• The Journal of the Acoustical Society of Korea
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• 제27권3E호
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• pp.69-76
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• 2008

Measurements of bubble size and distribution in the surface layer of the sea, wind speed, and variation of ocean environments were made continually over a four-day period in an experiment conducted in the South Sea of Korea during 17-20 September 2007. Theoretical background of bubble population model indicates that bubble population is a function of the depth, range and wind speed and bubble effects on sound speed shows that sound speed varies with frequency. Observational evidence exhibited that the middle size bubble population fit the model very well, however, smaller ones can not follow the model probably due to their short lifetime. Meanwhile, there is also a hysteresis effect of void fraction. Observational evidence also indicates that strong changes in sound speed are produced by the presence of swarms of micro bubbles especially from 7 kHz to 50 kHz, and calculation results are consistent with the measured data in the high frequency band, but inconsistent in the low frequency band. Based on the measurements of the sound speed and high frequency transmission configuration in the bubble layer, we present an estimation of underwater acoustic channel capacity in the bubble layer.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.1909-1914
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• 2003

Bubble growth on microheater has been experimentally investigated in this study. The experiment was performed using platinum micro heaters having dimensions of $100{\times}10{\times}0.2{\mu}m^3$ with constant heat flux. A high speed video camera was used to observe bubble growth at 250 frames per second. Microheater temperature was measured at the rate of 300Hz with a data acquisition system. When heater temperature was $139^{\circ}C$ a bubble was nucleated in the liquid FC-72. The temperature profiles and the high speed camera images were combined to explain heat transfer and bubble growth on microheater.

• 한국습지학회지
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• 제17권2호
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• pp.118-123
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• 2015

제강산업의 냉연 산회수 설비공정을 검토하였고, 공정에서 발생되는 염화수소 가스를 처리하기 위하여 마이크로버블이 발생되는 DIWS 시스템을 운전하였다. 염화수소 가스의 대기배출허용기준을 만족하기 위해서는 추가공정의 도입이 필요한 것으로 나타났다. DIWS 장치로 유입되는 평균 염화수소 가스의 농도는 22.3 ppm, 배출가스의 농도는 0.59 ppm으로 평균 제거율은 97.3%였다. TMS 장치에 의한 10시간 5분 간격 측정에서도 평균 0.69 ppm으로 안정적이었으며, 수동으로 측정하여 TMS 장치의 신뢰도를 검증하였다.

• 상하수도학회지
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• 제16권6호
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• pp.663-669
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• 2002

Electro-flotation (EF) has shown advantages, such as a high removal efficiency and easy control of bubble generation, over dissolved air flotation. However, the fundamental characteristics of the process have not been investigated in detail. According to recent modeling results from trajectory analysis, the size of the bubble is one of the most important factors that affect the efficiency of collision between bubble and particle. In this paper, the size characteristics of bubbles generated from EF under various conditions are measured using a new method for bubble size measurement, the Particle Counter Method (PCM). The size of the generated bubbles was found to be constant with respect to applied voltage but to vary with the electrode materials. These results and their implications are discussed.

• 대한기계학회논문집B
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• 제31권3호
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• pp.248-255
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• 2007

Thermal bubble formation is a fundamental process in nucleate boiling heat transfer and many microelectromechanical thermal systems. One of the established facts is that heterogeneous nucleation is originated from vapors trapped inside cavities. Based on this, we performed an experimental study on the formation of thermal bubbles from microcavity fabricated by microfabrication technology on a copper plate. The cavity was filled with aluminum particles to enhance thermal bubble formation. We observed the thermal bubble behaviors, such as bubble incipience, diameter, frequency and coalescence during nucleate boiling. The experimental data showed that the superheat required to trigger the bubble formation was significantly reduced when the cavity was filled with microparticles. We found that the initial increase of superheat led to the increase of both the departure diameter and frequency while the further increase of superheat caused multiple bubbles to coalesce resulting in the decrease of departure frequency.

• 환경기술인
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• 제25권통권257호
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• pp.56-60
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• 2008

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2012년도 춘계학술대회 논문집
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• pp.1171-1172
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• 2012

• 센서학회지
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• 제20권2호
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• pp.124-130
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• 2011

In this study, in order to evaluate the yield of bubble by ultrasonic cavitation in HIFU sonication, the bubble image analysis was performed. The changing phenomenon of cavitation effect according to the sonication condition was discussed by analyzing the bubble image. Especially the appearance of bubble cloud, the size of micro-bubble, and the yield of bubble were considered. The 500 KHz and 1.1 MHz concave type ultrasonic transducers were used for HIFU sonication. Computer controlled digital camera was used to obtain the bubble image, and the binary image processing(binarization coefficient : 0.15) was performed to analyze them. In results of 500 KHz and 1.1 MHz transducer, the area of bubble cloud was increased in proportion to the rise in sonication intensity($R^2$ : 0.7031 and 0.811). The mean size of single microbubble was measured as 98.18 um in 500 KHz sonication, and 63.38 um in 1.1 MHz sonication. In addition, the amount of produced bubble was increased in proportion to sonication intensity. Through the result of this study and further study for variable image processing method, the quantitative evaluation of ultrasonic cavitation effects in HIFU operation could be possible with the linearity associated with the sonication conditions.

• 한국가시화정보학회지
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• 제9권1호
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• pp.17-19
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• 2011

The bubble oscillations play an important role in ultrasonic cleaning processes. In the ultrasonic cleaning of semiconductor wafers, the cleaning process often damages micro/nano scale patterns while removing contaminant particles. However, the understanding of how patterns in semiconductor wafers are damaged during ultrasonic cleaning is far from complete yet. Here, we report the observations of the motion of bubbles that induce solid wall damage under 26 kHz continuous ultrasonic waves. We classified the motions into the four types, i.e. volume motion, shape motion, splitting or jetting motion and chaotic motion. Our experimental results show that bubble oscillations get unstable and nonlinear as the ultrasonic amplitude increases, which may exert a large stress on a solid surface raising the possibility of damaging microstructures.

• 한국가시화정보학회지
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• 제4권2호
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• pp.69-75
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• 2006

The microbubbles were used in various fields, such as turbulent control, drag reduction, material science and life science. The X-ray PTV using X-ray micro-imaging technique was employed to mea-sure the size and velocity of micro-bubbles moving in an opaque tube simultaneously. Micro-bubbles of $10{\sim}60{\mu}m$ diameter moving upward in an opaque tube (${\phi}$=2.7mm) were tested. Due to the different refractive indices of water and air, phase contrast X-ray images clearly show the exact size and shape of over-lapped microbubbles. In all of the working fluids tested (deionized water, tap water, 0.01 and 0.10M NaCl solutions), the measured terminal velocity of the microbubbles rising through the solution was proportional to the square of the bubble diameter. The rising velocity was increased with increasing mole concentration. The microbubble can be useful as contrast agent or tracer in life science and biology. The X-ray PTV technique should be able to extract useful information on the behavior of various bio/microscale fluid flows that are not amenable to analysis using conventional methods.