탄성매질에서의 분포형 음향 센싱 자료를 활용한 평면파 전파형역산

정서제,정우근,신성렬,김수민 한국지구물리.물리탐사학회 2022 지구물리와 물리탐사 Vol.25 No.4

Distributed acoustic sensing (DAS), an increasingly growing acquisition technique in the oil and gas exploration and seismology fields, has been used to record seismic signals using optical cables as receivers. With the development of imaging methods for DAS data, full waveform inversion (FWI) is been applied to DAS data to obtain high-resolution property models such as P- and S-velocity. However, because the DAS systems measure strain from the phase distortion between two points along optical cables, DAS data must be transformed from strain to particle velocity for FWI algorithms. In this study, a plane-wave FWI algorithm based on the relationship between strain and horizontal particle velocity in the plane-wave assumption is proposed to apply FWI to DAS data. Under the plane-wave assumption, strain equals the horizontal particle velocity, which is scaled by the velocity at the receiver position. This relationship was confirmed using a numerical experiment. Furthermore, 4-layer and modified Marmousi-2 velocity models were used to verify the applicability of the proposed FWI algorithm in various survey environments. The proposed FWI was implemented in land and marine survey environments and provided high-resolution P- and S-velocity models. 분포형 음향 센싱(distributed acoustic sensing, DAS)은 광섬유 케이블을 수신기로 활용하는 탐사기술로서, 석유탐사 및 지진분야에서 모 니터링 목적으로 활발히 적용되고 있다. 최근에는 지하매질의 물성정보를 도출하기 위해 분포형 음향 센싱 자료를 활용한 전파형역산 연 구가 수행되고 있다. 분포형 음향 센싱은 광섬유 케이블 상의 두 점 간의 위상 차이에 의한 변형률을 측정하기 때문에, 기존 전파형역산 알고리즘에 직접 활용하기 어렵다. 분포형 음향 센싱 자료를 전파형역산에 활용하기 위해, 본 연구에서는 평면파 가정에서의 변형률과 수 평입자속도의 관계식을 이용한 평면파 전파형역산 알고리즘을 개발하였다. 수치실험을 통해 평면파 가정에서의 변형률과 입자속도 간의 관계식이 성립함을 확인하였다. 다양한 탐사환경에서 분포형 음향 센싱 자료에 대한 전파형역산의 적용 가능성을 확인하기 위해, 육상 및 해저면 탄성파 탐사 환경을 모사한 4층 및 수정된 Marmousi-2 속도모델을 이용하였다. 제안된 전파형역산을 통해 육상 및 해저면 탄성파 탐사 환경하에서 P파 및 S파 속도구조를 정확히 도출할 수 있었다.

Shear-wave velocity structure of Jeju Island, Korea

Ki Young Kim,Myung Ho Hong 한국지질과학협의회 2012 Geosciences Journal Vol.16 No.1

To reveal shear-wave velocity (vs) structures of Jeju Island, the spatial autocorrelation (SPAC) method was applied to microtremors recorded at six sites on the island. At each site, four 3-component portable broadband seismometers were deployed at receiver intervals of 50–5944 m in a linear or an irregular array. SPAC functions of the vertical-component data were used to obtain dispersion curves defining phase velocities of Rayleigh waves. Shear-wave velocities derived by inverting the dispersion curves were compared with core data from nearby deep wells. The inversion models around the periphery of Mt. Halla indicate the existence of a low-velocity layer (LVL) beneath the extrusive volcanic outcrops of Quaternary age. This LVL correlates with Pleistocene marine sediments of the Seoguipo and U Formations that were sampled in nearby wells. Beneath the LVL at these sites, vs increases gradually with depth in welded tuffs that overlie a Cretaceous-Paleogene granite. The horizontal-to-vertical spectral ratio method was also applied to microtremor data to estimate depths to granitic basement rocks. The depths to the granitic basement rocks increase toward the center of the island, reaching a maximum of approximately 3.2 km below the summit of Mt. Halla.

상시미동 및 원거리 지진 자료로부터 구한 화천 지진관측소의 천부 횡파속도구조

윤원영 ( Won Young Yun ),박순천 ( Sun Cheon Park ),김기영 ( Ki Young Kim ) 한국지구물리·물리탐사학회 2013 지구물리와 물리탐사 Vol.16 No.3

We estimated near-surface shear-wave velocity (vs) at the Hwacheon seismic station using a geologic log of a well, microtremors recorded during a period of 56 days, and records of three teleseismic events (Mw ≥ 6.0). The vsof the 10-m thick soil layer ( = 296 m/s) was determined from horizontal-to-vertical spectral ratios of microtremors recorded at the surface. The average vs ( = 1,309 m/s) from the surface to the 96-m depth of a borehole sensor, was computed using spectral coherence analyses of data recorded by surface- and borehole-sensors for the three teleseismic events. Using these calculated values of and, the computed bedrock vs is 2,150 m/s and the time-averaged vs to a 30-m depth is 696 m/s. Accordingly the Hwacheon seismic station is regarded as a relatively good site. The deduced near-surface vs can be used for further quantitative evaluation of site amplification and earthquake hazard.

5개 중규모 지진의 속도 관측자료를 이용한 수평 응답스펙트럼 특성 분석

김준경(Jun-Kyoung Kim) 한국암반공학회 2011 터널과지하공간 Vol.21 No.6

최근 한반도 및 주변해역에서 발생한 규모 4.8 이상의 5개 중규모 지진으로부터 관측된 속도 지반운동 파형을 이용하여 수평 응답스펙트럼을 분석하고 결과를 우선 가속도 지반운동을 이용하여 얻어진 수평 응답스펙트럼, 국내 원자력 관련 구조물의 내진설계 기준, 마지막으로 국내 일반 구조물 및 건축물 내진설계기준과 각각 비교하였다. 연구에 이용된 지반운동은 수평성분 102개(NS 및 EW 성분 포함)이며 고유진동수에 따른 응답을 구하고 각각의 최대 지반 속도 값을 이용하여 정규화 분석을 수행하였다. 첫째, 가속도 응답스펙트럼과 비교한 결과 속도 응답스펙트럼 값은 특히 중간주기에서 높은 응답을 보여 주었고 이에 비해 가속도 응답스펙트럼은 특히 단주기 즉 높은 고유진동수 영역에서 높은 응답을 보여 주었다. 둘째, 국내 원자력시설물의 내진기준으로 이용되고 있는 Reg. Guide 1.60과 비교한 결과 속도 응답스펙트럼 값은 약 6-7Hz를 시작점으로 보다 낮은 장주기 영역에서 기준값을 초과하는 현상을 보여 주었다. 셋째, 500년 재래주기에 해당하는 국내 일반 구조물 및 건축물 내진설계기준인 표준 설계응답스펙트럼을 SC, SD 및 SE지반 조건과 같은 3개 지반조건과 동시에 비교한 결과 차례로 약 1.5초, 2초 및 3초에서 시작하여 보다 장주기 영역에서 국내 일반 구조물 표준 설계 응답스펙트럼값을 초과하였다. 동일한 부지에서 일반적으로 가속도 응답스펙트럼은 단주기에서 가장 큰 값을 나타내며, 속도 응답스펙트럼은 중간주기에서 가장 크며, 마지막으로 변위 응답스펙트럼은 장주기에서 가장 큰 값을 가진다는 국외 연구결과가 국내 지반운동을 이용한 결과에서 역시 적용가능하다는 점을 확인시켜 주었다. 최근 국내에서도 건축물의 초고층화 등으로 구조물의 디자인이 기존의 단주기에 비해 중간주기 및 장주기 영역이 상대적으로 강조되고 있어 이러한 중간주기영역에서 수평 응답스펙트럼의 정보는 향후 대단히 중요하다고 할 수 있다. The velocity horizontal response spectra using the observed ground motions from the recent 5 macro earthquakes, equal to or larger than 4.8 in magnitude, around Korean Peninsula were analysed and then were compared to the acceleration horizontal response spectra, seismic design response spectra (Reg Guide 1.60), applied to the domestic nuclear power plants, and finally the Korean Standard Design Response Spectrum for general structures and buildings. 102 velocity horizontal ground motions, including NS and EW components, were used for velocity horizontal response spectra and then normalized with respect to the peak velocity value of each ground motion. First, the results showed that velocity horizontal response spectra have larger values at the range of medium natural period, but acceleration horizontal response spectra have larger values at the range of short natural periods. Secondly, the results also showed that velocity horizontal response spectra exceed Reg. Guide 1.60 for longer natural periods bands less than 6-7 Hz. Finally, the results were also compared to the Korean Standard Response Spectrum for the 3 different soil types(SC, SD, and SE soil type) and showed that velocity horizontal response spectra revealed much higher values for the frequency bands below 1.5(SC), 2.0(SD), and 3.0(SE) seconds, respectively, than the Korean Standard Response Spectrum. The results suggest that the fact that acceleration, velocity, and displacement horizontal response spectra have larger values at the range of short, medium, and long natural periods, respectively, can be applied consistently to those form domestic ground motion, especially, the velocity ground motion. Information on response spectrum at such medium range periods can be very important since the domestic design of buildings and structures emphasizes recently medium and long natural periods than short one due to increased super high-rise buildings.

장애물 외관비에 따른 건물협곡에서의 수평대칭흐름에 관한 연구

손민우,김도용 한국환경기술학회 2020 한국환경기술학회지 Vol.21 No.2

In this study, the variation in wind velocity of horizontal flow formed inside the building canyon was investigated numerically according to the L(Length)/H(Height) ratios of the building. The variations in positive and negative values of horizontal wind velocity components in x- and y-direction were derived and analyzed with vector fields in x-y sections. In the case of L/H=1.0, symmetry vortex on the L/2 center basis was found to be formed in the building canyon. In the case of L/H=3.0, the horizontal wind flow was separated, and additional vortex was developed. The double-symmetry vortexes were reinforced by the increase of L/H ratios. The horizontal wind flow and symmetry development patterns formed in the building canyon can be also interpreted in conjunction with the reverse changes in horizontal wind velocity components. It is expected that these findings can be utilized for quantitative assessment of fine-scale local airflows and various wind environments in urban areas.

창던지기 선수들의 경기기록과 운동학적 요인의 관계

박재명(Park, Jae-Myoung),양진주(Yang, Jin-Joo),박종철(Park, Jong-Chul) 한국체육과학회 2021 한국체육과학회지 Vol.30 No.6

The purpose of this study was to investigate the relationship between javelin throw distance and factors affecting throw distance by world class male and female javelin throwers. This involved analysis of results from a total of 34 attempts by top 12 javelin throwing athletes (6 males and 6 females) participating in the 2019 Mokpo Throwing Competition. To achieve the research objectives, three high-speed cameras were used during the competition and analyzed using a three-dimensional analysis program (Kwon3D 3.1). The results show that males had a negative correlation with the horizontal velocity from the time of left foot landing (LC) to the time of right foot landing (RC) during cross-step (r= -.726, p=.01. Conversely, for women, the foot center distance, velocity, and LC-RC value before projection were positively correlated (r=.717, p=.001) appeared. The maximum angle and record of the knee are negatively correlated only in the female record (r= -.532, p=.028). Javelin posture angle and attack angle had negative correlation with record (r= -.489, p=.046; r= -.509, p=.037). For male athletes, the horizontal velocity before projection requires a maximum velocity that does not affect their posture during projection; for female athletes, the higher the velocity, the higher the record, and the higher javelin’s posture angle and attack angle. These results show there was a difference in the record factors between male and female athletes in the javelin throwing record, and guidance considering gender and individual characteristics is required.

대학 육상선수의 100m Medium Start 출발 구간에 대한 운동학적 비교 분석

최수남(Choi, Su-Nam),오정환(Oh, Cheong-Hwan) 한국체육교육학회 2015 한국체육교육학회지 Vol.20 No.2

본 연구는 대학부 여자선수 10명을 기준으로 지도방법에 대한 수준별 지도를 위해서 100m 기록을 12.5 s이하인 학생들을 A그룹으로 12.5∼13 s 이하의 학생을 B그룹으로 선정하여 고속카메라를 통해서 출발후 제3보까지 미디엄 스타트 동작의 3차원 영상분석 방법을 통하여 그에 따른 운동학적 요인을 규명하여 기록단축을 위한 유용한 정보를 제공하기 위한 목적으로 수행되었다. 단거리 경주의 기록은 보수와 보폭에 의해서 결정이 이루어진다. 출발에서 3보 스텝까지의 소요된 시간은 A그룹에서 소요된 시간이 빠르게 나타났으며, 이동거리의 변화에서는 출발에서 3보 스텝까지의 보폭은 A그룹에서 3보 스텝의 보폭이 더 큰 것으로 나타났다. 신체 중심의 수평속도의 변화는 전 스텝에서 A그룹에서 수평속도의 증가율이 크게 나타났다. 신체 중심의 수직속도의 상하의 변화는 B그룹에서 차이가 크게 나타났다. 단거리 스타트 동작의 기록 단축을 위해서는 구간별 수평속도와 거리를 증가시켜야 하며, 이를 개선하기 위해서는 블록 반응시간, 지면 접촉시간을 단축시키고, 착지시 족관절각, 슬관절각, 고관절각의 변화를 효율적으로 하여 각 관절의 각속도를 증가시키는 이상적인 스타트가 요구된다. Purpose: This study is performed to provide useful information to shorten the record by understanding the physical factor of the bunch start through three dimensional image analysis with excellent group Methods: (A) that is composed of female university players who have won first prizes in national contests and non-excellent group (B) of female university players. There were 8 female university players. Results: The record of short distance contest is determined by the piech and stride. The time from the start to three steps was 0.86 sec for the group A and 0.89 sec for the group B. It showed that group A was faster at the first three steps. The stride from the start to three steps was 3.14 m for the group A and 2.69m sec for the group B. It showed that group A had bigger stride. When we measured the change of horizontal velocity of physical center, the group A showed high increase of horizontal velocity in the all steps. When we measured the change of vertical velocity of physical center, the group Bshowed big change. Conclusion: For the angle of the coxa, the superior group had larger flection than the inferior, when the foot contacted on the ground for the first steps. In a conclusion, the horizontal speed and the stride per block should be increased for theshorter sprint start motion. For this, shortening the reaction time and the ground-contact time per block is prerequisite. The ideal start is therefore that the angles of the ankle, the knee joint and the coxa at landing should be so small as to accelerate the angle speed of each joint.

풍동실험시 소형 풍력발전기의 단면 폐쇄효과

조강표,정승환,창인태 한국풍공학회 2012 한국풍공학회지 Vol.16 No.3

In the paper, the blockage effect was considered for two vertical axis wind turbines, each of which had 0.8m and 1.5m as a blade length, and a horizontal axis wind turbine, of which blade length was 0.74m, to obtain power from the power performance testing of both vertical axis and horizontal axis wind turbines in a wind tunnel. As wind velocity increased, the power of two vertical axis wind turbines having different blade lengths and a horizontal axis wind turbine were measured and adjusted using blockage factors due to the blockage effect. For the vertical axis wind turbine having the blade length of 0.8m, the relationships between RPM and the blockage factor were nearly the same for wind velocity of 5m/s, 8m/s and 10m/s. The blockage factor for the vertical axis wind turbine having the blade length of 0.8m ranged from 0.91 to 0.88 as RPM increased, and the blockage factor for the vertical axis wind turbine having the blade length of 1.5m ranged from 0.85 to 0.82 as RPM increased. Also the blockage factor for the horizontal axis wind turbine having the blade length of 0.74m ranged from 0.84 to 0.77 as RPM increased. It was confirmed from the study that the larger the swept area of the vertical axis wind turbine in a wind tunnel was, the smaller the blockage factor was. 본 논문에서는 풍동에서 수행되는 날개 길이가 0.8m와 1.5m인 두 수직축형 풍력발전기 및 날개 길이가 0.74m인 수평축형 풍력발전기의 성능평가시험으로부터 출력량을 얻기 위하여 수직축형 풍력발전기 및 수평축형 풍력발전기의 폐쇄효과를 고려하였다. 풍속이 증가함에 따라 서로 다른 날개 길이를 갖는 두 수직축형 풍력발전기 및 수평축형 풍력발전기의 출력량을 측정하였고 폐쇄효과에 기인한 폐쇄계수를 사용하여 출력량을 보정하였다. 날개 길이가 0.8m인 수직축형 풍력발전기에 대해 RPM과 폐쇄계수 사이의 관계는 풍속이 5m/s, 8m/s 및 10m/s일 때 거의 동일하였다. 날개 길이가 0.8m인 수직축형 풍력발전기에 대한 폐쇄계수는 RPM이 증가함에 따라 0.91에서 0.88의 범위에 있었고, 날개 길이가 1.5m인 수직축형 풍력발전기에 대한 폐쇄계수는 RPM이 증가함에 따라 0.85에서 0.82의 범위에 있었다. 또한 날개 길이가 0.74m인 수평축형 풍력발전기에 대한 폐쇄계수는 RPM이 증가함에 따라 0.84에서 0.77의 범위에 있었다. 본 연구를 통해 풍동에서 수직축형 풍력발전기의 회전자 면적이 클수록 폐쇄계수는 작아진다는 것을 확인할 수 있었다.

수중 수평 공기-물 이젝터의 분류 거동에 대한 실험적 연구

양희천(Hei Cheon Yang),박상규(Sang Kyoo Park) 대한기계학회 2020 大韓機械學會論文集B Vol.44 No.3

본 연구는 공기-물 이젝터를 이용하여 수중에서 수평으로 주입되는 2상 분류의 유입 및 분류 거동에 대한 실험적 연구를 목적으로 한다. 이젝터의 구동 노즐 면적비를 변수로 유입율 및 유출 계수를 산출하였으며, 수조 내의 주유동 방향 속도 분포를 측정하여 분류의 정량적 거동을 분석하였다. 면적비가 커지면 유입률은 감소하였으며, 유출 계수는 약간 증가하였다. 구동 노즐 면적비가 작고 출구 속도가 감소하면 디퓨저 출구 부근을 제외하고 부력 분류의 특성이 나타나며, 면적비가 커지고 출구 속도가 증가하면 수평 분류에서 부력 분류로 천이되는 거리가 길어지고, 분류 중심선 부근의 주유동 방향 속도가 증가하였다. This study aimed to experimentally investigate the entrainment and jet behavior in a submerged, horizontal, two-phase flow using a central driven air-water ejector. The entrainment ratio and discharge coefficient were calculated with the primary nozzle area ratio, and the quantitative behaviour of submerged horizontal jet was analyzed by measuring the stream-wise velocity in a two-phase jet tank. It was found that as the primary nozzle area ratio increased the entrainment ratio decreased and the discharge coefficient increased slightly. As the primary nozzle area ratio and the primary nozzle exit velocity decreased the mixed jet exhibited buoyancy jet behavior except in the vicinity of diffuser exit. Also, as the primary nozzle area ratio and primary nozzle exit velocity increased the transfer distance from a horizontal jet to a buoyancy jet and the stream-wise velocity near the jet centerline increased.

Study on bubble and liquid velocities in an area-varying horizontal channel

Tran, Thanh Tram,Kim, Byoung Jae,Park, Hyun-Sik Elsevier 2018 Annals of nuclear energy Vol.118 No.-

<P><B>Abstract</B></P> <P>Two-fluid equations are widely used to simulate thermal-hydraulic phenomena in a nuclear reactor. Simulation accuracy depends on the modeling terms in the two-fluid equations. For a dispersed flow, the overall two-phase pressure drop by wall friction must be apportioned to each phase in proportion to the fraction of each phase (Kim et al., 2014). By applying this approach, the prediction of bubble phase velocity can be close to that of liquid for a fully developed flow in a horizontal pipe with a constant area. One may want to know what would happen in the area-varying channels. It is always true that the bubble density is much lower than the water density. Hence, the bubble would accelerate faster than the liquid in a nozzle in which the pressure decreases along the downstream; the bubbles would decelerate more quickly than the liquid in a diffuser in which the pressure increases along the downstream. The purpose of this study was to investigate those behaviors in an area-varying channel using the experimental data and MARS simulations. Experiments were made of turbulent bubbly flows in an area-varying horizontal channel. The velocities of two phases were measured with the help of the PIV technique. The experimental result showed that the two-phase velocities were no longer close to each other in the area-varying regions. The bubble was faster than the liquid in the nozzle region; in contrast, the bubble was slower than the liquid in the diffuser region. MARS code simulations were performed to assess the wall drag model. By replacing the original wall drag partition model in the MARS code with Kim’s one, the simulation results were consistent with experimental observations.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Bubble and water velocities in an area-varying channel are measured. </LI> <LI> The phase velocities are very close in the constant-area region. </LI> <LI> The bubble is faster than the water in the contraction region. </LI> <LI> The bubble is slower than the water in the diffuser region. </LI> <LI> Kim’s wall drag partition model well predicts experimental results. </LI> </UL> </P>