• Title/Summary/Keyword: anti fading

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Study of Anti-Fading Phenomena during Automotive Braking (자동차 제동시 나타나는 Anti-Fading현상에 관한 연구)

  • Lee, Jung-Ju;Jang, Ho
    • Tribology and Lubricants
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    • v.14 no.1
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    • pp.70-78
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    • 1998
  • Two different friction materials (organic and low-metallic pads) for automotive brakes were studied to investigate the anti-fading phenomena during stop. The anti-fading phenomena were pronounced more in the case of using low metallic friction materials than organic friction materials. The main cause of the anti-fading phenomena was the high dependence of friction coefficient on a sliding speed. The anti-fading was prominent when the initial brake temperature was high in the case of low-metallic friction materials due to the strong stick-slip event at high temperature. On the other hand, the anti-fading was not severe in organic friction materials and the effect was reduced at high braking temperature due to the thermal decomposition of organic friction materials. The strong stickslip phenomena of low metallic friction materials at high temperature induced high torque oscillations during drag test. During this experiment two different braking control modes (pressure controlled and torque controlled modes) were compared. The type of the control mode used for brake test significantly affected the friction characteristics.

Influence of Anti-Form in Contemporary Fashion - Focusing on Physicality - (현대 패션에 표현된 안티포름의 영향 - 물질성을 중심으로 -)

  • Yim, Eun-Hyuk
    • Journal of the Korean Society of Costume
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    • v.63 no.4
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    • pp.1-16
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    • 2013
  • Using the premise that fashion and art reflects the characteristics of its times, this study examines the influence of Anti-form in fashion with a focus on physicality. This study combines literary survey and case analysis of both Anti-form in 1960s and 1970s and the fashion collections since 1970s when the influence of Anti-form began to appear in fashion. The influence of Anti-form focusing on physicality is summarized as deconstruction of garment and visualization of the physicality of material. Deconstruction of garment visualizes the invisible structures of garment by deconstructing, restructuring, and deforming the construction and the shapes of the garment, which is illustrated by visualization of design process, overlapping and fusing of materials, loss of stitches, and use of fabrics with flaws, questioning and destroying the sartorial conventions and aesthetic standards. Visualization of the physicality of material exposes the imperfect inside of garment which is concealed conventionally by presenting unfinished garments with minimized sewing procedure, crumpling and flattening fabrics, rubbing and fading surfaces, pulling threads, as well as using the selvages of fabrics.

A New Multicarrier Multicode DS-CDMA Scheme for Time and Frequency Selective Fading Channels

  • Cao Yewen;Tjhung Tjeng Thiang;Ko Chi Chung
    • Journal of Communications and Networks
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    • v.7 no.1
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    • pp.13-20
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    • 2005
  • In this paper, a new multi carrier, direct sequence code division multiple access (MC-DS-CDMA) system is proposed. Our new signal construction is based on convolutional encoding of the transmitted data, serial-to-parallel (S/P) conversion of the encoded data, Walsh-Hadamard-transformation (WHT), a second S/P conversion of the WHT outputs, spread spectrum (SS) modulation with a common pseudo-noise (PN) sequence, and then multicarrier transmission. The system bit error rate (BER) performance in frequency selective fading channel in the presence of additive white Gaussian noise (AWGN) and a jamming tone is analyzed and simulated. The numerical results are compared with those from an orthogonal MC-DS-CDMA system of Sourour and Nakagawa [7]. It is shown that the two systems have almost the same BER performance, but the proposed scheme has better anti-jamming ability.

Performance Analysis of Link-16 Waveform considering Frequency Remapping under PBNJ (부분대역 잡음 재밍 환경에서의 주파수 재할당을 고려한 Link-16 성능 분석)

  • Lee, Kyuman;Noh, Hongjun;Lee, Jongkwan;Lim, Jaesung
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.38C no.11
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    • pp.955-965
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    • 2013
  • The joint tactical information distribution system (JTIDS) is used as the communication terminal of Link-16 by the United States armed forces, north atlantic treaty organization (NATO), and other allied forces. A portion of Link-16 frequencies may be shortly remapped to other systems owing to the growing demand for frequencies, especially in civil aviation, which is witnessing a constant increase in air traffic. This will affect the performance of Link-16. Therefore, in this paper, we analyze the effect of frequency band reduction on the performance of Link-16 waveform under partial-band noise jamming with Nakagami fading, via simulation and numerical analysis. The multi-net and anti-jamming performance of Link-16 with frequency remapping is compared with that of conventional Link-16 systems. The results show that the performance of Link-16 waveform is degraded with the reduction in frequencies. Nonetheless, Link-16 retains its jam resistance, and it can support multiple users in the same time slots.

Anti-jamming Performance Analysis of Link-16 Waveform (Link-16 웨이브폼 항재밍 성능 분석)

  • Noh, Hong-Jun;Kim, Jung-Bin;Lim, Jae-Sung;Nam, Jeong-Ho;Jang, Dhong-Woon
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.35 no.12A
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    • pp.1105-1112
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    • 2010
  • Link-16 is a up-to-date tactical data link used in the armed forces of U.S. and NATO. In order to guarantee the required capabilities of anti-jamming and low probability of detection, Link-16 uses the techniques of frequency hopping and spreading code etc. In this paper, under Nakagami fading channels, we ananlyze the symbol error rates (SERs) of JTIDS/Link-16-type waveform based on both the single- and double-pulse schemes by considering the partial band noise jamming and the pulse jamming models, respectively.

MTJ Performance Analysis of Hybrid DS/SFH Spread-Spectrum System using MSK or QPSK Modulation over Rayleigh Fading Channel (레이리 페이딩 채널상에서 MSK 혹은 QPSK 변조 방식의 하이브리드 DS/SFH 확산 스펙트럼 시스템의 다중톤 재밍 성능 분석)

  • Ryu, Heung-Gyoon;Chung, Byung-Ki
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.13 no.5
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    • pp.492-499
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    • 2002
  • Performance analysis and comparison of the hybrid DS-SFH spread-spectrum (SS) system using coherent MSK and QPSK modulation techniques over Rayleigh fading channel are considered in the presence of MTJ(multi-tone jamming). To analyze the BER performance of the hybrid systems with or without the Rake receiver, signal-to-noise plus interference ratio is derived as a function of the average signal-to-noise ratio, the jammer-to-signal ratio and other system parameters. Numerical results show that the performance difference between the two modulation schemes, MSK and QPSK, is negligible for low JSR, while it becomes significant with the increase of JSR. In multi-path Rayleigh fading channel without Rake receiver, the performances of the two modulation schemes are slightly improved as the DS spreading gain is increased when the total SS bandwidth is fixed. In particular, there is an optimum DS spreading gain for large JSR, in which a minimum BER is achieved, while only DS spreading gives the best performance for small JSR. For hybrid systems with Rake receiver, it is shown that the hybrid system of the MSK modulation scheme provides better anti-jamming performance and larger performance improvement with the increase of multi-path resolution capability of Rake receiver than that of QPSK modulation for all conditions.

Multi-Tone Anti-Jamming Performance Analyses of MSK & QPSK Modulation Hybrid DS-SFH Spread-Spectrum System (MSK와 QPSK 변조 DS-SFH 확산시스템의 다중톤 항재밍 성능 분석)

  • Kim, Yun-Yeong;Yu, Heung-Gyun;Kim, Gi-Geun;Choe, Yeong-Gyun
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.37 no.8
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    • pp.1-10
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    • 2000
  • Performance analyses of hybrid DS-SFH spread-spectrum systems using coherent MSK and QPSK modulation techniques are considered over Rayleigh fading channel in the presence of multi-tone jamming. The BER equations for MSK and QPSK systems with non-diversity reception in the receiver are derived as the concept of average signal-to-noise power ratio E$\_$b//N$\_$0/ and jamming-to-signal power ratio JSR, and the performances is evaluated for various system parameters. The evaluation of performance is done between fading and nonfading system, and between MSK and QPSK system. Results show that the performances of two systems are similar in low JSR. However, MSK system outperforms QPSK system as JSR increases. Overall performances of two systems are a little improved as the DS spreading gain increases for the total spread-spectrum bandwidth fixed. The performance difference between fading system and nonfading system is similar in low E$\_$b//N$\_$0/, however, it becomes very largewith increase of E$\_$b//N$\_$0/..

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Synthesis of Novel Polyol Based on ${\beta}$-Cyclodextrin and Its Rigid PU Foam with Low Thermal Conductivity and High Strength (${\beta}$-Cyclodextrin을 사용한 새로운 Polyol 합성 및 낮은 열전도도와 높은 강도를 갖는 경질 PU Foam의 제조)

  • Park, Juhan;Kim, Taeyoon;Kim, Dong Ho;Moon, Jin-Bok;Chung, Ildoo
    • Journal of Adhesion and Interface
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    • v.13 no.4
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    • pp.163-170
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    • 2012
  • Although ${\beta}$-cyclodextrin (${\beta}$-CD) has been used as medicine, agrichemical, food, cosmetic, antioxidant, anti-volatile agent, anti-hygroscopic agent, fading-protecting agent, and emulsifier due to its ability to form inclusion complex by enclosing another molecule (guest molecule), it has been restricted in practical application because of its low solubility in water and organic solvent. In this study, ${\beta}$-CD derivative as a new polyol with inclusion characteristics against Bisphenol A and cyclopropane, foaming agent for polyurethane (PU), and with improved solubility was synthesized, characterized and used to formulate rigid PU foam with better thermal conductivity and compressive strength compared to that from commercial polyols.

Performance of LDPC Coded OFDM/DS Under Fading and Jamming Environment (페이딩과 재밍 환경에서 LDPC 부호화된 OFDM/DS 시스템의 성능)

  • Seo, Dong-Cheul;Lee, Woo-Chan;Kim, Jong-Hun
    • Journal of the Korea Institute of Military Science and Technology
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    • v.11 no.5
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    • pp.23-33
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    • 2008
  • In this paper, we verify the performance of LDPC coded OFDM/DS system by Monte-Carlo simulation of BER on Eb/No. The simulation results show that LDPC coded OFDM/DS has a strong anti-jamming characteristic over pulse-noise jammer and partial-band noise jammer. The performance of LDPC coded OFDM/DS system is evaluated on both faded waveforms and non-faded waveforms. For non-faded waveforms, high coding gain is attained due to LDPC, even when waveforms have short PN sequence and JSR is only 5dB. Especially, the increase in the repeated number of LDPC decoding enhances coding gain. However, faded waveforms cannot achieve sufficient average effect when PN sequence is short. High coding gain of faded waveforms can be achieved by extending length of PN sequence. In addition, we compare LDPC coded OFDM/DS system with Convolutional coded OFDM/DS system. The simulation results illustrate that when LDPC coded OFDM/DS system with short PN sequence has sufficient average effects, the system shows lower BER than Convolutional coded OFDM/DS system with long PN sequence.

Attack-Proof Cooperative Spectrum Sensing Based on Consensus Algorithm in Cognitive Radio Networks

  • Liu, Quan;Gao, Jun;Guo, Yunwei;Liu, Siyang
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.4 no.6
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    • pp.1042-1062
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    • 2010
  • Cooperative spectrum sensing (CSS) is an effective technology for alleviating the unreliability of local spectrum sensing due to fading/shadowing effects. Unlike most existing solutions, this paper considers the use of CSS technology in decentralized networks where a fusion center is not available. In such a decentralized network, some attackers may sneak into the ranks of cooperative users. On the basis of recent advances in bio-inspired consensus algorithms, an attack-proof, decentralized CSS scheme is proposed in which all secondary users can maintain cooperative sensing by exchanging information locally instead of requiring centralized control or data fusion. Users no longer need any prior knowledge of the network. To counter three potential categories of spectrum sensing data falsification (SSDF) attacks, some anti-attack strategies are applied to the iterative process of information exchange. This enables most authentic users to exclude potentially malicious users from their neighborhood. As represented by simulation results, the proposed scheme can generally ensure that most authentic users reach a consensus within the given number of iterations, and it also demonstrates much better robustness against different SSDF attacks than several existing schemes.