• Title/Summary/Keyword: SSMA

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Estimation of Channel States for Adaptive Code Rate Change in DS-SSMA Communication Systems: Part 1. Estimation of Effective Number of Users

  • Youngkwon Ryu;Iickho Song;Taejoo Chang;Kim, Suk-Chan
    • Journal of Electrical Engineering and information Science
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    • v.1 no.1
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    • pp.17-22
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    • 1996
  • Adaptive code rate change schemes in DS-SSMA systems are proposed. In the proposed schemes, the error correcting code rate is changed according to the channel states. Two channel states having significant effects on the bit error probability are considered: one is the effective number of users, and the other is the fading environment. These channel states are estimated based on retransmission requests. The criterion for the change of the code rate is to maximize the throughput under given error bound.

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Estimation of Channel States for Adaptive Code Rate Change in DS-SSMA Communication Systems: Part 2. Estimation of Fading Environment

  • Youngkwon Ryn;Iickho Song;Kim, Kwang-Soon;Jinsoo Bae
    • Journal of Electrical Engineering and information Science
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    • v.1 no.1
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    • pp.23-28
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    • 1996
  • In this series of two papers, adaptive code rate change schemes in DS-SSMA systems are proposed. In the proposed schemes the error correcting code rate is changed according to the channel states. Two channel states having significant effects on the bit error probability are considered: one is the effective number of users considered in Part 1, and the other is the fading environment considered in Part 2. These channel states are estimated based on retransmission requests. The criterion for the change of the code rate is to maximize the throughput under given error bound. Simulation results show that we can transmit maximum amount of information if we change the code rate based on the channel states.

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Preparation of High Range Water Reducer Containing Carboxylic Acid and Their Cement Absorptivity(I) (카르본산계 고성능감수제의 제조 및 그들의 시멘트 흡착성(I))

  • 김화중;강인규;김성훈;김우성;권영도
    • Magazine of the Korea Concrete Institute
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    • v.7 no.2
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    • pp.175-182
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    • 1995
  • Styrene-Maleic anhydride copolymer (SMA) was prepared by the radical copolmerization of styrene and maleic anhydride using ${\alpha}-{\alpha}'$ azobis(isobutyronitrile) as an initiatrr. SMA was further reacted with m-amino phenol to obtain aminophenol-substituted SMR (mSMA). Sulfonated SMA and mSMA were also prepared by the reaction of copolymers with sulfuric acid The copolyniers were characterized by infrared spectroscopy. It was found from the results of elemental analysis that the substitution degree of aminophenol in the mSMR is 44% and the degree is lowered to 35% after sulfonation. The percentage of copolymers adsorbed on the surface of cement particles was increased with a decrease of added copolymers. While, the arnourit of sulfonated SMA absorbed on the surface of cement particles was larger than that of the sulfonated mSMA The copolymers synthesized in this study are probably expected as a high range water reducer for coiicxte.

Characteristic Analysis of Superelastic Shape Memory Alloy Long-Lasting Damper with Pretension (긴장력이 적용된 초탄성 형상기억합금 장수명 댐퍼의 특성 분석)

  • Lee, Heon-Woo;Kim, Young-Chan;Hu, Jong-Wan
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.44 no.1
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    • pp.11-17
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    • 2024
  • A seismic structure is an earthquake-resistant design that dissipates seismic energy by equipping the structure with a device called a damper. As research efforts to reduce earthquake damage continue to rise, technology for isolating vibrations in structures has evolved by altering the materials and shapes of dampers. However, due to the inherent nature of the damper, there are an unescapable restrictions on the extent of plastic deformation that occurs in the material to effectively dissipate energy. Therefore, in this study, we proposed a long-life damper that offers semi-permanently usage and enhances structural performance by applying additional tension which is achieved by utilizing super elastic shape memory alloy (SSMA), a material that self-recovers after deformation. To comprehensively understand the behavior of long-life dampers, finite element analysis was performed considering the design variables such as material, wire diameter, and presence of tension, and response behavior was derived to analyze characteristics such as load resistance, energy dissipation, and residual displacement to determine the performance of long-life dampers in seismic structure. Excellence has been proven from finite element analysis results.

Seismic Performance Evaluation of Recentering Braced Frame Structures Using Superelastic Shape Memory Alloys - Nonlinear Dynamic Analysis (초탄성 형상기억합금을 활용한 자동복원 가새 프레임 구조물의 내진성능 평가 - 비선형 동적해석)

  • Ban, Woo-Hyun;Hu, Jong-Wan;Ju, Young-Hun
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.40 no.4
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    • pp.353-362
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    • 2020
  • Korea was recognized as a relatively safe area for earthquake. However, due to considerable damage to facilities caused by the earthquake in Gyeongju and Pohang, interest in the maintenance and repair of structures is increasing. So interest in vibration damping technology applicable to existing structures is also increasing. However, vibration damping technology has a problem in that its usability is reduced due to damage of the damping device when a strong earthquake occurs. Recently, in order to solve such a problem, study is being conducted to apply a superelastic shape memory alloys (SSMA) capable of recentering bracing. Therefore, in this study, nonlinear dynamic analysis is performed to evaluate the seismic performance of the buckling-restrained braced frame (BRBF) applied SSMA to bracing.

A Study on the Diversity Reception Performance of Spread Spectrum Signals in Interference and Fading Environments (간섭과 페이딩환경에서 스펙트럼 확산(SS) 통신 신호의 다이버시티 수신 특성에 관한 연구)

  • 강희조;이권현;조성준
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.19 no.5
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    • pp.901-911
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    • 1994
  • The error performance of M-ary differential phase shift keying (MDPSK) through m-distribution fading channel in hybrid direct sequence/slow frequency hopped spread spectrum multiple access (DS/SFH-SSMA) systems has been evaluated, and also the error probability has been evaluate when adopting diversity technique and coding technique. From the results, we know that the error performance more deteriorates as depth of fading becomes deeper. In Rayleigh fading environment (m=1), increasing of the number of frequency hopping (q) reduces the effect of multiple access interference, because it decreases the probability a hit. When q is much larger than the number of user (K), the probability of error in high E/N region is dominated by the multipath interference while the multiple access interference is negligible. In lower E/N region, the probability of error is independent of q because the effect of gaussian noise becomes dominat.

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Application of PCM Technology to Concrete II : Effects of SSMA(Sulfonated Styrene-Maleic Anhydride) on the Properties of the 1-Dodecanol Micro-Capsule (PCM 기술의 콘크리트 적용 II : 계면중합법에 의한 1-도데카놀 마이크로 캡슐에 있어서 계면활성제로 사용된 SSMA의 표면활성도가 마이크로 캡슐의 특성에 미치는 영향)

  • Shin, Se-Soon;Jung, Jae-Yun;Lim, Myung-Kwan;Choi, Dong-Uk;Kim, Young-Ho
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.1 no.1
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    • pp.17-25
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    • 2013
  • Thermal storage technology used for indoor heating and cooling to maintain a constant temperature for a long period of time has an advantage of raising energy use efficiency. This, the phase changing material, which utilizes heat storage properties of the substances, capsulizes substances that melt at a constant temperature. This is applied to construction materials to block or save energy due to heat storage and heat protection during the process in which substances melt or freeze according to the indoor or outdoor temperature. The micro-encapsulation method is used to create thermal storage from phase changing material. This method can be broadly classified in 3 ways: chemical method, physical and chemical method and physical and mechanical method. In the physical and chemical method, a wet process using the micro-encapsulation process utilized. This process emulsifies the core material in a solvent then coats the monomer polymer on the wall of the emulsion to harden it. In this process, a surfactant is utilized to enhance the performance of the emulsion of the core material and the coating of the wall monomer. The performance of the micro-encapsulation, especially the coating thickness of the wall material and the uniformity of the coating, is largely dependent on the characteristics of the surfactant. This research compares the performance of the micro-capsules and heat storage for product according to molecular mass and concentration of the surfactant, SSMA (sulfonated styrene-maleic anhydride), when it comes to micro-encapsulation through interfacial polymerization, in which Dodecan-1 is transformed to melamin resin, a heat storage material using phase changing properties. In addition, the thickness of the micro-encapsulation wall material and residual melamine were reduced by adjusting the concentration of melamin resin microcapsules.

Channel Input-Traffic Control of FH/SSMA Systems with a Centralized Controller (기지국이 있는 주파수 도약 대역확산 통신 시스템에서의 채널 입력 트래픽 제어)

  • 김석찬;김정곤;송익호;김형명
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.21 no.1
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    • pp.175-186
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    • 1996
  • An optimal channel input-traffic control (OCIC) policy is proposed for slotted frequency-hopped spread-spectrum multiple access communication systems. When the number of channel input packets is set to the optimal number, the conditional throughput for the OCIC policy is analyzed. The state transition probability is derived, the steady state performance is analyzed, and the mean pracket delay is obtained. It is shown that the mean packet delay decreases considerably when the priority of transmission is given to backlogged users. The smaller is the number of requency slots, the larger are the differences between the preformance of the OCIC policy and that of the other policies.

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