Sharif Digital Repository

This paper develops metamodels (or surrogate models) to predict the fragility parameters of structures isolated with friction pendulum (FP) isolators. Anequivalent inelastic two-degree-of-freedom (2DoF) system is utilized to model the base-isolated structures.6000 system simulations are initially established based on the probability distribution of input parameters. Then, incremental dynamic analyses are carried out to achieve structural data for the fragility function generation. The developed dataset of the fragility parameters (median and dispersion) is divided into training and testing sets to train and testthe efficiency of thedeveloped metamodels, respectively.Powerful machine learning... 

This study aims to evaluate the influences of modeling-related uncertainties on the seismic response and fragility function of the four vulnerable components of electrical substation equipment, taking into account the dynamic interaction between apparatuses via bus slider-rigid bus conductors. The 3D finite element model for interconnected disconnect switch- circuit breaker-current transformer-surge arrester system is developed in OpenSees software. A sensitivity analysis is conducted to evaluate and rank the importance of individual random variables on the seismic responses. To incorporate modeling uncertainties into the failure fragility function, probabilistic structural interconnected... 

The present study investigates the effects of the degradation of mechanical properties (pinching, stiffness degradation, and strength degradation) in load-deformation relationship of the superstructures equipped with friction pendulum systems on the seismic fragility and reliability results. An equivalent two-degree-of-freedom model is employed, in which the Bouc-Wen hysteretic model characterizes the inelastic behavior of both the superstructure and the isolator. To examine a wide variety of system combinations with different structural properties and degradation severity, a comprehensive parametric study is performed. Incremental dynamic analyses are carried out to develop fragility... 

The flow behaviour of Al–SiC nanocomposites prepared by mechanical milling and hot powder extrusion methods was studied at different temperatures (350–500°C) and strain rates (0.005–0.5 s−1). The flow of the Powder metallurgy nanocomposites exhibited a peak stress followed by a dynamic flow softening behaviour. It was shown that mechanical milling increased high-temperature strain rate sensitivity of ultrafine-grained (UFG) aluminium while decreasing its flow dependence to temperature. Constitutive analysis of the hot deformation process by Zener–Hollomon parameter (Z) also indicated a remarkable increase in the deformation activation energy (about 40%). Likewise, SiC nanoparticles (up to... 

Event-related potential (ERP) extraction from ongoing electroencephalograph (EEG) and its enhancement is one of the long-established problems in EEG signal processing. Most of the previous studies have focused mainly on the ERP enhancement without considering the multi-dimentional structure of the signal. In order to take advantage of this property, we propose a tensor-based solution with trial-by-trial concatenated ERP data. Then we develop an algorithm based on low-rank Tucker decomposition to detect single trial ERP component with maximized signal to noise ratio (SNR). In other words, by using tensor algebra we consider both self-similarity in intratrials and global correlation in spatial... 

Event-related potential (ERP) data is essentially multi-dimensional, with correlated data in some spaces. Therefore, matrix and vector analysis results in structural information loss. Tensor decomposition can be used to explore the shared structural information of ERP signal among related conditions. Perceiving the decaying trends of the singular value changes of unfolding matrices indicate that they are low-rank matrices. Based on this assumption, in this work, a low-rank tensor restoration (LTR) method is proposed. An operator splitting method known as the alternating direction method of multipliers (ADMM) is adapted to tackle the proposed optimization problem with orthogonality and... 

Since low-cost RFID systems are applied in ubiquitous varied applications, privacy and security of their users became a great concern. Therefore, the various authentication protocols have been proposed. In this paper, we inspect the three new-found RFID authentication protocols based on quadratic residue property via one of the well-organized formal RFID privacy models instead of intuitive analysis. We formally prove that modular squaring is the suitable technique to guarantee RFID authentication protocols against backward traceability. Then, the flaws are alleviated to resist traceability attacks  

Conventional buffet onset methods for a 2D supercritical airfoil, SC0410, in transonic regime for various Mach number and various angles of attack have been surveyed. The existing methods give good results for high subsonic and transonic regimes, but demand a computational procedure to detect the buffet onset. One of these methods, trailing edge pressure divergence, that have been recognized inappropriate in other studies for supercritical airfoils, shows acceptable result at least for the present supercritical airfoil. A new method has been proposed by the authors for transonic regime that is based on the physical definition of the buffet onset from the surface pressure distribution... 

Structural, half-metallic, magneto-optic, and thermoelectric properties of CrTiZ (Z = As, P) half-Heusleres compounds are investigated based on density functional theory. These compounds have mechanical stability in the ferromagnetic state with a high bulk modulus. They are often half-metallic with a large and integer magnetic moment and are very attractive in spintronics, magneto-optics applications. The magnetic moments of CrTiAs and CrTiP were 2.9865 μB and 3.00 μB, respectively, which were attributed to their ferromagnetic phase. Additionally, the positive sign of the phonon branches indicates the dynamic stability of these compounds. Applying both GGA and mBJ approximations, CrTiAs and... 

In recent years, the incorporation of impurities (metallic or non-metallic) into diamond-like carbon films for industrial and biological applications has garnered considerable attention from researchers. In this study, gold nanoparticles and nitrogen impurities were introduced into diamond-like carbon using a co-deposition method involving Radio Frequency Plasma-Enhanced Chemical Vapor Deposition (RF-PECVD) and Radio Frequency Sputtering (RF-sputtering),modifying the working pressure from 14.5 to 19.5 mTorr. X-ray Diffraction (XRD) patterns confirmed the presence of gold nanocrystals in the samples. The surface morphology of the films was analyzed using images obtained from Scanning Electron...