Secure Optical Burst Switching: Framework and Research Directions [Topics in Optical Communications]

Optical burst switching has been positioned as a viable means of implementing optical communication efficiently. This article identifies potential threats to security in OBS networks. To alleviate the security threats in OBS networks, a secure Optical Burst Switching (S-OBS) framework is proposed. The S-OBS framework provides two levels of security measures: authentication of burst headers and confidentiality of data bursts. Candidate solutions in each category are examined, and research directions are presented.     

A spectral characterization of H-optimal feedback performance and its efficient computation

We study the spectral properties of a ‘Toeplitz⁺ Hankel’ operator which arises in the context of the mixed-sensitivity H^∞-optimization problem and whose largest eigenvalue characterizes the optimal achievable performance ε₀. The existence of such an operator was first shown by Verma and Jonckheere [26], who also'noted the potential numerical advantage of computing eo through its eigenvalue characterization rather than through the ε-iteration. Here, we investigate this operator in detail, with the objective of efficiency computing its spectrum. We define an ‘adjoint’ linear-quadratic problem that involves the same ‘Toeplitz⁺ Hankel’ operator, as shown by Jonckheere and Silverman [13–16]. Consequently, a finite polynomial algorithm allows ε₀ to be characterized as simply as the largest root of a polynomial. Finally, a computationally more attractive state space algorithm emerges from the H^t8/LQ relationship. This algorithm yields a very good accuracy evaluation of the performance ε₀ by solving just one algebraic Riccati equation. Thorough exploitation of this algorithm results in a drastic computation reduction with respect to the standard e-iteration.     

Factorization and feedback stabilization for nonlinear systems

We establish the equivalence of internal input-out stability for two feedback configurations of a nonlinear, time-varying plant P for which a related plant G is assumed to have a factorization G = R with both R and R⁻¹ incrementally stable; this extends a factorization principle for stabilizability previously given only for the linear, time-invariant case. As an application of a special case we recover a version of the Youla parametrization of stabilizing compensators for the nonlinear case previously presented in the literature. We use degree theory to parametrize a collection of solutions of the H_∞-control problem for the case of a 1-gain stable or lossless plant. In the case of a plant G having a J-inner-outer factorization, this last result combined with the above-mentioned factorization principle leads to results on the H_∞-control problem for P.     

Recommender system with grey wolf optimizer and FCM

Recommender systems are contributing a significant aspect in information filtering and knowledge management systems. They provide explicit and reliable recommendations to the users so that user can get information about all products in e-commerce domain. In the era of big data and large complex information delivery system, it is impossible to get the right information in the online environment. In this research work, we offered a novel movie-based collaborative recommender system which utilizes the bio-inspired gray wolf optimizer algorithm and fuzzy c-mean (FCM) clustering technique and predicts rating of a movie for a particular user based on his historical data and similarity of users. Gray wolf optimizer algorithm was applied on the Movielens dataset to obtain the initial clusters, and also the initial positions of clusters are obtained. FCM is used to classify the users in the dataset by similarity of user ratings. Our proposed collaborative recommender system performed extremely well with respect to accuracy and precision. We analyzed our proposed recommender system over Movielens dataset which is available publically. Various evaluation metrics were utilized such as mean absolute error, standard deviation, precision and recall. We also compared the performance of projected system with already established systems. The experiment results delivered by proposed recommender system demonstrated that efficiency and performance are enhanced and also offered better recommendations when compared with our previous work [1].

     

Matrix effect in soft metal-bonded samarium-cobalt (SmCo5) permanent magnets

This paper discusses the preparation of samarium-cobalt (SmCo₅) alloy powders by reduction-diffusion process. These powders were blended with equal weight percentages of soft metal/alloy powders, such as indium, tin and solder alloy (Pb-17Sn), to prepare bonded magnets. Important magnetic properties such as remanence, coercivity and energy product of these magnets were measured. Effect of matrix metal/alloy on the magnetic properties of processed magnets is outlined.     

Development of bimetal-grown multi-scale carbon micro-nanofibers as an immobilizing matrix for enzymes in biosensor applications

This study describes the development of a novel bimetal (Fe and Cu)-grown hierarchical web of carbon micro-nanofiber-based electrode for biosensor applications, in particular to detect glucose in liquids. Carbon nanofibers (CNFs) are grown on activated carbon microfibers (ACFs) by chemical vapor deposition (CVD) using Cu and Fe as the metal catalysts. The transition metal-fiber composite is used as the working electrode of a biosensor applied to detect glucose in liquids. In such a bi-nanometal-grown multi-scale web of ACF/CNF, Cu nanoparticles adhere to the ACF-surface, whereas Fe nanoparticles used to catalyze the growth of nanofibers attach to the CNF tips. By ultrasonication, Fe nanoparticles are dislodged from the tips of the CNFs. Glucose oxidase (GOx) is subsequently immobilized on the tips by adsorption. The dispersion of Cu nanoparticles at the substrate surface results in increased conductivity, facilitating electron transfer from the glucose solution to the ACF surface during the enzymatic reaction with glucose. The prepared Cu-ACF/CNF/GOx electrode is characterized for various surface and physicochemical properties by different analytical techniques, including scanning electron microscopy (SEM), electron dispersive X-ray analysis (EDX), Fourier-transform infrared spectroscopy (FTIR), BET surface area analysis, and transmission electron microscopy (TEM). The electrochemical tests show that the prepared electrode has fast response current, electrochemical stability, and high electron transfer rate, corroborated by CV and calibration curves. The prepared transition metal-based carbon electrode in this study is cost-effective, simple to develop, and has a stable immobilization matrix for enzymes.     

Bulk modulus and hardness of chalcopyrite structured solids

The bulk modulus and microhardness can be represented by an empirical linear relation that is a simple function of melting temperature T_m, atomic volume Ω and product of ionic charges (Z₁Z₂Z₃). Values of bulk modulus B and microhardness H of A^IB^IIIC₂^VI and A^IIB^IVC₂^V chalcopyrite semiconductors exhibit a linear relationship when plotted against the k_BT_m/Ω (k_B = Boltzmann's constant), but fall on two straight lines according to the product of ionic charges of the compounds. This correlation is similar in form to other correlations in the literature for diffusion data of materials that indicate the significance of the melting temperature as a scaling or lattice dynamic properties of materials. The calculated results are compared with available experimental data and previous calculations based on phenomenological models.     

Substitutional effect on structural and dielectric properties of Ni1−xAxFe2O4 (A = Mg,Zn) mixed spinel ferrites

The Ni_1−xA_xFe₂O₄ (A = Zn, Mg; x = 0.0, 0.5) ferrites synthesized by chemical co-precipitation method. X-ray diffraction and Raman spectroscopy reveals that all the ferrite samples are in single-phase cubic spinel structure with Fd3m space group. The lattice parameter enhances with Mg and Zn substitution. Raman spectroscopy identifies a doublet like nature of A_1g mode for all the three ferrites. A blue shift in Mg doped ferrite and a red shift in Zn doped ferrite has been observed as compared to parent NiFe₂O₄. Frequency dependent dielectric response confirms the dielectric polarization and electrical conduction mechanism. The minimum value of loss tangent (∼0.03) at 5 KHz suggests that Ni_1−xA_xFe₂O₄ is effective material for microwave application. The activation energy for NiFe₂O₄, Ni_0.5Mg_0.5Fe₂O₄ and Ni_0.5Zn_0.5Fe₂O₄ are found to be 0.28 eV, 0.29 eV and 0.31 eV, respectively.     

Correlation Between Structure and Ferromagnetism in Cobalt-Doped CdSe Nanorods

The present study deals with the investigation on structural and magnetic properties of pure and Co-doped CdSe nanorods synthesized by solvothermal route. The effects of Co-doping on structural, optical, and magnetic properties of nanorods have been explored using X-ray diffraction (XRD), transmission electron microscopy (TEM), High-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), Raman spectroscopy, energy dispersive spectroscopy (EDS), diffuse reflectance spectroscopy, electron spin resonance (ESR), and vibrating sample magnetometer (VSM), at room temperature. TEM images show that the synthesized nanorods having length in range of 80–150 nm and diameter of 10–20 nm. No ferromagnetic resonance signal has been observed in ESR spectra, indicating the absence of exchange interactions in pure and doped nanorods. The lattice contraction, increase in band gap, and ferromagnetic behavior have been observed with Co-doping concentration up to 5 %. However, at 10 % Co-doping concentration, reverse trend in above properties has been observed. The study reveals that there is a strong correlation between structural and magnetic properties of Co-doped CdSe nanorods.