Nonlinear fractional‐order power system stabilizer for multi‐machine power systems based on sliding mode technique

This paper presents two novel nonlinear fractional‐order sliding mode controllers for power angle response improvement of multi‐machine power systems. First, a nonlinear block control is used to handle nonlinearities of the interconnected power system. In the second step, a decentralized fractional‐order sliding mode controller with a nonlinear sliding manifold is designed. Practical stability is achieved under the assumption that the upper bound of the fractional derivative of perturbations and interactions are known. However, when an unknown transient perturbation occurs in the system, it makes the evaluation of perturbation and interconnection upper bound troublesome. In the next step, an adaptive‐fuzzy approximator is applied to fix the mentioned problem. The fuzzy approximator uses adjacent generators relative speed as own inputs, which is known as semi‐decentralized control strategy. For both cases, the stability of the closed‐loop system is analyzed by the fractional‐order stability theorems. Simulation results for a three‐machine power system with two types of faults are illustrated to show the performance of the proposed robust controllers versus the conventional sliding mode. Additionally, the fractional parameter effects on the system transient response and the excitation voltage amplitude and chattering are demonstrated in the absence of the fuzzy approximator. Finally, the suggested controller is combined with a simple voltage regulator in order to keep the system synchronism and restrain the terminal voltage variations at the same time. Copyright © 2014 John Wiley & Sons, Ltd.     

Adaptive control of pure-feedback systems with nonlinear parameterization via time-scale separation

International Journal of Control, Automation and Systems - In this paper an adaptive control approach for completely non-affine pure-feedback systems with nonlinear parameterization is proposed. By...     

Applying two optimization techniques in evaluating tensile strength of granitic samples

Engineering with Computers - The Brazilian tensile strength (BTS) test is the most common method to evaluate the tensile strength in mining and civil engineering projects. This paper aims to employ...     

Computer-assisted design and synthesis of a highly selective smart adsorbent for extraction of clonazepam from human serum

A computational approach was applied to screen functional monomers and polymerization solvents for rational design of molecular imprinted polymers (MIPs) as smart adsorbents for solid-phase extraction of clonazepam (CLO) form human serum. The comparison of the computed binding energies of the complexes formed between the template and functional monomers was conducted. The primary computational results were corrected by taking into calculation both the basis set superposition error (BSSE) and the effect of the polymerization solvent using the counterpoise (CP) correction and the polarizable continuum model, respectively. Based on the theoretical calculations, trifluoromethyl acrylic acid (TFMAA) and acrylonitrile (ACN) were found as the best and the worst functional monomers, correspondingly. To test the accuracy of the computational results, three MIPs were synthesized by different functional monomers and their Langmuir–Freundlich (LF) isotherms were studied. The experimental results obtained confirmed the computational results and indicated that the MIP synthesized using TFMAA had the highest affinity for CLO in human serum despite the presence of a vast spectrum of ions.     

Effect of halocarbon promoters on polyethylene properties using MgCl2 (ethoxide type)/TiCl4/AlEt3/H2 catalyst system

In our previous study we found that addition of proper amount of halocarbons (HC) including chlorocyclohexane (CHC), chlorocyclopentane (CHP), butylchloride (BC), 1,4‐dichlorobutane (DCB), and chloroform (C) to the MgCl₂ (Ethoxide type)/TiCl₄/AlEt₃ catalytic system leads to a strong productivity improvement. In this study, the effect of these halocarbons on the properties of resulting polymers was investigated using H₂ as chain transfer agent at optimum HC/Ti molar ratio. The nature of halocarbon compound had a strong effect on polymer properties as well as on development of polymerization activity. Effect of halocarbon promoters on the polymer melt flow index (MFI), melt flow ratio (MFR), particle size distribution (PSD), bulk density, wax amount, crystallinity, and thermal properties of the polymers were studied. Results showed that, in the presence of halocarbons, polyethylenes with higher MFI and bulk density, broader MFR and lower wax amount have been obtained. Also, sieve analysis showed that, in the presence of halocarbons as promoter, polymers had better particle size distribution (PSD). DSC analysis showed that the T_m of PEs prepared with the different promoters were in the region commonly reported for HDPE and was not affected substantially by halocarbons, but, the crystallinity of the polymers has been improved using halocarbon promoters. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Melting entropy and enthalpy of metallic nanoparticles

The lattice-type-sensitive model has been developed to predict the size-dependent depression of melting entropy and enthalpy of nanoparticles. The size-dependency of melting entropy and enthalpy of nanoparticles has been obtained based on the relation between cohesive energy and melting point of nanoparticles obtained in our previous work. In this model the effects of particle size, lattice and surface packing factors, and the coordination numbers of the lattice and surface crystalline planes are considered. The presented equations of melting entropy and enthalpy have been corroborated by the experimental data of In and molecular dynamic (MD) simulation results of Cu nanoparticles. The model confirms that the size-dependency of the entropy and enthalpy of melting for nanoparticles is quite dependent on their lattice structure.     

Feasibility of imperialist competitive algorithm to predict the surface settlement induced by tunneling

Surface settlement is considered as an adverse effect induced by tunneling in the civil projects. This paper proposes the use of the imperialist competitive algorithm (ICA) for predicting the maximum surface settlement (MMS) resulting from the tunneling. For this work, three forms of equations, i.e., linear, quadratic and power are developed and their weights are then optimized/updated with the ICA. The requirement datasets were collected from the line No. 2 of Karaj urban railway, in Iran. In the ICA models, vertical to horizontal stress ratio, cohesion and Young’s modulus, as the effective parameters on the MSS, are adopted as the inputs. The statistical performance parameters such as root mean square error (RMSE), mean bias error (MBE), and square correlation coefficient (R²) are presented and compared to validate the performance. The findings indicate that the developed ICA-based models with the R² of 0.979, 0.948 and 0.941, obtained from ICA power, ICA quadratic and ICA linear models, respectively, are the acceptable and accurate tools to estimate MSS, and furthermore prove their prediction capability for future research works in this field.

     

Energy management of a smart autonomous electrical grid with a hydrogen storage system

The problem of energy management in the smart autonomous electrical grids (SAEGs) is a main challenge in the active distribution networks. In such systems, the operator of the network decides on the optimal scheduling of the resources to supply the local demand. In this paper, a multi-objective optimization model is developed for a SAEG considering responsive consumers (RCs) and a hydrogen storage system (HSS). The objective functions are maximizing the reliability and minimizing both the operation cost and the gap between the energy consumption and its optimal value. The participation of the RCs is modeled through the demand shifting strategy and the local generation of the plug-in electric vehicles. To model the uncertainties of the renewable energy sources and the demand, the Monte Carlo simulation approach is used. The resulted model is solved using the shuffled frog leaping algorithm (SFLA) regarding which the non-dominated solutions are generated. Then, the best solution is obtained using the fuzzy and the weighted sum methods. To investigate the effectiveness of the proposed model, it is applied on a 24-node test system through defining four case studies. The results shown that in the presence of the RCs and the HSS, the operation cost and the reliability of the system both improve.     

Fe3 O4 /Ag nanocomposite biosynthesised using Spirulina platensis extract and its enhanced anticancer efficiency

In this work, the authors investigated the apoptotic activities of Fe₃ O₄ /Ag nanocomposite biosynthesised by Spirulina platensis extract against MCF‐7 (human breast cancer cells). The physico‐chemical properties of prepared Fe₃ O₄ /Ag nanocomposite were studied by different spectroscopic methods. To evaluate the in vitro cytotoxic effect, MCF‐7 cells were treated with different concentrations of Fe₃ O₄ /Ag nanocomposite and examined by 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyl‐tetrazolium bromide (MTT) assay. Moreover, apoptotic effects were also studied by Hoechst 33258 staining, caspase 3 activation assays, and annexin V‐fluorescein isothiocyanate (FITC) and propidium iodide staining. Microscopic observations of Fe₃ O₄ /Ag nanocomposites indicated approximately spherical shape and small particles in the size range of about 30–50 nm. The MTT assay result revealed that the Fe₃ O₄ /Ag nanocomposite causes a dose‐dependent cell proliferation reduction in MCF‐7 cells (IC₅₀  = 135 μg/ml). Regarding to the Annexin V/PI staining result, the increase percentage of apoptotic cells (28.09%) was detected as compared to untreated cells. According to the caspase assay, Fe₃ O₄ /Ag nanocomposite enhances caspase 3 level. Furthermore, in vitro anti‐cancer activity of the nanocomposite was performed by Hoechst 33258 staining method. The proposed data suggest that Fe₃ O₄ /Ag nanocomposite may be an effective agent for the inhibition of breast cancer cells at in vitro level.Inspec keywords: nanomedicine, nanocomposites, toxicology, cancer, drug delivery systems, nanofabrication, cellular biophysics, nanoparticlesOther keywords: MCF‐7 cells, 5‐diphenyl‐tetrazolium, apoptotic effects, propidium iodide staining, dose‐dependent cell proliferation reduction, apoptotic cells, untreated cells, nanocomposite, Hoechst 33258 staining method, human breast cancer cells, physico‐chemical properties, spectroscopic methods, in vitro cytotoxic effect, in vitro anticancer activity, biosynthesis, caspase 3 activation assays, annexin V‐fluorescein isothiocyanate, FITC, Fe₃ O₄ ‐Ag     

Compressive quasistatic and dynamic behavior of SiC/ZrO2 aluminum-based nanocomposite

Journal of Mechanical Science and Technology - This research investigated the mechanical properties of aluminum-based nanocomposite. The spark plasma sintering method was adopted to fabricate the...