• Atmosphere
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• v.23 no.1
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• pp.13-21
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• 2013

In this study, the effects of atmospheric stability and surface temperature on the microscale local airflow are investigated in a hydrological suburban area using a computational fluid dynamics (CFD) model. The model domain includes the river and industrial complex for analyzing the effect of water system and topography on local airflow. The surface boundary condition is constructed using a geographic information system (GIS) data in order to more accurately build topography and buildings. In the control experiment, it is shown that the topography and buildings mainly determine the microscale airflow (wind speed and wind direction). The sensitivity experiments of atmospheric stability (neutral, stable, and unstable conditions) represent the slight changes in wind speed with the increase in vertical temperature gradient. The differential heating of ground and water surfaces influences on the local meteorological factors such as air temperature, heat flow, and airflow. These results consequentially suggest that the meteorological impact assessment is accompanied by the changes of background land and atmospheric conditions. It is also demonstrated that the numerical experiments with very high spatial resolution can be useful for understanding microscale local meteorology.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.10 s.253
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• pp.935-941
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• 2006

Many important properties in colloidal systems are usually determined by surface charge $({\zeta}-potential)$ of the contacted solid surface. In this study, ${\zeta}-potential$ of glass ${\mu}-channel$ was evaluated from the electro-osmotic velocity distribution. The electro-osmotic velocity inside a glass f-channel was measured using a micro-PIV velocity field measurement technique. This evaluation method is more simple and easy to approach, compared with the traditional streaming potential technique. The ${\zeta}-potential$ in the glass ${\mu}-channel$ was measured fur two different mole NaCl solutions. The effect of an anion surfactant, sodium dodecyl sulphate (SDS), on the electro-osmotic velocity and f-potential in the glass surface was also studied. In the range of $0{\sim}6mM$, the surfactant SDS was added to NaCl solution in few different mole concentrations. As a result, the addition of SDS increases ${\zeta}-potential$ in the surface of the glass ${\mu}-channel$. The measured $\zeta-potential$ was found to vary from -260 to -70mV. When negatively charged particles were used, the flow direction was opposite compared with that of neutral particles. The ${\zeta}-potential$ has a positive sign for the negative particles.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.271-271
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• 2013

The defect states of a Ar-sputtered SiO2 surface on Si (001) were investigated using Auger electron spectroscopy (AES) and reflection electron energy loss spectroscopy (REELS). The REELS spectra at the primary electron energy of 500 eV showedthat three peaks at 2.5, 5.1, and 7.2 eV were found within the band gap after sputtering. These peaks do not appear at the primary electron energies of 1,000 and 1,500 eV, which means that the defect states are located at the extreme surface of a SiO2/Si thin film. According to the calculations, two peaks at 7.2 and 5.1 eV are related to neutral oxygen vacancies. However, the third peak at 2.5 eV has never been previously reported and the theories proposed that this defect state may be due to Si-Si bonding. Our Auger data showed that a peak for Si-Si bonding at 89 eV appears after Ar ion sputtering on the surface of the sample, which is consistent with the theoretical models.

• Journal of Environmental Science International
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• v.18 no.8
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• pp.857-865
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• 2009

The physical properties of an atmospheric boundary layer in Wolryong, a west coastal region of Jeju, South Korea, in terms of the atmospheric stability and roughness length, is important and relevant to both engineers and scientists. The study is aiming to understand the atmospheric stability around this region and its effect on the roughness length. We calculate the Monin-Obukhov length(L) against 3 typical regions of the atmospheric condition - unstable regime (-5$-0.2{\leq}H/L{\leq}0.2$) and stable regime (0.2

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.33 no.2
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• pp.58-67
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• 2001

MOW (Mixed Office Waste) mainly consisted of photocopied paper is being recycled to produce tissue or fine paper products. Toner particles that are fused and set on paper surface in photocopying process turns into large and plate-shaped particles after repulping which prevents them to be removed effectively in flotation deinking. The immediate purpose of this study is to find the effective deinking technology that increases the recycling potential of photocopied papers for manufacturing tissue and fine paper products. In this study the effects of pulping temperature and the type of hydrophobic groups of nonionic surfactants on the deinking efficiency of photocopied paper has been investigated. Particle size distribution of the toner particles after pulping and flotation, brightness, yield and ash removal were investigated. The size of toner particles after pulping increased as the pulping temperature was increased. When pulping at the low temperature finer toner particles were generated, however, greater amount of toner particles was found to attach to the fiber. When the pulping temperature was greater than Tg of the toner, the amount of coarse hairy particles increased. When nonionic surfactants with a double bond in hydrophobic groups were used, toner removal efficiency, brightness and ash removal were increased. As the addition level of surfactant was increased, yield decreased rather sharply without improving brightness.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2006.06a
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• pp.129-136
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• 2006

Although cleaner and cheaper deinking of ONP could be performed at the neutral or low alkaline condition excessive loss from froth-flotation is unavoidable and so reduction of alkali or caustic soda dosage sacrifices recycling yield. Now the new trade-off regarding alkali dosage versus flotation yield is urgently required in order to set the optimized neutral or low alkaline deinking process of ONP. Lipase from Thermomyces Lanuginosus has an effect on desizing and deacetylation reaction and it could be applied to the stock of pre flotation secondary stage in order to reduce the flotation reject without the sacrifice of optical properties of flotation accepts. Instead of inorganic base, lipase could be applied as a biochemical catalyst for the selective modification of valuable hydrophobic particles in deinking stock, for example cellulose fines and inorganic fillers covered by hydrophobic additives or contaminants. When the enzymatic hydrolysis of ester bond could be made on the surface of hydrophobic particulates, unwanted float of fine particles could be prevented. Now the enhancement of flotation selectivity or the modification of the hydrophobicity of deinking stock is expected to be promoted by the enzymatic pre treatment. And the reduction of recycling cost with the saves of raw material, recovered paper would be possible as a result.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 1999.11b
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• pp.50-55
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• 1999

Sizing development of AKD-sized paper by beta-ketoester formation has been debated until recent years because of absence of its obvious and direct spectroscopic evidence. In this study, reaction between AKD and cellulose was investigated to disclose the possibility of beta-ketoester formation between two components under no catalyzed neutral condition. In absence of water, AKD reacted with cellulose to form beta-ketoester linkage under no catalyzed neutral condition, while, in presence of water, most of AKD was hydrolyzed to a dialkyl ketone or beta-ketoacid. Therefore, the main mechanism of AKD sizing would not be the formation of beta-ketoester between AKD and cellulose in the papermaking process. It could be suggested that the sizing development of AKD-sized paper is obtained by next two mechanisms: 1) formation of a thin-layer of AKD on the fiber surface through melting and spreading of AKD emulsion particles by heat, and 2) the formation of ketone by the hydrolysis of AKD during drying and storage of AKD-sized papers.

• Journal of Korean Physical Therapy Science
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• v.17 no.3_4
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• pp.29-39
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• 2010

Purpose: The purpose of this study was to examine the effect of foot position and lifting an object on muscle activity and foot pressure during sit to stand(STS) in hemiparetic patients. Methods: Fourteen patients participated in this study. Surface electromyography was used to collect muscle activity and foot pressure measurement system was used to analyze foot pressure in hemiparetic side. Three different foot position was assumed(anterior, neutral, posterior) in hemiparetic side. The repeated two-way analysis of variance and multiple comparisons were conducted to determine statistical significance with a significance level of 0.05. Results: The results were as follows. 1) Lower extremity muscle activity was significantly higher(p<0.05) in biceps femoris and tibialis anterior muscle during STS without holding an object. With changing positions of the affected foot, muscle activity was significantly increased (p<0.05) in vastus medialis and lateral gastrocnemius when the foot was positioned in posterior. 2) There was no significant difference(p>0.05) in foot pressure during STS with object holding and foot positioning. Conclusion: Muscle activity showed a significant increase when the foot was positioned in posterior in comparison to the muscle activity when the foot was in neutral or anterior position.

• Journal of the Korean Society of Clothing and Textiles
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• v.21 no.7
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• pp.1196-1204
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• 1997

Cotton, rayon/cotton, and Tencel twill weave fabrics were used to investigate the effect of fiber types on the cellulase washing finish. And twill. basket, and derivative weave cotton fabrics were used to study the weave effect. Various fabrics were treated with neutral cellulase varying treatment times and with acid cellulase, stone, and stone-neutral cellulase respectively for two hours in a rotary washer. Weight loss decreased in the order of rayon/cotton> cotton> Tencel, and basket and derivative weave fabrics lost more weight than twill weave fabric. Color difference decreased in the order of cotton> Tencel> rayon/cotton, and twill weave fabric had larger color difference than derivative and basket weave fabrics. Back staining decreased in the order of cotton> rayon/cotton> Tencel, and twill weave fabric had larger back staining than derivative and basket weave fabrics. Tear strength retention decreased in the order of rayon/cotton> cotton> Tencet and twill weave fabric had larger tear strength retention than derivative and basket weave fabrics. Flex stiffness retention decreased in the order of cotton> Tencel> rayon/cotton, and in the order of derivative> twill> basket weave. In cotton fibers, damage of primary wall was observed. And the cellulase treatment on Tencel seemed to roughen the fabric surface slightly, and to fibril fibers along the fiber axis.

• Journal of Power Electronics
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• v.17 no.6
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• pp.1500-1511
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• 2017

The purpose of this paper is to study a high-performance control scheme for neutral-point-clamping three-level (NPC-3L) inverter fed dual three-phase permanent magnet synchronous motor (PMSM) drives by considering some asymmetric factors such as the non-identical parameters in phase windings. To implement this, the system model is analyzed for dual three-phase PMSM drives with asymmetric factors based on the vector space decomposition (VSD) principle. Based on the equivalent circuits, PI controllers with feedforward compensation are used in the d-q subspace for regulating torque, where the cut-off frequency of the PI controllers are set at the twice the fundamental frequency for compensating both the additional DC component and the second order component caused by asymmetry. Meanwhile, proportional resonant (PR) controllers are proposed in the x-y subspace for suppressing the possible unbalanced currents in the phase windings. A dual three-phase space vector modulation (DT-SVM) is designed for the drive, and the balancing factor is designed based on the numerical fitting surface for balancing the DC link capacitor voltages. Experimental results are given to demonstrate the validity of the theoretical analysis and the proposed control scheme.