Abnormal reduction of Eu ions and luminescence in CaB2O4: Eu thin films

Thin films of CaB2O4: Eu were deposited on glass substrates by spray pyrolysis. The abnormal reduction of Eu3+ to Eu2+ in as-grown thin films was found at the growth temperatures from 300 to 500 °C. Blue cathodoluminescence was observed by annealing films in air, correlating with further abnormal reduction of Eu ions and crystallization of compounds. These phenomena were explained by an electron transfer mechanism. The chromaticity coordinates were x = 0.193 and y = 0.089 with a dominant wavelength of 455 nm. Our results indicate calcium borate doped with Eu is a blue phosphor at temperatures suitable for the use of glass substrates in flat panel applications. © 2004 American Institute of Physics.published_or_final_versio

Magnetotransport and dielectric properties of perovskite ruthenate and titanate thin films

2007-2008 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Rectifying characteristics and transport behavior of SrTiO3-δ(110)/p-Si(100) heterojunctions

Introducing oxygen vacancy causes the dielectric insulator SrTi O3 to evolve to a n -type semiconductor. The authors have fabricated n-SrTi O3-δ (110) p-Si (100) heterojunctions, showing clear rectifying characteristics at different temperatures from 100 to 292 K. A forward-to-reverse bias ratio of about 1200 was found at V=±2 V for the p-n junction operated at T=292 K. The current-voltage characteristic follows Iexp (eVkT) for the p-n junction at relatively low forward-bias voltage, while the relation of I∼ V1.9 describes the transport behavior of p-n junction at relatively high forward-bias voltage. The measured results have been discussed in Anderson model and space charge limited model. © 2007 American Institute of Physics.published_or_final_versio

Effects of substrate on the dielectric and tunable properties of epitaxial SrTiO₃thin films

2006-2007 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Application of chaotic-motion motors to industrial mixing processes

Industrial mixers are among the most expensive and ineffective equipment in food, drug, chemical and semiconductor industries. Effects of this ineffectiveness are not only energy wastage, but also can be disastrous. Instead of using complicated mechanical means, this paper presents a new way which can electrically produce the desired chaotic motion for industrial mixing processes. Namely, chaoization of the DC motor (the agitator) using time-delay feedback control is proposed and implemented. Theoretical derivation and computer simulation are provided to illustrate the controllable chaotic motion. Moreover, the mixing effectiveness is experimentally verified by an acid-base neutralization reaction.published_or_final_versio

Titania Nanomaterials Produced from Ti-Salt Flocculated Sludge in Water Treatment

Titania is the most widely used metal oxide for the applications of pigments, paper, solar cells and environmental purification. In order to meet the demand of a large amount of titania, our group has developed a novel process which could significantly lower the cost of waste disposal in water treatment, protect the environment and public health and yield economically valuable titania. Titanium tetrachloride (TiCl4) or titanium sulfate (Ti(SO4)2) as an alternative coagulant in water treatment has been explored for the removal of various pollutants from contaminated water or wastewater. Flocculation efficiencies of the Ti-salts were superior to those of Al- and Fe- salts with additional benefits in that a large amount of titania can be produced by calcinating the flocculated floc. The produced titania showed high photocatalytic activity for the removal of volatile organic compounds. The large amount of titania can be applied to pigments, environment and construction materials which require a lot of titania usages. This review paper presents an historical progress from fundamental to application in terms of the detailed production process, characterization, photoactivity of titania produced from Ti-salt flocculated sludge, and its various applications. © 2011 Springer Science+Business Media, LLC

Age-related differences in neural activities during risk taking as revealed by functional MRI

Previous research has clearly documented that risky decision making is different in young and older adults. Yet, there has been a relative dearth of research that seeks to understand such age-related changes in the neural activities associated with risk taking. To address this research issue, 21 men (12 young men, mean age 29.9±6.2 years and 9 older men, mean age 65.2±4.2 years) performed a risky-gains task while their brain activities were monitored by an fMRI scanner. The older adults, relative to their younger peers, presented with contralateral prefrontal activity, particularly at the orbitofrontal cortex. Furthermore, stronger activation of the right insula was observed for the older-aged participants compared to the younger-aged adults. The findings of this study are consistent with the a priori speculations established in accordance with the HAROLD model as well as previous findings. Findings of this study suggest that when making risky decisions, there may be possible neuropsychological mechanisms underlying the change in impulsive and risk-taking behaviors during the course of natural ageing. © 2007 The Author(s).published_or_final_versio

Magnetoresistance in La- and Ca-doped YBa2Cu3O7–δ

We studied the microstructures, electronic, and magnetic properties on La-doped and La- and Ca-codoped YBa2Cu3O7−δ (YBCO). The superconducting transition temperature remains unchanged up to 10% for La-doped YBCO. The competition between electrons and holons was assumed according to the variation of Tc0 in La and Ca codopings in YBCO. The magnetoresistance (MR) effect is about 8%, which is observed obviously near the critical temperature and is independent of the content of La in La-doped YBCO. MR increases up to about 40% with the incorporation of Ca in La-doped YBCO. We present here possible explanations for the magnetoresistance effect in polycrystalline samples based on the microstructure and the increase of oxygen vacancies at grain-boundary interface. © 2006 American Institute of Physicspublished_or_final_versio

Heterogeneous mantle source and magma differentiation of quaternary arc-like volcanic rocks from Tengchong, SE margin of the Tibetan Plateau

The Tengchong volcanic field north of the Burma arc comprises numerous Quaternary volcanoes in the southeastern margin of the Tibetan Plateau. The volcanic rocks are grouped into four units (1-4) from the oldest to youngest. Units 1, 3 and 4 are composed of olivine trachybasalt, basaltic trachyandesite and trachyandesite, and Unit 2 consists of hornblende dacite. The rocks of Units 1, 3, and 4 form a generally alkaline suite in which the rocks plot along generally linear trends on Harker diagrams with only slight offset from unit to unit. They contain olivine phenocrysts with Fo values ranging from 65 to 85 mol% and have Cr-spinel with Cr# ranging from 23 to 35. All the rocks have chondrite-normalized REE patterns enriched in LREE and primitive mantle-normalized trace element patterns depleted in Ti, Nb and Ta, but they are rich in Th, Ti and P relative to typical arc volcanics. Despite minor crustal contamination, 87Sr/ 86Sr ratios (0.706-0.709), εNd values (-3.2 to -8.7), and εHf values (+4.8 to -6.4) indicate a highly heterogeneous mantle source. The Pb isotopic ratios of the lavas ( 206Pb/ 204Pb = 18.02-18.30) clearly show an EMI-type mantle source. The underlying mantle source was previously modified by subduction of the Neo-Tethyan oceanic and Indian continental lithosphere. The present heterogeneous mantle source is interpreted to have formed by variable additions of fluids and sediments derived from the subducted Indian Oceanic lithosphere, probably the Ninety East Ridge. Magma generation and emplacement was facilitated by transtensional NS-trending strike-slip faulting. © 2011 The Author(s).published_or_final_versionSpringer Open Choice, 28 May 201