Quantitative structure-property relationship study on first reduction and oxidation potentials of donor-substituted phenylquinolinylethynes and phenylisoquinolinylethynes: Quantum chemical investigation

The relationship between the chemical structure, first reduction and oxidation potentials of 30 Phenylquinolinylethyne (PhQE), and Phenylisoquinolinylethyne (PhIE) derivative compounds has been elucidated employing ab initio calculations. Quantum chemical calculations (HF/6-31G) were carried out to obtain: the optimized geometry, energy levels, quantum chemical indices, charges and dipole moments of these compounds. The quantitative structure-property relationship (QSPR) of PhQE and PhIE was studied for the first reduction (E_red), and the first oxidation (E_ox) potentials. The genetic algorithm (GA) was applied to select the variables that resulted in the best-fit models. After the variable selection, multiple linear regression (MLR) was utilized to construct linear QSPR models. The resulting QSPR equations indicated that the orbital energies, quantum chemical indices (i.e. electronegativity and softness) and localization of charge in molecules are important factors in the first oxidation and reduction potentials of PhQE and PhIE. The quantum-chemical calculations show that the HOMO and LUMO of both PhQE and PhIE derivatives are localized on the donor-substituted phenyl moiety, and the quinolinyl and isoquinolinyl acceptor moiety respectively. Thus, it was proposed that the first reduction and oxidation potentials can be ascribed to reduction at the quinolinyl acceptor moiety, and oxidation at the donor-substituted phenyl moiety.     

Solubility of celecoxib in N-methyl-2-pyrrolidone+water mixtures at various temperatures: Experimental data and thermodynamic analysis

Solubility is one of the most significant physicochemical properties of drugs, and improving the solubility of drugs is still a challenging subject in pharmaceutical sciences due to requirements of enhancing their bioavailability. Celecoxib, according to the biopharmaceutics classification system (BCS), is a class 2 drug, possessing low water solubility (<5 μg·mL^?1) and high permeability. Increasing the solubility of this group can lead to improved bioavailability, dose reduction and subsequently, increased efficiency and reduced side effects. In this study, celecoxib solubility was determined in binary mixtures of N-methyl-2-pyrrolidone (NMP)+water at 293.2, 298.2, 303.2, 308.2 and 313.2 K. The solubility of celecoxib is increased with the addition of NMP to the aqueous solutions and reaches a maximum value in neat NMP. In addition, increased temperature leads to enhanced solubility of celecoxib in a given solvent composition. The solubility data of celecoxib in NMP+water at different temperatures were correlated using different mathematical models including, the Jouyban-Acree model and a combination of the Jouyban-Acree and van’t Hoff models. Thermodynamic parameters, Gibbs energy, enthalpy and entropy of dissolution processes were performed based on Gibbs and van’t Hoff equations. Thermodynamic analysis allowed observing two main entropy or enthalpy-driven dissolution mechanisms, varying according to the composition of aqueous mixtures. Moreover, preferential solvation of celecoxib by water is observed in water-rich mixtures but preferential solvation by NMP was seen in mixtures with similar composition and also in NMP-rich mixtures.     

TiO2–BaTiO3 nanocomposite for electron capture in dye‐sensitized solar cells

Different compositions of TiO₂–BaTiO₃ nanocomposites are synthesized with various weight ratios for dye‐sensitized solar cell (DSSC) applications. TiO₂ and BaTiO₃ nanoparticles (NPs) are synthesized by sol‐gel and solvothermal methods, respectively and are employed as the photoanode electrodes. BaTiO₃ NPs have pure cubic perovskite crystal structure with an average size of 20‐40 nm, while TiO₂ NPs show pure anatase phase with 15‐30 nm size. The power conversion efficiency (PCE) enhancement of the cells is first attained by controlling the thickness of the films for light harvesting improvement. The fabricated DSSC composed of pure BaTiO₃ NPs with an optimal thickness of 25 μm shows efficiency of 6.83%, whereas that made of pure TiO₂ NPs with 14 μm thickness has cell efficiency of 7.24%. Further improvement of cell efficiency is achieved by preparation of binary oxide nanocomposites using TiO₂ and BaTiO₃ NPs with various weight ratios. The highest PCE of 9.40% is obtained for the nanocomposite with TiO₂:BaTiO₃=85:15 (wt%). The enhancement is assigned to less recombination of photo‐generated electrons and higher incident photon to current conversion yield as a result of rapid charge collection and higher dye sensitization.     

Case Study of Application of FRP Composites in Strengthening the Reinforced Concrete Headstock of a Bridge Structure

Worldwide interest is being generated in the use of fiber-reinforced polymer composites (FRP) in the rehabilitation of aged or damaged reinforced concrete structures. As a replacement for the traditional steel plates or external posttensioning in strengthening applications, various types of FRP plates, with their high strength-to-weight ratio and good resistance to corrosion, represent a class of ideal material in externally retrofitting. This paper describes a solution proposed to strengthen the damaged reinforced concrete headstock of the Tenthill Creeks Bridge, Queensland, Australia, using FRP composites. A decision was made to consider strengthening the headstock using bonded carbon FRP laminates to increase the load carrying capacity of the headstock in shear and bending. The relevant guidelines and design recommendations were compared and adopted in accordance with AS 3600 and Austroads bridge design code to estimate the shear and flexural capacity of a rectangular cracked FRP reinforced concrete section.     

Modified covariance intersection for data fusion in distributed nonhomogeneous monitoring systems network

Monitoring networks contain monitoring nodes that observe an area of interest to detect any possible existing object and estimate its states. Each node has characteristics such as probability of detection and clutter density that may have different values for distinct nodes in nonhomogeneous monitoring networks. This paper proposes a modified covariance intersection method for data fusion in such networks. It is derived by formulating a mixed game model between neighbor monitoring nodes as players and considering the inverse of the trace of fused covariance matrix as players' utility function. Monitoring nodes estimate the states of any possible existing object by applying joint target detection and tracking filter on their own observations. Processing nodes fuse the estimated states received from neighbor monitoring nodes by the proposed modified covariance intersection. It is validated by simulating target detection and tracking problem in 2 situations: 1 target and unknown number of targets.     

Beamforming and power allocation in the downlink of MIMO cognitive radio systems based on multiobjective optimization

In this paper, power allocation and beamforming are considered in a multiple input multiple output (MIMO) downlink cognitive radio (CR) communication system, which a base station (BS) serves one primary user (PU) and one secondary user (SU). In order to design the CR system, a constrained multiobjective optimization problem is presented. Two objectives are the signal to noise plus interference ratios (SINRs) of PU and SU. Since PU has a spectrum license for data communication, a constraint in the optimization problem is that the SINR of PU must be greater than a predefined threshold based on the PU demand requirement. Another constraint is a limitation on power in BS. By considering the mentioned model, three iterative algorithms are proposed. At each iteration of all algorithms, the receiver beamforming vectors are derived based on the maximization of PU and SU SINRs, by assuming that the allocated powers and BS beamforming vectors are known. Also, power is assigned to users such that the constraint of power limitation is satisfied. The difference between the algorithms is in the obtaining of transmitter beamforming parameters. We evaluate the performance of the proposed algorithms in terms of bit error rate (BER) in simulations. Also, the computational complexity of the proposed algorithms is obtained.     

On the time‐frequency symbol density of FBMC/QAM systems

Filter bank multicarrier (FBMC) systems suffer from an inherent interference, which needs to be eliminated at the detection process. Orthogonal frequency division multiplexing/offset quadrature amplitude modulation (OFDM/OQAM) is a well‐known FBMC system, which transmits real‐valued symbols. In OFDM/OQAM, the time and frequency spacing between adjacent transmitted symbols are organized such that the inherent interference becomes pure imaginary and can be removed by a real‐taking operation. Although OFDM/OQAM provides the maximal bandwidth efficiency, it falls short in handling the spatial multiplexing techniques in multi‐input multi‐output channels. In this regard, those modified FBMC systems, which transmit complex QAM symbols (FBMC/QAM) are used to support the spatial multiplexing techniques. In this article, we present a novel matrix formulation for the FBMC/QAM transmission procedure. On the basis of this presentation, we show that the maximal achievable time‐frequency symbol density of FBMC/QAM, with the ability of perfectly removing the interference, is equal to that of the primer OFDM/OQAM.     

Application of Froude dynamic similitude in anaerobic baffled reactors to prediction of hydrodynamic characteristics of a prototype reactor using a model reactor

An anaerobic baffled reactor is a system developed in recent decades and has been used as part of the treatment of high-strength wastewater. Since the function of this system is based on its hydrodynamic features, hydrodynamics and the regime of the flow through the reactor are crucial. In this study, a prototype reactor with eight chambers, which had a total volume of 48 L, and a model reactor, whose dimensions were half of those of the prototype reactor, were used. The Froude dynamic similitude in these reactors was investigated. The results show that the curve dimensionless variances were 0.089 and 0.096 for the prototype and model reactors, respectively, the short-circuiting indices were 0.483 and 0.489 for the prototype and model reactors, respectively, the effective volume and short-circuiting index measurement errors were both 1%, the hydraulic efficiency error was 2%, and the Peclet and dispersion number errors were both 7%. Most of the compared indices were close to one another in value. Therefore, the model reactor can be used based on the Froude dynamic similitude to determine hydrodynamic characteristics of a baffled reactor at a full scale.     

Modeling and simulation of ammonia removal from purge gases of ammonia plants using a catalytic Pd-Ag membrane reactor

In this work, the removal of ammonia from synthesis purge gas of an ammonia plant has been investigated. Since the ammonia decomposition is thermodynamically limited, a membrane reactor is used for complete decomposition. A double pipe catalytic membrane reactor is used to remove ammonia from purge gas. The purge gas is flowing in the reaction side and is converted to hydrogen and nitrogen over nickel-alumina catalyst. The hydrogen is transferred through the Pd-Ag membrane of tube side to the shell side. A mathematical model including conservation of mass in the tube and shell side of reactor is proposed. The proposed model was solved numerically and the effects of different parameters on the rector performance were investigated. The effects of pressure, temperature, flow rate (sweep ratio), membrane thickness and reactor diameter have been investigated in the present study. Increasing ammonia conversion was observed by raising the temperature, sweep ratio and reducing membrane thickness. When the pressure increases, the decomposition is gone toward completion but, at low pressure the ammonia conversion in the outset of reactor is higher than other pressures, but complete destruction of the ammonia cannot be achieved. The proposed model can be used for design of an industrial catalytic membrane reactor for removal of ammonia from ammonia plant and reducing NO(x) emissions.     

An operational matrix based on Chelyshkov polynomials for solving multi-order fractional differential equations

Recent advancement in learning and teaching methodology experimented with virtual reality (VR)-based presentation form to create immersive learning and training environment. The quality of such educational VR applications not only relies on the virtual model, but the 2D presentation materials such as text, diagrams and figures. However, manual designing or seeking these educational resources is both labor intensive and time-consuming. In this paper, we introduce a new automatic algorithm to detect and extract presentation slides in educational videos, which will provide abundant resources for creating slide-based immersive presentation environment. The proposed approach mainly involves five core components: shot boundary detection, training instances collection, shot classification, slide region detection and slide transition detection. We conducted comparison experiment to evaluate the performance of the proposed method. The results indicate that, in comparison with peer method, the proposed method improves the precision of slide detection from 81.6 to 92.6% and recall from 74.7 to 86.3% on average. With the detected slides, content analyzer can be employed to further extract reusable elements, which can be used for developing VR-based educational applications.