• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.9
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• pp.4166-4182
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• 2018

We consider the Device-to-Device (D2D) communications in cellular networks where each cellular user (CU) shares the same resource with multiple D2D users (DUs). In this paper, we aim to maximize the energy efficiency (EE) of the D2D networks, subject to an interference constraint required by the CU. Since the cellular and D2D communications belong to different networks, we consider to incentivize base station (BS) while assisting the DUs. To this end, we propose a Stackelberg game based interference pricing framework for the considered D2D communications in cellular networks. Unlike most of the existing methods, we use interference pricing framework to jointly address the EE resource allocation problem and the interference management in our networks rather than only improve the EE of the DUs or protect cellular networks. In particular, BS and all the users do not need all channel state information, which is more realistic in practice. In addition, two different pricing strategies are also proposed. Based on the two strategies, we analyze the equilibrium of the game. Moreover, in the first strategy, the upper and lower boundaries of the interference price are obtained. The closed-form expression is gained with a backward induction for the second strategy. Both offer valuable insights to the considered scenarios. Finally, compared with the existing work, the EE of the D2D communications is significantly improved. The advantageous performance of our scheme are demonstrated by the simulation results.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.39 no.8
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• pp.46-51
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• 2002

A new interleaved synchronous mirror delay(SMD) is proposed in order to reduce the circuit size and the power. The conventional interleaved SMD has multiple pairs of forward delay array(FDA) and backward delay away(BDA) in order to reduce the jitter. The proposed interleaved SMD. requires one FDA and one BDA by changing the position of multiplexer. Moreover, the proposed interleaved SMD solves the polarity problem with just one extra inverter. Simulation results show that about 30% power reduction and 40% area reduction are achieved in the proposed interleaved SMD. All circuit simulations and implementations are based on a 0.25um two-metal CMOS technology.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.10
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• pp.1065-1074
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• 2008

T-DMB(Terrestrial Digital Multimedia Broadcasting) system, is based on the Eureka-147 standard, provides various multimedia data services. However T-DMB system needs upgrades for more various services and better services. Therefore, we proposed advanced T-DMB system using unequal error protection system and hierarchical modulation in this paper while maintaing backward compatibility. And we simulated various bit split methods and double binary turbo code of DVB-RCS standard as method of LP data stream for additional service of advanced T-DMB. As the simulation results, double binary turbo code of proposed advanced T-DMB system have each coding gain of over 2 dB compared to conventional T-DMB.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.8B
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• pp.695-705
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• 2012

Due to recent advances in wireless devices and the automotive industry, Vehicular Ad hoc Networks (VANETs) have emerged as a very promising technology for transferring data collected on the road by moving cars. The delivered data may contain emergency information which affects the safety of passengers and drivers as well as the traffic congestion, and the routing protocols have thus a significant impact on the performance of VANETs. In this paper, we study the impact of movement direction of the participating cars which forward data packets on the performance of data delivery and present a new approach which extends the contention-based forwarding (CBF). The proposed reliable CBF (R-CBF) increases the reliability of data deliver on the traffic lights installed roads and reduces the overall propagation delay without routing loops or interruption of data forwarding that may be caused by changes of relative positions of involving cars in routing. Simulation demonstrates that the R-CBF diminishes propagation delay by 38% in comparison to G-SRMB which forwards data to moving cars in the backward direction and eliminates unnecessary retransmissions.

• The Journal of the Convergence on Culture Technology
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• v.6 no.1
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• pp.449-454
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• 2020

We propose an improved de-interlacing method that converts the interlaced images into the progressive images by one field. In the first, Inter-pixel values are calculated by applying Newton's forward difference, backward difference interpolation from upper and lower 5 pixel values. Using inter-pixel values obtained from upper and lower 5 pixel values, it makes more accurate a direction estimate by applying the correlation between upper and lower pixel. If an edge direction is determined from the correlation, a missing pixel value is calculated into the average of upper and lower pixel obtained from predicted direction of edge. From simulation results, it is shown that the proposed method improves subjective image quality at edge region and objective image quality at 0.2~0.3dB as quantitative calculation result of PSNR, compared to previous various de-interlacing methods.

• Journal of Communications and Networks
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• v.10 no.4
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• pp.412-421
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• 2008

We observe simultaneous transmission of relay stations (RSs) allowed in current IEEE 802.16j draft standard for multi-hop relay networks may involve severe interference among the RSs, hence leading to throughput degradation. Allowing only 1/3 of the RSs to simultaneously transmit instead of 1/2 RSs as in the current draft standard reduces the interference but results in reduced throughput. To remedy this problem, we devise schemes to incorporate network coding at link-layer level (decode-and-forward) into the simultaneous transmission of RSs. Data movement is rearranged to maximize coding gain. Formula is derived to dictate exact movement of packets traveling between base station (BS) and mobile stations (MSs) via intermediate RSs. The frame structure in the current IEEE 802.16j draft standard does not allow broadcast needed for network coding. We devise a new frame structure which supports the broadcast. A new R-MAP (pointers to the burst data) is introduced to implement the broadcast. Since our new frame structure is used only for BS to RS or RS to RS communication, our schemes retain backward compatibility with legacy MSs based on IEEE 802.16e standard. Simulation based on simple configuration of RSs shows considerable improvement in terms of system throughput and round trip delay. For a 4-hop relay network with 1 BS and 4 RSs with symmetric traffic in uplink (UL) and downlink (DL), throughput is improved by 49% in DL and by 84% in UL traffic compared with IEEE 802.16j draft standard under the assumption that omni-directional antennae are used in BS and RSs.

• Journal of Environmental Science International
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• v.32 no.8
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• pp.521-531
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• 2023

This study analyzed the impact of recirculation on high-concentration PM_2.5 in the coastal area. Through the analysis of observational data, it was observed that the development of sea breeze led to an increase in PM_2.5 and SO₄^2- concentrations. Hysplit backward trajectory analysis confirmed the occurrence of air mass recirculation. Results from WRF and CMAQ numerical simulations indicated that pollutants transported from land to sea during the night were re-transported to the land by daytime sea breeze, leading to high-concentration PM_2.5 in Busan. To quantitatively investigate the recirculation a recirculation factor (RF) was calculated, showing an increase in RF values during high-concentration PM_2.5 episodes. However, the RF values varied slightly depending on the time resolution of meteorological data used for the calculations. This variation was attributed to the terrain characteristics at observation sites. Additionally, during long-range transported days leading to nationwide high-concentration PM_2.5 events, synoptic-scale circulation dominated, resulting in weaker correlation between PM_2.5 concentration and RF values. This study enhances the understanding of the influence of recirculation on air pollution. However, it is important to consider the impact of temporal resolution and terrain characteristics when using RF for evaluating recirculation during episodes of air pollution.

• Membrane Journal
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• v.17 no.2
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• pp.146-160
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• 2007

A parametric study on pervaporation-facilitated esterification was performed by using a practical model based on non-perfect separation through membrane which is not perfectly permselective to water. Thus, membrane selectivity as well as membrane capability to remove water should be taken into account in establishing the simulation model to explain how the membrane separation influence the esterification reaction process. It was shown by simulation that in the reaction systems with non-perfect separation, the permeation of reactants which are acid or/and alcohol retards the reaction by inducing the backward reaction so that reaction conversion curve is located between a reaction system coupled with pervaporation process having a perfect permselectivity to water and a reaction system without pervaporation process. The volume change of reaction system occurs as a result of the permeation through the membrane. The reaction volume change which can be characterized by the reaction ratio of $r_{\Psi}\;to\;r_{{\Psi}=1}$ affects reaction kinetics by concentrating reactants and products, respectively, with different extent with time; reactant-concentrating effect is dominant during the initial stage of reaction, resulting in facilitating the reaction, and then product-concentrating effect is exerted more on reaction, causing to slow down the reaction. When pervaporative dehydration is applied to the reaction system plays an important role in the reaction as well. The effect of timing to impose pervaporation on reaction system affected the reaction kinetics in terms of reaction rate and reaction conversion. A relationship was derived to explain membrane unit capacity and reaction parameters that will be used as a design tool to determine membrane unit capacity at a given reaction conditions or reaction parameters at a membrane unit capacity.

• Journal of the Korean Society for Nondestructive Testing
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• v.35 no.5
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• pp.291-298
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• 2015

An array type probe for monitoring metal tubes is proposed in this paper which utilizes peak value and peak time of a pulsed eddy current(PEC) signal. The probe consists of an array of encircling coils along a tube and the outside of coils is shielded by ferrite to prevent source magnetic fields from directly affecting sensor signals since it is the magnetic fields produced by eddy currents that reflect the condition of metal tubes. The positions of both exciter and sensor coils are consecutively moved automatically so that manual scanning is not necessary. At one position of send-receive coils, peak value and peak time are extracted from a sensor PEC signal and these data are accumulated for all positions to form an array type peak value signal and an array type peak time signal. Numerical simulation was performed using the backward difference method in time and the finite element method for spatial analysis. Simulation results showed that peak value increases and the peak appears earlier as the defect depth or length increases. The proposed array signals are shown to be excellent in reflecting the defect location as well as variations of defect depth and length within the array probe.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.8
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• pp.582-594
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• 2016

Most studies on hybrid buses are on large-sized buses and not mid-sized low-floor buses. This study uses MATLAB simulation to evaluate the fuel efficiency of such buses powered by diesel. Based on the results, a hybrid electric vehicle system is recommended for the best combination of power and gear ratio. A parallel hybrid system was selected for the hybridization, which transmits front and rear wheel power independently. The necessary power to satisfy the target performance was calculated, and the applicable capacity area was designed. Dynamic programing was used to create and optimize a component sizing algorithm, which was used to scale the capacity of each component of the power source to satisfy the design criteria. The fuel efficiency rate, optimum power source capacity, and gear ratio can be improved by converting a conventional bus into a parallel hybrid bus.