Synthesis, electronic structure and luminescence properties of color-controllable Dy³⁺/Eu³⁺-codoped CaWO₄ phosphors

Du, P.,Wu, S.,Yu, J.S. Elsevier [etc.] 2016 Journal of luminescence Vol.173 No.-

<P>Color-tunable CaWO4:0.05Dy(3+)/xEu(3+) phosphors were synthesized via a solid-state reaction method and the electronic properties of CaWO4 host lattice were analyzed through density function theory calculation. Under the excitations of 250 and 351 nm, characteristic emissions corresponding to D-5(0)-> F-4(J) (J=0, 1, 2) transitions of Eu3+ ions and characteristic blue and yellow emissions corresponding to (F9/2 -> H15/2)-F-4-H-6 and F-4(9/2)-> H-6(13/2) transitions of Dy3+ ions, respectively, were observed in all the Dy3+/Eu3+ ions codoped CaWO4 phosphors. The photoluminescence spectra and decay curves revealed that there existed an energy transfer from Dy3+ to Eu3+ ions and this was certified to be a resonant type via a dipole-dipole interaction. Furthermore, color-tunable emissions were observed by adjusting the relative content between Dy3+ and Eu3+ ions and the excitation wavelength. In addition, the Dy3+/Eu3+ ions codoped CaWO4 phosphors exhibited strong cathodoluminescence properties and their emission intensity increased with the increment of accelerating voltage from 1 to 5 kV and filament current from 34 to 55 mu A. (C) 2016 Elsevier B.V. All rights reserved.</P>

AC over-current characteristics of YBCO coated conductor with copper stabilizer layer considering insulation layer

Du, H.I.,Kim, M.J.,Kim, Y.J.,Lee, D.H.,Han, B.S.,Song, S.S. North-Holland 2010 Physica. C, Superconductivity Vol.470 No.20

Compared with the first-generation BSCCO wire, the YBCO thin-film wire boasts low material costs and high J<SUB>c</SUB> and superior magnetic-field properties, among other strengths. Meanwhile, the previous BSCCO wire material for superconducting cables has been researched on considerably with regard to its post-wire quenching characteristics during the application of an alternating over-current. In this regard, the promising YBCO thin-film wire has yet to be further researched on. Moreover, still lacking is research on the YBCO thin-film wire with insulating layers, which is essential in the manufacture of superconducting cables, along with the testing of the application of an alternating over-current to the wire. In this study, YBCO thin-film wires with copper-stabilizing layers were used in testing alternating over-current application according to the presence or absence of insulating layers and to the thickness of such layers, to examine the post-quenching wire resistance increase and quenching trends. The YBCO thin-film wire with copper-stabilizing layers has a critical temperature of 90K and a critical current of 85A<SUB>rms</SUB>. Moreover, its current application cycle is 5.5 cycles, and its applied currents are 354, 517, 712, and 915A<SUB>peak</SUB>. These figures enabled the YBCO thin-film wires with copper-stabilizing layers to reach 90, 180, 250, and 300K, respectively, in this study. These temperatures serve as a relative reference to examine the post-quenching wire properties following the application of an alternating over-current.

Tailoring of the plasmonic and waveguide effect in bulk-heterojunction photovoltaic devices with ordered, nanopatterned structures

Wang, D.H.,Kyaw, A.K.K.,Du, Q.G.,Choi, D.G.,Park, J.H. Elsevier Science 2014 Organic Electronics Vol.15 No.11

Various nano-patterned bulk-heterojunction (BHJ) films with different diameters and pitches were fabricated by a stamping method to tailor the plasmonic effect. The nanopatterned BHJ active layers exhibit regular-ordered embossing structures, which were confirmed by the surface morphological analysis with SEM and AFM. The simulation results confirm that devices with nanopatterned BHJ film with a diameter/pitch of 265/400nm exhibit a strong improvement in E-field distribution intensity due to the combination of the plasmonic and waveguide modes compared to devices without a nanopattern, with 150/400nm, or with 265/800nm, which led to increased J<SUB>SC</SUB> and cell efficiency in J-V curves under solar light illumination. The optimized plasmonic effect plays an important role in the light harvesting of BHJ devices.

Phenolic Profile and Antioxidant Capacities of Dried Red Currant from Serbia, Extracted with Different Solvent

Milan N. Mitić,Mirjana V. Obradović,Danijela A. Kostić,Ružica J. Micić,Dušan Đ. Paunović 한국식품과학회 2011 Food Science and Biotechnology Vol.20 No.6

The antioxidant capacity and the phenolic content of 3 dried red currant samples from different geographical regions were studied. Three solvent systems were used (methanol, ethanol, and acetone) at the same concentrations (70%) and with 100% deionized water in presence 0.1% HCl. The antioxidant capacity of the dried fruit extracts was evaluated using DPPH radical scavenging assays. The efficiency of the solvents used to extract phenols from the 3 dried red currant samples varied considerably. The polyphenol content of the dried red currant samples was 3.26 to 12.68 mg gallic acid equivalent/g dried fruit. The high phenolic content was significantly correlated with the high antioxidant capacity. The following compounds were identified and quantified using HPLC with photodiode-array detection: 3 anthocyanins,2 flavonols, 2 flavan-3-ols, and 3 hydroxycinnamic acids in all samples. Generally, red currant fruits are a rich source of phenolics, which shows an evident antioxidant capacity.

Globalisation and cultural transformation: African and South African perspectives

( J. A. (Kobus) Du Pisani ) 한국외국어대학교 외국학종합연구센터 2004 International Area Studies Review Vol.7 No.1

Efficient activation of peroxymonosulfate by magnetic Mn-MGO for degradation of bisphenol A

Du, J.,Bao, J.,Liu, Y.,Ling, H.,Zheng, H.,Kim, S.H.,Dionysiou, D.D. Elsevier Scientific Pub. Co 2016 Journal of hazardous materials Vol.320 No.-

A heterogeneous manganese/magnetite/graphene oxide (Mn-MGO) hybrid catalyst was fabricated through the reduction of KMnO<SUB>4</SUB> by ethylene glycol in the presence of magnetite/GO (MGO) particles. The Mn-MGO catalyst exhibited high efficacy and long-term stability in activating peroxymonosulfate (PMS) to generate sulfate radicals for the removal of bisphenol A (BPA) from water. The results of the batch experiments indicated that an increase in the catalyst dose and solution pH could enhance BPA degradation in the coupled Mn-MGO/PMS system. Regardless of the initial pH, the solution pH significantly dropped after the reaction, which was caused by catalytic PMS activation. The production of sulfate radicals and hydroxyl radicals was validated through radical quenching and electron paramagnetic resonances (EPR) tests. BPA degradation pathways were proposed on the basis of LC@?MS and GC@?MS analyses. Finally, a possible mechanism of catalytic PMS activation was proposed that involved electron transfer from MnO or Mn<SUB>2</SUB>O<SUB>3</SUB> to PMS with the generation of sulfate radicals, protons and MnO<SUB>2</SUB>, as well as the simultaneous reduction of MnO<SUB>2</SUB> by PMS.

Nonorientable regular embeddings of graphs of order p²

Du, S.F.,Kwak, J.H. North-Holland Pub. Co ; Elsevier Science Ltd 2010 Discrete mathematics Vol.310 No.12

A map is called regular if its automorphism group acts regularly on the set of all flags (incident vertex-edge-face triples). An orientable map is called orientably regular if the group of all orientation-preserving automorphisms is regular on the set of all arcs (incident vertex-edge pairs). If an orientably regular map admits also orientation-reversing automorphisms, then it is regular, and is called reflexible. A regular embedding and orientably regular embedding of a graph G are, respectively, 2-cell embeddings of G as a regular map and orientably regular map on some closed surface. In Du et al. (2004) [7], the orientably regular embeddings of graphs of order pq for two primes p and q (p may be equal to q) have been classified, where all the reflexible maps can be easily read from the classification theorem. In [11], Du and Wang (2007) classified the nonorientable regular embeddings of these graphs for p<>q. In this paper, we shall classify the nonorientable regular embeddings of graphs of order p<SUP>2</SUP>where p is a prime so that a complete classification of regular embeddings of graphs of order pq for two primes p and q is obtained. All graphs in this paper are connected and simple.

A facile sol-gel method for synthesis of porous Nd-doped TiO₂ monolith with enhanced photocatalytic activity under UV-Vis irradiation

Du, J.,Chen, H.,Yang, H.,Sang, R.,Qian, Y.,Li, Y.,Zhu, G.,Mao, Y.,He, W.,Kang, D.J. Elsevier 2013 Microporous and mesoporous materials Vol.182 No.-

A porous Nd-doped TiO<SUB>2</SUB> monolith was successfully synthesized with polystyrene spheres as a template using a sol-gel method followed by calcination at high temperature. The porous Nd-doped TiO<SUB>2</SUB> monolith was characterized by X-ray diffractometry, scanning electron microscopy and Brunauer-Emmett-Teller measurements. Nd doping can increase the TiO<SUB>2</SUB> surface area by hindering the growth of large TiO<SUB>2</SUB> particles, and suppressing the recombination of photo-produced hole/electron (h<SUP>+</SUP>/e<SUP>-</SUP>) pairs. Moreover, its porous structure can provide a large surface area, facilitating enhanced adsorption and fast transfer of pollutants. To evaluate the photocatalytic activity of the porous Nd-doped TiO<SUB>2</SUB> monolith, the photo-degradation for methyl orange was investigated under UV-Vis irradiation. The porous 0.5% Nd-doped TiO<SUB>2</SUB> monolith showed better behavior than the other as-prepared samples and Degussa P25 due to its narrow band gap, high efficiency for h<SUP>+</SUP>/e<SUP>-</SUP> pair separation, and large surface area. The synergistic combination of Nd doping and the porous structure is a promising material design strategy for use in the degradation of organic pollutants.

Mesoporous sulfur-modified iron oxide as an effective Fenton-like catalyst for degradation of bisphenol A

Du, J.,Bao, J.,Fu, X.,Lu, C.,Kim, S.H. Elsevier 2016 Applied Catalysis B Vol.184 No.-

<P>A mesoporous sulfur-modified iron oxide (MS-Fe) was prepared as a heterogeneous H2O2 catalyst for degradation of BPA. The physico-chemical properties of MS-Fe and bare M-Fe were characterized by BET surface area measurement, SEM, XRD, MIR and XPS. Both M-Fe and MS-Fe composites appeared as cubic microparticles with abundant pores and cracks as well as large surface area. As depicted by XRD, EDX and XPS, M-Fe is mainly consisted of hematite while MS-Fe is a kind of S-doped iron oxide with about 5-6% of sulfur element in terms of atomic ratio. In contrast to the poor catalytic activity of bare M-Fe, the MS Fe composites showed greatly improved efficiencies for H2O2 activation for BPA degradation. The high catalytic activity of this new Fenton-like catalyst can be obtained at different initial pH in range of 3.0-9.0. The time evolution of degradation of BPA followed pseudo-first-order kinetics, and the first-order rate constants showed a linear relationship with parameters of initial pH, catalyst dosage and concentration of BPA. However, the H2O2 dosage showed a dual effect on BPA degradation because excessive H2O2 addition lead to scavenging of hydroxyl radicals ((OH)-O-center dot). The investigation of working mechanisms of MS Fe suggested a synergistic effect of homogeneous and heterogeneous degradation reaction, wherein a strong acidic environment, abundant surface-bonded hydroxyl group and electron-mediating effect of sulfur all contributed to fast activation of H2O2. Overall, this new material overcomes the limitation of narrow working pH range and shows a fast oxidation of BPA with a low H2O2 and catalyst dosage, would have a good potential for environmental application. (C) 2015 Elsevier B.V. All rights reserved.</P>

The Convective Heat Transfer for the Extended Surface with Uniform Cross-Section in a Channel

J. H. Du,B. X. Wang,X. F. Peng 대한기계학회 1998 Heat transter conference Vol.3 No.1