• Journal of Powder Materials
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• v.10 no.2
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• pp.123-128
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• 2003

$TiO_2$ nanopowder was synthesized by chemical vapor condensation (CVC) process and its photocatalytic property depending on microstructure was considered in terns of decomposition rate of organic compound. In order to control microstructure of $TiO_2$ nanopowder such as particle size and degree of agglomeration, precursor flow rate representing number concentration was changed as a process variable. In TEM observation, spherical $TiO_2$ nanoparticles with average size of 20 nm showed gradual increases in particle size and degree of agglomeration with increase of precursor flow rate. Also decomposition rate of organic compound increased with decreasing precursor flow rate. Thus, it was concluded that photocatalytic property was enhanced by targe surface area of disperse $TiO_2$ nanoparticles synthesized at lower precursor flow rate condition in CVC process.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.04a
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• pp.116-119
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• 1997

We investigated new type non-robbing liquid crystal (LC) alignment techniques in the cell with slanted non-polarized ultraviolet (UV) irradiation on polyimide (Pl) film. It is shown that the uniform alignment for nematic (N) LC is obtained by using slanted non-polarized UV irradiation on Pl surface. We successfully obtained that the pretilt ang1e of NLC is generated about 3 degree in the LC cells by using slanted non-polarized UV irradiation with 70 degree on Pl surface. We consider that the pretilt angle generation for NLC is attributed to interaction between the LC molecular and the PI surface. We conclude that the uniform LC alignment is attributed to anisotropic dispersion force effect due to photo depolymerization of polymer on Pl surface.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.11a
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• pp.198-201
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• 1997

We investigated the generation of pretilt angle for nematic liquid crystal (NLC) in a cell with slanted non-polarized ultraviolet (UV) light irradiation on mixtured polyimide (PI) surfaces. It was found that the monodomain alignment of NLC is obtained in a cell with an angle of incidence of 75∼85 degrees on PI surface. We consider that the monodomain alignment of NLC is attributed to anisotropic dispersion force effect due to photo-depolymerization of polymer on Pl surfaces. We successfully observed that the pretilt angle of NLC is generated above 5 degree with an angle of incidence of 75∼85 degree. It is considered that the pretilt angle generation in NLC is attributed to interaction between the LC molecules and the Polymer surfaces.

• Journal of Environmental Science International
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• v.25 no.2
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• pp.231-238
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• 2016

In this study, we have investigated to find optimal pre-treatment flocculation condition by analyzing the floc growth rate with mixing conditions and the membrane permeation flux for pre-treatment step of the membrane process. The higher mixing intensity showed a constant floc size index (FSI) values, and lower mixing intensity increased the degree of dispersion of the FSI values. Results of comparing the distribution characteristics of the FSI value and the permeation flux were more effective in increasing flux when the FSI values were 0.2 or higher. The degree of dispersion of FSI was relatively large in 40 rpm mixing condition compared to 120 rpm. In 40 rpm mixing condition, it decreased the permeation flux compared to 120 rpm because various sizes of flocs were distributed. Coagulation-UF membrane process enhanced 30%~40% of the flux rate compare to UF alone process, and the coagulation-MF process increased up to 5% of the flux rate compare to MF alone process. Pre-treatment, that is, coagulation process, has been found to be less effects on relatively larger pore size for MF membrane. For UF membrane, the flux was a little bit same when applying only the rapid mixing process or rapid mixing with slow mixing processes together. In case of MF membrane, the flux was improved when rapid mixing process applied with slow mixing process together.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.8 no.2
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• pp.1-20
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• 2005

The purpose of this paper is to classify two study sites into the biotope types and investigate the landscape ecological characteristics of them. This will be available for the rural planning in the aspect of environmental preservation. The summaries of the result are as follows. 1) In the result of the area assessment in biotope groups, a dry field (32%) and a paddy field (28%) are more than 50%, but settlement space and water space are less than 10%. The result shows the land use condition of rural areas. 2) In the investigation result of elongation, running water spaces are higher than other biotope groups relatively, it is because they long shaped and 1-3m narrow. 3) In case of Fractal index analysis, residential spaces and cultivated lands are investigated to be lower in numerical value, it is because they have the definite borders and get simple in the border of landscape by human intervention. 4) In case of dispersion degree, the dry field has the highest value because they are located close by forests spread widely around study sites. It means that the land which is used by artificial purpose get more value rather than natural lands 5) In the connectivity analysis, a paddy field and a residential space appear the highest. It is because residence spaces spread intensively through roads and a paddy field, through streams. 6) In rural landscape, the diversity of landscape is investigated to be simple. A paddy field and a dry field contain small sized patches that have been divided by human intervention. Besides, there appear much different vegetation around waterways and farm-roads.

• Polymer(Korea)
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• v.32 no.1
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• pp.1-6
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• 2008

The adhesion behaviors and processability of NBR as a sealing material were investigated. In order to find the optimum formulation, the adhesive properties and processability were observed as the change of the contents of acrylonitrile (ACN) in NBR. Effects of Mooney viscosity, filler, plasticizer and crosslinking agent on the adhesion behaviors were also studied. The contents of ACN in NBR have great effects on adhesion behaviors and processability in NBR sealing. To know the optimum condition of roll mixing, degree of dispersion was investigated. It was confirmed that degree of dispersion was influenced by various factors such as mixing order, time, and temperature. The crosslinking system was studied as the observation of sulfur system, peroxide system, crosslinking density, and structure. From the variation of the dry condition and hexamine contents, the relation between adhesive and NBR was studied. These results show the adhesion properties and processability are dependent on the contents of ACN and crosslinking system.

• Korean Chemical Engineering Research
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• v.51 no.4
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• pp.432-437
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• 2013

The CO preferential oxidation reaction (PROX) has been done using Cu catalytic active species supported on some of mesoporous silica materials which can facilitate the diffusion of the reactants in order to prevent the poisoning of anode active materials by CO molecules during driving polymer electrolyte fuel cells (PEMFC) in this study. As a result when SBA-15 with large pore used as a support showed excellent CO oxidation activity, especially the activity increased in proportion to the amount of supported Cu. Ti components which was inserted to increase the degree of dispersion of Cu, contributed to improving the performance for CO oxidation at low-temperature. The degree of dispersion of Cu ingredients was the best in the catalyst inserted 20 mol-% Ti into the framework of SBA-15, and CO oxidation activity was also improved.

• Nuclear Engineering and Technology
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• v.53 no.8
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• pp.2582-2590
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• 2021

The high-energy milling is one of the most extended techniques to produce Oxide dispersion strengthened (ODS) powder steels for nuclear applications. The consequences of the high energy mill process on the final powders can be measured by means of deformation level, size, morphology and alloying degree. In this work, an ODS ferritic steel, Fe-14Cr-5Al-3W-0.4Ti-0.25Y₂O₃-0.6Zr, was fabricated using two different mechanical alloying (MA) conditions (M_std and M_act) and subsequently consolidated by Spark Plasma Sintering (SPS). Milling conditions were set to evidence the effectivity of milling by changing the revolutions per minute (rpm) and dwell milling time. Differences on the particle size distribution as well as on the stored plastic deformation were observed, determining the consolidation ability of the material and the achieved microstructure. Since recrystallization depends on the plastic deformation degree, the composition of each particle and the promoted oxide dispersion, a dual grain size distribution was attained after SPS consolidation. M_act showed the highest areas of ultrafine regions when the material is consolidated at 1100 ℃. Microhardness and small punch tests were used to evaluate the material under room temperature and up to 500 ℃. The produced materials have attained remarkable mechanical properties under high temperature conditions.

• Carbon letters
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• v.10 no.1
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• pp.14-18
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• 2009

We measured the degree of macrodispersion of the various single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) using UV-VIS-NIR absorption spectroscopy. CNTs were dispersed with SDS of 2 wt % in deionized water using the homogenizer and then were further centrifugated at 6000 g for 10 min. The degree of macrodispersion, expressed by $D_m({\lambda})=A_a({\lambda})/A_b({\lambda})^*100$ (%), where ${\lambda}$ is the wavelength and $A_a({\lambda})$ and $A_b({\lambda})$ are the absorbance of the sample after and before centrifugation, respectively. In the case of MWCNTs, we evaluated the degree of macrodispersion by the average degree of macrodispersion ($D_m({\lambda})$) between 1000 and 1200 nm. The degree of macrodispersion of SWCNTs was evaluated at the wavelength in which van Hove singularity-related transition regions were excluded, i.e., the range was chosen between ${E_{11}}^S$ and ${E_{22}}^S$ peaks. We have estimated six samples with the same method. The standard deviation of each sample was lower than 5. Therefore, we presented a reliable evaluation method for the macrodispersion of CNTs for standardization.

• Korean Journal of Optics and Photonics
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• v.14 no.1
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• pp.72-79
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• 2003

We proposed a noble algorithm using DOP (degree of polarization) not only as feedback signal but alto as feed-forward signal for the compensation of higher-order PMD effect. In the proposed algorithm, DOP after the first-order PMD compensation is considered as the indicator of the amount of residual higher-order PMD. This algorithm has the merit that DOF (degree of freedom) of the system can be limited to the level of the first-order PMD compensation system. Owing to the limited DOF, the reliability of the system can be enhanced and the complexity of the implementation can be degraded. For the analysis of the algorithm, we simulated the 10Gbps NRZ transmission system and obtained the result that the system outage probability can be reduced as much as three times with respect to the only first-order PMD compensation case.