• Clean Technology
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• v.28 no.4
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• pp.285-292
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• 2022

Adsorption tower systems based on activated carbon adsorption towers have mainly been employed to reduce the emission of volatile organic compounds (VOCs), a major cause of air pollution. However, the activated carbon currently used in these systems has a short lifespan and thus requires frequent replacement. An approach to overcome this shortcoming could be to develop metal oxide photocatalysis-activated carbon composites capable of degrading VOCs by simultaneously utilizing photocatalytic activation and powerful adsorption by activated carbon. TiO₂ has primarily been used as a metal oxide photocatalyst, but it has low economic efficiency due to its high cost. In this study, ZnO particles were synthesized as a photocatalyst due to their relatively low cost. Silver nanoparticles (Ag NPs) were deposited on the ZnO surface to compensate for the photocatalytic deactivation that arises from the wide band gap of ZnO. A microfluidic process was used to synthesize ZnO particles and Ag NPs in separate reactors and the solutions were continuously supplied with a pack bed reactor loaded with activated carbon powder. This microfluidic-assisted pack bed reactor efficiently prepared a Ag-ZnO-activated carbon composite for VOC removal. Analysis confirmed that Ag-ZnO photocatalytic particles were successfully deposited on the surface of the activated carbon. Conducting a toluene gasbag test and adsorption breakpoint test demonstrated that the composite had a more efficient removal performance than pure activated carbon. The process proposed in this study efficiently produces photocatalysis-activated carbon composites and may offer the potential for scalable production of VOC removal composites.

• Journal of the Korean Geotechnical Society
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• v.17 no.1
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• pp.15-24
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• 2001

흙필터는 일반적으로 침식이나 파이핑으로부터 지반 구조물을 보호하기 위하여 사용된다. 세립자들이 유동하여 필터에 퇴적하는 폐색현상이 발생하는 경우, 간극수압이 증가하고 이로 인해 지반구조물의 불안정을 유발시키게 된다. 미세입자의 유동에 의한 폐색현상은 옹벽의 뒤채움재에 설치한 필터, 흙댐의 저부에 설치된 필터, 그리고 터널의 라이닝 뒤에 설치한 필터 등에서 발생할 수 있다. 폐색현상은 필터의 투수능을 저하시켜 배수능력에 상당한 위험을 초래할 수 있다. 본 연구에서는 필터의 폐색으로 인한 투수능 저하 정도를 실험을 통해 관찰하고 이론적인 모델을 통해 정량화 시키고자 하였다. 일정한 농도의 현탁액이 필터로 유입되는 분리형 실험과 현장상태를 모사하는 흙-필터 시스템의 결합형 실험을 통해 투수능의 저하현상이 압력 제어조건과 유량 제어조건에서 관찰되었고, 서로 비교 분석되었다. 미세입자가 통과하는 필터의 간극을 모세관으로 가정한 후 모세관에서 유체의 흐름 원리를 이용하여 물리적인 폐색에 의해 발생하는 투수능 저하현상을 이론적인 모델로 구성하였다. 일반적으로 투수능은 1/10 수준으로 감소되었으며, 분리형 실험에 의한 결과와 이론적인 모델의 결과는 잘 일치하였다. 또한, 결합형 실험결과와 분리형 실험결과가 비교적 잘 일치하여 투수능 저하예측은 분리형 실험이나 이론적 모델에 의하여 가능하리라 판단되었다.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.2
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• pp.144-153
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• 2008

A numerical analysis has been carried out to examine the flow characteristics and the collection efficiency for fine particles in a cyclone using Computational Fluid Dynamics (CFD) technique. The cyclone with the cylinder diameter of 60 mm has been considered for the investigation of the particle collection in a relatively smaller cyclone with somewhat higher inlet air velocities. Fundamental air flow patterns for different inlet velocities have been calculated and then the motions of particles of different sizes have been obtained. The calculated collection efficiencies for fine particles are compared with the experimental results, which shows a good agreement. The current result can be used for the design of cyclones with high collection efficiency.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.3
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• pp.47-52
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• 2021

Fine dust generated from vehicle brakes accounts for a significant amount of fine dust from non-exhaust system. Since such brake fine dust contains a large number of heavy metal components that are fatal to the human body, a device capable of collecting them needs to be developed. A mini cyclone, one of the devices that can effectively collect fine dust, has the advantage of relatively simple shape and high collection efficiency. Therefore, in this study, the collection efficiency of the mini-cyclone was numerically analyzed using CFD in order to find out whether such a mini-cyclone is suitable for collecting brake fine dust. As a result, the cut-off diameter was predicted to be about 1.5㎛, which means that the particle trapping load of the filter can be drastically reduced. Therefore, there is a possibility that the mini-cyclone can be used to collect fine dust from disc brakes.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.6 no.4
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• pp.375-388
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• 1994

When conducting movable bed tests in a narrow wave tank, the hydrodynamics and morphology are assumed to be two-dimensional; hence, any three-dimensional patterns such as cross-tank variations of the profiles are neglected or averaged to represent the mean profiles at the measuring time. In this paper, six movable bed tests were carried out with a fairly fine sand to investigate (1) whether or not three-dimensional features can occur in relatively narrow wave tanks, and (2) various possible interrelationships and causes of the three-dimensionality. These movable bed studies suggested that there was a relatively slow feedback between the hydrodynamics and the morphology that led to initiation and growth of 3-D morphological features, resulting in cross-tank profile variations under certain stages of profile development, especially when the profile approached an equilibrium with overall stability.

• Journal of the Semiconductor & Display Technology
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• v.16 no.3
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• pp.41-46
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• 2017

This study aims to select suitable co-solvents and to obtain optimal process conditions in order to improve process efficiency and productivity through experimental results obtained under various experimental conditions for the etching and rinsing process using liquid carbon dioxide and supercritical carbon dioxide. Acetone was confirmed to be effective through basic experiments and used as the etching solution for MEMS-wafer etching in this study. In the case of using liquid carbon dioxide as the solvent and acetone as the etching solution, these two components were not mixed well and showed a phase separation. Liquid carbon dioxide in the lower layer interfered with contact between acetone and Mems-wafer during etching, and the results after rinsing and drying were not good. Based on the results obtained under various experimental conditions, the optimum process for treating MEMS-wafer using supercritical CO2 as the solvent, acetone as the etching solution, and methanol as the rinsing solution was set up, and MEMS-wafer without stiction can be obtained by continuous etching, rinsing and drying process. In addition, the amount of the etching solution (acetone) and the cleaning liquid (methanol) compared to the initial experimental values can be greatly reduced through optimization of process conditions.

• Journal of Aerospace System Engineering
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• v.12 no.6
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• pp.1-8
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• 2018

ACF, which is used for the transparent electrode film is manufactured by the thermocompression method with conductive particles. However, the method has disadvantages since there are many wasted materials and the process is complex. To overcome the demerits of the conventional method, EHD printing technology with conductive particles ink is proposed. The line thickness of patterning is influenced by the characteristics of the inks and the printing conditions. Therefore, it is salient to find the most conducive conditions for the micro patterning. In this paper, the ink with conductive particles was manufactured, and the patterning results were obtained by varying the nozzle thickness and the flow rate. The electrical conductivity according to the ejection of the particles ink is obtained.

• Korean Chemical Engineering Research
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• v.57 no.2
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• pp.149-163
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• 2019

Under non-uniform electric field, a directional force along the electric field gradient is applied to matter having permanent or induced dipoles. The transport of particles by the directional force is called dielectrophoresis (DEP). Since the strength and direction of the DEP force depend on parameters, such as permittivity and conductivity of particles and surrounding media, and frequency of the applied AC electric field, particle can be precisely manipulated by controlling the parameters. Moreover, unlike electrophoresis, DEP can be applied to any particles where dipole is effectively induced by electric field. Such a DEP technique has been used in various fields, ranging from microfluidic engineering to biosensor and microchip research. This paper first describes the fundamentals of DEP, and discusses representative microelectrode designs used for DEP study. Then, exemplary applications of DEP, such as separation, capture and self-assembly of particles, are introduced.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.4
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• pp.251-257
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• 2011

In the present study, a 3-dimensional (3D) numerical model was developed to mimic the micro porous structure of a geological $CO_2$ storage reservoir. Especially, 3D modeling technique assigning random pore size to a 3D micro porous structure was devised. Numerical method using CFD (computational fluid dynamics) was applied for the 3D micro porous structure to calculate supercritical $CO_2$ flow field. The three different configurations of 3D micro porous model were designed and their flow fields were calculated. For the physical conditions of $CO_2$ flow, temperature and pressure were set up equivalent to geological underground condition where $CO_2$ fluid was stored. From the results, the characteristics of the supercritical $CO_2$ flow fields were scrutinized and the influence of the micro pore configuration on the flow field was investigated. In particular, the pressure difference and consequent $CO_2$ permeability were calculated and compared with increasing $CO_2$ flow rate.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.10 s.241
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• pp.1298-1306
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• 2005

In this paper, Part II, we realized the Serpentine Laminating Micromirer (SLM) which was proposed in the accompanying paper, Part I, by means of the injection molding process in mass production. In the SLM, the higher level of chaotic mixing can be achieved by combining two general chaotic mixing mechanisms of splitting/recombination and chaotic advection by the successive arrangement of 'F'-shape mixing units in two layers. Mold inserts for the injection molding process of the SLM were fabricated by SU-8 photolithography and nickel electroplating. The SLM was realized by injection molding of COC (cyclic olefin copolymer) with the fabricated mold inserts and thermal bonding of two injection molded COC substrates. To compare the mixing performance, a T-type micromixer was also fabricated. Mixing performances of micromixers were experimentally characterized in terms of an average mixing color intensity of a pH indicator, phenolphthalein. Experimental results show that the SLM has much better mixing performance than the I-type micromixer and chaotic mixing was successfully achieved from the SLM over the wide range of Reynolds number (Re). The chaotic micromixer, SLM proposed in this study, could be easily integrated in Micro-Total-Analysis- System , Lab-on-a-Chip and so on.