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Sub-lattice polarization states in anti-ferroelectrics and their relaxation process
M.M. Vopson,X. Tan,E. Namvar,M. Belusky,S.P. Thompson,V. Kuncser,F. Plazaola,I. Unzueta,C.C. Tang 한국물리학회 2019 Current Applied Physics Vol.19 No.4
We report studies of quasi-remanent polarization states in Pb0.99Nb0.02[(Zr0.57Sn0.43)0.94Ti0.06]0.98O3 (PNZST) anti-ferroelectric ceramics and investigation of their relaxation effects using unique in-situ electrically activated time-resolved Synchrotron X-ray powder diffraction (SXPD) and 119Sn Mössbauer Spectroscopy (MS). The SXPD patterns are consistent with a phase transition from quasi-tetragonal perovskite in 0 V relaxed anti-ferroelectric state to rhombohedral distortion in ferroelectric state under saturating applied voltages of±2 kV. The observed quasi-remanent polarization relaxation processes are due to the fact that tetragonal to rhombohedral distortion does not occur at the applied voltage required to access the quasi-remanent polarization states, and the tetragonal symmetry restored after the removal of the applied electric field is preserved. Since these quasi-remanent polarization states were seen as possibly suitable for memory applications, the implications of this study are that anti-ferroelectrics are more feasible for multi-state dynamic random access memories (DRAM), while their application to non-volatile memories requires development of more sophisticated “read-out” protocols, possibly involving dc electrical biasing.
Assessments of Dead Beat Current Control for High Speed Permanent Magnet Synchronous Motor Drives
M. Tang,A. Gaeta,K. Ohyama,P. Zanchehtta,G. Asher 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6
High bandwidth and accuracy of the current control loop are fundamental requisites for reducing torque ripples in high performance drives, especially at high speeds or when a fast torque response is required. One of the candidates for these purposes is a dead beat current control (DBCC). Many types of DBCC have been proposed and implemented. This paper discusses the performances of DBCC considering time delays due to a digital control, and compares with a classical dq PI current regulator to explain the DBCC’s advantages. Also a novel compensation method for the rotor movement is proposed to eliminate offsets error which come up at high speeds.
Tang, Q.,Li, L.,Lee, M. J.,Ge, Q.,Lee, J. M.,Jung, H. S. Springer Science + Business Media 2016 Cell and tissue research Vol.363 No.3
<P>Retinoic acid (RA)-induced cleft palate results from both extrinsic obstructions by the tongue and internal factors within the palatal shelves. Our previous study showed that the spatiotemporal expression of Rac1 regulates the fibronectin (FN) arrangement through cell density alterations that play an important role in palate development. In this study, we investigate the involvement of the Rac1 regulation of the FN arrangement in RA-induced cleft palate. Our results demonstrate that RA-induced intrinsic alterations in palatal shelves, including a delayed progress of cell condensation, delay palate development, even after the removal of the tongue. Further analysis shows that RA treatment diminishes the region-distinctive expression of Rac1 within the palatal shelves, which reversely alters the fibrillar arrangement of FN. Furthermore, RA treatment disrupts the formation of lamellipodia, which are indicative structures of cell migration that are regulated by Rac1. These results suggest that the Rac1 regulation of the FN arrangement is involved in RA-induced cleft palate through the regulation of cell migration, which delays the progress of cell condensation and subsequently influences the FN arrangement, inducing a delay in palate development. Our study provides new insights into the RA-induced impairment of palatal shelf elevation based on cell migration dynamics.</P>
Inductances of a Superconducting Magnet for Cyclotron K120
Tang, H.M.,Kim, D.L.,Choi, Y.S.,Lee, B.S.,Yang, H.S.,Kim, Y.S. The Korean Society of Superconductivity and Cryoge 2008 한국초전도저온공학회논문지 Vol.10 No.4
The design of a superconducting magnet system producing very high magnetic field is underway at Korea Basic Science Institute (KBSI) to accelerate three kinds of carbon irons (C+2, C+4, C+6) to 120 MeV. A quarter-scaled prototype will be manufactured in order to confirm the feasibility of our design. Magnet Inductances in the system have a great influence on the current ramping rates and contribute to the stored energy, which are usually considered to be unfavorable in magnet operation. The modeling and simulation scheme of a prototype superconducting magnet for the cyclotron K120 is described in this paper. The inductances are calculated by a numerical method with and without iron yokes, respectively. These calculation results will be used as engineering design details such as a current ramping rate and a quench protection design.
Tang Sylvia Y. F.,Wong P. M.,Wong Angel K. Y.,Cheng May M. H. 서울대학교 교육연구소 2018 Asia Pacific Education Review Vol.19 No.3
This article reports a comparative study on the reasons for pre-service student teachers becoming teachers in Hong Kong and Macau. The study adopted a mixed methods research design, with 459 and 137 student teachers completing a questionnaire on teaching motivation and 35 and 15 student teachers joining a follow-up interview in Hong Kong and Macau, respectively. The study found that student teachers in both societies share commonality in their altruistic and intrinsic motivations, i.e. a sense of vocation. The difference in student teachers’ motivation reflects the contrasting perceptions of teachers’ work and the teaching profession in connection with the different educational systemic factors in Macau and Hong Kong. Government-initiated quantitative expansion and quality enhancement in education set the backdrop of an aspiring teaching profession with promising prospects as perceived by the student teachers in Macau. In contrast, the move towards "centralized-decentralization" with a focus on excellence, competition and accountability in education at a time of teacher surplus results in a demanding profession with gloomy prospects as perceived by the Hong Kong student teachers. These differences add to our understanding of how the development trajectories of different education systems and teaching professions influence young people’s motivation to become teachers in different societies. The study also provides insights for initial teacher education and offers suggestions for the education communities of the two societies.
Tang, M.Y.,Ma, Q.G.,Chen, X.D.,Ji, C. Asian Australasian Association of Animal Productio 2007 Animal Bioscience Vol.20 No.12
An experiment was performed to evaluate the effects of dietary metabolizable energy (ME) and lysine on carcass characteristics and meat quality in Arbor Acres (AA) broilers from 1 to 56 days of age. A total of 2,970 1-d-old male broiler chicks were randomly allocated to nine dietary treatments (three ME levels in combination with three lysine levels), and dietary ME and lysine concentrations were formulated by varying corn, soybean meal, tallow, and L-lysine sulfate concentrations. Live body weight (BW), carcass weight (CW), dressing percent, breast muscle weight (BMW), yield of breast muscle, muscle color (CIE L*, a*, and b*), pH values 45 min and 24 h postmortem ($pH_{45}$, and $pH_{24}$), meat shear force value (SFV), and water loss rate (WLR) were evaluated. Results showed that live body weight and dressing percent increased (p<0.05) as dietary energy increased. Higher dietary lysine content improved breast muscle weight. Neither carcass weight nor yield of breast muscle was affected by dietary energy or lysine content. Higher ME increased the b* value (p = 0.067) and $pH_{24}$ value (p<0.05), whereas it decreased SFV (p<0.05) and WLR (p = 0.06). Only water loss rate was influenced (p<0.01) by dietary lysine, which was higher in broilers from the high lysine diet as compared to those from medium or low lysine diets. The $pH_{45}$ value and L* value of breast muscle were not affected by ME or lysine. Significant interaction of dietary ME and lysine was found on a* value of breast muscle. These results indicated that dietary ME and lysine had important effects on breast muscle growth and meat quality, however their effects were different. Different concentrations of dietary ME and lysine might be considered to improve meat quality.