Mechanochemical synthesis of YNbO4:Eu nanocrystalline powder and its structural,microstructural and photoluminescence properties

In this research we prepared nanocrystalline YNbO₄:Eu³⁺ phosphor, i.e. nanophosphor, powder using an efficient mechanochemical method followed by annealing. X-ray diffraction analysis revealed that YNbO₄:Eu³⁺ crystallizes in monoclinic structure C2/c where, from the point of view of A and B in ABO₄ compounds, cation coordination can be noted as [6+2, 4+2]. Crystallite size of about 40 nm, was estimated using Debye Scherrer's equation. Raman spectroscopy with 785 and 532 nm excitation wavelengths is performed to record a majority of materials phonon modes and to provide more in depth understanding of the YNbO₄ structure. Scanning electron microscopy observations indicate that the mechanical treatment during synthesis is causing non-uniformity of the powder microstructure. High resolution photoluminescent measurements upon UV excitation showed intense emission coming from f–f transitions of the europium ion with the lifetime of 0.68 ms, suggesting that the obtained YNbO₄:Eu³⁺ is a good potential phosphor. A comparison of emissive properties with microcrystalline YNbO₄:Eu³⁺ was made and it showed higher values of emission intensity and lifetime of the nanocrystalline sample.     

Towards understanding of the photosensitive properties in lead-vanadate-tellurate unconventional glasses

This paper describes photosensitive properties and spectroscopic studies on the xPbO(100 − x)[6TeO₂·4V₂O₅] (where x = 0-100 mol%) glass system. Our FTIR, UV-vis spectroscopic data and density measurements exhibit compositional dependent trends and the existence of characteristic vanadate (orthovanadate, pyrovanadate) structural units in these glasses. By laser exposures of the samples, variations observed in the FTIR and UV-vis spectra show that the existence a redox couple between lead ions and vanadate network.     

Wetting and surface tension measurements on gold alloys

The surface tension and the density of some gold alloys have been measured and their wetting behaviour investigated in relation to different ceramic supports. Relationships between surface tension and density as a function of temperature are proposed.     

On the entropy of partitions in product MV algebras

 Generalizing the entropy of fuzzy partitions, the entropy of a partition in recently introduced product MV algebra has been studied. The least common refinement of two partitions is defined and the algebraic properties of the entropies and conditional entropies are examined.     

Modeling diffraction in free-space optical interconnects by the mode expansion method

Free-space optical interconnects (FSOIs), made up of dense arrays of vertical-cavity surface-emitting lasers, photodetectors and microlenses can be used for implementing high-speed and high-density communication links, and hence replace the inferior electrical interconnects. A major concern in the design of FSOIs is minimization of the optical channel cross talk arising from laser beam diffraction. In this article we introduce modifications to the mode expansion method of Tanaka et al. [IEEE Trans. Microwave Theory Tech. MTT-20, 749 (1972)] to make it an efficient tool for modelling and design of FSOIs in the presence of diffraction. We demonstrate that our modified mode expansion method has accuracy similar to the exact solution of the Huygens-Kirchhoff diffraction integral in cases of both weak and strong beam clipping, and that it is much more accurate than the existing approximations. The strength of the method is twofold: first, it is applicable in the region of pronounced diffraction (strong beam clipping) where all other approximations fail and, second, unlike the exact-solution method, it can be efficiently used for modelling diffraction on multiple apertures. These features make the mode expansion method useful for design and optimization of free-space architectures containing multiple optical elements inclusive of optical interconnects and optical clock distribution systems.     

Definition of the optimal freezing rate-2. Investigation of the physico-chemical properties of beef M. longissimus dorsi frozen at different freezing rates

The influence of freezing rate on weight loss during the freezing, thawing and cooking, on water-binding capacity, on sensory and other physico-chemical properties of beef M. longissimus dorsi was investigated. The changes in myofibrillar proteins in muscle samples frozen at different freezing rates were also investigated.

The greatest weight losses during the freezing, thawing and cooking were registered at slow freezing procedures (freezing rate of 0·22 cm/h and 0·29 cm/h), when the meat was tougher and less soft. The solubility of myofibrillar proteins was least from those muscles frozen at such freezing rates.

The freezing of samples at freezing rates of 3·33 cm/h and 3·95 cm/h had less influence on their physico-chemical characteristics. The solubility of the myofibrillar proteins from such samples was greatest, and the cooked samples were the most tender.

From analysis of the results it was concluded that optimal conditions for meat freezing seem to be those when the average freezing rate is 2–5 cm/h.     

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Time-optimal velocity planning along predefined path for static formations of mobile robots

International Journal of Control, Automation and Systems - This paper is concerned with the problem of finding a time-optimal velocity profile along the predefined path for static formations of...