• Title/Summary/Keyword: Multi-Rate

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A Numerical Study of the Effects of Mass Flow Rate Distribution on the Flow Characteristics in a Two Dimensional Multi-Jet with Crossflow of the Spent Fluid (직교류를 가지는 이차원 다중젯트에서 유량분포가 유동특성에 미치는 영향)

  • 강동진;오원태
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.19 no.8
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    • pp.1940-1949
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    • 1995
  • A numerical study for a two dimensional multi-jet with crossflow of the spent fluid has been carried out. Three different distributions of mass-flow rate at 5 jet exits were assumed to see their effects upon the flow characteristics, especially in the jet-flow region. For each distribution, various Reynolds numbers ranging from laminar to turbulent flows were considered. Results show that a fully developed laminar flow exists above a certain Reynolds number whose exact value depends upon the mass flow rate distribution. AS the Reynolds number increases, the flow becomes transitional from downstream and finally a fully developed turbulent flow forms in the jet-flow region. The critical Reynolds number where the fully developed turbulent flow forms is quite dependent upon the distribution of mass-flow rate. One interesting result is that the distribution of the skin friction coefficient along the inpingement plate in the jet-flow region shows a consistent dependency on the Reynolds number, i.e. inversely proportional to the square root of the Reynolds number, regardless of flow regime.

Multi-level UnderVoltage Load Shedding Scheme Considering Rate of Change of Voltage for Voltage Stability (전압 변동률을 고려한 수도권 전압 안정화 다단계 부하차단 적용 방안)

  • Lee, Yun-Hwan;Kim, Tae-Gyun;Kim, Ji-Hun;Lee, Byong-Jun;Kang, Bu-Il;Cho, Jong-Man
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.58 no.12
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    • pp.2335-2341
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    • 2009
  • High technique growth of modem times and high industrial facility in consequence of buildings demand for electric power of an extensive scale with stability supply and maintenance of high quality. But, power system always have risk of network contingency. When power system break out disturbance, it circumstantially happen like uncontrolled loss of load developing from of cascading. Severely which would be raised wide area blackout, plan to prevent, which make stability through a little of load shedding and multi-level UnderVoltageLoadShdding should work. This paper presents target, sensitivity of bus voltage have choose appropriating load shedding location and load shedding decision making logic with considering rate of change of voltage have studied multi-level under voltage load shedding scheme. Calculation of rate of change of voltage applied method of least square. As a result, we are studied an dynamic analysis of 2008 summer peak data. We have been known that network analysis is a little development and developing UnderVoltageLoadShedding scheme.

Map-based Variable Rate Application of Nitrogen Using a Multi-Spectral Image Sensor (멀티스펙트랄 이미지 센서를 이용한 전자 지도 기반 변량 질소 살포)

  • Noh, Hyun-Kwon;Zhang, Qin
    • Journal of Biosystems Engineering
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    • v.35 no.2
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    • pp.132-137
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    • 2010
  • Site-specific N application for corn is one of the precision crop management. To implement the site-specific N application, various nitrogen stress sensing methods, including aerial image, tissue analysis, soil sampling analysis, and SPAD meter readings, have been used. Use of side-dressing, an efficient nitrogen application method than a uniform application in either late fall or early spring, relies mainly on the capability of nitrogen deficiency detection. This paper presents map-based variable rate nitrogen application based using a multi-spectral corn nitrogen deficiency(CND) sensor. This sensor assess the nitrogen stress by means of the estimated SPAD reading calculated from the corn leave reflectance. The estimated SPAD value from the CND sensor system and location information form DGPS of each field block was combined into the field map using a ArcView program. Then this map was converted into a raster file for a map-based variable rate application software. The relative SPAD (RSPAD = SPAD over reference SPAD) was investigated 2 weeks after the treatments. The results showed that the map-based variable rate application system was feasible.

Uncertainty Analysis of Interzonal Airflow Rates by Tracer Gas Methods (추적가스를 이용한 실간환기량 산정방법에 따른 불확실성 해석)

  • Han, Hwa-Taik;Cho, Seok-Hyo
    • Proceedings of the SAREK Conference
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    • 2008.06a
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    • pp.529-534
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    • 2008
  • Interzonal air movements are important to characterize overall ventilation performance of complicated multi-zone buildings. Tracer gas techniques are widely used to measure ventilation rates, ventilation effectiveness, and interzonal air movements. Depending on the number of gases used, they are divided into single and multi tracer gas methods. This paper deals with the comparison of the tracer gas methods in measuring air exchange rate between rooms. Experiments have been conducted in a simple two-room model with known airflow rates. In multi-gas procedure, the concentration decays of two tracer gases, i.e SF6 and R134a are measured after simultaneous injections in each room. The single tracer gas method is also applied by injecting SF6 gas with a time lag between two rooms. The data reduction procedures are developed to obtain the interzonal airflow rate using the matrix inversion, and various data manipulation methods are tested, such as data shift, interpolation, and smoothing. Uncertainty for each airflow rate is investigated depending on the parameters based on the setting values.

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BER Performance of Spatial Modulation in Uplink Multi-User Environment (상향 링크 다중 사용자 환경에서 공간 변조의 BER 성능)

  • Kim, Jin Kwan;Hyun, Kwangmin;Park, Sang Kyu
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.24 no.9
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    • pp.922-927
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    • 2013
  • In this paper, we evaluate the performance of up-link multi-user MIMO systems with SM. The receiver demodulates the received signal using ML method determines the signal which seems to be the most probable after comparing the received signal and all transmitted signal candidates. When transmitting with the same data rate, the SM method shows better performance of bit error rate(BER) than that of the space shift keying(SSK) of the previously proposed multi-user system.

Effects of Complex Agents and pH on the Deposition Behavior of Electroless Ni-Co-P Film (착화제와 pH가 무전해 Ni-Co-P 도금 피막의 석출거동에 미치는 영향)

  • Choi, Byuck-Keun;Yang, Seung-Gi;Shin, Ji-Wung;Hwang, Woon-Suk
    • Corrosion Science and Technology
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    • v.13 no.3
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    • pp.107-111
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    • 2014
  • Electroless plated Ni-Co-P films have been used to suppress the electromagnetic waves from magnetic recording media, and the suppression is known to be achieved with films made with optimized plating composition and plating condition. Effects of complexing agents on the deposition rate and bath stability of Ni-Co-P film were studied using sodium citrate, sodium tartrate and multi-complex agents containing both of them. Deposition of electroless Ni-Co-P platings was dependent upon the complexing agents. Deposition rate was twice when using sodium tartrate compared to that using sodium citrate. And it was slightly slower with multi-complex agents than with sodium tartrate, bath stability being declined in the former. Deposition rate increased with increasing pH until pH 11. Excellent bath stability and good deposition rate were obtained using multi-complex agent as sodium citrate 0.10 mol/L and sodium tartrate 0.15 mol/L in the electroless Ni-Co-P plating films.

A Study on Tracer Gas Methodology to Measure Interzonal Airflow Rates (실간환기량 측정을 위한 추적가스 실험방법론에 관한 연구)

  • Han, Hwa-Taik;Cho, Seok-Hyo
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.21 no.11
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    • pp.606-612
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    • 2009
  • Interzonal air movements are important to characterize overall ventilation performance of complicated multi-zone buildings. Tracer gas techniques are widely used to measure ventilation rates, ventilation effectiveness, and interzonal air movements. Depending on the number of gases used, they are divided into single and multi tracer gas methods. This paper deals with the comparison of the tracer gas methods in measuring air exchange rate between rooms. Experiments have been conducted in a simple two-room model with known airflow rates. In multi-gas procedure, the concentration decays of two tracer gases, i.e SF6 and R134a are measured after simultaneous injections in each room. The single tracer gas method is also applied by injecting SF6 gas with a time lag between two rooms. The data reduction procedures are developed to obtain the interzonal airflow rate using the matrix inversion, and various data manipulation methods are tested, such as data shift, interpolation, and smoothing. Uncertainty for each airflow rate is investigated depending on the parameters based on the setting values.

Performance analysis of Variable Rate Multi-carrier CDMA under an underwater acoustic channel (수중 음향 채널에서 가변 전송율 다중 반송파 CDMA의 성능 분석)

  • Kang, Hee-Hoon;Han, Wan-Ok
    • The Journal of the Korea institute of electronic communication sciences
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    • v.7 no.1
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    • pp.33-38
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    • 2012
  • As underwater channel is very complex and time-varying, don't supports good-quality for communication service. In this paper, a multi-carrier CDMA(MC-CDMA) system for the reliability and robust service in the underwater acoustic channel is proposed and analyzed for its performance. Applied variable rate algorithm to the proposed system gets a channel state information from relationship between SINR and user data-rate. Using channel state information make spectrum usage more efficient and overall system performance improved. In this paper, the performance of proposed system analyzed by simulation. And Pseudo-Random spread codes used in the system are discussed.

Performance Analysis of Multicode DS/CDMA-BPSK Signal in Nakagami Fading Channel (Nakagami 페이딩 채널에서 멀티코드 DS/CDMA-BPSK 신호의 성능 분석)

  • 조성언
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.4 no.1
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    • pp.201-209
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    • 2000
  • In this paper, the bit error rate (BER) performance of Multicode DS/CDMA-BPSK communication system is investigated in the presence of multi user interference and Nakagami fading channel environments. The DS/CDMA-BPSK communication system adopts multicode technique to enhance the data transmission rate. Using the calculated BER performance, BER figures of Multicode DS/CDMA-BPSK communication system are shown to discuss the effect of the number of multi user interference, Nakagami fading index, and data transmission rate. From the results, the transmission rate of DS/CDMA-BPSK signal improve by adopting Multicode technique. And we know that the major parameter of BER performance degradation in Multicode DS/CDMA system is the effect of multi user interference than the fading depth.

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A Numerical Analysis of Flow and Beat Transfer Characteristics of a Two-Dimensional Multi-Impingement Jet(I) (이차원 다중젯트의 유동 및 열전달 특성의 수치적 해석(I) -돌출열원이 없는 경우의 유동특성-)

  • 장대철;이기명
    • Journal of Biosystems Engineering
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    • v.20 no.1
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    • pp.58-65
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    • 1995
  • A numerical study for a two dimensional multi-jet with crossflow of the spent fluid has been carried out. Three different distributions of mass-flow rate at 5 jet exits were assumed to see their effects upon the flow characteristics, especially in the jet-flow region. For each distribution, various Reynolds numbers ranging from laminar to turbulent flows were considered. Calculations drew the following items as conclusion. 1) The development of the free jets issued from downstream jets was hindered by the crossflow formed due to jets. Consequently, the free jet was developed into the channel flow without any evident symptom of impingement jet flow characteristics 2) The crossflow induced the pressure gradient along the cross section of jet exits and the value of the pressure gradient increased as going downstream. The crossflow generated also the turbulent kinetic energy as it collied with the downstream jets. 3) The skin friction coefficient along the impingement plate was affected more by the distribution of mass flow rate at jet exits rather than by the Reynolds number. The skin friction coefficient was inversely proportional to the square root of the Reynolds number, regardless of flow regime when a fully developed flow was formed in the jet flow region. 4) The distribution of the skin friction coefficient along the impingement plate was found to be controlled by adjusting the distribution of mass flow rate at jet exits.

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