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545 results on '"Yang, Jinkyu"'

182. EXPERIMENTAL AND NUMERICAL INVESTIGATIONS OF STOCHASTIC THICKNESS EFFECTS IN DISCONTINUOUS FIBER COMPOSITES

Author

KO, SEUNGHYUN, primary, NAKAGAWA, TROY, additional, CHEN, ZHISONG, additional, DAVEY, JAMES, additional, ABDULLAH, TALAL, additional, KUKLENSKI, LUKE, additional, ADAMS, EBONNI J., additional, SOJA, MATTHEW R., additional, PARK, CHUL Y., additional, AVERY, WILLIAM B., additional, YANG, JINKYU, additional, and SALVIATO, MARCO, additional

Published
2021
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186. Disorder-induced topological phase transition in a one-dimensional mechanical system

Author

Shi, Xiaotian Kiorpelidis, Ioannis Chaunsali, Rajesh and Achilleos, Vassos Theocharis, Georgios Yang, Jinkyu

Subjects
Condensed Matter::Disordered Systems and Neural Networks
Abstract

We numerically investigate the topological phase transition induced purely by disorder in a spring-mass chain. We employ two types of disorders-chiral and random types-to explore the interplay between topology and disorder. By tracking the evolution of real-space topological invariants, we obtain the topological phase diagrams and demonstrate the bilateral capacity of disorder to drive topological transitions, from topologically nontrivial to trivial and vice versa. The corresponding transition is accompanied by the realization of a mechanical topological Anderson insulator. The findings from this study hint that the combination of disorder and topology can serve as an efficient control knob to manipulate the transfer of mechanical energy.

Published
2021

187. The Effects of tDCS with NDT on the Improvement of Motor Development in Cerebral Palsy.

Author

Salazar Fajardo, Jhosedyn Carolaym, Kim, RockHyun, Gao, Chang, Hong, JiYeon, Yang, JinKyu, Wang, DongGil, and Yoon, BumChul

Abstract

We investigated the effects of transcranial direct current stimulation (tDCS) over the primary motor cortex (M1) with neurodevelopmental treatment (NDT) on the improvement of motor development and reduction of spasticity in children with cerebral palsy (CP). Twenty-four children with CP were allocated to two groups: the tDCS + NDT group and the only NDT group, done 3 times per week for 5 weeks. The Gross Motor Function Measurement (GMFM-88) and Box and Block Test (BBT) were used to assess changes in motor development, and the Modified Ashworth Scale (MAS) was used to evaluate changes in spasticity. All measurements were carried out at 3 time points: baseline, post-intervention, and 1 month follow-up. We found improvements in the GMFM-88 total scores and in each individual GMFM-88 dimension scores, favoring the tDCS + NDT group over the only NDT group. The BBT scores improved only in the tDCS + NDT group. In addition, the MAS scores reduced in the hemibody with significant motor impairment only in the tDCS + NDT group. The present findings suggest that tDCS combined with NDT can be considered a promising intervention for children with CP, as it can enhance motor development and reduce spasticity in this population. [ABSTRACT FROM AUTHOR]

Published
2022
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197. An advanced stator winding insulation quality assessment technique for inverter-fed machines

Author

Yang, Jinkyu, Cho, Jintae, Lee, Sang Bin, Yoo, Ji-Yoon, and Kim, Hee Dong

Subjects
Electric resistance -- Evaluation, Electric inverters -- Design and construction, Electric insulators -- Design and construction, Business, Computers, Electronics, Electronics and electrical industries
Abstract

The lifetime of the stator winding insulation is reduced when operated with pulsewidth-modulation inverters, since insulation degradation is accelerated due to increased thermal and electrical stresses on the motor. This paper focuses on a new approach for monitoring the condition of the stator insulation for failure-prone inverter-fed machines. The main concept of the proposed technique is to apply a dc and/or variable-frequency ac test voltage to the stator insulation using the inverter and to perform standard offline insulation tests whenever the motor is not operating. This allows the stator insulation to be tested more frequently as compared to offline tests performed once every three to six years during periodic maintenance. Two methods for testing the insulation with minimal modifications to the inverter circuit are proposed and verified experimentally. The results show that the proposed technique provides a simple low-cost solution for detecting stator insulation degradation at an early stage for reliable operation of inverter-fed machine systems, since the insulation condition can be monitored frequently. This does not only helps prevent forced outages and safety risks due to insulation breakdown but also helps perform maintenance in an efficient manner, since individual motor maintenance can be prioritized and scheduled based on its present condition. Index Terms--AC electric machines, capacitance (C) test, condition monitoring, diagnostics, dissipation factor (DF), insulation resistance (IR), inverters, predictive maintenance, stator insulation.

Published
2008

198. A stator winding insulation condition monitoring technique for inverter-fed machines

Author

Yang, Jinkyu, Lee, Sang Bin, Yoo, Jiyoon, Lee, Sanghoon, Oh, Yongmin, and Choi, Changho

Subjects
Alternating current electric motors -- Design and construction, Electric inverters -- Usage, Business, Electronics, Electronics and electrical industries
Abstract

Stator insulation quality assessment is an important issue for pulsewidth modulation inverter-fed machines, since the stator insulation is exposed to increased thermal/electrical stresses. In this paper, a new approach for monitoring the condition of the stator insulation for inverter-fed machines is proposed. The main concept of the proposed approach is to apply various types of test voltages to the motor stator insulation using the inverter, to perform standard offline insulation tests whenever the motor is not operating. Two methods for testing the insulation with modifications to the inverter circuit are proposed and verified experimentally. The results show that the proposed technique provides a simple low cost solution for detecting stator insulation degradation at an early stage for reliable operation of inverter-fed machine systems, since the insulation condition can be monitored frequently. This not only helps prevent forced outages and safety risks due to insulation breakdown, but also helps perform maintenance in an efficient manner since individual motor maintenance can be prioritized and scheduled based on its present condition. Index Terms--AC motor drives, fault diagnosis, leakage currents, rotating machine insulation testing, variable speed drives.

Published
2007

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