• The Journal of Korean Institute of Communications and Information Sciences
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• v.37A no.10
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• pp.885-894
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• 2012

Currently, Demand of data traffic has rapidly increased by popular of smart device. It is very difficult to accommodate demand of data traffic by limited resource of base station (BS). To solve this problem, method has proposed that the Device-to-Device (D2D) reduce frequency overload of the BS and all of the user equipment (UE) inside the BS and neighbor BS don't allow communicating directly to BS. However, in LTE-Advance system cellular link and sharing radio resources of D2D link, the strong interference of the cellular network is still high. So we need to eliminate or mitigate the interference. In this paper, we use the transmission power control method and Soft Frequency Reuse (SFR) resource allocation method to mitigate the interference of the cellular link and D2D link. Simulation results show that the proposed scheme has high performance in terms of Signal to Noise Ratio (SINR) and system average throughput.

• Journal of Digital Contents Society
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• v.6 no.2
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• pp.101-106
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• 2005

In this paper, performance evaluation of mobile access layer for multiple-input multiple-output (MIMO) MultiCarrier(MC)/CDMA 16 QAM system is considered to mitigate multiple access interference and enhance system channel capacity in Rayleigh wireless fading channel. Traditionally, multi-path is viewed as an undesirable feature of wireless communications. Therefore, diversity and adaptive array schemes are proposed to mitigate its effects. Recently, to increase the spectrum efficiency and the link reliability, MIMO schemes is devised to exploit multi-path in a scattering wireless channel. In particular, the channel capacity of MIMO-MC/CDMA 16 QAM system is evaluated according to Eb/No, Mc, p. From the results, in order to improve the channel capacity, the signals at various elements must be uncorrelated. And if the paths are correlated due to inappropriate spacing or mutual coupling effects, the channel capacity of MIMO-MC/CDMA 16 QAM system becomes substantially smaller.

• Smart Structures and Systems
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• v.18 no.1
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• pp.75-92
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• 2016

The design of a semi-active (SA) control system addressed to mitigate wind induced structural demand to high wind turbine towers is discussed herein. Actually, the remarkable growth in height of wind turbines in the last decades, for a higher production of electricity, makes this issue pressing than ever. The main objective is limiting bending moment demand by relaxing the base restraint, without increasing the top displacement, so reducing the incidence of harmful "p-delta" effects. A variable restraint at the base, able to modify in real time its mechanical properties according to the instantaneous response of the tower, is proposed. It is made of a smooth hinge with additional elastic stiffness and variable damping respectively given by springs and SA magnetorheological (MR) dampers installed in parallel. The idea has been physically realized at the Denmark Technical University where a 1/20 scale model of a real, one hundred meters tall wind turbine has been assumed as case study for shaking table tests. A special control algorithm has been purposely designed to drive MR dampers. Starting from the results of preliminary laboratory tests, a finite element model of such structure has been calibrated so as to develop several numerical simulations addressed to calibrate the controller, i.e., to achieve as much as possible different, even conflicting, structural goals. The results are definitely encouraging, since the best configuration of the controller leaded to about 80% of reduction of base stress, as well as to about 30% of reduction of top displacement in respect to the fixed base case.

• Journal of the Korean Association of Geographic Information Studies
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• v.15 no.1
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• pp.133-143
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• 2012

The purpose of this study is to investigate the characteristics of urban heat island considering urban space at nighttime. We used to analyze landuse and landcover data of 1:1,000 scale, DTM, and surface temperature extracted ASTER image satellite of nighttime. According to the analytical results, heat intensity in single-family residential is higher than that in industrial area, public facility area, and commercial area because the anthropogenic heat by energy consumption is released. Likewise, the temperature difference were big in the buildings of industrial area depending on operating hours. Meanwhile, green and river area had cooling impacts mitigating the urban heat island. Therefore, we have to mitigate heat intensity through constructing green space and waterfront area. As mentioned above, we think that the results of this study will be used as base data for effective spatial planning when formulating development planning to mitigate urban heat island at nighttime.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.3
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• pp.45-52
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• 2006

In this paper, we analyze on the effect of LCR filter to mitigate transient overvoltage on the high voltage induction motor fed by H-bridge cascaded 7-level inverter. The switching surge voltage that it was occurred in inverter appears transient overvoltage at the motor input terminal. the transient overvoltage becomes the major cause to occur the insulation failure by serious voltage stress in the stator winding of high voltage induction motor. The effect of transient overvoltage appears more serious in high voltage induction motor than low voltage induction motor. We selected LCR filter for reduction of the transient overvoltage. Consequently, we demonstrated that the LCR filter connected to the invertor output terminals greatly reduces the transient voltage stress and ringing. The results of simulation show the suppression of transient overvoltage at the motor end of a long cable. using EMTP

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.808-811
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• 2015

Cognitive radio has been proposed as a promising dynamic spectrum allocation paradigm. In cognitive radio, spectrum sensing is a fundamental procedure that enables secondary users (unlicensed) employing unused portion of spectrum of primary users (licensed) without causing harmful interference. However, the performance of single-user spectrum-sensing scheme was limited by fading, noise uncertainty shadowing and hidden node problem. Cooperative spectrum sensing was proposed to mitigate these problem. In this paper, we observe cooperative sensing scheme with energy detection using three adaptive thresholds for local decision, which can mitigate sensing failure problem and improve sensing performance at local node. In cooperative scheme we employed OR rules as decision combining at fusion center. We evaluate our scheme through computer simulation, and the results show that with OR combination rule our scheme can achieve best performance than other schemes.

• KIEAE Journal
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• v.10 no.6
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• pp.11-19
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• 2010

To meet with the nation's policy of Green Growth, local governments are rushing to propose an ecological urban development plan. And although various studies stress on the need of ecological planning to harmonize development with preservation, we have come to a point in which a quantitative evaluation of how much ecological planning contributes to the environmental load is needed. Through the increasing tendency of making plans based on the development of IT technology, capability of gathering environmental data and scientific instrument, studies on ecological planning's effect towards environmental load has recently begun. This study aims to perform a quantitative evaluation on how ecological planning mitigate urban heat island in the region of Namyang-ju Wallsanli. Three theories were used to mitigate urban heat island ; White network, Green network and Blue network. As a result, the atmosphere temperature was reduced the whole site $1.1^{\circ}C$ and partly $7^{\circ}C$ and the mean radiant temperature was reduced the whole site $1.1^{\circ}C$ and partly $8.7^{\circ}C$ on the modified ecological landscape plan in summer. The PMV index is 0~1 in ecologically modified landscape plan otherwise almost 3 in landscape plan. This study has its limits on the fact that results may differ from the actual plan as the study was performed based on the land use plan and building plan. However, what is important is that it shows a quantitative result of the effect that ecological planning has on surrounding environment and reducing environmental load.

• Journal of Communications and Networks
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• v.17 no.6
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• pp.622-633
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• 2015

The coexistence among different systems is a major problem in communications. Mutual interference between different systems should be analyzed and mitigated before their deployment. The paper focuses on two aspects that have an impact on the system performance. First, the coexistence analysis, i.e. evaluating the mutual interference. Second aspect is the coexistence techniques, i.e. appropriate system modifications that guarantee the simultaneous use of the spectrum by different technologies. In particular, the coexistence problem is analyzed between ultra-wide bandwidth (UWB) and narrow bandwidth (NB) systems emphasizing the role of spectrum sensing to identify and classify the NB interferers that mostly affect the performance of UWB system. A direct sequence (DS)-time hopping (TH) code design technique is used to mitigate the identified NB interference. Due to the severe effect of Narrowband Interference on UWB communications, we propose an UWB transceiver that utilizes spectrum-sensing techniques together with mitigation techniques. The proposed transceiver improves both the UWB and NB systems performance by adaptively reducing the mutual interference. Detection and avoidance method is used where spectrum is sensed every time duration to detect the NB interferer's frequency location and power avoiding it's effect by using the appropriate mitigation technique. Two scenarios are presented to identify, classify, and mitigate NB interferers.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.9
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• pp.841-851
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• 2014

Wireless technologies sharing the same frequency band and operating in the same environment often interfere with each other, causing severe decrease in performance. In this paper, we propose a algorithm based on traffic scheduling techniques that mitigate interference between different wireless systems operating in the 2.4-GHz industrial, medical, and scientific band. In particular, we consider IEEE 802.11 wireless local area networks (WLANs) and Bluetooth data transfer, showing that the proposed algorithms can work when the two systems are able to exchange information as well as when they operate independently of one another. Results indicate that the proposed algorithm remarkably mitigate the interference between the WLAN and Bluetooth technologies at the expense of a small additional delay in the data transfer.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.2
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• pp.298-306
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• 2015

In this paper, we propose an efficient resource allocation scheme for the integrated satellite/terrestrial networks. The proposed scheme is a frequency sharing technique to mitigate the inter-component interferences which can be generated between a satellite beam and terrestrial cells that are operated in the same frequency. The proposed dynamic resource allocation scheme can mitigate the total inter-component interference by optimizing the total transmission power and it can expect a result of which can lead to an increase in capacity. In such a system, the interference situation can be affected by the distributed traffic demands or up/down link communications environments. In this point of view, we evaluate the performance of the total consumed power, the amount of inter-component interference with respect to different traffic distributions and interference environments between the satellite beam and terrestrial systems.