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eftekhari-yekta--bijan
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Investigation of Crystallization Behavior and Electrical Properties of Glass-Ceramics in the Li2O-TiO2-P2O5 System
, M.Sc. Thesis Sharif University of Technology ; Nemati, Ali (Supervisor) ; Eftekhari Yekta, Bijan (Supervisor) ; Banijamali, Sara (Co-Advisor)
Abstract
During the past two decades, much attention has been paid to rechargeable lithium batteries, because they have high energy density. Glass-ceramics is a category of this material, which may be of great potential as solid electrolytes.. The object of this thesis is preparation of Li2O-TiO2-P2O5 glass, glass-ceramic and investigation their electrical behavior. Prepared Samples were investigated by Differential thermal analysis (DTA), X-ray diffraction (XRD), Scanning electron microscopy (SEM), UV-Visible spectroscopy and Electrochemical impedance spectroscopy (EIS). In this study LiTi2(PO4)3 crystals were crystallized in a glass with the composition 45Li2O-25TiO2-30P2O5 (molar ratio). According...
Preparation and characterisation of diopside-based glass-ceramic foams
, Article Ceramics International ; Volume 38, Issue 3 , 2012 , Pages 2005-2010 ; 02728842 (ISSN) ; Nemati, A ; Eftekhari Yekta, B ; Alizadeh, P ; Sharif University of Technology
2012
Abstract
Foaming and crystallisation behaviours of compacted glass powders based on a diopside glass-ceramic composition were investigated using the sintering route. The foaming agent was 2 wt.% SiC particles. The effect of PbO on the foaming ability of glasses was investigated. The results showed that the addition of PbO not only improved the foaming ability, by improving the wettability of the glass-SiC particles but also increased the crystallisation temperature and widened the temperature interval between the dilatometric softening point and the onset of crystallisation. The glass-SiC wetting angle was decreased from 85°for the lead-free glass, to 55°for the glass that contains 15 wt.% PbO
Effects of Fe2O3 content on ionic conductivity of Li2O-TiO2-P2O5 glasses and glass-ceramics
, Article Materials Chemistry and Physics ; Volume 190 , 2017 , Pages 8-16 ; 02540584 (ISSN) ; Nemati, A ; Eftekhari Yekta, B ; Banijamali, S ; Sharif University of Technology
Elsevier Ltd
2017
Abstract
In this study, Li2O-TiO2-P2O5-x(Fe2O3) (x = 0, 2.5, 5 and 7.5 weight part) glass and glass-ceramics were synthesized through conventional melt-quenching method and subsequently heat treatment. Glass samples were studied by UV–visible spectroscopy and crystallized samples were characterized by differential thermal analysis, X-ray diffractometry and field emission scanning electron microscopy. Besides, electrical properties were examined according to the electrochemical impedance spectroscopy techniques. Experimental optical spectra of the Fe2O3-doped glasses revealed strong UV absorption band in the range of 330–370 nm, which were attributed to the presence of Fe3+ ions. The major crystalline...
The Cutoff Phenomenon in Reversible Markov Chains
, M.Sc. Thesis Sharif University of Technology ; Zohuri Zangeneh, Bijan (Supervisor)
Abstract
A sequence of Markov chains is said to exhibit (total variation) cutoff if the convergence to stationarity in total variation distance is abrupt. We consider reversible lazy chains. We prove a necessary and sufficient condition for the occurrence of the cutoff phenomena in terms of concentration of hitting time of “worst” (in some sense) sets of stationary measure at least , for some ... (0; 1). As an application of these methods, we prove that a sequence of lazy chains on finite trees exhibits cutoff if and only if the product of the mixing time and the spectral gap tends to
The effects of SiO 2 and K 2O on glass forming ability and structure of CaOTiO 2P 2O 5 glass system
, Article Ceramics International ; Volume 38, Issue 4 , 2012 , Pages 3281-3290 ; 02728842 (ISSN) ; Nemati, A ; Eftekhari Yekta, B ; Hamnabard, Z ; Sharif University of Technology
2012
Abstract
The effects of SiO 2 and K 2O were investigated on the glass forming ability (GFA) and structural characteristics of CaOTiO 2P 2O 5 system. Differential thermal analyzer (DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), FT-IR and 31P magic angle spinning NMR methods were applied for characterizations of the system. Unwanted crystallization in the initial three components base glass composition was observed by adding SiO 2 and crystalline phases such as TiP 2O 7, rutile (TiO 2) and cristobalite (SiO 2) were formed in it. The results showed that K 2O prevents crystallization of glasses and promotes the formation of glass. FT-IR and X-ray diffraction showed that the addition...
Synthesis and characterization of diopside glass-ceramic matrix composite reinforced with aluminum titanate
, Article Ceramics International ; Volume 35, Issue 4 , 2009 , Pages 1447-1452 ; 02728842 (ISSN) ; Alizadeh, P ; Eftekhari Yekta, B ; Molaie, F ; Ghafoorian, N ; Montazerian, M ; Sharif University of Technology
2009
Abstract
Glass-ceramic composites in the SiO2-CaO-MgO-(Na2O) system, reinforced with 5, 10 and 20 wt.% aluminum titanate were synthesized by pressureless sintering. Optimum sintering temperatures with maximum relative density were determined for each composition. The composites were fired above the crystallization peak temperature of glass-ceramic. Mechanical properties of glass-ceramic and sintered composites, such as fracture toughness, flexural strength and Vickers microhardness, were investigated. The sintered composites were characterized by scanning electron microscopy (SEM), energy dispersion spectroscopy (EDS) and X-ray diffraction (XRD). The results showed that the composite containing 10...
A frequency domain proof for the equivalence of the maximally flat FIR fractional delay filter and the Lagrange interpolator
, Article Digital Signal Processing: A Review Journal ; Volume 21, Issue 1 , 2011 , Pages 13-16 ; 10512004 (ISSN) ; Sharif University of Technology
2011
Abstract
One of the most important properties of the maximally flat (MF) FIR fractional delay (FD) filter is its equivalence with the Lagrange interpolator for uniformly sampled signals. In this article, to provide the required background for the reader, we first propose a straightforward algebraic proof for this equivalence. This proof is given by simply demonstrating that the system of linear equations governing the maximally flatness property of this filter is the same as the one from which the coefficients of the Lagrange interpolator are computed. We then present the main contribution of the paper, which is a frequency domain proof for the same equivalence. In contrast with its classic...
Low-order adaptive half-sample interpolators
, Article Electronics Letters ; Volume 46, Issue 13 , June , 2010 , Pages 897-898 ; 00135194 (ISSN) ; Sharif University of Technology
2010
Abstract
Although the fractional delay filtering literature is full of design methods and implementation techniques for fractional sample interpolators, a fundamental need for the proposition of low-order efficient designs still strongly exists. Proposed is such a system for half-sample interpolation. In contrast to the typical systems studied in the literature for fractional delay filtering, the system proposed continuously adapts its interpolation kernel to the statistical variations of the input signal, and this is in fact the reason for it being needless of having a high order. Satisfactory performance of the proposed structure has been demonstrated via simulation
Wideband maximally flat fractional-delay allpass filters
, Article Electronics Letters ; Volume 46, Issue 10 , May , 2010 , Pages 722-723 ; 00135194 (ISSN) ; Sharif University of Technology
2010
Abstract
The maximally flat (MF) fractional-delay (FD) allpass filter, also known as Thiran's allpass filter, is one of the most popular IIR FD systems which is typically deployed in its causal forms. It is shown that if this causality constraint is removed, MFFD allpass filters with considerably wider bandwidths can be obtained. In many applications this extra bandwidth is worth having a non-causal system
Equivalence of the Lagrange interpolator for uniformly sampled signals and the scaled binomially windowed shifted sinc function
, Article Digital Signal Processing: A Review Journal ; Volume 19, Issue 5 , 2009 , Pages 838-842 ; 10512004 (ISSN) ; Sharif University of Technology
2009
Abstract
The maximally flat (MF) fractional delay (FD) filter which is in fact a Lagrange interpolator for uniformly sampled signals, has previously been shown to be equal to the scaled binomially windowed shifted version of the sinc function; the ideal interpolation kernel for band-limited signals. In this paper, another proof for this equivalence is presented. Unlike its counterparts available in the literature, the proof given here is neither strictly algebraic, nor deploys the explicit coefficient formulas of the MFFD filter. It follows a frequency domain approach based on the definition of this filter instead, and aims to provide more insight into the corresponding equivalence. © 2009 Elsevier...
Equivalence of the Lagrange interpolator for uniformly sampled signals and the scaled binomially windowed shifted sinc function
, Article Digital Signal Processing: A Review Journal ; Volume 19, Issue 5 , 2009 , Pages 838-842 ; 10512004 (ISSN) ; Sharif University of Technology
2009
Abstract
The maximally flat (MF) fractional delay (FD) filter which is in fact a Lagrange interpolator for uniformly sampled signals, has previously been shown to be equal to the scaled binomially windowed shifted version of the sinc function; the ideal interpolation kernel for band-limited signals. In this paper, another proof for this equivalence is presented. Unlike its counterparts available in the literature, the proof given here is neither strictly algebraic, nor deploys the explicit coefficient formulas of the MFFD filter. It follows a frequency domain approach based on the definition of this filter instead, and aims to provide more insight into the corresponding equivalence. © 2009 Elsevier...
Half-band FIR fractional delay filters with closed-form coefficient formulas and modular implementation based on Lagrange interpolators
, Article Signal Processing ; Volume 88, Issue 12 , 2008 , Pages 2913-2916 ; 01651684 (ISSN) ; Sharif University of Technology
2008
Abstract
The Taylor series-based representation of the maximally flat (MF) FIR fractional delay (FD) filter is manipulated to obtain a FD filter with a wider band-width. The band-width of the proposed filter can approach π / 2 rads / s, which is 1.5 times that of the prototype one. The design has closed-form coefficient formulas as well as a modular implementation. These two properties make it a practically favourable one. © 2008 Elsevier B.V. All rights reserved
Erratum to: "Fast design of relatively wide band fractional delay all-pass filters" [Signal Process. 88 (3) (2008) 612-623] (DOI:10.1016/j.sigpro.2007.09.006)
, Article Signal Processing ; Volume 88, Issue 4 , 2008 , Pages 1082- ; 01651684 (ISSN) ; Sharif University of Technology
2008
Abstract
A fast and simple procedure for designing relatively wide band fractional delay (FD) all-pass filters is proposed and filters designed based on it are compared to those designed using Thiran’s method, which is one of the simplest, fastest and widely used approaches in designing FD all-pass filters. It is shown that filters designed using the introduced method have wider fractional group delay (fgpd) bandwidths compared to those obtained via Thiran’s technique, as well as some other desired properties. The designed filters are also demonstrated to be stable for several pairs of filter orders and fgpd values. r2007 Elsevier B.V. All rights reserved
Fast design of relatively wide band fractional delay all-pass filters
, Article Signal Processing ; Volume 88, Issue 3 , 2008 , Pages 612-623 ; 01651684 (ISSN) ; Sharif University of Technology
Elsevier
2008
Abstract
A fast and simple procedure for designing relatively wide band fractional delay (FD) all-pass filters is proposed and filters designed based on it are compared to those designed using Thiran's method, which is one of the simplest, fastest and widely used approaches in designing FD all-pass filters. It is shown that filters designed using the introduced method have wider fractional group delay (fgpd) bandwidths compared to those obtained via Thiran's technique, as well as some other desired properties. The designed filters are also demonstrated to be stable for several pairs of filter orders and fgpd values. © 2007 Elsevier B.V. All rights reserved
Pectic acid–graphene oxide nanocomposite as an adsorbent in vortex-assisted dispersive solid-phase extraction for preconcentration of copper ion followed by flame atomic absorption spectrometry
, Article Polymer Bulletin ; Volume 77, Issue 6 , 2020 , Pages 2821-2836 ; Shakerian, M ; Majeed, H. J ; Eftekhari, M ; Rezazadeh, N ; Sharif University of Technology
Springer
2020
Abstract
An efficient, green, novel and rapid vortex-assisted dispersive solid-phase extraction (VADSPE) technique was used for the preconcentration and determination of trace levels of Cu2+ followed by flame atomic absorption spectrometry. Graphene oxide (GO) was synthesized from graphite and then modified by pectic acid (poly-d-galacturonic acid, PA) to synthesize the pectic acid–graphene oxide (PA-GO) nanocomposite. The Fourier transform infrared spectrophotometry, field emission scanning electron microcopy, energy-dispersive X-ray spectroscopy and X-ray diffraction analysis were used to characterize the synthesized GO-PA nanocomposite. By using VADSPE technique, PA-GO was used as an adsorbent for...
Optimum mechanism for rehabilitation of fingers
, Article 5th RSI International Conference on Robotics and Mechatronics, IcRoM 2017, 25 October 2017 through 27 October 2017 ; 2018 , Pages 451-456 ; 9781538657034 (ISBN) ; Zohoor, H ; Shirzadi, H ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2018
Abstract
Nowadays, with the advancement of technology, humans are looking for ways to cure various diseases. Meanwhile, musculoskeletal injuries usually have a long treatment period. Therefore, in recent years, Researchers working one exoskeleton with rehabilitation application which conduct physiotherapy tasks. In current study, a portable two degree of freedom hand exoskeleton is designed which its mechanism is a combination of cable and link mechanism, MCP1 1Metacarpophalangeal joint between metacarpal and proximal phalanges joints move by link mechanism, DIP2 2Distal interphalangeal joint between proximal phalanges and middle phalanges and PIP3 3Proximal interphalangeal joint between middle...
An iterative signal recovery technique capable of decreasing the lossy effects of codecs
, Article 2007 IEEE International Conference on Telecommunications and Malaysia International Conference on Communications, ICT-MICC 2007, Penang, 14 May 2007 through 17 May 2007 ; February , 2007 , Pages 107-112 ; 1424410940 (ISBN); 9781424410941 (ISBN) ; Marvasti, F ; Sharif University of Technology
2007
Abstract
In this paper applications of an iterative method in some signal recovery problems are introduced. It is proved that the distorting effect of linear operators can be removed completely using the iterative scheme. The inverse of monotonic functions can also be made indirectly by the method. A novel approach for separating the messages of different subscribers in a CDMA network will be proposed as well, relying on the recursive approach. It would be shown that Sigma Delta Modulated signals can be decoded via the iterative procedure. We will prove both analytically and with simulations that a broad class of nonlinear operators including speech and image codecs can be approximately inverted with...
Tunning the tilt of the Dirac cone by atomic manipulations in 8Pmmn borophene
, Article Communications Physics ; Volume 6, Issue 1 , 2023 ; 23993650 (ISSN) ; Hadipour, H ; Jafari, A ; Sharif University of Technology
Nature Research
2023
Abstract
Two dimensional quantum materials possessing Dirac cones in their spectrum are fascinating due to their emergent low-energy Dirac fermions. In 8Pmmn borophene the Dirac cone is furthermore tilted, which is a proxy for spacetime geometry, since the future light-cone depends on the underlying metric. Therefore it is important to understand the microscopic origin of the tilt. Here, based on ab-initio calculations, we decipher the atomistic mechanism of the formation of tilt. First, nearest-neighbor hopping on a buckled honeycomb lattice forms an upright Dirac cone. Then, the difference in the renormalized anisotropic second-neighbor hopping, formed by virtual hoppings on one-dimensional chains...
Multivariate analytical figures of merit as a metric for evaluation of quantitative measurements using comprehensive two-dimensional gas chromatography–mass spectrometry
, Article Journal of Chromatography A ; Volume 1466 , 2016 , Pages 155-165 ; 00219673 (ISSN) ; Parastar, H ; Sharif University of Technology
Elsevier B.V
2016
Abstract
The present contribution is devoted to develop multivariate analytical figures of merit (AFOMs) as a new metric for evaluation of quantitative measurements using comprehensive two-dimensional gas chromatography–mass spectrometry (GC × GC–MS). In this regard, new definition of sensitivity (SEN) is extended to GC × GC–MS data and then, other multivariate AFOMs including analytical SEN (γ), selectivity (SEL) and limit of detection (LOD) are calculated. Also, two frequently used second- and third-order calibration algorithms of multivariate curve resolution-alternating least squares (MCR-ALS) as representative of multi-set methods and parallel factor analysis (PARAFAC) as representative of...
Evaluating Availability of Backend Logic in Enterprise Storage Systems
, M.Sc. Thesis Sharif University of Technology ; Asadi, Hossein (Supervisor)
Abstract
Data storage systems are an essential part of any Information Technology (IT) infrastructure. Unavailability of these systems can directly lead to service disruption to customers and can be very costly in enterprise applications such as ebanking, online reservation systems, and mobile services. Modeling availability of disk subsystem is a major step in design of data storage systems. Previous modeling techniques have mainly focused on data unavailability or data loss due to double or multiple disk failures. In this thesis, we present both simulation and analytical modeling techniques to investigate the effect of serviceability on the overall availability of disk subsystems. The proposed...