• 지구물리와물리탐사
• /
• 제26권1호
• /
• pp.8-17
• /
• 2023

해양 환경에서의 기포는 바람, 파도, 선박 및 해저 가스 누출을 포함한 여러 요인에 의해 생성된다. 수중에서의 기포는 강력한 산란 신호를 생성하여 음향 신호를 측정하는데 영향을 미친다. 이러한 기포의 특성은 음파 신호의 세기를 감쇠시켜 소음 차단 목적으로 주로 이용되고 있으며, 최근에는 해저에서 대규모로 누출되는 메탄가스 탐지를 위한 연구가 진행되고 있다. 이러한 가스 누출은 기포플룸의 형태를 취하며, 기포의 물리적 특성과 분포 구조를 이해하는 것은 누출된 가스를 기후 변화와 연관성을 파악하는데 중요한 요소 중 하나이다. 본 연구에서는 탄성파 영상화 기법을 이용하여 기포플룸의 분포를 추정하고자 수조환경에서 실험을 수행하였으며, 별도로 제작된 인공기포 발생기, 자료 취득 시스템을 이용하여 기포에 의한 음향 신호를 취득하였다. 기포플룸을 영상화하기 위해 지진파 영상기법 중 역시간 구조보정을 이용하였으며, 획득한 음향 신호의 포락선 신호를 이용하여 기포 분포 패턴을 효과적으로 추정하였다. 영상화 결과의 검증을 위해 추정된 기포플룸의 분포와 광학카메라 영상을 비교하였다. 실험결과 탄성파 영상화 기법 통해 인공 기포플룸의 산란신호를 이용한 영상화가 가능함을 확인하였다.

• Nuclear Engineering and Technology
• /
• 제53권4호
• /
• pp.1119-1126
• /
• 2021

Spacer grid with mixing vane had been widely used in nuclear reactor core. One of the main feather of spacer grid with mixing vane was that strong swirl flow was formed after the spacer grid. The swirl flow not only changed the bubble generation in the near wall field, but also affected the bubble behaviors in the center region of the subchannel. The interaction between bubble and the swirl flow was one of the basic phenomena for the two phase flow modeling in fuel assembly. To obatin better understanding on the bubble behaviors in swirl flow, full three dimension numerical simulations were conducted in the present paper. The swirl flow was assumed in the cylindral calculation domain. The bubble interface was captured by Volume Of Fluid (VOF) method. The properties of saturated water and steam at different pressure were applied in the simulation. The bubble trajectory, motion, shape and force were obtained based on the bubble parameters captured by VOF. The simulation cases in the present study included single bubble with different size, at different angular velocity conditions and at different pressure conditions. The results indicated that bubble migrated to the center in swirl flow with spiral motion type. The lateral migration was mainly related to shear stress magnitude and bubble size. The bubble moved toward the center with high velocity when the swirl magnitude was high. The largest bubble had the highest lateral migration velocity in the present study range. The effect of pressure was small when bubble size was the same. The prelimenery simulation result would be beneficial for better understanding complex two phase flow phenomena in fuel assembly with spacer grid.

• Journal of Industrial and Engineering Chemistry
• /
• 제68권
• /
• pp.24-32
• /
• 2018

Nanocellulose was surface-functionalized toward the applications in enhanced oil recovery (EOR) as a green alternative. The focus of this paper is on the effect of this material based nanofluid (NF) on foam lamella stabilization through studying its bubble breakup dynamics and flow behaviors in constricted mircofluidic devices. The NF stabilized foam produced an improved flow resistance across the capillary largely due to the capillary trapped bubbles at the contraction. The "snap-off" caused the NF stabilized foam to produce finer textured bubbles, which can migrate readily forward to the deep porous media, as revealed by the pressure profiles.

• 지구물리와물리탐사
• /
• 제13권4호
• /
• pp.336-348
• /
• 2010

한-중 해저터널 후보지로 선정된 대천-원산도 지역의 부지조사를 위해 버블펄서(Bubble pulser) 음원을 이용한 단일채널 탄성파 탐사와 시추조사가 2008년 및 2009년에 수행되었다. 본 연구는 이 단일채널 탐사자료를 정밀 처리하고 시추자료와 연계하여 후보지역의 해저터널 안정성 평가와 시공설계에 필요한 기반암 심도 및 특성을 분석하는데 목적이 있다. 이를 위해 일반적으로 다중채널 탄성파자료에 적용되던 자료처리 기법 중 주파수-파수영역 필터링(F-K filtering)을 적용하여 교류전원잡음 등을 제거하고, 중합후 심도구조보정(post-stack depth migration) 기법을 적용하여 심도단면을 제작하였다. 수행 결과 단일채널 탄성파자료로부터 향상된 심도영역단면을 제작할 수 있음을 확인하였고, 시추자료와 통합 해석을 통하여 조사지역의 개략적인 기반암 분포와 지질특성을 파악할 수 있었다. 단층, 파쇄대 등의 세밀한 구조 파악은 버블펄서 음원과 단일채널 자료의 특성상 어려웠으나, 좀 더 해상도가 높은 탄성파자료가 있을 시 가능할 것으로 보인다. 이에 향후 해저터널 탐사 시 고해상자료를 얻기 위한 추천사항을 수록하였다.

• 한국음향학회지
• /
• 제22권1호
• /
• pp.69-77
• /
• 2003

연안역의 천해 해저면에 설치된 ADCP (Acoustic Doppler Current Profiler, 300㎑, 1200 ㎑)를 이용, 천해에서 체적 산란강도 (volume scattering strength, Sv)의 수직분포에 대한 시변동성을 알아보았다. 수심 85m와 113m에서 ADCP로 측정한 후방 산란강도의 일주기 변동성은 동물플랑크톤 (zooplankton)으로 추측되는 산란체의 일주기 수직이동 (daily vertical migration)에 기인된 것으로 추정되었다. 그러나 수심 20m의 천해에서 관측된 산란강도의 시변동성은 경험적 직교함수 (Empirical Orthogonal Function, EOF) 분석 결과, 해저면 부근의 변화가 천해 체적 산란강도의 변동성에 큰 영향을 주는 것으로 나타났다.

• 한국지하수토양환경학회지:지하수토양환경
• /
• 제21권6호
• /
• pp.46-55
• /
• 2016

This experimental study was aimed to estimate interfacial tension of brine-$CO_2$ by using a pendant bubble method and image analysis. Measurements were performed for wide ranges of temperatures, pressures, and salinities covering reservoir conditions in Pohang basin, a possible candidate for $CO_2$ storage operation in Korea. The profiles of $CO_2$ bubbles in brine obtained from image analysis with the densities of brine and $CO_2$ from previous studies were applied to Laplace-Young equation for calculating interfacial twnsion in brine-$CO_2$ system. The experimental results reveals that the interfacial tension is significantly affected by reservoir conditions such as pressure, temperature and water salinity. For conditions of constant temperature and water salinity, the interfacial tension decreases as pressure increases for low pressures (P < $P_c$), and approaches to a constant value for high pressures. For conditions of constant pressure and water salinity, the interfacial tension increases as temperature increases for T < $T_c$, with an asymptotic trend towards a constant value for high temperatures. For conditions of constant pressure and temperature, the interfacial tension increases with increasing water salinity. The trends in changes of interfacial tension can be explained by the effects of the reservoir conditions on the density difference of brine and $CO_2$, and the solubility of $CO_2$ in brine. The information on interfacial tensions obtained from this research can be applied in predicting the migration and distribution of injecting and residual fluids in brine-$CO_2$-rock systems in deep geological environments during geological $CO_2$ sequestrations.

• 한국응용과학기술학회지
• /
• 제27권1호
• /
• pp.87-92
• /
• 2010

Silicone surfactants are widely used in many industrial area because of its thermal stability and lower foaming property. But it has limitation to expand the application because of migration and bubble generation issues when it is mixed with organic surfactant. In this study, epoxy functionalized fluoro-silicone surfactant, perfluoro glycidoxypropyl polyether siloxane(PFGES), was synthesized using hydrosilylation reaction among perfluoro methyl hydrogen siloxane, allyl glycidyl ether, and allyl ployether in order to get lower surface tension, better thermal stability than conventional silicone surfactant, and reactivity with anhydride function.

• 치과방사선
• /
• 제12권1호
• /
• pp.27-33
• /
• 1982

The purpose of this study is to obtain some informations for the differential diagnosis of ameloblastoma from dentigerous cyst by analysis of the radiographic findings of these lesions. The author studied age and sex distribution, the site of the lesion, tooth behavior and several radiographic features of ameloblastoma and dentigerous cyst. The material consisted of 65 patients of ameloblastoma and 37 patients of dentigerous cyst. The results were obtained as followings. 1) The incidence was highest in 2nd decade (29.2%) and total 65 cases consists of 35 males (53.8%) and 30 females (46.2%) in ameloblastoma. 62 cases were found in lower jaw (95.4%) and the highest site of occurence of ameloblastoma was mandibular molar. region 27 cases. (41.5%) 2) In 65 cases of amelobl!!stoma, 18 cases were seen in association with tooth and 15 cases (83.2%) out of those were associated with mandibular molar teeth. Mandibular molar were most frequently involved in dentigerous cyst (11/31 cases, 29.7%). 3) (a) 23 cases (35.3%) of tooth resorption were found in ameloblastoma and 11 cases (29.7%) of tooth resorption were found in dentigerous cyst. (b) 15 cases (23.1%) of tooth migration were found in ameloblastoma and 10 cases (27.0%) of tooth migration were found in dentigerous cyst. 4) Several radiographic features. (a) Monolocular type ameloblastoma were seen in 23 cases (35.4) and multilocular type of ameloblastoma were seen in 42 cases (64.6%). Monolocular type of dentigerous cyst were seen in 33 cases (89.2%) and multilocular type was seen in 4 cases. (b) Monolocular type ameloblastoma showed 20 cases (87.0%) of scalloped border but 32 cases (97.0%) of dentigerous cyst showed smooth border. (c) 34 cases (81.0%) of ameloblastoma showed honey-comb appearance, soap-bubble appearance or mixed appearance. but all 4 cases of dentigerous cyst showed multicystic appearance. (d) 12 cases (52.2%) of monolocular type ameloblastoma showed slightly increased radiopacity in surrounding bone, and 22 cases (66.7%) of monolocular type dentigerous cyst showed sharp osteosclerotic border. 27 cases (64.3%) of multilocular type ameloblastoma and 3 cases (75.0%) of multilocular type dentigerous cyst showed no changes in surrounding bone.

• Journal of Dental Anesthesia and Pain Medicine
• /
• 제15권1호
• /
• pp.31-34
• /
• 2015

Vascular injury caused by a central venous catheter (CVC) has been reported to be a rare complication, especially delayed vascular injury due to CVC has a few cases and it can be fatal because of delayed recognition and more serious complications. A 59-year-old woman with no available medical history was admitted for treatment of ovarian cancer. For the surgery, a triple-lumen CVC was placed through the left subclavian vein. Parenteral nutrition through the CVC was used for postoperative nutritional management in the first postoperative day. On the sixth postoperative day (POD), the patient suddenly complained of dyspnea. The CT revealed bilateral pleural effusion and irregular soft tissue density and air bubble in anterior mediastinum suggesting migration of the distal portion of the CVC into the anterior mediastium. In the intensive care unit (ICU) bilateral thoracentesis and percutaneous drainage were performed. She was discharged from the ICU in 3 days later and transferred to the general ward. This case emphasizes the possibility of the delayed vascular injury related to CVC and some strategies for prevention of vascular injury.