• 대한기계학회논문집B
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• 제40권4호
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• pp.227-236
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• 2016

본 논문에서는 $600{\times}600{\mu}m$ 사각 마이크로 채널에서 T자형 합류지점에서의 기체 및 액체의 주입방법이 기포 및 액체 슬러그의 생성에 미치는 영향을 실험을 통해 살펴보았다. 실험 유체로는 질소와 물을 사용하였으며, 액체 및 기체 겉보기 속도는 각각 0.05 - 1 m/s, 0.1 - 1 m/s 의 범위로 테일러 유동이 나타나는 구간에서 데이터를 얻었다. 기포 길이, 액체 슬러그 길이, 기포 속도 그리고 기포 생성 빈도를 고속 카메라를 사용하여 이미지 분석을 통해 측정하였다. 유사한 입구 겉보기 속도 조건에서, T-자형 합류지점의 main channel에 기체를 주입하는 방법(T_gas-liquid)이 액체를 주입하는 방법(T_liquid-gas)보다 기포와 액체 슬러그의 길이가 길었고 기포 생성 빈도는 낮았다. 한편, 두 주입방법에서 기포 속도는 유사하게 나타났다. T_liquid-gas 주입방법의 기존 예측 상관식은 T_gas-liquid 주입방법의 기포 길이, 기포 속도, 액체 슬러그 길이, 기포 생성 빈도 실험데이터를 각각 ~24 %, ~9 %, ~39 %, ~55 %로 예측하였다.

• 한국건축시공학회지
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• 제7권1호
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• pp.107-113
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• 2007

This study investigates the filed application in Daebul Free Trade Zone applying both a flowing method using drying shrinkage-reducing superplasticizer(SRS) and an insulating curing method using double layer bubble sheet. Test results showed that fresh concrete satisfied target slump and air content. A structure adding SRS significantly decreased the total bleeding capacity and accelerated the setting time. As for the crack occurrence, the structure applying the flowing method and double bubble sheets simultaneously exhibited the most favorable crack endurance, while conventional concrete showed more than 1mm size of crack in overall. In addition, a structure applying the flowing concrete method partially presented the micro crack. For the area proportion of crack occurrence, the structure using the double bubble sheets indicated 9.8%, while others applying flowing concrete method was 28%, compared with that of conventional one. For the compressive strength of specimens, standard curing specimens indicated $3{\sim}33%$ higher value than that of specimens cured besides the field construction. The specimens containing SRS improved the strength of $2{\sim}6MPa$, which is $10{\sim}22%$ higher than that of conventional concrete.

• 한국가시화정보학회지
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• 제14권1호
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• pp.40-45
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• 2016

Elimination of the smear layer and bacteria in the root canal is the most important in the endodontic treatment, and various irrigation devices have been developed. Nevertheless, it is hard to eliminate the smear layer and bacteria completely. In this paper, a micro bubble irrigation system has been developed for the root canal cleaning of tooth. Micro bubbles are generated when pressurized fluids passing through a porous material inside a hand-piece nozzle, and the bubbly flows excited by ultrasonic vibration are observed using a high-speed camera and a microscope. The results show that the diameter and number of bubbles increases with the applied pressure, and there found an optimum excitation frequency in order to minimize the bubble size. From in-vitro tests, it is also verified that the developed bubble irrigation system has the ability of antibacterial and infection removal. Thus, this biocompatible system would be well suited for root canal cleaning.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2013년도 춘계 학술논문 발표대회
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• pp.334-336
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• 2013

In this study, the temperature history was evaluated for the improved bubble sheets combining hot wires and PE films, which were developed under the extreme environmental condition of -10℃ and applied on the top surface of slab to prevent initial damage by freezing. Results can be summarized as follows. If improved bubble sheets combining hot wires with different capacity on double and quadruple bubble sheets are used, the temperature history for all materials decreased to 2~3℃ below zero but all test materials except Type 1 secured the accumulative temperature of 45° D·D at 7 days of material age, required for the prevention of initial freezing damage. This indicates the bubble sheets can prevent the initial damage by freezing.

• 한국방재안전학회논문집
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• 제11권1호
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• pp.1-5
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• 2018

발전소는 선진 산업사회에서의 중요한 사회기반시설이다. 이러한 발전소가 해초, 물고기, 해파리, 새우 등과 같은 해양생물의 유입으로 정지 될 경우, 사회-경제적으로 심각한 문제가 발생하기도 한다. 따라서, 발전소 취수구 유입구 부분의 해양생물 침투로 인한 발전소 가동이 정지되는 것을 방지하기 위하여, 에어버블 차단막 기술이 활용되고 있다. 본 연구에서는 에어버블 차단막 기술의 기초연구인 에어버블의 거동을 분석하기 위하여 수직형 에어버블 실험장치를 개발 및 에어버블수직 거동 특성을 분석하였다. 에어버블 수직 거동 특성을 분석하기 위하여 수직형 에어버블 실험 장치를 이용하여 에어 분사량에 따른 수심별 에어버블의 상승 속도를 측정하였으며, 실험결과를 바탕으로 수심구간별 에어버블 상승속도 경험식을을 제시하였다. 제시된 경험식은 향후 에어버블 차단막 설계의 기초자료로 활용될 것이며, 발전시설 운영 부분에서의 안정성을 확보하는 데 크게 기여할 것으로 기대된다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 세계 도시지반공학 심포지엄
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• pp.519-523
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• 2009

In this study, the base mixing ratio was determinated to estimate the optimal mixing ratio of material with a change of mixing ratio of micro cement, sand, foaming agent, plasticizer by testing the unconfined compressive strength test. The unconfined compressive strength test was performed to grasp a engineering characteristics of with a change of micro cement, bubble. The results of test, the unconfined compressive strength increased with a micro cement's increase and bubble's decrease. In the future, it will be secured that is reliable datas from laboratory of various condition and in-situ tests to develop optimal lightweight foamed concrete.

• 대한환경공학회지
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• 제35권12호
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• pp.929-936
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• 2013

DAF (Dissolved air flotation) 공정에서 공기포화장치(Saturator)와 미세기포 발생노즐은 미세기포 형성에 중요한 영향을 미치는 장치이다. 미세기포 발생 효율을 증가시키기 위해서는 공기포화장치 용기 안에서 기-액 접촉 효율을 증가시키고, 미세기포 발생노즐까지 이송 배관 내 압력을 일정하게 유지해 주어야 한다. 본 연구에서는 공기포화장치 내 순환수 유입 분사노즐과 포화수 이송 배관, 미세기포 발생노즐에 의한 미세기포 발생에 미치는 영향을 공기체적법과 기포 크기, 기포의 잔류시간 측정을 통해 비교해 보았다. 순환수 유입 분사노즐을 설치하고, 포화수의 이송 배관 내 압력손실이 발생하지 않는 구조, 미세기포 발생노즐의 통과유속을 증가시킬 경우 미세기포 발생 성능이 증가하였다.

• 한국물환경학회지
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• 제22권6호
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• pp.1119-1122
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• 2006

Aeration by using diffusers usually requires approximately 50~90% of the total electricity needed to operate WWTP (WasteWater Treatment Plant)s. Accurate evaluation of the oxygen transfer efficiency for an aeration system, and recommendation of a better alternative may help saving WWTP operational costs. Appropriate techniques and methods to achieve this purpose have not been introduced in Korea. In this study, in-process analysis was performed for a coarse bubble aeration system by the off-gas method to evaluate its applicability in Korea. To accomplish this analysis, an off-gas test, unsteady-state clean water test and steady-state off-gas column test was conducted and comparisons to other aeration systems were made. The ${\alpha}$ and the F estimated from the results of the unsteady-state clean water test and the steady-state off-gas column test were 0.61 and 0.90 respectively in a coarse bubble aeration system. The comparison of P.E tube diffusers laid out single spiral roll and ceramic dome diffusers laid out full floor coverage showed that the oxygen transfer efficiency of the coarse bubble aeration system was less than or similar to other aeration systems. But, airflow rates per unit area were 4~5 times greater than other aeration systems. In regards to the oxygen transfer efficiency for airflow rates per unit area, a retrofit to higher efficiency diffusers was urgently needed. This study showed proved that off-gas methods can apply to evaluate diffuser performances to estimate operating factors and to compare other aeration systems in Korea.

• 설비공학논문집
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• 제1권2호
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• pp.190-201
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• 1989

This experimental investigation has been conducted to determine the effects of swirling angle and flow patterns on distributions of void fraction, bubble velocity and two-phase pressure drop in a vertical straight tube. Swirling angles of $0^{\circ}$ (non swirling), $30^{\circ}$, and $45^{\circ}$ were tested with air-water two components over a range of superficial air velocities. A transparent lucite tube of 38mm in internal diameter was used for the test section. The void fraction and bubble velocities were measured by means of a optical fiber probe at the upper part of the swirler in the test section. Pressure drops which seem to be closely related with flow patterns and swirling angle were measured by a differential pressure transducer. It is shown that the probability density functions of pressure drop demonstrate peculiar features for both swirling angles and flow patterns, whereas the distributions of void fraction and bubble velocities are parabolic and flat shape in the vicinity of tube center, respectively except bubbly flow in any swirling angle cases, and the void fraction increases with increasing swirling angle around the center of tube.

• 대한치과기공학회지
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• 제11권1호
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• pp.103-109
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• 1989

Bond strength between alloy and ceramic plays an important role in deciding the quaring the processing of metalceramic restorations. Now the author had an experiment on the measurement of bond strength differences accoding to the contents of recast alloy used during the processing of metal-ceramic restorations. In the experiment, Anusavice's Planar Interface Shear Bond Test was employed to determine the bond strength. Total 25 specimens were divided as 5 groups, that is, 5 specimens in a group respections : Group I (new alloy 100%) Group II (new 75%$\cdot$recast 25%), Group III (new 50%$\cdot$recast 50%), Group IV (new 25%$\cdot$recast 75%), Group V(recast 100%). All specimens examined micropically and respective strength values of the group specimens were checked simultaneously. The results were as follows, 1. In the analtsis of variance the result showed the significant differences of 1%(P<0.01) among the each group classifid according to the recast contents. 2. When the interfaces of specimens were examined with an electron microscope, the air bubble were evenly occurred in all the specimens, and the occurrence frequencies and the sizes of air bubble were different between Group I and Group III, especially marked different Group I and Croup V. 3. In respective verification of each group through T-test, between Group I and Group II, between Group I and Group III did not show significant differences. 4. There was significant difference between Group I and Group IV, between Group I and Group V as 1%(P<0.01). 5. In the Shear Bond Test of all the groups, Croup V showed the lowest value. Explanatoion of Figures Fig 1. Main fracture type of metal-porcelain interlace showed in group I, II, III from shear Bond Test resets. Fig 2. Main fracture type of metal-porcelain interface showed In group Ⅳ, Ⅴ form shear Bond Test resets. Air bubble and their size appeared around interface of metal-porcelain. Fig 3. Group I, Fig 4. Group II Fig 5. Group III, Fig 6. Group IV, Fig 7. Group V.