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[en] The d"0 ferromagnetism in wurtzite GaN is investigated by the first-principle calculations. It is found that spontaneous magnetization occurs if sufficient holes are injected in GaN. Both Ga vacancy and Na doping can introduce holes into GaN. However, Ga vacancy has a high formation energy, and is thus unlikely to occur in a significant concentration. In contrast, Na doping has relatively low formation energy. Under N-rich growth condition, Na doping with a sufficient concentration can be achieved, which can induce half-metallic ferromagnetism in GaN. Moreover, the estimated Curie temperature of Na-doped GaN is well above the room temperature. - Highlights: • Hole-induced ferromagnetism in GaN is confirmed. • Both Ga Vacancy and Na-doping can introduce hole into GaN. • The concentration of Ga vacancy is too low to induce detectable ferromagnetism. • Na-doped GaN is a possible ferromagnet with a high curie-temperature.
[en] The dynamic responses of the soil-auxiliary buildings structure interaction system in the nuclear power plant are concerned. The main distinguished feature of this study is that the extreme un-symmetry of the auxiliary buildings and reactor containment are considered. A Synthetical mechanical model for study is established. Finally, the analysis of the dynamic response of the Qinshan Nuclear Power Plant structure is taken as a simple example of applying this method and the numerical results are given
[en] Layered double hydroxides (LDHs) with Mg2+ and Fe3+ cations in the brucite-like layers and having chloride or nitrate ions in the interlayer region have been prepared and characterized by powder X-ray diffraction (PXRD), elemental analysis and thermal analysis. Thermal decomposition of the LDH-nitrate occurs in two steps, with loss of water followed by simultaneous dehydroxylation of the layers and loss of NOx/O2 arising from the nitrate anions. Thermal decomposition of the LDH-chloride involves an additional step, with chloride ions becoming grafted to the layers, prior to loss of HCl. The interlayer anions may be readily replaced by sulfate, thiosulfate, tartrate and vinylbenzenesulfonate ions suggesting that these materials may be useful precursors to Mg-Fe(III) LDHs intercalated with a variety of inorganic and organic anions
[en] In this research communication, a novel method for improving magnetic properties of material containing MgFe2O4 spinel ferrite is presented. The key feature of this method is using a single molecular precursor. Mg-Fe(III) layered double hydroxide intercalated by [Fe(China)6]3- ions with the low Mg/Fe molar ratio can be prepared by coprecipitation method. Compared with conventional ceramic method, the saturation magnetization for MgFeO4 ferrite produced by calcination of the intercalated LDH precursor is improved obviously. The major advantage of the method is that it affords uniform distribution of all metal cations on an atomic level in the intercalated LDH precursor, and supplies additional Fe3+ ions from the interlayer [Fe(China)6]3- ions; hence the formation of a great amount of spinel ferrite starting from the LDH rather than a mixture requires a much shorter time and lower temperature
[en] Although switching systems have been investigated intensively, there are few results about limit cycles bifurcated from switching systems with degenerate singular point. In this paper, a method to compute focal values for degenerate critical point of switching systems was proposed. Furthermore, we studied a quartic system in order to illustrate the efficiency of our method.
[en] Layered double hydroxides (LDHs) with Cu2+/Zn2+/Al3+ atomic ratios from 1:1:1 to 3:1:1 have been synthesized by coprecipitation method. The physicochemical properties of both the as-synthesized LDHs and their calcined products obtained at 773 K for 3 h have been characterized by powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR), chemical analysis, transmission electron microscopy (TEM), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), N2 adsorption-desorption experiments and thermogravimetric analysis (TGA). The chemical states of metal species on the surface of the calcined LDHs were also characterized by temperature-programmed reduction (TPR) and X-ray photoelectron spectroscopy (XPS). The results indicate that Cu2+/Zn2+/Al3+ atomic ratio in the synthesis mixtures influences crystallinity, purity, and thermal stability of the LDHs, and hence, the composition of the resulting calcined LDHs. At room temperature and atmospheric pressure, oxidation of aqueous phenol solutions by hydrogen peroxide in the presence of the calcined LDHs was carried out. The results show that the calcined LDHs with the Cu2+/Zn2+/Al3+ atomic ratio of 1:1:1 has the highest catalytic activity for conversion of phenol, which may be related to the formation of a great amount of composite metal oxide containing Cu2+ ions and to good dispersion property of active Cu2+ centers present on the surface
[en] Electronic stopping powers for 80-350 keV 19F ions in AgGaS2 were obtained by range measurement. Depth profiles of 19F in AgGaS2 were measured by using the 19F(p,αγ)16O resonant nuclear reaction at ER=872.1 keV. A proper convolution calculation method was used to extract the true distribution of fluorine from the experimental excitation yield curves. The electronic stopping powers were derived through fitting the projected range distributions, simulated by using the TRIM/XLL code, to the experimentally measured range distributions. The electronic stopping cross sections were compared with those obtained from Monte Carlo simulation codes
[en] Efficient white organic light-emitting devices (OLEDs) are demonstrated by inserting a thin layer of tris (8-hydroxyquinoline) aluminum (Alq) doped with 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl) (DCJTB) into N,N'-diphenyl-N,N'-bis(1-naphthyl)-(1,1'-biphenyl)-4,4'-diamine (NPB) layer. Alq without doping is used as an electron-transporting layer and 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (bathocuproine or BCP) as an exciton-blocking layer. NPB layers are separated by the doped Alq layer, the layer that sandwiched between BCP and doped Alq layers acts as a blue-emitting layer, and the other as a hole-transporting layer. The doped Alq layer acts as a red and green-emitting as well as chromaticity-tuning layer, whose thickness and position as well as the concentration of DCJTB in Alq permit the tuning of the device spectrum to achieve a balanced white emission with Commission Internationale De L'Eclairage (CIE) coordinates of (0.33, 0.33). The device has a maximum luminance of 6745 cd/m2, a maximum external efficiency of 1.36 %, corresponding to 2.56 cd/A
[en] Range distributions for fluorine ions implanted in AgGaS2 in an energy range of 80-350 keV were measured by using the 19F(p,αγ)16O resonant nuclear reaction at ER=872.1 keV, with width Γ=4.2 keV. A proper convolution calculation method was used to extract the true distributions of fluorine from the experimental excitation yield curves. The range distribution parameters, Rp and ΔRp, were obtained and compared with those obtained from different Monte Carlo simulation computer codes
[en] The pressure and temperature transients with the time of the reactor pit during LOCA have been analyzed by using Catem computer code for Qinshan-2 nuclear power plant. The force and bending moment on the inlet and outlet nozzles of the reactor vessel also have been calculated by using Wformom code. Qinshan-2 NPP is a two-loop nuclear power plant. The cold water of the accumulators are directly injected into the downcomer of reactor vessel. Injection line of accumulators is located at the same level with the inlet and outlet nozzles. These geometry characteristics have been taken into account in the circumferential vessel pit nodding using five volumes around the vessel. The assumptions used in the analysis and calculation results have been presented. Many sensitive calculations have been performed for different break size and circumferential nodding