Optimal Control of Nonlinear Fractional-Order Systems with Multiple Time-Varying Delays

Journal of Optimization Theory and Applications - This paper considers an optimal control problem governed by nonlinear fractional-order systems with multiple time-varying delays and subject to...     

Effect of yttrium on the formation of nanostructured mesoporous CeO<Subscript>2</Subscript>

Mesoporous CeO₂ and yttrium doped CeO₂ (YDC) were prepared by a sol–gel process and characterized by a variety of techniques. XRD patterns showed that the undoped and doped samples had a cubic fluorite structure. The grain size decreased from 24.8 to 6.1 nm at 500 °C for pure CeO₂ and YDC, respectively. N₂ adsorption–desorption isotherms showed that the samples possessed typical mesopore characteristics. The BET specific surface area of the samples increased from 23.04 to 151.49 m²/g for 300 °C calcination after mesoporous CeO₂ was doped with Y. It is found that the introduction of Y can inhibit the grain growth, and the presence of the pores also can be related to this obstacle to grain growth. These results are of great significance for the control of porous microstructure, crystallinity, and applications for the development of nanostructured mesoporous materials.     

ZIF-Induced d-Band Modification in a Bimetallic Nanocatalyst: Achieving Over 44 % Efficiency in the Ambient Nitrogen Reduction Reaction

The electrochemical nitrogen reduction reaction (NRR) offers a sustainable solution towards ammonia production but suffers poor reaction performance owing to preferential catalyst–H formation and the consequential hydrogen evolution reaction (HER). Now, the Pt/Au electrocatalyst d-band structure is electronically modified using zeolitic imidazole framework (ZIF) to achieve a Faradaic efficiency (FE) of >44 % with high ammonia yield rate of >161 μg mg_cat⁻¹ h⁻¹ under ambient conditions. The strategy lowers electrocatalyst d-band position to weaken H adsorption and concurrently creates electron-deficient sites to kinetically drive NRR by promoting catalyst–N₂ interaction. The ZIF coating on the electrocatalyst doubles as a hydrophobic layer to suppress HER, further improving FE by >44-fold compared to without ZIF (ca. 1 %). The Pt/Au-N_ZIF interaction is key to enable strong N₂ adsorption over H atom.     

Individual cells immobilization for water-borne pathogen detection and enumeration

A cell counting device has been proposed and implemented for water-borne pathogen detection for drinking water quality monitoring applications. Our approach is based on magnetically-labelled cells immobilization in a high density array of individual cell for optical cell counting. The device has been tested for two water-borne pathogens: Giardia Lamblia & Cryptosporidium. An individual cell immobilization efficiency of 82% was achieved.     

Linearly independent vertices and minimum semidefinite rank

We study the minimum semidefinite rank of a graph using vector representations of the graph and of certain subgraphs. We present a sufficient condition for when the vectors corresponding to a set of vertices of a graph must be linearly independent in any vector representation of that graph, and conjecture that the resulting graph invariant is equal to minimum semidefinite rank. Rotation of vector representations by a unitary matrix allows us to find the minimum semidefinite rank of the join of two graphs. We also improve upon previous results concerning the effect on minimum semidefinite rank of the removal of a vertex.     

Physics and chemistry of silicene nano-ribbons

We review our recent discovery of silicene in the form of silicon nano-ribbons epitaxially grown on silver (1 1 0) or (1 0 0) surfaces, which paves the way for the growth of graphene-like sheets. We further draw some perspectives for this unique novel material upon mild hydrogenation.