[en] The nature of dark matter is one of the key outstanding problems in both particle and astrophysics. If dark matter decays or annihilates into electrons and positrons, it can affect diffuse radiation backgrounds observed in astrophysics. In this thesis, we propose a new, more general analysis of constraints on dark matter models. For any decaying dark matter model, constraints on mass and lifetime can be obtained by folding the specific dark matter decay spectrum with a response function. We derive these response functions from full-sky radio surveys and Fermi-LAT gamma-ray observations as well as from the local positron fluxes measured by the PAMELA satellite experiment and apply them to place constraints on some specific dark matter decay models. We also discuss the influence of astrophysical uncertainties on the response function, such as the uncertainties from propagation models and from the spatial distribution of the dark matter. Moreover, an anisotropy analysis of full-sky emission gamma-ray and radio maps is performed to identify possible signatures of annihilating dark matter. We calculate angular power spectra of the cosmological background of synchrotron emission from dark matter annihilations into electron positron pairs. We compare the power spectra with the anisotropy of astrophysical and cosmological radio backgrounds, from normal galaxies, radio-galaxies, galaxy cluster accretion shocks, the cosmic microwave background and Galactic foregrounds. In addition, we develop a numerical tool to compute gamma-ray emission from such electrons and positrons diffusing in the smooth host halo and in substructure halos with masses down to 10^-6M_sun. We show that, unlike the total gamma-ray angular power spectrum observed by Fermi-LAT, the angular power spectrum from the inverse Compton scattering is exponentially suppressed below an angular scale determined by the diffusion length of electrons and positrons. (orig.)

[en] Highlights: • Contrasting experiments between a rough and a smooth fracture were performed. • A numerical model of rough fracture was reconstructed based on CT scanning data. • Heat transfer in rough fracture was affected by channeling and disturbance effects. - Abstract: Convective heat transfer characteristics of supercritical pressure fluid in a rock fracture are important for building an accurate heat transfer model of enhanced geothermal systems. This paper presents experimental investigations of laminar convection heat transfer of supercritical pressure CO_2 in an artificial smooth parallel-plate fracture and a rough and tortuous fracture that was created using the Brazilian technique. Hot rock with a relatively high initial temperature reserves more heat, which can ensure a larger heat extraction rate for a longer time when cold fluid flows through the fracture. Compared with the smooth parallel-plate fracture, CO_2 flowing through the rough and tortuous fracture with an equivalent hydraulic aperture extracted less heat from the hot rock due to the less efficient heat exchange in a rough fracture caused by channeling effect. This was illustrated by numerical simulation results of the reconstructed fracture based on micro-computed tomography scan data. The overall Nusselt number obtained from the numerical results was larger in a rough fracture with a larger Reynolds number due to disturbance effect on the boundary layer development. The heat transfer performance in a rough fracture is therefore influenced by interactions of the channeling and disturbance effects caused by the tortuous flow path.

[en] Highlights: • High-quality PMN-PT 90/10 RFE thin films were prepared by RF magnetron sputtering. • The maximum discharged density of 31.3 J/cm"3 was obtained in the 750-nm-thick film. • PMN-PT RFE films might be a promising material for energy-storage application. - Abstract: 0.9Pb(Mg_1_/_3Nb_2_/_3)O_3-0.1PbTiO_3 (PMN-PT 90/10) relaxor ferroelectric thin films with different thicknesses were deposited on the LaNiO_3/Si (100) by the radio-frequency (RF) magnetron sputtering technique. The effects of thickness and deposition temperature on the microstructure, dielectric properties and the energy-storage performance of the thin films were investigated in detail. X-ray diffraction spectra indicated that the thin films had crystallized into a pure perovskite phase with a (100)-preferred orientation after annealed at 700 °C. Moreover, all the PMN-PT 90/10 thin films showed the uniform and crack-free surface microstructure. As a result, a larger recoverable energy density of 31.3 J/cm"3 was achieved in the 750-nm-thick film under 2640 kV/cm at room temperature. Thus, PMN-PT 90/10 relaxor thin films are the promising candidate for energy-storage capacitor application

[en] Hydrogen induced defects in annealed and plastically deformed pure aluminium have been studied mainly by the positron lifetime method and the transmission electron microscopy. It is revealed that the hydrogen charging can introduce blisters and dislocations in aluminium specimens. Inclusion particles in the specimens act as the nucleation sites of hydrogen induced defects. The effect of protons to shield defects from positron has been proved by the experimental results

[en] Objective: To analyze the clinical value of intravenous pyelogram (IVP), MDCT urography (CTU), and magnetic resonance urography (MRU) in the diagnosis of hydronephrosis. Methods: The image data of 96 patients with hydronephrosis were analyzed retrospectively. Among these patients, 72 cases were performed IVP examination, 43 cases were performed CTU examination, 36 cases were performed MRU examination, 23 patients underwent IVP and CTU examinations, 19 patients underwent IVP and MRU examinations, 6 patients underwent CTU and MRU examinations, and 3 patients underwent IVP, CTU, MRU examinations. Results: 52 cases (72%) with IVP examination were diagnosed definitely; 40 cases (93%) underwent CTU examination were diagnosed definitely; 35 patients (97%) with MRU examination were diagnosed definitely; 23 cases (100%) with IVP, CTU examination confirmed the diagnosis; 19 cases (100%) with IVP, MRU examinations confirmed the diagnosis; 6 cases (100%) with CTU, MRU examinations confirmed the diagnosis; the diagnosis of 3 patients (100%) with IVP, CTU, MRU examinations were clear. Conclusion: IVP, CTU and MRU each has its advantages and disadvantages. The combined application of these three methods is helpful to improve the diagnosis of hydronephrosis, and is important for guiding the clinical treatment. (authors)

[en] A series of nano-sized particle materials containing ZrO₂ was prepared and their compositions were determined by elemental analysis and thermogravimetric analysis (TGA). The effect of particle size and crystal structure type (lattice and space group) on the ER performance of these materials was investigated by X-ray diffraction (XRD) analysis, Raman spectra, the particle size analysis and rheological measurement. Their electrorheological (ER) effects show that the ER activities of the ZrO₂ materials doped with rare earth (RE=Y, La, Ce, Gd, Tb), whose grain sizes were less than that of pure ZrO₂, were lower than that of pure ZrO₂, which belongs to the tetragonal crystal system. The ER activity of Y₂O₃-ZrO₂ is the strongest among all the RE-doped ZrO₂ materials. The ER activity of the tetragonal phase ZrO₂ is higher than that of the monoclinic phase ZrO₂

[en] The Bi³⁺/Eu³⁺ singly and codoped double perovskite Ca₂LaTaO₆ phosphors were made via solid-phase sintering with the addition of H₃BO₃. X-ray powder diffraction patterns, morphology, particle size, and photoluminescence properties of them were researched. All of Bi³⁺/Eu³⁺ singly and codoped Ca₂LaTaO₆ phosphors have the same phase with pure Ca₂LaTaO₆. And all of phosphors have similar morphology and particle size. Exciting at 275 nm, Ca₂La_1−xEu_xTaO₆ (x = 0.1, 0.2, 0.3, 0.4, and 0.5) phosphors exhibit bands resulting from ⁵D₀ → ⁷F_J (J = 0, 1, 2, 3, and 4) transitions of Eu³⁺. It is found that the critical doping concentration of Eu³⁺ in Ca₂LaTaO₆ is about 0.4. Exciting at 272 nm, Ca₂La_1−yBi_yTaO₆ (y = 0.05, 0.1, and 0.15) phosphors exhibit emission bands corresponding to the ³P₁ → ¹S₀ transition of Bi³⁺. There is the occurrence of energy transfer in Bi³⁺/Eu³⁺ codoped Ca₂LaTaO₆ phosphors, which benefits to the enhancement of Eu³⁺ emission intensity.

[en] High energy electrons and positrons from annihilating dark matter can imprint unique angular anisotropies on the diffuse gamma-ray flux by inverse Compton scattering off the interstellar radiation field. We develop a numerical tool to compute gamma-ray emission from such electrons and positrons diffusing in the smooth host halo and in substructure halos with masses down to 10^-6M_sun. We show that, unlike the total gamma-ray angular power spectrum observed by Fermi-LAT, the angular power spectrum from inverse Compton scattering is exponentially suppressed below an angular scale determined by the diffusion length of electrons and positrons. For TeV scale dark matter with a canonical thermal freeze-out cross section 3 x 10^-26 cm³/s, this feature may be detectable by Fermi-LAT in the energy range 100-300 GeV after more sophisticated foreground subtraction. We also find that the total flux and the shape of the angular power spectrum depends sensitively on the spatial distribution of subhalos in the Milky Way. Finally, the contribution from the smooth host halo component to the gamma-ray mean intensity is negligibly small compared to subhalos. (orig.)

[en] Mass dispersion research of multi-mass plasma jet has important position in fields like separator or spectrometer. This paper studies the movement trajectory of multi-mass jet flow in inhomogeneous magnetic field and deduces an expression of mass dispersion. Considering the different incident angle and plume, we apply MATLAB to simulate motion trajectory of jet flow, calculate mass dispersion, and compare the result with mass dispersion in homogeneous magnetic field to confirm the effect of jet flow mass separation in this magnetic field. The simulation results show that the mass dispersion of multi-mass jet in inhomogeneous magnetic field is greater than that in homogeneous magnetic field, and that the mass separation of plasma jet can be efficiently realized. (authors)

[en] The particle trajectory varies exponentially at turning points in orthogonal electromagnetic field, causing the obvious difference of variety mass ion trajectories. So a new nuclides electromagnetic separation method can be created. From the Newton motion equation and based on the single particle track method, the article discusses the movement law of nuclide separated in orthogonal electromagnetic field and focuses on finding the turning point of the trajectories. The mass focusing characteristics of the multi-mass beam flowing in the orthogonal electromagnetic field are given. As an example, the particle trajectories of Li ion are simulated by MATLAB. The result shows the possibility of the mass separation for the multi-mass particle beam in the orthogonal electromagnetic field. According to the characteristics of the trajectory equation, the particles moving along a circular trajectory are summarized. Parameters such as space dimension for the engineering realization of multi-mass particle beam separation structure are provided. The research result can be applied to the development of some devices, such as the mass separator, the spectrum analyzer and the materials purification device. At the same time, it has certain reference significance for the related fields research of the special configuration electromagnetic field controlling multi-mass beam flow. (authors)