• 대한기계학회논문집B
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• 제27권2호
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• pp.197-205
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• 2003

A cascade impactor is a multistage impaction device used to separate airborne particles into aerodynamic size classes. A micro-orifice impactor uses micro-orifice nozzles to extend the cut sizes of the lower stages to as small as 0.05 ${\mu}{\textrm}{m}$ in diameter without resorting to low pressures or creating excessive pressure drops across the impactor stages. In this work, the phenomenon of particle clogging in micro-orifice nozzles was experimentally investigated for a commercial micro-orifice uniform deposit impactor (MOUDI). It was observed, using an optical microscope, that the micro-orifice nozzles of the final stages were partially clogged due to particle deposition during the aerosol sampling. Therefore the pressure drops across the nozzles were higher than the nominal values given by the manufacturer. To examine the effect of particle clogging in micro-orifice nozzles, the particle collection efficiency of the MOUDI was evaluated using an electrical method for fine particles with diameters in the range of 0.1-0.6 ${\mu}{\textrm}{m}$. The monodisperse liquid dioctyl sebacate (DOS) particles were used as test aerosols. A faraday cage was employed to measure the low-level current of the charged particles upstream and downstream of each stage. It was found that the collection efficiency curves shifted to correspond to smaller orifice sizes, and the 50-% cutoff sizes were much smaller than those given by the manufacturer for the three stages with nozzles less than 400 ${\mu}{\textrm}{m}$ in diameter.

• 한국기계가공학회지
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• 제17권1호
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• pp.82-88
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• 2018

An experimental study was performed on the orifice nozzle system that generates micro-bubbles by air self-suction using a venturi nozzle. This study experimentally investigates the amount of air sucked into the venturi nozzle and the number of micro-bubbles generated by the orifice nozzle system in Cases 1 and 2. The experimental conditions were varied by changing the diameter of the orifice nozzle (d=2~7 mm) and the number of holes of the perforated plate nozzle (n = 2-12). In Case 1, the air self-suction was more than 2 LPM at $d{\leq}4mm$. When d = 4 mm, the total number of bubbles was 29,777, and it was confirmed that micro-bubbles occupied approximately 65% of the total number of bubbles. In Case 2, the air self-suction was maintained constant at approximately 2.5 LPM regardless of the number (n) of holes. The total amount of bubbles increased when n increased but remained constant at approximately 44,000 when $n{\geq}7EA$. It was also confirmed that more than 80% of all bubbles were micro-bubbles when $n{\geq}10EA$. Thus, the number of micro-bubbles increased by approximately 15% compared to the experimental result of Case 1, which was optimized with d = 4 mm.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2010년도 춘계학술대회 논문집
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• pp.1169-1170
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• 2010

• 한국기계가공학회지
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• 제14권1호
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• pp.98-104
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• 2015

This experiment was a study of a Vortex nozzle designed to produce micro-bubbles due To investigate air self-suction and the generation of micro-bubble by the Vortex nozzle, the dimensions of air intake region, the nozzle shape, and the nozzle exit diameter ($d_n=5,7,9.2,12.3mm$)werevaried. The air self-suction rate was ~1,000 to 2,000 cc/min at the orifice nozzle (7 mm), and ~100 and ~22 cc/min at the sector nozzles (9.2 and 12.3 mm, respectively). The most bubbles were detected in the orifice nozzle, but bubbles less than $50{\mu}m$ were found in the 12.3-mm sector nozzle. The dissolved oxygen in the tank water was much greater in Case 2 than in Case 1, at both the orifice and sector nozzles. Moreover, the reduction rate of dissolved oxygen was found to be less at the sector nozzles, than at the orifice nozzle.

• 한국분말재료학회지
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• 제15권6호
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• pp.509-513
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• 2008

High-pressure abrasive entrained jet have rapidly become important machining technology over the last two decades. However, suspension jet by high-pressure has been recently developed for packaging sawing. Ideally, diamond materials should be used for components in abrasive water-jet systems that are subject to high erosive conditions. Using the diamond orifices improve maintenance and extend wear part life. This paper gives insights to using an abrasive suspension jet with diamond orifice. The influences of orifice material and orifice design are evaluated.

• 한국음향학회지
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• 제25권3호
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• pp.101-106
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• 2006

본 연구에서는 그릴에 뚫려 있는 구멍이 마이크로스피커의 전체 임피던스에 미치는 영향에 대하여 조사하였다 이들에 대한 영향을 이론적으로 접근하기 위하여 그릴의 구멍을 열린 짧은 길이를 갖는 파이프시스템의 일종인 올피스로 취급하였다. 이에 대한 결과는 실험적으로 얻어진 특성과 매우 잘 일치하였다. 다시 말하면, 이들의 구멍크기가 작아지게 되면 구멍에 의한 음향임피던스가 매우 커지게 된다. 그 결과로써, 마이크로스피커의 전체 음향임피던스에 미치는 영향이 커지는 것을 알 수 있었다. 이처럼 그릴의 구멍크기가 작을수록 전체 임피던스에 미치는 영향이 커져서 마이크로 스피커 유닛에서 발생한 음향특성이 그릴의 사용으로 인하여 달라질 수 있게 된다.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.426-427
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• 2006

Mono-sized silicon particles were effectively fabricated by a novel way named pulsated orifice ejection method (POEM). The particles are with very narrow particles size distribution and very small standard deviation of mean particle size. There are two different types spherical silicon particles were found. One consists of many grains mainly in random boundaries. The other consists of two or three grains with only twin orientation relationships, even single crystal in cross-section was also found within this type of spherical silicon particles.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.433-434
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• 2006

Monosized germanium micro particles are prepared by a newly developed Pulsated Orifice Ejection Method. The obtained particles are categorized into two kinds of the microstructures as refined and coarse ones. The morphological difference is estimated to be determined by the undercooling level during nucleation. Actually, the increase in the temperature of the melt was effective in coarsening the microstructure, because the temperature of the melt intensely relates to the undercooling level. The transition temperature of coarse and refined microstructures is found to be 1300-1350K. Furthermore, a triggered nucleation could improve the crystallinity of the particles in the short separation.

• 한국환경과학회지
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• 제25권6호
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• pp.829-837
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• 2016

The mechanism of micro-bubble generation with a pump is not clarified yet, so the design of water treatment systems with a micro-bubble generating pump is based on trial and error methods. This study tried to explain clearly quantitative relationships of experimental micro-bubble concentration ($C_{air}$) of continuous operation tests with a micro-bubble generating pump and theoretical air solubility. Operation parameters for the tests were discharge pressure ($P_g$), water ($Q_{w0}$) and air ($q_0$) flow rates, orifice diameter ($D_o$), and retention time (t). The experimental micro-bubble concentrations ($C_{air}$) at 4.8 atm of discharge pressure ($P_g$) were in the range of 21.04 to 25.29 mL/L. When the retention time (t) by changing the pipe line length ($L_p$) increased from 1.22 to 6.77s, the experimental micro-bubble concentrations ($C_{air}$) increased from 25.86 to 30.78 mL air/L water linearly. The dissolved and dispersed micro-bubble concentrations ($C_{air}$) are approximately 4 times more than the theoretical air solubility.

• 드라이브 ㆍ 컨트롤
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• 제16권1호
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• pp.1-6
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• 2019

The use of micro bubbles in industrial fields has been increasing in the recent years., particularly micro-bubble sterilization and water purification effects. Various methods have been developed for the generation of micro-bubbles. Depending on the method of generating bubbles, the micro-bubbles can be roughly classified into saturation molding, cavitation and rotation flow types. The objective of this study was to use ventilated tube type as a method of generating micro-bubbles in order to purify large amount of water quality such as lakes and reservoirs. This method shows a difference in efficiency in which micro-bubbles are generated depending on the contact ratio of gas to liquid. The study also investigated the optimal gas liquid contact ratio by applying various orifice methods and investigated the optimum condition of micro-bubble generation by gas Based on this, a technology to develop a micro-bubble generator with a venturi type nozzle shape that has a high water purification effect was developed.