• Journal of the Korean Chemical Society
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• v.66 no.2
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• pp.136-149
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• 2022

Chemistry focuses on explaining macroscopic phenomena at the microscopic level with particles, such as atoms or molecules. Explanation using particles are bound to be considered as abstract by students, because it was dealing with invisible objects. For that reason, the science national curriculum presented to middle school students the explanation of the units related to the composition of matter. Therefore, understanding about the composition of matter in middle school students becomes an important basis for learning of chemistry, and it is necessary to investigate their understanding about composition of matter. In this study, students' understanding about 'composition of matter' region, which is first presented to middle school students, was confirmed at an overall level. In this line, this study analyzed the results of the items in the composition of matter region, and analyzed items were used in the National Assessment of Educational Achievement (NAEA) from 2015 to 2019. We analyzed the 9 items presented in the NAEA according to the response rate of options and response rate distribution curve, and explained the characteristics of understanding derived by each achievement level were examined. According to the analyzed results by dividing the conceptions about elements, atoms, and ions, students above the proficient achievement-level had scientific conceptions overall, but students below the basic achievement-level had inconsistent or naive conceptions. Based on the results for each item, this study discussed some implications to be considered or to be improved on teaching-learning for 'composition of matter'.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.3
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• pp.297-303
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• 2007

Orimulsion, a bitumen-in-water emulsified fuel, has been used throughout the world as a substitute fuel for heavy oil and coal. Orimulsion has relatively high levels of sulfur, nickel, and vanadium, compared to other fuel oils and coals, and has been the subject of much debate regarding the environmental impacts. In Korea, Y power plant has operated boilers with Orimulsion as a fuel, and they has some drawbacks during the plant operation, such as plume opacity. In this study, we investigated the cause of formation mechanism and factors for the plume opacity by investigating the operation data, and measuring the particle size distribution at EP(Electrostatic Precipitator), FGD(Fuel Gas Desulfurization) and TMS(Telecommunications Management System) units. Resulting data showed the primary particles below 1 ${\mu}m$ formed were regrown by the recombination of $SO_3$ in wet-limestone FGD process, and thus the secondary particles are induced to cause the plume opacity.

• Applied Microscopy
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• v.34 no.2
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• pp.121-130
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• 2004

In this study, ultrastructural change of the bile duct fibroblast at infected rat with Clonorchis sinensis, and the distribution of lectin receptors and actin protein in cultured bile duct infected with Clonorchis sinensis. It explored using colloidal gold label complex with lectin WGA purified from wheat germ (Triticum vulgaris) and anti actin antibody purified actin (43 kDa) isolated from chicken back muscle. The lectin WGA with protein A gold complex labeled sections of the cultured fibroblast revealed gold particles specifically distributed on the multi vesicular form Golgi complex and cell surface of the fibroblast. The actin antibody with protein A gold complex labeled sections of the cultured fibroblast revealed gold particles specifically distributed on the cytoplasm of the fibroblast. Labeling of cultured fibroblast in rat bile duct infected with Clonorchis sinensis was then quantified and compared to that of cultured Fibroblast in Rat Bile duct. These results indicate that lectin WGA receptors are located in the multi vesicular form Golgi complex in the cytoplasm to the cytoplasmic process of the Rat bile duct fibroblast infected with Clonorchis sinensis. Therefore, the GlcNAc and NeuNac regions on the cell surface and cytoplasmic process appear to be functionally associated with cell-recognition and protection from other cell of the tissue, and linked with secretion and exocytosis of the fibroblst cytoplasm. GlcNAc and NeuNAc product in the multi vesicular form Golgi complex then it is transported to cell surface. Actin protein is many appears that infected fibroblast rather than normal fibroblast. The fibroblast of infected with Clonorchis sinensis are against of the physical and chemical stimulation. Then development of cytoplasmic process is relative some stimulation.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.8.1-8.1
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• 2011

Nanocrystalline titanium dioxide ($TiO_2$) materials have been widely used as an electron collector in DSSC. This is required to have an extremely high porosity and surface area such that the dye can be sufficiently adsorbed and be electronically interconnected, resulting in the generation of a high photocurrent within cells. In particular, their geometrical structures and crystalline phase have been extensively investigated as important issues in improving its photovoltaic efficiency. In this study, we present a new strategy to fabricate a photoelectrode having a periodic structured $TiO_2$ film templated from 1D or 3D polystyrene (PS) microspheres array. Monodisperse PS spheres of various radiuses were used for colloidal array on FTO glasses and two types of photoelectrode structures with different $TiO_2$ materials were investigated respectively. One is the igloo-shaped electrode prepared by $TiO_2$ deposition by RF-sputtering onto 2D microsphere-templated substrates. At the interface between the film and substrate, there are voids formed by the decomposition of PS microspheres during the calcination step. These holes might be expected to play the predominant roles as scattering spherical voids to promote a light harvesting effect, a spacious structure for electrolytes with higher viscosity and effective paths for electron transfer. Additionally the nanocrystalline $TiO_2$ phase prepared by the RF-sputtering method was previously reported to improve the electron drift mobility within $TiO_2$ electrodes. This yields solar cells with a cell efficiency of 2.45% or more at AM 1.5 illumination, which is a very remarkable result, considering its $TiO_2$ electrode thickness (<2 ${\mu}m$). This study can be expanded to obtain higher cell efficiency by higher dye loading through the increase of surface area or multi-layered stacking. The other is the inverse opal photonic crystal electrode prepared by titania particles infusion within 3D colloidal arrays. To obtain the enlargement of ordered area and high quality of crystallinity, the synthesis of titania particles coated with a organic thin layer were applied instead of sol-gel process using the $TiO_2$ precursors. They were dispersed so well in most solvents without aggregates and infused successfully within colloidal array structures. This ordered mesoporous structure provides the large surface area leading to the enough adsorption of dye molecules and have an light harvesting effect due to the photonic band gap properties (back-and-forth reflection effects within structures). A major advantage of this colloidal array template method is that the pore size and its distribution within $TiO_2$ photoelectrodes are determined by those of latex beads, which can be controlled easily. These materials may have promising potentials for future applications of membrane, sensor and so on as well as solar cells.

• Journal of the Korean Applied Science and Technology
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• v.38 no.5
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• pp.1325-1334
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• 2021

This study reports the development of a manufacturing method of synthesizing colloidal gold using catalysts available for cosmetics and an anti-aging ampoule with skin improvement effects using it. Nano-colloidal gold was synthesized by using ascorbic acid and sodium borohydride as a reducing catalyst in hydrogen tetrachloroaurate tetrahydrate. It was confirmed that the particles became smaller as the mass of the content of ascorbic acid, which is a catalyst, increased. On the other hand, as the mass of sodium borohydride increased, the particle size tended to increase. In order to control the colloidal gold reaction rate, particles having 100 to 500 nm of a particle diameter distribution could be obtained using xanthan gum and hydroxyethylcellulose. The optimal synthesis conditions could be obtained by reacting for 1 to 4 hours at 18℃, a reduced pressure state of 20 to 75 mmHg, a stirring speed of 10~50 rpm. The synthesized colloidal gold had a unique smell of dark pink, pH = 5.5, specific gravity of 1.0032, and viscosity of 80 to 310 cps. As an application of skin care cosmetics, anti-aging ampoule has been developed, and it is expected to be used for various prescriptions and formulations using it.

• International Journal of Highway Engineering
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• v.13 no.2
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• pp.187-193
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• 2011

The stormwater runoff from road or expressway is known as one of important nonpoint pollution sources. To reduce the pollutants discharge from road or expressway, many best management practices(BMPs) have been applied and planned. Among the BMPs, road sweeping can be effective way to prevent pollutant washoff to environment. This study is performed to evaluate the characteristics of particles collected from the road by sweeping car. Size distribution and pollutant concentration of particles were analyzed. Based on the pollutant concentration and the specification of road such as length, width, and unit for pollutant generation, total amount of pollutant to be removed by road sweeping was estimated. Most of sediments collected by road sweeping was classified into sandy soil and fraction of fine grained soil was low. Although the concentrations of pollutants such as heavy metals in road sediments did not exceed the soil contamination criteria, washout of pollutants during sweeping work by spraying water might cause leaching of pollutants contained in sediments and thus resulted in low pollutant concentrations. Reduced amounts of pollutant by road sweeping showed 31.4% TSS reduction for ${\bigcirc}{\bigcirc}$ region and 7.7% TSS for ${\triangle}{\triangle}$ region. Other pollutants showed low reduction rate, because of their leaching by water spraying. Results from this study indicate that detailed and well-planned investigation for the road sweeping is necessary for the accurate estimation of pollutant reduction from road or expressway.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.25 no.3
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• pp.301-311
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• 2015

Objectives: Operators of overhead traveling crane in a ship assembly factory perform work to transmit large vessel blocks to an appropriate working process. Hazardous matters such as metal dusts, carbon monoxide, carbon dioxide, ozone, loud noise and fine particles are generated by variable working activities in the factory. The operators could be exposed to the hazardous matters during the work. In particular, welding fumes comprised of ultra fine particles and heavy metals is extremely hazardous for humans when exposing a pulmonary through respiratory pathway. Occupational lung diseases related to welding fumes are increasingly on an upward tendency. Therefore, the objective of this study is to assess properly unknown occupational exposure to the welding fumes among the operators. Methods: This study intended to clearly determine an equivalence check whether or not chemical constituents and composition of the dusts, which existed in the driver's cab, matched up with generally known welding fumes. Furthermore, computational fluid dynamics program(CFD) was used to identify a ventilation assessment in respect of a contamination distribution of welding fumes in the air. The operators were investigated to assess personal exposure levels of welding fumes and respirable particulate. Results: The dust in an operation room were the same constituents and composition as welding fumes. Welding fumes, which caused by the welding in a floor of the factory, arose with an ascending air current up to a roof and then stayed for a long time. They were considered to be exposed to the welding fumes in the operation room. The personal exposure levels of welding fumes and respirable particulate were 0.159(n=8, range=0.073-0.410) $mg/m^3$ and 0.138(n=8, range=0.087-0.178) $mg/m^3$, respectively. They were lower than a threshold limit value level($5mg/m^3$) of welding fumes. Conclusions: These findings indicate that an occupational exposure to welding fumes can exist among the operators. Consequently, we need to be keeping the operators under a constant assessment in the operator process of overhead traveling crane.

• Journal of Environmental Science International
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• v.4 no.4
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• pp.367-377
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• 1995

The study of flocculation kinetics is of fundamental interest in the field of water treatment, because rational study of the factors affecting the coagulation process should be based on the rate of particle growth. The effect of sulfate on flocculation kinetics were examined using ferric nitrate as a coagulant to coagulate kaolin clay in water under several experimental conditions. Both the particle size distribution data obtained from the AIA and the on-line measurement of turbidity fluctuation by the PDA were used to measure flocculation kinetics. Results show that sulfate ion added to the kaolin suspension played an important role in the flocculation process, not only improving flocculation kinetics at more acidic pH levels but also changing surface charge of particles. The kinetics of flocculation were improved mainly by the enhanced rate and extent of Fe(III) precipitation attributed to the addition of sulfate, and thereby, better interparticle collision frequency, but little by the charge reductions resulting from the sulfate addition. The increase in sulfate concentration beyond $3\times10^{-4}M (up to 2\times10^{-3}M)$ did not induce further improvement in flocculation kinetics, although the higher concentrations of sulfate ion substantially increased the negative ZP value of particles. Key Words : Flocculation Kinetics, Fe(III) Coagulant, Sulfate ion, Turbidity Fluctuation.

• Membrane Journal
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• v.25 no.5
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• pp.373-384
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• 2015

In the past few decades, polymeric membrane has played an important role in gas separation applications. For the separation of $CO_2$, one of greenhouse gases, high permselectivity, long-term stability and scale-up are needed. However, conventional polymeric membranes have shown a trade-off relation between permeability and selectivity while inorganic materials are highly permeable but expensive. Mixed matrix membranes (MMMs) combining the advantages of both polymeric and inorganic materials have become a possible breakthrough for the next-generation gas separation membranes. The MMMs could be either symmetric or asymmetric but the latter is more preferred to improve the permeance. Important factors influencing the MMM fabrication include homogeneous distribution of inorganic particles and good interfacial contact between inorganic filler and organic matrix. Recently, metal organic frameworks (MOFs) have received much attention as a new class of porous crystalline materials and a potential candidate for $CO_2$ separation. Zeolitic imidazolate frameworks (ZIFs), a sub-branch of MOFs, are the most widely used in MMMs due to small particle size and appropriate pore size for $CO_2$ separation. One of the major issues associated with the incorporation of porous particles in a polymeric membrane is to control the microstructure of the porous particle materials such as particle size, orientation, and boundary conditions etc. In this review, major challenges surrounding MMMs and the strategies to tackle these challenges are given in detail.

• Applied Chemistry for Engineering
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• v.34 no.6
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• pp.674-678
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• 2023

The effect of Pt was investigated to the catalytic methane decomposition of CH₄ to H₂ over Pt(1)-Fe(30)/MCM-41 and Fe(30)/MCM-41 using a fixed bed flow reactor under atmosphere. The Fe₂O₃ and Pt crystal phase behavior of fresh Pt(1)-Fe(30)/MCM-41 were obtained via XRD analysis. SEM, EDS analysis, and mapping were performed to show the uniformed distribution of nano particles such as Fe, Pt, Si, O on the catalyst surface. XPS results showed O^2-, O^- species and metal ions such as Pt⁰, Pt²⁺, Pt⁴⁺, Ft⁰, Fe²⁺, Fe³⁺ etc. When 1 wt% of Pt was added to Fe(30)/MCM-41, automic percentage of Fe2p increased from 13.39% to 16.14%, and Pt4f was 1.51%. The yield of hydrogen over Pt(1)-Fe(30)/MCM-41 was 3.2 times higher than Fe(30)/MCM-41. The spillover effect of H₂ from Pt to Fe increased the reduction of Fe particles and moderate interaction of Fe, Pt and MCM-41 increased the uniform dispersion of fine nanoparticles on the catalyst surface, and improved hydrogen yield.