• Title/Summary/Keyword: Wave field measurement

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Physical Model Experiment for Estimating Wave Overtopping on a Vertical Seawall under Regular Wave Conditions for On-Site Measurements (현장 월파계측을 위한 규칙파 조건에서 직립식 호안의 월파량 추정에 관한 모형실험)

  • Dong-Hoon Yoo;Young-Chan Lee;Do-Sam Kim;Kwang-Ho Lee
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.35 no.4
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    • pp.75-83
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    • 2023
  • Apart from implementing hardware solutions like raising the crest freeboard of coastal structures to efficiently counter wave-overtopping, there is a simultaneous requirement for software-driven disaster mitigation strategies. These tactics involve the swift and accurate dissemination of wave-overtopping information to the inland regions of coastal zones, enabling the regulation of evacuation procedures and movement. In this study, a method was proposed to estimate wave-overtopping by utilizing the temporal variation of wave heights exceeding the structure's crown level, with the aim of developing an on-site wave measurement system for providing wave-overtopping information in the field. Laboratory model experiments were conducted on vertical seawall structures to measure wave-overtopping volumes and wave runup heights under different wave conditions and structural freeboard variations. By assuming that the velocity of water inundation on the top of the structure during wave-overtopping events is equivalent to the long-wave velocity, an overtopping discharge coefficient was introduced. This coefficient was utilized to estimate the rate of wave-overtopping based on the temporal changes in wave runup heights measured at the top of the structure. Upon reasonably calculating the overtopping discharge coefficient, it was verified that the estimation of wave-overtopping could be achieved solely based on the wave runup heights.

Evaluation of Stiffness Profile for a Subgrade Cross-Section by the CAP(Common-Array-Profiling)-SASW Technique (CAP SASW 기법에 의한 지반단면의 전단강성구조 평가)

  • Joh Sung-Ho;Jang Dae-Woo;Kang Tae-Ho;Lee Il-Wha
    • Journal of the Korean Geotechnical Society
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    • v.21 no.4
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    • pp.71-81
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    • 2005
  • Surface wave techniques were initially based on 2-D plane waves and were later improved to the techniques based the 3-D based cylindrical waves. However, body-wave interference, near-field effect and limited technology in surface wave measurements restricted the use of 3-D cylindrical waves to the 1-D evaluation of subgrade stiffness. In this study, by the numerical simulation of SASW measurements, the dispersion properties of surface waves including vertical, horizontal Rayleigh waves and Love waves were thoroughly investigated in the 3-D domain, and a new filter criteria to minimize the near-field effect was established, which led to CAP (common-array-profiling)-SASW technique. The CAP-SASW technique enabled the evaluation of subgrade stiffness fur a specific subgrade segment, not for a whole section of measurement array. Therefore, a contour plot of subgrade stiffness with a ground-truth quality can be obtained by the CAP-SASW technique. The procedure proposed in this study was verified by comparing the shear-wave velocity profiles with the shear-wave velocity profiles of downhole testing at two geotechnical sites.

A Methodology for Quality Control of Railroad Trackbed Fills Using Compressional Wave Velocities : II. Verification of Applicability (압축파 속도를 이용한 철도 토공노반의 품질관리 방안 : II. 적용성 검증)

  • Park, Chul-Soo;Mok, Young-Jin;Hwang, Seon-Keun;Park, In-Beom
    • Journal of the Korean Geotechnical Society
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    • v.25 no.9
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    • pp.57-66
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    • 2009
  • In the preliminary investigation (Park et al., 2009), the use of compressional wave velocity and its measurement techniques were proposed as a new quality control measure for trackbed fills. The methodology follows exactly the same procedure as the density control, except the density being replaced by the compressional wave velocity involving consistently with resilient modulus of design stage. The specifications for the control also include field compaction water content of optimum moisture content ${\pm}2%$ as well as the compressional wave velocity. In this sequel paper, crosshole and resonant column tests were performed as well direct-arrival method and laboratory compressional wave measurements to verify the practical applicability of a methodology far the new quality control procedure based upon compressional wave velocity. The stress-modified crosshole results reasonably well agree with the direct-arrival values, and the resonant column test results also agree well with the field crosshole results. The compressional wave velocity turned out to be an excellent control measure for trackbed fills both in the theoretical and practical point of view.

A Numerical Study on the Effectiveness of a Floating Breakwater in Wonjeon Port (부방파제를 이용한 원전항의 정온효과 수치해석)

  • Lee Jeong-Lyul;Song Museok
    • Journal of the Korean Society for Marine Environment & Energy
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    • v.8 no.1
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    • pp.23-30
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    • 2005
  • A numerical scheme is proposed which is applicable to the evaluation of wave field containing floating structures, and the method is utilized to estimate the effect of the floating breakwaters to be installed in Wonjeon port near Masan. The model is based on the mild-slope equation which is widely accepted for the calculation of wave modulation near shores and an additional term is introduced to consider the wave scattering associated with the thin floating structures such as floating breakwaters. The tranquility in Wonjeon port with the floating breakwater in the east side is calculated and compared with the one with a bottom-fixed breakwater. The present method is believed to provide an efficient way of quantitative measurement of the performance of floating breakwaters.

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Development of a 3.5 mm Coaxial Microcalorimeter for Microwave Power Standards (3.5 mm 동축형 미소열량계 개발과 전자파전력 측정표준 확립)

  • Kwon, Jae-Yong;Kim, Jeong-Hwan;Kang, Tae-Weon
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.20 no.9
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    • pp.989-996
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    • 2009
  • RF and microwave power is a basic quantity in electromagnetic metrology which linked directly to major electro-magnetic quantities such as attenuation, RF voltage, antenna characteristics and field strength. This paper deals with a power meter and power sensor with associated theory for RF and microwave power measurement. We study the theory and the key aspects in design of a 3.5 mm coaxial microcalorimeter which works from 50 MHz to 26.5 GHz as a primary microwave power standard.

Measurement of Sounds Radiated of Phantom Piezoelectric Extracorporeal Shock Wave Lithotripter and Their Analysis (체외 충격파 결석 파쇄 장치에 의한 대상물 파쇄시의 발생음의 측정과 해석)

  • Jang, Yun-Seok;Park, Mu-Hun
    • The Journal of the Acoustical Society of Korea
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    • v.16 no.6
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    • pp.36-40
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    • 1997
  • The effectiveness of Extracorporeal Shock Wave Lithotripter(ESWL) for the therapy of calculus has been generally known in the field of urology. However, there are very little paper investigated about physical characteristics of sounds radiated when phantom is shotting with shock waves. Therefore, this paper, firstly, investigates the sounds radiated when impact is applied to the phantom with a single shot by an impact hammer and a clinical ESWL Next, it determines the variance of the sounds radiated during the breaking process using a piece of chalk as a phantom of a calculus. These results will be applied to the examination of the existence of the calculus at the focus and the monitoring the breaking process.

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Electron Microburst Energy Dispersion Calculated by Test Particle Simulation

  • Lee, Jae-Jin;Kim, Yeon-Han;Park, Young-Deuk
    • The Bulletin of The Korean Astronomical Society
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    • v.36 no.2
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    • pp.94.2-94.2
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    • 2011
  • Electron microbursts, energetic electron precipitation having duration less than 1 sec, have been thought to be generated by chorus wave and electron interactions. While the coincidence of chorus and microburst occurrence supports the wave-particle interaction theory, more crucial evidences have not been observed to explain the origin of microbursts. We propose the measurement of energy dispersion of microbursts could be an evidence supporting wave-particle theory. During chorus waves propagate along magnetic field, the resonance condition should be satisfied at different magnetic latitude for different energy electrons. If we observed electron microbursts at low altitude, the arrival time of different energy electrons should make unique dispersion structures. In order to observe such energy dispersion, we need a detector having fast time resolution and wide energy range. Our study is motivated from defining the time resolution and energy range of the detectors required to measure microburst energy dispersions. We performed test particles simulation to investigate how electrons interact with simple coherent waves like chorus waves. We compute a large number of electron's trajectories and successfully produce energy dispersion structures expected when microbursts are observed with 10 msec time resolution detectors at the altitude of 600 km. These results provide useful information in designing electron detectors for the future mission.

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Electron Microburst Generation by Wave Particle Interaction

  • Lee, Jae-Jin;Hwang, Jung-A;Parks, George K.;Min, Kyoung-Wook;Lee, En-Sang
    • Bulletin of the Korean Space Science Society
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    • 2009.10a
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    • pp.43.2-43.2
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    • 2009
  • Electron microbursts are the intense electron precipitation which durations are less than one second. We measured the energy spectra of the microbursts from 170 keV to 340 keV with solid state detectors aboard the low-altitude (680km), polar-orbiting Korean STSAT-1 (Science and Technology SATellite). The data showed that the loss cone at these energies is empty except when microbursts abruptly appear and fill the loss cone in less than 50 msec. This fast loss cone filling requires pitch angle diffusion coefficients larger than ~ 10-2rad2/sec, while ~10-5 rad2/sec was proposed by a wave particle interaction theory. We recalculated the diffusion coefficient, and reviewed of electron microburst generation mechanism with test particle simulations. This simulation successfully explained how chorus waves make pitch angle diffusion within such short period. From considering the resonance condition between wave and electrons, we also showed ~ 100 keV electrons could be easily aligned to the magnetic field, while ~ 1MeV electrons filled loss cone partially. This consideration explained why precipitating microbursts have lower e-folding energy than that of quasi-trapped electrons, and supports the theory that relativistic electron microbursts that have been observed by satellite in-situ measurement have same origin with ~100 keV electron microbursts that have been usually observed by balloon experiments.

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Development of an Ultrasonic Gas Flow Meter Using Transit Time Difference (전달 시간차 방식 초음파 가스 유량계)

  • 박상국;황원호
    • Journal of Institute of Control, Robotics and Systems
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    • v.9 no.9
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    • pp.707-713
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    • 2003
  • We investigate the ultrasonic gas flow meter for the measurement of gas volume quantity, which passing through pipe, using the transit time difference method. We have designed a receiving system of an ultrasonic signal and hardware system of a flow meter Also, we have designed an experimental system for the characteristic test and calibration of a gas flow meter system. We have developed an ultrasonic gas flow meter, which has a measurement uncertainty within $\pm$ 1.7 %. For the test, we have compared our system with a difference pressure type flow meter for a few months in the real field. Through the test, we have confirmed that our system have a good reliability and durability. Also, we have confirmed that our system follows very well the variation of gas volume quantity, which was measured by a difference pressure type flow meter.

MEASUREMENT OF TELESCOPE ABERRATIONS USING CURVATURE SENSING TECHNIQUE (곡률감지방법을 이용한 망원경의 수차 측정)

  • YUK IN-SOO;SEON KWANG-IL
    • Publications of The Korean Astronomical Society
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    • v.19 no.1
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    • pp.71-76
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    • 2004
  • We have developed a tool for measuring optical aberrations of telescope. We adopt curvature sensing technique and use the least square method for finding the amplitudes of the Zernike polynomials. This tool runs under the PC Linux system and the PC windows system with Linux emulators such as Cygwin. The program for UNIX system is used for optical alignment of 1.8M optical telescope at the Bohyunsan Optical Astronomical Observatory (BOAO) and the PC based program is used for the Korea Astronomy Observatory (KAO) wide field telescope (named NEOPAT-3). Our tool is found to be efficient for precise measurement of the optical aberrations of telescopes.