• Journal of the Korean Chemical Society
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• v.42 no.2
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• pp.156-160
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• 1998

Probe diffusion with latex particles in two different types of chemically cross linked gel has been studied. The diffusion of particles in silica gel is decreased by decreasing the gel correlation length but the particles' diffusion in the acrylamide gel still shows the heterogeneity of the gel. By increasing the contents of the gel network the silica gel makes a more homogeneous and compact structure than that of acrylamide gel which has partial heterodyning. Dynamic light scattering study with the probe particles in two different gels reveals the heterogeneity of the gel network. The latex particles trapping in the gel has been investigated by using non-ergodic concepts.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.6
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• pp.127-136
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• 2006

Prediction of diesel particulate filtration is typically made by virtue of modeling of particulate matter(PM) collection. The model is closed with filtration parameters reflecting all small scale phenomena associated with PM trapping, and these parameters are to be traced back by inversely analyzing large-scale empirical data-the pressure drop histories. Included are soot cake permeability, soot cake density, soot density in the porous filter wall, and percolation constant. In the present study, a series of single channel DPF experiment is conducted, pressure histories are inversely analyzed, and the essential filtration parameters are deducted by DPF filtration model formulated with non-linear description of soot cake regression. Sensitivity analyses of model parameters are also made. Results showed that filtration transients are significantly altered by the extent of percolation constant, and the soot density in the porous filter wall is controlling the filtration qualities in deep-bed filtration regime. In addition, effect of soot particle size on filtration quality is distinct in a period of soot cake regime.

• Proceedings of the KIEE Conference
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• 2006.04b
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• pp.52-56
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• 2006

Some of factors affecting photo-conversion efficiency of dye sensitized solar cells (DSCs) are discussed in terms of $TiO_2$ electrodes. The first topic is on the surface modification of $TiO_2$ nano-particles, which is associated with electron traps on the surface of $TiO_2$ nano-particles. The surface is modified with dye molecules under pressurized $CO_2$ atmosphere to increase the surface coverage of $TiO_2$ nano-particles with dye molecules. This increases Jsc because of an increase in the amount of dye molecules and a decrease in the amount of trapping sites on $TiO_2$ nano-particles. In addition, the decrease in the amount of trap sites increases Voc because decreases in Voc are brought about by the recombination of $I_2$ molecules with electrons trapped on the $TiO_2$ surfaces. Selective staining for tandem cells is proposed. The second topic is on the contact between a $SnO_2$/F transparent conductive layer (TCL) and nano-particles. Polishing the TCL surfaces with silica nano-particles increases the contact, resulting in Jsc increases. The third topic is the fabrication of ion-paths in $TiO_2$ layers. Electro-spray coating of $TiO_2$ nano-particles onto TCL is shown to be effective for fabricating ion-paths in $TiO_2$ layers, which increases Jsc.

• Ocean and Polar Research
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• v.24 no.1
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• pp.63-71
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• 2002

This preliminary study on the changes of macrobenthic assemblages in experimental sediment fences was conducted as a part of tidal marsh restoration project. Intertidal sediment fences were designed to increase the efficiency of trapping sediments on unvegetated tidal flats in order to raise sediment elevation and to allow colonization of intertidal vegetation. Although increment of soil surface level was not observed over the first three months of the study, it was possible to obtain some effects of the sediment fence. Three months later, the particle sizes of the surface sediment at experimental plots became much finer compared to unfenced areas on the natural mudflats located in the same tide level as that of the plots. The difference was much greater on the plot with drainage canals than on the plot without ones. Species diversity of the experimental plots became much higher than that of natural sites. Perinereis aibuhitensis and Glauconome chinensis which were absent from initial community appeared with high density in the plot with drainage canals. Those species were significantly different in abundance between the experimental plot and the natural mudflat. Changes in species composition were not detected in another experimental plot without drainage canals.

• Current Optics and Photonics
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• v.2 no.2
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• pp.147-152
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• 2018

We propose a novel bi-focal metallic Fresnel zone plate (MFZP) with shallow depth-of-field (DOF) characteristics. We design the specific annular slit patterns, exploiting the phase-selection-rule method along with the particle swarm optimization algorithm, which we have recently proposed. We numerically investigate the novel characteristics of the bi-focal MFZP in comparison with those of another bi-focal MFZP having equivalent functionality but designed by the conventional multi-zone method. We verify that whilst both bi-focal MFZPs can produce dual focal spots at $15{\mu}m$ and $25{\mu}m$ away from the MFZP plane, the former exhibits characteristics superior to those of the latter from the viewpoint of axial resolution, including the axial side lobe suppression and axial DOF shallowness. We expect the proposed bi-focal MFZP can readily be fabricated with electron-beam evaporation and focused-ion-beam processes and further be exploited for various applications, such as laser micro-machining, optical trapping, biochemical sensing, confocal sensing, etc.

• 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 Wetlands Research
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• v.20 no.1
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• pp.63-71
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• 2018

The particle filtration mechanisms in an infiltration trench should be varying due to the different hydraulic conditions during stormwater runoff. The understanding of these variations associated with different filtration mechanisms and their effect on the particle removal efficiency is of vital importance. Therefore, a LID (Low Impact Development) system comprising of an infiltration trench packed with gravel and woodchip was investigated during the monitoring of several independent rainfall events. A typical rainfall event was divided into separate regimes and their corresponding flow conditions as well as filtration mechanisms in the trench were analyzed. According to hydraulic conditions, it was found out that filtration changes between vertical and horizontal flows as well as between unsaturated, saturated, and partially-saturated flows. Particle separation efficiency was high (55-76%) and was mainly governed by physical straining during the unsaturated period. It was then enhanced by diffusion during the saturated period (75-95%). When the trench became partially saturated at the end of the rainfall event, the efficiency decreased which was believed to be due to the existence of a negatively charged air-water interface which limited the removal to positively charged particles.

• The Journal of the Acoustical Society of Korea
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• v.27 no.7
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• pp.357-364
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• 2008

For the purpose of possibility study on development of an acoustic tweezer using standing waves and very high frequency ultrasound focused beams, a system which can manipulate the position of particles in water has been constructed. It can move the particles to near focal point of a focused beam by the radiation force of standing waves, and then the particles would be trapped by the radiating force of the focused beam. The results show that micro sphere particles were trapped well at nodes of the standing waves and their position can be easily manipulated by frequency control. And, even though the radiation force by single focused beam pushes a particle away from the transducer, two focused confronted beams can trap it at near center.

• Asian Journal of Atmospheric Environment
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• v.7 no.4
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• pp.191-198
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• 2013

Cryptomeria japonica pollen is the most common pollen, which are scattering during each spring season in Japan. Japanese cedar (Cryptomeria japonica) pollinosis is one of seasonal allergic rhinitis that mainly occurs in Japan. In addition, long range transportation of Yellow Sand from the East Asian continent was also found during the pollen scattering seasons in Japan. Therefore, the interaction or impact between pollen and Yellow Sand should be concerned. In this study, our objective was to investigate the airborne behaviour of Cryptomeria japonica pollen grains and its size-segregated allergenic (Cry j 1) particles as the airborne tracer of Cryptomeria japonica pollen during the Yellow Sand events. Airborne Cryptomeria japonica pollen grains and its size-segregated allergenic particles were collected at roadside of urban residential zones of Saitama city during the pollination periods from February to March in two year investigation of 2009 and 2010. The overlap of Yellow Sand events and dispersal peak of pollen grains was observed. According to the Meteorological data, we found that the peaks of airborne pollen grains appeared under higher wind speed and temperature than the previous day. It was thought that Yellow Sand events and airborne pollen counts were related to wind speed. From the investigation of the airborne behavior of the size-segregated allergen particles by determining Cry j 1 with Surface Plasmon Resonance (SPR), the higher concentrations of the allergenic Cry j 1 were detected in particle size equal to or less than $1.1{\mu}m$($PM_{1.1}$) than other particle sizes during Yellow Sand events, especially in the rainy day. We conclude that rainwater trapping Yellow Sand is one of the important factors that affect the release of allergenic pollen species of Cry j 1. Therefore, it is very important to clarify the relationships between Cryptomeria japonica pollen allergenic species and chemical contents of the Yellow Sand particles in further studies.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.10
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• pp.737-742
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• 2013

The purpose of this study was to remove sediments obtained from breeding ground using supersonics and micro-air flotation method. Sediments from Tongyong breeding grounds showed no contaminations of heavy metals but had great amount of organics. Thus, efficient removal of sediments was required to preserve water quality near breeding ground. Supersonics treatment for sediments was determined to be essential because higher removal efficiency of sediments was obtained when supersonics treatment was used. In addition, application of coagulants increased removal efficiency because its usage increased particle size of sediments, which enabled easy trapping of sediments particle into micro-air bubbles. Removal efficiency of sediments slightly decreased from 95.8% (1 g/L) to 83.9% (8 g/L) at the tests for different amount of sediments, but most of tiny particles were removed from water where sand size particles were left in the bottom of reactors.