• Title/Summary/Keyword: Bubble Size

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Highly-closed/-Open Porous Ceramics with Micro-Beads by Direct Foaming

  • Jang, Woo Young;Seo, Dong Nam;Park, Jung Gyu;Kim, Hyung Tae;Lee, Sung Min;Kim, Suk Young;Kim, Ik Jin
    • Journal of the Korean Ceramic Society
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    • v.53 no.6
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    • pp.604-609
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    • 2016
  • This study reports on wet-foam stability with respect to porous ceramics from a particle-stabilized colloidal suspension that is achieved through the addition of polymethyl methacrylate (PMMA) using a wet process. To stabilize the wet foam, an initial colloidal suspension of $Al_2O_3$ was partially hydrophobized by the surfactant propyl gallate (2 wt.%) and $SiO_2$ was added as a stabilizer. The influence of the PMMA content on the bubble size, pore size, and pore distribution in terms of the contact angle, surface tension, adsorption free energy, and Laplace pressure are described in this paper. The results show a wet-foam stability of more than 83%, which corresponds to a particle free energy of $2.7{\times}10^{-12}J$ and a pressure difference of 61.1 mPa for colloidal particles with 20 wt.% of PMMA beads. It was possible to control the uniform distribution of the open/closed pores by increasing the PMMA content and by adding thick struts, leading to the achievement of a higher-stability wet foam for use in porous ceramics.

Effective Heater-Area and Droplet-Volume Adjustable Microinjectors Using a Digitally Controlled Single Heater (단일 히터의 디지털 구동을 통한 유효 히터면적 변화 및 분사 액적크기 조절이 가능한 미소유체분사기)

  • Je Chang Han;Kang Tae Goo;Cho Young-Ho
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.29 no.1 s.232
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    • pp.67-73
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    • 2005
  • The paper presents a single-heater microfluid injector, whose ejected droplet volume is adjusted by digital current path control for a single microheater. The previous droplet volume adjustable methods have used the digital current control for multiple heaters or the analog current control for a single heater, while the present method uses the digital current control for a single microheater. Two different microinjectors, having a rectangular heater and a circular hearter, are designed and fabricated in the chip area of $7.64\;mm{\times}5.26\;mm$. The fabricated microinjectors have been tested and characterized for the number, size, shape and lifetime of the generated bubbles as well as for the volume and velocity of the ejected droplets. The input power for the rectangular heater and the circular heater has been varied in the ranges of $8.7{\sim}24.9{\mu}W\;and\;8.1{\sim}43.8{\mu}W$, respectively. The projected area of the generated bubble has been changed in the ranges of $440{\sim}l,3600{\mu}m^2\;and\;800{\sim}3,300{\mu}m^2$ for the rectangular heater and the circular heater, respectively. The microinjector with the rectangular heater ejects three discrete levels of the droplet in the volume range of $9.4{\sim}20.7pl$ with the velocity range of $0.8{\sim}1.7m/s$, while the microinjector with the circular heater achieves five discrete levels of the droplet in the volume range of $7.4{\sim}27.4pl$ with the velocity range of $0.5{\sim}2.8m/s$.

Colour Removal from Dyestuff Wastewater by Micro Bubbles Flotation Process (마이크로 버블 부상 공정에 의한 염료폐수의 색도 제거)

  • Kim, Myeng-Joo;Han, Sien-Ho
    • Applied Chemistry for Engineering
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    • v.33 no.6
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    • pp.606-612
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    • 2022
  • The purpose of this study is to convert hydrophobic dyestuff to hydrophilic dyestuff by reacting cationic collector with anionic dyestuff and reaction anionic collector with cationic dyestuff. The removal of colors from aqueous solutions and/or dispersions has been studied by dispersed-air flotation in a batch column. In this studies used generated micro bubble by ceramic gas diffuser having micro pore size for air flotation process. In this study, a ceramic gas diffuser with micro pore size was used to generate micro bubbles for the air flotation process. Two colours were used for the experiments: Basic Yellow 1 (cationic dyestuff) and Direct Orange 10 (anionic dyestuff). All two were effectively removed by flotation within 8 mins. Sodium dodecyl sulfate, sodium oleate (an anionic collector), and amines (a cationic collector) were found to be effective as collectors in the removal of color, which was found to be related to the pH of the solution and the amount of collector added to it, with high collector dosages causing the process to become pH-independent.

Verification of Microstructure Qualities of ACR-Approved Mammography Phantoms by Refraction-Enhanced Synchrotron Radiation Imaging

  • Imamura, Keiko;Ehara, Norishige;Inada, Yoichi;Miyamoto, Keiko;Kanemaki, Yoshihide;Umetani, Keiji;Uesugi, Kentaro;Ochiai, Yoshinori;Fukuda, Mamoru;Nakajima, Yasuo
    • Proceedings of the Korean Society of Medical Physics Conference
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    • 2002.09a
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    • pp.415-417
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    • 2002
  • Images of microcalcification specks showed large variation in conventional radiographs of phantoms which are approved for mammography image quality standard by the American College of Radiology (ACR). This kind of variation is not appropriate for image quality standards because the number of specks are visually counted in images and that number is important in image quality evaluation. Our study using synchrotron radiation (SR) imaging revealed the overlapping of micro-sized air bubble(s) to some specks, and also the structural deformation or crackings. Eight phantoms approved by ACR from two different makers and an air-bubble phantom were examined. SR imaging was performed at a synchrotron radiation facility, SPring-8, in Japan. The image-detector was a fluorescent-screen optical-lens coupling system using a CCD camera with a spatial resolution of 6 $\square$m. Objects when imaged with longer sample-to-detector distance show edge enhancement due to a difference in refraction indices, that is refraction enhancement. Refraction-enhanced SR images revealed that some of specks carried foreign objects, which were proven to be air. In phantoms provided by one maker, attaching/overlapping airs were observed for 62 out of 150 specks (41%) , with a higher incidence for the smallest specks. A speck becomes hardly visible in a conventional radiograph when air(s) overlaps the majority part of a speck, though depending on the size of the air-inclusion and on its configuration. Those airs might have been adsorbed on a speck surface before being embedded and then introduced into the matrix together with specks. Our study using SR imaging has clearly shown the nature of defects in some mammography phantoms which seriously degrade the quality as an image standard.

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Numerical Modeling of Free Surface Flow over a Broad-Crested Rectangular Weir (사각형 광정위어를 통과하는 자유수면 흐름 수치모의)

  • Paik, Joongcheol;Lee, Nam Joo
    • Journal of Korea Water Resources Association
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    • v.48 no.4
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    • pp.281-290
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    • 2015
  • Numerical simulations of free surface flow over a broad-crested rectangular weir are conducted by using the volume of fraction (VOF) method and three different turbulence models, the k-${\varepsilon}$, RNG k-${\omega}$ and k-${\omega}$ SST models. The governing equations are solved by a second-order accurate finite volume method and the grid sensitivity study of solutions is carried out. The numerical results are evaluated by comparing the solutions with experimental and numerical results of Kirkgoz et al. (2008) and some non-dimensionalized experimental results obtained by Moss (1972) and Zachoval et al. (2012). The results show that the present numerical model can reasonably reproduce the experimental results, while three turbulent models yield different numerical predictions of two distinct zones of flow separation, the first zone is in front of the upstream edge of the weir and the second is created immediately behind the upstream edge of the weir where the flow is separated to form the separation bubble. The standard k-${\varepsilon}$ model appears to significantly underestimate the size of both separation zones and the k-${\omega}$ SST model slightly over-estimates the first separation zone in front of the weir. The RNG k-${\varepsilon}$ model predicts both separation zones in overall good agreement with the experimental measurement, while the k-${\omega}$ SST model yields the best numerical prediction of separation bubble at the upstream edge of the weir.

The Correlation between Radiologic Findings and Clinicopathological Prognostic Factors in Small Peripheral Adenocarcinoma of Lung (말초 폐 발생 소형 선암에서 화상적 소견과 병리적, 임상적 예후와의 관계)

  • Park, Jae-Kil;Cho, Kyu-Do;Park, Kuhn;Moon, Seok-Whan;Rha, Suk-Joo;Choi, Si-Young;Jung, Jung-Im
    • Journal of Chest Surgery
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    • v.37 no.5
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    • pp.423-431
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    • 2004
  • Background : Tumor size in lung cancer is not as good a prognostic factor for adenocarcinoma as it is for other types of lung cancer; therefore it is difficult to estimate the prognosis preoperative. However, there have recently been some reports on the radiologic findings correlating to the clinicopathologic prognostic factors in peripheral small adenocarcinoma of lung. We tried to evaluate the prognostic importance of High-Resolution CT (HRCT) findings of such adenoearcinoma, Material and Method: One houndred and seventy-six surgically resected small peripheral adenocarcinoma measuring 3 cm or less in greatest dimension were reviewed radiologically and clinicopathologically. Result: The patients with greater extent of ground-glass attenuation (GGA) had better clinico-pathological factors. The tumors with gross appearance of GGA or bubble-like shape showed better clinicopathological prognostic factors than scar-like or solid shape. Conclusion: HRCT findings of small peripheral adenocarcinomas of the lung correlated well with the histologic and clinical prognostic factors. We can predict the post-operative prognosis with the radiologic findings.

Comparative Evaluation on Collision and Particle Separation Efficiency between CO2 Bubbles and Air Bubbles Using Contact Zone Model of Flotation Process (부상분리 공정의 접촉영역 모델을 이용한 이산화탄소와 공기 기포의 충돌 및 입자 분리효율 비교 평가)

  • Yang, Jong-Won;Choi, Yong-Ho;Chae, In-Seok;Kim, Mi-Sug;Jeong, Yong-Hoon;Kim, Tae-Geum;Kwak, Dong-Heui
    • Journal of Korean Society on Water Environment
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    • v.35 no.1
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    • pp.64-71
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    • 2019
  • In recent years, carbon dioxide ($CO_2$) bubbles emerged as the most widely applied material with the recycling of sequestrated storage to decrease global warming. Flotation using $CO_2$ as an alternative to air could be effective in overcoming the high power consumption in the dissolved air flotation (DAF) process. The comparison of DAF and DCF system indicated that, the carbon dioxide flotation (DCF) system with pressurized $CO_2$ only requires 1.5 ~ 2.0 atm, while the DAF system requires 3.0 ~ 6.0 atm. In a bid to understand the characteristics of particle separation, the single collector collision (SCC) model was used and a series of simulations were conducted to compare the differences of collision and flotation between $CO_2$ bubbles and air bubbles. In addition, laboratory experiments were sequentially done to verify the simulation results of the SCC model. Based on the simulation results, surfactant injection, which is known to decrease bubble size, cloud improved the collision efficiency of $CO_2$ bubbles similar to that of air bubbles. Furthermore, the results of the flotation experiments showed similar results with the simulation of the SCC model under anionic surfactant injection. The findings led us to conclude that $CO_2$ bubbles can be an alternative to air bubbles and a promising material as a collector to separate particles in the water and wastewater.

Electrochemical properties of porous AuCu dendrite surface for the oxygen reduction reaction in alkaline solutions (알칼리 수용액에서 산소환원반응에 대한 다공성 AuCu 덴드라이트 표면의 전기화학적 특성 평가)

  • Kim, Min-Yeong;Lee, Jong Won;Cho, Soo Yeon;Park, Da Jung;Jung, Hyun Min;Lee, Joo Yul;Lee, Kyu Hwan
    • Journal of Surface Science and Engineering
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    • v.54 no.1
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    • pp.1-11
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    • 2021
  • Porous dendrite structure AuCu alloy was formed using a hydrogen bubble template (HBT) technique by electroplating to improve the catalytic performance of gold, known as an excellent oxygen reduction reaction (ORR) catalyst in alkaline medium. The rich Au surface was maximized by selectively electrochemical etching Cu on the AuCu dendrite surface well formed in a leaf shape. The catalytic activity is mainly due to the synergistic effect of Au and Cu existing on the surface and inside of the particle. Au helps desorption of OH- and Cu contributes to the activation of O2 molecule. Therefore, the porous AuCu dendrite alloy catalyst showed markedly improved catalytic activity compared to the monometallic system. The porous structure AuCu formed by the hydrogen bubble template was able to control the size of the pores according to the formation time and applied current. In addition, the Au-rich surface area increased by selectively removing Cu through electrochemical etching was measured using an electrochemical calculation method (ECSA). The results of this study suggest that the alloying of porous AuCu dendrites and selective Cu dissolution treatment induces an internal alloying effect and a large specific surface area to improve catalyst performance.

Effect of Operating Variables on the Morphology of Precipitated Calcium Carbonate in a Slurry Bubble Reactor (슬러리 기포탑 반응기에서 침강성 탄산칼슘의 모폴로지에 대한 조업변수들의 영향)

  • Hwang, Jung-Woo;Lee, Yoong;Lee, Dong-Hyun
    • Clean Technology
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    • v.16 no.2
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    • pp.124-131
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    • 2010
  • Effects of $Ca(OH)_2$ concentration (0.16~0.64 wt%), surfactant concentration (2~16 wt%), total volumetric flow rate (3~6 L/min) and $CO_2$ volume fraction $(0.3{\sim}0.6)$ on morphology, crystal structure, mean particle diameter, aggregation and specific surface area of the precipitated $CaCO_3$ were investigated in the slurry bubble column reactor. Experiments were carried out in acrylic reactor ($0.11\;m-ID{\times}1.0\;m-high$) with a internal tube ($0.04\;m-ID{\times}1.0\;m-high$h). The reaction time of $CaCO_3$ synthesis decreased with adding Dispex N40 of the anionic surfactant. The reaction rate of $Ca(OH)_2$ increased with increasing the volumetric flow rate of $CO_2$. From SEM images, the single crystal of $CaCO_3$ increased with increasing the reaction rate in the saturated concentration of $Ca(OH)_2$ (0.16 wt %) and the concentration of Dispex N40 (2 wt%). The mean particle size of $CaCO_3$ varied with adding Dispex N40. In addition, the specific surface area of $CaCO_3$ increased with adding of surfactant (2 wt%) from $35m^2/g$ to $44m^2/g$ at the volumetric flow rate of $CO_2$ (0.9 L/min) and the concentration of $Ca(OH)_2$(0.64 wt %).

Effect of Microsparged Aeration on Oxygen Transfer Rate and Cell Viability in Mammalian Cell Culture Bioreactor (동물 세포 반응기에서의 초미세 통기법이 산소 전달 속도와 세포 생존율에 미치는 영향)

  • 김정모;장건희;최춘순;김정회
    • Microbiology and Biotechnology Letters
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    • v.29 no.4
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    • pp.240-247
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    • 2001
  • The effect of microsparged aeration in mammalian cell bioreactor on the oxygen transfer rate and cell viability was studied. The microspargers with differ- ent micron-sized pores were used to supply oxygen to the medium. The oxygen transfer coefficients (k$_{L}$a) measured in the bioreactor were markedly increased, which is due to the increase of the contacting area between air bubbles and liquid medium when the pore size of microsparger decreases. When the impellers of two different types (square-pitch marine impeller and $45^{\circ}$ pitched flat blade impeller) were used for agitation, the k$_{L}$a values were slightly higher with the marine impeller than with the blade impeller. The detrimental effect of direct gas sparging with microsparger on mammalian cells was investigated in bubble columns with various air flow rates and different pore sized microspargers. The first-order cell death rate constant ($k_{d}$ /7) was shown to be directly proportional to the air flow rate and inversely proportional to the pore size. During the cultivation of hybridoma cells using microsparger with the pore size of $0.57\mu$m in the mammalian cell culture bioreactor, the continuous sparging caused the cell death and suppressed the cell growth. However, cells grew normally and cell viability was maintained above 90% in the logarithmic phase when the air was intermittently sparked in order to maintain the dissolved oxygen level above 20%.

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