• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.20 no.2
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• pp.81-86
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• 2020

Ambient backscatter communication has a drawback in which the transmission power is limited because the data is transmitted using the ambient RF signal. In order to improve transmission efficiency between transceiver, a channel estimator capable of estimating channel state at a receiver is needed. In this paper, we consider the K-means algorithm to improve the performance of the channel estimator based on EM algorithm. The simulation uses MSE as a performance parameter to verify the performance of the proposed channel estimator. The initial value setting through K-means shows improved performance compared to the channel estimation method using the general EM algorithm.

• Journal of the Korea Society of Computer and Information
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• v.17 no.10
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• pp.55-60
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• 2012

An free-fall object is received only force of gravity. Movement that only accept gravity is free-fall movement, and a free-falling object is free falling body. In other words, free falling body is only freely falling objects under the influence of gravity, regardless of the initial state of objects movement. In this paper, we assume, ignoring the resistance of the air, and the free-fall acceleration by the height does not change within the range of the short distance in the vertical direction. Under these assumptions, we can know about time and maximum height to reach the peak point from jumping vertically upward direction, time and speed of the car return to the starting position, and time and speed when the car fall to the ground. It can be measured by jumping degree and risk of accident from car or motorcycle in telematics.

• Journal of Convergence for Information Technology
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• v.7 no.3
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• pp.97-103
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• 2017

In this paper, we aim to investigate the generalization of ZRC codes by performing performance analysis on various coding rates and channel conditions of Zero Reduction Code (ZRC) for dimming control in VLC system. Simulation results show that the ZRC codes with relatively high coding rate achieve the enhanced BER performance as the RMS (Root Mean Square) delay spread value increases in the NLOS channelse. Therefore, it is expected that the designing of the dimming control technology using ZRC in the future visible light communication system will help to determine the coding rate according to the channel state through the analysis result in this study.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.3
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• pp.1195-1211
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• 2016

The emerging video coding standard High Efficiency Video Coding (HEVC) has shown almost 40% bit-rate reduction over the state-of-the-art Advanced Video Coding (AVC) standard but at about 40% computational complexity overhead. The main reason for HEVC computational complexity is the inter prediction that accounts for 60%-70% of the whole encoding time. In this paper, we propose several fast coding unit (CU) encoding schemes based on the Merge mode and motion estimation information to reduce the computational complexity caused by the HEVC inter prediction. Firstly, an early Merge mode decision method based on motion estimation (EMD) is proposed for each CU size. Then, a Merge mode based early termination method (MET) is developed to determine the CU size at an early stage. To provide a better balance between computational complexity and coding efficiency, several fast CU encoding schemes are surveyed according to the rate-distortion-complexity characteristics of EMD and MET methods as a function of CU sizes. These fast CU encoding schemes can be seamlessly incorporated in the existing control structures of the HEVC encoder without limiting its potential parallelization and hardware acceleration. Experimental results demonstrate that the proposed schemes achieve 19%-46% computational complexity reduction over the HEVC test model reference software, HM 16.4, at a cost of 0.2%-2.4% bit-rate increases under the random access coding configuration. The respective values under the low-delay B coding configuration are 17%-43% and 0.1%-1.2%.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.1
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• pp.21-40
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• 2018

In this paper, we propose the distributed robust beamforming design scheme in cognitive two-way amplify-and-forward (AF) relay networks with imperfect channel state information (CSI). Assuming the CSI errors follow a complex Gaussian distribution, the objective of this paper is to design the robust beamformer which minimizes the total transmit power of the collaborative relays. This design will guarantee the outage probability of signal-to-interference-plus-noise ratio (SINR) beyond a target level at each secondary user (SU), and satisfies the outage probability of interference generated on the primary user (PU) above the predetermined maximum tolerable interference power. Due to the multiple CSI uncertainties in the two-way transmission, the probabilistic constrained optimization problem is intractable and difficult to obtain a closed-form solution. To deal with this, we reformulate the problem to the standard form through a series of matrix transformations. We then accomplish the problem by using the probabilistic approach based on two sorts of Bernstein-type inequalities and the worst-case approach based on S-Procedure. The simulation results indicate that the robust beamforming designs based on the probabilistic method and the worst-case method are both robust to the CSI errors. Meanwhile, the probabilistic method can provide higher feasibility rate and consumes less power.

• Journal of the Korean Ceramic Society
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• v.38 no.1
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• pp.100-105
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• 2001

An all solid-state thin film battery (TFB) was fabricated by growing, undoped and Pt-doped vanadium oxide cathode film ( $V_2$ $O_{5}$ ) on I $n_2$ $O_3$: Sn coated glass, respectively. Room temperature charge-discharge measurements based on Li/Lipon/ $V_2$ $O_{5}$ full-cell structure with a constant current clearly shows that the Pt-doped $V_2$ $O_{5}$ cathode film is superior, in terms of cyclibility. X-ray diffraction (XRD) results indicate that the Pt doping process induces a more random amorphous structure than an undoped $V_2$ $O_{5}$ film. In addition to its modified structure, the Pt-doped $V_2$ $O_{5}$ film has a smoother surface than the undoped sample. Compared to an undoped $V_2$ $O_{5}$ film, the Pt doped $V_2$ $O_{5}$ cathode film has a higher electron conductivity. We hypothesize that the addition of Pt alters electrochemical performance in a manner of making more random amorphous structure and gives an excess electron by replacing the $V^{+5}$. Possible mechanisms are discussed for the observed Pt doping effect on structural and electrochemical properties of vanadium oxide cathode films, which are grown on I $n_2$ $O_3$: Sn coated glass.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.44 no.1
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• pp.1-11
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• 2007

In this paper, a new fully digital control method for UPS inverter, which is based on the double control loop such as the outer voltage control loop and inner current control loop, is proposed. In the proposed control system, overshoots and oscillations due to the computation time-delay are compensated by explicit incorporation of the time-delay in the current control loop transfer function. The inner current control loop is adopted by an internal model controller. The internal model controller is designed to a second order deadbeat reference-to-output response which means that its response reaches the reference in two sampling time including computational time-delays. The outer voltage control loop employing P-Resonance controller is proposed. The resonance controller has an infinite gain at resonant frequency, and the resonant frequency is set to the fundamental frequency of the reference voltage in this paper. Thus the outer voltage control loop causes no steady state error as regard to both magnitude and phase. The effectiveness of the proposed control system has been verified by the simulation and experimental results respectively.

• The Journal of Information Technology
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• v.6 no.4
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• pp.69-80
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• 2003

The electronic commerce continues to grow dramatically. Also, consumer complaints and damages related to e-commerce grow rapidly. The analysis of consumer complaints showed that consumer of e-commerce tended to buy the various product categories including cloth and home appliance. The damages of delivery problem rapidly rose by 1,185.3%. In categories of transaction including of 'internet shopping mall', 'internet contents' and 'internet auction', about 90% of consumer damages was related to 'internet shopping mall' but consumer damages of 'internet contents' was anticipated to be increased in the near future. The major goods and services of damages was 'digital camera', notebook PC', 'internet game service' etc. Therefore, it is required to establish consumer protection measures to be prevent consumer fraud such as internet shopping mall, Halfplaza.com, and major goods and services of damages. Also, it is need to establish system of spontaneous consumer protection improving consciousness of e-commerce companies.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.2
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• pp.276-285
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• 2008

These days the automobile industry, which has rapidly progressed, has been an indispensable part in social and economic activities as well as its research and development have been activated in response to various needs of consumers and markets. The second and third generation control system, getting count on safety and convenience differently than early circuits, cause the hypertrophy of wire harness. The J/Box(Junction Box), which distributes power and wires, was developed to solve the problem. As vehicles have been better in quantity and intelligence, however, environment-friendly electric apparatus system has continuously increased and ITS(Intelligent Transport System) has been introduced in earnest. In result, wires got complicated and multilateral and also there has been a stronger probability that vehicles are out of order due to various problems including mechanical failure. In this study, ISJB(Intelligent Smart Junction Box) was introduced to solve the problem. The diagnosis system was applied to prevent the overload and short of ISJE. Also, the state of vehicles displayed so that drivers monitor it in motion. Likewise error data are saved in the memory so that such data can be analyzed retrospectively. The busbar was adopted in to the main power terminal and the part of power pattern was coverd by lead. Because ISJB is more sensitive to heat in comparison to the busbar type J/Box. With regard the circuits related with safe, alternative circuits were set up in order that electronic devices may be normally operated even when an error arises. ISJB is expected to improve the safety and quality of vehicles.

• Journal of Electrical Engineering and Technology
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• v.10 no.3
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• pp.1144-1153
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• 2015

The resonant mechanism of reradiation interference (RRI) over 1.7MHz from power transmission lines cannot be obtained from IEEE standards, which are based on researches of field intensity. Hence, the resonance is ignored in National Standards of protecting distance between UHV power lines and radio stations in China, which would result in an excessive redundancy of protecting distance. Therefore, based on the generalized resonance theory, we proposed the idea of applying model-based parameter estimation (MBPE) to estimate the generalized resonance frequency of electrically large scattering objects. We also deduced equation expressions of the generalized resonance frequency and its quality factor Q in a lossy open electromagnetic system, i.e. an antenna-transmission line system in this paper. Taking the frequency band studied by IEEE and the frequency band over 1.7 MHz as object, we established three models of the RRI from transmission lines, namely the simplified line model, the tower line model considering cross arms and the line-surface mixed model. With the models, we calculated the scattering field of sampling points with equal intervals using method of moments, and then inferred expressions of Padé rational function. After calculating the zero-pole points of the Padé rational function, we eventually got the estimation of the RRI’s generalized resonant frequency. Our case studies indicate that the proposed estimation method is effective for predicting the generalized resonant frequency of RRI in medium frequency (MF, 0.3~3 MHz) band over 1.7 MHz, which expands the frequency band studied by IEEE.