• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.5
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• pp.77-83
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• 2020

4WD technology is being actively applied to passenger cars. Therefore, dry multi-plate clutches are used for transfer cases. On the other hand, dry clutches have problems related to large vibrations and poor ride quality. To solve this problem, this paper proposes a multi-plate clutch with an MR fluid. When fastening the multi-plate clutch in the transfer case, the proposed MR clutch was applied to reduce the shock and friction, which is a key component in a four-wheel-drive system. MR multi-plate clutch has a fluid coupling mode and a compression mode. A torque model equation was derived for the optimal design. The analysis was performed using Ansys Maxwell to optimize the design parameters of the multi-plate clutch. Electromagnetic field analysis confirmed the strength of the magnetic field when the number of disks and plates were changed, and the maximum strength of the magnetic field was 0.45 Tesla. By applying this to the torque equation, the spacing between the plates was 2 mm, and the inner and outer diameters of the plates were selected to be 45 mm and 55 mm, respectively. Overall, this paper proposes an optimal design technique to maximize the performance of an MR multi-plate clutch.

• Restorative Dentistry and Endodontics
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• v.33 no.6
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• pp.499-506
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• 2008

The purpose of this study was to compare the push-out strength of a fiber post cemented with various resin cements. Newly extracted 36 human mandibular premolars which had single root canal were selected and their crown portions were removed. The root canal was instrumented using $PROTAPER^{TM}$ system and obturated using continuous wave technique. In each root, a 9-mm deep post space was prepared. #2 translucent fiber post (DT Light post, Bisco Inc., Schaumburg, IL, U.S.A.) was cemented using injection technique with Uni-dose needle tip (Bisco) and six different resin cements. The tested resin cements were Duo-Link (Bisco Inc., Schaumburg, IL, U.S.A.), Variolink II (Ivoclar-Vivadent AG, Schann, Liechtenstein), Panavia F (Kuraray Medical Inc., Okayama, Japan), Multilink Automix (Ivoclar-Vivadent AG, Schann, Liechtenstein), RelyX Unicem (3M ESPE Dental Products, St. Paul, MN, U.S.A.), and Maxcem (Kerr Co., CA, U.S.A.). After storage in distilled water for 24 hours, each root was transversally sectioned into approximately 1-mm thick sections. This procedure resulted in 6 serial sections per root. Push-out test wasperformed using a universal testing machine (EZ Test, Shimadzu Co.) with a crosshead speed of 1 mm/min. The data were analyzed with one-way ANOVA and Tukey HSD (p=0.05). The push-out strength of the groups which cemented fiber post with Panavia F and Multilink Automix were lower than those of the other groups. But, there were no statistically significant difference among groups at a probability level of 0.05.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.12
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• pp.603-610
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• 2016

Over 12 years have passed since the first commercial operation of a Korean high-speed train. Since then, the transport capacity of the high-speed lines has become almost saturated. Therefore, studies have been carried out to increase the operating speed of the trains in order to increase their transportation capacity. This study was carried out to improve the critical speed of the KTX-Sancheon, Korean high-speed train, in order to increase its operating speed. A dynamic analysis of the KTX-Sancheon train was performed using the contact data obtained from the wheel wear profiles that were measured from a KTX-Sancheon train in commercial operation. The analysis results were verified by comparing them with the measurement acceleration data obtained from KTX-Sancheon. The suspension parameters were optimized to improve the operation speed. The critical speed of KTX-Sancheon was increased by 9.4% after the optimization by the response surface method. The optimized suspension parameters are expected to be used for the new bogie design to increase the operating speed of KTX-Sancheon from 300km/h to 350km/h.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.16 no.2
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• pp.128-139
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• 2017

Railway is one of the public transportation systems along with shipping and aviation. With the recent introduction of high speed train, its proportion is increasing rapidly, which results in the higher risk of catastrophic failures. The wheel bearing to support the train is one of the important components requiring higher reliability and safety in this aspect. Recently, many studies have been made under the name of prognostics and health management (PHM), for the purpose of fault diagnosis and failure prognosis of the bearing under operation. Among them, the most important step is to extract a feature that represents the fault status properly and is useful for accurate remaining life prediction. However, the conventional features have shown some limitations that make them less useful since they fluctuate over time even after the signal de-noising or do not show a distinct pattern of degradation which lack the monotonic trend over the cycles. In this study, a new method for feature extraction is proposed based on the observation of relative frequency energy shifting over the cycles, which is then converted into the feature using the information entropy. In order to demonstrate the method, traditional and new features are generated and compared using the bearing data named FEMTO which was provided by the FEMTO-ST institute for IEEE 2012 PHM Data Challenge competition.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.9 no.4
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• pp.257-263
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• 2015

The purpose of this study was to survey the elderly patients through Basic information, Problems Wheelchair, Wheelchair Satisfaction, Usage and Requirements. The meaning of purpose is identify the problems and difficulties of wheelchair use in geriatric patients and an alternative for the correct use of wheelchairs elderly patients. The study investigated through questionnaires. That used questionnaires to modified to Gu Hyeon-Mo questionnaire (2005) and Quebec User Evaluation of Satisfaction with assistive Technology 2.0. 120 of 150 questionnaires were collected and one of them is excluded. Analysis results suggest the following. It was often feel joint pain results from physical damage. In addition when you use a wheelchair it was often feel discomfort in lower back and pelvis. And it feels uncomfortable when moving the tilt. Wheelchair satisfaction of the participants responded to the most 'Normal'. Results of the wheelchair operation ability is as follows. In the case of manual wheelchairs was feeling the difficulty to cross the threshold, Wheel lying, Stairs usage. Also In the case of an electric wheelchair was feeling the difficulty to use Tilt and Decline, Separate from the motor, and Replacement battery. In conclusion, To reduce of back pain and hip joints of elderly patients need to modify design and appearance of the wheelchair. In a later study will find to reduce discomfort and to improve satisfaction of the elderly who use wheelchairs. It will have to periodically examine the usage and satisfaction with them.

• Therapeutic Science for Rehabilitation
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• v.5 no.2
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• pp.35-47
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• 2016

Objective: The aim of this study was to identify the driving rehabilitation for on-road driving through a systematic review. Methods: We systematically examined papers published in journals from December 2014 to January 2015, using CINAH, Embase, Pubmed, PsycINFO, and The Cochrane Library. Eventually, 15 studies were included in the analyses. Results: The evidence of 15 studies was from levels I, III, and V. The subjects included in the analyses were patients with stroke(40.0%), older driver(20.0%), traumatic brain injury(20.0%), acquired brain injury(13.3%) and spinal cord injury(6.7%). The intervention types were driving simulator training(53.3%), cognitive skills training(26.6%), off-road educational training(6.7%), adaptation of assistive device(6.7%), and behind-the-wheel training(6.7%). The effects of driving rehabilitation were different depending on the types of intervention. However, driving simulator training showed significant improvement of on-road assessments in all studies included this study. Conclusions: Driving rehabilitation for on-road driving has been used in various types. Specially, the effect of the driving simulator training has been proved by many studies. Future studies are to be required with client from a range of diagnostic groups to establish evidence-based interventions and determine their effectiveness in improving on-road driving.

• Journal of The Korean Association For Science Education
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• v.30 no.2
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• pp.234-248
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• 2010

This study was conducted among 52 elementary pre service teachers not majoring in the natural sciences, who were taking Earth Science as an elective course at the University of Education located in central Korea. These elementary pre service teachers participated in story writing on the subject of earth system cycles over eight occasions. Changes in their understanding of the Earth's cycles were verified by comparing mind mapping exercises performed before and after the story writing. Afterwards, 43 out of the 52 subjects volunteered for structured interviews, in which they performed story-telling exercises. This study presents examples of story analysis that uses a variation of the wheel-shaped story map, and proposes story mapping as a preferred method of analysis. Before and after creative story writing activities, pre service teachers' mind mapping is analyzed to study possible positive changes. This study identified a gap between the instructional contents of the Earth system unit included in the 7th and current revised school curriculums on the one hand, and the conceptions expressed by the pre service teachers who studied these contents on the other.

• Journal of the Korean GEO-environmental Society
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• v.19 no.9
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• pp.13-19
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• 2018

Recently, there have been various problems aroused on the domestic infrastructures as the domestic cities become old. Accordingly, the national concerns grow on the urban railway and the related structures, which brings the national interests are brought on the research on the maintenance and rehabilitation of the old infrastructures. The underground structure of urban railway are checked with the strain gages or fiber brag grating (FBG) sensors on the railway. However, these methods are known to have resolution limitations on the investigations of the specified abnormal section. Therefore, the applicability of the Brillouin Optical Correlation Domain Analysis (BOCDA) based distributed fiber optic sensor system on the railway was evaluated in this study. The constructed BOCDA fiber optic sensor system shows high resolution of 10, 20, 50, 100 cm and capability of continuous monitoring on overall or specified section within 2 km range. The applicability evaluation was performed on the 250 m distribution of fiber optic sensors abandoned railway for continuous monitoring. The applicability of the system on the specified area was evaluated with wheel load testing. As a result, data loss tends to increase with the reduction of spatial resolution from 1.0 m to 0.1 m. Even though the measuring speed is reduced with lower spatial resolution, data accuracy increases on the location and deformation. The system can be applicable to various structures if the proper distribution method is invented later.

• Korean Journal of Oriental Medicine
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• v.2 no.1
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• pp.205-225
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• 1996

This study has been carried out to investigate the effects of Youngyanggaksan (YGS) extract on the anticonvulsive, antipyretic, anlgesic, sedative and GABAergic system of experimental animals. The results of this study were as follows : 1. YGS extract prolonged significantly the beginning time to convulsion and time to death induced by strychnine. 2. YGS extract prolonged significantly the time to death induced by electrical shock of ECT unit (3sec, 200F, 25mA). 3. On the experiment of hypothermic effects of YGS extract on the rectal temperature of rats, YGS extract decreased significantly the rectal temperature of rats. 4. On the experiment of antipyretic effects of YGS extract on the febrile induced by the subcutaneous injection of $150{\mu}g/kg$ endotoxin in rats, YGS extract decreased significantly the rectal temperature of rats. 5. On the experiment of analgesic effects of YGS extract on the writhing syndrome induced by intraperitoneal injection 0.7% acetic acid 1ml/100g in rats, the writhing syndrome was reduced significantly by administration of YGS extract. 6. On the experiment of sedative effects of YGS extract on spontaneous motor activity measured by wheel cage method in mice, the spontaneous motor activity was reduced significantly by administration of YGS extract. 7. On the experiment of effects of YGS extract on the activity of GABA-transaminase(GABA-T) in rat brains after 21 days of oral administration of YGS extract, the activity of GABA-T was reduced significantly by administration of YGS extract. 8. On the experiment of effects of YGS extract on the activity concentration of GABA in rat brains after 21 days of oral administration of YGS extract the activity concentration of GABA was reduced significantly by administration of YGS extract. 9. On the experiment of effects of YGS extract on the activity of GAD in rat brains after 21 days of oral adminstration of YGS extract, the activity of GAD was reduced significantly by administration of YGS extract. According to the those results, Youngyanggaksan extract reveals the effects on the anticonvulsive, antipyretic, anlgesic, sedative and GABAergic system.

• Journal of Astronomy and Space Sciences
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• v.21 no.2
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• pp.141-152
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• 2004

Optics fabrication process for precision space optical parts includes bound abrasive grinding, loose abrasive lapping and polishing. The traditional bound abrasive grinding with bronze bond cupped diamond wheel leaves the machine marks of about $20{mu}m$ rms in height and the subsurface damage of about 1 ${mu}m$ rms in height to be removed by subsequent loose abrasive lapping. We explored an efficient quantitative control of precision CNC grinding. The machining parameters such as grain size, work-piece rotation speed and feed rate were altered while grinding the work-piece surfaces of 20-100 mm in diameter. The input grinding variables and the resulting surface quality data were used to build grinding prediction models using empirical and multi-variable regression analysis. The effectiveness of such grinding prediction models was then examined by running a series of precision CNC grinding operation with a set of controlled input variables and predicted output surface quality indicators. The experiment achieved the predictability down to ${pm}20$ nm in height and the surface roughness down to 36 nm in height. This study contributed to improvement of the process efficiency reaching directly the polishing and figuring process without the need for the loose abrasive lapping stage.