Crystallization kinetics of Zr-33 at % Ni amorphous alloy

The amorphous to crystalline transition in Zr-33 at% Ni amorphous alloy has been found to occur by polymorphic crystallization. The product of the cyrstallization process has been identified as the equilibrium Zr₂Ni intermetallic phase. The kinetics of crystallization have been studied independently using differential scanning calorimetry (DSC) and transmission electron microscopy. The activation energy of crystallization has been evaluated by isothermal and continuous heating in DSC. The isothermal anneals have revealed that the crystallization follows the Johnson-Mehl-Avrami kinetics with an Avrami exponent close to 4. The microstructural changes accompanying crystallization have been studied for an interpretation of the Avrami exponent. The nucleation and growth rates of crystals have been estimated at different temperatures in order to determine the activation energies of the two processes. It has been found that nucleation is thermally activated and growth is interface controlled.     

A first principle approach toward circuit level modeling of electrically doped gated diode from single wall thymine nanotube-like structure

Microsystem Technologies - This article presents a circuit level representation from gated diode which is developed from Thymine single wall nanotube-like structure using density functional theory...     

Multi-level image thresholding using Otsu and chaotic bat algorithm

Multi-level thresholding is a helpful tool for several image segmentation applications. Evaluating the optimal thresholds can be applied using a widely adopted extensive scheme called Otsu’s thresholding. In the current work, bi-level and multi-level threshold procedures are proposed based on their histogram using Otsu’s between-class variance and a novel chaotic bat algorithm (CBA). Maximization of between-class variance function in Otsu technique is used as the objective function to obtain the optimum thresholds for the considered grayscale images. The proposed procedure is applied on a standard test images set of sizes (512 × 512) and (481 × 321). Further, the proposed approach performance is compared with heuristic procedures, such as particle swarm optimization, bacterial foraging optimization, firefly algorithm and bat algorithm. The evaluation assessment between the proposed and existing algorithms is conceded using evaluation metrics, namely root-mean-square error, peak signal to noise ratio, structural similarity index, objective function, and CPU time/iteration number of the optimization-based search. The results established that the proposed CBA provided better outcome for maximum number cases compared to its alternatives. Therefore, it can be applied in complex image processing such as automatic target recognition.

     

Social group optimization for global optimization of multimodal functions and data clustering problems

Neural Computing and Applications - Cost and physical constraints in the engineering applied problems obligate finding the best results that global optimization algorithms cannot realize. For...     

A complete temporal relational algebra

Various temporal extensions to the relational model have been proposed. All of these, however, deviate significantly from the original relational model. This paper presents a temporal extension of the relational algebra that is not significantly different from the original relational model, yet is at least as expressive as any of the previous approaches. This algebra employs multidimensional tuple time-stamping to capture the complete temporal behavior of data. The basic relational operations are redefined as consistent extensions of the existing operations in a manner that preserves the basic algebraic equivalences of the snapshot (i.e., conventional static) algebra. A new operation, namely temporal projection, is introduced. The complete update semantics are formally specified and aggregate functions are defined. The algebra is closed, and reduces to the snapshot algebra. It is also shown to be at least as expressive as the calculus-based temporal query language TQuel. In order to assess the algebra, it is evaluated using a set of twenty-six criteria proposed in the literature, and compared to existing temporal relational algebras. The proposed algebra appears to satisfy more criteria than any other existing algebra. Edited by Wesley Chu. Received February 1993 / Accepted April 1995     

Genetic algorithm-based initial contour optimization for skin lesion border detection

Multimedia Tools and Applications - Automated segmentation has an essential role in detecting several diseases, such as skin lesions. In segmentation, the active contour (AC) is an efficient method...     

Thermoelectric Power Studies on YBa2?xCaxCu3O7?δ System

The temperature dependence of the thermoelectric power of calcium substituted YBa_2–x Ca _x Cu₃O_7– pellets with 0x1.5 is presented between 60 K and 300 K. A metal–insulator transition was reported earlier by us in this system and was attributed to the ionic size-dependent localization effect. While the sign of thermoelectric power of all the calcium substituted samples was found to be positive, its magnitude increases significantly with calcium content in YBCO. The normal state thermoelectric power data of substituted YBa_2–x Ca _x Cu₃O_7– (0x1.5) are discussed in light of a two-band model originally proposed by Gottwick et al. for heavy fermion systems and later modified by Forro et al.     

On Kalman filtering over fading wireless channels with controlled transmission powers

We study stochastic stability of centralized Kalman filtering for linear time-varying systems equipped with wireless sensors. Transmission is over fading channels where variable channel gains are counteracted by power control to alleviate the effects of packet drops. We establish sufficient conditions for the expected value of the Kalman filter covariance matrix to be exponentially bounded in norm. The conditions obtained are then used to formulate stabilizing power control policies which minimize the total sensor power budget. In deriving the optimal power control laws, both statistical channel information and full channel information are considered. The effect of system instability on the power budget is also investigated for both these cases.     

Higher order finite strip analysis for curved bridge decks

The development of a higher order finite strip method for improved accuracy and its application to orthotropic curved bridge decks are discussed. A quintic polynomial in the radial direction is employed along with a basic function series in the angular direction which satisfy a priori the boundary conditions along the radial edges. Thus a two-dimensional plate bending problem is reduced to a one-dimensional one. As a result, both the size and bandwidth of the global stiffness matrix are greatly reduced. The method is easy to program, requires a minimum input data and small computer storage. In order to estimate the reliability of the present formulation, three examples of curved plates are solved and the results are compared with the existing solutions.