Sol-Gel Poly-Component Nano-Sized Oxide Powders

Nano-sized, amorphous and monodispersed poly-component powders in the Al₂O₃–TiO₂–MgO and Al₂O₃–TiO₂–SiO₂ systems have been obtained by the sol-gel method. These powders have been characterized by XRD, IR spectroscopy, DTA/TGA and EDAX spectrometry. This last method confirmed the composition of the ternary powders, which are formed during the gelation process.The powders were tested as precursors for obtaining advanced ceramics, as tialite, Al₂TiO₅. The samples prepared with powders obtained by sol-gel method have shown a high reactivity, and the formation of tialite was improved.     

Irradiation and measurement devices and methods development for LSNAA applications at the TRIGA-ACPR core

A Large Sample Neutron Activation Analysis (LSNAA) facility has been developed at the TRIGA-Annular Core Pulsed Reactor (ACPR) operated by the Institute for Nuclear Research in Pitesti. The central irradiation cavity of ACPR can accommodate a large irradiation device. The ACPR neutron flux characteristics are well known and spectrum adjustment techniques have been successfully applied to enhance the thermal component of the neutron flux in the central irradiation cavity. An analysis methodology was developed by employing the MCNP (a general Monte Carlo N-particle transport code) code in order to estimate counting efficiency and correction factors for the major perturbing phenomena. The paper presents the development of the experimental device, the results of the neutron flux-spectrum characterization, and preliminary steps to validate the analysis methodology.     

An ergodic theorem in the qualitative behavior of (non)linear semiflows

Take σ$\sigma$ to be a continuous semiflow on the locally compact metric space Θ$\Theta$, and let _{{A(θ)}θ∈Θ}${\left\{A\left(\theta \right)\right\}}_{\theta \in \Theta }$ be a family of (possibly unbounded) densely defined closed operators on the Banach space X$X$.     

Fractional derivative applied to the retrieval of phase distribution from an interferogram

This paper proposes a new method for determining the phase distribution of a 2D fringe pattern using 2D fractional derivatives. The fractional derivative of order?r (real 0??r??3), in the ?? direction (????[0,2??]) is defined by the Fourier transform and its inverse and gives as result a phase distribution. The fractional derivative of order r produces a phase displacement of r??/2 without significantly changes in normalized amplitude distribution. There are optimum values of r and ?? for which the phase distribution given by the fractional derivative represents the phase distribution for the fringe pattern. Also, we demonstrate the usefulness of a method based on four fractional derivatives to determine the phase and intensity distribution from a single interferogram and highlights small objects located in the fringe pattern. We demonstrate the proposed method using both numerical simulated and experimental interferograms.     

Pearson Global Indicator and the Quantum Mechanics of p-Dimensional Systems

We extend the results of Guiasu (1992a) top-dimensional systems. We use quantum mechanics in orderto extend the basic mathematical model from Guiasu(1992a) to systems with more dimensions. Twomultidimensional quantum systems are presented as applicationsof the mathematical results (the p-dimensional isotropicharmonic oscillator and the free particle in ap-dimensional box).     

Chiral Triptycenes in Supramolecular and Materials Chemistry

Triptycenes are an intriguing class of organic molecules with several unusual characteristics, such as a propeller-like shape, saddle-like cavities around a symmetrical scaffold, a rigid π-framework. They have been extensively studied and proposed as key synthons for a variety of applications in supramolecular chemistry and materials science. When decorated with an appropriate substitution pattern, triptycenes can be chiral, and, similarly to other popular chiral π-extended synthons, can express chirality robustly, efficiently, and with relevance to chiroptical spectroscopies. This minireview highlights and encompasses recent advances in the synthesis of chiral triptycenes and in their introduction as molecular scaffolds for the assembly of functional supramolecular materials.     

Platinum–polytyramine composite material with improved performances for methanol oxidation

Polytyramine (PTy) is shown to be a possible alternative to other conducting polymers as a support material for fuel cell electrocatalysts such as platinum. In this work, a Pt–PTy composite was prepared via potentiodynamic deposition of polytyramine on graphite substrate, followed by the electrochemical deposition of Pt nanoparticles. The material obtained by this straightforward method exhibited, for platinum loadings as low as ca. 0.12 mg cm⁻², a specific electrochemically active surface area of the electrocatalyst of ca. 54 m² g⁻¹, together with a good electrocatalytic activity for methanol oxidation in acidic media, thus ensuring better efficiency of Pt utilization. The system Pt–PTy appears to be worthy of development for methanol fuel cell applications also because the results suggested that, when deposited as small particles in a PTy matrix, platinum is less sensitive to fouling during CH₃OH oxidation.     

Thermal behaviour of the TiO<Subscript>2</Subscript>-based gels obtained by microwave-assisted sol–gel method

This work aims to elucidate whether the hypothesis of zero oxygen at the mixture layer when flame takes place is assumable for every kind of material. For that purpose, we investigated the oxygen concentration there by cone calorimeter tests. A modified holder was developed in order to collect oxygen in this mixture layer. In addition, thermogravimetric tests were carried out so as to relate the possible effects of the presence of oxygen in the atmosphere where the pyrolysis process takes place, since the cone calorimeter does not allow to control the oxygen level of the atmosphere during the experiment. The reaction rates and per cent of residue in the cone calorimetric tests were measured and compared with the results from thermogravimetric tests. Six products were analysed which can be classified in three main groups: lignocellulosic, thermoplastic polymers and thermoset polymers. Cone calorimetric results showed that for some of the materials analysed (PET, Nylon and PUR foam) the oxygen level at mixture layer decreased until values close to zero. The comparison of reaction rates between cone calorimetric and thermogravimetric tests revealed the char layer created in cone calorimetric tests over the exposed face for brushed fir, Nylon and PET established an important heat barrier that modifies the thermal behaviour of these materials.     

Nonlinear programming with E-preinvex and local E-preinvex functions

In this paper, we extend the class of E-convex sets, E-convex and E-quasiconvex functions introduced by [Youness, E.A., 1999. E-convex sets, E-convex functions and E-convex programming. Journal of Optimization Theory and Applications 102, 439–450], respectively by [Syau, Yu-Ru, Lee, E. Stanley, 2005. Some properties of E-convex functions. Applied Mathematics Letters 18, 1074–1080] to E-invex set, E-preinvex, E-prequasiinvex and corresponding local concepts. Some properties of these classes are studied. As an application of our results, we consider the nonlinear programming problem for which, we establish that, under mild conditions, a local minimum is a global minimum.