• Proceedings of the KIEE Conference
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• 1999.07a
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• pp.465-467
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• 1999

The data transmission system in MAGLEV is required a high quality and high speed for a train safety and reliability driving. In the transmission channel between a vehicle and a ground-site, Gaussian noise is negligible, but impulse noise from the chopper controlled propulsoin unit and the Power supplying device is very severe. The transmission channel must be protected from these noise. In this paper, we propose a DSSS (direct-sequence spread spectrum) modulation as a new data transmission technique in the railway and analyze this data transmission characteristics.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.10C
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• pp.999-1007
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• 2002

In this paper, the operation of matched filter for searching initial synchronization in direct sequence spread spectrum receiver is studied. The implementation model of the matched filter by HDL (Hardware Description Language) is proposed. The model has an architecture based on parallelism and pipeline for fast processing, which includes circular buffer, multiplier, adder, and code look-up table. The performance of the model is analyzed and compared with the implementation by a conventional digital signal processor. It is implemented on a FPGA (Field Programmable Gate Array) and its operation is validated in a timing simulation result.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.1
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• pp.81-86
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• 2008

Fast spreading Internet worms, such as Code Red and Slammer, have become one of the new major throne of the Internet recently. In order to defend against theses worms, it is essential to understand how Internet worms propagate and how different Internet factors affect worm spreading. In this paper, we intend to describe the spread of worms on Internet environments accurately. Therefore we model and analyze the spreading effects by various simulations considering Internet addressing and speed. The results lead to a better prediction of the worm spreading on current and future Internet environments.

• The Journal of the Korea institute of electronic communication sciences
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• v.4 no.3
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• pp.224-229
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• 2009

In this paper, an efficient signal interference control technique to improve the convergence speed of Adaptive transversal filter with LMS algorithm is introduced. The convergence characteristics of the proposed algorithm, whose coefficients are multiply adapted in a symbol time period by recycling the received data, are analyzed to prove theoretically the improvement of convergence speed. According as the step-size parameter ${\mu}$ is increased, the rate of convergence of the algorithm is controlled. Increasing the eigenvalue spread has the effect of controlling down the rate of convergence of the adaptive equalizer and also increasing the steady-state value of the average squared error and also demonstrate the superiority of signal interference control to the filter algorithm increasing convergence speed by (B+1) times due to the data-recycling LMS Algorithms.

• Proceedings of the Acoustical Society of Korea Conference
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• 1992.06a
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• pp.23-28
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• 1992

The purpose of this paper is to develop a new adaptive echo canceller improving convergence speed and near-end-talker detection performance of the conventional echo canceller. In a conventional adaptive echo canceller, an adaptive digital filter with TDL(Tapped-Delay Line) structure modelling the echo path uses the LMS(Least Mean Square) algorithm to cote the coefficients, and NET detector using energy comparison method prevents the adaptive digital filter to update the coefficients during the periods of the NET signal presence. The convergence speed of the LMS algorithm depends on the eigenvalue spread ratio of the reference signal and NET detector using the energy comparison method yields poor detection performance if the magnitude of the NET signal is small. This paper presents a new adaptive echo canceller which uses the pre-whitening filter to improve the convergence speed of the LMS algorithm. The pre-whitening filter is realized by using a low-order lattice predictor. Also, a new NET signal detection algorithm is presented, where the start point of the NET signal is detected by computing the cross-correlation coefficient between the primary input and the ADF(Adaptive Digital Filter) output while the end point is detected by using the energy comparison method. The simulation results show that the convergence speed of the proposed adaptive echo canceller is faster than that of the conventional echo canceller and the cross-correlation coefficient yield more accurate detection of the start point of the NET signal.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.6 no.2
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• pp.88-94
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• 2013

In this paper, an efficient signal interference control technique to improve the convergence speed of LMS algorithm is introduced. The convergence characteristics of the proposed algorithm,whose coefficients are multiply adapted in a symbol time period by recycling the received data,are analyzed to prove theoretically the improvement of convergence speed. According as thestep-size parameter ${\mu}$ is increased, the rate of convergence of the algorithm is controlled. Increasing the eigenvalue spread has the effect of controlling down the rate of convergence of the adaptive equalizer and also increasing the steady-state value of the average squared error and also demonstrate the superiority of signal interference control to the filter algorithm increasing convergence speed by (B+1) times due to the data-recycling LMS technique.

• Journal of Biosystems Engineering
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• v.15 no.2
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• pp.110-122
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• 1990

This study was undertaken to develop the feed rate control system for the head feed thresher by making use of the microprocessor and to evaluate the response of the system to a various threshing conditions. The control unit was composed of one-board microcomputer. The speed of the wet-paddy feeding chain was controlled by dc moter with PI controller. It was used the adaptive control method to maintain the constant feed rate regardless of the fed rice varieties. The sliding type potentiometer was used as the feed rate sensor, which was attached on the sheaf-holding apparatus. The mathematical models of the system components were derived and computer simulation was developed for investigating the parameters affecting on control performance and for estimating the response of the system. A one-board microcomputer-based feed rate control system developed in this study was properly functioned and assessed as adequate for the feed rate control system of the head feed thresher. Based on the simulation for the bundle feed, it was anticipated that the lower setting value of the cylinder speed(RL) is to be set higher than the limiting operational speed. In addition, the higher setting value of the cylinder speed(RH) is to be set lower than the limiting cylinder speed for threshing. The computer simulation for the continuous spread feed showed that the lower the setting value of straw layer thickness(LL) was set, the shorter the correction time. However, if too low LL may be established, the feed rate could not reach to its desired rate.

• Journal of Environmental Science International
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• v.20 no.7
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• pp.819-828
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• 2011

This research was done to clarify the cooling effect of water particles generated from a fountain. This effect is a one way to control the heat island effect of big cities. The result of this research was drawn by setting the jets of water in a certain height, and then studying the diffusion of water particles, which is affected by the size of the particles and the wind speed, and the cooling effect caused by the diffusion. 1) When a diameter of a water drop was 500 ${\mu}m$ and the wind speed was 2.0 to 6.0 m/sec, the water drop diffused 75 to 190m, and the water vapor spread over 175 to 440 m. As a result, there was more than $0.5^{\circ}C$ of cooling effect on the temperature in the atmosphere 130 to 330m around the water fountain. 2) When a diameter of a water drop was 750 ${\mu}m$ and the wind speed was 2.0 to 6.0 m/sec, the water drop diffused 65 to 150 m, and the water vapor spread over 160 to 405 m. Moreover, there was more than $0.5^{\circ}C$ of cooling effect on the temperature in the atmosphere 110 to 275 m around the water fountain. 3) After studying on the relationship between the diameter of water drop and the wind speed, and the diffusion of water particles and the range of the atmosphere that was cooled, a result could be drawn from the research that the smaller the diameter of the water vapor gets and the faster the wind speed becomes, the wider the water particles diffuse and the cooler the atmosphere around the fountain becomes. 4) This research further extrapolates that when the ordinary water(tap water, water from river and stream) is used in a fountain, the cooling effect of the air near the fountain can be approached similarly. If the seawater is used in a fountain, there is to be more to concern not only on cooling effect on the air, but also on other effects on surrounding environment generated by the salt in seawater.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.1
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• pp.22-28
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• 2021

This is a basic study on the development of deep learning-based algorithms to detect smoke before the smoke detector operates in the event of a ship fire, analyze and utilize the detected data, and support fire suppression and evacuation activities by predicting the spread of smoke before it spreads to remote areas. Proposed algorithms were reviewed in accordance with the following procedures. As a first step, smoke images obtained through fire simulation were applied to the YOLO (You Only Look Once) model, which is a deep learning-based object detection algorithm. The mean average precision (mAP) of the trained YOLO model was measured to be 98.71%, and smoke was detected at a processing speed of 9 frames per second (FPS). The second step was to estimate the spread of smoke using the coordinates of the boundary box, from which was utilized to extract the smoke geometry from YOLO. This smoke geometry was then applied to the time series prediction algorithm, long short-term memory (LSTM). As a result, smoke spread data obtained from the coordinates of the boundary box between the estimated fire occurrence and 30 s were entered into the LSTM learning model to predict smoke spread data from 31 s to 90 s in the smoke image of a fast fire obtained from fire simulation. The average square root error between the estimated spread of smoke and its predicted value was 2.74.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.7A
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• pp.554-561
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• 2009

In this paper, we propose a novel Vehicular Ad-hoc Network(VANET) which includes communication and ranging features, using Spread Spectrum(SS) multi-carrier modulation scheme. In existing methods, a spread spectrum technique was used to communicate with other vehicles and raging was possible by detecting phase difference between transmission/reception of the PN signal. However, the use of high-speed PN signals is mandatory to detect possible errors of phase difference and to increase the analysis capacity. In the proposed system, multi-carrier modulation scheme was used as solution of mentioned problem. The multi-carrier modulation scheme uses smaller PN signal and chip-rate than the single-carrier modulation, so it is possible to send multiple carrier waves using the same frequency range. This technique (multiple carrier waves) allows to have the Equal Gain Combing (EGC) diversity effect, providing better result in phase difference error detection and raging accuracy.