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부분 동결된 소금물에서의 초음파감쇠에 대한 다공성탄성 모델
( Jun Matsushima ),( Takao Nibe ),( Makoto Suzuki ),( Yoshibumi Kato ),( Shuichi Rokugawa ) 한국지구물리·물리탐사학회 2011 지구물리와 물리탐사 Vol.14 No.1
유체를 포함하는 혼합 매질에서의 탄성파 고유 감쇠에 대한 다양한 메커니즘 중, 탄성파 전파 시 고체와 유체 사이에서의 상대적 운동은 가장 중요한 감쇠 메커니즘 중의 하나이다. 선행 연구에서는 얼음의 미세 공극 안에 존재하는 소금물이 초음파의 전파에 미치는 영향을 분석하기 위하여 얼음과 소금물이 공존하는 매질에서 초음파 전파 실험하였다. 부분적으로 동결된 소금물에서 각기 다른 온도에서의 초음파 감쇠의 물리적인 메커니즘을 350~600 kHz의 주파수 대역에서 규명하기 위하여, Biot 이론에 입각한 다공성의 탄성 모델을 도입하여 초음파의 전파를 측정하였다. 고체상은 얼음으로, 액체상은 소금물로 가정한 뒤 펄스 핵자기공명기술로 측정한 유체의 성질을 이용하여 각각의 온도에서의 공극률을 계산한 결과, 실험으로 측정한 감쇠값은 500 kHz에서 계산된 고유 감쇠값과 다르게 나타났으며 이는 squirt-flow 메커니즘과 파의 산란 효과와 같은 다른 감쇠 메커니즘도 고려해야 한다는 것을 의미한다. Although there are many possible mechanisms for the intrinsic seismic attenuation in composite materials that include fluids, relative motion between solids and fluids during seismic wave propagation is one of the most important attenuation mechanisms. In our previous study, we conducted ultrasonic wave transmission measurements on an ice-brine coexisting system to examine the influence on ultrasonic waves of the unfrozen brine in the pore microstructure of ice. In order to elucidate the physical mechanism responsible for ultrasonic wave attenuation in the frequency range of 350-600 kHz, measured at different temperatures in partially frozen brines, we employed a poroelastic model based on the Biot theory to describe the propagation of ultrasonic waves through partially frozen brines. By assuming that the solid phase is ice and the liquid phase is the unfrozen brine, fluid properties measured by a pulsed nuclear magnetic resonance technique were used to calculate porosities at different temperatures. The computed intrinsic attenuation at 500 kHz cannot completely predict the measured attenuation results from the experimental study in an ice-brine coexisting system, which suggests that other attenuation mechanisms such as the squirt-flow mechanism and wave scattering effect should be taken into account.
A poroelastic model for ultrasonic wave attenuation in partially frozen brines
Matsushima, Jun,Nibe, Takao,Suzuki, Makoto,Kato, Yoshibumi,Rokugawa, Shuichi Korean Society of Earth and Exploration Geophysici 2011 지구물리와 물리탐사 Vol.14 No.1
유체를 포함하는 혼합 매질에서의 탄성파 고유 감쇠에 대한 다양한 메커니즘 중, 탄성파 전파 시 고체와 유체 사이에서의 상대적 운동은 가장 중요한 감쇠 메커니즘 중의 하나이다. 선행 연구에서는 얼음의 미세 공극 안에 존재하는 소금물이 초음파의 전파에 미치는 영향을 분석하기 위하여 얼음과 소금물이 공존하는 매질에서 초음파 전파 실험하였다. 부분적으로 동결된 소금물에서 각기 다른 온도에서의 초음파 감쇠의 물리적인 메커니즘을 350 ~ 600 kHz의 주파수 대역에서 규명하기 위하여, Biot 이론에 입각한 다공성의 탄생 모델을 도입하여 초음파의 전파를 측정하였다. 고체상은 얼음으로, 액체상은 소금물로 가정한 뒤 펄스 핵자기공명기술로 측정한 유체의 성질을 이용하여 각각의 온도에서의 공극률을 계산한 결과, 실험으로 측정한 감쇠값은 500 kHz에서 계산된 고유 감쇠값과 다르게 나타났으며 이는 squirt -flow 메커니즘과 파의 산란 효과와 같은 다른 감쇠 메커니즘도 고려해야 한다는 것을 의미한다.
Young-Jun Park,Tomotaro Nishikawa,Kazuhiro Nemoto,Kenichi Matsushima,Mineo Minami,Makoto Kawase 한국육종학회 2012 한국육종학회 심포지엄 Vol.2012 No.07
We investigated the expression patterns of a granule-bound starch synthase I (GBSSI = Waxy) gene at different developmental stages of storage and non-storage organs in Amaranthus cruentus. GBSSI transcripts were strongly expressed in the middle and mid-late stages of seed development and thereafter expression decreased. In addition, this gene was expressed in all non-storage organs tested (the leaf, stem, petiole and root) and showed a tendency to increase during plant development. Therefore, our results indicate that the amaranth GBSSI gene exhibits late expression in the perisperm, and that it is expressed in both storage and non-storage tissues. We also investigated the genetic diversity of GBSSI among 37 strains of amaranth grains originating from New World. A comparison of the GBSSI coding sequence revealed an extremely high level of sequence conservation, and a single nucleotide polymorphism between the sequences of non-waxy (Type I) and waxy (Type II) phenotypes was detected. This indicates that a G–T polymorphism in exon 10 (a nonsense mutation) was a unique event in the evolution of the GBSSI gene in amaranth grains.
Yokota Toshiyuki,Matsushima Jun Korean Society of Earth and Exploration Geophysici 2004 지구물리와 물리탐사 Vol.7 No.1
Frequency-space domain full-wave tomography is a promising technique for delineating detailed subsurface structure with high resolution. However, this method requires criteria for the selection of a set of optimal temporal frequency components, to achieve stability in the sequence of inversion processes together with computational efficiency. We propose a method of selecting optimal temporal frequencies, based on wavenumber continuity. The proposed method is tested numerically and is shown to be able to select an optimal set of frequency components that are sufficient to image the anomalies.
Yuto Sakakibara,Jun Matsushima 한국해양과학기술원 2019 Ocean science journal Vol.54 No.4
Seismic wraparound multiples which are produced by the previous shot and trapped between the sea surface and flat seabed in the two-dimensional marine seismic reflection data have the potential to provide information about oceanographic phenomena because their repetition in the water column could enhance the detectability of the disturbance of seismic wave propagation. By focusing on the disturbance of wraparound multiples, we inferred the possible presence of methane gas bubbles emitting from the seafloor over several kilometers within a submarine canyon with a flat seabed. We observed the significant disturbance of wraparound multiples in both pre-stacked gathers and common mid-point stacked sections, which may be caused by methane bubbles. The existence of a bottom simulating reflection, a fault, and Calyptogena colonies provides indirect evidence of methane gas bubble seeps, while the existence of a cold seep is direct evidence of them in the study area. Finally, we conducted preliminary numerical simulations of acoustic wave propagation to investigate the cause of disturbances of wraparound multiples. Our preliminary numerical simulations imply that the disturbance of wraparound multiples might be associated with the internal scattering caused by an aggregation of gas bubble seeps in the water column.