• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.4
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• pp.642-649
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• 2021

Energy saving standard for buildings are strengthened, the application of exterior insulation finishing system and thickness of insulation materials are increasing. Most buildings with exterior insulation finishing system is applied organic insulating material. Organic insulating material have workability, economic feasibility, reduction in construction cost, and excellent thermal insulation performance. However, Organic insulating material is very vulnerable to heat, so when a fire occurs, rapid fire spread and toxic gas are generated, causing many casualties. Inorganic insulating material can be non-combustible performance, but it is heavy and has low thermal insulation performance. Mineral wool has higher thermal insulation performance than other types of inorganic insulating material, but mineral wool is disadvantageous to workability and vulnerable to moisture. Glass bubble are highly resistant to water and chemically stable substances. In addition, the density of the glass bubble is very low and the particles are spherical, fluidity is improved by the ball bearing effect. Glass bubbles can be used with cement-based ino rganic insulating material to impro ve the weight and thermal insulatio n perfo rmance o f cement-based inorganic insulation. This study produced a inorganic insulating materials were manufactured using cement-based materials and glass bubble. In order to evaluate the insulation performance and flame retardant performance of cement-based super light-weight inorganic insulating materials using with glass bubble, insulation performance or flame retardant and non-combustible performance were evaluated after manufacturing insulating materials using micro cement and two types of glass bubbles. From the test result, Increasing the mixing ratio of glass bubbles improved the insulation performance of cement-based super light-weight inorganic insulating materials, and when the mixing ratio of glass bubbles was 10%, it sho wed sufficient flame retardant and no n-co mbustible perfo rmance.

• Korean Chemical Engineering Research
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• v.53 no.5
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• pp.597-602
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• 2015

Characteristics of continuous preparation of ZnO powder were investigated in a micro drop/bubble fluidized reactor of which diameter and height were 0.03 m and 1.5 m, respectively. The flow rate of carrier gas for transportation of precursors to the reactor was 6.0 L/min and the concentration of Zn ion in the precursor solutions was 0.4 mol/L, respectively. Effects of reaction temperature (973 K~1,273 K) and flow rate of micro bubbles (0~0.4 L/min) on the pore characteristics of prepared ZnO powder were examined. The optimum reaction temperature for the maximum porosity in the ZnO powder was 1,073 K within this experimental condition. The mean size of ZnO powder prepared continuously in the reactor decreased but the surface of the powder became smooth, with increasing reaction temperature. The injection of micro bubbles into the reactor could enhance the formation of pores in the powder effectively, and thus the mean BET surface area could be increased by up to 58%. The mean size of prepared ZnO powder was in the range of $1.25{\sim}1.75{\mu}m$ depending on the reaction temperature.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2006.11a
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• pp.407-410
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• 2006

This study describes a simulation of two-dimensional bubble forming and motion by the Lattice Boltzmann Method with the phase field equation. The free energy model is used to treat the interfacial force and deformation of binary fluids system, drawn into a T-junction the micro channel. A numerical simulation of a binary flow in a cross-junction channel is carried out by using the parallel computation method. The aim in this investigation is to examine the applicability of LBM to numerical analysis of binary fluid separation and motion in the micro channel.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.9
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• pp.605-613
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• 2017

Recently, efficient heat dissipation has become necessary because of the miniaturization of devices, and research on boiling on micro-channels has attracted attention. However, in the case of micro-channels, the friction coefficient and heat transfer characteristics are different from those in macro-channels. This leads to large errors in the micro scale results, when compared to correlations derived from the macro scale. In addition, due to the complexity of the mechanism, the boiling phenomenon in micro-channels cannot be approached only by experimental and theoretical methods. Therefore, numerical methods should be utilized as well, to supplement these methods. However, most numerical studies have been conducted on macro-channels. In this study, we applied the lattice Boltzmann method, proposed as an alternative numerical tool to simulate the boiling phenomenon in the micro-channel, and predicted the bubble growth process in the channel.

• Journal of Microbiology and Biotechnology
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• v.11 no.3
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• pp.369-375
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• 2001

Urushiol, a natural monomeric oil, was used to prepare a detergentless micro-emulsion with water and 2-propanol The formation of micro-emulsion was verified by conductivity measurements and dynamic light scattering. The conductivity data showed phase change dynamics, a characteristics of micro-emulsions, and subsequent dynamic light scattering study further confirmed the phenomenon. Average water droplet diameter was 10 nm to 500 nm when the molar ratio of 2-propanol ranged from 0.40 to 0.44 . Earlier studies were performed on toluene and hexane, in which the insoluble substrate in water phase was added to the solvents to be reacted on by enzymes. However, in the present urushiol system, urushiol was used as both solvent and substrate in the laccase polymerization of urushiol. The laccase activity in the system was examined using polymerization of urushiol. The laccase activity in the system was examined using syringaldezine as a substrate, and the activity increased rapidly near the molar ratio of 2-propanol at 0.4, where micro-emulsion started. The activity rose until 0.46 and fell dramatically thereafter. The study of laccase activity in differing mole fractions of 2-propanol showed the existence of an ‘optimal zone’, where the activity of laccase was significantly higher. In order to analyze urushiol polymerization by laccase, a bubble column reactor using a detergentless micro-emulsion system was constructed. Comparative study using other organic solvents systems were conducted and the 2-propanol system was shown to yield the highest polymerization level. The study of laccase activity at a differing mole fraction of 2-propanol showed the existence of an ‘optimal zone’ where the activity was significantly higher. Also, 3,000 cP viscosity was achieved in actual urushi processing, using only 1/100 level of laccase present in urushi.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2017.04a
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• pp.133-133
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• 2017

최근 딸기 생산이 확대 되면서, 고품질 다수확이 가능한 딸기 우량묘에 대한 수요가 빠르게 늘고 있으며, 딸기 육묘에 관한 관심이 더욱 늘고 있다. 그러나, 육묘시 작물에 따른 포트 혹은 트레이 선정에 대한 연구는 거의 이루어지지 않고 있다. 또한, 마이크로버블의 세정 능력은 이미 산업현장에서 널리 알려져 있으나 이를 이용한 시스템 개발은 농업분야에서는 미비한 실정이다. 따라서, 딸기 육묘에 적합한 마이크로버블 시스템을 설계하여 실증 개발함으로써 딸기 육묘 농가의 자립능력을 제고하고, 딸기 육묘 생산시스템의 확대 하여 농가소득 증대에 기여하고자 한다. 실험방법은 생육에 적합한 육묘용 트레이를 선정하고, 마이크로 버블 시스템을 적용한 육묘와 기존 방법에 의한 육묘의 비교 실험하였다. 포트의 용량에 따른 뿌린 근부의 성장변화를 관찰하고, SEM 촬영을 통하여 딸기 뿌리근부의 조직의 치밀성을 확인하였다. 기존 저면관수의 경우 딸기탄저병 확산을 억제하지만, 반입에 의한 감염주의 발병을 억제하는 것은 아니다. 따라서 포트 및 트레이를 청결하게 관리할 필요가 있으며 이를 해결하기 위해 미세기포(micro-bubble)를 사용한 클리닝이 상당한 효과가 있는 것으로 확인하였다. 또한 조직의 치밀도을 측정하기 위해 딸기 육묘 조직을 SEM 촬영하여 분석하였으며, 미세기포를 이용한 딸기 육묘 방법이 기존의 딸기 육묘 방법에 비하여 조직이 치밀한 것으로 확인 되었다. 또한 배지량 및 육묘 트레이가 딸기 육묘의 성장에 영향을 미치며 제1액아가 １개밖에 발생하지 않는 포기가 많아지고 '눈 없는 포기'의 발생 현상들이 발생하고 있어 적정 육묘 트레이의 선택 및 배지량 조절하는 비교 실험을 통하여 해결하였다. 본 연구의 결과 개선된 육묘트레이를 사용함으로써 제1액아의 형성이 촉진되어 정과방 후의 제1액과 방의 수확량이 증대한다는 것에 의해서 １월 혹은 ２월부터의 수량이 증대되어 소득향상이 기대되며, 마이크로버블을 저면관수에 적용함으로써 트레이의 청결을 유지하여 병해를 예방하고 딸기모종의 조직을 치밀하게 함으로써 딸기의 우량육묘를 얻는데 기여 할 것으로 기대된다.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.3.2-3.2
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• 2011

In recent years, inkjet printing technology has received significant attention as a micro/nanofabrication technique for flexible printing of electronic circuits and solar cells, as well for biomaterial patterning. It eliminates the need for physical masks, causes fewer environment problems, lowers fabrication costs, and offers good layer-to-layer registration. To fulfill the requirements for use in the above applications, however, the inkjet system must meet certain criteria such as high frequency jetting, uniform droplet size, high density nozzle array, etc. Existing inkjet devices are either based on thermal bubbles or piezoelectric pumping; they have several drawbacks for flexible printing. For instance, thermal bubble jetting has limitations in terms of size and density of the nozzle array as well as the ejection frequency. Piezoelectric based devices suffer from poor pumping energy in addition to inadequate ejection frequency. Recently, an electrohydrodynamic (EHD) printing technique has been suggested and proposed as an alternative to thermal bubble or piezoelectric devices. In EHD jetting, a liquid (ink) is pumped through a nozzle and a strong electric field is applied between the nozzle and an extractor plate, which induce charges at the surfaces of the liquid meniscus. This electric field creates an electric stress that stretches the meniscus in the direction of the electric field. Once the electric field force is larger than the surface tension force, a liquid droplet is formed. An EHD inkjet head can produce droplets smaller than the size of the nozzle that produce them. Furthermore, the EHD nano-inkjet can eject high viscosity liquid through the nozzle forming tiny structures. These unique features distinguish EHD printing from conventional methods for sub-micron resolution printing. In this presentation, I will introduce the recent research results regarding the EHD nano-inkjet and the printing system, which has been applied to solar cell or thin film transistor applications.

• Journal of Wetlands Research
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• v.22 no.4
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• pp.239-244
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• 2020

Prior to utilization of energy and power generation, the biogas from anaerobic digestion of sewage treatment plant(46,000㎡/d) should be purified particularly hydrogen sulfide among the various kinds of impurities. This study has focused on the methane decreasing rate and the removal of both hydrogen sulfide and carbon dioxide. In the case of partial circulation, 59.7% of methane gas was decreased to 57.4% in spite of oxidation process with micro-bubble. Carbon dioxide was removed from 38% to 32% and 76.1% of hydrogen sulfide was removed where 1,400ppm was introduced to the DIWS system, which indicated that DIWS system can be of use for the hydrogen sulfide removal of biogas from sewage treatment plant.

• Journal of Powder Materials
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• v.15 no.1
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• pp.46-52
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• 2008

The restrictor, which is a fluid channel from a reservoir to a chamber inside a thermal micro actuator, has been fabricated using ArF and KrF excimer lasers, Diode-Pumped Solid State Lasers (DPSSL) and femtosecond lasers for a feasibility study. A numerical model of fluid dynamics for the actuator chamber and restrictor is presented. The model includes bubble formation and growth, droplet ejection through nozzle, and dynamics of fluid refill through the restrictor from a reservoir. Since an optimized and well-fabricated restrictor is important for a high frequency actuator, some special beam delivery setups and post processing techniques have been researched and developed. The effects of variations of the restrictor length, diameter, and tapered shapes are simulated and the results are analyzed to determine the optimal design. The numerical results of droplet velocity and volume are compared with the experimental results of a cylindrical-shaped actuator. It is found that the micro actuators having tapered restrictors show better high frequency characteristics than those having a cylindrical shape without any notable decrease of droplet volume. The laser-fabricated restrictors demonstrate initial feasibility for the laser direct ablation technique although more development is required.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.27 no.2
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• pp.75-80
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• 2015

The effect of inlet mixer geometries on the two-phase flow patterns in square micro-channel with $600{\times}600{\mu}m$ was investigated experimentally in this paper. The 4 different mixer configurations based on the Y, Impacting, and two T types (gas and liquid inlets were switched) were used. The test fluids were nitrogen and water. The liquid and gas superficial velocities were 0.01~10 m/s and 0.1~100 m/s, respectively. Several distinctive flow patterns, namely, annular, slug-annular, slug, slug-bubbly, bubbly, and churn flow could be seen. The flow pattern maps for each mixer were suggested, and it can be concluded that two-phase flow patterns are not very sensitive to the mixer geometries. But the mixing behaviors of gas and liquid for each mixer were different for slug and bubbly flow. Thus, the characteristics of slug and bubble for each case were not same.