• Title/Summary/Keyword: Transmission Angle

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Measurements of mid-frequency transmission loss in shallow waters off the East Sea: Comparison with Rayleigh reflection model and high-frequency bottom loss model (동해 천해환경에서 측정된 중주파수 전달손실 측정: Rayleigh 및 HFBL 모델과의 비교)

  • Lee, Dae Hyeok;Oh, Raegeun;Choi, Jee Woong;Kim, Seongil;Kwon, Hyuckjong
    • The Journal of the Acoustical Society of Korea
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    • v.40 no.4
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    • pp.297-303
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    • 2021
  • When sound waves propagate over long distances in shallow water, measured transmission loss is greater than predicted one using underwater acoustic model with the Rayleigh reflection model due to inhomogeneity of the bottom. Accordingly, the US Navy predicts sound wave propagation by applying the empirical formula-based High Frequency Bottom Loss (HFBL) model. In this study, the measurement and analysis of transmission loss was conducted using mid-frequency (2.3 kHz, 3 kHz) in the shallow water of the East Sea in summer. BELLHOP eigenray tracing output shows that only sound waves with lower grazing angle than the critical angle propagate long distances for several kilometers or more, and the difference between the predicted transmission loss based on the Rayleigh reflection model and the measured transmission loss tend to increase along the propagation range. By comparing the Rayleigh reflection model and the HFBL model at the high grazing angle region, the bottom province, the input value of the HFBL model, is estimated and BELLHOP transmission loss with HFBL model is compared to measured transmission loss. As a result, it agrees well with the measurements of transmission loss.

Spectral element method in the analysis of vibrations of overhead transmission line in damping environment

  • Dutkiewicz, Maciej;Machado, Marcela
    • Structural Engineering and Mechanics
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    • v.71 no.3
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    • pp.291-303
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    • 2019
  • In the paper the analysis of natural vibrations of the transmission line with use of spectral elements and the laboratory experiments is performed. The purpose of the investigation is to analyze the natural vibrations of the transmission line and compare with the results obtained in the numerical simulations. Particular attention is paid to the hysteretic and aerodynamic damping analysis. Sensitivity of the wave number is performed for changing of the tension force, as well as for the different damping parameters. The numerical model is made using the Spectral Element Method. In the spectral model, for various parameters of stiffness, damping and tension force, the system response is checked and compared with the results of the accelerations obtained in the measurements. A frequency response functions (FRF) are calculated. The credibility of the model is assessed through a validation process carried out by comparing graphical plots of FRF and time history analysis and numerical values expressing differences in acceleration amplitude (MSG), phase angle differences (PSG) and differences in acceleration and phase angle total (CSG) values. The next aspect constituting the purpose of this paper is to present the wide possibilities of modelling and simulation of slender conductors using the Spectral Element Method. The obtained results show good accuracy in the range of both experimental measurements as well as simulation analysis. The paper emphasizes the ease with which the sensitivity of the conductor and its response to changes in density of spectral mesh division, tensile strength or material damping can be studied.

Ergodic Capacity Analysis of OFDM Transmission Channel Applied to the MIMO Antennas Considering Spatial Propagation Property (공간적 전파전파 특성을 고려한 MIMO 안테나에 적용한 OFDM 전송 채널의 에르고딕 용량 분석)

  • Kim Chang-Joong;Lee Ho-Kyoung
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.17 no.3 s.106
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    • pp.267-271
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    • 2006
  • In this paper, we use the OFDM transmission channel model applied to the MIMO antennas considering spatial propagation property to evaluate and investigate the ergodic capacity of the channel. Specially, we have applied our results to 3GPP TR 25.99 V1.1.0 case 1 LOS off channel description and calculated ergodic capacity with parameters, cluster angle spread and angle of arrival(AOA). Our results show that as the cluster angle spread increase the channel capacity increase until 35 degree, but for more than 35 degree channel capacity does not improved.

Angle-Resolved Photoemission Spectroscopy: Momentum-Space Microscope

  • Hwang, Chan-Cuk
    • Applied Microscopy
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    • v.45 no.3
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    • pp.115-118
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    • 2015
  • In this review paper, I'd like to introduce the basics of angle-resolved photoemission spectroscopy (ARPES) and some of my results taken at the Pohang Accelerator Laboratory (PAL), the only synchrotron radiation in South Korea. The results show that ARPES is very useful, in particular, for studying two-dimensional materials. It looks like a microscope in momentum space similar to transmission electron microscope imaging atoms in real space.

A Study of the Dependence on Incidence Angle of the Sensitivity of an Extraordinary Optical Transmission Sensor (특이 광 투과 센서에서 민감도의 입사각 의존성 연구)

  • Kwon, Yongjae;Lee, Seunghun;Kim, Taeyeon;Kim, Kyujung
    • Korean Journal of Optics and Photonics
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    • v.32 no.3
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    • pp.126-132
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    • 2021
  • In this research, we have investigated the sensitivity of an extraordinary optical transmission sensor depending on the angle of incident light. Three types of light, including a collimated beam and focused beams (4× and 10×), were designed for the sensor system. To compare the sensitivity of the sensor, we measured transmittance spectra using deionized water (n=1.333) and refractive-index-matching oils (n=1.360 and 1.380). Those spectra were analyzed in terms of redshifting of the peak, so that we could determine the sensitivity. The sensitivity tended to increase when the collimated beam is used on the system, and we have concluded that the sensitivity could be affected by the incidence angle on an extraordinary optical transmission sensor.

On discrete nonlinear self-tuning control

  • Mohler, R.-R.;Rajkumar, V.;Zakrzewski, R.-R.
    • 제어로봇시스템학회:학술대회논문집
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    • 1991.10b
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    • pp.1659-1663
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    • 1991
  • A new control design methodology is presented here which is based on a nonlinear time-series reference model. It is indicated by highly nonlinear simulations that such designs successfully stabilize troublesome aircraft maneuvers undergoing large changes in angle of attack as well as large electric power transients due to line faults. In both applications, the nonlinear controller was significantly better than the corresponding linear adaptive controller. For the electric power network, a flexible a.c. transmission system (FACTS) with series capacitor power feedback control is studied. A bilinear auto-regressive moving average (BARMA) reference model is identified from system data and the feedback control manipulated according to a desired reference state. The control is optimized according to a predictive one-step quadratic performance index (J). A similar algorithm is derived for control of rapid changes in aircraft angle of attack over a normally unstable flight regime. In the latter case, however, a generalization of a bilinear time-series model reference includes quadratic and cubic terms in angle of attack. These applications are typical of the numerous plants for which nonlinear adaptive control has the potential to provide significant performance improvements. For aircraft control, significant maneuverability gains can provide safer transportation under large windshear disturbances as well as tactical advantages. For FACTS, there is the potential for significant increase in admissible electric power transmission over available transmission lines along with energy conservation. Electric power systems are inherently nonlinear for significant transient variations from synchronism such as may result for large fault disturbances. In such cases, traditional linear controllers may not stabilize the swing (in rotor angle) without inefficient energy wasting strategies to shed loads, etc. Fortunately, the advent of power electronics (e.g., high-speed thyristors) admits the possibility of adaptive control by means of FACTS. Line admittance manipulation seems to be an effective means to achieve stabilization and high efficiency for such FACTS. This results in parametric (or multiplicative) control of a highly nonlinear plant.

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Effect of Angle and Density of Grooves between Friction Plate Segments on Drag Torque in Wet Clutch of Automatic Transmission (마찰재 그루브에 따른 습식 클러치 드래그 토크 변화 연구)

  • Ryu, Jin Seok;Sung, In-Ha
    • Tribology and Lubricants
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    • v.30 no.2
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    • pp.71-76
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    • 2014
  • As the importance of transmission efficiency to reducing fuel consumption and conserving the environment rapidly increases, reducing the drag torque in an automotive wet clutch is emerging as an important issue in the automotive industry. The drag torque in a clutch occurs from viscous drag generated by automatic transmission fluid in the narrow gap between separate friction plates. In this study, the drag torques in an automotive wet clutch are investigated with respect to the angle and density of the grooves between separate friction plates by three-dimensional finite element simulation of a single set of wet clutch disks considering the two-phase flow of air and oil. The simulation results shows that the drag torque generally increases with the rotational speed to a critical point and then decreases at the high-speed regime. The grooves between the plates plays an important role in reducing the drag peak, and the inclined angle of the grooves affects the oil flow. The grooves with an angle of $50^{\circ}$ shows the lowest drag torques at both low and high speeds. The flow vectors inside the $50^{\circ}$ grooves shows clear evidence that the fluid flows out more easily from the grooves compared with the flow vectors inside grooves with lower angles. The simulation results shows that increasing the number of grooves (density of grooves) decreases the drag torque.

Offset Slider-Rocker Linkage Synthesis Using Transmission Angles as Synthesis Parameters (전달각을 이용한 오프셋 슬라이더-로커 링크장치의 합성)

  • Gwon, Seong-Gyu
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.24 no.4 s.175
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    • pp.881-893
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    • 2000
  • An analytical synthesis technique for offset slider-rocker 4-bar linkages is devised where transmission angles are used as essential synthesis parameters. Finding the location where both the maximum and the minimum transmission angles arise leads to establishing the algorithm for limiting transmission angles of the slider-rocker linkage which has different offsets according to the direction of the slider. Position analysis by the algorithm gives formula for the dimensional synthesis for the linkage. Application to examples shows that the algorithm and the formula yield proper slider-rocker linkages with regard to limiting transmission angles to the maximum value.

Galloping characteristics of a 1000-kV UHV iced transmission line in the full range of wind attack angles

  • Lou, Wenjuan;Wu, Huihui;Wen, Zuopeng;Liang, Hongchao
    • Wind and Structures
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    • v.34 no.2
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    • pp.173-183
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    • 2022
  • The galloping of iced conductors has long been a severe threat to the safety of overhead transmission lines. Compared with normal transmission lines, the ultra-high-voltage (UHV) transmission lines are more prone to galloping, and the damage caused is more severe. To control the galloping of UHV lines, it is necessary to conduct a comprehensive analysis of galloping characteristics. In this paper, a large-span 1000-kV UHV transmission line in China is taken as a practical example where an 8-bundled conductor with D-shaped icing is adopted. Galerkin method is employed for the time history calculation. For the wind attack angle range of 0°~180°, the galloping amplitudes in vertical, horizontal, and torsional directions are calculated. Furthermore, the vibration frequencies and galloping shapes are analyzed for the most severe conditions. The results show that the wind at 0°~10° attack angles can induce large torsional displacement, and this range of attack angles is also most likely to occur in reality. The galloping with largest amplitudes in all three directions occurs at the attack angle of 170° where the incoming flow is at the non-iced side, due to the strong aerodynamic instability. In addition, with wind speed increasing, galloping modes with higher frequencies appear and make the galloping shape more complex, indicating strong nonlinear behavior. Based on the galloping amplitudes of three directions, the full range of wind attack angles are divided into five galloping regions of different severity levels. The results obtained can promote the understanding of galloping and provide a reference for the anti-galloping design of UHV transmission lines.

Stability behavior of the transmission line system under incremental dynamic wind load

  • Sarmasti, Hadi;Abedi, Karim;Chenaghlou, Mohammad Reza
    • Wind and Structures
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    • v.31 no.6
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    • pp.509-522
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    • 2020
  • Wind load is the principal cause for a large number of the collapse of transmission lines around the world. The transmission line is traditionally designed for wind load according to a linear equivalent method, in which dynamic effects of wind are not appropriately included. Therefore, in the present study, incremental dynamic analysis is utilized to investigate the stability behavior of a 400 kV transmission line under wind load. In that case, the effects of vibration of cables and aerodynamic damping of cables were considered on the stability behavior of the transmission line. Superposition of the harmonic waves method was used to calculate the wind load. The corresponding wind speed to the beginning of the transmission line collapse was determined by incremental dynamic analysis. Also, the effect of the yawed wind was studied to determine the critical attack angle by the incremental dynamic method. The results show the collapse mechanisms of the transmission line and the maximum supportable wind speed, which is predicted 6m/s less than the design wind speed of the studied transmission line. Based on the numerical modeling results, a retrofitting method has been proposed to prevent failure of the tower members under design wind speed.