Step size strategies for the numerical integration of systems of differential equations

In this study, the step size strategies are obtained such that the local error is smaller than the desired error level in the numerical integration of a type of nonlinear equation system in interval [_t0,T]$[t_0,T]$. The algorithms are given for calculating step sizes and numerical solutions according to these strategies. The algorithms are supported by the numerical examples.     

The stabilities, electronic structures and elastic properties of Rb-As systems

The structural, electronic and elastic properties of Rb–As systems (RbAs in NaP, LiAs and AuCu structures, RbAs2 in the MgCu2 structure, Rb3 As in Na3As, Cu3 P and Li3Bi structures, and Rb5 As4 in the A5B4 structure) are investigated with the generalized gradient approximation in the frame of density functional theory. The lattice parameters, cohesive energies, formation energies, bulk moduli and the first derivatives of the bulk moduli (to fit Murnaghan’s equation of state) of the considered structures are calculated and reasonable agreement is obtained. In addition, the phase transition pressures are also predicted. The electronic band structures, the partial densities of states corresponding to the band structures and the charge density distributions are presented and analysed. The second-order elastic constants based on the stress-strain method and other related quantities such as Young’s modulus, the shear modulus, Poisson’s ratio, sound velocities, the Debye temperature and shear anisotropy factors are also estimated.     

Simulation and hybrid fuzzy-PID control for positioning of a hydraulic system

Accuracy and precision of position control of hydraulic systems are key parameters for engineering applications in order to set more economical and quality systems. In this context, this paper presents modeling and position control of a hydraulic actuation system consisting of an asymmetric hydraulic cylinder driven by a four way, three position proportional valve. In this system model, the bulk modulus is considered as a variable. In addition, the Hybrid Fuzzy-PID Controller with Coupled Rules (HFPIDCR) is proposed for position control of the hydraulic system and its performance is tested by simulation studies. The novel aspect of this controller is to combine fuzzy logic and PID controllers in terms of a switching condition. Simulation results of the HFPIDCR based controller are compared with the results of classical PID, Fuzzy Logic Controller (FLC), and Hybrid Fuzzy-PID controller (HFPID). As a result, it is demonstrated that Hybrid Fuzzy PID Controller with Coupled Rules is more effective than other controllers.     

Structural and Morphological Properties of Boron Doped V2O5 Thin Films: Highly Efficient Photocatalytic Degradation of Methyl Blue

Russian Journal of Applied Chemistry - Boron doped vanadium thin films were fabricated on the micro-slide glass substrates by spray pyrolysis technique at substrate temperature of 400°C....     

Better Optimization of Nonlinear Uncertain Systems (BONUS): A New Algorithm for Stochastic Programming Using Reweighting through Kernel Density Estimation

Given a series-parallel queueing network topology with exponential servers of finite capacity, a systematic design methodology is presented that approximately solves the optimal routing and buffer space allocation problems within the network. The multi-objective stochastic nonlinear programming problem in integer variables is described and a two-stage iterative optimization procedure is presented which interconnects the routing and buffer space allocation problems. The algorithmic procedure couples the Expansion method, a decomposition method for computing performance measures in queueing networks with finite capacity, along with Powell's unconstrained optimization procedure which allocates the buffers and a multi-variable search procedure for determining the routing probabilities. The effectiveness and efficiency of the resulting two-stage design methodology is tested and evaluated in a series of experimental designs along with simulations of the network topologies.     

The effect of pressure on the elastic constants of Cu, Ag and Au: a molecular dynamics study

This paper describes the effect of pressure on some the mechanical properties of transition metals Cu, Ag, and Au, such as elastic constants and bulk modulus. Using molecular dynamics (MD) simulation, the present study was carried out using the modified many-body Morse potential function expression in the framework of the Embedded Atom Method (EAM). The effect of pressure on equilibrium volume, elastic constants, and bulk modulus were determined, and found to be in agreement with other theoretical calculations and experimental data.     

Polymerization of monoisocyanates by the Pruitt–Baggett adduct

n-Butyl isocyanate (nBIC) was polymerized in bulk by the Pruitt–Baggett adduct (PBA) at ?23, 0.0, and 25.0°C. Polymerization was accompanied by trimerization to the cyclicisocyanurates at all temperatures. Spectroscopic evidences supported the nylon-1 structure for both trimer and polymer. The polymer/trimer ratio and the molecular weight of produced polymers were found to increase with decreasing temperature. The Pruitt–Baggett catalyst (PBC), which is the reaction product of (PBA + H₂O) system, also polymerized nBIC, but with a relatively slower rate. In aromatic and etheric solutions, nBIC was only trimerized by PBA. Copolymerization of nBIC with propylene oxide by PBA and PBC failed. Some selected monoisocyanates were also polymerized by PBA. © 1993 John Wiley & Sons, Inc.     

3-Aminoquinazoline–phosphine ligands and their ruthenium(II) complexes: application in catalytic hydrogenation and transfer hydrogenation reactions

3-Aminoquinazolinone–phosphine proligands (5a–e) and their Ru(II) complexes (6a–e) were prepared and characterized by NMR (¹H, ¹³C, ³¹P{¹H}), FTIR and microanalysis. The 3-aminoquinazolinone–phosphine ligands were found to coordinate with the Ru(II) center via their phosphorus and nitrogen atoms. The Ru(II) complexes were applied as catalysts for the hydrogenation and transfer hydrogenation of prochiral ketones. The results showed that these complexes are efficient transfer hydrogenation catalysts.     

The separation–preconcentration and determination of ultra-trace gold in water and solid samples by dispersive liquid–liquid microextraction using 4-ethyl-1(2-(4-(4-nitrophenyl)piperazin-1-yl)acetyl)thiosemicarbazide) as chelating agent and flame atomic absorption spectrometry

A selective separation and preconcentration method for the determination of gold ions in water and ore samples has been developed using dispersive liquid–liquid microextraction, followed by flame atomic absorption spectrometry. 4-Ethyl-1(2-(4-(4-nitrophenyl)piperazin-1-yl)acetyl)thiosemicarbazide) (NPPTSC) has been used for the first time as new chelating reagent. A mixture of ethanol (dispersive solvent) and carbon tetrachloride (extraction solvent) was used. Some parameters affecting the extraction procedure including the type and volume of the extracting and dispersive solvents, HNO₃ concentration, the chelating agent amount, volume of sample, and foreign ions have optimized. Also, the complex formation between gold ions and the ligand has been investigated in a methanol–water solution (1:1) using UV–visible spectrometry. The spectrophotometric titration data showed that of Au–NPPTSC complex composition was found to be 3:2. After optimizing the instrumental and experimental parameters, we achieved a detection limit of 1.5 µg L^?1, a preconcentration factor of 50, and a linear dynamic range of 10.0–400.0 µg L^?1. The relative standard deviation obtained 2.1% at 50 µg L^?1 for gold ions (n = 10). The proposed method was successfully performed for the determination of gold in certified reference material, environmental water, and ore samples.     

Hydrogen sulfide determination by solid surface luminescence

In the analytical system suggested, atmospheric hydrogen sulfide reacts with the surface of a filter paper treated with aqueous cadmium chloride and yields a luminescent species whose intensity can be correlated with the analyte concentration in ambient air. It was shown that the luminescent species are CdS solid particles which were formed in a well defined size. The paper luminescence was also tried on polymeric surfaces; polyethyleneoxide, polyvinyl alcohol, ethylcellulose and carboxymethylcellulose were found to give a similar luminescence signal. The system can be used on the tip of an optical fiber for an irreversible, cumulative type of analytical device for hydrogen sulfide determination. The 3s detection limit for the paper luminescence detection system was 7.8 ppb H(2)S.