• Journal of Broadcast Engineering
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• v.26 no.6
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• pp.809-812
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• 2021

Air bubbles which may be generated during the PCB coating process can be a major cause of malfunction. so it is necessary to detect the bubbles in advance. In previous studies, candidates for bubbles were extracted using the brightness characteristics of bubbles, and the candidates were verified using CNN(Convolutional Neural Networks). In this paper, we propose a bubble detection method using a transfer learning-based CNN model. The VGGNet is adopted and sigmoid is used as a classification layer, and the last convolutional layer and classification layer are trained together when transfer learning is applied. The performance of the proposed method is F1-score 0.9044, which shows an improvement of about 0.17 compared to the previous study.

• Journal of Korean Society of Steel Construction
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• v.17 no.3 s.76
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• pp.253-262
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• 2005

Because the framed wall system using steel studs and runners with square steel tubes as structural elements is reinforced by the horizontal members called runners, it has more strength and load bearing capacity than the steel house wall system. Also, this system improves adiabatic and sound insulation performance by filling up the autoclaved lightweight concrete. We need to evaluate load bearing capacity according to the axial load and lateral load in case this system is applied in the housing system with 3~5 stories through variations in intervals for the runners under the placement effect of autoclaved lightweight concrete. Therefore, this study seeks to analyze axial and shear behavior of the framed wall system according to the placement effect of autoclaved lightweight concrete, and to secure safety for the vertical and lateral loads.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.10
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• pp.710-716
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• 2013

New and renewable energy sources have drawn attention because of climate change. Many studies have been carried out in waste-to-energy field. Fast pyrolysis of waste lignocelluosic biomass is one of the waste-to-energy technologies. Bubbling fluidized bed (BFB) reactor is widely used for fast pyrolysis of the biomass. In BFB pyrolyzer, bubble behavior influences on the chemical reaction. Accordingly, in the present study, hydrodynamic characteristics and fast pyrolysis reaction of waste lignocellulosic biomass occurring in a BFB pyrolyzer are scrutinized. The computational fluid dynamics (CFD) simulation of the fast pyrolysis reactor is carried out by using Eulerian-Granular approach. And two-stage semi-global kinetics is applied for modeling the fast pyrolysis reaction of waste lignocellulosic biomass. To summarize, generation and ascendant motion of bubbles in the bed affect particle behavior. Thus biomass particles are well mixed with hot sand and consequent rapid heat transfer occurs from sand to biomass particles. As a result, primary reaction is observed throughout the bed. And reaction rate of tar formation is the highest. Consequently, tar accounts for 66wt.% of the product gas. However, secondary reaction occurs mostly in the freeboard. Therefore, it is considered that bubble behavior and particle motions hardly influences on the secondary reaction.

• Journal of the Korean GEO-environmental Society
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• v.23 no.3
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• pp.23-29
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• 2022

In this study, we investigated the ozone nanobubble process in which nanobubble and ultrasonic cavitation were applied simultaneously to improve the dissolution and self-decomposition of ozone. To confirm the organic decomposition efficiency of the process, a 200 mm × 200 mm × 300 mm scale reactor was designed and phenol decomposition experiments were conducted. The use of nanobubble was 2.07 times higher than the conventional ozone aeration in the 60 minutes reaction and effectively improved the dissolution efficiency of ozone. Ultrasonic irradiation increased phenol degradation by 36% with nanobubbles, and dissolved ozone concentration was lowered due to the promotion of ozone self-decomposition. The higher the ultrasonic power was, the higher the phenol degradation efficiency. The decomposition efficiency of phenol was the highest at 132 kHz. The ozone nanobubble process showed better decomposition efficiency at high pH like conventional ozone processes but achieved 100% decomposition of phenol after 60 minutes reaction even at neutral conditions. The effect by pH was less than that of the conventional ozone process because of self-decomposition promotion. To confirm the change in bubble properties by ultrasonic irradiation, a Zetasizer was used to measure the bubbles' size and zeta potential analysis. Ultrasonic irradiation reduced the average size of the bubbles by 11% and strengthened the negative charge of the bubble surface, positively affecting the gas transfer of the ozone nanobubble and the efficiency of the radical production.

• Korean Journal of Poultry Science
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• v.16 no.1
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• pp.17-22
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• 1989

In order to dull heat sensitivity of egg albumen, metal ions (aluminium, ferric, ferrous, copper) were added and functional properties or egg albumen were determined before and after heat treatment at $60^{\circ}C$ for 5 minutes. Effect of pH on heat sensitivity of aluminium salt added egg albumen was also determined. Addition of metal ions increased turbidity of egg albumen before and after the heat treatment. Changes of the turbidity were minimized by addition of aluminium salt. The foaming power was markedly increased by addition of ferric salt before the heat treatment and increased by addition of aluminium, ferric and copper salt after the heat treatment. Before the heat treatment the foam was stable by addition of ferric and ferrous salt but after the heat treatment it was stable by addition of aluminium and ferric salt. The turbidity and foaming property of the egg albumen with aluminium salt were not largely changed after the heat treatment at pH range 7 to 8.5. Over pH 9 the turbidity and foaming power were not decreased, but the foam stability was increased before and after the heat treatment. Salmonella typhimurium ATCC 14028 (10$^{6}$ cells/$m\ell$) inoculated in egg albumen at pH range 7 to 8.5 was destructed by the heat treatment.

• Fire Science and Engineering
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• v.26 no.5
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• pp.73-78
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• 2012

This research is to evaluate the fire extinguishing performance of Compressed Air Foam System and this test was conducted using Foam Head System. Compressed Air Foam System adopt the methods of causing the foam by mixing compressed air in foam-aqueous solution, In Overseas, CAFS (Compressed Air Foam System) is generally used because long distance discharge is possible and the water damage can be minimized by reducing the water usage. In this study, Comparative analysis on fire extinguishing effect is done through test to compare the performance between Foam System applied existing air mixture method and Compressed Air Foam System applied AFFF 3 %, foam-extinguishing-agent based on UL162 standard. In Compressed Air Foam System, the volume proportion of air mixture to foam-aqueous solution is 1 to 1 and discharging flow rate is 140 L/min, 160 L/min, 180 L/min, 200 L/min each. As a result of the test, in terms of fire extinguishing performance, fire suppression time for Compressed Air Foam Systems is shorter than for General Air Mixture System in all flow conditions.

• 월간 기계설비
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• s.119
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• pp.71-83
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• 2000

점차 복잡해지고 있는 사회적 욕구를 만족시키기 위한 건물에서는 반드시 복잡한 설비가 요구되고 있고, 이러한 설비시스템 중에는 급수, 급탕 및 배수설비라고 하는 배관시스템이 없다면 기능유지에 막대한 지장을 초래할 것은 자명하다고 하겠다. 이러한 배관시스템에서는 항시 또는 일부 사용되어질 물이나 사용된 물이 흐르기 때문에 배관내부에 발생하는 스케일(scale)이나 슬라임(slime) 등은 피할 수 없는 사실인 것이다. 건축물 내에 설치된 각종 배관은 건물의 기능을 유지하고 보건위생과 직결되는 중요한 기능을 담당하고 있어 세척의 필요성이 매우 높음에도 불구하고 배관의 수명이 다할 때까지 거의 세척이 이루어지지 않고 사용되어 왔다. 이들 배관에 대한 세척은 배관의 수명연장과 관마찰 계수를 낮추어 급수의 수송동력을 절감할 수 있고, 난방관의 열전달 효과를 높여 에너지 절약 효과를 거두어 건물의 유지관리 비용 절감에 기여할 수 있음에도 적절한 세척공법이 개발되지 않고 있다. 이러한 관점에 맞추어 건물배관의 특성에 맞도록 고압 세척장치를 개발하고 이를 이용한 세척공법을 적용하고자 하였다. 즉, 배관 내에 압축공기를 주기적으로 분사하여 맥동현상이 일어나도록 하면서 기포를 발생시켜 기포가 관의 내벽에서 성장하여 파괴될 때 관내에 부착된 이물질을 제거할 수 있고, 또한 세척효과를 높이기 위하여 관의 벽면에 접촉하면서 배출되는 과정에서 이물질을 제거할 수 있도록 구조와 아울러 이들 장치를 이용한 세척방법의 적용성에 대해서 고찰하고자 한다.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.389-392
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• 2002

체외 충격파 쇄석술 (ESWL)은 인체 외부에서 발생된 충격파를 인체 내부의 결석 부위에 집속하여 결석을 분쇄하고 치료 효과를 얻는 혁신적 치료술이다. 충격파의 압력 및 파형은 결석의 분쇄 효과 즉 치료 효과를 좌우한다. 체외에서 충격파의 압력은 고감도 하이드로폰을 이용하여 측정할 수 있지만, 인체 체내에서, 특히, 비침습적으로 충격파를 측정하기는 매우 어렵다. 본 논문에서는 ESWL 충격파에 의해 활성화된 체내의 기포군으로부터 방출된 음향 신호 (CIAE)를 측정하여 비침습적으로 충격파의 압력을 추정하는 방법을 실험하였다. 충격파 압력의 추정은 측정된 CIAE 신호에서 1차 기포군 파열음과 2차 파열음 간의 시간 지연은 충격파의 압력과 선형적인 관련성 가진다는 실험 결과 (Coleman et al 1996)에 근거하고 있다. 본 논문에서는 충격파 압력 측정 시스템을 구성하여 생체 외 실험을 수행하였고, 개발된 시스템의 임상적인 활용 가능성을 확인하였다.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.489-490
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• 2009

In this study, the experiment was carried out to investigate the effect of metakaolin on the compressive strength of lightweight aggregate cellular concrete. For this purpose, five level replacement ratio of metakaolin were selected.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.319-322
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• 2000

솔레노이드 코일을 이용하여 전자기식 충격파 발생기를 제작하고 발생된 충격파의 음향학적인 특성을 측정하였다. 충격파의 생물학적 효과에 가장 중요한 과정으로 알려진 초점 부위의 기포군의 파열 현상을 바늘형 하이드로폰을 이용하여 평가하였다. 하이드로폰 신호의 웨이브렛 변환을 이용하여 초점 부근에서 기포 파열 지연 시간을 정확히 측정할 수 있음을 보였다.