• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.6
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• pp.1171-1176
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• 2016

VANET are a special kind of MANET adapted to the communications between vehicles. In this work, we propose the models used for representing the communication among vehicles, vehicles mobility features, and VANET simulator using realistic vehicular mobility models. VANET requires that a traffic and network simulator should be used together to perform this test. But, simulator tool has been preferred over traffic simulation because it simple, easy and cheap. Goal of this paper is to create a simulation of Vehicular Ad-Hoc network for urban scenario which can be used for testing purposes. Such environment can be used while designing better MAC protocols in VANETs. We are evaluating the performance of two routing protocols namely AODV and DSDV. The comparison was based on the throughout, packet loss and end-to-end delay. We found that DSDV has less throughput performance and high routing overhead than AODV. On average end-to-end delay and packet loss, AODV performs better than DSDV.

• Analytical Science and Technology
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• v.14 no.4
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• pp.364-370
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• 2001

The corrosion behaviors of reinforcing steels were investigated under chloride ion contained in cement mortar including gypsum by the implementation of half cell potential measurement, EPMA analysis, exterior features, weight loss and extraction experiment. The acceleration test equipment accelerated corrosion of mild steel bar in a short period of time. From observing the exterior features and weight loss, we could evaluate the measure of corrosion. Also, from the extraction experiment of ${SO_4}^{2-}$ with $Cl^-$ ions contained in the ceramic mortar, we concluded that ${SO_4}^{2-}$ ion affected more on the corrosion mechanism in comparison to pH.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.10 no.1
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• pp.102-110
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• 2017

In this paper, we have implemented an real-time adaptive feedback cancellation(AFC) algorithm that can be applied to multi-channel digital hearing aid. Multichannel digital hearing aid typically use the FFT filterbank based Wide Dynamic Range Compression(WDRC) algorithm to compensate for hearing loss. The implemented real-time acoustic feedback cancellation algorithm has one integrated structure using the same FFT filter bank with WDRC, which can be beneficial in terms of computation affecting the hearing aid battery life. In addition, when the AFC fails to operate due to nonlinear input and output, the reduction gain is applied to improve robustness in practical environment. The implemented algorithm can be further improved by adding various signal processing algorithm such as speech enhancement.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.4 no.3 s.8
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• pp.45-50
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• 2005

In this paper, a broadband single balanced mixer is presented using a wideband rat-race implementation by vertical coupling. Frequency is selected as $1.5{\sim}3$ GHz for RF, $1.64{\sim}3.14$ GHz for LO, and 140 MHz for IF signals. When LO signal with 6 dBm at 2.7 GHz is injected, a conversion loss of 7.5 dB and RF to LO isolation of 30 dB are obtained. Also, an average conversion loss of 10 dB, RF to LO isolation of 30 dB, and LO to IF isolation of 45 dB are obtained for frequency band of $1.5{\sim}3$ GHz.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.11
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• pp.1108-1115
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• 2004

A new type of a Rotman lens is presented in this paper fur millimeter-wave applications, such as collision avoidance radar. A dielectric slab Rotman lens is proposed to reduce the conductor loss and to create an appropriate farm for favorable implementation at millimeter-wave frequency. The proposed lens consists of a dielectric slab and slot lines whereas the conventional lenses are constructed with parallel conducting plates. The dielectric slab Rotman lens excited in TE$\_$0/ mode shows a high degree of confinement for the fields, low dispersion, and has an appropriate feed structure. A prototype lens has been designed and fabricated with 9 beam ports and 9 array ports together with 9 tapered slot antennas. This lens has been tested in the range from 10 GHz to 15 GHz and the measured beam widths are about 15$^{\circ}$ at 13 GHz. The measurements also show low mutual coupling between beam ports and an efficiency of about 34.6 %. The overall performance is comparable to that of conventional Rotman lenses even though the prototype was tested at lower than desired frequencies in the microwave frequency range due to our limited resources for fabrications and measurements. It is expected that at millimeter-wave frequency the dielectric slab Rotman lens will have lower conductor loss and lower mutual coupling than conventional Rotman lenses.an lenses.

• The Journal of the Acoustical Society of Korea
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• v.16 no.3
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• pp.57-63
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• 1997

This paper proposes a new stereophonic acoustic echo canceller to preven the performance degradation at the instant of far-end talker's movement or change in transmission room environment in stereophonic teleconferencing system. In stereophonic acoustic echo canceller, the filter coefficients of the adaptive filters for echo cancellation do not have unique solutions and not converge to their optimum values. Therefore, the change of the far-end transmission room environment leads to degradation of ERLE(Echo Return Loss Enhanceement). Moreover, their computational complexity increases as the number of the filter coefficient increases, and their adaptive filters converge very slowly. So the real-time implementation is very difficult. To overcome these problems we propose a pre-processor consisting of an adaptive filter for making pseudo stereophonic signal, and it results in improved performance at the instant of environment change at far-end side and reduction of the total complexity.

• Journal of Korea Multimedia Society
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• v.10 no.8
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• pp.958-966
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• 2007

In this paper, we implement a sound-enhanced MPEG-1 audio decoder on embedded OS Platform. Low bit rate lossy audio codecs such as MP3, OGG, and AAC for mitigating the problems in storage space and network bandwidth suffer a major common problem such as a loss of high frequency fidelity of audio signal. This high frequency loss will reproduce only a band-limited low-frequency part of audio in the standard CD-quality audio. In order to overcome this problem, we embedded a sound enhancement algorithm into the MPEG-1 audio decoder and then the algorithms optimized according to the characteristic of the MPEG-1 audio layer I, II, III were implemented on an embedded OS platform. From the experimental results with spectrum analysis and listening test, we confirm the superiority of the proposed system compared to the standard MPEG-1 audio decoder.

• Journal of Satellite, Information and Communications
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• v.11 no.4
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• pp.44-47
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• 2016

In these days, interest of systems and services using TVWS(TV White Space) are increased, communication systems and services for TVWS have been actively studied. The unoccupied frequency in TVWS is different according to the geographical location and the time of day. RF systems having a frequency tunable bandpass filter operated in TVWS could be efficiently used. In this paper, a frequency tunable bandpass filter operated in 470 ~ 698MHz is designed and implemented. In consideration of simple control and physical size, the tunable bandpass filter is designed with 2-pole. The implemented tunable bandpass filter has the operating frequency band of 470 ~ 698MHz with control voltages of 1.58 ~ 3.93V, the insertion loss of maximum 4.78dB and the return loss of below 10dB. The implemented frequency tunable bandpass filter can be directly used in the RF receiver for TVWS and the design procedures could be used for developing a high power tunable bandpass filter as the basic research data.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.12
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• pp.1307-1313
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• 2014

In this paper, we have proposed a tapered slot antenna for IR-UWB communication system suitable of indoor positioning in the building. The designed tapered slot antenna is designed using Ansys Inc. HFSS and its standing wave ratio, return loss, and radiation pattern is analyzed. In 2.36 GHz ~ 5.51 GHz and, the designed antenna shows satisfactory return loss at -10 dB and meets the requirement of $VSWR{\leq}2$. The presented designed showed a higher sensitivity for the end-fire propagation characteristics in a specific direction across all bands of the radiation pattern.

• Journal of the Korea Society of Computer and Information
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• v.12 no.6
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• pp.297-306
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• 2007

Bar-code based airway logistics systems have many problems like freight loss and data management error due to semiskilled air-cargo process and individual information system. To solve these problems, this paper analyzed how to process an air-cargo practically and designed and implemented the RFID-based airway logistics system. This system has an information service system which manages data from RFID systems in realtime and provides a communication interface for data sharing. And, this system precesses data queries from capture applications and access applications to provide various services to users such as the freight track and trace service. Also, this system includes a H/H reader agent to integrate existing bar-cord systems. It allows us to realize automation and information-oriented air-cargo process and achieve improvement of air-cargo services with reduction of freight loss and management error.