• Journal of the Korean Society for Precision Engineering
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• v.20 no.2
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• pp.112-119
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• 2003

Generally, PID controller is not suitable to control multi variable system because it is very difficult to tune the PID gains. However, this paper shows that it is not hard to tune the PID gains if we can find a Jacobian matrix of the system. The Jacobian matrix expresses the ratio of output variations according to input variations. It is possible to adjust the input values in order to reduce the output error using the Jacobian. When the colt function is composed of error related terms, the gradient approach can tune the PID gains to minimize the function. In simulation, a hydrofoil catamaran with two inputs and two outputs is applied as a multi variable system. We can easily get the multi variable PID controller by the proposed teaming method. When the controller is compared with LQR controller, the performance is as good as that of LQR controller with a modeling equation.

• MALSORI
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• no.63
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• pp.113-124
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• 2007

In this paper, we propose a use of confidence vector as an intermediate input feature for multi-stage based speech recognition architecture to improve recognition accuracy. A multi-stage speech recognition structure is introduced as a method to reduce the computational complexity of the decoding procedure and then accomplish faster speech recognition. Conventional multi-stage speech recognition is usually composed of three stages, acoustic search, lexical search, and acoustic re-scoring. In this paper, we focus on improving the accuracy of the lexical decoding by introducing a confidence vector as an input feature instead of phoneme which was used typically. We take experimental results on 220K Korean Point-of-Interest (POI) domain and the experimental results show that the proposed method contributes on improving accuracy.

• Journal of Communications and Networks
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• v.9 no.2
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• pp.150-158
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• 2007

We consider channel-coded multi-input multi-output (MIMO) orthogonal frequency-division multiplexing (OFDM) transmission and obtain a condition on its signal for it to attain the maximum diversity and coding gain. As this condition may not be realizable, we propose a suboptimal design that employs an orthogonal transform and a space-frequency interleaver between the channel coder and the multi-antenna OFDM transmitter. We propose a corresponding receiving method based on block turbo equalization. Attention is paid to some detailed design of the transmitter and the receiver to curtail the computational complexity and yet deliver good performance. Simulation results demonstrate that the proposed transmission technique can outperform the conventional coded MIMO OFDM and the MIMO block single-carrier transmission with cyclic prefixing.

• Journal of Advanced Navigation Technology
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• v.7 no.1
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• pp.51-58
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• 2003

Generally, multi-path is viewed as an undesirable feature of wireless communications. Therefore, diversity reception and adaptive array schemes are proposed to mitigate its effects. Recently, to increase the spectrum efficiency and the link reliability, multiple-input multiple-output (MIMO) scheme is devised to exploit multi-path in a scattering wireless channel. In this paper, we have evaluated the channel capacity of MIMO Multi-Carrier CDMA system in path correlation fading channel. And, the channel capacity of MIMO system is compared with single-input single-output (SISO) system. From the results, the MIMO multi-carrier CDMA system with path correlation yields better performance with respect to channel capacity than a SISO system.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.246-246
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• 2023

Multi-purpose dams are operated accounting for both physical and socioeconomic factors. This study aims to evaluate the utility of a deep learning algorithm-based model for three multi-purpose dam operation (Seomjin River dam, Juam dam, and Juam Control dam) in Seomjin River. In this study, the Gated Recurrent Unit (GRU) algorithm is applied to predict hourly water level of the dam reservoirs over 2002-2021. The hyper-parameters are optimized by the Bayesian optimization algorithm to enhance the prediction skill of the GRU model. The GRU models are set by the following cases: single dam input - single dam output (S-S), multi-dam input - single dam output (M-S), and multi-dam input - multi-dam output (M-M). Results show that the S-S cases with the local dam information have the highest accuracy above 0.8 of NSE. Results from the M-S and M-M model cases confirm that upstream dam information can bring important information for downstream dam operation prediction. The S-S models are simulated with altered outflows (-40% to +40%) to generate the simulated water level of the dam reservoir as alternative dam operational scenarios. The alternative S-S model simulations show physically inconsistent results, indicating that our deep learning algorithm-based model is not explainable for multi-purpose dam operation patterns. To better understand this limitation, we further analyze the relationship between observed water level and outflow of each dam. Results show that complexity in outflow-water level relationship causes the limited predictability of the GRU algorithm-based model. This study highlights the importance of socioeconomic factors from hidden multi-purpose dam operation processes on not only physical processes-based modeling but also aritificial intelligence modeling.

• Economic Analysis
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• v.26 no.4
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• pp.65-97
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• 2020

The purpose of this paper is to analyze the effects of exports on Korea's employment and to decompose driving factors of change in Korea's employment embodied in exports (EEX). This study uses a multi-regional input-output (MRIO) and structural decomposition analysis (SDA) for empirical analysis, and uses a dataset of World Input-Output Tables (WIOTs) and Socio-Economic Accounts (SEAs) from the World Input-Output Database (WIOD). The main findings of the empirical results are summarized as follows. First, Korea's EEX continues to increase and Korea's share of EEX compared to total employment shows an upward trend. However, Korea's employment inducement coefficient of value-added exports showed a downward trend during the 2000-2014 period. Second, final demand from three countries (China, the United States, and the Rest of the World (RoW)) has affected a significant portion of Korea's EEX. Finally, from the results of the SDA, the effect of changes in final demand was the most important driving factor for the increase in Korea's EEX. Based on the results of this empirical analysis, this study discusses useful policy implications that could increase domestic employment in Korea.

• Journal of the Korea Convergence Society
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• v.11 no.10
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• pp.45-51
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• 2020

Recently, many games provide data related to the users' game play, and there have been a few studies that predict opponent move by combining machine learning methods. This study predicts opponent move using match data of a real-time strategy game named ClashRoyale and a multi-label classification based on machine learning. In the initial experiment, binary card properties, binary card coordinates, and normalized time information are input, and card type and card coordinates are predicted using random forest and multi-layer perceptron. Subsequently, experiments were conducted sequentially using the next three data preprocessing methods. First, some property information of the input data were transformed. Next, input data were converted to nested form considering the consecutive card input system. Finally, input data were predicted by dividing into the early and the latter according to the normalized time information. As a result, the best preprocessing step was shown about 2.6% improvement in card type and about 1.8% improvement in card coordinates when nested data divided into the early.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.7
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• pp.1447-1456
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• 2011

In this paper, we propose a T-S fuzzy feedback linearization method for controlling a non-linear system with multi-input, and the method is applied for trajectory tracking control of wheeled mobile robot. First, an error dynamic equation of wheeled mobile robot is represented by a T-S fuzzy model, and then the T-S fuzzy model is transformed to a linear control system through the nonlinear fuzzy coordinate change and the nonlinear state feedback input. Simulation results showed that the trajectory tracking controller by using the proposed multi-input feedback linearization method gives better performance than the trajectory tracking controller by using the PDC(Parallel Distributed Compensation) method for controlling the T-S Fuzzy system.

• Journal of Korea Multimedia Society
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• v.13 no.8
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• pp.1235-1244
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• 2010

Most emerging smart phones support capacitive touch sensors. It renders existing gesture-based interfaces not suitable since they were developed for the resistive touch sensors and pen-based input. Unlike the flick gestures from the existing gesture interfaces, the finger flick gesture used in this paper reduces the workload about half by selecting the target and the command to perform on the target at a single touch input. With the combination with multi-touch interface, it supports various menu commands without having to learn complex gestures, and is suitable for the touch-based devices hence it minimizes input error. This research designs and implements the multi-touch and flick interface to provide an effective file management system on the smart phones with capacitive touch input. The evaluation proves that the suggested interface is superior to the existing methods on the capacitive touch input devices.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.12
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• pp.15-19
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• 2016

The gate bias dependence of kink phenomenon with a large deviation from the resistance circle in Smith chart is observed in the frequency response of $S_{11}$-parameter for large multi-finger RF MOSFETs. For the first time, this bias dependence is analyzed by measuring magnitude and phase of $S_{11}$-parameter, input resistance and input capacitance. As a result, $V_{gs}$ dependent $S_{11}$-parameter is largely changed by the magnitude of input capacitance as well as dominant pole and zero frequencies of input resistance. At $V_{gs}=0V$, the kink phenomenon occurs in the high frequency region because of very small phase difference of $S_{11}$-parameter and high pole frequency of input resistance. However, the kink phenomenon at higher $V_{gs}$ is generated in the low frequency region owing to large phase difference and low pole frequency.