Metastable behavior of vortex matter in the electronic transport processes of homogenous superconductors

We study numerically the effect of vortex pinning on the hysteresis voltage-temperature (V-T) loop of vortex matter. It is found that different types of the V-T loops result from different densities of vortex pinning center. An anticlockwise V-T loop is observed for the vortex system with dense pinning centers, whereas a clockwise V-T loop is brought about for vortices with dilute pinning centers. It is shown that the size of the V-T loop becomes smaller for lower experimental speed, higher magnetic field, or weak pinning strength. Our numerical observation is in good agreement with experiments

History effect in inhomogeneous superconductors

A model was proposed to account for a new kind of history effect in the transport measurement of a sample with inhomogeneous flux pinning coupled with flux creep. The inhomogeneity of flux pinning was described in terms of alternating weak pinning (lower jc) and strong pinning region (higher jc). The flux creep was characterized by logarithmic barrier. Based on this model, we numerically observed the same clockwise V-I loops as reported in references. Moreover, we predicted behaviors of the V-I loop at different sweeping rates of applied current dI/dt or magnetic fields Ba, etc. Electric transport measurement was performed in Ag-sheathed Bi2-xPbxSr2Ca2Cu3Oy tapes immersed in liquid nitrogen with and without magnetic fields. V-I loop at certain dI/dt and Ba was observed. It is found that the area of the loop is more sensitive to dI/dt than to Ba, which is in agreement well with our numerical results.Comment: To appear in Phys Rev B, October 1 Issu

Effect of Second-Phase Doping on Laser Deposited Al2O3 Ceramics

Direct fabrication of engineering ceramic components by additive manufacturing (AM) is a relatively new method for producing complex mechanical structures. This study investigates how a second-phase doping may affect Al2O3 ceramic parts deposited by AM with a laser engineered net shaping (LENS) system. In this study, ZrO2 and Y2O3 powders are respectively doped into Al2O3 powders at the eutectic ratio as second-phases to improve the quality of a deposited part. The deposited Al2O3, Al2O3/ZrO2 and Al2O3/YAG (yttrium aluminum garnet) parts are examined for their micro-structures and micro-hardness, as well as defects. The results show that doping of ZrO2 or Y2O3 as a second-phase performs a significant role in suppressing cracks and in refining grains of the laser deposited parts. The micro-hardness investigation reveals that the second-phase doping does not result in much hardness reduction in Al2O3 and the two eutectic ceramics are both harder than 1500 Hv. The study concludes that the second-phase doping is good for improving laser deposited ceramic parts.Mechanical Engineerin

A Critical Analysis Of The State-Of-The-Art On Automated Detection Of Deceptive Behavior In Social Media

Recently, a large body of research has been devoted to examine the user behavioral patterns and the business implications of social media. However, relatively little research has been conducted regarding users’ deceptive activities in social media; these deceptive activities may hinder the effective application of the data collected from social media to perform e-marketing and initiate business transformation in general. One of the main contributions of this paper is the critical analysis of the possible forms of deceptive behavior in social media and the state-of-the-art technologies for automated deception detection in social media. Based on the proposed taxonomy of major deception types, the assumptions, advantages, and disadvantages of the popular deception detection methods are analyzed. Our critical analysis shows that deceptive behavior may evolve over time, and so making it difficult for the existing methods to effectively detect social media spam. Accordingly, another main contribution of this paper is the design and development of a generic framework to combat dynamic deceptive activities in social media. The managerial implication of our research is that business managers or marketers will develop better insights about the possible deceptive behavior in social media before they tap into social media to collect and generate market intelligence. Moreover, they can apply the proposed adaptive deception detection framework to more effectively combat the ever increasing and evolving deceptive activities in social medi

Anterior Hippocampus and Goal-Directed Spatial Decision Making

Contains fulltext : 115487.pdf (publisher's version ) (Open Access

Effect of Na doping on flux pinning of YBa1.9Na0.1Cu3O7-d

We have prepared Na-doped YBa2Cu3Oy (YBa1.9Na0.1Cu3Oy +40mol%Y211) (YBNCO) and Na-free YBa2Cu3Oy (YBCO) samples by the Melt-Textured Growth (MTG) method to study the effect of doped Na ion on flux pinning. The ac susceptibility curves (acs) as well as the hysteresis loops were measured for the samples. Then the effective pinning energy (U(T,Hdc,J)), irreversibility line (Hirr(T)) and critical current density (jc(Hdc)) were determined, where T, Hdc and J are temperature, dc magnetic field and current density, respectively. We found that, with Na doping, the Hirr(T) line shifted to lower temperature while the Jc(Hdc) and U(T,Hdc,J) became smaller. It indicates that the Na ions play a negative role in the flux pinning of YBCO. The appearance of the second peak in the Jc(Hdc) curves and the enhancement of anisotropy in YBNCO further support this finding.Comment: 7 pages, 7figures. Submited to Physica.

Techniques for mesh density control

Proceedings of the Seventh International Conference on Hydroscience and Engineering, Philadelphia, PA, September 2006. http://hdl.handle.net/1860/732Mesh generation is crucial in computational fluids dynamic (CFD) analysis, which solves a set of partial differential equations (PDE) based on a computational mesh. To a large extent, the success of solving these equations depends on the mesh quality. In addition to the orthogonality and the smoothness, the mesh density distribution is the key to a desirable mesh. The objective of the current research is to develop methods which make the control of mesh density simple and effective. The resulting mesh is near-orthogonal but more desirable for the numerical simulation. In this study, two new techniques for mesh density control are proposed. The first one is a three-parameter stretching function which stretches the nodes along a line in two directions and control their location of the distribution. The second method is a modified RL system (Ryskin and Leal, 1983) in which the distortion function is evaluated by the averaged scale factors and the scale factors which are formulated by weighting functions of desired mesh density distribution

Chirality in odd-AA nucleus 135^{135}Nd in particle rotor model

A particle rotor model is developed which couples several valence protons and neutrons to a rigid triaxial rotor core. It is applied to investigating the chirality in odd-$A$ nucleus $^{135}$Nd with $\pi h_{11/2}^2\otimes\nu h^{-1}_{11/2}$ configuration for the first time in a fully quantal approach. For the two chiral sister bands, the observed energies and the $B(M1)$ and $B(E2)$ values for the in-band as well as interband transitions are reproduced excellently. Root mean square values of the angular momentum components and their probability distributions are used for discussing in detail the chiral geometry of the aplanar rotation and its evolution with angular momentum. Chirality is found to change from a soft chiral vibration to nearly static chirality at spin $I=39/2$ and back to another type of chiral vibration at higher spin.Comment: 16 pages, 5 figure