Synthesis of mixed metal oxide nanoparticles of SnO<Subscript>2</Subscript> with SrO via sol–gel technology: their structural,optical, and electrical properties

Mixed metal oxides of tin with strontium (xSnO₂.SrO) in different molar ratio {where x?=?1 (1), 2 (2), 4(3); SnO₂ doped with Sr⁺²(4), SnO₂ doped with Sr⁺² and co-doped with F^?(5)} have been prepared by sol–gel technology in basic medium using SnCl₂.2H₂O as precursor in isopropanol as solvent. Structural analysis by XRD patterns have shown formation of particles at nanoscale and phase separation of SnO₂ in tetragonal rutile framework in these mixed metal oxides. This fact was further supported by TEM. SEM images of all these samples have shown formation of various geometrical patterns ranging from spherical particles to nanorods. In the IR spectra of all these oxides, Sr–O absorption bands were present only in sample (1). UV–Vis spectroscopy has shown reduction in optical band gap in mixed metal oxides and the lowest value of band gap was observed for sample (3). Photoluminescence spectra of all these derivatives are found to be almost similar again indicated retention of tetragonal rutile SnO₂ framework. I–V curves of all these oxides are non-linear and lowest resistance was observed for sample (3). This fact was further supported by impedance measurements.

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Tunable 7 12-microm optical parametric oscillator using a Cr,Er:YSGG laser to pump CdSe and ZnGeP(2) crystals

A CdSe optical parametric oscillator (OPO) pumped by a 2.79-mum , Cr, Er:YSGG laser yielded a 59% signal-plus-idler slope efficiency (eta), a total idler output of 1.2-2.4mJ between 8.5 and 12.3 mum , and an idler beam that was 2.2-2.5 times the diffraction limit. A ZnGeP(2) OPO operated with a lower threshold, eta = 29% , and a forward idler output of 0.7-2.4 mJ from 6.9 to 9.9 microm . The signal and idler bandwidths were typically 4 cm(-1) for each OPO.     

Trigonometric approximation of functions in $$L_1$$ L 1 -norm

Periodica Mathematica Hungarica - In this paper, the authors have obtained $$L_1$$ -approximations of functions f in $$ {{\,\mathrm{Lip}\,}}(\alpha ,1) $$ $$ (0 &lt; \alpha \le 1) $$ by...     

An optimization model for combined selecting,planting and harvesting sugarcane varieties

The problem of selecting sugarcane varieties has been widely discussed due to its computational complexity and its great impact for the sugar and ethanol industry. This paper proposes a new integrated mathematical programming model to deal with the selection of sugarcane varieties to be planted and the determination of the optimal period for planting and harvesting in order to increase production in the sugarcane industry. The proposed model optimizes the production of sugarcane and improves the quality of biomass whilst satisfying the main constraints imposed by sugarcane companies. The problem is modelled as an integer linear program and solved using an exact method to generate optimal solutions for small and medium problems. For large problems, metaheuristic approaches based on Genetic Algorithm and Variable Neighbourhood Search are proposed. According to the results, the proposed methodology provides sugarcane company managers with decision support in selecting the most suitable varieties and in determining the best period to plant and harvest their sugarcane.

     

Fixed Point Theorems for Weakly Contractive Mappings in Ordered Metric Spaces with an Application

In this paper, we prove fixed point theorem for weakly contractive mappings using locally $T$-transitivity of binary relation and presenting an analogous version of Harjani and Sadarangani theorem involving more general relation theoretic metrical notions. Our fixed point results under universal relation reduces to Harjani and Sadarangani [Nonlinear Anal., 71 (2009), 3403–3410] fixed point theorems. In this way we also generalize some of the recent fixed point theorems for weak contraction in the existing literature.