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[en] X-ray photoemission spectroscopy and X-ray diffraction reveal that N+ ion irradiation causes the occurrence of the metallic bismuth and the surface decomposition in Bi2Sr2CaCu2Oy crystals. We think that such change results in the change of oxygen content. Due to this fact, a possible reason for the decrease of the superconducting transition temperature is suggested as the change of oxygen content. (author)
[en] Nuclear design and fuel management of submarine reactors and NPP reactors are based on solving 3D multi-group neutron diffusion equation accurately and efficiently. One of the methods for this equation is finite difference method (FDM), which is simple, accurate and mature. However, the computation burden of FDM is huge and the memory requirement is high, thus limiting FDM's scale and application scope. In this paper, FDM for 3D multi-group neutron diffusion equation based on large-scale parallel computation is researched. Mesh-centered FDM is used to discrete the neutron diffusion equation. Large-scale parallel computation is realized by domain decomposition based on MPI, and it's accelerated with multi-group multi-domain coupled PGMRES algorithm. ParaFiDi code is developed on high performance cluster and verified by several benchmarks such as IAEA3D and PHWR. Numerical results demonstrate that ParaFiDi code could obtain good efficiency and accuracy. (authors)
[en] The changes of profiles along the a, b and c directions of a Bi2Sr2CaCu2Oδ single crystal were examined by the X-ray diffraction method over the temperature range from 297 K to 77. Splitting of the (0k0) and (h00) diffraction peaks appeared in the temperature regions from 262 to 222 K and from 226 to 156 K, respectively. Changes of the modulation structure appear in the temperature regions from 207 to 202 K and from 112 to 102 K. Moreover, there is no remarkable change of the (00l) diffraction peaks. Below the temperature of 91 K, the (040) diffraction peak obviously begins to broaden. (authors)
[en] The temperature and carrier concentration dependence of the thermopower (TEP) S in Bi2Sr2Ca1-xRxCu2Oy (R=Gd, Pr) single crystals were carefully studied. Upon Gd or Pr doping, the superconductivity changes systematically from overdoping to underdoping with the TEP increasing monotonically. S(T)/S(Tscale) against T/Tscale for all the underdoped crystals can be well scaled into a universal curve, where Tscale is the temperature at which S begins to deviate from T-linear behaviour. This scaling behaviour is assumed to correlate with the opening of the pseudogap. Furthermore, the temperature dependence of the TEP is analysed and discussed in terms of two different two-band models and the Nagaosa-Lee model. (author)
[en] The Ailaoshan tectonic belt, where the effects of the Paleo-Tethyan ocean evolution and Indian–Eurasian plate collision are superimposed, is one of the most significant geological discontinuities in western Yunnan province of southeast Tibet. An Ailaoshan micro-block within the belt is bounded by the Ailaoshan suture zone to the west and the Red River Fault to the east, and consists of low- and high-grade metamorphic belts. Late Permian–Middle Triassic granitoids that are widely distributed to the west of the Ailaoshan suture zone and within the Ailaoshan micro-block may yield significant information on the Tethyan tectonic evolution of the Ailaoshan tectonic belt. This study reports new LA–ICP–MS zircon U–Pb geochronology and Hf isotope data of four granitoids from the Ailaoshan high-grade metamorphic belt. Zircon grains from the Yinjie granitoid do not have inherited cores and yield a weighted mean U–Pb age of 247.1 ± 2.0 Ma. The zircon εHf(t) values range from 7.8 to 12.1, and Hf model ages from 775 to 546 Ma, indicating that the granitoid was derived from juvenile crust. The rims of zircons from the Majie and Yuanjiang granitoids yield weighted mean U–Pb ages of 239.5 ± 1.8 and 237.9 ± 2.6 Ma, respectively, whereas the cores yield ages of 1608–352 Ma. The εHf(t) values of zircon rims range from −20.4 to −5.3, yielding Hf model ages from 2557 to 1606 Ma and suggesting that the source magma of the Majie and Yuanjiang granitoids was derived from ancient crust. An additional granitoid located near the Majie Village yields a zircon U–Pb age of 241.2 ± 1.0 Ma. Based on our geochronological and geochemical data, combined with geological observations, we propose that the Ailaoshan micro-block was derived from the western margin of the Yangtze block, and is comparable to the Zhongzan and Nam Co micro-blocks. The presence of late Permian mafic rocks with rift-related geochemical characteristics within the Ailaoshan micro-block, together with granitoids derived from partial melting of ancient/juvenile crust, indicates the presence of an Ailaoshan rift. This possible rift may correspond to the Ganzi–Litang Ocean to the northwest and the Jinping–Song Da rift to the southeast. It is suggested that westward subduction of the Jinshajiang–Ailaoshan–Song Ma oceanic lithosphere triggered the separation of the Zhongzan, Ailaoshan, and Nam Co micro-blocks from the western passive continental margin of the Yangtze block through the opening of the Ganzi–Litang–Ailaoshan–Jinping–Song Da ocean/rift. This ocean/rift may represent a subsidiary branch of the Paleo-Tethyan Ocean along the western margin of the Yangtze block.
[en] The traveling wave reactor (TWR) is an innovative nuclear system, whose discharge burnup is 400 GWd/tHM, about three to four times of existing fast reactor and six to eight times of pressurized water reactor. High discharge burnup forces the present codes to face the great challenges in precision.This paper studies the high burnup calculation characteristics of traveling wave reactor from energy spectrum, importance of fission production and calculation error accumulation of fuel consumption by KYLIN-1 code. The analysis results of typical traveling wave reactor hexagonal assembly show that the low enriched uranium assemblies have different energy spectra at beginning and end of life, which cause big calculation error of kinf by existing code system. To ensure the correctness of the traveling wave reactor burnup calculations, the burn chain should contain 70 kinds of important fission product nuclides. The calculation error accumulation of fuel consumption is small when the burnup step is increased. The calculation error of kinf is about 0.001% each burnup step. (authors)
[en] Matrix uranium was separated by using CL-TBP levextrel resin and then ICP-AES method was used to determine titanium content in sulphuric acid system (such as feed solution and mother solution) in uranium hydrometallurgical process. Under the optimum element analysis spectral line and working conditions, the relative standard deviation of the method was less than 10% and the recovery rate was 90%-109%. The method is rapid, simple, and the requirement of the analysis can be met. (authors)
[en] La0.67Ca0.33MnO3 (LCMO) films of 6-60 nm thickness were grown epitaxially on orthorhombic NdGaO3(1 1 0)Or (NGO) substrates by the pulsed laser deposition method. Like NGO, the films when relaxed should also have an orthorhombic structure that can be described by a pseudocubic perovskite unit, with the angle β between a and c axes deviating from 90 deg. Using high-resolution off-specular x-ray reciprocal space mapping, we clearly observed the angle deviations in pseudocubic LCMO(0 0 1)/NGO(0 0 1) and investigated the thickness evolution of lattice distortions in the films. At above 30 nm the films are angularly relaxed, while the thinner ones suffer from the shear strain. We argue that for this system although the lattice mismatch in between is negligible the shear strain is crucial for transport properties of the ultrathin LCMO films. (fast track communication)
[en] A determination of the Schottky barrier height at the interface between ferroelectric Pb(Zr,Ti)O3 thin films and Pt using in-situ photoelectron spectroscopy is presented. The barrier height for holes, given by the energy difference of the valence band maximum and the Fermi energy, varies reversibly between 1.1 and 2.2 eV for oxidizing and reducing treatments. The changes in barrier are accompanied by a varying amount of metallic Pb at the interface. The most severe reduction is observed after storage in vacuum, which is attributed to the strongly reducing environment because of the presence of hydrogen and water in the residual gas of the vacuum system and the catalytically active Pt surface.
[en] Transparent and conductive oxide (TCO) films with a cubic perovskite structure, lanthanum-doped strontium stannate LaxSr1-xSnO3 (x = 0-0.15) (LSSO), have been grown epitaxially on SrTiO3(0 0 1) substrates by the pulsed laser deposition method. The doping concentration and growth parameters were optimized based on the high-resolution x-ray diffraction and electric transport measurements. We found that the optimum doping level is around x = 0.07, and the epitaxial films can be grown at temperatures as low as 600 0C and in atmospheres compatible with many other perovskite oxide films. They are n-type TCO films, showing high optical transmittance in the visible range with a direct allowed band gap of 4.65 eV, and a weak metallic transport behaviour with a low resistivity of ∼4.0 mΩ cm within 10-300 K. Due to a very close lattice match with the ferroelectric Pb(Zr0.52Ti0.48)O3 (PZT) and multiferroic BiFeO3 (BFO), all-perovskite LSSO(Pt)PZT(BFO)/LSSO capacitors and p-PZT(≤20 nm)/n-LSSO [p-BFO (100 nm)/n-LSSO] p-n junctions have also been fabricated and characterized. The square polarization versus electric-field hysteresis loops, good rectifying characteristics, high optical transmittance, as well as the epitaxial growth exhibited by the heterostructures, strongly suggest that the LSSO films are potential candidates for use in transparent thin-film devices.