• Journal of Digital Contents Society
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• v.7 no.3
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• pp.139-145
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• 2006

Short-range wireless transmission and networking technologies are becoming increasingly important in enabling useful mobile applications. Bluetooth and IEEE 802.11b standards are the most commonly deployed technologies for WPAN and WLAN. This paper investigates the effect of short range wireless channel on the performance of MC-CDMA/BPSK system and Bluetooth GFSK signal transmission in AWGN and Rician fading environments. And we investigate performance degradation due to interference effects in short range wireless channel. We firstly derive a equation for the bit error probability in additive white Gaussian noise depending on MC-CDMA/BPSK signal and GFSK modulation signal parameters according to the Bluetooth RF standard. Then, from this error rate expression we calculate the mean error probability for MC-CDMA/BPSK signal and Bluetooth GFSK signal in Rician fading and interference channel. In particular, the impacts of the Rician fading depth and interference level on the error probability is shown in BER performance figures.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.49 no.7
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• pp.10-16
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• 2012

In this paper, we tried to realize a next generation MILES detection system which is robust to optical noise using a narrow band interference optical filter. Applying a narrow band interference optical filter which has the wavelength range of 895~915nm to the LASER wavelength of 900nm, we could obtain detection characteristics robust to strong optical noise which can be occurred in street battles. However, the MILES detection system has the blind range of detection in the incident angle range of $30^{\circ}{\sim}90^{\circ}$. To solve this problem we proposed a method of incident angle scatter using refractors. Applying a concave meniscus lens refractor which has diopter of 5.4 to the MILES detection system, we could eliminate the blind angle of detection.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.21 no.1
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• pp.95-102
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• 2018

Only the habitat characteristics and breeding status of Paridae have been studied, in addition to the lack of research on Parus varius varius, there is no study on the home-range in the post fledging period. This study was analyzed the home-range size of Parus varius varius in the post fledging period. The survey was conducted in the site located in Dankook Univ. Cheonan Campus(Middle Chungcheong Province). We captured five newborn Parus varius varius using artificial nest was installed before. Radio-tracking was carried out for analysis of home-range, and MCP (Minimum Convex Polygon) was used for analysis. We analyzed 1 individual tracked 15 days (VT5) and 4 individuals which missing radio-tracking transmitter within 3 days (VT1~VT4). Home-range of VT5 gradually increased to 1,38ha, 1.42ha, 2.14ha in the order of early, middle, late period. On the other hand, moving distance was decreased to 174.558m 125.129m, 120.180m. Home-range of V1~VT4 was estimated as 0.81ha which was 75.3% share of home-range of VT5 in early period. As the result it was found that home-range is formed far apart from artificial nest that has been influenced by human being interference, thereafter gradually adapting to interference and spreading close to artificial nest. through this research, we can construct basic ecological data for protecting habitat of Parus varius varius and increasing life rate. As first radio-tracking study of Parus varius varius home-range in the post fledging period, it is expected to be useful for the future study of home-range.

• The Journal of the Acoustical Society of Korea
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• v.18 no.3E
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• pp.9-20
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• 1999

To investigate the characteristics of internal waves (IWs) and their effects on acoustic wave propagation, a series of sea experiment were performed in the east coast of Donghae city, Korea in 1997 and 1998 where the water depth varies between 130 and 140 m. Thermistor strings were deployed to measure water temperatures simultaneously at 9 depths. CW source signals with the frequencies of 250,670 and 1000 Hz were received by an array of 15 hydrophones. Through the Wavelet transform analysis, the IWs are characterized as having typical periods of 2-17 min and duration of 1-2 hours. The IWs exist in a group of periods rather than in one period. Underwater acoustic signals also show obvious energy peaks in the periods of less than 12 min. Consistency in the periods of the two physical processes implies that acoustic waves react to the IWs through some mechanisms like mode interference and travel time fluctuation. Based on the thermistor string data, mode arriving structures are analyzed. As thermocline depth varies with time, it may cause travel time difference as much as 4-10 ms between mode 1 and 2 over 10 km range. This travel time difference causes interference among modes and thus fluctuation from range-independent stratified ocean structure. In real situations, however, there exist additional spatial variation of IWs. Model simulations with all modes and simple IWs show clear responses of acoustic signals to the IWs, i.e., fluctuations of amplitude and phase.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.45 no.6
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• pp.35-41
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• 2008

The most important requirement for the automotive radars is the simultaneous target range and velocity measurement under environment of multi-target, clutters, multi-path, and so on. If the many vehicles with 77GHz FMCW(Frequency Modulation Continuous Wave) radar system are in the near area we should consider the interference signals occurred by other radar systems because these signals reduce exact detection of range and velocity. In this paper, we propose the interference cancellation method, which each vehicle radar transmits chirp trains with the different frequency sweep shapes. The proposed method is applied into the various applications such as an intelligent vehicle, Robot, and UGV(Unmanned Ground Vehicle).

• Journal of Korea Multimedia Society
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• v.12 no.10
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• pp.1407-1417
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• 2009

Today is the Information age which Internet service acts a most important Information Source. So the Power Line Communication has been achieved to offer Internet service for Last-Mile area. And Research is achieved to frequence range from 30MHz to 80MHz for High-speed communication service. But, Power Line is not suitable for communication, So, electric wave is generated from flow of communication information. And the electric wave is interfered with Wireless Communication Service using the same frequence range. In this paper, a Notch Filter for reduce of interference between Power Line Communication and Wireless Communication Service is proposed. The proposed emulator is developed using TMS320C6416T DSP board of Texas Instruments.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.5
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• pp.374-379
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• 2002

A new active muffler system has been developed and its superior performance on both noise reduction and engine torque increase is demonstrated with experiment. Main characteristic of the proposed muffler system is the use of destructive interference by transmission path difference of divided exhaust pipes to reduce major exhaust noise components thereby overcoming problems of other active exhaust noise control methods. The exhaust pipe is divided into two sections and joined again downstream. One divided pipe has a sliding mechanism to vary its length, which is controlled to make half wavelength transmission path difference for the major engine rpm frequency. In this system one divided pipe is used to control major rpm frequency and its Harmonics and another pipe is used to control noise component double the frequency of rpm. An after-market tuning muffler, which has very simple internal structure and minimal back pressure, is also installed to remove remaining wideband noise. To make the system to be small enough to be practical, conventional muffler is also installed and used in low rpm range and active muffler is only employed in high rpm range. Noise reduction of the proposed system is comparable to conventional passive muffler. The engine dynamo test has proved the proposed system can recover almost all the torque lost by conventional muffler.

• Current Optics and Photonics
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• v.1 no.4
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• pp.295-307
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• 2017

An innovative system for the alternative continuous wide spectral spatial heterodyne spectrometer (ACWS-SHS) is proposed. The relationship between the ACWS-SHS and the wide spectral spatial heterodyne spectrometer (WS-SHS) at the resolution limit, the spectral range, the grating diffraction efficiency and the interference fringes contrast ratio has been analyzed theoretically. Through the comparison of the theoretical analysis and simulation results, it is found that the two systems for the WS-SHS and the ACWS-SHS have the same resolution limit and spectral range, which are ${\delta}{\sigma}$ and ${\sigma}_{01}$, while in the ACWS-SHS system the critical diffraction efficiency of echelle grating is 68.39% and the critical contrast ratio of interference fringes is 0.4135, which is much better than the performance of the WS-SHS system. Therefore, the ACWS-SHS reduces the high requirements for the precision of equipment and expands the application field of SHS effectively.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.12
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• pp.5820-5834
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• 2017

This paper investigates the channel selection problem with dynamic users and the asymmetric interference relation in distributed opportunistic spectrum access systems. Since users transmitting data are based on their traffic demands, they dynamically compete for the channel occupation. Moreover, the heterogeneous interference range leads to asymmetric interference relation. The dynamic users and asymmetric interference relation bring about new challenges such as dynamic random systems and poor fairness. In this article, we will focus on maximizing the tradeoff between the achievable utility and access cost of each user, formulate the channel selection problem as a directional graphical game and prove it as an exact potential game presenting at least one pure Nash equilibrium point. We show that the best NE point maximizes both the personal and system utility, and employ the stochastic learning approach algorithm for achieving the best NE point. Simulation results show that the algorithm converges, presents near-optimal performance and good fairness, and the directional graphical model improves the systems throughput performance in different asymmetric level systems.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.6
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• pp.1014-1023
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• 2015

This paper presents the method of antenna polarization isolation and resource control for frequency interference reduction due to the frequency reuse between opposite sectors. We have examined the frequency interference between opposite sectors which is occurred by operating base station for reducing frequency interference. The base station has a frequency reusing structure in opposite sector. So, the base station can make a in-band frequency interference. In order to minimize frequency interference, we proposed two methods. The first is the antenna polarization isolation method. The CINR was improved to 27dB from 17dB when using the antenna polarization isolation. The second is resource control which is the method for lining up the RF power and limiting RF power control range of each link. In this paper, by using the proposed two methods, presents a scheme that reduces frequency interference in the frequency reusing structure.