Magnetic and dielectric properties of polycrystalline La doped barium Z-type hexaferrite for hyper-frequency applications

La³⁺ ion substituted barium Z-type hexaferrite, Ba_3?XLa_XCo₂Fe₂₄O₄₁ powders (X = 0.0, 0.05, 0.10 and 0.15), have been synthesized using sol gel auto-combustion method. The phase identification, microstructure, complex permittivity, complex permeability and static magnetic properties of the samples were studied using X-ray diffraction, scanning electron microscopy, vector network analyzer and vibrating sample magnetometer. The results revealed that introducing La³⁺ ion instead of Ba²⁺ ion led to an obvious enhancement of the electromagnetic properties. The crystallite size of the produced powders was slightly increased with increasing La³⁺ content. The microstructure of the produced powders appeared as hexagonal-platelet like structure. As the La content increase, the static magnetic properties were increased, the real part of complex permittivity was increased while the imaginary part was decreased. Moreover, the real part of complex magnetic permeability was decreased and the imaginary part was increased. The reasons of the obtained results were discussed on basis of electromagnetic theory.     

Querying now-relative data

Now-relative temporal data play an important role in most temporal applications, and their management has been proved to impact in a crucial way the efficiency of temporal databases. Though several temporal relational approaches have been developed to deal with now-relative data, none of them has provided a whole temporal algebra to query them. In this paper we overcome such a limitation, by proposing a general algebra which is parametrically adapted to cope with the relational approaches to now-relative data in the literature, i.e., MIN, MAX, NULL and POINT approaches. Besides being general enough to provide a query language for several approaches in the literature, our algebra has been designed in such a way to satisfy several theoretical and practical desiderata: closure with respect to representation languages, correctness with respect to the “consensus” BCDM semantics, reducibility to the standard non-temporal algebra (which involves interoperability with non-temporal relational databases), implementability and efficiency. Indeed, the experimental evaluation we have drawn on our implementation has shown that only a slight overhead is added by our treatment of now-relative data (with respect to an approach in which such data are not present).     

A Constraint-Based Autonomous 3D Camera System

Camera control techniques for interactive digital entertainment (IDE) are reaching their limits in terms of capabilities. To enable future growth, new methods must be derived to address these new challenges. Existing academic research into camera control is typically devoted to cinematography and guided exploration tasks, and is not directly applicable to IDE. This paper describes a novel application of constraint satisfaction in the design of a camera system that addresses the unique and difficult challenges of IDE. It demonstrates a specialized constraint solver that exploits the spatial structure of the problem, enabling the real-time use of the camera system. The merit of our solution is highlighted by demonstrating the computational efficiency and ability to extend the cameras capabilities in a simple and effective manner.     

An entropy-based distance measure for analyzing and detecting metamorphic malware

Metamorphic malware is a kind of malware which evades signature-based anti-viruses by changing its internal structure in each infection. This paper, firstly, introduces a new measure of distance between two computer programs called program dissimilarity measure based on entropy (PDME). Then, it suggests a measure for the degree of metamorphism, based on the suggested distance measure. The distance measure is defined based on the Entropy of the two malware programs. Moreover, the paper shows that the distance measure can be used for classifying metamorphic malware via K-Nearest Neighbors (KNN) method. The method is evaluated by four metamorphic malware families. The results demonstrate that the measure can indicate the degree of metamorphism efficiently, and the KNN classification method using PDME can classify the metamorphic malware with a high precision.     

Breaking a novel image encryption scheme based on an improper fractional order chaotic system

In this paper, we analyze the security of a recent image encryption algorithm based on an improper fractional-order chaotic system suggested by Zhao et al. The fatal flaw in the cryptosystem is that the keystream generated depends on neither the plain-image nor the cipher-image. Another main issue with this algorithm is using the same key (the last key in the keystream) in all encryption equations. Based on these points, it is easy to recover the plain-image and the keystream by applying chosen plaintext attack in only one plain-image. Both mathematical analysis and experimental results confirm the feasibility of this attack. As a result, the cryptosystem under study is not suitable for cryptography.     

Batch kinetics and modelling of ethanolic fermentation of whey

The fermentation of whey by Kluyveromyces marxianus strain MTCC 1288 was studied using varying lactose concentrations at constant temperature and pH. The increase in substrate concentration up to a certain limit was accompanied by an increase in ethanol formation, for example, at a substrate concentration of 10 g L^?1, the production of ethanol was 0.618 g L^?1 whereas at 50 g L^?1 it was 3.98 g L^?1. However, an increase in lactose concentration to 100 g L^?1 led to a drastic decrease in product formation and substrate utilization. The maximum ethanol yield was obtained with an initial lactose concentration of 50 g L^?1. A method of batch kinetics was utilized to formulate a mathematical model using substrate and product inhibition constants. The model successfully simulated the batch kinetics observed at S₀ = 10 and 50 g L^?1 but failed in case of S₀ = 100 g L^?1 because of strong substrate inhibition.     

Effect of manganese substitution on the magnetic properties of nickel-zinc ferrite

The effect of manganese (Mn)-ion substitution on the structural, magnetic, and electrical properties of nickel-zinc (Ni-Zn) ferrite of chemical formula Ni_0.6−t Mn _t Zn_0.4Fe₂O₄ (t=0.0, 0.1, 0.2, 0.3, 0.4, 0.45, 0.5, 0.55, 0.6) has been studied. It was found that Mn ion substitution increases the average grain diameter and improves the magnetization as well as the initial permeability. At the same time, the direct current (dc) resistivity at room temperature was found to increase with Mn ion substitution. The increase of both magnetization and dc resistivity due to the Mn substitution in a Ni-Zn ferrite is a promising result for applications in high-frequency fields.     

Half-Metallic Ferromagnetism in New Half-Heusler Compounds: an Ab Initio Study of CrTiX (X = Si,Ge, Sn,Pb)

In this work, half-metallic (HM) properties of new Half-Heusler (HH) ferromagnetic compounds CrTiX (X = Si, Ge, Sn, Pb) are studied by means of first principle band structure calculation within the framework of density functional theory (DFT). From the spin-polarized calculations using full-potential linearized augmented plane-wave (FP-LAPW)method, we found that all of these compounds are stable in ferromagnetic MgAgAs-type crystal structure. The latticeparameters of CrTiX compounds increase with increasing atomic radius of X atom and ranges from 5.76 to 6.38 Å. The calculated electronic structure of these compounds in MgAgAs-type structure shows that they are HM materials with an integer magnetic moment of 4 μ _B. Densities of states, electronic band structure, and origin of ferromagnetism have been discussed, and robust HM nature of these compounds is analyzed which makes them fascinating compounds for spintronic devices.