• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.16 no.3
• /
• pp.247-254
• /
• 1983

In previous paper (Lee and Kim, 1983) the effect of moisture level and frequency on dielectric properties of sardine starch paste was mentioned. The effect of temperature and starch content of the paste upon dielectric permittivity and activation energy was discussed in this report. Addition of starch affected on dielectric property. Increases of starch in the mixtures resulted in higher complex permittivity and lower critical moisture content (hc) as shown in the mixtures with $20\%$ and $50\%$ starch which were ${\varepsilon}^{\ast}=2.97+j0.36,\;hc=8.0\%;\;{\varepsilon}^{\ast}=3.54+j0.44,\;hc=7.8\%$, respectively while being ${\varepsilon}^{\ast}=2.73+j0.29,\;hc=8.4\%$ for the plain ground sardine meat. When temperature was raised the complex permittivity tended to increase at above the critical moisture content in all cases. The activation energies for plain ground meat and $30\%$ starch added mixture at below the critical moisture of $8.4\%$ were 15.44 kcal/mol and 13.86 kcal/mol while those at the moisture of $12.2\%$ were 10.27 kcal/mol and 9.31 kcal/mol, respectively.

• Journal of the Korean Ceramic Society
• /
• v.29 no.10
• /
• pp.822-826
• /
• 1992

SiO2 doped sapphire single crystals were grown by Verneuil method using feed material which prepared by adding SiO2 in Al2O3. Crystal growing were attempted with varing doping amount of SiO2 from 0.01 to 1.0 wt% and when the doping amount of SiO2 were 0.01~0.04 wt%, single crystals could be attained. Starting materials for feed powder were 99.99% purity alumina and extra pure SiO2 powder. Mixing these two materials by wet milling for 24 hours and drying the mixture and then was calcined at 900~110$0^{\circ}C$ for 2~4 hours. The grown crystals had yellowish color and were somewhat transparent. During growing process the flow range of oxygen was 5~7.5ι/min and of hydrogen was 13~25ι/min, the average growth rate was 7.0~11 mm/hr. The pressure of gases were fixed at 5psi. The color of crystal was appeared and mechanical property of sapphire was developed by doping of SiO2.

• Journal of Hydrogen and New Energy
• /
• v.21 no.2
• /
• pp.129-135
• /
• 2010

Homogeneous charge compression ignition (HCCI) engines have the potential to provide both diesel-like efficiency and very low emissions of nitrogen oxide (NOx) and particulate matter(PM). However, several technical issues still must be resolved before HCCI can see application. Among these, steep pressure-rise rate which leads to narrow operating range of HCCI engine continues to be a major issue. This work investigates the combination of two methods to mitigate the excessive pressure-rise rates at high power output, namely fuel stratification and Cooled exhaust-gas recirculation (Cooled EGR), after identifying the each effects to pressure-rise rate. When applying the fuel stratification to simulation, total fuelling width of 0.15 at BDC is set as a equivalent ratio difference based on the previous research. In order to simulate the effects of cooled EGR, $CO_2$ mole fraction in pre-mixture is changed ranging from 0 to 30%. DME which has a characteristic of two-stage ignition is used as a fuel.

• Journal of Korean Society of Environmental Engineers
• /
• v.22 no.1
• /
• pp.133-139
• /
• 2000

In this study, activated carbon was prepared from solid residue after lignin pyrolysis by using zinc chloride as an activation agent. The steam activation method was adopted to manufacture activated carbon from solid residue after lignin pyrolysis. The effect of process operation variables such as activation temperature, activation time and mass of activation agent added to char on the pore structure and specific surface area of the activated carbon was investigated. Activated carbon with high surface area and well-developed pore structure could be prepared, when solid residue after lignin pyrolysis was mixed with zinc chloride of 300 wt% and then the mixture was activated for 1 hour at $1000^{\circ}C$ in a stream of nitrogen.

• Nuclear Engineering and Technology
• /
• v.50 no.6
• /
• pp.944-949
• /
• 2018

The mass attenuation coefficients (${\mu}/{\rho}$) of food waste samples (pomegranate peel, acorn cap, lemon peel, mandarin peel, pumpkin peel, grape peel, orange peel, pineapple peel, acorn peel and grape stalk) have been measured employing a Si(Li) detector at 13.92, 17.75, 20.78, 26.34 and 59.54 keV. Also, the theoretical values of the mass attenuation coefficients have been evaluated utilizing mixture rule from WinXCOM program. The results showed that the lemon peel has the highest values of ${\mu}/{\rho}$ among the selected samples. From the obtained mass attenuation coefficients, we determined some absorption parameters such as effective atomic number ($Z_{eff}$), electron density ($N_E$) and molar extinction coefficient (${\varepsilon}$). It was found that the $Z_{eff}$ values of all food wastes lie within the range of 4.034-7.595, whereas the $N_E$ of the studied food wastes was found to be in the range of $0.301-1.720{\times}10^{25}$ (electrons/g) for present energy region.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.08a
• /
• pp.256-256
• /
• 2013

Carbon nanotubes (CNT) / polyvinylidene fluoride (PVDF) piezoelectric composite films for nanogenerator devices were fabricated by spray coating method. When the CNT/PVDF mixture solution passes through the spray nozzle with small diameter by the compressed nitrogen gas, electric charges are generated in the liquid by a triboelectric effect. Then randomly distributed ${\beta}$ phase PVDF film could be re-oriented by the electric field resulting from the accumulated electrical charges, and might be resulted in extremely one-directionally aligned ${\beta}$ phase PVDF film without additional electric field for poling. X-ray diffraction patterns were used to investigate crystal structure of the CNT/PVDF composite films. It was confirmed that they revealed extremely large portion of the ${\beta}$ phase PVDF crystalline in the film. Therefore we could obtain the poled CNT/PVDF piezoelectric composite films by the spray coating method without additional poling process. Charge accumulation and resulting electric field generation mechanism by spray coating method were shown in Fig. 1. The capacitance of the CNT/PVDF films increased by adding CNTs into the PVDF matrix, and finally saturated. However, the I-V curves didn't show any saturation effect in the CNT concentration range of 0~4 wt%. Therefore we can control the performance of the devices fabricated from the CNT/PVDF composite film by adjusting the current level resulted from the CNT concentration with the uniform capacitance value.

• Steel and Composite Structures
• /
• v.25 no.6
• /
• pp.649-661
• /
• 2017

This paper is motivated by the lack of studies in the technical literature concerning to the influence of carbon nanotubes (CNTs) waviness and aspect ratio on the vibrational behavior of functionally graded nanocomposite annular sector plates resting on two-parameter elastic foundations. The carbon nanotube-reinforced (CNTR) plate has smooth variation of CNT fraction based on the power-law distribution in the thickness direction, and the material properties are also estimated by the extended rule of mixture. In this study, the classical theory concerning the mechanical efficiency of a matrix embedding finite length fibers has been modified by introducing the tube-to-tube random contact, which explicitly accounts for the progressive reduction of the tubes' effective aspect ratio as the filler content increases. Parametric studies are carried out to highlight the influence of CNTs volume fraction, waviness and aspect ratio, boundary conditions and elastic foundation on vibrational behavior of FG-CNT thick sectorial plates. The study is carried out based on three-dimensional theory of elasticity and in contrary to two-dimensional theories, such as classical, the first- and the higher-order shear deformation plate theories, this approach does not neglect transverse normal deformations. The annular sector plate is assumed to be simply supported in the radial edges while any arbitrary boundary conditions are applied to the other two circular edges including simply supported, clamped and free. For an overall comprehension on 3-D vibration of annular sector plates, some mode shape contour plots are reported in this research work.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.32 no.1
• /
• pp.34-39
• /
• 1987

This study was conducted to find out the adequate cutting method for propagation and the optimum treat-ing time of GA$_3$ to enhance the fruit setting of Pepino (Solanum muricatum AIT). Mixture of peat moss (50%) and vermiculite (50%) shows the best rooting for the Pepino stem cuttings. An active rooting was observed 15 days after the cuttings were treated with 1,000 ppm of NAA. Application of GA$_3$ at flowering stage was effective for fruit setting of Pepino and fruit setting was the most satisfactory when GA$_3$ was sprayed over the flowers.

• Computers and Concrete
• /
• v.34 no.2
• /
• pp.195-212
• /
• 2024

The use of basalt fibers in various types of fiber-reinforced mortars has been increasing. One of the factors that expands the use of basalt fibers is that it is a natural fiber and therefore the production costs are lower than fibers such as PVA fiber. Basalt fibers have some drawbacks such as reducing the workability of mortars in which basalt fibers are added due to their structure, and negatively affecting the mechanical properties when used above a certain proportional amount depending on the type of mixture. For this purpose, in this study, as a different application, the surface of basalt fibers with different lengths (6 and 12 mm) was treated with Triton X-100 surfactant, and these disadvantages were tried to be reduced. In the study, a two-step method was followed. In the first one, the effectiveness of adding untreated and treated basalt fiber at 1, 1.25, 1.5, 1.75 and 2% by weight to the mortar mixtures was determined by conducting flow spread and flow rate as fresh mortar characteristics. In the second one, microstructural characterization and mechanical tests were performed as hardened mortar properties. The results showed that the flow characteristics of basalt fiber reinforced mortars treated with surfactant improved compared to untreated basalt fiber reinforced mortars. In terms of mechanical properties, the addition of 2% treated basalt fiber by weight to the mixtures allowed to obtain %18, %12, and%48 higher values of compressive, flexural, and tensile strength values, respectively, compared to the same amount of untreated basalt fiber mixtures.

• Journal of Ceramic Processing Research
• /
• v.23 no.4
• /
• pp.535-540
• /
• 2022

Atmospheric pressure plasma (APP) systems operate at atmospheric pressure and low temperatures, eliminating the need forvacuum systems such as vacuum chambers and pumps. In this paper, we studied that silicon dioxide thin films were formedat room temperature (25 oC) and 400 oC by APP processes on silicon wafers. A mixture of hexamethyldisilazane, oxygen,helium, and argon was supplied to the plasma apparatus to form the SiO2 layer. It was observed that a heat insulating layerhaving a thickness of about 22 nm at 25 oC and about 75 nm at 400 oC was formed. Although the surface was clean in samplestreated at 400 oC, small grains were observed in samples processed at room temperature. However, no void or defect in allsamples is observed inside the thin film from the surface. The physical property of the SiO2 thin film carried out by measuringrefractive index and density. The experimental refractive index of silicon dioxide grown by applying heat can be fitted to theSellmeier equation. Also, the film density of the sample at 400 oC using a XRR was observed to be 2.25 g/cm3, similar to thatof the glass, but that of the sample treated at room temp. was very low at 1.68 g/cm3. We also investigated the voltagedependentcurrent change in the oxide material. The SiO2 layer coated at room temperature showed a breakdown electricalfield of 2.5 MV/cm, while oxides deposited at 400 oC showed a characteristic of 9.9 MV/cm.