Browsing by Author "Li, Yang"

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Conductive tail-to-tail domain walls in epitaxial BiFeO3 films
(2018-08-20)
Jin, Yaming
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Xiao, Shuyu
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Yang, Jan-Chi
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Zhang, Junting
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Lu, Xiaomei
The complex conductive behavior of ferroelectric domain walls is attracting more and more attention for their potential application as an independent nanoelectronic component. For the (001) epitaxial BiFeO3 films, we find that the domain wall conductivity varies among 71 degrees domain walls, with tail-to-tail (T-T) domain walls more conductive than head-to-head (H-H) and head-to-tail (H-T) ones. Furthermore, it is observed that most of the conductive areas are composed of two parallel lines around the T-T domain walls. These experimental results can be well simulated by our theoretical model based on the polarization configuration and a tunneling mechanism. Our work will help to understand the mechanism of domain wall conductance in ferroelectric materials and further promote the usage of domain walls in advanced nano-devices. Published by AIP Publishing.
Operational efficiency of ASEAN airlines: based on DEA and bootstrapping approaches
(2017-01-01)
Hu, Jin-Li
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Li, Yang
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Tung, Hsin-Jing
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經營管理研究所
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Institute of Business and Management
Purpose - For strategic and competitive insights, the purpose of this paper is to measure and benchmark the comparative operating efficiencies of Association of Southeast Asian Nations' (ASEAN) major airlines and present a new interpretation along with managerial implications. Design/methodology/approach - This research statistically tests returns to scale and the equality of mean efficiencies for 15 ASEAN airlines covering the period 2010-2014. The disaggregate input efficiency of ASEAN airlines is computed by comparing the target and actual inputs. Findings - The disaggregate input efficiency of ASEAN airlines shows that aircraft efficiency is the lowest, operating cost efficiency is better, and available seat efficiency is the best. Originality/value - This paper applies data envelopment analysis models, disaggregated input efficiency measures, and bootstrapping approaches to compute the operational efficiency of ASEAN airlines. Strategic suggestions are made to improve the operational efficiency of ASEAN airlines.
Rewritable ferroelectric vortex pairs in BiFeO3
(2017-08-04)
Li, Yang
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Jin, Yaming
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Lu, Xiaomei
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Yang, Jan-Chi
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Chu, Ying-Hao
Ferroelectric vortex in multiferroic materials has been considered as a promising alternative to current memory cells for the merit of high storage density. However, the formation of regular natural ferroelectric vortex is difficult, restricting the achievement of vortex memory device. Here, we demonstrated the creation of ferroelectric vortex-antivortex pairs in BiFeO3 thin films by using local electric field. The evolution of the polar vortex structure is studied by piezoresponse force microscopy at nanoscale. The results reveal that the patterns and stability of vortex structures are sensitive to the poling position. Consecutive writing and erasing processes cause no influence on the original domain configuration. The Z4 proper coloring vortex-antivortex network is then analyzed by graph theory, which verifies the rationality of artificial vortex-antivortex pairs. This study paves a foundation for artificial regulation of vortex, which provides a possible pathway for the design and realization of non-volatile vortex memory devices and logical devices.