local solutions.

• Journal of the Korean Society for Precision Engineering
• /
• v.33 no.5
• /
• pp.341-348
• /
• 2016

The solenoid valve is used widely across various industries; however, solenoid valves for use in high-temperature environments have to be highly specified, such as those used in thermal power plants and steel mills. As such, we have developed a solenoid valve, using an already developed solenoid, to allow for more specific use. In this type of development method, use of 3D printing is very effective, allowing for a reduction in errors in design and production. This study includes a mathematical model of the solenoid valve. Then, the simulation from the mathematical model was performed using the AMESim (Advanced Modeling Environment for Simulation of Engineering Systems). We made a prototype valve using the simulation results and also measured the flow rate and dynamic performance.

• Journal of the Korea Society of Computer and Information
• /
• v.7 no.4
• /
• pp.204-210
• /
• 2002

The self-organizing feature map of Kohonen has disadvantage that needs too much input patterns in order to converge into the equilibrium state when it trains. In this paper we proposed the method of improving the convergence speed and rate of self-organizing feature map converting the interaction set into Dynamic Gaussian function. The proposed method Provides us with dynamic Properties that the deviation and width of Gaussian function used as an interaction function are narrowed in proportion to learning times and learning rates that varies according to topological position from the winner neuron. In this Paper. we proposed the method of improving the convergence rate and the degree of self-organizing feature map.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.34 no.8C
• /
• pp.756-763
• /
• 2009

The Least Mean Square (LMS) algorithm is often used to restore signal corrupted by additive noise. A major defect of this algorithm is that the excess Mean Square Error (EMSE) increases linearly according to speech signal power. This result reduces the efficiency of performance significantly due to the large EMSE around the optimum value. Choosing a small step size solves this defect but causes a slow rate of convergence. The step size must be optimized to satisfy a fast rate of convergence and minimize EMSE. In this paper, the Instantaneous Gain Control (IGC) algorithm is proposed to deal with the situation as it exists in speech signals. Simulations were carried out using a real speech signal combined with Gaussian white noise. Results demonstrate the superiority of the proposed IGC algorithm over the LMS algorithm in rate of convergence, noise reduction and EMSE.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.19 no.5
• /
• pp.12-19
• /
• 1982

In general the design methods of adaptive filter are divided into two categories, one is based upon the local parameter optimization theory and the other is based upon stability theory. Among the various design techniques, the LMS algorithm by steepest-descent method which is based upon local parameter optimization theory is used widely. In designing the adaptive filter, the most important factor is the convergence rate of the algorithm. In this paper a new algorithm is proposed to improve the convergence rate of adaptive firter compared with the commonly used LMS algorithm. The faster convergence rate is obtained by adjusting the adaptation gain of LMS algorithm. And various aspects of improvement of the adaptive filter characteristics are discussed in detail.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.36 no.6C
• /
• pp.343-348
• /
• 2011

This paper introduces a design for real time wireless headset using ANC (active noise control) system based on NFxLMS adaptive filter algorithm. The training time of the proposed system is significantly reduced by using the RMS delay spread of a channel as an error correction parameter, and convergence rate of the FxLMS filter has been improved with updating the coefficients of the NFxLMS filter, which we have got during the training process. Our system has shorter training time and better convergence rate at the same noise reduction level than the conventional system under real noisy environment.