Sharif Digital Repository

In this paper fabrication of a 0-3 ceramic/ceramic composite lead zirconate titanate, Pb(Zr0.52Ti0.48)O3 thin film has been presented and then a pressure sensor based on multilayer thin-film PZT diaphragm contain of Lead Zirconate Titanate nanocrystalline powders was designed, modeled and optimized. This multilayer diaphragm in general acts as sensor or actuator. ANSYS was used for simulation of diaphragm. Dynamics characteristics of this multilayer diaphragm have been investigated. By this simulation the effective parameters of the multilayer PZT diaphragm for improving the performance of a pressure sensor in different ranges of pressure are optimized. The optimized thickness ratio of PZT... 

Flow through the pores of granular materials has many instances in practice. Therefore, it is interesting to realize how some parameters, such as the shape of the particles affect the passing flow. Following the recent mathematical theory proposed by the authors, this paper deals with the issue of how tortuosity and permeability are influenced by the particle shape. Comparison of the results with the experimental data reveals the competency of the theory in predicting the impact of particle geometry  

A facile hydrothermal method and subsequent electroactivation have been developed to fabricate three-dimensional (3D) CuO nanosheet arrays on the copper foil substrate, which can be used directly as a binder-free electrode for supercapacitor applications. Under optimum conditions, by using this facile method, a high capacitance of 125 mF/cm2 at a current density of 0.3 mA/cm2 is obtained. The prepared supercapacitor showed a good rate capability (46.4% capacitance retention, when the current density is increased to more than 30 times) and an excellent cyclability (more than 88% capacitance retention after 3000 cycles). © 2017 Elsevier B.V  

Nature, as a rich source of solutions, can be an inspirational guide to answer scientific expectations. Seed dispersal mechanism as one of the most common reproduction method among the plants is a unique technique with millions of years of evolutionary history. In this paper, inspired by plants survival, a novel method of optimization is presented, which is called Fertile Field Algorithm. One of the main challenges of stochastic optimization methods is related to the efficiency of the searching process for finding the global optimal solution. Seeding procedure is the most common reproduction method among all the plants. In the proposed method, the searching process is carried out through a... 

Nanostructured and mesoporous TiO2-Ta2O5 films and powders with various TiO2:Ta2O5 molar ratios and high specific surface area (SSA) have been prepared by a straightforward particulate sol-gel route. Titanium isopropoxide and tantalum ethoxide were used as precursors and hydroxypropyl cellulose (HPC) was used as a polymeric fugitive agent (PFA) in order to increase the SSA. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) revealed that powders contained both hexagonal δ-Ta2O5 and monoclinic β-Ta2O5 phases, as well as anatase and rutile. It was observed that Ta2O5 retarded anatase-to-rutile transformation. Furthermore, δ → β phase transformation temperature increased... 

The original article contained a mistake in Equation 1. The corrected Equation 1 is shown below: MX+Cx+Kx=f.The original article has been updated © Springer Nature B.V. 2022  

Transfer and scattering matrix methods are widely in use for description of the propagation of waves in multilayered media. When the profile of refractive index is continuous, however, a modified formulation of transfer matrices does exist, which provides a complete analytical solution of the wave phenomena in such structures. Previously reported variations of the so-called Differential Transfer Matrix Method (DTMM) had been limited to Cartesian geometry where layered media form one-dimensional structures and plane waves are used as basis functions. In this work, we extend the formalism to cylindrical geometry with radial symmetry, in which Bessel functions need to be employed as basis... 

A huge amount of energy consumption, the cost of this usage and environmental effects have become serious issues for commercial cloud providers. Solar energy is a promising clean energy source, to provide some portion of the Internet data center's (IDC's) energy usage which can reduce environmental effects and total energy costs. Moreover, due to the high energy consumption of the cooling system, considering cooling power in job scheduling can provide efficient solutions to reduce total energy consumption. In this article, we investigate the problem of minimizing the energy cost of an IDC and propose an algorithm which schedules heterogeneous IDC workloads, by considering available renewable... 

In this paper, the path independent interaction integral has been implemented in the framework of the extended finite element method for mixed mode adiabatic cracks under thermo-mechanical loadings particularly in orthotropic non-homogenous materials. The mesh insensitivity and increased accuracy due to the thermal and displacement asymptotic analytical solutions are discussed and the contour independency of the interaction integral is investigated in different examples. Finally, the problem of crack propagation in orthotropic FGM materials under the thermal loading is investigated to assess the accuracy and robustness of proposed approach  

In this paper we introduce two innovative image and video watermarking algorithms. The paper's main emphasis is on the use of chaotic maps to boost the algorithms' security and resistance against attacks. By encrypting the watermark information in a one dimensional chaotic map, we make the extraction of watermark for potential attackers very hard. In another approach, we select embedding positions by a two dimensional chaotic map which enables us to satisfactorily distribute watermark information throughout the host signal. This prevents concentration of watermark data in a corner of the host signal which effectively saves it from being a target for attacks that include cropping of the... 

An Al2O3/Si3N4 nanocomposite coating was successfully fabricated on commercial aluminum alloy. Hardness measurements, polarization and electrochemical impedance spectroscopy (EIS) were employed to study the mechanical and corrosion behaviors of the coatings. Field-Emission Scanning Electron Microscopy (FE-SEM) equipped with Energy Dispersive Spectroscopy (EDS) and X-ray diffraction (XRD) were utilized to characterize the surface morphology and phase composition of the coatings. Also, coatings abrasive wear properties were evaluated with a modified ASTM G105 standard. FE-SEM image, EDS and XRD analysis revealed the presence of Si3N4 in the coating. Furthermore, the results showed hardness of... 

Here in, for the first time, we report a new and simple procedure for preparing reduced graphene oxide/nickel-cobalt double layered hydroxide composite on the nickel foam (Ni-Co LDH/rGO/NF) via a fast and simple two-step electrochemical method including potentiostatic routes in the presence of CTAB as a cationic surfactant. Graphene oxide coated nickel foam prepared by simple immersion method. After that, the prepared electrode reduced electrochemically to obtain rGO/NF electrode. Finally, the rGO/NF electrode was used as cathode for electrodeposition of Ni-Co LDH in the presence of CTAB as cationic surfactant. The prepared electrodes were characterized by field emission scanning electron... 

A novel electrode consisting of 3D porous nickel‒cobalt‒copper sulfide dendritic structures is synthesized, in which, for the first time ternary Ni–Co–Cu foam is constructed through hydrogen bubble template and followed by sulfidization via a hydrothermal reaction in thiourea. The 3D, porous Ni–Co–Cu dendritic sulfide electrode exhibits a high specific capacitance of 1203.75 F g−1 (0.963 F cm−2) at current of 1.0 mA and excellent cycling stability, excellent ratability along with high cycle stability. An asymmetric supercapacitor (ASC) using dendritic sulfide structures and reduced electro-etched carbon fiber paper (RECF) as the positive and negative electrodes, respectively is developed.... 

Here in, for the first time, we report a new and simple procedure for preparing reduced graphene oxide/nickel-cobalt double layered hydroxide composite on the nickel foam (Ni-Co LDH/rGO/NF) via a fast and simple two-step electrochemical method including potentiostatic routes in the presence of CTAB as a cationic surfactant. Graphene oxide coated nickel foam prepared by simple immersion method. After that, the prepared electrode reduced electrochemically to obtain rGO/NF electrode. Finally, the rGO/NF electrode was used as cathode for electrodeposition of Ni-Co LDH in the presence of CTAB as cationic surfactant. The prepared electrodes were characterized by field emission scanning electron... 

This paper presents an optimal phasor measurement units (PMUs) placement algorithm for the purpose of power system observability and also increasing the performance of secondary voltage control scheme. The optimal placement problem (OPP) is formulated such that to minimize the number of PMU installations subject to full network observability and monitoring pilot buses of the system to improve secondary voltage control performance. The branch and bound optimization method is adopted to solve the OPP problem which is suitable for problems with integer and boolean variables. Topology-based algorithm is used for observability analysis. Constraint functions considering adjacent zero-injection... 

The universal paradigm shift towards green energy has accelerated the development of modern algorithms and technologies, among them converters such as Z-Source Inverters (ZSI) are playing an important role. ZSIs are single-stage inverters which are capable of performing both buck and boost operations through an impedance network that enables the shoot-through state. Despite all advantages, these inverters are associated with the non-minimum phase feature imposing heavy restrictions on their closed-loop response. Moreover, uncertainties such as parameter perturbation, unmodeled dynamics, and load disturbances may degrade their performance or even lead to instability, especially when... 

This paper presents a new point-to-face contact algorithm for contacts between two polyhedrons with planar boundaries. A new discrete numerical method called three-dimensional discontinuous deformation analysis (3-D DDA) is used and formulations of normal contact submatrices based on the proposed algorithm are derived. The presented algorithm is a simple and efficient method and it can be easily coded into a computer program. This approach does not need to use an iterative algorithm in each time step to obtain the contact plane, unlike the ‘Common-Plane’ method applied in the existing 3-D DDA. In the present 3-D DDA method, block contact constraints are enforced using the penalty method.... 

Developing a uniform polymer-based composite filament is a critical factor for a successful 3D printing process. In this regard, a novel technique for the fabrication of PLA-graphite filament with the potential to be applied to other PLA-based composite filaments was proposed and compared to the solvent casting method. This modified mixing technique involves partial dissolution of the PLA pellets surface by dichloromethane (DCM), which creates a sticky surface for the strong adhesion of reinforcement powders. The manufactured composite filament by this method exhibited excellent structural features, while the solvent casting method yielded a heterogeneous filament with a non-uniform diameter... 

Nowadays, as technology grows, human life formation changes every second. These changes sometimes create harmful habits and affect our lifestyle, which unfortunately bring various diseases and disorders. ADHD (Attention Deficit Hyperactivity Disorder) & SPD (Sensory Processing Disorder) are common disorders in children. By giving children the right treatment at the younger ages, we can help them overcome their disabilities and not face any symptoms in their adulthood. The multi-sensory balance board is designed and developed to help medics diagnose the disorders in patients at early stages and monitor the treatment progress. The balance board uses multiple sensors to detect common human... 

In speech production systems, the vocal tract is modeled by a filter and glottal pulse by an excitation signal. In most traditional systems impulse train or noise is used as the excitation. In this paper the effects of different excitation signals on Mel-generalized cepstral filters (LPC, warped LPC, mel cepstral and ML cepstral) are studied. Excitation signals with different pulse shapes are used. Furthermore, based on voicing power, noise factor is added to the excitation signals. Totally 600 different experiments with different filter types, number of coefficients, pulse shapes, pulse widths and noise power are preformed. Synthesized speech is evaluated by PESQ measure. A number of pulse...