Dynamics of Crossover from a Chaotic to a Power Law State in Jerky Flow

We study the dynamics of an intriguing crossover from a chaotic to a power law state as a function of strain rate within the context of a recently introduced model which reproduces the crossover. While the chaotic regime has a small set of positive Lyapunov exponents, interestingly, the scaling regime has a power law distribution of null exponents which also exhibits a power law. The slow manifold analysis of the model shows that while a large proportion of dislocations are pinned in the chaotic regime, most of them are pushed to the threshold of unpinning in the scaling regime, thus providing insight into the mechanism of crossover.Comment: 5 pages, 3 figures. In print in Phy. Rev. E Rapid Communication

Strong magnetic pair breaking in Mn substituted MgB_2 single crystals

Magnetic ions (Mn) were substituted in MgB_2 single crystals resulting in a strong pair-breaking effect. The superconducting transition temperature, T_c, in Mg_{1-x}Mn_xB_2 has been found to be rapidly suppressed at an initial rate of 10 K/%Mn, leading to a complete suppression of superconductivity at about 2% Mn substitution. This reflects the strong coupling between the conduction electrons and the 3d local moments, predominantly of magnetic character, since the nonmagnetic ion substitutions, e.g. with Al or C, suppress T_c much less effectively (e.g. 0.5 K/%Al). The magnitude of the magnetic moment, derived from normal state susceptibility measurements, uniquely identifies the Mn ions to be divalent, and to be in the low-spin state (S = 1/2). This has been found also in X-ray absorption spectroscopy measurements. Isovalent Mn^{2+} substitution for Mg^{2+} mainly affects superconductivity through spin-flip scattering reducing T_c rapidly and lowering the upper critical field anisotropy H_{c2}^{ab}/H_{c2}^c at T = 0 from 6 to 3.3 (x = 0.88% Mn), while leaving the initial slope dH_{c2}/dT near T_c unchanged for both field orientations.Comment: 9 pages, 9 figure

Multi-input Fuzzy Logic Controller for Brushless dc Motor Drives

The brushless dc motors are used in various applications such as defence, industries,robotics, etc. In these applications, the motor should be precisely controlled to give the desiredperformance. The proposed controller systems consist of multi-input fuzzy (two-and three-input)logic controller (FLC) and multi-input integrated fuzzy logic controller (IFLC) for the speed controlof brushless dc servomotor drive. The input for the controllers are error e(k), change in error[first derivative of error ce(k)] and change of change in error [second derivative of error cce(k)]with a single-output. The error cce(k) is substantial at the overshoots/undershoots and is thereforeessential for accurate speed control of brushless dc motor. The error cce(k) has been introducedfor the first time in the literature as one of the input in the FLC and IFLC design. The IFLC isdesigned using FLC and proportional derivation integral (PID) controllers. The controller systemshave been studied systematically for the transient and steady-state conditions. The three-inputIFLC is found to be superior, more robust, faster, flexible, and is insensitive to the parametervariations as compared with the FLC (with two-and three-input) and conventional two-inputIFL

Performance Evaluation of Energy Efficient Optimized Routing Protocol for WBANs Using PSO Protocol

A Wireless Body Area Network (WBAN) is a network that may be worn on the human body or implanted in the human body to transmit data, audio, and video in real-time to assess how vital organs are performing. A WBAN may be either an inter-WBAN or an intra-WBAN network. Intra-WBAN communication occurs when the various body sensors can share information. This is known as inter-WBAN communication, which occurs when two or more WBANs can exchange data with one another. One difficulty involves getting data traffic from wireless sensor nodes to the gateway with as little wasted energy, dropped packets, and downtime as possible. In this paper, the WBAN protocols have been compared with WBAN under Particle Swarm Optimization (PSO), and the performance of various parameters has been analysed for different simulation areas. The WBAN under the PSO protocol reduces the energy consumption by 43.2% against the SIMPLE protocoldue to the effective selection of forwarding nodes based on PSO optimization. In addition to that the experimental WBAN testbed is conducted in indoor environment to study the performance of the routing metrics towards energy and packet reception.

Born Effective Charges and Infrared Response of LiBC

Calculations of the zone center optical mode frequencies (including LO-TO splitting), Born effective charges Z$^*_{\alpha\alpha}$ for each atom, dielectric constants $\epsilon_{0}$ and $\epsilon_{\infty}$, and the dielectric response in the infrared, using density functional linear response theory, are reported. Calculated Raman modes are in excellent agreement with experimental values (170 cm$^{-1}$ and 1170 cm$^{-1}$), while it will require better experimental data to clarify the infrared active mode frequencies. The Born effective charges Z$^*_{\alpha \alpha}$ (i) have surprisingly different values for B and C, and (ii) show considerable anisotropy. Relationships between the effective charges and LO-TO splitting are discussed, and the predicted reflectivity in the range 0 -- 1400 cm$^{-1}$ is presented. These results hold possible implications for Li removal in LiBC, and C substition for B in MgB$_2$.Comment: 6 pages, 3 figure