Electrical transport and optical studies of ferromagnetic Cobalt doped ZnO nanoparticles exhibiting a metal-insulator transition

The observed correlation of oxygen vacancies and room temperature ferromagnetic ordering in Co doped ZnO1-o nanoparticles reported earlier (Naeem et al Nanotechnology 17, 2675-2680) has been further explored by transport and optical measurements. In these particles room temperature ferromagnetic ordering had been observed to occur only after annealing in forming gas. In the current work the optical properties have been studied by diffuse reflection spectroscopy in the UV-Vis region and the band gap of the Co doped compositions has been found to decrease with Co addition. Reflections minima are observed at the energies characteristic of Co+2 d-d (tethrahedral symmetry) crystal field transitions, further establishing the presence of Co in substitutional sites. Electrical transport measurements on palletized samples of the nanoparticles show that the effect of a forming gas is to strongly decrease the resistivity with increasing Co concentration. For the air annealed and non-ferromagnetic samples the variation in the resistivity as a function of Co content are opposite to those observed in the particles prepared in forming gas. The ferromagnetic samples exhibit an apparent change from insulator to metal with increasing temperatures for T>380K and this change becomes more pronounced with increasing Co content. The magnetic and resistive behaviors are correlated by considering the model by Calderon et al [M. J. Calderon and S. D. Sarma, Annals of Physics 2007 (Accepted doi: 10.1016/j.aop.2007.01.010] where the ferromagnetism changes from being mediated by polarons in the low temperature insulating region to being mediated by the carriers released from the weakly bound states in the higher temperature metallic region.Comment: 7 pages, 6 figure

Simulation and Modeling of a AC-DC Converter Controlled by Pulse Width Modulation Using Soft Switching topology

  This work presents the design, analysis, and simulation of AC-DC converter topology incorporating a voltage source converter (VSC) and a direct converter, connected with medium frequency transformer isolation. A control method is studied by which it is possible to reduce the transformer core losses by only magnetizing the transformer when a Pulse Width Modulation (PWM) pulse should be applied on the AC side of the system. By alternately commutating the two converters it is possible to achieve soft switching conditions for all of the semiconductor elements. Furthermore, it is shown that resonant commutation of the voltage source converter is possible by utilizing the cycloconverter for short circuiting the transformer terminals. converter. The PWM voltage is applied to aninductive filter and thereby the AC side current aswell as the power flow through the system can b

Simulation and Modeling of a AC-DC Converter Controlled by Pulse Width Modulation Using Soft Switching topology

  This work presents the design, analysis, and simulation of AC-DC converter topology incorporating a voltage source converter (VSC) and a direct converter, connected with medium frequency transformer isolation. A control method is studied by which it is possible to reduce the transformer core losses by only magnetizing the transformer when a Pulse Width Modulation (PWM) pulse should be applied on the AC side of the system. By alternately commutating the two converters it is possible to achieve soft switching conditions for all of the semiconductor elements. Furthermore, it is shown that resonant commutation of the voltage source converter is possible by utilizing the cycloconverter for short circuiting the transformer terminals. converter. The PWM voltage is applied to aninductive filter and thereby the AC side current aswell as the power flow through the system can b

Synthesis, Analytical and Theoretical Studies of (Z)-4-amino-3-hydroxy-2-((4-(N-(5-methylisoxazol-3-yl)Sulfamoyl)Phenyl)Diazenyl)Naphthalene-1-Sulfonic Acid

New azodye that characterize (Z)-4-amino-3-hydroxy-2-((4-(N-(5-methylisoxazol-3-yl) sulfamoyl) phenyl)diazenyl)naphthalene-1-sulfonic acid (1) was synthesized. The azodye has been characterized by IR, visible spectra and elemental (CHN) analysis. The results of visible spectra which recorded in the range (360-6540) nm were showed that the maximum wave length (λmax) of azodye was 500 nm. Analytical studies carried on the dye, the results of the solvent effect were showed high solubility in ethanol and water. But, the results of the pH effect in a range of buffer solution were gave three isopestic points. The ionization constant (pKa) and protonation constant (pKb) were calculated by using the half height method. The results were showed that the pKp1 and pKp2 of each nitrogen atom and pKa of OH-group were equal to 2.5, 4.5 and 8.5 respectively. Theoretical studies also carried on azodye (1). The actual and optimal bonds length of -N=N- was equal to 1.248 in each. Though, internal coordinate mechanics (ICM) of (1) was showed that the angle type in most of atoms was dihedral. But, the R and S configuration were observed in other atoms in the structure of azodye. The results also indicated that the torsion angles (ψ) of (1) were variable. High close contacts of atoms were observed in the structure of azodye. The molecular mechanics (MM2) properties was intended for (1), the results showed that the stretch, bend, stretch-bend, torsion, non-1,4 VDW, 1,4 VDW and the total energy were equal to 61.0809, 627.0240, -1.6517, 179.0634, 4686.8146, 33.0379 and 5585.3692 kcal/mol respectively. High VDW interactions of this molecule was observed, due to the results of dipole/dipole were not computed. Thus, the result of MM2 minimization for azodye (1) was showed high VDW interactions of this molecule higher than before the minimization, due to the result of dipole/dipole was also not computed. The high steric energy (1235.782) was affecting the results of minimization. However, the results of the molecular mechanics force field (MMFF94) energy and gradient for azodye (1) were showed that the total energy and RMS gradient were equal to 26223.422 kcal/ mol and 9113.745 respectively. Further, the results of MMFF94 minimization and MMFF94 minimization/sampling of azodye (1) were showed that the minimization was attended successfully using this method. Keywords: Internal coordinate, Molecular mechanics, Azodye

Decomposition of Continuity and Separation Axioms Via Lower and Upper Approximation

In this paper we study the rough set theory by defined the concepts of rough regularity and rough normality in the topological spaces which we can consider them as results from the general relations on the approximation spaces. Keywords: Topologized approximation space, rough regularity, rough normality, rough continuity, rough homeomorphism

Developing Scaling Laws to Predict Compressive Mechanical Properties and Determine Geometrical Parameters of Modified BCC Lattice Structures

The objective of this study is to develop generalized empirical closed-form equations to predict the compressive mechanical properties and determine geometrical parameters. To achieve that, 117 models are built and analyzed using ABAQUS/CAE 2016 to provide two types of reliable data: one for lattice mechanical properties based on finite element method and the other for geometrical parameters using the measurements of ABAQUS diagnostic tool. All the models are created by modifying the basic feature of body-centered cubic lattice structure based on a range of strut angles, a set of relative densities, and two design sets. Also, the influence of lattice cell tessellations and material distribution at strut intersections are considered within these models to provide accurate results. The first data set is fitted with the scaling laws, relating relative elastic modulus and stress with the relative density, to determine Gibson and Ashby\u27s coefficients. The second type of data regarding lattice geometries is correlated with the relative density to estimate actual lattice volume, strut radius, aspect ratio, and overall lattice volume. By this way, these equations can be used to predict directly the lattice characteristics and geometrical parameters without the need for ABAQUS. The results show that the generalized empirical closed-form equations can predict well both the lattice characteristics and geometries. In addition, the relative stresses and elastic modulus increase with increasing the strut angles since the main deformation mechanisms move toward stretch-dominated rather than bending. Besides, Gibson and Ashby\u27s coefficients along with the geometrical factors of aspect ratios are found to be approximately similar for both generations. This study contributes to developing efficient equations to provide the researchers with a preliminary insight about the best lattice design and its compatibility in a certain application before starting the fabrication process

Rough Probability In Topological Spaces

In this paper we study the rough probability in the topological spaces which we can consider them as results from the general relations on the approximation spaces. Keywords: Stochastic approximation space, rough expectation, rough variance, rough probability generating function, rough characteristic function.

Overview of the CLEF-2019 Checkthat! LAB: Automatic identification and verification of claims. Task 2: Evidence and factuality

We present an overview of Task 2 of the second edition of the CheckThat! Lab at CLEF 2019. Task 2 asked (A) to rank a given set of Web pages with respect to a check-worthy claim based on their usefulness for fact-checking that claim, (B) to classify these same Web pages according to their degree of usefulness for fact-checking the target claim, (C) to identify useful passages from these pages, and (D) to use the useful pages to predict the claim's factuality. Task 2 at CheckThat! provided a full evaluation framework, consisting of data in Arabic (gathered and annotated from scratch) and evaluation based on normalized discounted cumulative gain (nDCG) for ranking, and F1 for classification. Four teams submitted runs. The most successful approach to subtask A used learning-to-rank, while different classifiers were used in the other subtasks. We release to the research community all datasets from the lab as well as the evaluation scripts, which should enable further research in the important task of evidence-based automatic claim verification