• Title/Summary/Keyword: Spreading Length

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A Study on the Disintegration and Spreading Behavior of Fuel-spray Emanating from a Liquid-thruster Injector by Pseudo-3D Spatial Distribution Measurement (준3차원적 공간분포 계측에 의한 액체추력기 인젝터 연료분무의 분열 및 확산 거동에 관한 연구)

  • Kim, Jin-Seok;Kim, Jeong-Soo
    • Journal of the Korean Society of Propulsion Engineers
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    • v.12 no.5
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    • pp.9-17
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    • 2008
  • Pseudo-3D spatial distribution of spray droplets is investigated by using Dual-mode Phase Doppler Anemometry (DPDA) in order to examine the disintegration and spreading behavior of spray exiting from liquid-propellant thruster injector. Spray injected from nozzle orifice with length-to-diameter ratio ($L/d_o$) of 1.67 and under the injection pressure of 27.6 bar is aligned to the vertical. Vertical and horizontal mean velocities of droplets, Sauter Mean Diameter (SMD), and volumetric flux decrease as droplets travel from center/upstream toward outer region/downstream of spray. Although the distribution of spray characteristic parameters is symmetric against the geometric axis of nozzle orifice, their absolute values are asymmetric.

Disintegration and Spreading Behavior of the Spray emanating from a Liquid-thruster Injector (액체추력기 인젝터로부터 발생하는 분무의 분열 및 확산 거동)

  • Kim, Jin-Seok;Jung, Hun;Kim, Jeong-Soo;Kim, Sung-Cho;Park, Jeong
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2008.11a
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    • pp.113-116
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    • 2008
  • Pseudo-3D Spatial distribution of spray droplets is investigated by using Dual-mode Phase Doppler Anemometry (DPDA) in order to examine the disintegration and spreading behavior of spray exiting from liquid-thruster injector. Spray injected from nozzle orifice with length-to-diameter ratio $(L/d_o)$ of 1.67 and at the injection pressure of 27.6 bar is aligned to the vertical. Vertical and horizontal mean velocities of droplets, Arithmetic Mean Diameter (AMD), Sauter Mean Diameter (SMD), and volumetric flux decrease as droplets travel from center/upstream toward outer region/downstream of spray.

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CDMA Digital Mobile Communications and Message Security

  • Rhee, Man-Young
    • Journal of the Korea Institute of Information Security & Cryptology
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    • v.6 no.4
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    • pp.3-38
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    • 1996
  • The mobile station shall convolutionally encode the data transmitted on the reverse traffic channel and the access channel prior to interleaving. Code symbols output from the convolutional encoder are repeated before being interleaved except the 9600 bps data rate. All the symbols are then interleaved, 64-ary orthogonal modulation, direct-sequence spreading, quadrature spreading, baseband filtering and QPSK transmission. The sync, paging, and forward traffic channel except the pilot channel in the forward CDMA channel are convolutionally encoded, block interleaved, spread with Walsh function at a fixed chip rate of 1.2288 Mcps to provide orthogonal channelization among all code channels. Following the spreading operation, the I and Q impulses are applied to respective baseband filters. After that, these impulses shall be transmitted by QPSK. Authentication in the CDMA system is the process for confirming the identity of the mobile station by exchanging information between a mobile station and the base station. The authentication scheme is to generate a 18-bit hash code from the 152-bit message length appended with 24-bit or 40-bit padding. Several techniques are proposed for the authentication data computation in this paper. To protect sensitive subscriber information, it shall be required enciphering ceratin fields of selected traffic channel signaling messages. The message encryption can be accomplished in two ways, i.e., external encryption and internal encryption.

A Study on the Behavior of an Impacting Droplet on a Wall Having Obstacles (방해물이 존재하는 평판 위 충돌 액적 거동에 관한 연구)

  • Yang, W.J.;Kang, B. S.
    • Journal of ILASS-Korea
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    • v.17 no.1
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    • pp.27-34
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    • 2012
  • In this paper an experimental study is presented to investigate the effect of a step edge and a stationary droplet on the dynamic behavior of impacting droplet on a wall. The main parameters are the distance from the edge and the center-to-center distance between two droplets. Photographic images are presented to show coalescence dynamics, shape evolution and contact line movement. The emphasis is on presenting the spreading length of droplet for the step edge and two coalescing droplets along their original centers. It is clarified that the droplet exhibits much different dynamic behavior depending on the location of the step edge. The momentum of impacting droplet was better transferred to the stationary droplet as the center- to-center distance between two droplets was reduced, which results in more spreading of coalescing droplet.

Analysis of GNSS Signal Acquisition Performance Spreading Zadoff-Chu Codes

  • Jo, Gwang Hee;Choi, Yun Sub;Lim, Deok Won;Lee, Sang Jeong
    • Journal of Positioning, Navigation, and Timing
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    • v.8 no.1
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    • pp.13-18
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    • 2019
  • This paper analyzes the signal acquisition performance of the legacy GNSS spreading codes and a polyphase code. The code length and chip rate of a polyphase code are assumed to be same as those of the GPS L1 C/A and Galileo E1C codes. The autocorrelation and cross correlation characteristics are analyzed. In addition, a way to calculate a more accurate probability of false alarm for a code with sidelobe non-zero auto-correlation function is proposed. Finally, we estimate the probability of detection and the mean acquisition time for a given signal strength and the probability of false alarm.

A study on the bottom trawl gear by the trial of a stern trawler-II -On the net shape of a bottom trawl gear- (실선 시험에 의한 저층 트롤 어구에 관한 연구-II -어구의 수중 형태에 관하여-)

  • 조봉곤;고광수
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.36 no.4
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    • pp.281-286
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    • 2000
  • To analyze the shape of the net mouth of bottom trawl which is composed with 6 seams net, the field experiment was carried out on the sea near Kokunsan Is, Western sea of Korea. The distance of otter board, net height, trawl speed and resistance of the fishing gear were respectively measured according to the change of warp length and towing speed. The results obtained are summarized as follows : 1. The spreading distance of the otter board has been increased straightly according to the increment of towing speed and warp length. The rate of increase by the warp length has been greatly higher than the rate of increase by the towing speed. The total variation of the spreading distance was 57.0-82.8m, and it was occupied 43-62% of the hand rope, net pendent and the length of nets. 2. The height of net mouth has been decreased straightly according to the increment of towing speed and warp length. The rate of decrease by the towing speed has been greatly higher than the decrease rate of the warp length. The total variation of the net height was 3.1-4.0m. 3. When the distance of wing tip is increased, the height of net mouth is decreased, but the ratio of the decreasing rate of the height of net mouth for the increasing rate of the distance of wing tip was gradually low according to the increment of warp length. 4. The ratio of the distance of both wing tip for the height of net mouth has been increased gradually according to the increment of towing speed and warp length, and the total variation of the ratio was 4.17-7.81 times.

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Experimental Study on Characteristics of Micro-Supersonic Jet Flows (마이크로 초음속 제트유동 특성에 관한 실험적 연구)

  • Kim, Jong-Hun;Bang, Jin-Young;Lee, Yeol
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.36 no.8
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    • pp.774-779
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    • 2008
  • An experimental study on the micro-supersonic jet flow fields has been carried out. A sonic nozzle of 440 ${\mu}m$-exit diameter and a Laval nozzle of 800 ${\mu}m$ exit diameter with the nozzle exit Mach number 2.0 were fabricated by stretching a micro Pyrex glass tube for the present experiments. Schlieren flow visualization and Pitot pressure distribution of the jet flow field were obtained. Representative characteristics of the jet flow fields such as, supersonic length, jet core length, similarity of the velocity field, and jet spreading rates, have been observed. All the results were compared to previous observations of larger supersonic jets of higher Reynolds numbers, and it was found that overall characteristics of the micro supersonic jet are qualitatively similar as those of the higher Reynolds number jets, except the jet core length and the jet spreading rate.

A Study on the Friction Loss Reduction in Fire Hoses Used at a Fire Scene (화재현장에서 사용하는 소방호스의 마찰손실 감소 방안에 관한 연구)

  • Min, Se-Hong;Kwon, Yong-Joon
    • Fire Science and Engineering
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    • v.27 no.3
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    • pp.52-59
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    • 2013
  • It was described the measured friction loss depending on pressure used and changes in water flow rates for a fire hose used at a fire scene on this study. As a result of actual measurement based on the result obtained by analyzing the use situation of a fire hose such as the kind, quantity, pressure used, etc. of a fire hose, the friction loss in a fire hose under the condition of using by a fire officer at a fire scene was measured as up to 56.8 %. This is much different from the equivalent length of a fire hose used to calculate the pump head in an indoor and outdoor fire-fighting facility. There is no related restrictive regulation on friction loss, there are even no data on friction loss measured by fire hose makers, and spreading a fire hose without considering friction loss at a fire scene can result in an increased length of hose used and a high-pressure water discharge from a fire engine, so this study aims to establish a standard for an equivalent length to friction loss in a fire hose and to propose a spreading method considering friction loss in a fire hose at a fire scene.

Analysis for Series Resistance of Amorphous Silicon Thin Film Transistor (비정질 실리코 박막 트랜지스터의 직렬 저항에 관한 분석)

  • Kim, Youn-Sang;Lee, Seong-Kyu;Han, Min-Koo
    • The Transactions of the Korean Institute of Electrical Engineers
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    • v.43 no.6
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    • pp.951-957
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    • 1994
  • We present a new model for the series resistance of inverted-staggered amorphous silicon (a-Si) thin film transistors (TFT's) by employing the current spreading under the source and the drain contacts as well as the space charge limited current model. The calculated results based on our model have been in good agreements with the measured data over a wide range of applied voltage, gate-to-source and gate-to-drain overlap length, channel length, and operating temperature. Our model shows that the contribution of the series resistances to the current-voltage (I-V) characteristics of the a-Si TFT in the linear regime is more significant at low drain and high gate voltages, for short channel and small overlap length, and at low operating temperature, which have been verified successfully by the experimental measurements.

Blind Multi-User Detector Using Code-Constrained Minimum Variance Method (코드 제한 최소 분산 방법을 이용한 블라인드 다중 사용자 검파기)

  • 임상훈;정형성이충용윤대희
    • Proceedings of the IEEK Conference
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    • 1998.10a
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    • pp.215-218
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    • 1998
  • This paper proposes a blind multi-user detector using Code-Constrained Minimum Variance (CCMV) method which directly detects the DS-CDMA signals in a multipath fading channel without estimating the channels. This algorithm reduces the complexity of computation by making a small size data matrix with the order of the channel length. Advantageously it requires to know the spreading code and the time delay of only the desired user.

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