Sharif Digital Repository

We propose a nonlinear method for the analysis of the time series for the spatial position of a bead trapped in optical tweezers, which enables us to reconstruct its dynamical equation of motion. The main advantage of the method is that all the functions and parameters of the dynamics are determined directly (non-parametrically) from the measured series. It also allows us to determine, for the first time to our knowledge, the spatial-dependence of the diffusion coefficient of a bead in an optical trap, and to demonstrate that it is not in general constant. This is in contrast with the main assumption of the popularly-used power spectrum calibration method. The proposed method is validated... 

A time series study of the electrical energy generated by wind turbines and solar cells shows that the energy produced has a lot of fluctuations due to the geographic conditions. These ups and downs have caused not only the share of these sources to be marginal, but also they lead to the volatility of electric power plants. By examining several different data from different countries and regions with the frequency of second and minute, we show that different scale behaviors exist at different time intervals and reveal their other random and nonlinear characteristics. We also compare the non-Gaussian behavior of these regions together, showing that studying the properties of such data helps... 

In this study, we examined a typical high-voltage gas circuit breaker. The main goal of this study is to characterize arc plasma and to determine its behavior using the generalized Mayr-type equation model following the interruption of high-voltage circuit breakers according to a semi-empirical one, named conductance model. Here, we tried to evaluate some arc parameters that affect interrupting ability by performing a numerical analysis so that our model defines recorded experimental results of an actual test. © 2008 The Japan Society of Applied Physics  

Effects of both electron beam irradiation on the properties of polypropylene (PP) films and the irradiation on the different layers of a multilayer PP film are studied. A Fourier transform infrared spectroscope was used to investigate the chemical structure of the films. The results showed that the chemical properties of the first layer were improved, that is, more functional groups responsible for dye ability and hydrophilicity of the film were produced on its surface, while noticeable improvement was not detected on the surface of other layers. This was also confirmed by testing the dye ability of the layers. However, the results obtained by atomic force microscopy showed that the electron... 

A new photocatalytic filtration membrane was prepared by grafting of Ag–Au bi-plasmonic shell-on TiO2@Fe3O4 nanoparticles as a magnetically-separable heterogeneous photocatalyst to a poly acrylic acid-modified cellulose acetate membrane for decomposition and removal of methyl orange as a model pollutant from textile wastewater samples. Eight photocatalysts including five Au NPs-modified TiO2@Fe3O4 NPs and three Ag-Au bi-plasmonic NPs-decorated TiO2@Fe3O4 NPs with different shell thickness were synthesized and characterized by TEM, UV–vis, and SEM techniques and their photocatalytic activity was assessed using two radiation sources. After selection of optimum photocatalyst and modification of... 

We investigate short-term non-linearity of solar irradiance fluctuations using the multifractal detrended fluctuation analysis (MFDFA). The MFDFA shows that time series of solar irradiance have a long range correlation function with a multifractal behavior. We apply this method to solar irradiance time series from several regions around the world with resolutions of seconds and minutes. The obtained generalized Hurst and Renyi exponents h(q) and τ(q) suggest the non-linear and non-stationary essence of measured irradiance time series. Also, we analyze shuffled, random phase, and rank-wised surrogated data to reveal the nature of the multifractality and conclude that linear and non-linear... 

For the edge plasma parameters measurement, a movable Langmuir probe is fabricated and installed on the IR-T1 tokamak. The set-up consists of two sets of single Langmuir probes with tungsten tip movable in the radial direction. Edge plasma parameters including electron temperature, Ion density, floating potential and the corresponding radial changes are measured. Using two-point correlation technique clearly reveal that in the SOL region the poloidal propagation of floating potential fluctuation is in the direction of ion diamagnetic drift and in the edge it propagates in the electron diamagnetic drift direction. © 2009 Springer Science+Business Media, LLC  

Mechanical properties and microstructural analysis of Expanded Perlite Aggregate (EPA) concretes are presented. Using 10% EPA, the effects of using various types of fibre were investigated. For all specimens, fibrous and non-fibrous, the compressive and the splitting tensile strengths were obtained. Complete stress–strain curves for fibre-reinforced specimens were obtained. A new index for representing the toughness of fibre-reinforced Perlite concretes is introduced. The addition of fibres substantially increased the splitting tensile strength. Steel fibres with “indentations” had the best performance in this regard. Regarding the toughness, specimens with “hooked” steel fibres performed... 

We study the electronic properties of superlattice with rough interfaces in two and three dimensions using the transfer-matrix method and direct diagonalization of the Anderson Hamiltonian. The system consists of layers with an average constant width, but with stochastic roughness added to the interfaces between the layers. The numerical results indicate that, in the thermodynamic limit, the two-dimensional superlattice is an insulator in the presence of even small roughness. In three-dimensional systems, however, the superlattice exhibits a metal-insulator transition with a well-defined mobility edge located at an energy E c that we compute numerically. For three-dimensional superlattice,... 

This study investigates the durability of confined geopolymer concrete with fiber-reinforced polymer and compares the results with ordinary Portland cement concrete (OPCC). Two hundred and seventy geopolymer concrete (GPC) specimens with different mix designs (fly ash- and granulated blast furnace slag(GBFS)-based GPC) were prepared and then wrapped with two different fiber-reinforced polymers (carbon and glass FRPs). For 12,960 hrs (eighteen months), the specimens were exposed to four different pHs (2.5, 7 (water), 7.25 (saltwater), 12.5). The reliability analysis was performed after modeling the compressive strength over time. Based on the results, the ductility of all specimens decreased... 

Forced convective of water in horizontal tubes with conical tube inserts has been studied experimentally. The transient flow regime has been used for the tests. Experimental results are validated with existing well established correlation. The turbulators were placed in two different arrangements: converging conical ring, referred to as CR array and diverging conical ring, DR array. Two correlations for the Nusselt number based on the experiment are introduced for practical use. It is found that the insertion of turbulators has enhanced the Nusselt number for the DR arrangement up to 521%, and for the CR arrangement up to 355%, although using the turbulators cause a significant increase in... 

Low temperature plasma (LTP) is nowadays an intensively investigated superficial treatment of wool. In this work we have investigated the effect of LTP on wool fabric under different conditions. The effect of the position of samples inside the reactor and the kind of gases used as discharge medium has been also investigated. The results show that not only the topography of the surface is modified but also the chemical composition of the surface. It is shown that the hydrophilicity of the samples and also their shrink resistance and anti-felting behavior have improved significantly under LTP treatment. The results show that the shrinkage of 30.1% for untreated samples has reduced to about... 

Complex systems involving a large number of degrees of freedom, generally exhibit non-stationary dynamics, which can result in either continuous or discontinuous sample paths of the corresponding time series. The latter sample paths may be caused by discontinuous events - or jumps - with some distributed amplitudes, and disentangling effects caused by such jumps from effects caused by normal diffusion processes is a main problem for a detailed understanding of stochastic dynamics of complex systems. Here we introduce a non-parametric method to address this general problem. By means of a stochastic dynamical jump-diffusion modelling, we separate deterministic drift terms from different... 

Polypropylene (PP) has a very low value of the surface free energy (approximately 20-25 mJ m-2). And thus, has very weak hydrophilic properties and doesn't have any affinity to any dyestuffs, such as cationic or anionic dyes. In this study, we covered some parts of PP fabrics by mask, and then irradiated them by electrons with different energies. After electron irradiation, the samples were dyed by cationic dyestuff. The result showed that, electron irradiated parts could be dyed easily and the fabric could be printed and decorated simply. The treated surfaces were investigated by scanning electron microscope (SEM), reflective spectrophotometery, and Fourier transform infrared spectroscopy... 

In this article, we have studied the properties (especially water repellency) of cotton coated by a thin layer of aluminum. The process has been performed in a low temperature plasma medium, using a magnetron sputtering device. We have also investigated the effect of different gases such as argon and oxygen as the discharge medium on the properties of the obtained samples. The results which are exposure time dependent show a good repellent property for 30 min of treating in argon medium under the condition of our experiment. However, when O2 is used in the system, the cotton property changes to become hydrophilic of which the factor decreases as we increase the time of treating. © 2006... 

Ultrafiltration membranes were prepared from blend of the poly(vinylidene fluoride) (PVDF) with polyacrylonitrile (PAN) via phase inversion method induced by immersion precipitation. N,N-dimethylacetamide (DMAc) and water were used as solvent and coagulant (non-solvent), respectively. The effect of blending ratio on the morphology and antifouling behavior of the prepared membranes was investigated. The performance of the membranes was evaluated by using cross flow filtration of pure water and buffered bovine serum albumin (BSA) solution as feed. Contact angle measurements indicated that the hydrophilicities of the PVDF/PAN membranes increased by increasing PAN concentration in the casting... 

In the original publication, some parts of Fig. 7 were repeated twice. Also, the citations of Fig. 7 were given incorrectly in the text. The above mentioned are corrected as follows: 1. In the section titled, “Morphological Analysis of the Prepared Membranes”, the first sentence of second para should read, “As can be seen from Fig. 7a1, the neat PVDF membrane in the absence of PAN has a sponge like structure with small pores.” 2. In the third Para, the third sentence should read, “These finger like pores, formed under the skin layeras shown in Fig. 7b2–e2, have also been reported in a similar study.” In the section titled “Fouling Analysis”, the fifth sentence of fourth para should read, “By... 

Ultrafiltration membranes were prepared from blend of the poly(vinylidene fluoride) (PVDF) with polyacrylonitrile (PAN) via phase inversion method induced by immersion precipitation. N,N-dimethylacetamide (DMAc) and water were used as solvent and coagulant (non-solvent), respectively. The effect of blending ratio on the morphology and antifouling behavior of the prepared membranes was investigated. The performance of the membranes was evaluated by using cross flow filtration of pure water and buffered bovine serum albumin (BSA) solution as feed. Contact angle measurements indicated that the hydrophilicities of the PVDF/PAN membranes increased by increasing PAN concentration in the casting... 

Recently, membrane fouling has been one of the most important issues in the field of membrane technology. In this regard, TiO2 nanoparticles blended with polymeric membranes have shown to improve fouling performance. In this study, a new PVDF/PAN/TiO2 ultrafiltration blend membrane was prepared via phase inversion by dispersing TiO2 nanoparticles in the PVDF/PAN casting solutions. The effect of different concentrations of TiO2 on the characteristics of membranes (i.e., morphology, hydrophilicity, permeation performance, and antifouling properties) was investigated. Results of scanning electron microscopy analysis showed the finger-like pores and macrovoids decrease due to the presence of... 

Concrete compressive strength (CCS) is among the most important mechanical characteristics of this widely used material. This study develops a novel integrative method for efficient prediction of CCS. The suggested method is an artificial neural network (ANN) favorably tuned by electromagnetic field optimization (EFO). The EFO simulates a physics-based strategy, which in this work is employed to find the best contribution of the concrete parameters (i.e., cement (C), blast furnace slag ((Formula presented.)), fly ash ((Formula presented.)), water (W), superplasticizer (SP), coarse aggregate ((Formula presented.)), fine aggregate ((Formula presented.)), and the age of testing ((Formula...