Sharif Digital Repository

This paper presents a low-order and accurate method for the design of FIR fractional delay (FD) filters with complex coefficients. This method employs least square technique in Hilbert space to approximate the ideal FD transfer function with a FIR filter and to calculate its coefficients. The main advantages of the resulting filter are: very good response at all frequencies compared to other FD filter design methods and a good method to create very small delay. Design examples are presented to illustrate the effectiveness of this new design approach. © World Scientific Publishing Company  

This paper presents an improved low order technique for the design of FIR fractional delay (FD) filters. This method is based on a new use of the least square method in Hilbert space to approximate the ideal FD transfer function with a FIR filter. The main advantages of the resulting filter are: very good response at all frequencies and a good method to create very small delay. Design examples are demonstrated to illustrate the effectiveness of this new design approach. © 2004 IEEE  

In the expanding field of tissue engineering (TE), improvement of biodegradability and osteoconductivity of biomaterials are required. The use of non-toxic reagents during manufacturing processes is also necessary to decrease toxicity and increase cell viability in vivo. Herein, we present a novel approach to prepare hydroxyapatite (HA) nanorods from sea bio-wastes through a green and eco-friendly wet-chemical processing for bone TE. Highly porous natural polymer-ceramic nanocomposites made of HA, gelatin (Ge) and carboxymethyl cellulose (CMC) hydrogels are then introduced. It was found that cross-linking of the hydrogel matrix by glucose as a green reagent affected all characteristics of... 

We develop a fuzzy multi-objective linear programming (FMOLP) model for solving multi-objective mixed-model assembly line problem. In practice, vagueness and imprecision of the goals in this problem make the fuzzy decision-making complicated. The proposed model considers minimizing total utility work, total production rate variation, and total setup cost, using a two-phase linear programming approach. In the first phase, the problem is solved using a max-min approach. The max-min solution not being efficient, in general, we propose a new model in the second phase to maximize a composite satisfaction degree at least as good as the degrees obtained by phase one. To show the effectiveness of... 

Hematite is recognized as a promising photoanode for photoelectrochemical water oxidation to produce solar hydrogen due to its favorable properties. However, the high charge carrier recombination rate due to low electrical conductivity and sluggish oxygen reduction kinetics of pure hematite hinder its photocatalytic activity. This work proposed a new hematite-based heterostructure of Ti-Fe2O3/Fe2TiO5/FeOOH, synthesized through a hydrothermal method. The photoanode morphology was branched nanorods that expanded their surface area and improved charge transfer at the photoanode/electrolyte interface. In a novel and complement modification approach, a thin pseudobrookite interlayer was applied... 

We propose a circularly polarized antenna with a wide axial ratio (AR) beamwidth that consists of a normally magnetized ferrite disk mounted on a ground plane. The device uses the resonant modes of the disk, which rotate only in the clockwise or counter-clockwise sense in the frequency range where the effective permeability of ferrite is negative. A semianalytical model is derived for the antenna fed by a single, conventional current probe and is validated numerically by finite element method. For a yttrium iron garnet disk with the radius and height of 5 and 1 mm, respectively, the results show a 3 dB AR beamwidth of 90° with an operation frequency, which can be tuned in the 4-4.5 GHz range... 

This paper proposes, for the first time, a tunable left handed transmission line consisting of a strip line sandwiched between a ferrite superstrate and a dielectric substrate containing a metallic wire array. The left-handed behavior is realized by combining the negative permittivity of the wire array with the negative permeability of the longitudinally magnetized ferrite substrate despite them being spatially separated. Theoretical and numerical results demonstrate the tunability of the left-handed frequency band by changing the DC bias magnetic field applied to the ferrite. Compared to other tunable lefthanded structures, the fabrication requirements on this structure are not critical,... 

This article proposes a tunable composite right-/left-handed transmission line consisting of a transversely magnetized ferrite substrate periodically loaded by microstrip inductors. The gapless transition between the left- and right-handed bands (balanced response) is the main characteristic of this structure. This composite right-/left-handed transmission line is proposed in both reciprocal and nonreciprocal versions. Based on periodic structure analysis, the dispersion relation is estimated theoretically and validated numerically by the finite-element method in the reciprocal case. Theoretical and numerical results demonstrate the tunability of the proposed structures by changing the DC... 

We propose, for the first time, a tunable left-handed (LH) waveguide consisting of an array of complementary split-ring resonators built on the broad wall of a rectangular waveguide filled with ferrite material. The left-handed behavior is caused by the negative permittivity of the complementary split-ring resonators together with the negative permeability of the transversely magnetized ferrite. The electromagnetic behavior of this structure is studied by means of an equivalent circuit model. From this model, the dispersion relation of the guide is derived and validated numerically by the finite element method. It is shown that this structure has a left-handed frequency band that can be... 

Given measurement difficulties, earlier modeling studies have often used some constant ratios to predict lumbar segmental kinematics from measurements of total lumbar kinematics. Recent imaging studies suggested distribution of lumbar kinematics across its vertebrae changes with trunk rotation, lumbar posture, and presence of load. An optimization-based method is presented and validated in this study to predict segmental kinematics from measured total lumbar kinematics. Specifically, a kinematics-driven biomechanical model of the spine is used in a heuristic optimization procedure to obtain a set of segmental kinematics that, when prescribed to the model, were associated with the minimum... 

The effects of climate change have disturbed the living patterns of many people around the globe during the past decade and it has been a key contributing factor to mass migrations. The ‘adaptation’ approach is currently considered the most effective available solution for balancing out these effects. As a result, many researchers are trying to find out how to increase the adaptive capacity of individuals and communities in response to the effects of climate change. The effect of place attachment as a factor which connects human societies to the surrounding environment is undeniable. In this regard, the present study attempts to analyse the role of place attachment in increasing the... 

The asphalt industry has been at the forefront of sustainable development. Warm Mix Asphalt (WMA) has been developed to cope with issues such as high energy prices and air pollution. These mixes require less energy and generate fewer pollutants during production in comparison with conventional Hot Mix Asphalt (HMA). Although a promising technology, the durability of WMA is not clear because long-term WMA field performance data is limited. This study investigated the susceptibility of Sasobit-modified WMA to moisture, since moisture damage is a major cause of premature pavement failure in asphalt concrete. To this end, WMA samples were made using different concentrations of Sasobit and the... 

The effects of climate change have disturbed the living patterns of many people around the globe during the past decade and it has been a key contributing factor to mass migrations. The ‘adaptation’ approach is currently considered the most effective available solution for balancing out these effects. As a result, many researchers are trying to find out how to increase the adaptive capacity of individuals and communities in response to the effects of climate change. The effect of place attachment as a factor which connects human societies to the surrounding environment is undeniable. In this regard, the present study attempts to analyse the role of place attachment in increasing the... 

Objective(s): The molecular basis of “metabolically healthy obese” and “metabolically unhealthy non-obese” phenotypes is not fully understood. Our objective was to identify metabolite patterns differing in obese (metabolically healthy vs unhealthy (MHO vs MUHO)) and non-obese (metabolically healthy vs unhealthy (MHNO vs MUHNO)) individuals. Materials and Methods: This case-control study was performed on 86 subjects stratified into four groups using anthropometric and clinical measurements: MHO (21), MUHO (21), MHNO (22), and MUHNO (22). Serum metabolites were profiled using nuclear magnetic resonance (NMR). Multivariate analysis was applied to uncover discriminant metabolites, and enrichment... 

Singular spectrum analysis (SSA) is a well-studied approach in signal processing. SSA has originally been designed to extract information from short noisy chaotic time series and to enhance the signal-to-noise ratio. SSA is good for offline applications; however, many applications, such as modelling, analysis, and prediction of time-varying and non-stationary time series, demand for online analysis. This study introduces a recursive algorithm called recursive SSA as a modification to regular SSA for dynamic and online applications. The proposed method is based on eigenvector matrix perturbation approach. After recursively calculating the covariance matrix of the trajectory matrix, R-SSA... 

The time-varying Sun as the main source of space weather affects the Earth's magnetosphere by emitting hot magnetized plasma in the form of solar wind into interplanetary space. Solar and geomagnetic activity indices and their chaotic characteristics vary abruptly during solar and geomagnetic storms. This variation depicts the difficulties in modeling and long-term prediction of solar and geomagnetic storms. On the other hand, the combination of neurofuzzy models and spectral analysis has been a subject of interest due to their many practical applications in modeling and predicting complex phenomena. However, these approaches should be trained by algorithms that need to be carried out by an... 

The objective of the work ahead is presentation of a new carbon paste electrode (CPE) modified by TiO2 nanoparticles (TiO2NPs) and 1,2-bis-[o-aminophenyl thio] ethane (APTE) ligand as a selective cation receptor for determination of the Cd (II) ions using differential pulse anodic stripping voltammetry (DPASV). The electrode shows an excellent tendency to Cd (II) ions in presence of some interfering species. Under the optimum conditions, a linear calibration curve was obtained in the concentration range of 2.9 nM to 4.6 μM with a correlation coefficient of 0.9969 in the anodic potential of 0.54 (V vs. Ag/AgCl). The metal detection limit was 2.0 nM after 10 min preconcentration (S/N = 3). The... 

Line nanopatterns are produced on the positive photoresist by scanning near-field optical microscope (SNOM). A laser diode with a wavelength of 450 nm and a power of 250 mW as the light source and an aluminum coated nanoprobe with a 70 nm aperture at the tip apex have been employed. A neutral density filter has been used to control the exposure power of the photoresist. It is found that the changes induced by light in the photoresist can be detected by in situ shear force microscopy (ShFM), before the development of the photoresist. Scanning electron microscope (SEM) images of the developed photoresist have been used to optimize the scanning speed and the power required for exposure, in... 

A semicentralized joint cell muting and user scheduling scheme for interference coordination in a multicell network is proposed under two different temporal fairness criteria. In the proposed scheme, at a decision instant, each base station (BS) in the multicell network employs a cell-level scheduler to nominate one user for each of its inner and outer sections and their available transmission rates to a network-level scheduler which then computes the potential overall transmission rate for each muting pattern. Subsequently, the network-level scheduler selects one pattern to unmute, out of all the available patterns. This decision is shared with all cell-level schedulers which then forward... 

In a given graph G, a set S of vertices with an assignment of colors is a defining set of the vertex coloring of G, if there exists a unique extension of the colors of S to a χ(G)-coloring of the vertices of G. A defining set with minimum cardinality is called a smallest defining set (of vertex coloring) and its cardinality, the defining number, is denoted by d(G, χ)- Let d(n, r, χ = k) be the smallest defining number of all r-regular k-chromatic graphs with n vertices. Mahmoodian and Mendelsohn (1999) proved that for each n and each r ≥ 4, d(n, r, χ = 3) = 2. They raised the following question: Is it true that for every k, there exist n0(k) and r0(k), such that for all n ≥ n0(k) and r ≥...