• Title/Summary/Keyword: s-wave velocity

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Analysis on Shock Attenuation of STS Bulkhead Initiator (STS 격벽착화기의 충격파 감쇠 특성 해석)

  • Kim, Bohoon;Jang, Seung-gyo;Yoh, Jai-ick
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2017.05a
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    • pp.440-444
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    • 2017
  • Two-dimensional hydrodynamic analysis was performed to analyze the attenuating characteristics of shock waves generated by the detonation of the bulkhead initiator. Through the interlocking analysis between HNS and HMX stacking initiator and STS bulkhead, we have precisely simulated detonation growth and pressure wave attenuation phenomena. The free surface velocity at the surface of the bulkhead was measured for quantitative comparison with the test data by VISAR. As a result, it was confirmed that the pressure attenuating pattern of the shock wave exponentially decreased according to the bulkhead thickness. The observed inflection point at the particle velocity measured over time is due to the subsequent propagation of the shock wave due to the rapid spallation of the interface between the detonator and the bulkhead.

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Numerical studies on the effects of the lateral boundary on soil-structure interaction in homogeneous soil foundations

  • Li, Z.N.;Li, Q.S.;Lou, M.L.
    • Structural Engineering and Mechanics
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    • v.20 no.4
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    • pp.421-434
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    • 2005
  • In this paper, the finite element method is applied to investigate the effect of the lateral boundary in homogenous soil on the seismic response of a superstructure. Some influencing factors are presented and discussed, and several parameters are identified to be important for conducting soil-structure interaction experiments on shaking tables. Numerical results show that the cross-section width L, thickness H, wave propagation velocity and lateral boundaries of soil layer have certain influences on the computational accuracy. The dimensionless parameter L/H is the most significant one among the influencing factors. In other words, a greater depth of soil layer near the foundation should be considered in shaking table tests as the thickness of the soil layer increases, which can be regarded as a linear relationship approximately. It is also found that the wave propagation velocity in soil layer affects the numerical accuracy and it is suggested to consider a greater depth of the soil layer as the wave propagation velocity increases. A numerical study on a soil-structure experimental model with a rubber ring surrounding the soil on a shaking table is also conducted. It is found the rubber ring has great effect on the soil-structure interaction experiments on shaking table. The experimental precision can be improved by reasonably choosing the elastic parameter and width of the rubber ring.

A Linear Wave Equation Over Mild-Sloped Bed from Double Integration (이중적분을 이용한 완경사면에서의 선형파 방정식)

  • Kim, Hyo-Seob;Jung, Byung-Soon;Lee, Ye-Won
    • Journal of the Korean Society for Marine Environment & Energy
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    • v.12 no.3
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    • pp.165-172
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    • 2009
  • A set of equations for description of transformation of harmonic waves is proposed here. Velocity potential function and separation of variables are introduced for the derivation. The continuity equation is in a vertical plane is integrated through the water so that a horizontal one-dimensional wave equation is produced. The new equation composed of the complex velocity potential function, further be modified into. A set up of equations composed of the wave amplitude and wave phase gradient. The horizontally one-dimensional equations on the wave amplitude and wave phase gradient are the first and second-order ordinary differential equations. They are solved in a one-way marching manner starting from a side where boundary values are supplied, i.e. the wave amplitude, the wave amplitude gradient, and the wave phase gradient. Simple spatially-centered finite difference schemes are adopted for the present set of equations. The equations set is applied to three test cases, Booij's inclined plane slope profile, Massel's smooth bed profile, and Bragg's wavy bed profile. The present equations set is satisfactorily verified against existing theories including Massel's modified mild-slope equation, Berkhoff's mild-slope equation, and the full linear equation.

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Crustal Structure of the Southern Part of Korea (한국(韓國) 남부지역(南部地域)의 지각구조(地殼構造))

  • Kim, Sung Kyun;Jung, Bu Hung
    • Economic and Environmental Geology
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    • v.18 no.2
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    • pp.151-157
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    • 1985
  • Events detected by the KIER microearthquake network operated in the Southern Part of Korea for 265 days in 1982~1984 were reviewed, and some of them were identified to be a dynamite explosion from several construction sites. The purpose of the present work is to determine the crustal structure of the Southern Korea using the time-destance data obtained from such explosion seismic records. The time·distance data can be well explained by a crustal model composed of four horizontal layers of which thickness, p and s-wave velocity ($V_p$ and $V_s$) are characterized as follows. 1st layer (surface) ; 0~2km, $V_p=5.5km/sec$, $V_s=3.3km/sec$ 2nd layer (upper crust) ; 2~15km, $V_p=6.0km/sec$, $V_s=3.5km/sec$ 3rd layer (lower crust) ; 15~29km, $V_p=6.6km/sec$, $V_s=3.7km/sec$ 4th layer (upper mantle) ; 29km~ , $V_p=7.7km/sec$, $V_s=4.3km/sec$ The relatively shallow crust·mantle boundary and low $P_n$ velocity compared with the mean values for stable intraplate region are noteworthy. Supposedely, it is responsible for the high heat flow in the South-eastern Korea or an anomalous subterranean mantle. The mean $V_p/V_s$ ratio calculated from the relation between p-wave arrival and s-p arrival times appears to be 1.735 which is nearly equivalent to the elastic medium of ${\lambda}={\mu}$. However, the ratio tends to be slightly larger with the depth. The ratio is rather high compared with that of the adjacent Japanese Island, and the fact suggests that the underlying crust and upper mantle in this region are more ductile and hence the earthquake occurrences are apt to be interrupted. As an alternative curstal model, a seismic velocity structure in which velocities are successively increased with the depth is also proposed by the inversion of the time·distance data. With the velocity profile, it is possible to calculate a travel time table which is appropriate to determine the earthquake parameters for the local events.

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Shear Wave Velocity Profile Considering Uncertainty Caused by Spatial Variation of Material Property in Core Zone of Fill Dam (필댐 축조재료의 공간 변동성에 의한 불확실성이 고려된 국내 필댐 심벽부 전단파 속도 주상도 모델)

  • Park, Hyung-Choon;Nah, Byung-Chan;Lim, Heui-Dae
    • Journal of the Korean Geotechnical Society
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    • v.32 no.11
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    • pp.51-60
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    • 2016
  • In determining a shear wave velocity (Vs) profile model based on field tests for dams, the uncertainties always exist. These uncertainties are caused by spatial variations of material properties in each dam and between dams and should be considered in determining Vs profile model for dams. In this paper, these uncertainties are evaluated and Vs profile model for core zone of fill dam in Korea is proposed using the shear wave velocity profiles determined in seven fill dams. The proposed Vs profile model is compared with Kim's model and Sawada-Takahashi model widely used for evaluation of Vs profile of core zone of fill dam.

The Analysis of Pulse Wave Velocity of Jeju female divers (제주 해녀의 맥파전도속도 분석)

  • Lee, Han-Young
    • Journal of Digital Convergence
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    • v.13 no.9
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    • pp.515-521
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    • 2015
  • In this study, we tried to analyze arterial stiffness of Jeju female divers who diver into cold water without the assistance of oxygen. For this purpose we measured pulse wave velocity and ankle-brachial index of Jeju female divers and same aged females who didn't have any cardiovascular risk for comparing the vascular stiffness. The results were the following : First, the light-femoral pulse wave velocity of Jeju female divers was significantly lower than normal women of the same ages. Second, Jeju female divers's ABI showed higher tendency than normal same aged women. These result showed that Jeju female divers' body had been completed for adaptation to low temperature and high pressure water environment through a long-term immersion activities in old age, as well as due to higher physical activity levels of Jeju female divers peripheral vascular resistance was not reduced.

Pseudo 3D FEM analysis for wave passage effect on the response spectrum of a building built on soft soil layer

  • Kim, Yong-Seok
    • Earthquakes and Structures
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    • v.8 no.5
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    • pp.1241-1254
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    • 2015
  • Spatially variable ground motions can be significant on the seismic response of a structure due to the incoherency of the incident wave. Incoherence of the incident wave is resulted from wave passage and wave scattering. In this study, wave passage effect on the response spectrum of a building structure built on a soft soil layer was investigated utilizing a finite element program of P3DASS (Pseudo 3-dimensional Dynamic Analysis of a Structure-soil System). P3DASS was developed for the axisymmetric problem in the cylindrical coordinate, but it is modified to apply anti-symmetric input earthquake motions. Study results were compared with the experimental results to verify the reliability of P3DASS program for the shear wave velocity of 250 m/s and the apparent shear wave velocities of 2000-3500 m/s. Studied transfer functions of input motions between surface mat foundation and free ground surface were well-agreed to the experimental ones with a small difference in all frequency ranges, showing some reductions of the transfer function in the high frequency range. Also wave passage effect on the elastic response spectrum reduced the elastic seismic response of a SDOF system somewhat in the short period range.

Effects of folic acid supplementation on serum homocysteine levels, lipid profiles, and vascular parameters in post-menopausal Korean women with type 2 diabetes mellitus

  • Vijayakumar, Aswathy;Kim, Eun-kyung;Kim, Hyesook;Choi, Young Ju;Huh, Kap Bum;Chang, Namsoo
    • Nutrition Research and Practice
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    • v.11 no.4
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    • pp.327-333
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    • 2017
  • BACKGROUND/OBJECTIVES: Complications of diabetes, such as cardiovascular disease, are associated with increased mortality among type 2 diabetes mellitus patients. Homocysteine has been recently identified as a predictor of cardiovascular disease-related complications in diabetes. We investigated whether or not supplementation with folic acid tablets can lower homocysteine levels and improve parameters related with vascular complications. SUBJECTS/METHODS: We conducted a non-randomized 8-week trial involving postmenopausal diabetic women (n = 25) supplemented with $800{\mu}g$ of folic acid ($400{\mu}g$ twice a day) daily. Subjects' serum levels of folate, homocysteine, and vitamin $B_{12}$ were measured, along with vascular function and brachial-ankle pulse wave velocity. RESULTS: Folic acid supplementation significantly increased serum folate levels (P < 0.0001), reduced homocysteine levels (P < 0.0001), and increased vitamin $B_{12}$ levels (P = 0.0063). There were significant decreases in low-density lipoprotein cholesterol levels as well as the ratios of low-density lipoprotein cholesterol to high-density lipoprotein cholesterol and total cholesterol to high-density lipoprotein cholesterol. Brachial-ankle pulse wave velocities were not altered by supplementation. Changes in serum vitamin $B_{12}$ after folic acid supplementation were negatively correlated with changes in brachial-ankle pulse wave velocity. CONCLUSIONS: In this study on postmenopausal Korean women with type 2 diabetes mellitus, folic acid supplementation reduced serum homocysteine levels, increased serum folate and vitamin $B_{12}$ levels, and lowered lipid parameters.

Wave Propagation of Composite Materials Subjected to Dynamic Load (동하중을 받는 복합재의 파동전파에 관한 연구)

  • Ahn, Kook-Chan;Jeong, In-Jo;Jung, Dae-Sik
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.11 no.4
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    • pp.138-146
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    • 2012
  • This research is to analyze the wave propagation characteristics of anisotropic materials subjected to the low-velocity impact. For this purpose, a higher-order finite element program is used to simulate the dynamic behaviors according to the changes of material property, stacking sequence and dimension etc.. Materials for simulation are composed of $[0^{\circ}]_{10s}$, $[45^{\circ}/-45^{\circ}]_{5s}$ and $[90^{\circ}]_{10s}$ stacking sequences. Finally, the results of this simulation are compared with those of wave propagation theory and then the impact responses and wave propagation phenomena are investigated.

Measurement of a Blood Velocity by using Photoplethysmograph and Radial Artery Pulse Wave Equipped with Magnetic Hall Device (자성 홀소자 맥진기와 용적맥파계의 맥진파형을 이용한 혈류속도 측정 연구)

  • Jang, Deok-Hyeong;Kim, Dam-Bee;Choi, Suel-Gi;Lee, Sang-Suk
    • Journal of the Korean Magnetics Society
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    • v.22 no.4
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    • pp.130-135
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    • 2012
  • One prototype product of clip-type pulsimeter equipped with magnetic field sensing semiconductor Hall device after one permanent magnet attached "Chwan" position in center of a radial artery was developed. The clip-pulsimeter was composed of the hard ware system measuring to voltage signals. To measure the blood velocity, the radial artery pulsimeter is simultaneously connected the PPG (photoplethysmograph). Analysis and comparison of two pulse waves data has done obtained from a clinical test of forty subjects of 20 ages. The value of a blood velocity simultaneously measured from a radial artery puls wave and PPG is an average value of 0.8m/s. The usage of this research results is possible to store the biomedical signals for health care.