• Tribology and Lubricants
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• v.25 no.1
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• pp.61-65
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• 2009

Tribological properties of the semi-metallic friction materials containing different solid lubricants (graphite, $WS_2$, $MoS_2$) were investigated. The friction materials were fabricated with an experimental formulation and tested with gray cast iron disks. Results showed that graphite contributed to stabilize the friction coefficient during run-in processes. Also, graphite provided better fade resistance than that of $WS_2$ and $MoS_2$. At intermediate temperature ranges, however, friction materials with $WS_2$ or $MoS_2$ maintained higher friction effectiveness than that of graphite. On the other hand, friction materials containing $MoS_2$ showed increased wear rates than that with graphite or $WS_2$. Friction materials with proper combinations of two solid lubricants showed better friction and wear properties than that of the friction materials containing single solid lubricant.

• Knowledge Management Research
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• v.23 no.2
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• pp.83-98
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• 2022

The current study investigated the effect of user interface design on metaverse user's objective task performance, perceived usefulness, presence, and enjoyment. Using a 2 × 2 within-subject repeated measure experimental design, we found that users perceived the interface to be significantly more useful when additional visual cues existed and performed better for the given task. Additionally, a repeated-measure mediation analysis revealed that the effect of richer information in the interface on users' enjoyment as a function of need satisfaction was mediated by perceived usefulness. Theoretical and practical implication are derived from the result of the current study.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.11
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• pp.5076-5082
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• 2012

This study aims at re-considering an exemplary teacher in Confucian scholar tradition at the present time of education where teacher's authority gathers dust, the relationship between a teacher and a student is getting hard-hearted and the discussion on the role of a teacher and expertise does not reach an agreement. For this, the article discussed it by dividing an exemplary teacher into a conception of authority, benevolence and example. In view from a Confucian scholar's standpoint, this article found that teacher's authority is rational authority, and it is a product of social institution and social role of a teacher. Moreover, more important finding was that reconciliation is highlighted rather than authority. In a Confucian scholar, it is focused on love and benevolence between a teacher and a student by having humanity as the foundation and courtesy as ways and means. Also a Confucian scholar has demanded a good moral character and professional qualifications of a teacher. This study concludes that teacher's authority is made by teacher's professionalism, social roles and spirit of benevolence; also it has been making a conception of a teacher in Confucian scholar tradition. This study suggests that it needs to re-think about the values and meaning of Asian tradition in our educational settings in which western culture and values is influencing Asian societies too much.

• Korean Journal of Psychosomatic Medicine
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• v.28 no.1
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• pp.36-41
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• 2020

Objectives : Clozapine has been known to increase the possibility of developing cardio/cerebrovascular diseases, and the platelet activation has been deemed to be related to the occurrence of them. In author's previous study, we observed the increase of platelet activity with short-term clozapine administration. This study was conducted, as a follow-up study, to investigate the effect of clozapine on the platelet activity when administered continuously for long-term period of time of 1 year. Methods : The medical records of the patients with schizophrenia or schizoaffective disorder who were treated with clozapine for 1 year were retrospectively reviewed. The degree of platelet activation was assessed by measuring the mean platelet component. Results : Total of 24 patients were enrolled. 9 of them (37.5%) were male and 15 of them (62.5%) were female. In the Wilcoxon sign-ranks test, no significant change was observed between the mean platelet factor values at the beginning and at the end of one year. Conclusions : No significant changes of mean platelet activity were observed after continued administration of clozapine for 1 year. Considering the author's previous findings that observed a prominent decrease of mean platelet component after short-term clozapine administration, the result of this study suggests the possibility that the activity of the platelet may change depending on the duration of the clozapine administration.

• Journal of Energy Engineering
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• v.24 no.3
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• pp.96-108
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• 2015

A passive containment cooling system has been designed to remove the heat inside a containment during accidents without external power supply. In this work, the PCCS was introduced in the APR1400 plant to replace the containment spray system and, then, the thermal-hydraulic performance of the PCCS was analyzed using the system thermal-hydraulic computer code, MARS. A double-ended cold-leg break accident, which is known to induce the maximum pressure in the containment, is simulated, where the thermal hydraulics of the PCCS, the reactor coolant system, and the containment are simultaneously simulated. The results of the calculations showed that the PCCS can replace the existing spray system and that the containment building and its internal structure also play a very important role for the heat removal during the accident. Some sensitivity calculations were carried out to evaluate the model uncertainty and the effects of design parameters. The limitations of the PCCS are also discussed.

• Journal of the Korean Society of Food Science and Nutrition
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• v.36 no.3
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• pp.361-365
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• 2007

This study was conducted to improve the Prunus mume vinegar production. The most suitable concentration of the Prunus mume juice was 6%. Static fermentation was a more suitable process for acetic acid fermentation of the Prunus mume vinegar than shaking fermentation. Major components of the organic acids were acetic, citric, tartaric and malic acid at 4.2, 1.2, 0.3, and 0.1%, respectively. Also, major components of the free sugars were glucose and fructose, and 80.96 mg% of asparagine was included in the Prunus mume vinegar as a main free amino acid. Alcohol components of the Prunus mume vinegar were n-propyl alcohol, iso-butyl alcohol, n-butyl alcohol, iso-amyl alcohol, and n-amyl alcohol.

• Journal of the Korean Magnetics Society
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• v.27 no.1
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• pp.1-8
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• 2017

Flywheel Energy Storage System (FESS) is composed by flywheel generating rotating potential energy and motor/generator set charging and discharging electric potential energy. The flywheel and motor/generator is connected by rotating shaft. And torque characteristics of motor/generator part can influence charging and mechanical traits of FESS. This paper analyze about motor/generator design method of 5 [kWh] FESS and torque ripple, harmonic effects by change of slots. At First, this paper proposes a method to estimate the flywheel size and the rotor size of the motor from the the rotational kinetic energy by inertia of FESS. The number of induction motor rotor slots for torque ripple reduction in the high speed operation region is selected. This paper performs to reduce the noise and vibration of the flywheel composed of coaxial with motor/generator and flywheel and realize the high efficiency.

• Korean Medical Education Review
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• v.19 no.1
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• pp.47-55
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• 2017

This study was conducted to analyze the strengths and weaknesses of a 3-week family medicine clerkship program based on the results of an online survey taken by the students (N=127) and a structured interview with a focus group (n=10), aimed to improve the quality of the clerkship program. The online survey contained questions pertaining to goals, schedule, contents, arrangement, atmosphere, environment, evaluation, and satisfaction regarding the clerkship. The focus group interview addressed the schedule and achievements of the program. Scores were reported on a 5-point Likert scale. Most students were highly satisfied with the overall quality of the clerkship. The structured interview results showed that 97.6% of the clerkship program was executed according to the schedule. The focus group reported a perfect score of 5 points on several measures including: accomplishment of the educational goals of the family medicine clerkship, providing many chances to obtain medical histories and perform physical examinations on real patients, experience with various symptoms and diseases, positive attitudes of faculty members when teaching, notification of the guidelines for evaluation beforehand, well-constructed and effective clerkship schedule, and reflection of student feedback. However, the focus group gave low scores on: support for health accidents of students, access to patient information, enough opportunities to practice clinical skills, appropriate rest facilities for students, and fairness of clerkship evaluation process. In conclusion, the structured evaluation performed after the 3-week clerkship program motivated students and helped them ensure an efficient clerkship. This structured evaluation also suggested basic data to make the professor who is subject of the assessment. This study shows that structured assessment is an effective method which can be used to improve the quality of clerkships.

• Journal of the Microelectronics and Packaging Society
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• v.26 no.3
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• pp.75-80
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• 2019

Silicon solar cells have been widely used as a most promising renewable energy source due to eco-friendliness and high efficiency. As modules of silicon solar cells are connected in series for a practical electricity generation, a large voltage of 500-1,500 V is applied to the modules inevitably. Potential-induced degradation (PID), a deterioration of the efficiency and maximum power output by the continuously applied high voltage between the module frames and solar cells, has been regarded as the major cause that reduces the lifetime of silicon solar cells. In particular, the migration of the $Na^+$ ions from the front glass into Si through the anti-reflection coating and the accumulation of $Na^+$ ions at stacking faults inside Si have been reported as the reason of PID. In this research, the thickness effect of $SiO_x$ layer that can block the migration of $Na^+$ ions on the reduction of PID is investigated as it is incorporated between anti-reflection coating and p-n junction in p-type PERC solar cells. From the measurement of shunt resistance, efficiency, and maximum power output after the continuous application of 1,000 V for 96 hours, it is revealed that the thickness of $SiO_x$ layer should be larger than 7-8 nm to reduce PID effectively.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.490-492
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• 2008

고압 전원 장치(High Voltage Power Supply)는 근래에 와서 산업전반에 응용이 매우 광범위하게 확산되고 있고 고전압 장치가 필수적으로 이용 되어야 하는 분야가 점차 확산되고 있다. 응용분야로는 신소재 개발과 플라즈마 응용을 위한 공업용과 민생용, 의료기기용, 군사용, 또한 프린터에 이르기까지 다양하게 있다. 가정이나 사무실에서 쉽게 접할 수 있는 IT장비인 프린터인 경우에도 전원 공급 장치의 측면에서는 화상형성에 있어 가장 필수적인 안정적이고 다기능을 가지는 고압 전원장치를 적용하고 있고, 수요 또한 증가하고 있다. 본 논문은 낮은 입력 DC전압에서 높은 음의 DC전압을 출력하는 높은 전환 비의 극성 반전 형 DC/DC 전력 변환 회로에 관한 것으로써, 하나의 스위치, 하나의 인덕터, 그리고 다수개의 캐패시터와 다이오드로 구성된다. 기존의 극성 반전 형 DC/DC 컨버터 회로와 비교하여, 고압 변환 트랜스포머 대신에 인덕터를 사용할 수 있어, 자기 소자의 부피 및 크기는 물론 원가저감이 가능하다. 또한 반도체 소자의 Voltage Stress가 감소된다. 제안된 회로의 원리를 분석하고, 종래의 고압 전원장치와 비교함으로써 장점을 알아본 후, 동작원리에 대한 타당성을 Simulation 및 실험을 통하여 검증한다.