• 제목/요약/키워드: Propagation media

검색결과 466건 처리시간 0.023초

개별요소법에 의한 이차원 응력파의 전달특성에 관한 연구 (A Study on the Characteristics of Two Dimensional Stress Wave Propagation Using the Distinct Element Method)

  • 오금호;김문겸;원용호
    • 한국전산구조공학회:학술대회논문집
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    • 한국전산구조공학회 1998년도 봄 학술발표회 논문집
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    • pp.406-413
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    • 1998
  • The distinct element method is improved to consider the charateristics of stress wave propagation in media involving the discontinuous faces. The distinct element method has many advantages to analyse the characteristics of the reflection, refraction and deflection of the waves in nonhomogeneous media. The double-suing connection system is adopted instead of the single-spring connection system because the distinct element cannot be used for analysing the contact behavior between the different materials by only one contact spring. For the verification of the improved code, the results of the numerical analysis are compared with that of the photoelastic experiments which are one or two dimensional wave propagation problem of the nonhomogeneous media including the different accoustic impendence material or voids. It is shown that the characteristics of the stress wave propagation in nonhomogeneous media can be simulated appropriately using the improved distinct element method.

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Factors Influencing Resistance to the Metaverse: Focusing on Propagation Mechanisms

  • Mina Lee;Minjung Kim
    • International journal of advanced smart convergence
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    • 제13권2호
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    • pp.110-118
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    • 2024
  • This study examines factors influencing nonusers' resistance to the adoption of the metaverse, focusing on propagation mechanisms. It elucidates the role of innovation resistance within the metaverse adoption process. We applied the Innovation Resistance Model in the context of the metaverse and considers three major groups of factors influencing resistance to the metaverse: innovation characteristics (perceived usefulness, compatibility, perceived risk, and complexity), consumer characteristics (personal innovativeness), and propagation mechanisms (mass media, online media, and personal communication). An online survey of college students who do not use the metaverse revealed that perceived usefulness, compatibility, personal innovativeness, and online media were negative predictors of resistance to the metaverse. Conversely, perceived risk, mass media, and personal communication were positive predictors of resistance to the metaverse. Furthermore, innovation resistance was found to play a mediating role in the metaverse adoption process. Drawing upon the findings, we suggested marketing strategies to decrease resistance to the metaverse.

이방성 재료에서의 탄성파 전파 과정에 대한 시뮬레이션 (Simulation of Elastic Wave Propagation in Anisotropic Materials)

  • 김영환;이승석
    • 비파괴검사학회지
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    • 제17권4호
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    • pp.227-236
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    • 1997
  • 탄성파 전파 과정의 정량적인 이해와 그 가시화는 결함 탐지는 물론이고, 재료의 물성 평가에 매우 중요하다. 대상 재료가 이방성을 지닐 경우에 탄성파 전파 과정은 복잡해져서 전파 과정의 해석 및 가시화 작업은 탄성파를 이용하는 결함 탐지 및 재질 평가에서는 필수적이다. 이방성 재료에서는 탄성파의 속도가 방향에 따라서 달라짐은 물론이고, 위상 속도와 군 속도의 방향이 어긋나서 파면이 진행하는 방향과 에너지가 진행하는 방향이 달라진다(beam skewing 효과). 특히 복합재료와 같이 이방성이 큰 재료에서는 이 효과가 매우 크게 나타나므로 탄성파를 이용한 시험 결과를 해석하고자 할 때에는 반드시 전파 과정을 이해해야 한다. 이방성 재료에 대해 해석적인 접근에는 한계가 있어서 유한차분법(finite difference method: FDM)과 같은 수치 해석 방법이 유용하게 사용되고 있다. 본 연구에서는 탄성파 전파 과정을 해석할 수 있는 2차원 FDM 프로그램을 개발하고, 이를 이용하여 이방성 재료에서의 탄성파 전파에 대한 전산 시뮬레이션 결과를 비교 분석한다.

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유한차분법을 이용한 3차원 지진파 전파 모의 (Three-Dimensional Simulation of Seismic Wave Propagation in Elastic Media Using Finite-Difference Method)

  • 강태섭
    • 한국지진공학회:학술대회논문집
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    • 한국지진공학회 2000년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Fall 2000
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    • pp.81-88
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    • 2000
  • The elastic wave equation is solved using the finite-difference method in 3D space to simulate the seismic wave propagation. It is based on the velocity-stress formulation of the equation of motion on a staggered grid. The nonreflecting boundary conditions are used to attenuate the wave field close to the numerical boundary. To satisfy the stress-free conditions at the free-surface boundary, a new formulation combining the zero-stress formalism with the vacuum one is applied. The effective media parameters are employed to satisfy the traction continuity condition across the media interface. With use of the moment-tensor components, the wide range of source mechanism parameters can be specified. The numerical experiments are carried out in order to test the applicability and accuracy of this scheme and to understand the fundamental features of the wave propagation under the generalized elastic media structure. Computational results show that the scheme is sufficiently accurate for modeling wave propagation in 3D elastic media and generates all the possible phases appropriately in under the given heterogeneous velocity structure. Also the characteristics of the ground motion in an sedimentary basin such as the amplification, trapping, and focusing of the elastic wave energy are well represented. These results demonstrate the use of this simulation method will be helpful for modeling the ground motion of seismological and engineering purpose like earthquake hazard assessment, seismic design, city planning, and etc..

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In Vitro Germination and Propagation by Embryo Culture of Taxus cuspidata for the Taxol Production

  • Park, Myung-Suk
    • Journal of Plant Biotechnology
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    • 제2권1호
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    • pp.29-33
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    • 2000
  • To develop an efficient propagation method for yew tree, zygotic embryos were cultured under various conditions. When dissected embryos were cultured on GA$_3$ containing media, the highest germination frequency was observed on WPM medium contaning 1.0 mg/L GA$_3$. For germination of the embryos, two different conditions were compared; culturing embryos with endosperm (Method I), and 2) culturing embryos only (Method II). Maximum germination was achieved in 0.5 mg/L GA$_3$ when embryos with endosperm were cultured on the media. Of the media tested, White and WPM medium were the most suitable on germination of embryos. The abnormality of yew embryos found was observed when it cultured on GA$_3$ or culture media. About 40% of the precociously germinated embryos could be developed into full seedlings. Seedlings contained taxol in high quantity (535 $\mu\textrm{g}$/g dry weight). In vitro techniques will be sewed as a useful tool for the development of transformed root cultures and biosynthesis studies.

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GPU 에서의 고속 스테레오 정합을 위한 메모리 효율적인 Belief Propagation (Memory-Efficient Belief Propagation for Stereo Matching on GPU)

  • 최영규;윌리엄;박인규
    • 한국방송∙미디어공학회:학술대회논문집
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    • 한국방송공학회 2012년도 추계학술대회
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    • pp.52-53
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    • 2012
  • Belief propagation (BP) is a commonly used global energy minimization algorithm for solving stereo matching problem in 3D reconstruction. However, it requires large memory bandwidth and data size. In this paper, we propose a novel memory-efficient algorithm of BP in stereo matching on the Graphics Processing Units (GPU). The data size and transfer bandwidth are significantly reduced by storing only a part of the whole message. In order to maintain the accuracy of the matching result, the local messages are reconstructed using shared memory available in GPU. Experimental result shows that there is almost an order of reduction in the global memory consumption, and 21 to 46% saving in memory bandwidth when compared to the conventional algorithm. The implementation result on a recent GPU shows that we can obtain 22.8 times speedup in execution time compared to the execution on CPU.

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Empirical millimeter-wave wideband propagation characteristics of high-speed train environments

  • Park, Jae-Joon;Lee, Juyul;Kim, Kyung-Won;Kwon, Heon-Kook;Kim, Myung-Don
    • ETRI Journal
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    • 제43권3호
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    • pp.377-388
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    • 2021
  • Owing to the difficulties associated with conducting millimeter-wave (mmWave) field measurements, especially in high-speed train (HST) environments, most propagation channels for mmWave HST have been studied using methods based on simulation rather than measurement. In this study, considering a linear cell layout in which base stations are installed along a railway, measurements were performed at 28 GHz with a speed up to 170 km/h in two prevalent HST scenarios: viaduct and tunnel scenarios. By observing the channel impulse responses, we could identify single- and double-bounced multipath components (MPCs) caused by railway static structures such as overhead line equipment. These MPCs affect the delay spread and Doppler characteristics significantly. Moreover, we observed distinct path loss behaviors for the two scenarios, although both are considered line-of-sight (LoS) scenarios. In the tunnel scenario, the path loss exponent (PLE) is 1.3 owing to the waveguide effect, which indicates that the path loss is almost constant with respect to distance. However, the LoS PLE in the viaduct scenario is 2.46, which is slightly higher than the free-space loss.

포화된 다공성매체에서 파동의 전파특성 I. 이론해의 유도 (Wave Propagation Characteristics in Saturated Porous Media I. Theoretical Solution)

  • 김선훈;김광진
    • 한국전산구조공학회논문집
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    • 제20권2호
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    • pp.95-103
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    • 2007
  • 본 논문에서는 포화된 다공성매체에서 파동의 전파속도와 감쇠를 구할 수 있는 해석적 이론해를 유도하여 제시하였다. 이론해의 유도를 위하여 압축성의 고체입자와 간극수를 고려하는 완전 연계 Field모델을 사용하였다. 완전 포화된 다공성 매체의 해석을 위한 공학적인 접근방법이 채택되었으며, 균질 영역에서 1차원 파동의 전파를 위한 이론해가 유도되었다. 본 논문에서 유도한 이론해는 고체입자의 압축성, 간극수의 압축성, 다공성입자의 변형, 공간의 감쇠(Spatial damping) 등을 고려할 수 있어 매우 다양하게 사용될 수 있다. 또한 다양한 지반체에서 두 가지 종류의 파속(Wavespeed)과 감쇠계수를 계산하는데 이용 가능하다. 본 논문에서 제시한 이론해를 전산코드화하여 파동의 전파속도와 감쇠에 대한 파라미터연구를 수행한 결과는 본 연구의 II부에 제시할 예정이다.

Stress wave propagation in 1-D and 2-D media using Smooth Particle Hydrodynamics method

  • Liu, Z.S.;Swaddiwudhipong, S.;Koh, C.G.
    • Structural Engineering and Mechanics
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    • 제14권4호
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    • pp.455-472
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    • 2002
  • The paper involves the study on the elastic and elasto-plastic stress wave propagation in the 1-D and 2-D solid media. The Smooth Particle Hydrodynamics equations governing the elastic and elasto-plastic large deformation dynamic response of solid structures are presented. The proposed additional stress points are introduced in the formulation to mitigate the tensile instability inherent in the SPH approach. Both incremental rate approach and leap-frog algorithm for time integration are introduced and the new solution algorithm is developed and implemented. Two examples on stress wave propagation in aluminium bar and 2-D elasto-plastic steel plate are included. Results from the proposed SPH approach are compared with available analytical values and finite element solutions. The comparison illustrates that the stress wave propagation problems can be effectively solved by the proposed SPH method. The study shows that the SPH simulation is a reliable and robust tool and can be used with confidence to treat transient dynamics such as linear and non-linear transient stress wave propagation problems.

Computational mechanics and optimization-based prediction of grain orientation in anisotropic media using ultrasonic response

  • Kim, Munsung;Moon, Seongin;Kang, To;Kim, Kyongmo;Song, Sung-Jin;Suh, Myungwon;Suhr, Jonghwan
    • Nuclear Engineering and Technology
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    • 제53권6호
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    • pp.1846-1857
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    • 2021
  • Ultrasonic nondestructive testing is important for monitoring the structural integrity of dissimilar metal welds (DMWs) in pressure vessels and piping in nuclear power plants. However, there is a low probability of crack detection via inspection of DMWs using ultrasonic waves because the grain structures (grain orientations) of the weld area cause distortion and splitting of ultrasonic beams propagating in anisotropic media. To overcome this issue, the grain orientation should be known, and a precise ultrasonic wave simulation technique in anisotropic media is required to model the distortion and splitting of the waves accurately. In this study, a method for nondestructive prediction of the DMW grain orientations is presented for accurate simulation of ultrasonic wave propagation behavior in the weld area. The ultrasonic wave propagation behavior in anisotropic media is simulated via finite-element analysis when ultrasonic waves propagate in a transversely isotropic material. In addition, a methodology to predict the DMW grain orientation is proposed that employs a simulation technique for ultrasonic wave propagation behavior calculation and an optimization technique. The simulated ultrasonic wave behaviors with the grain orientations predicted via the proposed method demonstrate its usefulness. Moreover, the method can be used to determine the focal law in DMWs.