Load‐balanced data gathering in Internet of Things using an energy‐aware cuckoo‐search algorithm

This paper deals with the lifetime problem in the Internet of Things. We first propose an efficient cluster‐based scheme named “Cuckoo‐search Clustering with Two‐hop Routing Tree (CC‐TRT)” to develop a two‐hop load‐balanced data aggregation routing tree in the network. CC‐TRT uses a modified energy‐aware cuckoo‐search algorithm to fairly select the best cluster head (CH) for each cluster. The applied cuckoo‐search algorithm makes the CH role to rotate between different sensors round by round. Subsequently, we extend the CC‐TRT scheme to present two methods for constructing multi‐hop data aggregation routing trees, named “Cuckoo‐search Clustering with Multi‐Hop Routing Tree (CC‐MRT)” and “Cuckoo‐search Clustering with Weighted Multi‐hop Routing Tree (CC‐WMRT).” Both CC‐MRT and CC‐WMRT rely on a two‐level structure; they not only use an energy‐aware cuckoo‐search algorithm to fairly select the best CHs but also adopt a load‐balanced high‐level routing tree to route the aggregated data of CHs to the sink node. However, CC‐WMRT slightly has a better performance thanks to its low‐level routing strategy. As an advantage, the proposed schemes balance the energy consumption among different sensors. Numerical results show the efficiency of the CC‐TRT, CC‐MRT, and CC‐WMRT algorithms in terms of the number of transmissions, remaining energy, energy consumption variance, and network lifetime.     

Towards More Practical Linear Programming-based Techniques for Algorithmic Mechanism Design

R. Lavi and C. Swamy (FOCS 2005, J. ACM 58(6), 25, 2011) introduced a general method for obtaining truthful-in-expectation mechanisms from linear programming based approximation algorithms. Due to the use of the Ellipsoid method, a direct implementation of the method is unlikely to be efficient in practice. We propose to use the much simpler and usually faster multiplicative weights update method instead. The simplification comes at the cost of slightly weaker approximation and truthfulness guarantees.     

An Efficient Numerical Solution of Fractional Optimal Control Problems by using the Ritz Method and Bernstein Operational Matrix

This paper deals with the Ritz spectral method to solve a class of fractional optimal control problems (FOCPs). The developed numerical procedure is based on the function approximation by the Bernstein polynomials along with fractional operational matrix usage. The approximation method is computationally consistent and moreover, has a good flexibility in the sense of satisfying the initial and boundary conditions of the optimal control problems. We construct a new fractional operational matrix applicable in the Ritz method to estimate the fractional and integer order derivatives of the basis. As a result, we achieve an unconstrained optimization problem. Next, by applying the necessary conditions of optimality, a system of algebraic equations is obtained. The resultant problem is solved via Newton's iterative method. Finally, the convergence of the proposed method is investigated and several illustrative examples are added to demonstrate the effectiveness of the new methodology.     

MCM-41-supported NNO type Schiff base complexes: a highly selective heterogeneous nanocatalyst for esterification,Diels–Alder and aldol condensation

Solid catalysts have been synthesized by anchoring transition metal complexes into organically modified MCM-41. First, the surface of Si-MCM-41 was modified with 3-aminopropyl-triethoxysilane (3-APTES), the imine group of which upon condensation with DFP (4-methyl-2,6-diformylphenol) affords a N₂O-type Schiff base moiety in the mesoporous matrix. The Schiff base moieties were used to anchor Ni (II) and Cu (II) ions. The prepared catalyst have been characterized by DRS (Diffuse Reflectance Spectroscopy), FTIR (Fourier transform infrared) spectroscopy, small-angle X-ray diffraction (SAX), FESEM (Field Emission Scanning Electron Microscope), EDX (Energy-dispersive X-ray spectroscopy) and nitrogen sorption studies. The decrease of crystallinity in the multistep synthesis procedure, as evidenced by SAX (Small-angle X-ray) measurements, was observed. The prepared materials proved to be efficient catalysts for organic transformations such as esterification, Diels–Alder and Aldol condensation at ambient conditions. The immobilized complex does not leach or decompose during the catalytic reactions, showing practical advantages over the free metal complex.     

Theoretical studies on dimerization reactions of 4, 7-diphenyl-1,10-phenanthroline (BPhen) and bathocuproine (BCP) in organic semiconductors

The dimerization reactions of 4, 7-diphenyl-1,10-phenanthroline (BPhen) and bathocuproine (BCP) were studied theoretically. In this work, the molecular geometries, BPhen and BCP monomers, positively charged BPhen and BCP intermediates, and BPhen and BCP dimers were calculated in neutral state at different levels of ab initio methods for the dimerization reactions. The molecular geometries of the BPhen and the BCP monomers and their dimers in their cationic and anionic states were optimized using the B3LYP/6-31G(d) method. The π orbitals interactions in the phenyl groups are responsible for the shortening of the C₆-N₁ and C₇-N₁ bond distances in BPhen and BCP dimers. The large difference between the reorganization energy components of BCP dimer for hole transport process is due to larger energy required to reorganize C₅C₄N₂C₆ and C₈C₁N₁C₇ angles. The methyl groups and the phenyl rings act as sterically hindering groups in the BPhen and BCP dimers. In contrast to BPhen dimer where its electron hopping rate is less than BPhen monomer, the magnitude of electron hopping rate of BCP dimer is 12 times higher than BCP monomer.     

Nano-sized manganese oxides as biomimetic catalysts for water oxidation in artificial photosynthesis: a review

There has been a tremendous surge in research on the synthesis of various metal compounds aimed at simulating the water-oxidizing complex (WOC) of photosystem II (PSII). This is crucial because the water oxidation half reaction is overwhelmingly rate-limiting and needs high over-voltage (approx. 1 V), which results in low conversion efficiencies when working at current densities required for hydrogen production via water splitting. Particular attention has been given to the manganese compounds not only because manganese has been used by nature to oxidize water but also because manganese is cheap and environmentally friendly. The manganese–calcium cluster in PSII has a dimension of about approximately 0.5 nm. Thus, nano-sized manganese compounds might be good structural and functional models for the cluster. As in the nanometre-size of the synthetic models, most of the active sites are at the surface, these compounds could be more efficient catalysts than micrometre (or bigger) particles. In this paper, we focus on nano-sized manganese oxides as functional and structural models of the WOC of PSII for hydrogen production via water splitting and review nano-sized manganese oxides used in water oxidation by some research groups.     

Free vibration of magneto-electro-elastic nanobeams based on modified couple stress theory in thermal environment

In this paper, the size-dependent free vibration of magneto-electro-elastic (MEE) nanobeams in thermal environment is investigated. Size effects are taken into account using the modified couple stress theory, which is capable of accounting for higher-order electromechanical coupling, and the equations are developed on the basis of Euler–Bernoulli beam model and using von Karman nonlinear strain. The vibration of hinged–hinged nanobeams is investigated by way of example. Effects of various parameters such as temperature, thickness, and length on natural frequencies are demonstrated, and it is indicated that increased length and decreased thickness lead to decreased nanobeam natural frequencies.     

Ultrafast Thermal Plasma Preparation of Solid Si Films with Potential Application in Photovoltaic Cells: A Parametric Study

An innovative method, namely ultrafast plasma surface melting, is developed to fabricate solid films of silicon with very high rates (150 cm²/min). The method is composed of preparing a suspension of solid particles in a volatile solvent and spreading it on a refractory substrate such as Mo. After solvent evaporation, the resulting porous layer is exposed to the flame tale of inductively coupled RF plasma to sinter and melt the surface particles and to prepare a solid film of silicon. It is shown that by controlling the flow dynamics and heat transfer around the substrate, and managing the kinetic parameters (i.e., exposure time, substrate transport speed, and reaction kinetics) in the reactor, we can produce solid crystalline Si films with the potential applications in photovoltaic cells industry. The results indicate that the optimum formation conditions with a film thickness of 250-700 μm is when the exposure time in the plasma is in the range of 5-12.5 s for a 100 × 50 mm large layer. By combining the Fourier’s law of conduction with the experimental measurements, we obtained an effective heat diffusivity and developed a model to obtain heat diffusion in the porous layer exposed to the plasma. The model further predicts the minimum and maximum exposure time for the substrate in the plasma flame as a function of material properties, the porous layer thickness and of the imposed heat flux.     

Nearly zero-dispersion, low confinement loss, and small effective mode area index-guiding PCF at 1.55 μm wavelength

In this paper,a new simple structure of indexguiding photonic crystal fiber (PCF) is designed and presented.In this PCF,dispersion,confinement loss,and effective mode area characteristics are investiga...     

An efficient one-pot synthesis of tetrahydrothiazolo[3,2-a]quinolin-6-one derivatives

The cysteamine hydrochloride as a practical precursor of 2-(nitromethylene)thiazolidine in the one-pot synthesis of thiazoloquinoline derivatives from aromatic aldehydes and dimedone is described. This protocol involved Michael reaction, imine–enamine tautomerization, and cyclization sequence. Simple operation under mild conditions, easy accessibility of reactants, short reaction times, simple workup procedure, high atom economy, and the use of ethanol/water as a green medium make this approach attractive for the synthesis of variety of such derivatives.