• 제목, 요약, 키워드: mass propagation

검색결과 418건 처리시간 0.05초

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

  • 차민수;조계춘;박승형
    • 한국지반공학회:학술대회논문집
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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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수정개별요소법에 의한 불연속 구조체의 파전달 거동 해석 (The Application of the Medified Distinct Element Method to Wave Propagation in Structures with Discontinuous Faces)

  • 김문겸;오금호;김우진
    • 한국전산구조공학회:학술대회논문집
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    • pp.232-239
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    • 1997
  • The phenomenology of shock loading effects in brittle mass has been of interest to researchers and engineers. The shock loading as blasting causes strong stress waves in the structures. Discontinuous faces due to shock waves interrupt the tensile stress wave propagation and reflect the stress wave propagation. To predict the fracturing behavior of brittle mass, it is required for the numerical method that can analyze the colliding and slipping behavior of discontinuous faces and the wave propagation in the mass, simultaneously In this study, the wave propagation in the brittle materials is analyzed using the modified distinct element method to be able to predict the behavior of discontinuous structures. The behavior of an unsupported bar subjected to loading at the end is analyzed to verify the rigid body motion of a bar and the relative displacement in the bar. The colliding behavior of two bars is analyzed to investigate the propagation of stress waves in the bar. The fracturing behavior of a bar due to impact loading is analyzed to investigate the propagation of stress waves in the bar with and without the discontinuous faces. The applicability of the modified distinct element method to the wave propagation problems is investigated.

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마코브 체인을 이용한 Mass SQL Injection 웜 확산 예측에 관한 연구 (A Study on Prediction of Mass SQL Injection Worm Propagation Using The Markov Chain)

  • 박원형;김영진;이동휘;김귀남
    • 융합보안논문지
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    • v.8 no.4
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    • pp.173-181
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    • 2008
  • 최근 웜에 의한 사이버 위협이 증가함에 따라 웜의 확산 특성을 분석하기 위한 전파 모델이 연구되고 있다. 대표적인 예로 수학적 모델링 기법인 Epidemic(SI), KM(Kermack-MeKendrick), Two-Factor, AAWP(Analytical Active Worm Propagation)등의 모델 기법들이 제시되었다. 하지만, 기존 모델 방법들은 대부분 코드레드와 같은 네트워크를 대상으로 하는 랜덤 스캐닝 기법에 대해서만 모델링이 가능하다. 또한 거시적인 분석만 가능하고 특정 위협에 대해 예측하는데 한계점을 가지고 있다. 따라서 본 논문에서는 과거의 위협 발생 데이터를 근거로 하여 Mass SQL Injection 같은 사이버위협에 적용 가능한 마코브 체인(markov chain) 기반 예측 방법을 제시한다. 이를 통하여 각 위협별 발생 확률 및 발생빈도를 예측할 수 있다.

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정적연소기에서 점화장치가 열발생률과 잘량연소율에 미치는 영향에 관한 연구 (A Study on the Effects of Ignition Systems on the Heat Release Rate and Mass Fraction Burnt at a Constant Volume Combustion Chamber)

  • 송정훈;이기형;선우명호
    • 대한기계학회논문집B
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    • v.24 no.11
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    • pp.1486-1496
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    • 2000
  • The initial flame kernel development and flame propagation in a constant volume combustion chamber is analyzed by the heat release rate and the mass fraction burnt. The combustion pressure is measured with a piezoelectric type pressure sensor. In order to evaluate the effects of ignition system and ignition energy on the flame propagation, four different ignition systems are designed and tested, and the ignition energy is varied by the dwell time. Several different spark plugs are also tested and examined to analysis the effects of electrodes on flame kernel development. The results show that the when the dwell time is increased, and when the spark plug gap is extended, heat release rate and the mass burnt fraction are increased. The materials and shapes of electrodes affect the flame development, because they change the energy transfer efficiency from electrical energy to chemical energy. The diameter of electrodes influences not only the heat release rate but also the mass burnt fraction as well.

새우난초(Calanthe discolor Lindley)의 대량증식 시스템 확립 및 이용 (Establishment and Using of mass propagation system for Calanthe discolor Lindle)

  • 서병기
    • 한국자원식물학회지
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    • v.15 no.3
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    • pp.221-226
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    • 2002
  • 새우난초의 대량 증식 시스템을 확립하기 위하여 새우난초 종자 무균파종 및 순화 방법에 따른 생육특성 을 조사하였다. 발아율은 MS배지 에서 65% 이상이었고 유묘의 대량증식이 가능하였다. 계대배양한 유묘의 증식은 고체배지 보다는 액체배지에서 생육상태 가 더 양호한 경향을 보였다. 순화실험 결과, 70%차광조건에서 플라스틱 멀칭으로 습도를 80% 이상 유지하였을 때 100% 순화 생존하였다. 기내 육성된 배양묘는 백태로 뿌리를 감싸 심었을 때 발근이 가장 잘 이루어졌으나 순화과정 중에서 백태 대신에 질석과 펄라이트를 1:1 부피비로 이용한 경우에도 88%의 비교적 높은 생존율을 보였다.

정적연소기내 유동형태가 화염전파에 미치는 영향 연구 (An Experimental Study of the Effect of Flow on Flame Propagation in a Constant-Volume Combustion Chamber)

  • 정동수;오승묵;서승우;장영준
    • 한국자동차공학회논문집
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    • v.3 no.2
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    • pp.136-145
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    • 1995
  • The aim of this study is to gain a better understanding of the effect of a flow motion on the flame development by means of an optically-accessible constant-volume combustion chamber and the visualization technique of a combustion flame. At first, the characteristics of a flame propagation are investigated in the combustion field of the two kinds of flow conditions such as a quiescent and a flowing condition, and methane-air mixture is used as fuel. Then the same investigation is performed in two flow configurations : bulk flow motion type and turbulence generating type. In this study, the combustion phenomena are analyzed by measuring the combustion pressure, flame propagation speed, mean velocity, turbulent intensity, and mass fraction burned.

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Effective in Vitro Propagation by Bulb Scale Segments Culture of Muscari comosum var. plumosum

  • Ko Jeong-Ae;Choi Jeong-Ran;Xudong He;Kim Hyun-Soon
    • 한국자원식물학회지
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    • v.19 no.3
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    • pp.432-435
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    • 2006
  • A rapid and mass propagation method for multiple shoots and plant regeneration using bulb scales of Muscari comosum var. plumosum were developed. In vitro different parts of bulb scale as explants were cultured on 11 kinds of MS (1962) media supplemented with various plant growth regulators to induce shoot and callus. A combination of 2.0 mg/L 6-BA and 2.0 mg/L IBA on MS medium was the most favorable and induced the highest production (80%) of shoot formation after 30 days. We also found that the middle part of bulb scale was the best for mass propagation of Muscari comosum var. plumosum of which production could reach 64.4%.

초음파의 전파, 반사, 산란 현상에 대한 수치 시뮬레이션 (Numerical study of propagation, reflection, and scattering of ultrasonic waves)

  • 임현준
    • 한국전산구조공학회:학술대회논문집
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    • pp.401-406
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    • 2002
  • A numerical model is introduced to simulate propagation, reflection, and scattering of elastic waves in solids. The model consists of mass points and linear springs, interconnected with in a lattice structure; hence, its name, the mass-spring lattice model (MSLM). The MSLM has successfully been applied to the numerical simulation and visualization of various elastic wave phenomena involved in ultrasonic nondestructive testing (NDT). This method is useful to simulate, design, or analyze actual testing. Some representative examples of numerical simulation using the MSLM are presented, and future work necessary for its further development Is addressed.

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탄성지지된 시스템의 마운트 고체음저감 성능에 관한 연구 (A Study on Mount Performance for Structure-Borne Noise Reduction in Resiliently Mounted System)

  • 김현실;김재승;김봉기
    • The Journal of the Acoustical Society of Korea
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    • v.26 no.2E
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    • pp.50-55
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    • 2007
  • SBN (Structure-Borne Noise) reduction in resiliently mounted machineries are predicted by using mass-spring model and wave model. In mass-spring model, mount is modeled as a spring, while in wave model, mount is considered as an equivalent elastic rod for taking account into longitudinal wave propagation. The predictions for SBN reduction through mounts are compared to the measurements for four different pumps. It is found that the mass-spring model is valid only in low frequency range below few hundred Hz, while for high frequency ranges longitudinal wave propagation in the mount must be considered to explain the measurements. It is also shown that impedance of the floor slightly affects low frequency behaviour in mass-spring and wave model below 50 Hz - 80 Hz, so that in engineering practice the effect of floor impedance may be neglected in computing mount performance.

Generalized coupled non-Fickian/non-Fourierian diffusion-thermoelasticity analysis subjected to shock loading using analytical method

  • Hosseini, Seyed Amin;Abolbashari, Mohammad Hossein;Hosseini, Seyed Mahmoud
    • Structural Engineering and Mechanics
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    • v.60 no.3
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    • pp.529-545
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    • 2016
  • In this article, the generalized coupled non-Fickian diffusion-thermoelasticity analysis is carried out using an analytical method. The transient behaviors of field variables, including mass concentration, temperature and displacement are studied in a strip, which is subjected to shock loading. The governing equations are derived using generalized coupled non-Fickian diffusion-thermoelasticity theory, which is based on Lord-Shulman theory of coupled thermoelasticity. The governing equations are transferred to the frequency domain using Laplace transform technique and then the field variables are obtained in analytical forms using the presented method. The field variables are eventually determined in time domain by employing the Talbot technique. The dynamic behaviors of mass concentration, temperature and displacement are studied in details. It is concluded that the presented analytical method has a high capability for simulating the wave propagation with finite speed in mass concentration field as well as for tracking thermoelastic waves. Furthermore, the obtained results are more realistic than that of others.