• Korean Journal of Agricultural and Forest Meteorology
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• v.11 no.4
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• pp.185-191
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• 2009

Few studies have attempted to analyze variations of daily maximum temperature in the summer whereas many studies have analyzed warming trends in other seasons with respect to greenhouse gases or urban heat islands. We analyzed daily maximum temperature data for the summer season (June to August) at 18 locations in South Korea from 1983 to 2007. Compared to the climatic normal (from 1971 to 2000), an average increase of $0.1^{\circ}C$ was found for the summer daily maximum temperature along with an increase of $0.61MJ\;m^{-2}$ in daily solar radiation. Approximately 65% of the annual variations of the summer daily maximum temperature could be explained by the solar radiance alone. Higher atmospheric transmittance due to lower aerosol concentration (especially of sulfur dioxide) is believed to have caused the recent increase in solar irradiance. Daily maximum temperature of the summer is expected to keep rising if the clean air activities are maintained in the future.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.204-207
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• 2003

This paper presents the electrical properties of PTFE (polytetrafluoroethylene) nozzle for circuit breaker. PTFE has been used widely as a nozzle material for circuit breaker. In the arcing environment in a circuit breaker, radiation is considered to be the major energy transport mechanism from the arc to the wall. The fraction of the radiation power is emitted out of the arc and reaches the nozzle wall, causing ablation at the surface and in the depth of the wall. The energy concentration in the material lead to the depolymerization and eventually lead to the generation of decomposed gas as well as some isolated carbon particles. The generation of the decomposed gas in the depth of the material causes inner explosion. The surface of nozzle becomes uneven. The flow of gas is not uniform due to the unevenness of the surface. Adding some fillers into PTFE is expected to be efficient for improving the endurability against radiation. In this experiment, three kinds of fillers that have endurance in the high temperature environment were added into PTFE. Dielectric constant, dissipation factor, electrical resistivity and dielectric strength of PTFE composites were investigated.

• Polymer(Korea)
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• v.35 no.3
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• pp.216-222
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• 2011

A multi-walled carbon nanotube (MWNT) support with dual properties, an ionic property via tetra-amine and unpaired electrons via tri-amine, was prepared by radiation-induced graft polymerization of glycidyl methacrylate (GMA) and the subsequent amination of its epoxy group. The electrochemical microbial biosensor (EMB) was then fabricated by immobilization of a microbe (Alkaligenes spp.) onto the dual property-modified electrode, which was prepared with the mixture of the MWNT support and a $Nafion^{(R)}$ solution on a glass carbon (GC) electrode surface by a hand-casting method. The sensing range of the prepared EMB for phenol in a phosphate buffer solution was 0.005~7.0 mM. The total concentration of phenolic compounds in a commercial red wine was also determined using the EMB.

• Applied Chemistry for Engineering
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• v.19 no.3
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• pp.345-350
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• 2008

Polymer Impregnated Concrete (PIC) prepared from Ordinary Portland Cement Concrete (OPC) has excellent mechanical properties as well as physico-chemical properties. For the manufacturing of PIC, drying process of basis concrete (precast concrete), impregnation process with evacuation system and ultrasonic vibration system, polymerization process of monomers are essential. Modified microwave reactor using magnetron was used for polymerization of styrene/MMA (1 : 1) impregnated in pore volume of basis concrete. From the experimental results, the degree of polymerization increased up to 30% and more homogeneous PIC was prepared as compared to the conventional thermal method. Also the mechanical strengths increased more than 400% ($800{\sim}1200kg_f/cm^2$) and the resistance for corrosion to acids was improved up to 25%. AIBN and BPO as initiators for polymerization were used at the concentration less than 1%. Optimum conditions for polymerization were obtained at the frequency of microwave of 400 W and 2450 MHz, and optimum reaction temperature was $120^{\circ}C$ at an atmospheric pressure.

• Journal of Radiation Industry
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• v.6 no.2
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• pp.153-158
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• 2012

In this research, poly(acrylic acid) (PAAc) hydrogels containing zinc oxide particle were prepared by gamma-ray irradiation. PAAc powder was completely dissolved in distilled water at room temperature. Water-insoluble zinc oxide powder were added into the PAAc solution and stirred until totally dissolved. Finally, the mixture was irradiated by gamma-ray irradiation to make crosslinking. The effects of various parameters such as zinc ions' concentration, irradiation doses were varied and investigated in detail. PAAc hydrogels containing zinc oxide particle were characterized by gel content and swelling ratio. Moreover, the antibacterial properties of this material were evaluated by paper diffusion test against the Gram positive and Gram negative bacteria.

• Nuclear Engineering and Technology
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• v.56 no.7
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• pp.2842-2849
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• 2024

The amorphous glasses containing PbO, ZnO, MgO, and B₂O₃ have been fabricated using the melt quenching technique. The structural properties have been analysed using the Fourier-transform infrared (FTIR) and Raman spectroscopy. Derivative of Absorption Spectra Fitting (DASF) method have been used to estimate the band gap energy from the UV-Vis absorption data which decreases from 3.02 eV to 2.66 eV with increasing the concentration of the PbO.The four glass samples 0.284 and 0.826 MeV showed unique variations in terms of gamma attenuation ability. LZMB4 glass sample proved to be the mist effective in terms of shielding of gamma radiation as it requires little distance compared to LZMB3, LZMB2 and LZMB1 to attenuate. RPE revealed a raise with increase in the thickness of the material and reduces as the energy raises. TF is superior in LZMB1 compared to LZMB2, LZMB3 and LZMB4, confirming that, LZMB4 will attenuate better. The Z_Eff of the materials was seen falling as the energy increases, confirming that the linear attenuation coefficient of the glass materials decreases when the energy is increased. The results confirmed that, glass material LZMB4 is the best option especially for gamma radiation shielding applications compared to LZMB3, followed by LZMB2, then LZMB1.

• Journal of Radiation Industry
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• v.18 no.3
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• pp.155-166
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• 2024

In this study, a liquid scintillation spectrometer was developed for online continuous monitoring of tritium nuclides in water. The device consists of two photoelectron multiplier tubes (PMT), a simultaneous counting circuit, and a signal processing unit including a multi-channel analyzer (MCA). As a method to verify the performance of the equipment developed in this study, samples were prepared using a standard source, and the spectrum of tritium was measured to evaluate the detector characteristics such as efficiency, background (BKG), and minimum detectable activity (MDA). To evaluate the effect of pretreatment on tritium radioactivity measurement results, the MDA of water (seawater and groundwater) samples before and after pretreatment was calculated and compared. The results of the evaluation confirmed the satisfaction of the reference values of the Nuclear Safety Commission's "Discharge Control Standard in Drainage Water" and the World Health Organization's (WHO) "Tritium Radioactivity Concentration for Drinking Water Standards". The liquid scintillation spectrometer developed in this study, with or without pretreatment, confirmed detection performance equivalent to 1/100th of the discharge control standard for drainage water (40,000 Bq L^-1) and the WHO's drinking water standard for tritium radioactivity (10,000 Bq L^-1).

• Korean Journal of Environmental Agriculture
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• v.31 no.1
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• pp.9-15
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• 2012

BACKGROUND: A preliminary investigation of the radon ($^{222}Rn$) concentration has been conducted, employing solid-state nuclear-track detectors (SSNTD) and a continuous radon monitor (CRM), for fourteen randomly selected agricultural greenhouses in Jeju Island, where the underground-air was used for air conditioning and $CO_2$ supplement. METHODS AND RESULTS: The SSNTD was used to measure the average radon concentration for three months and the CRM was used for an instantaneous measurement. In order to obtain the radon concentration of a greenhouse, the SSNTDs were placed at a number of evenly distributed points inside the greenhouse and the mean of the measured values was taken. In addition, in order to assess the radon concentration of the underground-air itself, measurement was also made at the borehole of the underground-air in each agricultural facility, employing both the SSNTD and CRM. It is found that the radon concentration of the greenhouses ranges higher than those not using the underground-air and the average of Korean dwellings. While the radon concentration of most agricultural facilities is still lower than the reference level (1,000 Bq/$m^3$) recommended by the International Radiation Protection Committee (ICRP), three facilities at one site show higher concentrations than the reference level. The three-month-averaged radon concentration and the instantaneous radon concentration of the underground-air itself ranges 1,228- 5,259 and 3,322-17,900 Bq/$m^3$, respectively, and regional variation is more significant. CONCLUSION: From this results, radon concentration of the underground-air is assumed that it is associated with the geological characteristics and the boring depth of the region located of their.

• Radiation Oncology Journal
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• v.12 no.3
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• pp.301-305
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• 1994

Purpose :. To investigate the effect of aqueous extract of Ganoderma lucidum(G.I.) on the surival of tumor cells in vitro and on the growth of tumors in vivo. Materials and Methods : Dried G.I. was made into powder, extracted with distilled water, filtered and diluted from a maximum concentration of 100 mg/ml in sequence. The cytotoxicity of G.I, in vitro was evaluated from its ability to reduce the clonogenicity of SCK tumor cells. For the tumor growth delay study, about $2{\times}10^5$$ of SCK tumor cells were subcutaneously inoculated in the legs of A/J mice. The first experimental group of mice were injected i.p. with 0.2ml of 250 mg/kg of G.I. from the first day after tomor inoculation for 10 days. The second experimental group of mice were injected i.p. with 0.2ml of 250 mg/kg of G.I. either once a day for 10 days or twice a day for 5 days beginining from the 7th day after tumor inoculation Results : 1. Cytotoxicity in vitro;survival fraction, as judged from the curve, at G.I. concentration of 0.5, 1,5, 10, 25, 50 and 100 mg/ml were 1.0, $0.74{\pm}0.03$, $0.18{\pm}0.03$, $0.15{\pm}0.02$, $0.006{\pm}0.002$, 0.015 and 0.0015, respectively. 2. Tumor growth delay in vivo; a) the time required for the mean tumor volume to grow to $1,000mm^3$ was 11 days in the control group and 14 days in the experimental group. b) the time required for tumor volume to increase 4 times was 11 days in the control group while it was 10.5 and 12 days in the groups injected with G.I. once a day and twice a day from the 7th day after tumor inoculation respectively. Conclusion : Aqueous extracts of G.I. showed a marked cytotoxicity on the SCK mammary cells in vitro. Tumor growth delay was statistically signiricant when G.I. in-jection was started soon after tumor inoculation, but it was not significant when injection was started after the tumors were firmly established.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.17
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• pp.7297-7301
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• 2014

Objective: To explore the radiosensitization effect of overexpression of silent information regulator 6 (SIRT6) on A549 non-small cell lung cancer (NSCLC) cells. Methods: Adenovirus vector Ad-SIRT6 causing overexpression of SIRT6 was established. Western blotting and MTT assay were adopted to detect the level of SIRT6 protein and the inhibitory rate of A549 cell proliferation after different concentrations of adenovirus transduction (0, 25, 100, 200, and 400 pfu/cell) for 24 h. Control group, Ad-null group and Ad-SIRT6 group were designed in this experiment and virus concentration of the latter two groups was 200 pfu/cell. Colony formation assays were employed to test survival fraction (SF) of the 3 groups after 0, 2, 4, 6, 8, 10 X-ray irradiation. Flow cytometry was used to detect the status of cell cycle of 3 groups after 48 h of 4Gy X-ray irradiation and Western blotting was used to determine the expression of apoptosis-related genes of 3 groups after 48 h of 4GyX-ray irradiation. Results: In the range of 25~400 pfu/cell, the inhibitory rate of A549 cell proliferation increased as adenovirus concentration raised. The inhibitory rates under the concentrations of 0, 25, 100, 200, and 400 pfu/cell were 0%, $4.23{\pm}0.34%$, $12.7{\pm}2.57%$, $22.6{\pm}3.38%$, $32.2{\pm}3.22%$, $38.7{\pm}4.09%$ and $47.8{\pm}5.58%$ and there were significantly differences among groups (P<0.05). SF in Ad-SIRT6 group was lower than Ad-null and control groups after 4~10Gy X-ray irradiation (P<0.05) and the sensitization enhancement ratio (SER) was 1.35 when compared with control group. Moreover, after 48 h of 4Gy X-ray irradiation, there appeared a significant increase in G1-phase cell proportion, upregulated expression of the level of apoptosis-promoting genes (Bax and Cleaved caspase-3), but a obvious decline in S-phase and G2-phase cell proportion and a significant decrease of the level of apoptosis-inhibiting gene (Bal-2) in the Ad-SIRT6 group (P<0.05). Conclusion: The over-expression of adenovirus-mediated SIRT6, which has radiosensitization effect on A549 cells of NSCLC, can inhibit the proliferation of A549 cells and cause G0/G1 phase retardation as well as induce apoptosis of cells.