Browsing by Author "Wang, H. T."

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Effect of geometry on the magnetic properties of CoFe2O4-PbTiO3 multiferroic composites
(2013)
Wang, B. Y.
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Wang, H. T.
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Singh, Shashi B.
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Shao, Y. C.
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Wang, Y. F.
In this study, X-ray absorption near-edge structure (XANES), extended X-ray absorption fine structure (EXAFS), X-ray magnetic circular dichroism (XMCD) and element-and site-specific magnetic hysteresis (ESMH) are used to elucidate the effect of geometry (0-3- and 2-2-type) on the magnetic properties of CoFe2O4-PbTiO3 (CFO-PTO) multiferroic composites by comparison with those of the reference CFO and PTO powders. Magnetic Co ions in CFO have been confirmed to be located at both the tetrahedral (A)- and octahedral (B)-sites. CFO retains its mixed-spinel structure as verified by the EXAFS, XMCD and ESMH measurements. ESMH measurements further demonstrate that the magnetic moments of Co2+ and Fe3+/Fe2+ cations at both the A-and B-sites in the composites are smaller than those of the CFO powder. The reduction of the magnetic moments in the 2-2-type composite was larger than that in the 0-3-type composite. The reduction of the magnetic moments in the composites was attributable to the formation of anti-phase boundaries owing to the compressive strain in CFO, which is the largest strain in the 2-2-type composite. Based on the Ti L-3,L-2-edge XMCD measurements of the CFO-PTO composites, no induced magnetic moment was observed at the Ti sites in the PTO matrix, excluding the possibility that the Ti ions in the PTO matrix affect the magnetic properties of these CFO-PTO composites.
Estimation of a Modified Capability Index for Non-Normal Distributions
(2016-09)
Pearn, W. L.
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Tai, Y. T.
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Wang, H. T.
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工業工程與管理學系
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Department of Industrial Engineering and Management
Process capability indices (PCIs), which are very important in quality control have been one of a numerical measure index in manufacturing processes. Index C-pk is the most popular one used in the manufacturing industry. It is applied under the assumption that the processes are normally distributed. In real-world applications, non-normal processes may occur in industries, and the index C-Npk has been proposed for non-normal processes in which its exact sampling distribution is mathematically intractable. Quality practitioners commonly use the existing NCPPM (non-conformities in parts per million) table of C-pk to obtain process yields. However, the table could not be applied directly via the value of index CNpk. For the consistency of NCPPM mapping, we propose procedures to obtain the modified index C-Npk* and its approximately unbiased estimator C-Npk* for three non-normal distributions, involving Log-normal, Gamma, and Weibull distributions. The values of modified index C-Npk* could be used to inquire the existing popular NCPPM table of C-pk. In addition, four bootstrap methods were used to construct the lower confidence bounds of the index C-Npk*, which are useful to the practitioners for making reliable decisions regarding process performance based on process yield.
Experimental Techniques on the Understanding of the Charge Loss in a SONOS Nitride-storage Nonvolatile Memory
(2016)
Hsieh, E. R.
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Wang, H. T.
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Chung, Steve S.
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Chang, Wayne
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Wang, S. D.
The endurance and charge loss are the most critical issue in the design of a SONOS memory cell. The origin of the window closure and charge loss was partly caused by the electrons and holes mismatch along the channel lateral direction during the cycling. In this paper, two measurement techniques to observe the mismatch of programmed electrons and erased holes have been developed. It was demonstrated on an MTP (Multi-Time-Programming) SONOS flash memory. By observing the charge distribution, the mismatch which led to window closure and charge loss can be well understood, and better operating schemes can then be developed.