Sharif Digital Repository

Remotely sensed data obtained through satellite imaging is a useful tool for modeling environmental phenomena such as drought. In this manuscript, we apply optimized echo state networks to model and predict drought severity based on satellite images. To this end, a model is constructed in which the satellite-based vegetation index is fed as an input and drought severity index is obtained as output. We use a Kronecker-based approach to reduce the number of parameters of echo state networks to be optimized (i.e., the internal weights of reservoir). A number of evolutionary algorithms are used to optimize the parameters, of Differential Evolution results in the best performance as compared to... 

In this paper, three-dimensional amplification of plane harmonic SH, SV, and P waves in multilayered alluvial valleys is investigated by using a boundary element method in frequency domain. It is shown that in order to achieve real responses, the problem must be analyzed and modeled three-dimensionally. Also, for exact evaluation of surface ground motions in alluvial valleys all key parameters such as layering, material and geometrical characteristics of each layer, stimulation frequency, wave type, plus angle and azimuth of incidence must be taken into account altogether. The accuracy and efficiency of the proposed formulations for the computation of the surface displacement field... 

In order to safe design and optimize performance of some industrial systems, it's often needed to categorize two-phase flow into different regimes. In each flow regime, flow conditions have similar geometric and hydrodynamic characteristics. Traditionally, flow regime identification was carried out by flow visualization or instrumental indicators. In this research3 kind of neural networks have been used to predict system characteristic and flow regime, and results of them were compared: radial basis function neural networks, self organized and Multilayer perceptrons (supervised) neural networks. The data bank contains experimental pressure signalfor a wide range of operational conditions in... 

Co/Cu multilayers were deposited in a sulfate solution by controlling the current and potential for the deposition of cobalt and copper layer respectively. The electrochemical behavior of these multilayers was studied by cyclic voltammetry and current transients. In addition, a mathematical analysis was used to characterize the electrodeposition system. Simultaneously, the nucleation and growth mechanisms were monitored by these techniques. In this case, the results clearly showed that electrodeposition of cobalt layers was a kinetically controlled process while the reduction of copper ions was a diffusion-control process. Although nucleation mechanism of the single Co deposit was found as a... 

This paper illustrates the use of a combined neural network model for classification of electrocardiogram (ECG) beats. We present a trainable neural network ensemble approach to develop customized electrocardiogram beat classifier in an effort to further improve the performance of ECG processing and to offer individualized health care. We process a three stage technique for detection of premature ventricular contraction (PVC) from normal beats and other heart diseases. This method includes a denoising, a feature extraction and a classification. At first we investigate the application of stationary wavelet transform (SWT) for noise reduction of the electrocardiogram (ECG) signals. Then... 

A thermosensitive copolymer was synthesized by graft copolymerization of poly(lactide-co-glycolide) (PLGA) copolymers onto the surface of chitosan membranes. Acryloyl chloride was used as a coupling reagent for the covalent attachment of PLGA to the chitosan membranes. FTIR spectroscopy and DSC analysis were used to characterize the resulting graft copolymer. Thermosensitive swelling behaviors of the copolymer were investigated as well. The membranes exhibited reversible swelling-shrinking behavior; higher swelling ratios were obtained observed at higher temperatures. Drug permeation studies were carried out using vancomycin hydrochloride and betamethasone sodium phosphate as the model... 

In this paper, we propose what we believe is a novel sensitive micro-optoelectromechanical systems (MOEMS) accelerometer based on intensity modulation by using a one-dimensional photonic crystal. The optical sensing system of the proposed structure includes an air-dielectric multilayer photonic bandgap material, a laser diode (LD) light source, a typical photodiode (1550 nm) and a set of integrated optical waveguides. The proposed sensor provides several advantages, such as a relatively wide measurement range, good linearity in the whole measurement range, integration capability, negligible cross-axis sensitivity, high reliability, and low air-damping coefficient, which results in a wider... 

In the present work, the hot corrosion behavior of two types of multilayer plasma sprayed TBC were investigated and compared with functionally graded and conventional TBCs. These kinds of multilayer coatings consisted of nano/μ alumina as a top coat on YSZ layer, a metallic bond coat and a functionally graded intermediate layer deposited between YSZ and bond coat layers. All the layers were sprayed on the Ni-base super alloy substrate. The hot corrosion resistance of the plasma sprayed coatings was examined at 1050 °C for 40 h, using a fused mixture of 45 wt% Na2SO4 + 55wt%V2O5. Before and after hot corrosion, the microstructure and phase analysis of the coating were studied using scanning... 

Molecular dynamics simulations are employed to investigate material properties of nanocrystalline aluminum and nanocrystalline Al/Ni multilayers at low temperature. For this purpose, both single crystal and nanocrystalline multilayers with different grain sizes and grain morphology are used as the substrate. The results of the simulations show that hardness and elastic modulus decrease with refinement of grain size in nanocrystalline aluminum and refinement of grain size and layer thickness in nanocrystalline Al/Ni multilayers, regardless of grain morphology. Furthermore, the angle between two adjacent grains, which is directly connected to the grain boundary thickness, has a great influence... 

In the present work, spark plasma sintering (SPS) process was employed to prepare a nanostructured yttria-stabilized zirconia (8YSZ) coating on a nickel-based superalloy (INCONEL 738) with functionally graded structure. A stack layer of INCONEL 738/NiCrAlY powder/Al foil/NiCrAlY+YSZ powder/YSZ powder was SPSed in a graphite die at an applied pressure of 40 MPa under an vacuum atmosphere (8 Pa). The sintering temperature was ∼1040 °C. For comparison purpose, the air plasma spray (APS) technique was employed to prepare the thermal barrier coating (TBC). Microstructural studies by scanning electron microscopy showed that the SPSed coating was sound and free of interfacial cracks and large... 

In the present paper, neutron spectrum is reconstructed using the Artificial Neural Network (ANN) and Modified Least Square (MLSQR) methods. The detector's response (pulse height distribution) as a required data for unfolding of energy spectrum is calculated using the developed MCNPX-ESUT computational code (MCNPX-Energy engineering of Sharif University of Technology). Unlike the usual methods that apply inversion procedures to unfold the energy spectrum from the Fredholm integral equation, the MLSQR method uses the direct procedure. Since liquid organic scintillators like NE-213 are well suited and routinely used for spectrometry of neutron sources, the neutron pulse height distribution is... 

Recent strategies to locally deliver antimicrobial agents to combat implant-associated infections—one of the most common complications in orthopedic surgery—are gaining interest. However, achieving a controlled release profile over a desired time frame remains a challenge. In this study, we present an innovative multifactorial approach to combat infections which comprises a multilayer chitosan/bioactive glass/vancomycin nanocomposite coating with an osteoblastic potential and a drug delivery capacity. The bioactive drug-eluting coating was prepared on the surface of titanium foils by a multistep electrophoretic deposition technique. The adopted deposition strategy allowed for a high... 

In this paper, we propose a novel OCR system which can recognize and calculate handwritten Persian arithmetic expressions without using a keyboard or a memory to store the intermediate results. Our system is composed of two major phases: character recognition and calculation. The recognition phase is based on a new approach for feature extraction followed by a Fuzzy Support Vector Machines (FSVMs) as the classifier. In calculation phase a simple algorithm is used for calculating the recognized arithmetic expressions. The performance of the system was evaluated on a database consisting of 3400 digits and symbols written by 20 different people. 92 percent accuracy in recognition proves the... 

The effects of bath composition and deposition variables on the electrodeposition of Zn–Ni–P alloys were studied in order to develop a single bath for deposition of Ni–P/Zn–Ni compositionally modulated multilayer coatings (CMMCs). The basis for development of the bath was a large increase in the Ni deposition rate compared to that of Zn at low deposition overpotentials combined with the impossibility of codeposition of Zn with P. EDS analysis demonstrated that the deposits obtained from the Zn–Ni–P bath at low overpotentials were practically all Ni–P, while the alloy deposited at high overpotentials was mainly Zn–Ni with around 3.2 wt% P content. © 2017 Elsevier B.V  

The sol-enhanced pulse plating (PP) technique was utilized to deposit the Ni-TiO2/TiO2 multilayers on copper substrates from a Watts bath containing a TiO2 sol, and the obtained coatings were heat treated at various temperatures. The characteristics of coatings were examined using scanning electron microscopy (SEM), X-ray diffraction (XRD), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and UV-visible spectrophotometry. In order to estimate the wettability of these nanostructured multilayers after exposure to UV light, the contact angle of water droplets were measured, and the photocatalytic (PC) efficiency of the multilayers were analyzed by the degradation of methyl... 

Zn/Ni nanocrystalline multilayer coatings were electrodeposited using single bath method and switching current densities. Effect of deposition current densities (i1 and i2) and number of layers (n) on composition, surface morphology and roughness, microhardness, phase structure and corrosion resistance of Zn/Ni multilayers were studied and compared with that of single layer. Analyzing and optimizing the influences of mentioned parameters on corrosion resistance of multilayers carried out through Response Surface Methodology. The model based on RSM results demonstrated that improvement in corrosion resistance due to increase in “difference of deposition current densities” was more effective... 

The activity coefficient at infinite dilution is a representative of the limiting non-ideality of a solute in a mixture. Various methods for the prediction of infinite dilution activity coefficients (IDACs) have been developed. Artificial neural networks are powerful mapping tools for nonlinear function approximations. Accordingly, an artificial neural network model is proposed for the prediction of the IDACs of binary systems where the properties of the individual components are used as inputs to the network. The input parameters of the neural network are the mixture temperature, critical temperature, critical pressure, critical volume, molecular weight, dipole moment and the acentric... 

Due to increased atherosclerosis-caused mortality, identification of its genesis and development is of great importance. Although, key factors of the origin of the disease is still unknown, it is widely believed that cholesterol particle penetration and accumulation in arterial wall is mainly responsible for further wall thickening and decreased rate of blood flow during a gradual progression. To date, various effective components are recognized whose simultaneous consideration would lead to a more accurate approximation of Low Density Lipoprotein (LDL) distribution within the wall. In this research, a multilayer Fluid-Structure Interaction (FSI) model is studied to simulate the penetration... 

We introduce a theoretical method for simultaneous measurement of refractive index and thickness of multilayer systems using Fourier domain optical coherence tomography (FD-OCT) without any auxiliary arrangement. The input data to the formalism are the FD-OCT measured optical path lengths (OPLs) and properly selected spectral components of FD-OCT interference spectrum. The outputs of the formalism can be affected significantly by uncertainty in measuring the OPLs. An optimization method is introduced to deal with the relatively large amount of uncertainty in measured OPLs and enhance the final results. Simulation result shows that by using the optimization method, indices can be extracted... 

The present work developed a mixed-mode cohesive zone model (CZM) with a mode I failure criterion to predict the delamination bending loads of multilayer, composite printed circuit boards (PCBs) assembled with soldered ball grid array (BGA) components that were reinforced with an underfill epoxy adhesive. Two different delamination modes were observed in these microelectronic assemblies: delamination at the interface between the solder mask and the first conducting layer of the PCB, and PCB subsurface delamination at the interface between the epoxy and glass fibers of one of the prepreg layers. The cohesive parameters for each of the two crack paths were obtained from fracture tests of...