• The Transactions of the Korean Institute of Electrical Engineers P
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• v.62 no.4
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• pp.210-215
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• 2013

This paper analyze the bus voltage sags in the power distribution system with a small scale cogeneration system when the superconducting fault current limiter was introduced. Among the solutions to decrease the short-circuit current considering the locations of the small scale cogeneration system, the superconducting fault current limiter (SFCL) has been announced as one of the promising methods to reduce the fault current because the installation of the small scale cogeneration system which increases the short-circuit current. According to the application locations of the small scale cogeneration system in a power distribution system, it has caused the variations of voltage sag and duration which depends on the change of the short-circuit current, which can make the operation of the protective device deviate from its original set value when the fault occurs. To investigate the voltage sag when a SFCL was applied into a power distribution system where the small scale cogeneration system was introduced into various locations, the SFCL, small scale cogeneration system, and power system are modeled using PSCAD/EMTDC. In this paper, the effects on voltage sags are assessed when the SFCL is installed in power distribution system with various locations of the small scale cogeneration system.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.5
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• pp.68-75
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• 2014

Cascaded applications of surge protective devices(SPDs) are required in order to reduce the stress on the electrical and electronics equipment being protected, and the energy coordination between the cascaded SPDs is very important. This paper deals with the experimental results obtained from the installation conditions of full-scale SPDs. The energy coordination between the upstream Class I SPD and the downstream Class II SPD was measured using a $10/350{\mu}s$ impulse current due to direct lightning flashes. The distances between the cascaded SPDs were 3, 10, and 50m, and the maximum test current was 12.5kA. As a result, the energy sharing between cascaded SPDs was dependent on the voltage protection level of each SPD and the distance between two SPDs. An overview of how to select SPD ratings in applications of cascaded SPDs system was discussed based on the energy coordination between the two SPDs. The proposed test results for the energy coordination between two-stage cascaded SPDs can be used in effective applications of SPDs.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.6
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• pp.70-77
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• 2015

This paper describes the experimental results obtained from various installation conditions of cascaded metal oxide varistor(MOV)-based SPDs with the objectives to analyze the coordination of the cascaded surge protective devices(SPDs) and to propose the proper selection and installation methods of the cascaded SPDs. The residual voltage, discharge current and energy sharing between the upstream and downstream SPDs in the $10/350{\mu}s$ direct lightning current wave were measured and discussed. The coordination of cascaded MOV-based SPDs is closely related to the varistor voltage and installation methods of SPDs. In cascaded SPDs without dedicated decoupling elements, the natural impedance of leads connecting two SPDs can act as a decoupler for the coordination of MOV-based SPDs. Even if the varistor voltage of the upstream SPD is higher than that of the downstream SPD at long distances between two SPDs, the energy coordination of cascaded SPDs could effectively be fulfilled in the conditions of large surge currents and the optimum voltage protection level can be achieved. Consequently, if the distance between voltage limiting type SPDs is long, the coordination of the cascaded SPDs should be determined by taking into account the decoupling effects due to the intrinsic inductance of leads connecting the upstream and downstream SPDs.

• Safety and Health at Work
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• v.9 no.1
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• pp.25-29
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• 2018

Background: The understanding of the relationship between risk perception, knowledge, and protective behaviors could play a major role in occupational risk control and management. Research exploring how workers perceive, recognize, and react to risks in different occupational settings is scarce in Thailand. The aim of this study was to assess the relationship of noise-related risk perceptions and knowledge to the use of hearing protective devices (HPDs) among sawmill workers in Thailand. Methods: Sawmill workers (n = 540) from four factories in Trang, Southern Thailand, participated in a questionnaire interview from December 2015 to January 2016. Descriptive statistics and linear regression models were used to explore the risk factors related to HPD use. Path diagram analysis was demonstrated and used to evaluate associations. Results: Risk perception was significantly correlated with HPD use (p < 0.01), HPD training (p = 0.01), and the number of years of work experience (p = 0.03). Sawmill workers were likely to use HPDs based on their risk perception and HPD training. However, HPD training was inversely correlated with age and the number of years of work experience. Conclusion: The study highlights the importance of risk perceptions and knowledge, and these factors should be emphasized in the design and implementation of any personal safety intervention program for sawmill workers.

• KEPCO Journal on Electric Power and Energy
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• v.8 no.1
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• pp.5-7
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• 2022

KEPCO's plan is undergoing a trial operation to replace the open-loop section with ring main units configuration where underground distribution lines are installed, by linking the multi-way circuit breakers auto (MCA) on the power side of each pad-mounted transformer. However, ring main units application mentioned above may cause the ripple effects, when implementing the configuration without a study of protection coordination. Because ring main units with classical pre-set protection devices contribution in fault condition didn't consider yet. For the reliable ring main units operation, it is necessary to resolve several protection issues such as the protection coordination with substation side, prevention of the transformer inrush current. These issues can radically deteriorate the distribution system reliability Hence, it is essential to design proper protection coordination to reduce these types of problems. This paper presents a scheme of ring main units' configuration and MCA's settings of time-current curves to preserve the performance of protection coordination among the switchgears considering constraints, e.g. prevention of the ripple effects (on the branch section when a transformer failure occurs and the mainline when a branch line failure occurs). It was confirmed that the propagation of the failure for each interrupter segment could be minimized by applying the proposed TCC and the interrupter settings for the MCAs (branch, transformer). Further, it was verified that the undetected area of the distribution automation system (DAS) could be supplemented by having the MCA configurated ring main units operate first, instead of the internal protection equipment in the transformer such as the fuse, STP when a transformer failure occurs.

• Korean Journal of Agricultural Science
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• v.49 no.4
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• pp.771-783
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• 2022

In this study, the feasibility of alternative tractor Roll Over Protective Structure (ROPS) designed to evaluate conditions required for testing was confirmed. In accordance with Organization for Economic Cooperation and Development (OECD) code 4, the required load energy of the tractor ROPS was determined. First, the tractor ROPS test was performed and a repeated test was performed using a simplified ROPS as an alternative tractor ROPS. The test procedure is first rearward, second lateral, and last forward based on ROPS. The load test device consists of a load cell that measures force and a LVDT that measures deformation. Precision was confirmed by calculating the relative standard deviation of the simplified ROPS repeated test. Accuracy was analyzed by calculating the mean relative error between the mean measured values in the simplified ROPS test and the tractor ROPS test. As a result, the relative standard deviation was less than 2.5% for force and 3.3% for maximum deformation overall, showed the highest precision in lateral load. The mean relative error value for force measured at the lateral load of simplified ROPS was 0.5%, showing the highest accuracy. In the front load test, the mean relative error of maximum deformation was 20.5%, showing the lowest accuracy. The mean relative error (MRE) was high in the forward load test was because of structural factors of the ROPS. The simplified ROPS model is expected to save money and time spent preparing tractors.

• Fashion & Textile Research Journal
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• v.22 no.4
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• pp.407-412
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• 2020

This study investigated the technological development of Korean functional product design for posture correction. We analyzed registered and disclosed Korean patents (n=289) of KIPRIS. They were posture correction technology patents filed from 1999 to 2018. Keywords used in patent selection were posture correction, posture correction clothing, posture correction band, rehabilitation clothing, joint protection, protective equipment, and compression wear. These were then analyzed by patent application year, product type, effect pursued, and posture correction body part. The results showed that patent applications related to posture correction technology have increased since 2014. Products subject to patents for posture correction technology were device/brace (59.5%), footwear (22.5%), and clothing (18.0%). Patents for posture correction pursued various wearing effects. The effects pursued were dependent on the product type. The device/brace focused on joint protection (76.7%) and muscle reinforcement (40.7%). Footwear was focused on joint protection (90.8%). The clothes were focused on muscle reinforcement (50.0%) and body shaping (36.5%). The clothing and device/brace for posture correction were worn on various body parts of the upper limbs to feet. The posture correction product design patent was to correct various body parts. Patents pursuing upper body correction focused on spine posture correction (n=99). Patents for foot posture correction have steadily increased (n=102). Patents for posture correction of the pelvis and hip joints were relatively few (n=46). The results of this study implied the necessity to develop technology to correct posture by combining the functions of device/brace and clothing.

• Journal of the Semiconductor & Display Technology
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• v.21 no.2
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• pp.15-18
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• 2022

The ultraviolet-C emitting praseodymium doped yttrium phosphate (YPO₄:Pr³⁺) powder was synthesized by conventional solid-state reaction. The electroluminescence device was fabricated by simple screen-printing method using the synthesized YPO₄:Pr³⁺ powder, especially, polyvinylidene fluoride as an insulating layer was applied on the printed YPO₄:Pr³⁺ powder for stable performance of the electroluminescence. The electroluminescence properties were investigated under alternating current power system of 400 Hz. The device starts to emit at 350 V, which showed the ultraviolet-C emission peaking at the 233, 245, 264, 273 nm attributed to electronic transition of the Pr³⁺ ions. The electroluminescence intensity was increased as increasing the operating voltage and the device revealed stable performance up to 600 V due to the polyvinylidene fluoride serve as a protective layer.

• Journal of Appropriate Technology
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• v.6 no.2
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• pp.219-225
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• 2020

Importance of touch equipment and smart learning increases and public institutions and educational facilities are applying smart devices to their daily environments. However, users of public smart devices are at risk of being exposed to the direct and indirect spread of infectious diseases. This study develops an exo-finger that wraps the fingertips of smart device users and is intended to have a disease prevention effect when used on public equipment. An exoskeletal body was fabricated by inserting a secondary material which is a mixture of the activating material, carbon black (CB) and a macromolecular polymer (elastomer) into a mold. This device was confirmed to have a touch function when the CB content was 0.030 wt% or higher, and the content of the elastomer was varied so that it could have a friction force similar to that when a person touches a smart device (a friction coefficient of 2.5). Through experiments, it was concluded that the CB content had little effect on the friction coefficient. As a result of testing the completed prototype on a smart device, it was proven that the developed exoskeletal device can be useful in situations where it is impossible to touch due to wearing protective gears, or when equipment such as gloves is used to prevent the spread of infectious diseases.

• Biomedical Science Letters
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• v.14 no.4
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• pp.263-267
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• 2008

Photodynamic therapy (PDT) is a treatment utilizing the generation of singlet oxygen and other reactive oxygen species (ROS), which selectively accumulate in target cells. Peroxiredoxin (prx) plays an important role in eliminating peroxides generated during metabolism. Prx exert protective antioxidant role in cells though peroxidase activity. The aim of present work is to investigate the cytotoxicity of photofrin-mediated PDT in prx IV-transfectant AMC-HN3 cell lines. We confirmed that PDT has an effect on ROS generation in prx IV-induced cell lines. Treatment of PDT in prx IV-HN3 cell lines inhibits cytotoxic effects. Prx IV-induced HN3 cell lines resists in cell death during PDT. Also, prx IV-HN3 cell lines treated PDT inhibited ROS generation in contrast with vector control. We indicated that prx IV-induced AMC-HN3 cell lines have a function as inhibitors during PDT.