• Title, Summary, Keyword: SSMA

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Preparation of High Range Water Reducers Containing Carboxylic Acid and Their Cement Dispersion Properties(III) (카르본산계 고성능감수제의 제조 및 그들의 시멘트 분산특성(III))

  • 김원기;황재현;김우성;김영진;강인규
    • Magazine of the Korea Concrete Institute
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    • v.8 no.4
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    • pp.161-169
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    • 1996
  • Styrene-maleic anhydride copolymers with different composition (1:1SMA. 5:1SMA) were synthesized and further reacted with sulfuric acid to obtain water soluble copolymers (1:1SSMA, 5:1SSM.4). In the flow experiments of cement mortar mixed with copolymers, 5:1SSMA showed higher fluidity than 1:1SSMA. The cement mortar mixed with 1% 5:1SSMA maintained 95% of original flow after 60 min. On the other hand, the compressive strength of the hardened cement mortars containing 0.5% copolymers after 28 days curing was also examined. The compressive strength of hardened cement mortar containing 5:1SSMA was increased up to 41% compared to the plain while 1:1SSMA was increased up to 29%. As the results, the 5:1SSMA used in this study are greatly expected as a new high range water reducers for the concrete.

A Comparison of FFH/SSMA and DS/CDMA Communications in a Rician Fading Channel

  • Jeungmin Joo;Kim, Kiseon
    • Proceedings of the IEEK Conference
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    • pp.497-500
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    • 2000
  • In this paper, we compare the bit-error-rate performance of the fast-frequency-hopped spread-spectrum multiple-access (FFH/SSMA) and direct-sequence code-division multiple access (DS/CDMA) systems in a Rician fading channel. Each system has a same data rate, bandwidth and transmits over a Rician fading channel. The results illustrate tradoffs in performance between the FFH/SSMA and DS/CDMA systems as a function of the parameters such as average signal to noise ratio and processing gain. The performance of the FFH/SSMA system is shown to be less sensitive to the change of fading environments, while the change of processing gain and average signal to noise ratio gives considerable affect to the FFH/SSMA system compared with the DS/CDMA system. Without respect to the change of system parameters, for most of Rician fading channels (except non-fading channel), FFH/SSMA system gives better performance than DS/CDMA system in BBR < 10$\^$-3/.

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Error rate performance of DS / SSMA system in multipath fading channel (다경로 페이딩 채널에서 DS/SSMA 시스템의 오율특성)

  • 박성경;송왕철;강창언
    • The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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    • v.6 no.1
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    • pp.66-76
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    • 1995
  • In this paper, the error rate performance of DS/SSMA system in multipath fading channel is calculated by computer simulation. At first, the multipath fading channel is modeled with TDL(Tap Delay Line) model. The characteristics of channels, including multipath fading effects and error pattern, are examined by doppler frequency and signal bandwidth, and time spread variation. Using the multipath fading channel model, the error rateperformance of block code and convolutional code is compared, thus the coding sys- tem is applied to the DS / SSMA system. The BER results of DS / SSMA system show that the proposed receiver gives about 2~3[dB] improve- ment compared with the conventional receiver.

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Effects of Multione Interference on the Spectrum-Overlapped DS/SFH-SSMA System (스펙트럼 겹침이 있는 DS/SFH-SSMA 시스템의 다중톤 영향 분석)

  • Park, Jeong-Min;Ryu, Ho-Jin;Kim, Kie-Keun;Ryu, Heung-Gyoon
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.12 no.3
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    • pp.446-450
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    • 2001
  • Performance of spectrum-overlapped BPSK DS/SFH-SSMA communication system is considered in MAI and MTI channel. SSMA system is studied that the frequency spectrums of DS spread signals are overlapped. The increase of overlapping makes ACI and processing gain larger simultaneously. Therefore, BER performance can be optimized by controlling the amount of overlapping. BER equation are derived far the overlapping BPSK DS/SFH-SSMA communication system in multitone interference channel. From the numerical analyses and the simulation results, it can be concluded that the BER performance is considerably improved in optimized overlapping system.

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Error Probability of a DS/SSMA system with Hard-Limiting Correlators (부호상관기를 쓰는 DS/SSMA 계통의 오류확률)

  • 윤진선;송익호;박성일
    • The Journal of the Acoustical Society of Korea
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    • v.12 no.2E
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    • pp.27-32
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    • 1993
  • 이 논문에서는 충격성 잡음이 있는 비선택적 라이시안 페이딩 채널에서 부호 상관 수신기를 쓴 DS/SSMA 계통의 성능을 분석하였다. 이 계통의 평균 이진 오류 확률을 확산 수열이 짧을 때에는 정확한 계산으로, 확산 수열이 길 때에는 근사적인 방법으로 얻었다.

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Flow and Strength Properties of Cement Mortar Mixed with High Range Water Reducer Containing Carboxylic Acid (카르본산계 고성능감수제를 첨가한 시멘트 모르타르의 유동 특성)

  • 김화중;강인규;권영도;김우성;황재현;김원기;박기청
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.142-147
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    • 1995
  • In this study, styrene-maleic anhydride copolymer (SMA) was synthesized from styrene and maleic anhydride and further reacted with sulfuric acid to obtain water-soluble SMA and the flow and strength tests of cement mortar mixed with copolymers were carried out to evaluate the capability of copolymers as high range water reducer for the concrete. It was found from flow experiment that the fluidity of cement mortar mixed with sulfonated SMA (SSMA) was larger than that miced with aminophenol-substituted SSMA (SmSMA). The decreasing rate of the flow of cement mortar mixed with SSMA and SmSMA was decreasing rate of the flow of cement mortar mixed with SSMA and SmSMA was significantly lower than that mixed with naphthalene condensate (NSC). The compressive strength of the hardened cement mortars containing 0.5% copolymers after 28 days curing was examined. The compressive strength of hardened cement mortar containing SSMA and SmSMA was increased up to 32% and 13%, respectively, when compared to the plain. As the results, the copolymers (SSMA and SmSMA) used in this study are greatly expected as a good high range water reducers for the concrete.

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Surgical Strategies in Patients with the Supplementary Sensorimotor Area Seizure

  • Oh, Young-Min;Koh, Eun-Jeong;Lee, Woo-Jong;Han, Jeong-Hoon;Choi, Ha-Young
    • Journal of Korean Neurosurgical Society
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    • v.40 no.5
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    • pp.323-329
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    • 2006
  • Objective : This study was designed to analyze surgical strategies for patients with intractable supplementary sensorimotor area[SSMA] seizures. Methods : Seventeen patients who had surgical treatment were reviewed retrospectively. Preoperatively, phase I [non-invasive] and phase II [invasive] evaluation methods for epilepsy surgery were done. Seizure outcome was assessed with Engel's classification. The mean follow-up period was 27.2 months [from 12 months to 54 months]. Results : An MRI identified structural abnormality in eight patients and 3D-surface rendering revealed abnormal gyration in three. PET, SPECT, and surface EEG could not delineate the epileptogenic zone. Video-EEG monitoring with a subdural grid or depth electrodes verified the epileptogenic zone in all patients. Surgical procedures consisted of a resection of the SSMA and simultaneous callosotomy in two patients, a resection of the SSMA extending to the adjacent area in seven, a resection of a different area without a SSMA resection in seven, and a callosotomy in one. Seizure outcomes were class I in 11 [65%]. class II in five [29%], class III in one [6%]. Conclusion : In patients with intractable SSMA seizure, surgery was an excellent treatment modality. Precise delineation of the epileptogenic zone based on multimodal diagnostic methods can provide good surgical outcomes without neurological complications.

Multipath Diversity Reception of Noncoherent FSK DS/SSMA Communications (Noncoherent FSK DS/SSMA 통신의 다중 경로 다이버시티 수신 특성)

  • 안재영;이재경;황금찬
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.16 no.7
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    • pp.663-679
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    • 1991
  • 본 논문에서는 다중 경로 페이딩 채널에서 최대 다중 경로 지연폭이 한 비트 폭보다 큰 경우 발생할 수 있는 심볼간 간섭을 극복하기 위해 M-ary 신호 방식과 절환 신호 방식을 채용한 다중 경로 다이버시티 수신 noncoherent F나 ds / SSMA 통신 시스템의 평균 오율을 평가하였다. 시스템의 평균 오율은 가우스 근사법을 이용해 채널 파라메타와 PN 시퀀스의 길이와 같은 시스템 파라메타에 대한 식으로 표현하였고, 이러한 결과식을 이용해 M-ary FSK 시스템과 두 종류의 절환 수신기에 대한 FSK시스템의 평균 오율을 수치적으로 분석하였다.

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Performance Analysis of DS/SSMA DPSK Communication System with Diversity and Channel Coding in Mobile Radio Environment (이동 무선 채널에서 다이버시티와 채널 부호를 사용한 DS/SSMA DPSK 통신 시스템의 성능 분석)

  • 강병권;조병진;황금찬
    • Journal of the Korean Institute of Telematics and Electronics A
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    • v.30A no.7
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    • pp.1-11
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    • 1993
  • The bit error rates of DS/SSMA DPSK system with diversity and FEC channel coding in Rayleigh fading and log-normal shadowing channel are evaluated. Microscopic postdetection diversity and macroscopic selection diversiity are used to mitigate the effects of Rayleigh fading and log-normal shadowing, respectively. The numerical results show that the composite use of diversity and channel coding is very efficient for improving system performance compared to their respective uses.

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Performance of DS/SSMA communication systems over frequency selective rician fading channels with gaussian and impulsive noise (가우스 잡음과 임펄스 잡음이 혼합된 주파수 선택적 리시안 페이딩 채널에서 DS/SSMA 통신시스템의 성능분석)

  • 진익수;안재영;이동도;황금찬
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.21 no.2
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    • pp.461-470
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    • 1996
  • In this paper, the average probability of bit error of direct sequence spread spectrum multiple access (DS/SSMA) communication system is derived over frequency-selective rician fading channels with Gaussian and impulsive noise. Multiple access interference due to K asynchronous users transmitting simultaneously is computed using the characteristic function method, and compared with Gaussian approximation.

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