• Title/Summary/Keyword: wave propagation

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Theoretical and numerical analysis of the influence of initial stress gradient on wave propagations

  • Tao, Ming;Chen, Zhenghong;Li, Xibing;Zhao, Huatao;Yin, TuBing
    • Geomechanics and Engineering
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    • v.10 no.3
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    • pp.285-296
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    • 2016
  • The investigation of stress wave propagation in a medium with initial stress has very important application in the field of engineering. However, the previous research less consider the influence of initial stress gradient on wave propagation. In the present paper, the governing equation of wave propagation in elastic continuum material with inhomogeneous initial stress is derived, which indicated that the inhomogeneous initial stress changed the governing equation of wave propagation. Additionally, the definite problem of wave propagation in material with initial stress gradient is verified by using mathematical physics method. Based on the definite problem, the elastic displacement-time relationship of wave propagation is explored, which indicated that the inhomogeneous initial stress changed waveform and relationship of displacement-time histories. Furthermore, the spall process of blasting wave propagation from underground to earth surface is simulated by using LS-DYNA.

Elastic Wave Propagation in Jointed Rock Mass (절리암반에서의 탄성파 전파 특성)

  • Cha, Min-Su;Cho, Gye-Chun;Baak, Seung-Hyoung
    • Proceedings of the Korean Geotechical Society Conference
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    • 2005.03a
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    • pp.515-520
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    • 2005
  • The behavior of jointed rock mass is much different from that of intact rock due to the presence of joints. Similarly, the characteristics of elastic wave propagation in jointed rock are considerably different from those of intact rock. The propagation of elastic waves in jointed rock is greatly dependent on the state of stress. The roughness, filling materials, and spacing of joints also affect wave propagation in jointed rock. If the wavelength of elastic waves is much larger than the spacing between joints, wave propagation in jointed rock mass can be considered as wave propagation in equivalent continuum. A rock resonant column testing apparatus is made to measure elastic waves propagating through jointed rock in the state of equivalent continuum. Three types of wave, i.e, torsional, longitudinal and flexural waves are monitored during rock resonant column tests. Various roughness and filling materials are applied to joints, and rock columns with various spacings are used to understand how these factors affect wave propagation under a small strain condition. The experimental results suggest that the characteristics of wave propagation in jointed rock mass are governed by the state of stress and influenced by roughness, filling materials and joint spacings.

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Wave Propagation of Laminated Composites by the Hgih-Velocity Impact Experiment (고속 충격실험에 의한 적층 복합재의 파동전파에 관한 연구)

  • 김문생;김남식;박승범
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.17 no.8
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    • pp.1931-1939
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    • 1993
  • The wave propagation characteristics of laminated composites subjected to a transverse high-velocity impact of a steel ball is investigated. For this purpose, high-velocity impact experiments were conducted to obtain the strain response histories, and a finite element analysis based on the higher-order shear deformation theory in conjunction with the static contact law is used. Test materials for investigation are glass/epoxy laminated composite materials with $[0^{\circ}/45^{\circ}/0^{\circ}/-45^{\circ}]_{2s}$ and $[90^{\circ}/-45^{\circ}/90^{\circ}-45^{\circ}/90^{\circ}]_{2s}$ stacking sequences. As a result, the strain responses obtained from the experiments represented the wave propagation characteristics in the transversely impact, also the wave propagation velocities obtained from high-velocity impact experiments and wave propagation theory agree well.

The piezoelectricity of trabecular bone in cancellous bone wave propagation

  • Yoon, Young June;Chung, Jae Pil
    • The Journal of Korea Institute of Information, Electronics, and Communication Technology
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    • v.14 no.1
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    • pp.104-107
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    • 2021
  • The orientation of trabeculae and porosity determine the wave propagation in cancellous bone. Wave propagation, as well as charge density and piezoelectricity, stimulate bone remodeling. Also, Charged ions in the fluid affect wave propagation in cancellous bone. But the trabecular struts' piezoelectricity does not change the waveform of cancellous bone. However, the underlying mechanism is unknown yet why trabecula struts' piezoelectricity does not change wave propagation through cancellous bone. Thus, we derived the governing equation indicating that trabecular struts' piezoelectric properties show that those do not affect wave propagation in cancellous bone.

Optimal Wave Source Position Determination Based on Wave Propagation Simulation (전자파 영향 평가를 통한 최적의 전파 기지국 위치 결정 방법)

  • 박성헌;박지헌
    • Korean Management Science Review
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    • v.18 no.1
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    • pp.41-54
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    • 2001
  • In this paper, we proposed a method to determine optimal wave source for mobile telephone communication. The approach is based on wave propagation simulation. Given a wave source we can determine wave propagation effects on every surfaces of wave simulation environment. The effect is evaluated as a cost function while the source’s position x, y, z work as variables for a parameter optimization. Wave propagated 3 dimensional space generates reflected waves whenever it hits boundary surface, it receives multiple waves which are reflected from various boundary surfacers in space. Three algorithms being implemented in this paper are based on a raytracing theory. If we get 3 dimensional geometry input as well as wave sources, we can compute wave propagation effects all over the boundary surfaces. In this paper, we present a new approach to compute wave propagation. First approach is tracing wave from a source. Source is modeled as a sphere casting vectors into various directions. This approach has limit in computing necessary wave propagation effects on all terrain surfaces. The second approach proposed is tracing wave backwards : tracing from a wave receiver to a wave source. For this approach we need to allocate a wave receiver on every terrain surfaces modeled, which requires enormous amount of computing time. But the second approach is useful for indoor wave propagation simulation. The last approach proposed in this paper is tracing sound by geometric computation. We allow direct, 1-relfe tion, and 2-reflection propagation. This approach allow us to save in computation time while achieving reasonable results. but due to the reflection limitaion, this approach works best in outdoor environment.

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A Experimental Study on Train Speed and Wave Propagation Speed of Contact Wire according to the Speed-up (속도향상에 따른 열차속도와 전차선 파동전파속도에 대한 실험적 연구)

  • Lee, Kiwon
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.62 no.12
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    • pp.1820-1823
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    • 2013
  • An overhead catenary system is the one of the main subjects for increasing speed in electric railway. When a vehicle increases the speed over 350km/h, vibrations and wave propagation reflections occur severely. Therefore, the system suitable for the speed are needed. A wave propagation speed of contact wire is the main criteria to determine the tension for the system. Therefore, a train speed is restricted below 70% of wave propagation speed of it in European railway code. In this study, we measured a strain and uplift of contact wire while HEMU-430X tain is operated for the speed-up trial test in Kyungbu high-speed railway. The measured strain and uplift are analyzed with wave propagation speed according to the speed-up. The more a train speed reaches to a propagation speed, the more measured strain is high. Through the study, an experimental approach is performed about the code which a train speed is restricted below 70% of wave propagation speed of it.

Prediction of Electromagnetic Wave Propagation in Space Environments Based on Geometrical Optics

  • Kim, Changseong;Park, Yong Bae
    • Journal of electromagnetic engineering and science
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    • v.17 no.3
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    • pp.165-167
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    • 2017
  • We predict the electromagnetic wave propagation in space environments using geometrical optics. The effective indices of the troposphere, stratosphere, and ionosphere are computed, and the reflection, refraction, and attenuation of electromagnetic waves in space environments are calculated based on the ray tracing technique and geometrical optics. The influence of the refractive index and loss of atmosphere and the incident angle of the antenna on electromagnetic wave propagation is discussed.

Estimating Concrete Compressive Strength Using Wave Propagation Method (Wave Propagation 기법을 이용한 콘크리트의 압축강도 추정)

  • Kwon, Soo-Ahn;An, Ji-Hwan;Suh, Young-Chan;Cho, Yong-Joo
    • International Journal of Highway Engineering
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    • v.7 no.3 s.25
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    • pp.63-69
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    • 2005
  • For many years, the compressive strength of concrete has been regarded as an important index in determining concrete pavement quality. The compressive strength of the sample cores from the field has been used as quality index of concrete pavement. However, this process is time consuming and requires a lot of labor. Recently, the M-E Design Methodology in the pavement design based on the elastic modulus has been adopted. Therefore, several NDT methodologies have been adopted for QA/QC in the field and for the pavement design. Among various NDT methods, the wave propagation method can be used to measure the elastic modulus of concrete because the wave velocity is directly related to the elastic modulus. Therefore, in this study the wave propagation method was used for estimating the concrete modulus. The relationship between the compressive strength measured in he laboratory and the elastic modulus measured by the wave propagation method was analyzed, and the compressive strength was estimated from the elastic modulus for various mix types. The results showed that the relationship between the elastic modulus and the compressive strength was observed and the relationship varied depending on the aggregate types.

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Dispersion-corrected Finite Element Method for the Stress Wave Propagation (응력파 전파 수치모의를 위한 유한요소법의 분산오차 저감에 관한 연구)

  • Hwang, In-Ho;Choi, Don-Hee;Hong, Sang-Hyun;Lee, Jong-Seh
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2008.04a
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    • pp.39-44
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    • 2008
  • Stress wave propagation plays an important role in many engineering problems for reducing industrial noise and vibrations. In this paper, the dispersion-corrected finite element model is proposed for reducing the dispersion error in simulation of stress wave propagation. At eliminating the numerical dispersion error arising from the numerical simulation of stress wave propagation, numerical dispersion characteristics of the wave equation based finite element model are analyzed and some dispersion control scheme are proposed. The validity of the dispersion correction techniques is demonstrated by comparing the numerical solutions obtained using the present techniques.

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Pressure Wave Propagation in the Discharge Piping with Water Pool

  • Bang Young S.;Seul Kwang W.;Kim In-Goo
    • Nuclear Engineering and Technology
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    • v.36 no.4
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    • pp.285-294
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    • 2004
  • Pressure wave propagation in the discharge piping with a sparger submerged in a water pool, following the opening of a safety relief valve, is analyzed. To predict the pressure transient behavior, a RELAP5/MOD3 code is used. The applicability of the RELAP5 code and the adequacy of the present modeling scheme are confirmed by simulating the applicable experiment on a water hammer with voiding. As a base case, the modeling scheme was used to calculate the wave propagation inside a vertical pipe with sparger holes and submerged within a water pool. In addition, the effects on wave propagation of geometric factors, such as the loss coefficient, the pipe configuration, and the subdivision of sparger pipe, are investigated. The effects of inflow conditions, such as water slug inflow and the slow opening of a safety relief valve are also examined.