• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.3
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• pp.13-24
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• 1993

The influence of the bubble structure and strength characteristics on the freeze-thaw resistance of high strength concrete is investigated by the laboratory experiment. The test conditions are formed in the manner that water is continueusly supplied externally and the specimens were received severe weather actions from ordinary to significantly low temperatures. The experiments are performed in two stages. In the first stage, the relation between the durability to frost action and the bubble structure is analyzed especially with respect to the water-cement ratio and the amount of air. The AE and non-AE concrete specimens made of ordinary portland cement are used in the test. In the second stage, the non-AE concrete specimens using vibratory compaction to improve the durability to frost action, and the high watertight specimens of rapid hardening portland cement to increase their initial strength are produced and tested. The degree of watertightness of the specimens is determined by measuring the permeability of the specimens and the bubble structure of the high watertight concrete is also estimated.

• Applied Chemistry for Engineering
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• v.7 no.3
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• pp.573-579
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• 1996

Effects of operating variables on the conversion of the formation reaction of meta boric acid from ortho boric acid in a laboratory-scale bubble column reactor were investigated to obtain the basic data which are indispensable for the design, scale-up, control, development and operation of industrial bubble column reactors. Reaction time and pressure, particle size of reactant and gas flow rate were chosen as experimental variables. Effects of the experimental variables on the gas holdup in the bubble column reactor were also discussed in relation to the conversion of reaction. From the results of this study, the optimum conditions were drawn as follows : Reaction time ; 35~40(min), reaction pressure ; 92~95(kPa), particle size ; under $0.6{\times}10^{-3}(m)$, gas flow rate ; 0.07~0.08(m/s).

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.11
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• pp.2142-2144
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• 2015

3D FLS is a active sonar that can represent the underwater inside visually in forward direction. We discuss on the decrease of bubbles from breaking waves in 3D FLS frames. In the experiment using the bubbles reduction filter the effect of bubbles was decreased a lot.

• Proceedings of the KAIS Fall Conference
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• 2010.11b
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• pp.542-545
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• 2010

통상 분 당 $0.6{\ell}$, 최대 $2{\ell}$의 유량과 토출 압력 5atg의 운전 조건을 만족시키는 미세기포발생기용 소형 왕복동식 공기압축기를 개발하는 것이 본 연구의 목적이다. 미세기포발생기는 현재 농업, 어업, 미용, 수질오염방지 등 여러 방면에서 매우 널리 사용되고 있는데, 이러한 미세 기포를 발생시키기 위해서는 고압의 소형 공기압축기가 요구 된다. 이를 위해 비교적 간단한 구동방식의 왕복동식 압축방법을 선정하여 핵심 설계 항목인 실린더와 피스톤형상, 간극체적, 압축비, 구동모터 출력을 이론적 예측과 실험적 방법을 통하여 최적화하였다. 그 결과 미세기포 발생장치 시스템에서 가장 큰 공간을 차지하고 있는 압축기를 소형화시켰으며 압축기 개발 목표 성능을 달성하였다.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2003.11a
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• pp.49-52
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• 2003

The objective of this study the mechanical characteristics of prefoamed lightweight foamed concrete using the mineral foam agent which has high lightness, and strength. The compressive strength of lightweight foamed concrete using mineral foam agent are about 2 times degree high those the of lightweight foamed concrete using vegetable foam agent. Lightweight foamed concrete was able to obtain the result of 50kg/㎠ or more compressive strength, when was unit weight 0.8t/㎡. In the case of the same unit weight of concrete, it is influenced by w/c of foam agent ratio. The paper present extensive data on characteristics of compressive strength of the concrete manufatured with the different factors in mix design and also present optimum mix proportion.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2003.05a
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• pp.49.1-52
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• 2003

The objective of this study the mechanical characteristics of preformed lightweight foamed concrete using the mineral foam agent which has high lightness, and strength. The compressive strength of lightweight foamed concrete using mineral foam agent are about 2 times degree high those the of lightweight foamed concrete using vegetable foam agent. Lightweight foamed concrete was able to obtain the result of 50kg/$\textrm{m}^3$ or more compressive strength, when was unit weight 0.8t/$\textrm{m}^3$. In the can of the same unit weight of concrete, it is influenced by w/c of loan agent ratio. The paper present extensive data on characteristics of compressive strength of the concrete manufactured with the different factors in mix design and also present optimum mix proportion.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 1999.04a
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• pp.97-99
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• 1999

본 연구에서는 디젤로 오염된 토양을 효율적으로 정화하기 위해, 알칼리제와 과산화수소를 이용하는 새로운 방식의 토양세척기법에 대하여 일련의 회분식 실험을 통하여 최적의 운전조건을 검토하고자 하였다. 알칼리제인 NaOH를 이용하여 세척수의 pH를 상승시켜, 강알칼리 상태에서 과산화수소를 주입하면 미세기포가 발생되며, 이 미세기포에 의해 토양에 흡착되어 있는 유류 오염물질이 효과적으로 탈착.부상된다. #60(0.25mm) 이하의 자연토양을 6,500 mg TPH/kg dry soil로 오염시켜 사용하였으며, 세척수의 pH, 진탕비(토양 중량 : 세척용액 부피), 과산화수소 주입량, 세척시간에 의한 영향을 살펴보았다. 세척수의 pH는 12, 진탕비는 1:5, 과산화수소 주입량은 1%, 세척시간은 1시간으로 적용한 결과 최대효율(60%)을 얻을 수 있었다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.4 no.4
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• pp.79-93
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• 1984

The dissolved air flotation(DAF) has been shown to be efficient process for the removal of algae ftom water. The efficiency of DAF can be affected by the volume ratio of pressurized liquid to sample, the pressure pressurized liquid, the contact time, the appropriate coagulant and its amount, the water temperature, the turbulence of reactor, the bubble size and rising velocity etc. The purpose of this paper is to compare the practical bubble rising velocity with the theoretical one, to investigate the adhesion phenomenon of bubbles and floc, and the influence of bubble size and velocity upon the process. The results through theoretical review and experimental investigation are as follows: Ives' equation is more suitable than Stokes' equation in computation of the bubble rising velocity. The collection of bubble and algae floc is convective collection type and resulted from absorption than adhesion or collision. The treatment efficiency is excellent when the bubble sizes are smaller than $l00{\mu}m$, and the turbulence of reactor is small. In the optimum condition of continuous type DAF the volume ratio of pressurized liquid to sample is 15%, the contact time in reactor is 15 minutes, the pressure of pressurized liquid is $4kg/cm^2$ and the distance from jet needle to inlet is 30cm.

• Journal of the Korean Recycled Construction Resources Institute
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• v.2 no.3
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• pp.247-254
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• 2014

The present study prepared lightweight foam-soil concrete mixtures classified into three groups. Considering the sustainablility, workability, and compressive strength development of such concrete, high-volume supplementary cementitious materials (SCMs) were used as follows: 20% cement, 15% fly ash, and 65% ground granulated blast-furnace slag. As main test parameters selected for achieving the compressive strength of 1MPa and dry density of $1,000kg/m^3$, the unit solid content (dredged soil and binder) ranged between 900 and $1,807kg/m^3$, and soil-to-binder ratio varied between 3.0 and 7.0. Test results revealed that the flow of the lightweight foam-soil concrete tended to decrease with the increase of unit soil content. The compressive strength of such concrete increased with the increase with the unit binder content, whereas it decreased as soil-to-binder ratio increased, indicating that the compressive strength can be formulated as a function of its dry density and soil-to-binder ratio.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.3
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• pp.172-177
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• 2014

Low pressure air flotation (LAF) pilot plant for sludge thickening was installed in Chung Nam N.S. municipal waste water treatment plant to verify its application possibility. Effects of operating conditions such as coagulant dosages and microbubble water ratio on thickening of the mixed sludge were examined. Microbubbles which were generated in the chamber of $1.5kgf/cm^2$ by high speed collision method with foaming agent were used to float sludge. Solid loading of $30kg/m^2/hr$, solid contents in thickened sludge of 60,300 mg/L and SS removal efficiency of 99% were obtained through long period operating LAF in conditions of mixed sludge concentration of 14,400 mg/L, coagulant dosage of 27.6 mg/L, foaming agent addition of 4.0 mg/L and microbubble water injection ratio of 9.7%.