• Current Optics and Photonics
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• v.6 no.2
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• pp.202-211
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• 2022

In the pasteurization of escalator handrails using ultraviolet (UV) sterilizers, a combination of light distribution and escalator speed has priority over other important factors. Furthermore, since part of the escalator handrail has a curved structure, proper design is needed to improve the sterilization rate on the surfaces touched by users. In this paper, two types of sterilizers satisfying these conditions are manufactured with 275-nm UV-C LEDs, after modeling the three-dimensional (3D) structure of an escalator handrail and simulating optical distributions of UV-C irradiation on the handrail's surface according to light-emitting diode (LED) positions and reflector variations in the sterilizers. Pasteurization experiments with the UV-C LED sterilizers are conducted on six types of gram-positive and gram-negative bacteria, with exposure times of 0.2, 5, and 15 s at an actual installation distance of 20 mm. The sterilization rates for the gram-positive bacteria are 10.63% to 27.94% at 0.2 s, 89.44% to 96.30% at 5 s, and 99.64% to 99.88% at 15 s. Those for the gram-negative bacteria are 57.70% to 77.63% at 0.2 s, 98.90% to 99.49% at 5 s, and 99.88% to 99.99% at 15 s. The power consumption of the UV-C LED sterilizer is about 8 W, which can be supplied by a self-generation module instead of an external power supply.

• Korean Journal of Food Science and Technology
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• v.45 no.2
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• pp.248-251
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• 2013

The purpose of this study was to investigate the inactivation effect of intense pulsed light (IPL) on Micrococcus roseus, an irradiation-resistant bacterium isolated from laver, and the commercial feasibility of this sterilization method on dried laver. The inactivation of M. roseus in cultivated plates increased with increasing light intensity and treatment time. Approximately 6.6 log CFU/mL reduction of the cell viability was achieved with IPL treatment for 3 min at 1,000 V of light intensity, tailing was not shown. In addition, the inactivation rate of M. roseus increased with increasing pulse number at same light intensity and treatment time. The killing efficiency for M. roseus increased with by decreasing the distance between the light source and the sample surface.

• Journal of Korean Society of Forest Science
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• v.101 no.1
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• pp.77-82
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• 2012

Sterilization of oak sawdust at $65^{\circ}C$ for Lentinula edodes bed cultivation can be efficient in sterilization facility cost, but its effect on the mushroom production is uncertain due to high contamination probability. The effective conditions for L. edodes hyphal growth in the low temperature sterilized oak sawdust were investigated with combinations of three sterilization temperatures ($65^{\circ}C$, $100^{\circ}C$ and $121^{\circ}C$) and four cultivation temperatures ($15^{\circ}C$, $20^{\circ}C$, $25^{\circ}C$, and $30^{\circ}C$). L. edodes inoculation density effect was also tested with 1 cm, 2 cm, and 4 cm distance in the sawdust (4%, 11% and 25% inoculation rate by surface area). L. edodes hyphal growth in the sawdust sterilized at $65^{\circ}C$ was as much as at those $100^{\circ}C$ and $121^{\circ}C$ when the fungus cultured below $25^{\circ}C$, but it was greatly reduced when cultured at $30^{\circ}C$. And the sawdust medium with 1cm distance inoculation density was fully occupied with L. edodes hyphae, but those with 2~4cm distance inoculation were contaminated by 4~33%. Therefore, we conclude that low temperature sterilized oak sawdust needs to be cultured under $25^{\circ}C$ after sufficient inoculation by 25% for successful bed cultivation of L. edodes.

• Restorative Dentistry and Endodontics
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• v.30 no.2
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• pp.121-127
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• 2005

A variety files made of stainless steel (S-S) or nickel-titanium (Ni-Ti) are used during endodontic treatment. The purpose of tt)is study was to evaluate the corrosion susceptibility of S-S and Ni-Ti endodontic files. Three brands of files were used for this study: $K-flex^{(R)}$ S-S files (Maillefer, USA), $Profile^{(R)}$ Ni-Ti files (Maillefer, USA), $K-3^{(R)}$ Ni-Ti files (SybronEndo. USA). 120 files of each brands (21mm, ISO size $\#20$) were divided into 12 groups according to 1) sterilization methods using Autoclave or Ethylene Oxide (E-O) gas, 2) Irrigation solutions using $5.25\%$ NaOCl or Saline, 3) the number of sterilization (1, 5, 10 times), After above procedures, each of the files was inspected by three examiners with a light microscope and camera at X25. Each file was judged and ranked according to the following criteria: 0;, no corrosion, 1; mild corrosion, 2; moderate corrosion, and 3; severe corrosion. The files of high score were examined under the Scanning Electron Microscope. Data were statistically analyzed with the Kruskal-Wallis test (p < 0.05). Most of the ten time-autoclaved files had showed mild to moderate corrosion. But, one or five time-autoclaved files did not show corrosive surface. NaOCl treatment and E-O gas sterilization did not influence on corrosion. There was a significant difference in corrosion susceptibility between sterilization methods and the number of autoclaving. However, there was no significant difference between brands and file materials.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.360.2-360.2
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• 2016

CuSn thin films were fabricated by rf magnetron co-sputtering method on the Si(100) substrate for evaluation of the antibacterial effect. The co-sputtering process was performed with different rf powers and sputtering times to regulate the thickness of the films and relative atomic ratio of Cu to Sn. The physicochemical properties of the CuSn thin films were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray induced Auger electron spectroscopy (XAES), Optical microscope (OM), 4-point probe, and antibacterial test. An antibacterial test was conducted with Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) as changing contact times between CuSn fillms and bacteria suspension. We compared to the crystalline structures of films before sterilization and after sterilization by XRD measurement. The changes of oxidation states of Cu and Sn and the chemical environment of films before and after antibacterial test were investigated with high resolution XPS spectra in the regions of Cu 2p, Cu LMM, and Sn 3d. After antibacterial test, the morphology of the films was checked with an OM images. The electrical properties of the CuSn films such as surface resistance and conductivity were measured by using 4-point probe.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.522-522
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• 2013

Plasma can be used to various applications such as sterilization, inactivation/removal of microorganisms, wound healing, tooth bleaching, cancer treatment, surface modification and plasma polymerization. In this research, we studied the effect of plasma irradiation on the structural, optical, and biological properties of the polymer films. Several polymers were synthesized and then deposited on the glass substrates. The polymer films were treated by oxygen and nitrogen plasmas. Plasma-treated films were investigated by contact angle, infrared absorption spectroscopy, cathodoluminescence spectroscopy, and scanning electron microscopy. Functional materials were prepared on plasma-treated surface, and their performances were investigated using various techniques. Next, we discuss relationship between the performance of functional materials and the structural properties of plasma-treated polymer films.

• Journal of the Society of Disaster Information
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• v.18 no.3
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• pp.566-573
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• 2022

Purpose: This study attempted to verify the effectiveness of the application of air sterilizers in elementary schools at risk of group infection among vulnerable groups in order to address fears of new infectious diseases that have increased since the outbreak of Middle East Respiratory Syndrome (MERS) and Coronavirus infection-19 (COVID-19). Method: One air sterilizer was installed in each classroom, cafeteria, and bathroom of an elementary school in Seoul, and surface and air samples were collected at a distance of 2m from the air sterilizer, and the bacterial reduction effect was analyzed compared to the uninstalled control group. Result: The sterilization effect on the surface was less than 2log CFU/cm² in both the control group and the test group, and the test group showed 54 to 87% less general bacterial colony formation than the control group. In addition, the sterilization effect in the air differed depending on the location of the air sterilizer, and the wall installation showed a reduction effect of up to 91% compared to the control group, and the central installation showed a reduction effect of up to 93%. Conclusion: As a result of the study, it is expected that the prevention of infectious diseases can be increased by maintaining the current quarantine program in elementary schools that conduct regular disinfection while applying air sterilizers. In addition, it is considered desirable to facilitate the inflow of air into the air sterilizer.

• Food Science and Preservation
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• v.20 no.4
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• pp.459-466
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• 2013

This study was carried out in order to investigate sterilization effect and to extend storage periods of the Rubus coreanus by treating with tap water (TW), electrolyzed water (EW) and aqueous chlorine dioxide ($ClO_2$). After each treatment plot was soaked with 10, 50, 100, 200 ppm in each sterilizing solution within 30 sec, each treatment was compared during the storage time at room temperature and refrigerator temperature. As results of total plate count according to temperatures and periods, the microbial sterilizing power of each treatment plot was bigger at EW and $ClO_2$ treatment plots than the TW treatment plot; however, it sharply increased on the high concentration $ClO_2$ treatment plot. Futhermore, the cold storage treatment plot had more outstanding microbial sterilizing power than the room temperature treatment plot. As a result of observing the surface of the Rubus coreanus using scanning electron microscope (SEM), no microbe was seen in EW and $ClO_2$ treatment plot. The results of measuring enzyme activity showed a more significant decrease in EW and $ClO_2$ solutions treatment plot than TW treatment plot but gradually increased with time. The contents of total polyphenol revealed similar values on each treatment. The EW and $ClO_2$ treatment of the Rubus coreanus could be considered as good methods for inhibiting microbial growth in fresh vegetables and fruit, thereby contributing to quality maintenance.

• Journal of Periodontal and Implant Science
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• v.34 no.1
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• pp.1-17
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• 2004

It is improtant that performing prophylaxis procedure on an infected implant surface in order to treat peri-implantitis should not change the surface roughness and composition, so that the surface can be recovered to almost same condition as initial implant surface. This thesis, therefore, studied an effect of various oral hygiene instrument on implant surface. A surface roughness measurement instrument and an infection electron microscope were used to observe a change on surface. The purpose of this study was to obtain a clinical guidelines during implant care and peri-implantitis treatment. The result were as follows 1. Ra values (surface roughness value) at experimental group 1, group 2, and group 5 were increased significantly as compared with comparison group(p<0.05). 2. When compared experimental group 1 with each experimental groups at which prohylaxis procedure was performed, mean values of Ra at experimental group 2, group 3, group 6, and group 7 were decreased significantly(p<0.05). 3. Mean value of Ra was lowest at experimental group 2, and highest at experimental group 2, and highest at experimental group 5. 4. Analysis of SEM showed that was significant surface change at experimental group 2, group 3, group 4, group 5, and group 6 as compared with comparison group(X1000). 5. Analysis fo EDX showed that a quantity of Ti on surface for experimental group 6 was very similar to that for comparison group. In conclusion, air-powder abrasive and citric acid, plastic instrument are safe methods to use for performing prophylaxis procedure on implant care or for cleaning and sterilization process on treatment of peri-implantitis, based on the result that those method did not affect implant surface roughness and Ti composition.

• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.1202-1205
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• 2000

Germicidal lamps efficiently emit a large amount of ultraviolet rays 253.7nm which have excellent germicidal effect. The lamps are primarily useful for sterilization of air, the surface of various materials and water or liquid. In this paper, analysis of the charge pump power factor correction inverter for driving a 65W UV lamp and electrical characteristics of the lamp are discussed. The operation of the inverter circuit. in which the lamp is included as a load, is analyzed. Experimental results of the inverter circuit are also presented.