• Title/Summary/Keyword: High Peformance

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Noncoherent DPSK hybrid DS/SFH spread spectrum system over rayleigh fading channel in the presence of multiple tone jamming (다중 톤 방해신호가 존재하는 레일레이 페이딩 전송로에서 비동기 DPSK DS/SFH 복합 확산대역 시스템의 성능분석)

  • 박찬범;이재홍
    • Journal of the Korean Institute of Telematics and Electronics S
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    • v.34S no.1
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    • pp.9-15
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    • 1997
  • In this paper, the performance of a hybrid direct-sequence/slow-frequency-hoped (DS/SFH) spread-spectrum (SS) system with noncoherent DPSK modulation is considered. Th ebit error probability is derived ovef a rayleigh fading channel in the presence of multiple tone jamming. Numerical evaluations are presented for some combinations of system parameters. The performance of a hybrid DS/SFH SS system is shown to be inferior to that of a pure DS SS system at low jamming-to-signal power ratio (JSR). At high JSR, the performance of a pure DS SS system is shown to be the same as the worst case peformance of a hybrid DS/SFH SS system.

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Effects of $SiO_2$ on Catalytic Properties of Iron-Based Catalysts for Fischer-Tropsch Synthesis (FT 합성반응용 철촉매에 미치는 촉매특성에 미치는 $SiO_2$ 첨가효과)

  • Chun, Dong-Hyun;Kim, Hak-Joo;Hyun, Sun-Taek;Yang, Jung-Hoon;Lee, Ho-Tae;Yang, Jung-Il;Jung, Heon
    • 한국신재생에너지학회:학술대회논문집
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    • 2009.06a
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    • pp.861-862
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    • 2009
  • Precipitated iron-based catalysts are highly promising for the Fischer-Tropsch synthesis (FTS), in particular for the low temperature FTS below $280^{\circ}C$, because of their high activity and low cost. $SiO_2$ is an essential promoter for the precipitated iron-based catalysts to improve the attrition strength and physical stability. In this study, we carried out FTS over precipitated iron-based catalysts with and without $SiO_2$ in a fixed-bed reactor. The catalysts were prepared by a conventional co-precipitation method. In case of the catalysts with $SiO_2$, we used two comparative preparation methods, i.e., incorporation of $SiO_2$ before precipitation (denoted as precipitated $SiO_2$) and after precipitation (denoted as binder $SiO_2$), respectively. The addition of $SiO_2$ crucially affects both physico-chemical properties and catalytic peformance of precipitated iron-based catalysts.

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A Study on OFDM FFT Design for Peformance of Wireless Multimedia Network (무선 멀티미디어 통신망의 성능 향상을 위한 OFDM FFT 설계에 관한 연구)

  • Kang Jung-yong;Lee Seon-keun
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.30 no.1A
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    • pp.70-75
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    • 2005
  • The efficient hardware design of the the algorithm is important in wide variety of DSP. One example is OFDM(Orthogonal Frequency Division Multiplexing) based WLAN(Wireless Local Area Network) systems which place high requirements on throughput and power consumption on FFT. The output RAM is composed of two banks of $64{\times}W.$ The banks are swapped immediately following the falling edge or the start signal strobe. This bank swapping allows 64-Point FFT to continue Processing samples and to continue filling the alternative bank, without affecting the data flow outputs.

Peformance Comparisons of CDMA, OFDM, and MC-CDMA with Inaccurate Channel Estimates and Low-SNR Environments (신호대잡음비가 낮고 부정확한 채널추정값을 가질 때의 CDMA, OFDM, MC-CDMA의 성능 비교)

  • Rim Minjoong
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.30 no.1A
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    • pp.55-61
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    • 2005
  • Mobile communication systems are required not only to support high-data-rate transmissions in favorable channel conditions but also to be able to tolerate hostile environments possibly encountered by cellular communications. This paper compares CDMA(Code Division Multiple Access), OFDM(Orthogonal Frequency Division Multiplexing), and MC-CDMA(Multi-Carrier CDMA)with inaccurate channel estimates and low SNR environments. The equations and simulation results show that the performance losses in CDMA systems due to imprecise channel estimates are not considerable while frequency-hopping of OFDM systems can result in more than l0dB SNR losses. Also, this paper show that frequency-spreading of MC-CDMA can be very helpful for channel compensation performances than frequency-hopping or time-spreading of OFDM.

Design and Implementation of a High Performance Web Crawler (고성능 웹크롤러의 설계 및 구현)

  • 권성호;이영탁;김영준;이용두
    • Journal of Korea Society of Industrial Information Systems
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    • v.8 no.4
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    • pp.64-72
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    • 2003
  • A Web crawler is an important Internet software technology used in a variety of Internet application software which includes search engines. As Internet continues to grow, implementations of high performance web crawlers are urgently demanded. In this paper, we study how to support dynamic scheduling for a multiprocess-based web crawler. For high peformance, web crawlers are usually based on multiprocess in their implementations. In these systems, crawl scheduling which manages the allocation of web pages to each process for loading is one of the important issues. In this paper, we identify issues which are important and challenging in the crawl scheduling. To address the issue, we propose a dynamic crawl scheduling framework and subsequently a system architecture for a web crawler with dynamic crawl scheduling support. And we analysed the behaviors of Web crawler. Based on the analysis result, we suggest the direction for the design of high performance Web crawler.

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High Performance Control of IPMSM using SV-PWM Method Based on HAI Controller (HAI 제어기반 SV PWM 방식을 이용하나 IPMSM의 고성능 제어)

  • Choi, Jung-Sik;Ko, Jae-Sub;Chung, Dong-Hwa
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.23 no.8
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    • pp.33-40
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    • 2009
  • This paper presents the high performance control of interior permanent magnet synchronous motor(IPMSM) using space vector(SV) PWM method based on hybrid artificial intelligent(HAI) controller. The HAI controller combines the advantages between adaptive fuzzy control and neural network The SV PWM method is applied to a speed control system of motor in the industry field until now and is feasible to improve harmonic rate of output current, switching frequency and response characteristics. This HAI controller is used instead of conventional PI controller in order to solve problems happening when calculating a reference voltage. The HAI controller improves speed performance by hybrid combination of reference model-based adaptive mechanism method, fuzzy control and neural network. This paper analyzes response characteristics of parameter variation, steady-state and transient-state using proposed HAI controller and this controller compares with conventional fuzzy neural network(FNN) and PI controller. Also, this paper proves validity of HAI controller.

High Level Design and Performance Evaluation for the Implementation of WCDMA Base Station Modem (WCDMA 기지국 모뎀의 구현을 위한 상위 레벨 설계 및 통합 성능 평가)

  • Do Joo-Hyun;Lee Young-Yong;Chung Sung-Hyun;Choi Hyung-Jin
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.30 no.1A
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    • pp.10-27
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    • 2005
  • In this paper, we propose a high level design architecture of WCDMA(UMTS) base station modem and synchronization algorithms applied to the proposed architecture. Also analysis of each synchronization algorithm and performance evaluation of fixed point designed modem are shown. Since the target system is base station modem, each synchronization algorithm is designed for its stable operation. To minimize implementation complexity, optimum fixed point design for best operation of synchronization algorithms is performed. We performed symbol level link simulation with fixed point designed modem simulator for data rate of 12.2kbps, 64kbps, 144kbps, and 384kbps. We compared performance results to the minimum requirements specified in 3GPP TS 25.104(Release 5). Extensive computer simulation shows that the proposed modem architecture has stable operation and outperform the minimum requirement by 2 dB. The proposed modem architecture has been applied in the implementation of WCDMA reverse link receiver modem chip successfully.

The study about the effect of IT strategy and business process renovation (정보기술전략과 비즈니스 프로세스 개선이 기업성과에 미치는 영향에 관한 연구)

  • Park, Chan-Uk;Juhn, Sung-Hyun
    • Proceedings of the CALSEC Conference
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    • 2005.11a
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    • pp.131-136
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    • 2005
  • It appears that many companies have made good results by using information technology strategy and business process renovation simultaneously about information technology promotion lately. So this study divides the construct into information technology orientation and business process orientation and sets up business performance as a dependent variable about IT promotion to show whether business performances is high when companies use IT strategy and business process renovation simultaneously about IT promotion. According to this assumption, the information orientation affects business performances. Also it investigated that a interaction with information technology orientation and business process orientation makes a better beneficial effect. Summing up, this will come to the result that information technology orientation with business process orientation makes a better business performances than information technology.

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Simultaneous Determination of Chromium (III) and Chromium(VI) by High Performance Liquid Chromatography(HPLC) (고성능 액체크로마토그래피(HPLC)를 이용한 3가, 6가 크롬의 동시정량에 관한 연구)

  • Roh, Jae Hoon;Kim, Chi Nyon;Kim, Choon Sung;Kim, Kyoo Sang
    • Journal of Korean Society of Occupational and Environmental Hygiene
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    • v.4 no.2
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    • pp.189-197
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    • 1994
  • Analytic methods for Cr(VI) level in industrial hygienic field were suggested by the National Institute for Occupational Safety and Health(NIOSH method 7600, 7604). There were growing needs for measurement of Cr(III) and Cr(VI) levels simultaneously. Two analytical methods were suggested to determine Cr(III) and Cr(VI) levels simultaneously. The one is method by using reversed phase high peformance liquid chromatography(HPLC) and the other is by using ion exchange HPLC. The purpose of this work was to evaluate the usefulness of these two analytic methods. For the difference of ionic charges of Cr(III)-ethylendiamine tetraacetic acid(EDTA) chelate and $CrO_4{^-2}$, we could detect them simultaneously by ion exchange HPLC. Also, we attempted to determine the levels of Cr(III) and Cr(VI) chelated with sodium diethyldithiocarbamate(NaDDTC) by using reversed phase HPLC. The confirmation of Cr(III) and Cr(VI) were checked by fraction collector and nameless atomic absorption spectrometer. The optimal conditions for the formation of Cr(III)-EDTA chelate were two hours incubation period with pH 5. Cr(III)-EDTA and Cr(VI) in EDTA solution were successfully separated by anion exchange column using $Na_2CO_3/NaOH$ mixture as mobile phase. Peaks of Cr(III)-EDTA and Cr(VI) in EDTA were identified at 5 minutes and 7 minutes of retention time respectively by the ion exchange HPLC. The formation of Cr(III)-NaDDTC and Cr(VI)-NaDDTC chelates were twelve hours incubation period. Cr(III)-NaDDTC and Cr(VI)-NaDDTC chelates were separated by reversed phase column using methanol and water mixture as mobile phase. Peaks of Cr(VI)NaDDTC and Cr(III)-NaDDTC chelates were identified at 13 minutes and 26 minutes of retention time respectively by the reversed phase HPLC. Due to reduction of Cr(VI) to Cr(III), it seems to be not suitable for simultaneous determination of Cr(III)-NaDDTC and Cr(VI)-NaDDTC chelates by reversed phase HPLS. Simultaneos determination of Cr(III) and Cr(VI) by ion exchange HPLC was more accurate and simple method.

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Antimicrobial Activity of Soy Protein Hydrolysate with Asp. saitoi Pretense (콩 단백 효소 가수분해물의 항균활성)

  • 주정현;이상덕;이규희;이기택;오만진
    • Journal of the Korean Society of Food Science and Nutrition
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    • v.33 no.2
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    • pp.229-235
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    • 2004
  • Soy protein was hydrolyzed by 5 different pretenses and determinated antimicrobial activity of each hydrolysate. The soy protein hydrolysate treated by pretense from Aspergillus saitoi showed the highest antimicrobial activity among the protease studied and was used for further analysis. Soy protein hydrolysate was fractionated by ultrafiltration for M.W. 10,000,3,000 and 1,000. The M.W 1,000∼3,000 showed the highest antimicrobial activity. The minimum inhibition concentrations of obtained fraction were 0.5∼0.8 mg/mL for gram positive and negative microbials, and its activity was even observed after heating at 121$^{\circ}C$ for 10 min, suggesting that hydrolyzed protein having antimicrobial activity is quite heat-stable. Reverse-phase HPLC was further applied to separate the fraction and 8 peaks were found. Each 8 peaks were separated and pooled and measured antimicrobial activity. Among them, retention time of peak at 16.02 min showed the prominent antimicrobial activity.