• Elastomers and Composites
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• v.50 no.1
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• pp.18-23
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• 2015

Vinyl acetate (VA) contents of poly(ethylene-co-vinyl acetate) (EVA) analyzed by infrared spectroscopy (IR), nuclear magnetic spectroscopy (NMR), and thermogravimetric analysis (TGA) were compared. Four grade EVAs supplied by Aldrich Co. and four grade EVAs manufactured by DuPont Co. were used. For IR analysis, VA contents were determined using calibration curve (absorbance ratio of $1739cm^{-1}/2922cm^{-1}$ or $609cm^{-1}/1464cm^{-1}$) of reference EVAs. Correlation coefficients of the calibration curves were not sufficiently high ($r^2{\leq}0.96$). For NMR analysis, VA contents were determined using peaks of $CH_3$, $CH_2$, and CH. VA contents determined by NMR analysis were less than those marked by suppliers more than 10%. For TGA, VA contents were determined using weight loss through deacetylation. VA contents determined by TGA were slightly different with those marked by suppliers. Difference in the VA contents determined by different analytical methods was discussed, and difference in the analytical results according to the EVA suppliers was also examined.

• Journal of the Korean Wood Science and Technology
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• v.23 no.3
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• pp.28-32
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• 1995

The presteamed or prefrozen persimmon blocks of 10cm ${\times}$ 10cm ${\times}$ 15cm were air-dried at room temperature until about 30% moisture content, and then were dried in a MW oven. During drying their internal temperatures were monitored with thermo-couple probes. The presteamed and prefrozen blocks didn't show any improvement in drying rate and moisture gradient when compared with the controls. Checks appeared on the surfaces of most presteamed blocks during air-drying. It has been clearly revealed that the maximum weight, loss must, be less than 2g/min during MW drying to prevent internal checking and that MW drying reduced moisture gradients inside blocks. MW dried the persimmon blocks 440 times faster than conventional kiln.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.492-492
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• 2009

Nowadays in Republic of Korea, there is no distinct reference for the related design technology of rotor blade of wind turbine. Therefore the optimum design and evaluation of performance is carried out with foreign commercial code softwares. This paper shows in-house code software that evaluates the aerodynamic design of wind turbine rotor blade using blade element-momentum theory (BEMT) and processes that is applied through various aerodynamics theories such as momentum theory, blade element theory, prandtl's tip loss theory and strip theory. This paper presents the results of the numerical analysis such as distribution of aerodynamic properties and performance curves using in-house code POSEIDON.

• The Journal of Engineering Geology
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• v.4 no.2
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• pp.127-138
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• 1994

The stationary dual-porosity model is not sufficient to describe the hydraulic characteristics of fractured aquifers as the groundwater flow in fractured aquifers is often controlled by the fractal geometry of fractures. This study deals with new stationary dual-porosity fractal model. This model simulates pseudo-steady state flow from matrix block to fissure in the fractal aquifer. Furthermore, it considers storage capacity and well loss effect at the production well. Type curves for different flow dimensions with different drainage factors are plotted. This new model has been applied to experimental data. The result of the interpretation shows a good accordance between the theoretical model and the observed data.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.235-238
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• 2005

The seismic fragility analyses of reinforced concrete propelled beam are performed to evaluate safety margin. The models were simulated by Latin Hyper-Cube (LHC) method considering various aging-related deterioration of RC beam. Fragility curves under various condition subjected to static load are compared. It is found that the 20$\%$ loss of top and bottom steel 15$\%$ lower than the undegraded beam in the ultimate strength. Seismic fragility analyses were performed to find out the effect of aging-related deterioration on the dynamic behaviour of RC beam.

• Journal of electromagnetic engineering and science
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• v.1 no.1
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• pp.11-17
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• 2001

In this paper, spherical Luneburg lens antennas have been systematically analyzed using the Eigenfunction Expansion Method (EEM), The developed technique has capability of performing a complete 3-D analysis to characterize the multi-layered dielectric spherical lens with arbitrary permittivity and permeability. This paper describes the analysis technique, and presents the results of the parametric study of Luneburg lens antennas by varying design parameters suoh as the diameter of the lens antenna (up to 80 wavelength), number of spherical shells (up to 30 shells), air-gaps between spherical shells, and dielectric loss of the material. Many representative engineering design curves including the far-field patterns, wide-angle sidelobe characterizations, antenna efficiency have been presented.

• Journal of the Korean Institute of Navigation
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• v.18 no.2
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• pp.159-171
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• 1994

Hull roughness due to corrosions of outer hull and had applications on outer hull paints was analyzed theoretically. It's value which was gainable practically, was studied, and estimated power penalty formular correspon-ding to that value were reviewed. Local roughness penalty and roughness texture penalty that paint manahers in ship yard can easily were compared and studied by dotting actual ships in the issued curves. Losses and benifits of hull roughness & the specification choise of A/F paint which managers of ship maintenance were much interested in have been calculated through actual ships. The paper is illustrating that how much the specification choise and managing of A/F paint have effects on fuel consumption of ship in program. It is urgently required that recent developed antifouling paints of new A/F generation should be adopted to new ship building by big shipping companies in view of the environmental protection and the economical maintenance of ships.

• Journal of international Conference on Electrical Machines and Systems
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• v.2 no.3
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• pp.283-287
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• 2013

This paper presents a method for calculating iron losses in three-phase induction motors under the inverter supply through the field-circuit coupled time-stepping finite element method (FEM). Iron losses are calculated by using the three-term iron losses separated model and modifying the loss coefficients obtained by the iron losses curves which are provided by the manufacturer under the sinusoidal supply. Simulation results by the presented method are verified by the measured results with an error lower than 5%, confirming the validity of the proposed method. Finally, iron losses distribution of the inverter-fed three-phase induction prototype motor is shown.

• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.2166-2168
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• 2005

This paper presents the frequency - dependent characteristics of leakage currents flowing through ZnO varistor. The leakage current - voltage (V-I) characteristic curves of the commercial ZnO varistor were measured. The resistive leakage current was increased with increasing the magnitude and frequency of the applied voltage in the low conduction region. The power losses of ZnO varistor increase as the frequency of applied voltage increases, because of the dielectric loss related to the frequency of the test voltage.

• Journal of the Korean Society of Combustion
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• v.17 no.4
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• pp.38-43
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• 2012

Experimental study was conducted to elucidate flame extinction phenomena in counterflow flame. Using a curtain helium flow significantly reduced buoyancy such that the flame can be positioned at the center between the upper and lower nozzles even at the velocity ratio of 1.0. The curves of critical diluent mole fraction versus global strain rate have C-shapes. The flame oscillation was observed prior to low strain rate flame extinction at both flame conditions with and without minimizing buoyancy force. The results show that, at low strain rate flame, the self-excitation frequency with the order of 1.0 Hz in the case of utilizing pure helium gradually decreases in increase of $N_2$ mole fraction in the curtain flow, meaning that buoyancy suppresses the self-excitation of the outer edge flame.