Soon Hong Kwon

Development of a Hydroponic Recycle System using the Visible Light-reactive Titanium Dioxide Photocatalyst for Sterilization of Nutrient Solution(I) - Determination of factors -

We produced a basic system of sterilization of nutrient solution based on the characteristics of coated filter with the visible light-reactive titanium oxide photocatalyst according to the findings of the first stage. We developed a model system with a proper number and arrangement of filter elements, the visible light-reactive titanium oxide photocatalyst according to findings from the basic performance test. Main results of this study were as followers; The ceramic filters showed the best performance of sterilization of nutrient solution. The visible light-reactive titanium oxide photocatalyst sterilized more effectively the nutrient solution under the sunlight than UV light. The sterilization performance by passing repeatedly through a few filter was more efficient than that by treating simultaneously with a large number of filters. The filter with 15ppi in pore size, 20 mm in thickness, and 3 layers in titanium oxide coating was desirable in the intensity and sterilization performance.

Understanding Phytosanitary Irradiation Treatment of Pineapple Using Monte Carlo Simulation

th , 2013; Revised: May 17 th , 2013; Accepted: May 21 th , 2013 Purpose: Pineapple is now the third most important tropical fruit in wor ld production after banana and citrus. Phytosanitary irradiation is recognized as a promising alternative treatment to chemical fumigation. However, most of the phytosanitary irradiation studies have dealt with physiochemica l properties and its efficacy. Accurate dose calculation is crucial for ensuring proper process control in phytosanitary ir radiation. The objective of this study was to optimize phytosanitary irradiation treatment of pineapple in various radiation sources using Monte Carlo simulation. Methods: 3-D geometry and component densities of the pineapple, extracted from CT scan data, were entered into a radiation transport Monte Carlo code (MCNP5) to obtain simulated dose distribution. Radiation energy used for simulation were 2 MeV (low-energy) and 10 MeV (high-energy) for electron beams, 1.25 MeV for gamma-rays, and 5 MeV for X-rays. Results: For low-energy electron beam simulation, electrons penetrated up to 0.75 cm from the pineapple skin, which is good for controlling insect eggs laid just below the fruit surface. For high-energy electron beam simulation, electrons penetrated up to 4.5 cm and the irradiation area occupied 60.2% of the whole area at single-side irradiation and 90.6% at double-side irradiation. For a single-side only gamma- and X-ray source sim ulation, the entire pineapple was irradiated and dose uniformity ratios (Dmax/Dmin) were 2.23 and 2.19, respectively. Even though both sources had all greater penetrating capability, the X-ray treatment is safer and the gamma-ray treatment is more widely used due to their availability. Conclusions: These results are invaluable for optimizing phytosanitary irradiation treatment planning of pineapple.

Comparative Study on Efficiencies of Naturally-Ventilated Multi-Span Greenhouses in Korea

This research analyzed the ventilation effect of the multi-span greenhouse based on the types of greenhouse structure, weather conditions, and locations inside the greenhouse. To compare and analyze the ventilation effects with different types of greenhouse, the uniform environmental conditions should be selected in advance. But these factors are not controlled and require tense many precision facilities and labor forces. Thus, the CFD simulation was used for the air stream to be analyzed qualitatively and quantitatively. In addition, for the ventilation effect analysis, the TGD (Tracer Gas Decay) was used to overcome the shortcomings of the current ventilation measurement method. The calculation error of ventilation rate using TGD was low (10.5%). Thus, the TGD is very effective in calculating the ventilation efficiency. The wind direction of 90 degrees showed the best ventilation effect. The ventilation rate also decreased along the air circulation path, and the rate was the lowest around the outlet. The computed fluid method (CFD) turned out to be a power tool for simulating flow behavior in greenhouse.

The Friction and Wear Characteristic Comparison of PMMA and MC Nylon as Spreading Device Pad Material in Copper Coil Forming

The purpose of this study is to compare the frictions and wears characteristics of poly methyl methacrylate (PMMA) and MC Nylon. This study was carried out to investigate the material to be considered as the pad of spreading device material in the copper coil forming machine. To analyze the friction and wear characteristics of those materials the experiments were done as follows. Firstly, the friction characteristic was obtained using a pin-on-disk tester. The experiment was carried on dry and wet friction conditions under paraffin oil lubricant. Secondly, the state of lubrication was investigated using the Stribeck’s Curve. Thirdly, to investigate the wear characteristic, the weight of the pin was measured before and after the friction test. The wear rate is defined as the difference between the initial weight and the final weight. The experimental results show that the friction coefficient of PMMA material was higher than MC nylon. Furthermore, PMMA wear rate also higher than MC Nylon wear rate. The highest wear was achieved on PMMA in dry friction condition, which is 0.00290 grams. MC Nylon was recommended to be used as padding of the spreading device on the coil forming machine.

Monte Carlo Simulation of Phytosanitary Irradiation Treatment for Mangosteen Using MRI-based Geometry

Purpose: Phytosanitary irradiation treatment can effectively control regulated pests while maintaining produce quality. The objective of this study was to establish the best irradiation treatment for mangosteen, a popular tropical fruit, using a Monte Carlo simulation. Methods: Magnetic resonance image (MRI) data were used to generate a 3-D geometry to simulate dose distributions in a mangosteen using a radiation transport code (MCNP5). Microsoft Excel with visual basic application (VBA) was used to divide the image data into seed, flesh, and rind. R adiation energies used for the simulation were 10 MeV (high-energy) and 1.35 MeV (low-energy) for the electron beam, 5 MeV for X-rays, and 1.25 MeV for gamma rays from Co-60. Results: At 5 MeV X-rays and 1.25 MeV gamma rays, all areas (seeds, flesh, and rind) were irradiated ranging from 0.3 ~ 0.7 kGy. The average doses decreased as the number of fruit increased. For a 10 MeV electron beam, the dose distribution was biased: the dose for the rind where the electrons entered was 0.45 ± 0.03 kGy and the other side was 0.24 ± 0.10 kGy. Use of an electron kinetic energy absorber improved the dose distribution in mangosteens. For the 1.35 MeV electron beam, the dose was shown only in the rind on the irradiated side; no significant dose was found in the flesh or seeds. One rotation of the fruit while in front of the beam improved the dose distribution around the entire rind. Conclusion: These results are invaluable for determining the ideal irradiation conditions for phytosanitary irradiation treatment of tropical fruit.