Morphology and Orientation Selection of Non-Metallic Inclusions in Electrified Molten Metal

The effect of electric current on morphology and orientation selection of non-metallic inclusions in molten metal has been investigated using theoretical modelling and numerical calculation. Two geometric factors, namely the circularity (fc) and alignment ratio (fe) were introduced to describe the inclusions shape and configuration. Electric current free energy was calculated and the values were used to determine the thermodynamic preference between different microstructures. Electric current promotes the development of inclusion along the current direction by either expatiating directional growth or enhancing directional agglomeration. Reconfiguration of the inclusions to reduce the system electric resistance drives the phenomena. The morphology and orientation selection follows the routine to reduce electric free energy. The numerical results are in agreement with our experimental observations

Oxygen non-stoichiometry in Ru-1212 and Ru-1222 magnetosuperconductors

Here we report the results of thermogravimetric (TG) analysis on the oxygen non-stoichiometry of RuSr2GdCu2O8 (Ru-1212) and RuSr2(Gd0.75Ce0.25)2Cu2O10(Ru-1222) samples. With TG annealings carried out in O2 and Ar atmospheres it was found that the oxygen content in Ru-1212 remains less affected upon various annealings, while for Ru-1222 wider-range oxygen-content tuning is possible. When heated in H2/Ar atmosphere the both phases release oxygen upon breaking down to mixtures of metals (Ru and Cu) and binary oxides (CeO2, Gd2O3, and SrO) in two distinct steps around 300 and 450 oC. This reductive decomposition reaction carried out in a thermobalance was utilized in precise oxygen content determination for these phases. It was found that the 100-atm O2-annealed Ru-1212 sample was nearly stoichiometric, while the similarly treated Ru-1222 sample was clearly oxygen deficient. X-ray absorption near-edge (XANES) spectroscopy was applied to estimate the valence of Ru in the samples. In spite of the fact that the Ru-1212 phase was shown to possess less oxygen-deficient RuO2 layer, the valence of Ru as probed with XANES was found to be lower in Ru-1212 than that in Ru-1222.Comment: 11 pages text, 4 pages Figs. To ISS 2002 YOKOHAMA for PHYSICA

Directional point-contact spectroscopy of MgB2 single crystals in magnetic fields: two-band superconductivity and critical fields

The results of the first directional point-contact measurements in MgB2 single crystals, in the presence of magnetic fields up to 9 T either parallel or perpendicular to the ab planes, are presented. By applying suitable magnetic fields, we separated the partial contributions of the sigma and pi bands to the total Andreev-reflection conductance. Their fit with the BTK model allowed a very accurate determination of the temperature dependency of the gaps (Delta_sigma and Delta_pi), that resulted in close agreement with the predictions of the two-band models for MgB2. We also obtained, for the first time with point-contact spectroscopy, the temperature dependence of the (anisotropic) upper critical field of the sigma band and of the (isotropic) upper critical field of the pi band.Comment: 2 pages, 2 figures, proceedings of M2S-HTSC-VII conference, Rio de Janeiro (May 2003

VSCAN: An Enhanced Video Summarization using Density-based Spatial Clustering

In this paper, we present VSCAN, a novel approach for generating static video summaries. This approach is based on a modified DBSCAN clustering algorithm to summarize the video content utilizing both color and texture features of the video frames. The paper also introduces an enhanced evaluation method that depends on color and texture features. Video Summaries generated by VSCAN are compared with summaries generated by other approaches found in the literature and those created by users. Experimental results indicate that the video summaries generated by VSCAN have a higher quality than those generated by other approaches.Comment: arXiv admin note: substantial text overlap with arXiv:1401.3590 by other authors without attributio

Stripes, Pseudogaps, and Van Hove Nesting in the Three-band tJ Model

Slave boson calculations have been carried out in the three-band tJ model for the high-T_c cuprates, with the inclusion of coupling to oxygen breathing mode phonons. Phonon-induced Van Hove nesting leads to a phase separation between a hole-doped domain and a (magnetic) domain near half filling, with long-range Coulomb forces limiting the separation to a nanoscopic scale. Strong correlation effects pin the Fermi level close to, but not precisely at the Van Hove singularity (VHS), which can enhance the tendency to phase separation. The resulting dispersions have been calculated, both in the uniform phases and in the phase separated regime. In the latter case, distinctly different dispersions are found for large, random domains and for regular (static) striped arrays, and a hypothetical form is presented for dynamic striped arrays. The doping dependence of the latter is found to provide an excellent description of photoemission and thermodynamic experiments on pseudogap formation in underdoped cuprates. In particular, the multiplicity of observed gaps is explained as a combination of flux phase plus charge density wave (CDW) gaps along with a superconducting gap. The largest gap is associated with VHS nesting. The apparent smooth evolution of this gap with doping masks a crossover from CDW-like effects near optimal doping to magnetic effects (flux phase) near half filling. A crossover from large Fermi surface to hole pockets with increased underdoping is found. In the weakly overdoped regime, the CDW undergoes a quantum phase transition ($T_{CDW}\to 0$), which could be obscured by phase separation.Comment: 15 pages, Latex, 18 PS figures Corrects a sign error: major changes, esp. in Sect. 3, Figs 1-4,6 replace

Detection of herb-symptom associations from traditional chinese medicine clinical data

YesTraditional Chinese medicine (TCM) is an individualized medicine by observing the symptoms and signs (symptoms in brief) of patients. We aim to extract the meaningful herb-symptom relationships from large scale TCM clinical data. To investigate the correlations between symptoms and herbs held for patients, we use four clinical data sets collected from TCM outpatient clinical settings and calculate the similarities between patient pairs in terms of the herb constituents of their prescriptions and their manifesting symptoms by cosine measure. To address the large-scale multiple testing problems for the detection of herb-symptom associations and the dependence between herbs involving similar efficacies, we propose a network-based correlation analysis (NetCorrA) method to detect the herb-symptom associations. The results show that there are strong positive correlations between symptom similarity and herb similarity, which indicates that herb-symptom correspondence is a clinical principle adhered to by most TCM physicians. Furthermore, the NetCorrA method obtains meaningful herb-symptom associations and performs better than the chi-square correlation method by filtering the false positive associations. Symptoms play significant roles for the prescriptions of herb treatment. The herb-symptom correspondence principle indicates that clinical phenotypic targets (i.e., symptoms) of herbs exist and would be valuable for further investigations

Deflection of coronal rays by remote CMEs: shock wave or magnetic pressure?

We analyze five events of the interaction of coronal mass ejections (CMEs) with the remote coronal rays located up to 90^\circ away from the CME as observed by the SOHO/LASCO C2 coronagraph. Using sequences of SOHO/LASCO C2 images, we estimate the kink propagation in the coronal rays during their interaction with the corresponding CMEs ranging from 180 to 920 km/s within the interval of radial distances form 3 R. to 6 R. . We conclude that all studied events do not correspond to the expected pattern of shock wave propagation in the corona. Coronal ray deflection can be interpreted as the influence of the magnetic field of a moving flux rope related to a CME. The motion of a large-scale flux rope away from the Sun creates changes in the structure of surrounding field lines, which are similar to the kink propagation along coronal rays. The retardation of the potential should be taken into account since the flux rope moves at high speed comparable with the Alfven speed.Comment: Accepted for Publication in Solar Physic

Two-band Eliashberg equations and the experimental Tc of the diboride Mg1-xAlxB2

The variation of the superconducting critical temperature Tc as a function of x in the diboride Mg1-xAlxB2 has been studied in the framework of the two-bands Eliashberg theory and traditional phonon coupling mechanism. We have solved the two-bands Eliashberg equations using first-principle calculations or simple assumptions for the variation of the relevant physical quantities. We have found that the experimental Tc curve can be explained only if the Coulomb pseudopotential changes with x by tuning the Fermi level toward the sigma band edge. In polycrystal samples the x dependence of the sigma and pi-band gap has been found and is in agreement with experiments.Comment: 6 pages, 7 figure

Can one extract the electron-phonon-interaction from tunneling data in case of the multigap superconductor MgB2_2?

In the present work we calculate the tunneling density of states (DOS) of MgB% $_{2}$ for different tunneling directions by directly solving the two-band Eliashberg equations (EE) in the real-axis formulation. This procedure reveals the fine structures of the DOS due to the optical phonons. Then we show that the numeric inversion of the standard \emph{single-band} EE (the only available method), when applied to the \emph{two-band} DOS of MgB$_{2}$, may lead to wrong estimates of the strength of certain phonon branches (e.g. the $E_{2g}$) in the extracted electron-phonon spectral function $\alpha^{2}F(\omega)$. The fine structures produced by the two-band interaction at energies between 20 and 100 meV turn out to be clearly observable only for tunneling along the $ab$ planes, when the extracted $\alpha ^{2}F(\omega)$ contains the combination $\alpha ^{2}F_{\sigma \sigma}(\omega)$\textbf{+}$\alpha ^{2}F_{\sigma \pi }(\omega)$, together with a minor $\alpha ^{2}F_{\pi \pi}(\omega )$\textbf{+}$\alpha ^{2}F_{\pi \sigma} (\omega)$ component. Only in this case it is possible to extract information on the $\sigma$-band contribution to the spectral functions. For any other tunneling direction, the $\pi$-band contribution (which does not determine the superconducting properties of MgB$_{2}$) is dominant and almost coincides with the whole $\alpha^2F(\omega)$ for tunneling along the c axis. Our results are compared with recent experimental tunneling and point-contact data.Comment: 5 pages, 3 figures. Submitted to Phys. Rev. B (Brief Reports

A 2-Component Generalization of the Camassa-Holm Equation and Its Solutions

An explicit reciprocal transformation between a 2-component generalization of the Camassa-Holm equation, called the 2-CH system, and the first negative flow of the AKNS hierarchy is established, this transformation enables one to obtain solutions of the 2-CH system from those of the first negative flow of the AKNS hierarchy. Interesting examples of peakon and multi-kink solutions of the 2-CH system are presented.Comment: 15 pages, 16 figures, some typos correcte