• Applied Chemistry for Engineering
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• v.7 no.6
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• pp.1132-1141
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• 1996

Heterogeneous cation exchange membrane(HCEM) was prepared with LLDPE(Linear Low Density Poly-ethylene) as binder, powdered cation exchange resins($diameter{\leq}149{\mu}m$) as ion-exchange material and glycerol as additive for electrodialysis and electrodeionization system. The weight ratio of (binder/ion exchange)/glycerol was (60%/40%)/5%, (55%/45%)/5%, (50%/50%)/5% and (40%/60%)/5%. The characterization of prepared HCEM was evaluated on mechanical, electrochemical, morphology and ion permeable properties. It was compared with commercial membrane. Electrochemical properties of HCEM of (50%/50% )/5% were very similar to value of IONPURE(commercial membrane), in which ion exchange capacity, ion transfer number and membrane resistance were to be 1.733meq/g, 0.96 and $16.08{\Omega}/cm^2$, respectively. Ion permeability of the membrane was better than that of IONPURE membrane. Compared with IONPURE membrane, the HCEM had a higher tensile strength and lower elongation and modulus, in which HCEM had tensile strength of $62.33kg/cm^2$, elongation of 87.42% and modulus of $658.53kg/cm^2$. The HCEM of (50%/50% )15% was optimum combination.

• Journal of the Korean Solar Energy Society
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• v.32 no.4
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• pp.24-33
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• 2012

Recently, finishing materials at spandrel area, a part of curtain-wall system, are gradually forced to improve thermal insulation performance in order to enhance the building energy efficiency. Also, Building Integrated Photovoltaics(BIPV) systems have been installed in the exterior side of the spandrel area, which is generally composed of windows. Those BIPVs aim to achieve high building energy efficiency and supply the electricity to building. However, if transparent BIPV module is combined with high insulated spandrel, it would reduce the PV efficiency for two major reasons. First, temperature in the air space, located between window layer and finishing layer of the spandrel area, can significantly increase by solar heat gain, because the space has a few air density relative to other spaces in building. Secondly, PV has a characteristics of decreased Voltage(Voc and Vmp) with the increased temperature on the PV cell. For these reasons, this research analyzed a direct interrelation between PV Cell temperature and electricity generation performance under different insulation conditions in the spandrel area. The different insulation conditions under consideration are 1) high insulated spandrel(HIS) 2) low insulated spandrel(LIS) 3) PV stand alone on the ground(SAG). As a result, in case of 1) HIS, PV temperature was increased and thus electricity generation efficiency was decreased more than other cases. To be specific, each cases' maximum temperature indicated that 1) HIS is $83.8^{\circ}C$, 2) LIS is $74.2^{\circ}C$, and 3) SAG is $66.3^{\circ}C$. Also, each cases yield electricity generation like that 1) HIS is 913.3kWh/kWp, 2) LIS is 942.8kWh/kWp, and 3) SAG is 981.3kWh/kWp. These result showed that it is needed for us to seek to the way how the PV Cell temperature would be decreased.

• Korean Journal of Optics and Photonics
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• v.28 no.4
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• pp.153-157
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• 2017

An infrared camera and laser common-path optical system is applied to DIRCM (directional infrared countermeasures), to increase boresighting accuracy and decrease weight. Thermal effects of a laser beam in a common-path optical system are analyzed and evaluated, to predict any degradation in image quality. A laser beam with high energy density is absorbed by and heats the optical components, and then the surface temperature of the optical components increases. The heated optical components of the common-path optical system decrease system transmittance, which can degrade image quality. For analysis, the assumed simulation condition is that the laser is incident for 10 seconds on the mirror (aluminum, silica glass, silicon) and lens (sapphire, zinc selenide, silicon, germanium) materials, and the surface temperature distribution of each material is calculated. The wavelength of the laser beam is $4{\mu}m$ and its output power is 3 W. According to the results of the calculations, the surface temperature of silica glass for the mirror material and sapphire for the lens material is higher than for other materials; the main reason for the temperature increase is the absorption coefficient and thermal conductivity of the material. Consequently, materials for the optical components with high thermal conductivity and low absorption coefficient can reduce the image-quality degradation due to laser-beam thermal effects in an infrared camera and laser common-path optical system.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.236-236
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• 2008

(Bi,La)$Ti_3O_{12}$(BLT) thin film is one of the most attractive materials for ferroelectric random access memory (FRAM) applications due to its some excellent properties such as high fatigue endurance, low processing temperature, and large remanent polarization [1-2]. The authors firstly investigated and reported the damascene process of chemical mechanical polishing (CMP) for BLT thin film capacitor on behalf of plasma etching process for fabrication of FRAM [3]. CMP process could prepare the BLT capacitors with the superior process efficiency to the plasma etching process without the well-known problems such as plasma damages and sloped sidewall, which was enough to apply to the fabrication of FRAM [2]. BLT-CMP characteristics showed the typical oxide-CMP characteristics which were related in both pressure and velocity according to Preston's equation and Hernandez's power law [2-4]. Good surface roughness was also obtained for the densification of multilevel memory structure by CMP process [3]. The well prepared BLT capacitors fabricated by CMP process should have the sufficient ferroelectric properties for FRAM; therefore, in this study the electrical properties of the BLT capacitor fabricated by CMP process were analyzed with the process parameters. Especially, the effects of CMP pressure, which had mainly affected the removal rate of BLT thin films [2], on the electrical properties were investigated. In order to check the influences of the pressure in eMP process on the ferroelectric properties of BLT thin films, the electrical test of the BLT capacitors was performed. The polarization-voltage (P-V) characteristics show a decreased the remanent polarization (Pr) value when CMP process was performed with the high pressure. The shape of the hysteresis loop is close to typical loop of BLT thin films in case of the specimen after CMP process with the pressures of 4.9 kPa; however, the shape of the hysteresis loop is not saturated due to high leakage current caused by structural and/or chemical damages in case of the specimen after CMP process with the pressures of 29.4 kPa. The leakage current density obtained with positive bias is one order lower than that with negative bias in case of 29.4 kPa, which was one or two order higher than in case of 4.9 kPa. The high pressure condition was not suitable for the damascene process of BLT thin films due to the defects in electrical properties although the better efficiency of process. by higher removal rate of BLT thin films was obtained with the high pressure of 29.4 kPa in the previous study [2].

• Restorative Dentistry and Endodontics
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• v.25 no.1
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• pp.109-115
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• 2000

This study was designed to evaluate the microhardness of restorative composite resin and dual-cured composite resin cement which were light cured through the 1.5mm thickness composite overlay. For restorative materials, Z100 and Tetric Ceram were used. For dual cured composite cements, Variolink II((VL II) of three consistency (low, high, ultra high) were used. To determine the optimal microhardness of Z100, Tetric Ceram and Variolink II, each material was packed into the 1mm thickness teflon mold without composite overlay and light cured for 60 seconds. Then the microhardnesses of each sample were measured, averaged and regarded as optimal hardness of each material. To evaluate the microhardness of restorative composite resin and dual-cured composite resin cement which were light cured through the 1.5mm thickness composite overlay, the composites were packed into 1mm thickness teflon mold, coverd with celluloid strip, and then precured composite overlay which was made of Targis(Ivoclar/Vivadent, Liechtenstein) was positioned. 2 types of visible light curing machine, the power density of one of which was 400$mW/cm^2$ and the other was 900$mW/cm^2$, and one type of argon laser were used to cure the restorative composite and dual cured cement. For each group, 10 sample were assigned. The light curing tip was positioned over the composite overlay and light cured for 1min., 2min. or 3min with visible light curing machine or 15sec, 30 sec, 45sec, and 60 sec with argon laser. The Vickers hardnesses of upper and lower surface of Z100, Tetric Ceram, and 3 types of VL II cement were measured. When the 900 $mW/cm^2$ curing light was used, 2min. was needed for optimal curing of Z100 and Tetric Ceram. Variolink II did not be cured optimally even though the curing time was extended to 3min. When 400$mW/cm^2$ curing light was used, 3min. was necessary for Z100, whereas 3min. was not enough for Tetric Ceram. Variolink II was not cured optimally even though the curing time was extended to 3min. When argon laser was used, Z100, Tetric Ceram and Variolink II were not cured optimally in 60 seconds.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.3
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• pp.253-259
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• 2021

Plastic wastes generated from household waste are separated by mixed discharge with foreign substances, and recycling is relatively low. In this study, the effect of the ratio and content of mixed plastic waste coarse aggregate(MPWCA)s and mixed plastic waste fine aggregate(MPWFA)s filled with blast furnace slag fine powder on the slump and compressive strength of concrete was evaluated experimentally. The MPWCAs were found to have a similar fineness modulus, but have a single particle size distribution with a smaller particle size compared to coarse aggregates. However, the MPWFAs were found to have a single particle size distribution with a larger fineness modulus and particle size compared to fine aggregates. Meanwhile, the effect of improving the density and filling pores by the blast furnace slag fine power was found to be greater in the MPWFA compared to the MPWCA. As the amount of the mixed plastic waste aggregate(MPWA)s increased, the slump and compressive strength of concrete decreased. In particular, the lower the slump and compressive strength of concrete was found to decrease the greater the amount of MPWFA than MPWCA when the amount of MPWA was the same. This is because of the entrapped air and voids formed under the angular- and ROD-shaped aggregates among the MPWFAs. On the other hand, the addition of the admixture and the increase in the unit amount of cement were found to be effective in improving the compressive strength of the concrete with MPWAs.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.1
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• pp.21-27
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• 2019

R-404A, which is used widely in small-scale ice makers, is scheduled to be phased out because of its high global warming potential. In this study, drop-in tests were conducted using R-448A and R-449A, which replace R-404A, to modify the outdoor air and supply water temperatures. The results showed that the daily ice production rate of R-404A was 5.3% higher than that of R-448A and 4.2% higher than that of R-449A. This was attributed to the larger vapor density of R-404A, which resulted in a larger mass flow rate in the system. Between R-448A and R-449A, R-448A yielded a larger amount of ice at low air and water temperatures, whereas R-449A yielded a larger amount of ice at high air and water temperatures. The daily power consumption of R-404A was approximately 10% larger than those of R-448A and R-449A. The resulting COPs of R-448A and R-449A was similar, only 3.0% larger than that of R-404A. The literature survey showed that the condensation or evaporation data of R-448A or R-449A are very limited, and research on this issue is recommended.

• Composites Research
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• v.32 no.5
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• pp.284-289
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• 2019

In the present paper, the dynamic force-moment equilibrium equations, driving power and energy equations are analyzed to formulate the equation for fuel economy(km/liter) equivalent to the driving distance (km) divided by the fuel volume (liter) of the vehicle, a selected model of gasoline powered KIA K3 (1.6v). In addition, the effects of the dynamic parameters such as speed of vehicle (V), vehicle total weight(M), rolling resistance ($C_r$) between tires and road surface, inclined angle of road (${\theta}$), as well as the aerodynamic parameters such as drag coefficient ($C_d$) of vehicle, air density(${\rho}$), cross-sectional area (A) of vehicle, wind speed ($V_w$) have been analyzed. And the possibility of alternative materials such as lightweight metal alloys, fiber reinforced plastic composite materials to replace the conventional steel and casting iron materials and to reduce the weight of the vehicle has been investigated by Ashby's material index method. Through studies, the following results were obtained. The most influencing parameters on the fuel economy at high speed zone (100 km/h) were V, the aerodynamic parameters such as $C_d$, A, ${\rho}$, and $C_r$ and M. While at low speed zone (60 km/h), they are, in magnitude order, dynamic parameters such as V, M, $C_r$ and aerodynamic ones such as $C_d$, A, and ${\rho}$, respectively.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.33 no.6
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• pp.217-225
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• 2021

In this study, wave spectrum data were calculated using the water surface elevation data observed at 5Hz intervals from the HeMOSU-2 meteorological tower installed on the west coast of Korea, and wave parameters were estimated using wave spectrum data. For all significant wave height ranges, the peak enhancement parameter (γ_opt) of the JONSWAP spectrum and the scale parameter (α) and shape parameter (β) of the modify BM spectrum were estimated based on the observed spectrum, and the distribution of each parameter was confirmed. As a result of the analysis, the peak enhancement parameter (γ_opt) of the JONSWAP spectrum was calculated to be 1.27, which is very low compared to the previously proposed 3.3. And in the range of all significant wave heights, the distribution of the peak enhancement parameter (γ_opt) was shown as a combined distribution of probability mass function (PMF) and probability density function (PDF). In addition, the scale parameter (α) and shape parameter (β) of the modify BM spectrum were estimated to be [0.245, -1.278], which are lower than the existing [0.300, -1.098], and the result of the linear correlation analysis between the two parameters was β = -3.86α.

• Korean Journal of Agricultural Science
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• v.20 no.1
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• pp.68-87
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• 1993

Data acquisition system and computer program developed in this study could be well used in engine vibration analysis. The system and program developed were also operated to be able to control measuring interval, number of channels, number of data. The flywheel was specially studied to provide the proper weight with rubber damper for the engine design at low level of vibration. This study was conducted to obtain basic data which affect the engine vibration. The experiment of this study was performed on original weight flywheel, weight-reduced flywheel, weight-reduced and rubber-coated flywheel, weight-reduced and damper-attached flywheel. Avarage of peak value, maximum vibration, power spectrum density based on FFT analysis are major factors of this experiment. Results were obtained as follows : 1. When rubber was inserted in the flywheel rim of which weight was reduced from 32.2kgf to 24.4kgf, maximum vibration of the engine was decreased 48.3% at X axis, 35.5% at Y axis and 34.6% at Z axis in comparison with the flywheel of original weight. 2. When the flywheel of rubber damper was compared with the original flywheel, the average of absolute vibration for rubber damped flywheel was decreased at X, Y, Z axis and especially its decreasing rate was so high at X-axis comparing with the other flywheel, which implied that rubber damper was very useful to reducing the vibration of the engine at X axis. 3. Hysteresis losses of X, Y, Z axis were greatly decreased in the flywheel with rubber damper on rim. 4. Damped oscillation effect on X and Y axis vibration above average peak vibration by the flywheel of rubber damper on rim was larger than those by the other flywheels. 5. Power spectrums of vibration at real and imaginery part were bi-mode type. The vibration frequency of rubber dampered flywheel which weight is decreased was slightly increased as compared with original flywheel.