• Title/Summary/Keyword: Spreading Length

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Thermal Effluent through Extruded Side Channel

  • Yoon, Tae-Hoon;Yook, Woon-Soo;Yi, Young-Kon
    • Korean Journal of Hydrosciences
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    • v.6
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    • pp.67-79
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    • 1995
  • The reattachment of buoyant efflluent to a shore in a crossflow is investigated experimentally. The effluent is prodeced by discharging heated water through a projected side channel into a confined crossflow of the same depth. In the projecting effluent, the size of recirculating region, which is formed by deflected thermal plume on the lee of the effluent, tends to increase, but the maximum temperature decreases in the direction of the crossflow and it has more uniform transverse spreading compared to non-projected type. The heat flux across the crossflow is found to be independent of the projceted length of the side channel under relatively high buoyancy flux on the contrary to low buoyancy flux. The reattachment of th effluent can be specified by both velocity ratio and densimetric Froude number, whereas only the velocity ratio is governing factor to the reattachment of the effluent in the case of non-projecting type.

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Characteristics on the Variation of Ocean Wave Statistics in the Chujeon Sea (주전해역의 파랑의 통계적 변동 특성)

  • 손병규;류청로
    • Journal of Ocean Engineering and Technology
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    • v.15 no.3
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    • pp.20-27
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    • 2001
  • After using the filtering method, wave parameters are calculated by the spectral analysis and wave by wave analysis. Extreme environments and higher wave characteristics int he Chujeon Sea are analyzed using the observed wave data. Higher wave has been intensely emphasized as an important environmental force parameter in several recent research works. The aims of this study are to summarize the distribution of extreme environment for wind waves, and to find occurrence probability of higher wave in Chujeon Sea. Ocean wave statistics varying with sea state are found to respond linearly to the spectral peakedness parameter Qp, mean run-length and Ursell number. Although the spreading of the field results is large, it may be concluded that the tendency of wave group formation depends on the spectral peakedness parameter Qp. Extreme wave is estimated to apply various model distribution functions by using the monthly maximum significant wave parameters which can be used to the design and analysis of coastal structures.

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$\pi$-A Isotherm for LB Film Deposition (LB 막 제작을 위한 $\pi$-A Isotherm)

  • Song, Il-Seok;Kim, Tae-Wan;Shon, Byoung-Chung;Park, Hyuk;Kang, Dou-Yol
    • Proceedings of the KIEE Conference
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    • 1992.07b
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    • pp.864-867
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    • 1992
  • This paper describes optimum conditions for depositing Langumuir Blodgett(LB) films. $\pi$-A isotherm characteristics were studied with the following species, $C_{18}$-Quinolium(TCNQ), $C_{22}$-Quinolium(TCNQ), Azobenzene, Arachidic Acid, by varing length of alkyl chains, temperacture, pH, spreading amount, barrier moving speed and etc. We have observed the change of $\pi$-A isotherm depending on the above variations. From there we investigate the depositing conditions of LB films for each material.

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Analysis on Power Parameter of Multiuser Interference under various UWB Multiple Access Schemes (초광대역 다중접속 방식에 따른 다중사용자 간섭신호의 전력 파라미터 분석)

  • Lee, Joon-Yong;Kim, ChangKyeong
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.38A no.1
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    • pp.96-107
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    • 2013
  • In this study, we examine the effect of spreading sequence matched filtering on the power parameters of ultrawideband (UWB) multiuser interference (MUI) under different multiple access (MA) scenarios. More specifically, we investigate the manner in which the length of the sequence MF affects the average power, peak power, and the peak-to-average ratio (PAR) of the matched filtered version of an MUI signal. The results of the analysis performed for a simplified scenario are supported by the simulation results obtained for a realistic multipath environment.

Development of νt-κ-γ Turbulence Model for Computation of Turbulent Flows (난류유동 해석을 위한 νt-κ-γ 모델의 개발)

  • Choi, Won-Chul;Seo, Young-Min;Choi, Sang-Kyu;Chung, Myung-Kyoon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.33 no.12
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    • pp.1014-1021
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    • 2009
  • A new eddy viscosity equation was formulated from assumption of turbulence length scale equation and specific dissipation ratio equation. Then, a set of turbulence model equations for the turbulent kinetic energy ${\kappa}$, the viscosity ${\nu}_t$, and the intermittency factor ${\gamma}$ is proposed by considering the entrainment effect. Closure coefficients are determined by experimental data and resorting to numerical optimization. Present model has been applied to compute four representative cases of free shear flows and successfully compared with experimental data. In particular, the spreading rate, the centreline mean velocity and the profiles of intermittency are calculated with improved accuracy. Also, the proposed ${\nu}_t-{\kappa}-{\gamma}$ model was applied to channel flow by considering the wall effect and the results show good agreements with the Direct Numerical Simulation data.

Ventilation Effects on Smoke Behavior in Rescue Station for Tunnel Fires (철도터널 화재시 구난역 내의 연기거동에 미치는 배연효과에 관한 수치연구)

  • Jang, Won-Cheol;Kim, Dong-Woon;Ryou, Hong-Sun;Lee, Seong-Hyuk
    • Proceedings of the KSR Conference
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    • 2008.06a
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    • pp.2130-2138
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    • 2008
  • The present study investigates the ventilation effects on smoke spreading characteristics in railway tunnels with the rescue stations. Experiments were carried out for n-heptane pool fires with a square length 4 cm at different fire locations, and the heat release rates (HRR) were obtained by the measurement of burning rates. In addition, using the commercial code (FLUENT), the present article presents numerical results for smoke behavior in railway tunnels with rescue station, and it uses the MVHS (Modified Volumetric Heat Source) model for estimation of combustion products resulting from the fire source determined from the HRR measurement. As a result, it is found that smoke propagation is prevented successfully by the fire doors located inside the cross-passages and especially, the smoke behavior in the accident tunnel can be controlled through the ventilation system because of substantial change in smoke flow direction in the cross-passages.

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Taxonomic Study of Amphiroa misakiensis Yendo (Rhodophyta) in Korea (한국산 홍조 난쟁이게발에 관한 분류학적 연구)

  • Choi, Do Sung
    • Journal of Integrative Natural Science
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    • v.4 no.1
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    • pp.72-78
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    • 2011
  • Morphological and anatomical characters of Amphiroa misakiensis Yendo are investigated with field materials and taxonomic accounts are given to the species. The plants grow on rocks, mussels or non-articulated corallines from the subtidal zone of Cheju island, and is characterized by recumbent and spreading habit from the substrate. The species is well defined by about 4 cm height, loosely tufted thallus with irregularly dichotomous branches, flat and irregularly broad intergeniculum in upper part, geniculum developing by cracking and sloughing of calcified cortical tissue overlying uncalcified genicular tissue, five to thirteen-tiered geniculum with unequal length, and conceptacles buried in cortices of intergeniculum. Reproductive structures in tetrasporangial, male and female plants are typical of Amphiroa. The structure and developmental patterns of conceptacles are very similar to those shown in previous studies.

MF based Frequency Domain Iterative Equalization for Single-Carrier Transmission with EST Pre-coder (EST Pre-coder를 가진 Single Carrier 전송을 위한 MF기반의 주파수영역 반복 등화기법)

  • Choi, Yun-Seok;Lee, Yeon-Woo
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.36 no.5C
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    • pp.295-301
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    • 2011
  • In [1], it has been shown that the energy spreading transform (EST) based iterative equalizer (IE) could enhance its performance by improving the reliability of the decision feedback symbols without the help of the complicated channel decoder. In the matched filter (MF) based IE proposed in [1], however, its feedforward filter (FFF) has been designed in the frequency domain while its feedback filter (FBF) in the time domain. So its complexity increases proportional to the channel memory length. To solve this problem, in this paper, both FFF and FBF are designed in the frequency domain. This enables the proposed frequency domain IE (FD-IE) to achieve the lower complexity over the conventional method in the highly dispersive channel. In addition, simulation results demonstrate that the BER performance of the proposed method is the same as the conventional.

Performance Comparison and Improvement of STDR/SSTDR Schemes Using Various Sequences (여러 가지 수열을 적용한 STDR/SSTDR 기법의 성능 비교 및 개선)

  • Han, Jeong Jae;Park, So Ryoung
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.39A no.11
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    • pp.637-644
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    • 2014
  • This paper investigates the detection performance of fault location using STDR(sequence time domain reflectometry) and SSTDR(spread spectrum time domain reflectometry) with various length and types of sequences, and then, proposes an improved detection technique by eliminating the injected signal in SSTDR. The detection error rates are compared and analyzed in power line channel model with various fault locations, fault types, and spreading sequences such as m-sequence, binary Barker sequence, and 4-phase Frank sequence. It is shown that the proposed technique is able to improve the detection performance obviously when the reflected signal is weak or the fault location is extremely close.

Cyclic Prefix Reconstruction and Equalization for EST based Modulation (EST기반 변조에서 Cyclic Prefix 복원 및 등화기법)

  • Kwun, Soon-Ik;Kwon, Byung-Uk;Hwang, Tea-Won
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.35 no.9A
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    • pp.835-843
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    • 2010
  • Energy spreading transform (EST) based equalization is a very effective technique to remove inter symbol interference (ISI) in frequency selective channel. EST based system uses cyclic prefix (CP) similar to orthogonal frequency division multiplexing (OFDM) system. Since CP is a redundancy, it degrades the data transmission rate. RISIC is an algorithm that removes an inter block interference (IBI) caused by insufficient CP length and reconstructs CP. In this paper, we propose a system that combines the existing EST system with quadrature phase shift keying (QPSK) modulation and RISIC algorithm to enhance the efficiency of the transmission. Also we extend the proposed system to 16 quadrature amplitude modulation (QAM) modulation. The proposed system is shown to performance close to matched filter bound (MFB) even with insufficient CP.