Electrophoretic deposition of multiferroic BiFeO3 sub-micrometric particles from stabilized suspensions

The electrophoretic deposition (EPD) was applied to BiFeO₃ (BFO) powders, one of the most interesting multiferroic compounds characterized by simultaneous magnetic and ferroelectric activity, to form homogeneous films. The preparation and characterization of stable BFO colloidal suspensions in aqueous, organic and mixed solvents were investigated by zeta potential measurements at room temperature in the presence of surfactants. BFO thin films were then deposited on steel substrates from stabilized BFO suspensions, by adjusting the preparative parameters to optimize the film quality. The compositional, morphological and electrical characteristics of the obtained BFO films, together with thickness measurements, were studied using SEM, XRD, AFM, EIS and optical surface profilometer. EPD method applied to BFO stable suspensions produced homogeneous thickness BFO films, free from pinholes and cracks, that were successively sintered and characterized also in terms of photocatalytic response.     

An investigation of the thermal performance of cylindrical heat pipes using nanofluids

In this work, a two-dimensional analysis is used to study the thermal performance of a cylindrical heat pipe utilizing nanofluids. Three of the most common nanoparticles, namely Al₂O₃, CuO, and TiO₂ are considered as the working fluid. A substantial change in the heat pipe thermal resistance, temperature distribution, and maximum capillary heat transfer of the heat pipe is observed when using a nanofluid. The nanoparticles within the liquid enhance the thermal performance of the heat pipe by reducing the thermal resistance while enhancing the maximum heat load it can carry. The existence of an optimum mass concentration for nanoparticles in maximizing the heat transfer limit is established. The effect of particle size on the thermal performance of the heat pipe is also investigated. It is found that smaller particles have a more pronounced effect on the temperature gradient along the heat pipe.     

Synthesis of new red photoluminescent Zn(II)-salicylaldiminato complex

We report the preparation and photophysical properties of a new zinc (II) complex of the donor–acceptor–donor (D–A–D) type ligand N,N′-bis(2-hydroxy-1-naphthylidene)-diaminomaleonitrile (H₂L). The molecular structure of the [(ZnL)·DMF]·DMF complex was determined by single crystal X-ray crystallography. The complex exhibits remarkable optical features attributed to the intramolecular charge transfer (ICT) with a striking red emission. Fluorescence studies of H₂L and ZnL reveal that the quantum yield strongly increases upon coordination.     

Ferroelectric–relaxor crossover characteristics in Ba(ZrxTi1−x)O3 ceramics investigated by AFM-piezoresponse study

Ba(Zr_xTi_1?x)O₃ ceramics with x = 0.10 and 0.18 prepared via solid state, with high-density, homogeneous microstructures and similar grain size were investigated. The dielectric data showed that the relaxor properties are induced by increasing the Zr vs. Ti fraction x, both compositions showing a combined relaxor–ferroelectric character. The AFM-piezoresponse experiments revealed a few interesting characteristics, as follows: (1) none of the samples could be totally poled or switched, like the normal ferroelectrics; (2) the samples locally present different types of responses (ferroelectric with a strong piezoresponse, field-induced ferroelectric, polar but non-switchable and non-polar regions); (3) both the regions with a natural strong piezoresponse and the ones obtained after poling are larger in size and more stable in time for the sample with x = 0.10 than for x = 0.18; (4) the sample having x = 0.18 has a smaller piezoresponse than the one with x = 0.10. The observed local features are confirming the ferroelectric–relaxor crossover with increasing x, as observed by the analysis of the dielectric data.     

Hydrogen bonding at the water/quasi-freestanding graphene interface

Vibrational spectroscopy has been used to study the interaction of water with quasi-freestanding graphene grown on Pt(1 1 1). A sharp O–H (O–D) vibrational band centered at 457 (337) meV is a direct evidence of the existence of non-H- (non-D-) bonded water molecules at the water/graphene interface. This finding is expected to play a significant role in understanding the behavior of water at hydrophobic surfaces. Such finding is in agreement with results reported for water adsorbed on other hydrophobic surfaces and with the behavior of water confined in carbon nanotubes and between graphene sheets.     

An approximate dynamic programming approach to resource management in multi-cloud scenarios

The programmability and the virtualisation of network resources are crucial to deploy scalable Information and Communications Technology (ICT) services. The increasing demand of cloud services, mainly devoted to the storage and computing, requires a new functional element, the Cloud Management Broker (CMB), aimed at managing multiple cloud resources to meet the customers’ requirements and, simultaneously, to optimise their usage. This paper proposes a multi-cloud resource allocation algorithm that manages the resource requests with the aim of maximising the CMB revenue over time. The algorithm is based on Markov decision process modelling and relies on reinforcement learning techniques to find online an approximate solution.     

Ambient Abstract State Machines with applications

We define a flexible abstract ambient concept which turned out to support current programming practice, in fact can be instantiated to apparently any environment paradigm in use in frameworks for distributed computing with heterogeneous components. For the sake of generality and to also support rigorous high-level system design practice we give the definition in terms of Abstract State Machines. We show the definition to uniformly capture the common static and dynamic disciplines for isolating states or concurrent behavior (e.g. handling of multiple threads for Java) as well as for sharing memory, patterns of object-oriented programming (e.g. for delegation, incremental refinement, encapsulation, views) and agent mobility.